Aim: To investigate whether ORAI/ stromal interaction molecule 1 (STIM1) channel mediated store-operated Ca²⁺ entry (SOCE) contributes to the vascular hyporeactivity in severe hemorrhagic shock.
Methods: An in vivo rat model of severe hemorrhagic shock and an in vitro hypoxia-reoxygenation injury in rat mesenteric artery smooth muscle cells (MASMCs) were combined in the study. The Ca²⁺ sensitivity of mesenteric artery and vasoresponsiveness to PE was measured by DMT Myograph system. The expression of ORAI, STIM1 and CyPD in MASMCs were determined by QPCR, Western blot or ELISA. Adenovirus-induced STIM1 overexpressing or shRNA knockdown of STIM1 were constructed to further detect the effects of STIM1 expression on vasoreactivity. Cellular immunofluorescence was used to detect the effect of overexpression of STIM1 on the opening of MPTPs in MASMCs exposed to hypoxia and reoxygenation, and the intracellular Ca²⁺ signal was measured by TILLvisION system.
Results: The in vitro vascular tension measurements showed that after sarcoplasmic reticulum (SR) being depleted by 2 μM TG and phenylephrine (5 μM), the vascular contraction induced by extracellular Ca²⁺ in shock group significantly decreased. Accordingly, the protein expression of STIM1 in mesenteric arteries of shock group was down-regulated. The EC50 for PE was greatly increased in the mesenteric artery with STIM1 knocking down, while adenovirus-driven STIM1 overexpression remarkably reduced the EC50 for PE. The opening of mPTPs indicated by the mean fluorescence density of Calcein/CoCl₂ remarkably prolonged, and the expression of CyPD increased but STIM1 decreased greatly in MASMCs exposed to hypoxia for 24 h and reoxygenation for 24 h. However, the overexpression of STIM1 significantly inhibited the opening of MPTPs and increased expression of CyPD in MASMCs suffered from hypoxia/reoxygenation.
 

hemorrhagic shock,stim1,hypoxia,reoxygenation,mitchondria