[TLR4 is involved in hepatic ischemia/reperfusion injury in mice]

To explore the role of TLR4 in the mechanism of hepatic ischemia/reperfusion (I/R) injury in mice.

Wild-type (C3H/Heouj) mice and TLR4 deficient mice (C3H/Hej) were used to prepare the models of liver I/R injury. Partial hepatic ischemia was produced by inflow causing occlusion in the median and left lobes for 45 minutes. Blood was drawn to kill the mice at 1 hours and 3 hours after reperfusion. The blood was used to analyze aspartate aminotransferase (AST) and tumor necrosis factor-alpha (TNFalpha). TNF-alpha mRNA expression and myeloperoxidase (MPO) level in ischemic lobes was examined by northern blot and myeloperoxidase assay, respectively.

AST levels were significantly lower in TLR4 deficient mice, compared with those in wild-type mice at both time points (661.83U/L+/-106.09U/L vs. 1215.5U/L+/- 174.03U/L, t=-6.65, P<0.01; 1145.17U/L+/-132.42U/L vs. 2958.17U/L+/-186.81U/L, t=-5.57, P<0.01). Serum TNF-alpha level was lower in TLR4 deficient mice at 3 hours after reperfusion compared with that in wild-type mice (152.39pg/ml+/-43.3 pg/ml vs. 249.12pg/ml+/-51.89pg/ml, t=-3.13, P<0.05). This difference appeared to be mediated at the gene level, since TNF-alpha mRNA expression had decreased in TLR4 deficient mice at 1 hours after reperfusion, compared with that in wild type mice (80.3+/-28.8 vs. 189.4+/-24.6, t=-3.25, P<0.05). MPO level in ischemic lobes in TLR4 deficient mice at 3 hours after reperfusion was significantly lower than that in wild type mice (F=33.49, P<0.01).

I/R hepatic injury in TLR4 deficient mice is less than that in wild-type mice. TNF-alpha expression down-regulated at the mRNA level appears critical. These suggest that TLR4 be involved in the mechanism of hepatic ischemia/reperfusion injury in mice.