Role Of Mesenteric Lymph Drainage On ACE/ACE2 Balance In Kidney Following Hemorrhagic Shock In Mice

Acute kidney injury(AKI) caused by severe hemorrhagic shock and multiple organ dysfunction syndrome(MODS) and even multiple organ failure(MOF) is one of the important causes of death in patients. A great number of studies have indicated that mesenteric lymph duct(MLD) ligation and mesenteric lymph drainage alleviate the AKI following hemorrhagic shock. Hence, the gut-derived infection along with lymphatic pathway is one of the important factors of severe shock-induced AKI. Renin-angiotensin- aldosterone system(RAAS) is an important body fluid regulation system, presents in blood vessels associated with the circulatory system, heart and central nervous system, kidneys, adrenal glands and other tissues and organs. The current study shows that RAAS have two key axes: angiotensin-converting enzyme(ACE)- angiotensin II(Ang II)-1 receptor(AT1R), angiotensin-converting enzyme 2(ACE2)-Ang(1-7)-Mas receptors. Wherein, ACE2 cleavage Ang II to generate Ang(1-7), Mas receptor activation plays a negative regulatory role. Therefore, ACE2-Ang(1-7)-Mas receptor axis is considered ACE-Ang II-AT1 R reverse adjustment shaft, which together regulate RAAS balance. Moreover, in the course of AKI caused by hemorrhagic shock, the kidney tissue ACE and ACE2 balance how to change? The effect of mesenteric lymph drainage on the ACE/ACE2 balance in renal tissue of mice following hemorrhagic shock, it remains unknown.In order to investigate the effect of mesenteric lymph drainage on he ACE/ACE2 balance in renal tissue following hemorrhagic shock, twenty-four male BALB/c mice were randomized into control, sham, shock, shock+drainage(shock+mesenteric lymph drainage) groups. All of the animals were anesthetized. The right femoral vein was cannulated for the injection of heparin sodium. A minimally heparinized polyethylene catheter was introduced into the right femoral artery for continuously monitoring the MAP. Another catheter was inserted into the left femoral artery for acute hemorrhage. A laparotomy was carried out to separate the MLD. After a 30- min stabilization period, blood was withdrawn from the right femoral artery to a MAP of 40 mmHg within 10 min at an even speed and was maintained at this level by withdrawing or reinfusing shed blood as needed, thus, the hemorrhagic shock model was established. After 60 min of hypotension, the ejective blood and the equal Ringer’s solution were reperfused within 30 min through left femoral artery. The MAP was observed for 6 hours after the end of infusion. In the shock+drainage, after infusion finished, the mesenteric lymph duct was cannulated and mesenteric lymph was drained up to 6 hours after shock. The control of group drawn directly after anesthesia. In the sham group, the mice were anesthetized, cannulated and operated as described above, but no blood was withdrawn or infused. Specimens from the left kidney,-80 ℃ preservation, preparation of tissue homogenates, ELISA method to detect kidney tissue Ang II and Ang(1-7) index analysis; The return right kidney,-80 ℃ preservation, and QRT- PCR method to detect the ACE mRNA, ACE2 mRNA, AT1 R mRNA, Mas1 R mRNA expression.It was found that the levels of ACE mRNA, Ang II, AT1 R mRNA in sham group were higher than the control group; The levels of ACE mRNA, Ang II, AT1 R mRNA in shock group were significantly higher than the control group and the sham group; Mesenteric lymph drainage obviously reduced these indexes in shock group, but still higher than control group and the sham group. The levels of ACE2 mRNA, Ang(1-7), Mas1 R mRNA in sham group were lower than the control group, and ACE2 mRNA, Mas1 R mRNA were more significantly; The levels of ACE2 mRNA, Ang(1-7), Mas1 R mRNA in shock group were significantly lower than the control group, and ACE2 mRNA was more significantly lower than the sham group; Mesenteric lymph drainage obviously increased these indexes in shock group, but still lower than the control group and the sham group. The levels of ACE/ACE2 in sham group were higher than the control group; The levels of ACE/ACE2 in shock group were significantly higher than the control group and the sham group; Mesenteric lymph drainage obviously decreased these indexes in shock group, but still higher than control group and the sham group.These results in this study demonstrated that after hemorrhagic shock, in the renal tissue ACE-Ang II-AT1 R axis upregulation, while ACE2-Ang(1-7)-Mas axis downregulation. The mechanism of mesenteric lymph drainage alleviating acute kidney injury in hemorrhagic shock mice is related to its role in regulating ACE/ACE2 balance. These findings add and perfect the theory of “mesenteric lymphatic pathway in the pathogenesis of AKI”, and provide the experimental basis for clinical prevention and treatment of acute kidney injury patients, with a focus on lymphatic pathway and the regulation balance of ACE/ACE2.