Increased endothelin level after cyclosporine therapy

Cyclosporine A induces vascular fibrosis and heat shock protein expression in rat

The immunosuppressive drug Cyclosporine A (CsA) has been successfully used in several diseases with immunological basis and in transplant patients. However, the therapeutic treatment induces several side effects, which include the development of severe hypertension, renal failure and cardiotoxicity in the majority of the patients. Since the mechanism by which CsA induces hypertension is not well defined, the aim of this study is to evaluate the morphological changes and the expression of heat shock proteins (HSPs) in the thoracic aorta of CsA-treated rats. The study was carried out on 40 male Wistar rats with an average weight of 200-250 g. The animals were divided into four groups. Groups I and II were injected subcutaneously (sc) daily with castor oil for 15 or 30 days and used as control; group III and IV were injected sc daily with CsA (15 mg/Kg/day) for 15 or 30 days. After the end of the treatment, the thoracic aortae were removed and treated for morphological (Sirius Red) and immunohistochemical evaluation (HSP 25, alphaB-crystallin and HSP 47). The results indicate that CsA induces (1) time-dependent vascular damage visible as fibrosis mainly in intima-media tunica of aorta, and (2) a clear increase in HSP expression. In fact, after 30 days of treatment, HSP and alphaB-crystallin are increased in all tunicas, whereas HSP47 only in tunica media and adventitia. These findings could suggest that these proteins are up-regulated after CsA treatment in order to play a defensive role in vascular damage.

Cyclosporine A up-regulates expression of matrix metalloproteinase 2 and vascular endothelial growth factor in rat heart

Cyclosporine A (CsA) is the first immunosuppressant universally used in allotransplantation. However, it has been demonstrated that this drug produces side effects in several organs, particularly in the kidney and in the heart. Since the immunosuppressive therapy induces myocardial toxicity, the aim of this study was to evaluate in the myocardium of CsA-treated rats the expression variations of vascular endothelial growth factor (VEGF) and matrix metalloproteinase 2 (MMP2), to verify if: VEGF increased, VEGF increase was associated with MMP2 increase and they could be considered as repair proteins. The study was carried out on 28 Wistar rats divided into two groups. The group I animals served as control and so they were subcutaneously injected daily with castor oil for 21 days; group II: animals were subcutaneously injected daily with CsA (Sandimmun, Sandoz) at the therapeutic dose (15 mg/kg) for 21 days. The group I animals (control) showed normal heart architecture and low levels of MMP2 and VEGF. The group II animals (CsA-treated) showed structural degenerative changes with myocardial fibrosis and a clear increase both in MMP2 and VEGF. These data show that the immunosuppressant therapy induces a high increase in both the proteins and that VEGF variations are associated with MMP2 variations. These findings suggest that these proteins are involved in the endogenous emergency cell mechanisms induced by stress conditions, probably playing a role against myocardial injury as repair proteins.

Cyclosporine toxicity in renal transplant recipients detected by nailfold capillaroscopy with Na-fluorescein

BACKGROUND

Cyclosporine represented a major advance in the medical management of patients with organ transplantation, but its use is limited by the frequent occurrence of hypertension and renal toxicity diagnosed by invasive renal biopsy. Renal histology shows a specific arteriolopathy. It was hypothesized that cyclosporine may also induce subclinical microvascular changes in the skin that might be detected noninvasively by a combination of dynamic capillaroscopy [capillary blood cell velocity (CBV)] with and without intravenous Na-fluorescein (NaF) injection and laser Doppler fluxmetry (LDF).

METHODS

The nailfold skin microcirculation was evaluated in 112 consecutive renal transplant recipients (54 +/- 11 years old; 70 males and 42 females) receiving cyclosporine. The investigation was made the same day as a routine renal biopsy performed in all patients more than two years after transplantation. Renal biopsies were blindly classified as positive (N = 33) when significant specific signs of cyclosporine toxicity were clearly observed (AH2-AH3) and were otherwise negative (AH0-AH1, N = 79) according to the Banff classification.

RESULTS

Time to fluorescence peak after NaF injection (tpNaF) was significantly longer in patients with positive biopsies than in patients with negative biopsies (13.9 +/- 8.1 vs. 17.5 +/- 9.4 sec, P = 0.009). All patients but three with negative biopsies (93%) had a tpNaF less than 10 seconds (sensitivity 91%, negative predictive value 93%). On the other hand, CBV, LDF, plasma levels of cyclosporine, and endothelin were similar in the two groups.

CONCLUSION

Nailfold fluorescence capillaroscopy is an accurate and simple mean to rule out cyclosporine toxicity in renal transplant recipients. A normal test could avoid invasive renal biopsy in about 40% of the patients. Renal biopsy would, however, still be indicated when the test is abnormal.

Endothelin in organ transplantation

Solid organ allografts are often compromised by ischemia, acute rejection episodes associated with hemodynamic changes, and chronic rejection typically characterized by the development of obliterative vasculopathy, and in the case of the kidney, and glomerulosclerosis. Recent in vivo data indicate that endothelin (ET) production is locally upregulated in rejecting allografts, and that, in addition to endothelial cells, ET is also produced by graft-infiltrating mononuclear cells (monocytes/macrophages). In vitro data also indicate that ET production is regulated, at least in part, by certain T cell-and monocyte/macrophage-derived cytokines, which are abundant in rejecting allografts. These data and the findings of elevated plasma levels of ET after transplantation (in particular during rejection processes), the effects of immunosuppressive drugs (cyclosporine and tacrolimus in particular) on ET production, and the profound vasoconstrictive and mitogenic properties of this peptide suggest that endothelin may be involved in the initiation and propagation of posttransplantation complications; including systemic hypertension, acute allograft dysfunction, and perhaps most importantly, chronic allograft dysfunction. These observations provide the rational to use ET receptor antagonists to formally address the potential role of ET in these processes, and to develop therapeutic strategies that ameliorate or possibly prevent these complications.

ETA receptor-mediated constrictor responses to endothelin peptides in human blood vessels in vitro

1. We have characterized the constrictor endothelin receptors present in human isolated blood vessels using ETA and ETB selective agonists and antagonists. 2. Monophasic dose-response curves were obtained for ET-1 with EC50 values of 6.8 nM in coronary artery, 3.9 nM in internal mammary artery, 17.4 nM in pulmonary artery, 14.5 nM in aorta and 3.2 nM in saphenous vein. In coronary artery, ET-2 was equipotent with ET-1 with an EC50 value of 5.7 nM. The non-selective peptide, sarafotoxin 6b, was 2-3 times less potent than ET-1 but the maximum responses to these two were comparable. 3. In each vessel ET-3 was much less active than ET-1. No response was obtained to ET-3 in aorta and pulmonary artery or in up to 50% of coronary artery, mammary artery and saphenous vein preparations. In those preparations that did respond, dose-response curves were incomplete at 300 nM. Variable contractions were also obtained with the ETB-selective agonist, sarafotoxin 6c (S6c). Where responses were detected, although S6c was more potent than ET-1 (EC50 values of 0.6-1.2 nM), the maximum response produced was always less than 20% of that to ET-1. 4. The synthetic ETB agonists, BQ3020 and [1,3,11,15Ala]-ET-1, were without effect in any of the five blood vessels at concentrations up to 3 microM. 5. ET-1-induced vasoconstriction was blocked by the ETA-selective antagonists, BQ123 and FR139317. Schild-derived pA2 values were 7.0, 7.4 and 6.9 for BQ123 and 7.6, 7.9 and 7.3 for FR139317 in coronary artery, mammary artery and saphenous vein, respectively, consistent with antagonism of ETA receptors. Slopes of the Schild regressions were not significantly different from one. Comparable values of pA2 were estimated for 3ftM BQ123 in aorta (7.4+/-0.5) and pulmonary artery (6.9) from the Gaddum-Schild equation.6. In conclusion we have shown that in human isolated blood vessels, ET-1 is more potent than ET-3 suggesting the presence of vasoconstrictor ETA receptors. This is supported by the lack of effect of the ETB agonists, BQ3020 and [1,3,1,1,15Ala]-ET-l and the ability of the ETA antagonists, BQ123 andFR139317 to block ET-1 responses. Some preparations did contract in response to low concentrations of the ETB-selective sarafotoxin 6c but responses were variable and the maximum was always much less than that to ET-1 in the same preparations. Therefore although constrictor ETB receptors were present on the smooth muscle of human blood vessels, vasoconstriction elicited by the endothelin peptides in vitro is via ETA receptor activation.

[Follow-up of plasma endothelin and serum interleukin 2 receptor level after liver transplantation]

In a prospective study levels of interleukin-2 receptors (Il-2-R) in serum and of endothelin (ET) in plasma were sequentially determined in 97 patients (39 women, 58 men) before and after liver transplantation (Ltx). The aim of the study was no evaluate the correlation and the time course of these two parameters after Ltx. The postoperative levels of Il-2-R and ET were higher in transplant recipients with no postoperative complications than in patients who had undergone operations to the liver. Patients suffering from acute rejection episodes after transplantation had more markedly increased Il-2-R and ET levels than those with an uneventful course, and this persisted for 3 months. A significant rise of Il-2-R concentrations 3-6 days before a biopsy confirmed rejection proved to have a sensitivity of 68% and a specificity of 68% respectively. A corresponding ET increase preceded rejection episodes confirmed by biopsy with a sensitivity of 62% and a specificity of 67%, respectively. These laboratory data can be obtained daily: they cannot undermine the "gold standard" of liver biopsy, but they are extremely beneficial in determining the timing and indication for the liver biopsy.

Cyclosporine-induced hypertension after transplantation

OBJECTIVE

To describe the features and mechanisms of posttransplantation hypertension and suggest appropriate management of the disorder.

DESIGN

We review our own experience and reports from the literature on hypertension in cyclosporine A (CSA)-treated transplant recipients.

RESULTS

Soon after immunosuppression with CSA and corticosteroids, hypertension develops in most patients who undergo transplantation. The blood pressure increases, which are usually moderate, occur universally because of increased peripheral vascular resistance. Disturbances in circadian patterns of blood pressure lead to loss of the normal nocturnal decline, a feature that magnifies hypertensive target effects. Changes in blood pressure sometimes are severe and associated with rapidly developing target injury, including intracranial hemorrhage, left ventricular hypertrophy, and microangiopathic hemolysis. The complex mechanisms that underlie this disorder include alterations in vascular reactivity that cause widespread vasoconstriction. Vascular effects in the kidney lead to reduced glomerular filtration and impaired sodium excretion. Many of these changes affect local regulation of vascular tone, including stimulation of endothelin and suppression of vasodilating prostaglandins. Effective therapy includes use of vasodilating agents, often calcium channel blocking drugs. Caution must be exercised to avoid interfering with the disposition of CSA or aggravating adverse effects relative to kidney and electrolyte homeostasis.

CONCLUSION

Recognition and treatment of CSA-induced hypertension and vascular injury are important elements in managing the transplant recipient.

Vasoconstrictor endothelin receptors characterized in human renal artery and vein in vitro

1. We have identified the endothelin receptors present in the media of human main stem renal artery and vein and characterized the subtypes mediating vasoconstriction in these blood vessels in vitro. 2. Messenger RNA encoding both ETA and ETB receptors was identified in the smooth muscle layer of human renal artery and vein by reverse transcriptase-polymerase chain reaction assay. In cryostat-cut cross-sections of both vessels autoradiographical visualisation suggested a majority of ETA receptors. Intense binding was obtained to the non-selective ligand [125I]-ET-1 and the ETA-selective [125I]-PD151242 but only weak labelling of sites by the ETB-selective [125I]-BQ3020. 3. ET-1 potently constricted renal artery and vein preparations with EC50 values of 4.06 nM and 1.00 nM, respectively. Sarafotoxin 6b was approximately ten times less potent than ET-1 with EC50 values of 36.3 nM and 13.8 nM respectively. In the renal artery, ET-3 and sarafotoxin 6c showed little or no activity up to 300 nM. Responses to these peptides were more variable in the renal vein. Preparations from three individuals did not respond to ET-3 but in three further cases, although ET-3 was much less potent than ET-1, full dose-response curves were obtained. S6c elicited dose-related contractions in vein preparations from 5/6 individuals and although more potent than ET-1, the maximum response was 30-60% of that obtained to ET-1. 4. ET-1-induced vasoconstriction of renal artery and vein was antagonized by the ETA-selective, BQ123 (3-10 microM). The dose-response curves to ET-1 were displaced in a parallel rightward fashion with no attenuation of the maximum responses. pA2 values were estimated to be 6.8 +/- 0.1 and 6.8 +/- 0.4 for artery and vein respectively.5. These data suggest that mRNA encoding both ETA and ETB receptors is present in the media of human main stem renal artery and vein. However, autoradiographical studies indicate that the majority of ET receptors expressed are of the ETA subtype. The relative potencies of ET-1 and ET-3 as vasoconstrictors of renal blood vessels in vitro is consistent with this being an ETA-mediated response,and therefore whilst responses to S6c indicate that constrictor ETB receptors may be present in renal veins from some individuals these are likely to be of less importance in these blood vessels.

Hepatic and renal blood flow responses to a clinical dose of intravenous cyclosporine in the pig

The immunosuppressant Cyclosporine A (CsA) is considered to induce nephrotoxicity in part by causing vasoconstriction of the glomerular afferent arterioles. Although CsA is widely used in hepatic transplantation, little is known concerning its effects on hepatic blood flow. We used ultrasonic flow probes in an anesthetized swine model to measure the effects of a single 60 min infusion of a clinically comparable dose of CsA (5 mg/kg per h) on hepatic, renal, and supraceliac descending aortic blood flows (n = 7 swine). To account for any change in systemic output or systemic vascular resistance during the 60 min CsA infusion that may non-specifically affect hepatic and renal blood flows, the total hepatic (portal vein plus hepatic artery) and renal blood flows were reported relative to the supraceliac descending aortic blood flow (termed 'fractional' total hepatic and renal blood flows). The fractional total hepatic blood flow decreased significantly (p < 0.05) by 40 min of CsA infusion vs baseline, and continued to decrease throughout the infusion (baseline = 0.38 +/- 0.03 units vs 0.28 +2- 0.05 units by 60 min of CsA infusion). During the recovery period, the fractional total hepatic blood flow increased to a value which was not different from baseline (recovery = 0.38 +2- 0.03 units). Fractional right renal artery blood flow did not change significantly from baseline at any time during the CsA infusion or during the recovery period. We conclude that a single, clinically comparable dose of CsA results in a significant decrease in total hepatic blood flow, and that this decrease is greater than that seen in renal blood flow.

De novo hypertension after liver transplantation

Hypertension develops in most patients after transplantation when immunosuppression is based on cyclosporine and prednisone. The pathogenesis appears to be multifactorial but involves rapidly rising vasoconstrictor tone in renal and systemic vascular beds. Much of this tone reflects abnormal vascular function, characterized by impaired prostacyclin and EDRF effects, in conjunction with increased vasoconstriction due to endothelin and possibly other factors. Effective management of the transplant recipient depends on preventing excessive vasoconstriction, usually with calcium channel blocking agents.

Evidence in support of the spasm of resistance vessel concept of ischemic heart disease: an update in 1993

The goal of this communication is to provide more evidence for the ischemic heart disease (IHD) component of the spasm of resistance vessel (S-RV) concept of IHD and other ischemic diseases. The S-RV concept of IHD is considered to be an alternate paradigm which challenges the accepted understanding of this disorder. The theory asserts that primary S-RV directly induces symptoms in IHD, and this position is in opposition to the accepted view that symptoms are induced directly by primary occlusions of epicardial arteries by coronary artery disease, spasm, and thromboses. The theory, if valid, should be useful in reducing the impact of IHD, as it generally is accepted that the correct appreciation of basic pathophysiological mechanisms helps ensure the most appropriate prevention and treatment of disease.

The structure and specificity of endothelin receptors: their importance in physiology and medicine

In addition to involvement in vascular endothelium-smooth muscle communication, the secretion of and receptors for, endothelins are widely distributed. Two cloned receptor subtypes are G-protein-coupled to several intracellular messengers, predominantly inositol phosphates. From a knowledge of structure-activity relationships and peptide conformations, details of receptor architecture and selective agents, including nonpeptides and antagonists, have been discovered. From the nature of the actions of endothelins, receptor distributions (including CNS) and plasma levels, it is concluded that they are paracrine factors normally involved in long-term cellular regulation, but which may be important in several pathologies, many of which are stress-related.

Effects of endothelin on microcirculation of the pancreas

Endothelin, a newly described endothelial-derived peptide, has potent vasoconstrictive properties and has been speculated to play a physiological role in the regulation of blood flow in some organs. The present study was designed to evaluate the effects of endothelin-1, endothelin-2 and endothelin-3 on the pancreatic microcirculation. Pancreatic tissue blood flow was measured by a laser Doppler flow meter in anesthetized dogs and endothelin-1, endothelin-2 or endothelin-3 was injected intravenously in graduated doses. Endothelins induced dose-dependent decreases in pancreatic tissue blood flow. Endothelin-1, endothelin-2 and endothelin-3 at a dose of 100 pmol/kg reduced pancreatic blood flow by 45.4%, 19.6% and 51.9%, respectively, whereas systemic arterial blood pressure was not significantly affected. When endothelin-3 was administered at a dose of 1000 pmol/kg, pancreatic blood flow was decreased by 73.5% with a concomitant increase of systemic arterial blood pressure by 17.6%. Endothelins potently decreased pancreatic tissue blood flow, suggesting a possible role of these agents in regulating the pancreatic microcirculation.

Increased endothelin excretion in rats with renal failure induced by partial nephrectomy

1. Six weeks following partial nephrectomy in rats, significant increases in serum urea nitrogen and serum creatinine concentration and a significant decrease in creatinine clearance were observed. 2. Measurement of systolic blood pressure by tail plethysmography indicated that animals that had undergone partial nephrectomy were hypertensive. 3. Compared to sham-operated animals, there were 4 fold increases in both urinary protein excretion and urinary endothelin excretion. 4. There was a significant correlation between urinary protein and urinary endothelin excretion (r = 0.77). There was also a correlation (r = 0.65) between urinary endothelin excretion and systolic blood pressure. 5. Plasma endothelin concentrations were not different in sham-operated and partially nephrectomized rats. 6. The data indicate that there is an increased renal endothelin production in rats with chronic renal failure.