Thoracic Aorta Contraction Induced By TRPV4 In Diabetic Rats And Its Mechanism

Objective:To investigate the role of TRPV4 channel in thoracic aorta contraction of diabetic rats and its possible mechanism.Methods:（1）Healthy 6 weeks aged male Sprague-Dawley rats were randomly divided into control and diabetes mellitus（DM）groups.Diabetes was induced by a single intraperitoneal injection of streptozotocin（STZ）at 60mg/kg;The effect of TRPV4 agonist(GSK1016790A,10^-10-10^-7mol/L)and inhibitor（HC067047,1μM）on tension changes of thoracic aorta were measured using in vitro vascular tension measurement system;The effect of COX-1 specific inhibitor（SC560,1μM）and COX-2 specific inhibitor（NS398,3μM）on the tension changes of thoracic aorta were recorded using in vitro vascular tension measurement system of diabetic rats;Western blot technique was used to determine the protein expression of TRPV4 and P-e NOS in the thoracic aorta of diabetic rats;The content of NO in the thoracic aorta of diabetic rats was measured using nitrate reductase method;ELISA was used to assess the TXB₂（the stable metabolite of TXA₂）production;（2）Rat thoracic aortic endothelial cells were incubated in either normal glucose（5.5m M）or high glucose（25m M）.Western blot was used to determine the protein expression of TRPV4、COX-1 and COX-2 in rat thoracic aortic endothelial cells.Results:（1）Compared with rats in control group,the body weight of rats in DM group was significantly decreased（P<0.001）,the blood glucose was significantl y elevated（P<0.001）;（2）Compared with the control group,the protein expression of P-e NOS was significantly reduced（P<0.01）,and the NO content was significantly r educed（P<0.01）;（3）Compared to the control group,the expression of TRPV4 prot ein in the thoracic aorta of rats in diabetic group was increased（P<0.05）;Compare d with normal glucose group,the expression of TRPV4 protein in rat thoracic aorti c endothelial cells was increased（P<0.05）;（4）Compared with the control group,T RPV4-mediated thoracic aorta constriction in diabetic rats was enhanced（P<0.05）;（5）Compared with diabetic endothelial intact group,TRPV4-mediated aortic contract ion was significantly reduced in endothelium-denuded group（P<0.01）;（6）Compared with normal glucose group,the expression of COX-1 protein in rat thoracic aortic endothelial cells was up-regulated in high glucose（P<0.05）,while the expression of COX-2 protein was not significantly changed in high glucose（P>0.05）;（7）TRPV4-mediated thoracic aorta vasoconstriction was significantly reduced after incubating w ith COX-1-specific inhibitors（P<0.01）,while the COX-2-specific inhibitor had no ef fect on TRPV4-mediated thoracic aorta vasoconstriction（P>0.05）;（8）Compared with the control group,the production of TXB₂ in diabetes was significantly increased（P<0.05）.Conclusion:The increased expression of TRPV4 protein in thoracic aortic endo thelial cells of diabetic rats may mediate the endothelium dependent thoracic aortic abnormal contraction through increased production of COX-1-dependent TXA₂.