Regulation of P‐glycoprotein by human immunodeficiency virus‐1 in primary cultures of human fetal astrocytes

Abstract

P-glycoprotein (P-gp), a drug efflux pump, is known to alter the bioavailability of antiretroviral drugs at several sites, including the brain. We have previously shown that human immunodeficiency virus-1 (HIV-1) glycoprotein 120 (gp120) induces proinflammatory cytokine secretion and decreases P-gp functional expression in rat astrocytes, a cellular reservoir of HIV-1. However, whether P-gp is regulated in a similar way in human astrocytes is unknown. This study investigates the regulation of P-gp in an in vitro model of gp120-triggered human fetal astrocytes (HFAs). In this system, elevated levels of interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α were detected in culture supernatants. Pretreatment with CCR5 neutralizing antibody attenuated cytokine secretion, suggesting that gp120-CCR5 interaction mediated cytokine production. Treatment with gp120 (R5-tropic) resulted in reduced P-gp expression (64%) and function as determined by increased (1.6-fold) cellular accumulation of [3H]digoxin, a P-gp substrate. Exposure to R5 or R5/X4-tropic viral isolates led to a down-regulation in P-gp expression (75% or 90%, respectively), and treatment with IL-6 also showed lower P-gp expression (50%). Moreover, IL-6 neutralizing antibody blocked gp120-mediated P-gp downregulation, suggesting that IL-6 is a key modulator of P-gp. Gp120- or IL-6-mediated downregulation of P-gp was attenuated by SN50 (a nuclear factor-κB [NF-κB] inhibitor), suggesting involvement of NF-κB signaling in P-gp regulation. Our results suggest that, similarly to the case with rodent astrocytes, pathophysiological stressors associated with brain HIV-1 infection have a downregulatory effect on P-gp functional expression in human astrocytes, which may ultimately result in altered antiretroviral drug accumulation within brain parenchyma.

HIV-1 Alters Intestinal Expression of Drug Transporters and Metabolic Enzymes: Implications for Antiretroviral Drug Disposition

“…Statistically significant differences in protein expression between groups (negative versus HIV ϩ naïve, negative versus HIV ϩ on ART, and HIV ϩ naive versus HIV ϩ on ART) were determined using GraphPad Prism software, version 5.01 (Graph Pad Software, San Diego, CA) by applying the nonparametric two-tailed Mann-Whitney test with significance defined by a P value of Ͻ0.05. pha [TNF-␣]) which were found to regulate the expression of Pgp and MRP1 through NF-B and JNK signaling pathways (22,24,39). Pgp expression was upregulated by IL-1␤ and TNF-␣ but profoundly downregulated by IL-6, with an overall decrease in expression with gp120 treatment or HIV-1 isolates exposure (24,39).…”

“…pha [TNF-␣]) which were found to regulate the expression of Pgp and MRP1 through NF-B and JNK signaling pathways (22,24,39). Pgp expression was upregulated by IL-1␤ and TNF-␣ but profoundly downregulated by IL-6, with an overall decrease in expression with gp120 treatment or HIV-1 isolates exposure (24,39). In contrast, MRP1 expression was upregulated by TNF-␣ and unaltered by IL-1␤ or IL-6, with an overall increase in expression following gp120 treatment (22).…”

“…Tissue inflammation and cytokine secretion are known to alter functional expression of drug transporters and CYP enzymes in other disease states (e.g., inflammatory bowel syndrome) (21). Furthermore, we and other investigators have previously reported that the functional expression of drug transporters in brain parenchyma, blood-brain and bloodtestis barriers, and sigmoid colon epithelium is altered by the HIV antigens, viral infection-associated inflammation, and ARVs (22)(23)(24)(25)(26)(27)(28). The main objective of this study was to investigate the impact of HIV-1 infection and suppressive ART on the expression of intestinal drug transporters and metabolic enzymes in the intestinal mucosa of HIV-infected subjects.…”

Effects of HIV-1 Tat and Methamphetamine on Blood-Brain Barrier Integrity and FunctionIn Vitro

“…P-gp can also be expressed by microglia and astrocytes-the principal resident cell types that are infected within the CNS-suggesting that even if a drug such as atazanavir enters the CNS, it may be difficult to achieve therapeutic concentrations within HIV-infected cells in the CNS (41,74). Moreover, P-gp expression in rat astroglia can be downregulated by HIV gp120, resulting in a net decline in P-gp function (41,42).…”

“…Tat induces P-gp and multidrug resistance protein 1 (MRP-1) expression and function in brain microvascular endothelial cells (38)(39)(40). However, in primary human astrocytes, HIV can downregulate P-gp expression (41,42). Methamphetamine effects on the BBB can be variable and often transient.…”