Increased In Vivo Activation of Microglia and Astrocytes in the Brains of Mice Transgenic for an Infectious R5 Human Immunodeficiency Virus Type 1 Provirus and for CD4-Specific Expression of Human Cyclin T1 in Response to Stimulation by Lipopolysaccharides

Abstract

Inflammatory mediators and viral products produced by human immunodeficiency virus (HIV)-infected microglia and astrocytes perturb the function and viability of adjacent uninfected neuronal and glial cells and contribute to the pathogenesis of HIV-associated neurocognitive disorders (HAND). In vivo exposure to lipopolysaccharide (LPS) activates parenchymal microglia and astrocytes and induces cytokine and chemokine production in the brain. HIV-infected individuals display increased circulating LPS levels due to microbial translocation across a compromised mucosa barrier. We hypothesized that HIV-infected microglia and astrocytes display increased sensitivity to the proinflammatory effects of LPS, and this combines with the increased levels of systemic LPS in HIV-infected individuals to contribute to the development of HAND. To examine this possibility, we determined the in vivo responsiveness of HIV-infected microglia and astrocytes to LPS using our mouse model, JR-CSF/human cyclin T1 (JR-CSF/hu-cycT1) mice, which are transgenic for both an integrated full-length infectious HIV type 1 (HIV-1) provirus derived from the primary R5-tropic clinical isolate HIV-1 JR-CSF regulated by the endogenous HIV-1 long terminal repeat and the hu-cycT1 gene under the control of a CD4 promoter. In the current report, we demonstrated that in vivo-administered LPS more potently activated JR-CSF/hu-cycT1 mouse microglia and astrocytes and induced a significantly higher degree of monocyte chemoattractant protein production by JR-CSF/hu-cycT1 astrocytes compared to that of the in vivo LPS response of control littermate mouse microglia and astrocytes. These results indicate that HIV infection increases the sensitivity of microglia and astrocytes to inflammatory stimulation and support the use of these mice as a model to investigate various aspects of the in vivo mechanism of HIV-induced neuronal dysfunction.

Astrocyte- and Endothelial-Targeted CCL2 Conditional Knockout Mice: Critical Tools for Studying the Pathogenesis of Neuroinflammation

“…animals resulted in stimulated expression of CCL2 by both astrocytes and BMEC, in accord with previous reports (Thibeault et al, 2001; Sun et al, 2008). However, our observations that astrocytes in situ from endothelial KO mice showed only minimal CCL2 expression following LPS injection was surprising, as these cells in culture did not display the CCL2 gene deletion band and exhibited a robust CCL2 response on par with astrocytes cultured from their W.T.…”

“…CNS expression of CCL2 was induced by peripheral LPS injection (i.p. ), which has been shown to cause elevated CCL2 expression in the brain within hours (Thibeault et al, 2001; Sun et al, 2008; Qin et al, 2008; Thomspon et al, 2008). At 4 hr following LPS injection, astrocytes or BMEC were selectively retrieved from their in situ locales by immuno-LCM and then subject to qRT-PCR analysis of CCL2 RNA levels.…”

Statin Therapy Inhibits Remyelination in the Central Nervous System

“…We used IBA-1 and GFAP as markers for activated microglia and astrocytes, respectively, given the functional demonstration that these markers are upregulated on glial activation. 27,28 Interestingly, following statin treatment of animals on a normal diet, there was an increase in numbers of activated astrocytes (week 6) and microglia (week 9) relative to vehicle control ( Figure 7, B and C, respectively), suggesting a glial response to statin-induced damage to the CC.…”

Rodent models for HIV-associated neurocognitive disorders

“…Other pro-viral transgenic mouse models (full-length or gag-pol deleted mutant HIV-1pNL4-3 and full length HIV-1 JR-CSF ) were developed [24, 25]. Transgenic mice expressing CD4 targeted expression of hu-cycT1 and HIV-1 JR-CSF were capable of producing glial inflammatory responses [26]. A HIV-1 NL4-3 provirus devoid of gag and pol expressed in a transgenic rat (HIV-Tg) demonstrated immune dysfunction as well as behavioral and motor abnormalities [27].…”