Effects of ethanol on pulmonary inflammation in postburn intratracheal infection

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.

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.

Remote Burn Injury Increases Pulmonary Histone Deacetylase 1 and Reduces Histone Acetylation

Dermal burn injury causes profound physiological derangements. Respiratory failure is a primary cause of morbidity and mortality after burn injury, in part, because of excessive and prolonged release of local and systemic proinflammatory mediators. Clinical and preclinical evidence suggests histone deacetylases (HDACs) are key mediators of inflammatory responses. The study objective was to explore the effects of dermal burn injury on pulmonary HDAC activity, identify specific lung HDAC(s) altered by burn, and characterize histone lysine acetylation status. Mice were subjected to a 15% total body surface area scald burn or a sham injury and euthanized 24 hours later. Whole lungs were harvested, or alveolar macrophages were isolated from bronchoalveolar lavage fluid. HDAC specific activity assays were performed, Western blots were run to analyze HDACs1, 2, 3, 4, and 10 or histone lysine acetylation levels, and HDAC1 and phosphorylated-HDAC1 levels and localization were examined by immunofluorescence. Burned mice had higher HDAC specific activity and increased HDAC1 levels compared with controls, but levels of other HDACs were comparable between groups. Burn injury increased levels of HDAC1 and phosphorylated-HDAC1 in bronchioles and alveolar sacs and was associated with global and specific diminished levels of histone H3 and histone H4 lysine acetylation. Our analyses reveal that pulmonary inflammation after burn injury may be modulated by epigenetic mechanisms involving HDACs because HDAC activity, HDAC1 expression and activity, and downstream histone acetylation were all altered after burn. Future studies will explore the role of HDAC inhibitors in reversing inflammatory defects and may ultimately lead to new treatment interventions for burn patients.

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.

Ethanol intoxication prolongs post-burn pulmonary inflammation: role of alveolar macrophages

In this study, the role and fate of AMs were examined in pulmonary inflammation after intoxication and injury. Clinical evidence has revealed that half of all burn patients brought to the emergency department are intoxicated at the time of injury. This combined insult results in amplified neutrophil accumulation and pulmonary edema, with an increased risk of lung failure and mortality, relative to either insult alone. We believe that this excessive pulmonary inflammation, which also parallels decreased lung function, is mediated in part by AMs. Restoration of lung tissue homeostasis is dependent on the eradication of neutrophils and removal of apoptotic cells, both major functions of AMs. Thirty minutes after binge ethanol intoxication, mice were anesthetized and given a 15% total body surface area dorsal scald injury. At 24 h, we found a 50% decrease in the total number of AMs (P < 0.05) and observed a proinflammatory phenotype on the remaining lung AMs. Loss of AMs paralleled a 6-fold increase in the number of TUNEL⁺ lung apoptotic cells (P < 0.05) and a 3.5-fold increase in the percentage of annexin V⁺ apoptotic cells in BAL (P < 0.05), after intoxication and injury, relative to controls. In contrast to the reduction in the number of cells, AMs from intoxicated and injured mice had a 4-fold increase in efferocytosis (P < 0.05). In summary, these data suggest that loss of AMs may delay resolution of inflammation, resulting in the pulmonary complications and elevated mortality rates observed in intoxicated and burn-injured patients.

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.

Alcohol potentiates postburn remote organ damage through shifts in fluid compartments mediated by bradykinin

Of the 450,000 burn patients each year, 50% have a positive blood alcohol content, and this predisposes them to worsened clinical outcomes. Despite high prevalence and established consequences, the mechanisms responsible for alcohol-mediated complications of postburn remote organ damage are currently unknown. To this end, mice received a single dose of alcohol (1.12 g/kg) or water by oral gavage and were subjected to a 15% total body surface area burn. Animals with a burn alone lost ∼5% of their body weight in 24 h, whereas intoxicated and burned mice lost only 1% body weight (P < 0.05) despite a 17% increase in hematocrit (P < 0.05) and a 57% increase in serum creatinine (P < 0.05) over burn injury alone. This retention of water weight despite increased dehydration suggests that intoxication at the time of a burn causes a shift in fluid compartments that may exacerbate end-organ ischemia and damage as evidenced by a 3-fold increase in intestinal bacterial translocation (P < 0.05), a 30% increase (P < 0.05) in liver weight-to-body weight ratio, and an increase in alveolar wall thickness over a burn alone. Furthermore, administration of the bradykinin antagonist HOE140 30 min after intoxication and burn restored fluid balance and alleviated end-organ damage. These findings suggest that alcohol potentiates postburn remote organ damage through shifts in fluid compartments mediated by bradykinin.

Alcohol-induced miR-27a regulates differentiation and M2 macrophage polarization of normal human monocytes

Alcohol abuse is a leading cause of liver disease characterized by liver inflammation, fatty liver, alcoholic hepatitis, or liver cirrhosis. Immunomodulatory effects of alcohol on monocytes and macrophages contribute to alcoholic liver disease. Alcohol use, an independent risk factor for progression of hepatitis C virus (HCV) infection-mediated liver disease, impairs host defense and alters cytokine production and monocyte/macrophage activation. We hypothesized that alcohol and HCV have synergistic effects on the phenotype and function of monocytes. Our data show that acute alcohol binge drinking in healthy volunteers results in increased frequency of CD16(+) and CD68(+) and M2-type (CD206(+), dendritic cell [DC]-SIGN(+)-expressing and IL-10-secreting) circulating CD14(+) monocytes. Expression of HCV-induced CD68 and M2 markers (CD206 and DC-SIGN) in normal monocytes was further enhanced in the presence of alcohol. The levels of microRNA (miR)-27a was significantly upregulated in monocytes cultured in the presence of alcohol or alcohol and HCV as compared with HCV alone. The functional role of miR-27a in macrophage polarization was demonstrated by transfecting monocytes with an miR-27a inhibitor that resulted in reduced alcohol- and HCV- mediated monocyte activation (CD14 and CD68 expression), polarization (CD206 and DC-SIGN expression), and IL-10 secretion. Overexpression of miR-27a in monocytes enhanced IL-10 secretion via activation of the ERK signaling pathway. We found that miR-27a promoted ERK phosphorylation by downregulating the expression of ERK inhibitor sprouty2 in monocytes. Thus, we identified that sprouty2 is a target of miR-27a in human monocytes. In summary, our study demonstrates the regulatory role of miR-27a in alcohol-induced monocyte activation and polarization.

An alteration of the gut-liver axis drives pulmonary inflammation after intoxication and burn injury in mice

Approximately half of all adult burn patients are intoxicated at the time of their injury and have worse clinical outcomes than those without prior alcohol exposure. This study tested the hypothesis that intoxication alters the gut-liver axis, leading to increased pulmonary inflammation mediated by burn-induced IL-6 in the liver. C57BL/6 mice were given 1.2 g/kg ethanol 30 min prior to a 15% total body surface area burn. To restore gut barrier function, the specific myosin light chain kinase inhibitor membrane-permeant inhibitor of kinase (PIK), which we have demonstrated to reduce bacterial translocation from the gut, was administered 30 min after injury. Limiting bacterial translocation with PIK attenuated hepatic damage as measured by a 47% reduction in serum alanine aminotransferase (P < 0.05), as well as a 33% reduction in hepatic IL-6 mRNA expression (P < 0.05), compared with intoxicated and burn-injured mice without PIK. This mitigation of hepatic damage was associated with a 49% decline in pulmonary neutrophil infiltration (P < 0.05) and decreased alveolar wall thickening compared with matched controls. These results were reproduced by prophylactic reduction of the bacterial load in the intestines with oral antibiotics before intoxication and burn injury. Overall, these data suggest that the gut-liver axis is deranged when intoxication precedes burn injury and that limiting bacterial translocation in this setting attenuates hepatic damage and pulmonary inflammation.

Age-related differences in the neutrophil response to pulmonary pseudomonas infection

BACKGROUND

Pseudomonas aeruginosa pneumonia is more common and more lethal in the elderly. The immunologic underpinnings of this increased incidence and mortality have not been evaluated, however are assumed to be a complication of age-associated immune dysfunction.

METHODS

Young (10-12week old) and aged (18-20month old) BALB/c mice were subjected to intratracheal infection of P. aeruginosa. Animals were sacrificed 24h after inoculation. The lungs were collected for analysis of lung pathology, chemokine levels, neutrophil counts, and myeloperoxidase activity.

RESULTS

Pulmonary levels of the neutrophil chemokine KC are significantly higher in aged mice relative to young following P. aeruginosa infection. Despite this, neutrophil counts are higher in young mice compared to aged mice after infection. Furthermore, the neutrophils are predominantly found in the air space of young infected mice. This correlated with increased myeloperoxidase activity from bronchoalveolar lavage specimens of young mice relative to aged mice after infection.

CONCLUSIONS

Neutrophil migration into the lungs is impaired in aged mice 24h after intratracheal infection despite elevated chemokine levels, suggesting that immunosenescence is impairing neutrophil migration.

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.

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.

Combined radiation and burn injury results in exaggerated early pulmonary inflammation

Events such as a nuclear meltdown accident or nuclear attack have potential for severe radiation injuries. Radiation injury frequently occurs in combination with other forms of trauma, most often burns. Thus far, combined injury studies have focused mainly on skin wound healing and damage to the gut. Since both radiation exposure and remote burn have pulmonary consequences, we examined the early effects of combined injury on the lung. C57BL/6 male mice were irradiated with 5 Gy of total body irradiation followed by a 15% total body surface area scald burn. Lungs from surviving animals were examined for evidence of inflammation and pneumonitis. At 48 h post-injury, pathology of the lungs from combined injury mice showed greater inflammation compared to all other treatment groups, with marked red blood cell and leukocyte congestion of the pulmonary vasculature. There was excessive leukocyte accumulation, primarily neutrophils, in the vasculature and interstitium, with occasional cells in the alveolar space. At 24 and 48 h post-injury, myeloperoxidase levels in lungs of combined injury mice were elevated compared to all other treatment groups (P < 0.01), confirming histological evidence of neutrophil accumulation. Pulmonary levels of the neutrophil chemoattractant KC (CXCL1) were 3 times above that of either injury alone (P < 0.05). Further, monocyte chemotactic protein-1 (MCP-1, CCL2) was increased two- and threefold compared to burn injury or radiation injury, respectively (P < 0.05). Together, these data suggest that combined radiation and burn injury augments early pulmonary congestion and inflammation. Currently, countermeasures for this unique type of injury are extremely limited. Further research is needed to elucidate the mechanisms behind the synergistic effects of combined injury in order to develop appropriate treatments.

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.

Prolonged chemokine expression and excessive neutrophil infiltration in the lungs of burn-injured mice exposed to ethanol and pulmonary infection

Pulmonary infections are a major cause of mortality in the critically ill burn patient. Alcohol consumption before burn increases the risk of pulmonary infection. Previously, we have shown an elevated mortality and lung pathology in mice given ethanol before burn and intratracheal infection relative to controls. Here we examine the cellular composition at 24 and 48 h in the circulation and the alveoli of infected mice given alcohol and burn. At 24 h after injury, blood neutrophils obtained from mice exposed to ethanol before burn and infection were 2-fold above those of the experimental controls (P < 0.05). By 48 h, the number of circulating neutrophils decreased and was comparable to levels found in untreated animals. Moreover, at 24 h, bronchoalveolar lavage cells obtained from all treatment groups had similar frequencies and contained 80% neutrophils regardless of treatment. In contrast, the following day, neutrophils were elevated 2-fold only in the alveoli of infected burn animals and 5-fold when ethanol preceded the injury (P < 0.05). These data were confirmed by immunofluorescence microscopy using a neutrophil-specific marker (P < 0.05). Levels of neutrophil chemoattractants, KC and macrophage inflammatory protein 2, and the cytokine, IL-1β, were 2-fold greater in the lungs of infected mice given burn, regardless of ethanol exposure, relative to infected sham injured animals (P < 0.05). Like the number of neutrophils, by the second day after injury, KC and macrophage inflammatory protein 2 remained 5-fold higher in the animals given ethanol, burn, and infection, when compared with other groups (P < 0.05). A similar pattern was seen for pulmonary levels of IL-1β (P < 0.05). Additionally, a reduction in neutrophil apoptosis was observed at the 24-h time point in infected mice exposed to ethanol and burn (P < 0.05). Targeting proinflammatory mediators in mice exposed to ethanol before burn and infection may help alleviate prolonged neutrophil accumulation in the lungs.

Development of a combined radiation and burn injury model

Combined radiation and burn injuries are likely to occur after nuclear events, such as a meltdown accident at a nuclear energy plant or a nuclear attack. Little is known about the mechanisms by which combined injuries result in higher mortality than by either insult alone, and few animal models exist for combined radiation and burn injury. Herein, the authors developed a murine model of radiation and scald burn injury. Mice were given a single dose of 0, 2, 4, 5, 6, or 9 Gray (Gy) alone, followed by a 15% TBSA scald burn. All mice receiving ≤4 Gy of radiation with burn survived combined injury. Higher doses of radiation (5, 6, and 9 Gy) followed by scald injury had a dose-dependent increase in mortality (34, 67, and 100%, respectively). Five Gy was determined to be the ideal dose to use in conjunction with burn injury for this model. There was a decrease in circulating white blood cells in burn, irradiated, and combined injury (5 Gy and burn) mice by 48 hours postinjury compared with sham (49.7, 11.6, and 57.3%, respectively). Circulating interleukin-6 and tumor necrosis factor-α were increased in combined injury at 48 hours postinjury compared with all other treatment groups. Prolonged overproduction of proinflammatory cytokines could contribute to subsequent organ damage. Decreased leukocytes might exacerbate immune impairment and susceptibility to infections. Future studies will determine whether there are long lasting consequences of this early proinflammatory response and extended decrease in leukocytes.

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.

Alcohol and trauma: a summary of the Satellite Symposium at the 30th Annual Meeting of the Shock Society

This article highlights the research presented at the Alcohol and Trauma Satellite Symposium at the 30th Annual Meeting of the Shock Society. The satellite meeting was held on June 8 and 9 in Baltimore, MD. Its purpose was to discuss recent findings in the areas of alcohol and injury, including the effect of alcohol use on patients in the trauma unit of hospitals. The meeting consisted of three sessions, with plenary talks by invited speakers, short talks from selected abstracts, and a poster session. Participants presented data on the effects of alcohol on organ function, healing, and immune processes after a variety of injuries including burn, hemorrhagic shock, sepsis, and ischemia reperfusion.

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.

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.