C-reactive protein triggers inflammatory responses partly via TLR4/IRF3/NF-κB signaling pathway in rat vascular smooth muscle cells.
ABSTRACT C-reactive protein (CRP) plays an important role in the inflammatory process of atherosclerosis. Toll-like receptor 4 (TLR4) participates in atherogenesis by mediating the inflammatory responses. The aim of this experiment was to investigate the pro-inflammatory effects and mechanisms of CRP in rat vascular smooth muscle cells (VSMCs), especially focusing on the effects of CRP on IL-6 and peroxisome proliferator-activated receptor γ (PPARγ), and TLR4-dependent signal pathway.
rat VSMCs were cultured, and CRP was used as a stimulant for IL-6 and peroxisome proliferator-activated receptor γ (PPARγ). IL-6 level in the culture supernatant was measured by ELISA, and mRNA and protein expressions were assayed by quantitative real-time PCR and western blot, respectively. RNA interference was used to assess the roles of TLR4 and interferon regulatory factor 3 (IRF3) in the pro-inflammatory signal pathway of CRP.
CRP stimulated IL-6 secretion, and inhibited mRNA and protein expression of PPARγ in VSMCs in a concentration-dependent manner. Additionally, CRP induced TLR4 expression, promoted nuclear translocation of NF-κB (p65), and augmented IκBα phosphorylation in VSMCs. Taken together, CRP induces the inflammatory responses through increasing IL-6 generation and reducing PPARγ expression in VSMCs, which is mediated by TLR4/IRF3/NF-κB signal pathway.
CRP is able to stimulate IL-6 production and to inhibit PPARγ expression in VSMCs via MyD88-independent TLR4 signaling pathway (TLR4/IRF3/NF-κB). These provide the novel evidence for the pro-inflammatory action of CRP involved in atherogenesis.
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ABSTRACT: We aimed to determine in psoriatic arthritis (PsA) patients the Toll-like receptor (TLR) 4 and C-reactive gene (CRP) polymorphisms and allele frequency and to investigate the relationship between clinical parameters and gene polymorphisms. We enrolled in this study 31 PsA and 41 healthy control subjects. PsA diagnosis was according to CASPAR criteria. Bath ankylosing spondylitis diseases activity index, Maastricht ankylosing spondylitis enthesitis score, and Bath ankylosing spondylitis functional index were measured. C, A, and T alleles of CRP and A and G alleles of TLR 4 were determined using the analysis of melting curves after real-time PCR. CRP A, C, and T allele frequency in controls was 26.8, 73.2, and 36.6 %, respectively. In the PsA patient group, A, C, and T allele frequency was 9.7, 87.1, and 12.9 %, respectively. Between control and PsA groups, there was a significant difference in A, C, and T allele frequency (P = 0.008, 0.038, and 0.001, respectively). The frequency of CRP gene polymorphisms (CA, AA, CT, TA, and TT alleles) in the control group was 56.1 % and in the PsA group was 22.6 %. There was a significant difference between the two groups (P = 0.004). The absence of a CRP gene polymorphism was a risk factor for PsA (odds ratio 4.3, 95 % CI; 1.5-12.4, P = 0.005). TLR gene haploid frequency was investigated, and all control subjects had the wild-type AA allele. PsA patient GA allele frequency was 6.5 %. There was no significant difference between the two groups (P = 0.182). GA mutant allele frequency was related to PsA (odds ratio 7.03, 95 % CI; 0.32-151.9, P = 0.214). We have shown that CRP gene polymorphisms are higher in control subjects than PsA patients, and TLR 4 gene polymorphisms were found to be related to PsA.Clinical Rheumatology 04/2014; 34(2). DOI:10.1007/s10067-014-2581-7 · 1.77 Impact Factor
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ABSTRACT: Hypertension is associated with increased levels of circulating cytokines and recent studies have shown that innate immunity contributes to hypertension. The mechanisms which hypertension stimulates immune response remain unclear, but may involve formation of neo-antigens that activate the immune system. Toll like receptor 4 (TLR4) is an innate immune receptor that binds a wide spectrum of exogenous (lipopolysaccharide) and endogenous ligands. TLR4 signaling leads to activation of nuclear factor kappa B (NFκB) and transcription of genes involved in inflammatory response. We previously demonstrated that TLR4 blockade reduces blood pressure and the augmented vascular contractility in spontaneously hypertensive rats (SHR). Here we hypothesized that inhibition of TLR4 ameliorates the vascular inflammatory process by a NFκB signaling pathway. SHR and Wistar rats were treated with anti-TLR4 antibody (1μg/day) or unspecific IgG for 15 days (i.p.). Anti-TLR4 treatment decreased production of reactive oxygen species and expression of IL-6 cytokine in mesenteric resistance arteries from SHR, when compared with IgG-treated SHR. Anti-TLR4 treatment also abolished the increased vascular reactivity to noradrenaline observed in IgG-treated SHR, as described before, and inhibition of NFκB decreased noradrenaline responses only in IgG-treated SHR. Mesenteric arteries from SHR treated with anti-TLR4 displayed decreased expression of MyD88, but not TRIF, key molecules in TLR4 signaling. Phosphorylation of p38 and NF-κB p65 were decreased in arteries from anti-TLR4-treated SHR versus IgG-treated SHR. Together, these results suggest that TLR4 is a key player in hypertension and vascular inflammatory process by a NFκB signaling pathway. Copyright © 2014. Published by Elsevier Inc.Life Sciences 12/2014; 122. DOI:10.1016/j.lfs.2014.12.001 · 2.30 Impact Factor
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ABSTRACT: Stress can either enhance or suppress immune functions depending on a variety of factors such as duration of stressful condition. Chronic stress has been demonstrated to exert a significant suppressive effect on immune function. However, the mechanisms responsible for this phenomenon remain to be elucidated. Here, male C57BL/6 mice were placed in a 50-ml conical centrifuge tube with multiple punctures to establish a chronic restraint stress model. Serum IL-10 levels, IL-10 production by the splenocytes, and activation of STAT3 in the mouse spleen were assessed. We demonstrate that IL-10/STAT3 axis was remarkably activated following chronic stress. Moreover, TLR4 and p38 MAPK play a pivotal role in the activation of IL-10/STAT3 signaling cascade. Interestingly, blocking antibody against IL-10 receptor and inhibition of STAT3 by STAT3 inhibitor S3I-201 attenuates stress-induced lymphocyte apoptosis. Inhibition of IL-10/STAT3 dramatically inhibits stress-induced reduction in IL-12 production. Furthermore, disequilibrium of Th1/Th2 cytokine balance caused by chronic stress was also rescued by blocking IL-10/STAT3 axis. These results yield insight into a new mechanism by which chronic stress regulates immune functions. IL-10/STAT3 pathway provides a novel relevant target for the manipulation of chronic stress-induced immune suppression.Brain Behavior and Immunity 02/2014; 36:118–127. DOI:10.1016/j.bbi.2013.10.016 · 6.13 Impact Factor