Propofol Inhibits Lipopolysaccharide-Induced Inflammatory Responses in Spinal Astrocytes via the Toll-Like Receptor 4/MyD88-Dependent Nuclear Factor-κB, Extracellular Signal-Regulated Protein Kinases1/2, and p38 Mitogen-Activated Protein Kinase Pathways.

Zhou CH ，Zhu YZ ，Zhao PP ，Xu CM ，Zhang MX ，Huang H ，Li J ，Liu L ，Wu YQ ... -  《-》

Melatonin modulates TLR4-mediated inflammatory genes through MyD88- and TRIF-dependent signaling pathways in lipopolysaccharide-stimulated RAW264.7 cells.

Increasing evidence demonstrates that melatonin has an anti-inflammatory effect. Nevertheless, the molecular mechanisms remain obscure. In this study, we investigated the effect of melatonin on toll-like receptor 4 (TLR4)-mediated molecule myeloid differentiation factor 88 (MyD88)-dependent and TRIF-dependent signaling pathways in lipopolysaccharide (LPS)-stimulated macrophages. RAW264.7 cells were incubated with LPS (2.0 μg/mL) in the absence or presence of melatonin (10, 100, 1000 μm). As expected, melatonin inhibited TLR4-mediated tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6, IL-8, and IL-10 in LPS-stimulated macrophages. In addition, melatonin significantly attenuated LPS-induced upregulation of cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) in macrophages. Further analysis showed that melatonin inhibited the expression of MyD88 in LPS-stimulated macrophages. Although it had no effect on TLR4-mediated phosphorylation of c-Jun N-terminal kinase (JNK), p38, and extracellular regulated protein kinase (ERK), melatonin significantly attenuated the activation of nuclear factor kappa B (NF-κB) in LPS-stimulated macrophages. In addition, melatonin inhibited TLR4-mediated Akt phosphorylation in LPS-stimulated macrophages. Moreover, melatonin significantly attenuated the elevation of interferon (IFN)-regulated factor-3 (IRF3), which was involved in TLR4-mediated TRIF-dependent signaling pathway, in LPS-stimulated macrophages. Correspondingly, melatonin significantly alleviated LPS-induced IFN-β in macrophages. In conclusion, melatonin modulates TLR4-mediated inflammatory genes through MyD88-dependent and TRIF-dependent signaling pathways.

Xia MZ ，Liang YL ，Wang H ，Chen X ，Huang YY ，Zhang ZH ，Chen YH ，Zhang C ，Zhao M ，Xu DX ，Song LH ... -  《-》

Quercetin disrupts tyrosine-phosphorylated phosphatidylinositol 3-kinase and myeloid differentiation factor-88 association, and inhibits MAPK/AP-1 and IKK/NF-κB-induced inflammatory mediators production in RAW 264.7 cells.

Quercetin is a major bioflavonoid widely present in fruits and vegetables. It exhibits anti-inflammatory, anti-tumor, antioxidant properties and reduces cardiovascular disease risks. However, the molecular mechanism of action against inflammation in RAW 264.7 cells is only partially explored. Quercetin effect on LPS-induced gene and protein expressions of inflammatory mediators and cytokines were determined. Moreover, involvement of heme-oxygenase-1, protein kinases, adaptor proteins and transcription factors in molecular mechanism of quercetin action against inflammation were examined. Quercetin inhibited LPS-induced NO, PGE₂, iNOS, COX-2, TNF-α, IL-1β, IL-6 and GM-CSF mRNA and protein expressions while it promoted HO-1 induction in a dose- and time-dependent manner. It also suppressed I-κB-phosphorylation, NF-κB translocation, AP-1 and NF-κB-DNA-binding and reporter gene transcription. Quercetin attenuated p38(MAPK) and JNK1/2 but not ERK1/2 activations and this effect was further confirmed by SB203580 and SP600125-mediated suppressions of HO-1, iNOS, and COX-2 protein expressions. Moreover, quercetin arrested Src, PI3K, PDK1 and Akt activation in a time- and dose-dependent manner, which was comparable to PP2 and LY294002 inhibition of Src, PI3K/Akt and iNOS expressions. Quercetin further arrested Src and Syk tyrosine phosphorylations and their kinase activities followed by inhibition of PI3K tyrosine phosphorylation. Moreover, quercetin disrupted LPS-induced p85 association to TLR4/MyD88 complex and it then limited activation of IRAK1, TRAF6 and TAK1 with a subsequent reduction in p38 and JNK activations, and suppression in IKKα/β-mediated I-κB phosphorylation. Quercetin limits LPS-induced inflammation via inhibition of Src- and Syk-mediated PI3K-(p85) tyrosine phosphorylation and subsequent TLR4/MyD88/PI3K complex formation that limits activation of downstream signaling pathways.

Endale M ，Park SC ，Kim S ，Kim SH ，Yang Y ，Cho JY ，Rhee MH ... -  《-》

Lipopolysaccharide enhances decorin expression through the Toll-like receptor 4, myeloid differentiating factor 88, nuclear factor-kappa B, and mitogen-activated protein kinase pathways in odontoblast cells.

Lipopolysaccharide (LPS) has been shown to regulate the function of odontoblasts. However, the molecular mechanisms of the effect of LPS on odontoblasts are poorly understood. Decorin (DCN), one of the major matrix proteoglycans, is known to affect the mineralization of teeth. In this study, we investigated whether LPS can regulate the expression of DCN in odontoblasts and determined the intracellular signaling pathways triggered by LPS. The DCN messenger RNA and protein expression changes in mouse odontoblast-lineage cells (OLCs) were detected by real-time polymerase chain reaction (PCR) analysis and enzyme-linked immunosorbent assay (ELISA). Whether TLR4, myeloid differentiating factor 88 (MyD88), nuclear factor-kappa B (NF-κB), or mitogen-activated protein kinase (MAPK) pathways were involved in the LPS-induced DCN expression was determined by examined real-time PCR, ELISA, and luciferase activity assay. The activation of extracellular signal-regulated kinase (ERK), p38, and JNK in OLCs was measured by Western blot analysis. We found that the mouse OLCs expressed DCN. DCN messenger RNA was rapidly induced by LPS in a time- and dose-dependent manner. Pretreatment with a MyD88 inhibitory peptide, a TLR4 antibody, or a specific inhibitor for NF-κB or I Kappa B alpha (IκBα) significantly inhibited LPS-induced DCN expression. Moreover, the LPS-mediated increase in κB-luciferase activity in OLCs was suppressed by the overexpression of dominant negative mutants of TLR4, MyD88, and IκBα but not by a dominant negative mutant of TLR2. In addition, LPS stimulation activated the ERK, p38, and JNK MAPK pathways. The pretreatment of OLCs with specific inhibitors of the ERK, p38, and JNK MAPK pathways markedly offset the LPS-induced up-regulation of DCN expression. Our results show that LPS stimulation can up-regulate the gene expression of DCN via the TLR4, MyD88, NF-κB, and MAPK pathways in odontoblast cells.

He W ，Qu T ，Yu Q ，Wang Z ，Wang H ，Zhang J ，Smith AJ ... -  《-》

Astrocyte TLR4 activation induces a proinflammatory environment through the interplay between MyD88-dependent NFκB signaling, MAPK, and Jak1/Stat1 pathways.

There is increasing evidence that astrocytes play important roles in immune regulation in the brain. Astrocytes express toll-like receptors (TLR) and build up responses to innate immune triggers by releasing proinflammatory molecules. We investigate signaling pathways and released molecules after astrocyte TLR4 activation. Purified rodent brain astrocyte cultures were treated with the TLR4 activator bacterial lipopolysaccharide (LPS). Tools used to interfere with this system include small interference RNA, inhibitory drugs, and MyD88 or Stat1 deficient mice. LPS induced early activation of the transcription factor NFκB, through the MyD88 adaptor, and expression of TNF-α, VCAM-1, IL-15, and IL-27. LPS also induced delayed Jak1/Stat1 activation, which was MyD88-independent but was not mediated by IFN-β. Jak1/Stat1 activation induced the expression of negative cytokine regulator SOCS-1 and CXCL10 chemokine (IP-10). Mitogen-activated protein kinases (MAPK) were also involved in TLR4 signaling in a MyD88-independent fashion. p38 exerted a strong influence on LPS-induced gene expression by regulating the phosphorylation of Stat1 and the transcriptional activity of NFκB, while JNK regulated the Jak1/Stat1 pathway, and ERK1/2 controlled the expression of Egr-1 and influenced MyD88-dependent MMP-9 expression. Interplay between these signals was evidenced by the increased induction of MMP-9 in Stat1-deficient cells challenged with LPS, suggesting that Stat1 negatively regulates the expression of MMP-9 induced by LPS. Therefore, astrocytes are responsive to TLR4 activation by inducing a complex set of cell-dependent molecular reactions mediated by NFκB, MAPK and Jak1/Stat1 signaling pathways. Here we identified cross-talking signals generating a proinflammatory environment that will modulate the response of surrounding cells.

Gorina R ，Font-Nieves M ，Márquez-Kisinousky L ，Santalucia T ，Planas AM ... -  《-》