Pharmacodynamic monitoring of the immunosuppressive therapy in patients after heart transplantation: Whole blood flow cytometric analysis of lymphocyte function

The risk of cholelithiasis in patients after heart transplantation

INTRODUCTION

Extended immunosuppressive treatment in patients after heart transplantation modifies etiopathogenesis and occurrence of many diseases in this population. The aim of the present study was to evaluate the frequency and to define risk factors for cholelithiasis after heart transplantation (HTX).

MATERIAL AND METHODS

The study population consisted of 176 subjects. Of them, 24 patients (group A) presented with symptomatic cholelithiasis. Another group of 24 patients without cholelithiasis (group B) served as controls. Both groups were similar with respect to age, gender and follow-up after the transplant. Clinical interview, surgical and hospitalization data were collected from medical records.

RESULTS

The groups did not differ in demographic features. There were statistical differences (p < 0.05) between group A and B in rejection reaction, doses of immunosuppressive drugs, type 2 diabetes, serum lipid disorders and acute rejection episodes. These events were caused by modification of treatment, especially the immunosuppressive regimen. Group A consisted of 75% men and 25% women. The frequency of symptomatic cholelithiasis was 11.7% in men and 27.3% in women, on average 19.5%. Mean time to cholelithiasis following HTX was 37.9 ±4.9 (Me = 41.5) months, 27.7 ±8.2 (Me = 30.0) months in women and 41.3 ±5.9 (Me = 41.5) months in men. The female to male ratio was 2.3: 1.

CONCLUSIONS

Cholelithiasis following HTX was significantly more frequent as compared with the non-transplant population. Patients with cholelithiasis required more aggressive immunosuppression because of more frequent episodes of acute transplant rejection. Patients with cholelithiasis significantly more frequently showed increased glycemia and blood lipids, which could be the side effect of intensive immunosuppressive therapy.

Pharmacokinetics of Cyclosporine A in Chinese heart transplant recipients

AIM

To determine the steady state concentration and the pharmacokinetics of Cyclosporine A (CsA) in heart transplant recipients.

METHODS

A single dose of 100 mg CsA capsules twice daily was given to five heart transplant recipients of steady state. The concentrations of CsA in plasma were determined by streptavidin peroxidase fluorescent polarization immunoassay.

RESULTS

The main pharmacokinetic parameters of CsA were as follows: t(max) (1.60 ± 0.55) h, ρmax(951.60 ± 229.20) μg.L-1, t1/2(6.53 ± 2.40) h, and AUC0 -t(5162.10 ± 1355.01) μg.h.L-1.

CONCLUSION

The study obtained the steady state pharmacokinetic parameters of CsA in Chinese heart transplant recipients.

Pharmacodynamic monitoring of canine T-cell cytokine responses to oral cyclosporine

BACKGROUND

Pharmacodynamic assays measure the immunosuppressive effects of cyclosporine on T-cells and offer an alternative assessment of efficacy in individual patients.

OBJECTIVE

To assess the immunosuppressive effects of high and low dosage cyclosporine on canine T-cells and to develop a novel testing system for individualized dose adjustment.

ANIMALS

Seven healthy female Walker hounds.

METHODS

Experimental study using a paired comparison design. Flow cytometry was used to measure T-cell expression of IL-2, IL-4, and IFN-γ. Cytokine expression 8 days after oral administration of high and low dosages of cyclosporine was compared to baseline and washout values, respectively. The high dosage was initially 10 mg/kg q12h and was then adjusted to attain established immunosuppressive trough blood drug concentrations (>600 ng/mL). The low dosage was 5 mg/kg q24h.

RESULTS

High dosage cyclosporine resulted in significant decreases in IL-2 and IFN-γ expression (P = .0156, P = .0156), but not IL-4 expression (P = .2188). Low dosage cyclosporine was associated with a significant decrease in IFN-γ expression (P = .0156), while IL-2 expression was not affected (P = .1094).

CONCLUSIONS AND CLINICAL IMPORTANCE

T-cell function is suppressed at trough blood drug concentrations exceeding 600 ng/mL, and is at least partially suppressed in some dogs at low dosages. Direct evaluation of T-cell function could be an effective, more sensitive alternative to measuring blood drug concentrations for monitoring immunosuppressive therapy.

CD28 and KIR2D receptors as sensors of the immune status in heart and liver transplantation

Viral infections and cellular acute rejection (AR) condition immunosuppressive therapy and compromise the evolution of allografts. Immune monitoring can be useful for ascertaining rejection and for differentiating allo-reaction from activation induced by infections. This work analyzes the usefulness of monitoring the expression of CD28 and KIR2D receptors in peripheral blood T lymphocytes by flow cytometry, to ascertain the immune response in heart and liver transplant recipients. In both types of transplant, the up-regulation of CD28 in CD4(+) lymphocytes in the periods of greatest AR frequency indicates an effective allo-response, whereas the post-transplantation emergence of circulating CD8(+)CD28(-) and CD8(+)CD28(-)KIR2D(+) T cells correlates with better early clinical results. Cytomegalovirus (CMV) infection, but not hepatitis C virus (HCV) or other infections, abrogated both CD28 up-regulation and CD8(+)CD28(-)KIR2D(+) T-cell expansion. Our results show that monitoring the expression of CD28 and KIR2D receptors on T lymphocytes might be considered as sensors of the immune status of heart and liver recipients.

Whole blood flow cytometric measurement of NFATc1 and IL-2 expression to analyze cyclosporine A-mediated effects in T cells

The calcineurin inhibitor Cyclosporine A (CsA) is one of the crucial immunosuppressive drugs given after organ transplantation. The small therapeutic window of CsA generates the dilemma that efficient and toxic drug doses differ only slightly. Moreover, these threshold concentrations differ considerably between individuals; therefore, functional assays are urgently needed. We explored whether the transcription factor NFATc1, a direct as well as indirect target of CsA, can be used as a potential biomarker to determine the individual immunosuppressive activity of CsA. First, in isolated human T cells we showed that flow cytometry is practicable to measure NFATc1, the most abundant NFATc isoform in activated T cells. Second, for whole blood we developed a flow cytometric assay to determine in parallel the inducible transcription factor NFATc1 and the cytokine IL-2 in stimulated T cells. We found that added CsA inhibits both the expression of NFATc1 and IL-2 in T cells of stimulated whole blood samples with IC(50) values of 200 and 150 nM, respectively. The intra- and inter-assay variability was low, and clinical practicability was good. Further experiments have to demonstrate whether the parallel cytometric measurement of NFATc1 and IL-2 in whole blood is a good predictor of individual CsA efficacy and toxicity in CsA-treated patients.

Pharmacodynamic monitoring of calcineurin inhibition therapy: principles, performance, and perspectives

The calcineurin inhibitors (CNIs) cyclosporin A and tacrolimus are immunosuppressive drugs used extensively in allograft recipients. These drugs show large interindividual pharmacokinetic variation and are associated with severe adverse affects, including nephrotoxicity and cardiovascular disease. In current practice, CNIs are combined with other immunosuppressive drugs such as steroids and mycophenolate mofetil. Dosage is titrated based on blood concentration measurement. For further optimization of calcineurin (CN) inhibition therapy, new monitoring strategies are required. Pharmacodynamic-monitoring strategies constitute novel approaches for optimization of CNIs therapy. This review focuses on the general aspects of immunosuppressive drug pharmacodynamic monitoring and describes the methodologies used for monitoring CN inhibition therapy. Two different types of pharmacodynamic-monitoring strategies can be distinguished: (1) enzymatic strategies, which monitor inhibition of drug-target enzyme activity, and (2) immunologic strategies, which measure cellular responsiveness after in vitro simulated immunologic responses. Enzymatic tests are drug type-specific markers in which CN activity is directly determined. Immunologic strategies measure immune responsiveness at several levels, such as mRNA transcripts (intracellular) concentrations/excretion of cytokines, expression of surface activation markers, and cell proliferation. This review also discusses analytical issues and clinical experience with these techniques. The call for new methodologies to evaluate immunosuppressive therapy has led to the development of a large variety of pharmacodynamic-monitoring strategies. The first reports of their clinical relevance are available, but further understanding of the analytical and clinical variables involved are required for the development of accurate, reproducible, and clinically relevant markers.