Effect of acute alcohol ingestion prior to burn injury on intestinal bacterial growth and barrier function

Ethanol exacerbates pulmonary complications after burn injury in mice, regardless of frequency of ethanol exposures

Burn injuries are associated with significant morbidity and mortality, and lungs are the most common organ to fail. Interestingly, patients with alcohol intoxication at the time of burn have worse clinical outcomes, including pulmonary complications. Using a clinically relevant murine model, we have previously reported that episodic ethanol exposure before burn exacerbated lung inflammation. Specifically, intoxicated burned mice had worsened pulmonary responses, including increased leukocyte infiltration and heightened levels of CXCL1 and IL-6. Herein, we examined whether a single binge ethanol exposure before scald burn injury yields similar pulmonary responses. C57BL/6 male mice were given ethanol (1.2 g/kg) 30 min before a 15 % total body surface area burn. These mice were compared to a second cohort given episodic ethanol binge for a total of 6 days (3 days ethanol, 4 days rest, 3 days ethanol) prior to burn injury. 24 h after burn, histopathological examination of lungs were performed. In addition, survival, and levels of infiltrating leukocytes, CXCL1, and IL-6 were quantified. Episodic and single ethanol exposure before burn decreased survival compared to burn only mice and sham vehicle mice, respectively (p < 0.05). However, no difference in survival was observed between burned mice with single and episodic ethanol binge. Examination of H&E-stained lung sections revealed that regardless of ethanol binge frequency, intoxication prior to burn worsened pulmonary inflammation, evidenced by elevated granulocyte accumulation and congestion, relative to burned mice without any ethanol exposure. Levels of infiltrating granulocyte in the lungs were significantly higher in burned mice with both episodic and single ethanol intoxication, compared to burn injury only (p < 0.05). In addition, there was no difference in the granulocyte count between single and ethanol binge mice with burn injury. Neutrophil chemoattractant CXCL1 levels in the lung were similarly increased following single and episodic ethanol exposure prior to burn compared to burn alone (22-fold and 26-fold respectively, p < 0.05). Lastly, we assessed pulmonary IL-6, which revealed that irrespective of frequency, ethanol exposure combined with burn injury raised pro-inflammatory cytokine IL-6 in the lungs relative to burn mice. Again, we did not find any difference in the amount of IL-6 in lungs of burned mice with single and episodic ethanol intoxication. Taken altogether, these data demonstrate that both single and episodic exposure to ethanol prior to burn injury similarly worsens pulmonary inflammation. These results suggest that ethanol-induced exacerbation of the pulmonary responses to burn injury is due to presence of ethanol at the time of injury rather than longer-term effects of ethanol exposure.

Alcohol and Immunology: Mechanisms of multi-organ damage. Summary of the 2022 alcohol and Immunology research interest group (AIRIG) meeting

On October 26th, 2022 the annual Alcohol and Immunology Research Interest Group (AIRIG) meeting was held as a satellite symposium at the annual meeting of the Society for Leukocyte Biology in Hawaii. The 2022 meeting focused broadly on the immunological consequences of acute, chronic, and prenatal alcohol exposure and how these contribute to damage in multiple organs and tissues. These included alcohol-induced neuroinflammation, impaired lung immunity, intestinal dysfunction, and decreased anti-microbial and anti-viral responses. In addition, research presented covered multiple pathways behind alcohol-induced cellular dysfunction, including mitochondrial metabolism, cellular bioenergetics, gene regulation, and epigenetics. Finally, the work presented highlighted potential biomarkers and novel avenues of treatment for alcohol-induced organ damage.

Harnessing the potential of probiotics in the treatment of alcoholic liver disorders

In the current scenario, prolonged consumption of alcohol across the globe is upsurging an appreciable number of patients with the risk of alcohol-associated liver diseases. According to the recent report, the gut-liver axis is crucial in the progression of alcohol-induced liver diseases, including steatosis, steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Despite several factors associated with alcoholic liver diseases, the complexity of the gut microflora and its great interaction with the liver have become a fascinating area for researchers due to the high exposure of the liver to free radicals, bacterial endotoxins, lipopolysaccharides, inflammatory markers, etc. Undoubtedly, alcohol-induced gut microbiota imbalance stimulates dysbiosis, disrupts the intestinal barrier function, and trigger immune as well as inflammatory responses which further aggravate hepatic injury. Since currently available drugs to mitigate liver disorders have significant side effects, hence, probiotics have been widely researched to alleviate alcohol-associated liver diseases and to improve liver health. A broad range of probiotic bacteria like Lactobacillus, Bifidobacteria, Escherichia coli, Sacchromyces, and Lactococcus are used to reduce or halt the progression of alcohol-associated liver diseases. Several underlying mechanisms, including alteration of the gut microbiome, modulation of intestinal barrier function and immune response, reduction in the level of endotoxins, and bacterial translocation, have been implicated through which probiotics can effectively suppress the occurrence of alcohol-induced liver disorders. This review addresses the therapeutic applications of probiotics in the treatment of alcohol-associated liver diseases. Novel insights into the mechanisms by which probiotics prevent alcohol-associated liver diseases have also been elaborated.

Platelet-activating factor and microvesicle particles as potential mediators for the toxicity associated with intoxicated thermal burn injury

Thermal burn injuries (TBIs) in patients who are alcohol-intoxicated result in greater morbidity and mortality. The systemic toxicity found in human patients, which includes both immediate systemic cytokine generation with multiple organ failure and a delayed systemic immunosuppression, has previously been replicated in mouse models combining ethanol and localized TBI. Though considerable insights have been provided with these models, the exact mechanisms for these pathologic effects are unclear. In this review, we highlight the roles of the lipid mediator platelet-activating factor (PAF) and subcellular microvesicle particle (MVP) release in response to intoxicated thermal burn injury (ITBI) as effectors in the pathology. Particularly, MVP is released from keratinocytes in response to PAF receptor (PAFR) activation due to excess PAF produced by ITBI. These subcellular particles carry and thus protect the metabolically labile PAF which enable binding of this potent lipid mediator to several key sites. We hypothesize that PAF carried by MVP can bind to PAFR within the gut, activating myosin light chain kinase (MLCK). The subsequent gut barrier dysfunction in response to MLCK activation then allows bacteria to invade the lymphatic system and, eventually, the bloodstream, resulting in sepsis and resultant dysregulated inflammation in multiple organs. PAF in MVP also activate the skin mast cell PAFR resulting in migration of this key effector cell to the lymph nodes to induce immunosuppression. This review thus provides a mechanism and potential therapeutic approaches for the increased toxicity and immunosuppressive outcomes of TBI in the presence of acute ethanol exposure.

Illustration of Gut-Thyroid Axis in Alcohol Use Disorder: Interplay of Gut Dysfunction, Pro-Inflammatory Responses, and Thyroid Function

(1) Background: Heavy and chronic alcohol drinking leads to altered gut dysfunction, coupled with a pro-inflammatory state. Thyroid-associated hormones and proteins may be dysregulated by heavy and chronic alcohol intake; however, the mechanism for altered gut-derived changes in thyroid function has not been studied thus far. This study investigates the role of alcohol-induced gut dysfunction and pro-inflammatory cytokine profile in the thyroid function of patients with alcohol use disorder (AUD). (2) Methods: Male and female AUD patients (n = 44) were divided into Gr.1, patients with normal thyroid-stimulating hormone (TSH) levels (n = 28, 0.8 ≤ TSH ≤ 3 mIU/L); and Gr.2, patients with clinically elevated TSH levels (n = 16, TSH > 3 mIU/L). Demographics, drinking measures, comprehensive metabolic panels, and candidate thyroid markers (TSH, circulating triiodothyronine (T3), and free thyroxine (fT4)) were analyzed. Gut-dysfunction-associated markers (lipopolysaccharide (LPS), LPS-binding protein (LBP), and soluble LPS-induced pathogen-associated protein (sCD14)), and candidate pro-inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-8, MCP-1, PAI-1) were also evaluated. (3) Results: Patients in both groups presented with a borderline overweight BMI category. Gr.2 reported numerically higher indices of chronic and heavy drinking patterns than Gr.1. The fT4 levels were elevated, while T3 was within normal limits in both groups. The gut dysfunction markers LBP and sCD14 were numerically elevated in Gr.2 vs. Gr.1, suggesting subtle ongoing changes. Candidate pro-inflammatory cytokines were significantly elevated in Gr.2, including IL-1 β, MCP-1, and PAI-1. Gr.2 showed a strong and statistically significant effect on the gut–immune–thyroid response (r = 0.896, 36 p = 0.002) on TSH levels in a multivariate regression model with LBP, sCD14, and PAI-1 levels as upstream variables in the gut–thyroid pathway. In addition, AUROC analysis demonstrated that many of the cytokines strongly predicted TSH in Gr.2, including IL-6 (area = 0.774, 39 p < 0.001) and TNF-α (area = 0.708, p = 0.017), among others. This was not observed in Gr.1. Gr.2 demonstrated elevated fT4, as well as TSH, which suggests that there was subclinical thyroiditis with underlying CNS dysfunction and a lack of a negative feedback loop. (4) Conclusions: These findings reveal the toxic effects of heavy and chronic drinking that play a pathological role in thyroid gland dysregulation by employing the gut–brain axis. These results also emphasize potential directions to carefully evaluate thyroid dysregulation in the overall medical management of AUD.

Alcohol inhibits alveolar fluid clearance through the epithelial sodium channel via the A2 adenosine receptor in acute lung injury

Chronic alcohol abuse increases the risk of mortality and poor outcomes in patients with acute respiratory distress syndrome. However, the underlying mechanisms remain to be elucidated. The present study aimed to investigate the effects of chronic alcohol consumption on lung injury and clarify the signaling pathways involved in the inhibition of alveolar fluid clearance (AFC). In order to produce rodent models with chronic alcohol consumption, wild‑type C57BL/6 mice were treated with alcohol. A2a adenosine receptor (AR) small interfering (si)RNA or A2bAR siRNA were transfected into the lung tissue of mice and primary rat alveolar type II (ATII) cells. The rate of AFC in lung tissue was measured during exposure to lipopolysaccharide (LPS). Epithelial sodium channel (ENaC) expression was determined to investigate the mechanisms underlying alcohol‑induced regulation of AFC. In the present study, exposure to alcohol reduced AFC, exacerbated pulmonary edema and worsened LPS‑induced lung injury. Alcohol caused a decrease in cyclic adenosine monophosphate (cAMP) levels and inhibited α‑ENaC, β‑ENaC and γ‑ENaC expression levels in the lung tissue of mice and ATII cells. Furthermore, alcohol decreased α‑ENaC, β‑ENaC and γ‑ENaC expression levels via the A2aAR or A2bAR‑cAMP signaling pathways in vitro. In conclusion, the results of the present study demonstrated that chronic alcohol consumption worsened lung injury by aggravating pulmonary edema and impairing AFC. An alcohol‑induced decrease of α‑ENaC, β‑ENaC and γ‑ENaC expression levels by the A2AR‑mediated cAMP pathway may be responsible for the exacerbated effects of chronic alcohol consumption in lung injury.

Association Between Alcohol, Substance Use, and Inpatient Burn Outcomes

The use of alcohol and illicit substances has been associated with impaired judgment and health, but the effect on inpatient outcomes after burn injury remains unsettled. Our objective was to evaluate the effect of alcohol and illicit substance use on our inpatient burn outcomes. Adult patients admitted with burn injury-including inhalation injury only-between January 1, 2014 and June 30, 2019 were eligible for inclusion. Alcohol use and illicit drug use were identified on admission. Outcomes of interest included requiring mechanical ventilation, admission to the intensive care unit, length of stay, and inpatient mortality. Multivariable linear and logistic regression models were used to estimate the effects of use on inpatient outcomes. A total of 3476 patients were included in our analyses; 8% (n = 284) tested positive for alcohol, 10% (n = 364) tested positive for cocaine, and 27% (n = 930) tested positive for marijuana and at admission. Two hundred and eighty adults (18% of all positive patients) tested positive for at least two substances. Patients who tested positive for alcohol had longer lengths of stay and were more likely to be admitted to the intensive care unit. Patients who tested positive for cocaine had longer overall and intensive care unit lengths of stay. No differences in inpatient outcomes were seen among patients who tested positive for marijuana. Neither alcohol nor illicit substance use appears to affect inpatient mortality after burns. Alcohol and cocaine use significantly increased overall length of stay. Marijuana use had no impact on inpatient outcomes.

Innate Immunity and Alcohol

The innate immunity has evolved during millions of years, and thus, equivalent or comparable components are found in most vertebrates, invertebrates, and even plants. It constitutes the first line of defense against molecules, which are either pathogen-derived or a danger signal themselves, and not seldom both. These molecular patterns are comprised of highly conserved structures, a common trait in innate immunity, and constitute very potent triggers for inflammation mediated via extracellular or intracellular pattern recognition receptors. Human culture is often interweaved with the consumption of alcohol, in both drinking habits, its acute or chronical misuse. Apart from behavioral effects as often observed in intoxicated individuals, alcohol consumption also leads to immunological modulation on the humoral and cellular levels. In the last 20 years, major advances in this field of research have been made in clinical studies, as well as in vitro and in vivo research. As every physician will experience intoxicated patients, it is important to be aware of the changes that this cohort undergoes. This review will provide a summary of the current knowledge on the influence of alcohol consumption on certain factors of innate immunity after a hit, followed by the current studies that display the effect of alcohol with a description of the model, the mode of alcohol administration, as well as its dose. This will provide a way for the reader to evaluate the findings presented.

Mesenchymal stem cell treatment attenuates liver and lung inflammation after ethanol intoxication and burn injury

Cutaneous burn injury is one of the most devastating injuries one can obtain, with tissue damage extending beyond the skin wound to distal organs, including the gastrointestinal tract, liver, and lungs. Multiple organ failure is a leading cause of death after burn injury, resulting in excessive systemic and localized inflammation directly contributing to end organ damage. We postulated that the gut-liver-lung inflammatory axis underscores multiple organ failure in the context of burn injury and is hyper-activated when ethanol intoxication precedes burn. Mesenchymal stem cells (MSCs) are regenerative and anti-inflammatory, and MSC treatment has been shown to be beneficial in several immune disorders and injury models. Our objective was to determine whether intravenous infusion of exogenous bone marrow-derived MSCs could reduce post-burn and intoxication pulmonary, hepatic, and systemic inflammation. Vehicle- or ethanol- (1.6 g/kg) treated mice were subjected to sham or 15% total body surface area scald burn. One hour post-injury, mice were given 5 × 10⁵ CFSE-labeled MSCs or phosphate-buffered saline intravenously (i.v.) and were euthanized 24 h later. We assessed circulating biomarkers of inflammation and liver damage, measured cytokine and chemokine production, and quantified apoptosis in lung and liver tissue. Compared to intoxicated and burned mice, those treated with MSCs had less cellularity, limited apoptosis, and a slight reduction in the pro-inflammatory cytokine interleukin-6 (IL-6) and the neutrophil chemokine, KC (CXCL1) in lung tissue. Mice with MSCs treatment had more dramatic anti-inflammatory effects on systemic and hepatic inflammation, as serum IL-6 levels were diminished by 43%, and il6 and kc expression in liver tissue were markedly reduced, as were biomarkers of liver damage, aspartate transaminase (AST) and alanine transaminase (AST), compared with intoxicated and burned mice. Taken together, our results suggest intravenous MSCs treatment can diminish systemic inflammation, lessen hepatic damage, and decrease liver and lung apoptosis and inflammation, indicating MSCs as a novel therapy for restoring homeostasis of multiple organ systems in intoxicated burn patients.

The Effect of Illicit Drug Use on Outcomes Following Burn Injury

Illicit drug use is common among patients admitted following burn injury. The authors sought to evaluate whether drug abuse results in worse outcomes. The National Burn Repository (NBR) was queried for data on all patients with drug testing results available. Outcomes included mortality, hospital length of stay (LOS), intensive care unit (ICU) LOS, and duration of ventilator support. Propensity score weighting was performed to control for age, alcohol use, burn size, gender, and etiology of burn. A total of 20,989 patients had drug screen data available; 11,642 (55.5%) tested positive for at least one drug of abuse. Illicit drug use was associated with a higher proportion of patients with flame burn (53.2 vs 48.4%) and larger average burn size (11.2 vs 9.5% TBSA, P < .001). Attempted suicide was more likely if the patient had used drugs (2.8 vs 1.7%, P < .001). Drug use resulted in longer hospital and ICU LOS (14.2 vs 11.4 and 8.5 vs 5.6 days, P < .001), but did not increase the risk of mortality (5.7 vs 5.2, P = .08). After propensity score weighting, drug use did not affect mortality, hospital LOS, or duration of ventilator support, but did increase the average ICU LOS by 1.2 days (P = .001). Drug use does not affect mortality, hospital LOS, or duration of ventilator support among burned patients. After controlling for burn size, age, mechanism of injury, and gender, patients with a positive drug screen had an average increase in ICU LOS by 1 day.

Alcohol Modulation of the Postburn Hepatic Response

The widespread and rapidly increasing trend of binge drinking is accompanied by a concomitant rise in the prevalence of trauma patients under the influence of alcohol at the time of their injury. Epidemiological evidence suggests up to half of all adult burn patients are intoxicated at the time of admission, and the presence of alcohol is an independent risk factor for death in the early stages post burn. As the major site of alcohol metabolism and toxicity, the liver is a critical determinant of postburn outcome, and experimental evidence implies an injury threshold exists beyond which burn-induced hepatic derangement is observed. Alcohol may lower this threshold for postburn hepatic damage through a variety of mechanisms including modulation of extrahepatic events, alteration of the gut-liver axis, and changes in signaling pathways. The direct and indirect effects of alcohol may prime the liver for the second-hit of many overlapping physiologic responses to burn injury. In an effort to gain a deeper understanding of how alcohol potentiates postburn hepatic damage, the authors summarize possible mechanisms by which alcohol modulates the postburn hepatic response.

Therapeutic strategies for alcoholic liver disease: Focusing on inflammation and fibrosis (Review)

Excessive alcohol consumption is the most common cause of liver disease in the world. Chronic alcohol abuse leads to liver damage, liver inflammation, fibrosis and hepatocellular carcinoma. Inflammatory cytokines, such as tumor necrosis factor-α and interferon-γ, induce liver injury, which leads to the develo-pment of alcoholic liver disease (ALD). Hepatoprotective cytokines, such as interleukin (IL)-6 and IL-10, are also associated with ALD. IL-6 improves ALD via the activation of STAT3 and the subsequent induction of a variety of hepatoprotective genes in hepatocytes. Alcohol consumption promotes liver inflammation by incre-asing the translocation of gut-derived endotoxins to the portal circulation and by activating Kupffer cells through the lipopolysaccharide/Toll-like receptor 4 pathways. Oxidative stress and microflora products are also associated with ALD. Hepatic stellate cells play an important role in angiogenesis and liver fibrosis. Anti-angiogenic therapy has been found to be effective in the prevention of fibrosis. This suggests that blocking angiogenesis could be a promising therapeutic option for patients with advanced fibrosis. This review discusses the main pathways associated with liver inflammation and liver fibrosis as well as new therapeutic strategies.

Changes in blood microbiota profiles associated with liver fibrosis in obese patients: A pilot analysis

The early detection of liver fibrosis among patients with nonalcoholic fatty liver disease (NAFLD) is an important clinical need. In view of the suggested role played by bacterial translocation in liver disease and obesity, we sought to investigate the relationship between blood microbiota and liver fibrosis (LF) in European cohorts of patients with severe obesity. We carried out a cross-sectional study of obese patients, well characterized with respect to the severity of the NAFLD, in the cohort FLORINASH. This cohort has been divided into a discovery cohort comprising 50 Spanish patients and then in a validation cohort of 71 Italian patients. Blood bacterial DNA was analyzed both quantitatively by 16S ribosomal DNA (rDNA) quantitative polymerase chain reaction and qualitatively by 16S rDNA targeted metagenomic sequencing and functional metagenome prediction. Spanish plasma bile acid contents were analyzed by liquid chromatography/mass spectrometry. The 16S rDNA concentration was significantly higher in patients of the discovery cohort with LF. By 16S sequencing, we found specific differences in the proportion of several bacterial taxa in both blood and feces that correlate with the presence of LF, thus defining a specific signature of the liver disease. Several secondary/primary bile acid ratios were also decreased with LF in the discovery cohort. We confirmed, in the validation cohort, the correlation between blood 16S rDNA concentration and LF, whereas we did not confirm the specific bacterial taxa signature, despite a similar trend in patients with more-severe fibrosis.

CONCLUSION

Changes in blood microbiota are associated with LF in obese patients. Blood microbiota analysis provides potential biomarkers for the detection of LF in this population. (Hepatology 2016;64:2015-2027).

Alcohol and lung injury and immunity

Annually, excessive alcohol use accounts for more than $220 billion in economic costs and 80,000 deaths, making excessive alcohol use the third leading lifestyle-related cause of death in the US. Patients with an alcohol-use disorder (AUD) also have an increased susceptibility to respiratory pathogens and lung injury, including a 2-4-fold increased risk of acute respiratory distress syndrome (ARDS). This review investigates some of the potential mechanisms by which alcohol causes lung injury and impairs lung immunity. In intoxicated individuals with burn injuries, activation of the gut-liver axis drives pulmonary inflammation, thereby negatively impacting morbidity and mortality. In the lung, the upper airway is the first checkpoint to fail in microbe clearance during alcohol-induced lung immune dysfunction. Brief and prolonged alcohol exposure drive different post-translational modifications of novel proteins that control cilia function. Proteomic approaches are needed to identify novel alcohol targets and post-translational modifications in airway cilia that are involved in alcohol-dependent signal transduction pathways. When the upper airway fails to clear inhaled pathogens, they enter the alveolar space where they are primarily cleared by alveolar macrophages (AM). With chronic alcohol ingestion, oxidative stress pathways in the AMs are stimulated, thereby impairing AM immune capacity and pathogen clearance. The epidemiology of pneumococcal pneumonia and AUDs is well established, as both increased predisposition and illness severity have been reported. AUD subjects have increased susceptibility to pneumococcal pneumonia infections, which may be due to the pro-inflammatory response of AMs, leading to increased oxidative stress.

Intestine immune homeostasis after alcohol and burn injury

Traumatic injury remains one of the most prevalent reasons for patients to be hospitalized. Burn injury accounts for 40,000 hospitalizations in the United States annually, resulting in a large burden on both the health and economic system and costing millions of dollars every year. The complications associated with postburn care can quickly cause life-threatening conditions including sepsis and multiple organ dysfunction and failure. In addition, alcohol intoxication at the time of burn injury has been shown to exacerbate these problems. One of the biggest reasons for the onset of these complications is the global suppression of the host immune system and increased susceptibility to infection. It has been hypothesized that infections after burn and other traumatic injury may stem from pathogenic bacteria from within the host's gastrointestinal tract. The intestine is the major reservoir of bacteria within the host, and many studies have demonstrated perturbations of the intestinal barrier after burn injury. This article reviews the findings of these studies as they pertain to changes in the intestinal immune system after alcohol and burn injury.

Splenectomy attenuates severe thermal trauma-induced intestinal barrier breakdown in rats

The severe local thermal trauma activates a number of systemic inflammatory mediators, such as TNF-α, NF-κB, resulting in a disruption of gut barrier. The gastrointestinal tight junction (TJ) is highly regulated by membrane-associated proteins including zonula occludens protein-1 (ZO-1) and occludin, which can be modulated by inflammatory cytokines. As splenectomy has been shown to reduce secretion of cytokines, we hypothesized that (1) severe scald injury up-regulates TNF-α and NF-κB, meanwhile down-regulates expression of ZO-1 and occludin, leading to the increased intestinal permeability, and (2) splenectomy can prevent the burn-induced decrease in ZO-1 and occludin expression, resulting in improved intestinal barrier. Wistar rats undergoing a 30% total body surface area (TBSA) thermal trauma were randomized to receive an accessorial splenectomy meanwhile or not. Intestinal injury was assessed by histological morphological analysis, and serum endotoxin levels, TNF-α, NF-κB, ZO-1 and occludin levels were detected by Western blotting in the terminal ileum mucosal tissue. 30% TBSA burn caused a significant increase in serum endotoxin levels, but NF-κB, and TNF-α, and the average intestinal villus height and mucosal thickness were decreased significantly. Burn injury could also markedly decrease the levels of ZO-1 and occludin in terminal ileum mucosal tissue (all P<0.01). Splenectomy at 7th day after burn significantly reversed the burn-induced breakdown of ZO-1 and occludin (all P<0.01). The results of this study suggest that severe thermal injury damages the intestinal mucosal barrier. Splenectomy may provide a therapeutic benefit in restoring burn-induced intestinal barrier by decreasing the release of inflammatory cytokines and recovering TJ proteins.

Impaired respiratory function and heightened pulmonary inflammation in episodic binge ethanol intoxication and burn injury

Clinical data indicate that cutaneous burn injuries covering greater than 10% of the total body surface area are associated with significant morbidity and mortality, in which pulmonary complications, including acute respiratory distress syndrome (ARDS), contribute to nearly half of all patient deaths. Approximately 50% of burn patients are intoxicated at the time of hospital admission, which increases days on ventilators by 3-fold, and doubles the length of hospitalization, compared to non-intoxicated burn patients. The most common drinking pattern in the United States is binge drinking, where an individual rapidly consumes alcoholic beverages (4 for women, 5 for men) in 2 h. An estimated 38 million Americans binge drink, often several times per month. Experimental data demonstrate that a single binge-ethanol exposure, prior to scald injury, impairs innate and adaptive immune responses, thereby enhancing infection susceptibility and amplifying pulmonary inflammation, neutrophil infiltration, and edema, and is associated with increased mortality. Since these characteristics are similar to those observed in ARDS burn patients, our study objective was to determine whether ethanol intoxication and burn injury and the subsequent pulmonary congestion affect physiological parameters of lung function, using non-invasive and unrestrained plethysmography in a murine model system. Furthermore, to mirror young adult binge-drinking patterns, and to determine the effect of multiple ethanol exposures on pulmonary inflammation, we utilized an episodic binge-ethanol exposure regimen, where mice were exposed to ethanol for a total of 6 days (3 days ethanol, 4 days rest, 3 days ethanol) prior to burn injury. Our analyses demonstrate mice exposed to episodic binge ethanol and burn injury have higher mortality, increased pulmonary congestion and neutrophil infiltration, elevated neutrophil chemoattractants, and respiratory dysfunction, compared to burn or ethanol intoxication alone. Overall, our study identifies plethysmography as a useful tool for characterizing respiratory function in a murine burn model and for future identification of therapeutic compounds capable of restoring pulmonary functionality.

Review article: Alcohol and gut microbiota - the possible role of gut microbiota modulation in the treatment of alcoholic liver disease

BACKGROUND

Alcohol abuse represents the most common cause of liver disease in the Western countries. Pre-clinical and clinical studies showed that alcohol consumption affects amount and composition of gut microbiota. Moreover, gut flora plays an important role in the pathogenesis of alcoholic liver injury.

AIM

To review the relationship between alcohol administration and changes on gut microbiota, its involvement in the pathogenesis of alcoholic liver disease, and how gut microbiota modulation could be a target for the treatment of alcoholic liver disease.

METHODS

Articles were identified using the PubMed database with the search terms 'Alcohol', 'Gut Microbiota', 'Alcoholic liver disease', 'Probiotic', 'Prebiotic', 'Symbiotic' and 'Antibiotic'. English-language articles were screened for relevance. Full review of publications for the relevant studies was conducted, including additional publications that were identified from individual article reference lists.

RESULTS

Alcohol abuse induces changes in the composition of gut microbiota, although the exact mechanism for this alteration is not well known. The translocation of bacterial products into the portal blood appears to play a key role in alcohol-induced liver damage. Several studies show that the modulation of gut microbiota seem to be a promising strategy to reduce alcohol-induced liver injury.

CONCLUSIONS

Further studies are needed to better understand the relationship between alcohol administration and changes in gut microbiota, and its involvement in alcoholic liver disease. Moreover larger studies are needed to confirm the preliminary results on the therapeutic effects of gut microbiota modulation.

The effect of inflammatory cytokines in alcoholic liver disease

Alcohol is the most common cause of liver disease in the world. Chronic alcohol consumption leads to hepatocellular injury and liver inflammation. Inflammatory cytokines, such as TNF-α and IFN-γ, induce liver injury in the rat model of alcoholic liver disease (ALD). Hepatoprotective cytokines, such as IL-6, and anti-inflammatory cytokines, such as IL-10, are also associated with ALD. IL-6 improves ALD via activation of the signal transducer and activator of transcription 3 (STAT3) and the subsequent induction of a variety of hepatoprotective genes in hepatocytes. IL-10 inhibits alcoholic liver inflammation via activation of STAT3 in Kupffer cells and the subsequent inhibition of liver inflammation. Alcohol consumption promotes liver inflammation by increasing translocation of gut-derived endotoxins to the portal circulation and activating Kupffer cells through the LPS/Toll-like receptor (TLR) 4 pathways. Oxidative stress and microflora products are also associated with ALD. Interactions between pro- and anti-inflammatory cytokines and other cytokines and chemokines are likely to play important roles in the development of ALD. The present study aims to conduct a systemic review of ALD from the aspect of inflammation.

Intoxication by intraperitoneal injection or oral gavage equally potentiates postburn organ damage and inflammation

The increasing prevalence of binge drinking and its association with trauma necessitate accurate animal models to examine the impact of intoxication on the response and outcome to injuries such as burn. While much research has focused on the effect of alcohol dose and duration on the subsequent inflammatory parameters following burn, little evidence exists on the effect of the route of alcohol administration. We examined the degree to which intoxication before burn injury causes systemic inflammation when ethanol is given by intraperitoneal (i.p.) injection or oral gavage. We found that intoxication potentiates postburn damage in the ileum, liver, and lungs of mice to an equivalent extent when either ethanol administration route is used. We also found a similar hematologic response and levels of circulating interleukin-6 (IL-6) when either ethanol paradigm achieved intoxication before burn. Furthermore, both i.p. and gavage resulted in similar blood alcohol concentrations at all time points tested. Overall, our data show an equal inflammatory response to burn injury when intoxication is achieved by either i.p. injection or oral gavage, suggesting that findings from studies using either ethanol paradigm are directly comparable.

Intestinal barrier disruption as a cause of mortality in combined radiation and burn injury

Nuclear disaster associated with combined radiation injury (CRI) and trauma or burns results in higher mortality than component injuries. Early death is caused by sequelae of gastrointestinal (GI) leakiness such as bacterial translocation and shock. We developed a murine model to characterize GI injury after CRI and determine the extent of barrier disruption. Animals received radiation (5.5 Gy) alone or with 15% total body surface area (TBSA) scald burn and were euthanized at 24, 48, and 72 h. Mesenteric lymph node homogenate was plated on tryptic soy agar to assess for bacterial translocation. Tight junction protein, occludin, was characterized by Western blot and immunofluorescence. Intestinal histology was evaluated, and apoptosis was quantified using histone-associated DNA fragmentation enzyme-linked immunosorbent assay and Western blot for caspase-3 and caspase-8. At 72 h, a 100-fold increase in bacterial growth after CRI was observed. Occludin colocalization was reduced by radiation exposure, with largest differences in CRI at 24 and 48 h. Histopathology exhibited increased apoptosis in radiation alone and CRI animals at 24 and 48 h (P < 0.05). Further evidence of apoptotic activity in CRI was seen at 48 h, with 3-fold increases in enzyme-linked immunosorbent assay detection relative to all groups and caspase-8 activity relative to radiation alone and sham (P < 0.05). Prolonged epithelial apoptosis and disruption of tight junctions likely contribute to gut leakiness after CRI. Subsequent bacterial translocation to mesenteric lymph node potentially leads to sepsis and death and could serve as a target for mitigating agents to improve survival from CRI.

Anti-IL-6 antibody treatment but not IL-6 knockout improves intestinal barrier function and reduces inflammation after binge ethanol exposure and burn injury

Interleukin 6 (IL-6) is an inflammatory cytokine known to be elevated in chronic diseases and after insults such as trauma and infection. Although necessary for the development of B cells and Th17 cells, IL-6, at elevated levels, can also cause tissue damage and lead to a rise in inflammation. Previous work in our laboratory has shown that IL-6 is increased both systemically and in multiple organ systems including the ileum after ethanol exposure and burn injury. As this combined insult causes elevated intestinal morphological damage, tight junction protein localization alterations, and phosphorylated myosin light chain levels, we sought to determine the role of IL-6 in these intestinal responses using a model of binge ethanol exposure and burn injury. Interleukin 6 antibody treatment after the combined insult reduced morphological changes in the ileum, bacterial translocation, and phosphorylated myosin light chain levels relative to either injury alone. Zonula occludens protein 1 and occludin localization was also reestablished in wild-type mice given IL-6 antibody after ethanol and burn. Interleukin 6-knockout mice given ethanol and burn injury also had reduced intestinal damage; however, no changes in bacterial translocation or tight junction protein localization were observed as compared with similarly treated wild-type mice. These data suggest that IL-6 may have a role in intestinal tissue damage observed after the combined insult of binge ethanol exposure and burn injury, although complete loss of IL-6 does not seem to be beneficial in this model. Modulation of IL-6 may present a new option for preventing intestinal damage and associated inflammation after a combined insult of ethanol exposure and burn injury.

Adipose inflammation and macrophage infiltration after binge ethanol and burn injury

BACKGROUND

Ethanol (EtOH) exposure prior to traumatic injury, such as a burn, elevates systemic and local inflammatory responses and increases morbidity and mortality. Adipose is a large tissue mass that is often inflamed during obesity or other stresses, which disturbs metabolic homeostasis. To date, there has been little investigation into the inflammatory response of adipose tissue after combined EtOH exposure and burn injury.

METHODS

Two EtOH exposure regimens were utilized to examine the role of inflammation in adipose tissue after EtOH and burn injury. Mice were either given a single or episodic binge exposure to EtOH or saline followed by scald (burn) or sham injury 30 minutes later. Twenty-four hours post injury, serum and adipose tissue were collected for assessment of inflammatory mediators.

RESULTS

Single binge EtOH alone induced no inflammation in adipose when compared with sham vehicle-treated mice. However, single binge EtOH followed by burn injury induced significant elevations in mRNA and protein concentrations of pro-inflammatory mediators interleukin-6 (IL-6), KC, and monocyte chemoattractant protein 1 compared with either insult alone or sham vehicle group. Additionally, EtOH exposure and burn injury significantly blunted inducible nitric oxide synthase (iNOS), indicating a complex inflammatory response. Episodic binge EtOH exposure followed by burn injury exacerbated the postburn adipose inflammatory response. The magnitude of the episodic binge-induced inflammatory parameters postburn were 2- to 5-fold greater than the response detected after a single exposure of EtOH, indicating EtOH-induced potentiation of burn-induced inflammatory response. Finally, inflammatory loci and crown-like structures in adipose were significantly increased by episodic binge EtOH and burn injury.

CONCLUSIONS

This is the first report of binge and burn-induced crown-like structure formation. Evidence presented herein suggests an important role for alcohol and burn as an additional mediator of adipose inflammation in postburn injury, a common complication in burn patients.

Ethanol metabolism and its effects on the intestinal epithelial barrier

Ethanol is widely consumed and is associated with an increasing global health burden. Several reviews have addressed the effects of ethanol and its oxidative metabolite, acetaldehyde, on the gastrointestinal (GI) tract, focusing on carcinogenic effects or alcoholic liver disease. However, both the oxidative and the nonoxidative metabolites of ethanol can affect the epithelial barrier of the small and large intestines, thereby contributing to GI and liver diseases. This review outlines the possible mechanisms of ethanol metabolism as well as the effects of ethanol and its metabolites on the intestinal barrier. Limited studies in humans and supporting in vitro data have indicated that ethanol as well as mainly acetaldehyde can increase small intestinal permeability. Limited evidence also points to increased colon permeability following exposure to ethanol or acetaldehyde. In vitro studies have provided several mechanisms for disruption of the epithelial barrier, including activation of different cell-signaling pathways, oxidative stress, and remodeling of the cytoskeleton. Modulation via intestinal microbiota, however, should also be considered. In conclusion, ethanol and its metabolites may act additively or even synergistically in vivo. Therefore, in vivo studies investigating the effects of ethanol and its byproducts on permeability of the small and large intestines are warranted.

Interleukin-22 modulates gut epithelial and immune barrier functions following acute alcohol exposure and burn injury

Interleukin-22 (IL-22) maintains gut epithelial integrity and expression of antimicrobial peptides Reg3β and Reg3γ. Our laboratory has shown that acute alcohol/ethanol (EtOH) exposure before burn injury results in increased gut permeability, intestinal T-cell suppression, and enhanced bacterial translocation. Herein, we determined the effect of combined EtOH intoxication and burn injury on intestinal levels of IL-22 as well as Reg3β and Reg3γ expression. We further examined whether in vivo restitution of IL-22 restores gut permeability, Reg3β and Reg3γ levels, and bacterial load (e.g., gut bacterial growth) within the intestine after EtOH and burn injury. Male mice, ∼25g, were gavaged with EtOH (2.9 mg/kg) before receiving a ∼12.5% total-body-surface-area, full-thickness burn. Mice were immediately treated with saline control or IL-22 (1 mg/kg) by i.p. injection. One day after injury, there was a significant decrease in intestinal IL-22, Reg3β, and Reg3γ expression along with an increase in intestinal permeability and gut bacterial load after EtOH combined with burn injury, as compared with sham injury. Treatment with IL-22 normalized Reg3β and Reg3γ expression and attenuated the increase in intestinal permeability after EtOH and burn injury. Qualitatively, IL-22 treatment reduced the bacterial load in nearly half of mice receiving EtOH combined with burn injury. Our data indicate that IL-22 maintains gut epithelial and immune barrier integrity after EtOH and burn injury; thus, the IL-22/antimicrobial peptide pathway may provide a therapeutic target for the treatment of patients who sustain burn injury under the influence of EtOH.

The role of gut-liver axis in the pathogenesis of liver cirrhosis and portal hypertension

Because of the anatomical position and its unique vascular system, the liver is susceptible to the exposure to the microbial products from the gut. Although large amount of microbes colonize in the gut, translocation of the microbes or microbial products into the liver and systemic circulation is prevented by gut epithelial barrier function and cleansing and detoxifying functions of the liver in healthy subjects. However, when the intestinal barrier function is disrupted, large amount of bacterial products can enter into the liver and systemic circulation and induce inflammation through their receptors. Nowadays, there have been various reports suggesting the role of gut flora and bacterial translocation in the pathogenesis of chronic liver disease and portal hypertension. This review summarizes the current knowledge about bacterial translocation and its contribution to the pathogenesis of chronic liver diseases and portal hypertension.

Inhibition of long myosin light-chain kinase activation alleviates intestinal damage after binge ethanol exposure and burn injury

Laboratory evidence suggests that intestinal permeability is elevated following either binge ethanol exposure or burn injury alone, and this barrier dysfunction is further perturbed when these insults are combined. We and others have previously reported a rise in both systemic and local proinflammatory cytokine production in mice after the combined insult. Knowing that long myosin light-chain kinase (MLCK) is important for epithelial barrier maintenance and can be activated by proinflammatory cytokines, we examined whether inhibition of MLCK alleviated detrimental intestinal responses seen after ethanol exposure and burn injury. To accomplish this, mice were given vehicle or a single binge ethanol exposure followed by a sham or dorsal scald burn injury. Following injury, one group of mice received membrane permeant inhibitor of MLCK (PIK). At 6 and 24 h postinjury, bacterial translocation and intestinal levels of proinflammatory cytokines were measured, and changes in tight junction protein localization and total intestinal morphology were analyzed. Elevated morphological damage, ileal IL-1β and IL-6 levels, and bacterial translocation were seen in mice exposed to ethanol and burn injury relative to either insult alone. This increase was not seen in mice receiving PIK after injury. Ethanol-exposed and burn-injured mice had reduced zonula occludens protein-1 and occludin localization to the tight junction relative to sham-injured mice. However, the observed changes in junctional complexes were not seen in our PIK-treated mice following the combined insult. These data suggest that MLCK activity may promote morphological and inflammatory responses in the ileum following ethanol exposure and burn injury.

Alcohol, burn injury, and the intestine

A significant number of burn and other traumatic injuries are reported to occur under the influence of alcohol (EtOH) intoxication. Despite this overwhelming association between EtOH intoxication and injury, relatively little attention has been paid to determining the role of EtOH in post-injury pathogenesis. This article reviews studies which have evaluated the impact of EtOH on post-burn intestinal immunity and barrier functions. The findings from these studies suggest that while a smaller burn injury by itself may not have an adverse effect on host defense, when combined with prior EtOH intoxication it may become detrimental. Experimental data from our laboratory further supports the notion that EtOH intoxication before burn injury suppresses intestinal immune defense, impairs gut barrier functions, and increases bacterial growth. This results in increased bacterial translocation which may contribute to post injury pathogenesis. Altogether, the studies reviewed in this article suggest that EtOH intoxication at the time of injury is a risk factor, and therefore blood EtOH should be checked in burn/trauma patients at the time of hospital admission.

Laboratory models available to study alcohol-induced organ damage and immune variations: choosing the appropriate model

The morbidity and mortality resulting from alcohol-related diseases globally impose a substantive cost to society. To minimize the financial burden on society and improve the quality of life for individuals suffering from the ill effects of alcohol abuse, substantial research in the alcohol field is focused on understanding the mechanisms by which alcohol-related diseases develop and progress. Since ethical concerns and inherent difficulties limit the amount of alcohol abuse research that can be performed in humans, most studies are performed in laboratory animals. This article summarizes the various laboratory models of alcohol abuse that are currently available and are used to study the mechanisms by which alcohol abuse induces organ damage and immune defects. The strengths and weaknesses of each of the models are discussed. Integrated into the review are the presentations that were made in the symposium "Methods of Ethanol Application in Alcohol Model-How Long is Long Enough" at the joint 2008 Research Society on Alcoholism (RSA) and International Society for Biomedical Research on Alcoholism (ISBRA) meeting, Washington, DC, emphasizing the importance not only of selecting the most appropriate laboratory alcohol model to address the specific goals of a project but also of ensuring that the findings can be extrapolated to alcohol-induced diseases in humans.

Decreased pulmonary inflammation following ethanol and burn injury in mice deficient in TLR4 but not TLR2 signaling

BACKGROUND

Clinical and laboratory evidence suggests that alcohol consumption prior to burn injury leads to dysregulated immune function and subsequent higher rates of morbidity and mortality. Our laboratory previously observed higher levels of pro-inflammatory cytokines and leukocyte infiltration in the lungs of mice following ethanol and burn injury. To understand the mechanism of the increased inflammatory response, we looked at different signaling initiators of inflammation including toll-like receptors 2 and 4 (TLR2 and 4) pathways.

METHODS

Wild-type, TLR2, and TLR4 knockout mice were treated with vehicle or a single binge dose of ethanol (1.11 g/kg) and subsequently given a sham or burn injury. Twenty-four hours postinjury, systemic and pulmonary levels of pro-inflammatory cytokines were quantified, and differences in neutrophil infiltration were determined by histological examination.

RESULTS

Higher numbers of neutrophils were observed in the lungs of wild-type mice following the combined insult of ethanol and burn injury relative to either injury alone. This increase in leukocyte accumulation was absent in the TLR4 knockout mice. Circulating levels of IL-6 and tumor necrosis factor-α were also elevated in wild-type mice but not in TLR4 knockout mice. Consistent with these findings, pulmonary levels of KC and IL-6 were increased in wild-type mice following burn and ethanol compared to burn injury alone as well as to their TLR4 knockout counterparts. In contrast, TLR2 knockout mice displayed similar levels, to wild-type mice, of neutrophil infiltration as well as IL-6 and KC in the lung.

CONCLUSIONS

These data suggest that TLR4 signaling is a crucial contributory component in the exuberant inflammation after ethanol and burn injury. However, TLR2 does not appear to play a vital role in the aberrant pulmonary inflammation.

Alcoholic liver disease and the gut-liver axis

Alcoholic liver disease (ALD) is one of the leading causes of liver diseases and liver-related death worldwide. Of the many factors that contribute to the pathogenesis of ALD, gut-derived lipopolysaccharide (LPS) plays a central role in induction of steatosis, inflammation, and fibrosis in the liver. In this review, we discuss the mechanisms by which alcohol contributes to increased gut permeability, the activation of Kupffer cells, and the inflammatory cascade by LPS. The role of the Toll-like receptor 4 (TLR4) complex in LPS recognition and the importance of the TLR4-induced signaling pathways are evaluated in ALD.

Adverse clinical outcomes associated with elevated blood alcohol levels at the time of burn injury

Elevated blood alcohol content (BAC) on admission is associated with poorer outcomes, larger burns and more inhalation injury. This study's purpose was to examine the effects of alcohol through a matched case-controlled study, measuring early and extended markers of clinical outcomes. The hypothesis was that patients with an elevated admission BAC would require more resuscitation and have a longer hospital stay. Admissions 16 to 75 years of age with 15 to 75% TBSA and admission BACs were identified. Patients with BAC >30 mg/dl (BAC+, cases) were matched with patients with undetectable BAC (BAC-, controls), according to age, sex, TBSA, inhalation injury and mechanism. Screening identified 258 patients, 146 with admission BACs. Twenty-seven had a BAC > or = 30 mg/dl. There were 24 matched pairs. At 24 hours, BAC+ group had larger acute physiology and chronic health evaluation II scores (23.33 vs 18.75, P < .05), fluid requirements (5.25 vs 3.82 L (cc/kg/TBSA), P < .05), and base deficit (11.15 vs 7.15, P < .05). The duration of mechanical ventilation (14.85 vs 4.23 days, P < .05), intensive care unit length of stay (22.85 vs 9.38, P < .05), hospital length of stay (28.95 vs 15.68, P < .05), and mean hospital charges ($239,507 vs $144,598, P < .05) were increased in the BAC+ patients. Despite matched baseline injury characteristics, elevated BAC was associated with poorer short term and extended clinical outcomes, illustrating the impact of alcohol intoxication on physiologic derangement after burn injury.

Dose-dependent effects of ethanol and E. coli on gut permeability and cytokine production

INTRODUCTION

The gut may prime inflammatory responses following shock/trauma insults. Ethanol (EtOH) use is common in trauma patients and may impair intestinal barrier function. We compared varying concentrations of EtOH on proinflammatory cytokine production of Caco2 cell monolayers and the resultant changes in barrier function. We hypothesized that even low concentrations of EtOH would cause significant cytokine release and barrier dysfunction in vitro.

MATERIALS AND METHODS

Confluent Caco2 cell monolayers were grown in a two-chamber culture system and exposed to varying concentrations of EtOH (0.1%, 0.5%, 1.0%, 1.5%, and 2.0%) with/without Escherichia coli C-25 (EC). Supernatants were collected and TNF and IL6 quantified by ELISA (pg/mL). Monolayer integrity was assessed by apoptosis and permeability measurements.

RESULTS

Caco2 production of TNF-alpha increased in a dose-dependent manner when incubated with increasing concentrations of EtoH. A synergistic effect was seen when E. coli was added to the apical chamber. A similar result was seen with the production of IL-6. A dose-dependent effect was also noted with EtOH with or without E. coli on apoptosis and permeability measurements.

CONCLUSION

In addition to alterations in gut permeability, increasing concentrations of ethanol have a synergistic effect with E. coli on Caco2 production of proinflammatory cytokines TNF and IL-6. The creation of a proinflammatory cytokine milieu with an altered barrier integrity may be a mechanism by which ethanol may increase septic complications in the injured patient.

Alcohol, intestinal bacterial growth, intestinal permeability to endotoxin, and medical consequences: summary of a symposium

This report is a summary of the symposium on Alcohol, Intestinal Bacterial Growth, Intestinal Permeability to Endotoxin, and Medical Consequences, organized by National Institute on Alcohol Abuse and Alcoholism, Office of Dietary Supplements, and National Institute of Diabetes and Digestive and Kidney Diseases of National Institutes of Health in Rockville, Maryland, October 11, 2006. Alcohol exposure can promote the growth of Gram-negative bacteria in the intestine, which may result in accumulation of endotoxin. In addition, alcohol metabolism by Gram-negative bacteria and intestinal epithelial cells can result in accumulation of acetaldehyde, which in turn can increase intestinal permeability to endotoxin by increasing tyrosine phosphorylation of tight junction and adherens junction proteins. Alcohol-induced generation of nitric oxide may also contribute to increased permeability to endotoxin by reacting with tubulin, which may cause damage to microtubule cytoskeleton and subsequent disruption of intestinal barrier function. Increased intestinal permeability can lead to increased transfer of endotoxin from the intestine to the liver and general circulation where endotoxin may trigger inflammatory changes in the liver and other organs. Alcohol may also increase intestinal permeability to peptidoglycan, which can initiate inflammatory response in liver and other organs. In addition, acute alcohol exposure may potentiate the effect of burn injury on intestinal bacterial growth and permeability. Decreasing the number of Gram-negative bacteria in the intestine can result in decreased production of endotoxin as well as acetaldehyde which is expected to decrease intestinal permeability to endotoxin. In addition, intestinal permeability may be preserved by administering epidermal growth factor, l-glutamine, oats supplementation, or zinc, thereby preventing the transfer of endotoxin to the general circulation. Thus reducing the number of intestinal Gram-negative bacteria and preserving intestinal permeability to endotoxin may attenuate alcoholic liver and other organ injuries.

Inhibition of protein tyrosine phosphatases prevents mesenteric lymph node T-cell suppression following alcohol intoxication and burn injury

Previously, we have shown that acute alcohol (EtOH) intoxication before burn injury potentiates the suppression of mesenteric lymph node T-cell effector responses. Moreover, the suppression in T-cell was accompanied with a decrease in p-38 and extracellular-signal-regulated kinase (ERK) activation. This study examined the role of protein tyrosine phosphatases (PTP) in suppressed T-cell p-38, ERK, and cytokine production after EtOH intoxication and burn injury. A blood EtOH level of approximately 100 mg/dl in male rats (approximately 250 g) was achieved by gavaging animals with 5 ml of 20% EtOH suspension 4 hours before burn or sham injury (approximately 12.5% or 25% total body surface area [TBSA]). One day after injury, rats were killed and mesenteric lymph node T-cell cytokine (IL-2/IFN-gamma) production, p-38, and ERK activation were measured. As compared with shams, there was a significant decrease in T-cell cytokine production after 25% and not 12.5% TBSA burn injury. However, T-cell IL-2/IFN-gamma levels were significantly decreased in rats receiving a combined insult of EtOH and burn injury regardless of the percentage of burn area. Furthermore, we found a significant decrease in p-38 and ERK-1/2 phosphorylation in T-cells of rats receiving a combined insult of EtOH and 12.5% TBSA burn compared with shams. Treatment of cells with PTP inhibitor pervanadate (10 muM) prevented T-cell p-38/ERK suppression. The suppression in IL-2/IFN-gamma production was also attenuated in T-cells cultured in the presence of pervanadate. These findings suggest that an increase in PTP activity may contribute to T-cell suppression after EtOH intoxication and burn injury.

Organ-specific inflammation following acute ethanol and burn injury

Clinical and experimental evidence demonstrates that ethanol exposure prior to injury alters local and systemic inflammatory responses, increasing morbidity and mortality. Moreover, the aberrant inflammatory responses can directly and indirectly lead to the poor prognosis after injury by altering leukocyte infiltration into the wound site and remote organs and by suppressing immunity leading to increased susceptibility to opportunistic infections. Recent studies from our laboratory have focused on inflammatory responses at the wound site and in other distal organs after exposure to acute ethanol and burn injury. This combined insult leads to increased mortality after dermal or intratracheal pseudomonas infection, relative to infected mice given ethanol or burn injury alone. The increased mortality in mice given ethanol and burn injury parallels elevated serum levels of proinflammatory cytokines, IL-6 and TNF-alpha, marked infiltration of leukocytes into the lung and gut, as well as immunosuppression at the sites of infection. Bacterial translocation from the gut is likely to be responsible, in part, for the aberrant accumulation of leukocytes in the lungs of ethanol-exposed, burn-injured mice. Additionally, other factors, such as expression of adhesion molecules, increased chemokine production, and leakiness of the vascular endothelium, may also be involved.

A role for corticosterone in impaired intestinal immunity and barrier function in a rodent model of acute alcohol intoxication and burn injury

Alcohol (EtOH) intoxication and burn injury independently activate hypothalamic-pituitary-adrenal (HPA) axis, and glucocorticoids, the end product of the HPA axis, play a role in shaping the immune response under those conditions. By utilizing a rat model of acute EtOH intoxication and burn injury, studies in our laboratory have investigated the role of corticosterone (i.e., glucocorticoids in rodents) in altered intestinal immunity and barrier function following a combined insult of EtOH and burn injury. Results from these studies suggest that EtOH intoxication prior to burn injury augments corticosterone release, which in turn suppresses intestinal T cell function by inhibiting mitogen-activated protein kinase (i.e., p38 and ERK) pathway. Furthermore, we found that corticosterone does not directly alter the intestinal barrier function; rather, it up-regulates interleukin-18, which then directly or indirectly contributes to impaired intestinal barrier function. The loss of intestinal immunity/barrier function may result in increased bacterial translocation and thereby contribute to postinjury pathogenesis, leading to sepsis and organ dysfunction in burn patients as well as in patients with a history of EtOH intoxication.

Relations among circulating monocytes, dendritic cells, and bacterial translocation in patients with intestinal obstruction

BACKGROUND

Little evidence is available regarding the relations among circulating monocytes, dendritic cells (DCs), and bacterial translocation (BT) in patients with intestinal obstruction.

METHODS

We investigated alterations in DCs in mesenteric lymph nodes (MLNs), circulating immune cells (white blood cell, lymphocyte, and monocyte counts), and BT to MLNs in 21 patients undergoing abdominal surgery because of intestinal obstruction. We also examined whether BT correlated with the development of perioperative systemic inflammatory response syndrome (SIRS) and postoperative septic complications.

RESULTS

BT subsequent to intestinal obstruction was observed in 7 (33%) patients. Preoperative circulating immune cell counts were significantly lower in BT-positive patients than those in BT-negative patients. The presence of preoperative SIRS was also significantly related to BT-positive status. A preoperative monocyte count <290/mm(3) was the best predictive factor for BT in MLNs during intestinal obstruction: sensitivity 85.7%; specificity 92.3%; positive and negative predictive values 85.7% and 92.9%, respectively. The area under the receiver operating characteristic curve was 0.944. The expression of S-100 protein-positive DCs in MLNs significantly increased in BT-positive patients.

CONCLUSIONS

A significant inverse correlation was observed between the circulating monocyte count and the ratio of DCs among all cells in MLNs (r(2)= 0.259). Postoperative septic complications were 3.3 times more common in BT-positive patients than in BT-negative patients. A significant increase in the expression of DCs in MLNs was observed in patients with BT subsequent to intestinal obstruction. Our findings suggested that a low monocyte count (<290 /mm(3)) and the presence of preoperative SIRS might be useful factors for predicting BT in patients with intestinal obstruction.

A role of PP1/PP2A in mesenteric lymph node T cell suppression in a two-hit rodent model of alcohol intoxication and injury

This study examined the role of protein phosphatase type-1 (PP1), type-2A (PP2A), and mitogen-activated protein kinase phosphatase-1 (MKP-1) in altered mesenteric lymph node (MLN) T cell function in a two-hit model of alcohol (EtOH) intoxication and burn injury. Male rats (250 g) were gavaged with EtOH to achieve a blood EtOH level of approximately 100 mg/dL prior to burn or sham injury (25% total body surface area). MLN T cells harvested 24 h after injury show a significant decrease in p38 and extracellular signal-regulated kinase (ERK)-1/2 phosphorylation in T cells from rats receiving a combined insult of EtOH intoxication and burn injury compared with rats receiving EtOH intoxication or burn injury alone. Treatment of cells with inhibitors of PP1/PP2A [calyculin A (CA) and okadaic acid (OA)] prevented the suppression in T cells p38 and ERK-1/2 activation. In addition, the suppression in interleukin-2 and interferon-gamma production was attenuated in T cells cultured in the presence of CA and OA. MKP-1 inhibitor triptolide did not prevent the suppression in T cells p38/ERK-1/2 and cytokine production. Furthermore, there was a significant decrease in PP1alpha phosphorylation (Thr320) and an increase in PP2A (Tyr307) phosphorylation in T cells following a combined insult of EtOH intoxication and burn injury. As phosphorylation of PP1 at Thr320 and PP2A at Tyr307 led to an inhibition of their enzymatic activities, the decrease in the PP1alpha phosphorylation correlates with an increase in its enzyme activity. Thus, these results suggest that activation of PP1 is likely to play a predominant role in T cell suppression following a combined insult of EtOH intoxication and burn injury.

Corticosterone suppresses mesenteric lymph node T cells by inhibiting p38/ERK pathway and promotes bacterial translocation after alcohol and burn injury

Previous studies showed that alcohol (EtOH) intoxication before burn injury suppresses mesenteric lymph node (MLN) T cell functions and increases gut bacterial translocation. In this study, we examined whether corticosterone (Cort) plays any role in suppressing MLN T cell function and bacterial accumulation after EtOH intoxication and burn injury. Rats were gavaged with EtOH to achieve a blood EtOH level of approximately 100 mg/dl before receiving 25% total body surface area burn or sham injury. A group of rats was treated with the Cort synthesis inhibitor metyrapone (25 mg/kg) at the time of injury and on day 1 after injury. Two days after injury, a significant increase in blood Cort levels and suppression of MLN T cell proliferation and IL-2 production was observed in rats receiving combined insult of EtOH intoxication and burn injury compared with rats receiving EtOH intoxication or burn injury alone. There was no change in T cell apoptosis after combined insult of EtOH and burn injury. Furthermore, T cell suppression was accompanied by a significant decrease in p38 and ERK1/2 activation (phosphorylation). There was no difference in JNK activation after EtOH and burn injury. Treatment of rats with metyrapone prevented the suppression of MLN T cell proliferation, IL-2 production, and p38 and ERK1/2 phosphorylation. Restoration of T cell function in metyrapone-treated animals was also associated with the decrease in bacterial accumulation in MLN. These findings suggest that EtOH intoxication before burn injury augments Cort release, which suppresses MLN T cell function by inhibiting p38 and ERK1/2 activation and promotes bacterial accumulation in MLN after EtOH and burn injury.

Impaired intestinal immunity and barrier function: a cause for enhanced bacterial translocation in alcohol intoxication and burn injury

Alcohol intoxication is being recognized increasingly as the major factor in pathogenesis after burn injury. Findings from multiple studies support the suggestion that, in comparison with burn-injured patients who sustained injury in the absence of alcohol intoxication, burn-injured patients who sustained injury under the influence of alcohol exhibit higher rates of infection and are more likely to die. Thus, infection becomes the primary cause of death in burn-injured patients. Because the intestine is considered to be a major source of bacteria, studies in experimental animals have been designed to examine whether alcohol intoxication before burn injury enhances bacterial translocation from the intestine. Results of these studies have shown a several-fold increase in bacterial translocation from the intestine in the group of animals receiving combined insult of alcohol intoxication and burn injury compared with findings for the groups receiving either insult alone. Alcohol intoxication and burn injury independent of each other have also been shown to cause an increase in bacterial translocation. The gastrointestinal tract normally maintains a physical mucosal and immunologic barrier that provides an effective defense in keeping bacteria within the intestinal lumen. However, in injury conditions these defense mechanisms are impaired. Intestinal bacteria consequently gain access to extraintestinal sites. Intestine-derived bacteria are implicated in causing systemic infection and in subsequent multiple organ dysfunction in both immunocompromised patients and patients with injury, such as burn and trauma. In this article, we discuss three potential mechanisms that are likely to contribute to the increase in bacterial translocation in alcohol intoxication and burn injury: (1) increase in bacterial growth in the intestine, (2) physical disruption of mucosal barrier of the intestine, and (3) suppression of the immune defense in the intestine.