title: Apoptotic death of striatal neurons induced by human immunodeficiency virus-1 Tat and gp120: Differential involvement of caspase-3 and endonuclease G.
abstract: Human immunodeficiency virus-1 (HIV-1) infection affects the striatum, resulting in gliosis and neuronal losses. To determine whether HIV-1 proteins induce striatal neurotoxicity through an apoptotic mechanism, mouse striatal neurons isolated on embryonic day 15 and the effects of HIV-1 Tat(1-72) and gp120 on survival were assessed in vitro. Mitochondrial release of cytochrome c, caspase-3 activation, and neuron survival, as well as an alternative apoptotic pathway involving endonuclease G (endo G), were assessed at 4 h, 24 h, 48 h, and/or 72 h using enzyme assays and immunoblotting. Both HIV-1 Tat and gp120 significantly increased caspase-3 activation in a concentration-dependent manner in striatal neurons at 4 h following continuous exposure in vitro. Tat(1-72) and gp120 caused significant neuronal losses at 48 h and/or 72 h. Tat(1-72) increased cytochrome c release, and caspase-3 and endo G activation at 4 h, 24 h, and/or 72 h. By contrast, gp120 increased caspase-3 activation, but failed to increase cytochrome c or endo G levels in the cytoplasm at 4 h, 24 h, and/or 72 h. The cell permeant caspase inhibitor Z-DEVD-FMK significantly attenuated gp120-induced, but not Tat(1-72)-induced, neuronal death, suggesting that gp120 acts in large part through the activation of caspase(s), whereas Tat(1-72)-induced neurotoxicity was accompanied by activating an alternative pathway involving endo G. Thus, although Tat(1-72) and gp120 induced significant neurotoxicity, the nature of the apoptotic events preceding death differed. Collectively, our findings suggest that HIV-1 proteins are intrinsically toxic to striatal neurons and the pathogenesis is mediated through separate actions involving both caspase-3 and endo G.
authors.affiliation: Department of Anatomy and Neurobiology, University Kentucky College of Medicine, Lexington, 40536, USA.
authors.forename: Indrapal N
authors.initials: IN
authors.lastname: Singh
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Goody
authors.forename: Celeste
authors.initials: C
authors.lastname: Dean
authors.forename: Nael M
authors.initials: NM
authors.lastname: Ahmad
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Lutz
authors.forename: Pamela E
authors.initials: PE
authors.lastname: Knapp
authors.forename: Avindra
authors.initials: A
authors.lastname: Nath
authors.forename: Kurt F
authors.initials: KF
authors.lastname: Hauser
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000187:drug effects / Q000821:virology; D045304:Cytochromes c / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015696:Gene Products, tat / Q000494:pharmacology* / Q000502:physiology; D015699:HIV Envelope Protein gp120 / Q000494:pharmacology* / Q000502:physiology; D015497:HIV-1 / Q000502:physiology; D015151:Immunoblotting; D051379:Mice; D008813:Mice, Inbred ICR; D009410:Nerve Degeneration / Q000201:enzymology / Q000821:virology; D009474:Neurons / Q000187:drug effects* / Q000821:virology; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D004791:Enzyme Inhibitors; D015696:Gene Products, tat; D015699:HIV Envelope Protein gp120; D054322:tat Gene Products, Human Immunodeficiency Virus; D045304:Cytochromes c; D004706:Endodeoxyribonucleases; C052391:endonuclease G; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases