Positive Health Online

Abstract

MUDWAY and colleagues, Rayne Institute, St Thomas Hospital, London UK write that ozone (O3) imposes an oxidative burden on the lung as a consequence of its oxidising character during exposure, and indirectly by engendering inflammation. The authors studied the impact of O3 upon the oxidation/reduction (redox) state of the fluid lining of the respiratory tract 6 hours following a challenge.

Background

Methodology

9 people were exposed in a double blind crossover control trial to air and 200 ppb O3 for 2 hours with an intermittent exercise and rest protocol. Blood samples were taken and lung function (forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), were assessed prior to, immediately following and 6 hours after exposure. Bronchoalveolar lavage (BAL) was performed 6 hours following challenge. Inflammation was assessed in BAL fluid and plasma and BAL fluid redox state determined by measuring antioxidants and markers of oxidative damage concentrations.

Results

6 hours following exposure, neutrophil numbers in BAL fluid increased 2.2-fold, which was accompanied by increased myeloperoxidase concentrations in BAL fluid. BAL fluid macrophage and lymphocyte numbers decreased 2.5-fold and 3.1-fold respectively. Of the antioxidants studied, only ascorbate in BAL fluid was affected by O3, falling in all individuals relative to air values. A marginal decrease in plasma ascorbate was also detected. The decrease in macrophage numbers appeared to be causally related to the increase in neutrophils, myeloperoxidase concentrations and ascorbate concentrations,; however no clear association was apparent between ascorbate changes and neutrophils or myeloperoxidase concentration following O3.

Conclusion

Ascorbate in the fluid lining the respiratory tract is depleted as a consequence of O3 exposure at 6 hours following exposure, which was contemporaneous with but not quantitatively related to the increased neutrophil numbers and myeloperoxidase concentrations. Decreased macrophage numbers 6 hours following O3 related to the degree of neutrophilic inflammation with populations conserved where ascorbate concentration in the fluid lining the respiratory tract were high following exposure. These results imply that ascorbate has a critical protective role against inflammatory oxidative stress induced by O3 .

References

Mudway IS et al. Compromised concentrations of ascorbate in fluid lining the respiratory tract in human subjects after exposure to azone. Occupational and Environmental Medicine 56(7): 473-81. Jul 1999.