Tetrahydrobiopterin ameliorates hepatic ischemia-reperfusion Injury by coupling with eNOS in mice

In the liver, eNOS appears to have a central role in protecting against ischemia/reperfusion (I/R) injury. We hypothesized that tetrahydrobiopterin (BH4) would protect livers subjected to I/R injury by coupling with eNOS.

Chinese Kun Ming (KM) mice were subjected to 60 min of 70% hepatic ischemia 30 min after the administration of BH4 or saline. After reperfusion, survival was evaluated. The histologic appearance and ALT, BH4, nitrite/nitrate, 8-isoprostane, and eNOS protein expression levels were measured.

The 1-wk survival rate was 66.67% in the BH4 group and 33.33% in the saline group. The serum ALT values in the BH4 group 1, 3, 6, 12, and 24 h after reperfusion were significantly lower than those of the saline group. A histologic examination of the liver revealed only a small necrotic area in the BH4 group as opposed to massive necrosis in the saline group. The percentage values of the hepatic necrotic area 24 h after reperfusion were significantly less for the BH4 group than for the saline group. The nitrite/nitrate levels in the liver tissue were significantly increased by ~2-fold in the BH4 group compared with the saline group. The free radical indicator 8-isoprostane was reduced approximately 50% in the BH4 group compared with the saline group. Western blotting showed that the level of eNOS protein between the groups was not significantly different.

BH4 significantly improved the survival rate by reducing liver failure. This was supported by the histologic findings, and the mechanism was explored. According to the results, we suggest that BH4 prevents liver damage from I/R injury by attenuating reactive oxygen species and increasing NO synthesis, and might provide a novel and promising therapeutic option for preventing I/R injury.