Activation of microglia plays a vital role in the initiation and maintenance of specific neuropathic pain states. By activating microglia in central nervous system, Toll-like receptor 4 (TLR4) can promote the release of proinflammatory cytokines and neuroactive compounds, participate in the initiation and maintenance of neuropathic pain, and trigger the opiate side effects. Therefore, TLR4 may be a potential therapeutic target for neuropathic pain. Inhibition of TLR4 has shown some biological effects in neuropathic pain models and ibudilast (the TLR4 pathway-inhibiting agent) has been approved for for phase 2 clinical trials. This article briefly reviews the structure, function, and mechanism of TLR4 as well as the development of TLR4-targeted drugs.
Humans ; Neuralgia ; drug therapy ; physiopathology ; Toll-Like Receptor 4 ; antagonists & inhibitors ; physiology

Animals ; Drosophila Proteins ; Humans ; Lipopolysaccharides ; pharmacology ; Membrane Glycoproteins ; metabolism ; physiology ; Receptors, Cell Surface ; metabolism ; physiology ; Signal Transduction ; Toll-Like Receptor 4 ; Toll-Like Receptors

OBJECTIVETo investigate the TLR4 signaling in multiple myeloma cell proliferation and apoptosis.

METHODSTLR4 gene transcription and protein expression were detected by RT-PCR and PE flow cytometry staining; the cells proliferation were detected by MTT assay; doxorubicin-induced apoptosis of cells was detected by AnnexinV-PI double staining flow cytometry.

RESULTTLR4 gene transcription and protein expression was detected in the myeloma cell lines. Under the lipopolysaccharides (LPS) stimulation, MM1-s cells TLR4 positive proliferation significantly increased (P<0.05), but not found in U266 cells TLR4 negative; MM1-s cells showed the resistance to doxorubisin-induced apoptosis, but LPS did not protect doxorubicin-induced U266 cell apoptosis.

CONCLUSIONTLR4 signaling may play an important role both in multiple myeloma proliferation and survival.

Apoptosis ; physiology ; Cell Line, Tumor ; Cell Proliferation ; Humans ; Multiple Myeloma ; immunology ; metabolism ; pathology ; Signal Transduction ; Toll-Like Receptor 4 ; metabolism

This study is to evaluate the role of TLR-4 in lower laminar shear stress-induced interleukin-8 gene transcription activation in vascular endothelial cells by using gene mutation and transfection techniques. RT-PCR, Northern hybridization and immunocytochemical fluorescent staining showed that TLR-4 was expressed in human umbilical vein endothelial cells(HUVEC). When stimulated with 4.2 dyne/cm2 shear stress for 1 hour, an increase of TLR-4 mRNA expression was observed in HUVECs detected by RT-PCR and Northern hybridization. The intracellular domain deletion mutant TLR-4 cDNA (lacking the 155 COOH terminal amino acids of the wild type (TLR-4) and -102 -61 bp DNA sequence in 5'-flanking region of IL-8 gene (IL-8USCS) were isolated from endothelial cells by RT-PCR and PCR. These two DNA fragments were cloned into pcDNA3 and pEGFP1 respectively to construct TLR-4 dominant negative mutant pcDNA3-mTLR4 and IL-8 reporter gene pEGFP1-IL8USCS. ECV304 cells were transfected with the pEGFP1-IL8USCS or co-transfected with pEGFP1-IL8USCS and pcDNA3-mTLR4 by Dosper liposome transfectional reagent and selected by G418, then stimulated with 4.2 dyne/cm2 shear stress for 3 hours. Flow cytometric analysis showed that when exposed to 4.2 dyne/cm2 shear stress for 3 hours, there was a marked increase in the green fluorescent protein expression in pEGFP1-IL8USCS-transfected ECV304 cells. In contrast, there was almost no change in the green fluorescent protein expression in the cells co-transfected with pEGFP1-IL8USCS and pcDNA3-mTLR4 after the stimulation, suggesting the TLR-4 mutant depressed TLR-4 signaling. These experiments suggest that the inflammatory TLR-4/NF-kappa B signaling pathway would probably be involved in flow shear stress-induced IL-8 gene expression in human vascular endothelial cells.
Cells, Cultured ; Endothelium, Vascular ; cytology ; physiology ; Gene Expression Regulation ; Humans ; Interleukin-8 ; genetics ; Membrane Glycoproteins ; genetics ; physiology ; Mutation ; Receptors, Cell Surface ; genetics ; physiology ; Stress, Mechanical ; Toll-Like Receptor 4 ; Toll-Like Receptors ; Transcription, Genetic ; physiology ; Transfection ; Umbilical Veins ; cytology

BACKGROUNDCornea epithelial cells play early and crucial roles in the initiation of ocular surface responses to pathogens. Participation of toll-like receptor (TLR) 2 and TLR4, which are major forms of fungi receptors, may be involved in Aspergillus fumigatus induced immune responses. The objective of the present study was to examine whether inactive Aspergillus fumigatus conidia induce NF-kappaB activation and production of proinflammatory cytokines, and whether the expression of TLR2 and TLR4 were amplified by conidia in cultured immortalized human corneal epithelial cells (THCEs). This may contribute to our knowledge of the mechanism by which the host cornea can successfully defend against invasive fungi.

METHODSAspergillus fumigatus conidia were used to challenge THCE cells. THCE cells were harvested after 0.5, 1, 2 or 4 hours incubation. Real-time quantitative PCR was performed to determine the expression of TLR2, TLR4, TNF-alpha and IL-8. Western blotting was performed to determine the expression of NF-kappaB. Enzyme-linked immunosorbent assay (ELISA) was performed to determine the expression of TNF-alpha and IL-8. And the release of TNF-alpha and IL-8 in the cell supernatant were also assessed by ELISA with or without pretreatment with TLR2 and TLR4 neutralizing antibodies.

RESULTSAspergillus fumigatus conidia elicited the expression of TLR2, TLR4, TNF-alpha and IL-8 mRNA in THCEs. Exposure of THCE cells to Aspergillus fumigatus conidia resulted in NF-kappaB activation, which increased at 30 minutes (increased from 11.35+/-2.74 in the controls to 19.12+/-3.48, P<0.05) and thereafter increased steadily up to 4 hours after challenge (P<0.01). Concomitant with NF-kappaB activation, secretion of TNF-alpha and IL-8 in conidia-challenged cells was increased in a time-dependent manner. Incubation of THCE cells with TLR2 antibody or TLR4 antibody before conidia challenge resulted in inhibition of conidia-induced TNF-alpha and IL-8 secretion (P<0.05), TLR2 antibody and TLR4 antibody together significantly increased inhibition of the conidia-induced secretion of TNF-alpha and IL-8 from THCE cells (P<0.01).

CONCLUSIONAspergillus fumigatus conidia stimulates THCEs inflammatory response through a pathway dependent on TLR2 and TLR4 signaling.

Aspergillus fumigatus ; immunology ; Cells, Cultured ; Epithelium, Corneal ; cytology ; immunology ; Humans ; Interleukin-8 ; biosynthesis ; NF-kappa B ; metabolism ; Toll-Like Receptor 2 ; physiology ; Toll-Like Receptor 4 ; physiology ; Tumor Necrosis Factor-alpha ; biosynthesis

To study the effect and underlying mechanism of Mahuang Tang against influenza A virus ， the influenza virus-infected Madin-Darby canine kidney(MDCK) cells were used as the carrier in this study to detect the median tissue culture-infective dose(TCID₅₀) of influenza A virus strains(A/PR8/34) on MDCK cells with cytopathic effect(CPE) assay. Blocking influenza virus invading host cells and anti-influenza virus biosynthesis were used as two different administration methods， and then the methyl thiazolyl tetrazolium(MTT) assay was utilized to determine the antiviral effective rate(ER)， median efficacious concentration(EC₅₀) and therapeutic index(TI) of Mahuang Tang. The quantitative Real-time polymerase chain reaction(RT-PCR) was used to measure virus load and the mRNA expression levels of TLR4， TLR7， MyD88 and TRAF6 in MDCK cells at 24， 48 h after the treatment. The experiment results indicated that TCID₅₀ of A/PR8/34 for MDCK cells was 1×10-4.32/mL. The EC₅₀ values of two different treatment methods were 4.92，1.59 g·L⁻¹ respectively， the TI values were 12.53， 38.78 respectively， and when the concentration of Mahuang Tang was 5.00 g·L⁻¹， ER values were 50.21%， 98.41% respectively， showing that Mahuang Tang can block influenza virus into the host cells and significantly inhibit their biosynthesis. Meanwhile， as compared with the virus group， the virus load was significantly inhibited in Mahuang Tang groups， and Mahuang Tang high and middle doses had the significant effect on decreasing the mRNA expression of TLR4， TLR7，MyD88 and TRAF6 at 24， 48 h after the treatment. It can be demonstrated that the mechanisms of Mahuang Tang against influenza A virus are related to the inhibition of influenza virus replication and the mRNA expression of correlative genes in TLR4 and TLR7 signaling pathways.
Animals ; Antiviral Agents ; pharmacology ; Dogs ; Drugs, Chinese Herbal ; pharmacology ; Influenza A Virus, H1N1 Subtype ; drug effects ; physiology ; Madin Darby Canine Kidney Cells ; Orthomyxoviridae Infections ; Toll-Like Receptor 4 ; metabolism ; Toll-Like Receptor 7 ; metabolism ; Virus Replication ; drug effects

OBJECTIVECelastrol has been established as a nuclear factor-κB (NF-κB) activation inhibitor; however, the exact mechanism behind this action is still unknown. Using text-mining technology, the authors predicted that interleukin-1 receptor-associated kinases (IRAKs) are potential celastrol targets, and hypothesized that targeting IRAKs might be one way that celastrol inhibits NF-κB. This is because IRAKs are key molecules for some crucial pathways to activate NF-κB (e.g., the interleukin-1 receptor (IL-1R)/Toll-like receptor (TLR) superfamily).

METHODSThe human hepatocellular cell line (HepG2) treated with palmitic acid (PA) was used as a model for stimulating TLR4/NF-κB activation, in order to observe the potential effects of celastrol in IRAK regulation and NF-κB inhibition. The transfection of small interfering RNA was used for down-regulating TLR4, IRAK1 and IRAK4, and the Western blot method was used to detect changes in the protein expressions.

RESULTSThe results showed that celastrol could effectively inhibit PA-caused TLR4-dependent NF-κB activation in the HepG2 cells; PA also activated IRAKs, which were inhibited by celastrol. Knocking down IRAKs abolished PA-caused NF-κB activation.

CONCLUSIONThe results for the first time show that targeting IRAKs is one way in which celastrol inhibits NF-κB activation.

Hep G2 Cells ; Humans ; Interleukin-1 Receptor-Associated Kinases ; antagonists & inhibitors ; NF-kappa B ; antagonists & inhibitors ; metabolism ; Phosphorylation ; Toll-Like Receptor 4 ; antagonists & inhibitors ; physiology ; Triterpenes ; pharmacology

OBJECTIVESTo explore the role of TLR4 in the mechanism of hepatic ischemia/reperfusion (I/R) injury in mice.

METHODSWild-type (C3H/Heouj) mice and TLR4 deficient mice (C3H/Hej) were used to prepare the models of liver I/R injury. Partial hepatic ischemia was produced by inflow causing occlusion in the median and left lobes for 45 minutes. Blood was drawn to kill the mice at 1 hours and 3 hours after reperfusion. The blood was used to analyze aspartate aminotransferase (AST) and tumor necrosis factor-alpha (TNFalpha). TNF-alpha mRNA expression and myeloperoxidase (MPO) level in ischemic lobes was examined by northern blot and myeloperoxidase assay, respectively.

RESULTSAST levels were significantly lower in TLR4 deficient mice, compared with those in wild-type mice at both time points (661.83U/L+/-106.09U/L vs. 1215.5U/L+/- 174.03U/L, t=-6.65, P<0.01; 1145.17U/L+/-132.42U/L vs. 2958.17U/L+/-186.81U/L, t=-5.57, P<0.01). Serum TNF-alpha level was lower in TLR4 deficient mice at 3 hours after reperfusion compared with that in wild-type mice (152.39pg/ml+/-43.3 pg/ml vs. 249.12pg/ml+/-51.89pg/ml, t=-3.13, P<0.05). This difference appeared to be mediated at the gene level, since TNF-alpha mRNA expression had decreased in TLR4 deficient mice at 1 hours after reperfusion, compared with that in wild type mice (80.3+/-28.8 vs. 189.4+/-24.6, t=-3.25, P<0.05). MPO level in ischemic lobes in TLR4 deficient mice at 3 hours after reperfusion was significantly lower than that in wild type mice (F=33.49, P<0.01).

CONCLUSIONSI/R hepatic injury in TLR4 deficient mice is less than that in wild-type mice. TNF-alpha expression down-regulated at the mRNA level appears critical. These suggest that TLR4 be involved in the mechanism of hepatic ischemia/reperfusion injury in mice.

Alanine Transaminase ; blood ; Animals ; Liver ; blood supply ; metabolism ; Membrane Glycoproteins ; physiology ; Mice ; Mice, Inbred C3H ; Peroxidase ; metabolism ; RNA, Messenger ; analysis ; Receptors, Cell Surface ; physiology ; Reperfusion Injury ; etiology ; Toll-Like Receptor 4 ; Toll-Like Receptors ; Tumor Necrosis Factor-alpha ; analysis ; genetics

OBJECTIVETo investigate the role and significance of cardiac mast cells and Toll-like receptor 4 (TLR4) in the development and progression of viral myocarditis (VMC).

METHODSForty-eight Balb/c mice were randomly divided into a control group (n=24) and a model group (n=24). Coxsackievirus B3 was intraperitoneally injected into the model group mice to establish a VMC model. In each group, cardiac tissues were collected from 8 mice at 7, 14 and 28 days after the model was established. The cardiac tissues were stained with hematoxylin and eosin as well as Masson trichrome to observe pathological changes in cardiac tissues. The number and degranulation of cardiac mast cells at each time point were measured and evaluated by toluidine blue staining and transmission electron microscopy. The mRNA and protein expression of TLR4 in cardiac tissues was measured by RT-PCR and immunohistochemistry. In the model group, the correlation between number of cardiac mast cells and mRNA expression of TLR4 at all time points was analyzed.

RESULTSThe model group had significantly higher pathological scores of cardiac tissues than the control group at all time points (P<0.05). The myocardial collagen volume fraction in the model group at 28 days was significantly higher than in the control group at all time points and higher than in the model group at 7 and 14 days (P<0.05). At each time point, the model group had a significantly increased number of mast cells (P<0.05), and significantly increased mRNA and protein expression of TLR4 (P<0.05) compared with the control group. In the model group, the number of cardiac mast cells was positively correlated with the mRNA expression of TLR4 at all time points (R²=0.877, P<0.05).

CONCLUSIONSMice with VMC have significantly increased numbers of cardiac mast cells and expression of TLR4 compared with control mice at all time points, suggesting that mast cells and TLR4 may play important roles in the inflammatory response and fibrosis of VMC.

Animals ; Coxsackievirus Infections ; immunology ; Enterovirus B, Human ; Female ; Mast Cells ; physiology ; Mice ; Mice, Inbred BALB C ; Myocarditis ; immunology ; Myocytes, Cardiac ; pathology ; Toll-Like Receptor 4 ; analysis ; genetics ; physiology

BACKGROUNDIn patients suffering from acute pancreatitis, the pathogenesis is not completely understood, and several recent studies in vitro suggested that heat shock proteins might play an important role in cell signaling. To investigate the possible role of extracellular heat shock protein 70 (Hsp70) in pancreatitis, toll-like receptor-4 (TLR4)-deficient and wild-type mice were administered with exogenous Hsp70 during the course of cerulein-induced pancreatitis (CIP).

METHODSAcute pancreatitis was induced by 5 intraperitoneal injections of cerulein at hourly intervals, and then treated with recombinant Hsp70 through the caudal vein 4 hours after the start of cerulein injections. Subsequently serum amylase and serum cytokines levels were detected. Histologic alteration of the pancreas was evaluated. Tumor necrosis factor alpha (TNF-alpha) concentrations and myeloperoxidase (MPO) activity in both pancreas and lungs were analyzed. The nuclear factor kappa B (NF-kappaB) activation in pancreatic tissue was measured using a sensitive RelA enzyme-linked immunosorbent assay.

RESULTSTreatment with recombinant Hsp70 to wild-type mice in CIP resulted in significant aggravation of inflammation in pancreas, elevated levels of serum cytokines, up-regulation of pulmonary MPO activity and increase of lung tissues TNF-alpha concentrations. In contrast, treatment with Hsp70 to TLR4-deficient mice had little effect on serum cytokines levels, pancreatic inflammation, pulmonary MPO activity and TNF-alpha concentrations.

CONCLUSIONSThe results suggest that extracellular Hsp70 might induce systemic inflammatory response syndrome (SIRS)-like response in vivo and TLR4 might be involved in the Hsp70-mediated activation of inflammatory reaction in the progression of CIP without infection.

Acute Disease ; Animals ; Ceruletide ; toxicity ; Female ; HSP70 Heat-Shock Proteins ; physiology ; Male ; Mice ; Mice, Inbred C57BL ; Pancreatitis ; etiology ; Systemic Inflammatory Response Syndrome ; etiology ; Toll-Like Receptor 4 ; physiology