title: Cigarette smoke extract-induced suppression of caspase-3-like activity impairs human neutrophil phagocytosis.
abstract: Neutrophils are the primary inflammatory cell in smokers' lungs, but little is known about the ability of cigarette smoke to modulate neutrophil function. Neutrophils undergo caspase-3-dependent spontaneous, as well as phagocytosis-induced, apoptosis. This study investigated the ability of cigarette smoke extract (CSE) to alter neutrophil caspase-3 activity, apoptosis, and phagocytosis. CSE treatment resulted in a dramatic suppression of neutrophil caspase-3-like activity, which correlated with reduced cleavage of glutamate-L-cysteine ligase catalytic subunit, a known target of active caspase-3. CSE did not affect procaspase-3 processing to its active fragment, suggesting a direct effect of CSE on active caspase-3. Consistent with this, CSE inhibited active recombinant caspase-3 activity, which was abolished by dithiothreitol, suggesting a redox-sensitive mechanism. CSE-induced suppression of caspase-3 activity did not alter spontaneous apoptosis but did impair phagocytic activity. Since CSE treatment resulted in profound suppression of caspase-3 activity but did not alter apoptosis, the possibility of a threshold level of caspase-3 activity was investigated. CSE reduced caspase-3 activity in a concentration-dependent manner. Despite near complete suppression of caspase-3 activity, spontaneous apoptosis was not altered. Conversely, treatment with the pan-caspase inhibitor, Z-Val-Ala-Asp-fluoromethylketone, reduced spontaneous apoptosis. These data demonstrate that CSE does not suppress caspase-3 activity below a threshold level to prevent spontaneous apoptosis, but the level of inhibition is sufficient to impair neutrophil phagocytic activity. These divergent functions of caspase-3 may contribute to the persistence of neutrophils in the lungs of smokers, as well as be a factor in their higher incidence of community-acquired pneumonia.
authors.affiliation: Dept. of Clinical Pharmacy, School of Pharmacy, Box C238, Univ. of Colorado Health Sciences Center, 4200 East Ninth Ave., Denver, CO 80262, USA. stringek@umich.edu
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Stringer
authors.forename: Meghan
authors.initials: M
authors.lastname: Tobias
authors.forename: Heidi C
authors.initials: HC
authors.lastname: O'Neill
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Franklin
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000276:immunology; D053148:Caspase 3 / Q000378:metabolism*; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D009504:Neutrophils / Q000276:immunology*; D010587:Phagocytosis / Q000276:immunology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000276:immunology*; D012907:Smoking / Q000009:adverse effects* / Q000276:immunology*; D014028:Tobacco Smoke Pollution
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D014028:Tobacco Smoke Pollution; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D053148:Caspase 3