The Experimental Study Of Protective Effects And Underlying Mechanism Of Direct Renin Inhibition In Rats With Acute Pancreatitis

Objective: We observed the effects of the direct renininhibitors (aliskiren) on the serum amylase (AMY), tumor necrosis factoralpha (TNF-α), plasma renin activity (PRA), angiotensin II (Ang II) level,as well as the expressions of nuclear factor kappa B (NF-κB) andangiotensin II type1receptor (AT1R) in rats with acute pancreatitis (AP),in order to investigate the protective effect and underlying mechanisms ofaliskiren on inhibiting the first link of renin angiotensin system (RAS) inrats with AP model. Methods:72adult healthy Spague-Dawlay(SD) ratswere randomly divided into three groups: sham operation group(SOgroup,n=24), acute pancreatitis model group(AP group,n=24),aliskiren(Rasilez)therapy group(R group,n=24),24in each group.The APmodels of AP group and R group were induced by retrograde injection of3.5%sodium taurocholate(0.1ml/100g)into the biliopancreatic duct. SOgroup was opened abdomen and slightly moved the bowel andpancreas,and then sutured the cut. Aliskiren(Rasilez) solution wasadministered to the rats of R group by gavage at a dose of20mg／kgimmediately after modeling,and equivalent volume of normalsaline(NS)was given by gavage to the SO group and AP group. Rats divided into equal numbers according to8/group/batch,were takeninferior vena cava blood tested at6h,12h,24h respectively, and put themto death. We observed the pancreas pathological changes and assessed thepathologic grading of the rats in every group by haematoxylin and eosinstain(HE);AMY, TNF-α, Ang II, PRA were measured by centrifuginginferior vena cava blood. The express of NF-κB and AT1R in the pancreaswere determined by immunohistochemistry method.All experimentalresults were analyzed using statistical software SPASS13.0. Results:1.The pathological changes of pancreatic tissue:(1) with the naked eye: therat pancreas in SO group showed pink, soft, good glossiness, and noobvious edema, no hemorrhage and necrosis with time, nointra-abdominal ascites and saponification spots. The rat pancreas of SOgroup at three time points were no obvious change. The distribution areasurrounding the pancreatic duct in AP group appeared congestion, edemaimmediately after modeling, and lesion area gradually increased, the colorgradually deepened. Over time, rat pancreas at6h swelled significantlywith the pale color, dark red, dim, and formed a small amount of ascitesand pancreatic surface saponification spot; rat pancreas at12h washemorrhage and necrosis with dark brown. The saponification spot ofpancreas and omentum also increased, pancreatic tissue adhesion to theadjacent organ obviously, and flatulence was also obviously visible.Meanwhile, there were many bloody ascites; rat pancreas at24h was dark brown, extensive necrosis hemorrhage, calcification formed, largelyadhesion to the surrounding organs. Meanwhile, flatulence and abundentbloody ascites were obviously visible. Compared to AP group at the sametime point, the pancreatic edema, hemorrhage, necrosis, saponificationplaque formation and the volume of ascites were relieved in R group.(2)under light microscope: we found that pancreatic lobular structure in SOgroup was integrity in general, slight interstitial edema, a fewinflammatory cells infiltration, and the pancreatic tissue at the three timepoint under the microscope showe no difference. The pancreatic lobularstructure in AP group was disorder, pancreatic interstitial was edema,interlobular septal slightly widened, inflammatory cells infiltration at6h;the pancreatic lobular structure in AP group was disorder significantly,pancreatic interstitial was edema, lobular significantly widened gap, partof lobules were destroyed, necrosis, hemorrhage, and had inflammatorycells infiltration at12h; the degree of pancreatic pathological injury wasaggravated which lobule structure disappeared, the massive inflammatorycells infiltrated, massive hemorrhage, necrosis, fat liquefaction necrosisand acinar cell pyknosis, disintegration occurred at24h. Part of lobulesbecame worsen to non structural region with red dying.Group R and APgroup at the same time point, the pathological changes of bodies weresimilar, but the lesion degree of pancreatic interlobular septal,inflammatory cell infiltration, hemorrhage, necrosis were relieved in R group.2. The pancreatic morbid histology score.Compared to SO group,the score of AP group at each time point was significantly higher(P<0.05); while compared to AP group, the score of R group at each timepoint was significantly lower (P<0.05),but still higher than SOgroup(P<0.05);3. The changes of AMY, TNF-α, Ang II, PRA. Comparedto SO group, the above blood index in AP group at each time point wassignificantly higher (P<0.05); while compared to AP group,the aboveblood index in R group were significantly lower than in AP group at eachtime point (P<0.05), but still higher than SO group(P<0.05);4.Theexpression of NF-κ B and AT1R in pancreatic tissue. There was nosignificant changeable in the expression of SO group at different timepoints of NF-κ B and AT1R; compared to SO group, AP group and Rgroup at each time point increased (P<0.05), the above index in R groupwere lower than that in AP group at each time point (P<0.05).Conclusion:1. Aliskiren can protect acute pancreatitis in rats from inflammation andinjury;2.Ang II is the main effector molecule in RAS, which plays animportant role in the development of acute pancreatitis and the damageprocess, and can activate NF-κB signal transduction pathway,therebypromoting the synthesis and release of TNF-α and other inflammatorymediators;3.Active renin is the rate-limiting enzyme in the first link ofRAS,which can regulate the formation of Ang II.Direct renin inhibitors(aliskiren) can reduce the generation of Ang II through the inhibition of active renin,thus attenuating its role of lesion;4.Renin inhibitors (aliskiren)can also reduce the expression of NF-κB, and inhibit the inflammatorycascade effect of activated inflammatory signaling pathways.