Nicotinamide Phosphoribosyltransferase Inhibitor APO866 Prevents IL-1β-Induced Human Nucleus Pulposus Cell Degeneration via Autophagy

Abstract

Background/Aims: Intervertebral discs consist of an extracellular matrix (ECM) with a central gelatinous nucleus pulposus (NP) enclosed in an outer layer known as the annulus fibrosus. ECM metabolic disorders result in loss of boundary between the annulus fibrosus and NP, which can lead to intervertebral disc degeneration (IDD). Proinflammatory cytokines, such as interleukin (IL)-1β, mediate the progression of IDD. Nicotinamide phosphoribosyltransferase (Nampt) catalyzes the first step in the biosynthesis of nicotinamide adenine dinucleotide (NAD) and is known to be induced by IL-1β. APO866 is an inhibitor of NAD biosynthesis and is involved in autophagy. LC3 (microtubule-associated protein 1 light chain 3) is a key regulator of autophagy and is used as an indicator of increased autophagy. Herein, we investigate the role of APO866 in regulating autophagy in NP cells and IL-1β mediated NP cell degeneration and apoptosis. Methods: NP cells were extracted from IDD tissues and cultured in DMEM/F12 medium. Nampt was induced by different concentrations of IL-1β (0, 0.5, 1, 5, 10 ng/mL) for 24 h or NP cells were treated with 10 ng/mL IL-1β for 0, 6, 12, 48 h. QRT-PCR and western blots were used to detect Nampt and ECM-related protein expression in NP tissue of patients with IDD and in NP cells. Confocal analysis was used to detect membrane-bound LC3, Aggrecan, and Collagen II. Results: Nampt is expressed in NP tissue at higher levels in severe grades of IDD (Grade IV and V) compared with low grades (Grade II and III). In NP cells, 10 ng/mL IL-1β induced Nampt expression for 48 h, increased expression of the degradative-associated proteins, ADAMTS4/5 and MMP-3/13, and decreased expression of ECM-related proteins, Aggrecan and Collagen II. However, the Nampt inhibitor APO866 blocked IL-1β induction, and the knockdown of Nampt expression increased the expression of ECM proteins that were inhibited by IL-1β. Moreover, evidence provided by the autophagic markers LC3 and Beclin-1 indicated that APO866 induced NP cell autophagy. Furthermore, although APO866 inhibited the downregulated expression of ECM-related proteins by IL-1β, this function was blocked by autophagy inhibitor, 3-methyladenine. Conclusion: APO866 protects NP cells and induces autophagy by inhibiting IL-1β-induced NP cell degeneration and apoptosis, which may have therapeutic potential in IDD.

Identifying compositional and structural changes in the nucleus pulposus from patients with lumbar disc herniation using Raman spectroscopy

“…Decreased content of type II collagen and proteoglycans are the major features of IDD; however, the present study observed that the content of collagen increased with the Pfirrmann grade, which may contribute to metabolic disorders of the extracellular matrix. It has been reported that if the boundary between the outer AF and inner NP is disrupted, this may impair the mechanical function of the intervertebral disc (35).…”

Silencing of NAMPT leads to up-regulation of insulin receptor substrate 1 gene expression in U87 glioma cells

“…Previously it has been shown that inhibition of the nicotinamide phosphoribosyltransferase decreases the cell growth and enhances the susceptibility to oxidative stress through down-regulation 325 proteins in the FK866-treated 293T cells as well as through reduction of mitochondrial ribosomal proteins and subsequent mitochondrial dysfunction (Xu et al 2017). There are also data indicating that NAMPT inhibitor APO866 increased the expression of aggrecan and collagen II inhibited by IL-1beta and the autophagic markers, LC3 and beclin-1 (Shi et al 2018). These data clearly demonstrate that NAMPT is a pleiotropic protein implicated in the regulation of variable processes as well as in pathogenesis of cancer, diabetes, obesity, and other diseases because it is involved in the basic key cellular functions such as transcription, translation, cell signaling, and metabolism (Zhang et al 2017) and agree well with our results regarding the dependence of the expression of different genes on the level of NAMPT, which reflects fairly close relationships between different genes in the regulation of their functional activity.…”

“…NAMPT is involved in basic key cellular functions such as transcription, translation, cell signaling, and fundamental metabolism (Xu et al 2017;Cheleschi et al 2018;Liang et al 2018;Nielsen et al 2018;Shi et al 2018). However, the underlying molecular mechanisms of NAMPT in physiological and pathological processes are not fully understood.…”

Adipocytokines: Are they the Theory of Everything?

“…Insulin resistance &diabetes [11,12], psoriasis [88], vasoconstriction [156], atherosclerosis [142], coronary artery disease [144,145] [17], hyperlipidemia [25], IVDD [46], rheumatoid & osteoarthritis [66], joint damage in rheumatoid arthritis [67], atherosclerosis [157], diastolic hypertension [20] Abbreviations matrix proteolytic enzymes and their inhibitors) [44].…”

“…• Intervertebral Disc Degeneration (IVDD) It was found that progranulin (an adipokine) expression is increased in peripheral blood sera and disc tissues of patients with intervertebral disc degeneration (IVDD) and its blood levels were positively correlated with clinical symptoms [45]. Shi et al reported increased levels of visfatin in nucleus pulposus tissue in more severe IVDD grades than less severe grades [46]. Finally, ghrelin similarly is proved to have a role in nuclear pulposus degeneration [47].…”