Toll-like receptor 4 is protective against neonatal murine ischemia-reperfusion intestinal injury

Purpose

Premature infants receiving probiotics have a decreased incidence of necrotizing enterocolitis. This may be mediated by intestinal bacterial signaling via toll-like receptors (TLRs) 2 and 4 maintaining intestinal homeostasis. We hypothesized that TLRs 2 and 4 are protective against ischemia-reperfusion (I/R) intestinal injury.

Methods

Two-week-old C57BL/6 wild-type (WT), B6.TLR2^−/−, B6.TLR4^−/−, B6.TLR2^−/−4^−/−, and microbially reduced (antibiotic-treated) mice (MR) underwent 60 minutes of superior mesenteric artery occlusion (I) followed by 90 minutes of reperfusion (R). Small intestine was harvested for analysis of microscopic injury, apoptosis, and inflammatory gene expression using quantitative polymerase chain reaction.

Results

After I/R, the median histologic injury scores of the B6.TLR4^−/−, B6.TLR2^−/−4^−/−, and MR pups were higher than the WT or B6.TLR2^−/− pups that corresponded with greater apoptosis based on terminal deoxynucleotidyl transferase-mediated dUTP-FITC nick-end labeling and activated caspase-3 immunostaining. B6.TLR4^−/−, B6.TLR2^−/−4^−/−, and MR also had elevated tissue innate immunity-associated chemokine and cytokine expression.

Conclusions

Neonatal mice deficient in TLR4, either alone or also deficient in TLR2, as well as those lacking a normal commensal intestinal microbiome are more susceptible to an I/R model of intestinal injury. These results may provide a mechanism for commensal bacterial-mediated protection, which may help to direct further studies to elucidate the mechanism of probiotic protection.     

转录因子Sp1和核因子кB调节小鼠足细胞单核细胞趋化蛋白1基因的转录

以往的研究发现羰甲基赖氨酸（CML）修饰的白蛋白可以通过足细胞上晚期糖麟化产物受体（RAGE）激活足细胞。阻断足细胞中活性氧（ROS）及p21Ras和抑制ERK1／2，对CML诱导足细胞表达单核细胞趋化蛋向（MCP）1基因的作用不同，提示可能有不同的信号途径诱导MCP-1基因表达。     

Uromodulin基因启动子在真核细胞中表达的特异性及活性

目的 观察Uromodulin基因启动子在各种真核细胞中表达的特异性及活性.方法 对含Uromodulin基因启动子的真核表达质粒pEGFP-URO进行测序鉴定,利用脂质体转染技术,将质粒转染人近端肾小管上皮细胞株(HK-2)、人肾癌细胞株(ACHN)、人膀胱癌细胞株(T24)、大鼠系膜细胞株(HBZY-1),用荧光显微镜和流式细胞仪观察绿色荧光蛋白(EGFP)的表达.经激发光照射后发出绿色荧光的为阳性细胞,并和pEGFP-N3进行对照研究.结果 转染24 h后HK-2、ACHN阳性率较高(7～12/HP),流式检测结果为13.2%和11.4%;而T24、HBZY-1阳性率较低(0～1/HP),流式检测结果为0%和0.8%.pEGFP-N3在各组细胞中均有较高表达,其阳性率分别为23.08%(HK-2)、19.24%(ACHN)、26.14%(T24)和18.03%(HBZY-1).结论 小鼠Uromodulin基因启动子在HK-2及ACHN中具有特异性的启动活性,其活性约为CMV的50%.     

Toll样受体4的基因多态性与脓毒症

脓毒症是指机体感染微生物后发生的全身炎性反应综合征.在该疾病发生发展中是基因多态性影响着机体对该综合征的遗传易感性.其中Toll样受体4(toll-like receptor4,TLR4)作为识别病原微生物的主要受体之一,在自身免疫中起着重要的作用.已有研究表明TLR4的基因多态性与脓毒症的遗传易感性密切相关,其中TLR4基因的Asp299Gly和Thr399Ile位点的突变与脓毒症的发生发展及预后有关.现就TLR4的功能、信号转导通路及其基因多态性与脓毒症易感性的相关关系作一综述.     

Toll-like receptor 4 promotes tubular inflammation in diabetic nephropathy

Inflammation contributes to the tubulointerstitial lesions of diabetic nephropathy. Toll-like receptors (TLRs) modulate immune responses and inflammatory diseases, but their role in diabetic nephropathy is not well understood. In this study, we found increased expression of TLR4 but not of TLR2 in the renal tubules of human kidneys with diabetic nephropathy compared with expression of TLR4 and TLR2 in normal kidney and in kidney disease from other causes. The intensity of tubular TLR4 expression correlated directly with interstitial macrophage infiltration and hemoglobin A1c level and inversely with estimated glomerular filtration rate. The tubules also upregulated the endogenous TLR4 ligand high-mobility group box 1 in diabetic nephropathy. In vitro, high glucose induced TLR4 expression via protein kinase C activation in a time- and dose-dependent manner, resulting in upregulation of IL-6 and chemokine (C-C motif) ligand 2 (CCL-2) expression via IκB/NF-κB activation in human proximal tubular epithelial cells. Silencing of TLR4 with small interfering RNA attenuated high glucose-induced IκB/NF-κB activation, inhibited the downstream synthesis of IL-6 and CCL-2, and impaired the ability of conditioned media from high glucose-treated proximal tubule cells to induce transmigration of mononuclear cells. We observed similar effects using a TLR4-neutralizing antibody. Finally, streptozotocin-induced diabetic and uninephrectomized TLR4-deficient mice had significantly less albuminuria, renal dysfunction, renal cortical NF-κB activation, tubular CCL-2 expression, and interstitial macrophage infiltration than wild-type animals. Taken together, these data suggest that a TLR4-mediated pathway may promote tubulointerstitial inflammation in diabetic nephropathy.     

Toll-like receptor 4 mediates ischemia/reperfusion injury of the heart

BACKGROUND: Restoration of blood flow to the ischemic heart may paradoxically exacerbate tissue injury (ischemia/reperfusion injury). Toll-like receptor 4, expressed on several cell types, including cardiomyocytes, is a mediator of the host inflammatory response to infection. Because ischemia/reperfusion injury is characterized by an acute inflammatory reaction, we investigated toll-like receptor 4 activation in a murine model of regional myocardial ischemia/reperfusion injury. We used C3H/HeJ mice, which express a nonfunctional toll-like receptor 4, to assess the pertinence of this receptor to tissue injury after reperfusion of ischemic myocardium. METHODS: Wild-type mice (C3H/HeN) or toll-like receptor 4 mutant mice (C3H/HeJ) were subjected to 60 minutes of regional myocardial ischemia followed by 2 hours of reperfusion. At the end of reperfusion, the area at risk and the myocardial infarct size were measured as the end point of myocardial ischemia/reperfusion injury. Myocardial mitogen-activated protein kinase activation was measured by Western blotting, and nuclear translocation of nuclear factor-kappaB and activator protein-1 was determined by electrophoretic mobility shift assay. Ischemia/reperfusion-injured myocardium was also assessed by ribonuclease protection assay for expression of inflammatory mediators (tumor necrosis factor-alpha, interleukin-1beta, monocyte chemotactic factor-1, and interleukin-6). RESULTS: The area at risk was similar for all groups after myocardial ischemia/reperfusion injury. There was a 40% reduction in infarct size (as a percentage of the area at risk) in C3H/HeJ mice compared with C3H/HeN mice (P =.001). Within the myocardium, significant activation of c-Jun N-terminal kinase, p38, and extracellular signal-regulated kinase was observed in both strains after ischemia and during reperfusion as compared with an absence of mitogen-activated protein kinase activation during sham operations; however, c-Jun N-terminal kinase activity, but not p38 or extracellular signal-regulated kinase activity, was significantly reduced in C3H/HeJ mice (P <.05). In both groups, nuclear factor-kappaB and activator protein-1 nuclear translocation occurred in the myocardium during myocardial ischemia/reperfusion injury, but, by densitometric analysis, nuclear translocation of nuclear factor-kappaB and activator protein-1 was significantly decreased in C3H/HeJ mice compared with C3H/HeN mice. Interleukin-1beta, monocyte chemotactic factor-1, and interleukin-6 were detectable in reperfused ischemic myocardium but were not detected in sham-operated myocardium; the expression of each of these mediators was significantly decreased in the myocardial tissue of C3H/HeJ mice when compared with expression in the control C3H/HeN mouse strain. CONCLUSIONS: Our data suggest that toll-like receptor 4 may mediate, at least in part, myocardial ischemia/reperfusion injury. Inhibition of toll-like receptor 4 activation may be a potential therapeutic target to attenuate ischemia/reperfusion-induced tissue damage in the clinical setting.     

Toll—like receptor 4, a novel signal transducer for lipopolysaccharide

Lipopolysaccharide (LPS), or endotoxin, is the major component of the outer surface of gram-negative bacteria. LPS is a potent activator of the cells of the immune and inflammation systems, including macrophages, monocytes and endothelial cells, and contributes to systemic changes seen in septic shock.1,2 It has long been believed that LPS is responsible for several fatal consequences of gram-negative infection. Cell activation by LPS constitutes the first step in the cascade of events believed to lead to the manifestation of gram-negative sepsis, which results in approximately 20 000 annual deaths in the United States3 and 30% mortality rate of known cases in China.Therefore, the action mechanism of LPS is one of the most important problems in the research field of immunity, inflammation and surgery. Researchers have investigated the mechanism of cell activity and injury of LPS for a long time. In 1990, CD14，the glycosyl-phosphatidylinositol (GPI)-linked plasma membrane protein, was identified as a proximal LPS receptor on the cell surface of macrophages, and it was suggested that CD14 and LBP (lipopolysaccharide binding protein) played an important role in the effect mechanism of LPS. CD14 seemed to receive LPS via transfer from the plasma protein LBP. Then, two action patterns were recognized. CD14 positive cells, such as macrophages and leukocytes, were activated after LPS combined with LBP and interacted with CD14. But, CD14 negative cells (for example, endothelial cells), were activated through other receptors that we did not know of in the cell surface after LPS, LBP and soluble CD14 (sCD14) combined with the compounds. However, there are some questions to be answered. Firstly, because CD14 lacks cytoplasmic doman, it is unlikely to act as the transducer. Secondly, the action pattern of LPS through CD14 and LBP may be in dose-dependent mode, but, in conditions of high dosage and long exposure to LPS action, CD14 and LBP do not play an important role in LPS activation effect. Finally, for CD14 negative cells, the receptor combined LPS-LBP-sCD14 compound has not yet been identified. Some details indicated that a “co-receptor” for LPS signal transduction must exist. Although standard biochemical approaches, transfection assay, and immunologic tacties were all employed to search for this co-receptor, it has not yet been found. The find of Toll-like receptor 4 (TLR4) provides a new opportunity to study the mechanism of LPS action.     

血红素氧合酶-1及Toll样受体2/4在直肠癌组织中的表达及意义

目的：探讨血红素氧合酶-1（hemeoxyenase-1，HO-1）和Toll样受体2／4（Toll-like receptor 2／4，TLR2，4）在直肠癌中的表达及意义。方法：应用免疫组织化学法和RT—PCR检测30例直肠癌组织中HO-1蛋白以及HO-1mRNA、TLR2／4mRNA的表达。结果：直肠癌组织中HO-1蛋白表达（13／30）明显高于正常组织（3/30）（P〈0．05），HO-1mRNA表达也明显高于正常组织（t=15．24，P〈0．05）；直肠癌组织中TLR2／4mRNA的表达高于正常组织（P〈0．05），且HO-1 mRNA与TLR2／4mRNA表达之间存在相关性（P〈0．05）。结论：HO-1和TLR2／4在直肠癌组织中高表达且呈正相关，提示参与直肠癌的发生、发展。     

Toll样受体4在术后认知功能障碍中作用机制的研究进展

术后认知功能障碍（POCD）是由多种因素引起的麻醉和手术后认知功能减退,持续时间可达数周、数月甚至更长,对高危人群早期筛查和干预能够明显改善围术期POCD患者的转归。Toll样受体4（TLR4）是目前研究最多的免疫炎性模式识别受体,在多种类型的中枢神经细胞中表达并对神经认知发挥调控作用。在POCD发生过程中,TLR4可通过参与炎症反应、调控神经发生、激发氧化应激以及微生物-肠-脑轴等多种途径调控其进展。本文对TLR4的结构和功能和TLR4参与POCD进展的可能作用机制进行综述。