Cocaine and σ-1 receptors modulate HIV infection, chemokine receptors, and the HPA axis in the huPBL-SCID model

Abstract

Cocaine is associated with an increased risk for, and progression of, clinical disease associated with human immunodeficiency virus (HIV) infection. A human xenograft model, in which human peripheral blood mononuclear cells were implanted into severe combined immunodeficiency mice (huPBL-SCID) and infected with a HIV reporter virus, was used to investigate the biological interactions between cocaine and HIV infection. Systemic administration of cocaine (5 mg/kg/d) significantly increased the percentage of HIV-infected PBL (two- to threefold) and viral load (100- to 300-fold) in huPBL-SCID mice. Despite the capacity for cocaine to increase corticosterone and adrenocorticotropic hormone levels in control mice, the hypothalamic-pituitary-adrenal axis was suppressed in HIV-infected animals, and corticosterone levels were further decreased when animals were exposed to HIV and cocaine. Activating huPBL in vitro in the presence of 10(-8) M cocaine increased expression of CC chemokine receptor 5 (CCR5) and CXC chemokine receptor 4 (CXCR4) coreceptors. Expression of CCR5 was also increased at early time-points in the huPBL-SCID model following systemic exposure to cocaine (54.1+/-9.4% increase over control, P<0.01). This effect preceded the boost in viral infection and waned as HIV infection progressed. Cocaine has been shown to mediate immunosuppressive effects by activating sigma-1 receptors in immune cells in vitro and in vivo. Consistent with these reports, a selective sigma-1 antagonist, BD1047, blocked the effects of cocaine on HIV replication in the huPBL-SCID mouse. Our results suggest that systemic exposure to cocaine can enhance HIV infection in vivo by activating sigma-1 receptors and by modulating the expression of HIV coreceptors.