Elevated lymphotoxin-[alpha] is associated with intervertebral disc degeneration

• Published in: BMC musculoskeletal disorders 2021-01, Vol.22 (1)
• Main Authors: Guo, Zhu, Qiu, Chensheng, Mecca, Christina, Zhang, Yang, Bian, Jiang, Wang, Yan, Wu, Xiaolin, Wang, Tianrui, Su, Weiliang, Li, Xianglin, Zhang, Wei, Chen, Bohua, Xiang, Hongfei
• Format: Article
• Language: English
• Subjects: Development and progression; Health aspects; Inflammation; Risk factors; Spinal diseases; Tumor necrosis factor
• ISSN: 1471-2474; 1471-2474
• DOI: 10.1186/s12891-020-03934-7

Background Intervertebral disc degeneration (IVDD) is a primary cause of degenerative disc diseases; however, the mechanisms underlying the degeneration remain unclear. The immunoinflammatory response plays an important role in IVDD progression. The inflammatory cytokine lymphotoxin-[alpha] (LT[alpha]), formerly known as TNF[beta], is associated with various pathological conditions, while its role in the pathogenesis of IVDD remains elusive. Methods Real-time quantitative polymerase chain reaction (RT-qPCR), Western blotting (WB), and enzyme-linked immunosorbent assays were used to assess the levels of LT[alpha] in human nucleus pulposus (NP) tissues between degeneration and control groups. The plasma concentrations of LT[alpha] and C-reactive protein (CRP) were compared between healthy and IVDD patients. Rat primary NP cells were cultured and identified via immunofluorescence. Methyl-thiazolyl-tetrazolium assays and flow cytometry were used to evaluate the effects of LT[alpha] on rat NP cell viability. After NP cells were treated with LT[alpha], degeneration-related molecules (Caspase-3, Caspase-1, matrix metalloproteinase (MMP) -3, aggrecan and type II collagen) were measured via RT-qPCR and WB. Results The levels of both the mRNA and protein of LT[alpha] in human degenerated NP tissue significantly increased. Plasma LT[alpha] and CRP did not differ between healthy controls and IVDD patients. Rat primary NP cells were cultured, and the purity of primary NP cells was > 90%. Cell experiments showed inversely proportional relationships among the LT[alpha] dose, treatment time, and cell viability. The optimal conditions (dose and time) for LT[alpha] treatment to induce rat NP cell degeneration were 5 [mu]g/ml and 48 ~ 72 h. The apoptosis rate and the levels of Caspase-3, Caspase-1, and MMP-3 significantly increased after LT[alpha] treatment, while the levels of type II collagen and aggrecan were decreased, and the protein expression levels were consistent with their mRNA expression levels. Conclusions This study demonstrated that elevated LT[alpha] is closely associated with IVDD and that LT[alpha] may induce NP cell apoptosis and reduce important extracellular matrix (ECM) proteins, which cause adverse effects on IVDD progress. Moreover, the optimal conditions for LT[alpha] treatment to induce NP cell degeneration were determined. Keywords: Intervertebral disc degeneration, Lymphotoxin-[alpha], TNF[beta], Inflammatory response, Cytokine