Host response to mycobacterial infection in the alcoholic rat

A practical method of chronic ethanol administration in mice

Mice provide a useful model for the study of immune deficiency caused by chronic alcohol abuse. Their suitability is related to several factors, including in particular the extensive knowledge base in the immunology of mice already existing in the literature. Specific modeling of the immunodeficiency of the chronic human alcoholic requires that ethanol must be administered to the model for a significant portion of its life span. In mice, it has proven to be necessary to administer ethanol daily for up to 32 wk or longer to observe all the immune abnormalities that occur in middle-aged alcoholic humans. Such time spans are problematic with many of the common protocols for ethanol administration. It has been shown by others and confirmed by our group that the most practical way of accomplishing such long protocols is by administering ethanol in water as the only choice of water. Details of management of the chronic ethanol mouse colony are described here that are necessary for the success of such studies, including methods for initiating ethanol administration, maintenance of barrier protection, monitoring weight gain, strain differences and fetal alcohol exposure.

Influence of alcohol on antimicrobial immunity

Prolonged consumption of excessive amounts of alcohol by itself, as well as possibly leading to a state of alcoholism, has been a long-standing biological/social problem. As a major public health concern, there is an estimated expenditure of about 20% of total health care costs for medical/hospital care related to alcohol-induced illness. In addition, a significant proportion of both men and women who are hospitalized can be classified as alcoholics. This review focuses primarily on one of the many biomedical problems attributed to alcohol abuse--its adverse effects on our immune-defense system. A considerable body of evidence has mounted, over the past several decades, indicating that those who abuse alcohol are more susceptible to certain infectious disorders and are more prone to bacteremia. Such infections tend to be continuous and are often associated with a high rate of mortality. Also, along these lines, various and suitable animal models have been developed to further elucidate what the causes are for the greater frequency and severity of infectious illnesses, and this review deals primarily with those studies linking alcohol abuse to disruption in the normal functioning of the host's immune surveillance system. Based on the results from both clinical and experimental studies, it would seem that exposure to high levels of alcohol causes decreased humoral and cellular immune responses, thereby seriously limiting our ability to be protected from certain infectious agents.

Alcohol exacerbates murine pulmonary tuberculosis

Alcohol consumption has been described as a risk factor for infection with Mycobacterium tuberculosis, but its contribution to tuberculosis has been difficult to isolate from other adverse socioeconomic factors. Our objective was to evaluate the impact of alcohol consumption on pulmonary infection with M. tuberculosis in a murine model. BALB/c mice were maintained on the Lieber-DeCarli liquid ethanol diet or a liquid control diet and infected intratracheally with low-dose M. tuberculosis H37Rv. Lung organism burdens, lung and lung-associated lymph node CD4(+)- and CD8(+)- lymphocyte numbers and rates of proliferation, and CD4(+)-lymphocyte cytokine production levels were compared between the groups. The alcohol-consuming mice had significantly higher lung organism burdens than the control mice, and the CD4(+)- and CD8(+)-lymphocyte responses to pulmonary infection with M. tuberculosis were blunted in the alcohol group. Lymphocyte proliferation and production of gamma interferon were decreased in the CD4(+) lymphocytes from the alcohol-consuming mice. Additionally, lung granulomas were significantly smaller in the alcohol-consuming mice. In conclusion, murine alcohol consumption is associated with decreased control of pulmonary infection with M. tuberculosis, which is accompanied by alterations in the region-specific CD4(+)- and CD8(+)-lymphocyte responses and defective lung granuloma formation.

Microbial infections, immunomodulation, and drugs of abuse

The use of recreational drugs of abuse has generated serious health concerns. There is a long-recognized relationship between addictive drugs and increased levels of infections. Studies of the mechanisms of actions of these drugs became more urgent with the advent of AIDS and its correlation with abused substances. The nature and mechanisms of immunomodulation by marijuana, opiates, cocaine, nicotine, and alcohol are described in this review. Recent studies of the effects of opiates or marijuana on the immune system have demonstrated that they are receptor mediated, occurring both directly via specific receptors on immune cells and indirectly through similar receptors on cells of the nervous system. Findings are also discussed that demonstrate that cocaine and nicotine have similar immunomodulatory effects, which are also apparently receptor mediated. Finally, the nature and mechanisms of immunomodulation by alcohol are described. Although no specific alcohol receptors have been identified, it is widely recognized that alcohol enhances susceptibility to opportunistic microbes. The review covers recent studies of the effects of these drugs on immunity and on increased susceptibility to infectious diseases, including AIDS.

Impaired bactericidal activity and host resistance to Listeria monocytogenes and Borrelia burgdorferi in rats administered an acute oral regimen of ethanol

A rat model was used to examine how ethanol ingestion may interfere with antimicrobial immunity both in vitro and in vivo. Nonimmune Long-Evans rats were given a short-course treatment orally with excessive amounts of ethanol. Their spleens were removed at the time of sacrifice, and separate spleen cell suspensions were prepared and tested in vitro for their ability to kill two bacterial pathogens, Listeria monocytogenes and Borrelia burgdorferi. After the bacteria were mixed separately with various concentrations of spleen cells, it was found that spleen cells from the ethanol-treated rats killed fewer bacteria than matching pair-fed controls, based on counts of the number of cultured CFU (for Listeria) or based on microscopic examination (for Borrelia). For the in vivo studies, ethanol-treated and control rats were infected intraperitoneally with Listeria, and then, 1 to 3 days later, they were assessed for systemic infection based on the numbers of organisms present in their livers and spleens. Numbers of bacterial CFU for both organs were significantly higher in the group fed ethanol for the first 2 days after listerial challenge. These results support the concept that acute exposure to high levels of ethanol can impair host defense mechanisms, especially those expressed at the cellular level, which could lead to increased susceptibility to certain types of infections.

Cytokine response to BCG infection in alcohol-fed mice

Alcoholics have increased susceptibility to infections including tuberculosis. Chronic alcohol treatment impairs host response to bovine mycobacterium infection from BCG. This study assesses the role of four cytokines (TNFalpha, IFNgamma, IL-4, and IL-10) in this impaired response. Twenty male C57BL/6 mice were pair-fed on the Lieber DiCarli control (LCD) or ethanol (LED) diets for 28 days. The LED treated subjects ate ad lib and consumed a mean of 13 g/kg/d of ethanol. After 14 days, based on body weight, subjects were randomly divided into four treatment groups of five each. Ten infected with 2x10(6) colony-forming units (CFU) of BCG by tail-vein. On day 28, the mice were sacrificed. Liver was cultured to determine the mycobacteria CFU/g tissue. Spleens were assayed for the levels of TNFalpha, IFNgamma, IL-4, and IL-10 mRNA relative to mRNA levels for a housekeeping gene using a quantitative reverse transcriptase PCR. Without BCG infection, only the mRNA for IFNgamma was increased by LED treatment, 51% (p = 0.0001). BCG infection significantly increased TNFalpha, IFNgamma, and IL-10 mRNA (p<0.0001). IL-4 mRNA decreased (p = 0.0006). Chronic LED plus BCG infection further increased TNFalpha (p = 0.002) and IFN-gamma (p = 0.04); IL-10 was unchanged, whereas IL-4 was marginally further decreased (p = 0.06). CFU/liver increased with LED (mean +/- SD, 72+/-33x10(5) vs. 39+/-17x10(5); p = 0.004). A significant direct correlation was observed between CFU and TNFalpha, r = 0.70, p = 0.03. In conclusion, BCG infection increases TNFalpha, IFNgamma, & IL-10 and decreases IL-4. CFU numbers correlate with mRNA for TNFalpha, and LED inhibits host containment of BCG infection as measured by liver CFU. This study could not identify cytokine alterations in either Th1- or Th2-type immune responses that might contribute to the impaired host response to the BCG infection.

Host response to mycobacterial infection in the alcoholic rat: male and female dimorphism

Increased susceptibility to tuberculosis occurs in the alcoholic. One explanation for the altered susceptibility is a change in T-lymphocyte modulation. To evaluate this, 24 male and 24 female Sprague-Dawley rats were treated with either a Lieber-type liquid ethanol diet (LED) or an isocaloric control (LCD). After 2 weeks, half the subjects were infected with BCG (10(8) colony-forming units) and sacrificed after 42 days. Splenic helper (CD4) and suppressor/cytoxic (CD8) cells were quantitated by flow cytometry. By three-way analysis of variance, splenic cellularity was significantly increased by infection (p < 0.0001) but suppressed by LED (p = 0.0002). There was a marginal sexual difference (p = 0.065) with females exhibiting a 35% lower response while on alcohol. Examining lymphocyte subsets, the most significant changes were observed after infection (BCG) and alcohol treatment (LED). CD4 levels were diminished by LED (p = 0.0002) but markedly increased by infection (p < 0.0001), producing a highly significant interaction that affected both absolute number (p < 0.0001) and relative percent present (p = 0.0078). CD8 was influenced only by infection (p < 0.0001). This resulted in a infection-related increase in the CD4/CD8 ratio which was lower with LED (p = 0.0032). Splenic T-lymphocytes, predominately CD4, are involved in the host response to BCG hepatitis and are adversely influenced by LED, which may contribute to increased susceptibility.

II: the effects of recombinant human insulin-like growth factor-1 on immunological recovery in the malnourished alcoholic rat

BACKGROUND/AIMS

Immunological abnormalities are frequently observed in alcoholics with severe liver disease and are typically in association with immune abnormalities. Concomitantly, serum levels of insulin-like growth factor-1 (IGF-1) are frequently very low in these patients. Because IGF-1 is known to modulate both nutrition and immune status, the present study was undertaken to evaluate an in vivo rat model of alcoholism and malnutrition, the possibility of a therapeutic application for IGF-1.

METHODS

Controlled injury was induced by 14 days of calorie restriction and alcohol feeding that resulted in a 9% loss of body mass. Changes were compared with normal unrestricted control rats that gained 28% above their pretreatment body mass during the same period. Immunological impairment was assessed using thymus and spleen mass, cellularity and spleen T-lymphocyte function. Recovery was evaluated after 28 days of treatment using various combinations of: (1) high calorie intake, (2) cessation from alcohol feeding, and (3) IGF-1.

RESULTS

The thymus was most severely affected, losing 52.3% of its mass and 55.7% of its cellularity. The spleen was diminished, losing 31.2% of its mass and 41.9% of its cellularity. All of the spleen T-lymphocyte subsets were diminished, with CD5 affected the least (37.1 %) and CD8 affected the most severely (51.7%). During recovery, only the group treated with high calorie intake, no alcohol intake, and IGF-1 (group 8) had complete restoration of all immunological parameters, including a recovery of T-lymphocyte function. Continuous consumption of alcohol, even in the presence of high calories and IGF-1, produced an incomplete recovery.

CONCLUSIONS

Cessation of alcohol coupled with high calorie nutrition and IGF-1 treatment produced an accelerated improvement in host immunity. These animal studies suggest that IGF-1 is efficacious for this condition and supports the need for additional clinical studies.

Ethanol suppresses Mycobacteria tuberculosis-induced mRNA for nitric oxide synthase in alveolar macrophages, in vivo

Acute ingestion of alcohol [ethanol (ETOH)] adversely affects the immunocompetence of both naive individuals as well as chronic alcohol abusers. An increased incidence and severity of tuberculosis is found in chronic alcohol abusers. Nitric oxide (NO) produced by alveolar macrophages (AMs) may play a role in the in vitro killing of Mycobacterium avium and Mycobacterium tuberculosis (MTB). Moreover, tumor necrosis factor-alpha (TNF-alpha) is believed to be a primary cytokine mediator of NO production by AMs. Recent studies from our laboratory demonstrated that ETOH suppressed endotoxin-induced increases in both TNF-alpha and NO in AMs, in vivo. We tested the postulate that acute ingestion of ETOH can interfere with mycobacteria-induced upregulation of the NO system in AMs, in vivo. We show that heat-killed M. avium complex (MAC) and human virulent MTB instilled into rat lungs rapidly increased mRNA for inducible NO synthase II (iNOS) of AMs in fluid obtained by bronchoalveolar lavage (BAL fluid). This was associated with production of reactive nitrogen intermediates [(RNIs); NO2- and NO3-] in BAL fluid, lung homogenate, and AMs in the absence of a significant increase in BAL fluid TNF-alpha. A single dose of ETOH (5.5 g/kg, ip) administered 30 min before intratracheal administration of MAC or MTB attenuated both MAC and MTB-induced increases in RNI in BAL fluid, lung, and AMs, and the increase in mRNA for iNOS. Thus, mycobacteria upregulate iNOS mRNA and enhance RNI production by AMs without any increase in the production of TNF-alpha. Moreover, ETOH attenuates mycobacteria-induced upregulation of mRNA for iNOS and RNI production in the absence of ETOH-mediated suppression of TNF. Speculatively, ETOH-mediated inhibition of the AM NO system may offer an explanation for the increased severity of mycobacterial infections in alcoholics.

Alcohol, tumor necrosis factor, and tuberculosis

Alcohol exerts potent suppressive effects on the immune system that significantly increase host susceptibility to a variety of infections, particularly pneumonia. Historically, tuberculosis has been strongly associated with alcohol abuse. Although the relationship between alcohol abuse and tuberculosis is widely appreciated, the basic mechanisms by which alcohol immunosuppresses the host remain to be clarified. A major obstacle in furthering our understanding of this association has been the difficulty in distinguishing between the effects of alcohol per se and the other frequent sequelae of alcoholism such as nutritional deficiencies, liver disease, cigarette smoking, hygienic factors, and lifestyle. This article focuses on the role of tumor necrosis factor-alpha (TNF) in host defense and how alcohol modulates the activity of this important cytokine. While TNF's role in mediating the lethal consequences of infection has been the subject of much conjecture, this review focuses on the emerging evidence that TNF is an essential factor in the normal immune response to numerous infections, including tuberculosis.

Effects of ethanol on cellular immunity to facultative intracellular bacteria

Alcohol abuse has been associated with an increase in infectious diseases caused by pathogenic and opportunistic microorganisms. Study results obtained from this laboratory and other laboratories have shown that consumption of large amounts of ethanol is associated with numerous changes in the immune system. The purpose of this article is to report findings obtained from this laboratory, as well as review those obtained from other laboratories, from experiments designed to evaluate the effects of ethanol on various components of antimicrobial host-defense mechanisms. The effects of ethanol on various aspects of immunity obtained with the use of in vivo and in vitro model systems are reviewed as they pertain to antimicrobial defenses. All current data would support the suggestion that ethanol affects both the development of an antigen-specific immune response and the effector mechanisms of the cellular immune response. Findings obtained from animal models show that ethanol prevents the formation of granulomas in infected tissues, perhaps by inhibiting the response of macrophages to T-cell cytokines. Data obtained from this laboratory also support the suggestion that the inability of the immune system to control the intracellular growth of microorganisms results in an exaggerated inflammatory response that is responsible for at least a part of the tissue damage.

Diet and ethanol modulate immune responses in young C57BL/6 mice

Chronic ethanol (ETOH) ingestion adversely affects the immunocompetence of alcohol abusers. ETOH directly impairs host defense mechanisms and indirectly modulates immunocompetence by interfering with the nutritional status of the alcoholic. It is not clear from the current literature, however, to what extent ETOH, nutritional status, or the combination of the two factors modulates immune mechanisms in chronic alcoholics. To date, most animal studies investigating the immunotoxicity of ETOH have neglected the dietary factors, which may have masked additional immunotoxic effects of ETOH. To examine these dietary factors, we fed mice three liquid ETOH diets with different dietary sufficiencies for 7 weeks and investigated various immune responses. Spleen cell number and secretions of immunoreactive interleukin-2 and tumor necrosis factor were totally independent of the diet, being affected only by ETOH. Body, spleen, and thymus weights, interferon-gamma secretion, and natural killer cell and phagocytic activities were modulated by ETOH as well as by diet. Natural killer cell and phagocytic activities were also directly affected by the nutritional quality of the diet. These results suggest that animal diets used in experimental studies of ETOH-induced immunomodulation must be planned and controlled carefully in order to single out the direct effects that ETOH has on the host defense system.

Ethanol ingestion increases susceptibility of mice to Listeria monocytogenes

Excessive consumption of alcohol is associated with an increase in the frequency and severity of infectious diseases. Ethanol adversely affects specific and nonspecific aspects of the immune response. We used a murine model to determine whether ethanol ingestion impairs host mechanisms of resistance to Listeria monocytogenes. Naive mice and mice immune to L. monocytogenes were pair-fed either a Leiber-DeCarli liquid diet containing 7% (v/v) ethanol or an isocaloric control diet for 7 days. Then, nonimmune mice were given a sublethal dose of L. monocytogenes and studied 2 and 5 days after infection, and immune mice were challenged with a lethal dose of L. monocytogenes and studied 5 days after infection. Multifocal liver abscesses developed in nonimmune ethanol-treated and control mice 2 days after infection. Bacterial colony counts in the spleens were similar between the two groups; however, counts in the livers were slightly higher in ethanol-treated mice as compared with those in control mice. Five days after infection the nonimmune ethanol-treated mice had large necrotizing liver granulomas and organ bacterial colony counts 100 to 1000 times higher than those in control mice. Immune ethanol-treated mice had large areas of liver necrosis and inflammation containing numerous Gram-positive bacilli, whereas immune control mice had small, well-formed granulomas and much less necrosis. Organ bacterial colony counts were about 100 times higher in immune ethanol-treated mice as compared with those in immune control mice. Liver enzyme levels and mortality were significantly higher in ethanol-treated immune and nonimmune mice as compared with those in immune and nonimmune control mice. Data support the suggestion that ethanol consumption impairs the development and expression of T cell-mediated immunity of mice to L. monocytogenes, resulting in increased susceptibility to infection with this organism.