Agonists of epoxyeicosatrienoic acids reduce infarct size and ameliorate cardiac dysfunction via activation of HO-1 and Wnt1 canonical pathway.

Myocardial infarction (MI) is complicated by ventricular fibrosis and associated diastolic and systolic failure. Emerging studies implicate Wnt1 signaling in the formation of new blood vessels. Epoxyeicosatrienoic acids (EETs)-mediated up-regulation of heme oxygenase-1 (HO-1) protects against the detrimental consequences of MI in several animal models, however, the mechanism(s) by which this occurs remains unclear. The aim of this study was to examine these mechanisms in the LAD ligation animal model of post infarcted heart failure. Specifically, we sought to clarify the mechanistic basis of the interactions of the Wnt1 canonical pathway, HO-1 and associated angiogenesis. Human microvascular endothelial cells (HMECs) were exposed to anoxia and treated with the EET agonist, NUDSA, in the presence and absence of tin mesoporphyrin (SnMP). Increased capillary density, and Wnt1 and HO-1 expression occurred in cells treated with NUDSA. Anoxic HMECs treated with NUDSA and Wnt1 siRNA, exhibited decreased in the expression of ß-catenin and the Wnt1 target gene, PPARδ (p<0.05 vs. NUDSA). Furthermore, blocking the Wnt 1 antagonist, Dickkopf 1, by siRNA increased ß-catenin and PPARδ expression, and this effect was further enhanced by the concurrent administration of NUDSA. In in vivo experiments, C57B16 mice were divided into 4 groups: sham, mice with MI via LAD ligation and mice with MI treated with NUDSA, with and without SnMP. Increased fractional area change (FAC) and myocardial angiogenesis were observed in mice treated with NUDSA (p<0.05 vs. MI). Increased expression of HO-1, Wnt1, ß-catenin, adiponectin, and phospho-endothelial nitric oxide synthetase (p-eNOS), and a decrease in the glycosylated subunit of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, gp91(phox) expression occurred in cardiac tissue of mice treated with NUDSA (p<0.05 vs. MI). SnMP reversed these effects. This novel study demonstrates that increasing the canonical Wnt1 signaling cascade with the subsequent increase in HO-1, adiponectin and angiogenesis ameliorates fibrosis and cardiac dysfunction in a mouse model of MI and supports the hypothesis that HO-1 is an integral component of the EETs-adiponectin axis and is central for the control of resistance to fibrosis and vascular dysfunction and in part determine how they influence the cellular/vascular homeostasis and provides insight into the mechanisms involved in vascular dysfunction as well as potential targets for the treatment of CVD.

Therapeutic implications of disorders of cell death signalling: membranes, micro-environment, and eicosanoid and docosanoid metabolism.

Disruptions of cell death signalling occur in pathological processes, such as cancer and degenerative disease. Increased knowledge of cell death signalling has opened new areas of therapeutic research, and identifying key mediators of cell death has become increasingly important. Early triggering events in cell death may provide potential therapeutic targets, whereas agents affecting later signals may be more palliative in nature. A group of primary mediators are derivatives of the highly unsaturated fatty acids (HUFAs), particularly oxygenated metabolites such as prostaglandins. HUFAs, esterified in cell membranes, act as critical signalling molecules in many pathological processes. Currently, agents affecting HUFA metabolism are widely prescribed in diseases involving disordered cell death signalling. However, partly due to rapid metabolism, their role in cell death signalling pathways is poorly characterized. Recently, HUFA-derived mediators, the resolvins/protectins and endocannabinoids, have added opportunities to target selective signals and pathways. This review will focus on the control of cell death by HUFA, eicosanoid (C20 fatty acid metabolites) and docosanoid (C22 metabolites), HUFA-derived lipid mediators, signalling elements in the micro-environment and their potential therapeutic applications. Further therapeutic approaches will involve cell and molecular biology, the multiple hit theory of disease progression and analysis of system plasticity. Advances in the cell biology of eicosanoid and docosanoid metabolism, together with structure/function analysis of HUFA-derived mediators, will be useful in developing therapeutic agents in pathologies characterized by alterations in cell death signalling.

EET agonist prevents adiposity and vascular dysfunction in rats fed a high fat diet via a decrease in Bach 1 and an increase in HO-1 levels.

Recent reports have shown interplay between EETs (epoxides) and the heme oxygenase (HO) system in attenuating adipogenesis in cell culture models; prompting an examination of the effectiveness of EET agonist on obesity and associated cardio-metabolic dysfunction. Patho-physiological effects of an EET agonist (NUDSA) were contrasted in the absence and in the presence of stannous mesoporphyrin (an HO inhibitor) in SD rats fed a high fat (58%, HF) for 16 weeks. Animals on HF diet exhibited enhanced oxidative stress, increased levels of inflammatory cytokines and decreased levels of adiponectin along with reduced vascular and adipose tissue levels of EETs, HO-1; as compared to control rats (11% dietary fat). Treatment with NUDSA not only reversed serum adiponectin and vascular and adipose tissue levels of EETs and HO-1, but also, decreased blood pressure, subcutaneous and visceral fat content and serum TNFα and IL-6 levels in rats on HF diet. Aortic endothelial function, peNOS expression and adipose tissue markers of energy homeostasis i.e. pAMPK, Sirt1 and FAS, impaired in rats fed a HF diet, were restored in animals treated with this EET agonist. That NUDSA enhanced HO-1 expression, was accompanied by increase in p-GSK-3ß and pAKT levels along with attenuation of adipose tissue levels of Bach 1--the transcriptional suppresser of HO-1 expression. Prevention of these beneficial effects of NUDSA, in animals on HF diet and concurrently exposed to NUDSA and SnMP, supports the role of EET-HO interaction in mediating such effects. Taken together, our findings suggest that the EETs stimulate HO-1 expression via suppression of Bach 1 and interplay of these two systems affords vascular and metabolic protection in diet induced obesity.