Protective Effects Of Interleukin-22 On Severe Acute Pancreatitis Associated Kidney Injury In Mice

ObjectivesIn this experiment,we established severe acute pancreatitis mice models by intraperitoneal injections of L-arginine and investigated the significance of interleukin-22(IL-22)treatment.We aimed to explore the pathogenesis of severe acute pancreatitis associated kidney injury and the potential therapeutic role of IL-22 in it.Meanwhile we investigated the mechanisms of IL-22 effects and the relevant signaling pathways.Methods48 SPF male BALB/c mice were randomly divided into 4 groups(n=12):normal saline group(NS group),severe acute pancreatitis group(SAP group),IL-22 treatment group(IL-22 group)and phosphate-buffered saline group(PBS group).Severe acute pancreatitis mice were induced by intraperitoneal injection of 20%L-arginine(0.4g/kg bodyweight,twice,Ihr interval).NS group mice received intraperitoneal injection of normal saline at the same time.IL-22 group received recombinant mouse IL-22(200ng/dose,5 times,and 24h intervals)and the PBS group received same amount phosphate buffer solution at the same time point.General activity,eating behavior and survival of mice in each group were recorded.At 72 hr after injection of L-arginine,we recorded the mortality rate of mice in each group,collected blood and harvested the tissue samples including pancreas and kidney.The pathological changes of pancreas and kidney were observed under light microscope after hematoxylin-eosin staining(HE staining).Serum amylase(AMY),creatinine(Cr)and blood urea nitrogen(BUN)were measured by use of automatic biochemical analyzer.Western Blotting was used to detect protein expression of total signal transducer and activator of transcription 3(STAT3)and phosphorylated STAT3(p-STAT3)in renal tissue.The mRNA expressions of IL-22RA1,Bcl-2 and Bcl-XL in renal tissue were detected by quantitative real-time polymerase chain reaction(RT-PCR).Data were analyzed by using SPSS version 19.0 and presented as x ± s.Differences were compared by Student's t-test or Fisher's exact test.A P-value less than 0.05 was considered statistical significant.ResultsThe pancreas and kidney of NS group have no pathological changes under light microscope,HE-stained histological sections showed no pancreas or kidney damage in NS group mice.Compared with NS group,severe pancreas damage was detected in SAP group and PBS group,characterized by extensive acinar cell necrosis,interstitial edema and diffusive infiltration of inflammatory cells;renal tubular-dilatation and interstitial edema were observed;serum levels of AMY,Cr and BUN were significantly increased(P<0.05).In comparison with PBS group,the pancreatic tissue pathological damage was significantly lightened in IL-22 group;there were no obvious kidney lesion;serum AMY,Cr and BUN were significantly reduced;the mRNA expression of IL-22RA1,Bcl-2 and Bcl-XL and p-STAT3 protein in renal tissues were significantly increased(P<0.05).There were no significant differences between two groups for the total STAT3 protein expression of renal tissue.At 72 hr after the first L-arginine injection,the mortality rates for the PBS and IL-22 groups were 41.7%and 8.3%,respectively,with no statistically difference between the two groups(P=0.077)ConclusionsAdministration of high concentration L-arginine can make severe acute pancreatitis associated kidney injury models in mice.Treatment with exogenous IL-22 prevents L-arginine induced severe acute pancreatitis from becoming serious and ameliorates its kidney injury.The possible mechanism of IL-22 action is activating the STAT3 signal pathway,and then inducing the expressions of downstream anti-apoptosis genes which can maintain the stability of target cells and protect them from apoptosis.