Sodium Nitroprusside Regulates mRNA Expressions of LTC4 Synthesis Enzymes in Hepatic Ischemia/Reperfusion Injury Rats via NF-κB Signaling Pathway

Abstract

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 µg/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 µg/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-ĸB p65, p50 and IĸBα 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-ĸB 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 µg/kg/min) + I/R groups when compared with those in the I/R group. SNP (2.5 µg/kg/min) promoted the mRNA expressions of both MGST2 and MGST3, whereas SNP (10 µg/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 µg/kg/min) + I/R group, MGST3 mRNA was significantly declined in the SNP (5 and 10 µg/kg/min) + I/R groups. Immunohistochemistry staining revealed that I/R liver exhibited strong cytoplasmic and nuclear staining for NF-ĸB p65, but the livers of the SNP (2.5 µg/kg/min) + I/R group presented slight cytoplasmic and nuclear staining. But IĸBα protein in all groups remains unchanged. It was concluded that SNP downregulated LTC4S mRNA expression by inhibiting NF-ĸB activation independent of IĸBα, but appeared to have a dual influence on the mRNA expressions of MGST2 and MGST3 by other signaling pathways during hepatic I/R injury.

Leukotrienes Produced in Allergic Lung Inflammation Activate Alveolar Macrophages

“…In fact, the relationship between nitric oxide (NO) and cysteinyl LTs has been demonstrated in previous studies. Yang et al [40] have shown that sodium nitroprusside, a nitric oxide donor, down-regulates the mRNA expression of LTC 4 synthesis enzymes in hepatic ischemia/ reperfusion injury in rats via the NF-kappaB signaling pathway. Our results are consistent with those of Ko and Cho [41], who observed a reduction in the level of LTC 4 after administration of L-NAME (an inhibitor of nitric oxide synthesis).…”

Role of nitric oxide in hepatic ischemia-reperfusion injury

“…The main limitation of organic nitrates is the induction of drug tolerance with prolonged continuous use. NO release from nitroglycerin is likely via the enzyme, mitochondrial aldehyde dehydrogenase [53] . The mechanism of NO release from sodium nitroprusside, on the other hand, is more complex, as demonstrated by Yang et al [53] in a murine model of hepatic IRI.…”

“…NO release from nitroglycerin is likely via the enzyme, mitochondrial aldehyde dehydrogenase [53] . The mechanism of NO release from sodium nitroprusside, on the other hand, is more complex, as demonstrated by Yang et al [53] in a murine model of hepatic IRI. Sodium nitroprusside is thought to down-regulate the mRNA expression of several enzymes related to hepatic injury [54] .…”

The Influences of Nitric Oxide on Liver Ischemia-Reperfusion Injury

“…The main limitation of organic nitrates is the induction of drug tolerance with prolonged continuous use. NO release from nitroglycerin is likely via the enzyme mitochondrial aldehyde dehydrogenase (Yang, Chen, Kong, Xu, & Lou, 2007). On the other hand, the mechanism of NO release from sodium nitroprusside is more complex as demonstrated by Yang et al in a murine model of hepatic IRI.…”