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 Alheimer'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.