TRANSLATIONAL APPROACHES TO UNDERSTANDING THE ROLE OF CYTOCHROME P450-DERIVED EPOXYEICOSATRIENOIC ACIDS IN CORONARY ARTERY DISEASE

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality in the United States (US). Most notably, coronary artery disease (CAD) including its clinical complications (acute myocardial infarction [AMI] and heart failure) is the primary source of this public health burden. This burden highlights the need for new therapies that target biological pathways integral to the pathophysiology of CAD and its consequences. However, a more thorough understanding of the mechanisms underlying the pathophysiology is necessary to facilitate the development of new therapeutic strategies. Epoxyeicosatrienoic acids (EETs) are cytochrome P450 (CYP)-derived metabolites of arachidonic acid that are hydrolyzed by soluble epoxide hydrolase (sEH) into the less biologically active dihydroxyeicosatrienoic acids (DHETs). EETs yield potent cardiovascular protective effects in preclinical models of atherosclerosis, ischemia reperfusion (IR) injury, and post-AMI ventricular remodeling, suggesting that increasing EET levels may be a viable therapeutic strategy for CAD, AMI, and post-AMI maladaptive ventricular remodeling. Key questions, however, remain to be addressed prior to translation of therapeutic EET-promoting strategies into successful clinical trials. The overall aim of this dissertation is to advance our understanding of the role of the EET metabolic pathway across the full spectrum of CAD and post-AMI consequences as a means to determine the biological and therapeutic importance of EETs in the progression of this disease cascade. We used both pre-clinical and human studies to complete the specific aims of this work. We found that obstructive CAD is significantly and independently associated with lower circulating EET levels. In addition, we observed that a functionally relevant polymorphism linked with enhanced EET hydrolysis was potentially associated with mortality in a population of AMI patients. Moreover, we showed that mice with cardiomyocyte-specific overexpression of human sEH exhibited enhanced IR-induced myocardial collagen deposition. Overall, we demonstrated that the EET metabolic pathway may play a role in the pathophysiology of CAD and its associated complications including the development of coronary atherosclerosis, post-AMI early ventricular remodeling, and post-AMI mortality. These findings set the stage for future studies that investigate the therapeutic utility of modulating EETs in CAD patients.Doctor of Philosoph

Pharmacogenomics in Heart Failure: Where Are We Now and How Can We Reach Clinical Application?

Heart failure is becoming increasingly prevalent in the United States and is a significant cause of morbidity and mortality. Several therapies are currently available to treat this chronic illness; however, clinical response to these treatment options exhibit significant interpatient variation. It is now clearly understood that genetics is a key contributor to diversity in therapeutic response, and evidence that genetic polymorphisms alter the pharmacokinetics, pharmacodynamics, and clinical response of heart failure drugs continues to accumulate. This suggests that pharmacogenomics has the potential to help clinicians improve the management of heart failure by choosing the safest and most effective medications and doses. Unfortunately, despite much supportive data, pharmacogenetic optimization of heart failure treatment regimens is not yet a reality. In order to attenuate the rising burden of heart failure, particularly in the context of the recent paucity of new effective interventions, there is an urgent need to extend pharmacogenetic knowledge and leverage these associations in order to enhance the effectiveness of existing heart failure therapies. The present review focuses on the current state of pharmacogenomics in heart failure and provides a glimpse of the aforementioned future needs

Epoxyeicosatrienoic acids and cardioprotection: The road to translation

AbstractCardiovascular disease, including acute myocardial infarction (AMI), is the leading cause of morbidity and mortality globally, despite well-established treatments. The discovery and development of novel therapeutics that prevent the progression of devastating consequences following AMI are thus important in reducing the global burden of this devastating disease. Scientific evidence for the protective effects of epoxyeicosatrienoic acids (EETs) in the cardiovascular system is rapidly emerging and suggests that promoting the effects of these cytochrome P450-derived epoxyeicosanoids is a potentially viable clinical therapeutic strategy. Through a translational lens, this review will provide insight into the potential clinical utility of this therapeutic strategy for AMI by 1) outlining the known cardioprotective effects of EETs and underlying mechanisms demonstrated in preclinical models of AMI with a particular focus on myocardial ischemia–reperfusion injury, 2) describing studies in human cohorts that demonstrate a relationship between EETs and associated pathways with coronary artery disease risk, and 3) discussing preclinical and clinical areas that require further investigation in order to increase the probability of successfully translating this rapidly emerging body of evidence into a clinically applicable therapeutic strategy for AMI

The impact of adjusting for baseline in pharmacogenomic genome-wide association studies of quantitative change.

In pharmacogenomic studies of quantitative change, any association between genetic variants and the pretreatment (baseline) measurement can bias the estimate of effect between those variants and drug response. A putative solution is to adjust for baseline. We conducted a series of genome-wide association studies (GWASs) for low-density lipoprotein cholesterol (LDL-C) response to statin therapy in 34,874 participants of the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort as a case study to investigate the impact of baseline adjustment on results generated from pharmacogenomic studies of quantitative change. Across phenotypes of statin-induced LDL-C change, baseline adjustment identified variants from six loci meeting genome-wide significance (SORT/CELSR2/PSRC1, LPA, SLCO1B1, APOE, APOB, and SMARCA4/LDLR). In contrast, baseline-unadjusted analyses yielded variants from three loci meeting the criteria for genome-wide significance (LPA, APOE, and SLCO1B1). A genome-wide heterogeneity test of baseline versus statin on-treatment LDL-C levels was performed as the definitive test for the true effect of genetic variants on statin-induced LDL-C change. These findings were generally consistent with the models not adjusting for baseline signifying that genome-wide significant hits generated only from baseline-adjusted analyses (SORT/CELSR2/PSRC1, APOB, SMARCA4/LDLR) were likely biased. We then comprehensively reviewed published GWASs of drug-induced quantitative change and discovered that more than half (59%) inappropriately adjusted for baseline. Altogether, we demonstrate that (1) baseline adjustment introduces bias in pharmacogenomic studies of quantitative change and (2) this erroneous methodology is highly prevalent. We conclude that it is critical to avoid this common statistical approach in future pharmacogenomic studies of quantitative change

Blood pressure–associated polymorphism controls ARHGAP42 expression via serum response factor DNA binding

We recently demonstrated that selective expression of the Rho GTPase-activating protein ARHGAP42 in smooth muscle cells (SMCs) controls blood pressure by inhibiting RhoA-dependent contractility, providing a mechanism for the blood pressure–associated locus within the ARHGAP42 gene. The goals of the current study were to identify polymorphisms that affect ARHGAP42 expression and to better assess ARHGAP42’s role in the development of hypertension. Using DNase I hypersensitivity methods and ENCODE data, we have identified a regulatory element encompassing the ARHGAP42 SNP rs604723 that exhibits strong SMC-selective, allele-specific activity. Importantly, CRISPR/Cas9–mediated deletion of this element in cultured human SMCs markedly reduced endogenous ARHGAP42 expression. DNA binding and transcription assays demonstrated that the minor T allele variation at rs604723 increased the activity of this fragment by promoting serum response transcription factor binding to a cryptic cis-element. ARHGAP42 expression was increased by cell stretch and sphingosine 1-phosphate in a RhoA-dependent manner, and deletion of ARHGAP42 enhanced the progression of hypertension in mice treated with DOCA-salt. Our analysis of a well-characterized cohort of untreated borderline hypertensive patients suggested that ARHGAP42 genotype has important implications in regard to hypertension risk. Taken together, our data add insight into the genetic mechanisms that control blood pressure and provide a potential target for individualized antihypertensive therapies

Dual modulation of cyclooxygenase and CYP epoxygenase metabolism and acute vascular inflammation in mice

Cyclooxygenase (COX)-derived prostaglandins and cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids are important regulators of inflammation; however, functional interactions between these pathways in the regulation of vascular inflammation in vivo have not been studied. We investigated the relative and additive effects of endothelial CYP2J2 overexpression (Tie2-CYP2J2-Tr), global sEH disruption (Ephx2−/−), and pharmacologic COX inhibition with indomethacin on the acute vascular inflammatory response to endotoxin in mice. Compared to vehicle-treated wild-type C57BL/6 controls, induction of myeloperoxidase (MPO) activity in lung and liver was similarly attenuated in Tie2-CYP2J2-Tr mice, Ephx2−/− mice and wild-type mice treated with moderate dose indomethacin. Dual modulation of both pathways, however, did not produce an additive anti-inflammatory effect. These findings demonstrate that both COX and CYP epoxygenase-mediated eicosanoid metabolism are important regulators of the acute vascular inflammatory response in vivo, and suggest that the anti-inflammatory effects of modulating each pathway may be mediated, at least in part, by overlapping mechanisms

Cytochrome P450-derived epoxyeicosatrienoic acids and coronary artery disease in humans: a targeted metabolomics study

Cytochrome P450 (CYP)-derived epoxyeicosatrienoic acids (EETs) exhibit potent cardiovascular protective effects in preclinical models, and promoting the effects of EETs has emerged as a potential therapeutic strategy for coronary artery disease (CAD). The relationship between circulating EET levels and CAD extent in humans, however, remains unknown. A panel of free (unesterified) plasma eicosanoid metabolites was quantified in 162 patients referred for coronary angiography, and associations with extent of CAD [no apparent CAD (N = 39), nonobstructive CAD (N = 51), and obstructive CAD (N = 72)] were evaluated. A significant relationship between free EET levels and CAD extent was observed (P = 0.003) such that the presence of obstructive CAD was associated with lower circulating EET levels. This relationship was confirmed in multiple regression analysis where CAD extent was inversely and significantly associated with EET levels (P = 0.013), and with a biomarker of EET biosynthesis (P < 0.001), independent of clinical and demographic factors. Furthermore, quantitative enrichment analysis revealed that these associations were the most pronounced compared with other eicosanoid metabolism pathways. Collectively, these findings suggest that the presence of obstructive CAD is associated with lower EET metabolite levels secondary to suppressed EET biosynthesis. Novel strategies that promote the effects of EETs may have therapeutic promise for patients with obstructive CAD

Reproductive success and survivorship of damselfly Enallagma hageni infected with ectoparasite Arrenurus.

The reproductive success and survivorship of adult male damselflies Enallagma hageni infected with ectoparasitic larval water mite Arrenurus spp. was examined. Parasitic prevalence/incidence of non-mating vs. mating males was analyzed to determine reproductive success. Body mass of parasite vs. non-parasite infected males was analyzed to determine survivorship. It was discovered that parasites are more prevalent and incident on non-mating vs. mating males. The presence of parasites on male damselflies can significantly depress their mating success. The average body weight of male damselflies with parasites was significantly lower than that of males without parasites only if infected males had high levels of parasites. Thus, parasitic water mites significantly change the survivorship of male damselflies only at high parasite levels. Reproductive success of E. hageni is more sensitive to water mite Arrenurus than survivorship.http://deepblue.lib.umich.edu/bitstream/2027.42/55115/1/3560.pd