High-glucose environment accelerates annulus fibrosus cell apoptosis by regulating endoplasmic reticulum stress

Abstract

Diabetes mellitus (DM) is an important risk factor of intervertebral disc degeneration. However, how DM affects annulus fibrosus (AF) biology remains unclear. The present study was aimed to investigate the effects and mechanism of high glucose on AF cell biology. Rat AF cells were cultured in baseline medium and culture medium with 0.2 M glucose. The inhibitor 4-PBA was added along with the high glucose culture medium to study the role of endoplasmic reticulum (ER) stress in this process. Compared with the control cells, high glucose significantly increased cell apoptosis ratio and caspase-3/9 activity, up-regulated mRNA/protein expression of Bax and caspase-3/cleaved caspase-3, but down-regulated mRNA/protein expression of Bcl-2. Moreover, high glucose increased mRNA and protein expression of CHOP, ATF-6 and GRP78. However, once ER stress was inhibited by the inhibitor 4-PBA in the high glucose group, cell apoptosis ratio and caspase-3/9 activity were decreased, mRNA/protein expression of Bax and caspase-3/cleaved caspase-3 was down-regulated, but mRNA/protein expression of Bcl-2 was up-regulated. In conclusion, high glucose condition can promote AF cell apoptosis through inducing ER stress. The present study helps us understand the mechanism of disc degeneration in DM patients.

Pharmacological Disruption of Phosphorylated Eukaryotic Initiation Factor-2α/Activating Transcription Factor 4/Indian Hedgehog Protects Intervertebral Disc Degeneration via Reducing the Reactive Oxygen Species and Apoptosis of Nucleus Pulposus Cells

“…ATF4 promotes the induction of ER stress (ERS)-induced apoptosis, and its activation is intrinsically associated with the phosphorylation of eIF2α involving many stress signaling pathways ( Wek et al, 2006 ). Excessive ERS can activate Caspase12 precursors on the ER, further activate Caspase3, and perform an apoptotic response ( Zhao et al, 2010 ; Pang et al, 2020 ). In our study, TNF-α increased the Caspase3 expression and apoptosis, which was aggravated by BTd supplement.…”

Glis1 and oxaloacetate in nucleus pulposus stromal cell somatic reprogramming and survival

“…Previous findings in a different context showed that constant glucose availability and lactate removal alongside a likely oversupply of growth factors through routine medium changes does not reflect the in vivo situation of cells, especially not those of NP cells ( Cantor et al, 2017 ). Nutrient concentrations of commonly used media often differ from those in human plasma ( Cantor et al, 2017 ) and are frequently high in glucose (4.5 g/L), yet many stem or stromal cells, including those of the NP, perform better under low glucose conditions ( Saki et al, 2013 ; Liu et al, 2020 ; Pang et al, 2020 ). Low glucose medium (1 g/L, 5.5 mM), including the glucose contribution from 10% FBS, is not yet considered pre-diabetic (10 mM) ( Johnson et al, 2008 ; Wuertz et al, 2008 ; Turner et al, 2016 ; Lyu, 2022 ).…”

Endoplasmic reticulum stress associates with the development of intervertebral disc degeneration

“…In AF cells, high glucose stimulates ERS and increases the gene and protein expression of CHOP, ATF6, and GRP78, which are the important factors in ERS. In addition, the apoptosis of AF cells is also increased ( 126 ). Due to the high blood glucose level, the chemotaxis of leukocytes is decreased, and the outcome of IDD surgery is often worse ( 127 ).…”

“…Consistently, 4-PBA can inhibit tension-induced IDD development, as indicated by reduced apoptosis, ameliorated ERS, and decreased ROS generation in AF cells ( 119 ). 4-PBA can also inhibit high glucose-induced apoptosis by inhibiting ERS in AF cells ( 126 ). TUDCA, a hydrophilic bile acid, has been reported to inhibit ERS-induced catabolism and reduce excessive mechanical compression-stimulated apoptosis in NP cells ( 133 , 134 ).…”