Objective:To evaluate the role of monocyte chemoattractant protein-induced protein-1 (MCPIP-1) in acute lung injury in septic rats.Methods:Forty-eight healthy male Sprague-Dawley rats, aged 8-12 weeks, weighing 230-270 g, were divided into 6 groups ( n=8 each) using the random number table method: sham operation group (S group), different doses of ubiquitin-proteasome inhibitor groups (M 1 and M 2 groups), cecal ligation and perforation (CLP) group, and different doses of ubiquitin-proteasome inhibitor + CLP groups (M 1-CLP and M 2-CLP group). Sepsis was induced by CLP in anesthetized animals.Ubiquitin-proteasome inhibitor MG-132 5 and 10 mg/kg were intraperitoneally injected at 30 min before sham operation in M 1 and M 2 groups, respectively.MG-132 5 and 10 mg/kg were intraperitoneally injected at 30 min before CLP in M 1-CLP and M 2-CLP groups, respectively.The rats were sacrificed at 6 h after operation, bronchoalveolar lavage (BALF) was collected for determination of the concentrations of tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β) and IL-6 in BALF (by enzyme-linked immunosorbent assay) and lung tissues were obtained for microscopic examination of pathological changes which were scored and for determination of wet/dry lung weight ratio (W/D ratio) and expression of MCPIP-1 protein and mRNA (by Western blot and real-time polymerase chain reaction). Results:Compared with S group, the lung injury scores, W/D ratio, and concentrations of TNF-α, IL-1β and IL-6 in BALF were significantly increased in CLP group ( P<0.05), and no significant changes were found in the parameters mentioned above( P>0.05), and the expression of MCPIP-1 protein and mRNA in lung tissues was significantly up-regulated in M 1 and M 2 groups ( P<0.05), and no significant change was found in the expression of MCPIP-1 protein and mRNA in lung tissues in CLP group ( P>0.05). Compared with CLP group, the lung injury scores, W/D ratio, and concentrations of TNF-α, IL-1β and IL-6 in BALF were significantly decreased, and the expression of MCPIP-1 protein and mRNA in lung tissues was up-regulated in M 1-CLP and M 2-CLP groups ( P<0.05). Conclusions:MCPIP-1 exerts an endogenous protective mechanism during acute lung injury in septic rats.