The mitochondrial UPR induced by ATF5 attenuates intervertebral disc degeneration via cooperating with mitophagy

Intervertebral disc degeneration (IVDD) is an aging disease that results in a low quality of life and heavy socioeconomic burden. The mitochondrial unfolded protein response (UPRmt) take part in various aging-related diseases. Our research intents to explore the role and underlying mechanism of UPRmt in IVDD. Nucleus pulposus (NP) cells were exposed to IL-1 beta and nicotinamide riboside (NR) served as UPRmt inducer to treat NP cells. Detection of ATP, NAD + and NADH were used to determine the function of mitochondria. MRI, Safranin O-fast green and Immunohistochemical examination were used to determine the degree of IVDD in vivo. In this study, we discovered that UPRmt was increased markedly in the NP cells of human IVDD tissues than in healthy controls. In vitro, UPRmt and mitophagy levels were promoted in NP cells treated with IL-1 beta. Upregulation of UPRmt by NR and Atf5 overexpression inhibited NP cell apoptosis and further improved mitophagy. Silencing of Pink1 reversed the protective effects of NR and inhibited mitophagy induced by the UPRmt. In vivo, NR might attenuate the degree of IDD by activating the UPRmt in rats. In summary, the UPRmt was involved in IVDD by regulating Pink1-induced mitophagy. Mitophagy induced by the UPRmt might be a latent treated target for IVDD.Graphical Abstract center dot UPRmt was upregulated in the NP cells of degenerative intervertebral disc.center dot UPRmt regulated by Atf5 could activate mitophagy to protect NP cells from apoptosis.center dot Nicotinamide riboside as UPRmt inducer reduced NP cells apoptosis, thereby delaying the process of IVDD.Graphical Abstract center dot UPRmt was upregulated in the NP cells of degenerative intervertebral disc.center dot UPRmt regulated by Atf5 could activate mitophagy to protect NP cells from apoptosis.center dot Nicotinamide riboside as UPRmt inducer reduced NP cells apoptosis, thereby delaying the process of IVDD.Graphical Abstract center dot UPRmt was upregulated in the NP cells of degenerative intervertebral disc.center dot UPRmt regulated by Atf5 could activate mitophagy to protect NP cells from apoptosis.center dot Nicotinamide riboside as UPRmt inducer reduced NP cells apoptosis, thereby delaying the process of IVDD.