Role of preferential cyclooxygenase-2 inhibition by meloxicam in ischemia/reperfusion injury of the rat liver.

BACKGROUND: Ischemia/reperfusion injury (IRI) is one of the major clinical problems in liver and transplant surgery. Livers subjected to warm ischemia in vivo often show a severe dysfunction and the release of numerous inflammatory cytokines and arachidonic acid metabolites. Cyclooxygenase (COX)-2 is the inducible isoform of an intracellular enzyme that converts arachidonic acid into prostaglandins. The aim of the study was to evaluate the effect of COX-2 inhibition and the role of Kupffer cells in IRI of the liver. METHODS: Male Wistar rats [250- 280 g body weight (BW)] were anesthetized and subjected to 30-min warm ischemia of the liver (Pringle's maneuver) and 60-min reperfusion after median laparotomy. The I/R group received no additional treatment. In the COX-2 inhibitor (COX-2I) group, the animals received 1 mg/kg BW meloxicam prior to operation. Gadolinium chloride (GdCl3) (10 mg/kg BW) was given 24 h prior to operation in the GdCl3 and GdCl3 + COX-2I groups for the selective depletion of Kupffer cells. The GdCl3 + COX-2I group received both GdCl3 and meloxicam treatment prior to operation. Blood and liver samples were obtained at the end of the experiments for further investigations. RESULTS: After 30 min of warm ischemia in vivo, severe hepatocellular damage was observed in the I/R group. These impairments could be significantly prevented by the selective COX-2 inhibition and the depletion of Kupffer cells. Alanine aminotransferase was significantly reduced upon meloxicam and GdCl3 treatment compared to the I/R group: I/R, 3,240 ± 1,262 U/l versus COX-2I, 973 ± 649 U/l, p < 0.001; I/R versus GdCl3, 1,611 ± 600 U/l, p < 0.05, and I/R versus GdCl3 + COX-2I, 1,511 ± 575 U/l, p < 0.01. Plasma levels of tumor necrosis factor alpha (TNF-α) were significantly reduced in the COX-2I treatment group compared to I/R (3.5 ± 1.5 vs. 16.3 ± 11.7 pg/ml, respectively; p < 0.05). Similarly, the amount of TxB2, a marker for COX-2 metabolism, was significantly reduced in the meloxicam treatment groups compared to the I/R group: I/R, 22,500 ± 5,210 pg/ml versus COX-2I, 1,822 ± 938 pg/ml, p < 0.001, and I/R versus GdCl3 + COX-2I, 1,530 ± 907 pg/ml, p < 0.001. All values are given as mean ± SD (n = 6). CONCLUSION: These results suggest that the inhibition of COX-2 suppressed the initiation of an inflammatory cascade by attenuating the release of TNF-α, which is an initiator of the inflammatory reaction in hepatic IRI. Therefore, we conclude that preferential inhibition of COX-2 is a possible therapeutic approach against warm IRI of the liver.

Changes in the fatty acid composition of the liver with the administration of N-3 polyunsaturated fatty acids and the effects on warm ischemia/reperfusion injury in the rat liver.

Prostanoids play a pivotal role among the inflammatory mediators associated with I/R injury. The aim of this study was to determine the effects of oral supplementation of n-3 polyunsaturated fatty acids (PUFA)-rich oil on inflammatory reactions and microcirculatory disorders caused by a hepatic warm I/R in rats. The rats were orally supplemented with n-3 PUFA-rich oil, n-6 PUFA-rich oil, or the same volume of water for 7 days. The PUFA concentration in the blood and liver tissues were evaluated, and the effects on I/R injury of the liver were assessed. The n-3 PUFA supplementation elevated the n-3/n-6 ratio in the blood and liver tissues. After reperfusion, thromboxane B(2) in the blood and prostaglandin E(2) in the liver were significantly suppressed in the n-3 PUFA-treated rats. Hepatic microcirculation was well maintained from the early phase (30 min) of reperfusion, and the serum concentrations of TNF-alpha and IL-6 were significantly lower in this group. The transaminase blood levels were also suppressed in the n-3 PUFA-treated rats. Expression of COX-2 mRNA was increased in all groups at 2 h after reperfusion but there were no differences among three groups. In conclusion, preoperative n-3/n-6 ratio augmentation in the blood and in the liver can result in a successful alleviation of hepatic I/R injury.