In vitro and in vivo regulation of pro-inflammatory cytokines and drug efflux transporters by signal transduction pathways in glial cells: implications in HIV-1 neuropathogenesis and its treatment

Cognitive impairment remains highly prevalent in human immunodeficiency virus-1 (HIV-1) infected patients due to viral replication and associated brain inflammation. One obstacle to effective treatment is poor penetration of antiretroviral drugs across blood-brain barrier (BBB) and into HIV-1 brain cellular targets (microglia, astrocytes) due to functional expression of efflux transporters [P-glycoprotein (P-gp), Multidrug resistance-associated proteins (MRPs), breast cancer resistance protein (BCRP)]. Identifying therapeutic compounds that are not substrates of these transporters but target signaling pathways involved in inflammation may benefit treatment of HIV-associated neurological complications. The aim of this PhD project was: i) to investigate signaling pathways involved in the regulation of Mrp1 and P-gp in cultured rat/human astrocytes triggered with HIV-1 glycoprotein 120 (gp120) or cytokines, ii) to implement and characterize an in vivo model of gp120-associated brain inflammation, iii) to assess the efficacy of chloroquine, minocycline and simvastatin in reversing brain inflammation in vivo and iv) to elucidate key signaling pathways involved in gp120-associated brain inflammation in vivo. We demonstrated that gp120-associated TNF-alpha release resulted in increased Mrp1 functional expression in primary cultures of rat astrocytes and both c-jun N-terminal kinase (JNK) and nuclear factor-kB (NF-kappaB) pathways were involved. In human astrocytes, we demonstrated decreased P-gp expression following exposure to HIV- 1/gp120/interleukin-6 (IL-6) and involvement of NF-kB signaling in P-gp downregulation. In our in vivo model, gp120 administration resulted in a significant increase in inflammatory markers in different brain regions and in cerebrospinal fluid (CSF). Administration of antiinflammatory compounds partially or completely reduced upregulation of these markers. Activation of mitogen-activated protein kinases (MAPKs) was also observed both in vitro and in vivo which was attenuated by the anti-inflammatory compounds. Our data demonstrate that: i) gp120 generates an inflammatory response and alters expression of efflux transporters both in vitro and in vivo , in part, through an interaction with MAPK pathway and ii) anti-inflammatory agents could partially/completely reverse this response suggesting that they could serve as a promising novel therapeutic approach for HIV-1- associated brain inflammation.