Proinflammatory cytokine / chemokine expression in human astrocytes: Induction by HIV-1 Nef

The mortality and morbidity of HIV-1 infected individuals were declined significantly by the introduction of highly active antiretroviral therapy (HAART). Nevertheless, different forms of HIV-associated neurocognitive disorders (HAND) still persist. The importance of HIV-1 accessory protein Nef has been well established in the pathology of AIDS in the peripheral. The presence of HIV-1 Nef mRNA and protein has also been demonstrated in astroctytes of the brain, however, the role of HIV-1 Nef in the neurotoxicity or HAND has not been extensively studied. The present study was based on the central hypothesis that HIV-1 Nef expressed either endogenously or exogenously, can increase the production of various pro-inflammatory cytokines / chemokines by human astrocytes. The expression levels of three cytokines/chemokines (IL-6, IL-8 and CCL5) were determined in our study. Furthermore, we examined the cellular mechanisms responsible for the HIV-1 Nef-mediated induction of IL-6, IL-8 and CCL5.;In the first chapter, we investigate the effect of HIV-1 Nef on the induction of IL-6 in human astrocytes. The levels of IL-6 showed significant increase both in primary human fetal astrocytes treated with recombinant HIV-1 Nef and in SVGA astrocytic cell line transfected with a HIV-1 Nef-expressing plasmid. Also, the involvements of PI3K-Akt/PKC and p38MAPK pathways as well as the transcription factor NF-kB, C/EBP and AP-1 were determined in HIV-1 Nef-mediated induction of IL-6 by utilization of chemical inhibitors and siRNAs. In additional experiments, the translocation of NF-kB subunit p65 and the phosphorylation levels of various signaling molecules triggered by HIV-1 Nef were determined.;In the second chapter, the role of HIV-1 Nef on the chemokine IL-8/CXCL8 expression was investigated in astrocytes. The expression levels of IL-8 were significantly up-regulated by HIV-1 Nef. Moreover, the involvements of PI3K-Akt/PKC and p38MAPK pathways as well as the transcription factor NF-kB were determined in HIV-1 Nef-mediated induction of IL-8.;In the third chapter, the effect of HIV-1 Nef on CCL5 induction was investigated in astrocytes. The expression levels of CCL5 showed significant up-regulation induced by HIV-1 Nef. Moreover, the involvements of PI3K-Akt and p38MAPK pathways as well as the transcription factor NF-kB, C/EBP and AP-1 were determined in HIV-1 Nef-mediated induction of CCL5.;In conclusion, we showed that HIV-1 Nef was able to increase the production of pro-inflammatory cytokine/chemokines via different pathways. The underlying mechanisms provide possible therapeutic targets for the intervention of neuroinflammation in HAND.