N-acetylcysteine prevents HIV gp 120-related damage of human cultured astrocytes: correlation with glutamine synthase dysfunction.
BACKGROUND
HIV envelope gp 120 glycoprotein is released during active HIV infection of brain macrophages thereby generating inflammation and oxidative stress which contribute to the development of the AIDS-Dementia Complex (ADC). Gp120 has also been found capable to generate excitotoxic effect on brain tissue via enhancement of glutamatergic neurotransmission, leading to neuronal and astroglial damage, though the mechanism is still to be better understood. Here we investigated on the effect of N-acetylcysteine (NAC), on gp120-induced damage in human cultured astroglial cells and the possible contribution of gp120-related reacting oxygen species (ROS) in the imbalanced activity of glutamine synthase (GS), the enzyme that metabolizes glutamate into glutamine within astroglial cells playing a neuroprotective role in brain disorders.


RESULTS
Incubation of Lipari human cultured astroglial cells with gp 120 (0.1-10 nM) produced a significant reduction of astroglial cell viability and apoptosis as evaluated by TUNEL reaction and flow cytometric analysis (FACS). This effect was accompanied by lipid peroxidation as detected by means of malondialdehyde assay (MDA). In addition, gp 120 reduced both glutamine concentration in astroglial cell supernatants and GS expression as detected by immunocytochemistry and western blotting analysis. Pre-treatment of cells with NAC (0.5-5 mM), dose-dependently antagonised astroglial apoptotic cell death induced by gp 120, an effect accompanied by significant attenuation of MDA accumulation. Furthermore, both effects were closely associated with a significant recovery of glutamine levels in cell supernatants and by GS expression, thus suggesting that overproduction of free radicals might contribute in gp 120-related dysfunction of GS in astroglial cells.


CONCLUSIONS
In conclusion, the present experiments demonstrate that gp 120 is toxic to astroglial cells, an effect accompanied by lipid peroxidation and by altered glutamine release. All the effects of gp120 on astroglial cells were counteracted by NAC thus suggesting a novel and potentially useful approach in the treatment of glutammatergic disorders found in HAD patients.
Department of Pharmacobiological Sciences, Faculty of Pharmacy, University Magna Graecia, Catanzaro, Italy. vvisalli@libero.it
Valeria
V
Visalli
Carolina
C
Muscoli
Iolanda
I
Sacco
Francesca
F
Sculco
Ernesto
E
Palma
Nicola
N
Costa
Carmela
C
Colica
Domenicantonio
D
Rotiroti
Vincenzo
V
Mollace
D000111:Acetylcysteine / Q000494:pharmacology*; D000704:Analysis of Variance; D001253:Astrocytes / Q000187:drug effects*; D001254:Astrocytoma / Q000473:pathology; D001932:Brain Neoplasms / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004347:Drug Interactions; D005434:Flow Cytometry; D016166:Free Radical Scavengers / Q000494:pharmacology*; D005974:Glutamate-Ammonia Ligase / Q000502:physiology*; D005973:Glutamine / Q000378:metabolism; D015699:HIV Envelope Protein gp120 / Q000633:toxicity*; D006801:Humans; D020287:In Situ Nick-End Labeling / Q000379:methods; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D008875:Middle Aged
D016166:Free Radical Scavengers; D015699:HIV Envelope Protein gp120; D005973:Glutamine; D008315:Malondialdehyde; D005974:Glutamate-Ammonia Ligase; D000111:Acetylcysteine