Association Of CYP3A4, CYP3A5, ABCB1, ABCC2and HLA-B~*1502Polymorphisms With Post-transplant Liver Injury In Renal Transplant Recipients

BackgroundsPost-transplant liver injury, the incidence rate as high as20%-50%according to the report, is related to drug exposure level. Cyclosporine (CsA), known as calcineurin inhibitor, has a revolutionary effect on the overall success of renal transplantation through reduction in acute rejection rates and early immunologic injury. However, CsA is characterized by a narrow therapeutic index and large interindividual difference in both pharmacokinetics and pharmacodynamics. Moreover, hepatotoxicity is a main reason for minimizing or even withdrawal after transplantation. Tailoring of immunosuppressive therapy to the specific requirements of the individual patient remains one of the biggest challenges in renal transplantation. Therapeutic drug monitoring (TDM) is proved to relate to lower acute rejection rates as well as lower toxicities. But there are some limitations:firstly, TDM is a strategy of a starting dose only based on the bodyweight and therefore is necessary to have additional markers for initial dosing; secondly, TDM remains a time-consuming technique and can only be applied after a drug is used. It usually takes days to weeks while reaching adequate drug exposure, therefore TDM can not determine the optimal starting dose for an individual patient before treatment; thirdly, drug response to immunosuppressants is complex and is dertermined by many factors. For these limitations, it is necessary to find other tools to improve interindividual immunosuppressive therapy. Recently, some ongoing researchs in the field of immunosuppressive drug pharmacogenetics keep yielding new insights that might have future clinical implications.Pharmacogenetic and pharmacogenomic researches, investigating the genetic factors which influence drug metabolism and distribution, might be useful to predict initial dose requirements, to identify the increasing risk for adverse effects and to tailor maintaince therapy. It has been estimated that genetic factors can account for20%-95%of variability in drug disposition and effect. Genetic polymorphisms can have a significant impact on CsA pharmacokinetics and are well illustrated for Cytochrome P450(CYP) isoenzymes. Leading to inactivation of the CYP3A5enzyme, CYP3A5*3mutation has been proved to reduce CYP3A5activity and increase risk of developing severe toxicities. Although genotyping for polymorphisms before initiation of CNIs therapy can be used to identify patients at risk, no genetic test has made its way into daily clinical practice yet. Probably it is because of the low frequency of mutant alleles and the intensive monitoring after transplantation. Most of recent pharmacogenetic studies focus on a limited number of single nucleotide polymorphisms (SNPs) of gene encoding for drug metabolizing enzymes, drug transporters, or pharmacological target molecules. Some variations, when present in drug-metabolizing enzymes or drug transporters, may significantly alter the dosing of a given drug.ObjectiveThe purpose of this study is to investigate the associations between gene polymorphisms and post-transplant liver injury, and thus to clarify the machanisms of hepatotoxicity, which can provide the theoretic basis of the rational application of cyclosporine.MethodsA total of339renal transplant recipients were genotyped for CYP3A4*5、 CYP3A4*6、CYP3A4*18B、CYP3A5*3、ABCB11236C>T、ABCB12677G>T/A、 ABCB13435C>T、ABCC21249G>A polymorphisms by PCR followed by restriction fragment length polymorphism (RFLP) analysis. ABCC2rs717620SNP was genotyped using real-time PCR method. HLA-B*1502polymorphism was genotyped using PCR sequence spcific primers method.The CsA whole blood levels of renal transplant recipients were measured by fluorescence polarization immunoassay. All the subjects were divided into CsA hepatotoxicity group, non-CsA-hepatotoxicity group and the control group according to the liver injury occurrence. According to Hy’s law criteria, the patients were divided into post-transplant liver injury group, abnormal liver function group and the control group. All of the subjects were recorded the characters of sex, age, height, cadaveric kidney, weight and BMI, family history of diabetes, duration of dialysis, hepatitis B and hepatitis C infection history and other clinical characteristics, and7days,1,3,6,12,24,36and60months of CsA oral dose and blood trough concentrations, prednisone and MMF dose, liver function and kidney function, fasting plasma glucose (FPG), laboratory test results and so on.All continuous data were shown as mean values±standard deviations.One-way ANOVA, t test and repeated measurement were used to compare continuous variables between the groups. Skewed variables were logarithmically transformed to normalize their distribution. The χ2test was used to compare allele and genotype frequencies between groups. A univariate logistic regression test was used to identify risk factors for post-transplant liver injury and CsA hepatotoxicity. Statistical analyses were performed using the SPSS for Windows (version13.0) with P<0.05considered statistically significant.ResultsIn this study of339renal transplant recipients,237cases were diagnosed with CsA induced hepatotoxicity.3months,6months and12month after operation, FPG of CsA hepatotoxicity group appeared outstandingly higher than the control group (P<0.05). Compared with the control group,7days,1month,3months and6months after operation, trough CsA concentration in CsA induced hepatotoxicity group were higher (P<0.05).7days, one month and three months after operation, dose adjusted trough concentration in CsA induced hepatotoxicity group were significantly higher than the control group (P<0.05). A logistic regression model showed that high CsA trough concentration of six months after operation, high FPG of twelve months after operation and male were risk factors of CsA hepatotoxicity.In this study of339renal transplant recipients,125cases were diagnosed with post-transplant liver injury.7days,3months,6months and12month after operation, FPG of CsA induced hepatotoxicity group appeared outstandingly higher than the control group (P<0.05). Compared with the control group,7days,1month, and3months after operation, dose adjust trough concentration of post-transplant liver injury group is significantly higher (P<0.05).7days after operation, CsA trough concentration of CsA hepatotoxicity group was higher than the control group(P<0.05). A logistic regression model showed that male was a risk factor of post-transplant liver injury.No allele of CYP3A4*5and CYP3A4*6was found in this study. The frequency of the CYP3A4*18B mutation allele was38.99%. Compared with the control group, the distribution frequency of the CYP3A4*18B/*18B was significantly decreased in CsA induced hepatotoxicity group (P<0.01), and that of the CYP3A4*1/*1was significantly increased(P<0.05); the distribution frequency of the CYP3A4*1/*18B was significantly increased in non-CsA induced hepatotoxicity group (P<0.05) Moreover, CsA hepatotoxicity group showed obviously higher distribution frequency of CYP3A4*1/*1than non-CsA induced hepatotoxicity group (P<0.01). One and three months after renal transplantation, the blood trough concentrations of CsA in CYP3A*1/*1group was significantly elevated than that in*18B/*18B group (P<0.05). There were significant differences between post-transplant liver injury and the control groups (32.8%vs48.89%, P<0.05). The CYP3A4*18B polymorphism mutation allele was strongly associated with post-transplant liver injury.The frequency of the CYP3A5*3variant allele was73.54%in339renal transplant recipients. There were significant differences between CsA induced hepatotoxicity and the control groups (80.8%vs65.9%, P<0.01). The CYP3A5*3mutation allele was strongly associated with CsA hepatotoxicity. The distribution frequency of the CYP3A5*3/*3was significantly increased in CsA hepatotoxicity group (P<0.05). Genotype analysis revealed that the Co was lower in the7days and1month following surgery in CYP3A5*1/*1individuals than in carriers of allele*3. There were no significant differences between post-transplant liver injury groupand the control group (P>0.05). The CYP3A5*3polymorphism mutation allele was not associated with post-transplant liver injury.The frequency of the ABCB11236>T variant allele was64.25%in339renal transplant recipients. There were no significant differences between CsA induced hepatotoxicity group and the control group (P>0.05). The1236C>T polymorphism mutation allele was not associated with CsA induced hepatotoxicity. Genotype analysis revealed that there was no significant association between the ABCB11236C>T SNP and blood trough concentration. There were no significant differences between post-transplant liver injury and the control groups (P>0.05). The1236C>T polymorphism mutation allele was not associated with post-transplant liver injury.The frequency of the ABCB12677G>T/A variant allele was51.54%in339renal transplant recipients. There were no significant differences between CsA induced hepatotoxicity and the control groups (P>0.05). The mutation allele T/A was not associated with CsA inducded hepatotoxicity. Genotype analysis revealed that there was no significant association between the ABCB12677G>T/A SNP and blood trough concentration. There were no significant differences between post-transplant liver injury and the control groups (P<0.05). The2677G>T/A polymorphism mutation allele was not associated with post-transplant liver injury.The frequency of the ABCB13435C>T variant allele was35.75%in339renal transplant recipients. There were no significant differences between CsA induced hepatotoxicity and the control groups (P>0.05). The ABCB13435C>T polymorphism mutation allele was not associated with CsA induced hepatotoxicity. Genotype analysis revealed that there was no significant association between the ABCB13435C>T SNP and Co. There were no significant differences between post-transplant liver injury and the control groups (P>0.05). The3435C>T polymorphism mutation allele was not associated with post-transplant liver injury.The frequency of the rs717620variant allele was19.23%in339renal transplant recipients. Compared with the control group, the distribution frequency of the AA genotype was significantly decreased in CsA induced hepatotoxicity group(P<0.05), and that of the GG genotype was significantly increased(P<0.05); There were significant differences between CsA induced hepatotoxicity and the control groups (P<0.05). The A mutation allele was strongly associated with CsA induced hepatotoxicity. Genotype analysis revealed that there was no significant association between the ABCC2rs717620SNP and Co. There were significant differences between post-transplant liver injury and the control groups (P<0.05). The A mutation allele was strongly associated with post-transplant liver injury.The frequency of the ABCC21249G>A variant allele was10.72%in339renal transplant recipients. There were no significant differences between CsA induced hepatotoxicity and the control groups (P>0.05). There were no significant differences between CsA induced hepatotoxicity and the control groups (P>0.05). The ABCC21249G>A mutation allele was not strongly associated with CsA hepatotoxicity. Genotype analysis revealed that there was no significant association between the ABCC21249G>A SNP and Co. There were significant differences between post-transplant liver injury and the control groups (12.4%vs5.56%, P<0.05). The ABCC21249G>A polymorphism mutation allele was strongly associated with post-transplant liver injury.The frequency of the HLA-B*1502variant allele was22.64%in339renal transplant recipients. There were no significant differences between CsA induced hepatotoxicity and the control groups (P>0.05). The HLA-B*1502polymorphism mutation allele was not associated with CsA hepatotoxicity. Genotype analysis revealed that there was no significant association between the HLA-B*1502SNP and Co. There was also no significant association between the HLA-B*1502SNP and the dose-adjusted C0/D. There were no significant differences between post-transplant liver injury and the control groups (P>0.05). The mutation allele was not associated with post-transplant liver injury.ConclusionCYP3A4*18B and CYP3A5*3polymorphisms were associated with the levels of CsA trough concentration. The ABCB13435C>T polymorphism mutation allele was not associated with CsA induced hepatotoxicity. ABCB11236C>T, ABCB12677G>T/A, ABCB13435C>T, ABCC21249G>A and HLA-B*1502polymorphism mutation allele were not associated with CsA induced hepatotoxicity and post-transplant liver injury. CYP3A5*3and rs717620G genotypes, high FPG of12month, male, and high trough concentration of6month were risk factors of CsA related hepatotoxicity. Conversely, CYP3A4*18B genotype was protective factor of CsA related hepatotoxicity. Male, ABCC21249A and rs717620G genotypes were risk factors of post-transplant liver injury. Conversely, CYP3A4*18B genotype was protective factor of post-transplant liver injury.