Toll-Like Receptor 4 Signaling in the Ileum and Colon of Gnotobiotic Piglets Infected with Salmonella Typhimurium or Its Isogenic ∆rfa Mutants

Salmonella Typhimurium is a Gram-negative bacterium that causes enterocolitis in humans and pigs. Lipopolysaccharide (LPS) is a component of the outer leaflet of Gram-negative bacteria that provokes endotoxin shock. LPS can be synthesized completely or incompletely and creates S (smooth) or R (rough) chemotypes. Toll-like receptors (TLR) 2, 4, and 9 initiate an inflammatory reaction to combat bacterial infections. We associated/challenged one-week-old gnotobiotic piglets with wild-type S. Typhimurium with S chemotype or its isogenic ∆rfa mutants with R chemotype LPS. The wild-type S. Typhimurium induced TLR2 and TLR4 mRNA expression but not TLR9 mRNA expression in the ileum and colon of one-week-old gnotobiotic piglets 24 h after challenge. The TLR2 and TLR4 stimulatory effects of the S. Typhimurium ∆rfa mutants were related to the completeness of their LPS chain. The transcription of IL-12/23 p40, IFN-γ, and IL-6 in the intestine and the intestinal and plasmatic levels of IL-12/23 p40 and IL-6 but not IFN-γ were related to the activation of TLR2 and TLR4 signaling pathways. The avirulent S. Typhimurium ∆rfa mutants are potentially useful for modulation of the TLR2 and TLR4 signaling pathways to protect the immunocompromised gnotobiotic piglets against subsequent infection with the virulent S. Typhimurium.

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Atorvastatin suppresses LPS-induced rapid upregulation of Toll-like receptor 4 and its signaling pathway in endothelial cells

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01335.2008 ◽

2011 ◽

Vol 300 (5) ◽

pp. H1743-H1752 ◽

Cited By ~ 38

Author(s):

Ying Wang ◽

Ming Xiang Zhang ◽

Xiao Meng ◽

Fu Qiang Liu ◽

Guang Sheng Yu ◽

...

Keyword(s):

Endothelial Cells ◽

Mrna Expression ◽

Signaling Pathways ◽

P38 Mapk ◽

Umbilical Vein ◽

Enzyme Linked Immunosorbent Assay ◽

Toll Like Receptor ◽

Toll Like Receptor 4 ◽

Mapk Phosphorylation ◽

Tlr4 Mrna

In the present study, we tested our hypothesis that atorvastatin exerts its anti-inflammation effect via suppressing LPS-induced rapid upregulation of Toll-like receptor 4 (TLR4) mRNA and its downstream p38, ERK, and NF-κB signaling pathways in human umbilical-vein endothelial cells (HUVECs) and human aortic endothelial cells (HAECs). TLR4 mRNA expression and its downstream kinase activities induced by LPS alone or atorvastatin + LPS in endothelial cells were quantified using quantitative real-time PCR and enzyme-linked immunosorbent assay. Preincubation of LPS-stimulated endothelial cells with TLR4 siRNA was conducted to identify the target of the anti-inflammatory effects of atorvastatin. Atorvastatin incubation resulted in the reduction of LPS-induced TLR4 mRNA expression, ERK1/2 and P38 MAPK phosphorylation, and NF-κB binding activity. Pretreatment with MEK/ERK1/2 inhibitor PD98059 attenuated atorvastatin + LPS-induced NF-κB activity but had no effect on P38 MAPK phosphorylation. In contrast, pretreatment with P38 MAPK inhibitor SB203580 resulted in upregulation of atorvastatin + LPS-induced ERK1/2 phosphorylation but had no significant effects on NF-κB activity. On the other hand, blocking NF-κB with SN50 produced no effects on atorvastatin + LPS-induced ERK1/2 and P38 MAPK phosphorylation. Moreover, TLR4 gene silencing produced the same effects as the atorvastatin treatment. In conclusion, atorvastatin downregulated TLR4 mRNA expression by two distinct signaling pathways. First, atorvastatin stabilized Iκ-Bα, which directly inhibited NF-κB activation. Second, atorvastatin inactivated ERK phosphorylation, which indirectly inhibited NF-κB activation. Suppression of p38 MAPK by atorvastatin upregulates ERK but exerts no effect on NF-κB.

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Gamma Interferon Prevents the Inhibitory Effects of Oxidative Stress on Host Responses to Escherichia coliInfection

Infection and Immunity ◽

10.1128/iai.69.4.2621-2629.2001 ◽

2001 ◽

Vol 69 (4) ◽

pp. 2621-2629 ◽

Cited By ~ 7

Author(s):

Michael J. Parmely ◽

Fuan Wang ◽

Douglas Wright

Keyword(s):

Oxidative Stress ◽

Bacterial Infections ◽

Gamma Interferon ◽

Glutathione Depletion ◽

Intercellular Adhesion Molecule ◽

Necrosis Factor Alpha ◽

Gram Negative ◽

E Coli ◽

Redox Imbalance ◽

Ifn Γ

ABSTRACT Oxidative stress occurs in animals challenged with bacterial endotoxin and can affect the expression of important host inflammatory genes. However, much less is known about the effects of oxidative stress on responses to gram-negative bacteria. The current study compared the effects of redox imbalance on hepatic responses of mice to Escherichia coli bacteria versus purified endotoxic lipopolysaccharide (LPS). Oxidative stress induced by glutathione depletion virtually eliminated hepatic tumor necrosis factor alpha responses to both E. coli and LPS. Inducible NO synthase (iNOS) and intercellular adhesion molecule-1 (ICAM-1) expression was also markedly inhibited by glutathione depletion in LPS-challenged mice, but was unaffected in E. coli-infected animals. Three findings suggested that gamma interferon (IFN-γ) production explained the differences between LPS and bacterial challenge. Glutathione depletion completely inhibited the IFN-γ response to LPS, but only partially inhibited IFN-γ production in infected mice. Exogenous IFN-γ restored iNOS and ICAM-1 responses to LPS in stressed mice. Conversely, IFN-γ-deficient, glutathione-depleted mice showed a marked decrease in iNOS and ICAM-1 expression when challenged with E. coli. These findings indicate that both the nature of the microbial challenge and the production of IFN-γ can be important in determining the effects of redox imbalance during gram-negative bacterial infections.

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Endotoxin Modulates the Expression of Renal Drug Transporters in HIV-1 Transgenic Rats

Journal of Pharmacy & Pharmaceutical Sciences ◽

10.18433/jpps30017 ◽

2018 ◽

Vol 21 (1s) ◽

pp. 117s-129s ◽

Cited By ~ 4

Author(s):

Navaz Karimian Pour ◽

Micheline Piquette-Miller

Keyword(s):

Mrna Expression ◽

Bacterial Infections ◽

Drug Transporters ◽

Serum Levels ◽

Low Grade ◽

Western Blots ◽

Tnf Α ◽

Cytokine Levels ◽

Associated Conditions ◽

Ifn Γ

PURPUSE: Bacterial co-infections and low grade endotoxemia are common in HIV patients. Inflammation due to endotoxin or HIV may influence the expression and activity of transporters. Kidney transporters influence renal drug clearances including many antiretroviral agents. Our objective was to study the effect of endotoxin and HIV on the renal expression of drug transporters in an HIV-transgenic (HIV-Tg) rat model. These rats develop immune dysfunction and AIDS-associated conditions like humans. METHODS: Endotoxin or saline was administered intraperitoneally to HIV-Tg or wild type (WT) littermates and kidneys were collected 18 hours later. Expression of transporters and cytokines were measured by qRT-PCR and Western blots. Serum cytokine levels were measured by ELISA. RESULTS: Endotoxin induced serum levels of IL-6, TNF-α and IFN-γ in both HIV-Tg and WT animals. The basal mRNA expression of Oct2, Oct3, Octn1, Mate1, Urat1 and Ent1was significantly lower (33-60%) and the expression of Ent2 and Pept2 was significantly higher (33-45%) in HIV-Tg as compared to WT. While endotoxin significantly downregulated the mRNA expression of Mdra1 and Pept2 in both HIV and WT groups (69-78%), it imposed a significant reduction on the mRNA expression of Oct2, Oct3, Octn1, Mate1, Oat2, urat1, and Ent1 (54-83%) only in the WT group. Endotoxin significantly increased the mRNA expression of Pept1 (140%) in both WT and HIV groups. CONCLUSIONS: HIV and endotoxin each imposed alterations in the expression of many clinically important renal drug transporters although co-infection did not augment this effect. Viral and/or bacterial infections may impact the renal clearance of drug substrates in patients and could potentially be a source of drug-disease interactions.

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Divergent Role of Gamma Interferon in a Murine Model of Pulmonary versus Systemic Klebsiella pneumoniae Infection

Infection and Immunity ◽

10.1128/iai.70.11.6310-6318.2002 ◽

2002 ◽

Vol 70 (11) ◽

pp. 6310-6318 ◽

Cited By ~ 60

Author(s):

Thomas A. Moore ◽

Michelle L. Perry ◽

Andrew G. Getsoian ◽

Michael W. Newstead ◽

Theodore J. Standiford

Keyword(s):

Liver Injury ◽

Klebsiella Pneumoniae ◽

Knockout Mice ◽

Peripheral Blood ◽

Pulmonary Infection ◽

Wild Type ◽

Gram Negative ◽

Ifn Γ ◽

Intravenous Inoculation

ABSTRACT Klebsiella pneumoniae is a leading cause of both community-acquired and nosocomial gram-negative-bacterial pneumonia. A further clinical complication of pulmonary K. pneumoniae infection is dissemination of bacteria from the lung into the peripheral blood, resulting in bacteremia concurrent with the localized pulmonary infection. Here, we report studies detailing the divergent role of gamma interferon (IFN-γ) in pulmonary versus systemic K. pneumoniae infection. Intratracheal inoculation of IFN-γ knockout mice resulted in significantly increased mortality compared to that observed for wild-type infected animals. Increased mortality correlated with a 100-fold increase in pulmonary bacteria within 2 days postinfection and upregulation of lung-associated interleukin-10 (IL-10) mRNA. Interestingly, IFN-γ knockout mice had a twofold reduction in plasma aminospartate transferase activity, indicating diminished liver injury following peripheral blood bacterial dissemination. To study the host response towards blood-borne bacteria in the absence of the ongoing pulmonary infection, intravenous inoculation studies were initiated. IFN-γ knockout mice were no more susceptible to intravenous infection than their wild-type counterparts. The consistent observation in IFN-γ knockout mice was for improved survival correlating with increased clearance of blood- and liver-associated bacteria. Intravenous inoculation resulted in a two- to threefold increase in hepatic IL-10 production 24 and 48 h postinfection. Liver injury was also significantly reduced in IFN-γ knockout mice. These data indicate that IFN-γ secretion is a critical mediator in the resolution of localized gram-negative pulmonary pneumonia. Surprisingly, host responses towards systemic infection with the same bacteria appear to be IFN-γ independent.

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Heat stress inhibits TLR4-NF-κB and TLR4-TBK1 signaling pathways in broilers infected with Salmonella Typhimurium

International Journal of Biometeorology ◽

10.1007/s00484-021-02146-5 ◽

2021 ◽

Author(s):

Wei-Hao Li ◽

Yi-Lei Liu ◽

Jian-Chi Lun ◽

Yong-Ming He ◽

Lu-Ping Tang

Keyword(s):

Immune Response ◽

Global Warming ◽

Heat Stress ◽

Oral Administration ◽

Salmonella Typhimurium ◽

Immune Function ◽

Signaling Pathways ◽

Production Performance ◽

Tnf Α ◽

Ifn Γ

AbstractWith the global warming, the harm of heat stress (HS) to the breeding industry has become more common, which causes the decline of animal production performance and low immunity. This study aimed to analyze the effect of HS on the intestinal immune function of Salmonella-infected chickens. Fourteen-day-old broilers were divided into the following four groups of eight replicates: control (Control), heat stress (HS), Salmonella Typhimurium (ST), and heat stress + Salmonella Typhimurium (HS+ST). The broilers were subjected to a heat stress of 35 °C from 15 to 28 days of age. Salmonella Typhimurium (ST, 14028, 109 cfu/mL) was inoculated, via oral administration at 29 days of age, into ST and HS+ST group birds. On the 4th day after Salmonella Typhimurium administration, an increase in jejunum IgA levels was observed in chickens infected with Salmonella Typhimurium. Mechanistic regulation of TLR4-NFκB-NLRP3 and TLR4-TBK1 signaling by heat stress was evaluated in Salmonella Typhimurium–infected broilers. Heat stress markedly inhibited the expression of cytokines including TNF-α, IL-6, IL-1β, NLRP3, caspase-1, NF-κB-p65, and p-NF-κB-p65, and the TLR4-TBK1 cytokines IFN-α, IFN-γ, p-IRF3, and p-TBK1 in jejunum of broilers infected with Salmonella Typhimurium. Collectively, our results demonstrate that heat stress can inhibit intestinal immune response by downregulating the expression of TLR4-NFκB-NLRP3 and TLR4-TBK1 signaling pathways in broilers infected with Salmonella Typhimurium.

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Flagellar Localization of a Helicobacter pylori Autotransporter Protein

mBio ◽

10.1128/mbio.00613-12 ◽

2013 ◽

Vol 4 (2) ◽

Cited By ~ 17

Author(s):

Jana N. Radin ◽

Jennifer A. Gaddy ◽

Christian González-Rivera ◽

John T. Loh ◽

Holly M. Scott Algood ◽

...

Keyword(s):

Helicobacter Pylori ◽

Bacterial Infections ◽

Secreted Proteins ◽

Wild Type ◽

Gram Negative ◽

Content Type ◽

Ulcer Disease ◽

H Pylori ◽

Type V

ABSTRACTHelicobacter pyloricontains four genes that are predicted to encode proteins secreted by the autotransporter (type V) pathway. One of these, the pore-forming toxin VacA, has been studied in great detail, but thus far there has been very little investigation of three VacA-like proteins. We show here that all three VacA-like proteins are >250 kDa in mass and localized on the surface ofH. pylori. The expression of the threevacA-like genes is upregulated duringH. pyloricolonization of the mouse stomach compared toH. pylorigrowthin vitro, and a wild-typeH. pyloristrain outcompeted each of the three corresponding isogenic mutant strains in its ability to colonize the mouse stomach. One of the VacA-like proteins localizes to a sheath that overlies the flagellar filament and bulb, and therefore, we designate it FaaA (flagella-associated autotransporter A). In comparison to a wild-typeH. pyloristrain, an isogenicfaaAmutant strain exhibits decreased motility, decreased flagellar stability, and an increased proportion of flagella in a nonpolar site. The flagellar localization of FaaA differs markedly from the localization of other known autotransporters, and the current results reveal an important role of FaaA in flagellar localization and motility.IMPORTANCEThe pathogenesis of most bacterial infections is dependent on the actions of secreted proteins, and proteins secreted by the autotransporter pathway constitute the largest family of secreted proteins in pathogenic Gram-negative bacteria. In this study, we analyzed three autotransporter proteins (VacA-like proteins) produced byHelicobacter pylori, a Gram-negative bacterium that colonizes the human stomach and contributes to the pathogenesis of gastric cancer and peptic ulcer disease. We demonstrate that these three proteins each enhance the capacity ofH. pylorito colonize the stomach. Unexpectedly, one of these proteins (FaaA) is localized to a sheath that overliesH. pyloriflagella. The absence of FaaA results in decreasedH. pylorimotility as well as a reduction in flagellar stability and a change in flagellar localization. The atypical localization of FaaA reflects a specialized function of this autotransporter designed to optimizeH. pyloricolonization of the gastric niche.

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Limited Interleukin-18 Response inSalmonella-Infected Murine Macrophages and inSalmonella-Infected Mice

Infection and Immunity ◽

10.1128/iai.67.10.5021-5026.1999 ◽

1999 ◽

Vol 67 (10) ◽

pp. 5021-5026 ◽

Cited By ~ 19

Author(s):

Adam Elhofy ◽

Kenneth L. Bost

Keyword(s):

Immune Response ◽

Immune Responses ◽

Mrna Expression ◽

Bacterial Pathogen ◽

Intracellular Pathogen ◽

Wild Type ◽

Interleukin 18 ◽

Salmonella Dublin ◽

Murine Macrophages ◽

Ifn Γ

ABSTRACT Optimal immune responses against an intracellular bacterial pathogen, such as Salmonella, involve the production of gamma interferon (IFN-γ), which activates macrophages. It has recently been suggested that, interleukin-18 (IL-18), in addition to IL-12, contributes to the induction of IFN-γ following infection. Given this hypothesis, an optimal host immune response against intracellular bacterial pathogens would include the induction of IL-18 secretion by macrophages due to Salmonella infection. We questioned whether Salmonella could induce macrophages to upregulate their expression of IL-18 mRNA and secretion of IL-18. With cultures of murine macrophages, we were surprised to find that infection by wild-type Salmonella dublin resulted in decreased expression of IL-18 mRNA and IL-18 secretion rather than an increase. Reduction of macrophage-derived IL-18 expression by wild-typeSalmonella occurred early in the response, suggesting a direct effect. Furthermore, mice orally inoculated with wild-typeSalmonella were shown to have reduced IL-18 mRNA expression at mucosal sites within hours postinoculation. Together these studies demonstrate Salmonella-induced reductions in IL-18 expression, suggesting that this intracellular pathogen may be capable of limiting a potentially protective immune response.

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