A Study On The Effect Of Estrogen On The Vascular Hyporeactivity In Rat With Hemorrhagic Shock

Hemorrhagic shock is a common acute and critical illness characterized by acute circulatory disturbances and severe hypoxia.Severe tissue cell damage and dysfunction are one of the causes of death in trauma patients.Studies have shown that the low reactivity of microvasculature to vasoactive substances plays the key in the intractable hypotension in patients with hemorrhagic shock.Estrogen(E2)could improve the vascular reactivity in rats with hemorrhagic shock,because hormone receptor GPR30 is involved in the activation of Rho kinase(ROCK)pathway and protein kinase C pathway.E2 treatment can significantly increase the reactivity of mesenteric microvascular in female mice after ovariectomized,and its mechanism is related to Rho A-ROCKmyosin light chain phosphatase signaling pathways.But the relevant mechanisms still need further study.Endoplasmic reticulum stress(ERS)is a self-protective reaction of cells,but severe or persistent ERS will aggravate cell injury.ERS aggravated by hemorrhagic shock may induce vascular hyporesponsiveness by affecting the function of vascular smooth muscle cells(VSMCs).It is unclear whether estrogen improves the vascular reactivity after hemorrhagic shock by inhibiting ERS in VSMCs,it is still unclear.Therefore,basing on the result that E2 treatment can significantly improve the survival time and survival rate of hemorrhagic shock in rats,we investigated the effects of E2,estrogen receptor agonist(PPT,DPN,G-1)and ERS inhibitor 4-PBA on isolated microvascular reactivity in hemorrhagic shock rats.Furthermore,we observed the effects of estrogen receptor inhibitors(ICI,G15)on E2 therapy and the effect of ERS agonist XCT-790 on the beneficial effects of E2,PPT,DPN,and G-1,to reveal the role of E2 in improving vascular reactivity in hemorrhagic shock,and to clarify the relationship between the E2 and estrogen receptors.As a result,the current study would provide a new experimental basis for the prevention and treatment of hemorrhagic shock.Firstly,The 16 healthy male rats were used for observation of ERS inhibitor 4-PBA on survival time and survival rate in hemorrhagic shock rats.The results showed that 4-PBA prolonged the survival time and improved the survival rate of hemorrhagic shock in rat.144 SPF Wistar healthy male rats weighing 280±20 g were housed in a sterile animal room before the experiment.These rats were randomly divided into the vehicle group,E2 group,estrogen receptor agonist intervention group(PPT group,DPN group,G-1 group),estrogen receptor inhibitor group(E2+ICI group,E2+G15 group),ERS inhibitor group(4-PBA group),ERS agonist group(E2+ XCT-790 group,PPT+XCT-790 group,DPN+XCT-790 group,and G-1+XCT-790 group).Then,the above components were divided into sham group and shock group(conventional method to establish hemorrhagic shock model: 40±2 mm Hg for 1.5 h,followed by fluid resuscitation).The grouping as follows: Sham+Vehicle,Shock+Vehicle,Sham+E2,Shock+E2,Sham+PPT,Shock+PPT,Sham+DPN,Shock+DPN,Sham+G-1,Shock+G1,Sham+E2+ICI,Shock+E2+ICI,Sham+E2+G15,Shock+E2+G15,Sham+E2+XCT-790,Shock+E2+XCT-790,Sham+ PPT+XCT-790,Shock+PPT+XCT-790,Sham+DPN+XCT-790,Shock+ DPN+XCT-790,Sham+G-1+XCT-790,Shock+G-1+XCT-790,Sham+ 4-PBA,and Shock+4-PBA groups.Three hours after the end of resuscitation,each group of animals received a section of intestinal fistula at a fixed position.Under the operating microscope,the mesentery secondary arterioles were isolated and the microvascular rings were prepared,then hanged them into the four-chamber linear actin instrument perfusion bath tank with PSS solution at 4°C and filled into the mixed gas of 95% O2 and 5% CO2.Then,we observed the vascular contractile reactivity of microvascular to norepinephrine(NE),the vasodilation to acetylcholine(Ach)and sodium nitroprusside(SNP)at different concentration.The results of the study found that the shrinking reactivity of microvasculature in hemorrhagic shock rats was significantly lower than the sham group in response to multiple concentrations of NE.E2 and its receptor agonists PPT,DPN,G-1,ERS inhibitor 4-PBA treatment were significantly improved the reactivity of microvasculature.ICI treatment abolished the beneficial effect of E2 on vascular reactivity in hemorrhagic shock rats.ERS agonist XCT-790 partially inhibited the beneficial effects of vascular reactivity increased by E2 and its receptor agonists.Further studies have found that hemorrhagic shock reduces the rat microvascular reactivity to multiple concentrations of Ach and SNPs.ER agonist G-1,inhibitor ICI,ERS agonist XCT-790,and inhibitor4-PBA exerted similar results as the previous experiments.The results indicate that estrogen improves vascular reactivity in hemorrhagic shock rats through estrogen receptors,and its effect is related to inhibition of endoplasmic reticulum stress caused by hemorrhagic shock.The relevant mechanism has yet to be further studied.