Differential protein expression between normal and degenerated human nucleus pulposus cells by proteomic and bioinformatics analyses

Low back pain is a chronic disease associated with the degeneration of lumbar intervertebral disc (IVD). The molecular and cellular basis of degenerate IVD disorder remains largely unclear. Using 2-D electrophoresis, mass spectrometric analyses, database searching and western blot assay, we examined differential protein expression between normal surrogates and degenerated human nucleus pulposus (NP) cells. Ten protein spots with most altered differential expression levels between normal surrogates and degenerated NP cells were identified. Among these, five proteins showed decreased expression in degenerated NP cells, including SID 1 transmembrane family member 2, isoform 1 of proteasome activator complex subunit 3, transaldolase 1, isoform 1 of 26S protease regulatory subunit 8 and guanylate cyclase soluble subunit beta-1. Conversely, five proteins showed increased expression in degenerated NP cells including peroxiredoxin 2, superoxide dismutase, isoform 2 of neutrophil gelatinase-associ-ated lipocalin, peroxiredoxin-4 and isoform 4 of Calumenin. Further, bioinformatics analysis hints that these differentially expressed proteins bear characteristics of membrane-like molecules with antioxidant function. Collectively, differentially expressed proteins might serve as biomarkers of the degenerate IVD and help us to understand the pathogenesis of IVD.