The Relationship Between The Change Of ACE/ACE2 Expression In Kidney And The Renal Injury In Tourniquet Shock Mice

The mechanism of various types of shock is complex, in which humoral factors may be the basis for microcirculation disturbance and multiple organ dysfunction syndromes (MODS). The rennin angiotensin system (RAS) plays an important role in maintaining blood pressure in stable and the balance of sodium and water in the body. It was previously considered that excessive AngⅡ, formed from angiotensinⅠby the angiotensin converting enzyme (ACE) in vasoconstriction pathway, is strongly related to the pathogenesis of shock. Recently, some studies have shown that another pathway in RAS, in which angiotensin-coverting enzyme 2 (ACE2) mainly catalyzes AngⅡinto Ang (1-7) as a vasodilator, is also involved in shock.Objective:The aim of the present study is to illuminate the mechanism by observing the changes of ACE/ACE2 expression in kidney and the kidney injury in tourniquet shock mice.Methods:1. Forty-two male ICR mice of clean grade were used in experiment, wighting 45±10g, the mice were randomly divided into seven groups, including control group and six time point groups. According to the method described previously bilateral tourniquets were placed high in the inguinal region on both hind legs for the duration of 2h to induce ischemia. Reperfusion was initiated by cutting tourniquets, and then killed the mice at 0.5h, 1h, 2h, 4h, 6h, 12h reperfusion. Kidney tissue and blood samples were collected. The hindlimbs of control group were operated but not ligated. The expressions of ACE and ACE2 in mice’s kidney of each group were detected by means of Western blotting. Kidney SOD, MDA, Cr and BUN were detected by chemistry shade selection. The other kidney was made for paraffin section, treated by HE stain and immunohistochemisty for observing pathological changes and the ACE/ACE2 expression changes.2. Six wild-type mice, six ACE2 transgenic mice, and six ACE2 knock out mice were selected respectively for production of the tourniquet shock model. All animals were received 2h ischemia and 4h reperfusion. The expressions of ACE and ACE2 in mice’s kidney of each group were detected by means of Western blotting. Kidney’s SOD, MDA, Cr and BUN were detected by chemistry shade selection. The other kidney was made for paraffin section, treated by HE stain and immunohistochemisty for observing pathological changes and the ACE/ACE2 expression changes.Results:1. Western blotting showed that the ACE is increased and the ACE2 is decreased in kidney of the ToS mice.2. Pathological section stained by HE showed that the normal kidney tissue displayed a normal framework, and the kidneys in all the point time groups displayed obvious pathological changes including tubular epithelial cell necrosis, phlogocyte infiltrate and epithelial cells necrosis.3. Compared with the normal group, time point groups had a significant increase of kidney MDA (P<0.05), decrease of kidney SOD (P<0.05), and increase of BUN and Cr (both P<0.05).4. Immunohistochemisty showed that the expression of ACE in endochylema of the kidney tubular epithelial cell was increased and the expression of ACE2 in luminal membrane of renal epithelium was decreased in the ToS mice.5. The expression of ACE in the kidney of ACE2 konck out mice was increased. The expression of ACE in the kidney of ACE2 transgenic mice was not detected to have obvious change. 6. Compared to the wild-type (WT) mice, the ACE2 knock out mice had a more severe oxidative stress reaction and renal injury and ACE2 transgenic mice had lighter ones after 2h ischemia and 4h reperfusion.Conclusions:1. The kidney ACE is increased and the ACE2 is decreased in the ToS mouse. The imbalance between ACE and ACE2 may be related to pathogenesis of kidney injury in ToS mouse.2. The imbalance of ACE/ACE2 expression may contribute to the renal injury by oxidative stress mechanism, which may lead to kidney injury in the ToS mice.3. ACE2 may play a protective role in the kidney injury in the ToS mice; Re-establishment of RAS blance by regulating ACE2 expression may be strategy for prevention and treatment of ToS-induced acute renal injury.