To explore the effect of short-term hyperoxia on the mitochondrial Ca²⁺ / nicotinamide adenine dinucleotide (NAD⁺) / silence information regulator 3 (SIRT3) / superoxide dismutase 2 (SOD2) pathway and reactive oxygen species (ROS) in alveolar epithelial type Ⅱ cells (AECⅡ).

The RLE-6TN cells were randomly divided into a control group, a hyperoxia group and a mitochondrial calcium channel antagonist group (antagonist group). Cells in the control group were placed in a conventional cell culture box, cells in the hyperoxia group were placed in a box with an oxygen concentration of 90%, and cells in the antagonist group were given ruthenium red (2 μmol / L) and then placed in a box with an oxygen concentration of 90%. The cells in all groups were cultured continuously for 4 h. Subsequently, the mitochondrial Ca²⁺, ROS, NAD⁺ and reduced nicotinamide adenine dinucleotide (NADH) contents were measured, and the NAD⁺ / NADH level was calculated. The messenger RNA (mRNA) levels of SIRT3 and SOD2 were detected by real-time fluorescent quantitative PCR.

The mitochondrial Ca²⁺, ROS, NAD⁺, NADH, NAD⁺ / NADH, SIRT3 mRNA and SOD2 mRNA all showed significant differences among the three groups (F = 183.500, 135.900, 32.140, 51.520, 128.300, 59.970, 45.020; all P < 0.001). Compared with the control group and antagonist group, the contents of mitochondrial Ca²⁺ [(19.5 ± 0.8), (17.2 ± 0.7), (24.3 ± 0.3) nmol / L], ROS [(491 ± 9), (480 ± 5), (530 ± 6) relative fluorescence units] and NADH [(0.85 ± 0.03), (0.87 ± 0.04), (1.06 ± 0.06) nmol / 10⁴ cells] increased obviously, and the NAD⁺ content [(3.30 ± 0.12), (3.24 ± 0.14), (2.58 ± 0.29) nmol / 10⁴ cells], NAD⁺ / NADH [(3.89 ± 0.15), (3.71 ± 0.15), (2.44 ± 0.27)], SIRT3 mRNA [(1.01 ± 0.11), (0.96 ± 0.08), (0.45 ± 0.09)] and SOD2 mRNA [(1.01 ± 0.14), (1.05 ± 0.11), (0.48 ± 0.10)] decreased markedly in the hyperoxia group (all P < 0.05).

Short-term hyperoxia can increase the production of ROS by the Ca²⁺ / NAD⁺ / SIRT3 / SOD2 pathway in AECⅡ.