Research Program Area: Health & Exposure
This study measured ex-vivo production of pro-inflammatory cytokines by pulmonary macrophages. The macrophages were isolated from bronchoalveolar lavage fluid (BALF) obtained from human subjects who had under gone controlled exposures to ozone (O3), nitric acid (HNO3) or both together. The study was based on the premise that pulmonary macrophages are activated by exposure to O3 and HN03 vapor, and that they will continue to secrete cytokines after removal from BALF. The cytokines of interest included tumor necrosis factor-alpha (TNF-a), interleukin-l-beta (IL-I-p), interleukin-6 (IL-6), interleukin-8 (IL-8) and macrophage inflammatory protein-l-alpha (MIP-l-a). Cells from BALF were suspended in culture medium, and were plated in microwells. After one hour of incubation at 37°C in 95% air and 5% CO2 non-adherent cells were removed and fresh cell culture media was added to the microwells. Cell culture supernatant was removed after 3, 24 and 48 hours of incubation and was frozen for subsequent analysis by an enzyme-linked immunosorbent (ELISA) method. The results showed that the concentration of all five cytokines was greater at 24 hours than three hours of incubation. Only IL-8 and MIP-1-a were increased at 48 hours of incubation, compared to 24 hours. Since both IL-8 and MIP-1-a production are induced by TNF-a and IL-I-P, it makes sense that their peak values would occur after those for TNF-a and lL-1-p. There were no significant differences between production of any cytokine following a single four-hour exposure to 0.20 parts per million (PPM) 03 compared to equivalent exposures on four consecutive days. There were few significant differences in cytokine production between the exposures to 03 alone, HN03 alone and 03+HN03. After three hours of incubation, only TNF-a varied by protocol, with the lowest synthesis following the combination exposure and the largest following the HN03 exposure. A similar statistically significant pattern was present for MIP-1-a after 48 hours of incubation. This suggests that 03 may attenuate the effect of HN03, possibly by reduction in TNF-a secretion. Since TNF-a is one of the first inflammatory cytokines secreted, and since TNF-a induces secretion of other cytokines, reduction in production of TNF-a may lead to reduction in secretion of other inflammatory cytokines and thereby to reduction of inflammation with the combined exposure.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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