Sulfur dioxide induces apoptosis via reactive oxygen species generation in rat cardiomyocytes

Epidemiological evidence suggests that the incidence and mortality of cardiovascular diseases are closely related to sulfur dioxide (SO₂). In the present study, H9C2 cells were incubated with 100 μM NaHSO₃ with or without pretreatment of an antioxidant, N-acetyl-L-cysteine (NAC). The changes of apoptosis rate, mitochondrial membrane potential (MMP), ATP content, caspase-3 activity, and reactive oxygen species (ROS) were detected. Rats were inhaled 7 mg/m³ SO₂ and/or intraperitoneal injected with 50 mg/kg (bw) of NAC for 30 days. RT-PCR and Western blot were used to detect the mRNA and protein levels of apoptosis-related genes. We found that the apoptosis of H9C2 cells was induced by NaHSO₃, which decreased the content of MMP and ATP, and induced the expression of caspase-3. NAC can inhibit the apoptosis induced by NaHSO₃ treatment. SO₂ and NaHSO₃ decreased the expression of Bcl-2 and the ratio of Bcl-2/Bax, increased the expression of Bax and P53 accumulation and phosphorylation, and activated caspase-9 and caspase-3. Whereas NAC can reduce the changes of apoptosis-related proteins in rat heart. Our results suggest that SO₂ induces ROS-mediated P53 and caspase-dependent mitochondrial signaling pathways in H9C2 cells and rat hearts. Antioxidant therapy can reduce the adverse reactions of SO₂ and lead to a decline in the cardiovascular disease induced by SO₂.