1. ¹Center for Neurovirology and Neurodegenerative Disorders, University of Nebraska Medical Center, Omaha, Nebraska, USA
2. ²Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska, USA
3. ³Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, USA

Correspondence: Dr GD Kanmogne, Department of Pharmacology and Experimental Neuroscience, Center for Neurovirology and Neurodegenerative Disorders, University of Nebraska Medical Center, Omaha, Nebraska 68198-5215, USA. E-mail: gkanmogne@unmc.edu

Received 10 January 2006; Revised 30 March 2006; Accepted 4 April 2006; Published online 10 May 2006.

Abstract

Human immunodeficiency virus-1 (HIV-1) encephalitis is characterized by brain infiltration of virus-infected monocytes and macrophages. Cellular products and viral proteins secreted by infected cells likely play an important role in blood–brain barrier (BBB) impairment and the development of HIV-1-associated dementia (HAD). We previously demonstrated that HIV-1 envelope glycoprotein gp120 induces toxicity and alters expression of tight junction proteins in human brain microvascular endothelial cells (HBMECs). Here, we delineate the mechanisms of gp120-induced BBB dysfunction. Human brain microvascular endothelial cells expressed HIV-1 co-receptors (CCR5 and CXCR4). Exposure of HBMECs to gp120 derived from macrophage (CCR5) or lymphocyte (CXCR4)-tropic viruses decreased BBB tightness, increased permeability, and enhanced monocyte migration across in vitro BBB models. Blood–brain barrier integrity was restored after gp120 removal. CCR5 antibodies and inhibitors of myosin light chain kinase or protein kinase C (PKC) blocked gp120-enhanced monocyte migration and permeability of BBB in vitro. Exposure of HBMECs to gp120 induced release of intracellular calcium ([Ca²⁺]_i) that was prevented by CCR5 antibody and partially blocked by CXCR4 antagonist. Human immunodeficiency virus-1 gp120 activated three PKC isoforms in HBMECs [PKC-/II, PKC(pan)-II and PKC-/]. Furthermore, specific PKC inhibitors (acting at the ATP-binding and calcium release site) blocked gp120-induced PKC activation and prevented increase in BBB permeability, supporting the biologic significance of these results. Thus, gp120 can cause dysfunction of BBB via PKC pathways and receptor mediated [Ca²⁺]_i release leading to cytoskeletal alterations and increased monocyte migration.