The Effects And Potential Mechanisms Of PI3K/Akt Signaling Transduction Pathway In Rats With Early-stage Severe Acute Pancreatitis

ObjectiveIn the early stage of severe acute pancreatitis, monocytes/macrophages are activated under the stimulation of various injury factors, and release a large number of pro-inflammatory cytokines. Multiple pro-inflammatory cytokines(TNF-?, IL-1?, IL-6, etc.) play an important role in the occurrence and development of severe acute pancreatitis. Studies shows that the activation of NF-?B and p38 MAP kinase signaling pathway is an early and critical event in SAP. Production of pro-inflammatory cytokines are related to the activation of NF-?B and p38 MAPK pathway.We have found that NF-?B and p38 MAPK signaling pathway can be activated and play a significant role in the SAP by the release of massive cytokines.In recent years, the role of cell responses such as inflammation and stress mediated by phosphatidylinositol 3-kinase/ser-ine threonine kinase(PI3K/Akt) signaling pathway in the occurrence and development of acute pancreatitis has aroused widespread interest. Some research has shown that the expression and release of cytokines is associated with abnormal activation of PI3K/Akt signal pathway during SAP and PI3K/Akt pathway plays a role in systemic inflammatory response induced by SAP. While inhibition of PI3K/Akt signaling pathway's activation can significantly reduce inflammatory response of SAP, but the mechanism was still not clear. In this study, we observe the expression of PI3K/Akt signal transduction pathway in pancreatic tissue at the early stages of SAP. And we inhibit PI3K/Akt signal transduction pathway to research the effects on the transcription and expression of cytokines(TNF- ?, IL-1 beta, IL-6) and pathological scores of pancreatic tissue, to investigate the role of PI3K/Akt pathway in the activation of NF-?b and p38 MAPK pathways, and to clarify the effects of PI3K/Akt signaling pathway and its possible mechanisms during the early stages of severe acute pancreatitis.MethodsPart One: Sixty male Sprague-Dawley(SD) rats were randomly divided into five groups, including SAP group, sham operation group, normal saline group, DMSO control group, wortmannin group. The modified Aho's method was used to reproduce the SAP model. The rats were sacrificed 3 and 6 h after treatment. The levers of inflammatory cytokines TNF-?, IL-1? and IL-6 in serum were examined by ELISA.Transcription levers of these inflammatory cytokines in pancreatic tissue were determined by real-time PCR. In addition, the amount of serum amylase, the activities of serum amylase and ascites amylase, and the pathological scores of pancreatic tissue were also measured.Part Two: Seventy-two male Sprague-Dawley(SD) rats were randomly divided into three groups, including SAP group, sham operation group, wortmannin group. The modified Aho's method was used to reproduce the SAP model. The rats were sacrificed 3 and 6 h after treatment. The levers of inflammatory cytokines TNF-?, IL-1? and IL-6 in serum were examined by ELISA. Transcription levers of Akt, p38 MAPK and NF-?Bp65 in pancreatic tissue were determined by real-time PCR. Protein expression and phosphorylation of Akt, p38 MAPK, NF-?B p65 were detected by Western blot. In addition, the activities of serum amylase and pathological scores of pancreatic tissue were measured.ResultsPart One: After 3 and 6 h after treatment,all parameters tested, including the amount of ascites, the levels of serum and ascites amylase, the pathological scores of pancreatic tissue, serum levels of TNF-?, IL-1? and IL-6, and the transcription levels of TNF-?, IL-1?and IL-6 m RNAs in the pancreatic tissue in SAP group and DMSO group were significantly higher than those in the normal saline group and sham operation group(all P<0.05). Compared to the SAP group and DMSO group, The above parameters decreased significantly in the wortmannin group(all P<0.05).Part Two: After 3 and 6 h after treatment,all parameters tested, including the levels of protein phosphorylation of Akt, p38 MAPK, NF-?B p65, the transcription levels of Akt ?p38MAPK and NF-?Bp65 m RNAs in the pancreatic tissue,serum levels of TNF-?, IL-1? and IL-6,the levels of serum amylase, the pathological scores of pancreatic tissue in SAP group were significantly higher than those in sham operation group(all P<0.05). Compared to the SAP group, the above parameters decreased significantly in the wortmannin group(all P<0.05).ConclusionPI3K/Akt signaling transduction pathway induces the activation of p38 MAPK and NF-?B pathway, affects the transcription and expression of cytokines during severe acute pancreatitis(SAP), plays an important role in the early-stage inflammatory response in rats with SAP. By inhabiting PI3K/Akt signaling transduction pathway, the severity of inflammatory response of SAP is attenuated through down-regulateing the activation of Akt?p38MAPK and NF-?B and decreaseing the transcription and expression of cytokines(TNF-??IL-1? and IL-6).