Endothelial-specific deletion of methyltransferase Set7 protects mice from obesity-induced endothelial dysfunction

Abstract Background The prevalence and incidence of obesity is alarmingly increasing worldwide. Among the constellation of weight-related comorbidities, cardiovascular disease (CVD) carries the largest burden. A large body of evidence supports the notion that endothelial dysfunction contributes to the pathogenesis of obesity-related CVD. Seminal work has revealed that oxidative stress is a key event preceding the development of endothelial dysfunction in this setting. Epigenetic connections underpinning oxidative stress and vascular dysfunction in experimental and human obesity are emerging. We and others have previously demonstrated that histone methyltransferase Set7 may participate to adverse vascular phenotypes in elevated cardiometabolic risk. Purpose To investigate whether Set7 contributes to endothelial dysfunction in a mouse model of diet-induced obesity. Methods Aortas were isolated from obese mice fed with high fat diet (HFD, 15.5% fat) for 12 weeks and control littermates fed with standard diet (STD, regular unrestricted diet). To specifically investigate Set7 role in obesity-driven endothelial dysfunction, endothelium-dependent (EDR) and independent relaxations were assessed in aortas isolated from control and obese mice, with or without endothelium-specific conditional genetic deletion of Set7. Endothelium-specific Set7 conditional knockout (mice have been generated in our facilities. Conditional Set7flox/flox mice were crossed with TekCre mice to generate E-Set7−/− mice. Set7 deletion was induced by tamoxifen. Body weight, glucose/insulin and lipid plasma levels were measured in all experimental groups. Set7 expression in endothelial cells isolated from mice aorta was assessed by RT-PCR and confocal microscopy. Reactive oxygen species (ROS) production was determined by electron spin resonance spectroscopy. Results Set7 was upregulated in endothelial cells isolated from aortas of obese WT mice as compared to lean controls. Confocal microscopy and RT-PCR of aortic tissue confirmed selective endothelial deletion of Set7 in the E-Set7−/− mice. Both WT and E-Set7−/− animals fed with HFD had similarly elevated body weight and plasma lipids (triglycerides, total and LDL cholesterol), as well as decreased HDL cholesterol. EDR to acetylcholine were impaired in aortas isolated from WT mice fed with HFD as compared to STD. Higher production of superoxide anion (O2-) was observed in aortas isolated from WT, but not in E-Set7−/−, HFD fed mice. Accordingly, apocynin and free radical scavenger TEMPOL rescued HFD-induced EDR in WT mice. Interestingly enough, E-Set7−/− HFD fed mice were protected against obesity-induced endothelial dysfunction. Conclusions Our findings demonstrate that chromatin-modifying enzyme Set7 is upregulated in obesity and involved in oxidative stress, and endothelial dysfunction. Targeting Set7 might represent a promising option to dampen oxidative stress and to prevent atherosclerotic vascular disease in this setting. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Swedish Research Council, the Swedish Heart & Lung Foundation, and King Gustav V and Queen Victoria Foundation.