Sepsis remains one of the leading causes of death in burn patients who survive the initial insult of injury. Disruption of the intestinal epithelial barrier has been shown after burn injury; this can ...lead to the translocation of bacteria or their products (e.g., endotoxin) from the intestinal lumen to the circulation, thereby increasing the risk for sepsis in immunocompromised individuals. Since the maintenance of the epithelial barrier is largely dependent on the intestinal microbiota, we examined the diversity of the intestinal microbiome of severely burned patients and a controlled mouse model of burn injury. We show that burn injury induces a dramatic dysbiosis of the intestinal microbiome of both humans and mice and allows for similar overgrowths of Gram-negative aerobic bacteria. Furthermore, we show that the bacteria increasing in abundance have the potential to translocate to extra-intestinal sites. This study provides an insight into how the diversity of the intestinal microbiome changes after burn injury and some of the consequences these gut bacteria can have in the host.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The gastrointestinal (GI) tract is a highly dynamic structure essential for digestion, nutrient absorption, and providing an interface to prevent gut bacterial translocation. In order to maintain the ...barrier function, the gut utilizes many defense mechanisms including proliferation, apoptosis, and apical junctional complexes. Disruption of any of these parameters due to injury or disease could negatively impact the intestinal barrier function and homeostasis resulting in increased intestine inflammation, permeability, bacterial dysbiosis, and tissue damage. MicroRNAs are small noncoding RNA sequences that are master regulators of normal cellular homeostasis. These regulatory molecules affect cellular signaling pathways and potentially serve as candidates for providing a mechanism of impaired gut barrier integrity following GI‐related pathologic conditions, ethanol exposure, or trauma such as burn injury. MicroRNAs influence cellular apoptosis, proliferation, apical junction complex expression, inflammation, and the microbiome. Due to their widespread functional affiliations, altered expression of microRNAs are associated with many pathologic conditions. This review explores the role of microRNAs in regulation of intestinal barrier integrity. The studies reviewed demonstrate that microRNAs largely impact intestine barrier function and provide insight behind the observed adverse effects following ethanol and burn injury. Furthermore, these studies suggest that microRNAs are excellent candidates for therapeutic intervention or for biomarkers to manage gut barrier integrity following trauma such as burn injury and other GI‐related pathologic conditions.
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Review on microRNAs, their impact on intestine barrier integrity and potential for therapeutic intervention to manage gut barrier integrity in GI related pathological conditions.
Ethanol remains a confounder in postburn pathology, which is associated with an impaired intestinal barrier. Previously, we demonstrated that ethanol and burn injury reduce intestinal oxygen delivery ...(hypoxia) and alters microRNA (miR) expression in small intestinal epithelial cells. Hypoxia has been shown to influence expression of miRs and miR biogenesis components. Therefore, we examined whether hypoxia influences expression of miR biogenesis components (drosha, dicer, and argonaute‐2 ago‐2) and miRs (‐7a and ‐150) and whether these changes impacted other parameters following ethanol and burn injury. Mice were gavaged with ethanol (∼2.9 g/kg) 4 h before receiving a ∼12.5% total body surface full thickness burn. Mice were resuscitated at the time of injury with normal saline with or without 5 mg/kg PX‐478, a hypoxia‐inducible factor‐1α inhibitor. One day following injury mice were euthanized, and the expression of miRs and their biogenesis components as well as bacterial growth, tight junction proteins, intestinal transit, and permeability were assessed. Ethanol combined with burn injury significantly reduced expression of drosha, ago‐2, miRs (‐7a and ‐150), occludin, zonula occludens‐1, claudin‐4, zonula occludens‐1, mucins‐2 and ‐4, and intestinal transit compared to shams. Furthermore, there was an increase in intestinal permeability, total bacteria, and Enterobacteriaceae populations following the combined injury compared to shams. PX‐478 treatment improved expression of drosha, ago‐2, miRs (‐7a and ‐150), occludin, claudin‐4, zonula occludens‐1, and mucin‐2. PX‐478 treatment also improved intestinal transit and reduced dysbiosis and permeability. These data suggest that PX‐478 improves miR biogenesis and miR expression, and restores barrier integrity while reducing bacterial dysbiosis following ethanol and burn injury.
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PX‐478 increases microRNA biogenesis, and reduces bacterial dysbiosis and intestine permeability following ethanol and burn injury.
Excessive alcohol users have increased risk of developing respiratory infections in part due to oxidative stress-induced alveolar macrophage (AM) phagocytic dysfunction. Chronic ethanol exposure ...increases cellular oxidative stress in AMs via upregulation of NADPH oxidase (Nox) 4, and treatment with the peroxisome proliferator-activated receptor gamma (PPARγ) ligand, rosiglitazone, decreases ethanol-induced Nox4. However, the mechanism by which ethanol induces Nox4 expression and the PPARγ ligand reverses this defect has not been elucidated. Since microRNA (miR)-92a has been predicted to target Nox4 for destabilization, we hypothesized that ethanol exposure decreases miR-92a expression and leads to Nox4 upregulation. Previous studies have implicated mitochondrial-derived oxidative stress in AM dysfunction. We further hypothesized that ethanol increases mitochondrial-derived AM oxidative stress and dysfunction via miR-92a, and that treatment with the PPARγ ligand, pioglitazone, could reverse these derangements. To test these hypotheses, a mouse AM cell line, MH-S cells, was exposed to ethanol in vitro, and primary AMs were isolated from a mouse model of chronic ethanol consumption to measure Nox4, mitochondrial target mRNA (qRT-PCR) and protein levels (confocal microscopy), mitochondria-derived reactive oxygen species (confocal immunofluorescence), mitochondrial fission (electron microscopy), and mitochondrial bioenergetics (extracellular flux analyzer). Ethanol exposure increased Nox4, enhanced mitochondria-derived oxidative stress, augmented mitochondrial fission, and impaired mitochondrial bioenergetics. Transfection with a miR-92a mimic in vitro or pioglitazone treatment in vivo diminished Nox4 levels, resulting in improvements in these ethanol-mediated derangements. These findings demonstrate that pioglitazone may provide a novel therapeutic approach to mitigate ethanol-induced AM mitochondrial derangements.
•Ethanol increases mitochondrial Nox4 via decreases in miR-92a.•Ethanol impairs mitochondrial bioenergetics in alveolar macrophages.•Pioglitazone reverses ethanol-induced mitochondrial dysfunction.
Excessive alcohol use increases the risk of developing respiratory infections partially due to impaired alveolar macrophage (AM) phagocytic capacity. Previously, we showed that chronic ethanol (EtOH) ...exposure led to mitochondrial derangements and diminished oxidative phosphorylation in AM. Since oxidative phosphorylation is needed to meet the energy demands of phagocytosis, EtOH mediated decreases in oxidative phosphorylation likely contribute to impaired AM phagocytosis. Treatment with the peroxisome proliferator-activated receptor gamma (PPARγ) ligand, pioglitazone (PIO), improved EtOH-mediated decreases in oxidative phosphorylation. In other models, hypoxia-inducible factor-1 alpha (HIF-1α) has been shown to mediate the switch from oxidative phosphorylation to glycolysis; however, the role of HIF-1α in chronic EtOH mediated derangements in AM has not been explored. We hypothesize that AM undergo a metabolic shift from oxidative phosphorylation to a glycolytic phenotype in response to chronic EtOH exposure. Further, we speculate that HIF-1α is a critical mediator of this metabolic switch. To test these hypotheses, primary mouse AM (mAM) were isolated from a mouse model of chronic EtOH consumption and a mouse AM cell line (MH-S) were exposed to EtOH
Expression of HIF-1α, glucose transporters (Glut1 and 4), and components of the glycolytic pathway (Pfkfb3 and PKM2), were measured by qRT-PCR and western blot. Lactate levels (lactate assay), cell energy phenotype (extracellular flux analyzer), glycolysis stress tests (extracellular flux analyzer), and phagocytic function (fluorescent microscopy) were conducted. EtOH exposure increased expression of HIF-1α, Glut1, Glut4, Pfkfb3, and PKM2 and shifted AM to a glycolytic phenotype. Pharmacological stabilization of HIF-1α
cobalt chloride treatment
mimicked EtOH-induced AM derangements (increased glycolysis and diminished phagocytic capacity). Further, PIO treatment diminished HIF-1α levels and reversed glycolytic shift following EtOH exposure. These studies support a critical role for HIF-1α in mediating the glycolytic shift in energy metabolism of AM during excessive alcohol use.
Excess alcohol consumption is a global crisis contributing to over 3 million alcohol-related deaths per year worldwide and economic costs exceeding $200 billion dollars, which include productivity ...losses, healthcare, and other effects (e.g., property damages). Both clinical and experimental models have shown that excessive alcohol consumption results in multiple organ injury. Although alcohol metabolism occurs primarily in the liver, alcohol exposure can lead to pathophysiological conditions in multiple organs and tissues, including the brain, lungs, adipose, liver, and intestines. Understanding the mechanisms by which alcohol-mediated organ dysfunction occurs could help to identify new therapeutic approaches to mitigate the detrimental effects of alcohol misuse. Hypoxia-inducible factor (HIF)-1 is a transcription factor comprised of HIF-1α and HIF-1β subunits that play a critical role in alcohol-mediated organ dysfunction. This review provides a comprehensive analysis of recent studies examining the relationship between HIF-1α and alcohol consumption as it relates to multiple organ injury and potential therapies to mitigate alcohol's effects.
Alcohol misuse contributes to the dysregulation of immune responses and multiorgan dysfunction across various tissues, which are associated with higher risk of morbidity and mortality in people with ...alcohol use disorders. Organ‐specific immune cells, including microglia in the brain, alveolar macrophages in the lungs, and Kupffer cells in the liver, play vital functions in host immune defense through tissue repair and maintenance of homeostasis. However, binge drinking and chronic alcohol misuse impair these immune cells' abilities to regulate inflammatory signaling and metabolism, thus contributing to multiorgan dysfunction. Further complicating these delicate systems, immune cell dysfunction associated with alcohol misuse is exacerbated by aging and gut barrier leakage. This critical review describes recent advances in elucidating the potential mechanisms by which alcohol misuse leads to derangements in host immunity and highlights current gaps in knowledge that may be the focus of future investigations.
Alcohol use disorders cause multi‐organ damage, which are associated with high mortality and morbidity. Resident tissue immune cells are crucial in regulating tissue repair, yet immune defenses are impaired following alcohol misuse. This critical review highlights how chronic or binge alcohol impairs resident immune cell inflammatory signaling and metabolism, which can be exacerbated by multi‐organ crosstalk or aging. We aim to draw attention to potential mechanisms of host immune impairment and accentuate current gaps in knowledge for future investigation.
ABSTRACTIntestine barrier disruption and bacterial translocation can contribute to sepsis and multiple organ failure, leading causes of mortality in burn-injured patients. In addition, findings ...suggest that ethanol (alcohol) intoxication at the time of injury worsens symptoms associated with burn injury. We have previously shown that interleukin-22 (IL-22) protects from intestinal leakiness and prevents overgrowth of gram-negative bacteria following ethanol and burn injury, but how IL-22 mediates these effects has not been established. Here, utilizing a mouse model of ethanol and burn injury, we show that the combined insult results in a significant loss of proliferating cells within small intestine crypts and increases Enterobacteriaceae copies, despite elevated levels of the antimicrobial peptide lipocalin-2. IL-22 administration restored numbers of proliferating cells within crypts, significantly increased Reg3β, Reg3γ, lipocalin-2 AMP transcript levels in intestine epithelial cells, and resulted in complete reduction of Enterobacteriaceae in the small intestine. Knockout of signal transducer and activator of transcription factor-3 (STAT3) in intestine epithelial cells resulted in complete loss of IL-22 protection, demonstrating that STAT3 is required for intestine barrier protection following ethanol combined with injury. Together, these findings suggest that IL-22/STAT3 signaling is critical to gut barrier integrity and targeting this pathway may be of beneficial clinical relevance following burn injury.
Over 1.4 million Americans have been diagnosed with inflammatory bowel disease (IBD), and ulcerative colitis (UC) makes up approximately half of those diagnoses. As a disease, UC cycles between ...periods of remission and flare, which is characterized by intense abdominal pain, increased weight loss, intestinal inflammation, rectal bleeding, and dehydration. Interestingly, a widespread recommendation to IBD patients for avoidance of a flare period is “Don't Drink Alcohol” as recent work correlated alcohol consumption with increased GI symptoms in patients with IBD. Alcohol alone not only induces a systemic pro‐inflammatory response, but can also be directly harmful to gut barrier integrity. However, how alcohol could result in the exacerbation of UC in both patients and murine models of colitis has yet to be elucidated. Therefore, we conducted a retrospective analysis of patients admitted for IBD with a documented history of alcohol use in conjunction with a newly developed mouse model of binge alcohol consumption following dextran sulfate sodium (DSS)‐induced colitis. We found that alcohol negatively impacts clinical outcomes of patients with IBD, specifically increased intestinal infections, antibiotic injections, abdomen CT scans, and large intestine biopsies. Furthermore, in our mouse model of binge alcohol consumption following an induced colitis flare, we found alcohol exacerbates weight loss, clinical scores, colonic shortening and inflammation, and propensity to infection. These findings highlight alcohol's ability to potentiate symptoms and susceptibility to infection in UC and suggest alcohol as an underlying factor in perpetuating symptoms of IBD.
This study builds on previous findings that alcohol has adverse effects in IBD and establishes these effects in a mouse model of colitis.
IL‐6 and TGF‐β do not appear to influence IL‐23‐mediated restoration of Th17 effector cytokines after ethanol and burn injury.
T cells play a critical role in host defense against intestinal ...bacteria. We have shown that ethanol combined with burn injury suppresses Peyer's patch (PP) Th17 cytokines 1 d after injury. We assessed the mechanism of suppressed Th17 effector functions. Mice were gavaged with ethanol 4 h before burn injury and euthanized 1, 3, and 7 d after injury. Mesenteric lymph nodes (MLNs), PPs, and spleen Th1 and Th17 cytokines were assessed. A significant decrease in IL‐17, IL‐22, IL‐2, and IFN‐γ were observed in all 3 lymphoid organs 1 and 3 d after injury. We used splenic cells to study the role of IL‐6, IL‐23, TGF‐β, and aryl hydrocarbon receptor (AHR) in suppressing Th17 cytokines. We also assessed whether the AHR agonist 6‐formylindolo (3, 2‐b) carbazole (FICZ) modulates Th17 cytokines. We found a significant decrease in IL‐6 and TGF‐β after ethanol and burn; IL‐23 was undetectable. The reconstitution of IL‐23 in culture medium increased IL‐17 by 2‐fold and IL‐22 by 20‐fold in cells from burn ethanol mice. The restoration of IL‐6 and TGF‐β combined did not influence the release of Th17 cytokines. We observed that AHR was necessary for IL‐23 restoration of IL‐22 after ethanol and burn injury. The AHR agonist FICZ enhanced IL‐22, but not IL‐17. None of these treatments influenced the release of Th1 cytokines. Together, these results suggest that IL‐23 plays a critical role in regulation of Th17 cytokines. Furthermore, IL‐6 and TGF‐β do not appear to influence IL‐23‐mediated restoration of Th17 cytokines after ethanol and burn injury.
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