Nestin expression in human tumors and tumor cell lines.

Oxidative stress‐related phenotypic changes and a decline in the number of viable cells are crucial contributors to intervertebral disc degeneration. The polyphenol epigallocatechin 3‐gallate (EGCG) can interfere with painful disc degeneration by reducing inflammation, catabolism, and pain. In this study, we hypothesized that EGCG furthermore protects against senescence and/or cell death, induced by oxidative stress. Sublethal and lethal oxidative stress were induced in primary human intervertebral disc cells with H₂O₂ (total n = 36). Under sublethal conditions, the effects of EGCG on p53‐p21 activation, proliferative capacity, and accumulation of senescence‐associated β‐galactosidase were tested. Further, the effects of EGCG on mitochondria depolarization and cell viability were analyzed in lethal oxidative stress. The inhibitor LY249002 was applied to investigate the PI3K/Akt pathway. EGCG inhibited accumulation of senescence‐associated β‐galactosidase but did not affect the loss of proliferative capacity, suggesting that EGCG did not fully neutralize exogenous radicals. Furthermore, EGCG increased the survival of IVD cells in lethal oxidative stress via activation of prosurvival PI3K/Akt and protection of mitochondria. We demonstrated that EGCG not only inhibits inflammation but also can enhance the survival of disc cells in oxidative stress, which makes it a suitable candidate for the development of novel therapies targeting disc degeneration.

Intervertebral disc (IVD) disease, which is characterised by age-related changes in the adult disc, is the most common cause of disc failure and low back pain. The purpose of this study was to analyse the potential of the biologically active polyphenol epigallocatechin 3-gallate (EGCG) for the treatment of painful IVD disease by identifying and explaining its anti-inflammatory and anti-catabolic activity. Human IVD cells were isolated from patients undergoing surgery due to degenerative disc disease (n = 34) and cultured in 2D or 3D. An inflammatory response was activated by IL-1β, EGCG was added, and the expression/activity of inflammatory mediators and pathways was measured by qRT-PCR, western blotting, ELISA, immunofluorescence and transcription factor assay. The small molecule inhibitor SB203580 was used to investigate the involvement of the p38 pathway in the observed effects. The analgesic properties of EGCG were analysed by the von Frey filament test in Sprague-Dawley rats (n = 60). EGCG significantly inhibited the expression of pro-inflammatory mediators and matrix metalloproteinases in vitro, as well as radiculopathic pain in vivo, most probably by modulation of the activity of IRAK-1 and its downstream effectors p38, JNK and NF-κB.

Degenerative disc disease is associated with increased expression of pro-inflammatory cytokines in the intervertebral disc (IVD). However, it is not completely clear how inflammation arises in the IVD and which cellular compartments are involved in this process. Recently, the endoplasmic reticulum (ER) has emerged as a possible modulator of inflammation in age-related disorders. In addition, ER stress has been associated with the microenvironment of degenerated IVDs. Therefore, the aim of this study was to analyze the effects of ER stress on inflammatory responses in degenerated human IVDs and associated molecular mechanisms. Gene expression of ER stress marker GRP78 and pro-inflammatory cytokines IL-6, IL-8, IL-1β, and TNF-α was analyzed in human surgical IVD samples (n = 51, Pfirrmann grade 2–5). The expression of GRP78 positively correlated with the degeneration grade in lumbar IVDs and IL-6, but not with IL-1β and TNF-α. Another set of human surgical IVD samples (n = 25) was used to prepare primary cell cultures. ER stress inducer thapsigargin (Tg, 100 and 500 nM) activated gene and protein expression of IL-6 and induced phosphorylation of p38 MAPK. Both inhibition of p38 MAPK by SB203580 (10 µM) and knockdown of ER stress effector CCAAT-enhancer-binding protein homologous protein (CHOP) reduced gene and protein expression of IL-6 in Tg-treated cells. Furthermore, the effects of an inflammatory microenvironment on ER stress were tested. TNF-α (5 and 10 ng/mL) did not activate ER stress, while IL-1β (5 and 10 ng/mL) activated gene and protein expression of GRP78, but did not influence [Ca²⁺]_i flux and expression of CHOP, indicating that pro-inflammatory cytokines alone may not induce ER stress in vivo. This study showed that IL-6 release in the IVD can be initiated following ER stress and that ER stress mediates IL-6 release through p38 MAPK and CHOP. Therapeutic targeting of ER stress response may reduce the consequences of the harsh microenvironment in degenerated IVD.