Nuclear Receptor RORα In Cardiac Hypertrophy: Its Role And Underlying Mechanisms

Objective:.To investigate the effects of RORαon cardiac hypertrophy and its underlying mechanisms in cardiac hypertrophy.Methods:10-12 weeks C57BL/6J,RORα^sg/sg and mice with cardiac-specific overexpression of RORαwere randomly subjected to TAC or sham surgery,8 weeks after TAC,results were measured as following:cardiac function was assessed by echocardiographic measurements,images of whole hearts and the heart weight were measured.In addition,the effects of RORαon TAC-induced cardiac hypertrophy were determined by biochemical detection and immunohistochemistry.The accumulation of reactive oxygen species（ROS）was evaluated by dihydroethidium（DHE）staining,the content of nitrotyrosine was evaluated by histomorphological analysis and enzyme-linked immunosorbent assay（ELISA）Kit.The expression of SOD2 was assessed by Western Blot.In vitro experiment,during RORαgain-of-function/loss-of-function research,CMs were randomly subjected to control（Ad GFP/Adsh RNA）and RORαoverexpression/RORαdeficiency（Ad RORα/Adsh RORα）.After adenovirus infection,the CMs were randomly subjected to PBS or Ang II（1μM）for 48h.Results were measured as following:the change of cardiomyocyte surface area（CSA）was evaluated byα-actinin immunofluorescence staining,the expression of fetal genes in transcriptional level was assessed by RT-PCR.And during the following potential mechanism research,we used the SOD2-gain and loss-of-function experiments to definite if the cardioprotective effects of RORαdepend on SOD2,after adenovirus infection the CMs were randomly subjected to PBS or Ang II（1μM）for 48h.Results were measured as following:the change of cardiomyocyte surface area（CSA）was evaluated byα-actinin immunofluorescence staining,the expression of fetal genes in transcriptional level was assessed by RT-PCR.Results:1.RORαhad a high expression in the normal myocardial tissue and cardiomyocyte.However,both in vivo experiments and in vitro experiments,the protein and m RNA level of RORαwas significantly down-regulated after TAC and Ang II.2.RORαalleviated myocardial interstitial fibrosis and inhibited the expression of fibrotic and hypertrophic markers in the transcription levels.3.RORαdecreased the cardiomyocyte surface area and inhibited the expression of fetal genes in Ang II-induced cardiomyocyte compared with vehicle group.4.Both in vivo experiments and in vitro experiments,RORαdeficiency aggravated the accumulation of ROS and the content of nitrotyrosine.However,RORα overexpression alleviated the accumulation of ROS and the content of nitrotyrosine.5.In Ang II-induced cardiomyocytes hypertrophy,SOD2 overexpression can reverse cardiomyocytes hypertrophy and the up-regulating of the fetal genes induced by RORαdeficiency,however,SOD2 deficiency reduced the the anti-hypertrophic effects of RORα.Conclusions:RORαimproved the pathological cardiac hypertrophy and dysfunction upon chronic pressure overload.The cardioprotective effect of RORαmight be through upregulating the expression of SOD2 in the pathological cardiac hypertrophy.