Objectives: To explore the role of TLR4 in the mechanism of hepatic ischemia/reperfusion (I/R) injury in mice.
Methods: 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.
Results: 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).
Conclusions: 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.