Cytokine gene polymorphism in kidney transplantation — Impact of TGF-β1, TNF-α and IL-6 on graft outcome

Potential influence of interleukin-6 -174G/C gene polymorphism on kidney graft function and tacrolimus dose requirements: five-year follow-up

1. INTRODUCTION

The study aimed to investigate the influence of interleukin (IL)-6 -174 G/C gene polymorphism on graft function (defined as estimated glomerular filtration rate, eGFR), as well as on the tacrolimus (Tac) pharmacokinetics during the five years after kidney transplantation.

2. METHODS

The study included 115 Caucasian kidney transplant recipients on Tac-based immunosuppression. The patients were followed between 6 and 60 post-transplantation months. Interleukin-6 and CYP3A5 genotyping were performed.

3. RESULTS

Patients carrying the IL-6 -174GG genotype had lower eGFR values compared to the patients with the IL-6 -174GC and -174CC genotypes at the 12th, 48th and 60th post-transplantation months. The linear regression analysis indicated that eGFR at the 6th post-transplantation month and IL-6 -174 G/C polymorphism are independent predictors of eGFR values in the late post-transplantation period. The IL-6 -174GG genotype carriers had lower dose-adjusted trough concentration (C0/D) of Tac compared to the IL-6 C allele carriers during the entire observation period (except at the 24th month), while this effect was independent of the CYP3A5 genotype within three years post-transplantation.

4. CONCLUSION

Interleukin-6 genotyping could be an additional tool to categorise patients towards the risk of graft deterioration in the long-term post-transplantation period. The IL-6 genotyping could be supportive in genotype-guided dosing of Tac.

Immunosenescence, immunotolerance and rejection: clinical aspects in solid organ transplantation

As a consequence of increased lifespan and rising number of elderly individuals developing end-stage organ disease, the higher demand for organs along with a growing availability for organs from older donors pose new challenges for transplantation. During aging, dynamic adaptations in the functionality and structure of the biological systems occur. Consistently, immunosenescence (IS) accounts for polydysfunctions within the lymphocyte subsets, and the onset of a basal but persistent systemic inflammation characterized by elevated levels of pro-inflammatory mediators. There is an emerging consensus about a causative link between such hallmarks and increased susceptibility to morbidities and mortality, however the role of IS in solid organ transplantation (SOT) remains loosely addressed. Dissecting the immune-architecture of immunologically-privileged sites may prompt novel insights to extend allograft survival. A deeper comprehension of IS in SOT might unveil key standpoints for the clinical management of transplanted patients.

Pharmacogenetic analysis of interleukin-10 variants and tacrolimus metabolism in kidney transplant patients from Pakistani population

BACKGROUND

End stage renal disease (ESRD) occurs when the kidneys are unable to filter the waste products and excessive fluids from the blood that results into the accumulation of toxins and fluid in the body. Tacrolimus is commonly used immunosuppressant while sirolimus and cyclosporin are rarely used drugs to stop solid organ transplant rejection. The host's immunological response following transplantation produces interleukin-10 (IL-10), which influences the varied CYP3A-dependent drug disposition of tacrolimus. The aim of this study was to determine the genetic polymorphisms of IL-10 (rs1800871, rs1800872 and rs1800896) gene associated with tacrolimus metabolism in kidney transplant patients from Lahore Punjab, Pakistan.

METHODS

The study collected blood samples of 103 healthy individuals and 137 kidney transplant patients as control and treatment groups, respectively. We employed Tetra ARMS PCR for the genotype analysis of extracted DNA. The alleles were called on 2% agarose gel. Moreover, the study utilized SPSS software to analyze statistical significance of polymorphism.

RESULTS

It was found that genotypic frequencies of IL-10 (rs1800871), IL-10 (rs1800872), and IL-10 (rs1800896) were (TT: 66.4%; TC: 31.4%; CC: 2.2%), (AA: 27.7%; AC: 54%; CC: 18.2%), (AA: 64.2%; GA: 17.5%; GG: 18.3%), respectively among kidney transplant patients. All parameters show significant association at different points after transplantation. Genetic analysis showed that TC and CC genotypes in rs1800871 (OR (95%CI) = 5.721 (3.231-10.131), P < 0.001; OR (95%CI) = 3.370 (0.642-17.672), P = 0.150), AC and CC genotypes in rs1800872 (OR (95%CI) = 1.294 (0.695-2.410), P = 0.415; OR (95%CI) = 1.453 (0.671-3.147), P = 0.342), GA and GG genotypes in rs1800896 (OR (95%CI) = 42.952 (17.566-105.021), P = 0.001; OR (95%CI) = 7.040 (2.563-19.333), P = 0.342) was associated with risk of renal rejection in kidney transplant patients. Besides, genetic models showed that TT in rs1800871, AA genotypes in rs1800872 and rs1800892 were associated with risk of renal rejection under dominant model when compared to controls (OR (95%CI) = 5.721 (3.231-10.131), P < 0.001; OR (95%CI) = 1.335 (0.735-9.290), P < 0.341; OR (95%CI) = 24.629 (10.599-57.230), P < 0.001), respectively.

CONCLUSION

From the results, it is concluded that genetic polymorphism of IL-10 (rs1800871, rs1800872 and rs1800896) has a highly significant association with risk of renal rejection in Pakistani kidney transplant patients.

Genetic Risk Factors Related to Coronary Artery Disease and Role of Transforming Growth Factor Beta 1 Polymorphisms

Coronary artery disease (CAD) is one of the leading causes of mortality globally and has long been known to be heritable; however, the specific genetic factors involved have yet to be identified. Recent advances have started to unravel the genetic architecture of this disease and set high expectations about the future use of novel susceptibility variants for its prevention, diagnosis, and treatment. In the past decade, there has been major progress in this area. New tools, like common variant association studies, genome-wide association studies, meta-analyses, and genetic risk scores, allow a better understanding of the genetic risk factors driving CAD. In recent years, researchers have conducted further studies that confirmed the role of numerous genetic factors in the development of CAD. These include genes that affect lipid and carbohydrate metabolism, regulate the function of the endothelium and vascular smooth muscles, influence the coagulation system, or affect the immune system. Many CAD-associated single-nucleotide polymorphisms have been identified, although many of their functions are largely unknown. The inflammatory process that occurs in the coronary vessels is very important in the development of CAD. One important mediator of inflammation is TGFβ1. TGFβ1 plays an important role in the processes leading to CAD, such as by stimulating macrophage and fibroblast chemotaxis, as well as increasing extracellular matrix synthesis. This review discusses the genetic risk factors related to the development of CAD, with a particular focus on polymorphisms of the transforming growth factor β (TGFβ) gene and its receptor.

The rs1800470 Polymorphism of the TGFB1 Gene Is Associated with Myocardial Fibrosis in Heart Transplant Recipients

The transforming growth factor β1 (TGFβ1), whose level may depend on the polymorphism of the TGFB1 gene, is involved in the formation of myocardial fibrosis. Myocardial fibrosis in a cardiac allograft may lead to a heart's structural and functional remodeling and subsequent dysfunction. The frequency of occurrence of alleles and genotypes of the TGFB1 gene polymorphic regions rs1800469, rs1800470, and rs1800471 in heart transplant recipients and their association with graft myocardial fibrosis were analyzed. Carriers of the CC genotype (p = 0.023, OR = 0.12, 95% CI: 0.017-1.0), and more often the G allele of rs1800471 (p = 0.023, OR = 7.76, 95% CI: 1.0-60.20), were found among heart transplant recipients less frequently than among healthy individuals. In patients with ischemic heart disease (IHD), the GG genotype was less common (p = 0.035, OR = 2.68, 95% CI: 1.061-6.793), while the A allele of rs1800469 was found more frequently (p = 0.035, OR = 0.37 95% CI: 0.148-0.942) than in patients with dilated cardiomyopathy (DCM). In heart transplant recipients with the AA genotype of rs1800470, myocardial fibrosis, verified by endomyocardial biopsy, was detected more often than in carriers of the G allele (OR = 10.4, 95% CI: 1.152-94.538, p = 0.013). The revealed differences suggest a relationship between TGFB1 gene polymorphism and graft myocardial fibrosis. Studies on a larger group of patients would make it possible to characterize the influence of genetic factors on the formation of myocardial fibrosis in heart transplant recipients.

Influence of TGFB1 and CTLA4 polymorphisms on calcineurin inhibitors dose and risk of acute rejection in renal transplantation

Organ transplant is often the treatment of choice as it extends and improves patient life. Immunosuppressive treatment, which prevents acute rejection of the organ, is used in transplant patients to prevent the loss of transplant. The aim of the study was to determine the impact of the CTLA4 (+49A>G, rs231775) and the TGF-β1 (-800G>A, rs1800468) polymorphisms on the therapeutic effect of immunosuppressive drugs (cyclosporine-CsA, tacrolimus-TAC) and the risk of acute rejection in renal transplant patients. The analysis of the CTLA4 +49A>G and the TGF-β1 -800G>A polymorphisms was carried out in 392 patients after kidney transplant using real-time PCR. The CTLA4 +49A>G polymorphism did not affect CsA or TAC dose, ratio of drug concentration to dose (C/D), and blood concentrations. As for the TGF-β1 -800G>A polymorphism, patients with the GA genotype required lower TAC doses compared to the GG genotype (TAC 12 h: 3.63 mg vs 5.3 mg, TAC 24 h: 2.38 mg vs 3.29 mg). Comparing the C/D ratio in both groups (TAC 12 h and TAC 24 h), higher C/D ratio was observed in patients with the GA genotype. These results indicate that patients with the A allele require slightly lower doses of TAC. The results suggest that the TGF-β1 -800 G>A polymorphism may influence the TAC dose, while the +49A>G polymorphism of the CTLA4 gene does not correlate with the dose of CsA or TAC. The analysis of the biochemical parameters of the renal profile showed no impact of the CTLA4 and the TGF-β1 polymorphisms on the risk of organ rejection.

Impact of Proinflammatory Cytokine Gene Polymorphisms and Circulating CD3 on Long-Term Renal Allograft Outcome in Egyptian Patients

The extant study aimed to explore the influence of two cytokines TNF-α - 308 and IFN-γ + 874 gene polymorphism on development of renal transplant rejection and to investigate the feasibility of Th1 cytotoxic immune reaction (CD3). It includes 152 kidney recipients were divided into two subgroups: 76 stable graft functions (SGF) and 76 allograft dysfunctions (AD) compared with 56 healthy individuals as control group. TNF-α - 308 G > A and IFN-γ + 874 A > T genetic polymorphisms were characterized using ARMS-PCR technique. CD3 protein expression was measured using ELISA Kit. The effect on transplant outcome was analyzed where, statistically significant differences of TNF-a-308 G/A were observed between AD group when compared to SGF group (OR = 0.296, 95% CI = 0.091-0.965, p = .031) in AG genotype (intermediate producer genotype). Also, AD group displayed a statistically significant increase of IFN-γ + 874 TT (high producer genotype) when compared to SGF group (OR = 0.290, 95% CI = 0.127-0.665, p = .003). The expression of CD3⁺ T lymphocytes in recipients with allograft dysfunction was statistically higher than that with stable allograft function and control groups (732 ± 76, 235 ± 51 and 442 ± 50) respectively and (p ≤ 0.001). In conclusion, IFN-γ + 874 T and TNF-α - 308 A alleles are risk alleles for renal transplant rejection and these two single nucleotide polymorphisms (SNPs) may be implicated in the tendency of rejection after renal transplantation. CD3 may be used as non-invasive biomarker in monitoring of rejection and avoid exposing patients for biopsy risks and sampling error.

Genetic Polymorphism in Cytokines and Costimulatory Molecules in Stem Cell and Solid Organ Transplantation

There is growing evidence supporting the genetic variability outside of HLA system that is contributing to the variation in transplant outcomes. Determining novel predictors could help to identify patients at risk and tailor their immunosuppressive regimens. This article discusses the various single nucleotide polymorphisms in costimulatory molecules and cytokines that have been evaluated for their effect on transplantation. An overview of how gene polymorphism studies are conducted and factors to consider in the experimental design to ensure meaningful data can be concluded are discussed.

Biomarkers and Pharmacogenomics in Kidney Transplantation

This review is focused on present and future biomarkers, along with pharmacogenomics used in clinical practice for kidney transplantation. It aims to highlight biomarkers that could potentially be used to improve kidney transplant early and long-term graft survival, but also potentially patient co-morbidity. Future directions for improving outcomes are discussed, which include immune tolerance and personalising immunosuppression regimens.

Validation of systems biology derived molecular markers of renal donor organ status associated with long term allograft function

Donor organ quality affects long term outcome after renal transplantation. A variety of prognostic molecular markers is available, yet their validity often remains undetermined. A network-based molecular model reflecting donor kidney status based on transcriptomics data and molecular features reported in scientific literature to be associated with chronic allograft nephropathy was created. Significantly enriched biological processes were identified and representative markers were selected. An independent kidney pre-implantation transcriptomics dataset of 76 organs was used to predict estimated glomerular filtration rate (eGFR) values twelve months after transplantation using available clinical data and marker expression values. The best-performing regression model solely based on the clinical parameters donor age, donor gender, and recipient gender explained 17% of variance in post-transplant eGFR values. The five molecular markers EGF, CD2BP2, RALBP1, SF3B1, and DDX19B representing key molecular processes of the constructed renal donor organ status molecular model in addition to the clinical parameters significantly improved model performance (p-value = 0.0007) explaining around 33% of the variability of eGFR values twelve months after transplantation. Collectively, molecular markers reflecting donor organ status significantly add to prediction of post-transplant renal function when added to the clinical parameters donor age and gender.

The functionality of African-specific variants in the TGFB1 regulatory region and their potential role in HIVAN

BACKGROUND

Transcription of transforming growth factor beta-1 (TGF-β1) is regulated by a polymorphic promoter region containing African-specific single nucleotide polymorphisms (SNPs). Some of these SNPs have higher frequencies among Southern Africans compared to other African populations and their functionality has only been partially studied. Due to the high prevalence of HIV-associated nephropathy (HIVAN) in Africans we hypothesized that functional African TGFB1-promoter SNPs may contribute to HIVAN pathogenesis.

METHODS

The functionality of the TGFB1 -1347 C>T variant and African-specific variants (-1287 G>A, -1154 C>T, -387 C>T and -14 G>A) were examined by measuring reporter gene expression in kidney and fibroblast cell lines co-transfected with TGFB1-promoter constructs and an HIV-Tat expression vector. TGF-β1 immunohistochemical staining was performed on kidney biopsies with HIVAN (n = 18) and compared to control biopsies without HIVAN or tubulointerstitial disease (n = 12) using semi-quantitative and digital image analysis. HIVAN cases were genotyped for TGFB1 -1347 and -387 SNP variants.

RESULTS

TGFB1-promoter haplotypes containing the African -387 T-allele resulted in ~ five-fold repression of TGFB1-promoter activity compared to -387 C haplotypes (p ≤ 0.024). HIV-Tat upregulated TGFB1-promoter activity for haplotypes containing -1347 T and -387 T in transfected renal cells (≈ 1.6-fold; p ≤ 0.030) and fibroblasts (≈ 1.3-fold; p ≤ 0.016). The renal interstitium from HIVAN biopsies, compared to HIV-positive and -negative controls, differed in the semi-quantitative TGF-β1 staining and digital optical density analyses. The TGFB1 -1347 and -387 genotypes in HIVAN cases were similar to population controls.

CONCLUSION

African-specific haplotypes lower TGFB1-promoter activity and expression levels and HIV-Tat upregulates TGFB1 promoter activity irrespective of the haplotype.

Association of cytokine gene polymorphisms with the complications of allogeneic haematopoietic stem cell transplantation

The purpose of our study was to confirm the prevalence of the association between single nucleotide polymorphisms present in genes encoding cytokines and the complications occurring after haematopoietic stem cell transplantation (HSCT). 108 recipients and 81 donors were typed for TNF-α (-308), TGF-β1 (codon 10, 25), IL-10 (-1082, -819, -592), IL-6 (-174) and INF-γ (+874). Our studies have shown a tendency toward association between the occurrence of acute form of graft versus host disease (aGVHD) and IL-6 genotype. Homozygote C/C was less likely to develop aGVHD (p=0,09). Genotype GCC/ATA in IL-10 recipient gene alone had protective effect against the occurrence of aGVHD (p=0,01). Furthermore, GCC/ATA protected the host against developing the disease in the clinically relevant grades (II-IV) (p=0,03). In addition, the recipient's T/T G/G genotype (TGF-β1) predisposed to the development of both acute (p=0,06 - trend) and chronic (p=0,04) GVHD and also severe aGVHD (p=0,004). We also observed a statistically significant association between the genotype of recipient and the risk of infection - the protective function of the G/C IL-6 in the bloodstream infections (p=0,001). Our results suggest that IL-6, IL-10 and TGF-β1 genotypes of recipient are the most associated with the risk of complications after HSCT.

Association between TGFB1 genetic polymorphisms and chronic allograft dysfunction: a systematic review and meta-analysis

BACKGROUND

Epidemiological studies have investigated the role of transforming growth factor-β1 (TGF-β1) in chronic allograft dysfunction (CAD) following kidney transplantation. TGFB1 gene polymorphisms (SNP rs1800470 and rs1800471) may be associated with the risk of CAD. In this meta-analysis, the relationship between these two variations and the risk of CAD was explored.

MATERIALS AND METHODS

MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), Embase, the Chinese CNKI and WANFANG databases were searched. Data were extracted and pooled results were estimated from odds ratios (ORs) with 95% confidential intervals (95% CIs). Quality assessments were performed, and publication bias of all eligible studies examined.

RESULTS

Eight studies with 1038 subjects were included in our analysis. According to the effects on TGF-β1 secretion, haplotypes were categorized as "HIGH", "INTERMEDIATE" and "LOW". The combined results showed a statistically significant difference of TGFB1 haplotypes between the CAD recipients and control subjects when "HIGH" with "INTERMEDIATE" and "LOW" ("HIGH" vs. "INTERMEDIATE" + "LOW": OR: 3.56, 95% CIs: 2.20, 5.78, P < 0.001) were compared. No significant association was found between the TGFB1 codon 10 or codon 25 and the CAD risk in all five genetic models.

CONCLUSIONS

Our meta-analysis has found the haplotype of TGFB1 codon 10/25 T/T G/G and T/C G/G genotypes, associated with increased production of TGF-β1, was linked with CAD risk following kidney transplantation. Moreover, no significant difference was found between TGFB1 codon 10 or codon 25 and the development of CAD.

Transforming growth factor-β1 functional polymorphisms in myeloablative sibling hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) with sibling donors (s.d.) is a life-saving intervention for patients with hematological malignancies. Numerous genetic factors have a role in transplant outcome. Several functional polymorphisms have been identified in TGF-β1 gene, such as single-nucleotide polymorphism (SNP) at +29C>T within exon 1. Two hundred and forty five patient/donor pairs who underwent a s.d. HSCT in our centers were genotyped for this SNP. In the myeloablative cohort, +29CC donors were associated with an increase in severe chronic GvHD (32% vs 16%, hazard ratio (HR) 9.0, P=0.02). Regarding survival outcomes, +29CC patients developed higher non relapse mortality (NRM) (1-5 years CC 28-32% vs TC/TT 7-10%; HR 5.1, P=0.01). Recipients of +29TT donors experienced a higher relapse rate (1-5 years TT 37-51% vs TC 19-25% vs CC 13%-19%; HR 2.4, P=0.01) with a decreased overall survival (OS) (1-5 years TT 69-50% vs TC/CC 77-69%; HR 1.9, P=0.05). Similar to previous myeloablative unrelated donors HSCT results, we confirmed that +29CC patients had higher NRM. In addition we found that +29TT donors might be associated with a higher relapse rate and lower OS. These results should be confirmed in larger series. Identification of these SNPs will allow personalizing transplant conditioning and immunosuppressant regimens, as well as assisting in the choice of the most appropriate donor.

The Polymorphism -308G/A of Tumor Necrosis Factor-α Gene Modulates the Effect of Immunosuppressive Treatment in First Kidney Transplant Subjects Who Suffer an Acute Rejection

The -308G/A SNP of tumor necrosis factor-alpha (TNF-α) gene affects TNF-α production. As its impact on transplant outcome remains open to debate, we decided to genotype it in a cohort of transplant subjects. A retrospective analysis of 439 first kidney recipients randomly divided into two subgroups (discovery and validation cohorts) was performed to identify the best predictors of acute rejection (AR). The effect on transplant outcome was analyzed by an adjusted logistic regression model. Carriers of the A allele, associated with elevated TNF-α production, presented a higher risk of AR (OR = 2.78; 95% CI = 1.40-5.51). Logistic regression analyses for AR showed an interaction between the polymorphism and treatment with thymoglobulin (p-interaction = 0.03). In recipients who did not receive thymoglobulin, carriers of A allele had higher risk of AR (OR = 4.05; 95% CI = 1.76-9.28). Moreover, carriers of A allele not treated with thymoglobulin presented higher risk of AR than those who received thymoglobulin (OR = 13.74; 95% CI = 1.59-118.7). The AUC of the model in the discovery cohort was 0.70 and in the validation cohort was 0.69. Our findings indicate that the -308G/A TNF-α polymorphism is associated with AR risk and it modulates the effectiveness of thymoglobulin treatment. This pharmacogenetic effect lets us propose this SNP as a useful predictor biomarker to tailor immunosuppressive regimens.

TNF receptors: signaling pathways and contribution to renal dysfunction

Tumor necrosis factor (TNF), initially reported to induce tumor cell apoptosis and cachexia, is now considered a central mediator of a broad range of biological activities from cell proliferation, cell death and differentiation to induction of inflammation and immune modulation. TNF exerts its biological responses via interaction with two cell surface receptors: TNFR1 and TNFR2. (TNFRs). These receptors trigger shared and distinct signaling pathways upon TNF binding, which in turn result in cellular outputs that may promote tissue injury on one hand but may also induce protective, beneficial responses. Yet the role of TNF and its receptors specifically in renal disease is still not well understood. This review describes the expression of the TNFRs, the signaling pathways induced by them and the biological responses of TNF and its receptors in various animal models of renal diseases, and discusses the current outcomes from use of TNF biologics and TNF biomarkers in renal disorders.

Association of cytokine/costimulatory molecule polymorphism and allograft rejection: a comparative review

One reason for genetic variations among human individuals is SNP which may confer diverse disease susceptibility or resistance in a population. Genetic variations in a key immunoregulatory agent can manifest various immunological responses, such as graft rejection. In fact, the outcome of organ transplantation can be impacted by several genetic causes including polymorphisms in genes encoding cytokines and costimulatory molecules in the donor or recipient. Thus, it can be helpful to contemplate the SNPs relating to these immunological determinants in order to achieve an improved transplantation therapy.

Contribution of genetics and epigenetics to progression of kidney fibrosis

Chronic kidney disease (CKD) which can lead to end-stage renal failure remains a principal challenge in Nephrology. While mechanistic studies provided extensive insights into the common pathways of fibrogenesis which underlie the progression of CKD, these pre-clinical studies fail to fully explain the vastly different progression slopes of individual patients. Recent studies provide evidence that genetic polymorphisms and epigenetic variations determine the individual susceptibility of patients to develop chronic progressive kidney disease. Here, we review recent insights that were provided by genome-wide association studies (GWASs), gene-linkage studies and epigenome analysis. The progression of CKD towards end-stage renal failure remains a principal unsolved problem in Nephrology as effective therapies and predictive tests are still not available [ 1, 2]. Chronic progressive kidney disease is caused by a wide range of diseases, with diabetes mellitus, hypertension and primary glomerulopathies being the most common causes in the Western world [ 3]. Infections, physical obstruction, interstitial nephritides and genetic cystic kidney diseases are also common causes of end-stage renal disease (ESRD) [ 3]. Regardless of the primary underlying disease, chronically injured kidneys are histomorphologically characterized by tubulointerstitial fibrosis [ 1]. In fact, the extent of tubulointerstitial fibrosis is the best predictor for kidney survival, irrespective of the underlying disease. For this reason, fibrosis is considered the common pathway of chronic progressive kidney disease [ 1]. Fibrogenesis is a pathological scarring process which involves accumulation of activated fibroblasts, excessive deposition of extracellular matrix, failed regeneration of tubular epithelium, microvascular rarefaction and (mostly sterile) inflammation [ 4]. Fibrogenesis depends on a complex interaction of the involved cell types which is orchestrated by an extensive network of growth factors and signalling pathways (which are reviewed extensively elsewhere) [ 1]. In view of the detailed mechanistic knowledge of the pathways that orchestrate renal fibrogenesis, it is puzzling why progression rates of CKD differ dramatically among patients with identical underlying diseases [ 1, 2]. The fibrotic pathways are known, but the switches that control their intensities and which determine the speed at which fibrosis moves along the progression slope are not yet understood [ 1, 2]. The concept that genetic polymorphisms are the basis for individual progression rates of CKD is an obvious and attractive one. Distinct susceptibilities of different mouse and rat strains to experimental CKD are a strong testament of the impact of genetic variations on renal fibrogenesis. Identification of the underlying genetic polymorphisms and mechanistic proof of their involvement in the progression of CKD, however, is an ongoing challenge. There are two basic approaches: one strategy is to perform unbiased screening to identify genes which are associated with chronic progressive kidney disease and to then prove their mechanistic relevance in experimental studies ('genotype to phenotype approach'). The second strategy is to selectively analyse polymorphisms of genes which have been identified in mechanistic studies as drivers of renal fibrogenesis with regard to their association with CKD (phenotype to genotype approach). The puzzling observation, however, is that genetic analysis and mechanistic studies so far rarely complement each other. The current state of affairs is reviewed in more detail below.

Tumor necrosis factor alpha promoter polymorphism and severity of acute kidney injury

BACKGROUND

Tumor necrosis factor-alpha is a proinflammatory cytokine that has been implicated in the pathobiology of acute kidney injury (AKI).

METHODS

We explored the association of a functional polymorphism in the promoter region (rs1800629) of the TNFA gene with severity of AKI, as defined by level of glomerular filtration (serum cystatin C and creatinine) and tubular injury (urinary NAG, KIM-1, α-GST, and π-GST) markers, in 262 hospitalized adults.

RESULTS

In unadjusted analyses, compared with the GG genotype, the TNFA GA and AA genotype groups tended to have higher enrollment (p = 0.08), peak (p = 0.004), and discharge (p = 0.004) serum creatinine levels, and the AA genotype tended to have a higher enrollment serum cystatin C level (p = 0.04). Compared with the GG genotype, the TNFA GA and AA genotype groups tended to have a higher urinary KIM-1 level (p = 0.03), and the AA genotype group tended to have a higher urinary π-GST level (p = 0.03). After adjustment for sex, race, age, baseline estimated glomerular filtration rate, sepsis, and dialysis requirement, compared with the GG genotype, the TNFA minor A-allele group had a higher peak serum creatinine of 1.03 mg/dl (0.43, 1.63; p = 0.001) and a higher urinary KIM-1 (relative ratio: 1.73; 95% CI: 1.16, 2.59; p = 0.008). The TNFA minor A-allele group also had a higher Multiple Organ Failure score of 0.26 (95% CI: 0.03, 0.49; p = 0.024) after adjustment for sex, race, age, and sepsis.

CONCLUSIONS

The TNFA rs1800629 gene polymorphism is associated with markers of kidney disease severity and distant organ dysfunction among patients with AKI. Larger studies are needed to confirm these relationships.

Inflammation in the setting of chronic allograft dysfunction post-kidney transplant: phenotype and genotype

BACKGROUND

Chronic allograft dysfunction (CGD) is a common outcome in kidney transplants, but its pathogenesis is unclear. We investigated the CGD phenotype and single-nucleotide polymorphisms (SNPs) associated with CGD.

METHOD

This prospective study enrolled 2336 transplants from seven transplant centers in North America. CGD was defined as a >25% rise in serum creatinine relative to a three-month post-transplant baseline, requiring a kidney biopsy. We genotyped 2724 SNPs in the initial 979 transplants, which form the test cohort.

RESULTS

CGD occurred 11.2 times per 100 person-years at a median of 509 ± 387 days from the three-month baseline. CGD was independently associated with death-censored, allograft failure, in an adjusted analysis [HR=20.6 (11.8-35.8, p < 0.001)]. Among 366 transplant recipients with CGD, 91% had inflammation on biopsy scores. 94 (26%) had inflammatory changes consistent with a diagnosis of concomitant acute rejection. SNPs in FM06 and FM03, potential drug metabolism genes, were associated with CGD, after accounting for multiple testing.

CONCLUSION

CGD phenotype with concomitant inflammation is associated with increased risk of allograft failure. SNPs associated with CGD in novel drug metabolism and transport genes, will be validated in subsequent transplants.

A study of the impact of cytokine gene polymorphism in acute rejection of renal transplant recipients

Acute rejection is a common phenomenon in transplantation. Inflammatory and anti-inflammatory mediators affect the graft microenvironment. Th1 responses cause acute rejection while Th2 immune responses help the survival of the graft. In this study, we evaluated gene polymorphisms of IL-6 G-174C, TGF-β T+869C, IL-4 C-590T, and IFN-γ T+874A cytokines in renal transplant patients. ARMS-PCR method was used to characterize IL-6 G-174C (rs76144090), TGF-β T+869C (rs1800471), and IFN-γ T+874A (rs2430561) polymorphisms and PCR-RFLP, for characterization of IL-4 C-590T (rs2243250) in 100 renal transplant patients. Acute rejection episodes were diagnosed according to the standard criteria. Analysis of the results showed that IL-6-174 GG genotype (P=0.018, OR=3.023, 95% CI=1.183-7.726) and IL-6-174G allele (P=0.046, OR=2.114, 95% CI=1.005-4.447) were more frequent, but IL-6-174GC genotype was less frequent in acute rejection of kidney transplantation in comparison with control group (P=0.024, OR=0.302, 95% CI=0.103-0.883). IFN-γ+874 T allele was associated with a higher risk of acute rejection (P=0.019, OR=2.088, 95% CI=1.124-3.880) while IFN-γ+874 AA genotype was associated with a lower risk of rejection (P=0.023, OR=0.318, 95% CI=0.115-0.875). Frequencies of TGF-β T+869C and IL-4 C-590T were not significantly different (P>0.05). Consequently, our results show that IL-6 G-174C and IFN-γ T+874A gene polymorphisms have predictive values for acute rejection after renal transplantation in Iranian patients.

Influence of interleukin-6 promoter polymorphism -174 g/c on kidney graft outcome

BACKGROUND

The cytokine interleukin-6 (IL-6) is important in both immune responses and cardiovascular diseases. The IL-6 promoter polymorphism -174 G/C is associated with increased plasma concentrations of IL-6. The relationship between IL-6 polymorphisms and graft survival, cardiovascular events, and new-onset diabetes mellitus after kidney transplantation is controversial.

OBJECTIVE

To analyze whether IL-6 (-174 G/C) polymorphism influences kidney graft survival or development of chronic allograft nephropathy, cardiovascular events, or new- onset diabetes.

METHODS

The IL-6 promoter polymorphism (-174 G/C) was analyzed using the polymerase chain reaction with sequence-specific primers in 335 kidney transplant recipients. Data for graft survival, chronic graft nephropathy, cardiovascular events, and new-onset diabetes were obtained retrospectively from clinical records. Categorical variables were compared between individuals with CC, GG, and GC genotypes using χ2 tests. Survival analysis was performed using the Kaplan-Meier method, comparing groups using the log-rank test.

RESULTS

No significant differences were observed in 5-year graft survival between individuals with CC and GC/GG genotypes (85.3% vs 77.1%; P=.22). Nor were significant differences noted in the rates of chronic allograft nephropathy (37.5% vs 33.8%; P=.48), cardiovascular events (10.0% vs 23.0%; P=.10), or new-onset diabetes (7.5% vs 11.8%; P=.28).

CONCLUSION

There is no association between IL-6 (-174 G/C) polymorphism and graft survival or development of chronic allograft nephropathy, cardiovascular events, or new- onset diabetes.

Association of functional polymorphisms of the transforming growth factor B1 gene with survival and graft-versus-host disease after unrelated donor hematopoietic stem cell transplantation

BACKGROUND

Many genetic factors play major roles in the outcome of hematopoietic stem cell transplants from unrelated donors. Transforming growth factor beta1 is a member of a highly pleiotrophic family of growth factors involved in the regulation of numerous immunomodulatory processes.

DESIGN AND METHODS

We investigated the impact of single nucleotide polymorphisms at codons 10 and 25 of TGFB1, the gene encoding for transforming growth factor beta1, on outcomes in 427 mye-loablative-conditioned transplanted patients. In addition, transforming growth factor beta1 plasma levels were measured in 263 patients and 327 donors.

RESULTS

Patients homozygous for the single nucleotide polymorphism at codon 10 had increased non-relapse mortality (at 3 years: 46.8% versus 29.4%, P=0.014) and reduced overall survival (at 5 years 29.3% versus 42.2%, P=0.013); the differences remained statistically significant in multivariate analysis. Donor genotype alone had no impact, although multiple single nucleotide polymorphisms within the pair were significantly associated with higher non-relapse mortality (at 3 years: 44% versus 29%, P=0.021) and decreased overall survival (at 5 years: 33.8% versus 41.9%, P=0.033). In the 10/10 HLA matched transplants (n=280), recipients of non-wild type grafts tended to have a higher incidence of acute graft-versus-host disease grades II-IV (P=0.052). In multivariate analysis, when analyzed with patients' genotype, the incidences of both overall and grades II-IV acute graft-versus-host disease were increased (P=0.025 and P=0.009, respectively) in non-wild-type pairs.

CONCLUSIONS

We conclude that increasing numbers of single nucleotide polymorphisms in codon 10 of TGFB1 in patients and donors are associated with a worse outcome following hematopoietic stem cell transplantation from unrelated donors.

Expression of regulatory T-cell-related molecule genes and clinical outcome in kidney transplant recipients

BACKGROUND

Naturally occurring regulatory T cells have been associated with long-term allograft survival. We investigated whether gene transcripts of Treg-related molecules are upregulated or downregulated in kidney transplant recipients with different clinical outcomes and may serve as markers of operative tolerance.

METHODS

Expression levels of transcription factor (forkhead box P3 [FOXP3], t-bet, and GATA3), regulatory molecule (cytotoxic T-lymphocyte antigen-4, glucocorticoid-induced tumor necrosis factor receptor-related protein, tribbles protein-1, and transforming growth factor-beta), and chemokine receptor (CCR7 and CXCR4) genes were measured in kidney graft recipients with long-term (> or = 9 years) stable renal function (LTS) or chronic rejection (ChrRx). Patients on dialysis and healthy individuals served as controls.

RESULTS

The level of FOXP3 transcripts was lower in ChrRx patients than in LTS patients (P<0.01). The highest transforming growth factor-beta transcripts were observed in ChrRx and the highest CCR7 and CXCR4 transcripts were observed in LTS patients. In LTS patients, FOXP3 gene expression was associated with CXCR4 gene expression (P=0.015). FOXP3 and CCR7 transcript levels were higher in LTS patients without calcineurin inhibitor therapy than in LTS patients with calcineurin inhibitors.

CONCLUSION

Our results suggest that high expression of FOXP3 and chemokine receptor genes in LTS patients are possible indicators of a regulatory process that contributes to long-term allograft acceptance. Markers that were increased in LTS patients were found to be decreased in ChrRx patients, suggesting that rejection may partly be the result of a lack of this regulatory process. FOXP3 and CCR7 and CXCR4 transcripts might be used as markers to distinguish patients who developed long-term allograft acceptance from patients who are prone to ChrRx.

Immunoregulatory role of TNFalpha in inflammatory kidney diseases

Tumor necrosis factor alpha (TNFalpha), a pleiotropic cytokine, plays important inflammatory roles in renal diseases such as lupus nephritis, anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis and renal allograft rejection. However, TNFalpha also plays critical immunoregulatory roles that are required to maintain immune homeostasis. These complex biological functions of TNFalpha are orchestrated by its two receptors, TNFR1 and TNFR2. For example, TNFR2 promotes leukocyte infiltration and tissue injury in an animal model of immune complex-mediated glomerulonephritis. On the other hand, TNFR1 plays an immunoregulatory function in a murine lupus model with a deficiency in this receptor that leads to more severe autoimmune symptoms. In humans, proinflammatory and immunoregulatory roles for TNFalpha are strikingly illustrated in patients on anti-TNFalpha medications: These treatments are greatly beneficial in certain inflammatory diseases such as rheumatoid arthritis but, on the other hand, are also associated with the induction of autoimmune lupus-like syndromes and enhanced autoimmunity in multiple sclerosis patients. The indication for anti-TNFalpha treatments in renal inflammatory diseases is still under discussion. Ongoing clinical trials may help to clarify the potential benefit of such treatments in lupus nephritis and ANCA-associated glomerulonephritis. Overall, the complex biology of TNFalpha is not fully understood. A greater understanding of the function of its receptors may provide a framework to understand its contrasting proinflammatory and immunoregulatory functions. This may lead the development of new, more specific anti-inflammatory drugs.

Effect of cytokine and pharmacogenomic genetic polymorphisms in transplantation

Consolidating the information that we have on pharmacogenetics and on cytokine genetics to produce patient-oriented individualized drug regimens is an important challenge in transplantation medicine. Using a multi-variant approach based on genetic profile and other relevant clinical factors a score system may be developed to predict the severity of rejection, infection, or other complications associated with transplantation. The ultimate goal of these studies is to improve patient outcome through individualized drug regimens.