Effect of low molecular weight heparin on the expressions of TLR4 and VEGF expression in severe acute pancreatitis combined with lung injury

Abstract

Objective To investigate the effect of low molecular weight heparin on lung Injury complicated by severe acute pancreatitis and explore its mechanism. Methods Ninety Wistar rats were randomly divided into 3 groups, namely sham operation (SO) group, acute necrotizing pancreatitis (ANP) group, low molecular weight heparin treatment (LH) group. 4% sodium taurocholate was injected into the pancreatic duct to induce ANP model. Subcutaneous low molecular weight heparin (10 U/100 g body weight) was injected in the LH group, the equivalent amount of normal saline was injected in the SO and ANP group. After 6, 12, 24 h, rats were sacrificed respectively, pancreas and lung tissues were harvested to observe the pathological changes and the pathological changes were scored; and the changes of TLR4 and VEGF protein expression in lung tissue was determined by immunohistochemical method. Serum and lung levels of IL-6, IL-10, TNF-α were determined by ELASA method. Results The pancreas and lungs tissues were normal in SO group, diffuse hemorrhage, necrosis and a large number of inflammatory cells infiltration was observed in pancreas tissue in ANP group. Lung alveolar wall rupture, interstitial hyperemia, edema, a large number of infiltrating neutrophils could be seen in lung tissue in ANP group. The pancreas and lungs tissues injuries were significantly alleviated. The pancreas and lungs pathological scores of ANP group at 12 h were 6.34±1.09, 7.01±1.16, and those were 5.48±0.86, 6.24±0.86 in LH group, the values in LH group were significantly lower than those in ANP group (P<0.05), and there was a positive association between lung and pancreas scores (r=0.812, P<0.01). The expressions of TLR4, VEGF, IL-6, TNF-α, IL-10 in lung tissue of ANP group at 12 h were 0.68±0.10, 0.50±0.11 and (2617.2±485.3), (1603.1±519.7), (608.3±137.5)pg/g, which were 0.61±0.09, 0.41±0.06 and (2398.5±503.7), (1302.4±389.8), (753.2±100.0)pg/g in LH group, and the expressions of TLR4, VEGF, IL-6, TNF-α in LH group were significantly lower than those in ANP group, but the expression of IL-10 was significantly up-regulated, and the difference between the two groups was statistically significant (P<0.05). The serum levels of IL-6, TNF-α, IL-10 in ANP group at 12 h were (184.3±45.7), (289.7±60.4), (143.2±30.4)μg/L, which were (143.8±31.8), (256.4±40.7), (189.3±50.9)μg/L in LH group, and the levels of IL-6, TNF-α in LH group were significantly lower than those in ANP group, but the expression of IL 10 was significantly increased, and the difference was statistically significant (P<0.05). The expression of TLR4, VEGF in lung tissue was positively associated with the degree of lung injuries (r=0.524, 0.503, P<0.05). Conclusions Low molecular weight heparin may improve lung injury complicated by ANP. The mechanism may involve inhibiting the expression of TLR4 and VEGF protein, IL-6, TNF-α, and up-regulation of the expression of IL-10. Key words: Pancreatitis, acute necrogizing; Heparin, low-molecular-weight; Lung injury; Toll-like receptor 4; Vascular endothelial growth factor