Renal failure after clinical heart transplantation is associated with the TGF-beta 1 codon 10 gene polymorphism

Nephrotoxicity of Calcineurin Inhibitors in Kidney Epithelial Cells is Independent of NFAT Signaling

Background: Calcineurin inhibitors (CNIs) such as cyclosporine A and tacrolimus are commonly used after renal transplantation to suppress the immune system. In lymphoid cells, cyclosporine A acts via the calcineurin/nuclear factor of activated T-cell (NFAT) axis. In non-lymphoid cells, such as kidney epithelial cells, cyclosporine A induces calcineurin inhibitor toxicity. It is unknown via which off-targets cyclosporine A induces calcineurin inhibitor toxicity in kidney epithelial cells.

Methods: To measure a compound’s potential to induce nephrotoxicity, the expression of the surrogate marker Fn14 was measured by flow cytometry. Compounds were tested for their potential to induce Fn14 either chemically or plasmid-mediated. Mice were injected with various compounds, and changes in nephrotoxic gene expression levels of the kidney epithelial cells were then analyzed.

Results: Fn14 is specifically upregulated due to calcineurin inhibitor toxicity inducing agents. Inhibition of the NFAT axis showed no increase of the Fn14 expression on the surface of kidney cells. However, inhibition of p38 MAPK, phosphoinositide-3-kinase (PI3K)/Akt, protein kinase C (PKC), and inhibitor of nuclear factor-κB (IκB) kinase (IKK) showed clear induction of Fn14 and increased expressions of nephrotoxic, inflammatory, and fibrotic genes in vitro and in vivo.

Conclusions: These findings show that cyclosporine A acts independently of NFAT on kidney epithelial cells. Moreover, inhibition of serine/threonine protein kinases mimics cyclosporine A’s activity on kidney epithelial cells. This mimicking effect indicates that these protein kinases are off-targets of cyclosporine A and damage structural renal cells when inhibited and therefore contributes likely to the development and progression of calcineurin inhibitor toxicity.

Association Between Variants in Calcineurin Inhibitor Pharmacokinetic and Pharmacodynamic Genes and Renal Dysfunction in Adult Heart Transplant Recipients

Background: The goal of the study was to assess the relationship between single nucleotide variants (SNVs) in calcineurin inhibitor (CNI) pharmacokinetic and pharmacodynamic genes and renal dysfunction in adult heart transplant (HTx) recipients. Methods: This retrospective analysis included N = 192 patients receiving a CNI at 1-year post-HTx. Using a candidate gene approach, 93 SNVs in eight pharmacokinetic and 35 pharmacodynamic genes were chosen for investigation. The primary outcome was renal dysfunction 1-year after HTx, defined as an estimated glomerular filtration rate (eGFR) <45 ml/min/1.73m2. Results: Renal dysfunction was present in 28.6% of patients 1-year after HTx. Two SNVs [transforming growth factor beta 1 (TGFB1) rs4803455 C > A and phospholipase C beta 1 (PLCB1) rs170549 G > A] were significantly associated with renal dysfunction after accounting for a false discovery rate (FDR) of 20%. In a multiple-SNV adjusted model, variant A allele carriers of TGFB1 rs4803455 had lower odds of renal dysfunction compared to C/C homozygotes [odds ratio (OR) 0.28, 95% CI 0.12-0.62; p = 0.002], whereas PLCB1 rs170549 variant A allele carriers had higher odds of the primary outcome vs. patients with the G/G genotype (OR 2.66, 95% CI 1.21-5.84, p = 0.015). Conclusion: Our data suggest that genetic variation in TGFB1 and PLCB1 may contribute to the occurrence of renal dysfunction in HTx recipients receiving CNIs. Pharmacogenetic markers, such as TGFB1 rs4803455 and PLCB1 rs170549, could help identify patients at increased risk of CNI-associated renal dysfunction following HTx, potentially allowing clinicians to provide more precise and personalized care to this population.

Non-HLA Genetic Factors and Their Influence on Heart Transplant Outcomes: A Systematic Review

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Background

Improvement of immunosuppressive therapies and surgical techniques has increased the survival rate after heart transplantation. Nevertheless, a large number of patients still experience complications, such as allograft rejection, vasculopathy, kidney dysfunction, and diabetes in response to immunosuppressive therapy. Variants in HLA genes have been extensively studied for their role in clinical outcomes after transplantation, whereas the knowledge about non-HLA genetic variants in this setting is still limited. Non-HLA polymorphisms are involved in the metabolism of major immunosuppressive therapeutics and may play a role in clinical outcomes after cardiac transplantation. This systematic review summarizes the existing knowledge of associations between non-HLA genetic variation and heart transplant outcomes.

Methods

The current evidence available on genetic polymorphisms associated with outcomes after heart transplantation was identified by a systematic search in PubMed and Embase. Studies reporting on polymorphisms significantly associated with clinical outcomes after cardiac transplantation were included.

Results

A total of 56 studies were included, all were candidate gene studies. These studies identified 58 polymorphisms in 36 genes that were associated with outcomes after cardiac transplantation. Variants in TGFB1, CYP3A5, and ABCB1 are consistently replicated across multiple studies for various transplant outcomes.

Conclusions

The research currently available supports the hypothesis that non-HLA polymorphisms are associated with clinical outcomes after heart transplantation. However, many genetic variants were only identified in a single study, questioning their true effect on the clinical outcomes tested. Further research in larger cohorts with well-defined phenotypes is warranted.

Pharmacokinetics, Pharmacodynamics and Pharmacogenetics of Tacrolimus in Kidney Transplantation

Background:

Tacrolimus (Tac, or FK506), a calcineurin inhibitor (CNI), is the first-line immu-nosuppressant which consists of the footstone as immunosuppressive regimens in kidney transplantation. However, the drug toxicity and the significant differences of pharmacokinetics (PK) and pharmacodynam-ics (PD) among individuals are hidden troubles for clinical application. Recently, emerging evidences of Tac pharmacogenetics (PG) regarding drug absorption, metabolism, disposition, excretion and response are discovered for better understanding of this drug.

Method:

We reviewed the published articles regarding the Tac PG and its effects on PK and PD in kidney transplantation. In addition, we summarized information on polygenic algorithms.

Results:

The polymorphism of genes encoding metabolic enzymes and transporters related to Tac were largely investigated, but the results were inconsistent. In addition to CYP3A4, CYP3A5 and P-gp (also known as ABCB1), single nucleotide polymorphisms (SNPs) might also affect the PK and PD parameters of Tac.

Conclusion:

The correlation between Tac PK, PD and PG is very complex. Although many factors need to be verified, it is envisaged that thorough understanding of PG may assist clinicians to predict the optimal starting dosage, help adjust the maintenance regimen, as well as identify high risk patients for adverse ef-fects or drug inefficacy

Heart Transplantation

Although the number of available donor hearts severely limits the epidemiologic impact of heart transplantation on patients with heart failure, patients with end-stage heart failure unresponsive to medical management currently have no other viable alternatives. Destination therapy with a ventricular assist device is the closest toward approaching clinical reality but has been plagued with problems of infection and stroke. The purpose of this review is to summarize recent developments in the field that may broaden the clinical impact of heart transplantation. For example, novel methods of cardiac preservation are being designed to safely evaluate and utilize “extended criteria” donors. Surgical techniques and medical management have reduced the incidence of postoperative right heart failure, and immunosuppressive regimens promise to limit chronic graft vascular disease.

TT genotype of transforming growth factor beta1 +869C/T is associated with the development of chronic kidney disease after liver transplantation

BACKGROUND

Chronic kidney disease (CKD) is a frequent complication in patients with liver transplantation (LT), and calcineurin inhibitor chronic nephrotoxicity, mediated by transforming growth factor beta1 (TGF-β1) is an important contributing factor. The aim of this study was to assess the influence of genetic polymorphisms of TGF-β1 in the development of CKD at 6 months after transplantation.

METHODS

One hundred sixty-four LT patients (63.4% male; overall mean age, 48.7 ± 11.6 years) were included in the analysis. CKD was considered at the 6th month after LT and was defined as an estimated glomerular filtration rate (eGFR) of <60 mL/min/1.73 m(2) as calculated on the basis of Modification of Diet in Renal Disease 4-variable equation. TGF-β1 +869 C/T and +915 G/C polymorphisms were analyzed with the use of hybridization with fluorescent probes and analysis by means of flow cytometry with the Luminex system. The association between the presence of CKD at 6 months and these polymorphisms, as well as with other known risk factors for CKD after LT, was considered.

RESULTS

In the univariate analysis, the TT genotype of TGF-β1 +869 (P = .036; odds ratio, 2.1; 95% confidence interval, 1.1-4.2), age at LT (P < .001), pre-transplantation serum creatinine levels (P = .03), eGFR (P < .001), CKD (P = .027), and immunosuppression with cyclosporine (P = .017) were associated with CKD at 6 months after transplantation. In the multivariate analysis, TGF-β1 +869TT genotype (P = .017), immunosuppression with cyclosporine (P = .002), age at LT (P = .024), and pre-transplantation CKD (P < .001) remained as independent variables associated with the development of CKD at 6 months after transplantation.

CONCLUSIONS

The genetic polymorphism TGF-β1 +869 C/T may be an independent risk factor for CKD after liver transplantation.

Renal complications following lung and heart-lung transplantation

As survival improves after lung and heart-lung transplants, the long term detrimental impact of current management on renal function becomes more apparent as the number of non-renal solid organ transplant recipients on renal transplant waiting lists increases. Progressive chronic kidney disease (CKD) is a significant cause of morbidity and mortality in the transplant population. In this review we discuss the specific problems prior to lung or heart-lung transplant that predispose to CKD, as well as potential renal complications encountered during the peri- and post-transplant period. Significant acute and chronic nephrotoxicity is caused by calcineurin inhibitors (CNI). Mechanisms to decrease CNI exposure exist but have yet to be adopted in routine clinical care. Modifiable risk factors and the current screening and management approach taken at our institution are described. Pediatric nephrologists should be involved from an early stage. Future work will need to focus on identifying more accurate measures of renal function, given the limitations of current glomerular filtration rate estimation equations in a population where nutritional status may rapidly change post transplant. Multicentre studies of CNI minimisation strategies are required to guide future therapy that aims to minimise CKD development and progression in this vulnerable population.

PRKCB is associated with calcineurin inhibitor-induced renal dysfunction in heart transplant recipients

OBJECTIVES

Single nucleotide polymorphisms (SNPs) in the transforming growth factor-β1 gene (TGFB1) have been inconsistently associated with calcineurin inhibitor (CNI)-induced renal dysfunction following cardiac transplantation. The impact of genetic variants related to the renin-angiotensin-aldosterone system (RAAS) and natriuretic peptides, which are implicated in CNI nephrotoxicity, is unknown. The primary objective of this study was to validate the association between two common variants in TGFB1 (rs1800470, rs1800471) and postcardiac transplant renal function. The secondary objective was to investigate the effect of candidate genes related to the RAAS, natriuretic peptides, and other elements involved in the intracellular signaling of these pathways.

METHODS

We conducted a retrospective cohort study of 158 heart transplant recipients treated with CNIs, and evaluated the association between select SNPs and the estimated glomerular filtration rate as calculated by the Modification of Diet in Renal Disease simplified formula. A total of 273 SNPs distributed in 44 genes were tested.

RESULTS

No association was observed between TGFB1 variants and renal function. One polymorphism in the protein kinase C-β gene (PRKCB; rs11074606), which is implicated in the RAAS intracellular signaling, was significantly associated with post-transplant estimated glomerular filtration rate after adjusting for possible confounders (P=0.00049). This marker is in linkage disequilibrium with two variants located in putative regulatory regions of the gene (rs2283541, rs1013316).

CONCLUSION

Our results suggest that PRKCB may be a potential predictor of CNI-induced nephrotoxicity in heart transplant recipients, and could therefore be a promising candidate to identify patients who are most susceptible to this adverse drug reaction.

Renal function and genetic polymorphisms in pediatric heart transplant recipients

BACKGROUND

Common genetic variations influence rejection, infection, drug metabolism, and side effect profiles after pediatric heart transplantation. Reports in adults suggest that genetic background may influence post-transplant renal function. In this multicenter study, we investigated the association of genetic polymorphisms (GPs) in a panel of candidate genes on renal function in 453 pediatric heart transplant recipients.

METHODS

We performed genotyping for functional GPs in 19 candidate genes. Renal function was determined annually after transplantation by calculation of the estimated glomerular filtration rate (eGFR). Mixed-effects and Cox proportional hazard models were used to assess recipient characteristics and the effect of GPs on longitudinal eGFR and time to eGFR < 60 mL/min/1.73m(2).

RESULTS

Mean age at transplantation was 6.2 ± 6.1 years. Mean follow-up was 5.1 ± 2.5 years. Older age at transplant and black race were independently associated with post-transplant renal dysfunction. Univariate analyses showed FASL (C-843T) T allele (p = 0.014) and HO-1 (A326G) G allele (p = 0.0017) were associated with decreased renal function. After adjusting for age and race, these associations were attenuated (FASL, p = 0.075; HO-1, p = 0.053). We found no associations of other GPs with post-transplant renal function, including GPs in TGFβ1, CYP3A5, ABCB1, and ACE.

CONCLUSIONS

In this multicenter, large, sample of pediatric heart transplant recipients, we found no strong associations between GPs in 19 candidate genes and post-transplant renal function. Our findings contradict reported associations of CYP3A5 and TGFβ1 with renal function and suggest that genotyping for these GPs will not facilitate individualized immunosuppression for the purpose of protecting renal function after pediatric heart transplantation.

Endothelial nitric oxide synthase gene variation associated with chronic kidney disease after liver transplant

OBJECTIVE

To identify single nucleotide polymorphisms (SNPs) associated with risk of developing chronic kidney disease (CKD), a prevalent comorbidity, after liver transplant (LT).

PATIENTS AND METHODS

This study consists of a cohort of adult (> or =18 years) primary-LT recipients who had normal renal function before LT and who survived 1 year or more after LT at a high-volume US LT program between January 1, 1990, and December 31, 2000. Patients with adequate renal function (estimated glomerular filtration rate, > or =40 mL/min per 1.73 m(2) during follow-up; n=308) and patients with incident CKD (estimated glomerular filtration rate, <40 mL/min per 1.73 m(2) after LT; n=92) were identified. To investigate the association of 6 candidate genes with post-LT CKD, we selected SNPs that have been associated with renal function in the literature. Hazard ratios were estimated using Cox regression, adjusted for potential confounding variables.

RESULTS

The variant allele (298Asp) of the Glu298Asp SNP in the endothelial nitric oxide synthase gene (NOS3) was significantly associated with CKD after LT (P=.05; adjusted for multiple comparisons). The 5-year incidence of CKD was 70% among patients homozygous for the NOS3 variant allele (298Asp) compared with 42% among those not homozygous for the NOS3 variant allele. Specifically, homozygosity for the NOS3 variant allele conferred a 2.5-fold increased risk of developing CKD after LT (P=.005, adjusted for confounding variables).

CONCLUSION

Homozygosity for the variant allele of NOS3 (298Asp) is associated with CKD after LT and may be useful for identifying recipients at higher risk of post-LT CKD.

The G/G genotype of transforming growth factor beta 1 (TGF-beta1) single nucleotide (+915G/C) polymorphism coincident with other host and environmental factors is associated with irreversible bronchoconstriction in asthmatics

Irreversible airflow obstruction may develop in some cases of asthma even in absence of known risk factors such as smoking and environmental insults and despite implementing apparently appropriate therapy. This implies that genetic factors may significantly contribute to determining the severity in the course of the disease. The published reports on genetic predisposition to irreversible bronchoconstriction in asthma, however, are relatively scarce, and disregard its potential association with transforming growth factor (TGF)-beta1 gene polymorphism despite established role that TGF-beta1 plays in airway remodelling. We tested TGF-beta1 single-nucleotide polymorphisms (SNPs) at position +869 of codon 10 (leucine or proline) and position +915 of codon 25 (arginine or proline) for association with irreversible bronchoconstriction in a case-control study involving 110 patients with asthma and 109 controls. Multivariate logistic regression analysis revealed that genotype G/G at codon 25 was significantly associated with irreversible bronchoconstriction in asthmatics (odds ratio = 4.44; 95% confidence interval: 1.00-19.61; P = 0.05), but only after adjustment for gender, disease duration and smoking index. The influence of SNPs at codon 10 on irreversible airway obstruction was not significant. Our results suggest that presence of SNP (+915G/G) at codon 25 in TGF-beta1 gene may predispose to the development of irreversible bronchoconstriction in asthmatic patients, but only when coincident with the male gender, habitual smoking and relevant duration of the disease.

Calcineurin inhibitor nephrotoxicity

The use of the calcineurin inhibitors cyclosporine and tacrolimus led to major advances in the field of transplantation, with excellent short-term outcome. However, the chronic nephrotoxicity of these drugs is the Achilles' heel of current immunosuppressive regimens. In this review, the authors summarize the clinical features and histologic appearance of both acute and chronic calcineurin inhibitor nephrotoxicity in renal and nonrenal transplantation, together with the pitfalls in its diagnosis. The authors also review the available literature on the physiologic and molecular mechanisms underlying acute and chronic calcineurin inhibitor nephrotoxicity, and demonstrate that its development is related to both reversible alterations and irreversible damage to all compartments of the kidneys, including glomeruli, arterioles, and tubulo-interstitium. The main question--whether nephrotoxicity is secondary to the actions of cyclosporine and tacrolimus on the calcineurin-NFAT pathway--remains largely unanswered. The authors critically review the current evidence relating systemic blood levels of cyclosporine and tacrolimus to calcineurin inhibitor nephrotoxicity, and summarize the data suggesting that local exposure to cyclosporine or tacrolimus could be more important than systemic exposure. Finally, other local susceptibility factors for calcineurin inhibitor nephrotoxicity are reviewed, including variability in P-glycoprotein and CYP3A4/5 expression or activity, older kidney age, salt depletion, the use of nonsteroidal anti-inflammatory drugs, and genetic polymorphisms in genes like TGF-beta and ACE. Better insight into the mechanisms underlying calcineurin inhibitor nephrotoxicity might pave the way toward more targeted therapy or prevention of calcineurin inhibitor nephrotoxicity.

Association of four DNA polymorphisms with acute rejection after kidney transplantation

Renal transplant outcomes exhibit large inter-individual variability, possibly on account of genetic variation in immune-response mediators and genes influencing the pharmacodynamics/pharmacokinetics of immunosuppressants. We examined 21 polymorphisms from 10 genes in 237 de novo renal transplant recipients participating in an open-label, multicenter study [Cyclosporine Avoidance Eliminates Serious Adverse Renal-toxicity (CAESAR)] investigating renal function and biopsy-proven acute rejection (BPAR) with different cyclosporine A regimens and mycophenolate mofetil. Genes were selected for their immune response and pharmacodynamic/pharmacokinetic relevance and were tested for association with BPAR. Four polymorphisms were significantly associated with BPAR. The ABCB1 2677T allele tripled the odds of developing BPAR (OR: 3.16, 95% CI [1.50-6.67]; P=0.003), as did the presence of at least one IMPDH2 3757C allele (OR: 3.39, 95% CI [1.42-8.09]; P=0.006). BPAR was almost fivefold more likely in patients homozygous for IL-10 -592A (OR: 4.71, 95% CI [1.52-14.55]; P=0.007) and twice as likely in patients with at least one A allele of TNF-alpha G-308A (OR: 2.18, 95% CI [1.08-4.41]; P=0.029). There were no statistically significant interactions between polymorphisms, or the different treatment regimens. Variation in genes of immune response and pharmacodynamic/pharmacokinetic relevance may be important in understanding acute rejection after renal transplant.

Adverse drug reactions and pharmacogenomics: recent advances

The concept of pharmacogenomics, the study of how variation in the human genome affects response to drugs, attracts attention from clinicians and the pharmaceutical industry alike. The aim is to distinguish, using appropriate genetic tests, individuals who may be harmed by certain drugs from those who may benefit from them. Adverse drug reactions cause significant morbidity and mortality and incur a large cost to healthcare systems. Pharmacogenomics may help in the prediction and prevention of adverse reactions to drugs. While some recent studies (e.g., abacavir hypersensitivity) have shown strong associations with single genetic factors, whether these represent the exceptions rather than the rule is unclear. Further studies on adverse drug reaction pharmacogenetics are needed – these should be adequately powered and utilize the most appropriate study design that allows for an evaluation of both genetic and environmental factors. For pharmacogenetic testing to become acceptable in clinical practice, it is important that such studies are also able to provide evidence of clinical validity and clinical utility.

Renal disease in recipients of nonrenal solid organ transplantation

Worldwide, more than 250,000 individuals who have received a liver, heart, lung, or intestinal transplant are living longer. Twenty percent to 25% of these recipients experience perioperative acute renal failure, with 10% to 15% requiring renal replacement therapy. Chronic kidney disease (CKD) is also highly prevalent, affecting 30% to 50% of the nonrenal organ transplant population with an annual end-stage renal disease risk of 1.5% to 2.0%. Both acute renal failure and CKD contribute to increased morbidity and premature mortality. The dominant causative factor for renal disorders seen in nonrenal transplant recipients are the calcineurin inhibitors (CNI) and rapamycin analogues, which singly or in combination lead to a variety of nephrotoxic injury. However, 25% to 30% of nonrenal transplant recipients with CKD have other conditions such as hypertension, focal segmental glomerulosclerosis, diabetes mellitus, and hepatitis C infection as the principal underlying cause. Management strategies for renal disease in the nonrenal transplant recipients include the following: (1) delayed introduction of CNI after graft implantation, (2) withdrawal or minimization of long-term CNI therapy, (3) timely use of an appropriate dialysis modality, and (4) expeditious introduction of supportive measures such as anemia management, phosphate binding therapy, and dietary modification. Compared with maintenance dialysis, kidney transplantation reduces long-term mortality by 60% to 70% in nonrenal transplant recipients with end-stage renal disease.

Statin therapy associated with a reduced risk of chronic renal failure after cardiac transplantation

BACKGROUND

Chronic renal failure (CRF) after heart transplantation is common, although risk factors for its development and potential preventive interventions are not well established.

METHODS

In this study we retrospectively assessed the cumulative incidence of CRF and identified independent predictors of CRF in heart transplant recipients between August 1986 and January 2003.

RESULTS

Among the 218 patients included in the analysis, the cumulative incidence of CRF was 4.5% at 5 years, and 19.6% at 10 years after transplant. Multivariate Cox modeling revealed that diabetes mellitus prior to transplant was associated with an increased risk of CRF (hazards ratio [HR] 7.11, p < 0.01), whereas factors associated with a reduced risk of CRF included a pre-transplant creatinine clearance > or = 60 ml/min/1.73 m2 (HR 0.30, p = 0.01) and treatment with a statin after transplant (HR 0.25, p < 0.01). Patients who developed CRF after transplant were at higher risk of death (HR 8.5, p < 0.01).

CONCLUSIONS

CRF is common after cardiac transplantation and is associated with substantial mortality. The reduced risk of CRF observed with statin therapy warrants prospective study, with particular emphasis on the mechanisms of progression to CRF in this population.

TGF-β1 gene polymorphism in psoriasis vulgaris

Overexpression of TGF-beta(1) has been implicated in the pathology of many inflammatory diseases, including psoriasis. This study was performed to investigate the association between TGF-beta(1) single nucleotide polymorphism and susceptibility for psoriasis vulgaris. DNA from 78 patients with psoriasis vulgaris and 74 healthy volunteers was investigated. Polymorphism of TGF-beta(1) gene in codon 10 (T/C) and codon 25 (G/C) was evaluated by PCR-SSP and the results were compared between group of psoriatic patients, divided into early onset of psoriasis (type I) and late onset of psoriasis (type II) subgroups, and control healthy subjects. Frequencies in genotypes were similar between patients and control group (p >0.7), but between type I and type II psoriasis patients highly significant difference was found (p <0.0003). Higher frequency of CC/GG (intermediate producer) and TC/GG (high producer) was noted in the type I group, but the second high producer genotype (TT/GG) was more common in type II group. Also between type II psoriasis patients and healthy controls statistically significant difference was found (p <0.000001). In analyzing frequencies of carriage and alleles no significant differences were found. TGF-beta(1) gene polymorphism in codon 10 and 25 is not associated with susceptibility to psoriasis vulgaris, but may be important for the type of the disease.

The challenge of renal function in heart transplant children

Renal dysfunction may occur after pediatric heart transplantation and impacts on long-term prognosis. This study aims to review the incidence and mechanisms of chronic nephropathy following heart transplantation, and suggest therapeutic directions. The proportion of pediatric heart-transplant recipients with impaired renal function varies from 22 to 57%, and end-stage renal failure from 3 to 10%, depending on the method used for estimating the glomerular filtration rate. The pathophysiology of renal dysfunction is in part due to calcineurin inhibitor-induced renal vasoconstriction, through activation of the intrarenal renin-angiotensin system, TGF-beta1 upregulation and TGF-beta1 gene polymorphisms. Overproduction of angiotensin II, associated with angiotensin-converting-enzyme genotype, might be associated with poor prognosis and pharmacological factor gene polymorphisms, and may contribute to variation of calcineurine inhibitor exposure in the kidney. Strategies to prevent renal dysfunction include reducing calcineurine inhibitor exposure or delaying calcineurine inhibitor administration from the early post-transplant period. Calcium channel blockers and angiotensin-converting-enzyme inhibitors, blockade of angiotensin II, or anti-TGF-beta1 antibodies might limit nephrotoxicity. No accurate marker can predict the potential of renal lesions to develop. Lowering calcineurine inhibitors levels with immunosuppressive agents that are either less nephrotoxic or non-nephrotoxic should be formally studied. Of high interest is the impact of genetic polymorphism on the development of renal dysfunction.

Genomic Biomarkers and Heart Transplantation

Clinicians have entered into a new paradigm for managing heart transplant patients with use of multimarker gene expression profiling. Early after transplantation, when corticosteroid modification is the main concern, gene expression testing might assist in optimizing the balance of immunosuppression, defraying the occurrence of rejection, and avoiding crisis intervention. Late after transplantation, the reliance on endomyocardial biopsy could be lessened. These advances, if continually validated in practice, could usher in an era of decreased immunosuppression complications, lesser need for invasive surveillance, and more clinical confidence in immunosuppressive strategies.

Logistic regression

The Medical Subject Headings (MeSH) thesaurus used by the National Library of Medicine defines logistic regression models as "statistical models which describe the relationship between a qualitative dependent variable (that is, one which can take only certain discrete values, such as the presence or absence of a disease) and an independent variable." Logistic regression models are used to study effects of predictor variables on categorical outcomes and normally the outcome is binary, such as presence or absence of disease (e.g., non-Hodgkin's lymphoma), in which case the model is called a binary logistic model. When there are multiple predictors (e.g., risk factors and treatments) the model is referred to as a multiple or multivariable logistic regression model and is one of the most frequently used statistical model in medical journals. In this chapter, we examine both simple and multiple binary logistic regression models and present related issues, including interaction, categorical predictor variables, continuous predictor variables, and goodness of fit.

The Impact of Transforming Growth Factor-β1 Gene Polymorphism on End-Stage Renal Failure After Heart Transplantation

BACKGROUND

Nephrotoxicity is a major side effect of calcineurin inhibitors (CNI). Earlier we reported 8% of our heart transplant recipients reaching end-stage renal failure (ESRF). Now, with an extended follow up of 20 years, we re-evaluated the development of ESRF and studied its influence on survival and the impact of polymorphisms in codon 10 and 25 of the promoter region of transforming growth factor (TGF)-beta on the risk of ESRF.

METHODS

In all, 465 patients were transplanted between June 1984 and June 2005. All were on maintenance CNI treatment. Development of ESRF was studied in 402/465 (86.5%) patients surviving at least one year. Their median follow up was eight years, total observation time of 3,414 years. TGF-beta polymorphisms in codon 10 (Leu to Pro) and codon 25 (Arg to Pro) were analyzed with real-time polymerase chain reaction in a cohort of 237 patients, with an observation time of 2,329 years.

RESULTS

Ten-year survival of patients surviving at least one year was 58.5%. Seventy-three patients (18.2%) developed ESRF. Dialysis-free survival was 60% at 15 years. The relative risk for ESRF in Pro carriers was 2.9 (CI 1.5-5.8) compared to patients with the Leu/Leu genotype (P = 0.002), while Pro carriers had a RR of 2.6 (CI 1.4-4.8) compared to the Arg/Arg25 genotype (P = 0.002). Survival of patients with ESRF was 1.5 years (median).

CONCLUSION

We found a highly significant association between TGF-beta polymorphisms and CNI induced ESRF after heart transplantation (HTx). Pro carriers of either codon 10 or 25 had a 2.6 to 2.9 times increased risk of developing ESRF. As ESRF after HTx results in high mortality rates these patients should no longer receive CNI-based immunosuppression.

Determination of renal function in long-term heart transplant patients by measurement of urinary retinol-binding protein levels

Significant improvements have been noted in heart transplantation with the advent of cyclosporine. However, cyclosporine use is associated with significant side effects, such as chronic renal failure. We were interested in evaluating the incidence of long-term renal dysfunction in heart transplant recipients. Fifty-three heart transplant recipients were enrolled in the study. Forty-three patients completed the entire evaluation and follow-up. Glomerular (serum creatinine, creatinine clearance measured, and creatinine clearance calculated) and tubular functions (urinary retinol-binding protein, uRBP) were re-analyzed after 18 months. At the enrollment time, the prevalence of renal failure ranged from 37.7 to 54% according to criteria used to define it (serum creatinine > or = 1.5 mg/dL and creatinine clearance <60 mL/min). Mean serum creatinine was 1.61 +/- 1.31 mg/dL (range 0.7 to 9.8 mg/dL) and calculated and measured creatinine clearances were 67.7 +/- 25.9 and 61.18 +/- 25.04 mL min-1 (1.73 m(2))-1, respectively. Sixteen of the 43 patients who completed the follow-up (37.2%) had tubular dysfunction detected by increased levels of uRBP (median 1.06, 0.412-6.396 mg/dL). Eleven of the 16 patients (68.7%) with elevated uRBP had poorer renal function after 18 months of follow-up, compared with only eight of the 27 patients (29.6%) with normal uRBP (RR = 3.47, P = 0.0095). Interestingly, cyclosporine trough levels were not different between patients with or without tubular and glomerular dysfunction. Renal function impairment is common after heart transplantation. Tubular dysfunction, assessed by uRBP, correlates with a worsening of glomerular filtration and can be a useful tool for early detection of renal dysfunction.

The Relationship of Transforming Growth Factor-β1 Gene Polymorphism, Its Plasma Level, and Gingival Overgrowth in Renal Transplant Recipients Receiving Different Immunosuppressive Regimens

BACKGROUND

Cyclosporin A (CsA) induces gingival overgrowth (GO) in patients who seem to be prone to this disorder. It is still impossible to determine which patients will develop GO. Patients treated with the new immunosuppressive drug tacrolimus seem not to have GO. The aims of this study were to investigate transforming growth factor-beta1 (TGF-beta1) gene polymorphisms in renal transplant recipients treated with CsA or tacrolimus and to establish an association between these polymorphisms and TGF-beta1 plasma concentration and the incidence of GO.

METHODS

The examined group consisted of 134 renal transplant recipients. Ninety-two underwent CsA treatment (50 with and 42 without GO), and 42 underwent tacrolimus treatment. Age, gender, time after transplantation, calcineurin inhibitor total dosage, number of teeth, and sulcus bleeding index were analyzed. TGF-beta1 plasma levels were estimated in 60 CsA- and 30 tacrolimus-treated patients. Two biallelic polymorphisms of the TGF-beta1 gene were studied at codon 10 (at position +869) and at codon 25 (at position +915) in patients from the examined group and in 108 healthy volunteers (the control group).

RESULTS

The distribution of the high, intermediate, and low TGF-beta1 producer phenotypes was comparable in all the studied groups and in the healthy controls. The high producer phenotype was more frequent in patients with GO. TGF-beta1 levels in the CsA group showed correlation with the phenotypes. The lowest incidence of GO was observed in the 10C/C genotype, whereas the highest was observed in the 10T/C genotype.

CONCLUSION

High and intermediate TGF-beta1 producer phenotypes and heterozygous genotype 10T/C might be considered risk factors for GO in patients treated with CsA.

The promise of protein-based and gene-based clinical markers in heart transplantation: from bench to bedside

Advances in immunosuppression, guided by invasive endomyocardial biopsy for the assessment of graft rejection, have ushered heart transplantation into the clinical arena by the demonstration of acceptable 1-year outcomes. Further decreases in the risk of malignancy and cardiac allograft vasculopathy that improve long-term outcomes, are, however, still desired. Attention has become directed towards the use of markers that can be detected noninvasively to provide insight into underlying molecular and cellular events associated with the immune response and graft function. Various candidate, protein-based markers have been identified: those of alloimmune activation; those of microvascular injury, such as cardiac-specific troponins; those of inflammation, including C-reactive protein; and surrogate markers of cardiac function, including natriuretic peptides such as brain natriuretic peptide. In the realm of genomics, it is becoming increasingly clear that a single molecular marker is unlikely to prove to be useful, but rather that multiple genes from a number of pathways are needed to capture biological complexity and overcome variability in the general population. Thus, the field of protein-based and gene-based biomarkers is advancing rapidly to define its place in clinical therapeutics and to guide immunosuppression according to molecular mechanisms of disease. We discuss here the main findings for the more-successful protein markers identified so far, and the genomic molecular approaches being used to improve heart transplant outcomes.

Posttransplantation chronic renal damage in nonrenal transplant recipients

BACKGROUND

The growing problem of relentless deterioration of renal function in patients who undergo transplantation of nonrenal solid organs is bound to have an increasingly important impact as it may not only worsen patient morbidity and mortality but also increase transplantation costs.

METHODS

We reviewed the literature in order to provide a sum of the most important data on the incidence, clinical picture, renal pathology pattern, damage mechanisms, and risk factors, along with strategies for prevention and treatment of chronic renal damage following nonrenal solid organ transplantation.

RESULTS

Literature data report that 10% to 80% of transplanted patients have some degree of renal dysfunction and that they share a common clinical picture characterized by relentless asymptomatic progression, frequent hypertension, mild urinary abnormalities, and pathology features of vascular, glomerular, tubular, and interstitial involvement. These changes are very similar to those reported for chronic nephrotoxicity from calcineurin inhibitors. The occurrence of end-stage renal disease (ESRD) requiring chronic dialysis has been reported in up to 20% of nonrenal transplant recipients. Although there are some organ-specific differences, a group of common risk factors has been recognized, including the use of calcineurin inhibitors as immunosuppressive agents, age, pretransplantation renal function, intraoperative/perioperative factors, concomitant use of other nephrotoxic drugs, infections, and posttransplantation acute renal failure.

CONCLUSION

Calcineurin inhibitor-induced nephrotoxicity is a growing problem and, as the age of recipients of nonrenal organs is increasing, this problem is destined to increase. It would therefore be advisable for nephrologists to share their experiences in immunomodulation with other specialties, so as to favor the cautious extension of calcineurin inhibitor-sparing protocols to the area of life-saving transplants.

Transforming growth factor-beta1 SNPs: genetic and phenotypic correlations in progressive kidney insufficiency

Associations have been described between polymorphisms of cytokine and growth factor genes and susceptibility to, or progression of, an increasing number of diseases. TGF-beta1 plays an important role in the pathogenesis of experimental and clinical glomerulosclerosis and tubulointerstitial fibrosis. In this study, single nucleotide polymorphisms (SNPs) in the TGFbeta1 gene were investigated as possible markers for the progression of chronic kidney failure (CKF). 145 Caucasian patients with CKF were screened for four TGFbeta1 SNPs: T-509C in the promoter region; Arg25Pro and Leu10Pro in exon 1 and Thr263Ile in exon 5. There were significant differences between CKF patients and controls in allele frequencies of two of the SNPs, Leu10Pro (p = 0.038) and C-509T (p = 0.02) and in haplotype distributions (p = 0.0175), indicating an association with susceptibility to CKF. We also observed a significant association between progression of CKF and homozygosity for Arg25 (odds ratio 3.77, 95% confidence interval 1.57-9.04, p = 0.002). Homozygosity for Arg25 was also associated with severity of proteinuria at diagnosis (p = 0.038), plasma TGF-beta1 protein levels (p = 0.01), and severity of glomerulosclerosis (p = 0.04). Homozygosity for -509T was associated with severity of proteinuria at diagnosis (p = 0.0017), level of renal tubular TGF-beta1 immunostaining (p = 0.0006) and with severity of renal interstitial inflammatory cellular infiltration (p = 0.01). Tubular TGF-beta1 immunostaining was significantly higher in biopsies with inflammatory cellular infiltration compared those without inflammation (p = 0.0048). There was a significant difference in haplotype distributions between CKF patients with progressive, as opposed to non-progressive disease (p = 0.0484). TGFbeta1 SNPs may be useful prognostic indicators for the progression of CKF.

Improvement of Renal Function in Pediatric Heart Transplant Recipients Treated with Low-Dose Calcineurin Inhibitor and Mycophenolate Mofetil

BACKGROUND

Renal dysfunction is a major complication in heart transplant recipients treated with calcineurin inhibitors. The goal of the study was to investigate the effect of a reduction of calcineurin inhibitor dosage with the concomitant introduction of mycophenolate mofetil on both renal function and cardiac allograft function.

METHODS

Fourteen of 52 consecutive pediatric cardiac allograft recipients experienced a progressive decrease of renal function. A renal biopsy was performed before the dose of calcineurin inhibitors was reduced by 50% and azathioprine was replaced by mycophenolate mofetil. Renal function was evaluated by inulin clearance and maximal urinary osmolality before and yearly after the therapeutic changes. Acute rejection was monitored clinically, by echocardiography and endomyocardial biopsies.

RESULTS

Inulin clearance in the fourteen children decreased from 84.2 mL/min/1.73 m at one year posttransplantation to 46.5+/-9.6 mL/min/1.73 m at the time of the change in immunosuppressive therapy. Significant renal lesions were observed in the renal biopsies performed before the change. At 1 year, inulin clearance had increased by 67%. In six patients who had a second determination 2 years after the switch, inulin clearance was not significantly different from the value at 1 year. There were three reversible acute rejection episodes in three patients. The incidence of rejection episodes was not different from a control group of patients whose treatment was not changed.

CONCLUSION

The reduction of calcineurin inhibitor dosage and replacement of azathioprine by mycophenolate mofetil is a safe way to improve renal function in children with heart transplants and calcineurin inhibitor induced nephrotoxicity.

Gender-related association between the TGFB1+869 polymorphism and multiple sclerosis

Our objective was to investigate whether polymorphisms and haplotypes in the TGFB1 gene are associated with susceptibility or disease characteristics of multiple sclerosis (MS). In 247 MS patients and 194 controls, single nucleotide polymorphisms (SNPs) at position +869 (Leu10Pro) and position +915 (Arg25Pro) in the signaling sequence of the TGFB1 gene were determined, and the distribution of alleles, genotypes, and haplotypes was related to clinical data. In addition, magnetic resonance imaging (MRI) data were studied in a subgroup of patients (n = 96). The allele distribution of the two polymorphisms studied was in Hardy-Weinberg equilibrium in patients and in controls. No association was found with any of the three haplotypes found in the Dutch population, denoted as haplotype 1 (TGFB1+869T-TGFB1+915G), haplotype 2 (TGFB1+869C-TGFB1+915G), and haplotype 3 (TGFB1+869C-TGFB1+915C). However, the TGFB1+869 genotype CC was significantly more frequent in patients (p = 0.031, chi2 test). The highest frequency of the TGFB1+869 genotype CC was observed in male patients (25.2% vs. 10.0% in controls, p = 0.004, chi2 test), and carriership of TGFB1+869 allele C was correspondingly increased in male patients (74.8% vs. 56.7%, p = 0.008, chi2 test, OR 2.27, 95% CI 1.23-4.17). Although there was no association with clinical markers of disease progression, patients homozygous for TGFB1+869 allele C showed a significantly higher annual increase in two MRI parameters: ventricular fraction (central atrophy) and T1-hypointense lesion load (matrix destruction). The TGFB1 T+869C (Leu10Pro) gene polymorphism is associated with MS susceptibility, especially in males, and with a more destructive course of the disease as illustrated by MRI.

Impact of TGFβ1 gene polymorphisms on late renal function in pediatric heart transplantation

Late renal dysfunction may affect long-term outcome of nonrenal transplant recipients. We hypothesized that transforming growth factor beta1 (TGFbeta1) might play a role in the fibrogenic mechanisms leading to renal dysfunction. The aim was to determine whether TGFbeta1 gene polymorphisms are associated with renal outcome in pediatric heart recipients. Eighty-eight patients underwent a first heart transplantation at the age of 7.1 +/- 6.5 years, received tacrolimus-based immunosuppression, and were followed for > or =1 year (6.7 +/- 3.2 years). Creatinine clearance (CrCl; ml/mn/1.73 m2) was calculated (Schwartz) before transplant, then at 1 month, 6 months, and 1 year, and yearly up to 7 years. Impaired function was defined as CrCl <80 ml/mn/1.73 m2. Mean CrCl decreased from 120 +/- 53 ml/mn/1.73 m2 before transplant to 98 +/- 40, 96 +/- 37, 102 +/- 30, and 101 +/- 38 ml/mn/1.73 m2 at, respectively, 6 months and 1, 5 (n = 58), and 7 years (n = 33). The TGFbeta1 high-producer genotype had worse CrCl than intermediate and low producers at every time point, despite similar pretransplant CrCl (pretransplant = 120 +/- 53 vs 118 +/- 55 ml/mn/1.73 m2 [p = 0.8], 1 year = 92 +/- 38 vs 113 +/- 30 ml/mn/1.73 m2 [p = 0.03]) and similar tacrolimus levels. The TGFbeta1 high-producer genotype was associated with CrCl < 80 ml/mn/1.73 m2. The TGFbeta1 high-producer genotype is associated with renal dysfunction in pediatric heart recipients.

Transforming growth factor-beta1 gene polymorphism modifies the histological and clinical manifestations in Japanese patients with IgA nephropathy

Transforming growth factor (TGF)-beta1, a multifunctional cytokine, which regulates proliferation and differentiation of a variety of cell types, has the central role in the development and progression of renal injury in both animal models and human. Although it has been suggested that genetic variations in the TGF-beta1 gene are associated with the activity of the gene product, their clinical significance in glomerular disease is unknown. We investigated whether the polymorphisms of C-509T and T869C in TGF-beta1 account for interindividual variation in manifestations of IgA nephropathy (IgAN) using 626 Japanese subjects including 329 patients with histologically proven IgAN and 297 healthy controls with normal urinalysis. The frequencies of genotypes, alleles, and major haplotypes were similar between the patients and controls. The C-509T and T869C polymorphisms were in tight linkage disequilibrium, and the major haplotypes were C-C and T-T, which accounted for more than 95% of the total. In patients with -509CC and in those with the 869CC, urinary protein excretion was higher than in those with other genotypes, whereas no difference in other clinical manifestations was noted. Moreover, patients with -509CC and those with 869CC genotypes presented with a significant higher score of mesangial cell proliferation than in those with other genotypes. These results suggest that TGF-beta1 gene polymorphisms are specifically associated with heavy proteinuria and mesangial cell proliferation in Japanese patients with IgAN, although they do not confer susceptibility to this disease.

Surrogate markers for late cardiac allograft survival

While no definite well-validated surrogate marker for late cardiac allograft outcome is available, the early detection of cardiac allograft vasculopathy represents the 'key' candidate as an effective surrogate. Intravascular ultrasound detected intimal thickening has been noted to possess prognostic capability despite the presence of a normal coronary angiogram. Several prospective investigations have pointed to accurate thresholds of intimal thickening that are prognostically relevant and predict not only future angiographic disease but also hard allograft related endpoints including ischemic cardiac events, allograft failure, and death. Because of the resolution of intravascular ultrasound, this technique accords reproducibility and the ability to standardize the degree of intimal thickening over time. Other candidates that may serve as surrogates once appropriately evaluated include measures of allograft pump function, intragraft histology, and peripheral markers including but not limited to structural proteins (cardiac specific troponins), inflammatory markers (CRP), fibrogenic markers (TGF-beta, fibroblast growth factor), and immune markers (anti-HLA Ab and indirect alloantibodies).

Analysis of the transforming growth factor-beta1 (TGF-beta1) codon 25 gene polymorphism by LightCycler-analysis in patients with chronic hepatitis C infection

The polymorphism at position 25 of the gene encoding transforming growth factor-beta1 (TGF-beta1), which changes the amino acid sequence of the signal peptide sequence (arginine to proline), is causing a variation in TGF-beta1 production. The homozygous genotype (Arg25Arg) is associated with higher TGF-beta1 production than the heterozygous (Arg25Pro) genotype. Therefore, the possible involvement of this genetic variation in the TGF-beta1 gene for induction and progression of various diseases is under close investigation. At present, several labor-intensive established assays ranging from amplification refractory mutation system (ARMS)-PCR methodologies, sequence specific oligonucleotide probing (SSOP), restriction fragment length polymorphism (RFLP) analysis, 5' nuclease assays, and specialized fingerprinting protocols are applied to analyze the polymorphism in question. We developed a novel approach for analyzing this polymorphism in a LightCycler system and determined the allele frequency distributions between patients with different degrees of hepatic fibrosis induced by chronic hepatitis C virus infection. In patients with severe hepatic fibrosis (METAVIR-score 3-4), the Pro25 allele was twice as frequent compared to patients with mild fibrosis (METAVIR-score 0-2). However, we found no association of necroinflammatory activity and genotype distribution. This suggests that the stage of hepatic fibrosis, rather than the grade (inflammation), is influenced by the presence of proline at codon 25 in patients with chronic hepatitis C.

Cyclosporine renal dysfunction

Cyclosporine (CsA), introduced as an immunosuppressive agent in the 1980s, quickly become the first-line treatment in organ transplantation. However, these improvements were associated with an increased incidence of renal dysfunction. CsA causes histopathological changes in renal transplants that are often difficult to distinguish from other processes, especially chronic allograft nephropathy. Enhanced angiotensin II, transforming growth factor-beta, and vascular endothelial growth factor expression together with down-regulation of nitric oxide synthesis may play roles in chronic CsA nephropathy. Efforts have recently focused upon protocols that minimize the risk of CsA nephrotoxicity while preserving low rates of acute rejection. Four types of CsA-sparing studies have emerged from recent clinical experience: (1) conversion studies in which a nonnephrotoxic drug is substituted to allow CsA reduction, (2) minimal CsA exposure studies in which reduced CsA doses are combined with nonnephrotoxic drugs, (3) withdrawal studies in which CsA is completely discontinued at some time after transplantation, and (4) CsA-free studies in which the drug is completely avoided from the time of transplantation. Monitoring of CsA immunosuppression according to C2 blood levels, which better correlate with the area under the time-concentration curve than trough concentrations, should reduce the risk for toxicity; however, the most appropriate target range has not yet been clearly established. Because of interindividual differences in CsA absorption and susceptibility to renal dysfunction, the current therapeutic drug monitoring should be supplemented with pharmacogenetic information on genetic variability of relevant genes for pharmacokinetic parameters and therapeutic targets. This approach may guide choices for immunosuppressants for particular patients, with low toxicity. Thus, despite of 20 years of its history, CsA renal dysfunction remains an important clinical challenge.

End-stage renal failure and cardiac mortality after heart transplantation

BACKGROUND

Coronary artery disease (CAD) is the leading cause of mortality after the first year of heart transplantation. End-stage renal failure (ESRF) is more frequent because of long-term survival. Impact of ESRF on cardiac mortality in heart transplant patients is unappreciated. The hypothesis of accelerated CAD in uremic patients has been suggested.

METHODS

In Pitié La Salpêtrière hospital, 1211 heart transplants have been performed between 1982 and 2001. Thirty-three patients have reached ESRF. A case-control study was performed to identify risk factors responsible for ESRF and to appreciate the impact of ESRF on cardiac mortality.

RESULTS

In cases at 6 months, serum creatinine tended to be higher (159 +/- 31 micromol/L vs. 141 +/- 44 micromol/L, p = 0.06) and cyclosporine (CSA) dosage (mg/kg) was significantly lower (5.4 +/- 1.8 mg/kg vs. 7.7 +/- 2.7 mg/ kg, p = 0.002). Mean triglyceride level after transplantation until dialysis was significantly lower in cases (2.18 +/- 0.82 mmol/L vs. 1.48 +/- 0.62 mmol/L, p = 0.002). In cases and controls, cardiac mortality was responsible for 67% (10 of 15) and 38% (three of eight) of all deaths, respectively. High triglyceride level (> or = 2 mmol/L) was associated with cardiac mortality [p < 0.03, hazard ratio (HR) = 3.89]. Kaplan Meier cardiac free survival rates were significantly lower in cases than in controls (p < 0.03).

CONCLUSION

These data suggest that CSA nephrotoxicity could result from individually determined susceptibility and that hypertriglyceridemia may have a negative impact on renal function and cardiac mortality. The risk of cardiac mortality is increased in heart transplant patients with ESRF. The hypothesis of accelerated atherosclerosis in ESRF patients after heart transplantation leading to higher cardiac mortality incidence needs further study.

Cyclosporine nephrotoxicity

After more than 20 years of cyclosporine use its nephrotoxicity remains a significant clinical problem. Cyclosporine-induced renal injury has been described in solid organs recipients and in patients treated for autoimmune diseases. It is manifested in 2 distinct and well characterized forms, acute nephrotoxicity and chronic nephrotoxicity. This communication reviews the current literature analyzing the available data about the pathogenesis and mechanisms of acute and chronic cyclosporine-induced nephrotoxicity. A working hypothesis for the possible mechanisms of chronic cyclosporine nephrotoxicity will be provided.

RNA expression profiling as prognostic tool in renal patients: toward nephrogenomics

Damage to the kidney generally elicits tissue repair mechanisms, but these processes themselves conversely may result in the progression of chronic renal disease. In a majority of patients chronic renal insufficiency progresses to a common histological end point, marked by the presence of a vast amount of scar tissue, that is, glomerulosclerosis and interstitial fibrosis. These lesions are the result of an excessive production of extracellular matrix (ECM) components. Studies on RNA expression in experimental kidney disease have shown that renal mRNA levels for ECM components and cytokines can function as prognostic tools. This suggests that mRNA levels potentially predict outcome and reaction to therapy in patients with renal diseases. Timely detection of molecular alterations could allow early therapeutic intervention that slows down or even prevents the development of sclerotic and fibrotic lesions. This review first provides a short introduction on mechanisms of initiation and progression of renal disease. Molecular techniques are available to identify renal RNA sequences potentially involved in disease progression. We discuss several molecular techniques that are being used in kidney research for quantitation and detection of mRNA. This is followed by a brief overview of investigation in experimental renal diseases, which reveal that alterations in tissue ECM mRNA levels precede histological damage and can function as predictors of clinical outcome. In particular, studies in human kidney biopsies that evaluate the prognostic value of mRNA levels with respect to renal function are examined, paying special attention to the pitfalls that potentially are encountered when interpreting the results of such studies. Then, we elaborate on ways of optimal exploitation of mRNA quantification as a prognostic tool. The potential and limitations of microarray technology in the search for genes specifically involved in progression of renal disease are reviewed, including RNA expression profiling and large-scale DNA mutation screening. Finally, the future utilities of microarray in nephrology and renal pathology are discussed.

Does variability in normal tissue reactions after radiotherapy have a genetic basis – where and how to look for it?

Cancer patients exhibit large patient-to-patient variability in normal tissue reactions after radiotherapy. Several observations support the hypothesis that clinical normal tissue radiosensitivity is influenced by genetic factors. However, very little is known about the genetic variation possibly underlying inter-individual differences in normal tissue reactions when unselected cancer patients undergo radiotherapy. It seems reasonable to assume that clinical radiosensitivity of normal tissues should be regarded as a so-called complex trait depending on the combined effect of several different genetic alterations. Single nucleotide polymorphisms (SNPs) make up 90% of naturally occurring sequence variation in the human genome and SNPs in genes related to the biological response to ionising radiation may affect clinical radiosensitivity. Rare genetic variants could also possibly play an important role. Thus, the 'allelic architecture' underlying differences in normal tissue reactions may be rather complicated. Recent advances in high throughput genotyping and bio-informatics provide unprecedented opportunities to unravel the genetic basis of clinical normal tissue radiosensitivity. However, to achieve maximum benefit from these advances, carefully designed clinical studies with an accrual of hundreds or thousands of patients are probably needed.

Cytokine gene polymorphisms and acute human liver graft rejection

Interindividual differences exist in the capacity to produce cytokines. It has been reported that levels of in vitro cytokine production measured after stimulated cell culture are associated with polymorphisms in cytokine genes. Moreover, a correlation between heart, kidney, liver, and lung graft rejection or survival with cytokine gene polymorphisms has been described. In the present study, we analyzed the association of gene polymorphisms in T helper subtype 1 (T(H)1-), T(H)2-, and regulatory-type cytokines with human liver allograft rejection. Patients who received a primary liver graft from 1992 onward and were seen at the transplant outpatient clinic since then were included on this study (n = 89). Patients were HLA typed routinely. Biopsy-proven acute rejection occurred in 41 of 89 patients. After informed consent, blood was collected and DNA was obtained. Using amplification-refractory mutation system polymerase chain reaction, the following cytokine gene polymorphisms were determined: IL-2+166, IL-2-330, IL-15+13689, IL-15-80, TNF-A-308, TNFd3, IFN-G+874 (T(H)1-type cytokines), IL-4+33, IL-4-590, IL-6-174, IL-10-592, IL-10-819, IL-10-1082, IL-13+2043, IL-13-1055 (T(H)2 type cytokines), TGF-B1+869, and TGF-B1+915 (regulatory-type cytokines). Univariate analysis showed that polymorphisms of IL-10-1082, TGF-B1+869, and HLA-DR6 were significantly related to liver graft rejection. Multiple logistic regression analysis was used to assess which variables remained significantly predictive of acute rejection. Multivariate analysis showed that TGF-B1+869 and HLA-DR6 were independently associated with the occurrence of acute rejection. These findings suggest a role for the regulatory-type cytokine transforming growth factor-beta1 in human liver graft rejection.