Influence of vitamin D treatment on functional expression of drug disposition pathways in human kidney proximal tubule cells during simulated uremia

Abstract

1. Effects of cholecalciferol (VitD₃) and calcitriol (1,25-VitD₃), on the expression and function of major vitamin D metabolizing enzymes (cytochrome P450 [CYP]2R1, CYP24A1) and select drug transport pathways (ABCB1/P-gp, SLCO4C1/OATP4C1) were evaluated in human kidney proximal tubule epithelial cells (hPTECs) under normal and uraemic serum conditions.

2. hPTECs were incubated with 10% normal or uraemic serum for 24 h followed by treatment with 2% ethanol vehicle, or 100 and 240 nM doses of VitD₃, or 1,25-VitD₃ for 6 days. The effects of treatment on mRNA and protein expression and functional activity of select CYP enzymes and transporters were assessed

3. Under uraemic serum, treatment with 1,25-VitD₃ resulted in increased mRNA but decreased protein expression of CYP2R1. Activity of CYP2R1 was not influenced by serum or VitD analogues. CYP24A1 expression was increased with 1,25-VitD₃ under normal as well as uraemic serum, although to a lesser extent. ABCB1/P-gp mRNA expression increased under normal and uraemic serum, with exposure to 1,25-VitD₃. SLCO4C1/OATP4C1 exhibited increased mRNA but decreased protein expression, under uraemic serum + 1,25-VitD₃. Functional assessments of transport showed no changes regardless of exposure to serum or 1,25-VitD₃.

4. Key findings indicate that uraemic serum and VitD treatment led to differential effects on the functional expression of CYPs and transporters in hPTECs.

Keywords:

• Renal metabolism
• renal transport
• cell culture
• CYP enzymes
• P-glycoprotein
• organic anion transporter
• vitamin D
• uraemia
• proximal tubule cells

Disclosure statement

JMT receives royalties from Alexion Pharmaceuticals, Inc. and is a consultant for Q32 Bio, Inc., a company developing complement inhibitors. He also holds stock and will receive royalty income from Q32 Bio, Inc.

Additional information

Funding

This work was supported by National Institute of General Medical Sciences.