[The effect of heme oxygenase-1 on apoptosis and aquaporin-1 expression in type II primary alveolar epithelial cells in rat].

OBJECTIVE: To explore the effect of heme oxygenase-1 (HO-1) on apoptosis and expression of aquaporin-1 (AQP-1) in primary type II alveolar epithelial cells (AECII) in rats with hydrogen peroxide (H₂O₂) induced oxidative damage. METHODS: Lung tissue of male Sprague-Dawley (SD) rats was collected. Primary AECII were isolated, purified, and cultured for 24 hours, then they were divided into four groups: (1) normal group (treated with normal saline); (2) H₂O₂ injury group (treated with H₂O₂ 0.5 mmol/L); (3) HO-1 control group (treated with HO-1 1 μmol/L); (4) HO-1 protection group (treated with HO-1 1 μmol/L and H₂O₂ 0.5 mmol/L). Cells of each group were cultured for 12 hours after various treatment. The cell suspension was collected before and 1, 3, 6, 12 hours after treatment, the expression of AQP-1 was determined by Western blotting and the apoptosis rate was assessed with flow cytometer. RESULTS: The expression of AQP-1 in H₂O₂ injury group was significantly declined with time, and was lower than that in normal group at each time point after treatment. The expression of AQP-1 in HO-1 control group and HO-1 protection group was significantly increased with time, and was higher than that of other groups at each time point after treatment. The expression of AQP-1 in HO-1 protection group was significantly up-regulated compared with that in H₂O₂ injury group (1 hour: 60.81 ± 5.78 vs. 46.21 ± 4.81, 3 hours: 63.05 ± 9.61 vs. 39.32 ± 4.96, 6 hours: 92.59 ± 8.21 vs. 36.82 ± 4.32, 12 hours: 86.16 ± 14.84 vs. 34.88 ± 2.66, all P<0.05). No significant difference in apoptosis rate was found between normal group and HO-1 control group. The apoptosis rate in H₂O₂ injury group was increased with time, and was significantly higher than that of normal group at each time point. The apoptosis rate in HO-1 protection group was gradually increased within 3 hours after treatment, then decreased and remained stable after 6 hours, while it was significantly lower than that of H₂O₂ injury group at each time point [1 hour: (9.04 ± 2.17)% vs. (15.14 ± 2.47)%, 3 hours: (12.90 ± 2.04)% vs. (22.37 ± 4.84)%, 6 hours: (10.42 ± 1.68)% vs. (27.83 ± 3.93)%, 12 hours: (11.97 ± 1.91)% vs. (33.63 ± 6.61)%, all P<0.05]. A negative correlation was found between AQP-1 and apoptosis rate in H₂O₂ injury group (r=-0.723, P<0.001), and a regression correlation was found [y=672.548(0.914) (x), R²=0.597]. AQP-1 was not correlated with apoptosis rate in HO-1 protection group (r=0.210, P=0.193), but a regression correlation was found [y=e((3.130 - 59.654/x )), R²=0.225]. CONCLUSIONS: HO-1 could increase the expression of AQP-1 in H₂O₂ injured AECII of rat, and lower its apoptosis rate. Increase in the expression of AQP-1 may be the underlying mechanism of anti-oxygenation property of HO-1.