NFAT-regulated Gene Expression Research Articles

THU-519 - Tailored immunosuppression with LCPT extended release Tacrolimus based on NFAT-regulated gene expression

THU-519 - Tailored immunosuppression with LCPT extended release Tacrolimus based on NFAT-regulated gene expression

Monitoring of gene expression in tacrolimus‐treated de novo renal allograft recipients facilitates individualized immunosuppression: Results of the IMAGEN study

Calcineurin inhibitors (CNI) have a small therapeutic window, and drug monitoring is required. Pharmacokinetic monitoring does not correlate sufficiently with clinical outcome. Therefore, the expression of nuclear factor of activated T cells (NFAT)-regulated genes in the peripheral blood has been suggested as a potentially useful immune monitoring tool to optimize CNI therapy. NFAT-regulated gene expression (RGE) was evaluated in renal allograft recipients as predictive biomarker to detect patients at risk of acute rejection or infections. NFAT-RGE (interleukin-2, interferon-γ, granular-macrophage colony-stimulating factor) was evaluated by quantitative real-time polymerase chain reaction in whole blood samples at day 7, day 14, month 1, 3, and 6 after transplantation in 64 de novo renal allograft recipients from 3 European centres. Immunosuppression consisted of tacrolimus (Tac), mycophenolic acid, and corticosteroids. Tac concentrations (C0 and C1.5) correlated inversely with NFAT-RGE (P <.01). NFAT-RGE showed a high interindividual variability (1-61%). Patients with high residual gene expression (NFAT-RGE ≥30%) were at the increased risk of acute rejection in the following months (35 vs. 5%, P =.02), whereas patients with low residual gene expression (NFAT-RGE <30%) showed a higher incidence of viral complications, especially cytomegalovirus and BK virus replication (52.5 vs. 10%, P =.01). NFAT-RGE was confirmed as a potential noninvasive early predictive biomarker in the immediate post-transplant period to detect patients at risk of acute rejection and infectious complications in Tac-treated renal allograft recipients. Monitoring of NFAT-RGE may provide additional useful information for physicians to achieve individualized Tac treatment.

Improved Pulse Wave Velocity and Renal Function in Individualized Calcineurin Inhibitor Treatment by Immunomonitoring: The Randomized Controlled Calcineurin Inhibitor-Sparing Trial.

A new immune monitoring tool which assesses the expression of nuclear factor of activated T cells (NFAT)-regulated genes measures the functional effects of cyclosporine A. This is the first prospective randomized controlled study to compare standard pharmacokinetic monitoring by cyclosporine trough levels to NFAT-regulated gene expression (NFAT-RE). Expression of the NFAT-regulated genes was determined by qRT-PCR at cyclosporine trough and peak level. Cardiovascular risk was assessed by change of pulse wave velocity from baseline to month 6. Clinical follow-up was 12 months. In total, 55 stable kidney allograft recipients were enrolled. Mean baseline residual NFAT-RE was 13.1 ± 9.1%. Patients in the NFAT-RE group showed a significant decline in pulse wave velocity from baseline to month 6 versus the standard group (-1.7 ± 2.0 m/s vs 0.4 ± 1.4 m/s, P < 0.001). Infections occurred more often in the standard group compared with the immune monitoring group. No opportunistic infections occurred with NFAT-RE monitoring. At 12 months of follow-up, renal function was significantly better with NFAT-RE versus standard monitoring (Nankivell glomerular filtration rate: 68.5 ± 17.4 mL/min vs 57.2 ± 19.0 mL/min; P = 0.009). NFAT-RE as translational immune monitoring tool proved efficacious and safe in individualizing cyclosporine therapy, with the opportunity to reduce the cardiovascular risk and improve long-term renal allograft function.

NFAT-regulated cytokine gene expression during tacrolimus therapy early after renal transplantation.

Despite pharmacokinetic monitoring of calcineurin inhibitors, the long-term outcome after transplantation (Tx) is still hampered by the side effects of these drugs. The aim of the present study was to characterize nuclear factor of activated T cells (NFAT)-regulated gene expression as a potential pharmacodynamic biomarker for further individualization of tacrolimus (Tac) therapy. In 29 renal allograft recipients, samples were drawn once pre-Tx, and before and 1.5h after Tac dosing at approximately 1week, 6weeks and 1year post-Tx. Tac concentrations were measured by immunoassay, while the expression of genes encoding NFAT-regulated cytokines [interleukin 2 (IL2), interferon gamma (IFNG), colony stimulating factor 2 (CSF2)] and cytochrome P450 3A5 (CYP3A5) genotyping were determined by real-time polymerase chain reaction. The cytokine response after Tac dosing varied up to 46-fold between patients and changed significantly with time post-engraftment. Tac concentrations 1.5h postdose (C1.5 ) >15μg l-1 were associated with strong cytokine inhibition and residual gene expression (RGE) ≤10%, while lower Tac C1.5 resulted in more variable responses (RGE 2.5-68.7%). Patients with ongoing subclinical acute rejection (n = 5) demonstrated limited cytokine inhibition (RGE 39.7-72.6%), while patients with polyoma virus viraemia (n = 3) had relatively strong inhibition of cytokines (RGE 2.5-32.5%). By contrast, there was no association between Tac exposure and rejection or viraemia. The findings of our study support the potential of NFAT-regulated gene expression measurements as a pharmacodynamic tool for additional monitoring of Tac therapy, especially in the context of overimmunosuppression and viraemia.

Correlation between pharmacokinetics of tacrolimus and pharmacodynamics on NFAT-regulated gene expression in stable kidney transplant recipients .

Gene expression regulated by the transcription factor NFAT (nuclear factor of activated T-cells) has been proposed for monitoring the pharmacodynamic effect of calcineurin inhibitors. We aimed to correlate the pharmacokinetics of tacrolimus with the suppression of NFAT-regulated gene expression. Tacrolimus trough (C_trough) and peak concentrations (C_peak) were measured by LC-MS. The effect on NFAT-regulated gene expression at trough (E_trough) and at peak levels (E_peak) were determined by qRT-PCR. The pharmacodynamic concentration producing the half-maximum effect (CE₅₀) and the Hill coefficient (H) were estimated from E_trough and from E_peak. Ten stable kidney transplant recipients on triple immunosuppression with prednisolone, mycophenolate, and tacrolimus were analyzed. Median age was 58years, median time since transplant was 84months, and median serum creatinine was 249µmol/L. The immunosuppressive effect on NFAT-regulated genes at trough concentrations was 38% (E_trough), and the effect at peak concentrations was 59% (E_peak) of maximum immunosuppression (E_max). The pharmacodynamic parameters of the action of tacrolimus were estimated with the Hill coefficient H at 1.5 and the CE50 at 6.7ng/mL. Accordingly, the pharmacodynamic threshold concentration was estimated at 0.9ng/mL and the ceiling concentration at 48ng/mL, indicating a wide span between target trough and peak levels. The low Hill coefficient indicates concentration-dependent pharmacodynamics of tacrolimus on NFAT transcripts. Therefore, the extension of the administration interval to 24hours is not likely to jeopardize the immunosuppressive effect of the prolonged-release tacrolimus preparations. .

Analytical Validation and Cross-Validation of an NFAT-Regulated Gene Expression Assay for Pharmacodynamic Monitoring of Therapy With Calcineurin Inhibitors.

Analysis of residual gene expression of the nuclear factor of activated T cell (NFAT)-regulated genes has been developed as a pharmacodynamic biomarker to monitor therapy with calcineurin inhibitors. The availability of commercial primer sets (Search-LC) and the well-established assay protocol makes this biomarker a promising candidate to be used clinically in different laboratories. However, implementation of the method in routine practice requires analytical robustness and comparable results across laboratories. Therefore, a protocol originally established at the Institute of Immunology, Heidelberg was verified at the Institute of Laboratory Medicine, Klinikum Stuttgart, and a comparison study was conducted between the 2 laboratories. For the analytical verification, whole blood samples of healthy individuals were incubated with tacrolimus in vitro. Linearity, imprecision, and limit of quantification, as well as sample stability, were investigated. For interlaboratory comparison, samples of patients under cyclosporine A therapy were analyzed in Heidelberg and then reanalyzed in Stuttgart within 24 hours. Tacrolimus (6.25-50 mcg/L) decreased the expression of NFAT-regulated genes in vitro dose dependently (15%-89%). Within- and between-assay coefficient of variations (n = 6 each) were <17%. The limit of quantification was <200 cDNA copies for each of the interleukin-2, interferon-γ, and granulocyte-macrophage colony-stimulating factor genes. Samples were stable for 24 hours. Interlaboratory comparison using patient samples correlated well (r = 0.951) but showed an inconsistent bias depending on the magnitude of residual gene expression. The assay can be set up with a satisfactory analytical performance in a routine molecular biological laboratory and shows comparable results between laboratories. The reproducibility of the NFAT-regulated gene expression assay across laboratories can facilitate the implementation of this assay for pharmacodynamic routine monitoring of calcineurin inhibitors in different centers.

Nuclear Factor of Activated T Cells-Regulated Gene Expression as Predictive Biomarker of Personal Response to Calcineurin Inhibitors.

Calcineurin inhibitors (CNIs) represent the most widely used immunosuppressive agents in kidney transplantation. Both CNIs show a narrow therapeutic window; thus, monitoring is necessary to balance efficacy and toxicity. Several approaches have been undertaken to measure the biological effects of CNI-based immunosuppression. A quantitative analysis of gene expression was established to calculate the functional effects of calcineurin inhibition, the assessment of nuclear factor of activated T cells (NFAT)-regulated gene expression. This assay is based on the quantitative analysis of interleukin-2, interferon-γ, and granulocyte macrophage colony-stimulating factor gene expression in whole blood samples collected at the time cyclosporine A/tacrolimus troughs (C0) and 2 hours after oral uptake (C2). In this comprehensive review, analytical aspects of the assay and also clinical benefits and limitations are presented and discussed. Several observational studies underline the beneficial effect of NFAT-regulated gene expression as biomarker of personal response on CNI therapy, especially in infectious complications, malignancies, and acute rejection episodes. Data are more comprehensive in cyclosporine A compared with tacrolimus therapy. However, results on prospective interventional studies are sparse. A randomized controlled study evaluating the opportunity for NFAT-guided immunosuppression is ongoing. NFAT-regulated gene expression is a promising biomarker in CNI therapy concerning infectious complications, malignancies, and acute rejection. Prospective interventional studies and randomized controlled studies are ongoing to confirm the encouraging results.

Monitoring of calcineurin inhibitors by NFAT-regulated gene expression in de novo renal allograft recipients on cyclosporine A.

Calcineurin inhibitors are critical-dose drugs with a narrow therapeutic range and optimal monitoring strategies are discussed in terms of safety and efficacy. A new pharmacodynamic monitoring tool - assessing the expression of nuclear factor of activated T-cells (NFAT)-regulated genes - has been established to directly measure the functional effect of cyclosporine A (CsA) in an individual patient. Until now, only sparse data on NFAT-regulated gene expression within the early post-transplant period have been available. Altogether 80 de novo renal transplant patients were enrolled in this non-interventional cohort-study. Immunosuppression consisted of interleukin (IL)-2 receptor antagonist induction, CsA, mycophenolic acid and steroids. Expression of NFAT-regulated genes (IL-2, granulocyte-macrophage colony stimulating-factor (GM-CSF), interferon-γ (IFN-γ)) was determined by qRT-PCR (real-time reverse transcription-PCR) at CsA C0 (prior to CsA intake) and C2 (2 hours after CsA intake) at regular follow-up visits within 6 months after transplantation. The median age of all patients was 47.9 ± 13.7 years (54 male). Residual NFAT-regulated gene expression showed a high interindividual variability. Inversely to reduction of CsA doses, NFAT-regulated genes increased from 1.78 ± 1.33% to 8.04 ± 7.36% in month 1 to month 6. Despite comparable CsA C0 levels, NFAT-regulated gene expression was significantly less inhibited in patients with treated biopsy-proven acute rejections (2.9 ± 2.2% vs. 2.0 ± 1.7%, p = 0.047). Patients with very low residual expression of NFAT-regulated genes were at an increased risk for early infectious episodes. Residual expression of IFN-γ and GM-CSF genes correlated significantly with clinical outcomes. NFAT-regulated gene expression is highly inhibited in the early post-transplant period in renal allograft recipients on CsA treatment. High residual NFAT-regulated gene expression was related to acute rejection episodes and low residual expression with infectious complications. Thus, NFAT-monitoring has the potential to support pharmacokinetic monitoring during the early post-transplant period.

Pharmacodynamic monitoring of immunosuppressive effects indicates reduced cyclosporine activity during telaprevir therapy.

Drug interactions with immunosuppressive drugs are a major problem associated with protease inhibitor-based antiviral triple therapy for hepatitis C virus (HCV) reinfection after liver transplantation. In this retrospective cohort study, we analyzed biomarkers of the immunosuppressive effects of cyclosporine A (CSA) by quantifying nuclear factor of activated T cells (NFAT)-regulated gene expression during telaprevir (TVR) therapy in 5 liver transplant patients. Furthermore, dose adjustments and blood concentrations of CSA as well as the clinical course were analyzed. We observed a clear impact of TVR not only on doses and blood concentrations but also on the immunosuppressive effects of CSA. Despite apparently adequate CSA trough concentrations, the CSA peak concentration decreased to 68% (range = 44%-90%). This was associated with a 1.9-fold (1.6- to 4.1-fold) increase in the residual gene activity of NFAT-regulated genes, which indicated reduced immunosuppressive activity of CSA with TVR co-medication. The median dose of CSA was reduced to 25% (range = 16%-48%) and 31% (range = 22%-64%) after 1 and 2 weeks, respectively. The CSA drug clearance was reduced to 38.7% (range = 31.0%-49.4%). We report excellent antiviral efficacy. At the end of the observation period, all patients were HCV RNA-negative (1 patient at 18 weeks, 1 patient at 12 weeks, and 3 patients at 4 weeks after the end of therapy). Safety was acceptable, with mild acute rejection and reactivation of cytomegalovirus being the most serious adverse events. One patient with histologically proven recurrent cholestatic hepatitis before therapy underwent retransplantation during the course of antiviral therapy. In conclusion, the immunomonitoring of NFAT-regulated gene expression indicated reduced immunosuppressive activity of CSA during antiviral therapy with TVR in our cohort of liver transplant patients. Thus, the immunosuppressive effects of CSA may be overestimated if one is looking only at trough concentrations during co-medication with protease inhibitors or other strong cytochrome P450 3A inhibitors. Immunomonitoring of NFAT-regulated gene expression could, therefore, help to prevent overimmunosuppression or underimmunosuppression.

Regulatory T cells suppress CD4+ T cells through NFAT-dependent transcriptional mechanisms.

Regulatory T cells (Tregs) control autoreactive T cells by inhibiting activation-induced proliferation and cytokine expression. The molecular mechanisms responsible for the inactivation of effector T cells by Tregs remain yet to be fully characterized. We report that T-helper cells stimulated in the presence of Tregs quickly activate NFAT1 and have increased NFAT1-dependent expression of the transcription repressor Ikaros. NFAT1 deficiency or dominant-negative Ikaros compromises Treg-mediated inhibition of T-helper cells in vitro and in vivo. Thus, our results place NFAT-dependent mechanisms as general regulators of T-cell tolerance and show that Treg-mediated suppression of T-helper cells results from the activation of NFAT-regulated gene expression.

Pharmacodynamic Monitoring of NFAT- Regulated Gene Expression and P70S6 Kinase Activity in Kidney Transplant Patients With BKV Infection.

Purpose: Measuring drug levels has been unhelpful in guiding management of patients with BKV infection. We measured NFAT-regulated gene expression and p70S6k activity in kidney transplant recipients (KTR) with BKV and correlated the results with clinical outcome. Methods: KTR with BK viruria > 1 million copies/ml or any detectable viremia on tacrolimus (TAC), mycophenolic acid (MPA) and prednisone were randomized to MPA reduction or conversion to everolimus (EVR). The primary endpoint (PE) was clearance of viremia or halving of viruria at 3 months (M). As a sub-study, peripheral blood was collected pre- (T0) and 1.5 hours post- (T1.5) TAC dose at enrollment and 3 M after randomization. Cells were stimulated with PMA/ionomycin. RT- PCR quantified the expression of NFAT-regulated genes IL-2, IFN-γ, and GM-CSF. Residual expression of each gene was calculated as T1.5/T0 x 100 and the average value expressed as mean residual expression (MRE). P70S6K activity was detected by flow cytometry and expressed as mean fluorescence intensity (MFI). The Mann-Whitney U test for comparison of median values was used. Results: 14 KTR with BKV enrolled. At enrollment, KTR with BKV viremia had significantly (SS) lower MRE than those with viruria alone (17.1% CI 14.3-36.4 vs. 43.3% CI 27.7-74.3 P= 0.04) despite similar TAC troughs (8.4, CI 7.0-10.4 vs 9.4, CI 8.6-10, P= 0.35) and P70S6K activity (5264 MFI CI 3379-8659 vs. 8128 MFI CI 2830-11593, P= 0.5). 12/14 KTR have data at 3 M of which 3 reached the PE. Median MRE at enrollment was SS higher in KTR who reached the PE (70.9% CI 27.5-98.1 vs. 17.1% CI 14.4-35, P =0.01). There was no SS difference between those that did and did not reach the PE in TAC levels at enrollment (9.7 CI 6.7-12.7 vs. 8.4 CI 7.4-10.4, P=0.35); at 3 M (5.7 CI 3.7-8.8 vs. 7.6 CI 5.6-8.8, P= 0.35) or P70S6K at enrollment (6765 CI-2904-15434 vs. 4151 CI 2390-7008, P=0.48); at 3 M (2959 CI -5777-14215 vs. 6508 CI 3109-7626, P=1.0). MRE at 3 M did not correlate with outcome (64.01 CI -7.2-128 vs. 53.1 CI 32.3-65.8, P=0.37). Conclusion: MRE of NFAT regulated genes at the time of BKV diagnosis, but not TAC levels or P70S6K activity, correlated with severity of BKV infection and outcome. Pharmacodynamic monitoring of NFAT regulated gene expression may play an important role in prognosis of BKV infection and may aid providers in the management of BKV associated disease. DISCLOSURES:Webber, A.: Grant/Research Support, Novartis, Astellas. Wojciechowski, D.: Grant/Research Support, Novartis, Bristol-Myers Squibb. Vincenti, F.: Grant/Research Support, Pfizer, Alexion, Novartis, Astellas, Bristol-Myers Squibb, Genetech.

Reduced residual gene expression of nuclear factor of activated T cells‐regulated genes correlates with the risk of cytomegalovirus infection after liver transplantation

Pharmacokinetic monitoring of calcineurin inhibitors (CNIs) is unsatisfactory because, at comparable blood concentrations, side effects vary considerably. We recently confirmed the applicability of a pharmacodynamic (PD) assay that measures the suppression of CNI target genes, specifically the suppression of nuclear factor of activated T cells (NFAT)-regulated genes in liver transplant (LT) recipients. The aim of this prospective study was to prove the clinical reliability of this assay. Therefore, we quantified the residual gene expression (RGE) of NFAT-regulated genes and evaluated the association between the RGE of NFAT-regulated genes and the incidence of cytomegalovirus (CMV) infection. In 20 LT recipients, 10 patients on cyclosporine (CsA) and 10 patients on tacrolimus (Tac) therapy, who presented with CMV infection, the RGEs of interleukin-2, interferon-γ (IFNγ), and granulocyte-monocyte colony-stimulating factor were measured and compared with the RGEs of these cytokines in 40 healthy dose-matched LT controls. CsA-treated CMV patients demonstrated a lower RGE of all NFAT-regulated genes compared with controls (30 ± 17 vs. 44 ± 20, P = 0.067). For IFNγ, the level of significance was reached (26 ± 17 vs. 43 ± 17, P = 0.0125). Daily CsA dosage, CsA baseline (C0 ) and 2 h (C2 ) concentrations were comparable (CsA dosage 169 mg/day vs. 165 mg/day; CsA C0 94 μg/L vs. 85 μg/L; CsA C2 389 μg/L vs. 381 μg/L). In addition, Tac-treated CMV patients demonstrated a lower RGE of all NFAT-regulated genes compared with controls (68 ± 25 vs. 84 ± 22, P = 0.0769). Analogous to CsA-treated CMV patients, the level of significance was reached for IFNγ (61 ± 24 vs. 88 ± 29, P = 0.0154). Daily Tac dosage and Tac 1.5 h concentrations (C1.5 ) were comparable in both groups (Tac dosage 4 mg/day vs. 4 mg/day; Tac C1.5 8 μg/L vs. 10 μg/L), whereas Tac C0 concentrations were significantly higher in controls (Tac C0 4 μg/L vs. 6 μg/L, P = 0.0276). Measuring the RGE of NFAT-regulated genes is appropriate to assess the risk of infections in LT recipients. Measuring the RGE of IFNγ is particularly suitable to assess the risk of CMV infection. PD monitoring of CNIs in LT recipients is an approach to individualize immunosuppression, which may help to reduce infectious complications.

Immunomonitoring of NFAT-regulated gene expression in liver allograft recipients under telaprevir based hepatitis C therapy reveals significant impact on residual gene activity

Immunomonitoring of NFAT-regulated gene expression in liver allograft recipients under telaprevir based hepatitis C therapy reveals significant impact on residual gene activity

Combination of nifedipine and subtherapeutic dose of cyclosporin additively suppresses mononuclear cells activation of patients with rheumatoid arthritis and normal individuals via Ca2+–calcineurin–nuclear factor of activated T cells pathway

Abnormal Ca(2+) -mediated signalling contributes to the pathogenesis of rheumatoid arthritis (RA). However, the potential implication of calcium channel blocker in RA remained unknown. We hypothesized that nifedipine, an L-type calcium channel blocker, combined with a calcineurin inhibitor, could suppress T cell activation via targeting different level of the Ca(2+) signalling pathway. The percentage of activated T cells and the apoptotic rate of mononuclear cells (MNCs) was measured by flow cytometry. The MNC viability, cytokine production, cytosolic Ca(2+) level and activity of the nuclear factor of activated T cells (NFAT) were measured by enzyme-linked immunosorbent assay (ELISA). The NFAT-regulated gene expression, including interleukin (IL)-2, interferon (IFN)-γ and granulocyte-macrophage colony-stimulating factor (GM-CSF), was measured by real-time polymerase chain reaction (PCR). We found that the percentage of activated T cells in anti-CD3 + anti-CD28-activated MNC was higher in RA patients. High doses of nifedipine (50 µM) increased MNCs apoptosis, inhibited T cell activation and decreased T helper type 2 (Th1) (IFN-γ)/Th2 (IL-10) cytokine production in both groups. The Ca(2+) influx was lower in anti-CD3 + anti-CD28-activated MNC from RA patients than healthy volunteers and suppressed by nifedipine. When combined with a subtherapeutic dose (50 ng/ml) of cyclosporin, 1 µM nifedipine suppressed the percentage of activated T cells in both groups. Moreover, this combination suppressed more IFN-γ secretion and NFAT-regulated gene (GM-CSF and IFN-γ) expression in RA-MNCs than normal MNCs via decreasing the activity of NFATc1. In conclusion, we found that L-type Ca(2+) channel blockers and subtherapeutic doses of cyclosporin act additively to suppress the Ca(2+) -calcineurin-NFAT signalling pathway, leading to inhibition of T cell activity. We propose that this combination may become a potential treatment of RA.

Cyclosporine‐induced gingival overgrowth correlates with NFAT‐regulated gene expression: a pilot study

To determine whether incidence and severity of cyclosporine A (CsA)-induced gingival overgrowth (GO) is related to expression nuclear factor of activated T cells-regulated genes (NFAT-regulated genes). Expression of NFAT-regulated genes was determined in 36 transplant patients medicated with CsA by real-time PCR before and 2 h after drug intake and residual NFAT activity was estimated as ratio of both measurements. Demographic, periodontal and pharmacologic parameters were recorded and GO assessed from models. Subjects were divided into two groups according to the degree of GO (responders: GO score≥10%). Groups were compared using parametric and non-parametric tests. The association of various CsA-specific and periodontal parameters on incidence and extent of GO were determined using regression analysis. Responders had a more than twofold lower residual NFAT activity than non-responders (7.9% and 18.1%, respectively; p<0.001). Multiple regression analysis revealed gingival inflammation, salivary CsA concentration, and residual NFAT activity to be significant factors influencing the expression of GO. Seventy-seven percent of the variability of GO could be explained by these parameters. This study showed that pharmacodynamic parameters such as residual NFAT activity may be promising prognostic indicators to identify patients with increased risk for GO.

Pharmacodynamic Disparities in Tacrolimus-Treated Patients Developing Cytomegalus Virus Viremia

The optimal balance between efficacy and toxicity of tacrolimus (Tac) treatment remains unsolved. The quantification of nuclear factor of activated T cell (NFAT)-regulated gene expression may provide a tool to monitor the individual susceptibility to Tac. Expression of NFAT-regulated genes (interleukin-2, interferon-gamma, and granulocyte-macrophage colony stimulating factor) in peripheral blood from renal transplant patients (N = 73) was measured by quantitative real-time polymerase chain reaction (at C0, C1.5, and C4) and correlated to clinical endpoints in a 1-year observation period. In a subgroup (n = 10), NFAT expression was quantified over a 12-hour dose interval. Median daily Tac dose of 73 stable renal transplant patients [median age 47 years (range 19-69 years)] was 5 mg (1-13), Tac trough (C0), 1.5-hour (C1.5) and 4-hour (C4) concentrations were 8.5 mcg/L (3-20), 20 mcg/L (4.7-50.4), and 14.5 mcg/L (4.5-37.5), respectively. The mean residual expression of all 3 NFAT-regulated genes was 21% at C1.5 (1-84) and 35% at C4 (2-88). The relative reduction of gene transcripts was inversely correlated with the individual Tac blood concentrations. Seven patients had cytomegalus virus viremia during the observation period, and their residual NFAT-regulated gene expression at C1.5 was significantly lower [13% (1-21) versus 26% (1-84), P = 0.02] compared with those without viremia despite comparable Tac blood concentrations (6.3 versus 8.6 mcg/L). Monitoring of NFAT-regulated gene expression in Tac-treated transplant recipients provides a tool to assess the individual response to Tac, identify patients at the risk of developing cytomegalus virus viremia, and may, thus, help to select the optimal Tac dose with respect to safety and toxicity.

Immunomonitoring of nuclear factor of activated T cells-regulated gene expression: The first clinical trial in liver allograft recipients

Long-term calcineurin inhibitor (CNI) treatment can cause serious side effects in liver allograft recipients. An optimal risk-to-benefit ratio for CNI blood levels has not been established. Pharmacodynamic drug monitoring through the measurement of the CNI biological activity, that is, the expression of nuclear factor of activated T cells (NFAT)-regulated genes, seems to be a promising approach. The residual gene expression (RGE) of NFAT-regulated genes 2 and 1.5 hours after cyclosporine A (CsA) and tacrolimus (FK-506) intake was measured in 100 liver allograft recipients with 1 or more years of follow-up post-transplantation. The mean RGE in all patients was 62% ± 33%. A significant negative correlation between the CsA (P < 0.0001, r = -0.8026) and FK-506 peak levels (P < 0.0001, r = -0.6982) and the RGE of all NFAT-regulated genes was observed. Clinical reliability was proven too. In conclusion, the data presented in this pilot study reveal the applicability of the pharmacodynamic monitoring of CNI efficacy in liver allograft recipients. To confirm the advantage of individualized pharmacodynamic drug monitoring over pharmacokinetic drug monitoring with respect to clinical outcomes, controlled, prospective studies are needed.

Pharmacodynamic monitoring of cyclosporine A by NFAT‐regulated gene expression and the relationship with infectious complications in pediatric renal transplant recipients

Pharmacokinetic monitoring of CsA is unsatisfactory, because at comparable CsA blood concentrations, the frequency and severity of adverse effects vary considerably among patients. We have therefore recently developed a precise, reliable, and robust whole-blood pharmacodynamic assay that measures the suppression of CsA-target genes in T lymphocytes. Because of the different characteristics of CsA pharmacokinetics in children and the higher propensity for infectious complications, this assay requires validation in the pediatric patient population. We therefore quantified in a prospective study of 45 pediatric renal transplant recipients the residual expression of NFAT-regulated genes in lymphocytes by RT-PCR and correlated these findings with the frequency of recurrent infections in the maintenance period post-transplant. Patients with recurrent infections showed a significantly stronger inhibition of NFAT-regulated gene expression (18.2%) than patients without recurrent infections (31.7%; p = 0.012). This difference was specific, because various PK parameters of CsA and the concomitant immunosuppressive therapy were comparable between patients. Multivariate regression analysis showed that patient age and residual NFAT-regulated gene expression were the only independent determinants of recurrent infections. By ROC curve analysis, a cutoff value of 23% residual NFAT-regulated gene expression had the highest sensitivity (71.1%) and specificity (65.4%) for the discrimination of patients with and without recurrent infections. Pharmacodynamic monitoring of CsA by measurement of residual NFAT-regulated gene expression in T lymphocytes has the potential to identify over-immunosuppressed pediatric renal transplant recipients and is therefore a useful tool for the optimization of CsA therapy.

Individualized Monitoring of Nuclear Factor of Activated T Cells-Regulated Gene Expression in FK506-Treated Kidney Transplant Recipients

The suggested key mechanism of both cyclosporine A (CsA) and FK506 is the inhibition of calcineurin phosphatase activity, preventing nuclear factor of activated T cells (NFAT)-translocation into the nucleus of T cells, with a subsequent transcriptional block of crucial cytokine genes. However, the two drugs exert different clinical activities as exemplified by the ability of FK506 to treat acute rejections. Inhibition of calcineurin activity by FK506 occurs in vitro at the same or even higher dose as for CsA; however, the magnitude of clinical and experimental immunosuppression is higher, indicating that FK506 may act in a calcineurin-independent way. To test this hypothesis, we measured the inhibition of NFAT-regulated gene expression in 262 stable kidney transplanted patients after FK506 intake. Previously, we showed that the optimal degree of NFAT inhibition in patients treated with CsA is between 15% and 30% residual gene expression. A considerable number of patients treated with FK506 do not achieve this level of immunosuppression despite therapeutic drug concentrations. Importantly, FK506 does inhibit protein translation. This insufficient degree of NFAT inhibition was associated with a higher rate of biopsy-proven acute rejection but also with a lower incidence of recurrent infections. Conversion of CsA to FK506 causes immediately reduced inhibition of NFAT-regulated gene expression. We could demonstrate that a considerable number of FK506-treated patients benefit from the drug, irrespective of the potency of NFAT inhibition in T cells by a yet unknown mechanism. Nevertheless, residual expression of NFAT-regulated genes seems to be a useful pharmacodynamic method to monitor FK506 therapy in renal transplant patients.

NIP45 controls the magnitude of the type 2 T helper cell response

Nuclear factor of activated T cell (NFAT) transcription factors are key regulators of gene transcription within immune cells. The NFAT-interacting protein, (NIP45), augments NFAT-driven IL-4 expression by a mechanism that relies on arginine methylation. To establish the function of NIP45 in vivo, we generated mice with a targeted deletion of the gene encoding this cofactor. NIP45-deficient T helper cells displayed profound defects in the expression of NFAT-regulated cytokine genes, including IL-4. Whereas NIP45 deficiency does not interfere with T helper cell NFAT activation or lineage-specific transcription-factor expression, NIP45 acts as an enhancer for the assembly of protein arginine methyltransferase 1 and the protein arginine methyltransferase 1-linked histone 4 arginine 3 methylation with the IL-4 promoter. Our study reveals an essential role for NIP45 in promoting robust cytokine expression in vivo, which is required for the efficient handling of parasites. We propose that NIP45 acts as a molecular rheostat serving to amplify the type-2 immune response.