Kupffer cells, expressing toll-like receptor 4 (TLR4), play a central role in hepatic ischemia/reperfusion (I/R) injury. Hyaluronic acid (HA) fragments, degradative products of high-molecular-weight HA (HMW-HA), acqui...Kupffer cells, expressing toll-like receptor 4 (TLR4), play a central role in hepatic ischemia/reperfusion (I/R) injury. Hyaluronic acid (HA) fragments, degradative products of high-molecular-weight HA (HMW-HA), acquire the ability to activate immune cells under inflammatory conditions. Here we inves- tigated whether HA fragments could activate Kupffer cells and analyzed the underlying mechanism. Kupffer cells were isolated from wild-type mice (WT, C3H/HeN) and TLR4 mutant mice (C3H/HeJ) and HA fragments were produced by the methods of enzyme digestion and chromatography. Then Kupffer cells were stimulated by HA fragments or other control stimuli. The activation of Kupffer cells was estimated as the release of pro-inflammatory cytokines. The activation of p38 MAPK pathway of Kupffer cells was checked and blocking experiments were done as well. The results indicated that HA fragments acquired the ability to activate Kupffer cells in vitro, which was TLR4 dependent and not due to contamination of lipopolysaccharide. Experiments of p38 MAPK kinase inhibition by SB-203580 verified p38 MAPK was required in HA fragments induced Kupffer cells activation. This suggests that HA fragments, degradative products of one of the major glycosaminoglycans of the extracellular matrix, play critical roles in Kupffer cell activation mediated by TLR4 signaling pathway, which is, at least partially, de- pendent on p38 MAPK activation.展开更多
Background Inflammation and immunity play a vital role in the pathogenesis of early brain injury after subarachnoid hemorrhage （SAH）. Nuclear factor-kappa B （NF-κB） regulates many genes essential for inflammation...Background Inflammation and immunity play a vital role in the pathogenesis of early brain injury after subarachnoid hemorrhage （SAH）. Nuclear factor-kappa B （NF-κB） regulates many genes essential for inflammation and immunity and is activated by toll-like receptor （TLR）. This study aimed to detect the expression of the toll-like receptor 4/nuclear factor-kappa B （TLR4/NF-κB） signaling in the rat brain after early SAH. Methods The rats were decapitated and their brains were removed at 0, 2, 4, 6, 12, 24 and 48 hours after a single injection of blood into the prechiasmatic cistern, mRNA expression of TLR4 was measured by Taqman real-time RT-PCR, and protein expression by immunohistochemistry and Western blotting. NF-κB activity and concentrations of tumor necrosis factor-alpha （TNF-α）, interleukin-lbeta （IL-1β） and interleukin-6 （IL-6） were measured by enzyme-linked immunosorbent assay （ELISA）. Results TaqMan real-time RT-PCR and Western blotting identified a biphasic change in TLR4 expression in both mRNA and protein： an initial peak （2-6 hours） and a sustained elevation （12-48 hours）. Immunohistochemical staining showed the inducible expression of TLR4-like immunoreactions predominantly in glial cells and vascular endothelium. A similar biphasic change in the activation of NF-κB subunit p65 as well as the production of NF-κB-regulated proinflammatory cytokines （TNF-α, IL-1β and IL-6） were detected by ELISA. Conclusions These data suggest that experimental SAH induces significant up-regulation of TLR4 expression and the NF-κB signaling in early brain injury. Activation of the TLR4/NF-κB signaling may regulate the inflammatory responses after SAH.展开更多
Both TLR4 and TLR2 participated in the mediation of the inflammatory injury in the process of partial cerebral ischemia/reperfusion.However,it still remains unclear whether a crosstalk exists between TLR2 and TLR4 in ...Both TLR4 and TLR2 participated in the mediation of the inflammatory injury in the process of partial cerebral ischemia/reperfusion.However,it still remains unclear whether a crosstalk exists between TLR2 and TLR4 in ischemic cerebral damage.In the present study,we investigated the effect of TLR4 signaling on TLR2 expression during mimic cerebral I/R in vitro.BV-2 cells were cultured and treated with ischemia/reperfusion,then transfected with the plasmid pEGFP-H1/TLR4-siRNA,the plasmid pEGFP-H1/control sequence-siRNA and the blank plasmid,respectively.Interestingly,the expression of TLR2 and TLR4 mRNA and protein,NF-κB p65 mRNA and supernatant TNF-α level were significantly higher in ischemia/reperfusion treated cells than those lack of ischemia/reperfusion treatment,and as compared with those in ischemia/reperfusion treated cells without transfection,no significant differences about the above mentioned gene and protein expression were found in the blank plasmid tranfected cells and the plasmid pEGFP-H1/control sequence-siRNA transfected cells respectively,while the expression levels in the plasmid pEGFP-H1/TLR4-siRNA transfected cells were significantly lower.Additionally,in order to determine the effects of pyrrolidinediethyldithiocarbamate (PDTC),an NF-κB inhibitor,on the TLR4-induced TLR2 expression in BV-2 cells treated with ischemia/reperfusion,it was found that TLR4 and TLR2 mRNA expressions in PDTC pretreated cells were significantly lower in comparison with normal saline pretreated cells and non-pretreated cells.The data suggested that TLR2 activation,signaled by TLR4 and regulated by NF-κB,might be directly involved play an important role in ischemia/reperfusion induced brain damage.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 30500487 and 30700792)
文摘Kupffer cells, expressing toll-like receptor 4 (TLR4), play a central role in hepatic ischemia/reperfusion (I/R) injury. Hyaluronic acid (HA) fragments, degradative products of high-molecular-weight HA (HMW-HA), acquire the ability to activate immune cells under inflammatory conditions. Here we inves- tigated whether HA fragments could activate Kupffer cells and analyzed the underlying mechanism. Kupffer cells were isolated from wild-type mice (WT, C3H/HeN) and TLR4 mutant mice (C3H/HeJ) and HA fragments were produced by the methods of enzyme digestion and chromatography. Then Kupffer cells were stimulated by HA fragments or other control stimuli. The activation of Kupffer cells was estimated as the release of pro-inflammatory cytokines. The activation of p38 MAPK pathway of Kupffer cells was checked and blocking experiments were done as well. The results indicated that HA fragments acquired the ability to activate Kupffer cells in vitro, which was TLR4 dependent and not due to contamination of lipopolysaccharide. Experiments of p38 MAPK kinase inhibition by SB-203580 verified p38 MAPK was required in HA fragments induced Kupffer cells activation. This suggests that HA fragments, degradative products of one of the major glycosaminoglycans of the extracellular matrix, play critical roles in Kupffer cell activation mediated by TLR4 signaling pathway, which is, at least partially, de- pendent on p38 MAPK activation.
文摘Background Inflammation and immunity play a vital role in the pathogenesis of early brain injury after subarachnoid hemorrhage （SAH）. Nuclear factor-kappa B （NF-κB） regulates many genes essential for inflammation and immunity and is activated by toll-like receptor （TLR）. This study aimed to detect the expression of the toll-like receptor 4/nuclear factor-kappa B （TLR4/NF-κB） signaling in the rat brain after early SAH. Methods The rats were decapitated and their brains were removed at 0, 2, 4, 6, 12, 24 and 48 hours after a single injection of blood into the prechiasmatic cistern, mRNA expression of TLR4 was measured by Taqman real-time RT-PCR, and protein expression by immunohistochemistry and Western blotting. NF-κB activity and concentrations of tumor necrosis factor-alpha （TNF-α）, interleukin-lbeta （IL-1β） and interleukin-6 （IL-6） were measured by enzyme-linked immunosorbent assay （ELISA）. Results TaqMan real-time RT-PCR and Western blotting identified a biphasic change in TLR4 expression in both mRNA and protein： an initial peak （2-6 hours） and a sustained elevation （12-48 hours）. Immunohistochemical staining showed the inducible expression of TLR4-like immunoreactions predominantly in glial cells and vascular endothelium. A similar biphasic change in the activation of NF-κB subunit p65 as well as the production of NF-κB-regulated proinflammatory cytokines （TNF-α, IL-1β and IL-6） were detected by ELISA. Conclusions These data suggest that experimental SAH induces significant up-regulation of TLR4 expression and the NF-κB signaling in early brain injury. Activation of the TLR4/NF-κB signaling may regulate the inflammatory responses after SAH.
文摘Both TLR4 and TLR2 participated in the mediation of the inflammatory injury in the process of partial cerebral ischemia/reperfusion.However,it still remains unclear whether a crosstalk exists between TLR2 and TLR4 in ischemic cerebral damage.In the present study,we investigated the effect of TLR4 signaling on TLR2 expression during mimic cerebral I/R in vitro.BV-2 cells were cultured and treated with ischemia/reperfusion,then transfected with the plasmid pEGFP-H1/TLR4-siRNA,the plasmid pEGFP-H1/control sequence-siRNA and the blank plasmid,respectively.Interestingly,the expression of TLR2 and TLR4 mRNA and protein,NF-κB p65 mRNA and supernatant TNF-α level were significantly higher in ischemia/reperfusion treated cells than those lack of ischemia/reperfusion treatment,and as compared with those in ischemia/reperfusion treated cells without transfection,no significant differences about the above mentioned gene and protein expression were found in the blank plasmid tranfected cells and the plasmid pEGFP-H1/control sequence-siRNA transfected cells respectively,while the expression levels in the plasmid pEGFP-H1/TLR4-siRNA transfected cells were significantly lower.Additionally,in order to determine the effects of pyrrolidinediethyldithiocarbamate (PDTC),an NF-κB inhibitor,on the TLR4-induced TLR2 expression in BV-2 cells treated with ischemia/reperfusion,it was found that TLR4 and TLR2 mRNA expressions in PDTC pretreated cells were significantly lower in comparison with normal saline pretreated cells and non-pretreated cells.The data suggested that TLR2 activation,signaled by TLR4 and regulated by NF-κB,might be directly involved play an important role in ischemia/reperfusion induced brain damage.
