Tobacco smoke modulates ozone-induced toxicity in rat lungs and central nervous system

Abstract

Adult Sprague-Dawley (SD) male rats were exposed for a single 3 h period to air, ozone (O3) or O3 followed by tobacco smoke (O3/TS). For pulmonary effects, bronchoalveolar lavage (BAL) cells and fluid were analyzed. Data revealed a significant increase in polymorphonuclear leukocytes (PMN), total protein and albumin concentrations in the O3 group, reflecting inflammatory and toxic responses. A subsequent exposure to TS attenuated PMN infiltration into the airspaces and their recovery in the BAL. A similar reduction was observed for BAL protein and albumin in the O3/TS group, but it was not statistically significant. We also observed a significant increase in BAL total antioxidant capacity following O3 exposure, suggesting development of protective mechanisms for oxidative stress damage from O3. Exposure to TS attenuated the levels of total antioxidant capacity. Lung tissue protein analysis showed a significant reduction of extracellular superoxide dismutase (EC-SOD) in the O3 or O3/TS group and catalase in the O3/TS group. TS further altered O3-induced EC-SOD and catalase protein expression, but the reductions were not significant. For effects in the central nervous system (CNS), we measured striatal dopamine levels by HPLC with electrochemical detection. O3 exposure produced a nonsignificant decrease in the striatal dopamine content. The effect was partially reversed in the O3/TS group. Overall, the results show that the toxicity of O3 in the lung is modulated by TS exposure, and the attenuating trend, though nonsignificant in many cases, is contrary to the synergistic toxicity predicted for TS and O3, suggesting limited cross-tolerance following such exposures.