脂多糖通过NF-κB途径调节大鼠星形胶质细胞Toll样受体表达

目的 研究脂多糖（LPS）对大鼠星形胶质细胞Toll样受体表达的影响及其机制。方法 在原代培养的第3代星形胶质细胞中加入不同浓度的LPS作用24h,通过免疫荧光、western blot观察星形胶质细胞 Toll样受体的表达和NF-κB p65的表达,同时研究NF-κB通路抑制剂对其的影响。结果 在正常状况下,星形胶质细胞胞浆和胞膜表达大量的TLR3受体,很少的TLR4受体。在LPS的刺激下,星形胶质细胞的TLR3表达保持不变,TLR4受体的表达随予以LPS的量增加而增高。LPS可刺激星形胶质细胞NF-κB的表达升高,抑制NF-κB通路活化抑制TLR4受体的上调。 结论 星形胶质细胞Toll样受体的表达是不同源的,TLR4受体随环境的变化而改变,其分子机制可能与NF-κB信号途径有关。     

青蒿琥酯对小鼠巨噬细胞RAW264.7中TLR4介导的炎症通路的抑制作用

目的观察青蒿琥酯(artesunate,AS)对脂多糖(lipopolysaccharide,LPS)刺激小鼠RAW264.7细胞Toll样受体4(Toll-like receptor 4,TLR4)介导炎症通路活化的影响,以探讨AS的抗炎作用机制。方法采用免疫荧光观察胞内TLR4表达和分布;免疫印迹检测TLR4及下游炎症通路关键分子的表达和活化;酶联免疫吸附法检测细胞培养上清中TNF-α、IL-6浓度。结果 AS对LPS诱导的TLR4表达及其在细胞中的聚集均有抑制作用;AS同时抑制TLR4衔接蛋白髓分化因子88和含TIR结构域干扰素诱导衔接蛋白表达,也抑制依赖于二者活化的肿瘤坏死因子受体相关因子6表达;对下游MAPK通路,AS抑制p38表达和磷酸化、JNK磷酸化,但对ERK1/2无显著影响;对下游NF-κB通路,AS下调抑制性-κBα(inhibitory-κBα,IκBα)的磷酸化,进而减少NF-κB亚基p50和p65活化入核的数量;最后,AS能够抑制LPS诱导的TNF-α和IL-6释放。结论 AS通过抑制LPS诱导的TLR4通路活化,减少致炎细胞因子的释放,从而发挥其抗炎作用。     

人参皂苷Rg1对脓毒症所致心肌损伤大鼠NF-κB磷酸化水平及炎症相关通路的影响北大核心CSCD

目的：探究人参皂苷Rg1对脓毒症所致心肌损伤大鼠核因子-κB(NF-κB)磷酸化水平及炎症相关通路的影响。方法：盲肠结扎穿孔法（CLP）构建大鼠脓毒症心肌损伤模型,60只大鼠随机分为假手术（sham）组、CLP组、人参皂苷Rg1低剂量（CLP+Rg1L）组、人参皂苷Rg1中剂量（CLP+Rg1M）组、人参皂苷Rg1高剂量（CLP+Rg1H）组、瑞沙托维（CLP+TAK-242）组,每组10只。LPS构建体外脓毒症心肌细胞模型,H9C2细胞分为对照（control）组、LPS组、LPS+Rg1L组、LPS+Rg1M组、LPS+Rg1H组、LPS+TAK-242组。右颈总动脉插管法检测各组大鼠平均动脉压（MABP）、心率×左心室发展压（LVDP×HR）、左心室压力最大上升/下降速率（±dp/dtmax）水平;HE染色观察心肌组织病理学改变;Annexin V-FITC/PI双染法检测心肌组织和H9C2细胞凋亡;ELISA检测大鼠血清和H9C2细胞肌酸激酶（CK）、乳酸脱氢酶（LDH）、天冬氨酸转氨酶（AST）、肌钙蛋白Ⅰ（cTnⅠ）、肿瘤坏死因子-α(TNF-α)、IL-6、IL-1β含量;CCK-8及EdU染色检测H9C2细胞增殖能力;RT-qPCR检测心肌组织Toll样受体4(TLR4)、NF-κB p65、p38丝裂原活化蛋白激酶（p38MAPK） mRNA表达;Western blot检测心肌组织TLR4、NF-κB p65、p-NF-κB p65、p38MAPK、p-p38MAPK、核苷酸结合寡聚化结构域样受体蛋白3(NLRP3)蛋白表达。结果：人参皂苷Rg1能够提高MABP、LVDP×HR、±dp/dtmax水平,降低CK、LDH、AST活力,降低cTnⅠ、TNF-α、IL-6、IL-1β、TLR4、NF-κB p65、p38MAPK mRNA与TLR4、p-NF-κB p65/NF-κB p65、p-p38MAPK/p38MAPK、NLRP3蛋白水平（P<0.05）,促进心肌细胞增殖,抑制细胞凋亡与炎症水平,改善心肌损伤。结论：人参皂苷Rg1能够抑制心肌组织细胞凋亡及炎症水平,提高心功能,从而减轻脓毒症所致心肌损伤,其机制可能与TLR4/NF-κB、p38MAPK信号通路有关。     

布托啡诺抑制TLR4/MyD88/NF-κB信号通路对卵巢癌细胞增殖、凋亡、迁移和侵袭的影响

目的 探讨布托啡诺抑制Toll样受体4(TLR4)/髓样分化因子88(MyD88)/核因子-κB(NF-κB)信号通路对卵巢癌细胞增殖、凋亡、迁移和侵袭的影响。方法 实验分组1:(2.5、5.0、10、20、40、80、160、320)μg/mL布托啡诺处理人卵巢癌细胞A2780,计算细胞半数抑制浓度（IC50）。实验分组2：对照组（正常培养）、布托啡诺组（13.24μg/mL布托啡诺）、布托啡诺+LPS组（13.24μg/mL布托啡诺+1μg/mL LPS）,CCK-8检测细胞增殖情况;流式细胞术检测细胞凋亡情况;Transwell检测细胞侵袭和迁移情况;蛋白质免疫印迹检测细胞中TLR4、MyD88、NF-κB蛋白表达情况。结果 细胞IC50为13.24μg/mL。与对照组相比,布托啡诺组细胞OD450水平、迁移和侵袭数量、细胞中TLR4、MyD88、NF-κB蛋白水平降低（P<0.05）,细胞凋亡率升高（P<0.05）;与布托啡诺组相比,布托啡诺+LPS组细胞OD450水平、迁移和侵袭数量、细胞中TLR4、MyD88、NF-κB蛋白水平升高（P<0.05）,细胞凋...     

过表达SIRT1抑制脂多糖诱导的胰岛β细胞炎症因子表达及NF-κB信号通路激活

目的研究沉默信息调节因子1(SIRT1)对脂多糖(LPS)诱导的胰岛β细胞炎症因子表达及核因子-κB(NF-κB)信号通路激活的影响。方法用LPS处理胰岛β细胞,qRT-PCR和Western blot测定细胞中SIRT1表达变化。用pcDNA3.1-SIRT1慢病毒感染胰岛β细胞,qRT-PCR检测细胞中白细胞介素-6(IL-6)mRNA和肿瘤坏死因子-α(TNF-α)mRNA表达水平,流式细胞术测定细胞凋亡变化,Western blot检测细胞中Bcl-2相关X蛋白(Bax)、活化型Caspase-3(cleaved Caspase-3)、核因子-κBp65亚型(NF-κBp65)、Toll样受体4(TLR4)蛋白表达水平。结果 LPS处理后的胰岛β细胞中SIRT1表达水平降低。pcDNA3.1-SIRT1慢病毒感染可以提高LPS条件下胰岛β细胞中SIRT1表达水平。LPS处理后的胰岛β细胞中IL-6 mRNA和TNF-αmRNA表达水平升高,凋亡率升高,细胞中Bax、Cleaved Caspase-3、NF-κBp65、TLR4蛋白表达升高。过表达SIRT1可以降低LPS条件下胰岛β细胞中IL-6 mRNA和TNF-αmRNA表达水平,抑制细胞凋亡,减少细胞中Bax、cleaved Caspase-3、NF-κBp65、TLR4蛋白表达。结论 SIRT1减少LPS诱导的胰岛β细胞炎症因子表达并下调细胞中NF-κB信号激活水平。     

金黄色葡萄球菌通过TLR2/PI3K信号诱导巨噬细胞的炎症反应和自噬北大核心CSCD

目的探究巨噬细胞表面Toll样受体2(TLR2)在介导金黄色葡萄球菌(SA)诱导哮喘炎症反应中的分子机制。方法通过SA刺激小鼠RAW264.7巨噬细胞系建立炎症反应模型,分别用TLR2小干扰RNA(si RNA)和磷脂酰肌醇3激酶(PI3K)抑制剂3-甲基腺嘌呤(3-MA)处理。Western blot法检测细胞裂解液中TLR2、髓样分化因子88(My D88)、PI3K、核因子κBp65(NF-κBp65)磷酸化的NF-κBp65(p-NF-κBp65)以及自噬蛋白beclin-1和微管相关蛋白1轻链3B(LC3B)的水平,ELISA检测细胞上清液肿瘤坏死因子α(TNF-α)和白细胞介素6(IL-6)的分泌水平,激光共聚焦显微镜观察自噬溶酶体的数量。结果 SA刺激巨噬细胞活化TLR2等多种信号通路。TLR2 si RNA显著抑制PI3K、p-NF-κBp65以及自噬蛋白beclin-1和LC3B的表达,此外,自噬溶酶体的数量和TNF-α和IL-6的分泌也显著减少。3-MA在抑制自噬和炎症反应方面与TLR2 si RNA的作用效果相同。结论 TLR2通过PI3K信号通路调控金黄色葡萄球菌诱导巨噬细胞的炎症反应和自噬。     

Notch1信号通过TRAF6参与TLR4介导的NF-κB激活

目的观察Notch1和TLR4信号交叉调控NF-κB激活并探讨其可能的作用机制。方法体外培养RAW264.7细胞,LPS刺激RAW264.7细胞后检测Notch1信号激活以及Notch1信号抑制剂DAPT对TNF-α、IL-6和IL-1β表达的影响,Western blot检测DAPT对IKKα/β磷酸化以及NF-κB p65活化的影响,并检测DAPT对TLR4信号通路IKKα/β上游信号My D88和TRAF6表达的影响。结果 LPS刺激RAW264.7细胞后能显著提高Notch1信号蛋白NICD和目的蛋白Hes1表达,DAPT能明显抑制NICD和Hes1的表达。LPS诱导TNF-α、IL-6和IL-1β表达和释放能被DAPT抑制但被Notch1信号激动剂jagged1增强。DAPT能够抑制LPS介导的TRAF6表达和IKKα/β磷酸化,促进NF-κB p65核转位,但DAPT对LPS诱导My D88的表达没有明显的影响。结论 Notch1和TLR4信号存在交叉对话,Notch1通过TRAF6调控NF-κB活化参与TLR4介导的免疫应答。     

MyD88/PI3-K/NF-κB途径介导脂氧素A4拮抗LPS诱导大鼠内皮细胞的白细胞介素合成

目的研究脂氧素A4（LXA4）对脂多糖（LPS）诱导血管内皮细胞合成白细胞介素（IL）-1β、IL-6、IL-8的影响，并探讨其机制。方法对体外培养大鼠肺微血管内皮细胞（PMVEC），用LXA4孵育，再加入LPS；或单用LPS刺激PMVEC。在孵育后用酶联免疫吸附法（ELISA）检测培养上清中的IL-1β、IL-6、IL-8蛋白表达；用RT-PCR法检测IL-1β、IL-6、IL-8的mRNA表达。应用Western blot法检测磷酸化的磷脂酰肌醇-3-激酶（PI3-K）、髓细胞分化因子88（MyD88）的表达。应用凝胶电泳迁移率试验（EMSA）测定核因子-κB（NF-κB）和活化蛋白-1（AP-1）的DNA结合活性。结果LXA4呈剂量依赖性地抑制LPS诱导的PMVEC的IL-1β、IL-6、IL-8的蛋白合成与mRNA表达，抑制PI-3K的表达，抑制NF-κB和AP-1的DNA结合活性，但不影响LPS诱导的MyD88表达。结论LXA4通过下调PI3-K的表达和NF-κB、AP-1的DNA结合活性，拮抗LPS对PMVEC的IL-1β、IL-6、IL-8合成的诱导作用。     

MD-2 regulates LPS-induced NLRP3 inflammasome activation and IL-1beta secretion by a MyD88/NF-κB-dependent pathway in alveolar macrophages cell line

Myeloid differentiation protein 2 (MD-2) is required in the recognition of lipopolysaccharide (LPS) by toll-like receptor 4 (TLR4), and participates in LPS-induced alveolar macrophage (AM) inflammation during acute lung injury (ALI). Activation of the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome aggravates inflammation in LPS-induced ALI. However, there is currently little known about the relationship between MD-2 signaling and the NLRP3 inflammasome. This study showed that NLRP3 expression, IL-1beta (IL-1β) secretion, and pyroptosis were up-regulated after LPS stimulation in the NR8383 AM cell-line. MD-2 gene knock-down reduced LPS-induced mRNA and protein expression of NLRP3 and IL-1β secretion in NR8383 cells, and inhibited the MyD88/NF-κB signaling pathway. Conversely, over-expression of MD-2 not only heightened NLRP3, MyD88, and NF-κB p65 protein expression, it also aggravated the LPS-induced inflammatory response. Furthermore, the NF-κB inhibitor SN50 had a beneficial role in decreasing NLRP3 and caspase-1 mRNA and protein expression. The observations suggest that MD-2 helps to regulate LPS-induced NLRP3 inflammasome activation and the inflammatory response in NR8383 cells, and likely does so by affecting MyD88/NF-κB signaling.     

1-[4-Fluoro-2-(2-nitrovinyl)phenyl]pyrrolidine Suppresses Toll-Like Receptor 4 Dimerization Induced by Lipopolysaccharide

Toll-like receptor 4 (TLR4) recognizes LPS and triggers the activation of the myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter, inducing interferon-β (TRIF)-dependent major downstream signaling pathways. Previously, we presented biochemical evidence that 1-[4-Fluoro-2-(2-nitrovinyl)phenyl]pyrrolidine (FPP), which was synthesized in our laboratory, inhibits NF-κB activation induced by LPS. Here, we investigated whether FPP modulates the TLR4 downstream signaling pathways and what anti-inflammatory target in TLR4 signaling is regulated by FPP. FPP inhibited LPS-induced NF-κB activation by targeting TLR4 dimerization. These results suggest that FPP can modulate the TLR4 signaling pathway at the receptor level to decrease inflammatory gene expression.     

GEF-H1-RhoA signaling pathway mediates LPS-induced NF-κB transactivation and IL-8 synthesis in endothelial cells

Secretion of proinflammatory cytokines by LPS activated endothelial cells contributes substantially to the pathogenesis of sepsis. However, the mechanism involved in this process is not well understood. In the present study, we determined the roles of GEF-H1 (guanine-nucleotide exchange factor-H1)-RhoA signaling in LPS-induced interleukin-8 (IL-8, CXCL8) production in endothelial cells. First, we observed that GEF-H1 expression was upregulated in a dose- and time-dependent manner as consistent with TLR4 (Toll-like receptor 4) expression after LPS stimulation. Afterwards, Clostridium difficile toxin B-10463 (TcdB-10463), an inhibitor of Rho activities, reduced LPS-induced NF-κB phosphorylation. Inhibition of GEF-H1 and RhoA expression reduced LPS-induced NF-κB and p38 phosphorylation. TLR4 knockout blocked LPS-induced activity of RhoA, however, MyD88 knockout did not impair the LPS-induced activity of RhoA. Nevertheless, TLR4 and MyD88 knockout both significantly inhibited transactivation of NF-κB. GEF-H1-RhoA and MyD88 both induced significant changes in NF-κB transactivation and IL-8 synthesis. Co-inhibition of GEF-H1-RhoA and p38 expression produced similar inhibitory effects on LPS-induced NF-κB transactivation and IL-8 synthesis as inhibition of p38 expression alone, thus confirming that activation of p38 was essential for the GEF-H1-RhoA signaling pathway to induce NF-κB transactivation and IL-8 synthesis. Taken together, these results demonstrate that LPS-induced NF-κB activation and IL-8 synthesis in endothelial cells are regulated by the MyD88 pathway and GEF-H1-RhoA pathway.     

Effect of chlorogenic acid on LPS-induced proinflammatory signaling in hepatic stellate cells

Objective and design

This study was aimed at investigating the effect of chlorogenic acid (CGA) on lipopolysaccharide (LPS)-induced proinflammatory signaling in hepatic stellate cells (HSCs).

Methods

An immortalized rat HSC line was cultured in vitro and treated with LPS in the absence or presence of CGA. Reactive oxygen species (ROS) production in the HSCs was monitored by flow cytometer using DCFH-DA. The protein expression levels of toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), nuclear factor-κB (NF-κB), and p-IκB-α were determined by Western blot. The mRNA expression levels of TLR4, MyD88, monocyte chemotactic protein 1(MCP-1), and interleukin 6 (IL-6) were detected by RT-PCR. The levels of MCP-1 and IL-6 in the culture supernatant of HSCs were measured by ELISA.

Results

CGA had no effect on expression of TLR4 and MyD88. However, the treatment of CGA can inhibit LPS-induced production of ROS in HSCs. Meanwhile, CGA can inhibit LPS-induced nuclear translocation of NF-κB and IκB-α phosphorylation in HSCs, as well as NAC (a ROS scavenger). The mRNA expression and the levels of MCP-1 and IL-6 in the culture supernatant of the HSCs in this study were elevated by LPS stimulation and inhibited by CGA treatment, as well as NAC and PDTC (a NF-κB inhibitor).

Conclusion

Our results indicate that CGA can efficiently inhibit LPS-induced proinflammatory responses in HSCs and the anti-inflammatory effect may be due to the inhibition of LPS/ROS/NF-κB signaling pathway.     

黄芪总皂苷对脂多糖诱导的BV2小胶质细胞的抗炎机制

目的:探讨黄芪总皂苷(TAS)对脂多糖(LPS)诱导的BV2小胶质细胞炎症损伤的抗炎作用机制.方法:用CCK-8法筛选出对细胞活力无抑制的药物浓度;用浓度为1 mg/L的LPS刺激BV2细胞24 h,建立细胞炎症模型;实验分为正常组、LPS组、高剂量(75 mg/L)TAS组和低剂量(50 mg/L)TAS组;应用流式...     

黄芪甲苷通过toll样受体4/核因子κB通路介导辐射所致肾损伤的防护作用

目的 探讨黄芪甲苷(AS-Ⅳ)是否通过toll样受体4(TLR4)/核因子κB(NF-KB)介导的信号通路对辐射诱导肾脏损伤起到保护作用.方法 将小鼠分为正常对照组、DMSO溶剂组、辐射组(IR)、IR+AS-Ⅳ20 mg/kg组和IR+AS-Ⅳ 40 mg/kg组.小鼠给予AS-Ⅳ腹腔注射1个月后,以8Gy的60Co...     

Potential autocrine regulation of interleukin-33/ST2 signaling of dendritic cells in allergic inflammation

This study identified a novel phenomenon that dendritic cells (DCs) produced interleukin (IL)-33 via Toll-like receptor (TLR)-mediated innate pathway. Mouse bone marrow–derived DCs were treated with or without microbial pathogens or recombinant murine IL-33. IL-33 mRNA and protein were found to be expressed by DCs and largely induced by several microbial pathogens, highly by lipopolysaccharide (LPS) and flagellin. Using two mouse models of topical challenge by LPS and flagellin and experimental allergic conjunctivitis, IL-33-producing DCs were observed in ocular mucosal surface and the draining cervical lymph nodes in vivo. The increased expression levels of myeloid differentiation primary-response protein 88 (MyD88), nuclear factor (NF)-κB1, NF-κB2, and RelA accompanied by NF-κB p65 nuclear translocation were observed in DCs exposed to flagellin. IL-33 induction by flagellin was significantly blocked by TLR5 antibody or NF-κB inhibitor quinazoline and diminished in DCs from MyD88 knockout mice. IL-33 stimulated the expression of DC maturation markers, CD40 and CD80, and proallergic cytokines and chemokines, OX40L, IL-4, IL-5, IL-13, CCL17 (C-C motif chemokine ligand 17), TNF-α (tumor necrosis factor-α), and IL-1β. This stimulatory effect of IL-33 in DCs was significantly blocked by ST2 antibody or soluble ST2. Our findings demonstrate that DCs produce IL-33 via TLR/NF-κB signaling pathways, suggesting a molecular mechanism by which local allergic inflammatory response may be amplified by DC-produced IL-33 through potential autocrine regulation.     

Propofol Attenuates Airway Inflammation in a Mast Cell-Dependent Mouse Model of Allergic Asthma by Inhibiting the Toll-like Receptor 4/Reactive Oxygen Species/Nuclear Factor κB Signaling Pathway

Propofol, an intravenous anesthetic agent widely used in clinical practice, is the preferred anesthetic for asthmatic patients. This study was designed to determine the protective effect and underlying mechanisms of propofol on airway inflammation in a mast cell-dependent mouse model of allergic asthma. Mice were sensitized by ovalbumin (OVA) without alum and challenged with OVA three times. Propofol was given intraperitoneally 0.5 h prior to OVA challenge. The inflammatory cell count and production of cytokines in the bronchoalveolar lavage fluid (BALF) were detected. The changes of lung histology and key molecules of the toll-like receptor 4 (TLR4)/reactive oxygen species (ROS)/NF-κB signaling pathway were also measured. The results showed that propofol significantly decreased the number of eosinophils and the levels of IL-4, IL-5, IL-6, IL-13, and TNF-α in BALF. Furthermore, propofol significantly attenuated airway inflammation, as characterized by fewer infiltrating inflammatory cells and decreased mucus production and goblet cell hyperplasia. Meanwhile, the expression of TLR4, and its downstream signaling adaptor molecules—–myeloid differentiation factor 88 (MyD88) and NF-κB, were inhibited by propofol. The hydrogen peroxide and methane dicarboxylic aldehyde levels were decreased by propofol, and the superoxide dismutase activity was increased in propofol treatment group. These findings indicate that propofol may attenuate airway inflammation by inhibiting the TLR4/MyD88/ROS/NF-κB signaling pathway in a mast cell-dependent mouse model of allergic asthma.     

Differential induction of the toll-like receptor 4-MyD88-dependent and -independent signaling pathways by endotoxins

The biological response to endotoxin mediated through the Toll-like receptor 4 (TLR4)-MD-2 receptor complex is directly related to lipid A structure or configuration. Endotoxin structure may also influence activation of the MyD88-dependent and -independent signaling pathways of TLR4. To address this possibility, human macrophage-like cell lines (THP-1, U937, and MM6) or murine macrophage RAW 264.7 cells were stimulated with picomolar concentrations of highly purified endotoxins. Harvested supernatants from previously stimulated cells were also used to stimulate RAW 264.7 or 23ScCr (TLR4-deficient) macrophages (i.e., indirect induction). Neisseria meningitidis lipooligosaccharide (LOS) was a potent direct inducer of the MyD88-dependent pathway molecules tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein 3alpha (MIP-3alpha), and the MyD88-independent molecules beta interferon (IFN-beta), nitric oxide, and IFN-gamma-inducible protein 10 (IP-10). Escherichia coli 55:B5 and Vibrio cholerae lipopolysaccharides (LPSs) at the same pmole/ml lipid A concentrations induced comparable levels of TNF-alpha, IL-1beta, and MIP-3alpha, but significantly less IFN-beta, nitric oxide, and IP-10. In contrast, LPS from Salmonella enterica serovars Minnesota and Typhimurium induced amounts of IFN-beta, nitric oxide, and IP-10 similar to meningococcal LOS but much less TNF-alpha and MIP-3alpha in time course and dose-response experiments. No MyD88-dependent or -independent response to endotoxin was seen in TLR4-deficient cell lines (C3H/HeJ and 23ScCr) and response was restored in TLR4-MD-2-transfected human embryonic kidney 293 cells. Blocking the MyD88-dependent pathway by DNMyD88 resulted in significant reduction of TNF-alpha release but did not influence nitric oxide release. IFN-beta polyclonal antibody and IFN-alpha/beta receptor 1 antibody significantly reduced nitric oxide release. N. meningitidis endotoxin was a potent agonist of both the MyD88-dependent and -independent signaling pathways of the TLR4 receptor complex of human macrophages. E. coli 55:B5 and Vibrio cholerae LPS, at the same picomolar lipid A concentrations, selectively induced the MyD88-dependent pathway, while Salmonella LPS activated the MyD88-independent pathway.     

Regulation of the polymeric immunoglobulin receptor by the classical and alternative NF-κB pathways in intestinal epithelial cells

The polymeric immunoglobulin receptor (pIgR) transports IgA antibodies across intestinal epithelial cells (IECs). Expression of pIgR is upregulated by proinflammatory signaling pathways via activation of nuclear factor-κB (NF-κB). Here, we examined the contributions of the RelA-dependent classical and RelB-dependent alternative pathways of NF-κB to pIgR regulation in the HT-29 human IEC line following stimulation with tumor necrosis factor (TNF), lipopolysaccharide (LPS; Toll-like receptor 4 (TLR4) ligand), and polyinosinic: polycytidylic acid (pIC; TLR3 ligand). Whereas induction of proinflammatory genes such as interleukin-8 (IL-8) required only RelA, pIgR expression was regulated by complex mechanisms that involved both RelA and RelB. Upregulation of pIgR expression by ligation of the lymphotoxin-β receptor suggested a direct role for the alternative NF-κB pathway. Inhibition of mitogen-activated protein kinases reduced the induction of IL-8, but enhanced the induction of pIgR by TNF and TLR signaling. Regulation of pIgR through unique signaling pathways could allow IECs to sustain high levels of IgA transport while limiting the proinflammatory responses.