Approximately 70% of HIV-1 infected patients acquire ocular opportunistic infections and manifest eye disorders during the course of their illness. The mechanisms by which pathogens invade the ocular site, however, are unclear. Under normal circumstance, vascular endothelium and retinal pigment epithelium (RPE) that possess a well-developed tight junction complex form the blood-retinal barrier (BRB) to prevent pathogen invasion. We hypothesize that the disruption of BRB allows pathogen entry into the ocular sites. The hypothesis was tested using in vitro models. We discovered that human RPE cells could bind to either HIV-1 gp120 glycoproteins or HIV-1 viral particles. Furthermore, the binding was mediated by dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) expressed on RPE cells. Upon gp120 binding to DC-SIGN, cellular NF-κB signaling was triggered, leading to the induction of matrix metalloproteinase (MMPs), which subsequently degraded tight junction proteins and disrupt the BRB integrity. DC-SIGN knocking down or prior-blocking with specific antibody abolished the gp120-induced MMPs expression and reduced the degradation of tight junction proteins. This study elucidates a novel mechanism by which HIV-1 invades ocular tissues, and provides additional sights into the translocation or invasion process of ocular complications associated pathogens.
HIV-1 gp120 interacting with DC-SIGN down-regulates tight junction proteins to disrupt the blood retinal barrier and increase its permeability.