A pilot study of leukocyte expression patterns for drug metabolizing enzyme and transporter transcripts in autoimmune glomerulonephritis

Melanie S Joy,Ronald J Falk,Brittney V Roberts,Yichun Hu,Jinzhao Wang,Susan L Hogan

doi:10.5414/cp201972

Abstract

Objective: Leukocyte mRNA expression patterns of drug metabolizing enzyme genes and transporter genes that are relevant for the disposition of cyclophosphamide and mycophenolate were studied. The relationships between expression and patient-level data and pharmacokinetics were evaluated. Methods: The study included patients with glomerulonephritis secondary to lupus nephritis (SLE, n = 36), small vessel vasculitis (SVV, n = 35), healthy controls (HC, n = 10), and disease controls (VC, n = 5; LC, n = 5). Transcript assays targeted metabolizing enzymes (UGT1A7, UGT1A9, UGT2B7, CYP3A4, CYP2C9, CYP2B6) and transporters (ABCB1, ABCC2, ABCG2, SLCO1A2). Genotyping for specific variants was conducted. Group transcript fold-changes were evaluated. Patient level data was evaluated for transcript fold-change and disease, treatment, gender, race, and genotype. Results: Significant differences were noted in expression of UGT1A7, ABCB1, and ABCC2; for UGT1A7, SVV (0.17 ± 0.42; p < 0.05) and SLE (0.03 ± 0.1; p < 0.05) groups had lower expression than HC (0.79 ± 2.02). For ABCB1, SLE had a lower expression (0.33 ± 0.21; p < 0.05) than HCs (1 ± 0.82). For ABCG2, SVV group had a lower expression (0.17 ± 0.14; p < 0.05) than HCs (1 ± 1.82). Differences in expression of ABCC2 approached statistical significance with VC patients (2.02 ± 1.13) exhibiting higher expression than SVV patients (1.06 ± 1.11; p = 0.05). The relationships between transcript expression and patient-level data demonstrated; ABCC2 expression was different by race (1.26 ± 1.82 Caucasian versus 1.37 ± 0.86 non-Caucasian; p = 0.049) and CYP2B6 expression was different by treatment (2.07 ± 2.94 cyclophosphamide versus 0.45 ± 0.5 mycophenolate; p = 0.01). Conclusions: The current study showed differential expression of drug metabolizing enzyme and transporter transcripts and contributes to the literature on transcript expression of drug transporters in leukocytes. The implications of altered local metabolism and transport in leukocytes may be important in autoimmune diseases and transplant patients where treatment is targeted to leukocytes.

Highlights

The mRNA expression patterns of drug metabolizing enzymes and transporters in peripheral blood cells are thought to be important in patient responses to treatments for glomerulonephritis since the localized target of the pharmacological agents are the leukocytes
The pharmacologically active 4-hydroxycyclophosphamide metabolite of cyclophosphamide is first formed by phase I metabolism through cytochrome P450 enzymes and further converted to the phosphoramide mustard
The current study showed differential expression patterns of drug metabolizing enzyme and transporter transcripts in patients with active glomerulonephritis as compared to healthy subjects and disease control subjects without active glomerulonephritis

Summary

Introduction

The mRNA expression patterns of drug metabolizing enzymes and transporters in peripheral blood cells (neutrophils, lymphocytes, and monocytes) are thought to be important in patient responses to treatments for glomerulonephritis since the localized target of the pharmacological agents (e.g., mycophenolate and cyclophosphamide) are the leukocytes. Expression of drug metabolizing enzymes may modulate the exposure of the tissue to active (4-hydroxycyclophosphamide) versus inactive (mycophenolic acid glucuronide) pharmacologic moieties. The peripheral blood cells have been largely ignored for assessment of drug metabolism genes and limited studies have reported mRNA expression of selected transporters and cytochrome P450s [5, 6, 7]. These studies reported limited correlation between expression in leukocytes and intestine and liver and altered expression in subsets of leukocytes [5, 6, 7].

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Discussion

Conclusion