Role Of Ca²⁺ Sensor STIM1 On Smooth Muscle Contractile Function Of Coronary Artery In Diabetic Mice

Objective:Diabetes is the common metabolic disease in the world.Diabetes is always accompanied by vascular smooth muscle dysfunction,which has a close relationship to the abnormal regulation of intracellular Ca²⁺.Furthermore,the regulation of Ca²⁺homeostasis in sarcoplasmic reticulum（SR）has closely related to STIM1,a Ca²⁺sensor,which can mediate Ca²⁺channels and regulate Ca²⁺exchange in cells.The physiological significance of STIM1 in smooth muscle contractile dysfunction of coronary arteries in diabetes still remains unclear.Therefore,this study intended to investigate the effect of STIM1 on calcium regulation in coronary smooth muscle contraction,and the role of STIM1 in the changes of vascular reactivity in diabetic coronary arteries.Methods:（1）The specific knockout of STIM1 in smooth muscles（sm-STIM1 KO）of mice were established using the Cre/lox P site-specific recombination system.（2）Type 1 diabetic mice were induced through intraperitoneal injection of streptozotocin.Blood glucose level and body weight were detected.（3）The Multi Myograph system was used to detect the smooth muscle contractile response of mouse coronary arteries mediating by various vasoconstrictors or calcium channel blockers.Results:（1）The blood glucose level was significantly increased（>16 mmol/L）and the body weight was significantly lost in diabetic mice.These implied that type 1 diabetic mice were successfully established.（2）In sm-STIM1 KO mouse coronary arteries,5-HT-evoked vasoconstriction significantly decreased,but had no effect on U46619-induced contraction.Furthermore,in sm-STIM1 KO mouse coronary arteries,5-HT-elicited contraction was also remarkably reduced after incubating with nifedipine in high-potassium solutions.These indicated that STIM1 took part in the vasoconstriction of mouse coronary arteries.（3）In sm-STIM1 KO mouse coronary arteries,the inhibition rates of nifedipine on the contractile responses induced by vasoconstrictors（5-HT or U46619）were obviously increased.Meanwhile,we found that the vascular reactivities,caused by high potassium or L-type calcium channels agonist Bay K8644,were remarkably enhanced in the coronary arteries of sm-STIM1 KO mice.These indicated that STIM1 inhibited the contractile response mediated by L-type calcium channels in vascular smooth muscles.（4）In sm-STIM1 KO mouse coronary arteries,vasocontractions,mediated by non-L type calcium channels and SR Ca²⁺release channels,were smaller than that in wild type mice.We also discovered that Caffeine-induced vasoconstriction significantly decreased in sm-STIM1 KO mice.Besides,we didn’t observe the Ca Cl₂-elicited contractile response in sm-STIM1 KO mouse coronary arteries after incubating with nifedipine and TG(a Ca²⁺-ATPase inhibitor)in Ca²⁺-free K-H solutions.These indicated that STIM1influenced the function of SR Ca²⁺release channels（IP₃R and Ry R）and SOC channel didn’t take part in coronary arterial contraction.（5）The contractile response of the coronary artery was obviously diminished in diabetic mice.The inhibition rate of nifedipine and the response to exogenous Ca²⁺in vascular smooth muscles were both remarkably diminished as well.Moreover,the vasocontractions mediated by non-L type calcium channels and SR Ca²⁺release channels in diabetic mice were lower than that in wild type mice.（6）In diabetic sm-STIM1 KO mice,5-HT-evoked contractile response was significantly enhanced,but U46619-induced constriction had no changes.The inhibition rate of nifedipine obviously raised in 5-HT-or U46619-triggered contraction.Moreover,in U46619-induced vasocontraction,the effects of non-L type calcium channels and SR Ca²⁺release channels were both decreased in diabetic sm-STIM1 KO mice,but the effects were not observed in 5-HT-induced vasocontraction.Conclusions:Contractile dysfunctions of diabetic coronary arteries are primarily related to the down-regulation of L-type calcium channel and Ca²⁺release from SR of vascular smooth muscles.STIM1-mediated SOC channel exists obvious organ specificity.SOC channel does not participate in the contractile response of coronary arteries,but STIM1 can take part in it through regulating L-type calcium channel and Ca²⁺release from SR.STIM1-deletion can partly restore vascular smooth muscle contractile dysfunction in diabetes through up-regulating L-type calcium channel.