HIV-1 Tat and Methamphetamine interaction in the mouse brain

Our goal was to examine whether the HIV Tat peptide, which is usually secreted from infected cells and has the potential to act in other cell types, alters gene expression in the Central Nervous System, and whether a drug abuse co-morbidity, in the case Methamphetamine, can play a role in further modifying gene expression. In order to address the effects of HIV Tat and Methamphetamine, alone and combined, we used an in vivo mouse model that has been described to mimic several aspects of neuroHIV, including changes in inflammatory markers, and decreased expression of dopamine receptors. These animals are transgenic mice, which upon treatment with with doxycycline for 10 days, express TAT protein under the control of the glial fibrilary associated protein (GFAP) promoter in the brain. They were treated with Meth and Saline for identification of gene expression changes that result from Tat or Methamphetamine alone, or from their interaction. There was an overall suppression of gene expression by Methamphetamine, in Tat- mice. The expression of Tat caused most Meth-induced changes to remain at control levels. A total of 20 male mice, 6 weeks old, 10 containing the GFAP promoter-controlled Tet-binding protein (TAT−) and 10 containing both the GFAP promoter-controlled Tet-binding protein and the TRE promoter-TAT protein transgene (TAT+) were tested. Inducible Tat transgenic mouse colonies with a C57BL/6J background are obtained by generation of two separate transgenic lines Teton-GFAP mice and TRE-Tat86 mice, and then cross-breeding of these two transgenic mouse lines, as previously described (Kim et al., 2003). The mice were housed in groups of 2–4 in a humidity- and temperature-controlled animal facility on a 12 h/12 h reverse light/dark cycle (lights off at 7:00 AM) with ad libitum access to food and water. All mice were treated with a doxycycline regimen (doxycycline hyclate; Sigma) of 100 mg/kg, intraperitoneally, once a day for 7 days. This regimen is based on the previously demonstrated efficacy of Tat induction at this dose of doxycycline (Carey et al., 2012; Paris et al., 2014a). Only mice containing both the GFAP promotor-controlled Tet-binding protein and the TRE promoter-TAT protein transgene (TAT+) generate TAT protein after doxycycline administration. Control TAT- animals had the GFAP promoter-controlled Tet-binding protein, but did not have TRE promoter-TAT protein transgene. All mice (TAT+ and TAT-) were administered doxycycline injections in the evening (17:00 h), beginning the day before the first injection of Methamphetamine or Saline. The Methamphetamine administration procedure followed a sensitization paradigm, and consisted of seven consecutive days of intraperitoneal injection with either saline (0.9%) or 2 mg/kg methamphetamine (methamphetamine hydrochloride; Sigma, St. Louis, MO, USA). The animals were anesthesized and perfused with ice cold PBS 24 hrs after the last injection, and the brains were snap frozen for the determination of changes in the gene expression. The animals were divided in 4 groups: G1=Tat-Meth+, G2=Tat-Meth-, G3=Tat+Meth+, G4=Tat+Meth-, and 5 mice per group.