Ribosomal RNA in Alzheimer's disease and aging.

Ribosomal RNA genes are involved in cell transcription and translation processes and can modulate gene expression. In an earlier cytogenetic study, (Payão, S.L.M., Smith, M.de A.C., Kormann-Bortolotto, M.H., Toniolo, J., 1994 (Investigation of the nucleolar organizer regions in Alzheimer's disease. Gerontology 40, 13-17), reported a decreased activity of ribosomal genes in Alzheimer's disease (AD). We studied the ratio of mature rRNA 28S and 18S in peripheral blood samples derived from eight patients with AD, eight healthy elderly sisters of these patients (SA), eight healthy elderly (EC) and eight healthy young (YC) controls, all female. Our results showed a statistically significant decrease of mature rRNA 28S and 18S ratio in the elderly groups (AD, SA, EC) in relation to the young one, probably by fragmentation of 28S rRNA. The Alzheimer's patient group had the lowest 28S/18S ratio. Thus, we can suggest that there is a possible change in the transcriptional or maturation process, or a preferential degradation of the 28S subunit with ageing.