Background:  Protease inhibitors (PI) used to treat HIV are, for the most part, inefficient at crossing the blood–brain barrier to inhibit productive infection in the brain. The multi-drug resistance protein, P-glycoprotein (P-gp), located on the apical surface of cerebral endothelial cells, is responsible for this phenomenon since PI are efflux substrates. Although PI are successful in suppressing plasma virus, these drugs are also associated with lipodystrophy, hyperlipidemia, and insulin resistance in some patients suggesting that cellular dysregulation may result from the use of these drugs.

Methods:  To address how exposure of cerebral endothelial cells to PI might effect cell signaling and possibly blood–brain barrier integrity, cRNA was prepared from human brain microvascular endothelial cells exposed to physiological levels of the PI indinavir (INV) for increasing lengths of time and analyzed with the Affymetrix Human Genome U133 Plus 2.0 GeneChip and GeneChip Operating Software. Genes were selected as relevant and significant, if a difference in expression within the time course measurements showed a 2-fold (p ≤ 0.05) or greater change. Select data were confirmed by quantitative RT-PCR, and genes of interest were further investigated using Western blot analysis, pharmacological inhibitors, and gene transfer.

Results:  Results indicate that out of the approximately 14,500 characterized human genes analyzed, 32 genes showed a significant increase in expression at 1 hour with a downward trend during the remaining 96 hours of exposure to INV. The early response genes that spiked at 1 hour largely consist of genes responsive to vascular growth factors and those involved in cerebral endothelial cell fitness including immediate early response, Cyr61, early growth response, Nur77, Cox2, IL-1b, IL-6, IL-8, and GCP2 (CXCL6). Likewise, 14 genes showed upward trends after INV exposure with the most significant increase at 96 hours. The late response genes include stanniocalcin-1, CRIM-1, UDP-Gal:b GclNAc, calreticulin, calcineurin, and C-terminal binding protein.

Conclusions:  These results indicate that exposure of cerebral endothelial cells to INV affects signaling events that may affect downstream signaling pathways and could contribute to patient responses to HAART or to the patterns of central nervous system/ blood–brain barrier damage observed in the HAART-adherent patient.

Keywords: Indinavir; HIV; blood-brain barrier