Acetaminophen decreases intracellular glutathione levels and modulates cytokine production in human alveolar macrophages and type II pneumocytes in vitro

Recent epidemiological observations suggest that acetaminophen (paracetamol) may contribute to asthma morbidity. Impaired endogenous antioxidant defences may have a role in the pathogenesis of a number of inflammatory pulmonary diseases, including asthma. We studied the effect of acetaminophen on the intracellular level of reduced glutathione (GSH) with and without inhibitors of cytochrome P450 or prostaglandin H synthetase, and TNF-α, IL-6 and IL-8 protein production in human alveolar macrophages and type II pneumocytes in vitro. Following a 20 h incubation with acetaminophen, cytotoxicity was apparent from ≥5 and ≥10 mM in macrophages and type II pneumocytes, respectively. A time- and concentration-dependent decrease of intracellular GSH occurred after acetaminophen (0.05-1 mM) exposure (1-4 h) in pulmonary macrophages (up to 53%) and type II pneumocytes (up to 34%). Diethyldithiocarbamic acid, potassium ethyl xanthate, and indomethacin decreased significantly acetaminophen-induced GSH depletion in the two cell types tested, suggesting the involvement of cytochrome P450 (mainly CYP2E1) and/or prostaglandin H synthetase. In macrophages, acetaminophen decreased the secretion of TNF-α (at 4 and 24 h, concentration-related) and IL-6 (at 24 h, at 0.1 mM), and did not affect significantly IL-8 production. These in vitro observations demonstrate that clinically relevant concentrations of acetaminophen decreased: (i) intracellular GSH in human pulmonary macrophages and type II pneumocytes and (ii) the secretion of TNF-α and possibly IL-6 by human pulmonary macrophages. These findings provide experimental plausibility to the challenging observations that frequent use of APAP may be a risk factor for asthma morbidity.