Involvement of CYP3A4 and MDR1 in altered metabolism and transport of indinavir in 1,25(OH)2D3-treated Caco-2 cells

Altered drug concentrations may induce unexpected toxicity or treatment failure; thus, understanding the factors that alter the pharmacokinetic profiles of drugs is crucial for optimal disease treatment. Vitamin D receptor (VDR), a nuclear receptor, regulates the expression of cytochrome P450 3A4 (CYP3A4) and multidrug resistance protein 1 (MDR1), which are crucial determinants of drug pharmacokinetics. In this study, we investigated the effects of 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3], a VDR ligand, on the metabolism, transport, and phar-macokinetics of indinavir, a dual substrate of CYP3A4 and MDR1. 1,25(OH)(2)D-3 treatment for three days upre-gulated the expression levels of CYP3A4 and MDR1 in Caco-2 cells and consequently led to an increase in the level of a metabolite formed via CYP3A4 (indinavir M6) and the efflux ratio of indinavir in transport study. The increase in the metabolic reaction was also confirmed through a metabolism assay performed using the lysate of 1,25(OH)(2)D-3-treated Caco-2 cells. In the Ussing chamber study conducted with the rat intestine, 1,25(OH)(2)D-3 treatment did not alter the transport of indinavir into the basolateral side but increased indinavir M6 formation. Similarly, plasma levels of the metabolite increased in 1,25(OH)(2)D-3-treated rats; however, systemic exposure to indinavir led to insignificant alterations. Considering the overlapping substrate specificities for CYP3A4 and MDR1 and their significant roles in drug pharmacokinetics, VDR may play an important role in drug interactions of CYP3A4 and MDR1 substrates for accessing more effective and safe disease treatments.

Automated summary

Understanding the factors that alter drug pharmacokinetics is crucial for optimal disease treatment to prevent unexpected toxicity or treatment failure. In this study, the effects of 1,25-dihydroxyvitamin D3 (VDR ligand) on the metabolism, transport, and pharmacokinetics of indinavir were investigated. The results showed that treatment with 1,25(OH)2D3 upregulated the expression of CYP3A4 and MDR1, leading to increased indinavir metabolism and efflux ratio. This study suggests that VDR may play an important role in drug interactions and improving disease treatments.