Platelet-derived growth factor B chain is a novel target gene of cocaine-mediated Notch1 signaling: implications for HIV-associated neurological disorders.

Neuroinflammation associated with HIV-1 infection is exacerbated in cocaine-abusing, HIV+ individuals. The underlying mechanisms are, in part, attributable to disruption of the blood-brain barrier modulated by cocaine via platelet-derived growth factor B chain (PDGF-B). Since Notch signaling plays a critical role in CNS homeostasis, we hypothesized that it may have a role in cocaine-mediated induction of PDGF-B. The goal of this study was to link Notch signaling with PDGF-B. Using Western blot analysis, we demonstrate the role of Notch1 signaling in cocaine-mediated induction of PDGF-B in human brain microvascular endothelial cells. Exposure of cells to the γ-secretase inhibitor-DAPT or silencing of Notch1 resulted in abrogation of cocaine-mediated induction of PDGF-B. Reciprocally, activation of the Notch1 receptor by exposing cells to the Notch ligand Jagged-1 resulted in upregulation of PDGF-B expression. Furthermore, it was demonstrated that cocaine-mediated activation of Notch1 signaling leading to targeted expression of PDGF-B involved activation of the downstream effector CSL. Functional implication of Notch1 signaling in regulating expression of the vascular permeant PDGF-B was confirmed in vitro using cell permeability assays. In vivo relevance was further corroborated in cocaine-treated mice that demonstrated increased permeability of the endothelial barrier as evidenced by Evans blue and sodium fluorescein extravasation. Specificity of Notch1 signaling in vivo was validated in mice exposed to DAPT, which failed to demonstrate barrier disruption following cocaine exposure. This is the first evidence of involvement of Notch1 activation in cocaine-mediated regulation of PDGF-B expression.