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

Alcohol 33 (2004) 199–208

Impaired intestinal immunity and barrier function: a cause for enhanced bacterial translocation in alcohol intoxication and burn injury Mashkoor A. Choudhrya,b,*, Shadab N. Ranaa, Michael J. Kavanaughc, Elizabeth J. Kovacsc–f, Richard L. Gamellic–e, Mohammed M. Sayeedc–e a

Center for Surgical Research, University of Alabama at Birmingham, Birmingham, AL 35294, USA b Department of Surgery, University of Alabama at Birmingham, Birmingham, AL 35294, USA c Burn and Shock Trauma Institute, Loyola University Chicago Medical Center, Maywood, IL 60153, USA d Alcohol Research Program, Loyola University Chicago Medical Center, Maywood, IL 60153, USA e Department of Surgery, Loyola University Chicago Medical Center, Maywood, IL 60153, USA f Department of Cell Biology, Neurobiology and Anatomy, Loyola University Chicago Medical Center, Maywood, IL 60153, USA Received 9 March 2004; received in revised form 12 May 2004; accepted 19 May 2004

Abstract 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. 쑖 2004 Elsevier Inc. All rights reserved. Keywords: Ethanol; Thermal injury; Infection; Mucosal immunity; Cell signaling

1. Introduction An analysis of clinical data supports the suggestion of a close association between alcohol intoxication and injury, such as burn and trauma (Maier, 2001; McGill et al., 1995; McGwin et al., 2000; Soderstrom et al., 1998). More than 1 million burn injuries are reported every year within the United States (American Burn Association, 2000). Nearly 50% of these injuries occur while the individual is under

* Corresponding author. Center for Surgical Research, University of Alabama at Birmingham, Volker Hall G 094, 1670 University Boulevard, Birmingham, AL 35294, USA. Tel.: ⫹1-205-975-9712; fax: ⫹1-205-9759715. E-mail address: [email protected] (M.A. Choudhry). Editor: T.R. Jerrells 0741-8329/04/$ – see front matter 쑖 2004 Elsevier Inc. All rights reserved. doi: 10.1016/j.alcohol.2004.05.004

the influence of alcohol (Maier, 2001; McGill et al., 1995; McGwin et al., 2000). These findings further indicate that, in comparison with burn-injured patients who did not consume alcohol before injury, patients who suffer burn injury while under the influence of alcohol and survive initial injury are likely to die because of secondary complications. These patients have a longer hospital stay and are more susceptible to infection. Furthermore, such patients are more likely to suffer complications such as multiple organ dysfunction/failure than are burn-injured patients who sustain a similar degree of burn injury but did not consume alcohol before injury (Bone, 1996; Gentilello et al., 1993; Maier, 2001; McGill et al., 1995; McGwin et al., 2000; Messingham et al., 2002; Moss & Burnham, 2003). The onset of multiple organ dysfunction/failure is probably induced by a series of events, including uncontrolled

200

M.A. Choudhry et al. / Alcohol 33 (2004) 199–208

production of inflammatory mediators and suppression of the immune response (Baue et al., 1998; Fitzwater et al., 2003; Hassoun et al., 2001; Messingham et al., 2002; Yao et al., 1998). Findings from both clinical and experimental studies have shown that burn injury or trauma alone results in activation of some cells of the immune system, such as macrophages and monocytes. These activated cells produce increased amounts of inflammatory mediators, namely interleukin (IL)-6, IL-10, tumor necrosis factor-alpha, transforming growth factor-beta, and prostaglandin E2 (Faist et al., 1996; Messingham et al., 2002; Miller-Graziano et al., 1995; Schwacha & Chaudry, 2002; Yao et al., 1998). Other functions of the immune system, as determined by the ability of the macrophage to present antigen, T cell proliferation, and IL-2 production, are severely suppressed (Fig. 1) (Choudhry et al., 2001a; Faist et al., 1996; Hoyt et al., 1994; Kelly et al., 1999; Moore, 1999; O’Sullivan & O’Connor, 1997). Similarly, the effect of alcohol on the immune system independent of injury, such as burn or trauma, includes a decrease in macrophage antigen-presenting ability, T cell proliferation, and IL-2 production (Cook, 1998; Diehl, 2000; Goral et al., 2004; Jayasinghe et al., 1992; Jerrells et al., 1992, 1998; Messingham et al., 2002; Mikszta et al., 1995; Peterson et al., 1998; Szabo, 1998). It is likely that a combined insult of alcohol intoxication and burn injury exacerbates such changes in the injured host. This results in a

failure to generate an effective immune response, thereby leading to decreased host resistance and enhanced susceptibility to infection (Choudhry et al., 2000; Faunce et al., 1997; Maier, 2001; McGill et al., 1995; Messingham et al., 2002).

2. Bacterial translocation in alcohol intoxication and burn injury At least during the past two decades, intestinal bacteria have been considered as the source of infection in burn injury and trauma (Bahrami et al., 1996; Barber et al., 1993; Baron et al., 1994; Berg, 1992, 1999; Deitch et al., 1986; Deitch & Berg, 1987a; Dijkstra et al., 1996; Fukushima et al., 1995; Gianotti et al., 1993, 1996; Herndon & Zeigler, 1993; Horton, 1994; Jones et al., 1990a, 1990b; Maejima et al., 1984b; Peitzman et al., 1991; Schindel et al., 1997; Wells et al., 1988). Maejima et al. (1984b) have shown that rats receiving a 40% total body surface area burn injury exhibited viable bacteria in their mesenteric lymph nodes (MLNs) 2 days after burn injury. A similar increase in viable bacterial counts in MLNs was observed in rats receiving a 30% total body surface area burn injury on day 1 after injury (Fazal et al., 2000; Jones et al., 1990b). The passage of viable bacteria from the gastrointestinal tract to the MLNs

Fig. 1. Diagram of events leading to intestinal bacterial translocation and subsequent development of sepsis and multiple organ dysfunction in alcohol intoxication and burn injury. Alcohol intoxication and burn injury independent of each other can suppress immune cell function and impair intestinal barrier function. However, a combined insult of alcohol intoxication and burn injury exacerbates such changes in an injured host, resulting in severe deficiencies in intestinal barrier and immune competence. This results in decreased host resistance and enhanced susceptibility to infection. IFN-γ ⫽ Interferon-gamma; IL ⫽ interleukin; MHC ⫽ major histocompatibility complex; PGE2 ⫽ prostaglandin E2; TNF-α ⫽ tumor necrosis factor-alpha.

M.A. Choudhry et al. / Alcohol 33 (2004) 199–208

and other organs is referred to as bacterial translocation (Berg, 1999). Gianotti et al. (1993) have shown that bacterial translocation is influenced directly by the severity of burn injury. Findings from several studies have shown that burn injury results in bacterial translocation in the first few days after injury (Barber et al., 1993; Berg, 1992; Deitch et al., 1986; Deitch & Berg, 1987a; Dijkstra et al., 1996; Jones et al., 1991; Tokyay et al., 1991). However, this process is prolonged if the burn injury is superimposed with additional stress factors, such as burn wound sepsis (Baron et al., 1994; Jones et al., 1990b; Manson et al., 1992), viral infection (Erickson et al., 1990), smoke inhalation (Herndon & Zeigler, 1993; Morris et al., 1990), manipulation of intestinal flora (Berg, 1999; Deitch & Berg, 1987a; Dijkstra et al., 1996; Fukushima et al., 1995; Jones et al., 1990a), and fluid resuscitation and endotoxin challenge (Deitch & Berg, 1987b; Horton, 1994; Jones et al., 1991; Maejima et al., 1984a; Tokyay et al., 1991). Similarly, alcohol intoxication independent of burn injury is also associated with an increase in bacterial translocation (Alnadjim et al., 2002; Bode & Bode, 2003; Keshavarzian et al., 1999; Souza et al., 2003; Tabata et al., 2002). In a few studies, bacterial translocation has been evaluated in the combined insult of alcohol intoxication and burn injury. In one such attempt by Napolitano et al. (1995), rats were given alcohol by gavage for 14 days and subsequently given a 30% total body surface area burn injury. Bacterial translocation was determined 4 days after burn injury. Results from this study show that rats receiving a combined insult of alcohol intoxication and burn injury exhibit a significant increase in bacterial translocation compared with findings for rats receiving either insult alone. Consistent with these findings, results obtained in a study from our laboratory have shown that alcohol intoxication 4 h before burn injury significantly exacerbates bacterial translocation (Choudhry et al., 2002a). Together, these findings support the suggestion that alcohol intoxication before injury may have a synergistic effect on bacterial translocation. It is likely that in a combined insult of alcohol intoxication and burn injury, the translocated bacteria are not cleared. Instead, they multiply, disseminate to extraintestinal sites, and become the cause of systemic infections and sepsis in immunocompromised patients (Bahrami et al., 1996; Deitch, 2001; Hassoun et al., 2001; Napolitano et al., 1995; Peitzman et al., 1991; Swank & Deitch, 1996; Tabata et al., 2002; Woodman et al., 1996). In addition, their infiltration in organs, such as liver, lung, and spleen, may cause organ dysfunction in the injured host. To determine the role of gut-derived bacteria in an injured host, many investigators have used approaches to selectively decontaminate the gastrointestinal tract by oral administration of antibiotics in high-risk patients, such as bone marrow transplant recipients and granulocytopenic patients with hematologic malignancies, as well as in patients with, and in experimental models of, burn injury (Barber et al., 1993; Berg, 1999; Deitch et al., 1986; Jones et al., 1990a; Maejima

201

et al., 1984a, 1984b; Tokyay et al., 1991; Wells et al., 1988). Results from these studies, as reviewed by Swank and Deitch (1996), indicate that selective antibiotic decontamination of the gastrointestinal tract reduces the incidence of bacteremia and respiratory tract, urinary tract, and wound infections. However, a caveat in these studies is that the reduction in bacterial translocation did not influence the survival rate. The gut is also being recognized increasingly as the organ that initiates many of the inflammatory responses. Results from a number of studies have shown that the intestine in an injured host also serves as a source of bacterial products, endotoxin, and peptidoglycan (Bahrami et al., 1996; Bode & Bode, 2003; Bone, 1996; Deitch, 2001; Hassoun et al., 2001; Keshavarzian et al., 1999; Messingham et al., 2002; Souza et al., 2003; Swank & Deitch, 1996; Tabata et al., 2002; Yao et al., 1998). Both endotoxin and peptidolgycan are strong activators of many of the immune cell functions and thus participate in the aftermath of burn injury and trauma. In addition, mesenteric lymph from injured rats is shown to cause neutrophil activation, endothelial cell permeability, and expression of adhesion molecules on endothelial cells (Bahrami et al., 1996; Bone, 1996; Deitch, 2001; Hassoun et al., 2001; Keshavarzian et al., 1999; Swank & Deitch, 1996; Tabata et al., 2002; Zallen et al., 1999). These findings collectively support the concept that the intestine, besides serving as a source of infection, may serve as the motor of immune perturbation and subsequent development of multiple organ dysfunction/failure in an injured host.

3. Mechanisms of intestinal bacterial translocation Multiple pathways exist through which intestinal bacteria can reach systemic organs. In this article, however, we focus on three potential mechanisms: (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. 3.1. Bacterial growth in the intestine There is evidence that burn injury and trauma result in increased bacterial growth in the intestine (Berg et al., 1988; MacDonald & Pettersson, 2000). Furthermore, preliminary findings from studies in our laboratory have shown that alcohol intoxication before burn injury enhances bacterial growth in the intestine and that such increase in bacterial counts in the intestine is in direct proportion to the number of bacteria present in MLNs (Kavanaugh et al., in press). The mechanism (or mechanisms) by which alcohol intoxication before burn injury enhances bacterial growth in the intestine remains to be established. In a review article, Swank and Deitch (1996) presented experimental evidence supporting the suggestion of a relation between the number of anaerobic and the number of gram-negative bacteria in the intestine and that any change

202

M.A. Choudhry et al. / Alcohol 33 (2004) 199–208

in this relation may result in bacterial translocation. The number of anaerobic versus gram-negative bacteria, with the former estimated to be 100- to 1,000-fold higher than the latter, seems to be closely associated with the intestinal epithelial lining. Thus, this large number of anaerobic bacteria prevents enterocyte attachment to potentially pathogenic gram-negative enteric bacilli. However, by changing the normal intestinal flora with administration of broad-spectrum antibiotics, to which the anaerobes are more sensitive, this protective mechanism is lost (Fry & Schermer, 2000). This increases the possibility of both the attachment of potential gram-negative pathogens to intestinal epithelial lining and their subsequent translocation to extraintestinal sites. Thus, any change in the bacterial population of the intestine, as observed in alcohol intoxication and burn injury, may potentially result in bacterial translocation. Another potential mechanism is likely the modulation of hormonal control in alcohol intoxication and burn injury. There are reports, in which a role of neuroendocrine hormones in the pathogenesis of many infectious diseases and, in particular, with enteric infections is suggested (Lyte, 2004). These reports support the suggestion that neurochemicals can influence directly the growth and virulence of bacteria. For example, in one study catecholamines were shown to promote growth of Escherichia coli (Freestone et al., 2002). Lyte et al. (2004) has presented evidence in support that the intestine contains more than 100 million neurons that form a complex network of enteric nervous system extending throughout the intestine. There is no doubt that hormonal changes after alcohol intoxication and burn injury do occur, and that these changes do participate in shaping immune responses. However, whether these hormonal changes affect bacterial growth or virulence remains unknown. Another possibility is that alcohol intoxication before burn injury impairs the normal intestinal peristalsis by promoting stasis. This increases both the likelihood of bacterial growth and the proximity of bacteria to the intestinal wall. It has been demonstrated that impaired peristalsis, as occurs with small bowel obstruction, is associated with bacterial translocation in both human beings and animals (Madl & Druml, 2003). 3.2. Permeability of the intestine Increased permeability of the intestine is a common finding in patients and experimental animals with trauma, burn injury, hemorrhagic shock, and sepsis (Fig. 1) (Bahrami et al., 1996; Bone, 1996; Deitch, 2001; Hassoun et al., 2001; Swank & Deitch, 1996; Zallen et al., 1999). A similar increase in permeability of the intestine has also been observed after alcohol intoxication (Alnadjim et al., 2002; Bode & Bode, 2003; Keshavarzian et al., 1999; Tabata et al., 2002; Zallen et al., 1999). Findings from studies in our laboratory have shown a further increase in permeability of the intestine after a combined insult of alcohol intoxication and burn injury. We observed that transfer of lactulose and mannitol

from the intestine into circulation was several-fold higher in rats that received a combined insult of alcohol intoxication and burn injury compared with findings for rats that received either burn injury or sham injury alone (Choudhry et al., 2002a). Furthermore, lactulose and mannitol transfer occurred in rats that received a combined insult of alcohol intoxication and burn injury as early as 30 min after infusion. However, for the group that received burn injury alone, the transfer was evident only at the end of the experimental procedure (90 min). This observation supports the notion that damage in rats that receive a combined insult of alcohol intoxication and burn injury is more severe compared with findings for rats that receive burn injury in the absence of alcohol intoxication (Kavanaugh et al., in press). In studies from our laboratory, demonstrable morphologic changes of the intestine after alcohol intoxication and burn injury have not been observed (Choudhry et al., 2002a). However, the findings reported by Napolitano et al. (1995) have shown intestinal damage in rats receiving combined alcohol intoxication and burn injury. The differences in these findings could be due to the fact that rats in the studies from our laboratory received a single dose of alcohol 4 h before burn injury, whereas rats in the studies reported by Napolitano et al. (1995) received alcohol by gavage daily for 14 days before burn injury. A multitude of factors, ranging from submucosal leukocytes to the production of cytokines, such as IL-6 and IL-10, and the chemokines IL-8 and cytokine-induced neutrophil chemoattractant, have been proposed to contribute to the loss of mucosal integrity in burn injury, hemorrhagic shock, and sepsis (Bahrami et al., 1996; Bone, 1996; Choudhry et al., 2002a; Deitch, 2001; Hassoun et al., 2001; Swank & Deitch, 1996; Wang et al., 1998; Zallen et al., 1999). Although findings of some of these studies have shown that these cytokines/mediators can cause tissue damage directly, others have indicated that cells such as neutrophils recruited by these mediators are responsible for the observed increase in intestinal permeability (Fig. 1) (Sir et al., 2000). Findings from a number of studies have shown that insults, such as alcohol intoxication or burn injury, result in neutrophil activation and release of free oxygen radicals (O2⫺) (Messingham et al., 2002; Sayeed, 2000). Although an intracellular O2⫺ release in neutrophils leads to oxidant-mediated pathogen killing and thus to an efficient host defense, excessive O2⫺ release in the environment in close proximity outside neutrophils can cause tissue damage. Neutrophil-mediated oxidant injury is demonstrated in pathologic conditions of acute and chronic alcohol intoxication, rheumatoid arthritis, acute respiratory distress syndrome, and tissue ischemia. It is interesting to note that in many of the injury situations, the chemotactic factors for neutrophil recruitment to tissues/ organs, including the intestine, originate from the cells at sites of inflammation and thus inflamed tissues/organs become the source for such chemotactic response. Findings from our laboratory have shown a role for IL18 in increased neutrophil recruitment to the intestine in rats

M.A. Choudhry et al. / Alcohol 33 (2004) 199–208

that received a combined insult of alcohol intoxication and burn injury (unpublished observations, M. A. Choudhry, R. L. Gamelli, I. H. Chaudry, and M. M. Sayeed, 2003). These preliminary findings support the suggestion that a combined insult of alcohol intoxication and burn injury upregulates IL-18 production in both lymphoid organs and tissue in the intestine. Interleukin-18, like IL-12, was discovered initially to be a factor that drives the T cell toward T helper cell subtype 1 cytokine production and thereby enhances interferon-gamma production (Gracie et al., 2003). However, study findings have indicated that IL-18 also has a role in pathogenesis of many disease conditions (Faggioni et al., 2001; Jordan et al., 2001; Kashiwamura et al., 2002; Netea et al., 2000; Sivakumar et al., 2002). Interleukin-18 can cause tissue damage in an animal model of arthritis and has been found to be the central mediator in intestinal damage in an animal model of colitis (Kashiwamura et al., 2002; Sivakumar et al., 2002). Although a definitive mechanism for IL-18–induced tissue or intestinal damage remains unclear, Netea et al. (2000) have shown that neutralization of IL-18 during lethal endotoxemia reduces neutrophil accumulation in tissues and protects mice from endotoxemia. Consistent with these observations, findings from studies performed in our laboratory support the suggestion that IL18 up-regulation in intestine after alcohol intoxication and burn injury is accompanied by an increase in intestinal myeloperoxidase content (an index for neutrophil accumulation). Furthermore, treatment of rats with a combined insult of alcohol intoxication and burn injury with inhibitor of IL-18 at the time of injury prevents the increase in myeloperoxidase content (unpublished observations, S. Rana, I. H. Chaudry, and M. A. Choudhry, 2004). These findings support the hypothesis that IL-18 up-regulation may help in neutrophil recruitment to intestinal tissue. However, whether neutrophil recruitment is a direct effect of IL-18 or is due to an up-regulation of neutrophil chemotactic factors such as cytokine-induced neutrophil chemoattractant remains to be established. Regardless of the mechanism, once neutrophils are recruited they can either potentiate a microvascular blockade, leading to tissue hypoperfusion, or penetrate through extracellular spaces into the submucosal region to cause tissue damage, leading to the increase in permeability of the intestine (Fig. 1). 3.3. Suppression of immune defense in the intestine The intestinal immune system, often referred to as gutassociated lymphoid tissue, comprises the Peyer’s patches, MLNs, and a large number of cells distributed throughout the lamina propria and epithelium of the intestine (Heel et al., 1997; Kelsall et al., 2002; MacDonald & Pettersson, 2000; Mowat & Viney, 1997; Neutra et al., 1996). Peyer’s patches are small opaque pouches scattered throughout the small intestine. They contain T and B cells, dendritic cells, and macrophages. In addition, Peyer’s patches have specialized epithelial cells called M cells. M cells are considered

203

the gateway for entry of enteric bacteria and other luminal antigens (Heel et al., 1997; Neutra et al., 1996). Although M cells are highly selective and do not allow entry of all microbes, their unique glycosylation and adhesion-molecule patterns can be used by many microbes (Heel et al., 1997; Mowat & Viney, 1997; Neutra et al., 1996; Sansonetti, 2002). For example, Salmonella typhimurium can trigger massive cytoskeletal rearrangement of M cells, promoting its engulfment (Neutra et al., 1996; Sansonetti, 2002). The role for M cells in the subsequent process of bacterial translocation and in the development of immune response is not clearly defined as they probably do not express class II major histocompatibility complex antigens and thus cannot present antigen. However, pathogens that cross the gut epithelial barrier through M cells directly encounter macrophage and dendritic cells, which are present in intraepithelial pockets under M cells (Heel et al., 1997; Kelsall et al., 2002; MacDonald & Pettersson, 2000; Mowat & Viney, 1997; Neutra et al., 1996; Rescigno et al., 2001; Sansonetti, 2002). Thus a role for both dendritic cells and macrophages in bacterial transport from gut to MLNs and from MLNs to the systemic circulation is speculated. The next major interface for absorption of soluble antigens from the lumen of the gastrointestinal tract is the columnar epithelial cell layer, which contains a large number of T cells commonly called intraepithelial lymphocytes (MacDonald & Pettersson, 2000; Mowat & Viney, 1997). Most intraepithelial lymphocytes are T cells, with an approximately equal frequency of CD3⫹ cells expressing γδ or αβ T cell receptor heterodimeric chains. Both γδ or αβ T cells are helpful in the defense against the initial phase of bacterial translocation during the passage of bacteria from the intestinal lumen across the mucosal epithelium to lamina propria. The third population of intestinal T cells is lamina propria T cells. Most lamina propria T cells are CD4⫹ cells that express αβ T cell receptor. Only a few are positive for γδ. T cell receptor. The fourth and final lymphoid organ is the MLNs, a complex network of lymph nodes draining from various parts of the intestine. A few indigenous bacteria continuously translocate to MLNs, but because of intact Peyer’s patches and immune cell functions of the MLNs, these bacteria do not survive. The MLNs obtained from healthy animals remain relatively sterile. Any alteration in immune cell functions will potentially impair immune defense both locally and globally. This results in bacterial multiplication/accumulation in MLNs as well as bacterial spread to other organs, such as spleen and circulation. The effects of alcohol intoxication before burn injury on immune cell functions have been examined. Results obtained from these studies have shown that acute alcohol exposure (30 min to 4 h) before burn injury impaired delayed type hypersensitivity, produced a greater suppression (than that observed with burn injury without alcohol exposure before injury) of mitogen-induced splenic-lymphocyte proliferation, and decreased serum immunoglobulin levels (Choudhry et al., 2000; Faunce et al., 1997, 1998; Kawakami et al.,

204

M.A. Choudhry et al. / Alcohol 33 (2004) 199–208

1991; Messingham et al., 2002). There were no demonstrable changes in leukocyte number, nor in apoptosis. However, compared with mice subjected to either alcohol exposure or burn injury alone, mice that received a combined insult of alcohol exposure and burn injury were more susceptible to infectious challenge (Faunce et al., 1997, 1998; Messingham et al., 2002). To determine organ-specific effects, studies in our laboratory were designed to examine whether alcohol intoxication before burn injury modulates immune defense of the intestine. Findings of these studies (Choudhry et al., 2002a) have shown that rats receiving alcohol by gavage 4 h before burn injury exhibited a significant suppression in intestinal T cell proliferation and IL-2 production. The results support the suggestion that, although there was a decrease in proliferation of T cells in intestinal lymphoid organs (i.e., in Peyer’s patches and MLNs) after burn injury alone, the suppression was greater in the group of animals that received a combined insult of alcohol exposure and burn injury. The suppression of T cell proliferation was accompanied by a significant decrease in interferon-gamma production. Furthermore, the experimental findings of studies from our laboratory have shown that depletion of T cells in healthy rats resulted in increased bacterial accumulation in MLNs. A similar depletion of T cells in rats that received a combined insult of alcohol intoxication and burn injury further enhanced bacterial accumulation in MLNs and in other distant organs, including spleen and blood. These results support findings of earlier studies by Sibley and Jerrells (2000), in which they have shown that the loss of lymphoid cells after chronic alcohol abuse diminishes host resistance to enteric pathogens. Owens and Berg (1980) noted spontaneous gut bacterial translocation to MLNs, spleen, and liver in athymic (nu/nu) mice, whereas no translocation was noticed in heterozygous (nu/⫹) or nude (⫹/⫹) mice grafted with thymus. Furthermore, findings from multiple studies have shown that depletion of CD4⫹ and CD8⫹ T cells resulted in increased bacterial translocation (Berg, 1999; Choudhry et al., 2002a). Others have shown that adoptive transfer of T cells provides protection against a number of bacterial infections, including E. coli, S. typhimurium, or Bordetella pertussis (Berg, 1999; Kerksiek & Pamer, 1999; MacDonald & Pettersson, 2000; Messingham et al., 2002). Together, these findings support the suggestion that T cell–mediated immunity is critical in the defense against enteric bacteria.

3.3.1. Intracellular signaling and immune cell dysfunction Although the role of intracellular signaling molecules in modulation of immune cell functions after alcohol intoxication alone has been examined separately from that after burn injury alone (Choudhry et al., 1998, 1999a, 1999b, 2001a, 2002b), there are only a few published studies in which an attempt was made to delineate the role of intracellular

signaling molecules with a combined insult of alcohol intoxication and burn injury. As shown in Fig. 2, activation of the T cell by means of the T cell receptor precedes a cascade of intracellular signaling events. T cell receptor, which serves as the primary signal for T cell activation, is a multisubunit complex composed of at least two signal-transducing modules: CD3 and zeta chain subunits (Chan et al., 1994). Both CD3 and zeta chain have within their cytoplasmic domains a common region of peptide sequences termed antigen recognition activation motifs. The antigen recognition activation motifs are responsible for transducing signaling events. The stimulation of T cell receptor by means of anti-CD3 or with an antigen results in P56lck and P59fyn activation (Berridge, 1997; Chan et al., 1994; Ivashkiv, 2000; Sayeed, 2000). These proteins subsequently phosphorylate Zap-70, which, in turn, phosphorylates phospholipase C-gamma to hydrolyze phosphatidylinositol 4,5-bisphosphate into inositol 1,4,5-trisphosphate and 1,2-diacylglycerol. Inositol 1,4,5trisphosphate releases Ca2⫹ from intracellular stores and from extracellular source; 1,2-diacylglycerol activates protein kinase C. The increase in intracellular Ca2⫹ concentrations is a prerequisite for T cell activation (Berridge, 1997; Sayeed, 2000). Protein kinase C with or without calcium signal initiates the subsequent events of the cascade, as depicted in Fig. 2. These include activation of mitogenactivated protein kinases and other nuclear events, which subsequently lead to T cell activation. The activated T cells divide and produce IL-2, which, on release, interacts with IL-2 receptor on T cells and sends a second wave of signaling cascade, resulting in T cell proliferation (Berridge, 1997; Ivashkiv, 2000). However, this whole cascade of signaling events is kept in check by counterregulatory molecules, referred to as protein tyrosine phosphatases, at each step of protein phosphorylation (Dong et al., 2002; Keyse, 2000; Neel, 1997). These counterregulatory molecules are present within the cells and are simultaneously activated intracellularly or extracellularly by means of receptors present on the T cell surface such as CD45 (Fig. 2). Although, a definitive mechanism of how CD45 regulates the T cell activation remains unknown, research findings from multiple studies have shown that CD45 activates members of protein tyrosine phosphatases (SHP-1 and SHP-2) (Chan et al., 1994; Neel, 1997). SHP-1 and SHP-2 are known to negatively regulate P56lck and P59fyn activation (Choudhry et al., 2001b; Plas et al., 1996; Somani et al., 1997). Similarly, a family of mitogen-activated protein kinase phosphatases has been shown to counterregulate the activation of mitogen-activated protein kinases (Dong et al., 2002; Keyse, 2000). Studies have been conducted to determine the role of signaling molecules in altered T cell functions after burn injury, trauma, and sepsis (Choudhry et al., 1998, 1999a, 1999b; Faist et al., 1996; Hoyt et al., 1994; Sayeed, 2000). Findings from some of these studies support the role of src-family kinases, P56lck and P59fyn, in decreased T cell proliferation (Choudhry et al., 1998, 1999a, 1999b; Sayeed, 2000). Other findings support the suggestion that alterations

M.A. Choudhry et al. / Alcohol 33 (2004) 199–208

205

Fig. 2. Intracellular cascade of signaling molecules involved in T cell activation and proliferation. As discussed in the text, a combined insult of alcohol intoxication and burn injury potentially disturbs the balance between protein tyrosine phosphatases (SHP-1/2) and protein tyrosine kinases (P59fyn and P56lck). This eventually impairs subsequent signaling events, leading to deranged T cell functions as observed after alcohol intoxication and burn injury. DAG ⫽ 1,2-diacylglycerol; IL-2 ⫽ interleukin 2; IL-2R ⫽ interleukin-2 receptor; IP3 ⫽ inositol 1,4,5-trisphosphate; JAK-STAT ⫽ Janus kinase (JAK)-signal transducer and activator of transcription (STAT); Lck/Fyn/Zap-70 ⫽ member of protein tyrosine kinases (PTK); MAPK ⫽ mitogen-activated protein kinase; PI3-K ⫽ phosphatidylinositol 3-kinase; PIP2 ⫽ phosphatidylinositol 4,5-bisphosphate; PKC ⫽ protein kinase C; PLC-γ ⫽ phospholipase C-gamma; SHP ⫽ member of protein tyrosine phosphatases; TCR ⫽ T cell receptor.

in protein kinase C and Ca2⫹ signaling play the primary role in T cell dysfunction after burn injury and trauma (Faist et al., 1996; Sayeed, 2000). Additional results obtained from these studies further indicate that alterations in the signaling component could result from a shift in the cytokine milieu in the vicinity of T cells, such as elevated levels of IL-10, transforming growth factor-beta, and prostaglandin E2 (Choudhry et al., 1998, 1999a, 1999b, 2000, 2002b; Faist et al., 1996; Hoyt et al., 1994). Results of previous studies from our laboratory showed that prostaglandin E2–mediated inhibition of P59fyn kinase activity could be a component that impaired downstream signaling, including the increase in intracellular calcium concentration and transcriptional regulation of IL-2 (Choudhry et al., 1999a, 1999b, 2002b). Findings of studies from our laboratory have shown a suppression of P59fyn kinase activity and the phosphorylation of subsequent signaling molecules p38 and extracellular signalregulated kinase (ERK)1/2 in isolated MLN T cells derived from rats receiving either burn injury or combined alcohol intoxication and burn injury compared with observations for T cells obtained from sham-injured rats (Choudhry et al., 2004). Furthermore, preliminary results from these studies also support the suggestion of an up-regulation of SHP-1, a member of the protein tyrosine phosphatases known to negatively regulate P59fyn protein (unpublished observation, M. A. Choudhry, 2004). Because a balance between protein tyrosine phosphatases and protein tyrosine kinases (see

Fig. 2) is critical for T cell activation, it is likely that alcohol intoxication and burn injury disturb this balance between the two, thereby causing functional disturbances in the T cell. Whether the diminished p38 and ERK1/2 phosphorylation in T cells in the MLNs obtained from rats receiving a combined insult of alcohol intoxication and burn injury is due to a direct effect of alcohol and burn injury or is mediated by means of alteration in P59fyn, a molecule upstream to p38 and ERK1/2, remains to be established. Because P59fyn activation precedes p38 and ERK1/2 activation (Berridge, 1997; Chan et al., 1994; Ivashkiv, 2000; Sayeed, 2000), it is likely that alterations in P59fyn may potentially contribute to suppression in the subsequent signaling molecules, including protein kinase C–Ca2⫹ signaling or mitogen-activated protein kinase (p38 and ERK1/2) activation in T cells after alcohol intoxication and burn injury. Nonetheless, a more direct effect of alcohol intoxication and burn injury on p38 and ERK1/2 is not ruled out. The findings from these preliminary studies collectively support the suggestion that T cell suppression after alcohol intoxication and burn injury could result from alterations at multiple steps of T cell activation. However, additional studies will delineate such roles of signaling molecules in the regulation of the T cell and thereby the immune responses in an injured host. Results of these studies at the cellular level will provide a better understanding of the mechanisms leading to impaired intestinal immune and barrier functions.

206

M.A. Choudhry et al. / Alcohol 33 (2004) 199–208

4. Conclusion In conclusion, the pathogenesis after burn injury and trauma is a complex process and is influenced by many factors. The addition of alcohol increases this complexity. Efforts have helped identify some of the mechanisms, such as the difference in immune responses and ability to handle bacterial load observed for burn-injured patients who sustained injury in the presence of alcohol compared with patients who were injured in its absence. Furthermore, experimental data from our laboratory support the suggestion that the intestine can be a potential source of infections in an injured host. These findings support the suggestion that alcohol intoxication before burn injury suppresses intestinal immune defense, impairs gut barrier functions, and increases bacterial growth. Finally, preliminary findings from our laboratory have shown that impaired immune cell functions in the intestine could result from alterations in intracellular signaling processes. Although these alterations in intestinal barrier and immune responses are likely to cause bacterial translocation in alcohol intoxication and burn injury, mechanisms underlying impaired barrier function in the intestine are complex and are not fully elucidated. Therefore, more studies are needed to delineate these mechanisms. The delineation of cell-signaling derangements in injury conditions such as those described in this article would help in designing more specific therapeutic interventions against the disturbed cellular responses and thus in the treatment of patients who have suffered injury, such as burn or trauma, and sustained such injury in a state of alcohol intoxication.

Acknowledgments This study was supported by National Institute on Alcohol Abuse and Alcoholism grant AA12901 to M.A.C. We acknowledge the help from Mary Sue Pruett in organizing the References section.

References Alnadjim, Z., Kayali, Z., Haddad, W., Holmes, E. W., Keshavarzian, A., Mittal, N., Ivancic, D., Koehler, R., Goldsmith, D., Waltenbaugh, C., & Barrett, T. A. (2002). Differential effects of T-cell activation on gastric and small bowel permeability in alcohol-consuming mice. Alcohol Clin Exp Res 26, 1436–1443. American Burn Association. (August 7, 2000). Burn incidence and treatment in the US: 2000 fact sheet. Available at http://www.ameriburn.org/pub/ BurnIncidenceFactSheet.htm. Accessed May 10, 2004. Bahrami, S., Redl, H., Yao, Y. M., & Schlag, G. (1996). Involvement of bacteria/endotoxin translocation in the development of multiple organ failure. Curr Top Microbiol Immunol 216, 239–258. Barber, A., Illner, H., & Shires, G. T. (1993). Bacterial translocation in burn injury. Semin Nephrol 13, 416–419. Baron, P., Traber, L. D., Traber, D. L., Nguyen, T., Hollyoak, M., Heggers, J. P., & Herndon, D. N. (1994). Gut failure and translocation following burn and sepsis. J Surg Res 57, 197–204. Baue, A. E., Durham, R., & Faist, E. (1998). Systemic inflammatory response syndrome (SIRS), multiple organ dysfunction syndrome

(MODS), multiple organ failure (MOF): are we winning the battle? Shock 10, 79–89. Berg, R. D. (1992). Bacterial translocation from the gastrointestinal tract. J Med 23, 217–244. Berg, R. D. (1999). Bacterial translocation from the gastrointestinal tract. Adv Exp Med Biol 473, 11–30. Berg, R. D., Wommack, E., & Deitch, E. A. (1988). Immunosuppression and intestinal bacterial overgrowth synergistically promote bacterial translocation. Arch Surg 123, 1359–1364. Berridge, M. J. (1997). Lymphocyte activation in health and disease. Crit Rev Immunol 17, 155–178. Bode, C., & Bode, J. C. (2003). Effect of alcohol consumption on the gut. Best Pract Res Clin Gastroenterol 17, 575–592. Bone, R. C. (1996). Sir Isaac Newton, sepsis, SIRS, and CARS. Crit Care Med 24, 1125–1128. Chan, A. C., Desai, D. M., & Weiss, A. (1994). The role of protein tyrosine kinases and protein tyrosine phosphatases in T cell antigen receptor signal transduction. Annu Rev Immunol 12, 555–592. Choudhry, M. A., Ahmed, Z., & Sayeed, M. M. (1999a). PGE2-mediated inhibition of T cell p59fyn is independent of cAMP. Am J Physiol 277, C302–C309. Choudhry, M. A., Fazal, N., Goto, M., Gamelli, R. L., & Sayeed, M. M. (2002a). Gut-associated lymphoid T cell suppression enhances bacterial translocation in alcohol and burn injury. Am J Physiol Gastrointest Liver Physiol 282, G937–G947. Choudhry, M. A., Fazal, N., Namak, S. Y., Haque, F., Ravindranath, T., & Sayeed, M. M. (2001a). PGE2 suppresses intestinal T cell function in thermal injury: a cause of enhanced bacterial translocation. Shock 16, 183–188. Choudhry, M. A., Hockberger, P. E., & Sayeed, M. M. (1999b). PGE2 suppresses mitogen-induced Ca2⫹ mobilization in T cells. Am J Physiol 277(6 Pt 2), R1741–R1748. Choudhry, M. A., Mao, H., Haque, F., Khan, M., Fazal, N., & Sayeed, M. M. (2002b). Role of NFAT and AP-1 in PGE2-mediated T cell suppression in burn injury. Shock 18, 212–216. Choudhry, M. A., Messingham, K. A. N., Namak, S., Colantoni, A., Fontanilla, C. V., Duffner, L. A., Sayeed, M. M., & Kovacs, E. J. (2000). Ethanol exacerbates T cell dysfunction after thermal injury. Alcohol 21, 239–243. Choudhry, M. A., Ren, X., Romero, A., Kovacs, E. J., Gamelli, R. L., & Sayeed, M. M. (2004). Combined alcohol and burn injury differentially regulate P-38 and ERK activation in mesenteric lymph node T cell. J Surg Res 121, 62–68. Choudhry, M. A., Sir, O., & Sayeed, M. M. (2001b). TGF-β abrogates TCR-mediated signaling by upregulating tyrosine phosphatases in T cells. Shock 15, 193–199. Choudhry, M. A., Uddin, S., & Sayeed, M. M. (1998). Prostaglandin E2 modulation of p59fyn tyrosine kinase in T lymphocytes during sepsis. J Immunol 160, 929–935. Cook, R. T. (1998). Alcohol abuse, alcoholism, and damage to the immune system—a review. Alcohol Clin Exp Res 22, 1927–1942. Deitch, E. A. (2001). Role of the gut lymphatic system in multiple organ failure. Curr Opin Crit Care 7, 92–98. Deitch, E. A., & Berg, R. (1987a). Bacterial translocation from the gut: a mechanism of infection. J Burn Care Rehabil 8, 475–482. Deitch, E. A., & Berg, R. D. (1987b). Endotoxin but not malnutrition promotes bacterial translocation of the gut flora in burned mice. J Trauma 27, 161–166. Deitch, E. A., Winterton, J., & Berg, R. (1986). Thermal injury promotes bacterial translocation from the gastrointestinal tract in mice with impaired T-cell-mediated immunity. Arch Surg 121, 97–101. Diehl, A. M. (2000). Cytokine regulation of liver injury and repair. Immunol Rev 174, 160–171. Dijkstra, H. M., Manson, W. L., Blaauw, B., Klasen, H. J., & de Smet, B. (1996). Bacterial translocation in d-galactosamine-treated rats in a burn model. Burns 22, 15–21.

M.A. Choudhry et al. / Alcohol 33 (2004) 199–208 Dong, C., Davis, R. J., & Flavell, R. A. (2002). MAP kinases in the immune response. Annu Rev Immunol 20, 55–72. Erickson, E. J., Saffle, J. R., Morris, S. E., Sullivan, J. J., Eichwald, E. J., & Shelby, J. (1990). Cytomegalovirus infection promotes bacterial translocation in thermally injured mice. J Burn Care Rehabil 11, 428–435. Faggioni, R., Cattley, R. C., Guo, J., Flores, S., Brown, H., Qi, M., Yin, S., Hill, D., Scully, S., Chen, C., Brankow, D., Lewis, J., Baikalov, C., Yamane, H., Meng, T., Martin, F., Hu, S., Boone, T., & Senaldi, G. (2001). IL-18-binding protein protects against lipopolysaccharide- induced lethality and prevents the development of Fas/Fas ligand–mediated models of liver disease in mice. J Immunol 167, 5913–5920. Faist, E., Schinkel, C., & Zimmer, S. (1996). Update on the mechanisms of immune suppression of injury and immune modulation. World J Surg 20, 454–459. Faunce, D. E., Gregory, M. S., & Kovacs, E. J. (1997). Effects of acute ethanol exposure on cellular immune responses in a murine model of thermal injury. J Leukoc Biol 62, 733–740. Faunce, D. E., Gregory, M. S., & Kovacs, E. J. (1998). Acute ethanol exposure prior to thermal injury results in decreased T-cell responses mediated in part by increased production of IL-6. Shock 10, 135–140. Fazal, N., Shamim, M., Zagorski, J., Choudhry, M. A., Ravindranath, T., & Sayeed, M. M. (2000). CINC blockade prevents neutrophil Ca2⫹ signaling upregulation and gut bacterial translocation in thermal injury. Biochim Biophys Acta 1535, 50–59. Fitzwater, J., Purdue, G. F., Hunt, J. L., & O’Keefe, G. E. (2003). The risk factors and time course of sepsis and organ dysfunction after burn trauma. J Trauma 54, 959–966. Freestone, P. P., Williams, P. H., Haigh, R. D., Maggs, A. F., Neal, C. P., & Lyte, M. (2002). Growth stimulation of intestinal commensal Escherichia coli by catecholamines: a possible contributory factor in trauma-induced sepsis. Shock 18, 465–470. Fry, D. E., & Schermer, C. R. (2000). The consequences of suppression of anaerobic bacteria. Surg Infect 1, 49–56. Fukushima, R., Alexander, J. W., Gianotti, L., Pyles, T., & Ogle, C. K. (1995). Bacterial translocation-related mortality may be associated with neutrophil-mediated organ damage. Shock 3, 323–328. Gentilello, L. M., Cobean, R. A., Walker, A. P., Moore, E. E., Wertz, M. J., & Dellinger, E. P. (1993). Acute ethanol intoxication increases the risk of infection following penetrating abdominal trauma. J Trauma 34, 669–674. Gianotti, L., Alexander, J. W., Fukushima, R., & Pyles, T. (1996). Steroid therapy can modulate gut barrier function, host defense, and survival in thermally injured mice. J Surg Res 62, 53–58. Gianotti, L., Alexander, J. W., Pyles, T., James, L., & Babcock, G. F. (1993). Relationship between extent of burn injury and magnitude of microbial translocation from the intestine. J Burn Care Rehabil 14, 336–342. Goral, J., Choudhry, M. A., & Kovacs, E. J. (2004). Acute ethanol exposure inhibits macrophage IL-6 production: role of p38 and ERK1/2 MAPK. J Leukoc Biol 75, 553–559. Gracie, J. A., Robertson, S. E., & McInnes, I. B. (2003). Interleukin18. J Leukoc Biol 73, 213–224. Hassoun, H. T., Kone, B. C., Mercer, D. W., Moody, F. G., Weisbrodt, N. W., & Moore, F. A. (2001). Post-injury multiple organ failure: the role of the gut. Shock 15, 1–10. Heel, K. A., McCauley, R. D., Papadimitriou, J. M., & Hall, J. C. (1997). Review: Peyer’s patches. J Gastroenterol Hepatol 12, 122–136. Herndon, D. N., & Zeigler, S. T. (1993). Bacterial translocation after thermal injury. Crit Care Med 21(2 Suppl), S50–S54. Horton, J. W. (1994). Bacterial translocation after burn injury: the contribution of ischemia and permeability changes. Shock 1, 286–290. Hoyt, D. B., Junger, W. G., Loomis, W. H., & Liu, F. C. (1994). Effects of trauma on immune cell function: impairment of intracellular calcium signaling. Shock 2, 23–28. Ivashkiv, L. B. (2000). Jak-STAT signaling pathways in cells of the immune system. Rev Immunogenet 2, 220–230.

207

Jayasinghe, R., Gianutsos, G., & Hubbard, A. K. (1992). Ethanol-induced suppression of cell-mediated immunity in the mouse. Alcohol Clin Exp Res 16, 331–335. Jerrells, T. R., Saad, A. J., & Domiati-Saad, R. (1992). Effects of ethanol on parameters of cellular immunity and host defense mechanisms to infectious agents. Alcohol 9, 459–463. Jerrells, T. R., Sibley, D. A., Slukvin, I. I., & Mitchell, K. A. (1998). Effects of ethanol consumption on mucosal and systemic T-cell-dependent immune responses to pathogenic microorganisms. Alcohol Clin Exp Res 22(5 Suppl), 212S–215S. Jones, W. G. II, Barber, A. E., Minei, J. P., Fahey, T. J., Shires, G. T. III, & Shires, G. T. (1990a). Antibiotic prophylaxis diminishes bacterial translocation but not mortality in experimental burn wound sepsis. J Trauma 30, 737–740. Jones, W. G. II, Barber, A. E., Minei, J. P., Fahey, T. J. III, Shires, G. T. III, & Shires, G. T. (1991). Differential pathophysiology of bacterial translocation after thermal injury and sepsis. Ann Surg 214, 24–30. Jones, W. G. II, Minei, J. P., Barber, A. E., Rayburn, J. L., Fahey, T. J. III, Shires, G. T. III, & Shires, G. T. (1990b). Bacterial translocation and intestinal atrophy after thermal injury and burn wound sepsis. Ann Surg 211, 399–405. Jordan, J. A., Guo, R.-F., Yun, E. C., Sarma, V., Warner, R. L., Crouch, L. D., Senaldi, G., Ulich, T. R., & Ward, P. A. (2001). Role of IL-18 in acute lung inflammation. J Immunol 167, 7060–7068. Kashiwamura, S., Ueda, H., & Okamura, H. (2002). Roles of interleukin18 in tissue destruction and compensatory reactions. J Immunother 25(Suppl 1), S4–S11. Kavanaugh, M. J., Clark, C., Goto, M., Kovacs, E. J., Gamelli, R. L., Sayeed, M. M., & Choudhry, M. A. (In press). Effect of acute alcohol ingestion prior to burn injury on intestinal bacterial growth and barrier functions. Burns. Kawakami, M., Switzer, B. R., Herzog, S. R., & Meyer, A. A. (1991). Immune suppression after acute ethanol ingestion and thermal injury. J Surg Res 51, 210–215. Kelly, J. L., O’Suilleabhain, C. B., Soberg, C. C., Mannick, J. A., & Lederer, J. A. (1999). Severe injury triggers antigen-specific T-helper cell dysfunction. Shock 12, 39–45. Kelsall, B. L., Biron, C. A., Sharma, O., & Kaye, P. M. (2002). Dendritic cells at the host-pathogen interface. Nat Immunol 3, 699–702. Kerksiek, K. M., & Pamer, E. G. (1999). T cell responses to bacterial infection. Curr Opin Immunol 11, 400–405. Keshavarzian, A., Holmes, E. W., Patel, M., Iber, F., Fields, J. Z., & Pethkar, S. (1999). Leaky gut in alcoholic cirrhosis: a possible mechanism for alcohol-induced liver damage. Am J Gastroenterol 94, 200–207. Keyse, S. M. (2000). Protein phosphatases and the regulation of mitogenactivated protein kinase signalling. Curr Opin Cell Biol 12, 186–192. Lyte, M. (2004). Microbial endocrinology and infectious disease in the 21st century. Trends Microbiol 12, 14–20. MacDonald, T. T., & Pettersson, S. (2000). Bacterial regulation of intestinal immune responses. Inflamm Bowel Dis 6, 116–122. Madl, C., & Druml, W. (2003). Gastrointestinal disorders of the critically ill. Systemic consequences of ileus. Best Pract Res Clin Gastroenterol 17, 445–456. Maejima, K., Deitch, E., & Berg, R. (1984a). Promotion by burn stress of the translocation of bacteria from the gastrointestinal tracts of mice. Arch Surg 119, 166–172. Maejima, K., Deitch, E. A., & Berg, R. D. (1984b). Bacterial translocation from the gastrointestinal tracts of rats receiving thermal injury. Infect Immun 43, 6–10. Maier, R. V. (2001). Ethanol abuse and the trauma patient. Surg Infect 2, 133–141. Manson, W. L., Coenen, J. M., Klasen, H. J., & Horwitz, E. H. (1992). Intestinal bacterial translocation in experimentally burned mice with wounds colonized by Pseudomonas aeruginosa. J Trauma 33, 654–658. McGill, V., Kowal-Vern, A., Fisher, S. G., Kahn, S., & Gamelli, R. L. (1995). The impact of substance use on mortality and morbidity from thermal injury. J Trauma 38, 931–934.

208

M.A. Choudhry et al. / Alcohol 33 (2004) 199–208

McGwin, G. Jr., Chapman, V., Rousculp, M., Robison, J., & Fine, P. (2000). The epidemiology of fire-related deaths in Alabama, 1992–1997. J Burn Care Rehabil 21(1 Pt 1), 75–83. Messingham, K. A. N., Faunce, D. E., & Kovacs, E. J. (2002). Alcohol, injury, and cellular immunity. Alcohol 28, 137–149. Mikszta, J. A., Waltenbaugh, C., & Kim, B. S. (1995). Impaired antigen presentation by splenocytes of ethanol-consuming C57BL/6 mice. Alcohol 12, 265–271. Miller-Graziano, C. L., De, A. K., & Kodys, K. (1995). Altered IL-10 levels in trauma patients’ Mφ and T lymphocytes. J Clin Immunol 15, 93–104. Moore, F. A. (1999). Posttraumatic complications and changes in blood lymphocyte populations after multiple trauma. Crit Care Med 27, 674–675. Morris, S. E., Navaratnam, N., & Herndon, D. N. (1990). A comparison of effects of thermal injury and smoke inhalation on bacterial translocation. J Trauma 30, 639–643; discussion 643–645. Moss, M., & Burnham, E. L. (2003). Chronic alcohol abuse, acute respiratory distress syndrome, and multiple organ dysfunction. Crit Care Med 31(4 Suppl), S207–S212. Mowat, A. M., & Viney, J. L. (1997). The anatomical basis of intestinal immunity. Immunol Rev 156, 145–166. Napolitano, L. M., Koruda, M. J., Zimmerman, K., McCowan, K., Chang, J., & Meyer, A. A. (1995). Chronic ethanol intake and burn injury: evidence for synergistic alteration in gut and immune integrity. J Trauma 38, 198–207. Neel, B. G. (1997). Role of phosphatases in lymphocyte activation. Curr Opin Immunol 9, 405–420. Netea, M. G., Fantuzzi, G., Kullberg, B. J., Stuyt, R. J. L., Pulido, E. J., McIntyre, R. C. Jr., Joosten, L. A. B., Van der Meer, J. W. M., & Dinarello, C. A. (2000). Neutralization of IL-18 reduces neutrophil tissue accumulation and protects mice against lethal Escherichia coli and Salmonella typhimurium endotoxemia. J Immunol 164, 2644–2649. Neutra, M. R., Frey, A., & Kraehenbuhl, J.-P. (1996). Epithelial M cells: gateways for mucosal infection and immunization. Cell 86, 345–348. O’Sullivan, S. T., & O’Connor, T. P. F. (1997). Immunosuppression following thermal injury: the pathogenesis of immunodysfunction. Br J Plast Surg 50, 615–623. Owens, W. E., & Berg, R. D. (1980). Bacterial translocation from the gastrointestinal tract of athymic (nu/nu) mice. Infect Immun 27, 461– 467. Peitzman, A. B., Udekwu, A. O., Ochoa, J., & Smith, S. (1991). Bacterial translocation in trauma patients. J Trauma 31, 1083–1086. Peterson, J. D., Herzenberg, L. A., Vasquez, K., & Waltenbaugh, C. (1998). Glutathione levels in antigen-presenting cells modulate Th1 versus Th2 response patterns. Proc Natl Acad Sci U S A 95, 3071–3076. Plas, D. R., Johnson, R., Pingel, J. T., Matthews, R. J., Dalton, M., Roy, G., Chan, A. C., & Thomas, M. L. (1996). Direct regulation of ZAP-70 by SHP-1 in T cell antigen receptor signaling. Science 272, 1173–1176. Rescigno, M., Urbano, M., Valzasina, B., Francolini, M., Rotta, G., Bonasio, R., Granucci, F., Kraehenbuhl, J.-P., & Ricciardi-Castagnoli, P. (2001). Dendritic cells express tight junction proteins and penetrate gut epithelial monolayers to sample bacteria. Nat Immunol 2, 361–367. Sansonetti, P. (2002). Host-pathogen interactions: the seduction of molecular cross talk. Gut 50(Suppl 3), III2–III8. Sayeed, M. M. (2000). Signaling mechanisms of altered cellular responses in trauma, burn, and sepsis: role of Ca2⫹. Arch Surg 135, 1432–1442. Schindel, D., Maze, R., Liu, Q., Williams, D., & Grosfeld, J. (1997). Interleukin-11 improves survival and reduces bacterial translocation

and bone marrow suppression in burned mice. J Pediatr Surg 32, 312–315. Schwacha, M. G., & Chaudry, I. H. (2002). The cellular basis of post-burn immunosuppression: macrophages and mediators. Int J Mol Med 10, 239–243. Sibley, D., & Jerrells, T. R. (2000). Alcohol consumption by C57BL/6 mice is associated with depletion of lymphoid cells from the gutassociated lymphoid tissues and altered resistance to oral infections with Salmonella typhimurium. J Infect Dis 182, 482–489. ¨ ., Fazal, N., Choudhry, M. A., Gamelli, R. L., & Sayeed, M. M. Sir, O (2000). Neutrophil depletion prevents intestinal mucosal permeability alterations in burn-injured rats. Am J Physiol Regul Integr Comp Physiol 278, R1224–R1231. Sivakumar, P. V., Westrich, G. M., Kanaly, S., Garka, K., Born, T. L., Derry, J. M., & Viney, J. L. (2002). Interleukin 18 is a primary mediator of the inflammation associated with dextran sulphate sodium induced colitis: blocking interleukin 18 attenuates intestinal damage. Gut 50, 812–820. Soderstrom, C. A., Dischinger, P. C., Kerns, T. J., Kufera, J. A., McDuff, D. R., Gorelick, D. A., & Smith, G. S. (1998). Screening trauma patients for alcoholism according to NIAAA guidelines with alcohol use disorders identification test questions. Alcohol Clin Exp Res 22, 1470–1475. Somani, A.-K., Bignon, J. S., Mills, G. B., Siminovitch, K. A., & Branch, D. R. (1997). Src kinase activity is regulated by the SHP-1 proteintyrosine phosphatase. J Biol Chem 272, 21113–21119. Souza, H. S., Elia, C. C., Braulio, V. B., Cortes, M. Q., Furtado, V. C., Garrofe, H. C., & Martinusso, C. A. (2003). Effects of ethanol on gutassociated lymphoid tissues in a model of bacterial translocation: a possible role of apoptosis. Alcohol 30, 183–191. Swank, G. M., & Deitch, E. A. (1996). Role of the gut in multiple organ failure: bacterial translocation and permeability changes. World J Surg 20, 411–417. Szabo, G. (1998). Monocytes, alcohol use, and altered immunity. Alcohol Clin Exp Res 22(5 Suppl), 216S–219S. Tabata, T., Tani, T., Endo, Y., & Hanasawa, K. (2002). Bacterial translocation and peptidoglycan translocation by acute ethanol administration. J Gastroenterol 37, 726–731. Tokyay, R., Zeigler, S. T., Heggers, J. P., Loick, H. M., Traber, D. L., & Herndon, D. N. (1991). Effects of anesthesia, surgery, fluid resuscitation, and endotoxin administration on postburn bacterial translocation. J Trauma 31, 1376–1379. Wang, W., Smail, N., Wang, P., & Chaudry, I. H. (1998). Increased gut permeability after hemorrhage is associated with upregulation of local and systemic IL-6. J Surg Res 79, 39–46. Wells, C. L., Maddaus, M. A., & Simmons, R. L. (1988). Proposed mechanisms for the translocation of intestinal bacteria. Rev Infect Dis 10, 958–979. Woodman, G. E., Fabian, T. C., Croce, M. A., & Proctor, K. G. (1996). Acute ethanol intoxication and endotoxemia after trauma. J Trauma 41, 61–72. Yao, Y.-M., Redl, H., Bahrami, S., & Schlag, G. (1998). The inflammatory basis of trauma/shock-associated multiple organ failure. Inflamm Res 47, 201–210. Zallen, G., Moore, E. E., Johnson, J. L., Tamura, D. Y., Ciesla, D. J., & Silliman, C. C. (1999). Posthemorrhagic shock mesenteric lymph primes circulating neutrophils and provokes lung injury. J Surg Res 83, 83–88.