The enhancing action of d-galactosamine on lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophage cells

Cerium oxide nanoparticles alleviate oxidative stress and decreases Nrf-2/HO-1 in D-GALN/LPS induced hepatotoxicity

Translocation of the master regulator of antioxidant-response element-driven antioxidant gene, nuclear factor erythroid 2 (Nrf-2) from the cytoplasm into the nucleus and triggering the transcription of hemoxygenase-1 (HO-1) to counteract the oxidative stress is a key feature in D-galactoseamine and lipopolysaccharide (D-GALN/LPS) induced hepatotoxicity. We mainly aimed to study the effect of cerium oxide (CeO2) nanoparticles on Nrf-2/HO-1 pathway whereas; it has previously shown to have an antioxidant effect in liver models. Administration of CeO2 nanoparticles significantly decreased the translocation of the cytoplasmic Nrf-2 with a concomitant decrement in the gene expression of HO-1 as it reveals a powerful antioxidative effect as indicated by the significant increase in the levels of glutathione (GSH), glutathione peroxidase (GPX1), glutathione reductase (GR), superoxide dismutase (SOD) and catalase. In synchronization, a substantial decrement in the levels of inducible nitric oxide synthase (iNOS), TBARS and percentage of DNA fragmentation was established. These results were confirmed by histopathology examination which showed a severe degeneration, haemorrhages, widened sinusoids and focal leukocyte infiltration in D-GALN/LPS treatment and these features were alleviated with CeO2 administration. In conclusion, CeO2 is a potential antioxidant that can effectively decrease the translocation of the cytoplasmic Nrf-2 into the nucleus and decrease HO-1 in D-GALN/LPS induced hepatotoxicity.

D-Galactosamine/Lipopolysaccharide-Induced Hepatotoxicity Downregulates Sirtuin 1 in Rat Liver: Role of Sirtuin 1 Modulation in Hepatoprotection

D-Galactosamine/Lipopolysaccharide (D-GalN/LPS) is a well known model of hepatotoxicity that closely resembles acute liver failure (ALF) seen clinically. The role of sirtuin 1 in this model has not yet been documented. However, there have been a number of studies about the cytoprotective effects of resveratrol, a SIRT1 activator, in the liver. This study was aimed at elucidating the roles of SIRT1 protein expression or catalytic activity in D-GalN/LPS model of hepatotoxicity. ALF was induced in male Wistar rats by intraperitoneal injection of D-GalN and LPS. Some groups of animals were pretreated with resveratrol and/or EX-527 (SIRT1 inhibitor). The effects of these treatments were evaluated by biochemical and Western blot studies. D-GalN/LPS treatment was able to induce hepatotoxicity and significantly increase all markers of liver damage and lipid peroxidation. A dramatic decrease of SIRT1 levels in response to D-GalN/LPS treatment was also documented. Resveratrol pretreatment attenuated D-GalN/LPS-induced hepatotoxicity. EX-527 blocked the cytoprotective effects of resveratrol. However, both resveratrol and EX-527 pretreatments did not exhibit any significant effect on SIRT1 protein expression. Collectively, these results suggest that downregulation of SIRT1 expression is involved in the cytotoxic effects of D-GalN/LPS model and SIRT1 activity contributes to the cytoprotective effects of resveratrol in the liver.

BRP, a polysaccharide fraction isolated from Boschniakia rossica, protects against galactosamine and lipopolysaccharide induced hepatic failure in mice

The aim of this study was to investigate the hepatoprotective effect of BRP, a polysaccharide fraction isolated from Boschniakia rossica, against galactosamine and lipopolysaccharide induced fulminant hepatic failure. Mice were injected with a single dose of galactosamine/lipopolysaccharide with or without pretreatment of BRP. Results showed marked reduction of hepatic necrosis, serum marker enzymes and levels of tumor necrosis factor-α and interleukin-6 in BRP pretreated mice when compared with galactosamine/lipopolysaccharide-challenged mice. Mice pretreated with BRP decreased the activation of caspases-3 and caspase-8, and showed a reduced level of DNA fragmentation of liver cells. BRP also reduced hepatic lipid peroxidation, increased potential of hepatic antioxidative defense system, and reduced hepatic nitric oxide level which was elevated by galactosamine/lipopolysaccharide injection. Immunoblot analysis showed down-regulation of inducible nitric oxide synthase and cyclooxygenase-2 proteins of liver tissues in BRP pretreated group when compared with galactosamine/lipopolysaccharide-challenged group. Furthermore, treatment with galactosamine/lipopolysaccharide markedly increased toll-like receptor 4, nuclear level of nuclear factor-κB, and phosphorylation of both extracellular signal-regulated kinase and c-Jun N-terminal kinase in liver tissues. However, these increases were attenuated by pretreatment with BRP. The results suggest that BRP alleviates galactosamine/lipopolysaccharide-induced liver injury by enhancing antioxidative defense system, suppressing inflammatory responses and reducing apoptotic signaling.

Hydrogen peroxide induces the production of tumor necrosis factor-alpha in RAW 264.7 macrophage cells via activation of p38 and stress-activated protein kinase

The effect of hydrogen peroxide (H(2)O(2)) on production of tumor necrosis factor (TNF)-alpha was examined in RAW 264.7 murine macrophage cells. H(2)O( 2) led to production of TNF-alpha up to 24 h after the treatment, but not nitric oxide in RAW 264.7 cells. H(2)O(2) induced TNF-alpha production in mouse peritoneal macrophages as well as RAW 264.7 cells. The H(2)O(2)induced TNF-alpha production was prevented by inhibitors of p38 and stress-activated protein kinase (SAPK/JNK), and H(2)O( 2) induced the phosphorylation of p38 and SAPK. Further, H(2)O( 2) significantly augmented the AP-1 activity, but not nuclear factor (NF)-kappaB activity in RAW 264.7 cells. A high level of intracellular reactive oxygen radicals (ROS) was detected in H(2)O(2)-exposed RAW 264.7 cells. Ebselen, a cell permeable antioxidant, prevented the H( 2)O(2)-induced TNFalpha production. H(2)O(2) significantly enhanced lipopolysaccharide (LPS)-induced TNF-alpha production. Therefore, H( 2) O(2) was suggested to induce TNF-alpha production in macrophages via activating p38 and SAPK/JNK as oxidative stress-related signal pathways.

Ikarisoside A inhibits inducible nitric oxide synthase in lipopolysaccharide-stimulated RAW 264.7 cells via p38 kinase and nuclear factor-kappaB signaling pathways

This study examined the anti-inflammatory properties of Ikarisoside A, isolated from Epimedium koreanum (Berberidaceae), in lipopolysaccharide (LPS)-stimulated macrophages. Ikarisoside A inhibited the expression of LPS-stimulated inducible nitric oxide synthase (iNOS) and the production of nitric oxide (NO) in LPS-stimulated RAW 264.7 cells and mouse bone marrow-derived macrophages (BMMs) in a concentration-dependent manner. In addition, Ikarisoside A reduced the release of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta). Furthermore, Ikarisoside A inhibited the activity of p38 kinase and nuclear factor-kappaB (NF-kappaB), which are signaling molecules involved in NO production. NO production was inhibited when the cells were treated with LPS and either SB 203580 (a p38 inhibitor) or Bay 11-7082 (an inhibitory kappaB kinase 2 inhibitor). These results suggest that Ikarisoside A inhibits the production of NO by inhibiting the activity of p38 MAPK and NF-kappaB. As a result of these properties, Ikarisoside A has the potential to be used as an effective anti-inflammatory agent.

The role of STAT1/IRF-1 on synergistic ROS production and loss of mitochondrial transmembrane potential during hepatic cell death induced by LPS/d-GalN

Previously, we demonstrated that signal transducer and activator of transcription factor 1 (STAT1) plays an essential role in liver injury induced by lipopolysaccharide (LPS)/D-galactosamine (D-GalN); however, the underlying mechanism involved remains unclear. Here, we showed that LPS/D-GalN administration induced secretion of tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma), which mediated apoptosis synergistically. Moreover, LPS/D-GalN-induced apoptosis was associated with increased inducible nitric oxide synthase (iNOS) and nitric oxide (NO) production, as well as elevated reactive oxygen species (ROS) production, which were all strongly inhibited by treatment with the antioxidant N-acetyl-L-cysteine (NAC) and an iNOS/NO inhibitor, L-NMMA. Although STAT1 activation and expression did not change significantly in TNF-alpha/IFN-gamma-cotreated cells compared with cells treated with IFN-gamma alone, the absence of STAT1 or interferon regulatory factor 1 (IRF-1) in genetic knockout mice strongly abrogated the observed effects of TNF-alpha/IFN-gamma on iNOS/NO induction, ROS production, loss of mitochondrial transmembrane potential (DeltaPsim), and apoptosis compared with STAT1(+/+) and IRF-1(+/+) mice. Additionally, the synergistic effects of TNF-alpha/IFN-gamma on iNOS/NO induction, ROS production, and apoptosis were significantly inhibited by overexpression of dominant negative STAT1 in contrast to overexpression of wild-type STAT1. In STAT1-deficient mice, nuclear factor kappaB (NF-kappaB) activation by TNF-alpha/IFN-gamma was attenuated and strongly inhibited by both NAC and L-NMMA. Moreover, the proteasome inhibitor, MG132, inhibited NF-kappaB activation and strongly inhibited iNOS/NO induction, ROS production, and loss of DeltaPsim induced by TNF-alpha/IFN-gamma, thereby inhibiting apoptosis. Interestingly, it appears peroxynitrite, which is produced by TNF-alpha/IFN-gamma, may interfere with STAT1 phosphorylation by inducing STAT1 nitration. Collectively, these findings demonstrate that TNF-alpha/IFN-gamma synergistically potentiates iNOS/NO induction, ROS production, and loss of DeltaPsim via STAT1 overexpression, playing an important role in promoting apoptosis and liver injury induced by LPS/D-GalN.

Identification of a regulatory cis-element within the 3'-untranslated region of the murine inducible nitric oxide synthase (iNOS) mRNA; interaction with heterogeneous nuclear ribonucleoproteins I and L and role in the iNOS gene expression

The aim of this study was to investigate the role of heterogeneous nuclear ribonucleoprotein I (hnRNPI) and hnRNPL in the regulation of the murine inducible nitric oxide synthase (iNOS) gene during inflammation. Treatment of mice with lipopolysaccharide (LPS)/D-galactosamine, or of RAW 264.7 cells with LPS/interferon-gamma (IFN-gamma), strongly increased iNOS expression while reducing hnRNPI levels and complex formation between hnRNPI/hnRNPL and the 3'-untranslated region (3'-UTR) of iNOS mRNA. Introduction of the iNOS 3'-UTR to a luciferase reporter gene reduced its expression in RAW 264.7 cells. However, when hnRNPI and hnRNPL binding sites were deleted, luciferase expression was recovered. LPS/IFN-gamma increased the luciferase activity of the full-length 3'-UTR construct compared to control, while its effects on the deletion constructs were modest. The results indicate that LPS/IFN-gamma induce iNOS through a mechanism involving hnRNPI and hnRNPL binding to iNOS 3'-UTR. Our data suggest that iNOS mRNA degradation is promoted upon binding of hnRNPI and hnRNPL to a destabilizing region within its 3'-UTR, while inflammatory stimuli causing dissociation of the mRNA-protein complex, yield a more stable transcript. This appears to be particularly significant during extended inflammatory stimuli, resulting in sustained nitric oxide production. The critical event launching this process appears to be the degradation of hnRNPI.