Nuclear respiratory factor 1 protects H9C2 cells against hypoxia‐induced apoptosis via the death receptor pathway and mitochondrial pathway

Abstract

Hypoxia-induced cardiomyocyte apoptosis is one of the leading causes of heart failure. Nuclear respiratory factor 1 (NRF-1) was suggested as a protector against cell apoptosis; However, the mechanism is not clear. Therefore, the aim of this study was to elucidate the role of NRF-1 in hypoxia-induced H9C2 cardiomyocyte apoptosis and to explore its effect on regulating the death receptor pathway and mitochondrial pathway. NRF-1 was overexpressed or knocked down in H9C2 cells, which were then exposed to a hypoxia condition for 0, 3, 6, 12, and 24 h. Changes in cell proliferation, cell viability, reactive oxygen species (ROS) generation, and mitochondrial membrane potential (MMP) were investigated. The activities of caspase-3, -8, and -9, apoptosis rate, and the gene and protein expression levels of the death receptor pathway and mitochondrial pathway were analyzed. Under hypoxia exposure, NRF-1 overexpression improved the proliferation and viability of H9C2 cells and decreased ROS generation, MMP loss, caspase activities, and the apoptosis rate. However, the NRF-1 knockdown group showed the opposite results. Additionally, NRF-1 upregulated the expression of antiapoptotic molecules involved in the death receptor and mitochondrial pathways, such as CASP8 and FADD-like apoptosis regulator, B-cell lymphoma 2, B-cell lymphoma-extra-large, and cytochrome C. Conversely, the expression of proapoptotic molecules, such as caspase-8, BH3-interacting domain death agonist, Bcl-2-associated X protein, caspase-9, and caspase-3 was downregulated by NRF-1 overexpression in hypoxia-induced H9C2 cells. These results suggest that NRF-1 functions as an antiapoptotic factor in the death receptor and mitochondrial pathways to mitigate hypoxia-induced apoptosis in H9C2 cardiomyocytes.

Inhibition of mitochondrial respiration has fundamentally different effects on proliferation, cell survival and stress response in immature versus differentiated cardiomyocyte cell lines

“…Given that the majority of insults applied in these studies directly or indirectly increase oxidative stress in cardiac mitochondria, our data confirm that mitochondrial dysfunction by complex III inhibition requires NRF2 for normal growth and survival of H9c2 cells. Importantly, the closely related transcription factor NRF1 protects H9c2 cells from hypoxia induced cell death (Li et al, 2021) and has recently been shown to be a major driver of myocardial regeneration in mice by regulating proteostasis and redox balance (Cui et al, 2021). Our data, however, revealed no detectable effect of NRF1 silencing on growth and survival of AMA treated H9c2 cells, suggesting that NRF2 is primarily responsible for redox homeostasis of immature cardiomyocytes upon mitochondrial complex III inhibition.…”

MCP mediated active targeting calcium phosphate hybrid nanoparticles for the treatment of orthotopic drug-resistant colon cancer

“…There are two main apoptosis pathways, including death receptor-mediated apoptosis pathway and mitochondria-mediated apoptosis pathway [30,31]. The death receptor pathway mainly promotes the production of caspase-8, and then activates the downstream caspase factor, thus initiating the apoptosis process dependent on the caspase-enzyme cascade [32]. Mitochondrial apoptosis mainly regulates the Bcl-2 protein family [33].…”