Sodium nitroprusside regulates mRNA expressions of LTC4 synthesis enzymes in hepatic ischemia/reperfusion injury rats via NF-kappaB signaling pathway

Leukotriene (LT) C4 (LTC4) synthesis enzymes including LTC4 synthase (LTC4S), microsomal glutathione S-transferase (MGST) 2 and MGST3 can all conjugate LTA4 and reduced glutathione (GSH) to form LTC4, which is related to hepatic ischemia/reperfusion (I/R) injury. The relationship between nitric oxide (NO) and cysteinyl LTs has been shown in previous studies. However, the mechanisms of NO action on gene expression of LTC4 synthesis enzymes are still largely unclear during hepatic I/R. Adult male Sprague-Dawley rats were divided into 5 groups: a sham group (control), an I/R group, and sodium nitroprusside (SNP, 2.5, 5 and 10 microg/kg/min)+I/R groups. Livers were subjected to 60 min of partial hepatic ischemia followed by 5 h of reperfusion, saline or SNP (2.5, 5 and 10 microg/kg/min) administered intravenously. The mRNA levels of LTC4 synthesis enzymes, inducible NO synthase (iNOS) and endothelial No synthase (eNOS) in rat liver tissue were examined by RT-PCR; the protein expressions of NF-kappaB p65, p50 and IkappaBalpha in liver cell lysates and nuclear extracts were detected by Western blot analysis, and serum NO2. levels were also evaluated. Serum NO2. levels, the protein expressions of NF-kappaB p65 and p50 in the nucleus extract, and hepatic mRNA expressions of LTC4S and iNOS were decreased while hepatic mRNA of eNOS was increased in the SNP (5 and 10 microg/kg/min)+I/R groups when compared with those in the I/R group. SNP (2.5 microg/kg/min) promoted the mRNA expressions of both MGST2 and MGST3, whereas SNP (10 microg/kg/min) increased MGST2 mRNA but decreased MGST3 mRNA compared to those in I/R group. Compared with control, the mRNA expression of MGST2 and MGST3 were elevated in SNP (2.5 microg/kg/min)+I/R group, MGST3 mRNA was significantly declined in the SNP (5 and 10 microg/kg/min)+I/R groups. Immunohistochemistry staining revealed that I/R liver exhibited strong cytoplasmic and nuclear staining for NF-kappaB p65, but the livers of the SNP (2.5 microg/kg/min)+I/R group presented slight cytoplasmic and nuclear staining. But IkappaBalpha protein in all groups remains unchanged. It was concluded that SNP downregulated LTC4S mRNA expression by inhibiting NF-kappaB activation independent of IkappaBalpha, but appeared to have a dual influence on the mRNA expressions of MGST2 and MGST3 by other signaling pathways during hepatic I/R injury.