Background:  We previously reported a positive correlation between the expression of drug transporters and chemokine receptors in peripheral blood mononuclear cells (PBMC). Here we examine the effect of cytokines on expression of transporters and chemokine receptors in PBMC from healthy volunteers, ex vivo over 48 hours. The association of single nucleotide polymorphisms in interferon (IFN) -γ (874T >A) and interleukin (IL) -2 (–330T >G) with expression of transporters and chemokine receptors in HIV⁺ patients was also assessed.
Methods:  PBMC were isolated from 9 healthy volunteers, and expression of Pgp, MRP1, MRP2, CXCR4, and CCR5 measured by polymerase chain reaction (qPCR) and flow cytometry after 0, 2, 4, 8, 24, and 48 hours incubation with IL-2, IL-4, IL-6 IL-7, IL-10, IL-12, IL-13, IL-15, transforming growth factor (TGF) -β, tumor necrosis factor (TNF) –α, and IFN-γ (10 ng/mL). Genotyping for 874T > A and –330T > G was conducted in HIV⁺ patients (n = 66) by allelic discrimination and Pgp, MRP1, CXCR4, and CCR5 quantified by flow cytometry. Median (range) viral load and CD4 counts were 249 (<50, 646,000) and 327 (8, 1318), respectively. Of the 44 patients receiving therapy, 42 were male and 53 were Caucasian. Statistical analysis was conducted by Mann-Whitney U test (effect of cytokines), linear regression (relationship between changes in expression), and multiple linear regression using best subset selection (differences between genotypes).
Results:  All studied cytokines altered the expression of the transporters and co-receptors at the mRNA level although the time course was cytokine specific. Some, but not all, of these changes were also observed at the protein level. A significant positive correlation was observed between the degree of change in expression of Pgp and CXCR4 (r² = 0.583, p <0.01), MRP1 and CXCR4 (r² = 0.622, p <0.01), and MRP1 and Pgp (r² = 0.803, p <0.001). The IFN-γ 874T > A allele and viral load were independently associated with CCR5 expression in patients (see the table). No other associations with cytokine genotypes were observed.
Conclusions:  The relationship between the change in expression of transporters and HIV co-receptors in response to cytokines supports the hypothesis that similar mechanisms regulate their expression. The combined effect of cytokines on transporter and co-receptor expression may have important pharmacological and virological implications. The 874T > A allele was significantly associated with CCR5 expression and further studies are now required to assess the impact on disease progression.