Toll-like receptor 4, nitric oxide, and myocardial depression in endotoxemia

The molecular mechanisms that mediate gram-negative sepsis-associated myocardial dysfunction remain elusive. Myocardial expression of inflammatory mediators is Toll-like receptor 4 (TLR4) dependent. However, it remains to be elucidated whether TLR4, expressed on cardiac myocytes, mediates impairment of cardiac contractility after lipopolysaccharide (LPS) application. Cardiac myocyte contractility, measured as sarcomere shortening of isolated cardiac myocytes from C3H/HeJ (with nonfunctional TLR4) and C3H/HeN (control), were recorded at stimulation frequencies between 0.5 and 10 Hz and after incubation with 1 and 10 mug/mL LPS for up to 8 h. Control cells treated with LPS were investigated with and without a competitive LPS inhibitor (E5564) and a specific inducible nitric oxide synthase (iNOS) inhibitor S-methylisothiourea. In control mice, LPS reduced sarcomere shortening amplitude and prolonged duration of relaxation, whereas sarcomere shortening of C3H/HeJ cells was insensitive to LPS. NFkappaB and iNOS were upregulated after LPS application in control mice compared with C3H/HeJ. Inhibition of TLR4 by E5564 as well as inhibition of iNOS prevented the influence of LPS on contractile activity in control myocytes. LPS-dependent suppression of cardiac myocyte contractility was significantly blunted in C3H/HeJ mice. Competitive inhibition of functional TLR4 with E5564 protects cardiac myocyte contractility against LPS. These findings suggest that TLR4, expressed on cardiac myocytes, contributes to sepsis-induced myocardial dysfunction. E5564, currently under investigation in two clinical phase II trials, seems to be a new therapeutic option for the treatment of myocardial dysfunction in sepsis associated with endotoxemia.     

The lethal effects of cytokine-induced nitric oxide on cardiac myocytes are blocked by nitric oxide synthase antagonism or transforming growth factor beta.

Inducible nitric oxide (NO) produced by macrophages is cytotoxic to invading organisms and has an important role in host defense. Recent studies have demonstrated inducible NO production within the heart, and that cytokine-induced NO mediates alterations in cardiac contractility, but the cytotoxic potential of nitric oxide with respect to the heart has not been defined. To evaluate the role of inducible nitric oxide synthase (iNOS) on cardiac myocyte cytotoxicity, we exposed adult rat cardiac myocytes to either cytokines alone or to activated J774 macrophages in coculture. Increased expression of both iNOS message and protein was seen in J774 macrophages treated with IFN gamma and LPS and cardiac myocytes treated with TNF-alpha, IL-1 beta, and IFN gamma. Increased NO synthesis was confirmed in both the coculture and isolated myocyte preparations by increased nitrite production. Increased NO synthesis was associated with a parallel increase in myocyte death as measured by CPK release into the culture medium as well as by loss of membrane integrity, visualized by trypan blue staining. Addition of the competitive NO synthase inhibitor L-NMMA to the culture medium prevented both the increased nitrite production and the cytotoxicity observed after cytokine treatment in both the isolated myocyte and the coculture experiments. Because transforming growth-factor beta modulates iNOS expression in other cell types, we evaluated its effects on cardiac myocyte iNOS expression and NO-mediated myocyte cytotoxicity. TGF-beta reduced expression of cardiac myocyte iNOS message and protein, reduced nitrite production, and reduced NO-mediated cytotoxicity in parallel. Taken together, these experiments show the cytotoxic potential of endogenous NO production within the heart, and suggest a role for TGF-beta or NO synthase antagonists to mute these lethal effects. These findings may help explain the cardiac response to sepsis or allograft rejection, as well as the progression of dilated cardiomyopathies of diverse etiologies.     

Comparison of tumor necrosis factor-alpha effect on the expression of iNOS in macrophage and cardiac myocytes

Proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha), are elevated during cardiopulmonary bypass (CPB), heart failure, and inflammatory cardiac and systemic diseases. Elevated TNF-alpha has been linked to diminished cardiac function, decreased systemic vascular resistance, as well as renal and pulmonary dysfunction. It is understood that myocardial tissues can express TNF-alpha, which results in the induction of inducible nitric oxide synthase (iNOS) leading to a significant decline in cardiac function and other direct effects. The hypothesis of this study was to determine if TNF-alpha would stimulate iNOS and its product nitric oxide (NO) similarly in immortalized macrophage and cardiac myocytes. Cultured macrophages (RAW 264.7) and cardiac myocytes (HL-1) were placed into two treatment groups and a control. The treatments included: (1) TNF-alpha and lipopolysaccharide (LPS); and (2) LPS, TNF-alpha, interleukin-1beta (IL-1beta) and interferon-gamma (IFN-gamma) incubated for 8 h. The macrophage expression of iNOS increased by 365% (p < 0.01) and its product, NO, increased proportionally. The expression of iNOS in the cardiac myocyte did not increase with TNF-alpha and LPS. However, with the addition of IFN-alpha and IL-1beta iNOS increased to 140% of control (p < 0.05). Myocyte cGMP and NO did not increase significantly with TNF-alpha treatment. This study suggests that HL-1 myocyte iNOS cannot be induced by TNF-alpha, unlike macrophage iNOS. Furthermore, the resultant cardiac dysfunction, secondary to proinflammatory cytokines effects, is regulated via diverse pathways.     

人Toll样受体4胞浆内段融合蛋白表达载体的构建与表达

目的：构建人Toll样受体4胞浆内段（hTLR4C)His融合蛋白表达载体并在原核表达与纯化，以研究其功能及鉴定与其相互作用的蛋白。方法：采用PCR方法扩增hTLR4基因编码区的胞浆内段，并将其重组于pET-DsbA2.0载体中。重组质粒经酶切、序列鉴定分析后，转化大肠杆菌BL21（DE3）。结果：用异丙基β－D硫代半乳糖（IPTG）诱导产生hTLR4胞浆内段的His-DsbA融合蛋白，继而纯化获得了分子量约42kd的融合蛋白。结论：本研究成功地构建了hTLR4胞浆内段融合蛋白表达载体并获得高效表达，为进一步研究提供了重要的实验材料。     

白细胞介素-6和白细胞介素-10在急性小鼠巨细胞病毒性心肌炎中的表达

目的研究IL-6和IL-10在小鼠巨细胞病毒性(MCMV)心肌炎中的表达和在心肌保护中的作用。方法60只4周龄BALB/C小鼠随机分为2组:实验组[36只小鼠,腹腔注射巨细胞病毒(MCMV)]和对照组(24只小鼠,注射3T3细胞裂解液)。应用免疫组化方法检测IL-6和IL-10在心肌组织中的表达,用病理切片观察心肌的病变。结果心肌病理结果显示,心肌组织出现灶性或弥散性炎性细胞浸润、心肌细胞的变性和坏死。心肌病理积分显示MCMV心肌炎属轻度炎症。免疫组化技术结果显示,在实验组,IL-6和IL-10蛋白主要表达在炎性浸润细胞、变性或坏死的心肌细胞,而在对照组,仅有IL-6和IL-10蛋白微量表达。结论IL-6和IL-10蛋白在MCMV心肌炎心肌组织中表达,并可能在病毒性心肌炎中起保护心肌作用。     

HMGB1 signals through toll-like receptor (TLR) 4 and TLR2

In response to bacterial endotoxin (e.g., LPS) or endogenous proinflammatory cytokines (e.g., TNF and IL-1beta), innate immune cells release HMGB1, a late cytokine mediator of lethal endotoxemia and sepsis. The delayed kinetics of HMGB1 release makes it an attractive therapeutic target with a wider window of opportunity for the treatment of lethal systemic inflammation. However, the receptor(s) responsible for HMGB1-mediated production of proinflammatory cytokines has not been well characterized. Here we demonstrate that in human whole blood, neutralizing antibodies against Toll-like receptor 4 (TLR4, but not TLR2 or receptor for advanced glycation end product) dose-dependently attenuate HMGB1-induced IL-8 release. Similarly, in primary human macrophages, HMGB1-induced TNF release is dose-dependently inhibited by anti-TLR4 antibodies. In primary macrophages from knockout mice, HMGB1 activates significantly less TNF release in cells obtained from MyD88 and TLR4 knockout mice as compared with cells from TLR2 knockout and wild-type controls. However, in human embryonic kidney 293 cells transfected with TLR2 or TLR4, HMGB1 effectively induces IL-8 release only from TLR2 overexpressing cells. Consistently, anti-TLR2 antibodies dose-dependently attenuate HMGB1-induced IL-8 release in human embryonic kidney/TLR2-expressing cells and markedly reduce HMGB1 cell surface binding on murine macrophage-like RAW 264.7 cells. Taken together, our data suggest that there is a differential usage of TLR2 and TLR4 in HMGB1 signaling in primary cells and in established cell lines, adding complexity to studies of HMGB1 signaling which was not previously expected.     

Bupivacaine inhibits the TLR4- and TLR2-Myd88/NF-κB pathways in human leukocytes

Local anesthetics have anti-inflammatory effects. Because most previous experiments were performed with supra-therapeutic concentrations, we measured the effects of clinically relevant concentrations of bupivacaine on the Toll like receptor 4 (TLR4)- and TLR2-myeloid differentiation primary response 88 (MyD88)-nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) pathways. We measured tumor necrosis factor alpha (TNF-α) and prostaglandin E2 (PGE2) release, p38 mitogen-activated protein kinase (MAP-kinase) phosphorylation and translocation of NF-κB in human peripheral blood mononuclear cells (hPBMCs) and human monocytes challenged with lipopolysaccharide (LPS) or tripalmitoylated lipopeptide Pam3CysSerLys4 (Pam3CSK4) in the presence or absence of bupivacaine. Similarly, we measured the effect of bupivacaine on HEK293 cells expressing the hTLR4 and the hTLR2 genes and challenged with LPS or Pam3CSK4. Finally, molecular docking simulations of R(+)- and S(−)-bupivacaine binding to the TLR4-myeloid differentiation protein 2 (MD-2) complex and to the TLR2/TLR1 heterodimer were performed. In PBMCs, bupivacaine from 0.1 to 100 μM inhibited LPS-induced TNF-α and PGE2 secretion, phosphorylation of p38 and nuclear translocation of NF-κB in monocytes. Bupivacaine similarly inhibited the effects of Pam3CSK4 on TNF-α secretion. Bupivacaine inhibited the effect of LPS on HEK293 cells expressing the human TLR4 receptor and the effect of Pam3CSK4 on HEK293 cells expressing the human TLR2 receptor. Molecular docking showed that bupivacaine binds to the MD-2 co-receptor of TLR4 and to the TLR2 receptor. Contrary to numerous experiments performed with supratherapeutic doses, our results were obtained with concentrations of bupivacaine as low as 0.1 μM. We conclude that bupivacaine modulates the inflammatory reactions such as those observed after surgery or trauma, at least partly by inhibiting the TLR4- and TLR2-NF-κB pathways.     

Differential responses of mast cell Toll-like receptors 2 and 4 in allergy and innate immunity

Toll-like receptor 2 (TLR2) and TLR4 play important roles in the early innate immune response to microbial challenge. To clarify the functional roles of TLRs 2 and 4 in mast cells, we examined bone marrow-derived mast cells (BMMCs) from TLR2 or TLR4 gene-targeted mice. Peptidoglycan (PGN) from Staphylococcus aureus stimulated mast cells in a TLR2-dependent manner to produce TNF-alpha, IL-4, IL-5, IL-6, and IL-13, but not IL-1beta. In contrast, LPS from Escherichia coli stimulated mast cells in a TLR4-dependent manner to produce TNF-alpha, IL-1beta, IL-6, and IL-13, but not IL-4 nor IL-5. Furthermore, TLR2- but not TLR4-dependent mast cell stimulation resulted in mast cell degranulation and Ca2+ mobilization. In a mast cell-dependent model of acute sepsis, TLR4 deficiency of BMMCs in mice resulted in significantly higher mortality because of defective neutrophil recruitment and production of proinflammatory cytokines in the peritoneal cavity. Intradermal injection of PGN led to increased vasodilatation and inflammation through TLR2-dependent activation of mast cells in the skin. Taken together, these results suggest that direct activation of mast cells via TLR2 or TLR4 by respective microligands contributes to innate and allergic immune responses.     

烧伤早期心肌组织几种炎症相关基因表达变化的实验研究

目的 :观察烧伤后心肌组织几种炎症相关基因表达变化 ,探讨其与心肌损害的关系。方法 :采用大鼠4 0 %体表面积 度烫伤模型 ,于伤后 0 h(正常组 )、1h、3h、6 h、12 h、2 4 h用逆转录聚合酶链反应 (RT PCR)方法检测心肌组织肿瘤坏死因子 α(TNFα)、白介素 1β(IL 1β)、诱导型一氧化氮合酶 (i NOS)及胞浆型磷脂酶 A2 (c PL A2 ) m RNA水平 ,四道生理记录仪监测左室收缩压 (L VSP)、左室舒张末压 (L VEDP)和左室压力最大上升 /下降速率 (± dp/dtmax)变化。结果 :烫伤后 1h TNFα和 c PL A2 m RNA表达显著上调 (P均 <0 .0 1) ,此后一直维持高表达状态 ;IL 1β m RNA于伤后 3h表达明显升高 (P<0 .0 1) ,伤后 12 h降至正常水平 ;i NOS m RNA水平除伤后 1h稍上调外 ,其余时间点反而下降。左室收缩功能 (L VSP、+dp/dtmax)和舒张功能 (L VEDP、 dp/dtmax)于伤后 3h显著下降 (P均 <0 .0 1) ,12 h达谷底。左心功能变化与 TNFα、c PL A2表达呈负相关 (P均 <0 .0 5 )。结论 :炎症相关基因 TNFα、c PL A2 及 IL 1β参与了烧伤后心肌局部失控性炎症反应 ,其上调表达可能是烧伤后心肌损害的重要原因之一。     

The negative inotropic effect of beta3-adrenoceptor stimulation is mediated by activation of a nitric oxide synthase pathway in human ventricle.

Beta1- and beta2-adrenoceptors in heart muscle cells mediate the catecholamine-induced increase in the force and frequency of cardiac contraction. Recently, in addition, we demonstrated the functional expression of beta3-adrenoceptors in the human heart. Their stimulation, in marked contrast with that of beta1- and beta2-adrenoceptors, induces a decrease in contractility through presently unknown mechanisms. In the present study, we examined the role of a nitric oxide (NO) synthase pathway in mediating the beta3-adrenoceptor effect on the contractility of human endomyocardial biopsies. The negative inotropic effects of a beta3-adrenoceptor agonist, BRL 37344, and also of norepinephrine in the presence of alpha- and beta1-2-blockade were inhibited both by a nonspecific blocker of NO, methylene blue, and two NO synthase (NOS) inhibitors, L-N-monomethyl-arginine and L-nitroarginine-methyl ester. The effect of the NOS inhibitors was reversed by an excess of L-arginine, the natural substrate of NOS, but not by D-arginine. Moreover, the effects of the beta3-adrenoceptor agonist on contractility were associated with parallel increases in the production of NO and intracellular cGMP, which were also inhibited by NOS inhibitors. Immunohistochemical staining of human ventricular biopsies showed the expression of the endothelial constitutive (eNOS), but not the inducible (iNOS) isoform of NOS in both ventricular myocytes and endothelial cells. These results demonstrate that beta3-adrenoceptor stimulation decreases cardiac contractility through activation of an NOS pathway. Changes in the expression of this pathway may alter the balance between positive and negative inotropic effects of catecholamines on the heart potentially leading to myocardial dysfunction.     

人胰腺组织Toll样受体4 表达的研究

目的：研究人胰腺组织Toll样受体4(TLR4)的表达分布。方法：采用免疫组化方法观察20例正常人胰腺组织冰冻切片TLR4的表达分布情况。结果：正常人胰腺主胰管上皮、血管内皮、胰岛和胰腺腺泡细胞可见TLR4的表达,其中胰管上皮和血管内皮表达尤为明显。结论：正常人胰腺胰管上皮及血管上皮存在TLR4的表达分布,此结果提示TLR4可能参与胰腺感染时识别和清除入侵病原体的免疫防御反应。     

Enhancement of murine cardiac chronotropy by the molecular transfer of the human beta2 adrenergic receptor cDNA.

Cardiac pacemaking offers a unique opportunity for direct gene transfer into the heart. An experimental system was developed to assay the effects of transferring the human beta2 adrenergic receptor (beta2AR) under in vitro, ex vivo, and finally in vivo conditions. Constructs encoding either beta2AR or LacZ were used in chronotropy studies with isolated myocytes, and transplanted as well as endogenous murine hearts. Murine embryonic cardiac myocytes were transiently transfected with plasmid constructs. The total percentage of myocytes spontaneously contracting was greater in beta2AR transfected cells, as compared with control cells (67 vs. 42+/-5%). In addition, the percentage of myocytes with chronotropic rates > 60 beats per minute (bpm) was higher in the beta2AR population, as compared with control cells (37 vs. 15+/-5%). The average contractile rate was greater in the beta2AR transfected myocytes at baseline (71+/-14 vs. 50+/-10 bpm; P < 0.001) as well as with the addition of 10(-)3 M isoproterenol (98+/-26 vs. 75+/-18 bpm; P < 0.05). Based on these results, a murine neonatal cardiac transplantation model was used to study the ex vivo effects of targeted expression of beta2AR. The constructs were transfected into the right atrium of transplanted hearts. Injection of the beta2AR construct increased the heart rate by approximately 40% (224+/-37 vs. 161+/-42 bpm; P < 0.005). Finally, the constructs were tested in vivo with injection into the right atrium of the endogenous heart. These results were similar to the ex vivo data with injection of the beta2AR constructs increasing the endogenous heart rates by approximately 40%, as compared with control injected hearts (550+/-42 vs. 390+/-37 bpm; P < 0.05). These studies demonstrate that local targeting of gene expression may be a feasible modality to regulate the cardiac pacemaking activity.     

n-3多不饱和脂肪酸对慢性心力衰竭大鼠心肌组织TLR2／4表达的影响及机制初探

目的 观察n-3多不饱和脂肪酸（n-3 PUFA）对心力衰竭大鼠心肌组织中Toll样受体2/4（TLR2/4）表达的影响,并初步探讨作用机制.方法 采用腹主动脉缩窄法复制慢性心力衰竭大鼠模型,分为正常对照组10只、假手术组10只、心力衰竭组10只和n-3 PUFA组10只.进行超声心动图心功能检测和心肌病理组织学检查;ELISA法检测各组大鼠血清中炎性细胞因子IL-1β、TNF-α的表达,real-time PCR法检测假手术组、心力衰竭组及n-3 PUFA治疗组心肌组织TLR2、TLR4、NF-κB、IL-1β、TNF-α mRNA 表达;Western blot检测心肌组织TLR2、TLR4蛋白表达.结果 n-3 PUFA组大鼠与心力衰竭模型组相比各项心功能指标均明显改善,左心室舒张末期内径（LVEDD）和左心室收缩末期内径（LVESD）明显降低,左心室射血分数（LVEF）及左心室短轴缩短率（LVFS）明显升高（P均〈0.05）;而且心肌损害明显减轻.心力衰竭组与假手术组相比,血清炎性细胞因子水平均明显升高（P均〈0.01）;经过n-3 PUFA喂养后的心力衰竭大鼠血清IL-1β、TNF-α与心力衰竭组相比明显降低（P均〈0.05）,但仍高于假手术组（P均〈0.05）.n-3 PUFA治疗组与心力衰竭组相比,心肌组织中TLR2、TLR4、NF-κB、IL-1β、TNF-α mRNA 的表达水平明显下降（P均〈0.05）;心力衰竭组心肌组织TLR2/4蛋白表达均高于假手术组（P均〈0.05）,而n-3 PUFA治疗组与心力衰竭模型组相比,TLR2、TLR4表达则是下调的（P均〈0.05）.结论 n-3 PUFA可能通过下调心力衰竭模型心肌组织中TLR2/4表达,抑制NF-κB激活和前炎性细胞因子如IL-1β、TNF-α的表达来减轻心力衰竭大鼠的症状.     

Interleukin-8 gene induction in the myocardium after ischemia and reperfusion in vivo.

Neutrophil adhesion and direct cytotoxicity for cardiac myocytes require chemotactic stimulation and are dependent upon CD18-ICAM-1 binding. To characterize the potential role of IL-8 in this interaction, canine IL-8 cDNA was cloned and the mature recombinant protein expressed in Escherichia coli BL21 cells. Recombinant canine IL-8 markedly increased adhesion of neutrophils to isolated canine cardiac myocytes. This adhesion resulted in direct cytotoxicity for cardiac myocytes. Both processes were specifically blocked by antibodies directed against CD18 and IL-8. In vivo, after 1 h of coronary occlusion, IL-8 mRNA was markedly and consistently induced in reperfused segments of myocardium. IL-8 mRNA was not induced in control (normally perfused) myocardial segments. Minimal amounts of IL-8 mRNA were detected after 3 or 4 h of ischemia without reperfusion. Highest levels of induction were evident in the most ischemic myocardial segments. IL-8 mRNA peaked in the first 3 h of reperfusion and persisted at high levels beyond 24 h. IL-8 staining was present in the inflammatory infiltrate near the border between necrotic and viable myocardium, as well as in small veins in the same area. These findings provide the first direct evidence for regulation of IL-8 in ischemic and reperfused canine myocardium and support the hypothesis that IL-8 participates in neutrophil-mediated myocardial injury.     

Role of MyD88 and TLR9 in the innate immune response elicited by serotype 5 adenoviral vectors

A replication-incompetent adenoviral (Ad) vector is generating interest for both gene therapy and immunotherapy. A major limitation of the use of Ad vectors is the innate immune response, which causes inflammatory cytokine production and tissue damage; however, the precise mechanism of the innate immune response remains to be clarified. Here, we show that serotype 5 human Ad vectors elicit innate immune responses through a myeloid differentiating factor 88 (MyD88)/Toll-like receptor (TLR)-9-dependent and/or -independent manner according to cell type. After stimulation with Ad vectors, the production of interleukin (IL)-6 and IL-12 was significantly decreased in MyD88- or TLR9-deficient dendritic cells (DCs), compared with wild-type DCs. In addition, the surface expression of maturation marker proteins, such as CD40, CD80, CD86, and MHC class II, in MyD88- or TLR9-deficient granulocyte-macrophage colony-stimulating factor (GM-CSF)-DCs was similar to that in wild-type DCs. On the other hand, MyD88- or TLR9-deficient peritoneal macrophages produced the same level of IL-6 as wild-type macrophages after infection with Ad vectors. We did not find any differences in the mRNA expression levels of the molecules involved in innate immunity, such as MyD88, TLR3, TLR7, and TLR9, between DCs and macrophages. The intravenous injection of luciferase-expressing Ad vectors into MyD88- or TLR9-deficient mice resulted in almost comparable levels of IL-6 and IL-12 production and luciferase expression with wild-type mice. These results suggest that Ad vectors can activate innate immunity via MyD88/TLR9-dependent and -independent mechanisms.     

Selective predisposition to bacterial infections in IRAK-4-deficient children: IRAK-4-dependent TLRs are otherwise redundant in protective immunity

Human interleukin (IL) 1 receptor–associated kinase 4 (IRAK-4) deficiency is a recently discovered primary immunodeficiency that impairs Toll/IL-1R immunity, except for the Toll-like receptor (TLR) 3– and TLR4–interferon (IFN)-a/b pathways. The clinical and immunological phenotype remains largely unknown. We diagnosed up to 28 patients with IRAK-4 deficiency, tested blood TLR responses for individual leukocyte subsets, and TLR responses for multiple cytokines. The patients' peripheral blood mononuclear cells (PBMCs) did not induce the 11 non-IFN cytokines tested upon activation with TLR agonists other than the nonspecific TLR3 agonist poly(I:C). The patients' individual cell subsets from both myeloid (granulocytes, monocytes, monocyte-derived dendritic cells [MDDCs], myeloid DCs [MDCs], and plasmacytoid DCs) and lymphoid (B, T, and NK cells) lineages did not respond to the TLR agonists that stimulated control cells, with the exception of residual responses to poly(I:C) and lipopolysaccharide in MDCs and MDDCs. Most patients (22 out of 28; 79%) suffered from invasive pneumococcal disease, which was often recurrent (13 out of 22; 59%). Other infections were rare, with the exception of severe staphylococcal disease (9 out of 28; 32%). Almost half of the patients died (12 out of 28; 43%). No death and no invasive infection occurred in patients older than 8 and 14 yr, respectively. The IRAK-4–dependent TLRs and IL-1Rs are therefore vital for childhood immunity to pyogenic bacteria, particularly Streptococcus pneumoniae. Conversely, IRAK-4–dependent human TLRs appear to play a redundant role in protective immunity to most infections, at most limited to childhood immunity to some pyogenic bacteria.     

Toll样受体4小干扰RNA表达载体的构建及鉴定筛选

目的构建并筛选到能有效抑制TLR4基因表达的小干扰RNA表达载体,用于研究TLR4基因功能。方法 RNA干扰采用体外构建小干扰RNA表达载体法,将构建好的表达载体转染单核细胞株,分别用流式细胞术和实时荧光定量RT-PCR法检测TLR4蛋白和mRNA表达变化,筛选抑制效率最高的小干扰RNA表达载体。结果成功构建了TLR4小干扰RNA表达载体,并经电泳及测序证实;编号为S8-1的载体转染入细胞后,TLR4阳性率为27.03%,显著低于对照组的35.12%;流式细胞术和实时荧光定量RT-PCR法检测均证实编号为S8-1小干扰RNA表达载体的抑制效率最高,可用于后续实验。结论本实验所构建的编号为S8-1小干扰RNA表达载体可有效抑制TLR4基因表达,小干扰RNA表达载体法能够抑制体外培养细胞株TLR4的表达,可用于研究TLR4基因功能。     

Viral interleukin-10 gene transfer prevents liver ischemia-reperfusion injury: Toll-like receptor-4 and heme oxygenase-1 signaling in innate and adaptive immunity

Ischemia-reperfusion injury (IRI) contributes to early and late dysfunction of liver transplants. We have shown that sentinel Toll-like receptor-4 (TLR4) plays a key role in the activation of T cell immune responses during hepatic IRI. We have also documented that overexpression of heme oxygenase-1 (HO-1) exerts potent cytoprotective effects. This study analyzes how adenovirus (Ad)-based viral interleukin-10 (vIL-10) gene transfer affects TLR4 and HO-1 signaling in host innate and adaptive immunity during liver IRI. Using a partial lobar warm IRI model, groups of wild-type and HO-1(+/-) knockout (KO) mice were assessed for severity of hepatocellular damage after 90 min of warm ischemia followed by 6 hr of reperfusion. Both wild-type and HO-1 (+/-) KO mice treated with Ad-vIL-10 have shown improved hepatic function (serum glutamic-oxaloacetic transaminase levels), ameliorated histological signs of IRI (Suzuki's score), decreased neutrophil accumulation (myeloperoxidase activity), and depressed tumor necrosis factor-alpha/IL-1beta, IL-2/interferon-gamma, E-selectin, and macrophage inflammatory protein-2 expression. These effects were IL-10 dependent as treatment with neutralizing antibody re-created liver IRI. In contrast, untreated wild-type and HO-1 (+/-) KO mice, as well as wild-type and HO-1 (+/-) KO mice treated with Ad-beta-Gal, showed severe hepatocellular damage due to IRI. Unlike in controls, wild-type and HO-1 (+/-) KO mice treated with Ad-vIL-10 revealed markedly depressed TLR4 and NF-kappaB expression, along with increased HO-1 and Bcl-2/Bcl-x(L) expression, as compared with respective controls. Thus, vIL-10 gene transfer prevents hepatic IRI in association with depressed expression of innate TLR4, and adaptive Th1 cytokine/chemokine programs. The induction of antioxidant HO-1 and anti-apoptotic Bcl-2/Bcl-x(L) by vIL-10 exerts synergistic cytoprotective function against antigen-independent hepatic inflammatory response triggered by IRI.     

Alterations in the cardiac inflammatory response to burn trauma in mice lacking a functional Toll-like receptor 4 gene

Our group and others have previously shown that Toll-like receptor 4 (TLR-4) inactivation prevents burn-induced myocardial contractile dysfunction; however, the molecular mechanisms that are involved in this cardioprotection are not well defined. This present study examines the involvement of TLR-4 in the cardiac inflammatory response to thermal insult. C3H/HeJ (TLR-4 mutant mice) and C3H/HeN wild-type (WT) mice were subjected to either a sham burn or 40% full-thickness burn injury and were fluid resuscitated with lactated Ringer using the Parkland formula. Mice (n = 7-9 per group) were killed at 2, 4, or 24 h postsham or burn, and heart tissue was harvested. Immunoblotting was performed to evaluate phosphorylated p38 mitogen-activated protein kinase (MAPK), nuclear p50, and cytoplasmic p50. Nuclear factor-kappaB was also characterized via electrophoretic mobility shift assay. Systemic and cardiac myocyte secretion of TNF-alpha, IL-1 beta, IL-6, and IL-10 were measured by enzyme-linked immunosorbent assay. Burn injury in WT mice promoted myocardial inflammatory signaling that included increased expression of phosphorylated p38 MAPK, nuclear p50, and increased cardiac myocyte secretion of cytokines. Systemic cytokines were also increased in WT animals, although not to the extent of the myocardial cytokine expression. Toll-like receptor 4 inactivation resulted in an attenuation of several burn-induced responses, including phosphorylation of p38 MAPK, nuclear translocation of nuclear factor-kappaB, and cytokine secretion. These data suggest that burn injury initiates an inflammatory response via Toll/IL-1 signaling in the heart, which contributes to cardiac injury and contractile dysfunction.