The study evaluated whether the activity of the indoleamine 2,3 dioxygenase (IDO) enzyme is increased post-stroke and contributes to the development of post-stroke depression (PSD) via tryptophan (TRP) depletion and neurotoxic kynurenine (KYN) metabolite production. The activity of IDO was measured using the KYN/TRP ratio. Participants were assessed for depression severity using the Center for Epidemiological Studies Depression Scale (CES-D). Blood TRP, KYN, large neutral amino acids and cytokines were measured and compared. Fifty-four (mean age=69.9±15.2, male=52.7%, mean NIHSS=7.3±4.6) patients within 28.9±40.3 days of stroke were separated into two groups: non-depressed (n=38, CES-D=6.1±4.9) and those with significant depressive symptoms (n=16, CES-D=26.8±10.8). Higher mean KYN/TRP ratios were demonstrated in stroke patients with depressive symptoms (non-depressed=69.3±36.9 vs. depressive symptoms=78.3±42.0, F3,50=4.61, p=0.006) after controlling for LNAA (p=0.026) and hypertension (p=0.039). As the KYN/TRP ratio reflects decreased TRP and increased neurotoxic KYN metabolites, both mechanisms may play an etiological role in PSD.

Depression is highly prevalent in coronary artery disease (CAD) and confers an increased risk of morbidity and mortality, yet mechanisms are unknown. Platelet activating factor (PAF) lipids are associated not only with CAD but also with inflammation, oxidative/nitrosative stress, vascular endothelial dysfunction and platelet reactivity which are proposed etiopathological mechanisms for depression. This study investigated the relationship between PAF species and depressive symptoms in 20 CAD patients. Plasma analyses were performed using electrospray ionization mass spectrometry (precursor ion scan). Primary analysis revealed no association between the potent pro-inflammatory PAF PC(O-16:0/2:0) and depressive symptoms measured by the Hamilton Depression Rating Scale [HAM-D] (F=0.405, p=0.533) or Beck Depression Inventory [BDI]-II (F=0.120, p=0.733) in a linear regression. Exploratory analyses revealed potential associations between greater PC(O-18:1/0:0) and greater HAM-D score and greater PC(O-22:6/2:0) concentrations with a greater BDI-II score. This study suggests that specific PAFs might be biomarkers for depressive symptoms in CAD patients.

The study evaluated whether the activity of the indoleamine 2,3 dioxygenase (IDO) enzyme is increased post-stroke and contributes to the development of post-stroke depression (PSD) via tryptophan (TRP) depletion and neurotoxic kynurenine (KYN) metabolite production. The activity of IDO was measured using the KYN/TRP ratio. Participants were assessed for depression severity using the Center for Epidemiological Studies Depression Scale (CES-D). Blood TRP, KYN, large neutral amino acids and cytokines were measured and compared. Fifty-four (mean age=69.9±15.2, male=52.7%, mean NIHSS=7.3±4.6) patients within 28.9±40.3 days of stroke were separated into two groups: non-depressed (n=38, CES-D=6.1±4.9) and those with significant depressive symptoms (n=16, CES-D=26.8±10.8). Higher mean KYN/TRP ratios were demonstrated in stroke patients with depressive symptoms (non-depressed=69.3±36.9 vs. depressive symptoms=78.3±42.0, F3,50=4.61, p=0.006) after controlling for LNAA (p=0.026) and hypertension (p=0.039). As the KYN/TRP ratio reflects decreased TRP and increased neurotoxic KYN metabolites, both mechanisms may play an etiological role in PSD.

Depression is highly prevalent in coronary artery disease (CAD) and confers an increased risk of morbidity and mortality, yet mechanisms are unknown. Platelet activating factor (PAF) lipids are associated not only with CAD but also with inflammation, oxidative/nitrosative stress, vascular endothelial dysfunction and platelet reactivity which are proposed etiopathological mechanisms for depression. This study investigated the relationship between PAF species and depressive symptoms in 20 CAD patients. Plasma analyses were performed using electrospray ionization mass spectrometry (precursor ion scan). Primary analysis revealed no association between the potent pro-inflammatory PAF PC(O-16:0/2:0) and depressive symptoms measured by the Hamilton Depression Rating Scale [HAM-D] (F=0.405, p=0.533) or Beck Depression Inventory [BDI]-II (F=0.120, p=0.733) in a linear regression. Exploratory analyses revealed potential associations between greater PC(O-18:1/0:0) and greater HAM-D score and greater PC(O-22:6/2:0) concentrations with a greater BDI-II score. This study suggests that specific PAFs might be biomarkers for depressive symptoms in CAD patients.

The present research examined the hypothesis that omega-3 polyunsaturated fatty acids would increase seizure threshold in rats in vivo, and reduce neuronal excitability in mouse hippocampal slices. Seizure thresholds were measured in rats using the maximal pentylenetetrazol and electrical stimulation seizure tests following α-linolenic acid (ALA) or docosahexaenoic acid administration. ALA raised seizure threshold in the maximal PTZ seizure test, but this effect probably occurred because ALA displaced DHA from liver to the brain. DHA itself was therefore tested in the PTZ and electrical stimulation seizure tests. Direct administration of DHA by subcutaneous injection raised seizure thresholds in the PTZ seizure test, which models tonic-clonic attacks in humans. Dietary enrichment with DHA raised afterdischarge seizure thresholds in the cortex and amygdala, which model simplex and complex partial seizures in humans, although this effect took some time to occur. In vitro, the application of DHA also reduced the incidence of excitatory sharp waves in mouse hippocampal slices. This effect did not appear to be due to either an increase in GABAergic inhibitory tone, nor to a decrease in glutamatergic drive. The fatty acid composition of phospholipids and unesterified fatty acids were measured in the brain following microwave fixation in order to determine whether the effects of DHA on seizure thresholds were due to its de-esterification from the phospholipid membrane. The assay surprisingly revealed that subcutaneous administration of DHA at a dose that raised seizure threshold, increased unesterified arachidonic acid, but not unesterified DHA concentrations during seizures. The results of these studies support the hypothesis that DHA raises seizure threshold in rats, and reduces neuronal excitability in vitro. The effects of DHA on seizure threshold are possibly mediated by the de-esterification of arachidonic acid, which is known to have effects on the voltage-dependent sodium channel.

Kawasaki disease (KD) is a multisystem vasculitis that results in localized coronary artery elastin breakdown and aneurysm formation. It is the leading cause of acquired heart disease of children in North America. Despite conventional treatment, a significant proportion of patients continue to develop coronary sequelae. The mechanisms of arterial aneurysm formation in KD are not known. Using a murine model of KD, Lactobacillus casei cell wall extract-induced coronary arteritis, the processes leading to coronary aneurysm formation were examined. Vessel damage occurred as a result of the increased enzymatic activity of the elastase, matrix metalloproteinase (MMP)-9. MMP-9 protein and activity levels were elevated in the heart post-disease induction. Expression and activity were specific for and localized to inflamed coronary arteries. The pro-inflammatory cytokine, tumour necrosis factor (TNF)-α, was required for increasing local MMP-9 expression. Importantly, MMP-9-deficient animals had a significantly reduced incidence of elastin breakdown. Furthermore, in a cohort of KD patients, serum MMP-9 did not correlate with coronary outcome, highlighting the importance of local expression of this elastase. Intravenous immunoglobulin (IVIG) and aspirin/salicylate are therapeutic agents in current use for the treatment of KD, though their exact mechanisms of action in KD are not known. The biologic effects of IVIG and salicylate on critical stages of disease development were examined. IVIG and salicylate had differential effects on TNF-α expression, with therapeutic concentrations of IVIG inhibiting, and salicylate inducing, TNF-α expression leading to an indirect modulation of MMP-9 expression. Interestingly, TNF-α expression and MMP-9 activity were both directly inhibited by the metal-chelating drug doxycycline. Treatment of affected mice with doxycycline significantly improved coronary outcome. Inhibiting both the inflammatory response as well as the downstream effects of inflammation were of therapeutic value in this model of KD. These results taken together demonstrate the importance of MMP-9 in the pathogenesis of coronary artery aneurysms in KD. Targeting MMP activity holds the promise of transforming KD from the leading cause of acquired heart disease to a self-limited febrile illness.

Master of Science / Department of Clinical Sciences / Elizabeth Davis / The first aim of the current study was to investigate the pharmacokinetics of oral meloxicam tablets and the gastrointestinal and renal effects after a 14-day treatment period. Meloxicam was orally administered to six adult horses once daily at a dosage of 0.6 mg/kg for 14 consecutive days. Blood was collected prior to each administration and at 20 and 40 min, and 1, 2, 4, 8, 12, and 24 hours after administration on days 1, 7, and 14 for the determination of meloxicam plasma concentrations by mass spectrometry. In addition, trough samples were taken on days 3 and 10. Complete blood count, serum biochemical analysis, urinalysis, and gastroscopy were performed at baseline and conclusion of the investigation. Complete blood count, serum chemistry, and urinalysis results were unchanged through the study period. Gastroscopy scores were not significantly increased. The Cmax was 1.82 ± 0.80 µg/mL at Tmax 3.48 ± 3.30 hr on day 1, 2.07 ± 0.94 µg/mL at Tmax 1.24 ± 1.24 hr on day 7, and 1.81 ± 0.76 µg/mL at 1.93 ± 1.30 h on day 14 (p = 0.30). The mean half-life was 4.99 ± 1.11 h. The second aim of the study was to compare the analgesic effects and gastrointestinal and renal adverse effects of oral meloxicam tablets (0.6 mg/kg) to oral phenylbutazone tablets (4.4 mg/kg) orally once daily for 4 days in induced and naturally occurring lameness in adult horses. The study was performed on 4 healthy but lame adult horses. Complete blood count, serum biochemistry, urinalysis, and gastroscopy were performed prior to entrance to the study. Lameness was exacerbated in two horses using lipopolysaccharide (LPS; E. coli O55:B5) injected into the right metacarpophalangeal joint. The remaining two horses had Grade 3 or Grade 4 lameness due to naturally occurring laminitis. Meloxicam or phenylbutazone was administered to two horses each in a blinded, randomized manner once daily for four days. Lameness was evaluated using a pressure mat system and contact pressure, force, and stride length were evaluated at baseline and twice daily. Complete blood count, serum chemistry, and urinalysis were unremarkable for all four horses except one horse with an increased GGT. This horse experienced hepatic rupture secondary to amyloidosis the final day of the study. Gastric ulcer scores did not change during the study period. Phenylbutazone administration resulted in a greater response (force and contact area) in the right front and left hind limbs compared to meloxicam administration. There were not enough data points to evaluate the other two limbs. A third aim of the study was two-fold and first evaluated the effects of ex vivo stimulation of peripheral blood mononuclear cells (PBMCs) with LPS on cyclooxygenase (COX) messenger RNA (mRNA) expression. The second portion documented the effects of LPS-induced joint inflammation and treatment with non-steroidal anti-inflammatory drugs on the mRNA and protein expression of COX-2 in PBMCs. The results indicate that LPS upregulates COX-2 gene expression in PBMCs. Additionally, injection of LPS into the metacarpophalangeal joint increases both COX-2 mRNA and protein expression in PBMCs at 24 hours after injection. The relative expression of COX-2 after treatment with meloxicam or phenylbutazone indicates a stronger inhibition with phenylbutazone; however, further study with additional horses is needed. Pharmacokinetic analysis of the oral tablet formulation of meloxicam indicates the pharmacokinetics are similar to the oral suspension formulation. Meloxicam appears to be inferior to phenylbutazone in its analgesic properties for induced lameness and naturally occurring laminitis, however the small sample size used in the study makes interpretation difficult.

Gestational diabetes, a common medical complication in pregnancy, may lead to severe fetal consequences if left untreated. A major concern with the use of antidiabetic drugs in pregnancy is the potential for placental transfer and fetal toxicity. The presence of endocytic pathways and several ABC transporter proteins has been demonstrated in the human placenta and are believed to play an important role in determining fetal exposure to drugs used in pregnancy. The objective of this thesis is to investigate the safety and transfer of the oral hypoglycemic agent, glyburide, and the new long acting insulin analog, insulin glargine, across the human placenta. The oral antidiabetic, glyburide, has been shown to be actively effluxed across the placenta in the fetal to maternal direction. The transport of glyburide in the presence of a breast cancer resistance protein (BCRP) inhibitor was investigated in the dually perfused human placenta model. The results of the perfusion studies indicate that BCRP plays a role in protecting the fetus from the accumulation of glyburide. Subsequently, cellular studies were carried out to determine the effect of the naturally occurring single nucleotide polymorphism within the coding region of BCRP (C421A/Q141K) on glyburide transport. Results suggest that glyburide transport may be reduced in the presence of the Q141K polymorphism. While insulin remains as the gold standard, the potential for maternal hypoglycemia with insulin injection has resulted in the development of insulin analogs. Insulin glargine, a human insulin analog, has a long half life with no pronounced peak when compared to currently used NPH insulin. Human placental perfusion experiments examining the extent and rate of transfer of insulin glargine across the placenta demonstrated that, at therapeutic concentrations, insulin glargine does not cross the placenta to a measurable extent. To further determine the fetal safety of insulin glargine therapy compared with NPH insulin, a systematic review and meta-analysis were performed. No evidence was identified for increased adverse fetal outcomes with the use of insulin glargine during pregnancy. Overall, the results of this research serve to provide improved treatment options for women with diabetes in pregnancy.

Atrial fibrillation (AF) is a common and serious arrhythmia. Current treatments are of limited efficacy, and most do not treat the atrial structural remodeling (hypertrophy and fibrosis) that underlies most clinical AF. Our group has created an experimental dog model of atrial mechanical stretch called the simultaneous atrial and ventricular pacing (SAVP) model (which results in atrial fibrosis and susceptibility to AF) in order to study novel treatments for structural remodeling induced AF. Omega-3 polyunsaturated fatty acids (n3 PUFAs), particularly the marine derived forms eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been shown to be effective in treating arrhythmias (including AF) in some animal studies and clinical trials. The mechanism for this effect of n3 PUFAs is not well understood. In this study we sought to characterize the n3 PUFA effect on AF vulnerability, atrial electrophysiology, histology, and gene expression, and determine relevant mechanisms. Dogs were paced for 0, 2, 7 or 14 days and given n3 PUFAs, olive oil or nothing. Prophylactic n3 PUFAs significantly reduced both AF vulnerability and conduction slowing in SAVP dogs (%AF inducibility: 9.2±8.8 vs. 4.7±6.3; global atrial conduction time: 75±11ms vs. 65±6ms [SAVP 14 days vs. SAVP 14 days with n3 PUFAs, P<0.05 for both comparisons]). Prophylactic n3 PUFAs also reduced inflammation (mean CD18 grade: 2.1±0.8 vs. 1.3±0.6 [SAVP 2 days vs. SAVP 2 days with n3 PUFAs, P=0.055]), hypertrophy (myocyte cross-sectional area: 498±64µm2 vs. 322±111µm2 [SAVP 14 days vs. SAVP 14 days with n3 PUFAs, P<0.05]), and fibrosis (%collagen area vs. unpaced dogs: 178±58 vs. 127±37 [SAVP 14 days vs. SAVP 14 days with n3 PUFAs, P<0.05]). N3 PUFAs were also found to reduce the expression of structural remodeling related molecules such as TGF-β, EGF, ERK and Akt. N3 PUFAs given after some pacing had already occurred were found to be less effective at reducing AF vulnerability and structural remodeling. The results of this study suggest that, in the SAVP model, n3 PUFAs reduce vulnerability to AF by attenuation of adverse structural remodeling at the genetic level.

The endothelium is an integral mediator of vascular homeostasis and a dysfunctional endothelium is now recognized as an early marker of atherosclerosis. Importantly, the non-invasive measurement of endothelial function by flow-mediated dilation (FMD) predicts future cardiovascular events. However, the appropriate method of its assessment and the mechanisms that govern FMD are still poorly understood. We investigated alternative parameters and methods of FMD measurement in healthy volunteers and cardiovascular disease patients. We found time to peak FMD to be highly variable both within and between individuals. Accordingly, continuous arterial diameter measurement post-cuff release was more sensitive in discriminating between health and disease compared to the measurement of diameter at 60’’ post-cuff release. Reperfusion to an ischemic tissue can paradoxically contribute to endothelial dysfunction development and further tissue damage, in a phenomenon known as ischemia and reperfusion (IR) injury. Previous exposure to sublethal ischemia (ischemic preconditioning (IPC)) can reduce sensitivity to IR injury and pharmacologic agents have since been shown to mimic this response. Using the FMD technique, we investigated various preconditioning strategies to prevent IR-induced endothelial dysfunction in the forearm vasculature of healthy volunteers. The sodium-hydrogen exchanger inhibitor amiloride and the angiotensin-converting enzyme inhibitor captopril were found not to provide endothelial protection from IR. In contrast, potent protection from IR-induced endothelial dysfunction was observed during the high-estrogen, late follicular phase of the menstrual cycle in pre-menopausal women. Finally, daily episodes of IPC were found to provide endothelial protection equipotent to an acute episode of IPC. The findings from the FMD methodological study highlight the importance of continuous arterial diameter measurement post-cuff deflation, and provide mechanistic insight that may contribute to measurement standardization and normalization. The results of the preconditioning studies improve our understanding of potential approaches to mitigate the detrimental effects of IR on the endothelium in humans.