Ethanol Impairs Mechanisms of Macrophage Phagocytosis and Cytokine Production

<p>Extensive evidence indicates that alcohol (ethanol) consumption affects human health by altering normal physiological functions of the immune system. This study investigated the effect of a single <italic>in vivo</italic> exposure of macrophages to clinically relevant levels of ethanol (1.2 and 2.2 g/kg). Following 3 hour exposure, both doses of ethanol decreased <italic>ex vivo</italic> TNF&alpha; production by splenic and alveolar macrophages (AMs). Interestingly, the higher dose of ethanol resulted in sustained suppression of LPS-induced TNF&alpha; production at 3 and 6 hours post ethanol administration, as well as decreased IL-6 and IL-12 production after 6 hours, compared control treated groups. LPS or <italic>E. coli</italic>-stimulated production of TNF&alpha; and IL-6 by AMs were reduced at 3 hours after ethanol administration, compared to the saline treated animals. Additionally, acute <italic>in vivo</italic> (2.2 g/kg) or <italic>in vitro</italic> (50 mM) ethanol exposure transiently decreased AMs and RAW264.7 murine macrophage phagocytosis of <italic>Pseudomonas aeruginosa</italic> as early as 3 hours after initial exposure, with functional recovery by 24 hours. To investigate a single receptor pathway, we focused on Fcgamma-receptor (FcgammaR) mediated phagocytosis. In ethanol treated murine AMs and the RAW264.7 cells, phagocytosis of IgG-coated beads demonstrated a 40 and 50% reduction in actin recruitment to the site of the phagosome compared control conditions. Prior to actin polymerization, the phagocytic response requires recruitment of the adhesion molecules paxillin and vinculin, forming a structure we term "phagosomal adhesion". Ethanol did not alter paxillin phosphorylation during phagocytosis via the FcgammaR-pathway but suppressed vinculin phosphorylation, suggesting a defect in phagosomal adhesion maturation. Small GTPases are known to regulate normal actin polymerization. RAW264.7 cells exposed to NSC23766 (a Rac1 inhibitor) show 45% suppression in actin polymerization to the phagosome, regardless of ethanol exposure. This underscores the importance of normal Rac activity during FcgammaR-mediated phagocytosis. Following 15 minutes of IgG-coated bead phagocytosis, Rac activation increases by only 50% in ethanol exposed cells, compared to 175% in control conditions. Taken together, we conclude that the suppressive effects of clinically observed levels of ethanol are dose dependent, have effects that last after clearance of the ethanol from circulation, and can affect multiple macrophage functions.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Cell Biology, Neurobiology and Anatomy

Year dc:date.available

2010

Author dc:creator

• Karavitis, John

• actin
• adhesion
• Alcohol
• cytoskeleton
• Fc gamma Receptor
• phagosomal adhesion
• Immunology and Infectious Disease

Repository record dc:identifier

https://ecommons.luc.edu/luc_diss/165

OAI identifier oai:identifier

oai:ecommons.luc.edu:luc_diss-1164