The study was carried out to examine whether chronic exposure to smoke during daily household cooking with biomass fuel (BMF) elicits changes in airway cytology and expressions of Nrf2 (nuclear factor erythroid 2 [NF-E2]-related factor 2 [Nrf2]), Keap1 (Kelch-like erythroid-cell-derived protein with CNC homology [ECH]-associated protein 1), and NQO1 (NAD(P)H:quinone oxidoreductase 1) proteins in the airways. For this, 282 BMF-using women (median age 34 year) and 236 age-matched women who cooked with liquefied petroleum gas (LPG) were enrolled. Particulate matter with diameters of < 10 µm (PM10) and < 2.5 µm (PM2.5) were measured in indoor air with real-time laser photometer. Routine hematology, sputum cytology, Nrf2, Keap1, NQO1, and generation of reactive oxygen species (ROS) along with the levels of superoxide dismutase (SOD) and catalase were measured in both groups. PM10 and PM2.5 levels were significantly higher in BMF-using households compared to LPG. Compared with LPG users, BMF users had 32% more leukocytes in circulation and their sputa were 1.4-times more cellular with significant increase in absolute number of neutrophils, lymphocytes, eosinophils, and alveolar macrophages, suggesting airway inflammation. ROS generation was 1.5-times higher in blood neutrophils and 34% higher in sputum cells of BMF users while erythrocyte SOD was 31% lower and plasma catalase was relatively unchanged, suggesting oxidative stress. In BMF users, Keap1 expression was reduced, the percentage of AEC with nuclear expression of Nrf2 was two- to three-times more, and NQO1 level in sputum cell lysate was two-times higher than that of LPG users. In conclusion, cooking with BMF was associated with Nrf2 activation and elevated NQO1 protein level in the airways. The changes may be adaptive cellular response to counteract biomass smoke-elicited oxidative stress and inflammation-related tissue injury in the airways.
Keywords: Biomass smoke; Inflammation; Nrf 2/Keap1/NQO1; Oxidative stress; Particulate pollution; Sputum cytology.