Inhibition of endothelin-1 improves survival and vasculopathy in rat cardiac transplants treated with cyclosporine

Association of Endothelin-1 With Accelerated Cardiac Allograft Vasculopathy and Late Mortality Following Heart Transplantation

BACKGROUND

Endothelin-1 (ET-1) has been implicated in the development of post-heart transplantation (HT) cardiac allograft vasculopathy (CAV), but has not been well studied in humans.

METHODS AND RESULTS

In 90 HT patients, plasma ET-1 was measured within 8 weeks after HT (baseline) via a competitive enzyme-linked immunosorbent assay. Three-dimensional volumetric intravascular ultrasound of the left anterior descending artery was performed at baseline and at 1 year. Accelerated CAV (lumen volume loss) was defined with the 75th percentile as a cutoff. Patients were followed beyond the first year after HT for late death or retransplantation. A receiver operating characteristic (ROC) curve demonstrated that a baseline ET-1 concentration of 1.75 pg/mL provided the best accuracy for diagnosis of accelerated CAV at 1 year (area under the ROC curve 0.69, 95% confidence interval [CI] 0.57-0.82; P = .007). In multivariate logistic regression, a higher baseline ET-1 concentration was independently associated with accelerated CAV (odds ratio [OR] 2.13, 95% CI 1.15-3.94; P = .01); this relationship persisted when ET-1 was dichotomized at 1.75 pg/mL (OR 4.88, 95% CI 1.69-14.10; P = .003). Eighteen deaths occurred during a median follow-up period of 3.99 (interquartile range 2.51-9.95) years. Treated as a continuous variable, baseline ET-1 was not associated with late mortality in multivariate Cox regression (hazard ratio [HR] 1.22, 95% CI 0.72-2.05; P = .44). However, ET-1 >1.75 pg/mL conferred a significantly lower cumulative event-free survival on Kaplan-Meier analysis (P = .047) and was independently associated with late mortality (HR 2.94, 95% CI 1.12-7.72; P = .02).

CONCLUSIONS

Elevated ET-1 early after HT is an independent predictor of accelerated CAV and late mortality, suggesting that ET-1 has durable prognostic value in the HT arena.

Tacrolimus preserves vasomotor function and maintains vascular homeostasis

BACKGROUND

Post-transplant immunosuppression is associated with endothelial dysfunction that may lead to vasculopathy. We have previously demonstrated that cyclosporine causes vascular dysfunction. In this we study examined the effect of tacrolimus (Tac) in an identical model.

METHODS

Lewis rats (n = 8 per group) were injected with Tac (low, medium or high dose) or saline (Con) daily for 2 weeks. Segments of thoracic aorta (TAo) were assessed for endothelium-dependent (Edep) and -independent (Eind) vasorelaxation (E(max)) and sensitivity to endothelin (ET)-induced vasoconstriction (C(max)). ET(A) and ET(B) receptor (Rc) expression levels were determined in TAo. Tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-β) expression were determined in myocardial (LV) tissue. Plasma ET levels and tissue oxidative injury were quantified by enzyme-linked immunoassay.

RESULTS

Tac did not impair Edep relaxation when compared with Con (p = 0.69). Impairment of sodium nitroprusside-mediated Eind vasorelaxation was noted with Tac (E(max): Con 69 ± 2%, Tac high 54 ± 2%; p = 0.0001), whereas no such impairment was seen with diltiazem-mediated Eind vasorelaxation (p = 0.06). Tac decreased sensitivity to ET (C(max): Con 222 ± 19%, Tac high 162 ± 11%; p = 0.0002) and ET levels (Con 0.8 ± 0.1 fmol/ml, Tac 0.4 ± 0.1 fmol/ml; p = 0.02). Tac did not alter ET(A) Rc expression (p = 0.28), but increased ET(B) Rc levels (p = 0.02). Oxidative injury was similar in both LV (p = 0.43) and Ao (p = 0.73) tissue. Similarly, TNF-α expression (p = 0.16) was not different between groups, whereas expression of TGF-β demonstrated a significant decrease with Tac treatment (p = 0.02).

CONCLUSION

Our findings suggests that tacrolimus has beneficial effects with respect to endothelial function.

Toxicodynamic effects of ciclosporin are reflected by metabolite profiles in the urine of healthy individuals after a single dose

WHAT IS ALREADY KNOWN ABOUT THE SUBJECT * Ciclosporin's nephrotoxicity initially targets the proximal tubule and is, at least in part, driven by increased formation of oxygen radicals. * (1)H-nuclear magnetic resonance spectroscopy (NMR)- and mass spectrometry (MS)-based biochemical profiling (metabolomics) allows for the sensitive detection of metabolite pattern changes in urine. * In systematic studies in rats we showed that ciclosporin caused urine metabolite pattern changes typical for proximal tubule damage and that these pattern changes seemed to be more sensitive than established clinical kidney function markers such as serum creatinine concentrations. WHAT THIS PAPER ADDS * This study showed that urine metabolite pattern changes as assessed by (1)H-NMR and HPLC-MS are sensitive enough to detect the effect of ciclosporin as early as 4 h after a single oral dose. * In our previous rat studies, changes in urine metabolite pattern in response to ciclosporin translated into healthy humans, indicating the involvement of the same toxicodynamic mechanisms. * The results provide proof of concept for further development of this combination molecular marker strategy into diagnostic tools for the detection and monitoring of drug nephrotoxicity. AIMS The immunosuppressant ciclosporin is an efficient prophylaxis against transplant organ rejection but its clinical use is limited by its nephrotoxicity. Our previous systematic studies in the rat indicated urine metabolite pattern changes to be sensitive indicators of the negative effects of ciclosporin on the kidney. To translate these results, we conducted an open label, placebo-controlled, crossover study assessing the time-dependent toxicodynamic effects of a single oral ciclosporin dose (5 mg kg(-1)) on the kidney in 13 healthy individuals. METHODS In plasma and urine samples, ciclosporin and 15-F(2t)-isoprostane concentrations were assessed using HPLC-MS and metabolite profiles using (1)H-NMR spectroscopy. RESULTS The maximum ciclosporin concentrations were 1489 +/- 425 ng ml(-1) (blood) and 2629 +/- 1308 ng ml(-1) (urine). The increase in urinary 15-F(2t)-isoprostane observed 4 h after administration of ciclosporin indicated an increase in oxidative stress. 15-F(2t)-isoprostane concentrations were on average 2.9-fold higher after ciclosporin than after placebo (59.8 +/- 31.2 vs. 20.9 +/- 19.9 pg mg(-1) creatinine, P < 0.02). While there were no conclusive changes in plasma 15-F(2t)-isoprostane concentrations or metabolite patterns, non-targeted metabolome analysis using principal components analysis and partial least square fit analysis revealed significant changes in urine metabolites typically associated with negative effects on proximal tubule cells. The major metabolites that differed between the 4 h urine samples after ciclosporin and placebo were citrate, hippurate, lactate, TMAO, creatinine and phenylalanine. CONCLUSION Changes in urine metabolite patterns as a molecular marker are sufficiently sensitive for the detection of the negative effects of ciclosporin on the kidney after a single oral dose.

The use of cyclosporine in dermatology: part II

Cyclosporine is highly effective in the treatment of a multitude of dermatoses. Concern over its side effect profile has limited its use in dermatology. Adverse effects are, for the most part, dose dependent and related to duration of therapy. Using the recommended monitoring protocols results in a significant decrease in the incidence of cyclosporine-related toxicities. This article provides a comprehensive review of the pharmacokinetics of cyclosporine, potential drug interactions, adverse effects, and recommendations for monitoring in patients treated with cyclosporine. The use of cyclosporine in pregnancy and in the pediatric population is also addressed.

LEARNING OBJECTIVES

After completing this learning activity, participants should be familiar with the monitoring guidelines of cyclosporine, its contraindications, its possible drug interactions, its adverse effect profile, and its use in pregnancy and the childhood and adolescent populations.

Rosiglitazone Suppresses Cyclosporin-Induced Chronic Transplant Dysfunction and Prolongs Survival of Rat Cardiac Allografts

BACKGROUND

The lack of effective treatment for chronic transplant dysfunction restricts the long-term survival of solid organ allografts. Peroxisome proliferator-activated receptor ligands can suppress vascular inflammation. The aim of this study was to analyze the effects of rosiglitazone on chronic transplant dysfunction in a rat cardiac transplant model.

METHODS

Inbred male Fisher 344 (F344, RT1lvl) and Lewis (LEW, RT1(1)) rats were subjected to heterotopic abdominal heart transplantation according to standard procedures. Cyclosporine A was administered intraperitoneally to cover acute rejection, and rosiglitazone was administered orally by gavage daily from 3 days before the operation to the end of experiments.

RESULTS

Rosiglitazone significantly prolonged the survival of cardiac allografts in rats (F344 to LEW) that had received a 10-day course of cyclosporin A compared to treatment with immunosuppressant alone. Analysis of allografts at 120 days posttransplantation showed that rosiglitazone reduced the inflammatory cell infiltrate in both the vessels and graft parenchyma as were neointimal formation, vascular occlusion, and fibrosis. Expression of transforming growth factor-beta and related proteins was less abundant after cyclosporin A/rosiglitazone treatment.

CONCLUSIONS

The findings reported here demonstrate that rosiglitazone given under the cover of short-term treatment with cyclosporin A prolongs cardiac allograft survival and reduces the severity of chronic transplant dysfunction. This may be mediated in part through the downregulation of transforming growth factor-beta and related proteins. The combined effects of rosiglitazone and immunosuppressive drugs are potentially beneficial to patients receiving organ transplants.

Influence of mast cells on outcome after heterotopic cardiac transplantation in rats

Correlative data suggest that mast cells adversely affect cardiac transplantation. This study uses a mast cell-deficient rat model to directly address the role of mast cells in cardiac allotransplantation. Standardized cardiac heterotopic transplantation with cyclosporine immunosuppression was performed in mast cell-deficient and mast cell-competent rats. Rejection, ischemia, fibrosis, fibrin deposition, numbers of T-cell receptor alpha/beta positive cells, expression of transforming growth factor-beta (TGF-beta), and of endothelin-1 (ET-1) and its receptors ETA and ETB were assessed. Differences in baseline cardiac gene expression were quantified by real-time PCR in a separate group of untransplanted animals. Baseline cardiac gene expression levels of all investigated growth factors, cytokines, ET-1, ETA, and ETB were similar in mast cell-deficient and mast cell-competent rats. Surprisingly, upon heterotopic transplantation, donor heart survival was significantly reduced in mast cell-deficient rats. Moreover, in mast cell-deficient donor hearts rejection was more severe, although nonsignificant, and extracellular matrix associated TGF-beta immunoreactivity was significantly lower than in mast cell-competent donor hearts. Fibrin immunoreactive area, on the other hand, was only increased in mast cell-deficient donor hearts, but not in mast cell-competent donor hearts. Histopathological changes in all donor hearts were accompanied by increased immunoreactivity for ET-1. In conclusion, this study shows that mast cells play a protective role after cardiac transplantation.

Role of endothelin-1 and nitric oxide bioavailability in transplant-related vascular injury: comparative effects of rapamycin and cyclosporine

BACKGROUND

Cyclosporine (CyA) is associated with many side effects, including endothelial dysfunction and transplant vasculopathy (TxV). We previously demonstrated that CyA results in impairment of nitric oxide bioavailability and enhanced sensitivity to endothelin-1 (ET-1). In this study, we evaluated rapamycin (SRL) for its effects on the endothelium.

METHODS AND RESULTS

Lewis rats (n = 8) were injected with SRL (1.5 mg/kg), CyA (5 mg/Kg), or saline (Con) intraperitoneally daily for 2-weeks. Thoracic aortic segments were assessed for endothelial-dependent (Edep) and independent (Eind) relaxation after exposure to acetylcholine and sodium nitroprusside by deriving the percent maximum relaxation (Emax). ET-1 plasma levels were also measured. Thoracic aortic expression of endothelial nitric oxide synthase (eNOS), ET(A) and ET(B) receptors (Rc), were determined. Oxidative injury was assessed by changes in 8-isoprostane levels. CyA exposure resulted in lower Edep vasorelaxation compared with control and SRL (Emax: SRL, 58+/-4%; CyA, 24+/-7%; Con, 52+/-8%; P=0.001). No differences in Eind vasorelaxation were seen. CyA exposure also increased sensitivity to ET-1 (% maximum contraction [Cmax]: Con, 211+/-8%; SRL, 230+/-5%; CyA, 259+/-3%; P=0.04). Only SRL treatment reduced ET-1 plasma levels. CyA reduced eNOS expression by 30% and increased ETA Rc expression by 34% compared with both Con and SRL (P=0.02). CyA resulted in higher 8-isoprostane levels (CyA, 50+/-2%; SRL, 3+/-3%; Con, 2+/-5%; P=0.02).

CONCLUSIONS

CyA results in vascular dysfunction characterized by impairment of Edep vasorelaxation and enhanced sensitivity to vasospasm. SRL did not impair Edep vasorelaxation or increase sensitivity to vasospasm while lowering ET-1 levels and preserving eNOS protein expression. We conclude that SRL is less deleterious to the vasculature than CyA and may prevent TxV by these mechanisms.

Endothelin-1 plasma levels and hypertension in cyclosporine-treated renal transplant patients

Experimental models suggest that endothelin-1 (ET-1) has a significant role in the pathogenesis of cyclosporin A (CyA)-induced hypertension. However, its serum levels evaluated in different studies, including patients who received solid organ transplants, exhibited controversial results. Our study population consisted of 43 renal transplant patients: 33 were taking CyA as a component of their immunosuppressive regimen (CyA group) and 10 that were not taking CyA (control group). Baseline laboratory data, blood pressure and ET-1 levels were taken at baseline and 3 and 4 h after the ingestion of CyA. In the control group samples were collected in the corresponding periods of time. Blood pressure was significantly higher in the CyA group (mean blood pressure: 101.2 +/- 9.5 vs. 91.1 +/- 10.7 mmHg; p < 0.001), who also presented higher serum creatinine (1.2 +/- 0.28 vs. 0.97 +/- 0.13 mg/dL; p < 0.001) and ET-1 levels. In the CyA group an ET-1 peak was evident by the third hour after CyA ingestion that showed its maximum concentration after 1-2 h; the control group exhibited significantly lower levels of ET-1 (p = 0.044). ET-1 levels compared between patients with and without hypertension showed a non-statistically significant difference (1.54 +/- 0.76 vs. 1.27 +/- 0.62 ng/mL; p = 0.27, respectively). In conclusion, in the present study chronic CyA ingestion was associated with higher blood pressure and plasma ET-1 levels.

A novel polymorphism of the gene encoding furin, a TGF-β1 activator, and the influence on cardiac allograft vasculopathy formation

BACKGROUND

Coronary vasculopathy (CV) is an important determinant of survival following cardiac transplantation. We have previously shown that G915C polymorphism of the Transforming Growth Factor-beta1 (TGF-beta1) gene strongly influences CV development. Furin is a proprotein convertase enzyme important in TGF-beta1 activation. We investigated for polymorphism within the promoter region of the gene for furin (fur). Allelic variation of the fur gene, in conjunction with TGF-beta1 polymorphism, was subsequently related to the development of CV.

METHODS AND RESULTS

The fur gene promoter region (position -1199 to +39) was analysed by SSCP and sequencing. A C/T single nucleotide substitution polymorphism at position -231* was identified. Using PCR the fur and TGFB1 genotypes were identified in 115 cardiac transplant recipients. CV was diagnosed at routine surveillance post-transplant coronary angiography. Fur polymorphism had no influence on vasculopathy development; median time to diagnosis, *C/C homozygotes, 2.27 years (2.10-4.32), *C/T heterozygotes 2.97 years (2.09-4.24), *T/T homozygotes 2.65 years (2.33-4.08), (P=0.95). Allelic variation did not influence Kaplan Meier actuarial analysis of disease onset (P=0.54). Ninety-three percent of recipients were high TGF-beta1 producers. We used fur polymorphism to substratify patients with the +915*G/G TGFB1 (high producing) allele. Fur polymorphism did not influence CV development within this TGF-beta1 high producer cohort, when analysed by time to first diagnosis and Kaplan Meier testing.

CONCLUSIONS

We have described a novel polymorphism at position -231* in the gene encoding furin. The fur -231* single nucleotide polymorphism in isolation, or in conjunction with TGFB1 polymorphism, is not useful as a genetic risk marker for cardiac transplant associated coronary vasculopathy.

Adipose differentiation-related protein and regulators of lipid homeostasis identified by gene expression profiling in the murine db/db diabetic kidney

We investigated the molecular basis of progressive diabetic renal injury in db/db mice by profiling kidney gene expression. Using high-density microarrays, we identified 482 RNA transcripts differentially expressed in 8-wk db/db vs. nondiabetic db/m kidneys, a time characterized by hyperglycemia but by little renal histopathology. By 16 wk significant mesangial expansion had developed. Sixteen-week db/db kidneys differentially expressed 639 RNA transcripts. Diabetic kidneys specifically expressed several genes normally found in adipocytes, including adipocyte differentiation-regulated protein (ADRP; or adipophilin in humans). ADRP mRNA was specifically upregulated 5.4-fold in 16-wk db/db kidneys. This finding was confirmed at the protein level by Western blotting, and immunohistochemistry localized ADRP diffusely to tubular epithelium throughout the cortex. ADRP is a perilipin family protein that forms lipid storage vesicles and controls triglyceride utilization; we showed that accumulation of lipid storage droplets correlated with the magnitude and localization of ADRP in db/db kidneys. Other genes involved in lipid transport, oxidation, and storage were differentially regulated in db/db kidneys, and peroxisome proliferator-activated receptor-alpha (PPAR alpha) has been shown to regulate their expression in adipocytes. In our experiments, PPAR alpha mRNA was elevated in db/db diabetic kidneys, and PPAR alpha protein was upregulated in glomeruli, cortical tubules, and renal arterial vessels of db/db mice. In conclusion, these studies furnish new RNA-based data for mechanistic investigation into renal injury in the diabetic kidney and identify a switch of kidney phenotype in favor of lipid accumulation in diabetic kidney.

Cardiac allograft vasculopathy and dysregulation of the NO synthase pathway

Cardiac allograft vasculopathy is the most aggressive form of atherosclerosis in humans and is the leading cause of death after the first year of heart transplantation. Endothelial dysfunction is a major contributing factor to the acceleration of coronary vascular disease in these individuals. A reflection of this endothelial dysfunction is the severe impairment in endothelium-dependent vasodilation that occurs early after transplantation. The etiology of this allograft endothelial alteration is multifactorial and may include preexisting atherosclerosis of the graft vessels, reperfusion injury during transplantation, denervation, disruption of the lymphatic system, and acute and chronic immune injury, as well as traditional risk factors for coronary artery disease (hyperlipidemia, diabetes, hypertension, or hyperhomocysteinemia) and pathogens, such as cytomegalovirus. The alteration in endothelial function affects vasomotor tone of the coronary arteries. Evidence indicates that there may be an impairment of endothelial production and/or activity of NO. Because NO is a potent vasodilator, its deficiency would explain the abnormal vasomotor tone in these individuals. In addition, because NO inhibits key processes in vascular inflammation and atherosclerosis, its absence may contribute to the acceleration of transplant vascular disease. Recent studies from our group and others have shed light on the mechanisms of endothelial dysfunction and its importance in cardiac allograft vasculopathy. In addition, the alteration in endothelial function contributes to vascular inflammation and progression of the disease.