Abstract
PurposeHigh density lipoprotein (HDL) protects against myocardial infarction via mechanisms that remain unclear. STAT3 (signal transducer and activator of transcription 3) plays a key role in HDL-induced cardioprotection. In the heart, microRNAs (miRNAs) are involved in ischemia reperfusion injury. We therefore investigated whether the cardioprotective effect of HDL modulates miRNAs as a downstream target of STAT3 activation.MethodsSTAT3 cardiomyocyte deficient mice (STAT3-KO) and wildtype littermates (STAT3-WT) were submitted to left coronary ligature and reperfused (IR) with or without injection of HDL. Infarct size (IS) was determined and cardiac miRNA expression was evaluated after reperfusion in sham, IR and IR+HDL hearts by microarray analysis.In vitro, neonatal rat ventricular cardiomyocytes were submitted to hypoxia with or without HDL incubation. Cell viability and miRNA expression were analysed.ResultsIn vivo, HDL reduced IS from 40.5±4.3% to 24.4±2.1% (p<0.05) in STAT3-WT mice. HDL failed to protect in STAT3-KO mice. In STAT3-WT mice, both miR-34b and miR-337 were increased in IR compared to sham and IR+HDL groups (p<0.05). These miRNAs were not modulated in STAT3-KO mice. In vitro, incubation with HDL improved cell viability against hypoxia (p<0.05). The expression of miR-34b and miR-337 was increased by hypoxia and reduced by HDL treatment (p<0.05). In cardiomyocytes transfected with miRNA mimics, HDL failed to improve cell viability against hypoxia.ConclusionsOur study, performed both in vivo and in vitro, delineates a novel cardioprotective signalling pathway activated by HDL, involving STAT3-mediated decrease of miR-34b and miR-337 expression.
Highlights
High density lipoproteins (HDL) have been identified as a strong negative predictor of cardiovascular events
In cardiomyocytes transfected with miRNA mimics, high density lipoproteins (HDL) failed to improve cell viability against hypoxia
The direct actions of HDL on the heart have not been extensively investigated experimental data show that HDL protects from ischemia reperfusion injury (IR) [3,4], hypoxia [5,6], and apoptosis induced by doxorubicin, a potent anti-cancer drug with cardiotoxic side effects [7]
Summary
High density lipoproteins (HDL) have been identified as a strong negative predictor of cardiovascular events. Their beneficial effect on the cardiovascular system was attributed, in the first instance, to their ability to facilitate cholesterol excretion [1]. We demonstrated that the protective effect of HDL against oxidative stress and IR is mediated via the activation of the Survivor Activating Factor Enhancement (SAFE) pathway which involves the activation of intracellular signalling factors including Tumour Necrosis Factor alpha (TNFα) and Signal Transducer and Activator of Transcription 3 (STAT3) [6,8]. Multiple studies including ours have demonstrated the anti-apoptotic role of STAT3 in cardiac conditioning [9]
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