Improving prediction of tacrolimus concentration using a combination of population pharmacokinetic modeling and machine learning in chinese renal transplant recipients.

Aims: The population pharmacokinetic (PPK) model-based machine learning (ML) approach offers a novel perspective on individual concentration prediction. This study aimed to establish a PPK-based ML model for predicting tacrolimus (TAC) concentrations in Chinese renal transplant recipients. Methods: Conventional TAC monitoring data from 127 Chinese renal transplant patients were divided into training (80%) and testing (20%) datasets. A PPK model was developed using the training group data. ML models were then established based on individual pharmacokinetic data derived from the PPK basic model. The prediction performances of the PPK-based ML model and Bayesian forecasting approach were compared using data from the test group. Results: The final PPK model, incorporating hematocrit and CYP3A5 genotypes as covariates, was successfully established. Individual predictions of TAC using the PPK basic model, postoperative date, CYP3A5 genotype, and hematocrit showed improved rankings in ML model construction. XGBoost, based on the TAC PPK, exhibited the best prediction performance. Conclusion: The PPK-based machine learning approach emerges as a superior option for predicting TAC concentrations in Chinese renal transplant recipients.

Influence of Calcineurin Inhibitors and Genetic Polymorphism of Transporters on Enterohepatic Circulation and Exposure of Mycophenolic Acid in Chinese Adult Renal Allograft Recipients.

There is significant enterohepatic circulation (EHC) during the disposition of mycophenolic acid (MPA). The aim of this study was to elucidate factors influencing the EHC of MPA in Chinese adult renal allograft recipients. After 2 weeks of therapy with mycophenolate mofetil or enteric-coated mycophenolate sodium, blood samples were collected from 125 patients at 0 to 12 hours post-administration and MPA concentrations were determined. The influence of calcineurin inhibitors (CNIs) and genetic polymorphisms on MPA exposure and EHC was studied. The Shapley additive explanations method was used to estimate the impact of various factors on the area under the plasma drug concentration-time curve (AUC0-12h ) for MPA. An extreme gradient boosting (XGboost) machine learning-based model was established to predict AUC0-12h . Results showed that the dose-normalized AUC6-12h (dn-AUC6-12h ) of MPA was significantly lower in patients co-administered with cyclosporine (CsA) than in patients co-administered with tacrolimus (TAC) (P < .05). For patients co-administered with TAC, patients with ABCC2 C-24T CC or SLCO1B1 T521C TT genotypes had significantly higher values of dn-AUC6-12h (P < .05). Patients with SLCO1B3 334T/699G alleles had significantly lower dn-AUC6-12h values than homozygotes (P < .05). By introducing body weight, age, and EHC-related factors, including co-administered CNIs and genetic polymorphism of drug transporters, as covariates in the XGboost machine learning model, the prediction performance of AUC0-12h for MPA in Chinese adult renal allograft recipients can be improved.

The pharmacokinetics of tacrolimus in peripheral blood mononuclear cells and limited sampling strategy for estimation of exposure in renal transplant recipients.

PURPOSE: Intracellular exposure of tacrolimus (TAC) may be a better marker of therapeutic effect than whole blood exposure. We aimed to evaluate the influence of genetic polymorphism on the pharmacokinetics of TAC in peripheral blood mononuclear cells (PBMCs) and develop limited sampling strategy (LSS) models to estimate the area under the curve (AUC0-12h) in the PBMC of Chinese renal transplant patients. METHODS: Ten blood samples of each of the 23 renal transplant patients were collected 0-12h after 14 (10-18) days of TAC administration. PBMCs were separated and quantified. The TAC level in PBMCs was determined, and pharmacokinetic parameters were estimated by noncompartmental study. The AUC0-12h of TAC in whole blood was estimated by Bayesian approach based on a population pharmacokinetic model established in 65 renal transplant patients. The influence of CYP3A5 and ABCB1 genotypes on exposure was estimated. By applying multiple stepwise linear regression analysis, LSS equations for TAC AUC0-12h in the PMBC of renal transplant patients were established, and the bias and precision of various equations were identified and compared. RESULTS: We found a modest correlation between TAC exposure in whole blood and PBMC (r2 = 0.5260). Patients with the CYP3A5 6986GG genotype had a higher AUC0-12h in PBMCs than those with the 6986 AA or GA genotype (P = 0.026). Conversely, patients with the ABCB1 3435TT genotype had a higher AUC0-12h in PBMC than those with the 3435 CC and CT genotypes (P = 0.046). LSS models with 1-4 blood time points were established (r2 = 0.570-0.989). The best model for predicting TAC AUC0-12h was C2-C4-C6-C10 (r2 = 0.989). The model with C0.5-C6 (r2 = 0.849) can be used for outpatients who need monitoring to be performed in a short period. CONCLUSIONS: The CYP3A5 and ABCB1 genotypes impact TAC exposure in PBMCs, which may further alter the effects of TAC. The LSS model consisting of 2-4 time points is an effective approach for estimating full TAC AUC0-12h in Chinese renal transplant patients. This approach may provide convenience and the possibility for clinical monitoring of TAC intracellular exposure.

Gastric cancer: An epigenetic view.

Gastric cancer (GC) poses a serious threat worldwide with unfavorable prognosis mainly due to late diagnosis and limited therapies. Therefore, precise molecular classification and search for potential targets are required for diagnosis and treatment, as GC is complicated and heterogeneous in nature. Accumulating evidence indicates that epigenetics plays a vital role in gastric carcinogenesis and progression, including histone modifications, DNA methylation and non-coding RNAs. Epigenetic biomarkers and drugs are currently under intensive evaluations to ensure efficient clinical utility in GC. In this review, key epigenetic alterations and related functions and mechanisms are summarized in GC. We focus on integration of existing epigenetic findings in GC for the bench-to-bedside translation of some pivotal epigenetic alterations into clinical practice and also describe the vacant field waiting for investigation.

Population Pharmacokinetics and Bayesian Estimation of the Area Under the Concentration-Time Curve for Ganciclovir in Adult Chinese Renal Allograft Recipients After Valganciclovir Administration.

Valganciclovir (VGCV) is the prodrug of ganciclovir (GCV). The objective of this study was to establish a population pharmacokinetic model (PPK) of GCV to investigate the PK characteristics of GCV after administration of VGCV in adult Chinese renal allograft recipients. Seventy Chinese renal allograft recipients were given 450 mg (n = 41) or 900 mg (n = 29) VGCV daily. Blood samples were drawn 0-24 hours after 5 days' therapy, and GCV plasma levels were determined. The PPK model was constructed using nonlinear mixed-effects modeling, and the Bayesian estimation of AUC0-24h was constructed for an individual patient based on limited plasma samples. The PK of GCV was best described by a 2-compartment model with a first-order absorption process. The CL/F, V2 /F, Q/F, V3 /F, Ka , and lag time of GCV were 15.8 ± 0.71 L/h, 10.9 ± 2.38 L, 3.98 ± 0.40 L/h, 167 ± 44.0 L, 0.23 ± 0.0078 1/h, and 0.93 ± 0.017 hours, respectively. Clearance of creatinine was found to have a significant impact on the CL/F of GCV (P < .01). Sampling strategies consisted of plasma concentrations 0 and 2 and 0, 2, and 4 hours after VGCV administration were shown to be suitable for the estimation of the GCV AUC0-24h . The PPK model was acceptable and can describe the PK of GCV in Chinese renal transplant patients administered VGCV. The AUC0-24h of GCV in Chinese renal transplant patients can be calculated by a limited sampling strategy method.

Establishment of a Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of Immunosuppressant Levels in the Peripheral Blood Mononuclear Cells of Chinese Renal Transplant Recipients.

BACKGROUND: Monitoring immunosuppressant levels, such as mycophenolic acid (MPA), cyclosporin A (CsA), and tacrolimus (TAC), in peripheral blood mononuclear cells (PBMCs) could be useful in organ transplant patients administered individualized therapy. The authors developed a liquid chromatography-tandem mass spectrometry assay technique to simultaneously determine immunosuppressant levels in PBMCs and assess their pharmacokinetics in Chinese renal allograft recipients. METHODS: PBMCs were isolated from the whole blood of 27 Chinese renal transplant patients using Ficoll-Paque Plus solution, and cell number was determined; acetonitrile treatment for protein precipitation, and gradient elution was performed on an Agilent Eclipse XDB-C18 column (3.5 µm, 2.1 × 100 mm) with mobile phase: water and methanol (containing 2 mM ammonium formate); flow rate: 0.3 mL·min. RESULTS: The calibration curves of MPA, CsA, and TAC had a linear range (ng·mL): 0.098-39.2 (r = 0.9987), 0.255-102 (r = 0.9969), and 0.028-11.2 (r = 0.9993), respectively. The extraction effects, matrix effects, and mean relative recovery of these immunosuppressants were 70.4%-93.2%, 72.7%-96.5%, and 90.1%-112.4%, respectively. The within-day and between-day coefficients of variation were <15%. The AUC0-12 of MPA in PBMCs correlated well with those in plasma. The level of MPA, CsA, and TAC in PBMCs might be more stable during dosing interval. CONCLUSIONS: The derived liquid chromatography-tandem mass spectrometry assay is suitable for simultaneously monitoring different immunosuppressants in PBMCs. Pharmacokinetic of MPA, CsA, and TAC displayed considerable interindividual variability. Intracellular monitoring of immunosuppressants may facilitate individualized therapy for renal allograft recipients.

Limited sampling strategy for the estimation of the area under the concentration-time curve for ganciclovir in Chinese adult renal allograft recipients.

OBJECTIVES: Valganciclovir (VGCV) treatment is recommended for the prevention of cytomegalovirus (CMV) infection in renal allograft recipients. The aim of the present study is to investigate the pharmacokinetic characteristics of ganciclovir (GCV) after administration of VGCV in Chinese adult renal allograft recipients and estimate the exposure to GCV using limited sampling strategy (LSS). METHODS: Forty Chinese renal allograft recipients were given 450 mg or 900 mg VGCV daily. Blood samples were drawn before treatment and 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 h after 5 days of VGCV therapy, and the plasma concentrations of VGCV and GCV were determined using a liquid chromatography-mass spectrometry assay. The major pharmacokinetic parameters for GCV and VGCV were determined using a noncompartmental assay. Multiple stepwise linear regression analysis was conducted to establish a model equation for the estimation of the GCV AUC0-24 h in Chinese patients using LSS. RESULTS: In the 450 and 900 mg groups, the Cmax for VGCV was 0.2 ± 0.10 and 0.4 ± 0.16 mg/L, respectively; the Cmax for GCV was 4.2 ± 1.1 and 8.6 ± 1.6 mg/L, respectively; and the AUC0-24 h for GCV was 28.4 ± 8.4 and 60.7 ± 17.5 mg·h/L, respectively. For the establishment of LSS models, 40 patients were divided into the training group (n = 24) and validation group (n = 16). The model equations used for the calculation of AUC0-24 h for GCV were established in the training group by using multiple linear regression assay. Equations including AUC = 8.1 + 29.7 × C0 + 5.7 × C4 (r2 = 0.91) and AUC = - 0.4 + 11.0 × C0 + 2.1 × C2 + 13.7 × C8 (r2 = 0.98) were acceptable. The %MPE and %MAPE values obtained from the validation group for the two model equations were 5.89 ± 14.5% and 12.1 ± 9.53%, and - 1.30 ± 4.40% and 3.28 ± 3.11%, respectively. CONCLUSIONS: The LSS models that included C0 and C4 or C0, C2, and C8 in the estimation of AUC0-24 h for GCV had favorable performance and can be used for therapeutic drug monitoring in the prevention of CMV infection using VGCV in Chinese renal allograft recipients.

Population Pharmacokinetics and Bayesian Estimation of Mycophenolic Acid Exposure in Chinese Renal Allograft Recipients After Administration of EC-MPS.

The aim of the present study is to establish a population pharmacokinetic (PPK) model of mycophenolic acid (MPA) and limited sampling strategy models for the estimation of MPA exposure in Chinese adult renal allograft recipients following oral administration of enteric coated mycophenolate sodium (EC-MPS). A total of 74 sets of full pharmacokinetic profiles and 47 sets of MPA-sparing samples were collected from 102 renal transplant recipients who received oral EC-MPS. The MPA concentration was determined by an enzyme-multiplied immunoassay technique, and the pathophysiologic data were recorded. The PPK model was constructed using nonlinear mixed-effects modeling, and the limited sampling strategy models for MPA were established by using multiple regression analysis and the maximum a posteriori Bayesian assay based on 2 to 4 sampling time points following EC-MPS administration. The pharmacokinetics of MPA were best described by a 2-compartment model with a first-order absorption process and a lag time of absorption. The clearance of MPA was 12.3 ± 1.14 L/h. Comedicating with cyclosporine A was found to have a significant impact on the clearance/bioavailability of MPA (P < .01). Sampling strategies consisted of plasma concentration at 1.5, 2, 4 (C1.5-C2-C4) hours and 1.5, 2, 4, 6 (C1.5-C2-C4-C6) hours after EC-MPS administration were shown to be suitable for the estimation of the MPA area under the concentration-time curve in these patients. The PPK model was acceptable and can describe the pharmacokinetics of MPA in Chinese renal transplant recipients administered EC-MPS. The area under the concentration-time curve of MPA in Chinese renal transplant recipients could be estimated through a limited sampling strategy method, based on which individualized immunosuppressive regimens could be designed.

Population pharmacokinetics and Bayesian estimation of mycophenolic acid concentrations in Chinese adult renal transplant recipients.

Mycophenolate mofetil (MMF) is an important immunosuppressant used in renal transplantation, and mycophenolic acid (MPA) is the active component released from the ester prodrug MMF. The objective of this study was to investigate the population pharmacokinetics of mycophenolic acid (MPA) following oral administration of MMF in Chinese adult renal transplant recipients and to identify factors that explain MPA pharmacokinetic variability. Pharmacokinetic data for MPA and covariate information were retrospectively collected from 118 patients (79 patients were assigned to the group for building the population pharmacokinetic model, while 39 patients were assigned to the validation group). Population pharmacokinetic data analysis was performed using the NONMEM software. The pharmacokinetics of MPA was best described by a two-compartment model with a first-order absorption rate with no lag time. Body weight and serum creatinine level were positively correlated with apparent clearance (CL/F). The polymorphism in uridine diphosphate glucuronosyltransferase gene, UGT2B7, significantly explained the interindividual variability in the initial volume of distribution (V1/F). The estimated population parameters (and interindividual variability) were CL/F 18.3 L/h (34.2%) and V1/F 27.9 L (21.3%). The interoccasion variability was 13.7%. These population pharmacokinetic data have significant clinical value for the individualization of MMF therapy in Chinese adult renal transplant patients.

[Molecular Identification on Three Medicinal Phlomis Species Produced in Yunnan Province Based on ITS and matK].

Objective: To analyze ITS region and matK gene sequences of three medicinal Phlomis plants,in order to provide molecular basis for identifying and protecting their wild resources. Methods: PCR and sequencing were conducted on Phlomis likiangensis,Phlomis melanantha and Phlomis betonicoides wild populations by primers pairs ITS4 / ITS5 and matKXF / matK5 R. Results: The smallest inter-K2 P genetic distance was further than the largest intra-K2 P genetic distance in Phlomis likiangensis, Phlomis melanantha and Phlomis betonicoides. Different samples of three medicinal Phlomis plants were gathered together and could be distinguished from other exogenous species by Neighbor-Joining( NJ) tree. Phlomis likiangensis, Phlomis melanantha and Phlomis betonicoides had three, three and one sites on ITS2 for their effective identification, and had three,three and three sites on ITS1 for their effective identification respectively. Phlomis betonicoides had three sites on matK for its effective identification, while Phlomis likiangensis or Phlomis melanantha needed multiple sites for their effective identification. Conclusion: The study implies that ITS1,ITS2 and matK fragments could be used for molecular identification of Phlomis likiangensis, Phlomis melanantha and Phlomis betonicoides.

[Study on ITS sequences of Aconitum vilmorinianum and its medicinal adulterant].

OBJECTIVE: To analyze and compare the ITS sequences of Aconitum vilmorinianum and its medicinal adulterant Aconitum austroyunnanense. METHODS: Total genomic DNA were extracted from sample materials by improved CTAB method, ITS sequences of samples were amplified using PCR systems, directly sequenced and analyzed using software DNAStar, ClustalX1.81 and MEGA 4.0. RESULTS: 299 consistent sites, 19 variable sites and 13 informative sites were found in ITS1 sequences, 162 consistent sites, 2 variable sites and 1 informative sites were found in 5.8S sequences, 217 consistent sites, 3 variable sites and 1 informative site were found in ITS2 sequences. Base transition and transversion was not found only in 5.8S sequences, 2 sites transition and 1 site transversion were found in ITS1 sequences, only 1 site transversion was found in ITS2 sequences comparting the ITS sequences data matrix. By analyzing the ITS sequences data matrix from 2 population of Aconitum vilmorinianum and 3 population of Aconitum austroyunnanense, we found a stable informative site at the 596th base in ITS2 sequences, in all the samples of Aconitum vilmorinianum the base was C, and in all the samples of Aconitum austroyunnanense the base was A. CONCLUSION: Aconitum vilmorinianum and Aconitum austroyunnanense can be identified by their characters of ITS sequences, and the variable sites in ITS1 sequences are more than in ITS2 sequences.

CpG oligodeoxynucleotide stimulates protective innate immunity against human renal cell carcinoma xenografted in nude mice.

Renal cell carcinoma easily develops metastasis, which is highly resistant to a variety of therapies. Oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODN) are potent activators of innate and adaptive immunity. CpG ODN is inclined to be used as vaccine adjuvant or in combination with other therapies to exert antitumor effect mediated by the adaptive immunity. Herein, we examined the antitumor effect of CpG ODN monotherapy and the role of innate immunity on human RCC Caki-1 cells xenografted in nude mice. Our results indicated that the peritumoral subcutaneous injections of CpG ODN1826 once a week resulted in significant inhibition of the growth of Caki-1 xenografts compared with the control groups, and the survival of tumor-bearing mice were also prolonged significantly. When cytotoxicity of splenic cells from host mice was assessed, it was found that CpG ODN1826 significantly promoted the cytotoxicities of splenocytes targeting primary Caki-1 cells or YAC-1 cells, indicating that the activity of natural killer cells in tumor-bearing nude mice was enhanced by CpG ODN1826 monotherapy. The serum concentrations of interleukin-12 were increased in mice treated with CpG ODN1826. Thus, CpG ODN1826 monotherapy induces significant inhibitory effects on the growth of human RCC xenografted in athymic immunodeficient mice, and the tumor-bearing mice achieves long-term survival, which might be attributed to enhanced innate immunity.

Pharmacokinetics of mycophenolic acid and estimation of exposure using multiple linear regression equations in Chinese renal allograft recipients.

OBJECTIVES: To investigate the pharmacokinetics of mycophenolic acid (MPA) in Chinese adult renal allograft recipients, and to generate the validated model equations for estimation of the MPA area under the plasma concentration-time curve from 0 to 12 hours (AUC(12)) with a limited sampling strategy. PATIENTS AND METHODS: The pharmacokinetics in 75 Chinese renal allograft recipients treated with mycophenolate mofetil 2 g/day in combination with cyclosporin and corticosteroids were determined. The MPA concentration was assayed by high-performance liquid chromatography at pre-dose (C(0)) and at 0.5 (C(0.5)), 1 (C(1)), 1.5 (C(1.5)), 2 (C(2)), 4 (C(4)), 6 (C(6)), 8 (C(8)), 10 (C(10)) and 12 (C(12)) hours after dosing on day 14 post-transplant. Patients were randomly divided into: (i) a model group (n = 50) to generate the model equations by multiple stepwise regression analysis for estimation of the MPA AUC by a limited sampling strategy; and (ii) a validation group (n = 25) to evaluate the predictive performance of the model equations. RESULTS: The mean MPA AUC(12) was 52.97 +/- 15.09 mg . h/L, ranging from 24.0 to 102.3 mg . h/L. The patient's age and serum albumin level had a significant impact on the MPA AUC(12). The correlation between the pre-dose MPA trough level (C(0)) and the MPA AUC(12) was poor (r(2) = 0.02, p = 0.33). Model equations 7 (MPA AUC(12) = 14.81 + 0.80 . C(0.5) + 1.56 . C(2) + 4.80 . C(4), r(2) = 0.70) and 11 (MPA AUC(12) = 11.29 + 0.51 . C(0.5) + 2.13 . C(2) + 8.15 . C(8), r(2) = 0.88) were selected for MPA AUC calculation in Chinese patients, resulting in good agreements between the estimated MPA AUC and the full MPA AUC(12), with a mean prediction error of +/-10.1 and +/-6.9 mg . h/L, respectively. CONCLUSION: In Chinese renal allograft recipients, MPA pharmacokinetics manifest substantial interindividual variability, and the MPA AUC(12) tends to be higher than that in Caucasian patients receiving the same dose of mycophenolate mofetil. Two validated model equations with three sampling timepoints are recommended for MPA AUC estimation in Chinese patients.

[Pharmacokinetics of mycophenolic acid in Chinese patients with liver transplant].

AIM: To investigate the pharmacokinetics of mycophenolic acid (MPA), an active metabolite of mycophenolate mofetil (MMF) in Chinese adult liver transplant patients. METHODS: Thirty-eight liver transplant patients (male 30, female 8) receiving MMF 1.0 g, twice daily in accordance with the recommended regimen were included in this study. Plasma MPA concentrations were measured by high performance liquid chromatography at 0.5, 1, 1.5, 2, 4, 6, 8, 10 and 12 h after the administration of a single dose. Pharmacokinetic parameters were calculated with 3P97 software. RESULTS: The plasma MPA concentration-time curve was characterized with an early sharp peak reached at 0.5 - 6.0 h after oral administration. And in some patients there was a small second peak due to enterohepatic circulation of mycophenolic acid glucuronide (MPAG), which underwent deglucuronidation and re-absorption as MPA at 4 to 12 h postdose. The mean peak plasma concentration (C(max)) and area under concentration-time curve (AUC(0-12 h)) were (12 +/- 7) microg x mL(-1) and (44 +/- 16) microg x h x mL(-1), respectively. However, a large variability of pharmacokinetic parameters existed in these patients. CONCLUSION: In view of the inter-individual variability of MMF pharmacokinetics, plasma MPA concentration should be monitored routinely after MMF administration for individual patient.

Anergic cells induced by the blockade of CD40-CD154 and CD28-B7 costimulatory pathways act as potent immunoregulatory cells in vitro and vivo.

BACKGROUND: This study was to evaluate whether anergic cells induced by the blockade of CD40-CD154 and CD28-B7 costimulatory pathways can act as potent immunoregulatory cells in vitro and prolong cardiac allograft survival after adoptive transfer. METHODS: Anergic cells were induced in vitro by the addition of anti-CD154 and anti-CD80 monoclonal antibodies (mAbs) to primary MLR (mixed lymphocyte reaction) consisting of BALB/c as responder and C3H as stimulator. Anergic cells were added to a newly formed MLR in assessing the regulatory capacity and antigen specificity of anergic cells. The ability of anergic cells to respond to antigen and/or exogenous recombinant mouse interleukin-2 (rmIL-2) was tested. For in vivo studies, anergic cells were intravenously injected into 3.0-Gy gamma-irradiated BALB/c mice immediately after heterotopic abdominal cardiac transplantation. To prolong allograft survival, recipient mice injected with anergic cells received rapamycin therapy [1 mg.day(-1).kg(-1)]. RESULTS: Anergic cells strongly suppressed the proliferation of naicaron;ve BALB/c splenocytes against the original (C3H) stimulator in a dose-dependent manner, but they failed to suppress the proliferation of naicaron;ve BALB/c splenocytes against the third-party (C57BL/6J) stimulator. The anergic state was reversed by both original (C3H) stimulator and additional exogenous IL-2. In in vivo studies, untreated irradiated BALB/c mice rejected C3H cardiac allografts with a mean survival time of (8.6 +/- 1.1) days, whereas those injected with the anergic cells rejected the allografts with a mean survival time of (11.8 +/- 1.9) days, which was slightly longer than that of the untreated mice. The protocol based on anergic cells injection plus rapamycin therapy could prolong allograft survival significantly [(29.6 +/- 4.4) days]. CONCLUSIONS: Anergic cells induced by the blockade of CD40-CD154 and CD28-B7 costimulatory pathways can act as potent immunoregulatory cells in vitro, and prolong cardiac allograft survival after adoptive transfer in the presence of rapamycin therapy. This procedure might be clinically useful for prolonging allograft survival if optimal protocols are developed.

[Expression of fractalkine and its receptor in acute cardiac allografts rejection].

OBJECTIVE: To investigate the expression of fractalkine (FKN) and its receptor CX3CR1 in cardiac allografts and the effect of Cyclosporin A (CsA). METHODS: Three groups of rats underwent heterotopic cardiac transplantation, 45 cases in each group and 5 cases in control group: SD to SD regarded as isograft group (group A), Wistar to SD divided into CsA untreated allograft group (group B) and CsA treated allograft group (group C), normal SD rats as control group. The FKN mRNA expression was detected by one-step RT-PCR method and the expression of FKN and CX3CR1 protein was detected by standard ABC immunohistochemical technique. RESULTS: The expression of FKN mRNA and protein was weak in both isografts and normal heart specimens. The changes of FKN mRNA expression were correlated with the process of acute allograft rejection. The peak of FKN mRNA expression (0.8 +/- 0.26) appeared on the seventh day after transplantation, which could be down-regulated by CsA significantly (t = 2.390, P < 0.05). FKN protein was located in endothelia cells and its receptor CX3CR1 was located in infiltrating mononuclear cells in allografts. CONCLUSIONS: Upregulation of FKN and its receptor was significantly correlated with the trafficking of mononuclear cells which play an important role in acute allograft rejection. It may be one of the important mechanisms of CsA to intervene the acute rejection by inhibiting the activation of the FKN-CX3CR1 pathway.