Protection against hepatic ischemia/reperfusion injury via downregulation of toll-like receptor 2 expression by inhibition of Kupffer cell function

AIM: To elucidate the mechanism of liver protection by inhibition of Kupffer cells (KCs) function. METHODS: All the animals were randomly divided into three groups. Blockade group (gadolinium chloride solution (GdCl3) injection plus ischemia/reperfusion (I/R) injury): GdCl3 solution was injected once every 24 h for 2 d via the tail vein before I/R injury. Non-blockade group (saline solution injection plus I/R injury): saline instead of GdCl3 as a control was injected as in the blockade group. Sham group: saline was injected without I/R injury. Liver samples were collected 4 h after blood inflow restoration. The blockade of the function of KCs was verified by immunostaining with an anti-CD68 mAb. Toll-like receptor 2 (TLR2) was immunostained with a goat antimouse polyclonal anti-TLR2 antibody. Membrane proteins were extracted from the liver samples and TLR2 protein was analyzed by Western blot. Portal vein serum and plasma were taken respectively at the same time point for further detection of the levels of tumor necrosis factor-alpha (TNF-alpha) and alanine aminotransferase (ALT), an indicator of liver function. RESULTS: Compared to non-blockade group, CD68+ cells significantly reduced in blockade group (OPTDI, optical density integral): 32.97+/-10.55 vs 185.65+/-21.88, P<0.01) and the liver function impairment was relieved partially (level of ALT: 435.89+/-178.37 U/L vs 890.21+/-272.91 U/L, P<0.01). The expression of TLR2 protein in blockade group significantly decreased compared to that in non-blockade group (method of immunohistochemistry, OPDTI: 75.74+/-17.44 vs 170.58+/-25.14, P<0.01; method of Western blot, A value: 125.89+/-15.49 vs 433.91+/-35.53, P<0.01). The latter correlated with the variation of CD68 staining (r = 0.745, P<0.05). Also the level of portal vein TNF-alpha decreased in blockade group compared to that in non-blockade group (84.45+/-14.73 ng/L vs 112.32+/-17.56 ng/L, P<0.05), but was still higher than that in sham group (84.45+/-14.73 ng/L vs 6.07+/-5.33 ng/L, P<0.01). CONCLUSION: Inhibition of the function of KCs may protect liver against I/R injury via downregulation of the expression of TLR2.