The expression and role of protease nexin-1 in intervertebral disc cells nucleus pulposus

Abstract

Objective To investigate the expression of Protease nexin-1 (PN-1) in Intervertebral Disc nucleus pulposus (NP) cells and the related signal pathways. Methods Human primary NP cells were isolated and cultured, and divided into control group, interleukine-1β (IL-1β), TNF-α group. Histological examinations were undertaken to observe the morphologic changes of NP cells during the process of differentiation at day 3, 7, 14 and 21. MMPs expression in NP cells were accessed by Western blot. Then, NP cells were cultured in medium containing 10 ng/ml IL-1β and different concenration of PN-1 (0, 10, 50, 100 ng/ml) for 24h. Protein were extracted, and The expression level of Interleukin-1 receptor-associated kinase 1 (IRAK1) , p38 mitogen-activated protein kinase (p38 MAP Ki-nase), phosphos-P38 MAP Kinase (P-P38) wereanalyzed by using Western blot. Results Histologically, under induction with IL-1β, both morphological and biological properties of NP cells were changed, cell proliferation became slowly, cell density was sparse within disordered arrangement, and obvious cell necrosis appeared. The results also showed the degenerative process of NP cells, MMPs production increased and Agg and Col II protein decreased significantly. PN-1 administration could inhibit the activation of MMP3,MMP9 and MMP13 induced by IL-1β, and enhance the expression of AGG and Col2. IL-1β administration could stimulate Nuclear factor κB (NF-κB) signal pathway through the up-regulated expression of IRAK1 and P-P38, while PN-1 could inhibit the inductive effects by suppress the expression of IRAK1 and the phosphorylation of P-38, thereby, inhibit the degeneration of NP cells. Conclusion PN-1 is involved during the degeneration of NP cells. PN-1 administration could antagonize IL-1β-induced proteases and inhibit the activation of MMPs, and potentially preserve NP cells, and reverse its degeneration via IRAK1/NF-κB signaling pathway. Key words: Intervertebral disc degeneration; Interleukin-1 Receptor-Associated Kinases; NF-kappa B