The effect of HIV-1 Tat and methamphetamine on expression of cytokines/chemokines and synaptic genes: Implications in HIV neuroAIDS
Human immunodeficiency virus-1 (HIV-1) enters the brain through blood brain barrier (BBB) early after the infection and leads to various neurological complications including HIV associated dementia (HAD). Introduction of combined Anti Retro Viral therapy (cART) has significantly reduced the incidence of HAD and increased the life expectancy of people infected with HIV. Increase in the life span of people resulted in the development of less severe forms of cognitive dysfunctions, including asymptomatic neurocognitive impairment (ANI) and Mild neurocognitive disorder (MND). These neurological deficits affect approximately 50% of HIV-1 infected people. The neurotoxicity of HIV-1 has been attributed to the virus itself or the viral proteins like HIV-1 Tat shed after the infection via several mechanisms including production of cytokines/chemokines and decreased expression of neuroplasticity genes. The present study was based on the central hypothesis that HIV-1 Tat and methamphetamine work synergistically in mediating pro-inflammatory cytokines and decreasing synaptic proteins. The level of cytokine expression mediated by HIV-1 Tat is determined. Furthermore, we examined the cellular mechanisms responsible for HIV-1 Tat mediated cytokine production, and the role of synaptic proteins in HIV-1 Tat and methamphetamine induced neurocognitive impairment. In the first chapter, we investigated the effect of HIV-1 Tat on pro-inflammatory cytokine expression in SVGA astrocytes. We measured levels of the IL-6, IL-8 and CCL5 in SVGA astrocytes after exposure with HIV-1 Tat. The results showed that HIV-1 Tat induced expression of IL-6, IL-8 and CCL5 in a time-dependent manner. These results were also confirmed by detecting their intracellular expression in SVGA astrocytes using confocal microscopy. Next, we sought to explore the mechanism(s) by which HIV-1 Tat induces the cytokine response. The involvement of PI3K/Akt, p38 MAPK, JNK MAPK pathways and various transcription factors, including NF-κB and AP-1 were determined by using selective inhibitors and siRNAs. In the second chapter, we investigated combined the effect of HIV-1 Tat and methamphetamine on expression of IL-6 and its underlying signaling mechanism(s). In the third chapter, the effect of HIV-1 Tat and methamphetamine on neurocognition was determined in HIV-1 Tat transgenic mice. Y maze and Morris water maze were employed to determine neurocognition. We also determined the effect of Tat and methamphetamine on expression of synaptic proteins in various brain regions. Furthermore, the role of HIV-1 Tat and methamphetamine on neurotrophic factors and CaMKII were determined by western blot. In conclusion, we showed that HIV-1 viral protein Tat and methamphetamine were able to induce cytokine expression in astrocytes. The underlying mechanism(s) provides potential therapeutic target for neuroAIDS.
Table of Contents
General introduction -- General materials and methods -- Role of HIV-1 TAT in the expression of various pro-inflammatory cytokines/chemokines and their underlying mechanism(s) -- HIV-1 Tat and methamphetamine mediated expression of IL-6 involves NF-Kb and PI3K/Akt pathways -- Effect of HIV-1 Tat and Meth on cognition and expression of various synaptic genes -- Summary and future directions