PRIMARY AND IMMORTALIZED (BEAS 2B) HUMAN BRONCHIAL EPITHELIAL-CELLS HAVE SIGNIFICANT ANTIOXIDATIVE CAPACITY IN-VITRO

Antioxidant enzymes located in the bronchial epithelium can be expecte d to be important in protecting these cells against both endogenous an d exogenous oxidants. In this study, human bronchial epithelial cells were isolated and cultured from specimens obtained from donors for lun g transplantation. The levels and relative importance of different ant ioxidant enzymes were also assessed using an immortalized human bronch ial epithelial cell line (BEAS 2B cells). Immunocytochemical studies s howed a similar pattern of intracellular localization with the moderat e degrees of labeling for Mn superoxide dismutase (SOD), CuZn SOD, and catalase in freshly isolated bronchial epithelial cells, bronchial ep ithelial cells in primary culture, and BEAS 2B cells. CuZn SOD and cat alase decreased in labeling density whereas Mn SOD was unchanged when bronchial epithelial cells were placed in primary cultures. In contras t, Mn SOD and catalase were decreased in BEAS 2B cells compared with p rimary cultures. Although Mn SOD was low in BEAS 2B cells, it could be significantly induced by tumor necrosis factor treatment. Biochemical analysis showed remarkably similar catalase and glutathione reductase activities in primary cultured epithelial cells and BEAS 2B cells. Pr imary cultured cells and BEAS 2B cells also consumed exogenous H2O2 at approximately the same rate (100 and 80 nmol H2O2/mg protein/15 min, respectively), indicating similar antioxidative capacities against exo genous H2O2. In BEAS 2B cells, neither catalase nor the glutathione re dox cycle alone was responsible for the H2O2 consumption; inactivation of catalase and glutathione reductase decreased H2O2 consumption mark edly (77% during a 40-min incubation). In conclusion, BEAS 2B cells ma y represent an appropriate, stable, in vitro model to investigate the role and regulation of antioxidant enzymes in epithelial cell defense and injury.