P-glycoprotein expression in patients before and after kidney transplantation

MDR1 gene expression in peripheral blood mononuclear cells after liver transplantation

BACKGROUND

The multidrug resistance pump, P-glycoprotein 170 (P-gp), the MDR1 gene expression product, is expressed in peripheral blood mononuclear cells (PBMC). Cyclosporine (CsA) and tacrolimus are inhibitors and substrates of the pump, and can induce its expression. The aim of the present study was to assess MDR1 gene expression in PBMC after liver transplantation.

METHODS

P-gp expression was examined in PBMC from 23 adult patients by flow cytometry analysis using UIC2, a monoclonal anti-Pgp antibody, on days 7, 14, 21, 28, 90, and 180, and whenever a rejection episode was suspected. MDR1 mRNA was estimated by reverse transcription-polymerase chain reaction.

RESULTS

P-gp expression, assessed as the ratio of the mean fluorescence, increased from 1.59 before transplantation to 2.05 after transplantation, and did not vary significantly thereafter. There was no significant difference in P-gp expression between CsA and tacrolimus-based treatments. MDR1 mRNA levels did not vary significantly under CsA or tacrolimus therapy until day 28. P-gp expression was marginally higher in patients before acute rejection (P=0.054), and was lower in patients with severe infection (P=0.003) than in those with uneventful evolution. Alcoholic patients exhibited higher levels of P-gp expression than other patients.

CONCLUSION

P-gp expression increases after liver transplantation. Its variations do not allow the ability to predict acute rejection, but could help in making the diagnosis of overimmunosuppression.

Effect of calcineurin inhibitor therapy on P-gp expression and function in lymphocytes of renal transplant patients: a preliminary evaluation

Cyclosporine and tacrolimus are substrates and potent inhibitors of the multidrug transporter, P-glycoprotein, in vitro. The authors have investigated the effect of chronic therapy with these and other immunosuppressive drugs on the expression and function of P-glycoprotein in T lymphocytes. Using a P-gp antibody, the authors studied the level of expression of P-gp in CD4 and CD8 T cells over a period of time in renal transplant patients. For comparison, a group of healthy volunteers and patients who did not receive any calcineurin inhibitors but were maintained on mycophenolate mofetil was included. The P-gp expression on lymphocytes from these two groups remained constant (over several months' time). However, patients who were started on tacrolimus or cyclosporine had an initial decline in expression of P-gp on CD4 T cells. Patients who were initiated on calcineurin therapy on day 1 posttransplant also had a decrease in expression of P-gp on CD4 T lymphocytes. This preliminary analysis suggests that the calcineurin inhibitors might be modulating the expression and function of transporters in lymphocytes, thus changing not only the drug concentration but also the apparent efficacy of these drugs. Further understanding and elucidation of such effects would be important in understanding the relationship between pharmacokinetics and pharmacodynamics of these and other drugs, especially for immunosuppressive and anti-AIDS therapy.

SEX AND ETHNICITY MAY CHIEFLY INFLUENCE THE INTERACTION OF FLUCONAZOLE WITH CALCINEURIN INHIBITORS12

BACKGROUND

Calcineurin inhibitors (CNI) and azole antifungal agents have been reported to interact in a disparate manner. The azole dose and route and the level of involvement of the liver and intestines have been implicated, although data are limited. A significant interaction may result in CNI toxicity, and withdrawal of the azole may result in subtherapeutic CNI concentrations. Fluconazole, available in both intravenous and oral formulations, is commonly used in transplant recipients and is ideal for determining the presence of a disparate effect on CNI concentrations. We retrospectively investigated the interaction of CNIs with fluconazole, evaluating CNI blood troughs corrected for daily CNI dose, the factors influencing the interaction, and the effect on clinical outcomes in renal and simultaneous pancreas kidney transplant recipients.

METHODS

Twenty-eight patients received a CNI and fluconazole during the calendar year 1999, but only 19 patients had documented CNI blood troughs and outpatient follow-up. There were 25 episodes of use in the 19 included patients. CNI blood troughs were evaluated for changes induced by fluconazole, given by both routes, and clinical outcomes were tracked.

RESULTS

Data demonstrated both intravenous and oral fluconazole alter CNI blood concentrations. Two metabolic patterns were observed, and we termed these convergent and divergent. Divergent metabolizers did not have significant interaction (n=5), and convergent metabolizers did have a significant interaction (n=15). One patient had a divergent episode after a previous convergent episode. The main contributors to the lack of interaction appeared to be female sex and African American ethnicity. Additionally, tacrolimus levels were significantly more affected than cyclosporine, during and after fluconazole administration. No patient experienced nephrotoxicity or cellular rejection related to antifungal therapy.

CONCLUSIONS

Oral and intravenous fluconazole appear to increase oral CNI trough concentrations to a similar extent even after adjusting for daily calcineurin dose. These interactions appear to be chiefly influenced by sex and ethnicity. Further prospective study is necessary to clarify this issue.