Proinflammatory cytokines and HIV‐1 synergistically enhance CXCL10 expression in human astrocytes

Abstract

HIV encephalitis (HIVE), the pathologic correlate of HIV‐associated dementia (HAD) is characterized by astrogliosis, cytokine/chemokine dysregulation, and neuronal degeneration. Increasing evidence suggests that inflammation is actively involved in the pathogenesis of HAD. In fact, the severity of HAD/HIVE correlates more closely with the presence of activated glial cells than with the presence and amount of HIV‐infected cells in the brain. Astrocytes, the most numerous cell type within the brain, provide an important reservoir for the generation of inflammatory mediators, including interferon‐γ inducible peptide‐10 (CXCL10), a neurotoxin and a chemoattractant, implicated in the pathophysiology of HAD. Additionally, the proinflammatory cytokines, IFN‐γ and TNF‐α, are also markedly increased in CNS tissues during HIV‐1 infection. In this study, we hypothesized that the interplay of host cytokines and HIV‐1 could lead to enhanced expression of the toxic chemokine, CXCL10. Our findings demonstrate a synergistic induction of CXCL10 mRNA and protein in human astrocytes exposed to HIV‐1 and the proinflammatory cytokines. Signaling molecules, including JAK, STATs, MAPK (via activation of Erk1/2, AKT, and p38), and NF‐κB were identified as instrumental in the synergistic induction of CXCL10. Understanding the mechanisms involved in HIV‐1 and cytokine‐mediated up‐regulation of CXCL10 could aid in the development of therapeutic modalities for HAD.