Objective:To discuss the possible mechanism of lipopolysaccharide(LPS) pretreatment in alleviating acute pancreatitis (AP) in rats by detecting the changes in expressions of interleukin-1 receptor associated kinase 4(IRAK-4) in the pancreas. Methods: Sixty three male Sprague-Dawley rats were divided randomly into three groups:sham group

acute pancreatitis group (AP group) and LPS pretreatment group(LPS group). LPS was injected intraperitoneally to the rats in LPS group while equal amount of normal saline was injected to the rats in the other two groups. Samples were achieved at 3 h after the model was built in sham group while at 3

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12 h and 24 h after modeling in the other two groups. The morphology of pancreatic tissue was analyzed by light microscopy respectively. The expressions of IRAK-4 gene and protein level of pancreas were determined by reverse RT-PCR and western blot

the activities of NF-κB were detected by immunohistochemical method and the serum TNF-α level was estimated by ELISA.Results: The pathological damage was most serious in AP group

followed by LPS group and sham group. The expressions of IRAK-4 mRNA and protein in AP group reached the peak at 12 h then decreased. The expressions of IRAK-4 mRNA and protein were obviously lower in LPS group and were maintained a lower level (P>0.05) compared with those in AP group after the pretreatment (P<0.01).The activities of NF-κB and the level of serum TNF-α were obviously lower in LPS group compared with those in AP group at all time periods (P<0.01)

both group reaching the peak simultaneously at 12 h(P<0.01). Conclusion: Down-regulating the expression of IRAK-4

NF-κB and TNF-α may be one of the protective mechanisms of LPS pretreatment for AP.