Effects of p38MAPK inhibitor on fetal lung injury in a rat model of acute pancreatitis in late pregnancy

Objective To investigate the effect and underlying mechanisms of p38 mitogen-activated protein kinase inhibitor SB203580 on fetal lung injury in a rat model of acute pancreatitis in late pregnancy. Methods Twenty-four pregnant Sprague-Dawley rats in last gestation were randomly(random number) divided into the SO group, APILP group, and SB203580 treatment (SB) group. APILP model was induced by retrograde injection of 5% sodium taurocholate into the biliary-pancreatic duct. SB203580 administration (10 mg/kg body weight, intraperitoneal injection) was performed 0.5 h before surgery. All the rats in the SO and APILP groups received intraperitoneal injection of equivoluminal solvent at the same time point. Animals were sacrificed at 12 h after the induction of APILP, then the blood and tissue samples were harvested. Serum levels of AMY and TNF-α were analyzed. Histopathological changes of maternal pancreas and fetal lung were observed and evaluated. The expression and location of NF-κB in fetal lungs were detected by immunohistochemistry and MPO expression in fetal lungs was examined by immunofluorescence. The expression of p-p38MAPK, p38MAPK, TNF-α and ICAM-1 was determined by Western blot. One-way ANOVA and Tukey's multiple comparison tests were used for statistical analysis. Results The levels of AMY and TNF-α in maternal serum were markedly increased after APILP [(7 871.3±623.5) vs (1 915.3±452.3), (193.8±25.4) vs (107.0±13.3), (P<0.05)]. Obvious pathological changes presented in maternal pancreas and fetal lung after the attack of APILP, and their pathological scores were significantly higher than those of the SO group [(12.44±1.08) vs (1.56±0.56), (2.50±0.53) vs (0.88±0.64), (P<0.05)]. The number of NF-κB and MPO positive cells in fetal lungs were significantly higher than those in the SO group [(150.63±34.58) vs(29.50±8.80), (53.38±8.30) vs (11.75±3.33); P<0.05)]. In addition, the expression and nuclear translocation were pervasive in fetal lungs in the APILP group. Furthermore, the levels of p-p38MAPK [(0.6367±0.0386) vs (0.2282±0.0220)], TNF-α [(0.6313±0.0395) vs (0.0725±0.0076)], ICAM-1 [(0.8958±0.0776) vs (0.1372±0.0388)] and HMGB1 [(0.6478±0.0209) vs (0.2825±0.0533)] expression in fetal lungs were significantly increased after the establishment of APILP model (P<0.05). However, with the pre-administration of SB203580, the pathological scores of maternal pancreases (9.38±1.58) and fetal lungs (1.63±0.52) were decreased significantly (P<0.05), as well as the levels of AMY (4162.1±642.1) and TNF-α (139.6±21.1) in maternal serum (P<0.05). The number of NF-κB (93.00±18.88) and MPO (27.38±4.75) positive cells in fetal lungs were dramatically reduced (P<0.05) and fewer nuclear translocation was observed in the SB group. Interestingly, the expression levels of p-p38MAPK (0.2578±0.0170), TNF-α (0.3240±0.0326), ICAM-1 (0.4177±0.0823) and HMGB1 (0.4923±0.0457) in fetal lungs were markedly decreased with the treatment of SB203580 (P<0.05). Conclusions P38MAPK and its downstream inflammatory signaling pathway were involved in the process of APILP-related fetal lung injury; SB203580 administration could significantly attenuate fetal lung injury induced by APILP, which may be closely related to the inhibition of p38MAPK phosphorylation and inflammatory cascade caused by the activation of downstream signal pathways. Key words: Acute pancreatitis; Pregnancy; Fetal rat; Lung injury; Inflammation; p38MAPK, NF-κB; SB203580