The bioavailability of HIV protease inhibitors is altered by P-glycoproteins (P-gp). The aim of this study was to elucidate the impact of sodium butyrate (NaBut), a unique product of the bacterial fermentation found in elevated concentrations in AIDS patients on P-gp expression. As prostaglandin production is upregulated under inflammatory conditions, we determined the role of 15-deoxy-Delta(12,14)-prostaglandin J(2)(15d-PGJ(2)) in the NaBut-induced P-gp functionality in colonic epithelial cells. Treatment with NaBut significantly increased MDR1 transcription and P-gp expression on the surface of both types of cells. Nevertheless, the addition of 15d-PGJ(2) to NaBut-stimulated cells significantly upregulated MDR1 mRNA expression and P-gp expression and functionality, leading to an important diminution of saquinavir accumulation by these cells. Our data provide evidence that both NaBut and prostaglandins may profoundly affect the intracellular accumulation of saquinavir in AIDS patients with compromised colonic walls. (C) 2012 Elsevier Inc. All rights reserved.