Correlation of ambient pollution levels and heavily-trafficked roadway proximity on the prevalence of smear-positive tuberculosis

Air Pollution Particulate Matter Alters Antimycobacterial Respiratory Epithelium Innate Immunity

“…Iztapalapa is the most populated of 16 municipalities in Mexico City and characterized by dense traffic, unregulated small industrial emissions, and elevated levels of air contamination (20). PM were sampled using continuously operating high-volume PM 10 and PM 2.5 samplers (GMW model 1200, volumetric flow control high-volume PM10 sampler; Sierra Andersen, Smyrna, GA, USA) with an airflow rate of 1.13 m 3 /min Ϯ 10%. PM 2.5 and PM 10 samples were collected on 20.3-by 25.4-cm cellulose nitrate membranes (Sartorius, Goettingen, Germany) with a nominal pore size of 3 m. Nitrocellulose membranes were removed from the samplers on alternate days, at least twice a week, and PM mechanically recovered from the membranes and pooled by month and particle size (PM 2.5 and PM 10 ).…”

“…PM 2.5 and PM 10 were weighed on a semimicrobalance (CPA225D; Sartorius, Bohemia, NY, USA) and placed into prewashed and baked (4 h at 200°C) glass flasks. Stock suspensions of PM 2.5 and PM 10 (1 mg/ml) were prepared by 5 min of sonication (model 351OR-DTH; Branson, Danbury, CT, USA) in F-12K medium enriched with 2% FBS and further diluted in complete culture medium to final concentrations of 0.1, 1, 10, and 50 g/ml.…”

“…A549 cells were exposed to either PM alone or to PM prior to infection with M. tuberculosis. For exposure to PM alone, after two washing steps with 1ϫ phosphate-buffered saline (PBS), semiconfluent A549 cells in 12-well plates (Corning) were exposed to PM 2.5 or PM 10 at final concentrations of 0 (unexposed controls), 0.1, 1, 10, and 50 g/ml in 1 ml of 2% FBS-enriched F-12K medium and incubated (37°C) for 18 h. For exposure to PM prior to infection with M. tuberculosis, semiconfluent A549 cells were exposed to PM 2.5 or PM 10 (0, 0.1, 1, 10, and 50 g/ml) (37°C for 18 h), washed twice with 1ϫ PBS, and then, in F-12K medium enriched with 2% FBS, infected with M. tuberculosis at an MOI of 10 (37°C for an additional 18 h). In detail, 2 h after the addition of M. tuberculosis suspension to the A549 cells, cells were washed twice with warm PBS to remove extracellular M. tuberculosis.…”

“…The viability of A549 cells following PM exposure and M. tuberculosis infection was assessed by an MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] proliferation assay using the CellTiter 96 aqueous one solution cell kit (Promega, Madison, WI, USA) according to the manufacturer's protocol. Briefly, A549 cells were plated in triplicate 96-well plate wells per condition, allowed to grow to semiconfluence, washed twice with 1ϫ PBS, and exposed to PM 2.5 or PM 10 at concentrations of 0, 0.1, 1, 10, 50, and 100 g/ml in 100 l of complete culture medium. The viability of the A549 cells was determined at 24, 48, and 72 h following exposure to PM alone or at 36 h following the initial 18-h exposures to PM and subsequent 18-h infection with M. tuberculosis.…”

“…Epidemiological studies have linked inhalation exposure to cigarette smoke (5-7), indoor air pollution (8,9), and urban air pollution (10) with increased risk of TB development. Mechanistic studies have demonstrated that cigarette smoke impairs antimycobacterial immune responses by decreasing the production of tumor necrosis factor alpha (TNF-␣) and interleukin 12 and increasing the production of IL-10.…”