Vitamin D3 protects against prednisolone-induced liver injury associated with the impairment of the hepatic NF-κB/iNOS/NO pathway.

The study was carried out to define whether prednisolone-induced damage to hepatic cells is accompanied by excessive nitric oxide (NO) levels associated with nuclear factor kappa B (NF-κB)/inducible NO synthase (iNOS) activation and evaluate the efficacy of the treatment with vitamin D3. Histopathological examination, activities of liver transaminases (alanine aminotransferase and aspartate aminotransferase), and cell death assays consistently showed that prednisolone (5 mg/kg body weight, 30 days) induces chronic liver injury in female Wistar rats. Specifically, increased hepatocellular necrosis and caspase-3-dependent apoptosis were observed. Prednisolone enhanced iNOS protein expression, NO generation, and tyrosine nitration in liver cells. Despite unchanged hepatic level of the NF-κB/p65 protein, prednisolone increased inhibitory κB-α (IκB-α) degradation, nuclear translocation, and phosphorylation of NF-κB/p65 at Ser311, indicating that NF-κB activation can be involved in the induction of iNOS/NO. All changes were associated with a 2.9-fold decrease in the serum content of 25-hydroxyvitamin D3 and significant reduction of hepatic vitamin D3 receptor (VDR) expression that points reliably to vitamin D3 deficiency and failures in VDR signaling. Vitamin D3 co-administration (100 IU/rat, 30 days) prevented glucocorticoid-evoked abnormalities in hepatic tissue. In conclusion, prednisolone-induced liver disturbances were associated with the impairment of NF-κB/iNOS/NO responses that can be ameliorated by vitamin D3 treatment through VDR-mediated mechanisms.

Pleiotropic effects of 5-aminolevulinic acid in mouse brain.

5-Aminolevulinic acid (ALA) seems to be responsible for the neuropsychiatric manifestations of acute intermittent porphyria (AIP). Our aim was to study the effect of ALA on the different metabolic pathways in the mouse brain to enhance our knowledge about the action of this heme precursor on the central nervous system. Heme metabolism, the cholinergic system, the defense enzyme system, and nitric oxide metabolism were evaluated in the encephalon of CF-1 mice receiving a single (40 mg/kg body mass) or multiple doses of ALA (40 mg/kg, every 48 h for 14 days). We subsequently found ALA accumulation in the encephalon of the mice. ALA also altered the brain cholinergic system. After one dose of ALA, a decrease in superoxide dismutase activity and a reduction in glutathione levels were detected, whereas malondialdehyde levels and catalase activity were increased. Heme oxygenase was also increased as an antioxidant response to protect the encephalon against injury. All nitric oxide synthase isoforms were induced by ALA, these changes were more significant for the inducible isoform in glial cells. In conclusion, ALA affected several metabolic pathways in mouse encephalon. Data indicate that a rapid response to oxidative stress was developed; however, with long-term intoxication, the redox balance was probably restored, thereby minimizing oxidative damage.

Distant effects of unilateral renal ischemia/reperfusion on contralateral kidney but not lung in rats: the roles of ROS and iNOS.

Acute kidney injury is usually associated with distant organ dysfunction. The roles of inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS) in this phenomenon were investigated following 2 h unilateral renal ischemia and 24 h reperfusion. There were 3 groups of rats subjected to either unilateral ischemia/reperfusion (UIR group), unilateral nephrectomy (UNX group), or sham operation. Two further groups were given α-tocopherol and aminoguanidine with UIR (treated-UIR group) and UNX (treated-UNX group). Plasma nitrite/nitrate and malondialdehyde were elevated only in the UIR group. Creatinine clearance and blood flow increased in non-ischemic kidney of the UIR, but not to the same extent as remnant kidney of the UNX group, while they had equal compensatory rises in absolute Na(+) and K(+) excretion and urine flow. Non-ischemic kidney of the treated-UIR group, but not remnant kidney of the treated-UNX group, showed more elevation in blood flow, whereas both kidneys had reductions in absolute Na(+) excretion and urine flow. Respiratory functional variable were not different between all groups. Therefore, 2 h unilateral renal ischemia and 24 h reperfusion did not affect lung but had distant effects on contralateral kidney partly mediated by ROS and NO-derived from iNOS to dampen compensatory increases in renal hemodynamics and to decrease tubular reabsorption.

Jak2/Stat1 pathway mediated tetrahydrobiopterin up-regulation contributes to nitric oxide overproduction in high-glucose cultured rat mesangial cells.

Nitric oxide (NO) is crucial for the progression of early diabetic nephropathy (DN). It is important to clarify the mechanism for the production of NO in mesangial cells (MCs). In this study, the amounts/activities of related factors such as reactive oxygen species (ROS), NO, 3 isoforms of nitric oxide synthase (NOS), tetrahydrobiopterin (BH4), GTP cyclohydrolase I (GTPCH I), Jak2, and Stat1 were determined using high-glucose cultured rat MCs. The results showed that the production of BH4 under oxidative stress was strongly stimulated by its rate-limiting enzyme GTP cyclohydrolase, which increased the expression and activity of inducible NOS to facilitate NO synthesis. Furthermore, the relative quantities of activated-Jak2 and activated-Stat1 were increased. Therefore, Jak2/Stat1 pathway mediated BH4 up-regulation can contribute to excessive NO in high-glucose cultured MCs. Our results will be helpful for screening new targets to improve the therapy for early DN.