Chronic alcohol consumption perturbs the balance between thymus-derived and bone marrow-derived natural killer cells in the spleen

Natural killer cell effector function is critical for host defense against alcohol-associated bacterial pneumonia

Alcohol use is an independent risk factor for the development of bacterial pneumonia due, in part, to impaired mucus-facilitated clearance, macrophage phagocytosis, and recruitment of neutrophils. Alcohol consumption is also known to reduce peripheral natural killer (NK) cell numbers and compromise NK cell cytolytic activity, especially NK cells with a mature phenotype. However, the role of innate lymphocytes, such as NK cells during host defense against alcohol-associated bacterial pneumonia is essentially unknown. We have previously shown that indole supplementation mitigates increases in pulmonary bacterial burden and improves pulmonary NK cell recruitment in alcohol-fed mice, which were dependent on aryl hydrocarbon receptor (AhR) signaling. Employing a binge-on-chronic alcohol-feeding model we sought to define the role and interaction of indole and NK cells during pulmonary host defense against alcohol-associated pneumonia. We demonstrate that alcohol dysregulates NK cell effector function and pulmonary recruitment via alterations in two key signaling pathways. We found that alcohol increases transforming growth factor beta (TGF-β) signaling while suppressing AhR signaling. We further demonstrated that NK cells isolated from alcohol-fed mice have a reduced ability to kill Klebsiella pneumoniae. NK cell migratory capacity to chemokines was also significantly altered by alcohol, as NK cells isolated from alcohol-fed mice exhibited preferential migration in response to CXCR3 chemokines but exhibited reduced migration in response to CCR2, CXCR4, and CX3CR1 chemokines. Together this data suggests that alcohol disrupts NK cell-specific TGF-β and AhR signaling pathways leading to decreased pulmonary recruitment and cytolytic activity thereby increasing susceptibility to alcohol-associated bacterial pneumonia.

Roles of innate lymphoid cells in metabolic and alcohol-associated liver diseases

Innate lymphoid cells (ILCs) have been identified as potent regulators of inflammation, cell death and wound healing, which are the main biological processes involved in the progression of chronic liver disease. Obesity and chronic alcohol consumption are the leading contributors to chronic liver diseases in developed countries, due to inappropriate lifestyles. In particular, inflammation is a key factor in these liver abnormalities and promotes the development of more severe lesions such as fibrosis, cirrhosis and hepatocellular carcinoma. Opposite roles of ILC subsets have been described in the development of chronic liver disease, depending on the stage and aetiology of the disease. The heterogeneous family of ILCs encompasses cytotoxic natural killer cells, the cytokine-producing type 1, 2 and 3 ILCs and lymphoid tissue inducer cells. Dysfunction of these immune cells provokes uncontrolled inflammation and tissue damage, which are the basis for tumour development. In this review, we provide an overview of the recent and putative roles of ILC subsets in obesity and alcohol-associated liver diseases, which are currently the major contributors to end-stage liver complications such as fibrosis/cirrhosis and hepatocellular carcinoma.

Natural killer cells immunosenescence and the impact of lifestyle management

Natural killer cells (NKs) are lymphocytes of the innate immune system that quickly respond to viruses, infections, and tumors during their short cell life cycle. However, it was recently found that NKs undergo quantitative, distributional, structural, and functional phenotypic changes during aging that suppress immune responses, which is known as immunosenescence. The aging host environment, cytokine regulation, cytomegalovirus status, and hypothalamic‒pituitary‒adrenal axis have significant effects on NK function. Different lifestyle management interventions modulate the number and cytotoxic activity of NKs, which are essential for rebuilding the immune barrier against pathogens in elderly individuals. Based on recent studies, we review the phenotypic changes of and potential threats of NKs during aging and explore the underlying mechanisms. By summarizing the effects of lifestyle management on NKs and their application prospects, we aim to provide evidence for enhancing immune system function against immune diseases in elderly individuals.

Regulation of Natural Killer Cell TGF-β and AhR Signaling Pathways Via the Intestinal Microbiota is Critical for Host Defense Against Alcohol-Associated Bacterial Pneumonia

Alcohol use is an independent risk factor for the development of bacterial pneumonia due, in part, to impaired mucus-facilitated clearance, macrophage phagocytosis, and recruitment of neutrophils. Alcohol consumption is also known to reduce peripheral natural killer (NK) cell numbers and compromises NK cell cytolytic activity, especially NK cells with a mature phenotype. However, the role of innate lymphocytes, such as NK cells during host defense against alcohol-associated bacterial pneumonia is essentially unknown. We have previously shown that indole supplementation mitigates increases in pulmonary bacterial burden and improves pulmonary NK cell recruitment in alcohol-fed mice, which were dependent of aryl hydrocarbon receptor (AhR) signaling. Employing a binge-on-chronic alcohol-feeding model we sought to define the role and interaction of indole and NK cells during pulmonary host defense against alcohol-associated pneumonia. We demonstrate that alcohol dysregulates NK cell effector function and pulmonary recruitment via alterations in two key signaling pathways. We found that alcohol increases transforming growth factor beta (TGF-β) signaling, while suppressing AhR signaling. We further demonstrated that NK cells isolated from alcohol-fed mice have a reduced ability to kill Klebsiella pneumoniae. NK cell migratory capacity to chemokines was also significantly altered by alcohol, as NK cells isolated from alcohol-fed mice exhibited preferential migration in response to CXCR3 chemokines but exhibited reduced migration in response to CCR2, CXCR4, and CX3CR1 chemokines. Together this data suggests that alcohol disrupts NK cell specific TGF-β and AhR signaling pathways leading to decreased pulmonary recruitment and cytolytic activity thereby increasing susceptibility to alcohol-associated bacterial pneumonia.

Characterization of spleen and lymph node cell types via CITE-seq and machine learning methods

The spleen and lymph nodes are important functional organs for human immune system. The identification of cell types for spleen and lymph nodes is helpful for understanding the mechanism of immune system. However, the cell types of spleen and lymph are highly diverse in the human body. Therefore, in this study, we employed a series of machine learning algorithms to computationally analyze the cell types of spleen and lymph based on single-cell CITE-seq sequencing data. A total of 28,211 cell data (training vs. test = 14,435 vs. 13,776) involving 24 cell types were collected for this study. For the training dataset, it was analyzed by Boruta and minimum redundancy maximum relevance (mRMR) one by one, resulting in an mRMR feature list. This list was fed into the incremental feature selection (IFS) method, incorporating four classification algorithms (deep forest, random forest, K-nearest neighbor, and decision tree). Some essential features were discovered and the deep forest with its optimal features achieved the best performance. A group of related proteins (CD4, TCRb, CD103, CD43, and CD23) and genes (Nkg7 and Thy1) contributing to the classification of spleen and lymph nodes cell types were analyzed. Furthermore, the classification rules yielded by decision tree were also provided and analyzed. Above findings may provide helpful information for deepening our understanding on the diversity of cell types.

Increased Natural Killer Cells Are Associated with Alcohol Liver Fibrosis and with T Cell and Cytotoxic Subpopulations Change

Natural killer (NK) cells play a therapeutic role in liver fibrosis (LF). We aimed to analyze NK cells in heavy drinkers without cirrhosis or decompensated liver disease and establish correlations with other related subpopulations. Data on sociodemographic characteristics, alcohol consumption, laboratory parameters, and immunophenotyping of NK (CD16⁺/CD56⁺), T (CD3⁺), B (CD19⁺), NKT (CD16⁺/CD56⁺/CD3⁺), and cytotoxic (CD3^-CD8⁺) cells were collected. Fibrosis-4 (FIB-4) scores were used to compare patients without (FIB-4 < 1.45) and with (FIB-4 > 3.25) advanced LF (ALF). We included 136 patients (76% male) with a mean age of 49 years who had a 15-year alcohol use disorder (AUD) and alcohol consumption of 164 g/day. Patients with ALF (n = 25) presented significantly lower absolute total lymphocyte, T cell, B cell, and NKT cell numbers than patients without LF (n = 50; p < 0.01). However, the NK cells count was similar (208 ± 109 cells/µL vs. 170 ± 105 cells/µL) in both groups. The T cells percentage was lower (80.3 ± 5.6% vs. 77 ± 7%; p = 0.03) and the NK cells percentage was higher (9.7 ± 5% vs. 13 ± 6%; p = 0.02) in patients with ALF than in those without LF. The percentages of NK cells and T cells were inversely correlated in patients without (r = –0.65, p < 0.01) and with ALF (r = −0.64; p < 0.01). Additionally, the NK cells and CD3^-CD8⁺ cell percentages were positively correlated in patients without (r = 0.87, p < 0.01) and with (r = 0.92; p < 0.01) ALF. Conclusions: Heavy drinkers without decompensated liver disease showed an increase in NK cells related to T cells lymphopenia and an increase in cytotoxic populations. The interaction of NK cells with other subpopulations may modify alcohol-related liver disease progression.

Possible Immunotherapeutic Strategies Based on Carcinogen-Dependent Subgroup Classification for Oral Cancer

The oral cavity serves as an open local organ of the human body, exposed to multiple external factors from the outside environment. Coincidentally, initiation and development of oral cancer are attributed to many external factors, such as smoking and drinking, to a great extent. This phenomenon was partly explained by the genetic abnormalities traditionally induced by carcinogens. However, more and more attention has been attracted to the influence of carcinogens on the local immune status. On the other hand, immune heterogeneity of cancer patients is a huge obstacle for enhancing the clinical efficacy of tumor immunotherapy. Thus, in this review, we try to summarize the current opinions about variant genetic changes and multiple immune alterations induced by different oral cancer carcinogens and discuss the prospects of targeted immunotherapeutic strategies based on specific immune abnormalities caused by different carcinogens, as a predictive way to improve clinical outcomes of immunotherapy-treated oral cancer patients.

Alcoholic hepatitis and metabolic disturbance in female mice: a more tractable model than Nrf2-/- animals

Alcoholic hepatitis (AH) is the dramatic acute presentation of alcoholic liver disease, with a 15% mortality rate within 28 days in severe cases. Research into AH has been hampered by the lack of effective and reproducible murine models that can be operated under different regulatory frameworks internationally. The liquid Lieber-deCarli (LdC) diet has been used as a means of ad libitum delivery of alcohol but without any additional insult, and is associated with relatively mild liver injury. The transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) protects against oxidative stress, and mice deficient in this molecule are suggested to be more sensitive to alcohol-induced injury. We have established a novel model of AH in mice and compared the nature of liver injury in C57/BL6 wild-type (WT) versus Nrf2-/- mice. Our data showed that both WT and Nrf2-/- mice demonstrate robust weight loss, and an increase in serum transaminase, steatosis and hepatic inflammation when exposed to diet and ethanol. This is accompanied by an increase in peripheral blood and hepatic myeloid cell populations, fibrogenic response and compensatory hepatocyte regeneration. We also noted characteristic disturbances in hepatic carbohydrate and lipid metabolism. Importantly, use of Nrf2-/- mice did not increase hepatic injury responses in our hands, and female WT mice exhibited a more-reproducible response. Thus, we have demonstrated that this simple murine model of AH can be used to induce an injury that recreates many of the key human features of AH - without the need for challenging surgical procedures to administer ethanol. This will be valuable for understanding of the pathogenesis of AH, for testing new therapeutic treatments or devising metabolic approaches to manage patients whilst in medical care.This article has an associated First Person interview with the joint first authors of the paper.

Recent Insights Into the Role of Immune Cells in Alcoholic Liver Disease

Accumulating clinical and experimental evidences have demonstrated that both innate and adaptive immunity are involved in the pathogenesis of alcoholic liver disease (ALD), in which the role of immunity is to fuel the inflammation and to drive the progression of ALD. Various immune cells are implicated in the pathogenesis of ALD. The activation of innate immune cells induced by alcohol and adaptive immune response triggered by oxidative modification of hepatic constituents facilitate the persistent hepatic inflammation. Meanwhile, the suppressed antigen-presenting capability of various innate immune cells and impaired function of T cells may consequently lead to an increased risk of infection in the patients with advanced ALD. In this review, we summarized the significant recent findings of immune cells participating in ALD. The pathways and molecules involved in the regulation of specific immune cells, and novel mediators protecting the liver from alcoholic injury via affecting these cells are particularly highlighted. This review aims to update the knowledge about immunity in the pathogenesis of ALD, which may facilitate to enhancement of currently available interventions for ALD treatment.

Chronic alcohol consumption exacerbates murine cytomegalovirus infection via impairing nonspecific and specific NK activation in mice

Chronic alcohol consumption increases the susceptibility to infectious diseases by compromising the immune system. Cytomegalovirus infection is common in humans and usually is asymptomatic in immunocompetent people. However, it can induce life‐threatening medical complications in immunocompromised individuals such as alcoholics. How chronic alcohol consumption exacerbates cytomegalovirus infection is not known. Herein, we used a mouse cytomegalovirus model to study the underlying cellular and molecular mechanism. We found that alcohol consumption increased viral titers in spleen after 4 days of infection, enhanced body weight loss and inhibited splenomegaly during the acute phase of infection. Blood level of IFN‐β, splenic IFN‐γ and granzyme B‐producing NK cells were lower in alcohol‐consuming mice than in water‐drinking mice at 12 hours after viral infection. Moreover, alcohol consumption decreased IL‐15‐producing DC after 36 hours infection, inhibited NK cell, specifically Ly49H⁺ NK cell maturation and proliferation 3‐6 days after viral infection. Surprisingly, alcohol consumption enhanced NK cell and CD8⁺ T‐cell continuous activation and increased granzyme B‐producing cells. However, alcohol consumption decreased the expression of perforin in spleen and liver. Taken together, chronic alcohol consumption exacerbates cytomegalovirus infection via impairing nonspecific and specific NK cell activation, specifically IFN‐γ and perforin production.

The Nrf2 activator tBHQ inhibits the activation of primary murine natural killer cells

Tert-butylhydroquinone (tBHQ) is a commonly used food preservative with known immunomodulatory activity; however, there is little information regarding its role on natural killer (NK) cell activation and function. tBHQ is a known activator of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which results in induction of cytoprotective genes. Activation of Nrf2 has been shown to modulate immune responses in a number of different models. In addition, studies in our laboratory have shown that tBHQ inhibits numerous early events following T cell activation. In the current study, we investigated whether activated NK cells are impacted by tBHQ, since many signaling cascades that control NK cell effector function also contribute to T cell function. Splenocytes were isolated from female, wild-type C57Bl/6J mice and treated with 1 μM or 5 μM tBHQ. NK cell function was assessed after activation with phorbol 12-myristate 13-acetate (PMA) and ionomycin for 24 h. Activation of NK cells in the presence of tBHQ decreased total NK cell percentage, production of intracellular interferon gamma (IFNɣ), granzyme B, and perforin, and induction of the cell surface proteins CD25 and CD69, which are markers of NK cell activation. In addition to NK cell effector function, NK cell maturation was also altered in response to tBHQ. Notably, this is the first study to demonstrate that the Nrf2 activator, tBHQ, negatively impacts effector function and maturation of NK cells.

Chronic alcohol consumption inhibits peripheral NK cell development and maturation by decreasing the availability of IL-15

NK cells are innate immune cells and have important roles in antiviral and antitumor immunity. Based on the transcriptional regulation, organ distribution, and cell function, NK cells have recently been further divided into cytotoxic conventional NK cells (cNK) and noncytotoxic helper-like group 1 innate lymphoid cells (ILC1s). It is well known that chronic alcohol consumption decreases peripheral NK cell number and cytolytic activity; however, the underlying mechanism remains to be elucidated. How chronic alcohol consumption affects ILC1s is, to our knowledge, completely unexplored. Herein, we used a well-established mouse model of chronic alcohol consumption to study the effects of alcohol on transcription factor expression, maturation, and cytokine production of cNK cells and ILC1s in various organs. We found that alcohol consumption significantly decreased Eomes-expressing cNK cells in all the examined organs, except BM, but did not significantly affect ILC1s. Alcohol consumption compromised cNK cell development and maturation. Exogenous IL-15/IL-15Rα treatment caused full recovery of Eomes-expressing cNK cell number and maturation. Taken together, our data indicated that chronic alcohol consumption decreases cNK cell number and cytolytic activity by arresting cNK cell development at the CD27⁺CD11b⁺ stage. This developmental arrest of NK cells results from a lack of IL-15 availability in the microenvironment. IL-15/IL-15Rα treatment can recover alcohol consumption-induced developmental defect in NK cells.

Murine Models of Acute Alcoholic Hepatitis and Their Relevance to Human Disease

Alcohol-induced liver damage is a major burden for most societies, and murine studies can provide a means to better understand its pathogenesis and test new therapies. However, there are many models reported with widely differing phenotypes, not all of which fully regenerate the spectrum of human disease. Thus, it is important to understand the implications of these variations to efficiently model human disease. This review critically appraises key articles in the field, detailing the spectrum of liver damage seen in different models, and how they relate to the phenotype of disease seen in patients. A range of different methods of alcohol administration have been studied, ranging from ad libitum consumption of alcohol and water to modified diets (eg, Lieber deCarli liquid diet). Other feeding regimens have taken more invasive routes using intragastric feeding tubes to infuse alcohol directly into the stomach. Notably, models using wild-type mice generally produce a milder phenotype of liver damage than those using genetically modified mice, with the exception of the chronic binge-feeding model. We recommend panels of tests for consideration to standardize end points for the evaluation of the severity of liver damage-key for comparison of models of injury, testing of new therapies, and subsequent translation of findings into clinical practice.

Ethanol supports macrophage recruitment and reinforces invasion and migration of Lewis lung carcinoma

BACKGROUND

Inflammation plays a critical role in cancer progression, and our data suggested that ethanol (EtOH) could promote the progression of breast cancer via increased monocyte chemo-attractant protein-1 (MCP-1). Thus, we investigated the effects of EtOH on lung cancer growth and metastasis to explore whether immunosuppression had a role.

METHODS

C57BL/6 mice (n = 10) implanted with Lewis lung cancer (LLC) cells were used to model physiologically relevant EtOH intake on tumor growth and inflammation after macrophage polarization. Tumors were isolated and measured, and MCP-1 expression was measured via immunohistochemistry and Western blot. Recruitment of macrophages using CD11b and F4/80 antibodies was detected with immunohistochemistry and flow cytometry. Changes in arginase I and inducible nitric oxide synthase (iNOS) expression were measured with immunofluorescent microscopy. EtOH's effect on in vitro tumor angiogenesis was evaluated in culture, and the tumor microvessel density was assessed with CD31 immunohistochemistry. Matrix metalloproteinase 9 and interleukin 10 expressions were measured by Western blot, ELISA, and immunohistochemistry. Finally, we treated a macrophage cell line RAW264.7 with EtOH and measured changes in arginase I and iNOS expression.

RESULTS

With EtOH exposure, macrophage density was positively correlated with MCP-1 expression. Macrophages infiltrated the tumor site, becoming tumor-associated macrophages that polarized to M2 phenotypes (ArgI(high) /iNOS(low) ) after EtOH treatment. Cancerous cells interacted with immune cells, especially M2 macrophages, and promoted tumor angiogenesis, progression, and invasiveness. RAW264.7 cells stimulated with EtOH expressed more arginase I and less iNOS than controls. These results agreed with the features of M2 phenotype macrophages (ArgI(high) /iNOS(low) ).

CONCLUSIONS

Data show that EtOH induced M2 phenotype macrophages, suggesting that progression and metastasis of LLC may be mediated by recruitment of M2 macrophages, especially under the influence of EtOH.

Chronic alcohol consumption inhibits melanoma growth but decreases the survival of mice immunized with tumor cell lysate and boosted with α-galactosylceramide

Alcohol consumption increases the incidence of multiple types of cancer. However, how chronic alcohol consumption affects tumor progression and host survival remains largely unexplored. Using a mouse B16BL6 melanoma model, we studied the effects of chronic alcohol consumption on s.c. tumor growth, iNKT cell antitumor immune response, and host survival. The results indicate that although chronic alcohol consumption inhibits melanoma growth, this does not translate into increased host survival. Immunizing mice with a melanoma cell lysate does not significantly increase the median survival of water-drinking, melanoma-bearing mice, but significantly increases the median survival of alcohol-consuming, melanoma-bearing mice. Even though survival is extended in the alcohol-consuming mice after immunization, the median survival is not different from the immunized mice in the water-drinking group. Immunization with tumor cell lysate combined with α-galatosylceramide activation of iNKT cells significantly increases host survival of both groups of melanoma-bearing mice compared to their respective non-immunized counterparts; however, the median survival of the alcohol-consuming group is significantly lower than that of the water-drinking group. Alcohol consumption increases NKT cells in the thymus and blood and skews NKT cell cytokine profile from Th1 dominant to Th2 dominant in the tumor-bearing mice. In summary, these results indicate that chronic alcohol consumption activates the immune system, which leads to the inhibition of s.c. melanoma growth and enhances the immune response to immunization with melanoma lysate. With tumor progression, alcohol consumption accelerates iNKT cell dysfunction and compromises antitumor immunity, which leads to decreased survival of melanoma-bearing mice.

Alcohol and HCV: implications for liver cancer

Liver cancers are one of the deadliest known malignancies which are increasingly becoming a major public health problem in both developed and developing countries. Overwhelming evidence suggests a strong role of infection with hepatitis B and C virus (HBV and HCV), alcohol abuse, as well as metabolic diseases such as obesity and diabetes either individually or synergistically to cause or exacerbate the development of liver cancers. Although numerous etiologic mechanisms for liver cancer development have been advanced and well characterized, the lack of definite curative treatments means that gaps in knowledge still exist in identifying key molecular mechanisms and pathways in the pathophysiology of liver cancers. Given the limited success with current therapies and preventive strategies against liver cancer, there is an urgent need to identify new therapeutic options for patients. Targeting HCV and or alcohol-induced signal transduction, or virus-host protein interactions may offer novel therapies for liver cancer. This review summarizes current knowledge on the mechanistic development of liver cancer associated with HCV infection and alcohol abuse as well as highlights potential novel therapeutic strategies.

Alcohol consumption and antitumor immunity: dynamic changes from activation to accelerated deterioration of the immune system

The molecular mechanisms of how alcohol and its metabolites induce cancer have been studied extensively. However, the mechanisms whereby chronic alcohol consumption affects antitumor immunity and host survival have largely been unexplored. We studied the effects of chronic alcohol consumption on the immune system and antitumor immunity in mice inoculated with B16BL6 melanoma and found that alcohol consumption activates the immune system leading to an increase in the proportion of IFN-γ-producing NK, NKT, and T cells in mice not injected with tumors. One outcome associated with enhanced IFN-γ activation is inhibition of melanoma lung metastasis. However, the anti-metastatic effects do not translate into increased survival of mice bearing subcutaneous tumors. Continued growth of the subcutaneous tumors and alcohol consumption accelerates the deterioration of the immune system, which is reflected in the following: (1) inhibition in the expansion of memory CD8+ T cells, (2) accelerated decay of Th1 cytokine-producing cells, (3) increased myeloid-derived suppressor cells, (4) compromised circulation of B cells and T cells, and (5) increased NKT cells that exhibit an IL-4 dominant cytokine profile, which is inhibitory to antitumor immunity. Taken together, the dynamic effects of alcohol consumption on antitumor immunity are in two opposing phases: the first phase associated with immune stimulation is tumor inhibitory and the second phase resulting from the interaction between the effects of alcohol and the tumor leads to immune inhibition and resultant tumor progression.

Chronic alcohol consumption enhances iNKT cell maturation and activation

Alcohol consumption exhibits diverse effects on different types of immune cells. NKT cells are a unique T cell population and play important immunoregulatory roles in different types of immune responses. The effects of chronic alcohol consumption on NKT cells remain to be elucidated. Using a mouse model of chronic alcohol consumption, we found that alcohol increases the percentage of NKT cells, especially iNKT cells in the thymus and liver, but not in the spleen or blood. Alcohol consumption decreases the percentage of NK1.1(-) iNKT cells in the total iNKT cell population in all of the tissues and organs examined. In the thymus, alcohol consumption increases the number of NK1.1(+)CD44(hi) mature iNKT cells but does not alter the number of NK1.1(-) immature iNKT cells. A BrdU incorporation assay shows that alcohol consumption increases the proliferation of thymic NK1.1(-) iNKT cells, especially the NK1.1(-)CD44(lo) Stage I iNKT cells. The percentage of NKG2A(+) iNKT cells increases in all of the tissues and organs examined; whereas CXCR3(+) iNKT cells only increases in the thymus of alcohol-consuming mice. Chronic alcohol consumption increases the percentage of IFN-γ-producing iNKT cells and increases the blood concentration of IFN-γ and IL-12 after in vivo α-galactosylceramide (αGalCer) stimulation. Consistent with the increased cytokine production, the in vivo activation of iNKT cells also enhances the activation of dendritic cells (DC) and NK, B, and T cells in the alcohol-consuming mice. Taken together the data indicate that chronic alcohol consumption enhances iNKT cell maturation and activation, which favors the Th1 immune response.

NK cell maturation and function in C57BL/6 mice are altered by caloric restriction

NK cells are a heterogenous population of innate lymphocytes with diverse functional attributes critical for early protection from viral infections. We have previously reported a decrease in influenza-induced NK cell cytotoxicity in 6-mo-old C57BL/6 calorically restricted (CR) mice. In the current study, we extend our findings on the influence of CR on NK cell phenotype and function in the absence of infection. We demonstrate that reduced mature NK cell subsets result in increased frequencies of CD127(+) NK cells in CR mice, skewing the function of the total NK cell pool. NK cells from CR mice produced TNF-α and GM-CSF at a higher level, whereas IFN-γ production was impaired following IL-2 plus IL-12 or anti-NK1.1 stimulation. NK cells from CR mice were highly responsive to stimulation with YAC-1 cells such that CD27(-)CD11b(+) NK cells from CR mice produced granzyme B and degranulated at a higher frequency than CD27(-)CD11b(+) NK cells from ad libitum fed mice. CR has been shown to be a potent dietary intervention, yet the mechanisms by which the CR increases life span have yet to be fully understood. To our knowledge, these findings are the first in-depth analysis of the effects of caloric intake on NK cell phenotype and function and provide important implications regarding potential ways in which CR alters NK cell function prior to infection or cancer.

A dynamic flux in natural killer cell subsets as a function of the duration of alcohol ingestion

BACKGROUND

Chronic ethanol (EtOH) consumption is associated with a wide variety of immune abnormalities including changes in T cells, B cells, dendritic cells, and natural killer (NK) cells. However, there is conflicting information as to the direction of such immune changes. The hypothesis that was tested in this report is that, for NK cells, the changes can vary as a function of the duration of alcohol ingestion.

METHODS

Using the Meadows-Cook murine model of chronic alcohol ingestion, the changes in NK cell function and subset distribution were examined as a function of the duration of alcohol ingestion.

RESULTS

Acute alcohol ingestion resulted in decreased number and cytotoxic function of NK cells with no effect on intracellular interferon gamma expression. These abnormalities normalized after 12 to 14 days of alcohol ingestion and there was an increase of NK cell number and cytotoxicity after 8 weeks of continued EtOH ingestion. Ten weeks of continued alcohol consumption results in a significant decrease in the Ly49H+ CD11b+ CD27- splenic NK cell subset; this difference continued to be significant at 30 weeks.

CONCLUSIONS

This report may explain some of the conflicting data in the literature that examined NK cell activity in alcoholic patients. It is apparent that various abnormalities can be seen in NK cell activity and subset distribution with the flux being a function of the duration of alcohol ingestion. The demonstration of a decrease in the Ly49H+ subset (which is known to be involved in resisting murine cytomegalovirus infection) may explain the reported increase in susceptibility to some viral infections in chronic alcohol abuse. Another novel finding is that changes of some subsets of NK cells are not evident until at least 10 weeks of continued EtOH consumption.

Atherosclerosis amelioration by moderate alcohol consumption is associated with increased circulating levels of stromal cell-derived factor-1

BACKGROUND

A moderate intake of alcohol is associated with lower cardiovascular mortality, and the role of circulating progenitor cells in the beneficial effect of alcohol on atherosclerosis is unclear. The hypothesis of this study was that alcohol ameliorates atherosclerosis by modulating the circulating levels of stromal cell-derived growth factor (SDF)-1 and vascular progenitor cells.

METHODS AND RESULTS

Atherosclerosis was induced by infusion of angiotensin II in apolipoprotein-E deficient mice, which were treated with high and low doses of ethanol for 28 days by intraperitoneal injection. Mice treated with low-dose ethanol had significantly less dilatation and fewer atheromatous lesions than mice receiving the high-dose ethanol. The number of circulating fibrocytes was significantly lower in mice treated with high-dose ethanol compared with mice with atherosclerosis untreated with ethanol. The plasma CXCL12/SDF-1 level was significantly increased in mice treated with low-dose ethanol compared with mice treated with a high dose, and the plasma concentration of transforming growth factor-β1 was significantly increased in mice treated with high-dose ethanol compared with control mice. Ethanol regulated the secretion of SDF-1 and vascular endothelial growth factor from fibroblasts in a dose-dependent and bimodal fashion.

CONCLUSIONS

The circulating level of CXCL12/SDF-1 may be involved, at least in part, in the differential effects of alcohol consumption on atherosclerosis.

IFN-γ is essential for the inhibition of B16BL6 melanoma lung metastasis in chronic alcohol drinking mice

We previously found that chronic alcohol consumption (20% w/v in drinking water) that models the level consumed by human alcoholics, when administered to female C57BL/6 mice inhibits B16BL6 melanoma metastasis to the lung; however, the mechanism is not known. Chronic alcohol consumption increases IFN-γ producing NK, NKT, CD4(+), and CD8(+) T cells. To examine the impact of IFN-γ on metastasis, we inoculated B16BL6 melanoma cells i.v. into control and chronic alcohol drinking IFN-γ knockout (KO) mice. Knockout of the ifn-γ gene abrogated the anti-metastatic effects associated with alcohol consumption. We examined metastasis in common gamma-chain (γC) KO mice, which are deficient in NK, NKT and CD8(+) T cells, and in Vα14Jα281(-/-) KO mice, which are deficient in invariant NKT (iNKT) cells, in order to assess the importance of specific IFN-γ producing cell types to this effect. We found that the antimetastatic effect of alcohol was still present in γC KO mice and also in γC KO mice depleted of Gr-1(+) cells. Knockout of iNKT cells reduced the degree but not the antimetastatic effect associated with alcohol. These results indicate that the antimetastatic effect induced by chronic alcohol consumption is IFN-γ dependent and that multiple IFN-γ producing cell types contribute to this effect.

Chronic alcohol consumption decreases the percentage and number of NK cells in the peripheral lymph nodes and exacerbates B16BL6 melanoma metastasis into the draining lymph nodes

NK cells in the lymph nodes play important roles in inhibiting tumor metastasis into draining lymph nodes. Previously, we reported that chronic alcohol consumption interferes with NK cell trafficking from the bone marrow to the spleen. Herein, we found that alcohol consumption decreases the numbers of NK cells in lymph nodes. Adoptive transfer experiments indicated that continued exposure of donor splenocytes to alcohol inhibits NK but not T cell trafficking to lymph nodes. Alcohol did not negatively affect CCR7(+) and CXCR3(+) NK cells, but decreased the percentage and number of CD62L(+) NK cells in the spleen, which are an important source of NK cell trafficking into the lymph nodes. These data suggest that modulation of the microenvironment associated with alcohol consumption impairs the trafficking of NK cells to lymph nodes. The decreased number of NK cells in the lymph nodes was associated with increased melanoma metastasis into the draining lymph nodes.

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

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

Chronic alcohol consumption enhances myeloid-derived suppressor cells in B16BL6 melanoma-bearing mice

We previously found that chronic alcohol consumption decreases the survival of mice bearing subcutaneous B16BL6 melanoma. The underlying mechanism is still not completely understood. Antitumor T cell immune responses are important to inhibiting tumor progression and extending survival. Therefore, we examined the effects of chronic alcohol consumption on the functionality and regulation of these cells in C57BL/6 mice that chronically consumed 20% (w/v) alcohol and subsequently were inoculated subcutaneously with B16BL6 melanoma cells. Chronic alcohol consumption inhibited melanoma-induced memory T cell expansion and accelerated the decay of interferon (IFN)-gamma producing T cells in the tumor-bearing mice. Foxp3(+)CD4(+)CD25(+) regulatory T cells were not affected; however, the percentage of myeloid-derived suppressor cells (MDSC) was significantly increased in the peripheral blood and spleen. T cell proliferation as determined by carboxyfluorescein succinimidyl ester labeling experiments in vitro was inhibited by alcohol consumption relative to control water-drinking melanoma-bearing mice. Collectively, these data show that chronic alcohol consumption inhibits proliferation of memory T cells, accelerates the decay of IFN-gamma producing CD8(+) T cells, and increases MDSC, all of which could be associated with melanoma progression and reduced survival.

Chronic alcohol consumption is associated with an increased cytotoxic profile of circulating lymphocytes that may be related with the development of liver injury

BACKGROUND

Apoptosis has recently emerged as a key component of acute and chronic liver diseases and it could be related to alcoholic liver disease. In the present study, we attempted to analyze the cytotoxic profile of circulating lymphocytes in chronic alcoholic patients grouped according to ethanol intake status and presence of liver disease.

METHODS

We investigate the phenotypic and functional behavior of different compartments of peripheral blood (PB) cytotoxic T and natural killer (NK) cells in chronic alcoholic patients without liver disease and active ethanol intake (AWLD group; n = 22), and in subjects with alcohol liver cirrhosis (ALC group; n = 22).

RESULTS

AWLD patients showed an expansion of both CD4+/CD8+ cytotoxic T cells and NK/T cells, in association with an enhanced cytolytic activity against K562 cells and a higher ability to induce in vitro expression of the pro-apoptotic protein APO2.7 in HepG2 cells. Conversely, ethanol intake in ALC patients was associated with decreased NK cell numbers, a reduced cytotoxic activity against K562 cells without significant changes in the expression of APO2.7, and a pro-fibrotic profile of cytokine secretion.

CONCLUSIONS

Overall, our results suggest that alcoholic patients display different phenotypical and functional changes in circulating PB cytotoxic lymphocytes according to the presence of alcoholic liver disease, which could be related to the development and progress of liver injury.

Exogenous IL-15 in combination with IL-15R alpha rescues natural killer cells from apoptosis induced by chronic alcohol consumption

BACKGROUND

Chronic alcohol consumption reduces the percentage and number of peripheral natural killer (NK) cells in mice and in humans. The underlying mechanism for these changes is only partly known. We recently found that chronic alcohol consumption inhibits NK cell release from the bone marrow (BM) and that this is associated with a decrease in splenic NK cells. The number of peripheral NK cells is tightly controlled by homeostatic proliferation. It is not known whether this mechanism is initiated in response to the reduction in splenic NK cells, or if so, why the steady state levels of NK cells are not restored.

METHODS

To examine this mechanism, female C57BL/6 mice were given 20% w/v alcohol in the drinking water for 3 months. NK cell proliferation and apoptosis were determined before and after treatment with IL-15 alone or combined with its alpha receptor.

RESULTS

Chronic alcohol consumption invoked homeostatic proliferation of splenic NK cells in an attempt to return NK cells to normal levels; however, this did not happen due to enhanced apoptosis of NK cells relative to proliferation. Chronic alcohol consumption decreased IL-15 producing cells in the spleen but not in the BM. The numbers of NK cells in the alcohol-consuming mice returned to normal levels in the spleen and were higher than normal in the BM after 2 daily injections of IL-15; however, the enhanced rate of apoptosis due to alcohol consumption was not decreased in the spleen or BM. Combined IL-15 and IL-15R alpha treatment decreased apoptosis of NK cells from alcohol-consuming mice to levels similar to untreated water-drinking mice and greatly increased the percentage and number of NK cells in both the spleen and BM.

CONCLUSION

Chronic alcohol consumption causes a self-unrecoverable loss of NK cells in the spleen by compromising NK cell release from the BM and enhancing splenic NK cell apoptosis that can be reversed with IL-15/IL-15R alpha treatment.