Crocetin protects cardiomyocytes against hypoxia/reoxygenation injury by attenuating Drp1-mediated mitochondrial fission via PGC-1α

 BACKGROUND  Saffron (Crocus sativus L.) has been traditionally used as food, spice, and medicine. Crocetin (CRT), as main bioactive component of saffron, has accumulated pieces of beneficial evidence on myocardial ischemia/reperfusion (I/R) injury. However, the mechanisms are poorly explored. This study aims to investigate the effects of CRT on H9c2 cells under hypoxia/reoxygenation (H/R) and elucidated the possible underlying mechanism.

 METHODS  H/R attack was performed on H9c2 cells. Cell counting kit-8 was used to detect the cell viability. Cell samples and culture supernatants were evaluated via commercial kits to measure the superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and cellular adenosine triphosphate (ATP) content. Various fluorescent probes were used to detect cell apoptosis, intracellular and mitochondrial reactive oxygen species (ROS) content, mitochondrial morphology, mitochondrial membrane potential (MMP), and mitochondrial permeability transition pore (mPTP) opening. Proteins were evaluated via Western Blot.

 RESULTS  H/R exposure severely reduced cell viability and increased LDH leakage. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) suppression and dynamin-related protein 1 (Drp1) activation were coincided with excessive mitochondrial fission, mitochondrial permeability transition pore (mPTP) opening and mitochondrial membrane potential (MMP) collapse in H9c2 cells treated with H/R. Mitochondria fragmentation under H/R injury induced ROS over-production, oxidative stress, and cell apoptosis. Notably, CRT treatment significantly prevented mitochondrial fission, mPTP opening, MMP loss, and cell apoptosis. Moreover, CRT sufficiently activated PGC-1α and inactivated Drp1. Interestingly, mitochondrial fission inhibition with mdivi-1 similarly suppressed mitochondrial dysfunction, oxidative stress and cell apoptosis. However, silencing PGC-1α with small interfering RNA (siRNA) abolished the beneficial effects of CRT on H9c2 cells under H/R injury, accompanied with increased Drp1 and p-Drp1^ser616 levels. Furthermore, over-expression of PGC-1α with adenovirus transfection replicated the beneficial effects of CRT on H9c2 cells.

 CONCLUSIONS  Our study identified PGC-1α as a master regulator in H/R-injured H9c2 cells via Drp1-mediated mitochondrial fission. We also presented the evidence that PGC-1α might be a novel target against cardiomyocyte H/R injury. Our data revealed the role of CRT in regulating PGC-1α/Drp1/mitochondrial fission process in H9c2 cells under the burden of H/R attack, and we suggested that modulation of PGC-1α level may provide a therapeutic target for treating cardiac I/R injury.