Ethanol ingestion impairs neutrophil bactericidal mechanisms against Streptococcus pneumoniae

Ethanol ingestion impairs both killing of selected pneumococcal strains by rat polymorphonuclear leukocytes (PMNL) in vitro and clearance of these same strains from experimentally infected rat lungs. To determine the mechanism(s) of this impairment, we isolated neutrophils (PMNL) by a magnetic cell sorting technique from the peripheral blood of chow-fed rats (C-PMNL) or rats pair fed for 7 days with a liquid diet providing 36% of its calories as either ethanol (E-PMNL) or dextrin-maltose (P-PMNL). Phagocytosis of fluorochrome-labeled bacteria and oxygen radical production, as determined by oxidation of dihydrorhodamine 123, were measured by flow cytometry. Degranulation, as determined by lysozyme release, was measured as lysis of a suspension of Micrococcus lysodeikticus. E-PMNL, P-PMNL, and C-PMNL were equivalent in their ability to phagocytose pneumococci and to produce an oxidative burst in response to stimulation by opsonized zymosan. However, E-PMNL produced fewer oxygen radicals and released less lysozyme than either P-PMNL or C-PMNL when stimulated by exposure to S. pneumoniae. There was no difference in oxygen radical production by E-PMNL and P-PMNL when stimulated with phorbol myristate acetate, but both cell types mounted a significantly reduced response in comparison to C-PMNL. These data suggest that ingestion of ethanol for 7 days significantly reduces both the oxidative burst and degranulation of rat PMNL in response to S. pneumoniae, thereby compromising anti-pneumococcal activity.