PPARγ signaling is required for mediating EETs protective effects in neonatal cardiomyocytes exposed to LPS

Abstract

Lipopolysaccharide (LPS) is a bacterial wall endotoxin producing many pathophysiological conditions including myocardial inflammation leading to cardiotoxicity. Epoxyeicosatrienoic acids (EETs) are biologically active metabolites of arachidonic acids capable of activating protective cellular pathways in response to stress stimuli. EETs evoke a plethora of pathways limiting impairments of cellular structures, reducing cell death, and promoting anti-inflammatory reactions in various cell types. Considering EETs are capable of producing various biological protective effects, we hypothesized that EETs would protect rat neonatal cardiomyocytes (NCM) against LPS-induced cytotoxicity. In this study, we used a dual-acting, synthetic analog of EETs, UA-8 [13-(3-propylureido)tridec-8-enoic acid], possessing both EET-mimetic and soluble epoxide hydrolase selective inhibitory properties and 14,15-EET as a model of canonical EET molecules. We found that both UA-8 and 14,15-EET significantly improved cell viability and mitochondrial function of cardiomyocytes exposed to LPS. Furthermore, treatment with UA-8 or 14,15-EET resulted in significant attenuation of LPS-triggered pro-inflammatory response, caspase-3 activation and reduction in the total antioxidant capacity in cardiomyocytes. Importantly, EET-mediated effects were significantly reduced by pharmacological inhibition of peroxisome proliferator-activated receptors γ (PPARγ) suggesting that PPARγ signaling was required for EETs exerted protective effects. Data presented in the current study demonstrate that activation of PPARγ signaling plays a crucial role in EET-mediated protection against LPS-cytotoxicity in cardiomyocytes.

CYP epoxygenase metabolites of docosahexaenoic acid protect HL-1 cardiac cells against LPS-induced cytotoxicity through SIRT1

“…In our previous studies, we demonstrated LPS triggered an inflammatory response in cardiomyocytes, which was partially associated with caspase activation and cell death. 18 , 19 As expected, treatment with LPS promoted significant upregulation of NF- κ B DNA-binding activity initiating an inflammatory cascade ( Figure 3a ). Consistent with this observation, LPS caused release of the major pro-inflammatory cytokine TNF α from HL-1 cells ( Figure 3b ).…”

Novel Roles of Epoxyeicosanoids in Regulating Cardiac Mitochondria

“…An important element of the mitochondrial quality is the biogenesis of mitochondrial proteins. EETs are recognized agonists for peroxisome proliferator-activated receptors (PPARs) [ 36 , 46 ], which play a significant role in promoting expression of several mitochondrial proteins [ 47 , 48 ] Recently, Wang et al reported that 14,15-EET induced mitochondrial biogenesis in cortical neuronal cells via activation of cAMP-response element binding protein (CREB), which in turn activated the peroxisome proliferator-activated receptor gamma-coactivator 1 (PGC1) [ 49 ]. In order to investigate the involvement of mitochondrial biogenesis in the protective effect of EETs in HL-1 cardiac cells, we assessed several regulators of mitochondrial biogenesis following 6 and 24 hours of starvation.…”

“…To measure cellular energy levels, we used a bioluminescence-based kit (Sigma–Aldrich, Oakville, ON, CAN) to assay the ratio between ATP and ADP in HL-1 cells as described previously [ 36 ]. Briefly, cells were cultured on a 96-well plate then treated accordingly to the starvation protocol.…”

Inhibition of Soluble Epoxide Hydrolase Limits Mitochondrial Damage and Preserves Function Following Ischemic Injury

“…We have previously demonstrated that EETs enhance cardiomyocyte cell survival via a protective cascade targeting the mitochondria (Katragadda et al, 2009 ; Batchu et al, 2012a ; Samokhvalov et al, 2013 , 2014 ). Emerging evidence suggests the cardioprotective effect of EETs is due to inhibition of mitochondrial damage.…”