Human brain S100β and S100β mRNA expression increases with age: Pathogenic implications for Alzheimer's disease

S100β is a neurite extension factor that has been implicated in the development of neuritic plaques in Alzheimer's disease. We analyzed the expression of S100β and its encoding mRNA, using immunohistochemistry, enzyme-linked immunosorbent assay, and Northern blot analysis, in postmortem brain tissue from 26 neurologically normal patients, aged 1–80 years. Tissue levels of S100β and S100β mRNA, as well as the number of S100β-immunoreactive (S100β +) astrocytes, increased with advancing age ( r = 0.60, p = 0.008; r = 0.65, p = 0.007; and r = 0.73, p = 0.001, respectively). In patients more than 60 years old, the number of S100β + astrocytes and the tissue levels of S100β and S100β mRNA were significantly higher than those in patients less than 60 years of age ( p = 0.001, p = 0.035, and p = 0.047, respectively). All of these values, however, were significantly less than those found in Alzheimer patients ( p < 0.05 or better). Our findings, together with the known functions of S100β, suggest that age-related increases in S100β expression are important in the pathogenesis of Alzheimer's disease and may explain in part the increased incidence of this disease with advancing age.