Lymphocyte sensitivity to cyclosporine and tacrolimus in chronic renal failure patients and clinical significance in renal transplantation

The IMBG Test for Evaluating the Pharmacodynamic Response to Immunosuppressive Therapy in Kidney Transplant Patients: Current Evidence and Future Applications

Immunosuppressive drugs are widely used to prevent rejection after kidney transplantation. However, the pharmacological response to a given immunosuppressant can vary markedly between individuals, with some showing poor treatment responses and/or experiencing serious side effects. There is an unmet need for diagnostic tools that allow clinicians to individually tailor immunosuppressive therapy to a patient’s immunological profile. The Immunobiogram (IMBG) is a novel blood-based in vitro diagnostic test that provides a pharmacodynamic readout of the immune response of individual patients to a range of immunosuppressants commonly used in kidney transplant recipients. Here, we discuss the current approaches used to measure the pharmacodynamic responses of individual patients to specific immunosuppressive drugs in vitro, which can then be correlated with patient’s clinical outcomes. We also describe the procedure of the IMBG assay, and summarize the results obtained using the IMBG in different kidney transplant populations. Finally, we outline future directions and other novel applications of the IMBG, both in kidney transplant patients and other autoimmune diseases.

The Immunobiogram, a novel in vitro diagnostic test to measure the pharmacodynamic response to immunosuppressive therapy in kidney transplant patients

BACKGROUND

Diagnostic tools to measure the response to individual immunosuppressive drugs for transplant patients are currently lacking. We previously developed the blood-based Immunobiogram bioassay for in-vitro characterization of the pharmacodynamic response of patients' own immune cells to a range of immunosuppressants. We used Immunobiogram to examine the association between patients' sensitivity to their prescribed immunosuppressants and clinical outcome.

METHODS

We conducted an international, multicenter, observational study in a kidney transplant population undergoing maintenance immunosuppressive therapy. Patients were selected by clinical course poor [PCC] N = 53 (with renal dysfunction, and rejection signs in biopsy or/and an increase in DSA strength in last 12 months) versus good [GCC] N = 50 (with stable renal function and treatment, no rejection and no DSA titers). Immunobiogram dose-response curve parameters were compared between both subgroups in patients treated with mycophenolate, tacrolimus, corticosteroids, cyclosporine A or everolimus. Parameters for which significant inter-group differences were observed were further analyzed by univariate and subsequent multivariate logistic regression.

RESULTS

Clinical outcome was associated with following parameters: area over the curve (AOC) and 25% (ID25) and 50% (ID50) inhibitory response in mycophenolate, tacrolimus, and corticosteroid-treated subgroups, respectively. These statistically significant associations persisted in mycophenolate (OR 0.003, CI95% <0.001-0.258; p = 0.01) and tacrolimus (OR < 0.0001, CI95% <0.00001-0.202; p = 0.016) subgroups after adjusting for concomitant corticosteroid treatment, and in corticosteroid subgroup after adjusting for concomitant mycophenolate or tacrolimus treatment (OR 0.003; CI95% <0.0001-0.499; p = 0.026).

CONCLUSIONS

Our results highlight the potential of Immunobiogram as a tool to test the pharmacodynamic response to individual immunosuppressive drugs.

Pharmacodynamic Drug-Drug Interaction on Human Peripheral Blood Mononuclear Cells Between Everolimus and Tacrolimus at the Therapeutic Concentration Range in Renal Transplantation

Background

Everolimus (EVL) plus tacrolimus (TAC) therapy is effective and safe in renal transplantation. However, the pharmacokinetic and pharmacodynamic information for EVL combined with TAC is limited. We investigated the pharmacodynamic drug–drug interaction between EVL and TAC at their therapeutic concentration range.

Material/Methods

Isolated peripheral blood mononuclear cells (PBMCs) from 22 healthy participants aged 22 to 24 years were cultured with concanavalin A (Con A) in the presence of EVL and/or TAC for 4 days, and the proliferation rate of the PBMCs was calculated.

Results

TAC promoted the inhibitory efficacy of EVL against the mitogen-activated proliferation of PBMCs at the EVL therapeutic concentration range. When 0.175 ng/mL or more of TAC was combined with 30 ng/mL or more of EVL, the antagonistic effect of TAC on the inhibitory efficacy of EVL against the mitogen-activated proliferation of PBMCs was observed. Conversely, when 0.4 ng/mL TAC and 10 ng/mL or more of EVL were combined, the antagonistic effect of EVL on the inhibitory efficacy of TAC against the mitogen-activated proliferation of PBMCs was observed.

Conclusions

The pharmacodynamic synergistic efficacy of EVL and TAC in combination on mitogen-activated PBMCs was evident at the therapeutic concentration range, which is used in renal transplantation. However, these drugs antagonize each other to suppress the proliferation of activated PBMCs at concentrations higher than those clinically used.

Increased Sensitivities of Peripheral Blood Mononuclear Cells to Immunosuppressive Drugs in Cirrhosis Patients Awaiting Liver Transplantation

Successful immunosuppressive therapy is critical for liver transplantation. However, a considerable number of patients show clinical resistance to the therapy and experience rejection episodes, or alternatively exhibits serious adverse effects of drugs. We examined the in vitro response of peripheral blood mononuclear cells (PBMCs) to immunosuppressive drugs in cirrhosis patients awaiting liver transplantation. We evaluated the suppressive efficacy of prednisolone, methylprednisolone, cyclosporine, and tacrolimus on the in vitro blastogenesis of PBMCs obtained from 22 cirrhosis patients and 31 healthy subjects. In vitro drug concentrations giving 50% inhibition of PBMC blastogenesis (IC50s) were calculated. Two out of these 22 patients received liver transplantation from living donors, and their clinical courses were surveyed until 5 weeks after operation. The median IC50 values for prednisolone, cyclosporine, and tacrolimus against blastogenesis of PBMCs from cirrhosis patients were significantly lower than those of PBMCs from healthy subjects (p < 0.01). However, large individual differences were observed in the IC50 values of the immunosuppressive drugs examined, especially in the cirrhosis patients. One recipient exhibiting high PBMC sensitivity to tacrolimus (IC50 = 0.001 ng/ml) showed good clinical course without rejection until 5 weeks after liver transplantation. The other recipient exhibiting relatively low PBMC sensitivity to taclolimus (IC50 = 0.30) showed allograft rejection at 1 week after operation. We concluded from these observations that PBMCs of cirrhosis patients are vulnerable to the immunosuppressive effects of prednisolone and calcineurin inhibitors. However, large individual variations in the IC50 values suggest that patients exhibiting relatively lower sensitivity to these drugs may have risks of rejection, whereas highly sensitive patients are possibly able to reduce the dose of immunosuppressive drugs to avoid serious drug-adverse effects, after liver transplantation.

Steroid withdrawal based on lymphocyte sensitivity to endogenous steroid in renal transplant recipients

Though steroid withdrawal is done in many renal transplant recipients, some patients must restart steroids. Little report has investigated steroid withdrawal under pharmacodynamic monitoring. We assessed lymphocyte sensitivity to endogenous cortisol as a biomarker for determining the safety of steroid withdrawal in renal transplant patients, as we hypothesized that patients hyposensitive to cortisol could not be sufficiently immunosuppressed by their intrinsic cortisol as a substitute for the reduced or withdrawn steroid. Lymphocyte sensitivity to cortisol was examined in 30 long stable renal transplant recipients. Lymphocyte sensitivity to cortisol and its relationship with the clinical outcome after steroid reduction and withdrawal was investigated. The lymphocyte sensitivities to cortisol were estimated as IC(50) of lymphocyte blastogenesis. The lymphocyte proliferation rate for concentration of serum cortisol compared between incident and non-incident groups. Serum creatinine levels (S-Cr) increased in a significantly higher number of patients hyposensitive to cortisol (IC(50)≧10000 ng/ml) than in normally sensitive patients (IC(50)<10000 ng/ml). The incidences of steroid withdrawal syndrome and necessity for increasing steroid dose or restarting steroid administration were also higher in the patients hyposensitive to cortisol. The patients in whom the lymphocyte proliferation rate was less than 60% did not show increase in S-Cr, experience steroid withdrawal symptoms, or require an increase in the steroid dose or restart of steroid administration. The patients who have the normal IC(50) values of cortisol, can withdraw steroid more safely. The lymphocyte sensitivity to cortisol may be a useful biomarker for selecting patients who can sustain steroid withdrawal.

Clinical Significance of the Pharmacological Efficacy of Tacrolimus Estimated by the Lymphocyte Immunosuppressant Sensitivity Test (LIST) Before and After Renal Transplantation

The lymphocyte immunosuppressant sensitivity test (LIST) with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay procedure can predict the pharmacological efficacy of immunosuppressive agents. A previous study reported the pharmacological efficacy of tacrolimus evaluated by LIST just before renal transplantation significantly correlated with the incidence of acute rejection episodes. However, the pharmacological efficacy of tacrolimus has not been estimated after renal transplantation. Therefore, the present study evaluated the pharmacological efficacy of tacrolimus by LIST using the MTT assay procedure before and 1, 3, and 12 months after transplantation in 17 renal transplant recipients that received tacrolimus-based immunosuppressive therapy. The tacrolimus pharmacological efficacies before and after the procedure were also compared with incidence of acute rejection and cytomegalovirus (CMV) infection episodes. The individual values of tacrolimus 50% inhibition of lymphocyte proliferation (IC50) varied widely before transplantation, and the mean value of the IC50 was 126.4 ± 337.7 ng/ml. The patients were divided into two groups according to the tacrolimus IC50 values evaluated before transplantation. The rate of acute rejection episodes in the tacrolimus high-sensitivity group was significantly lower than that in the tacrolimus low-sensitivity group (p = 0.005). The tacrolimus IC50 deviation between patients expanded further at one and three months after surgery. However, the sensitivity deviation almost converged at 1 year after surgery. Moreover, the pharmacological efficacy of tacrolimus evaluated at 1, 3, and 12 months after transplantation did not significantly correlate with the incidence of acute rejection episodes. The pharmacological efficacies of tacrolimus evaluated at both before and after surgery were not significantly correlated with the episodes of CMV infection. These findings suggest that the pharmacological efficacy of tacrolimus evaluated with LIST before surgery is a useful biomarker for predicting the occurrence of acute allograft rejection in renal transplantation.

Comparative Study of the Cellular Pharmacodynamics of Tacrolimus in Renal Transplant Recipients Treated with and without Basiliximab

Basiliximab is a recently developed immunosuppressive agent for the prevention of acute allograft rejection in renal transplant recipients. The combination use of basiliximab and a calcineurin inhibitor was suggested to be more effective in comparison to immunosuppressive therapy using calcineurin inhibitor without basiliximab. Cyclosporine has been generally administered with basiliximab for renal transplant recipients. However, in cases of tacrolimus-based immunosuppressive regimen, the clinical efficacy and safety of combined use of tacrolimus and basiliximab remains to be elucidated. This study evaluated the tacrolimus pharmacological efficacy using a lymphocyte immunosuppressant sensitivity test (LIST) with MTT assay procedures in 16 cases of renal transplant recipients treated by tacrolimus without basiliximab and in 13 cases treated by tacrolimus in combination with basiliximab. The rate of acute rejection episodes in the recipients treated with tacrolimus plus basiliximab was 1/13 (7.7%), whereas the rate in the recipients treated with tacrolimus without basiliximab was 6/16 (37.5%). The recipients were divided into two groups according to their peripheral blood mononuclear cell (PBMC) sensitivity to tacrolimus [i.e., including a tacrolimus high sensitivity group (IC50 <1.0 ng/ml) and a low sensitivity group (IC50 >1.0 ng/ml). In the recipients treated with tacrolimus without basiliximab, the rate of acute rejection episodes in the tacrolimus high sensitivity group was 1/10 (10.0%), which was significantly lower than the rate in the low sensitivity group of 5/6 (83.3%; p = 0.008). The incidence of cytomegalovirus infection was not significantly different between the tacrolimus high and the low sensitivity groups of the recipients treated with tacrolimus with and without basiliximab. Therefore, in the case of selected tacrolimus-based immunosuppressive therapy for renal transplant recipients, the tacrolimus pharmacological efficacy should be evaluated using LIST at a time just before the transplant procedure in order to accurately predict allograft rejection. The data also suggested that low tacrolimus sensitivity recipients should be treated with tacrolimus-based immunosuppressive therapy in combination with basiliximab.

Comparative study of the cellular pharmacodynamics of calcineurin inhibitors between patients with chronic renal failure awaiting renal transplantation and cirrhosis patients awaiting liver transplantation

The in vitro response of peripheral blood mononuclear cells (PBMCs) to the suppressive effects of calcineurin inhibitors is known to correlate with the clinical efficacy of drugs used in renal transplantations. The present study was conducted to examine the differences of PBMC responses to calcineurin inhibitors between chronic renal failure (CRF) patients awaiting renal transplantation and cirrhosis patients awaiting liver transplantation. The study included 99 CRF patients awaiting renal transplantation and 27 cirrhosis patients awaiting liver transplantation. Twenty milliliters of venous blood was taken 1-7 days before transplantation. The in vitro drug concentrations giving 50% inhibition of PBMC blastogenesis stimulated with concanavalin A (IC(50)s) were calculated. The suppressive effects of tacrolimus against PBMC blastogenesis were more than 10-100 times stronger than those of cyclosporine. The median IC(50) value for cyclosporine against the CRF PBMCs was not significantly different from the median IC(50) value against the cirrhosis PBMCs. In contrast, tacrolimus sensitivity in cirrhosis PBMCs is approximately seven times higher than that in CRF PBMCs. The median IC(50) value for tacrolimus against cirrhosis PBMCs was significantly lower and therefore the effect was stronger in comparison to the CRF PBMCs (p < 0.001). These data suggest that the PBMCs of cirrhosis patients, in comparison to those of CRF patients, are highly sensitive to the suppressive effect of tacrolimus. However, PBMC sensitivity to cyclosporine was not significantly different between the CRF and cirrhosis patients. These observations raise the possibility that treatment with tacrolimus, rather than cyclosporine, may therefore be a better choice to reduce the risks of allograft rejection in liver transplantation.

Can we personalize treatment for kidney diseases?

The idea of individualizing therapies to obtain optimal clinical results is not new but has only recently been applied to kidney diseases. Nonetheless, kidney disorders present a variety of opportunities to personalize medicine. Here, the heterogeneity of kidney disorders is reviewed to provide a rationale for pursuing personalized medicine. Data on adjusting therapy on the basis of pharmacogenetics/genomics and pharmacodynamics are summarized to demonstrate where the field is, and biomarker studies that reflect the future of personalized medicine are discussed. The goal of this review is to demonstrate that we can personalize therapy for kidney diseases but that considerable investment in new research will be required for personalized medicine to be routinely used in nephrology clinics.

Influence of bacterial superantigen TSST-1 against the anti-proliferative efficacy of immunosuppressive drugs and interleukin 2 production in peripheral blood mononuclear cells of hemodialysis patients and healthy subjects

We investigated the influence of bacterial superantigen on the efficacies of immunosuppressive drugs on the blastogenesis of peripheral-blood mononuclear cells of 27 hemodialysis patients awaiting renal transplantation. The IC(50) values for prednisolone, methylprednisolone, cyclosporine, and tacrolimus evaluated in the superantigen-stimulated cells were significantly higher than those evaluated in concanavalin A-stimulated cells (p = 0.0002-0.018). Interleukin-2 amounts produced from superantigen-stimulated cells were significantly larger than those from concanavalin A-stimulated cells (p = 0.0363). These results suggest that superantigen attenuates the suppressive efficacies of glucocorticoids and calcineurin inhibitors by stimulating lymphocytes of hemodialysis patients awaiting transplantation to overproduce interleukin-2.

Comparative study of the effects of betamethasone butyrate propionate, vitamin D3 derivatives, and cyclosporine on human lymphocyte-proliferation stimulated with a hemolytic streptococci-derived superantigen

Bacterial infection might influence the clinical response of patients with immunological disorders including psoriasis to the therapeutic efficacies of immunosuppressive drugs, but few studies have been carried out to investigate the implication of bacterial superantigens. We evaluated the suppressive efficacies of betamethasone butyrate propionate, vitamin D3 derivatives, and cyclosporine against concanavalin A- or superantigen-induced proliferation of peripheral-blood mononuclear cells obtained from 18 healthy subjects. In vitro drug concentrations giving 50% inhibition (IC50s) of peripheral-blood mononuclear cell-proliferation stimulated with concanavalin A or streptococcal pyrogenic enterotoxin A were estimated. Concentrations of tumor necrosis factor-alpha, interferon-gamma, interleukin-2, -4, -5, or -10, in a peripheral-blood mononuclear cell-culture medium were measured with beads-array procedures. The median (range) IC50 value for betamethasone butyrate propionate evaluated in the streptococcal pyrogenic enterotoxin A-stimulated peripheral-blood mononuclear cells was 291.6 (0.001-1171.5) ng/ml, which was significantly higher than the value 0.072 (0.01-222.5) ng/ml found in concanavalin A-stimulated peripheral-blood mononuclear cells (P=0.0245). However, the median (range) IC50 value for calcipotriol in the streptococcal pyrogenic enterotoxin A-stimulated peripheral-blood mononuclear cells was 0.3 (0.24-1357.4) ng/ml, which was significantly lower than the value 128.6 (0.1-776.9) ng/ml found in concanavalin A-stimulated peripheral-blood mononuclear cells (P=0.0323). The IC50 value for cyclosporine was not significantly different between the concanavalin A- and streptococcal pyrogenic enterotoxin A-stimulated PBMCs. Concentration for none of the cytokines was significantly different between concanavalin A- and streptococcal pyrogenic enterotoxin A-stimulated peripheral-blood mononuclear cell cultures. The effects of betamethasone butyrate propionate to suppress these cytokine productions were rather stronger than those of calcipotriol. Streptococcal pyrogenic enterotoxin A induced by hemolytic streptococci colonization is suggested to attenuate the therapeutic efficacy of betamethasone butyrate propionate. While the mechanistic background of calcipotriol to suppress streptococcal pyrogenic enterotoxin A-induced peripheral-blood mononuclear cell-proliferation remains to be elucidated, vitamin D3 derivatives appears to be effective in suppressing anomalistic immunity in patients having hemolytic streptococci colonization.

Cellular pharmacodynamics of immunosuppressive drugs for individualized medicine

The therapeutic effects of immunosuppressive drugs are known to deviate largely between patients, but efficient strategies for the differentiation of patients who show clinical resistance to immunosuppressive therapies have not been established. Accordingly, a considerable number of patients receive treatment with immunosuppressive drugs despite the onset of serious side effects and poor responses. Cellular pharmacodynamics of immunosuppressive drugs in vitro using peripheral lymphocytes derived from each patient, an attractive way to distinguish resistant patients, is respected and has been applied to the carrying out of individualized immunosuppressive therapy. In this article, I summarize experimental procedures for assaying immune cell responses to immunosuppressive drugs in vitro, and highlight the relationship between cellular sensitivity to immunosuppressive drugs and the therapeutic efficacy of drugs in organ transplantation and several immunological disorders. I will also overview the molecular mechanisms and genetic bases for cellular and clinical resistance to immunosuppressive drugs. Lastly, the future clinical prospects for the application of in vitro drug sensitivity tests for "patient-tailored" immunosuppressive therapies are discussed.

Correlation Between Pharmacological Efficacy of Cyclosporine A and Tacrolimus, Evaluated by Lymphocyte Immunosuppressant‐Sensitivity Test (LIST) with MTT Assay Procedure in Renal Transplant Recipients

The dose of calcineurin inhibitors in renal transplantation has been adjusted, based on the therapeutic drug monitoring data. However, the data do not always correlate with clinical drug efficacy. In vitro response of peripheral-blood mononuclear cells to immunosuppressive drugs is reported to correlate with the recipient-response to therapeutic efficacy of the drug. We report, here, usefulness of a lymphocyte immunosuppressant sensitivity test for the estimation of individual drug sensitivity in renal transplant recipients. The LIST we have developed includes MTT assay procedures without the use of radioisotope-labeled compounds, which is convenient for general hospital use. Utilizing this procedure, we compared the pharmacological efficacy between cyclosporine A and tacrolimus in 41 renal transplant recipients.

Peripheral blood lymphocytes P-glycoprotein (P-gp, gp-170) expression in allogenic kidney transplant patients

AIM AND METHODS

P-glycoprotein (gp-170, P-gp) is a transmembrane transporter involved in drug, for example cyclosporine A, efflux from the cells thus limiting their intracellular concentration. Expression of the transporter on the surface of immune competent cells may be associated with poor prognosis in kidney transplant patients. The aim of the present study was to evaluate P-gp expression on the surface of CD4(+), CD8(+), CD19(+) and CD56(+) cells in kidney transplant patients treated with cyclosporine A as a main immunosuppressant, using flow cytometry.

RESULTS

It was found that P-gp expression in kidney transplant patients with acute rejection did not differ significantly from transplanted patients without rejection studied in the same period after transplantation, as well as from the healthy controls. Administration of 3-day course of 1,000 mg/24 h methylprednisolone did not affect the expression of P-gp in the studied cells, except for significant elevation in CD56(+) cells, which disappeared at 2 weeks after cessation of steroid administration.

CONCLUSION

Based on the results from the present study it can be concluded that P-gp expression is not a prognostic factor of acute kidney graft rejection.

Bacterial superantigen TSST-1 attenuates suppressive efficacy of glucocorticoids and calcineurin inhibitors against blastogenesis of peripheral blood mononuclear cells from patients with antineutrophil cytoplasmic antibody-associated vasculitis and nephrosis

Successful immunosuppressive therapy is critical for the treatment of patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis and nephrosis. However, a considerable number of patients have shown clinical resistance to therapy. Bacterial infection might influence the clinical response of patients to immunosuppressive drugs, but few studies have been carried out to investigate the effect of bacterial superantigens on the efficacy of the drugs in these patients. We evaluated the suppressive efficacy of prednisolone, methylprednisolone, cyclosporine, and tacrolimus on the blastogenesis of PBMCs obtained from 12 ANCA-associated vasculitis patients (ANCA patients), eight patients with nephrotic syndrome, and eight healthy subjects. PBMC-stimulation index was calculated from the formula: [3H]thymidine incorporated in the presence of stimulant (dpm)/[3H]thymidine incorporated in the absence of stimulant (dpm). In vitro drug concentrations giving 50% inhibition (IC50s) of PBMC blastogenesis stimulated with concanavalin A (con A) or toxic shock syndrome toxin 1 (TSST-1) derived from Staphylococcus aureus (S. aureus) were calculated. The IC50 values for the four drugs evaluated in TSST-1-stimulated PBMCs were significantly higher than those evaluated in con A-stimulated PBMCs in both ANCA patients and nephrosis patients (p<0.012-0.044). Whereas, the IC50 values for these immunosuppressive drugs, except methylprednisolone, were not significantly different between con A- and TSST-1-stimulated PBMCs in healthy subjects. The stimulation index was not significantly different between the con A- and TSST-1-stimulated PBMCs in either of the subject groups. These observations raise the possibility that TSST-1 induced by S. aureus infection attenuates the clinical efficacy of glucocorticoids and calcineurin inhibitors in ANCA patients and nephrosis patients.

Optimal Dose and Target Trough Level in Cyclosporine and Tacrolimus Conversion in Renal Transplantation as Evaluated by Lymphocyte Drug Sensitivity and Pharmacokinetic Parameters

We evaluated the relative clinical potency of cyclosporine (CyA) and tacrolimus (Tac) using pharmacodynamic and pharmacokinetic parameters of the drug to obtain the most suitable converting dose and target trough level. The relative pharmacodynamic potency was examined by the mean ratio of drug concentrations giving 50% inhibition of blastogenesis of lymphocytes (IC50) in 66 chronic renal failure patients. The relative potency estimated from clinical pharmacokinetic parameters was examined by the mean ratio of each pharmacokinetic parameter value of CyA versus Tac. The pharmacokinetic parameters were estimated by 12-hour monitoring of drug blood concentrations in seven CyA patients and seven Tac patients. The mean IC50 ratio of CyA and Tac (CyA/Tac of IC50) was 25.1. The mean area under the concentration-time curve (AUC) ratio (CyA/Tac of AUC) was 25.5, the mean trough level (C(min)) ratio (CyA/Tac of C(min)) was 13.2, and the mean dose per body weight ratio was 25.2. The relative potency estimated from AUC that is the most reliable pharmacokinetic parameter for the estimation of clinical efficacy of calcineurin inhibitors appeared to agree with the relative pharmacodynamic potency estimated from IC50. The data suggest that TAC 25-fold more potent than CyA, which represents a suitable converting dose ratio, and that target trough level of CyA is about 13-fold greater than Tac based on CyA/Tac of C(min). We conclude that these relative values may be useful to estimate the suitable dose and target trough levels to convert between CyA and Tac.

Immunosuppressant pharmacodynamics on peripheral-blood mononuclear cells from patients with ulcerative colitis

We investigated peripheral-blood mononuclear cell (PBMC) response to immunosuppressive drugs and its influence on glucocorticoid therapy in ulcerative colitis (UC). IC50s of immunosuppressive drugs on in vitro blastogenesis of PBMCs stimulated with concanavalin A were estimated in 76 UC and 146 healthy subjects. Individual differences in IC50s for prednisolone, methylprednisolone, cyclosporine, and tacrolimus on blastogenesis of PBMCs from UC patients were spread from 11.0 to 1000, 0.6 to 1000, 0.01 to 1000, and 0.001 to 4.6 ng/ml, respectively. Normal upper thresholds for IC50s of these drugs were estimated from the mean + 2 S.D. of the IC50s of healthy PBMCs, and the patients exhibiting IC50s over these levels were arbitrarily considered as resistant. The incidences of resistance to glucocorticoids and cyclosporine in UC were significantly higher than those in healthy subjects (p < 0.0005). In 14 UC patients, there was a significant correlation between amounts of prednisolone (p < 0.05) or period of prednisolone administration (p < 0.05) for UC treatment and prednisolone IC50. The results showed that large individual deviations in PBMC response to the drugs were observed in UC, and UC patients exhibiting low PBMC sensitivity to prednisolone required a high prednisolone amount as well as long period of prednisolone administration for treatment. Thus, the drug sensitivity tests could be informative to single out refractory patients to the immunosuppressive therapy.

Matrix accumulation in mesangial cells exposed to cyclosporine A requires a permissive genetic background

BACKGROUND

Chronic nephrotoxicity is an important adverse effect of cyclosporine A (CsA) therapy. Tubulo-interstitial lesions and arteriolopathy are common histologic findings. Glomerular lesions are also described, but they are of variable severity. The aim of our study is to determine whether CsA has a direct effect on mesangial cells and whether the cellular response depends on the genetic background.

METHODS

We studied mesangial cells isolated from mice susceptible (ROP/Le-+Es1(b)+Es1(a), ROP) and resistant to glomerulosclerosis (B6SJLF1, C57). We previously showed that sclerosis-prone and sclerosis-resistant phenotypes are maintained in vitro. We examined whether CsA exposure directly affected extracellular matrix turnover in mesangial cells and whether the response is determined by the genetic background. Extracellular matrix synthesis and degradation were studied by proline incorporation, ELISA, reverse transcription-polymerase chain reaction, zymography, and reverse zymography. We chose a CsA dose that induced neither cytotoxicity nor apoptosis (1 microg/ml).

RESULTS

At the dose of 1 microg/ml total collagen accumulation was increased in ROP but not in C57 cells. Matrix metalloproteinase (MMP)-2 activity and mRNA levels were selectively decreased in ROP cells. CsA exposure did not affect tissue inhibitors of MMP (TIMP)-1 and -2 activity or TGF-beta1 mRNA expression and protein synthesis in either cell line.

CONCLUSION

CsA increases total collagen accumulation in mesangial cells from sclerosis-prone mice by decreasing MMP-2 activity, but does not affect cells from sclerosis-resistant mice. Thus, CsA directly affects mesangial cells, but only those with a permissive genetic background for glomerulosclerosis.

Tacrolimus: a further update of its pharmacology and therapeutic use in the management of organ transplantation

Tacrolimus (FK-506) is an immunosuppressant agent that acts by a variety of different mechanisms which include inhibition of calcineurin. It is used as a therapeutic alternative to cyclosporin, and therefore represents a cornerstone of immunosuppressive therapy in organ transplant recipients. Tacrolimus is now well established for primary immunosuppression in liver and kidney transplantation, and experience with its use in other types of solid organ transplantation, including heart, lung, pancreas and intestinal, as well as its use for the prevention of graft-versus-host disease in allogeneic bone marrow transplantation (BMT), is rapidly accumulating. Large randomised nonblind multicentre studies conducted in the US and Europe in both liver and kidney transplantation showed similar patient and graft survival rates between treatment groups (although rates were numerically higher with tacrolimus- versus cyclosporin-based immunosuppression in adults with liver transplants), and a consistent statistically significant advantage for tacrolimus with respect to acute rejection rate. Chronic rejection rates were also significantly lower with tacrolimus in a large randomised liver transplantation trial, and a trend towards a lower rate of chronic rejection was noted with tacrolimus in a large multicentre renal transplantation study. In general, a similar trend in overall efficacy has been demonstrated in a number of additional clinical trials comparing tacrolimus- with cyclosporin-based immunosuppression in various types of transplantation. One notable exception is in BMT, where a large randomised trial showed significantly better 2-year patient survival with cyclosporin over tacrolimus, which was primarily attributed to patients with advanced haematological malignancies at the time of (matched sibling donor) BMT. These survival results in BMT require further elucidation. Tacrolimus has also demonstrated efficacy in various types of transplantation as rescue therapy in patients who experience persistent acute rejection (or significant adverse effect's) with cyclosporin-based therapy, whereas cyclosporin has not demonstrated a similar capacity to reverse refractory acute rejection. A corticosteroid-sparing effect has been demonstrated in several studies with tacrolimus, which may be a particularly useful consideration in children receiving transplants. The differences in the tolerability profiles of tacrolimus and cyclosporin may well be an influential factor in selecting the optimal treatment for patients undergoing organ transplantation. Although both drugs have a similar degree of nephrotoxicity, cyclosporin has a higher incidence of significant hypertension, hypercholesterolaemia, hirsutism and gingival hyperplasia, while tacrolimus has a higher incidence of diabetes mellitus, some types of neurotoxicity (e.g. tremor, paraesthesia), diarrhoea and alopecia.

CONCLUSION

Tacrolimus is an important therapeutic option for the optimal individualisation of immunosuppressive therapy in transplant recipients.