Cognitive decline due to extensive neurodegeneration occurs in unabated AIDS. HIV-1 productively infects brain microglia and invasive macrophages, shedding proteins in particular, gp120 and Tat--that promote glial-dependent neurotoxicity. While the proteins apparently use diverse neurotoxic mechanisms, chemokine receptor (CR)-based signaling and excitotoxic-apoptotic-oxidative stress cascades may be common to both. Consistent with efforts to clarify neurotoxic mechanisms, we are exploring the interactions of alcohol (ethanol) with the proteins; chronic abuse can worsen AIDS dementia, but the effects of moderate consumption are unclear. Our studies with rat organotypic hippocampal-cortical slice cultures show that moderate ethanol pre-conditioning (MEP, 20-30 mM) for >4 days prevents the neurotoxic effects of gp120 or Tat. That MEP increases a heat shock protein (HSP70) while suppressing early induction by gp120 of intracellular Ca ++,glial-derived apoptotic mediators(glutamate (Glu), arachidonic acid (AA), superoxide (O2"""""""")), and IL-10 (a cytokine that induces CRs), as well as CR density on chemokine-stimulated astroglia, suggests key roles for glia. We hypothesize that, as with gp120, MEP similarly suppresses Tat's induction of glial-regulated Glu, AA and 02, and that MEP neuroprotects against both retroviral proteins by promoting CR downregulation, induction of neuroprotective HSPs, and anti-apoptotic signal transduction. These hypotheses will be examined in four aims with rat brain slice cultures and human brain cell lines.
Aim I will assess whether Tat, and gp120 with human cells, increases Glu, AA, O2 and other mediators, and in which cells, as well as the effects of MEP on these mediators and neurodegeneration/apoptosis.
Aim II will investigate MEP potentiation of CR down-regulation during gp120 or Tat exposure, and the role of receptor phosphorylation.
Aim III will ascertain whether HSP induction is critical to MEP neuroprotection, using Western blotting, antibodies, and slice cultures from HSP70 transgenic mice.
Aim I V will examine whether MEP promotes activation of survival signal transduction kinases (PI3-kinase/Akt) in concert with reduction in pro-apoptotic (p38/JNK) pathways, and in which cells, and whether HSPs and CR reductions are upstream or downstream of these changes. The studies could shed light on the unexplored area of ethanol pre-conditioning as it relates to HSPs and CR receptor/anti-apoptotic signal transduction, while providing further insights into neuroprotective strategies that might eventually be therapeutically beneficial in AIDS dementia or other neurological diseases involving protein-mediated neurotoxicity.
