Role of EP4 prostaglandin E2 receptor in the ischemic liver.

Prostaglandin E(2) (PGE(2)) mediates a variety of both innate and adaptive immunity responses through 4 distinct receptors, EP1-4. Recent studies have suggested the physiological and pathological role of EP4 in various inflammatory diseases. In this study, we investigated the importance of the EP4 receptor, and the efficacy of a selective EP4 agonist to alter hepatic ischemia/reperfusion (I/R) injury, an important cause of damage in liver resection and transplantation. We used an established murine I/R injury model, 70% partial hepatic ischemia for 90 minutes in male C57BL/6 mice. The local expression of EP4 messenger RNA (mRNA) in the naive and the ischemic liver at 2 hours after reperfusion was examined using RT-PCR analysis. Some mice received the EP4 selective agonist during I/R. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were measured as markers of hepatic injury. EP4 expression in the liver was significantly up-regulated at 2 hours after reperfusion. Furthermore, treatment with EP4 agonist significantly inhibited hepatic injury at 6 hours after reperfusion. Our data suggest an inhibitory role of EP4 PGE(2) receptor in hepatic I/R injury and the therapeutic efficacy of a selective EP4 agonist for liver protection.

Effect of the aldose reductase inhibitor fidarestat on experimental diabetic neuropathy in the rat.

AIMS/HYPOTHESIS: Fidarestat, an aldose reductase inhibitor (ARI), has been reported to improve clinical symptoms and nerve conduction deficits in human diabetic neuropathy. We evaluated the dose-dependency and some of the mechanisms of the drug action in experimental diabetic neuropathy (EDN). METHODS: Control rats and rats with EDN were fed on normal pellets or pellets containing 0.00066% (1 mg/kg) or 0.00263% (4 mg/kg) fidarestat for 10 weeks. We evaluated the effect of fidarestat on nerve blood flow (NBF), electrophysiology, and sorbitol and fructose content in sciatic nerve in control and diabetic rats. For detection of oxidative stress in peripheral nerve, we measured sciatic nerve reduced glutathione (GSH) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) immunolabelling of dorsal root ganglion (DRG) neurons. RESULTS: NBF, compound muscle action potential and amplitude of C-potential were significantly improved in diabetic rats fed on the diet supplemented with fidarestat. Fidarestat suppressed the increase in sorbitol and fructose, normalised GSH in sciatic nerve, and reduced the number of 8-OHdG-positive cells in DRG. CONCLUSIONS/INTERPRETATION: Fidarestat improves neuropathy, presumably via an improvement in oxidative stress. This study supports a role for fidarestat in the treatment of diabetic neuropathy.