Erythrocyte glycohydrolases in subjects with trisomy 21: could Down's syndrome be a model of accelerated ageing?

We studied some erythrocyte glycohydrolases, erythrocyte membrane fluidity, plasma hydroperoxides and total antioxidant defences in 23 Down syndrome (DS) individuals in comparison with healthy age-matched and elderly controls. With regard to erythrocyte plasma membrane fluidity, plasma hydroperoxides and total plasma oxidative defences, DS subjects resembled the age-matched controls more than the elderly ones. Membrane glycohydrolases in DS, however, presented a pattern partly similar to age-matched controls and partly to elderly controls. Concerning cytosol glycohydrolases, DS subjects had lower levels of hexosaminidase and N-acetyl-beta-D-glucosaminidase, the latter specific for the hydrolysis of GlcNAc residues O-linked to proteins. In general, erythrocyte membrane and cytosol glycohydrolases decreased during erythrocyte ageing in DS subjects and in all controls. The increased levels of the same enzymes in DS plasma might be attributed to an alteration of their release-uptake mechanisms between the two different compartments, on account of the higher plasma hydroperoxide levels. These findings indicate that erythrocyte ageing in DS differs partially from that of age-matched and elderly controls. In any case, the accelerated ageing seen in DS is no fully comparable to physiological ageing.