Oxidative Stress Aggravates Apoptosis of Nucleus Pulposus Cells through m6A Modification of MAT2A Pre-mRNA by METTL16.

Peng-Bo Chen,Bo Li,Sheng-Dan Jiang,Gui-Xun Shi,Lei-Sheng Jiang,Tao Liu,Xin-Feng Zheng,Sidong Yang

doi:10.1155/2022/4036274

Abstract

The process of intervertebral disc degeneration (IVDD) is complex, and its mechanism is considered multifactorial. Apoptosis of oxidative stressed nucleus pulposus cells (NPCs) should be a fundamental element in the pathogenesis of IVDD. In our pilot study, we found that the expression of MAT2A decreased, and METTL16 increased in the degenerative nucleus pulposus tissues. Previous studies have shown that the balance of splicing, maturation, and degradation of MAT2A pre-mRNA is regulated by METTL16 m6A modification. In the current study, we aimed to figure out whether this mechanism was involved in the aberrant apoptosis of NPCs and IVDD. Human NPCs were isolated and cultured under oxidative stress. An IVDD animal model was established. It showed that significantly higher METTL16 expression and lower MAT2A expression were seen in either the NPCs under oxidative stress or the degenerative discs of the animal model. MAT2A was inhibited with siRNA in vitro or cycloleucine in vivo. METTL16 was overexpressed with lentivirus in vitro or in vivo. Downregulation of MAT2A or upregulation of METTL16 aggravated nucleus pulposus cell apoptosis and disc disorganization. The balance of splicing, maturation, and degradation of MAT2A pre-mRNA was significantly inclined to degradation in the NPCs with the overexpression of METTL16. Increased apoptosis of NPCs under oxidative stress could be rescued by reducing the expression of METTL16 using siRNA with more maturation of MAT2A pre-mRNA. Collectively, oxidative stress aggravates apoptosis of NPCs through disrupting the balance of splicing, maturation, and degradation of MAT2A pre-mRNA, which is m6A modified by METTL16.

Highlights

As the main cause of low back pain, intervertebral disc degeneration (IVDD) imposes a great social and economic burden and leads to a poor life quality for sufferers [1,2,3]
Oxidative stress exists in intervertebral discs, and the apoptosis of nucleus pulposus cells (NPCs) induced by oxidative stress should be a fundamental element in the pathogenesis of IVDD
Similar change patterns of exon1-3, harpin1, and intron8 were found in NPCs with overexpression of methyltransferase like 16 (METTL16) (Figure 4(c)). These results suggested that m6A modification of MAT2A pre-mRNA by METTL16 should have an essential role in the mechanism of increased apoptosis of NPCs under oxidative stress and in the pathogenesis of disc degeneration

Summary

Introduction

As the main cause of low back pain, intervertebral disc degeneration (IVDD) imposes a great social and economic burden and leads to a poor life quality for sufferers [1,2,3]. It has been reported that a mutation of MAT2A predisposes individuals to thoracic aortic aneurysms and reduces SAM in aortic smooth muscle cells, which in turn reduces glutathione activity and increases oxidative stress responses [16]. Li et al reported that SAM was able to attenuate oxidative stress and neuroinflammation through glutathione metabolism modulation against amyloid-β [19]. There is a strong relationship between MAT2A-SAM and oxidative stress in tissues and cells. The role of MAT2A in the pathogenesis of disc degeneration and in the apoptosis of NPCs under oxidative stress has never been investigated. We speculate that oxidative stress aggravates the apoptosis of the NPCs through m6A modification of MAT2A by METTL16 and leads to disc degeneration

Materials and Methods

Results

Discussion

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