Effect of phenobarbital on hepatic cell proliferation and apoptosis in mice deficient in the p50 subunit of NF-kappaB

Evaluation of ameliorating effect of lycopene against testicular toxicity due to diethylnitrosamine using biochemical, spermatological and histopathological data

The aim of this study was to evaluate the possible therapeutic or protective effects of lycopene on diethylnitrosamine (DEN)-induced testicular lipid peroxidation and on the associated changes in spermatological parameters and histopathological architecture of rat testis. DEN is a carcinogenic substance that can be derived from chemicals used in agriculture, such as insecticides and nitrate. The rats were assigned to control, lycopene, DEN(1), DEN(2), lycopene + DEN(1), lycopene + DEN(2), DEN(1) + lycopene and DEN(2) + lycopene groups. During the study, lycopene was administered by oral gavage at a dose of 10 mg kg^-1  bw^-1 every other day for 10 days and DEN was administered at a dose of 200 mg  kg^-1  bw^-1 as a single dose intraperitoneally. DEN was applied for 30 days in group DEN(1) and for 90 days in group DEN(2). Malondialdehyde (MDA) and reduced glutathione (GSH) levels, antioxidant enzymes activities, spermatological parameters, the weight of the reproductive organs (v. seminalis, prostate, testis and epididymis) and the histopathological structure were determined. MDA levels significantly increased, while GSH and antioxidant enzymes' activities decreased in DEN groups (p < 0.001). There was an increase in the rate of abnormal spermatozoa and a decrease in sperm density and motility, and reproductive organ weight (the weight of the right and left testis) in both DEN groups. Lycopene has normalised biochemical and spermatological parameters and reproductive organ weight. The histopathological examination of testicular tissue showed that the most significant histopathological change in DEN groups was the seminiferous tubule dilatation. These results suggest that besides the protective effects, the therapeutic effect of lycopene is possibly due to its antioxidant effects on DEN-induced testicular toxicity.

Mutant DD genotype of NFKB1 gene is associated with the susceptibility and severity of coronary artery disease

Nuclear factor κappa B (NF-κB) is an important transcription factor in the development and progression of coronary artery disease (CAD). Recent evidence suggests that -94 ATTG ins/del mutant in the promoter of NFKB1 gene is an essential functional mutant. The present study demonstrated the frequencies of the del/del (DD) genotype and del (D) allele were significantly higher in CAD patients than in controls. CAD patients carrying mutant DD genotype had worse stenosis of diseased coronary arteries compared to those carrying ins/ins (II) or ins/del (ID) genotype. Plasma levels of endothelial nitric oxide synthase (eNOS) were lower, while inflammatory cytokine incnterlukin-6 (IL-6) was higher in CAD patients with DD genotype than those with II or ID genotype (both P<0.05). In vitro study showed that mutant human umbilical vein endothelial cells (DD genotype HUVECs) were more susceptible to H₂O₂-induced apoptosis, which was accompanied with a decreased Bcl-2 expression. Further, mutant HUVECs had lower eNOS but higher IL-6 mRNA levels and decreased phosphorylation of eNOS under H₂O₂-stimulation (both P<0.05). Compared to wild type cells (II genotype), significantly downregulated protein expression of total NF-κB p50 subunit were observed in mutant HUVECs with or without oxidative stress, and a lower expression of unclear p50 was associated with a decreased p50 nuclear translocation in mutant HUVECs versus wild type cells under H₂O₂-stimulation (both P<0.05). In conclusion, mutant DD genotype of NFKB1 gene is associated with the risk and severity of CAD. Dwonregulation of NF-κB p50 subunit leads to exacerbated endothelial dysfunction and apoptosis and enhanced inflammatory response that is the potential underlying mechanism.

Effect of vitamin E on hepatic cell proliferation and apoptosis in mice deficient in the p50 subunit of NF-κB after treatment with phenobarbital

Phenobarbital (PB) is an efficacious and well-studied hepatic tumor promoting agent. Nuclear factor-κB (NF-κB) is a transcription factor activated by reactive oxygen and is involved in cell proliferation and apoptosis. We previously found that PB activates NF-κB and that dietary vitamin E is effective in decreasing PB-induced NF-κB DNA binding. We therefore hypothesized that dietary vitamin E influences PB-induced changes in cell proliferation and apoptosis through its action on NF-κB. NF-κB1 deficient mice (p50-/-) and wild-type B6129 mice were fed a purified diet containing 10 or 250ppm vitamin E (α-tocopherol acetate) for 28days. At that time, half of the wild-type and half of the p50-/- mice were placed on the same diet with 0.05% PB for 10days. Compared to wild-type mice, the p50-/- mice had higher levels of cell proliferation and apoptosis. Cell proliferation was significantly increased by PB, but vitamin E did not affect hepatic cell proliferation. Apoptosis was not changed in mice fed PB, and there was no significant difference in apoptosis between control and high vitamin E treated mice. Thus, vitamin E does not appear to influence cell growth parameters in either wild-type or p50-/- mice.

Inactivation of NF-kappaB p50 leads to insulin sensitization in liver through post-translational inhibition of p70S6K

In this study, we investigated the metabolic phenotype of the NF-kappaB p50 knock-out (p50-KO) mice. Compared with wild type mice, the p50-KO mice had an increase in food intake, but a decrease in body fat content. On chow diet, their blood glucose dropped much more than the wild type (WT) mice in the insulin tolerance test. Their glucose infusion rate was 30% higher than that of the WT mice in the hyperinsulinemic-euglycemic clamp. Their hepatic glucose production was suppressed more actively by insulin, and their insulin-induced glucose uptake was not altered in skeletal muscle or adipose tissue. In the liver, their p70S6K (S6K1) protein was significantly lower, and tumor necrosis factor-alpha (TNF-alpha) expression was much higher. Their S6K1 protein was reduced by TNF-alpha treatment in the primary culture of hepatocytes. S6K1 reduction was blocked by the proteasome inhibitor MG132. In their livers, IKK2 (IKKbeta) activity was reduced together with IKKgamma. Their S6K1 degradation was dependent on IKK2 deficiency. Reconstitution of the S6K1 protein in their liver blocked the increase in insulin sensitivity. S6K1 degradation was not observed in hepatocytes of the WT mice. The data suggest that inactivation of NF-kappaB p50 leads to suppression of IKK2 activity in the liver. IKK2 deficiency leads to S6K1 inhibition through TNF-induced protein degradation. The S6K1 reduction may contribute to insulin sensitivity in p50-KO mice. This study suggests that hepatic S6K1 may be a drug target in the treatment of insulin resistance.