Inhibition of inducible nitric-oxide synthase expression by (5R)-5-hydroxytriptolide in interferon-gamma- and bacterial lipopolysaccharide-stimulated macrophages.

(5R)-5-Hydroxytriptolide (LLDT-8) is a novel analog of triptolide that has antiarthritic, hepatoprotective, and antiallogenic transplantation-rejective effects. In the present study, we report that LLDT-8 inhibited nitric oxide (NO) production and inducible nitric-oxide synthase (iNOS) expression in macrophages. LLDT-8 significantly attenuated NO production, in a dose-dependent manner, in primary peritoneal macrophages and a macrophage cell line of Raw 264.7 cells following stimulation with interferon (IFN)-gamma, lipopolysaccharide (LPS), and IFN-gamma plus LPS. It also reduced the production of tumor necrosis factor-alpha from LPS-stimulated Raw 264.7 cells. To further elucidate the mechanism responsible for the inhibition of NO, we examined the effect of LLDT-8 on IFN-gamma and LPS-induced iNOS expression. Indeed, LLDT-8 prevented NO generation by inhibiting iNOS expression at mRNA level and protein level, rather than by interfering its enzymatic activity. In IFN-gamma-stimulated Raw 264.7 cells, LLDT-8 suppressed the gene transcription of signal transducer and activator of transcription 1alpha and interferon regulatory factor (IRF)-1, but it displayed no apparent effect on IFN-gamma receptor level on cell surface. After LPS challenge, LLDT-8 further abrogated the expression of LPS receptor complex, including CD14, Toll-like receptor 4, and myeloid differentiation protein-2; decreased the LPS-induced phosphorylation of stress-activated protein kinase/c-Jun NH(2)-terminal kinase, extracellular signal-regulated kinase 1/2, and p38 mitogen-activated protein kinase (MAPK); retarded the degradation of IkappaBalpha; and ameliorated the DNA binding activity of nuclear factor-kappaB (NF-kappaB) to nuclear proteins that accounts for transcriptional regulation of iNOS. Taken together, these results suggest that LLDT-8 reduces NO production and iNOS expression by inhibiting IFN-gamma-triggered IRF-1 expression and LPS-triggered MAPK phosphorylation and NF-kappaB activation.

Zhou R ，Zheng SX ，Tang W ，He PL ，Li XY ，Yang YF ，Li YC ，Geng JG ，Zuo JP ... -  《JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS》

Rengyolone inhibits inducible nitric oxide synthase expression and nitric oxide production by down-regulation of NF-kappaB and p38 MAP kinase activity in LPS-stimulated RAW 264.7 cells.

Nitric oxide (NO) is recognized as a mediator and regulator of inflammatory responses. Rengyolone, a cyclohexylethanoid isolated from the fruits of Forsythia koreana, exhibits anti-inflammatory activity with unknown mechanism. In this study, we found that rengyolone has a strong inhibitory effect on the production of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha). Rengyolone also inhibited inducible nitric oxide synthase (iNOS) gene expression and cyclooxygenase 2 (COX-2) by lipopolysaccharide (LPS). In order to explore the mechanism responsible for the inhibition of iNOS gene expression by rengyolone, we investigated its effect on LPS-induced nuclear factor-kappaB (NF-kappaB) activation. The LPS-induced DNA binding activity of NF-kappaB was significantly inhibited by rengyolone, and this effect was mediated through inhibition of the degradation of inhibitory factor-kappaBalpha and phosphorylation of p38 MAP kinase. Furthermore, rengyolone suppressed the expression of ICE protein in IL-1beta-treated D10S cells. Taken together, these results suggest that rengyolone attenuates the inflammation through inhibition of NO production and iNOS expression by blockade of NF-kappaB and p38 MAPK activation in LPS-stimulated RAW 264.7 cells.

Kim JH ，Kim DH ，Baek SH ，Lee HJ ，Kim MR ，Kwon HJ ，Lee CH ... -  《BIOCHEMICAL PHARMACOLOGY》

Suppressive effect of novel aromatic diamine compound on nuclear factor-kappaB-dependent expression of inducible nitric oxide synthase in macrophages.

N1-benzyl-4-methylbenzene-1,2-diamine (BMD) is a novel synthetic compound. In the present study, BMD compound was discovered to inhibit nitric oxide (NO) production in macrophages RAW 264.7. BMD compound attenuated lipopolysaccharide (LPS)-induced synthesis of both mRNA and protein of inducible nitric oxide synthase (iNOS), and inhibited LPS-induced iNOS promoter activity, indicating that the aromatic diamine compound could down-regulate iNOS expression at the transcription level. As a mechanism of the anti-inflammatory action, suppression of BMD compound on nuclear factor (NF)-kappaB activation has been documented. BMD compound exhibited dose-dependent inhibitory effect on LPS-mediated NF-kappaB transcriptional activity in the macrophages. Further, the compound inhibited LPS-mediated nuclear translocation of NF-kappaB p65 and DNA binding activity of NF-kappaB complex, in parallel, but did not affect LPS-mediated degradation of inhibitory kappaBalpha protein (IkappaBalpha). These results indicate that BMD compound could inhibit nuclear localization step of NF-kappaB p65 without affecting IkappaBalpha degradation. Finally, BMD compound could provide an invaluable tool to investigate NF-kappaB-dependent iNOS expression, in addition to its therapeutic potential in NO-associated inflammatory diseases.

Shin HM ，Byung Hak Kim ，Eun Yong Chung ，Jung SH ，Yeong Shik Kim ，Kyung Rak Min ，Kim Y ... -  《EUROPEAN JOURNAL OF PHARMACOLOGY》

Withaferin A inhibits iNOS expression and nitric oxide production by Akt inactivation and down-regulating LPS-induced activity of NF-kappaB in RAW 264.7 cells.

Induction of inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production is thought to have beneficial immunomodulatory effects in acute and chronic inflammatory disorders. In Raw 264.7 cells stimulated with lipopolysaccharide (LPS) to mimic inflammation, withaferin A inhibited LPS-induced expression of both iNOS protein and mRNA in a dose-dependent manner. To investigate the mechanism by which withaferin A inhibits iNOS gene expression, we examined activation of mitogen-activated protein kinases (MAPKs) and Akt in Raw 264.7 cells. We did not observe any significant changes in the phosphorylation of p38 MAPK in cells treated with LPS alone or LPS plus withaferin A. However, LPS-induced Akt phosphorylation was markedly inhibited by withaferin A, while the phosphorylation of p42/p44 extracellular signal-regulated kinases (ERKs) was slightly inhibited by withaferin A treatment. Withaferin A prevented IkappaB phosphorylation, blocking the subsequent nuclear translocation of nuclear factor-kappaB (NF-kappaB) and inhibiting its DNA binding activity. LPS-induced p65 phosphorylation, which is mediated by extracellular signal-regulated kinase (ERK) and Akt pathways, was attenuated by withaferin A treatment. Moreover, LPS-induced NO production and NF-kappaB activation were inhibited by SH-6, a specific inhibitor of Akt. Taken together, these results suggest that withaferin A inhibits inflammation through inhibition of NO production and iNOS expression, at least in part, by blocking Akt and subsequently down-regulating NF-kappaB activity.

Oh JH ，Lee TJ ，Park JW ，Kwon TK ... -  《EUROPEAN JOURNAL OF PHARMACOLOGY》

(5R)-5-hydroxytriptolide inhibits IFN-gamma-related signaling.

(5R)-5-hydroxytriptolide (LLDT-8) displayed anti-arthritis and anti-allogenic transplantation rejection activities in our previous studies. Here, we aim to further clarify the effect of LLDT-8 on the pro-inflammatory cytokine IFN-gamma. T cells were activated with anti-CD3 antibody or concanavalin A (ConA). The expression of cell surface molecules was detected with flow cytometry. Cells were labeled with carboxyfluorescein diacetate succinimidyl ester (CFSE) to test cell division. IFN-gamma production was determined by enzyme-linked immunosorbent assay. Cell proliferation was evaluated by [3H]-thymidine uptake. Mice were immunized with ovalbumin to assess the in vivo immune response. RT-PCR and Real-time PCR were applied to determine the mRNA expression. The protein phosphorylation levels were detected by Western immunoblot assay. LLDT-8 at 100 nmol/L did not change the CD25, CD69, and CD154 expressions in anti-CD3-stimulated T cells. LLDT-8 markedly blocked the cell division of CD4 and CD8 T cells after ConA stimulation. LLDT-8 inhibited T cell-derived IFN-gamma production. Moreover, LLDT-8 suppressed the ovalbumin-specific T cell proliferation and IFN-gamma generation. In anti-CD3-activated T cells, LLDT-8 abrogated the mRNA expression of signal transducer and activator of transcription1 (STAT1), T-box transcription factor, IL-12 receptor beta2, STAT4, and interferon regulatory factor 1 in the IFN-gamma expression pathway. Western blot analysis showed that LLDT-8 blocked the phosphorylation levels of extracellular signal-regulated kinase, stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase in anti-CD3 plus anti-CD28-activated T cells. In addition, LLDT-8 reduced the transcripts of macrophage inflammatory protein (Mip)-1alpha, Mip-1beta, regulated upon activation normally T-cell expressed and secreted, inducible protein-10, IFN-inducible T cell a chemoattractant, and monokine induced by IFN-gamma in IFN-gamma-stimulated murine macrophage cell line Raw 264.7 cells. LLDT-8 was a potential inhibitor for IFN-gamma-associated signaling.

Zhou R ，Wang JX ，Tang W ，He PL ，Yang YF ，Li YC ，Li XY ，Zuo JP ... -  《ACTA PHARMACOLOGICA SINICA》