Proteomic identification of oxidative-stress-reporting biomarkers differentially secreted from human neuroblastoma SH-SY5Y cells

The free-radical theory predicts that the oxidative stress accelerates the rate of aging and increases the onset of degenerative disorders in the elderly. Dopaminergic neurons are especially vulnerable to age-related neuronal disorders due to reactive oxygen species generated in the pathway of dopamine metabolism. Biochemical changes occurring in substantia nigra of Parkinson's disease patients suggest that the oxidative-stress-induced cell damages may be involved in the neurodegeneration. In our previous researches, we found that the dephosphorylation of elongation factor-2 and phosphorylation of nuclear lamin A/C might be neuronal cell specific response to oxidative stress. (Nakamura et al. BBA, 1763(9), 977-989, 2006) The dephosphorylation and phosphorylation of those proteins are significant biomarkers for analyzing the molecular mechanisms of the stress response, however, such a phosphoproteome analysis is thought to be inappropriate for clinical investigation of neurodegeneration if it was not detectable in cerebrospinal fluid or serum of patients. Thus, we proceeded to the 2D-DIGE analysis of secretome, proteome of secreted proteins, using the culture system in which oxidative stress was applied to human SH-SY5Y neuroblastoma cells. As the result of our secretome analysis, we identified ubiquitin-activating enzyme E1, ubiquitin-conjugating enzyme E2 N, ubiquitin C-terminal hydrorase-L1, 14-3-3 protein isoforms, Rab GDP dissociation inhibitor β, Rho GDP-dissociation inhibitor 1, peroxiredoxin-2, glutathione S-transferase P, α enolase, LDH B chain as oxidative-stress-reporting biomarker candidates.