Abstract
Both c-Jun N-terminal kinase (JNK) and reactive oxygen species (ROS) play important roles in myocardial ischemia/reperfusion (I/R) injury. Our previous studies suggest that N-n-butyl haloperidol iodide (F2) exerts cardioprotection by reducing ROS production and JNK activation caused by I/R. In this study, we hypothesized that there is a JNK/Sab/Src/ROS pathway in the mitochondria in H9c2 cells following hypoxia/reoxygenation (H/R) that induces oxidative stress in the mitochondria and that F2 exerts mitochondrial protective effects during H/R injury by modulating this pathway. The results showed that H/R induced higher-level ROS in the cytoplasm on the one hand and JNK activation and translocation to the mitochondria by colocalization with Sab on the other. Moreover, H/R resulted in mitochondrial Src dephosphorylation, and subsequently, oxidative stress evidenced by the increase in ROS generation and oxidized cardiolipin in the mitochondrial membranes and by the decrease in mitochondrial superoxide dismutase activity and membrane potential. Furthermore, treatment with a JNK inhibitor or Sab small interfering RNA inhibited the mitochondrial translocation of p-JNK, decreased colocalization of p-JNK and Sab on the mitochondria, and reduced Src dephosphorylation and mitochondrial oxidative stress during H/R. In addition, Src dephosphorylation by inhibitor PP2 increased mitochondrial ROS production. F2, like inhibitors of the JNK/Sab/Src/ROS pathway, downregulated the H/R-induced mitochondrial translocation of p-JNK and the colocalization of p-JNK and Sab on the mitochondria, increased Src phosphorylation, and alleviated the above-mentioned mitochondrial oxidative stress. In conclusion, F2 could ameliorate H/R-associated oxidative stress in mitochondria in H9c2 cells through the mitochondrial JNK/Sab/Src/ROS pathway.
Highlights
Ischemia/reperfusion (I/R) injury refers to an increase in organic damage that occurs with the restoration of blood flow after ischemia
Flow cytometry analysis revealed that H/R time-dependently increased reactive oxygen species (ROS) levels (Figure 2(a)), with a significant difference beginning at 2 hours of hypoxia and 1 hour of reoxygenation (H: 2 hours/R: 1 hour), respectively
The results showed that mitochondrial membrane potential, Manganese SOD (MnSOD) activity, and nonyl acridine orange (NAO) levels decreased after H/R in H9c2 cells, indicating that there were too many ROS produced in the mitochondria to clear, which resulted in oxidation of the cardiolipin membrane and subsequent mitochondrial oxidative stress injury
Summary
Ischemia/reperfusion (I/R) injury refers to an increase in organic damage that occurs with the restoration of blood flow after ischemia. Coronary revascularization has become a routine treatment approach for patients with significant STsegment elevation, but reperfusion of blood into the previous ischemic area is always accompanied by increased myocardial injury. A large number of studies have shown that overgenerated ROS play a vital role in the pathological process of myocardial I/R injury, which induces oxidative stress injury and participates in other I/R-associated damages [4]. As our previous studies show, ROS accumulation leads to oxidation of the lipid structure of the cell membrane, increases cell membrane permeability, and subsequently causes the leakages of CK, LDH, and cTnI from cardiomyocyte [5, 6] in hypoxia/reoxygenation (H/R). The specific pathogenesis about the relationship between ROS and myocardial I/R injury remains obscure
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