Tumor necrosis factor gene polymorphism and cardiac allograft vasculopathy

The Relationship Between Genetic Variants at Loci 9p21, 6q25.1, and 2q36.3 and the Development of Cardiac Allograft Vasculopathy in Heart Transplant Patients

BACKGROUND

Cardiac allograft vasculopathy (CAV) is an accelerated form of coronary artery disease (CAD) that is characterized by concentric fibrous intimal hyperplasia along the length of coronary vessels, and is recognized as long-term complication after heart transplantation. The chromosomal loci 9p21, 6q25.1, and 2q36.3, represented by their respective leading variants rs10757274, rs6922269 and rs2943634, have been linked with a history of CAD by genome-wide association studies. We aimed to investigate the associations of genetic variants at the loci 9p21, 6q25.1, and 2q36.3 with CAV as genetic risk factors for early prediction.

METHODS

Genomic DNA was extracted from paired aortic samples of 727 heart recipients (average age 50.8 ± 12.2 years; 21.3% women) and corresponding donors (average age 39.7 ± 12.0 years; 26.1% women). The variants within the loci 9p21, 6q25.1, and 2q36.3 were genotyped using PCR-RFLP.

RESULTS

The recipients' variants of 9p21 (OR 1.97; 95% CI, 1.21-3.19 for GG vs. +A comparison, p = 0.0056) and 2q36.3 (OR 2.46; 95% CI, 1.12-6.17 for +C vs. AA comparison, p = 0.0186) were associated with higher incidence of CAV during the first year following heart transplantation. No such association was found for donor genotypes.

CONCLUSIONS

Our data suggest that variants at the locus 9p21 (rs10757274) and 2q36.3 (rs2943634) are associated with early CAV development.

The Biological Parallels Between Atherosclerosis and Cardiac Allograft Vasculopathy: Implications for Solid Organ Chronic Rejection

Atherosclerosis and solid organ chronic rejection are pervasive chronic disease states that account for significant morbidity and mortality in developed countries. Recently, a series of shared molecular pathways have emerged, revealing biological parallels from early stages of development up to the advanced forms of pathology. These shared mechanistic processes are inflammatory in nature, reflecting the importance of inflammation in both disorders. Vascular inflammation triggers endothelial dysfunction and disease initiation through aberrant vasomotor control and shared patterns of endothelial activation. Endothelial dysfunction leads to the recruitment of immune cells and the perpetuation of the inflammatory response. This drives lesion formation through the release of key cytokines such as IFN-y, TNF-alpha, and IL-2. Continued interplay between the adaptive and innate immune response (represented by T lymphocytes and macrophages, respectively) promotes lesion instability and thrombotic complications; hallmarks of advanced disease in both atherosclerosis and solid organ chronic rejection. The aim of this study is to identify areas of overlap between atherosclerosis and chronic rejection. We then discuss new approaches to improve current understanding of the pathophysiology of both disorders, and eventually design novel therapeutics.

The Evaluation and Management of Coronary Artery Disease in the Lung Transplant Patient

Lung transplantation can greatly improve quality of life and extend survival in those with end-stage lung disease. In order to derive the maximal benefit from such a procedure, patients must be carefully selected and be otherwise healthy enough to survive a high-risk surgery and sometimes prolonged immunosuppressive therapy following surgery. Patients therefore must be critically assessed prior to being listed for transplantation with close attention paid towards assessment of cardiovascular health and operative risk. One of the biggest dictators of this is coronary artery disease. In this review article, we discuss the assessment and management of coronary artery disease in the potential lung transplant candidate.

Ferroptosis in the post-transplantation inflammatory response

Transplantation is a life-saving therapy for patients with end-stage organ disease. Successful outcomes after transplantation require mitigation of the post-transplant inflammatory response, limiting alloreactivity, and prevention of organ rejection. Traditional immunosuppressive regimens aim to dampen the adaptive immune response; however, recent studies have shown the feasibility and efficacy of targeting the innate immune response. Necroinflammation initiated by donor organ cell death is implicated as a critical mediator of primary graft dysfunction, acute rejection, and chronic rejection. Ferroptosis is a form of regulated cell death that triggers post-transplantation inflammation and drives the activation of both innate and adaptive immune cells. There is a growing acceptance of the clinical relevance of ferroptosis to solid organ transplantation. Modulating ferroptosis may be a potentially promising strategy to reduce complications after organ transplantation.

A20 Haploinsufficiency Aggravates Transplant Arteriosclerosis in Mouse Vascular Allografts: Implications for Clinical Transplantation

BACKGROUND

Inflammation is central to the pathogenesis of transplant arteriosclerosis (TA). We questioned whether physiologic levels of anti-inflammatory A20 influence TA severity.

METHODS

We performed major histocompatibility complex mismatched aorta to carotid artery interposition grafts, using wild type (WT) or A20 heterozygote (HET) C57BL/6 (H-2) donors and BALB/c (H-2) recipients, and conversely BALB/c donors and WT/HET recipients. We analyzed aortic allografts by histology, immunohistochemistry, immunofluorescence, and gene profiling (quantitative real-time reverse-transcriptase polymerase chain reaction). We validated select in vivo A20 targets in human and mouse smooth muscle cell (SMC) cultures.

RESULTS

We noted significantly greater intimal hyperplasia in HET versus WT allografts, indicating aggravated TA. Inadequate upregulation of A20 in HET allografts after transplantation was associated with excessive NF-кB activation, gauged by higher levels of IkBα, p65, VCAM-1, ICAM-1, CXCL10, CCL2, TNF, and IL-6 (mostly localized to SMC). Correspondingly, cytokine-induced upregulation of TNF and IL-6 in human and mouse SMC cultures inversely correlated with A20 expression. Aggravated TA in HET versus WT allografts correlated with increased intimal SMC proliferation, and a higher number of infiltrating IFNγ and Granzyme B CD4 T cells and natural killer cells, and lower number of FoxP3 regulatory T cells. A20 haploinsufficiency in allograft recipients did not influence TA.

CONCLUSIONS

A20 haploinsufficiency in vascular allografts aggravates lesions of TA by exacerbating inflammation, SMC proliferation, and infiltration of pathogenic T cells. A20 single nucleotide polymorphisms associating with lower A20 expression or function in donors of vascularized allografts may inform risk and severity of TA, highlighting the clinical implications of our findings.

Single nucleotide polymorphisms for genes encoding cytokines in the context of cardiac surgery. Part I: Heart transplantation

Cardiovascular diseases remain the leading cause of death in Poland and other countries of the European Union. Patients with end-stage heart failure constitute a patient subgroup for whom the treatment of choice is heart transplantation. Despite advances in immunosuppressive therapy, acute or chronic graft rejection occurs in 20-30% of cases in the first six months after transplantation. The significance of the immune response and inflammation in graft rejection implies the important role of cytokines. Molecular markers are sought to facilitate risk assessment and improve patient care. At present, genetic tests are not used for this purpose, but studies aiming to rectify that have been conducted for years, including studies on single nucleotide polymorphisms of cytokine genes. This paper presents the results of research on the single nucleotide polymorphisms (SNPs) of the IL-2, IL-4, IL-6, IL-10, TGF-β1, PDGF, VEGF, and TNF-α genes in conjunction with heart transplantation. The analyzed data do not allow for reliable application of these genetic tests in clinical practice, but suggest that it is a promising direction which may improve the options of treatment individualization in the future.

Cardiac allograft vasculopathy: diagnosis, therapy, and prognosis

Development of cardiac allograft vasculopathy represents the major determinant of long-term survival in patients after heart transplantation. Due to graft denervation, these patients seldom present with classic symptoms of angina pectoris, and the first clinical presentations are progressive heart failure or sudden cardiac death. Although coronary angiography remains the routine technique for coronary artery disease detection, it is not sensitive enough for screening purposes. This is especially the case in the first year after transplantation when diffuse and concentric vascular changes can be easily detected only by intravascular ultrasound. The treatment of the established vasculopathy is disappointing, so the primary effort should be directed toward early prevention and diagnosis. Due to diffuse vascular changes, revascularization procedures are restricted only to a relatively small proportion of patients with favorable coronary anatomy. Percutaneous coronary intervention is preferred over surgical revascularization since it leads to better acute results and patient survival. Although there is no proven long-term advantage of drug-eluting stents for the treatment of in-stent restenosis, they are preferred over bare-metal stents. Severe vasculopathy has a poor prognosis and the only definitive treatment is retransplantation. This article reviews the present knowledge on the pathogenesis, diagnosis, treatment, and prognosis of cardiac allograft vasculopathy.

Tumor necrosis factor alpha -308 gene locus promoter polymorphism: an analysis of association with health and disease

Tumor necrosis factor-alpha (TNF-alpha) is a potent immunomediator and proinflammatory cytokine that has been implicated in the pathogenesis of a large number of human diseases. The location of its gene within major histocompatibility complex and biological activities has raised the possibility that polymorphisms within this locus may contribute to the pathogenesis of wide range of autoimmune and infectious diseases. For example, a bi-allelic single nucleotide substitution of G (TNFA1 allele) with A (TNFA2 allele) polymorphism at -308 nucleotides upstream from the transcription initiation site in the TNF-alpha promoter is associated with elevated TNF-alpha levels and disease susceptibilities. However, it is still unclear whether TNF-alpha -308 polymorphism plays a part in the disease process, in particular whether it could affect transcription factor binding and in turn influence TNF-alpha transcription and synthesis. Several studies have suggested that TNFA2 allele is significantly linked with the high TNF-alpha-producing autoimmune MHC haplotype HLA-A1, B8, DR3, with elevated serum TNF-alpha levels and a more severe outcome in diseases. This review discusses the genetics of the TNF-alpha -308 polymorphism in selected major diseases and evaluates its common role in health and disease.

Elevated serum uric acid levels following heart transplantation predict all-cause and cardiac mortality

AIMS

We evaluated the relationship between elevated serum uric acid (SUA) and mortality as well as cardiac allograft vasculopathy (CAV) among 184 heart transplant (HTx) recipients. We also measured inflammatory, neurohormonal, and oxidative stress markers to explore pathophysiological mechanisms.

METHODS AND RESULTS

There were 28 (15%) deaths, patients with SUA > or = 502 micromol/L (upper quartile) at 1 year post-HTx had an increased risk of total mortality (adjusted HR 2.21, P = 0.03) and cardiac mortality (adjusted HR 4.38, P = 0.03). Elevated SUA was a significant risk factor for development of moderate/severe angiographic CAV (adjusted HR 4.79, P = 0.01). A smaller decline in SUA (<97 micromol/L) during the first year post-HTx was also associated with an increased risk of mortality (P = 0.02). Patients with elevated SUA had significantly higher levels of high-sensitivity C-reactive protein (P = 0.008) and N-terminal probrain natriuretic peptide (P = 0.022), but there was no significant difference in oxidative stress parameters.

CONCLUSION

Elevated SUA at 1 year post-HTx, or a modest rather than a marked decline in SUA levels during the first year post-HTx, is associated with an increased risk of mortality. Although the pathophysiological mechanism is unclear, our data indicate a potential relationship between SUA and inflammation which should be explored further.

Clinical impact of cytokine and growth factor genetic polymorphisms in thoracic organ transplantation

Demographic and clinical risk factors may only partially predict short- and long-term outcomes after thoracic transplantation. The interindividual variability seen in rejection profiles could be related to the recipient's or donor's genetic background. Rejection, either acute or chronic, elicits an alloimmune response that involves a complex network of cytokines, growth factors, adhesion molecules, and other molecules, which may modulate the immune response toward rejection or, conversely, mediate graft acceptance. Herein, the authors discuss the current evidence regarding the importance of genetic polymorphisms as independent predictors of allograft outcome. They believe that pretransplant genotype profiling of patients, in combination with other relevant clinical information, might be useful to predict the risk for posttransplant adverse events and also to facilitate the implementation of individualized immunosuppression.

Inhibition of TNF-alpha reduces transplant arteriosclerosis in a murine aortic transplant model

Experimental and clinical data provide evidence that TNF-alpha contributes to acute and chronic allograft rejection. In this study, we explored the effect of TNF-alpha blockade using the chimeric monoclonal antibody infliximab on the development of transplant arterisoclerosis in a fully mismatched aortic allograft model. Post-transplant treatment of CBA (H2(k)) recipients with 250 mug infliximab (cumulative dose 1.25 mg) reduced luminal occlusion of C57Bl/6 (H2(b)) aortic grafts on day 30 from 77 +/- 5% in untreated controls to 52 +/- 6%. Increasing the dose of anti-TNF-alpha antibody had no further beneficial effect. Treatment with human control immunoglobulin had no effect on intima proliferation. Under TNF-alpha blockade, ICAM-1 and PDGF mRNA expression within the grafts was strongly reduced, whereas iNOS expression was enhanced. The data show that TNF-alpha blockade using infliximab can reduce the development of transplant arteriosclerosis in fully mismatched murine aortic grafts.

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.

The TNF (-308A) polymorphism is associated with microchimerism in transfused trauma patients

Microchimerism (MC), defined as the persistence of allogeneic cells at low concentrations, is well documented in transfused trauma patients. We hypothesized that genetic polymorphisms linked to cytokine production could contribute to trauma-induced immune modulation and development of microchimerism after transfusion of trauma patients. We used high-throughput SYBR-green-based genotyping of single nucleotide polymorphisms (SNPs) to characterize 59 transfused trauma patients, with MC (n=30) and without MC (n=29), for 4 functionally significant SNPs: TNF (-308), IL 10 (-1082), IFNG (+874), and TGFB1 (+915). We then compared likelihood for development of MC and the magnitude of immune suppression among subjects with and without these selected immune response SNPs. We identified a significant association between TNF (-308A) SNP and both development of MC and diminished immune responsiveness. Hence predisposing genetic factors may explain, in part, why only a subset of trauma patients develops transfusion-associated microchimerism.

Disparate Distribution of 16 Candidate Single Nucleotide Polymorphisms Among Racial and Ethnic Groups of Pediatric Heart Transplant Patients

BACKGROUND

Allograft failure in African-Americans remains higher than in Caucasians. Single nucleotide polymorphisms (SNPs) have been associated with altered allograft outcomes.

METHODS

In this multi-center study we compared SNP frequencies in 364 pediatric heart recipients from three ethnic/racial groups: Caucasian (n = 243), African-American (n = 39), and Hispanic (n = 82). The target genes were: tumor necrosis factor-alpha, interleukin (IL)-10, IL-6, interferon (IFN)-gamma, vascular endothelial growth factor (VEGF), transforming growth factor-beta1, Fas, FasL, granzyme B, ABCB1, CYP3A5.

RESULTS

Compared to Caucasians, African-Americans exhibited a higher prevalence of genotypes associated with low expression of IFN-gamma (24% vs. 45.7%, P < 0.001) and IL-10 (33% vs. 57.1%, P = 0.052). African-Americans also exhibited an increased prevalence of high IL-6 (82.9% vs. 38.1%; P < 0.001). VEGF -2578 C/C and -460 C/C genotypes were found more frequently in African-Americans and Hispanics as compared to Caucasians (P < 0.001). G/G genotype of Fas and T/T genotype of FasL were expressed more often by African-American recipients. The prevalence of Granzyme B (-295A/G) genotype was differentially distributed in the three groups. Compared with Caucasians, African-Americans were twice as likely to carry the ABCB1 2677 G/G genotype (78.6% vs. 33.7%, P < 0.0025), and they were more frequent carriers of the CYP3A5 *1/*1 genotype (35.7% vs. 0.6% in Caucasians and 7.2% in Hispanics; P < 0.001).

CONCLUSION

African-Americans have a genetic background that may predispose to proinflammatory/lower regulatory environment, reduced drug exposure and immunosuppressive efficacy. In this ongoing multicenter study, these gene polymorphisms differences among ethnic/racial groups are being documented so that therapeutic strategies can be devised to optimize outcomes for pediatric transplant recipients.

Clinical tolerance following liver transplantation: long term results and future prospects

The ongoing quest of achieving clinical transplantation tolerance has been fueled, in large part, by the success of solid organ transplantation. Long term morbidity following transplantation now is primarily related to complications of immunosuppression (IS) such as malignancy, drug toxicity, or infection. This report provides long term follow-up on a large cohort of operationally tolerant patients, provides clinical guidelines to be considered in IS withdrawal, and identifies future prospects for achieving consistent clinical tolerance following liver transplantation (LT).