Transposable elements account for the almost half of the sequence encoded by mammalian genomes, which become silenced during early embryonic development. This thesis sought to explore the hypothesis of the involvement of the RNAi pathway in the silencing of transposable elements in mammals, predominantly through the identification of transposon-associated RNA of -20-25nt using a gel blotting technique. Initially cell lines of embryonic and tumour origin were analysed. This lead to the identification of several previously unreported transposon-associated RNA ranging from 70-90nt. However, it was not until a more detailed analysis of the embryonic cell lines, with the induction of differentiation in cell culture that several discrete RNA of -20nt were detected for the mouse transposons L1 and B2. The differentiation of embryonic cell lines in culture also serendipitously lead to the detection of several short 55 rRNA of -22-26nt, these were also later detected in several human cell lines of breast cancer origin and healthy breast tissue. Intriguingly the -20-26nt repeat-associated identified were predominantly observed after two-days of differentiation in cell culture in several cell lines and often coincided with an ethidium bromide stainable band of -19nt. The latter may indicate a large proportion of these RNAs. Further analysis of the B2 and 55 rRNA repeat-associated short RNA revealed both to have reduce accumulation in Dicer-null embryonic stem cells, implicating a possible association with a known component of the RNAi pathway. Dicer was also observed to process the longer -50-80nt 55rRNA to -20-26nt in vitro. BLAST was also used to identify possible mRNA targets for the short B2 and 55 rRNA. One of these, the mRNA encoding sialic acid acetylesterase (SIAE) was consistently observed to be reduced with the accumulation of the short RNA using end-point RT-PCR, consistent with targeting through the RNAi or a similar pathway. However, no further links with the RNAi pathway were established, with no targeting detected for the short B2 or 55 rRNA using dual luciferase sensor assays. The repeat-associated RNA identified in this thesis are among the first of their type and further work will be required to establish what relevance they have to the RNAi pathway and transposon regulation.

The G-protein coupling specificity of D2-like dopamine receptors was investigated using both receptor-G protein fusions and membranes of cells in which pertussis toxin-resistant mutants of individual Gi-family G proteins could be expressed in an inducible fashion. A range of ligands displayed agonism at the long isoform of the human dopamine D2 receptor. However, varying degrees of efficacy were observed for individual ligands as monitored by their capacity to load [35S] GTPγS onto each of Gi1, Gi2, Gi3 and Go1. By contrast, S-(-)-3-(3-hydroxyphenyl)-N-propylpiperidine (S-(-)-3PPP) was a partial agonist when Go1 was the target G protein but an antagonist/inverse agonist at Gi1, Gi2, Gi3. In ligand binding assays dopamine identified both high and low affinity states at each of the dopamine D2 receptor-G protein fusion proteins and the high affinity state was eliminated by guanine nucleotide. S-(-)-3PPP bound to an apparent single state of the constructs where the D2 receptor was fused to Gi1, Gi2 or Gi3. However, it bound to distinct high and low affinity states of the D2 receptor-Go1 fusion with the high affinity state being eliminated by guanine nucleotide. Similarly, although dopamine identified guanine nucleotide-sensitive high affinity states of the D2 receptor when expression of pertussis toxin-resistant forms of either Gi2 or Go1 was induced, S-(-)-3PPP identified a high affinity site only in the presence of Go1. These results demonstrate S-(-)-3PPP to be a protean agonist at the D2l receptor and may explain in vivo actions of this ligand. Furthermore, in agreement with previous studies, the ability of the dopamine D2l receptor to couple promiscuously to Gαi1-3, and Gαo1 was demonstrated. However, despite high homology between dopamine D2l and D3 receptors, the G protein-coupling specificity of the D3 receptor has not been well characterised. Again using both receptor-G protein fusions and membranes of cells in which pertussis toxin-resistant mutants of individual Gi-family G proteins could be expressed in an inducible fashion, we confirmed the selective coupling of the D3 receptor to Gαo1. A range of ligands displayed agonism at the D2l receptor and the D3 receptor when coupled to Gαo1. As a general trend, agonists, including dopamine, displayed a higher potency at the D3 receptor. This perhaps reflects the role of D3 as an autoreceptor. Of particular interest was the demonstration that S-(-)-3PPP has both a higher efficacy and potency at the D3 receptor when coupled to Gαo1. The investigations into dopamine receptor-G protein coupling highlighted the utility of the [35S]GTPγS binding assay as a method of directly measuring receptor catalysed nucleotide exchange on the α subunit of G proteins. However, the expense associated with the use of radiolabels makes this assay less attractive, particularly for high-throughput screening programmes. In an attempt to develop a non-radioactive assay equivalent to the [35S] GTPγS assay an immunisation programme was initiated to generate antibodies selective against the active (GTP bound) conformation of G proteins. 4 way primary screening of 1632 hybridomas generated from mice immunized with GTPS-loaded Gi1 and isolated using an automated robotic colony picker, identified 3 antibodies that interacted with the constitutively active Q204L but neither the constitutively inactive G203A nor wild type form of Gi1. This profile extended to other closely related Gi-family G proteins but not to the less closely related Gs and Gq/G11 families. Each of these antibodies was, however, also able to identify wild type, GDP-bound Gi- family G proteins in the presence of AlF4- which mimics the presence of the terminal phosphate of GTP and hence generates an active conformation of the G protein. Stimulation of cells co-expressing a wild type Gisubunit and the dopamine D2 receptor with the agonist ligand nor-apomorphine also allowed these conformation selective antibodies to bind the G protein. Such reagents allow the development of label- free assays for G protein-coupled receptor-mediated activation of Gi- family G proteins.

Smokers with asthma display reduced responses to both inhaled and oral corticosteroids with associated increased symptoms, accelerated decline in lung function and increased use of health care services. Little work has been undertaken to address the possible causes of this reduced response and to find effective replacement therapies. Therefore this thesis was carried out with the aim of identifying potential mechanisms and new therapies for this group. The oral bronchodilator theophylline has been suggested as a treatment for corticosteroid insensitivity due to its ability to increase HDAC activity in-vitro. I undertook an exploratory proof of concept clinical trial based on the hypothesis that low dose theophylline would restore corticosteroid sensitivity in smokers with asthma through theophylline induced recovery of HDAC activity. Low dose oral theophylline added to inhaled corticosteroid increased pre-bronchodilator lung function and reduced symptoms of asthma whilst low dose theophylline given alone reduced symptoms but had no effect on pre-bronchodilator lung function. This research provides a foundation for future studies designed to examine the efficacy of theophylline in smokers with asthma. Agonists of the nuclear hormone receptor peroxisome proliferator activated receptor-γ (PPARγ) have been demonstrated to be effective at reducing inflammation in both in-vitro and animal models of asthma. Therefore to examine the hypothesis that PPARγ stimulation would reduce the inflammation present in smokers with asthma I undertook an exploratory, proof of concept clinical trial using the PPARγ agonist rosiglitazone. Treatment with rosiglitazone was associated with a trend to improvement in FEV1 and improvement in a marker of small airway lung function and as such may provide an alternative treatment for small airways obstruction in conditions such as asthma and chronic obstructive airways disease. This trial will enable powering of future confirmatory studies. Altered cytokine profiles, specifically the combination of increased interleukin (IL)-2 and 4, are observed in asthmatic subjects with corticosteroid insensitivity. Based on this work I examined the hypothesis that the altered response to corticosteroids in smokers with asthma was associated with an altered cytokine milieu including raised levels of IL-2 and 4. Smokers with asthma, characterised as corticosteroid resistant by oral corticosteroid trial, demonstrated significantly raised sputum supernatant IL-6 levels and raised levels of a number of other sputum cytokines compared to non smokers with asthma. This altered phenotype suggests cigarette smoking in asthma may be associated with a deviation to Th1 mediated inflammation and could provide an explanation for the reduced corticosteroid response of smokers with asthma. The cell type/s responsible for both this shift in immunological phenotype and production of increased levels of sputum cytokines is unclear and will require further study. Previous in-vitro and in-vivo research has identified altered histone acetylation patterns in subjects with relative corticosteroid resistance. Therefore I examined the hypothesis that smokers with asthma displayed reduced responses to corticosteroids as a result of a cigarette smoke induced reduction in histone de-acetylase (HDAC) activity. Smokers with asthma provided sputum macrophages and blood for peripheral blood borne monocytes to examine total HDAC activity. Sputum and blood macrophage total HDAC activity was equivalent in smokers and non-smokers with asthma. Therefore reduced blood total HDAC activity does not appear to explain the altered corticosteroid response in this group. However the number of sputum macrophages obtained may have been too low to allow conclusive examination of this endpoint. Another consideration is that contamination of the sample due to the technique used may be altering the signal obtained. Further work either through modification of sputum induction techniques to increase macrophage number or bronchoscopic sampling is required to conclusively address the role of alveolar macrophage HDAC activity in the reduced corticosteroid response displayed by smokers with asthma. Exhaled nitric oxide has been exploited as a useful exploratory and confirmatory endpoint in asthma. However exhaled nitric oxide, measured using standard flow rates and methodology, is unhelpful in smokers with asthma as cigarette smoking is associated with a marked reduction in exhaled nitric oxide levels in the majority of subjects. Recent research has demonstrated that measurement of exhaled nitric oxide at multiple flow rates followed by mathematical modelling reveals increased levels of alveolar nitric oxide that were unaltered by current smoking. Therefore to examine the hypothesis that smokers with asthma display altered levels of alveolar nitric oxide and flow independent parameters compared to non-smokers with asthma I carried out a cross-sectional study. Alveolar nitric oxide, determined by linear modelling, was significantly reduced in smokers with asthma compared to non smokers with asthma. The concentrations observed were within the range for normal subjects and therefore this method does not overcome the problems inherent in measuring exhaled nitric oxide at standard flows. The use of non-linear modelling did demonstrate parity between smokers and non-smokers with asthma for alveolar nitric oxide. Nitric oxide flux was lower in smokers with asthma when derived by both linear and non-linear modelling and displayed sensitivity to oral corticosteroids. Therefore nitric oxide flux is worthy of further investigation as an exploratory endpoint in smokers with asthma. In conclusion treatment of smokers with asthma with low dose theophylline alone, the combination of low dose theophylline and inhaled corticosteroid and the PPARγ agonist rosiglitazone was associated with clinical improvements and further clinical trials to assess the role for these treatments in the management of smokers with asthma are justified. Smokers with asthma display an altered sputum cytokine profile with raised levels of the proinflammatory cytokine IL-6, equivalent blood total HDAC activity and reduced alveolar nitric oxide compared to non-smokers with asthma. Sputum HDAC activity requires further development before it can be confidently employed as a method of assessing total pulmonary HDAC activity.

African trypanosomiasis is a disease caused by the Kinetoplastida parasites Trypanosoma brucei rhodesiense and T. b. gambiense. The distribution of the disease is split geographically with T. b. rhodesiense found in eastern sub-Saharan Africa and T. b. gambiense in the west of the continent. Current treatment for this fatal disease is wholly unsatisfactory with problems such as extreme toxicity, affordability and the emergence of resistance. The case for the generation of new potential chemotherapies is compelling and urgent. Phosphodiesterase (PDE) enzymes degrade the secondary signalling molecule cyclic adenosine monophosphate (cAMP) to AMP by hydrolysis, thereby modulating and regulating the signal transduction to the effector proteins. The phosphodiesterase enzymes in the PDEB family in T. brucei were shown to be essential to the host-infective bloodstream forms and validated as good drug targets using RNA-interference (Zoraghi, R. and Seebeck, T., 2002; Oberholzer, M., 2007). Prompted by these findings, two series of putative trypanosomal PDE inhibitors, from different sources, were thoroughly assessed in this project for their anti-trypanosomal activity and their intracellular effects on the trypanosome. The whole-cell in vitro efficacy for each compound, against T. brucei wildtype and the drug-resistant strain TbAT1 knockout, was established by the standard resazurin reduction assay. 25 compounds from Series 1 had EC50 values below 0.5 µM, with 7 under 100 nM and the most active having an EC50 value of 5.8 ± 3.4 nM. For the much smaller Series 2 (GJS Compounds), the most active compound was GJS-128 with an EC50 value of 79.4 ± 10.3 nM. This demonstrates that a number of compounds from both series have potent in vitro activity against trypanosomes that is better than or equal to the current chemotherapeutic compound diminazene, and some Series 1 compounds are on a par with pentamidine and melarsoprol. No major cross-resistance was displayed by the TbAT1 knockout strain to either Series 1 or the GJS series. Similarly, a panel of Series 1 compounds tested against the B48 strain (resistant to pentamidine and melaminophenyl arsenical drugs), and also against Trypanosoma equiperdum wildtype and diminazene resistant (PBR) strains, showed no major cross-resistance displayed by the other resistant strains. This suggests that there would also be little or no cross-resistance from refractory strains in the field, and also that the compounds are active against multiple Trypanosoma species. A small panel of Series 1 compounds were also tested for efficacy against trypanosomes in infected mice. 4 daily doses of 20 mg/kg bodyweight of Compound 48 significantly reduced parasitaemia by approximately 60% compared to untreated controls, however higher concentrations were not tolerated by the mice so a cure could not be demonstrated. A high-throughput method for monitoring the speed of action of test compounds on trypanosomes in real time was developed, based on the fluorescence of propidium iodide when bound with DNA. Optimisation of the protocol to 96-well plates and low cell densities provided higher resolution and accurate traces of the lysis of trypanosomes in a cell suspension compared to previously used methods, as well as a greatly increased capacity. The propidium iodide assay could also be converted to provide end-point EC50 values that were directly comparable to those established by the standard resazurin reduction assay. The majority of Series 1 compounds did not increase the intracellular concentration of cAMP on incubation with bloodstream form trypanosomes; those that did only induced a minor elevation of the intracellular concentration of the signalling molecule. Since genetic disruption to phosphodiesterase enzymes resulted in large increases in cAMP levels (Oberholzer, M. et al, 2007; Zoraghi, R. and Seebeck, T., 2002), the lack of increase in cAMP by the Series 1 compounds strongly suggest that they do not sufficiently inhibit the PDEs in live trypanosomes and kill the cells via an alternative pathway. In contrast, incubation with the GJS compounds did result in significant increases in intracellular cAMP concentration with the most active being GJS-128 recording an approximately 3-fold increase in cAMP over 3 hours at just 30 nM. The concentrations that begin to increase cAMP level are consistent with the EC50 values for trypanosomes cultured in vitro (this study), and is also in line with inhibition data of recombinant TbrPDEB enzymes (work conducted by Dr. Herrmann Tenor, ALTANA Pharma, and Prof. Thomas Seebeck, University of Bern). This gives a clear and consistent link between the cause of cAMP rise (inhibition of PDEB by GJS compounds) and the effect of that concentration increase on bloodstream form trypanosomes (cell death), demonstrating that the GJS series are inhibitors of trypanosomal PDEs and chemically validate PDEs as drug targets for potential new chemotherapies against African trypanosomiasis. The effect of PDE inhibition on the physiology of the bloodstream form trypanosomes was also investigated. Flow cytometry analysis and the assessment of DNA configuration by fluorescence microscopy after DAPI staining determined that PDE inhibition by GJS-128 resulted in a precise block of the cell cycle in cytokinesis. The replicating trypanosome synthesized and segregated its DNA into two nuclei and kinetoplasts as normal and proceeded to initiate the physical separation of mother and daughter cells. The cleavage furrow between the old and new flagella progressed normally until the point of abscission, at which point division was halted with only a small section of plasma membrane connecting the two almost separated cells. Both cells appeared viable and underwent subsequent rounds of DNA replication, segregation and attempted physical separation that was always blocked near completion. This indicates cAMP signalling plays an important role in the correct physical separation of the replicating bloodstream form trypanosomes. A trypanosome cell line resistant to GJS-128 was developed by chemical mutagenesis and continuous culture with gradually increasing, but sub-lethal concentrations of the PDE inhibitor. This cell line, termed R0.8, was >15-fold less sensitive to GJS-128 and displayed significant cross-resistance to the other GJS compounds, as well as to stable, membrane permeable cAMP analogues. The mode of resistance was investigated by comparing the cAMP profile of the R0.8 and parental wildtype strains on incubation with GJS-128. No major differences were observed suggesting that both the adenylyl cyclase and phosphodiesterase activities remained unchanged in the PDE inhibitor-resistant strain. In support of this, the sequencing of TbrPDEB1 and TbrPDEB2 in both strains, while uncovering the loss of heterozygosity in the R0.8 line, revealed no mutations that would impact on enzyme function or inhibitor binding in the resistant cell line. These data strongly suggest that the adaptation resulting in resistance to PDE inhibitors is located in the effector proteins downstream of the PDEs and adenylyl cyclases in the cAMP signalling pathway. Identifying a compound that inhibits phosphodiesterases in trypanosomes and elevates cAMP concentrations, along with the generation of a PDE inhibitor-resistant cell line will allow more detailed examination of all aspects of the cAMP signalling pathway in T. brucei and across the Kinetoplastida. Phosphodiesterases have also been demonstrated to be chemically inhibitable in trypanosomes and could prove to be the target of a new generation of chemotherapies against African trypanosomiasis.

Epilepsy affects 50 million people world-wide. Since 1982, the Western Infirmary Epilepsy Unit has provided a specialist service for over 6900 people with suspected and established seizure disorders. The twelve studies detailed in this thesis discuss the management of epilepsy in different patient populations, and explore beneficial and adverse effects of antiepileptic drugs (AEDs). AED development has allowed advances in pharmacological treatment of localisation-related epilepsies. Thus, outcomes were investigated in 550 such patients followed-up at the epilepsy clinic over 13 years (Paper i). Of these, 312 (57%) became seizure-free on medication. Those with hippocampal sclerosis had the poorest outcome (p<0.01), and a higher incidence of febrile convulsions (p<0.001). Although many patients benefited from AED therapy, results may be biased, given this cross-sectional study analysed data from both newly diagnosed patients, and those with drug-resistant seizures. Many people with epilepsy take more than one AED, although supportive evidence is sparse. Hence, polytherapy outcomes in 2881 patients registered with the Epilepsy Unit database were examined (Paper ii). Of these, 1617 (56%) were seizure-free, with 332 (21%) taking more than one AED (287 on two, 86%; 42 on three, 13%; 3 on four, 1%). There were 40 duotherapy and 28 triple therapy combinations resulting in seizure freedom. Therefore, combining two or three, but rarely four AEDs may be useful for patients not responding to monotherapy. Because this was a retrospective analysis of newly treated patients and those with refractory epilepsy, the analysis was subject to bias. Lack of a control group was also a weakness. Epilepsy Unit staff are therefore now examining similar outcomes in a large population of newly treated patients only. To establish the place of recently marketed AEDs in clinical practice, four studies examined prospectively the efficacy and tolerability of the novel agent, topiramate, in uncontrolled epilepsy. Adjunctive topiramate was administered in 170 patients with refractory seizures (Paper iii). Seizure frequency and adverse events were monitored. Patients were followed-up until seizure freedom for ≥ 6 months, ≥ 50% or <50% seizure reduction, intolerable side-effects, or lack of efficacy occurred. Seizure freedom was achieved in 39 (23%) patients. A ≥50% reduction in seizure frequency was reported in 80 (47%) others. Doses were often lower than those in regulatory studies. Efficacy as monotherapy was also demonstrated. Using the same end-points, topiramate was added to AED regimens of 64 patients with learning disabilities and epilepsy (Paper iv). Remission from seizures was established in 16 (25%). In similar fashion, levetiracetam was started in 156 patients with uncontrolled epilepsy (Paper v). Of these, 40 (26%) became seizure-free, many on low doses. When the drug was added to AED regimens in 64 patients with learning disabilities, 24 (38%) became seizure-free for at least 6 months (Paper vi). Caregiver quality-of-life scores improved significantly with levetiracetam (p<0.001). It is important to recognise that for all four audits results may be biased due to their observational nature, and the fact that they were undertaken at a single centre, with no control group. For patients with learning disabilities, small numbers, and retrospective baseline recordings for some could also have introduced bias. In Papers vii, viii and ix, findings from longitudinal studies in teenagers, people with learning disabilities and epilepsy, and newly diagnosed elderly patients attending the Epilepsy Unit, are reported. At the Teenager Clinic, 301 adolescents were reviewed over four years (Paper vii). Epilepsy was excluded in 135 (45%), five taking AEDs. A single seizure occurred in 22 others. In the 144 with epilepsy, seizure freedom for ≥ 12 months was attained in 76 (53%), but outcomes were poorer than expected. Neuroimaging was abnormal in 27 (43%). Newly diagnosed patients fared better than those taking treatment (p<0.05). More teenagers with primary generalised seizures (60%) attained remission, compared to those with focal-onset seizures (46%) (p<0.02). The retrospective natures of the analysis, and lack of control group may have biased results, thus making statistical conclusions inaccurate. Findings suggested the need for improved services. Over four years, 214 patients with learning disabilities and refractory epilepsy were followed-up (Paper viii). Although it is generally thought these individuals’ seizures are difficult to control, 59 (43%) became seizure-free for ≥ 12 months with AEDs. There was no change in quality-of-life scoring during this time, and no relationship between extent of learning disability and seizure control. The observational nature of the audit, and lack of control group may have biased results. Currently, there are few data on elderly people with epilepsy. Thus, outcomes over a 20-year period in 117 newly diagnosed senior citizens were examined (Paper ix). After starting AED treatment, 93 (79%) became seizure-free for ≥ 12 months, 73 (62%) with their first drug. Prognosis was better than in younger patients, and for those with fewer pre-treatment seizures (p=0.0078). Again bias may have been introduced because of the study’s observational nature and lack of control group. The final studies concentrate on AED-related adverse effects (Papers x, xi and xii). Bone changes have been reported with AED use. Hence, the relationship between bone mineral density, and long-term AED treatment in 78 older adults (47 post-menopausal women, 31 men), taking hepatic enzyme-inducing or non-inducing AEDs, was explored in a case-controlled study (Paper x). Men had significantly lower bone mineral density than controls at the lumbar spine (p<0.01), and neck of femur (p<0.005). Women had statistically reduced bone mineral density at the femoral neck (p<0.05). It was concluded that long-term AED treatment is an independent risk factor for reduced bone mineral density in people with epilepsy. As sodium valproate may be associated with metabolic changes and polycystic ovarian syndrome, hormone profiles were compared in 76 young men and women taking sodium valproate or lamotrigine monotherapy, to assess whether a pharmacological effect of valproate was responsible (Paper xi). Results revealed only four obese females exhibiting biochemical characteristics of polycystic ovarian syndrome (p=0.05), with obese patients of both sexes (p=0.01), and valproate-treated men (p=0.03) having higher insulin concentrations. Results are not significant when corrected for multiple comparisons. It can therefore be concluded that no differences in metabolic indices between patients taking sodium valproate or lamotrigine existed. To examine further effects on androgenic hormones, and the efficacy and tolerability of sodium valproate and lamotrigine monotherapy, a randomised, prospective study in 225 patients was performed (Paper xii). Patients were recruited if they presented with a minimum of two unprovoked seizures of any type, or a single seizure and underlying neuropathology. Of patients with partial-onset seizures, 81 received sodium valproate and 80 were randomised to receive lamotrigine. Of those with idiopathic generalised epilepsies, 30 received sodium valproate and 34 took lamotrigine. Seizure-free rates were identical in both arms at twelve months between the valproate and lamotrigine cohorts. There was a trend towards superiority for valproate (57% seizure-free) over lamotrigine (35% seizure-free) for patients with idiopathic generalised epilepsies (p=0.09), but a converse separation of outcomes for localisation-related epilepsies (43% seizure-free with valproate, 53% seizure-free with lamotrigine, p=0.24). More patients taking sodium valproate withdrew due to adverse events (p=0.046), eight because of weight gain.

Introduction: Chronic heart failure (CHF) is associated with an increased incidence of atrial fibrillation (AF) and elevated levels of catecholamines and endothelin-1 (ET-1), each of which affects the atrial L-type calcium current (ICaL) and consequently action potentials. Hypotheses: ET-1 modulates the effects of isoproterenol (ISO) on ICaL and action potentials in human atrial myocytes. Methods: Atrial myocytes were isolated enzymatically from samples of right atrial appendage obtained from consenting patients in sinus rhythm undergoing cardiac surgery. The nystatin-perforated whole cell patch clamp technique was used at 37ºC to record ICaL and action potentials in voltage-clamp and current-clamp mode respectively. Results: The current-voltage relationship of ICaL was bell-shaped, peaking at +10 mV with a current density of -4.8±0.4 pA/pF (mean± s.e.m., n=89 cells, 34 patients). ISO, 0.1 nM to 1 µM, increased peak ICaL in a concentration-dependent manner (n=4-46 cells) with a maximum response of 250± 53% above control and an approximate EC50 of 0.06 µM. Isoproterenol at 0.05 µM significantly increased peak ICaL from -4.7± 0.4 to -12.2± 0.9 pA/pF (P<0.05, Students t-test; n=64 cells). This adrenergic effect was reversed by ET-1 at all concentrations tested from 0.01 to 10 nM and was partially reversible upon ET-1 washout and in the presence of the specific ET-A receptor antagonist, FR139317 (n=5-12 cells). Neither ET-1 alone nor the ET-B receptor agonist Sarafotoxin S6c, at 10 nM, had an effect on ICaL. Isoproterenol (0.05 µM) prolonged the action potential duration at 50% repolarisation (APD50) from 30± 7 to 46± 7 ms (P< 0.05, n=15 cells), but had no effect on APD90 nor the cellular ERP. These adrenergic effects on APD50 and SDs were also abolished by ET-1 at 10 nM (P< 0.05, n=15 cells). Superfusion with ET-1 (10 nM) alone had no significant effect on APD50, APD90, nor ERP (n=21 cells). There were no significant interactions between these electrophysiological effects and diseases states or chronic pre-operative drug therapy. Spontaneous activity, defined as a depolarisation occurring during phase 3 of action potential repolarisation or a depolarisation of greater than 3 mV amplitude during phase 4, frequently interrupted action potential recordings during, but not prior to, superfusion with ISO. Using a repetitive stimulation protocol, ISO at 0.05 µM produced spontaneous depolarisations in 5 of 7 cells studied (P< 0.05, chi-2 test). Endothelin-1 at 10 nM abolished these depolarisations in all 5 cells (P< 0.05). Superfusion with ET-1 (10 nM) alone was associated with spontaneous depolarisations in significantly fewer cells (P< 0.05, n=2 of 13 cells). In a retrospective univariate analysis, patient comorbidity and pre-operative drug therapy were not found to influence the electrophysiological effects observed. Conclusions: ET-1 reversed adrenergically induced increases in peak ICaL, APD50 and SDs in human atrial myocytes. This anti-adrenergic effect may be expected to influence the occurrence of AF in patients irrespective of comorbidity or pre-operative drug therapy.

Chronic myeloid leukaemia (CML) is a clonal myeloproliferative disorder of the haemopoietic stem cell, defined by the Philadelphia chromosome (Ph) - the outcome of a balanced, reciprocal translocation between the long arms of chromosomes 9 and 22. The novel fusion oncogene generated on chromosome 22 as a result of this translocation is called BCR-ABL. In the majority of patients, this oncogene transcribes a 210-kDa constitutively active protein tyrosine kinase, often referred to as p210BCR-ABL, which is necessary for the transformation of the disease. The introduction of the orally available, tyrosine kinase inhibitor (TKI) - imatinib mesylate (IM) - marked a major advance in CML treatment in terms of efficacy and tolerability and has now become the first line of therapy. IM acts by competing with ATP to block ABL-kinase activity, resulting in the selective apoptosis induction of BCR-ABL+ cells. However, despite the success of IM as standard therapy for CML, only a small proportion of patients obtain a complete molecular response, where they become negative for BCR-ABL transcripts by RTPCR. It is hypothesised that this minimal residual disease is the result of a primitive quiescent subpopulation of leukaemic cells, which may be the cause for relapse at a later date. Another major clinical concern is the observation of molecular resistance in IM-treated patients. Proposed mechanisms of resistance include BCR-ABL amplification, decreased intracellular IM concentrations caused by drug efflux proteins such as multi drug resistance-1 and the development of point mutations within the ABL-kinase domain. In an attempt to overcome IMresistance, a second generation of BCR-ABL inhibitors has been developed. Dasatinib (BMS-354825, Sprycel) is a TKI developed for the treatment of IM resistant or -intolerant patients with Ph+ leukaemias, which has a 325-fold greater potency than IM against cells expressing wild-type BCR-ABL, and is effective against all IM-resistant BCR-ABL mutants tested in vitro, except T315I. Previously, we showed that dasatinib induced durable inhibition of BCR-ABL and impressive clearance of Ph+ cells, however, the primitive quiescent cell population did not appear to undergo apoptosis even after several days TKI exposure. Therefore, it was still not clear whether early CML progenitor cells depend on BCR-ABL for their growth and survival. In this study we have attempted to determine whether CML stem cells are dependent on BCR-ABL TK activity for their survival and/or proliferation using dasatinib treatment and aimed to characterise the cells which survived drug exposure. We found that 10% of the CML cells were able to survive the dasatinib treatment. We also showed that maximal BCR-ABL TK inhibition was achieved in the surviving CML cells, both in the bulk population of cells and the more problematic primitive stem cell population. Those cells which survived the dasatinib treatment were found to be primitive, residing mainly in the undivided cell fraction and the very early cell divisions. Since these BCR-ABL TK-inhibited, resistant cells were also able to grow when re-cultured in cytokines and form longterm culture-initiating cell (LTC-IC) colonies; these data suggested that ~10% of primitive CD34+ CML cells are not addicted to BCR-ABL TK activity for their survival. This also suggested that these primitive, resistant CML cells appeared to survive and proliferate by BCR-ABL-independent mechanisms. Therefore, the next experiments were then designed to investigate the cellular process of autophagy as a potential means of primitive CML cell survival. Analysis of the properties of CD34+ CML cells which remained viable following dasatinib treatment, revealed the existence of cytoplasmic autophagic structures determined by electron microscopy and significantly increased autophagosome-asociated LC3-II, particularly in the cells cultured without growth factors (GF)s. This suggested that autophagy is induced following GF deprivation of CML cells and is significantly increased within these cells, upon BCR-ABL inhibition following dasatinib treatment. Furthermore, we also found that the inhibition of autophagy greatly potentiated the effect of TKI treatment on the reduction of primitive CML progenitor cells, in terms of the effective eradication of functionally defined colony forming cells and LTC-ICs. Overall, this thesis has shown for the first time that the most TKI-resistant primitive CML cells are likely to be independent of BCR-ABL TK activity for their proliferation and/or survival. Furthermore, we have shown that these resistant CML stem cells rely on the BCR-ABL independent autophagy process for survival in response to stressful conditions, such as, GF deprivation and TKI treatment.

Percutaneous coronary intervention (PCI) improves the blood supply to the heart by unblocking narrowed coronary arteries. Implantation of a coronary stent is usually required to scaffold the artery and improve long-term vessel patency. Drug-eluting stents (DES) have been developed to decrease the incidence of stent renarrowing, known as in-stent restenosis (ISR), the main limitation of bare metal stents (BMS). DES release potent drugs into the artery wall to inhibit cell division and attenuate ISR. However, this strategy can also impair vascular healing and increase the risk of stent thrombosis, which is a serious concern. Novel approaches to this problem are urgently required. Oxidative stress reflects a state in which reactive oxygen species (ROS) prevail over antioxidant defences. PCI causes a major release of ROS from the injured artery wall and these molecules appear to play an important role in critical signalling pathways involved in vascular repair. Numerous animal studies have found that oral antioxidants may reduce ISR and improve healing, yet these strategies have not been effective in humans. Stent-based delivery of antioxidants may offer more efficacious, targeted protection against oxidative stress than oral administration. The role of oxidative stress in endothelial repair mediated by bone marrow-derived endothelial progenitor cells (EPCs) in patients with coronary heart disease is also poorly defined. The main aims of this thesis were: to determine the in vitro effects of oxidative stress on key aspects of thrombosis and vascular healing; to evaluate a novel antioxidant-eluting stent in an in vivo porcine model; and to examine the relationship between oxidised low-density lipoprotein (oxLDL), EPCs and coronary endothelial function in patients with stable angina. Oxidative stress, generated by the xanthine/xanthine oxidase reaction, inhibited whole blood aggregation in a concentration-dependent fashion. This was probably due to an excess of ROS which impaired, rather than stimulated, thrombosis. Healthy endothelial cells (ECs) also inhibited whole blood aggregation, but this was not mitigated by oxidative stress. EC migration was assessed using an in vitro endothelial wound scratch assay. Oxidative stress was highly toxic to ECs and inhibited migratory activity. Nitrone D, a novel spin trapping antioxidant, was evaluated for its suitability as a novel DES coating. Nitrone D displayed weak antithrombotic effects, but markedly inhibited EC migration. Nitrone D was therefore unsuitable for a DES that was intended to improve re-endothelialisation. Oral probucol has established efficacy in animal models of restenosis, but not in humans. Probucol has been successfully incorporated as a dual DES coating with rapamycin in clinical trials. Succinobucol is a novel derivative of probucol with more potent antioxidant, anti-inflammatory and antiproliferative effects. A novel polymer-free succinobucol-eluting stent (SES) and succinobucol/rapamycin-eluting stent (SRES) were developed and compared to a commercially available polymer-free rapamycin-eluting stent (RES) and BMS. Pharmacokinetic studies demonstrated optimal drug elution from the SES. However, in a porcine coronary model, the SES significantly increased neointimal thickness and aggravated ISR. The RES reduced neointimal thickness non-significantly, whereas the SRES caused no difference in neointimal thickness, compared with the BMS. The SES was associated with greater inflammation and persistent fibrin deposition around the stent struts, which are signs of defective healing. There were no significant differences in endothelial regeneration between the groups. Subsequent cell culture studies found that succinobucol was toxic to ECs and smooth muscle cells. In the clinical study, circulating levels of EPCs were strongly correlated with coronary endothelial function, which is a novel finding. Plasma oxLDL levels were not correlated with EPCs or coronary endothelial function. In conclusion, ROS reflect a large array of molecules released after PCI that are multi-faceted regulators of platelets and vascular cells. As such, they represent a complex target for novel DES technologies. Excessive ROS may inhibit thrombus formation and delay re-endothelialisation. However, potent antioxidants delivered to injured arterial tissue after PCI may not necessarily encourage the physiological processes required to accelerate vascular repair. At high dose, local delivery of antioxidants may actually promote inflammation and aggravate ISR. Although oxLDL is known to induce endothelial dysfunction, it is not correlated with the number of circulating EPCs. These findings underline the complicated role of oxidative stress in vascular repair after PCI. Further studies are required to clarify whether antioxidants will ever provide advantages over existing options in the rapidly evolving field of interventional cardiology.

GPR40, GPR41 and GPR43 are a small family of GPCRs. Fatty acids were identified as the ligands for these receptors in 2003. High levels of circulating fatty acids have been linked to a variety of diseases, including type 2 diabetes mellitus, cancer, and high levels of fatty acids are produced by anaerobic bacteria at the site of infection. High levels of GPR40 have been detected in the beta cells of the pancreas and all three receptors have been shown to be expressed in immune cells. Due to the recent identification of the ligand for these receptors, their pharmacology, function and oligomerisation was investigated during this study. A [35S]GTPgammaS binding assay was developed to monitor the activation of GPR41 using a GPR41-Gαi3 Cys351Ile fusion protein. Using the fusion protein improved the signal to background ratio and allowed the potency of a variety of short chain fatty acids to be determined. A GPR40-Gαq fusion protein was also generated, but basal levels of [35S]GTPgammaS binding in Gαq immunoprecipitates was high and did not increase significantly upon the addition of long chain fatty acids. Treatment of membranes expressing GPR40-Gαq with fatty acid free BSA reduced the basal [35S]GTPgammaS binding in a concentration dependent manner and allowed the responsiveness of GPR40 to fatty acids to be uncovered. This also allowed the potency of a variety of thiazolidinediones and small molecule agonists to be determined. It was found that troglitazone was the most potent thiazolidinedione tested. Rosiglitazone also acted as an agonist of GPR40, albeit with lower potency than troglitazone, whereas ciglitazone and pioglitazone displayed little potency. Using clones of Flp-In TREx HEK293 cells where GPR40-eYFP was cloned into the Flp-In locus, the expression of GPR40-eYFP could be controlled by the addition of doxycycline. Using this cell line confirmed that GPR40 mediated the rise in [Ca2+]i induced by the addition of troglitazone. The expression of GPR40 was detected in the rat beta cell line, INS-1E. Addition of lauric acid or troglitazone to these cells induced a large, transient rise of [Ca2+]i. Membranes prepared from INS-1E cells also displayed high basal [35S]GTPgammaS binding, which could be reduced by fatty acid free BSA. The combination of fatty acid free BSA and lauric acid or troglitazone increased [35S]GTPgammaS binding. The high levels of [35S]GTPgammaS binding observed in membranes expressing GPR40 may reflect the binding of an endogenous ligand to GPR40. Homology models of all three receptors based on the crystal structure of rhodopsin indicated that a conserved Arg residue in TM5 may co-ordinate the carboxylate group of the fatty acid. To confirm this observation a series of mutant receptors were generated, with the Arg residue in TM5 mutated to alanine. Neutralisation of the charge in TM5 in GPR41 and GPR43 resulted in receptors that were unable to respond to short chain fatty acids. Further mutants of GPR43 were generated in which the Arg in TM5 was replaced by Lys, Leu or Ser. None of these mutants were able mediate a rise in [Ca2+]i in response to short chain fatty acids. The equivalent mutation in GPR40 did not abolish the receptors ability to respond to long chain fatty acids. There are two further conserved basic residues in TM regions of the receptors; an Arg/Lys in TM2 and a His in TM4. These residues were also mutated to alanine. In GPR41 and GPR43, both mutants had similar function to the wild type receptors. Both GPR40 mutants were also able to respond to a variety of fatty acids measured by their ability to mediate a rise in [Ca2+]i in a FLIPR based assay system. A series of further GPR40 mutants were generated where two of the three basic TM residues were mutated. The most striking observation was found with the mutant in which the His in TM4 and Arg in TM5 mutated to alanine, this mutant was unable to mediate a rise in [Ca2+]i in response to a variety of saturated fatty acids. This may indicate that upon loss of charge in TM5 the His in TM4 compensates and vice versa. None of the small molecule agonists or thiazolidinediones were able to activate the TM4 or TM5 mutants. This indicated that the synthetic agonists of GPR40 require a more conserved binding pocket which may be due to their more rigid structure. The ability of GPR40 and GPR43 to form homo-oligmers was also investigated. It was found that GPR40 and GPR43 formed homo-oligomers as monitored by co-immunoprecipitation, FRET in single, living cells and by time resolved FRET.

Heart failure (HF) and chronic obstructive pulmonary disease (COPD) are common partners with common problems. Both are chronic systemic disorders incurring significant morbidity and mortality. Although around one third of patients with HF have concurrent COPD,1 remarkably few reports have addressed this often ignored combination. The systematic review presented within this thesis defines the diagnostic challenges, prevalence and prognostic implications of HF with coexistent COPD. I then critically appraise the twin controversies of β-blockade in COPD and β-agonists in HF. The two are inextricably linked, each therapy exerting the reverse pharmacologic activity of the other. The evidence for symptomatic or prognostic benefit from either therapy is limited, and in the case of β-agonists adverse consequences appear more likely. A Cochrane meta-analysis concluded that long term cardioselective β-blockade is safe and well tolerated in patients with moderate to severe or reversible COPD.2 Although often cited,3 these conclusions are simply not true. Of the 20 randomised controlled trials included in the meta-analysis, 11 involved single doses and only one lasted longer than a month. The 9 ‘long term’ studies (defined as more than a single treatment dose) involved 147 young, predominantly male patients with moderate airways obstruction (mean forced expiratory volume in 1 second (FEV1) 1.8 litres). The effect on health status has never been assessed in any cohort with COPD. The long term impact of β-blockade on pulmonary function, symptoms and quality of life is therefore largely unknown. Most importantly, no study has included patients with HF. I randomised 27 patients with HF and coexistent moderate or severe COPD to receive bisoprolol or placebo, titrated to maximum tolerated dose over 4 months. Patients were elderly and predominantly male. Cardiovascular comorbidity, smoking history and pulmonary function were similar in each group (mean FEV1 1.37L vs 1.26L). There were several key findings. A reduction in FEV1 occurred after 4 months following treatment with bisoprolol compared with placebo (–70 ml vs +120 ml, p=0.01). Reversibility following inhaled β2-agonist and static lung volumes were not impaired by bisoprolol. All measures of health status exhibited a consistent non-significant improvement, including the Short Form 36 physical and mental component scores, Minnesota Living with Heart Failure Questionnaire, and Chronic Respiratory Questionnaire. The mean number of COPD exacerbations was similar in the bisoprolol and placebo groups. Although recruitment was limited, the results pose crucial questions and provide direction for larger randomised controlled trials. I analysed cross-sectional data from 61 primary care practices (377,439 patients) participating in the Scottish Continuous Morbidity Recording scheme. The prevalence of COPD in patients with HF increased year on year from 19.8% in 1999 to 23.8% in 2004. These changes may previously have been attributed to an ageing population or increasing age of presentation. However, the trend remained significant after age standardisation. A clear socioeconomic gradient was observed, with prevalence greatest in the most deprived. Consultation rates for HF or COPD in those with both conditions were greater than disease specific contact rates in patients with either condition alone. Cardiovascular comorbidity was similar in HF patients with and without COPD, despite differences in smoking history (respectively 76% vs 47%, p<0.001). This is concerning and suggests that common cardiovascular conditions are being under diagnosed (and likely under treated) in patients with HF and COPD. Although overall β-blocker prescribing increased over time, the adjusted odds of β-blocker prescription in patients with COPD was low (odds ratio 0.30 [95% CI 0.28–0.32], p<0.001). Whether the gap between patients with and without COPD is improving was previously unknown. Despite the overall improvement in beta-blocker prescribing, the relative difference in prescribing between those with and without COPD remained unchanged. By 2004, only 18% of individuals with HF and COPD were prescribed β-blockers. COPD is consistently an independent predictor of death and HF hospitalisation in patients with HF. However, the causes of increased mortality were unclear. I examined the relationship between COPD and cardiovascular outcomes in patients with myocardial infarction (MI) complicated by heart failure, left ventricular systolic dysfunction (LVSD), or both enrolled in the Valsartan in Acute Myocardial Infarction (VALIANT) trial. COPD was an independent predictor of mortality, largely due to increased non-cardiovascular (HR 1.86 [1.43–2.42]) and sudden death (HR 1.26 [1.03–1.53]). However, after multivariate adjustment COPD was not an independent predictor of atherosclerotic events (MI or stroke: HR 0.98 [0.77–1.23]). This is an important finding, as atherosclerotic consequences of chronic systemic inflammation in COPD have been postulated. These appear of limited clinical significance, at least during intermediate follow-up. Part of the adverse risk associated with COPD may be attributable to bronchodilators. The prognosis of patients with HF prescribed bronchodilators is however ill defined. I examined the prognostic implications of bronchodilator use in patients with HF enrolled in the Candesartan in Heart failure Assessment of Reduction in Mortality and morbidity (CHARM) programme. The diversity and magnitude of adverse outcomes associated with bronchodilator therapy was surprising. Bronchodilator use was associated with increased all cause mortality (HR 1.26 [1.09–1.45]), cardiovascular death (HR 1.21 [1.03-1.42]), death due to HF progression (HR 1.40 [1.07-1.82]) and HF hospitalisation (HR 1.49 [1.29-1.72]). Although association is not causation, it is possible that bronchodilators compound maladaptive remodeling and further depress myocardial function. Finally, β-blockers were independently associated with better survival in both VALIANT and CHARM. No significant interaction was observed between either COPD or bronchodilators and β-blockade with respect to mortality. Furthermore, β-blocker use was not associated adversely with any pre-specified outcome in patients with COPD or those prescribed bronchodilators, including non-cardiovascular mortality. Although recruitment bias and the absence of spirometry limit inference to patients with severe or reversible airflow obstruction, the results should encourage β-blockade in patients with COPD. In summary, the studies presented in this thesis extend our understanding of HF with concurrent COPD. Only large randomised controlled trials will solve the quandary of β-blockers and β-agonists. Justification for these trials evolves from observational data and smaller prospective studies such as my own. In the meantime, I hope the evidence presented will stimulate physicians to re-evaluate the management of patients with HF and COPD.