Degradation Of Inhibitory kappaB Research Articles

Selenium inhibits Staphylococcus aureus-induced inflammation by suppressing the activation of the NF-κB and MAPK signalling pathways in RAW264.7 macrophages

Inflammation is the hallmark of Staphylococcus aureus (S. aureus)-induced mastitis. Given the interesting relationship between selenium levels and inflammation, this study aimed to demonstrate that selenium modulated the inflammation reaction by suppressing the nuclear factor kappa B (NF-κB) and mitogen activated protein kinase (MAPK) signalling pathways. RAW264.7 macrophages were treated with three different concentrations (1μmol/l, 1.5μmol/l, and 2μmol/l) of Na2SeO3 for 12h before infection with S. aureus for 6h, 8h, and 10h. The results showed that selenium significantly reduced the mRNA expression levels of tumour necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6). Furthermore, the release of TNF-α, IL-1β, and IL-6 was decreased significantly with selenium supplementation. In addition, selenium influenced the NF-κB signalling pathway by suppressing the activation of NF-κB p65 and degradation of inhibitory kappa-B (IκB). Selenium also suppressed extracellular regulated protein kinase (Erk), c-Jun N-terminal kinase (Jnk), and p38 phosphorylation through the MAPK signalling pathway. In conclusion, selenium played an anti-inflammation role in RAW264.7 macrophages infected with S. aureus by suppressing the activation of the NF-κB and MAPK signalling pathways.

Potent anti‐inflammatory effects of two quinolinedione compounds, OQ1 and OQ21, mediated by dual inhibition of inducible NO synthase and cyclooxygenase‐2

Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) have been suggested as key components in various inflammatory diseases. Here we examined the effects of new quinolinedione derivatives, 6-(4-fluorophenyl)-amino-5,8-quinolinedione (OQ1) and 6-(2,3,4-trifluorophenyl)-amino-5,8-quinolinedione (OQ21) on activity and expression of iNOS and COX-2 to explore their anti-inflammatory properties. The effects of OQ1 and OQ21 were assessed on lipopolysaccharide (LPS)-induced iNOS and COX-2 in murine macrophage cell line (RAW264.7), along with isolated enzyme assays to measure enzyme inhibition. Nuclear factor-kappaB (NFkappaB) activation pathways were investigated to elucidate mechanisms underlying OQ-mediated suppression of the expression of iNOS and COX-2. In vivo anti-inflammatory activities of OQ compounds were evaluated in mouse ear oedema, induced by topical 12-O-tetradecanoylphorbol-13-acetate (TPA). LPS-induced NO production in RAW264.7 cells was inhibited by OQ1 and OQ21 through the attenuation of iNOS expression as well as iNOS activity. Down-regulation of iNOS followed blocking of NFkappaB activation, as assessed by inhibitory kappaB degradation and electrophoretic mobility shift assay for NFkappaB. Synthesis and accumulation of prostaglandin E(2) were also suppressed by OQ1 and OQ21. LPS-induced COX-2 expression and cellular COX-2 activities were attenuated by OQ1 and OQ21. Consistent with these results, OQ1 showed potent anti-inflammatory effects in mouse ear oedema induced by TPA. The novel quinolinedione derivatives, OQ1 and OQ21, showed potent anti-inflammatory activity through dual inhibitory effects on iNOS and COX-2, suggesting that OQ derivatives might provide a new therapeutic modality for chronic inflammatory diseases, refractory to conventional drug therapies.

Inhibitory effect of sesaminol glucosides on lipopolysaccharide-induced NF-κB activation and target gene expression in cultured rat astrocytes

The inflammatory reaction plays an important role in the pathogenesis of the neurodegenerative disorder including Alzheimer's disease (AD). Sesame lignan compounds such as sesaminol glucosides (SG) exhibit a range of pharmacological activities including anti-oxidative and anti-inflammatory action. In this study, we tried to elucidate possible effects of SG on lipopolysaccharide (LPS)-induced inflammatory reaction and its underlying mechanism in cultured astrocytes. SG (10–100 μg/ml) inhibited LPS-induced generation of nitric oxide (NO) and reactive oxygen species (ROS), as well as inhibited LPS-induced cytosolic phospholipase A 2 (cPLA 2), cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS) expression dose-dependently. This inhibitory effect of SG on NO and ROS generation was enforced by addition of glutathione (GSH) in culture. In addition, SG prevented LPS-induced DNA binding and transcriptional activity of nuclear factor KappaB (NF)-κB. Consistent with the inhibitory effect on NF-κB activity, SG inhibits phosphorylation and degradation of inhibitory KappaB (IκB), thereby translocation of p50 of NF-κB. These data show that SG has an anti-inflammatory effect through inhibition of NF-κB, and may be a useful agent for prevention of inflammatory disease like AD.

Inhibitors of poly(ADP-ribose) polymerase modulate signal transduction pathways and secondary damage in experimental spinal cord trauma.

Poly(ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with stroke and neurotrauma. The aim of our study was to evaluate the therapeutic efficacy of in vivo inhibition of PARP in an experimental model of spinal cord trauma, which was induced by the application of vascular clips (force of 24g) to the dura via a four-level T5-T8 laminectomy. Spinal cord injury in mice resulted in severe trauma characterized by edema, neutrophil infiltration (measured as an increase in myeloperoxidase activity), and apoptosis (measured by terminal deoxynucleotidyltransferase-mediated UTP end labeling coloration). Infiltration of spinal cord tissue with neutrophils was associated with a marked increase in immunoreactivity for poly(ADP-ribose) (PAR), index of PARP activation, in the spinal cord tissue. These inflammatory events were associated with the activation of nuclear factor-kappaB (NF-kappaB) at 4 h after spinal cord damage. Treatment of the mice with the PARP inhibitors 3-aminobenzamide (3-AB) or 5-aminoisoquinolinone (5-AIQ) significantly reduced the degree of 1) spinal cord inflammation and tissue injury (histological score), 2) PAR formation, 3) neutrophil infiltration, and 4) apoptosis. Treatment with these PARP inhibitors also reduced DNA binding of NF-kappaB and inhibitory kappaB degradation. In a separate set of experiments, we have also demonstrated that PARP inhibitors significantly ameliorated the recovery of limb function (evaluated by motor recovery score). Taken together, our results clearly demonstrate that treatment with PARP inhibitors reduces the development of inflammation and tissue injury events associated with spinal cord trauma.

Histamine Enhances the Production of Granulocyte-Macrophage Colony-Stimulating Factor via Protein Kinase Cα and Extracellular Signal-Regulated Kinase in Human Keratinocytes

The production of granulocyte-macrophage colony-stimulating factor (GM-CSF) in keratinocytes is related to the chronicity of atopic dermatitis. Mast cell-derived histamine contributes to the cross-talk between mast cells and keratinocytes. We examined the effects of histamine on GM-CSF production in human keratinocytes. Histamine increased GM-CSF secretion, mRNA stability and promoter activity. Activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) elements on the promoter were responsible for the activation by histamine. Histamine enhanced transcriptional activity and DNA binding of AP-1 and NF-kappaB. Histamine shifted AP-1 composition form c-Jun homodimers to c-Fos/c-Jun heterodimers, and transiently expressed c-Fos protein. Histamine rapidly induced the phosphorylation and degradation of inhibitory kappaB. Histamine induced membrane translocation of protein kinase Calpha. Histamine-induced GM-CSF production was completely abolished by H1 antagonist pyrilamine and conventional protein kinase C inhibitor Gö6976, and partially suppressed by PD98059 which inhibits the activation of extracellular signal-regulated kinase. Gö6976 and PD98059 suppressed histamine-induced c-Fos expression and AP-1 activation. Gö6976 and PD98059 suppressed histamine-induced enhancement of NF-kappaB transcriptional activity. Histamine-induced phosphorylation and degradation of inhibitory kappaB was suppressed by Gö6976, but not by PD98059. These results suggest that histamine may enhance GM-CSF production at transcriptional and posttranscriptional levels via H1 receptor, protein kinase Calpha and extracellular signal-regulated kinase.

CDNA microarray analysis reveals a nuclear factor-kappaB-independent regulation of macrophage function by adenosine.

Adenosine is released into the extracellular space from nerve terminals and cells subjected to ischemic stress. This nucleoside modulates a plethora of cellular functions via occupancy of specific receptors. Adenosine is also an important endogenous regulator of macrophage function, because it suppresses the production of a number of proinflammatory cytokines by these cells. However, the mechanisms of this anti-inflammatory effect have not been well characterized. We hypothesized that adenosine may exert some of its anti-inflammatory effects by decreasing activation of the transcription factor nuclear factor-kappaB (NF-kappaB), because gene expression of most of the proinflammatory cytokines inhibited by adenosine is dependent on NF-kappaB activation. Using bacterial lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages, we found that adenosine as well as adenosine receptor agonists decreased the production of tumor necrosis factor (TNF)-alpha, a typical NF-kappaB-regulated cytokine. This effect of adenosine was not due to an action on the process of TNF-alpha release, because adenosine suppressed also the intracellular levels of TNF-alpha. However, cDNA microarray analysis revealed that mRNA levels of neither TNF-alpha nor other cytokines were altered by adenosine in either LPS-activated or quiescent macrophages. In addition, although LPS induced expression of a number of other, noncytokine genes, including the adenosine A2b receptor, adenosine did not affect the expression of these genes. Furthermore, adenosine as well as adenosine receptor agonists failed to decrease LPS-induced NF-kappaB DNA binding, NF-kappaB promoter activity, p65 nuclear translocation, and inhibitory kappaB degradation. Together, our results suggest that the anti-inflammatory effects of adenosine are independent of NF-kappaB.