TFEB protects nucleus pulposus cells against apoptosis and senescence via restoring autophagic flux

Abstract

s u m m a r yObjective: Excessive apoptosis and senescence of nucleus pulposus (NP) cells are major pathological changes in intervertebral disc degeneration (IVDD) development; previous studies demonstrated pharmacologically or genetically stimulation of autophagy may inhibit apoptosis and senescence in NP cells. Transcription factor EB (TFEB) is a master regulator of autophagic flux via initiating autophagy-related genes and lysosomal biogenesis. This study was performed to confirm whether TFEB was involved in IVDD development and its mechanism. Methods: TFEB activity was detected in NP tissues in puncture-induced rat IVDD model by immunofluorescence as well as in tert-Butyl hydroperoxide (TBHP), the reactive oxygen species (ROS) donor to induce oxidative stress, treated NP cells by western blot. After TFEB overexpression in NP cells with lentivirus transfection, autophagic flux, apoptosis and senescence percentage were assessed. In in vivo study, the lentivirus-normal control (LV-NC) or lentivirus-TFEB (LV-TFEB) were injected into the center space of the NP tissue, after 4 or 8 weeks, Magnetic resonance imaging (MRI), X ray, Hematoxylin-Eosin (HE) and Safranin O staining were used to evaluate IVDD grades. Results: The nuclear localization of TFEB declined in degenerated rat NP tissue as well as in TBHP treated NP cells. Applying lentivirus to transfect NP cells, TFEB overexpression restored the TBHP-induced autophagic flux blockage and protected NP cells against apoptosis and senescence; these protections of TFEB are diminished by chloroquine-medicated autophagy inhibition. Furthermore, TFEB overexpression ameliorates the puncture-induced IVDD development in rats. Conclusions: Experimental IVDD inhibited the TFEB activity. TFEB overexpression suppressed TBHPinduced apoptosis and senescence via autophagic flux stimulation in NP cell and alleviates punctureinduced IVDD development in vivo.

TGF-β signaling in intervertebral disc health and disease

“…Regrettably, there have been no additional studies to discuss the effect of TGF-b on the necroptosis of IVD cells. Growing evidences demonstrate that cellular senescence is one of the major contributors to IVD degeneration 89 , and TGF-b signaling can regulate cellular senescence in many other cell types 90,91 . However, the effect of TGF-b signaling on the regulation of cellular senescence in IVD is still unclear, and further studies are needed.…”

Restoration of Autophagic Flux Rescues Oxidative Damage and Mitochondrial Dysfunction to Protect against Intervertebral Disc Degeneration

“…Notably, Xu et al found that treatment of rat NP cells with rapamycin (Rap), a classical autophagy activator, can potently prevent ECM degradation induced by inflammatory factors such as tumor necrosis factor-α and interleukin-1β [17]. Recently, autophagic flux was also reported to be markedly impaired in rat NP cells under oxidative stress [18]. Therefore, autophagy upregulation coupled with autophagic flux enhancement might represent a promising therapeutic strategy for IDD.…”

Bone-derived mesenchymal stem cells alleviate compression-induced apoptosis of nucleus pulposus cells by N6 methyladenosine of autophagy

“…Moreover, clinical trials using BMSCs for the treatment of chronic low back pain caused by IVD degeneration have been conducted, and long-term results indicate that injection of BMSCs into IVDs is well tolerated and provides substantial improvement in pain and function 2 . Furthermore, recent studies confirmed that NPCs can be protected from apoptosis through induction of autophagy during the process of IVD degeneration 11,54,55 . In the compression-induced model, BMSCs could inhibit the mitochondrial pathway to protect NPCs from apoptosis 39 .…”