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The intestinal microbiota are necessary for stressor-induced enhancement of splenic macrophage microbicidal activity.

ABSTRACT: The indigenous microbiota impact mucosal, as well as systemic, immune responses, but whether the microbiota are involved in stressor-induced immunomodulation has not been thoroughly tested. A well characterized murine stressor, called social disruption (SDR), was used to study whether the microbiota are involved in stressor-induced enhancement of macrophage reactivity. Exposure to the SDR Stressor enhanced the ability of splenic macrophages to produce microbicidal mediators (e.g., inducible nitric oxide synthase (iNOS), superoxide anion, and peroxynitrite) and to kill target Escherichia coli. Exposure to the SDR Stressor also increased cytokine production by LPS-stimulated splenic macrophages. These effects, however, were impacted by the microbiota. Microbicidal activity and cytokine mRNA in splenic macrophages from Swiss Webster germfree mice that lack any commensal microbiota were not enhanced by exposure to the SDR Stressor. However, when germfree mice were conventionalized by colonizing them with microbiota from CD1 conventional donor mice, exposure to the SDR Stressor again increased microbicidal activity and cytokine mRNA. In follow-up experiments, immunocompetent conventional CD1 mice were treated with a cocktail of antibiotics to disrupt the intestinal microbiota. While exposure to the SDR Stressor-enhanced splenic macrophage microbicidal activity and cytokine production in vehicle-treated mice, treatment with antibiotics attenuated the SDR Stressor-induced increases in splenic macrophage reactivity. Treatment with antibiotics also prevented the stressor-induced increase in circulating levels of bacterial peptidoglycan, suggesting that translocation of microbiota-derived peptidoglycan into the body primes the innate immune system for enhanced activity. This study demonstrates that the microbiota play a crucial role in stressor-induced immunoenhancement.

SUBMITTER: Allen RG

PROVIDER: S-EPMC3288745 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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The intestinal microbiota are necessary for stressor-induced enhancement of splenic macrophage microbicidal activity.

Allen Rebecca G RG Lafuse William P WP Galley Jeffrey D JD Ali Mohamed M MM Ahmer Brian M M BM Bailey Michael T MT

Brain, behavior, and immunity 20111112 3

The indigenous microbiota impact mucosal, as well as systemic, immune responses, but whether the microbiota are involved in stressor-induced immunomodulation has not been thoroughly tested. A well characterized murine stressor, called social disruption (SDR), was used to study whether the microbiota are involved in stressor-induced enhancement of macrophage reactivity. Exposure to the SDR Stressor enhanced the ability of splenic macrophages to produce microbicidal mediators (e.g., inducible nitr ...[more]

PMID: 22100833

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Project description:BackgroundThe gut-liver axis plays a crucial role in various liver diseases. Therefore, targeting this crosstalk may provide a new treatment strategy for liver diseases. However, the exact mechanism underlying this crosstalk and its impact on drug-induced liver injury (DILI) requires clarification.AimThis study aimed to investigate the potential mechanism and therapeutic effect of MgIG on MTX-induced liver injury, which is associated with the gut-liver axis and gut microbiota.MethodsAn MTX-induced liver injury model was generated after 20-mg/kg/3d MTX application for 30 days. Meanwhile, the treatment group was treated with 40-mg/kg MgIG daily. Histological examination, aminotransferase, and aspartate aminotransferase enzyme levels were estimated to evaluate liver function. Immune cells infiltration and inflammatory cytokines were detected to indicate inflammation levels. Colon histological score, intestinal barrier leakage, and expression of tight junctions were employed to assess the intestinal injury. Bacterial translocation was observed using fluorescent in situ hybridisation, colony-forming unit counting, and lipopolysaccharide detection. Alterations in gut microbial composition were analysed using 16s rDNA sequencing and relative quantitative polymerase chain reaction. Short-chain-fatty-acids and lactic acid concentrations were then utilized to validate changes in metabolites of specific bacteria. Lactobacillus sp. supplement and fecal microbiota transplantation were used to evaluate gut microbiota contribution.ResultsMTX-induced intestinal and liver injuries were significantly alleviated using MgIG treatment. Bacterial translocation resulting from the intestinal barrier disruption was considered a crucial cause of MTX-induced liver injury and the therapeutic target of MgIG. Moreover, MgIG was speculated to have changed the gut microbial composition by up-regulating probiotic Lactobacillus and down-regulating Muribaculaceae, thereby remodelling the intestinal barrier and inhibiting bacterial translocation.ConclusionThe MTX-induced intestinal barrier was protected owing to MgIG administration, which reshaped the gut microbial composition and inhibited bacterial translocation into the liver, thus attenuating MTX-related DILI.

Project description:Diet-induced obesity impairs mitochondrial respiratory responses in tissues that are highly metabolically active, such as the heart. However, less is known about the impact of obesity on the respiratory activity of specific cell types, such as splenic B cells. B cells are of relevance, as they play functional roles in obesity-induced insulin resistance, inflammation, and responses to infection. Here, we tested the hypothesis that high-fat-diet (HFD)-induced obesity could impair the mitochondrial respiration of intact and permeabilized splenic CD19+ B cells isolated from C57BL/6J mice and activated ex vivo with lipopolysaccharide (LPS). High-resolution respirometry was used with intact and permeabilized cells. To reveal potential mechanistic targets by which HFD-induced obesity dysregulates B cell mitochondria, we conducted proteomic analyses and 3D serial block face scanning electron microscopy (SBFEM). High-resolution respirometry revealed that intact LPS-stimulated B cells of obese mice, relative to controls, displayed lower ATP-linked, as well as maximal uncoupled, respiration. To directly investigate mitochondrial function, we used permeabilized LPS-stimulated B cells, which displayed increased H2O2 emission and production with obesity. We also examined oxidative phosphorylation efficiency simultaneously, which revealed that oxygen consumption and ATP production were decreased in LPS-stimulated B cells with obesity relative to controls. Despite minimal changes in total respiratory complex abundance, in LPS-stimulated B cells of obese mice, three of the top ten most downregulated proteins were all accessory subunits of respiratory complex I. SBFEM showed that B cells of obese mice, compared to controls, underwent no change in mitochondrial cristae integrity but displayed increased mitochondrial volume that was linked to bioenergetic function. Collectively, these results establish a proof of concept that HFD-induced obesity dysregulates the mitochondrial bioenergetic metabolism of activated splenic B cells.

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The intestinal microbiota are necessary for stressor-induced enhancement of splenic macrophage microbicidal activity.

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The intestinal microbiota are necessary for stressor-induced enhancement of splenic macrophage microbicidal activity.

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