Sequestosome 1 (SQSTM1, p62), a ubiquitin binding protein, plays a role in cell signaling, oxidative stress, and autophagy. However, its functional role in inflammatory signaling is controversial. Recent studies have shown that p62 is negatively implicated in inflammatory responses. But, the precise molecular mechanisms by which p62 regulates inflammatory responses remain unclear. In this study, we report on a new regulatory role for p62 in TLR4-mediated signaling. p62 overexpression led to the suppression of NF-κB activation and the production of pro-inflammatory cytokines, TNF-α, IL-6, and IL-1β in response to TLR4 stimulation. In contrast, p62(−/−) mouse embryonic fibroblast (MEF) cells exhibited marked enhancement of NF-κB activation and production of pro-inflammatory cytokines by TLR4 stimulation, compared to p62(+/+) MEF cells. Additionally, the TLR4-induced activation of signal transduction was significantly augmented in p62(−/−) MEF cells, indicating that p62 was negatively implicated in TLR4-mediated signaling. Biochemical studies revealed that p62 interacted with the internal domain of evolutionarily conserved signaling intermediate in Toll pathways (ECSIT), which is critical for associating with the TNF receptor associated factor 6 (TRAF6)-ECSIT complex to activate NF-κB in TLR4 signaling. Interestingly, p62-ECSIT interaction inhibited the interaction between TRAF6 and ECSIT and attenuated the ubiquitination of ECSIT. Furthermore, upon LPS challenge, the mortality of p62(−/−) (p62-knockout) mice was markedly enhanced compared to p62(+/+) (p62 wild-type) mice. Taken together, our data demonstrate that p62 negatively regulated TLR4 signaling via functional regulation of the TRAF6-ECSIT complex.
Animals ; Autophagy ; Carrier Proteins ; Cytokines ; Fibroblasts ; Interleukin-6 ; Mice ; Mortality ; Oxidative Stress ; Signal Transduction ; TNF Receptor-Associated Factor 6 ; Toll-Like Receptor 4 ; Ubiquitin ; Ubiquitination

Cell death and survival are tightly controlled through the highly coordinated activation/inhibition of diverse signal transduction pathways to insure normal development and physiology. Imbalance between cell death and survival often leads to autoimmune diseases and cancer. Death receptors sense extracellular signals to induce caspase-mediated apoptosis. Acting upstream of CED-3 family proteases, such as caspase-3, Bcl-2 prevents apoptosis. Using short hairpin RNAs (shRNAs), we suppressed Bcl-2 expression in Jurkat T cells, and this increased TCR-triggered AICD and enhanced TNFR gene expression. Also, knockdown of Bcl-2 in Jurkat T cells suppressed the gene expression of FLIP, TNF receptor-associated factors 3 (TRAF3) and TRAF4. Furthermore, suppressed Bcl-2 expression increased caspase-3 and diminished nuclear factor kappa B (NF-kappaB) translocation.
Apoptosis ; Autoimmune Diseases ; Caspase 3 ; Cell Death* ; Gene Expression ; Humans ; NF-kappa B ; Peptide Hydrolases ; Physiology ; Receptors, Death Domain ; RNA, Small Interfering ; Signal Transduction ; T-Lymphocytes* ; TNF Receptor-Associated Factor 4 ; Tumor Necrosis Factor Receptor-Associated Peptides and Proteins

BACKGROUND/OBJECTIVES: Carnosic acid (CA), found in rosemary (Rosemarinus officinalis) leaves, is known to exhibit anti-obesity and anti-inflammatory activities. However, whether its anti-inflammatory potency can contribute to the amelioration of obesity has not been elucidated. The aim of the current study was to investigate the effect of CA on Toll-like receptor 4 (TLR4) pathways in the presence of lipopolysaccharide (LPS) in 3T3-L1 adipocytes. MATERIALS/METHODS: 3T3-L1 adipocytes were treated with CA (0-20 microM) for 1 h, followed by treatment with LPS for 30 min; mRNA expression of adipokines and protein expression of TLR4-related molecules were then measured. RESULTS: LPS-stimulated 3T3-L1 adipocytes showed elevated mRNA expression of tumor necrosis factor (TNF)-alpha, interleukin-6, and monocyte chemoattractant protein-1, and CA significantly inhibited the expression of these adipokine genes. LPS-induced up regulation of TLR4, myeloid differentiation factor 88, TNF receptor-associated factor 6, and nuclear factor-kappaB, as well as phosphorylated extracellular receptor-activated kinase were also suppressed by pre-treatment of 3T3-L1 adipocytes with CA. CONCLUSIONS: Results of this study suggest that CA directly inhibits TLR4-MyD88-dependent signaling pathways and decreases the inflammatory response in adipocytes.
Adipocytes* ; Adipokines ; Chemokine CCL2 ; Inflammation ; Interleukin-6 ; Myeloid Differentiation Factor 88 ; Obesity ; Phosphotransferases ; RNA, Messenger ; TNF Receptor-Associated Factor 6 ; Toll-Like Receptor 4 ; Tumor Necrosis Factor-alpha ; Up-Regulation

OBJECTIVETo investigate the influence of Yiqi Huoxue Recipe (YHR) containing drug-serum on the expression of Toll-like receptor-4 (TLR4) and its downstream signaling components MyD88, as well as the tumor necrosis factor receptor related factor-6 (TRAF-6) in human vein endothelial cells (HUVECs) induced by lipopolysaccharide (LPS), and to study its possible anti-atherosclerotic mechanism from the gene and protein levels.

METHODSTwenty New Zealand male rabbits were equally divided into four groups in random: the normal control group and the three YHR groups, 5 in each group. They were gastric perfused daily with normal saline and YHR in low, moderate and high concentration respectively. Blood drawn from rabbits' heart 2 h after ending perfusion on the 7th day, and the serum separated (that is the drug-serum) was taken for testing. HUVECs were cultured in vitro and equally divided into six groups in random: the normal control group, the model group, the Western medicine group and the three YHR groups. HUVECs were stimulated with LPS, then treated separately with the drug-serum containing different concentrations of YHR for 24 h. Then the mRNA expressions of TLR4, MyD88 and TRAF-6 were measured with Real-time PCR, and their protein expressions were analyzed using Western blotting.

RESULTSProtein and mRNA expressions of TLR4, MyD88 and TRAF-6 increased significantly after LPS stimulation (P < 0.01), but the changes in the drug-serum treated groups were significantly lower than those in the saline control group respectively (P < 0.01 or P < 0.05).

CONCLUSIONYHR can block the high expression of TLR4, and also influence the MyD88-dependent signaling pathway of TLR4, suppress the downstream expression of NF-kappaB and various related gene expressions, which may be one of its mechanisms of action for anti-atherosclerosis.

Animals ; Drugs, Chinese Herbal ; pharmacology ; Human Umbilical Vein Endothelial Cells ; drug effects ; metabolism ; Humans ; Male ; Myeloid Differentiation Factor 88 ; metabolism ; Rabbits ; Serum ; TNF Receptor-Associated Factor 6 ; metabolism ; Toll-Like Receptor 4 ; metabolism

Ankylosing spondylitis (AS) is a type of autoimmune disease that predominantly affects the spine and sacroiliac joints. However, the pathogenesis of AS remains unclear. Some evidence indicates that infection with bacteria, especially Gram-negative bacteria, may have an important role in the onset and progression of AS. Recently, many studies have demonstrated that mesenchymal stem cells (MSCs) dysfunction may contribute to the pathogenesis of many rheumatic diseases. We previously demonstrated that MSCs from AS patients exhibited markedly enhanced osteogenic differentiation capacity in vitro under non-inflammatory conditions. However, the properties of MSCs from AS patients in an inflammatory environment have never been explored. Lipopolysaccharide (LPS), a proinflammatory substance derived from the outer membrane of Gram-negative bacteria, can alter the status and function of MSCs. However, whether MSCs from AS patients exhibit abnormal responses to LPS stimulation has not been reported. Autophagy is a lysosome-mediated catabolic process that participates in many physiological and pathological processes. The link between autophagy and AS remains largely unknown. The level of autophagy in ASMSCs after LPS stimulation remains to be addressed. In this study, we demonstrated that although the basal level of autophagy did not differ between MSCs from healthy donors (HDMSCs) and ASMSCs, LPS-induced autophagy was weaker in ASMSCs than in HDMSCs. Specifically, increased TRAF4 expression in ASMSCs impaired LPS-induced autophagy, potentially by inhibiting the phosphorylation of Beclin-1. These data may provide further insight into ASMSC dysfunction and the precise mechanism underlying the pathogenesis of AS.
Autoimmune Diseases ; Autophagy* ; Bacteria ; Gram-Negative Bacteria ; Humans ; In Vitro Techniques ; Membranes ; Mesenchymal Stromal Cells* ; Pathologic Processes ; Phosphorylation ; Rheumatic Diseases ; Sacroiliac Joint ; Spine ; Spondylitis, Ankylosing* ; Tissue Donors ; TNF Receptor-Associated Factor 4*

TRAF4 is a unique member of TRAF family, which is essential for innate immune response, nervous system and other systems. In addition to be an adaptor protein, TRAF4 was identified as a regulator protein in recent studies. We have determined the crystal structure of TRAF domain of TRAF4 (residues 292-466) at 2.60 Å resolution by X-ray crystallography method. The trimericly assembled TRAF4 resembles a mushroom shape, containing a super helical "stalk" which is made of three right-handed intertwined α helixes and a C-terminal "cap", which is divided at residue L302 as a boundary. Similar to other TRAFs, both intermolecular hydrophobic interaction in super helical "stalk" and hydrogen bonds in "cap" regions contribute directly to the formation of TRAF4 trimer. However, differing from other TRAFs, there is an additional flexible loop (residues 421-426), which contains a previously identified phosphorylated site S426 exposing on the surface. This S426 was reported to be phosphorylated by IKKα which is the pre-requisite for TRAF4-NOD2 complex formation and thus to inhibit NOD2-induced NF-κB activation. Therefore, the crystal structure of TRAF4-TRAF is valuable for understanding its molecular basis for its special function and provides structural information for further studies.
Amino Acid Sequence ; Binding Sites ; Crystallography, X-Ray ; Humans ; Hydrophobic and Hydrophilic Interactions ; Models, Molecular ; Phosphorylation ; Protein Conformation, alpha-Helical ; Protein Domains ; Protein Structure, Quaternary ; Recombinant Proteins ; chemistry ; Sequence Homology, Amino Acid ; TNF Receptor-Associated Factor 4 ; chemistry

OBJECTIVETo investigate weather there is a toll-like receptor 4 (TLR4)-mediated myeloid differentiation factor 88 (MyD88)-dependent pathway in hippocampal neurons of rats and the probable role of the pathway in neuroinflammation.

METHODSTo establish the proper model, primarily cultured hippocampal neurons were treated with lipopolysaccharides (LPS), or pretreated with TLR4 antibody then co-treated with LPS. The expression of mRNA of MyD88 and TNF-alpha receptor associated factor 6 (TRAF6) were tested by RT-qPCR. The content of MyD88 and TRAF6 were tested by Western blot. The nuclear translocation of nuclear factor-kappaB/P65 (NF-kappaB/p65) was tested by immunofluorescence. The content of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and nitric oxide (NO) were tested by ELISA.

RESULTSLPS could increase MyD88 and TRAF6 mRNA, upregulate protein level of MyD88 and TRAF6 and increase the level of TNF-alpha, IL-1beta and NO in cell culture supernatant. LPS also could promote NF-kappa B/p65 translation to the nucleus. The pretreatment with TLR4 antibody reduced the translocation to nucleus for NF-kappaB/P65 and the contents of TNF-alpha, IL-1beta and NO in the culture supernatant.

CONCLUSIONThere is a TLR4-mediated MyD88-dependent pathway in hippocampal neurons. The activation of this pathway can increase the level of TNF-alpha, IL-1beta and NO in cell culture supernatant. TLR4-mediated MyD88-dependent pathway in hippocampal neurons participate in neuroinflammation, that means neurons are not passive in inflammation.

Animals ; Cells, Cultured ; Hippocampus ; cytology ; metabolism ; Interleukin-1beta ; metabolism ; Myeloid Differentiation Factor 88 ; metabolism ; Neuritis ; metabolism ; Neurons ; metabolism ; Nitric Oxide ; metabolism ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; TNF Receptor-Associated Factor 6 ; metabolism ; Toll-Like Receptor 4 ; metabolism ; Transcription Factor RelA ; metabolism ; Tumor Necrosis Factor-alpha ; metabolism

OBJECTIVETo study the effect of Buyang Huanwu Decoction (BHD), Xuefu Zhuyu Decoction (XZD), and Sijunzi Decoction (SD) contained serums on expressions of Toll-like receptor 4 (TLR4)/nuclear factor (NF)-κB signals, lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), tumor necrosis factor-α (TNF-α), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and to explore possible anti-atherosclerotic mechanisms.

METHODSTwenty New Zealand rabbits were divided into 4 groups at random, i.e., the normal control group, the BHD group (6.7 g/kg), the XZD group (3.6 g/kg), and the SD group (1.6 g/kg), 5 in each group. All medication lasted for 7 successive days. Two h after the final medication, about 50 mL blood was withdrawn from rabbit heart for preparing serums. Human umbilical vein endothelial cell ECV304 were cultured in vitro for 18 h and randomly divided into the blank control group, the model group, the Western medicine (WM) control group, the BHD group, the XZD group, and the SD group at random. ECV304, except in the blank control group, were stimulated with lipopolysaccharide (LPS) for 2 h. Those in the WM control group and CM groups were treated respectively with corresponding CM contained serum for 24 h. Finally gene and protein expressions of TLR4, myeloid differentiation factor 88 (MyD88), tumor necrosis factor receptor-associated factor-6 (TRAF-6), NF-κB, LOX-1, TNF-α, ICAM-1, and VCAM-1 were detected by fluorescent quantitative PCR and Western blot.

RESULTSCompared with the blank control group, mRNA expressions of TLR4, MyD88, TRAF-6, NF-KB, LOX-1 , TNF-cx, ICAM-1, and VCAM-1 increased significantly; protein expressions of TLR4, NF-κB, LOX-1, TNF-α, ICAM-1, and VCAM-1 also increased significantly in the model group (P < 0.01). Compared with the model group, mRNA and protein expressions of each index could be significantly inhibited in the BHD group, the XZD group, and the WM control group (P < 0.05). Besides, mRNA and protein expressions of each index could be significantly elevated more in the BHD group and the XZD group than in the WM control group (P < 0.05). No statistical difference existed in each index between the SD group and the rest groups (P > 0.05).

CONCLUSIONSThe mechanism of BHD and XZD for fighting against atherosclerosis might be associated with inhibiting TLR4/NF-κB signal transduction pathway and expressions of its downstream inflammatory factors such as LOX-1, TNF-α, ICAM-1, and VCAM-1. But SD showed no associated effect on atherosclerosis.

Animals ; Atherosclerosis ; drug therapy ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Endothelial Cells ; Intercellular Adhesion Molecule-1 ; metabolism ; Lipopolysaccharides ; Myeloid Differentiation Factor 88 ; metabolism ; NF-kappa B ; metabolism ; Rabbits ; Scavenger Receptors, Class E ; Signal Transduction ; TNF Receptor-Associated Factor 6 ; metabolism ; Toll-Like Receptor 4 ; metabolism ; Tumor Necrosis Factor-alpha ; metabolism ; Umbilical Veins ; Vascular Cell Adhesion Molecule-1 ; metabolism

Liopxin A4 (LXA4) is considered to be a crucial modulator in the inflammatory responses. In the present study, we aimed to study the effect of LXA4 on the inflammatory cytokines production induced by lipopolysaccharide (LPS) and the possible mechanism in normal human epidermal keratinocytes (NHEKs). NHEKs were isolated and cultured. The expression of toll-like receptor 4 (TLR4), LXA4 receptor (ALXR) and aryl hydrocarbon receptor (AhR) in NHEKs was detected by reverse transcription polymerase chain reaction (RT-PCR). The mRNA and protein levels of tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) were determined in NHEKs stimulated by LPS (10 μg/mL) with or without preincubation with LXA4 (100 nmol/L) for 30 min by real-time quantitative PCR (real-time qPCR) and enzyme-linked immunosorbent assay (ELISA), respectively. The expression levels of tumor necrosis factor receptor-associated factor 6 (TRAF6) and suppressors of cytokine signaling 2 (SOCS2) mRNAs and proteins, and nuclear translocation of NF-kB-p65 were measured by real-time qPCR and Western blotting, respectively. The results showed that NHEKs expressed TLR4, ALXR and AhR. LXA4 significantly inhibited the mRNA and protein expression levels of TNF-α, IL-1β and TRAF6 induced by LPS in NHEKs, and LXA4 obviously increased the expression of SOCS2 at mRNA and protein levels. The nuclear NF-kB-p65 protein expression induced by LPS was inhibited after preincubation with LXA4 in NHEKs. It was concluded that LXA4 inhibits the LPS-induced production of TNF-α and IL-1β in NHEKs by up-regulating SOCS2 and down-regulating TRAF6.
Anti-Inflammatory Agents, Non-Steroidal ; pharmacology ; Cells, Cultured ; Gene Expression Regulation ; drug effects ; Humans ; Keratinocytes ; Lipopolysaccharides ; pharmacology ; Lipoxins ; pharmacology ; NF-kappa B ; genetics ; metabolism ; Suppressor of Cytokine Signaling Proteins ; genetics ; metabolism ; TNF Receptor-Associated Factor 6 ; genetics ; metabolism ; Toll-Like Receptor 4 ; genetics ; metabolism ; Tumor Necrosis Factor-alpha ; genetics ; metabolism

OBJECTIVETo study the protective effect of lipoxin A4 (LXA4) against sepsis induced by lipopolysaccharide (LPS) in rats with obesity and its effect on the expression of Toll-like receptor 4 (TLR4) and TNF receptor-associated factor 6 (TRAF6) in the liver.

METHODSA total of 60 male Sprague-Dawley rats aged three weeks were randomly divided into a normal group and an obesity group, with 30 rats in each group. A rat model of obesity was established by high-fat diet. Each of the two groups was further randomly divided into control group, sepsis group, and LXA4 group, and 8 rats were selected from each group. The rats in the control, sepsis, and LXA4 groups were treated with intraperitoneal injection of normal saline, LPS, and LXA4+LPS respectively. Twelve hours later, blood samples were collected from the heart and liver tissue samples were also collected. ELISA was used to measure the serum levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Western blot was used to measure the protein expression of TLR4 and TRAF6 in liver tissue. Quantitative real-time PCR was used to measure the mRNA expression of TLR4 and TRAF6.

RESULTSAfter being fed with high-fat diet for 6 weeks, the obesity group had significantly higher average weight and Lee's index than the normal group (P<0.05). Compared with the normal group, the obesity group had significant increases in the serum levels of IL-6 and TNF-α (P<0.05). In the normal group or the obesity group, the sepsis subgroup had significant increases in the serum levels of IL-6 and TNF-α compared with the control subgroup (P<0.05), while the LXA4 subgroup had significant reductions in the two indices compared with the sepsis subgroup (P<0.05). Compared with the normal group, the obesity group had significant increases in the protein and mRNA expression of TLR4 and TRAF6 (P<0.05). In the normal group or the obesity group, the sepsis subgroup had significant increases in the protein and mRNA expression of TLR4 and TRAF6 compared with the control subgroup (P<0.05). Compared with the sepsis subgroup, the LXA4 subgroup had significant reductions in the protein and mRNA expression of TLR4 and TRAF6 (P<0.05).

CONCLUSIONSLXA4 can reduce the serum levels of IL-6 and TNF-α and alleviate inflammatory response. LXA4 can inhibit the expression of TLR4 and TRAF6 in the liver of septic rats, possibly by inhibiting the TLR4 signaling pathway.

Animals ; Humans ; Interleukin-6 ; genetics ; metabolism ; Lipoxins ; administration & dosage ; Liver ; drug effects ; metabolism ; Male ; Obesity ; complications ; drug therapy ; genetics ; metabolism ; Rats ; Rats, Sprague-Dawley ; Sepsis ; complications ; drug therapy ; genetics ; metabolism ; Signal Transduction ; drug effects ; TNF Receptor-Associated Factor 6 ; genetics ; metabolism ; Toll-Like Receptor 4 ; genetics ; metabolism ; Tumor Necrosis Factor-alpha ; genetics ; metabolism