Role Of P38MAPK In Pathogenesis Of Severe Acute Pancreatitis In Rats And The Effect Of Pioglitazone On Its Activity

Objective: To study the role of p38MAPK signal in the pathogenesis of severe acute pancreatitis in rats, and effect of pioglitazone,a ligand of peroxisome proliferator-activated receptor gamma, on the activity of p38MAPK.METHODS: 54 male Sprague-Dawley rats (160-200g weight) were randomly allocated into three groups: sham group; pretreatment with pioglitazone group(P group); SAP group. The model of SAP was induced by the retrograde injection of 5% sodium taurocholate in the pancreatic duct, 10% dimethyl sulphoxide (DMSO) was injected intraperitoneally two hours prior to STC; but which was replaced by pioglitazone(50mg/kg) in P group.Sham-operated animals was executed operation, but nothing was injected, pancreas was just flipped and striked gently a few times.Rats were killed by abdominal aorta exsanguination at 3h, 6h and 12h after pancreatitis induced.The levels of serum and ascitic amylase were measured,other blood serum for ELISA assay was restored at -80℃, pancreatic tissue,pancreas was divided into two parts:one for immunohistochemistryIMH) was fixed in 4% formalin,anther for western blotting was rapidly frozen in liquid nitrogen and then restored at -80℃.The activity of p38MAPK was tested by western blotting,,the expression of pancreatic PPARγprotein was examinated by IMH, and observed the effects of pioglitazone on themRESULTS:1.Levels of serum amylase:The levels of serum amylase rapidly rised in SAP group compared with sham group, which was decreased significantly in P group at 6,12h compared with SAP group(P<0.05).2.Levels of ascitic amylase: No ascites was found in sham group.There were no significant differences between P group and SAP group at all pionts(P>0.05).3.Pancreatic macroscopic score: The scores of SAP group were obviously increased compared with sham group(P<0.01). Pretreatment with pioglitazone reduced pancreatic scores compared with SAP group at 6h,12h (P<0.05).4.Pancreatic histologic score: The scores were significantly elevated in SAP group compared with sham group (P<0.01),which were decreased by pioglitazone at 6h,12h(P<0.05).5.Levels of serum TNF-α:The levels of TNF-αin SAP group were significantly higher than sham group at all points after pancreatitis,which were reduced by adiministration of pioglitazone (P<0.05).6. The activity of p38 MAPK: p38 MAPK was rapidly activited after pancreatitis induced much higher than sham group(P<0.01),which was down regulated significantly by pioglitazoneat at 3h, 6h (P<0.05). 7. Expression of pancreatic PPARγprotein:The positive stains mainly located in cytoplasm of pancreatic acinar which was weaker in sham group.The expressions of PPARγprotein were significantly increased after SAP induced compared with sham group at 6, 12h(P<0.05), but there were no obvious differences between P group and sham group (P>0.05).Conclusions:The signal of p38 MAPK was rapidly activated and lasted for 12 hours after operation in early stage of SAP,which was well associated with the progress and aggravation of SAP;Pioglitazone played a protective role by inhibiting p38MAPK activation and attenuating inflammatory response,which maybe a critical contrbutor to its antiinflammoty role.