• Yuan Wei, Wu Zhi-Hong, Qiu Gui-Xing, Yu Bin, Chen Jun, and Wang Yi-Peng.
• Department of orhopedic surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
• Spine. 2013 Aug 1;38(17):E1075-81.

Study DesignRat annulus fibrosus (AF) cells were activated with interleukin-1 (IL-1) with or without extracellular signal-regulated kinase (ERK) inhibition. Factors associated with the anabolic/catabolic balance of the disc were determined.ObjectiveTo clarify the role of ERK pathway in AF cells response to IL-1.Summary Of Background DataIL-1 plays an important role in intervertebral disc degeneration. ERK is an important inflammatory pathway that plays a crucial role in the expression of inflammatory and catabolic genes induced by IL-1 in chondrocytes. However, the role of the ERK pathway in AF cells response to IL-1 has not been fully investigated.MethodsRat AF cells in monolayer culture were exposed to IL-1, with or without ERK inhibition; ribonucleic acid was isolated for real time polymerase chain reaction analysis of gene expression, conditioned media analyzed for nitrite, prostaglandin E-2, and IL-6, Western blot was performed to detect the changes of protein expression.ResultsERK specific inhibitor U0126 significantly inhibited IL-1-induced ERK activation. IL-1-dependent upregulation of iNOS, IL-6, Cox-2, (MMP)-3, and MMP-13 was significantly reduced by ERK inhibition. The decreased gene expression of collagen I, collagen II, collagen IX, and IGF-1 induced by IL-1 was also reversed by U0126. Gene expression of ADAMTS-4, ADAMTS-5, and TGF-b were not affected by IL-1 or ERK inhibition. IL-1 moderately upregulated aggrecan and TIMP-1 expression, ERK inhibition had no significant effect on aggrecan expression but decreased TIMP-1 expression in the presence of IL-1. ERK inhibition reversed the changes of protein expression of MMP-3, MMP-13, TIMP-1, aggrecan and collagen II induced by IL-1. IL-1-induced nitric oxide, prostaglandin E-2, and IL-6 accumulation were also reduced by ERK inhibition.ConclusionThese results suggest that IL-1 induces an imbalance between anabolic and catabolic events in AF cells, ERK inhibition could provide some protection against the adverse effects of IL-1.Level Of EvidenceN/A.

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