[The role of heme oxygenase 1 in hydrogen peroxide induced apoptosis and mitochondrial trans membrane potential change in rat primary type II alveolar epithelium cells].

OBJECTIVE: To understand the role of heme oxygenase-1 (HO-1) in hydrogen peroxide [H(2)O(2)] induced apoptosis and mitochondrial trans-membrane potential (MTMP) change in primary alveolar epithelial cell type II(AEC II). METHODS: Primary AEC II collected from healthy Sprague Dawley (SD) rats were cultured for 24 hours, then divided into four groups to be treated with: (1) saline; (2) H(2)O(2) (0.5 mmol/L); (3) H(2)O(2) +HO-1 (0.2 mmol/L); (4) H(2)O(2) +zinc original porphyrin IX (HO-1 inhibitor, 20 μmol/L). The morphology of cells in the cultures was examined by fluorescent microscopy 2.5 hours later, and the number of apoptotic cells / the MTMP determined by flow-cytometry 0.5, 1.0, 1.5, 2.0 and 2.5 hours later. RESULTS: Large number of cells in with green (early apoptotic) or red (later apoptotic) fluorescence were observed by microscope in cultures treated with H(2)O(2) , and H(2)O(2) + HO-1 inhibitor, but such cells were obviously fewer in HO-1 treated cultures. Compared with saline treated cells, H(2)O(2) treated cells had significantly higher apoptosis rate, that increased with time, reaching peak value 2.5 hours into the treatment [0.5 hour: (30.27 ± 0.74)% vs. (3.76 ± 0.81)%, 2.5 hours: (40.46 ± 0.91)% vs. (22.74 ± 0.60)%, both P < 0.05], while the rate of MTMP depolarization was significantly lower (0.99 ± 0.21 vs. 1.91 ± 0.16, P < 0.05) in these cells. Compared with H(2)O(2) treated cells, the apoptosis rate in HO-1 treated cells was significantly lower [0.5 hour: (5.99 ± 0.60)% vs. (30.27 ± 0.74)%, 2.5 hours: (22.69 ± 1.69)% vs. (40.46 ± 0.91)%, both P < 0.05], and their rate of MTMP depolarization higher (2.02 ± 0.12 vs. 0.99 ± 0.21, P < 0.05). Compared with HO-1 treated cells, HO-1 inhibitor treated cells had significantly higher apoptosis rate which reached peak value 2.5 hours into the treatment [0.5 hour: (30.73 ± 1.08)% vs. (5.99 ± 0.60)%, 2.5 hours: (41.38 ± 0.57)% vs. (22.69 ± 1.69)%, both P < 0.05], while rate of MTMP depolarization in these cells was significantly lower (0.98 ± 0.09 vs. 2.02 ± 0.12, P < 0.05). CONCLUSION: HO-1 could maintain the integrity of AEC II and stabilize their mitochondria membrane potential, protecting the cells from H(2)O(2) induced damage.