TRPC6 Participates In The Development Of Blood Pressure Variability Increase In Sino-Aortic Denervated Rats

ObjectiveIncreased blood pressure variability(BPV)has been proved to be associated with cardiovascular morbidity and mortality.BPV increase occurs not only in hypertensive patients but also in persons with normal blood pressure or controlled hypertension,which is easily neglected,and take extremely adverse impact for human health.However,the specific molecular mechanism of BPV increase is not clear at present.So,it is of great significance to elucidate the mechanism of BPV increase.The cation channel transient receptor potential canonical 6(TRPC6)is involved in a series of cardiovascular disease.Our preliminary experiment showed that the protein expression levels of TRPC6 in aortic tissue in SAD rats were substantially increased,So we speculate that TRPC6 participates in the development of blood pressure variability increase in sino-aortic denervated rats.In this study,we investigated the TRPC6 expression in myocardial and thoracic aortic tissue in SAD rats,as well as the role of TRPC6 in SAD-induced BPV elevation.MethodsOur experiment aimed to explore the role of TRPC6 in the development of BPV increase.Sino-aortic denervation(SAD)operation was applied to establish the model of BPV increase in rats.Animal studies have demonstrated that SAD rats possess an augmented BPV without blood pressure elevation.The BPV was presented as the standard deviation to the mean of systolic or diastolic blood pressure every one hour during 12 h of the light period.SAD was performed in male Sprague-Dawley(SD)rats at the age of 10 weeks.At 8 weeks after SAD operation,the hemodynamic parameters were determined non-invasively via a Rodent Blood Pressure Analysis System.The TRPC6 expression in myocardial and aortic tissue was determined utilizing Western Blot,immunofluorescence and quantitative RT-PCR.Since TRPC3 and TRPC6 are highly homological and always function in heteromultimeric assembly,the change of TRPC3 expression in SAD rats was also examined with Western Blot as well.We designed three different doses of TRPC6 activator and inhibitor.To investigate whether TRPC6 was a causative factor of BPV increase in SAD rats,TRPC6 activator and inhibitor with three progressively increasing doses were intraperitoneally injected to the SAD rats.And then TRPC6activator(2mg/kg)and inhibitor(10mg/kg)were intraperitoneally injected to the SAD rats to explore the role of TRPC6-Ca N-NFAT in the development of BPV increase,the activity of Ca N in myocardial and aortic tissue in SAD rats was determined utilizing Ca N activity assay kit,Theprotein expression levels of NFAT in myocardial and aortic tissue was determined utilizing Western Blot.ResultsWe found that SAD rats presented significant augmentation of systolic and diastolic BPV with no change of BP level and heart rate.The m RNA and protein expression levels of TRPC6 in myocardial and aortic tissue in SAD rats were substantially increased,but there was no obvious change in TRPC3 expression.The systolic and diastolic BPV increase were dose-dependently exacerbated after TRPC6 activation with GSK1702934 A,but were dose-dependently attenuated after TRPC6 inhibition with SAR7334.In addition,the activity of Ca N and protein expression levels of NFAT increase significantly in myocardial and aortic tissue in SAD rats,and after TRPC6 activation and inhibition,the activity of Ca N and protein expression levels of NFAT presented relevant augmentation or attenuated.ConclusionIn Conclusion,the TRPC6(but not TRPC3)expressions in myocardial and aortic tissue were substantially increased in SAD rats,and TRPC6 probably played an important role via Ca N-NFAT molecular pathway in the development of BPV elevation.