Effects of ethanol and acetaldehyde on phagocytic functions

Alteration of Fermentative Metabolism Enhances Mucor circinelloides Virulence

The fungus Mucor circinelloides undergoes yeast-mold dimorphism, a developmental process associated with its capability as a human opportunistic pathogen. Dimorphism is strongly influenced by carbon metabolism, and hence the type of metabolism likely affects fungus virulence. We investigated the role of ethanol metabolism in M. circinelloides virulence. A mutant in the adh1 gene (M5 strain) exhibited higher virulence than the wild-type (R7B) and the complemented (M5/pEUKA-adh1 ⁺) strains, which were nonvirulent when tested in a mouse infection model. Cell-free culture supernatant (SS) from the M5 mutant showed increased toxic effect on nematodes compared to that from R7B and M5/pEUKA-adh1 ⁺ strains. The concentration of acetaldehyde excreted by strain M5 in the SS was higher than that from R7B, which correlated with the acute toxic effect on nematodes. Remarkably, strain M5 showed higher resistance to H₂O₂, resistance to phagocytosis, and invasiveness in mouse tissues and induced an enhanced systemic inflammatory response compared with R7B. The mice infected with strain M5 under disulfiram treatment exhibited only half the life expectancy of those infected with M5 alone, suggesting that acetaldehyde produced by M. circinelloides contributes to the toxic effect in mice. These results demonstrate that the failure in fermentative metabolism, in the step of the production of ethanol in M. circinelloides, contributes to its virulence, inducing a more severe tissue burden and inflammatory response in mice as a consequence of acetaldehyde overproduction.

Clearance of Apoptotic Cells by Tissue Epithelia: A Putative Role for Hepatocytes in Liver Efferocytosis

Toxic substances and microbial or food-derived antigens continuously challenge the liver, which is tasked with their safe neutralization. This vital organ is also important for the removal of apoptotic immune cells during inflammation and has been previously described as a “graveyard” for dying lymphocytes. The clearance of apoptotic and necrotic cells is known as efferocytosis and is a critical liver function to maintain tissue homeostasis. Much of the research into this form of immunological control has focused on Kupffer cells, the liver-resident macrophages. However, hepatocytes (and other liver resident cells) are competent efferocytes and comprise 80% of the liver mass. Little is known regarding the mechanisms of apoptotic and necrotic cell capture by epithelia, which lack key receptors that mediate phagocytosis in macrophages. Herein, we discuss recent developments that increased our understanding of efferocytosis in tissues, with a special focus on the liver parenchyma. We discuss the impact of efferocytosis in health and in inflammation, highlighting the role of phagocytic epithelia.

Ethanol suppresses phagosomal adhesion maturation, Rac activation, and subsequent actin polymerization during FcγR-mediated phagocytosis

Clinical and laboratory investigations have provided evidence that ethanol suppresses normal lung immunity. Our initial studies revealed that acute ethanol exposure results in transient suppression of phagocytosis of Pseudomonas aeruginosa by macrophages as early as 3 h after initial exposure. Focusing on mechanisms by which ethanol decreases macrophage Fcγ-receptor (FcγR) phagocytosis we targeted the study on the focal adhesion and cytoskeletal elements that are necessary for phagosome progression. Ethanol inhibited macrophage phagocytosis of IgG-coated bead recruitment of actin to the site of the phagosome, dampened the phosphorylation of vinculin, but had no effect on paxillin phosphorylation suggesting a loss in "phagosomal adhesion" maturation. Moreover, our observations revealed that FcγR-phagocytosis induced Rac activation, which was increased by only 50% in ethanol exposed cells, compared to 175% in the absence of ethanol. This work is the first to show evidence of the cellular mechanisms involved in the ethanol-induced suppression of FcγR-mediated phagocytosis.

Late preconditioning by ethanol is initiated via an oxidant-dependent signaling pathway

Ingestion of alcoholic beverages at low to moderate levels 24 h prior to ischemia and reperfusion (I/R) prevents postischemic leukocyte/endothelial cell adhesive interactions, a phenomenon referred to as late ethanol preconditioning (EtOH-PC). The aim of this study was to determine whether oxidants act as initiators of late EtOH-PC. Ethanol was instilled into the stomachs of C57BL/6 mice as a bolus by gavage at a dose that produced a peak plasma concentration of 45 mg/dl 30 min after administration and returned to control levels 60 min after ingestion. Twenty four hours later, the superior mesenteric artery was occluded for 45 min followed by 70 min of reperfusion. The numbers of rolling and firmly adherent leukocytes were quantified in postcapillary venules of the small intestine in sham animals (no EtOH-PC, no I/R), in mice subjected to I/R alone or EtOH-PC + I/R, and in animals treated with Mn-TBAP (a cell-permeant superoxide dismutase mimetic), oxypurinol (a XO inhibitor), the NAD(P)H oxidase inhibitors PR-39 or apocynin, or oxypurinol plus PR39 during the period of EtOH-PC on Day 1 followed by I/R on Day 2. In separate groups of mice, oxypurinol or apocynin were also administered 1 h after ethanol ingestion on Day 1, with induction of I/R 24 h later. I/R induced marked increases in leukocyte rolling and adherence, effects that were completely prevented by EtOH-PC. Coincident treatment with Mn-TBAP, oxypurinol, PR-39, apocynin, or oxypurinol plus PR-39 with ethanol attenuated these anti-inflammatory actions of EtOH-PC. However, administration of oxypurinol or apocynin 1 h after ethanol ingestion failed to prevent these protective effects of EtOH-PC. Our results indicate that reactive oxygen species formed during the period of ethanol exposure on Day 1 trigger the development of an anti-inflammatory phenotype that renders the small bowel resistant to the proadhesive effects of I/R 24 h later.

Isotonic ethanol inhibits the generation of superoxide anion in neutrophils by inducing cell expansion

The effects of ethanol on the production of oxygen-derived free radicals by neutrophils are controversial. Osmolarity-mediated alteration of cell volume appears to be an important mechanism for regulating neutrophil activity. We investigated in neutrophils from healthy volunteers the effect of isotonic/hypertonic ethanol on both chemiluminescence amplified by a Cypridina luciferin analog in response to N-formyl-Met-Lue-Phe and cell volume measured with a Coulter counter. Both isotonic and hypertonic ethanol significantly decreased chemiluminescence in a dose-dependent manner. Isotonic ethanol produced a greater magnitude of inhibition than hypertonic ethanol (P<0.01). Another permeable molecule, urea, and hypotonic solution had the same effects on chemiluminescence. Isotonic and hypertonic ethanol caused a prompt cell expansion and shrinking, respectively. On the other hand, isotonic sucrose, an impermeable molecule, was ineffective in both chemiluminescence and cell volume changes. These data suggest that isotonic ethanol inhibits the superoxide anion production by inducing cell expansion probably due to increased intracellular osmotic pressure caused by rapid ethanol permeation through the plasmalemma. This impaired neutrophil function may, in some part, contribute to the susceptibility to infection in alcoholics.

A low concentration of ethanol reduces the chemiluminescence of human granulocytes and monocytes but not the tumor necrosis factor alpha production by monocytes after endotoxin stimulation

The ability of polymorphonuclear neutrophils (PMNs) and monocytes (Mphi) to produce reactive oxygen species (ROS) has been related closely to their potential in the killing of microorganisms. Ethanol has been shown to impair the generation of ROS in these phagocytes after stimulation with some immunogens and to increase the susceptibility of alcohol abusers to infectious diseases. As endotoxemia is common in alcohol abusers, we investigated the effect of ethanol (21.7 mmol/liter) on the luminol-amplified chemiluminescence of PMNs and Mphi after endotoxin stimulation and the release of tumor necrosis factor alpha (TNF-alpha) from Mphi. Further, the efficiency of ethanol to inactivate chemically generated ROS was tested. Significant stimulation of ROS release occurred at endotoxin concentrations of 1 ng/ml or higher in both PMNs and Mphi. Ethanol significantly suppressed the formation of ROS in both cell types, the decrease being more pronounced in Mphi (-73. 8%) than in PMNs (-45.7%). The correlations between endotoxin concentration and the amount of released ROS showed a dose-dependent, sigmoidal course. Concentrations of endotoxin necessary for half-maximum stimulation were nearly identical (6 to 8 ng/ml) in both PMNs and Mphi, independent of the presence of ethanol. In contrast to ROS formation, ethanol had no effect on the amount of TNF-alpha produced by endotoxin-stimulated Mphi. Ethanol was shown to be unable to decrease the levels of chemically generated ROS under physiological conditions. Therefore, ethanol cannot be assumed to be an "antioxidative" compound but rather seems to modify processes of endotoxin recognition, intracellular signal transduction, or metabolism.

Ethanol enhances the IFN-gamma, TGF-alpha and IL-6 secretion in psoriatic co-cultures

Evidence suggests an association between alcohol consumption and psoriasis. This relationship is still undefined, although long-term alcohol intake influences the immune system. Interactions between T cells and keratinocytes are important for the pathogenesis of psoriasis, by secretion of pro-inflammatory cytokines and growth factors in psoriatic skin. IL-2, IL-6, IL-8, IFN-gamma and TGF-alpha are hallmark cytokines in a psoriatic cytokine network. We investigated whether ethanol influences the secretion of these cytokines using a co-culture model with keratinocytes from psoriatic patients (n = 9) or from healthy controls (n = 9), with HUT 78 lymphocytes, and determined the cytokine levels with or without ethanol treatment in the culture supernatants. TGF-alpha and IFN-gamma levels were elevated in the ethanol-treated psoriatic co-cultures, to 150% and 175% respectively, but neither in co-cultures with keratinocytes derived from healthy control individuals nor in monocultures. Treatment with ethanol elevated slightly the IL-6 levels in the monocultures from psoriatic and control keratinocytes to 125% but not in HUT 78 monocultures. In the psoriatic co-cultures, IL-6 levels were elevated in the culture supernatants to almost 160%, but they were not influenced by ethanol in co-cultures with control keratinocytes. The cytokine levels of IL-8 or IL-2 were not significantly influenced in the psoriatic mono- and co-cultures or in HUT 78 cultures. If ethanol influences the cytokine secretion of psoriatic keratinocytes and HUT 78 lymphocytes in co-culture conditions, these data suggest that ethanol could also influence the psoriatic cytokine network in vivo, which may explain the explain the aggravation of this disease in alcohol-consuming psoriatic patients.

In vitro effects of ethanol on polymorphonuclear leukocyte membrane receptor expression and mobility

The hampered inflammation and host defense seen in alcoholics may be due to impairment of functional responses of neutrophil polymorphonuclear leukocytes (PMN). We have shown that ethanol inhibits the oxidative metabolism of PMN induced by surface receptor dependent stimuli, such as N-formyl-methionyl-leucyl-phenylalanine (fMLP) and opsonized zymosan. Because the unresponsiveness might be due to reduced numbers of surface receptors, we assessed the expression of CR1, Fc-gamma, and fMLP receptors as well as membrane fluidity after treatment of PMN with ethanol in vitro. Ethanol impaired the induced expression of CR1 and fMLP receptors to 71% and 51% of control, respectively, but did not affect the resting level of CR1 nor Fc-gamma receptor expression. Furthermore, the mobility of cell membrane glycoconjugates was increased by ethanol. However, phagocytosis, a functional response dependent on membrane rheology, was unaffected. Because the results indicated an effect of ethanol on mobilization of receptors from intracellular stores, we assessed lactoferrin release, which was reduced to 59%. Thus, ethanol appeared to hamper the upregulation of PMN surface receptors or functional subsets of those stored in granules. Ethanol also increased the mobility of the cell membrane. These reactions were accompanied by reductions in the functional responses mediated by either class of receptors.

Ethanol affects leukotriene generation and leukotriene-induced functional responses in human polymorphonuclear granulocytes

Since ethanol has been shown to inhibit the inflammatory response, we evaluated whether ethanol affected generation of leukotrienes in polymorphonuclear granulocytes (PMN) in vitro. Using the calcium ionophore A23187 as stimulus, the leukotriene B4 (LTB4) and leukotriene C4 (LTC4) generation were dose-dependently impaired by ethanol. No significant difference in the levels of the omega-oxidized metabolites was observed. However, the total LTB4 production (LTB4 plus omega-oxidized metabolites) was significantly decreased in the samples treated with ethanol. Furthermore, ethanol also modulated LTB4-induced functional responses. PMN aggregation, oxidative metabolism and elastase release were all inhibited in the presence of 1% ethanol (to 74 +/- 15%, 50 +/- 4% and 57 +/- 3% of controls, respectively). However, ethanol had no effect on intracellular calcium mobilization or on the change of the PMN membrane potential induced by either LTB4 or A23187. Thus, a possible mechanism for the reduced functional PMN responses in the presence of ethanol might be impaired generation of leukotrienes, but it is conceivable that ethanol impairs also other steps of the stimulus response coupling since the LTB4-induced functional responses were inhibited.

Rabbit polymorphonuclear granulocyte function during ethanol administration--migration and oxidative responses in a joint with immune complex synovitis

Functional impairments of polymorphonuclear granulocytes (PMN) are believed to contribute to hampered inflammation and host defence in alcoholics. We studied effects of i.v. ethanol administration on PMN responses in rabbits during induction of a knee-joint synovitis. The synovitis conferred systemic effects, since chemiluminescent responses of peripheral blood PMN to opsonized zymosan and phorpbol myristate acetate (PMA) increased 6.4- and 17.9-fold, respectively. Chemiluminescent responses of synovial PMN were further amplified. This up-regulation was reduced to 33% in rabbits treated with ethanol when opsonized zymosan was used as the PMN stimulus; in contrast, PMA responses were unaffected. The appearance and migration of PMN to the synovitis joint were normal despite a blood ethanol concentration of 0.5%. Thus, ethanol impaired release of oxygen metabolites from PMN, but not the delivery of cells at an inflammatory site.

Immunosuppression in adult female B6C3F1 mice by chronic exposure to ethanol in a liquid diet

The overall objective of these studies was to characterize the effects of ethanol on the immunocompetence of adult female B6C3F1 mice. To obtain a significant suppression in the antibody response to SRBC, splenocytes from untreated mice had to be directly exposed to concentrations of ethanol from 0.3% to 3.0%, or to acetaldehyde at concentrations greater than 0.03%. We do not believe that these results are consistent with a role by a direct effect by either ethanol or its primary metabolite because these concentrations are higher than what could be obtained as reasonable blood levels. For in vivo exposure, we employed a pair-feeding regimen which was based on a liquid diet containing 5% ethanol (v/v) that provided 36% of the caloric intake as ethanol. Our results indicated that there was a definite temporal relationship to the consequent suppression of the antibody response to SRBC in that no effect was observed after 14 days exposure, and that the magnitude of the suppression increased from 18% after 21 days to 70% after 42 days. We also monitored the liver for histopathology and observed that the ethanol-induced liver damage was restricted to steatosis (fatty liver), which was also manifested with time and which was most pronounced after 42 days exposure. In contrast to our results with the in vivo antibody response, we saw no effect on mitogen-induced proliferation by splenocytes from ethanol-treated mice. These results prompted us to measure in vitro antibody responses by splenocytes from ethanol-treated mice. We saw no suppression of the in vitro antibody responses to SRBC, DNP-Ficoll or LPS after any length of exposure to ethanol, and speculated that the basis for the suppression of the in vivo antibody response was an indirect consequence of exposure. We subsequently determined that when normal splenocytes were cultured in 5% serum from ethanol-exposed mice (42-day group), there was a > 80% suppression relative to the serum from the pair-fed controls. As important controls for these studies, we have demonstrated that there was no difference between the responses of normal lymphocytes cultured in 5% normal mouse serum and in 5% serum taken from the pair-fed restricted controls. A determination of the ethanol content in the serum from ethanol-exposed mice (42-day group) indicated that the amount of ethanol present in these cultures was < 0.003%.(ABSTRACT TRUNCATED AT 400 WORDS)

Ethanol causes accelerated G1 arrest in differentiating HL-60 cells

The effects of clinically relevant ethanol concentrations on myeloid differentiation in the HL-60 cell promyelocytic leukemia line have been studied. The exposure of noninduced stem cells to 60 mM ethanol results in an increase in G1 cells, but there is no increase in superoxide production or expression of the Mo1 antigen. When HL-60 cells are induced to differentiate along the myeloid line with dimethylsulfoxide (DMSO) or retinoic acid (RA), there is a shift to smaller cell size, an increase in G1 cells and acquisition of the ability to produce superoxide as reported previously by several authors. When ethanol is present during differentiation, there are further increases in G1 cells, and increases in the percentage of cells which produce superoxide and express Mo1, and decreases in mean cell size and total growth during the incubation period. Regrowth experiments after periods of differentiation indicate that the increased G1 arrest seen in the presence of ethanol represents terminal commitment if inducer is present, but in the absence of inducer the increased G1 percentage is readily reversible. Examination of RNA content by flow cytometry reveals a decrease in both the peak and mean G1 RNA content during DMSO or RA induced differentiation. These decreases are accentuated by the presence of ethanol, resulting in a higher G1A/G1B ratio than in nonexposed cells. These findings indicate that ethanol enhances G1 growth arrest in HL-60 cells exposed to myeloid inducers. Partial differentiation occurs during this process, resulting in terminally arrested cells, some of which have undergone fewer postinduction cell divisions than normal and may not be fully competent.

Ethanol-induced injury to the rat gastric mucosa. Role of neutrophils and xanthine oxidase-derived radicals

Ethanol-induced gastric mucosal injury closely resembles an inflammatory response. Thus, in vivo and in vitro experimental models were used to assess whether ethanol is proinflammatory in concentrations likely to be encountered by the gastric mucosa during acute intoxication. Perfusing the rat gastric lumen with progressively increasing concentrations of ethanol (10%, 20%, and 30%) resulted in a dose-dependent increase in 51Cr-ethylenediaminetetraacetic acid clearance from blood-to-gastric lumen. Rendering the animals neutropenic (with antineutrophil serum) ameliorated the ethanol-induced mucosal injury; the degree of protection was directly related to the severity of neutropenia. Neither superoxide dismutase, catalase, nor sodium benzoate offered any protection against ethanol-induced injury, indicating that neither superoxide anion, hydrogen peroxide, nor the hydroxyl radical is involved. To assess further whether ethanol could exert proinflammatory effects an in vitro model consisting of cultured bovine microvascular endothelial cells and isolated human neutrophils was used. Ethanol at concentrations of 1.0%-4.0% (but not at 0.1%-0.5%) increased neutrophil adherence to endothelial cells and enhanced neutrophil-mediated endothelial cell injury. We conclude that ethanol is proinflammatory at concentrations that may be achieved in the gastric mucosa during acute intoxication. The ethanol-induced, neutrophil-mediated cell injury does not appear to involve oxy radicals.

Kupffer cell function in chronic ethanol-fed rats

In an attempt to clarify the Kupffer cell function in alcoholism, chronic ethanol-fed rats were investigated. The clearance of latex particles in the rat was analysed to estimate the function of the reticuloendothelial system in the liver, and the phagocytic function of Kupffer cells was measured by counting particles in the cell after isolation of non-parenchymal cells by collagenase digestion of the liver following an injection of latex particles and subsequently by staining of endogenous peroxidase activities. In addition, the number of Kupffer cells and their phagocytic function were examined histologically in fresh frozen sections of liver after an injection of particles. Serum ethanol concentration in the ethanol-fed rats was 10-60 mumol/l. The clearance of latex particles was markedly reduced in the ethanol-fed rats as compared with the paired controls (P less than 0.01). Markedly decreased-phagocytic function was found in 20% of Kupffer cells in the chronic ethanol-fed rats. The number of Kupffer cells in the ethanol-fed rats was increased as compared with the paired control rats. Chemotaxis analysis revealed that hepatocytes when incubated with ethanol, produced chemotactic factor for Kupffer cells and polymorphonuclear cells. These abnormal Kupffer cell functions may contribute to the pathogenesis of alcoholic liver disease.

Reduced IgG Fc-receptor-mediated phagocytosis in human monocytes isolated from alcoholics

Blood monocytes (MC) were isolated from alcoholics and from age-matched controls. Phagocytosis mediated by the IgG Fc-receptor (Fc-R) was assessed in the MC immediately after isolation by using IgG-opsonized sheep erythrocytes as test particles. Experiments were also performed after preincubating the MC in medium containing 10% autologous serum with or without ethanol (80 mM) in vitro at 37 degrees C for 15 min, and with or without ethanol (80 mM) present during the internalization assay in vitro (37 degrees C for 60 min). MC from alcoholics exhibited lower phagocytic capacity via the Fc-R than MC from healthy controls, approximately 50% versus 70% phagocytosing cells. Preincubation of the MC in medium containing 10% autologous serum with 80 mM ethanol, reduced the percentage of phagocytosing MC from controls to 55%, whereas no further reduction occurred in cells from alcoholics. When present during the assays of Fc-R function, ethanol decreased MC phagocytosis of IgG-coated particles significantly in both test groups, to about 30% phagocytosing cells. Blood samples disclosed increased serum levels of markers of liver dysfunction, immunoglobulins, increased sedimentation rate, and white blood cell counts among the alcoholics, while their serum levels of 1,25-dihydroxyvitamin D3 were reduced.

Effects of ethanol on mechanisms for secretory and aggregatory responses of human granulocytes

Since the mechanisms for inhibitory effects of ethanol on polymorphonuclear (PMN) leukocyte function are largely unknown we studied secretory and aggregatory responses after in vitro treatment of PMN with ethanol. Oxidative metabolism (assessed by chemiluminescence, superoxide ion production and oxygen consumption) and aggregation were reduced dose-dependently in the presence of ethanol when elicited by stimuli binding to surface receptors or other structures (fMLP and ConA). Similar results were obtained with non-receptor-dependent stimuli, as NaF and the calcium ionophore A23187. In contrast, phorbol myristate acetate peak responses were not affected. FMLP induced changes in Fura-2AM fluorescence (as a probe for fast intracellular calcium concentration changes) were, however, not influenced by ethanol. Neither were membrane potential changes [assessed by di-O-C5(3) fluorescence]. Thus, it is suggested that ethanol may impair a step of the stimulus-response-coupling in PMNs distal to the initial intracellular calcium mobilization.

Effects of two macrolide antibiotics on human leukocyte membrane receptors and functions

Polymorphonuclear granulocytes (PMNs) and lymphocytes from healthy persons were incubated in varying concentrations of erythromycin and RU 28965, a new macrolide antibiotic. Incubation in erythromycin - even in high dilutions - caused a significant increase in the percentage of PMNs bearing receptors for the Fc portion of IgG (Fc gamma R) and for C3b (C3bR) as measured by rosette formation with EA (erythrocyte-antibody) and EAC (erythrocyte-antibody-complement) indicator cells. This effect could not be removed by extended washing of the cells. Incubation in RU 28965 had a similar effect, except for a decrease in EA and EAC rosetting cells at high concentrations (200 mg/l). Phagocytosis, as measured by chemiluminescence, and random migration of PMNs were unaffected by erythromycin. Chemotaxis under agarose was decreased after incubation in erythromycin or RU 28965. Erythromycin incubation increased the percentage of lymphocytes bearing receptors for sheep erythrocytes (E), but had no effect on the proportion of lymphocytes rosetting with EA or EAC, or on lymphocyte responses to mitogens PHA, conA, or PWM.

Effects of ethanol on human monocyte IgG Fc receptors

The IgG Fc receptor function of human monocytes (Mo) exposed to ethanol in vitro was assessed by a rosette assay in which IgG-coated sheep red blood cells were used as test particles. Pre-incubation of Mo in autologous serum with ethanol (55 mM and above) for 15 min at 37 degrees C, caused a significantly lower percentage of Mo-forming rosettes. This reduction by ethanol was not observed when Mo were preincubated with ethanol in fetal calf serum or in serum-free conditions, but was present when Mo were pre-incubated with ethanol in serum-free media to which IgG (10-150 micrograms/ml) had been added. Donor-dependent differences were observed in the reduction of Mo-forming rosettes in the presence of autologous serum and ethanol. Mo allowed to form rosettes without ethanol were exposed to ethanol during a subsequent phagocytosis process. A dose-dependent inhibition of the internalization of test particles was found in Mo from all donors.