Cell survival assay (MTT assay)
The cell viability was measured using a colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Briefly, 2 × 105 astrocyte cells were seeded in 12-well plates and treated with either the inhibitor or saline with subsequent treatment with MA and/or gp120 for 48 h. Upon termination of the treatments, the medium was replaced with 0.2 mM MTT containing medium and incubated at 37 °C for 4 h. The medium was carefully removed and purple formazan crystals were dissolved in 500 μl DMSO containing 125 μl of Sorenson's glycine buffer. The color formation was measured using Benchmark Microplate Reader (Bio-Rad Laboratories, Hercules, CA, USA) with absorbance at 570 nm and reference at 650 nm.