Comparative analysis of proteins in the culture supernatants of human intestinal epithelial cells infected with the wild-type and rtxE mutant of Vibrio vulnificus

Bacterial virulence factors and secreted extracellular proteins from damaged host cells following infection have been recognized as key mediators in the pathophysiological alterations observed in septic shock, and have also been shown to have a synergistic influence on bacterial pathogenicity. We hypothesized that during infections, virulence factors as well as host-shed proteins may synergistically influence aspects of the pathogenicity of V. vulnificus, such as primary septic shock and overproduction of proinflammatory cytokines. However, virulence factors and host-derived proteins have yet to be clearly evaluated during V. vulnificus infection. In this study, we analyzed and compared the proteins in conditioned supernatants generated from co-cultures of host cells and either wild-type or rtxE mutant V. vulnificus using LC-QTOF-MS/MS analysis. In a previous study, we determined that the culture supernatants of the rtxE mutant V. vulnificus-infected INT-407 cells induced significantly lower levels of IL-8 production from human intestinal epithelial cells than did the culture supernatants of wild-type V. vulnificus-infected INT-407 cells. LC-QTOF-MS/MS analysis results demonstrated that levels of proteins such as HSP90 α/β, 14-3-3 γ, PRX II, hnRNP K, β-actin, α-tubulin and V. vulnificus flagellin were significantly lower in the culture supernatants of rtxE mutant V. vulnificus-infected INT-407 cells than in the culture supernatants of wild-type V. vulnificus-infected INT-407 cells. These results demonstrate that V. vulnificus RTX toxins acting via rtxE, a transporter of virulence factors, play a very important role in the pathogenesis of V. vulnificus, as well as in its initial role in inducing pathogenic mediators from host cells.     

CagA对幽门螺杆菌诱导胃黏膜上皮细胞分泌IL-8水平的影响

目的：利用小分子干扰RNA（siRNA）探讨CagA在幽门螺杆菌诱导胃黏膜上皮细胞分泌IL-8中的作用。 方法： 设计5条siRNA，采用电穿孔法转入CagA+幽门螺杆菌 NCTC11637,与胃黏膜上皮细胞共培养后测定IL-8水平，并以 RT-PCR、Western blotting法检测穿孔前、后不同时点细菌的CagA表达。采用CagA-株NCTC11639作对照。 结果： CagA+NCTC11637诱导胃黏膜上皮细胞分泌IL-8水平明显高于CagA-NCTC11639［（1 200.00±32.51) ng/L vs (100.00±8.58） ng/L］（P<0.01）。siRNAⅢ转化的幽门螺杆菌诱导胃黏膜上皮细胞分泌IL-8 水平显著低于转化前［(400.00±17.35)ng/L vs （1 200.00±32.51 )ng/L］(P<0.05)；siRNA Ⅲ转化的幽门螺杆菌CagA mRNA水平显著低于转化前, 穿孔后6 h mRNA水平最低为31.3%(0.270/0.861), 抑制率为68.7%。Western blotting显示siRNA Ⅲ组CagA蛋白水平低于穿孔前（P<0.01）；其余4条siRNA未见显著变化。 结论： CagA在幽门螺杆菌诱导胃黏膜上皮细胞分泌IL-8中起重要作用，小分子干扰RNA可能通过抑制CagA基因表达而减少幽门螺杆菌诱导胃黏膜上皮细胞IL-8的分泌。     

Grain dust induces IL-8 production from bronchial epithelial cells: the effect of dexamethasone on IL-8 production.

BACKGROUND: Recent publications have suggested an active participation of neutrophils to induce bronchoconstriction after inhalation of grain dust (GD). OBJECTIVE: To further understand the role of neutrophils in the pathogenesis of GD-induced asthma, this investigation was designed to determine whether human bronchial epithelial cells could produce IL-8 production and to observe the effect of dexamethasone on IL-8 production. MATERIALS AND METHODS: We cultured Beas-2B, a bronchial epithelial cell line. To observe GD-induced responses, four concentrations (1 to 200 microg/mL) of GD were incubated for 24 hours and compared with those without incubation of GD. To evaluate the effect of pro-inflammatory cytokines on IL-8 production, epithelial cells were incubated with peripheral blood mononuclear cell (PBMC) culture supernatant, which was derived from the culture of PBMC from a GD-induced asthmatic subject under the exposure to 10 microg/mL of GD, and compared with those cultured without addition of PBMC supernatant. The level of released IL-8 in the supernatant was measured by enzyme-linked immunosorbent assay. To evaluate the effect of dexamethasone on IL-8 production, four concentrations (5 to 5000 ng/mL) of dexamethasone were pre-incubated for 24 hours and the same experiments were repeated. RESULTS: There was significant production of IL-8 from bronchial epithelial cells with additions of GD in a dose-dependent manner (P < .05), which was significantly augmented with additions of PBMC supernatant (P < .05) at each concentration. Compared with the untreated sample, pretreatment of dexamethasone could induced a remarkable inhibitions (15% to 55%) of IL-8 production from bronchial epithelial cells in a dose-dependent manner. CONCLUSION: These results suggest that IL-8 production from bronchial epithelial cells may contribute to neutrophil recruitment occurring in GD-induced airway inflammation. The downregulation of IL-8 production by dexamethasone from bronchial epithelial cells may contribute to the efficacy of this compound in reducing cellular infiltration and ultimately to its anti-inflammatory property.     

Grain dust induces IL-8 production from bronchial epithelial cells: effect on neutrophil recruitment.

BACKGROUND: There have been several investigations suggesting an involvement of activated neutrophils in the development of grain dust (GD)-induced occupational asthma. Interleukin-8 in the sputa from GD-induced asthmatic patients increased significantly after the exposure to GD. OBJECTIVE: To confirm IL-8 production from bronchial epithelial cells when exposed to GD, and to evaluate the role of IL-8 on neutrophil recruitment. MATERIALS AND METHOD: We cultured Beas-2B, a bronchial epithelial cell line. To observe GD-induced responses, four different concentrations ranging from 1 to 200 microg/mL of GD were incubated for 24 hours and compared with those without incubation of GD. To evaluate the effect of pro-inflammatory cytokines on IL-8 production and neutrophil chemotaxis, epithelial cells were incubated with peripheral blood mononuclear cell (PBMC) culture supernatant derived from subjects with GD-induced asthma exposed to 10 microg/mL of GD, and then compared with those without addition of PBMC supernatant. The level of released IL-8 in the supernatant was measured by enzyme-linked immunosorbent assay. Neutrophil chemotactic activity of the culture supernatant was determined by modified Boyden chamber method. RESULTS: Interleukin-8 production and neutrophil chemotactic activity from bronchial epithelial cells significantly increased with additions of GD in a dose-dependent manner (P < .05, respectively), and were significantly augmented with additions of PBMC supernatant (P < .05, respectively) at each concentration. Close correlation was noted between neutrophil chemotactic activity and IL-8 level (r = 0.87, P < .05). Compared with the untreated sample, pre-treatment of anti-IL-8 antibody induced a significant suppression (up to 67.2%) of neutrophil chemotactic activity in a dose-dependent manner. CONCLUSION: These results suggest that IL-8 produced from bronchial epithelial cells may be a major cytokine, which induces neutrophil migration into the airways when exposed to GD.     

PLTP 在香烟诱导HBECs 合成IL-8 中的作用

目的:研究磷脂转运蛋白(PLTP)对香烟诱导人支气管上皮细胞(HBECs)合成白介素8(IL-8)的影响。方法:Wistar 大鼠连续3 d 被动吸烟,收集支气管肺泡灌洗液(BALF),苏木精-伊红(HE)染色,免疫组织化学法(IHC)检测蛋白表达;体外培养HBECs,不同浓度烟草提取物(CSE)刺激;PLTP siRNA 干扰后,进行CSE 刺激。MTT 法检测细胞增殖,同时检测IL-8 含量及PLTP 表达。结果:烟熏组BALF 白细胞计数以及分类计数较对照组均明显升高(P<0.01),IHC 显示烟熏组PLTP 和IL-8 蛋白表达高于对照组;高浓度CSE(2%、4%)抑制HBECs 增殖(P<0.001);不同浓度的CSE 作用24 h 后,IL-8mRNA 及蛋白表达量增加,而PLTP 蛋白表达量下降,并且IL-8 蛋白分泌呈现时间依赖性;PLTP siRNA 处理后,IL-8 表达量明显升高(P<0.001)。结论:PLTP 基因缺失促进香烟诱导HBECs 合成IL-8。     

Autophagy is required for toll-like receptor-mediated interleukin-8 production in intestinal epithelial cells

Autophagy is an evolutionarily conserved process that maintains cellular homeostasis via synthesis, degradation, and subsequent recycling of cellular products under various physiological conditions. However, the link between autophagy and the innate immune system remains unknown. In the present study, we evaluated Toll-like receptor (TLR)-mediated autophagy induction in intestinal epithelial cells (IECs) and its relationship to interleukin (IL)-8 production. IEC-6, HCT-15, RAW264.7, and THP-1 cells were cultured with or without various TLR ligands, followed by evaluation of the expressions of pro-inflammatory cytokines [IL-8, cytokine-induced neutrophil chemoattractants (CINC)-2β, macrophage inflammatory protein (MIP)-2] by real-time PCR and ELISA. To reveal the status of autophagy in IECs and macrophages, light chain 3 (LC3)-II expression was examined using Western blotting and immunofluorescence with confocal microscopy. Also, to evaluate the influence of TLR ligands on autophagy-mediated innate-immune responses, autophagy-related gene (Atg)7 specific siRNA was transfected into intestinal epithelial cells and IL-8 expression was determined following exposure to various TLR ligands. Cells treated with the TLR ligands produced considerable amounts of pro-inflammatory cytokines (IL-8, CINC-2β, MIP-2). Furthermore, the basal levels of LC3-II were markedly higher in IECs as compared to those in macrophages. Our findings indicated that autophagy induction following TLR ligand stimulation was not significantly evident in IECs as compared to macrophages. In addition, Atg7 gene expression silencingled to down-regulation of TLR-mediated IL-8 expression in IECs, which indicates a potential role of autophagy in generating innate-immune responses. In conclusion, autophagy may be an important intracellular machinery for inducing the innate immune system in IECs.     

Regulation and production of IL-8 by human proximal tubular epithelial cells in vitro

A number of inflammatory kidney diseases are associated with interstitial nephritis and influx of leucocytes in the renal interstitium. Potentially the influx of neutrophils in the interstitium may be induced by the chemotactic cytokine IL-8. In the present study we have analysed the production of IL-8 by cultured human proximal tubular epithelial cells (PTEC) in response to a number of proinflammatory cytokines. Primary cell lines of proximal tubular epithelium obtained from ten different kidneys, and cultured under serum-free conditions, were found to produce IL-8 to different degrees from not detectable levels up to 10·8±1·5 ng IL-8 per 1×10⁵ cells in 72 h. Gel filtration chromatography of PTEC supernatant indicated that the size of IL-8 of PTEC is 15·1 and 8·1 kD, and is chemotactically active for polymorphonuclear neutrophils (PMN). Addition of 0·5 ng/ml rIL-1α or 1000 U/ml recombinant tumour necrosis factor-alpha (TNF-α) to the culture media of PTEC induced an up-regulation of IL-8 production up to 6·3-fold and 3·0-fold, respectively. The up-regulation by IL-1α and TNF-α was dose- and time-dependent. In contrast, 500 U/ml recombinant interferon-gamma (rIFN-γ) down-regulated the production of IL-8 3·4-fold. Northern blot analysis showed that IL-1α and TNF-α increased the expression of IL-8 mRNA, whereas IFN-γ reduced IL-8 mRNA expression. Taken together, these experiments indicate that human PTEC are a potential source of IL-8 in the kidney, and that IL-8 produced in the proximal tubule can be induced by various proinflammatory cytokines.     

Monocyte chemoattractant protein-1 production by intestinal epithelial cells in vitro: a role for p38 in epithelial chemokine expression.

The intestinal epithelial cell (IEC) represents the first cellular barrier to infection. Consistent with this sentinel role, IEC are known to produce a variety of chemokines in response to bacterial infection or proinflammatory cytokines. These chemokines act as potent leukocyte activators and chemoattractants in vivo. In this report, we begin to characterize the regulation of expression of the chemokine monocyte chemoattractant protein-1 (MCP-1) in the rat small intestinal IEC-18 line. Following stimulation with either interleukin-1beta (IL-1beta) or lipopolysaccharide (LPS), IEC-18 cells produced MCP-1, with IL-1 proving a more effective stimulus than LPS at both the mRNA and protein levels. Expression of MCP-1 due to either stimulus was inhibited by tyrosine kinase inhibitors, prompting us to investigate potential phosphotyrosine-dependent targets responsible for MCP-1 expression. We detected activation of p38, a member of the mitogen-activated protein kinase family, following either IL-1 or LPS treatment. Specific inhibition of this kinase using the compound SB203580 caused a destabilization of MCP-1 mRNA. These data point to a role for p38 in the regulation of MCP-1 mRNA expression by the IEC.     

Human intestinal epithelial cells down-regulate IL-8 expression in human intestinal microvascular endothelial cells; role of transforming growth factor-beta 1 (TGF-β1)

Cytokines produced from intestinal epithelial cells may function as signals to neighbouring immune cells. In the present study we analysed the effects of colonic epithelial cell lines (HT-29, Caco-2, HCT-116, Colo-320) and freshly isolated intestinal epithelial cells on IL-8 expression in the SV-40T transfected human microvascular endothelial cell line (HMEC-1). Epithelial cell-conditioned media and transwells preventing physical contact between epithelial and endothelial cells were used. TGF-β1 and IL-8 levels were determined by ELISA and Northern blot analysis. Increasing concentrations of IL-1β led to increasing production of IL-8. The addition of epithelial cell-conditioned medium or epithelial cells to HMEC-1 cells in a two-compartment co-culture system resulted in a strong decrease in IL-8 at the protein and mRNA level. Decrease of IL-8 was markedly stronger when epithelial cells were co-cultured in contact with HMEC-1 cells, indicating that not only soluble factor(s) play a role in the induction of IL-8 suppression in HMEC-1 cells. MoAbs against TGF-β1 partially inhibited down-regulation of endothelial IL-8 expression. In further studies, IL-8 expression in freshly isolated human intestinal microvascular endothelial cells (HIMEC) was also down-regulated by intestinal epithelial cells. Our results demonstrate that intestinal epithelial cells down-regulate IL-8 expression in HMEC-1 cells. TGF-β1 is a candidate factor of epithelial–endothelial communication in the colonic mucosa.     

Exposure to toluene diisocyanate (TDI) induces IL-8 production from bronchial epithelial cells: effect of pro-inflammatory cytokines

This investigation was designed to confirm IL-8 production from human bronchial epithelial cells with toluene diisocyanate (TDI) exposure and to examine the effects of pro-inflammatory cytokine and dexamethasone. We cultured Beas-2B, a bronchial epithelial cell line with TDI-HSA conjugate and compared with those without conjugate. IL-8 in the supernatant was measured by ELISA. To evaluate the effect of proinflammatory cytokines, peripheral blood mononuclear cells (PBMC) were collected from TDI- and non-TDI asthma patients, and were added to the epithelial cell culture. Dexamethasone or antibodies to TNF-alpha and IL-1beta were pre-incubated with PBMC supernatant. There was a significant production of IL-8 from bronchial epithelial cells with addition of TDI-HSA conjugate in a dose-dependent manner, which was significantly augmented with addition of PBMC supernatant. Higher production of IL-8 was noted with addition of PBMC supernatant from TDI-asthma patients than in those from non-TDI asthma patients. IL-1beta and IL-1beta/TNF alpha antibodies were able to suppress the IL-8 productions. Pre-treatment of dexamethasone induced dose-dependent inhibition of the IL-8 production. These results suggest that the IL-8 production from bronchial epithelial cells contribute to neutrophil recruitment occurring in TDI-induced airway inflammation. IL-1beta released from PBMC of TDI-induced asthma patients may be one of the pro-inflammatory cytokines to enhance IL-8 production.     

IL-4, IL-10 and IL-13 down-regulate monocyte-chemoattracting protein-1 (MCP-1) production in activated intestinal epithelial cells

Several studies have demonstrated that intestinal epithelial cells play a major role in the initiation and perpetuation of intestinal inflammation by secreting proinflammatory cytokines and chemokines. MCP-1 is suggested to be a chemokine that plays a major part during intestinal inflammation in inflammatory bowel disease (IBD). Immunoregulatory cytokines such as IL-4, IL-10 and IL-13 have been described to exert anti-inflammatory properties on various cell types. The aim of our study was to determine the effect of Th2 cytokines on the production of MCP-1 by activated intestinal epithelial cells. We examined Caco-2 cells as well as intestinal epithelial cells which were isolated from surgical specimens. Production of the chemokine MCP-1 was determined under stimulated and non-stimulated conditions. IL-4, IL-10 and IL-13 were added to stimulated epithelial cells under various culture conditions. Supernatants were analysed for cytokine concentrations using ELISAs. Under stimulation with physiological agents like IL-1β or tumour necrosis factor-alpha (TNF-α), we observed markedly increased concentrations of MCP-1 in supernatants of Caco-2 cells and intestinal epithelial cells. IL-4, IL-10 and IL-13 all had the capacity to down-regulate the production of MCP-1 in Caco-2 cells as well as in freshly isolated epithelial cells. Caco-2 cells which were primed with Th2 cytokines 24 h before stimulation were subsequently decreased in their ability to be stimulated by IL-1β or TNF-α for MCP-1 production. As MCP-1 has been shown to play a major role during intestinal inflammation, the in vitro suppression of MCP-1 in enterocytes suggests the in vivo use of regulatory cytokines in patients with active IBD.     

Cytolytic action of Vibrio vulnificus haemolysin on mast cells from rat peritoneal cavity.

The mode of action of Vibrio vulnificus haemolysin (VVH) on mast cells from the peritoneal cavity of the rat was examined. VVH induced histamine release, and damage to the mast cells, in a dose-dependent fashion. When 1 microgram of VVH was added to c. 10(5) mast cells at 37 degrees C, histamine release was observed after a lag period of 5-10 s, and was complete within 5 min. The action was temperature-dependent, and was not induced at 4 degrees C. Disodium cromoglycate, a membrane stabiliser for mast cells, inhibited the histamine release significantly, but the effect was not dose-dependent. Moreover, leakage of lactate dehydrogenase from VVH-treated mast cells was observed. These results suggest that VVH acts on the cell membrane of mast cells and is cytolytic.     

Shigella infection of Henle intestinal epithelial cells: role of the bacterium.

Epithelial cell infection by Shigella flexneri 2a was studied in an in vitro model system. Using the Henle 407 human intestinal epithelial cell line as host cells, a standardized experimental protocol which allowed quantitative measurement of infection was developed. Intravellular residence of infecting organisms was confirmed by indirect fluorescent-antibody staining of unfixed and methanol-fixed (Henle 407) cells and by quantitative bacteriological culture of disrupted host cells after infection. The process of shigella entry into cells was evaluated by chemical or physical modulation of the bacterium under controlled experimental conditions. Shigella were subjected to mild heat, ultraviolet radiation aminoglycoside antibiotics, and immunoglobulins raised against S. flexneri 2a. The data show that heat-stable antigens on the bacterial surface are not solely responsible for infectivity of S. flexneri 2a. Furthermore, it was shown that physiological and synthetic functions of shigellae are required for entry into host cells.     

甲酰肽受体在缺氧时对血管平滑肌细胞IL-6和IL-8产生的作用

目的探讨甲酰肽受体(formyl peptide receptor,FPR)在缺氧时对血管平滑肌细胞(vascular smooth muscle cells,VSMCs)炎症因子产生的作用。方法按照缺氧时间将大鼠血管平滑肌细胞随机分为0 h、12 h、24 h组,将各组细胞放入缺氧培养箱(1%O2、5%CO2、99%N2)培养相应时间后,用Western blot检测平滑肌细胞中IL-6、IL-8的蛋白水平,用RT-PCR检测其m RNA水平。同时使用FPR拮抗剂t BOC预处理细胞并缺氧不同时间(0 h、12 h、24 h、)后,检测IL-6、IL-8的表达水平。另外,为了进一步明确FPR与炎症因子表达的关系,用FPR激动剂f MLP直接处理细胞之后,检测IL-6、IL-8的表达水平。然后使用细胞在缺氧条件下培养后的上清液作用于未缺氧的细胞,检测IL-6、IL-8的表达水平变化,并通过观察FPR拮抗剂处理后的变化,明确FPR在其中的作用。用f MLP刺激p38抑制剂预处理过的细胞,检测IL-6、IL-8的表达水平变化,以观察FPR激活后引起炎症因子表达对p38途径的依赖性。结果缺氧后血管平滑肌细胞的IL-6、IL-8 m RNA和蛋白含量均显著高于0 h组;当t BOC处理细胞后显著削弱了这一效应(P<0.05)。而且FPR激动剂能直接显著提高未缺氧的细胞的IL-6、IL-8的表达水平(P<0.05)。使用缺氧细胞的上清作用于常氧细胞后IL-6、IL-8的表达水平显著高于常氧细胞上清的作用效果;FPR拮抗剂处理显著削弱了这一效应(P<0.05)。用p38抑制剂预处理过的细胞加入f MLP与单纯加入f MLP的细胞相比,血管平滑肌细胞IL-6、IL-8表达水平显著低于单纯加入f MLP组(P<0.05)。结论缺氧引起血管平滑肌细胞IL-6、IL-8的表达,FPR在这一过程中发挥了重要的介导作用,而FPR是被缺氧细胞释放出来的激动剂激活。激活后的FPR引起IL-6、IL-8的表达依赖于p38信号途径。