A necessidade de buscar novos tratamento para a Insuficiência Cardíaca (IC) crônica levanta o questionamento da eficácia e segurança de drogas que não foram adequadamente testadas ou que ainda não tiveram sua eficácia aceita pela comunidade científica. O sildenafil é um vasodilatador com potencial eficácia na redução da pressão sistólica da artéria pulmonar (PSAP), mas com pequenos estudos e sem demonstração de impacto em desfechos duros. Os diuréticos de alça são utilizados rotineiramente em pacientes com IC sem sinais de congestão e tal prática não está recomendada nas diretrizes terapêuticas, desconhecemos sua eficácia e segurança neste cenário. No intuito de elucidar estas questões, foram desenvolvidos I) revisão sistemática com metanálise para estudo uso de sildenafil. II) revisão sistemática com metanálise para estudo uso de diurético de alça, III) Delineamento e execução em andamento de ensaio clínico randomizado multicêntrico testando a retirada de diurético de alça. I e II) Métodos e resultados: Ambas revisões sistemáticas foram realizadas no Pubmed, Embase e Cochrane, e termos relacionados à insuficiência cardíaca crônica diurético de alça e sildenafil foram utilizados, respectivamente. Após avaliação de texto completo, apenas estudos em humanos foram incluídos na metanálise. A droga sildenafil foi avaliada em 9 estudos randomizados contra placebo e demonstrou redução de hospitalização (RR 0.29, 95% C.I 0.11 to 0.78) e melhora progressiva em parâmetros funcionais e hemodinâmicos O uso de diurético de alça foi testado em 7 ensaios clínicos e não mostrou significância em piora da função renal, distúrbio eletrolítico e mudança de peso. III) Métodos e resultados: Em um estudo duplo-cego randomizado, de não inferioridade, multicêntrico compara-se o a segurança e tolerabilidade da retirada de furosemida de pacientes com IC crônica e estável com disfunção ventricular. Com início da coleta em setembro de 2015, até o momento 96 pacientes foram randomizados. Conclusão: Quanto ao sildenafil, já temos evidências que apontam para um efeito benéfico e progressivo na melhora da capacidade funcional, perfil hemodinâmico e redução de hospitalização em pacientes com IC com disfunção ventricular e pressão da artéria pulmonar elevada A recomendação para uso de diurético de alça em pacientes estáveis com IC permanece uma incógnita e o ensaio clínico em andamento nos trará uma resposta de importante impacto clínico na tomada de decisão para manutenção do uso de diurético. / The challenges and promises of new treatments for chronic heart failure (CHF) raises the question of the efficacy and safety of drugs that have not been properly tested or that have not yet had their efficacy accepted by the scientific community. Sildenafil is a vasodilator with potential efficacy in reducing pulmonary artery systolic pressure (PSAP), but with small studies and no demonstration of impact on hard outcomes. Routinely, Loop diuretics are used in patients with HF without signs of congestion and such practice is not recommended in the therapeutic guidelines, we do not know its efficacy and safety in this scenario. In order to elucidate these questions, I) systematic review with meta-analysis were developed to study the use of sildenafil. II) systematic review with meta-analysis to study the use of loop diuretics, III) Design and execution in progress of a multicenter randomized clinical trial testing for loop diuretic withdrawal. I and II) Methods and results: Both systematic reviews were performed in PubMed, Embase and Cochrane, and terms related to chronic diuretic heart failure of the loop and sildenafil were used, respectively. After full-text evaluation, only human studies were included in the meta-analysis. The drug sildenafil was evaluated in 9 randomized placebo-controlled studies and demonstrated a reduction in hospitalization (RR 0.29, 95% CI 0.11 to 0.78) and progressive improvement in functional and hemodynamic parameters. The use of a loop diuretic was tested in 7 clinical trials and did not show significant deterioration in renal function, electrolyte disturbance and weight change. III. METHODS AND RESULTS: In a double-blind randomized, non-inferiority, multicenter study, the safety and tolerability of furosemide withdrawal from patients with chronic and stable HF with ventricular dysfunction were compared. Randomization started at September 2015, to the moment 96 patients were randomized. CONCLUSION: Regarding sildenafil, we already have evidence of a beneficial and time-related effect on the improvement of functional capacity, hemodynamic profile and reduction of hospitalization in patients with HF with ventricular dysfunction and elevated pulmonary artery pressure. The recommendation for the use of a loop diuretic in stable patients with HF remains an unknown and the ongoing clinical trial will provide us with an important clinical impact response in the decision making to maintain the use of diuretics.

Calmodulin (CaM) is a ubiquitous intracellular protein that regulates biological activities of numerous enzymes and ion channels. Upon responding Ca2+ concentration change, Ca2+- dependent CaM activates the hydrolyzation of cGMP by PDE and Ca2+ releasing channel activity of ryanodine receptor. In this dissertation, a series of CaM variants were engineered to enhance Ca2+ binding affinities by increasing the number of negative charged residues in individual EF-hand. The capability of shifting the biphasic Ca2+-activation profile of RyR1 is significantly altered by changing Ca2+ binding affinity of CaM at the C-terminal. This indicates that examining Ca2+-CaM affinity is a valid strategy to tune the activation profile of CaM-regulated ion channels. To further understand interactions between CaM and RyR1, NMR was used to determine their binding mode. To dissect roles of structural components of CaM in metal binding and regulation of biological functions of target proteins, we created half-CaMs and Del-CaM. Binding affinities of these variants to Ca2+, Tb3+ and Gd3+ were determined by fluorescence spectroscopy; functional studies were conducted using single channel analysis and PDE function assay. Another objective of my dissertation is to design a protein based contrast agent for molecular imaging. CaM was selected as the scaffold protein for designing Gd3+ based MRI contrast agent by modifying metal binding sites as well as grafting a biomarker peptide into the linker region to specifically target cancers with efficient and optimized modifications. The physical kinetic properties and animal imaging effects of these designed contrast agents were investigated by various methods.

The pharmacological development of non-steroidal contraceptives has yet to be achieved. Arresting oocyte maturation without blocking ovulation has been evaluated using different inhibitors of the phosphodiesterase 3A (PDE3A). Unfortunately, PDE3A is also expressed in the heart and blood vessels, and inhibition of PDE3A in oocytes can produce cardiovascular side effects. We reviewed the literature on available PDE3 inhibitors and selected cilostazol (CLZ), which is an FDA approved therapeutic. CLZ has the ability to decrease cellular adenosine uptake and consequently antagonizes side effects of PDE3A inhibition in vital organs. CLZ inhibited oocyte meiotic maturation in vitro. CLZ has more degenerative impact on arrested oocytes than matured oocytes, indicating that prolonged meiotic arrest of oocytes is harmful. Administration of CLZ any time from 9h before the ovulatory stimulus to 4h after the stimulus resulted in ovulation of immature oocytes. Controlling CLZ dose, time of CLZ administration, and time of oocyte collection resulted in ovulation of oocytes at different meiotic stages. Oral administrations of CLZ in naturally cycling mice were also observed to block pregnancy whereas remating of those previously treated females resulted in normal offspring and litter sizes. Therefore, CLZ does not only have a wide margin of contraception but also is reversible. Ovulated immature oocytes were observed to have higher rates of advanced chromatin configuration and cortical granule distribution, normal spindle and chromosomal organization, maturation, and in vitro fertilization (IVF) than ovarian immature oocytes. Ovulated metaphase I oocytes that were matured in vitro or in vivo had higher IVF rates than ovulated mature oocytes. Ovulated germinal vesicle (GV) oocytes that were in vitro matured also showed higher IVF rates but when in vivo matured, they had lower IVF rates than ovulated mature oocytes because of the high degeneration and low fertilization rates associated with in vivo maturation of GV oocytes. In summary, CLZ merits further evaluation as a non-steroidal contraceptive and is capable of producing oocytes of various meiotic stages with advanced developmental features.

Since sildenafil's (Viagra®), a phospodiesterase type 5 (PDE5) inhibitor, approval for the treatment of male erectile dysfunction (MED) in the United States early 1998, 274 adverse event reports were filed by the Food and Drug Administration (FDA) between 4 Jan. 1998 and 21 Feb. 2001 with sildenafil as the primary suspect of various neurological disturbances, including amnesia and aggressive behaviour (Milman and Arnold, 2002). These and other research findings have prompted investigations into the possible central effects of sildenafil. The G protein-coupled muscarinic adetylcholine receptors (mAChRs) and serotonergic receptors (5HT-Rs), have been linked to antidepressant action (Brink et al. 2004). GPCRs signal through the phosphatidylinositol signal transduction pathway known to activate protein kinases (PKs). Since the nitric oxide (NO)-guanylyl cyclase signal transduction pathway is also known to involve the activation of PKs (via cyclic guanosine monophosphate (cGMP)), the scope is opened for sildenafil to possibly modulate the action of antidepressants by elevating cGMP levels. It is generally assumed that excitotoxic delayed cell death is pathologically linked to an increase in the release of excitatory neurotransmitters e.g. glutamate. Glutamate antagonists, especially those that block the define NMDA-receptors, are neuroprotective, showing the importance of the NMDA-NO-cGMP pathway in neuroprotection (Brandt et al., 2003). Sildenafil may play a role in neuroprotection by elevating cGMP levels. Aims: The aims of the study were to investigate any neuroprotective properties of sildenafil, as well as modulating effects of sildenafil pre-treatment on mAChR function. Methods: Human neuroblastoma SH-SY5Y or human epithelial HeLa cells were seeded in 24-well plates and pre-treated for 24 hours in serum-free medium with no drug (control), PDE5 inhibitors sildenafil (100nM and 450 nM), dipiridamole (20 µM) or zaprinast (20 µM), non-selective PDE inhibitor 3-isobutyl-I-methylxanthine (IBMX - ImM), cGMP analogue N2,2'-0-dibutyrylguanosine 3'5'-cyclic monophosphate sodium salt (500 µM), guanylcyclase inhibitor 1H-[1 ,2,4]oxadiazolo[4,3-a]quinoxalin-I-one (ODQ - 3 µM) or sildenafil + ODQ (450 nM and 3 µM respectively). Thereafter cells were used to determine mAChR function by constructing dose-response curves of methacholine or to determine cell viability utilising the Trypan blue, propidium iodide and MTT tests for cell viability. Results: Sildenafil pre-treatments induced a 2.5-fold increase in ,the Emax value of methacholine in neuronal cells but did not show a significant increase in epithelial cells The Trypan blue test suggests that neither the PDE5 inhibitors nor a cGMP analogue show any neuroprotection. Rather, sildenafil 450 nM, dipiridamole and IBMX displayed a neurodegenerative effect. The MTT test was not suitable, since pre-treatment with the abovementioned drugs inhibited the formation of forrnazan. The propidium iodide assay could also not be used, due to severe cell loss. Conclusion: Sildenafil upregulates mAChR function in SH-SY5Y cells and displays a neurodegenerative, and not a protective property, in neuronal cells. This is not likely to be associated with its PDE5 inhibitory action, but may possibly be linked to an increase in cGMP levels via the NO-cGMP pathway. / Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2005.

Previous studies have suggested that phosphodiesterase (PDE) hydrolysis of cyclic adenosine monophosphate (cAMP) is important in the generation of specific and segregated cAMP signals within cells. The purpose of this study was to determine if PDE compartmentation was important in cardiac ventricular myocytes. Therefore, we investigated the effects of β-adrenergic (β-AD) stimulation with isoproterenol in the presence of cilostamide, a PDE3 inhibitor, or Ro 20-1724, a PDE4 inhibitor, on unloaded cell shortening, L-type calcium currents and intracellular calcium levels in freshly dissociated adult rat ventricular myocytes. PDE3 inhibition resulted in a 216 ± 17 % (n=8) increase in unloaded cell shortening after ten minutes of isoproterenol exposure, whereas isoproterenol produced a statistically smaller increase of 155 ± 12 % (n=8) in the presence of PDE4 inhibition. There was a non-significant trend for PDE4 inhibition to produce larger increases in calcium currents (179 ± 17 % (n=4) of controls) than PDE3 inhibition (155 ± 10 % (n=6) of controls). Both PDE3 and PDE4 inhibitors had similar effects on isoproterenol-stimulated increases of calcium transient amplitude with values of 209 ± 14 % (n=8) and 185 ± 12 % (n=8), respectively. Determination of sarcoplasmic reticulum (SR) calcium load using caffeine pulse experiments demonstrated that PDE4 inhibition and isoproterenol superfusion produced a statistically larger increase in SR-calcium loading (139 ± 9 % (n=6)) than PDE3 inhibition and isoproterenol superfusion (113 ± 9 % (n=6)). These results suggest that PDE3 may be active in proximity to the contractile apparatus of cardiac myocytes, whereas PDE4 may be localized in a domain consisting of the L-type calcium channel and junctional SR. Consequently, our study provides functional evidence for differential localization of PDE isoforms in cardiac myocytes. / Thesis (Master, Physiology) -- Queen's University, 2008-01-18 10:14:29.671 / CIHR OGS OGSST

The ubiquitous second messenger cAMP acts to integrate and translate information encoded by extracellular messenger molecules, including hormones and neurotransmitters. Intracellular cAMP concentrations are regulated through coordinated changes in the activities of adenylyl cyclases (ACs) and cyclic nucleotide phosphodiesterases (PDEs). Freely diffusing cAMP can reach concentrations sufficient to activate cAMP effector proteins, such as protein kinase A (PKA) or the exchange protein activated by cAMP (EPAC), except in defined compartments where PDEs are localized which allows for spatial and temporal control of the cAMP signal. In human aortic vascular endothelial cells (HAECs) and HEK293T cells we recently identified a macromolecular complex consisting of PDE3B and EPAC and showed that this complex coordinated cAMP-induced effects on adhesion of these cells to fibronectin-coated surfaces. Using “pull-down” assays and peptide array-based approaches we have identified the molecular determinants which coordinate the formation of this complex. Our evidence suggests that the extreme N-terminal 13 amino acids of PDE3B represent the portion of PDE3B that interacts with EPAC. In addition, although several EPAC-encoded peptides were shown to bind PDE3B, immunoprecipitation-based studies identified a region proximal to the cAMP-binding domains as likely to have a dominant role in this binding. Of functional relevance, a cell permeable peptide containing these amino-terminal 13 amino acids of PDE3B antagonizes PDE3B-EPAC interactions in cells. In addition, this peptide impacted the ability of cAMP-elevating agents to coordinate EPAC-dependent cell adhesions. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2009-10-06 19:07:12.01

Since sildenafil's (Viagra®), a phospodiesterase type 5 (PDE5) inhibitor, approval for the treatment of male erectile dysfunction (MED) in the United States early 1998, 274 adverse event reports were filed by the Food and Drug Administration (FDA) between 4 Jan. 1998 and 21 Feb. 2001 with sildenafil as the primary suspect of various neurological disturbances, including amnesia and aggressive behaviour (Milman and Arnold, 2002). These and other research findings have prompted investigations into the possible central effects of sildenafil. The G protein-coupled muscarinic adetylcholine receptors (mAChRs) and serotonergic receptors (5HT-Rs), have been linked to antidepressant action (Brink et al. 2004). GPCRs signal through the phosphatidylinositol signal transduction pathway known to activate protein kinases (PKs). Since the nitric oxide (NO)-guanylyl cyclase signal transduction pathway is also known to involve the activation of PKs (via cyclic guanosine monophosphate (cGMP)), the scope is opened for sildenafil to possibly modulate the action of antidepressants by elevating cGMP levels. It is generally assumed that excitotoxic delayed cell death is pathologically linked to an increase in the release of excitatory neurotransmitters e.g. glutamate. Glutamate antagonists, especially those that block the define NMDA-receptors, are neuroprotective, showing the importance of the NMDA-NO-cGMP pathway in neuroprotection (Brandt et al., 2003). Sildenafil may play a role in neuroprotection by elevating cGMP levels. Aims: The aims of the study were to investigate any neuroprotective properties of sildenafil, as well as modulating effects of sildenafil pre-treatment on mAChR function. Methods: Human neuroblastoma SH-SY5Y or human epithelial HeLa cells were seeded in 24-well plates and pre-treated for 24 hours in serum-free medium with no drug (control), PDE5 inhibitors sildenafil (100nM and 450 nM), dipiridamole (20 µM) or zaprinast (20 µM), non-selective PDE inhibitor 3-isobutyl-I-methylxanthine (IBMX - ImM), cGMP analogue N2,2'-0-dibutyrylguanosine 3'5'-cyclic monophosphate sodium salt (500 µM), guanylcyclase inhibitor 1H-[1 ,2,4]oxadiazolo[4,3-a]quinoxalin-I-one (ODQ - 3 µM) or sildenafil + ODQ (450 nM and 3 µM respectively). Thereafter cells were used to determine mAChR function by constructing dose-response curves of methacholine or to determine cell viability utilising the Trypan blue, propidium iodide and MTT tests for cell viability. Results: Sildenafil pre-treatments induced a 2.5-fold increase in ,the Emax value of methacholine in neuronal cells but did not show a significant increase in epithelial cells The Trypan blue test suggests that neither the PDE5 inhibitors nor a cGMP analogue show any neuroprotection. Rather, sildenafil 450 nM, dipiridamole and IBMX displayed a neurodegenerative effect. The MTT test was not suitable, since pre-treatment with the abovementioned drugs inhibited the formation of forrnazan. The propidium iodide assay could also not be used, due to severe cell loss. Conclusion: Sildenafil upregulates mAChR function in SH-SY5Y cells and displays a neurodegenerative, and not a protective property, in neuronal cells. This is not likely to be associated with its PDE5 inhibitory action, but may possibly be linked to an increase in cGMP levels via the NO-cGMP pathway. / Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2005.

Studying the biosynthesis, utilization and transport of cholesterol as well as the balance between these pathways may allow us to understand better how to keep its harmful deposition in arteries to a minimum. The goal of my thesis was to identify a novel player, namely the acid sphingomyelinase (ASM), in cellular and plasma cholesterol metabolism by elucidating its regulatory and mechanistic functions. / In our families with high-density lipoprotein-cholesterol (HDL-C) deficiency, one kindred was found to have mutations for the sphingomyelin phosphodiesterase-1 (SMPD-1). This gene codes for lysosomal and secretory ASM and its mutations cause the recessive disorder of Niemann-Pick type A/B (NPD-A/B). My thesis, based on the study of the gene and the protein defect in this family, has led to four important discoveries. First, SMPD-1 mutations are significantly associated with low HDL-C. Second, in order to unveil the mechanism by which ASM contributes to the regulation of HDL-C levels, we investigated the cellular lipid transport in NPD-B fibroblasts. We showed that lysosomal ASM defects lead to co-segregation and co-localization of sphingomyelin (SM) and cholesterol. However, the SM accumulation does not rate-limit the efflux ability of NPD-B cells. Third, we set up the electrospray ionization-mass spectrometry to give an in-depth qualitative and quantitative phospholipid characterization of HDL particles generated from NPD-B. We found that their SM content is significantly elevated. We subsequently provided evidence that the SM content of HDL could be modulated by secretory ASM. Together with other plasma enzymes including lecithin-cholesterol acyl transferase, secretroy ASM appears to regulate the maturation and clearance of HDL-C from the plasma. Finally, we examined the molecular nature of the NPD-B pathophysiology by investigating the structure-function relationship of ASM. We demonstrated that the C-terminal region of ASM plays a critical role in the enzyme conformation that dictates its enzymatic function and secretion. / In summary, our lessons on NPD-B have enabled us to identify ASM as an important player in lipoprotein cholesterol metabolism. Because HDL-C is inversely associated with coronary heart disease, our findings opened a novel therapeutic avenue in the search of preventive strategies against heart disease in our society.

Thesis (M.Sc.). / Written for the Dept. of Experimental Medicine. Title from title page of PDF (viewed 2008/12/07). Includes bibliographical references.

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted. Errata slip inserted. Includes bibliographical references.