Brain aging in acquired immunodeficiency syndrome: increased ubiquitin-protein conjugate is correlated with decreased synaptic protein but not amyloid plaque accumulation

Abstract

Two neuropathological changes that are linked with biological and pathological aging were examined in subjects with end-stage acquired immunodeficiency syndrome (AIDS). Autopsy brain specimens were examined from 25 people who died from complications of AIDS and 25 comparison subjects who were human immunodeficiency virus (HIV)-negative, matched for age, gender, ethnicity, and postmortem time interval. These adults were stratified into three age groups: elderly (62 to 75 years), intermediate (55 to 60 years), and young (21 to 42 years). Ubiquitin-stained dotlike deposits (Ub-dots) and diffuse extracellular plaques containing the beta-amyloid (Abeta) fragment of the amyloid precursor protein (Abeta plaque) were both increased significantly in the hippocampal formation of older subjects. In subjects with AIDS, Ub-dots were increased whereas Abeta plaque counts were not significantly different. Western blotting confirmed that high-molecular-weight ubiquitin-protein conjugates (HMW-Ub-conj) were increased in AIDS. The band intensity of one HMW-Ub-conj species with an approximate molecular mass of 145 kDa was correlated significantly with increased acute phase inflammatory protein (a-1-antichymotrypsin) and decreased synaptophysin and growth-associated protein-43 band intensities. These results raise the possibility that HIV-related brain inflammation disturbs neuronal protein turnover through the ubiquitin-proteasome apparatus, and might increase the prevalence of age-associated neurodegenerative diseases by decreasing synaptic protein turnover through the proteasome.