The Role of Big Endothelin-1 in Colorectal Cancer

Introduction

Changes in liver blood flow caused by an unknown splanchnic vasoconstrictor have been noted in colorectal cancer patients with liver metastases. This prospective study was performed to assess whether plasma levels of big endothelin-1 (big ET-1) were raised in patients with colorectal cancer.

Methods

Plasma samples from peripheral vein of patients who underwent surgery for primary colorectal cancer (n=60) and those with known colorectal liver metastases (n=45) for a period of 15 months were taken prior to treatment and compared to age- and sex-matched controls (n=20). Plasma samples were analysed by using a single-step sandwich enzyme immunoassay. Immunohistochemistry and in situ hybridisation were also performed on tumour sections to investigate the expression of ET-1 by cancer cells.

Results

The median (range) plasma concentration of big ET-1 in controls was 2.1 pg/mL (1.2–13.4 pg/mL). The median (range) plasma concentration of big ET-1 in colorectal cancer patients with no overt hepatic metastases was 3.8 pg/mL (1.2–15.8 pg/mL), p=0.002, and the median (range) plasma concentration of big ET-1 in colorectal cancer patients with hepatic metastases was 5.2 pg/mL (1.7–30 pg/mL), p=0.0001; both were significantly elevated compared to the control group. A significant difference in immunostaining for big ET-1 was noted between paired normal colonic mucosa (median score-1) and tumour sections (median score-3), p=0.01.

Conclusion

This study has demonstrated elevated concentrations of big ET-1 in colorectal cancer patients, especially in those with hepatic metastases. Upregulation of ET activity in colorectal cancer could be inferred by the increased immunostaining of big ET-1 in cancer cells. Therefore, plasma big ET-1 levels should be evaluated as a potential tumour marker for the identification of hepatic metastases at an earlier stage.

[Endothelins and dopamine levels in tears for assessment of neurovascular disorders in glaucoma]

PURPOSE

To estimate the possibility of detection of neurovascular ocular disorders in glaucoma by assessing the content of catecholamines and endothelins in lacrimal fluid.

MATERIAL AND METHODS

The study included 47 patients with primary open-angle glaucoma (POAG). Tear eluate was analyzed by high performance liquid chromatography (HPLC) for catecholamines concentrations, and enzyme-linked immunoassay (ELISA) was used for evaluation of endothelins content.

RESULTS

Endothelin-1 (ET-1) and big endothelin (bET) content in tears of patients with POAG was higher than in healthy controls. Concentration of dopamine (DA) in tears was lower and concentrations of L-dioxyphenylalanine and dihydroxyphenylacetic acid had a tendency for decrease. Noradrenaline content was equal in patients with POAG and controls. Adrenaline was not detected in any tear samples.

CONCLUSION

Multidirectional changes of endothelins and DA levels in tears of patients with POAG was found. The increased concentration of ET-1 and its precursor bET promote vasoconstriction and decrease of aqueous humor outflow. The decrease of DA concentration is typical for neurodegenerative processes. Estimation of DA and endothelins concentrations in tears can enable early detection of neurovascular disorders in glaucoma patients and help evaluate their severity.

Up-regulation of the Endothelin Receptor A in Placental Tissue From First Trimester Delayed Miscarriages

OBJECTIVE

This study tested the hypothesis that the endothelin (ET)/ET receptor (ETR) system in biologic fluids and in the human placenta is altered in delayed miscarriages as compared to apparently normal early pregnancies (reference group).

METHODS

Immunoreactive ET (irET) concentrations were measured in plasma, urine, and cervical smears from 57 pregnant women in the weeks 6 to 14 of gestation (46 delayed miscarriages, 11 references) with radioimmunoassay (RIA). ET-1, ETR-A, and ETR-B mRNA, and ETR protein expression were measured in placental tissue of 45 early pregnancies (31 delayed miscarriages, 14 references) using semiquantitative reverse-transcription polymerase chain reaction (RT-PCR) and immunoblotting, respectively.

RESULTS

irET levels in plasma, urine, and cervical smears did not differ between groups. Two prevailing ETR-A and ETR-B proteins were found at 45 and 55 kd, and were distributed similarly in delayed miscarriages and references. ETR-A protein and mRNA levels were 54% (P = .009) and threefold (P = .021) higher, respectively, in delayed miscarriages versus references. There was no difference in placental ETR-B and ET-1 mRNA levels between groups.

CONCLUSION

Neither irET nor ET-1 mRNA levels differ between delayed miscarriages and normal early pregnancies. Pregnancies at risk for miscarriage cannot be identified by measurement of ET in plasma, urine, or cervical smears. Within the ET/ETR system, ETR-A is selectively up-regulated in placental tissue of delayed miscarriages as compared to normal pregnancies. ETR protein processing is similar in both groups.

Estrogen and progesterone regulate expression of the endothelins in the rhesus macaque endometrium

BACKGROUND

Endothelins (EDNs) are thought to modulate endometrial blood flow during menses, stromal healing and endometrial growth during the proliferative phase. Our goal was to assess the effects of estrogen and progesterone on the EDN paracrine system in the endometrium of rhesus macaques.

METHODS

In this study, archived samples were used. These samples were collected from oophorectomized rhesus macaques that were treated sequentially with estradiol (E(2)) and then E(2) plus progesterone to create artificial menstrual cycles. Endometrium from animals in the menstrual, proliferative and secretory phases of the artificial cycle were analyzed by real-time PCR, in situ hybridization and immunocytochemistry to detect changes in EDN peptides (EDN1, EDN2, EDN3), EDN receptors (EDNRA, EDNRB), EDN-converting enzyme 1 (ECE1) and membrane metalloendopeptidase (MME)-an enzyme that degrades the EDNs.

RESULTS

Compared with the late secretory phase, progesterone withdrawal at the end of the artificial menstrual cycle triggered an increase (P< 0.05) in EDN1, EDNRB and ECE1 in the upper functionalis zone during menses of the next cycle. Treatment with E(2) alone in the proliferative phase increased (P< 0.05) EDNRA transcript, which was confined predominantly to the stromal cells. E(2) plus progesterone in the artificial secretory phase suppressed (P< 0.05) the expression of EDN3 in the functionalis zone stroma and epithelia, tended (P= 0.08) to attenuate levels of epithelial EDN2 and markedly up-regulated (P< 0.05) the stromal expression of MME.

CONCLUSIONS

Our results indicate that estrogen and progesterone regulate the EDN family during the menstrual cycle. The changes in the EDN paracrine system during the mid-secretory phase may indicate a role for EDN during embryo implantation.

Human follicular fluid levels of endothelins in relation to oocyte maturity status

The levels of endothelins 1 and 2 (ET-1 and ET-2) have been examined in 415 follicular fluids of 57 women participating in the IVF-ET programme in the University Women's Hospital, Marburg, in relation to the morphological appearance ("maturity") and fertilizability of harvested oocytes as well as to the levels of inhibin, FSH, IGF-1, estradiol and progesterone. Follicular aspiration was done transvaginally in all patients after down regulation with nafareline and ovarian stimulation using urofollitropin and menotropin. Ovulation was induced by hCG. ETs were measured by RIA using commercial kits supplied by Peninsula Laboratories, Belmont, CA. For FF samples, ET-1 and ET-2 RIAs were revalidated. Immunoreactive ET-1 was detectable in all follicular samples, the average level being 18.5 +/- 11.8 pg/ml, ET-2 was present only in 67.5% of the samples, the average level being 13.6 +/- 16.3 pg/ml. There was no significant difference in the average levels of ET-1 in the fluids of small, medium and large follicles. However, there was a significantly higher level of ET-2 in the fluids of medium compared to large follicles and there was a negative correlation of the ET-2 levels to the volume of the follicle (p < 0.01) which suggests that ET-2 could play a role during the maturation of the ovarian follicles. Unlike ET-1, the mean concentrations of ET-2 were significantly higher in the fluids with oocytes which could be fertilized and cleaved than in those with oocytes which did not fertilize or cleave, thus indicating a role for ET-2 in the process of oocyte maturation. No correlations of ET levels were found with the levels of inhibin, FSH, estradiol and progesterone. However, ET-2 levels significantly correlated with the levels of IGF-1 (p < 0.001) indicating a possible synergistic effect of endothelins and IGF-system. In conclusion, this study is further evidence for a physiological role of the ETs in the human ovary.

Angiotensin II and Endothelin in the Renal Cortex During the Evolution of Glycerol-Induced Acute Tubular Necrosis

Hypertonic glycerol injection is one of the most frequently used models of experimental acute renal failure. Late structural changes such as interstitial fibrosis in the renal cortex and tubular atrophy have been detected after severe acute tubular necrosis (ATN). The aim of this study was to investigate the expression of angiotensin II (AII) and endothelin during the evolution of the ATN induced by glycerol and their relationships with the late structural changes observed in the kidneys. Forty-nine male Wistar rats were injected with a 50% glycerol solution, 8 mL/kg, divided into equal amounts, each administered into one hind leg, and 18 with 0.15 M NaCl solution. Blood and urine samples were collected 1, 5, 30, and 60 days after the injections to quantify sodium and creatinine; the animals were killed and the kidneys removed for histologic and immunohistochemical studies. The results of the immunohistochemical studies were scored according to the extent of staining in the cortical tubulointerstitium. Glycerol-injected rats presented a transitory increase in plasma creatinine levels and in fractional sodium excretion. The immunohistochemical studies showed increased AII and endothelin staining in the renal cortex from rats killed 5 days after glycerol injection (p<0.001) compared with control that persisted until day 60. The animals killed on days 30 and 60 also presented chronic lesions (fibrosis, tubular dilatation, and atrophy) in the renal cortex, despite the recovery of renal function. AII and endothelin may have contributed to the development of renal fibrosis in these rats.

[Effects of tetramethylpyrazine on endothelin and nitric oxide contents in plasma and cerebrospinal fluid after subarachnoid hemorrhage]

OBJECTIVE

To observe the variation of endothelin (ET) and nitric oxide (NO) in plasma and cerebrospinal fluid (CSF) in rabbits, and evaluate the effects of tetramethylpyrazine (TMP) on the prevention and cure of cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH).

METHODS

24 New Zealand rabbits were randomly assigned into three groups: contrast group, experiment group and blank group. Every group contained 8 rabbits. SAH was established according to inject blood into the cisterna magna. The experiment group was administrated with TMP (20 mg/kg x d) transperitoneally. ET and NO of plasma and CSF were detected by radical immunoassay at 72 h and 168 h after SAH. Neurofunction were detected in every group at all the time scales.

RESULTS

(1) After SAH, the level of ET in CSF increased significantly in contrast group compared with that in experiment and blank groups (P<0.05). The value of ET at 168 h was higher than that at 72 h. The level of ET in plasma increased significantly in contrast group compared with blank and experiment groups (P<0.05), and no significant contrast could be found between blank and experiment group. (2) After SAH, the value of NO in CSF was lower in contrast group than in other groups (P<0.05), and the level of NO in CSF continued to decrease in all groups on some extent. As time went by, no significant contrast could be found in all groups. The value of NO in plasma was lower in contrast group than in other groups (P<0.05). There was no significant difference between experiment and blank groups. (3) The neuro-function score continued to be increased in contrast group, but decreased in experiment one. The neuro-function score was lower in experiment group than in contrast one at every time point (P<0.05).

CONCLUSION

After administration of TMP, the variation of ET has the continued decrease in plasma and CSF; the variation of NO shows the continued increase in plasma and CSF; neurological function gets possibly protected. TMP may prevent from and cure CVS after SAH.

Pathogenesis of salt sensitivity of blood pressure

The effect of sodium in human blood pressure has been a contentious subject of considerable debate for decades. Nonetheless, it is generally conceded that there is heterogeneity to alterations in sodium and extracellular fluid volume in the blood pressure responses of normal and hypertensive humans. Although there are many forms of experimental and clinical hypertension that are clearly related to abnormalities of sodium handling and metabolism, it has been only the advent of the genetic revolution that has provided critical new insight into the mechanisms involved in many of these conditions. In this review, the clinical manifestations of salt sensitivity and several clinical syndromes associated with abnormal sodium metabolism are discussed, and factors that appear to be involved in many of the clinical abnormalities as well as relevant new insights derived from basic research are elucidated.

Endothelin and endothelin receptor antagonism in portopulmonary hypertension

Portopulmonary hypertension (PPHT) is a rare but devastating complication in patients with portal hypertension, characterized by pulmonary arterial obliterative disease with a concomitant rise in pulmonary vascular resistance. A broad body of evidence has accumulated, indicating that endothelin (ET) peptides and their cognate receptors are causally involved in the pathophysiology of pulmonary arterial hypertension (PAH) owing to different aetiologies, including PPHT. In addition, the ET system may be involved in hepatic fibrotic remodelling and portal hypertension. Several experimental models have provided evidence that ET receptor antagonism may have therapeutic potential in PPHT. Initial experience has accumulated during the last 2 years, suggesting that targeting the ET system may have beneficial effects in the clinical setting. In these studies, the orally active, dual ET receptor antagonist bosentan improved pulmonary haemodynamics and functional capacity. These effects were sustained and occurred in the absence of adverse events. If these observations can be corroborated by controlled clinical trials, bosentan would offer several advantages over available therapies, which have major drawbacks owing to their invasive and demanding mode of application.

Effects of chronic cold exposure on the endothelin system

Cold temperatures have adverse effects on the human cardiovascular system. Endothelin (ET)-1 is a potent vasoconstrictor. We hypothesized that cold exposure increases ET-1 production and upregulates ET type A (ETA) receptors. The aim of this study was to determine the effect of cold exposure on regulation of the ET system. Four groups of rats (6–7 rats/group) were used: three groups were exposed to moderate cold (6.7 ± 2°C) for 1, 3, and 5 wk, respectively, and the remaining group was maintained at room temperature (25°C) and served as control. Cold exposure significantly increased ET-1 levels in the heart, mesenteric arteries, renal cortex, and renal medulla. Cold exposure increased ETA receptor protein expression in the heart and renal cortex. ET type B (ETB) receptor expression, however, was decreased significantly in the heart and renal medulla of cold-exposed rats. Cold exposure significantly increased the ratio of ETA to ETB receptors in the heart. An additional four groups of rats (3 rats/group) were used to localize changes in ETA and ETB receptors at 1, 3, and 5 wk of cold exposure. Immunohistochemical analysis showed an increase in ETA, but a decrease in ETB, receptor immunoreactivity in cardiomyocytes of cold-exposed rats. Increased ETA receptor immunoreactivity was also found in vascular smooth muscle cells of cold-exposed rats. Cold exposure increased ETA receptor immunoreactivity in tubule epithelial cells in the renal cortex but decreased ETB receptor immunoreactivity in tubule epithelial cells in the renal medulla. Therefore, cold exposure increased ET-1 production, upregulated ETA receptors, and downregulated ETB receptors.

Comprehensive immunohistological analysis of the endothelin system in human kidney grafts

BACKGROUND

In experimental models of renal transplantation, upregulation of the endothelin (ET) system and amelioration of renal injury by ET-receptor blockers have been documented. In contrast, little information is available on the expression of the ET system in human kidney allografts. It was the purpose of the present study to analyse by immunohistology the expression of ET-1 as well as of the two ET receptors (ET-RA and ET-RB) in the different cells and compartments of kidney grafts and control kidneys.

METHODS

Fifty-five graft biopsies were taken from 55 kidney allograft recipients (mean age: 32+/-2.8 years) who were all on a calcineurin inhibitor. The indication for biopsies was delayed graft function or suspected rejection. The underlying diagnoses were acute allograft rejection (n = 14), chronic allograft nephropathy (n = 14), cyclosporin A (CSA) toxicity (n = 10), post-operative acute tubular necrosis (ATN) (n = 11) and recurrent primary disease (n = 6). As control, tissues of non-grafted kidneys with ATN (mean age: 35+/-24 years), of primary glomerulonephritis (mean age: 69+/-10 years) and of non-tumour-bearing parts of eight tumour nephrectomy specimens (mean age: 67+/-5 years) were assessed. The biopsies were scored using the 1997 Banff criteria. Expression of ET-1, ET-RA and ET-RB as well as of vascular endothelial growth factor was evaluated by immunohistochemistry and a semi-quantitative scoring system. Interstitial infiltrating cells were characterized using antibodies against T cells, B cells and macrophages (CD3, CD20 and CD68).

RESULTS

Control cases showed only faint expression of ET-1 in glomeruli (in podocytes and endothelial cells), whereas marked expression was seen in distal, but less in proximal tubular cells. The interstitium was completely negative. ET-1 expression was seen in vascular endothelial cells (VEC) and vascular smooth muscle cells (VSMC). Only faint expression of ET-RA and ET-RB was found in glomeruli and tubuli (distal more than proximal). Marked ET-RA and ET-RB expression was seen in VEC and VSMC. In all transplanted kidneys, irrespective of the underlying diagnosis, expression of ET-1, ET-RA and ET-RB was markedly higher compared with control kidneys. ET-1 was strikingly upregulated in glomeruli and tubuli, but surprisingly not in the vasculature of grafts with CSA toxicity. Expression of ET-RB was markedly increased in CSA toxicity in glomeruli, tubuli and vessels. In grafts with ATN and acute rejection, pronounced expression of ET-RA was noted. There was a strong correlation between proteinuria and expression of ET-1 in glomeruli and proximal tubuli and of ET-RB in proximal tubuli.

CONCLUSIONS

The above data in human kidney allograft biopsies are consistent with an important role of the ET system in different types of renal allograft damage. This finding extends and clarifies the somewhat contradictory results in animal models.

Amniotic fluid endothelin levels and the incidence of premature rupture of membranes

Objective. The purpose of this prospective study was to record Endothelin 1 (ET1) concentrations in the second trimester amniotic fluid and in women who develop premature rupture of membranes (PROM), preterm premature rupture of the membranes (PPROM) and in women with uneventful pregnancies. Method. Amniotic fluid was retrieved by amniocentesis from 125 women in the second trimester of pregnancy. The levels of Endothelin were measured by a sensitive and specific radioimmunoassay. Results. From the 125 women included in the study 20 developed PROM and preterm PROM (13 PPROM and 7 PROM). The ET1 concentration was significantly higher (P<0.001) in PROM and PPROM than in normal pregnancy (96.4 vs. 43 pg/ml). The sub-analysis of the two rupture of membranes groups found that the concentration of ET1 was higher in the PPROM than in PROM (118 vs. 72 pg/ml). Conclusion. The amniotic fluid concentration of ET1 is elevated by the second trimester in women who later develop preterm PROM or term PROM.

Association of Endothelin with Lung Hemorrhage Induced by Immune Complexes in Rats

The participation of endothelins (ETs) in a model of neutrophil-dependent lung injury induced by intrabronchial instillation of rabbit antibodies to ovalbumin followed by i.v. injection of the antigens (Arthus reaction) was investigated. Hemorrhagic lesions were evaluated by measuring the extravasations of hemoglobin in lung parenchyma. From 5 min to 24 h after the Arthus reaction (AR), endothelin (ir-ET) levels in bronchoalveolar lavage fluid (BALF) and in plasma were measured by radioimmunoassay. BALF levels of ir-ET were not different between control and AR animals for the first 90 min after the antigen challenge but increased from 2 to 24 h after induction of AR. ET levels in the plasma did not change from the respective controls over the same 24 h period. Increased ir-ET in BALF was not affected by pretreatment with L-NAME (30 mg/kg, i.v.). A PAF antagonist (BN52021; 5 and 10 mg/kg, i.v.) increased ET content in BALF and decreased the intensity of the AR. Thiorphan (2 mg/kg, i.v.) inhibited the AR-induced hemorrhagic lesions in lungs. An ET(A) receptor antagonist, BQ-123 (1 mg/kg, i.v.) potentiated, whereas the ET(B) antagonist, BQ-788 (1 mg/kg, i.v.) inhibited the lung hemorrhage. It is concluded that ETs are released during and play a role in the lung AR.

Ischemia-reperfusion injury of the intestine and protective strategies against injury

Ischemia-reperfusion injury of the intestine is a significant problem in abdominal aortic aneurysm surgery, small bowel transplantation, cardiopulmonary bypass, strangulated hernias, and neonatal necrotizing enterocolitis. It can also occur as a consequence of collapse of systemic circulation, as in hypovolemic and septic shock. It is associated with a high morbidity and mortality. This article is a comprehensive review of the current status of the molecular biology and the strategies to prevent ischemia-reperfusion injury of the intestine. Various treatment modalities have successfully been applied to attenuate reperfusion injury in animal models of reperfusion injury of the intestine. Ischemic preconditioning has been found to be the most promising strategy against reperfusion injury during the last few years, appearing to increase the tolerance of the intestine to reperfusion injury. Although ischemic preconditioning has been shown to be beneficial in the human heart and the liver, prospective controlled studies in humans involving ischemic preconditioning of the intestine are lacking. Research focused on the application of novel drugs that can mimic the effects of ischemic preconditioning to manipulate the cellular events during reperfusion injury of the intestine is required.

Isoform-specific quantification of endothelins in HUVEC culture supernatants by on-line high-performance liquid chromatography/electrospray mass spectrometry

A method for the quantitative analysis of endothelin peptides in human umbilical vein endothelial cell (HUVEC) culture supernatants is reported. The analysis is isoform-specific and employs solid-phase extraction and subsequent HPLC fractionation followed by HPLC-ESIMS analysis. The peptide vasoactive-intestinal-contractor (VIC) was used as internal standard for the HPLC-ESIMS analysis. Linearity of calibration curves was from 50 fmol to 25 pmol. The limit of detection of the HPLC-ESIMS step using a buffer matrix was estimated at 50 fmol (S/N > 3). The overall limit of detection for supernatants of HUVEC was 500 fmol/mL. In HUVEC culture supernatants only ions of endothelin-1 (ET1) were observed. Basal levels were determined to be 1.8 +/- 0.3 pmol/mL. Quantitative results obtained for ET1 were in agreement with those obtained by using a standard addition method and by an ELISA method.

Expression of endothelial protein C receptor and thrombomodulin in the intestinal tissue of patients with inflammatory bowel disease

OBJECTIVE

Inflammatory bowel diseases are characterized by disorders of immunity, thrombosis of large vessels, and microthrombosis of mucosal vessels. The expression of endothelial protein C receptor (EPCR) and thrombomodulin-two receptors of the protein C pathway involved in thrombin scavenging and inflammation-was studied in intestinal resection specimens or mucosal biopsies from patients with inflammatory bowel disease and from controls. The soluble forms of the receptors in plasma were measured.

DATA SOURCE

This study involved patients from two large university hospitals. After surgery or biopsy, tissue samples were either frozen or fixed in formalin and embedded in paraffin. Sections for immunohistochemistry examination were cut and tested with the specific antibodies to EPCR and thrombomodulin. RNA was extracted from frozen tissue for amplification via reverse-transcriptase polymerase chain reaction. Normal intestinal and diverticulitis tissue was used as a control. Resection samples from 36 patients with ulcerative colitis, 38 with Crohn's disease, 38 with colonic cancer, and 32 with diverticulitis were studied by immunohistochemistry, and frozen sections from the same patients were studied by immunofluorescence. Twelve biopsy specimens of adjacent intestinal areas from six patients with inflammatory bowel disease were included in the study for reverse-transcriptase polymerase chain reaction. Soluble receptors were measured in the plasma of 52 inflammatory bowel disease patients and 52 controls.

DATA SUMMARY

EPCR and thrombomodulin were expressed on the mucosal endothelium of controls, and the intensity of the signal decreased in inflammatory bowel disease patients. EPCR was expressed by dendritic-like cells in controls, which also stained positive for CD21. The EPCR/CD21 dendritic-like cells were not as commonly observed in sections from ulcerative colitis patients as they were in sections from control patients (12.0 +/- 3.6 cells per high-power field vs. 23.8 +/- 10.4 cells per high-power field, p =.03), and this decrease was less evident in sections from Crohn's disease patients. Levels of messenger RNA for EPCR paralleled protein expression. Soluble thrombomodulin and EPCR levels were both higher in patients than in controls: 41.5 vs. 26.0 ng/mL (p <.0001) and 141 vs. 130 ng/mL (p <.05), respectively.

CONCLUSIONS

EPCR expression on dendritic-like cells that bear the key complement receptor CD21 suggests a role for EPCR in innate immunity. The reduced expression of thrombomodulin and EPCR in the mucosal vessels in inflammatory bowel disease impairs protein C activation, favoring microthrombosis.

Interstitial alterations in renal cortex in acute tubular necrosis (ATN) post-renal transplantation and in patients with ATN not related to renal transplant

BACKGROUND

Abnormalities of renal function with long-term implications can persist after acute tubular necrosis (ATN), probably because of permanent loss of nephrons. Residual areas of fibrosis are also observed in the renal cortex post-ATN. In this study, we investigate the interstitial alterations post-ATN using histological and immunohistochemical methods.

METHODS

We studied 11 patients with ATN of different etiologies and 19 patients with ATN post-renal transplantation. Eleven patients with ATN post-renal transplantation and one with ATN not related to renal transplantation were submitted to more than one biopsy because of delayed renal function recovery. The immunohistochemical studies were performed using alpha-smooth muscle-actin (alpha-SM-actin), endothelin, nuclear factor-kappaB (NF-kappaB), Jun-N-terminal kinase (p-JNK) and fibronectin antibodies. We also analyzed the urinary content of transforming growth factor-beta (TGF-beta) during the acute phase of ATN.

RESULTS

The immunohistochemical studies showed increased alpha-SM-actin, fibronectin, endothelin, p-JNK and NF-kappaB staining in the tubulointerstitium area from the renal cortex of all patients when compared with controls (p < 0.001), and these increase persisted in the patients submitted to sequential biopsies. One of the patients with ATN without renal transplant and six patients with ATN post-renal transplant developed chronic renal failure. There was a significant increase of TGF-beta excretion in the urine of patients with acute renal failure (p < 0.01) compared with control.

CONCLUSIONS

Our data show that the enhancement of renal TGF-beta production and the persistent increase of myofibroblasts, fibronectin, endothelin, p-JNK and NF-kappaB in renal cortex tubulointerstitium post-ATN may explain the impaired recovery of renal function observed in patients post-ATN frequently observed in patients with ATN post-renal transplant.

Protective effects of the angiotensin II type I (ATI) receptor blockade in low-renin deoxycorticosterone acetate (DOCA)-treated spontaneously hypertensive rats

The present study evaluates the participation of oxidative stress, tissue angiotensin II (Ang II) and endothelin (ET) in the effects of losartan on blood pressure (BP), ventricular hypertrophy and renal injury in spontaneously hypertensive rats (SHRs), and explores how these effects are modified when spontaneous hypertension is transformed in a low-renin model by the administration of deoxycorticosterone acetate (DOCA). The following groups were used: SHR-control, SHR+DOCA, SHR+losartan and SHR+DOCA+losartan. Tail systolic BP was measured once a week. After 9 weeks of treatment, direct BP and metabolic, morphological, biochemical and renal variables were measured. DOCA administration to SHRs produced an increase in BP, ventricular hypertrophy, renal weight, proteinuria, renal histopathological lesions, urinary excretion of isoprostane F2α and ET levels in the renal cortex. Losartan reduced BP, plasma malondialdehyde levels, urinary excretion of isoprostane F2α, renal Ang II and renal and urinary levels of ET in the SHR and DOCA-treated SHR groups. Losartan increased plasma nitrite/nitrate in SHRs, but not in low-renin DOCA-treated SHRs. Losartan reduced ventricular hypertrophy and ventricular Ang II in SHRs, but not in DOCA-treated SHRs. Losartan significantly decreased proteinuria and renal injury in DOCA-treated SHRs. We conclude that (i) the DOCA-induced aggravation of hypertension, ventricular hypertrophy and renal injury in SHRs is accompanied by augmented oxidative stress and increased levels of ET in the renal cortex, which could contribute to their development; and (ii) losartan reduced oxidative stress and renal Ang II and ET in SHRs and DOCA-treated SHRs, which might contribute to its antihypertensive and renoprotective effects, regardless of renin status.

Endogenous endothelin increases gallbladder tone and leads to acute cholecystitis in the Australian possum

Endothelins are bioactive peptides produced by gallbladder epithelial cells. We aimed to determine the role of endothelins in acute cholecystitis. Escherichia coli lipopolysaccharide vs saline (sham) was instilled into the gallbladder lumen of Australian possums. Some animals received the non-selective endothelin antagonist, tezosentan. At 4 or 24 h, plasma and gallbladder endothelins and white blood cell count (WBCC) were determined. Acute cholecystitis was assessed using a histopathology score. In other animals gallbladder tone was determined. At 4h, a dose-dependent 60-fold increase in gallbladder endothelin level occurred (P = 0.001) but other parameters remained comparable with sham animals. Epithelial cells were endothelin-immunoreactive. At 24 h, the WBCC rose (P < 0.007), and severe cholecystitis developed. Gallbladder but not plasma endothelin levels remained elevated. Tezosentan pre-treatment resulted in a histologically normal gallbladder, but the WBCC and gallbladder endothelin levels were elevated. Lipopolysaccharide or saline instillation also caused a time-dependent increase in gallbladder tone over 4 h (P < 0.001), but not in control animals. This increase was reduced by tezosentan treatment. Gallbladder endothelin production is an early event in acute cholecystitis, increases gallbladder tone and plays a crucial role in the inflammatory process.

Physiologic determinants of endothelin concentrations in human saliva

BACKGROUND

Salivary endothelin (ET) concentrations have been shown to correlate with disease severity in patients with chronic heart failure (CHF). We undertook the present study to evaluate the stability of salivary ET under different handling conditions to assess its suitability as a biochemical marker in screening, diagnosis, and management of CHF.

METHODS

Saliva samples were collected from healthy individuals and/or CHF patients, subjected to different handling conditions, and then stored at -80 degrees C until assayed by an ELISA for ET.

RESULTS

Salivary ET concentrations showed a time-dependent increase during storage at room temperature. After 72 h of incubation at room temperature, ET increased approximately 2.8-fold (P = 0.03). Simultaneously, salivary big ET showed a time-dependent 11.2-fold decrease (P <0.0001). This activity was blocked by an ET-converting enzyme (ECE) inhibitor, suggesting that these changes were attributable to ECE-dependent cleavage of endogenous big ET in saliva. Ex vivo conversion was also observed when samples were stored at 4 degrees C, but the magnitude of these changes was markedly smaller (P <0.0001). Posture also affected salivary ET concentrations in CHF patients. With a change from supine to seated rest, salivary ET concentrations increased 1.5- and 1.8-fold after 20 and 40 min, respectively (P = 0.01). With a return to supine rest, salivary ET concentrations returned to baseline concentrations (P = 0.008).

CONCLUSIONS

These data suggest that saliva sampling and handling conditions could markedly affect measurement of salivary ET. In particular, care should be taken to minimize ECE-dependent enzymatic conversion of endogenous big ET in saliva.

Expression of endothelins and their receptors in cells from human periodontal tissues

OBJECTIVE

The present study investigated the presence of ET-1 in gingival crevicular fluid (GCF) from patients with periodontitis, and the expression of endothelins (ETs) and their receptors mRNA in cultured cells from human periodontal tissues.

BACKGROUND

ET was originally discovered as a potent vasoconstrictive peptide from endothelial cells. It has been reported that ETs are produced by various cells besides endothelial cells. ETs are related to inflammatory and sclerotic lesions, such as arteriolosclerosis and hepatic cirrhosis. Therefore, ETs may be involved in periodontal disease. However, the roles of ETs in development and progression of periodontal disease are not clear.

METHODS

ET-1 released from the cultured cells was measured by enzyme-linked immunosorbent assay. mRNA expressions for ETs and their receptors were examined by reverse transcription-polymerase chain reaction and Northern blotting analysis.

RESULTS

ET-1 levels in GCF from patients with periodontitis were higher than those from healthy subjects. Human gingival keratinocytes (HGK) expressed mRNA for ETs and their receptors, ET-Ar and ET-Br. ET-1 mRNA expression and ET-1 peptide production from HGK were enhanced by interleukin-1beta and tumor necrosis factor-alpha.

CONCLUSIONS

These results suggest that ET-1 plays a significant role in periodontal disease.

Effects of tibolone on human breast cancer cells and human vascular coronary cells

Tibolone is a synthetic progestin with estrogenic and progestogenic properties, used to alleviate menopausal syndromes and for osteoporosis prophylaxis in postmenopausal women. However, only little data are available on tibolone and breast cancer risk and on the effects of tibolone on the cardiovascular system. Therefore, in the present in vitro study, we investigated the effect of tibolone on the growth of the human breast cancer cell line, MCF-7, and on the direct effects of tibolone on the vasculature, i.e. human female coronary endothelial and smooth muscle cells. In the breast cancer cell experiments, tibolone was examined alone and in the presence of 0.1 nM estradiol in the concentration range from 0.001 microM to 1 microM. Tibolone lead to significant cell growth in the concentration range of 0.01 micro M to 1 microM and was not able to inhibit estradiol-induced proliferation at the concentrations of 0.01 microM and 0.1 microM. In the vascular endothelial cell culture experiments, tibolone was tested at the concentrations 0.1 microM, 1 microM and 10 microM. Tibolone reduced the synthesis of endothelin as well as the concentrations of E-selectin, PAI-1 and pro-MMP-1. The magnitude of the effects on these markers varied and was in the range of 11%-42%. Concerning smooth muscle cells, tibolone elicited no changes in the proliferation compared to control values. These data suggest that tibolone does have tumour cell-growth promoting effects in vitro. However, tibolone can positively influence the synthesis of markers in cell cultures of human female coronary artery, which modulate vascular tone and which play a decisive role in the various stages of atherosclerosis. Drawing a clinical consequence from our experiments would result in not recommending the use of tibolone in postmenopausal women at high risk for breast cancer development until long-term controlled clinical studies have been performed on the effect of tibolone administration and breast cancer risk. Experimental studies, such as the present one, are useful to explore mechanisms, but clearly cannot replace clinical studies.

Evolution of hypoxemia in patients with severe cirrhosis

BACKGROUND AND AIM

Hypoxemia is common in patients with cirrhosis but the natural history of this syndrome is unknown. The aim of this study was to follow a series of patients with cirrhosis and to compare patients with and without hypoxemia to determine their risk of complications and survival rate.

METHODS

Fifty-eight consecutive Child-Pugh C patients with cirrhosis were included and followed up for 1-18 months. Blood gas measurements and plasma endothelin levels were measured in all patients. Blood gas measurements were repeated in 34 patients.

RESULTS

Hypoxemia was present in 35 patients (60%) (alveolar-arterial oxygen (AaO2) gradient > 20 mmHg) but none had pulmonary symptoms. There was no significant difference in liver tests and plasma endothelin levels between hypoxemic and non-hypoxemic patients. The occurrence of variceal bleeding and survival rate was not significantly different between the two groups. The AaO2 gradient worsened in nine patients and normalized in six of the hypoxemic patients. The AaO2 gradient increased to more than 20 mmHg in seven non-hypoxemic patients. There was no relationship between AaO2 gradient changes and Child-Pugh score grade changes.

CONCLUSION

Asymptomatic hypoxemia is common in patients with severe cirrhosis but it is not a predictive factor of short-term complications or mortality. These results should be considered when deciding on liver transplantation.

Medroxyprogesterone acetate versus norethisterone: effect on estradiol-induced changes of markers for endothelial function and atherosclerotic plaque characteristics in human female coronary endothelial cell cultures

OBJECTIVE

Progestin addition to estradiol (E(2)) replacement therapy may lead to a deterioration of beneficial effects on the vasculature. The effect of the two clinically most common progestins, medroxyprogesterone acetate (MPA) and norethisterone (NET), during continuous combination with E(2) on the synthesis of markers for coronary endothelial function, atherosclerotic plaque initiation, and plaque formation was investigated in human female vascular cell cultures and compared with that of E(2) alone.

DESIGN

Endothelial cell cultures from human female coronary arteries were used to evaluate the effect of progestin addition to E(2) on the production of the following endothelial markers: prostacyclin, endothelin, plasminogen activator inhibitor-1, E-selectin, intercellular adhesion molecule-1, monocyte chemoattractant protein-1 (MCP-1), and the precursor of matrix metalloproteinase-1 (pro-MMP-1). E(2) was tested at 0.1 microM, 1 microM, and 10 microM alone and in equimolar combinations with MPA or NET. The markers were determined by enzyme immunoassays in the cell supernatant.

RESULTS

E(2) induced a significant increase of endothelial prostacyclin production and was able to significantly decrease the synthesis of endothelin, plasminogen activator inhibitor-1, E-selectin, and intercellular adhesion molecule-1. Neither MPA nor NET addition negatively interfered with these E(2)-induced benefits. However, MPA antagonized the E(2)-induced significant reduction of MCP-1 synthesis, with the difference between both progestins being significant (p < 0.01). Interestingly, an enhancement of the positive E(2)-effect on pro-MMP-1 production was observed by the addition of both MPA and NET (p < 0.01).

CONCLUSION

E(2) can positively influence various markers of endothelial function. Addition of MPA or NET can elicit different effects, which has been demonstrated for the first time in human coronary cell cultures. No impact was found on markers representing primarily vasotonus and thrombogenicity. In terms of MMP-1, which is crucial for atherosclerotic plaque stability, an enhancement of the beneficial E(2) effect was observed. However, regarding MCP-1, contrary effects of progestins cannot be excluded. This indicates that progestins may differ in their effects, particularly in the early stages of atherosclerosis, which has also been supported by other studies.

The role of endothelin in oxygen-induced contraction of the ductus arteriosus in rabbit and rat fetuses

The role of endothelin in oxygen-induced contraction remains controversial. The present study was designed to investigate the role of endothelin in O2-induced contraction in the isolated ductal preparation of rabbit and rat, using the endothelin receptor antagonists, bosentan (antagonist for both ET-A and ET-B receptors) and BQ 485 (an ET-A selective antagonist). The ductus was isolated from fetal rabbits at 30 days of gestation (term 31 days) and fetal rats at 21 days of gestation (term 22 days). In the rabbit ductus with intact endothelium, 13% of the O2-induced contraction was inhibited by bosentan and 14% by BQ 485. In the rabbit ductus without endothelium, bosentan did not cause significant inhibition of the oxygen-induced contraction. In the rat ductus with intact endothelium, about 44% of the O2-induced contraction was inhibited by bosentan. In the rat ductus without endothelium, O2-induced contraction was 20% less than that in the ductus with intact endothelium. In the rat ductus without endothelium, bosentan further decreased the oxygen-induced contraction by about 24%. These data suggest that (1) endothelin plays a significant role in O2-induced contraction in the isolated ductus arteriosus, (2) there is a species difference in the degree of contribution of endothelin to the O2-induced ductal contraction, and (3) there is a species difference in the degree of contribution of the endothelium and vascular smooth muscle cells to the release of endothelin from the ductus arteriosus.

Localization of immunoreactive endothelin and characterization of its receptors in aortic cusps

BACKGROUND AND AIM OF THE STUDY

Aortic valve cusp tissue has been shown to have contractile properties in response to a range of common vasoactive agents. Of these, endothelin (ET) is both the most potent and efficacious.

METHODS

In an attempt to define the mechanism of action and localization of ET, the response of porcine aortic valve cusps to ET and the selective ET(B) receptor agonist sarafotoxin 6c (S6c) was examined, in the presence and absence of ET(A) and ET(B) receptor antagonists. An attempt was made, using immunocytochemical techniques, to localize ET in cusp tissue.

RESULTS

Addition of 90 mM KCl produced a mean contractile response of 1.02+/-0.09 mN (n = 27). ET (10- to 10(-7)M) produced a concentration-dependent contraction of aortic valve cusps, with a maximum response of 116.7+/-12.7% (n = 6) of that obtained with 90 mM KCl. In a similar manner, 10(-5)M of the selective ET(A) receptor antagonist BQ123 (n = 4) and 10(-5)M of the selective ET(B) receptor antagonist BQ788 (n = 4) each partially inhibited the effect of ET. The ET(B)-selective agonist S6c (10(-9) to 10(-7)M) also induced a concentration-dependent contraction of valve cusps (n = 4), with a maximum response of 99.1+/-11.1%. This response was completely inhibited by 10(-5)M BQ788 (n = 4). Immunoreactive ET was localized to the endothelial cells that lined both the ventricular and aortic side of the cusps.

CONCLUSION

These results show that aortic valve cusps contract to ET via an action at both ET(A) and ET(B) receptors. The presence of immunoreactive ET in the endothelial cells of the cusps also suggests that it might play a role in valve function. Further studies are required to elucidate the role of these receptors in the physiology and pathophysiology of the aortic valve.

[Macrophages and the expression of endothelin in sulphur dioxide induced bronchitis in rats]]

The aim of the study was to evaluate the influence of SO2 on bronchial mucosa in rats. Our interest was focused on macrophages function and expression of endothelin. 20 animals were used in the study; 5 of them constituted the control group, 15 of them were submitted to long term SO2 irritation. In animals exposed to SO2 the BALF evaluation revealed the increase of inflammatory cells concentration: neutrophils, macrophages, lymphocytes. Electron microscope examination demonstrated that macrophages from study group were activated in comparison with healthy rats. Immunoreactive endothelin was found in bronchial specimens and mainly in alveolar macrophages (we used a computer-assisted system of image analysis). The expression of endothelin was significantly increased in study group in comparison with control group.

Plasma levels and vascular effects of endothelin and big endothelin in patients with stable and unstable angina pectoris undergoing coronary bypass grafting

OBJECTIVES

The aim of this study was to determine the plasma and pericardial levels of endothelin-1 (ET-1) and its precursor big endothelin-1 (Big ET-1) in patients with unstable and stable angina prior to and following coronary bypass surgery. To further investigate the content of ET-1, tissue levels were studied in the internal mammary artery (IMA) in patients with stable and unstable angina pectoris. Finally, the difference in reactivity of the IMA to ET-1 and Big ET-1 in stable and unstable patients was evaluated.

METHODS

Plasma and pericardial levels of ET-1 and Big ET-1 were determined with radioimmunoassay in 81 patients (33 unstable) immediately before coronary bypass surgery, and at 6, 14, 40 and 64 h following the procedure. Specimens of the distal IMA from 12 patients (six unstable) were collected at the beginning of surgery for determination of tissue levels of ET-1. Additionally, distal internal mammary arteries were obtained from another 24 patients (12 unstable). These vessels were mounted in organ baths for functional studies on vascular reactivity to ET-1 and Big ET-1.

RESULTS

The peripheral plasma levels of ET-1 in unstable patients were significantly lower in patients with unstable angina compared with patients with stable angina pectoris at all points of measurement. The levels of Big ET-1 were significantly higher pre-operatively in the unstable group, but decreased to similar levels to those of stable patients following coronary bypass grafting. There was no difference in ET-1 tissue content in the IMA between the patients. ET-1 and Big ET-1 caused an endothelin(A) (ET(A))-receptor blocker sensitive, concentration-dependent contraction of the IMA obtained from stable as well as unstable patients.

CONCLUSIONS

It is concluded that unstable angina pectoris is associated with an increased ET-1 turnover. This increased turnover may participate in the local regulation of coronary vascular tone with subsequent influence of the condition of the patients. The present investigation also implies that ET(A)-blockade may be useful as an additional pharmacological principal in the treatment of unstable angina pectoris prior to revascularization, as well as to prevent post-operative arterial graft spasm.

Big endothelin-1 but not endothelin-1 is present in the smooth muscle stroma of the prostate gland of the rat

Immunohistochemical techniques were employed to localize the presence of endothelins in the mature rat prostate gland. Immunoreactivity for big endothelin-1 but not endothelin-1 was observed in the fibromuscular stroma of the rat prostate gland. No immunoreactivity was seen in the glandular epithelium. Double staining procedures showed big endothelin-1 immunoreactivity to be co-localized with alpha-actin immunoreactivity. The stroma of the prostate gland also contained nerve fibres coursing through it which are immunopositive for tyrosine hydroxylase. These results suggest that big endothelin-1 but not endothelin-1 is co-localized with alpha-actin in the smooth muscle cells of the rat prostate gland. This implies that endothelin-1 is synthesized on demand from big endothelin-1 in the fibromuscular stroma of the rat prostate.

Thiazolidinediones, peroxisome proliferator-activated receptor gamma agonists, regulate endothelial cell growth and secretion of vasoactive peptides

Insulin resistance has been highlighted as a common causal factor for glucose intolerance, hypertension and dyslipidemia, all of which are cardiovascular risk factors. A new class of antidiabetic agents, thiazolidinediones (TZDs), has been developed and demonstrated to improve insulin sensitivity. TZDs are high affinity ligands for peroxisome proliferator-activated receptor gamma (PPARgamma), the crucial transcription factor for adipocytes. Recent studies showed that PPARgamma is also expressed in monocytes/macrophages and is suggested to be involved in atherosclerosis. We could detect PPARgamma gene transcript in several cultured endothelial cells (human aortic endothelial cells (HAoECs), human coronary artery endothelial cells (HCAECs), human umbilical vein endothelial cells (HUVECs) and bovine carotid artery endothelial cells (BAECs)) as well as human coronary arteries we examined. Since endothelial dysfunction is critical for atherosclerosis, we investigated the effects of TZDs, troglitazone (TRO) and pioglitazone (PIO), on endothelial cell growth and secretion of C-type natriuretic peptide (CNP), which we demonstrated as a novel endothelium-derived relaxing peptide, and endothelin (ET), a potent vasoconstrictor, using HAoECs, HCAECs, HUVECs and BAECs. When all these cultured endothelial cells were daily treated with TRO and PIO for 5 days, both TRO and PIO (10(-8)M) significantly stimulated (3)H-thymidine incorporation of all these endothelial cells. In contrast, higher dose of TRO and PIO (10(-5)M) significantly suppressed DNA synthesis. TRO and PIO also exerted the compatible effect on the increase of cell numbers. TRO and PIO significantly enhanced CNP secretion from BAECs. In contrast, ET secretion from BAECs was suppressed by both TRO and PIO in a dose-dependent manner. The results of the present study suggest that TZDs modulate endothelial functions, including regulation of endothelial cell growth and secretion of endothelium-derived vasoactive substances, which affect vascular tone and remodeling in the process of atherosclerosis.

Up-regulation of parathyroid hormone-related protein in folic acid-induced acute renal failure

BACKGROUND

Parathyroid hormone (PTH)-related protein (PTHrP) is present in many normal tissues, including the kidney. Current evidence supports that PTHrP is involved in renal pathophysiology, although its role on the mechanisms of renal damage and/or repair is unclear. Our present study examined the changes in PTHrP and the PTH/PTHrP receptor (type 1) in folic acid-induced acute renal failure in rats. The possible role of PTHrP on the process of renal regeneration following folic acid administration, and potential interaction between angiotensin II (Ang II) and endothelin-1, and PTHrP, were examined in this animal model.

METHODS

PTHrP, PTH/PTHrP receptor, ACE, and preproendothelin-1 (preproET-1) mRNA levels in the rat kidney were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and/or RNase protection assay. Immunohistochemistry also was performed for PTHrP, the PTH/PTHrP receptor, and Ang II in the renal tissue of folic acid-injected rats. The role of PTHrP on tubular cell proliferation following folic acid injury was investigated in vitro in rat renal epithelial cells (NRK 52E). PTHrP secretion in the medium conditioned by these cells was measured by an immunoradiometric assay specific for the 1-36 sequence.

RESULTS

Using RT-PCR, PTHrP mRNA was rapidly (1 hour) and maximally increased (3-fold) in the rat kidney after folic acid, decreasing after six hours. At 72 hours, renal function was maximally decreased in these rats, associated with an increased PTHrP immunostaining in both renal tubules and glomeruli. In contrast, the PTH/PTHrP receptor mRNA (RNase protection assay) decreased shortly after folic acid administration. Moreover, PTH/PTHrP receptor immunostaining dramatically decreased in renal tubular cell membranes after folic acid. A single subcutaneous administration of PTHrP (1-36), 3 or 50 microg/kg body weight, shortly after folic acid injection increased the number of tubular cells staining for proliferating cell nuclear antigen by 30% (P < 0.05) or 50% (P < 0.01), respectively, in these rats at 24 hours, without significant changes in either renal function or calcemia. On the other hand, this peptide failed to modify the increase (2-fold over control) in ACE mRNA, associated with a prominent Ang II staining into tubular cell nuclei, in the kidney of folic acid-treated rats at this time period. The addition of 10 mmol/L folic acid to NRK 52E cells caused a twofold increase in PTHrP mRNA at six hours, without significant changes in the PTH/PTHrP receptor mRNA. The presence of two anti-PTHrP antibodies, with or without folic acid, in the cell-conditioned medium decreased (40%, P < 0.01) cell growth.

CONCLUSIONS

Renal PTHrP was rapidly and transiently increased in rats with folic acid-induced acute renal failure, featuring as an early response gene. In addition, changes in ACE and Ang II expression were also found in these animals. PTHrP induces a mitogenic response in folic acid-damaged renal tubular cells both in vivo and in vitro. Our results support the notion that PTHrP up-regulation participates in the regenerative process in this model of acute renal failure and is a common event associated with the mechanisms of renal injury and repair.

PreproEndothelin-1 Expression in Human Mesangial Cells: Evidence for a p38 Mitogen-Activated Protein Kinase/Protein Kinases-C—Dependent Mechanism

Abstract. Endothelin-1 (ET-1) has been implicated in the pathogenesis of renal inflammation. This study investigated the mechanisms underlying the synergistic upregulation of preproET-1 gene expression in human mesangial cells after co-stimulation with thrombin and tumor necrosis factor α (TNFα). Whereas thrombin induced a moderate upregulation of preproET-1 mRNA, co-stimulation with TNFα resulted in a strong and protracted upregulation of this mRNA species. Thrombin+TNFα-induced upregulation of preproET-1 expression was found to require p38 mitogen-activated protein kinase and protein kinases C, whereas activation of extracellular signal-regulated kinase, c-Jun-N-terminal kinase, or intracellular Ca2+ release were not required. Actinomycin D chase experiments suggested that enhanced stability of preproET-1 mRNA did not account for the increase in transcript levels. PreproET-1 promoter analysis demonstrated that the 5′-flanking region of preproET-1 encompassed positive regulatory elements engaged by thrombin. Negative modulation of thrombin-induced activation exerted by the distal 5′ portion of preproET-1 promoter (-4.4 kbp to 204 bp) was overcome by co-stimulation with TNFα, providing a possible mechanism underlying the synergistic upregulation of preproET-1 expression by these two agonists. In conclusion, human mesangial cell expression of preproET-1 may be increased potently in the presence of two common proinflammatory mediators, thereby providing a potential mechanism for ET-1 production in inflammatory renal disease.

Benidipine inhibits expression of ET-1 and TGF-beta1 in Dahl salt-sensitive hypertensive rats

Endothelin and growth factors such as transforming growth factor (TGF)-beta1 are important regulators of the cardiovascular system. Although increased production of endothelin-1 (ET-1) and TGF-beta1 have been reported in left ventricular hypertrophy, the detailed roles of these substances in hypertrophy remain to be determined. To elucidate the cardioprotective effects of calcium antagonists in left ventricular hypertrophy, we evaluated the effects of long-term treatment with benidipine, a long-acting calcium antagonist, on preproET-1, ET(A) receptor (ETAR) and TGF-beta1 expression in the left ventricle and evaluated the relations between these effects and myocardial remodeling in Dahl salt-sensitive hypertensive (DS) rats fed a high-salt diet. After 5 weeks of feeding an 8% NaCl diet to 6-week-old DS rats (i.e., at 11 weeks of age), a distinct stage of concentric left ventricular hypertrophy (DSLVH) was noted. Benidipine (DSLVH-B group, n= 8; 1 mg/kg/day, subdepressor dose) or vehicle (DSLVH-V group, n=8) was administered to 6-week-old DS rats for 5 weeks, or until the onset of DSLVH stage, and age-matched (11-week-old) Dahl salt-resistant rats fed the same diet served as a control group (DR-C, n=8). Blood pressure was similar between the DSLVH-B and DSLVH-V groups, but was significantly lower in DR-C rats. The preproET-1, ETAR and TGF-beta1 expressions in the left ventricle were significantly higher in DSLVH-V than in DR-C rats, and significantly lower in DSLVH-B than in DSLVH-V. Benidipine administration resulted in significant improvements in the wall-to-lumen ratio and perivascular fibrosis in the coronary arterioles, and in myocardial fibrosis. We therefore concluded that myocardial remodeling and left ventricular hypertrophy in DS hypertensive rats fed a high-salt diet were significantly ameliorated by a subdepressor dose of benidipine, and that this amelioration was partly due to decreases in the expression of ET-1 and TGF-beta1 in the left ventricle.

Determination of the levels of novel 31-amino acid endothelins and endothelins in human lungs

An effective method for determination of the levels of newly discovered 31-amino acid endothelins [ETs(1-31)] as well as big ETs and 21-amino acid ETs [ETs(1-21)], in human lungs has been developed. About 85% of ETs in human lung homogenates were recovered on acid extraction 8 times. Most of the published protocols for the determination of tissue ETs involve a reverse-phase minicolumn to separate proteins from peptides, after which the levels of ETs are directly determined by enzyme immunoassay. The levels determined, however, include fairly high amounts of non-bioactive ET metabolites in tissues and the data reported are diverse. We established an effective methods for the extraction and the separation of nine different muscle constricting ETs from their metabolites on a reverse-phase C18 column. Using this protocol, the levels of ETs in human lungs were determined by means of a sandwich-enzyme immunoassay specific for each ET derivative. The levels of ET-2(1-21) were the highest among those of ETs, and the levels of ETs(1-31) were in a similar range to those of big ETs but were lower than those of ETs(1-21). This method can be utilized to assess the pathophysiological roles of ETs(1-31) in various human organs.

[Clinical and immunohistoenzymatic investigations in patients with vasomotor and perennial allergic rhinitis]

The aim of our study was evaluation of the results of clinical examination in patients with vasomotor and perennial allergic rhinitis and assessment of number of blood vessels, nerve fibres and mast cells on the basis of immunohistoenzymatic examination. There were 42 patients examined aged from 18 to 50 and divided into three groups: I--16 patients with vasomotor rhinitis and II--14 patients with perennial allergic rhinitis and III--12 patients (control) with nasal septum deviation. On the basis of the patient's history data, clinical otorhinolaryngologic examination and active anterior rhinomanometry the patients were qualified to bilateral inferior turbinectomy. The nasal mucosa removed during surgery underwent immunohistoenzymatic examination using the monoclonal antibody against the tryptase of mast cells (MCT company, DAKO), the endothelin of blood vessels (EC - DAKO) and the neurospecific enolase (NSE - DAKO). In examined groups of patients with vasomotor and perennial allergic rhinitis and control group similar escalation of clinical symptoms expressed by means of points index were stated. In immunohistoenzymatic studies the differences in mean number of blood vessels and nerve fibres between examined groups were not statistically significant, however statistically significant difference concerned higher number of mast cells patients with vasomotor rhinitis in comparison to perennial allergic rhinitis.

Changes of nitric oxide and growth factors during gastric ulcer healing

We measured the concentrations of vascular endothelial growth factor (VEGF), nitric oxide and endothelin-1 (ET-1) in the gastric mucosa and examined the relationships between these factors. VEGF, nitric oxide and ET participate in angiogenesis and vascular remodeling, important elements of gastric ulcer healing. We studied cases of gastric ulcer as confirmed by endoscopic examination. All 61 cases in the angulus were positive for Helicobacter pylori (Hp). Fifteen cases were active stage (GA), 23 were healing stage (GH), and 23 were scarring stage (GS). As control, 17 cases of Hp-positive gastritis (gast+) and 14 cases of Hp-negative gastritis (gast-) were studied. Biopsy samples taken from the angulus during endoscopic examination were frozen and sliced into thin sections. ET was measured by enzyme immunoassay, VEGF was measured by enzyme-linked immunosorbent assay (ELISA) and nitric oxide was measured in terms of metabolite oxides of nitrogen (NOx) as described by Griess. ET, VEGF and inducible nitric oxide synthase (iNOS) were immunostained. The GA group had the highest concentration of NOx, suggesting that nitric oxide participates in the early stage of mucosal repair. In the GH group, all three factors showed high concentrations, suggesting that all may be involved in increased production. In the GS group, all three factors were significantly lower than in the GA and GH groups. Immunohistochemical studies showed that the distribution of ET- and iNOS-positive cells differed according to the ulcer stage. In particular, ET- and iNOS-positive cells in the vascular wall were primarily endothelial cells during GA and GH and vascular smooth muscle cells (VSMCs) during GS. These findings suggest that endothelial cells produce increased amounts of ET, nitric oxide and VEGF early in ulcer healing, a period of active endothelial cell repair and angiogenesis. During the scarring stage, vascular remodeling may result from the effects of ET and nitric oxide in regulating the proliferation of VSMCs. Our results suggest that VEGF. nitric oxide and ET participate in angiogenesis, vascular remodeling and mucosal regeneration during ulcer healing.

Cardioprotection from ischemia and reperfusion injury by an endothelin A-receptor antagonist in relation to nitric oxide production

It has previously been shown that endothelin (ET)-receptor antagonists protect the myocardium from ischemia and reperfusion (I/R) injury. The mechanism behind this effect is unclear. The aim of this study was to elucidate the possible interaction between ET(A)-receptor antagonism and nitric oxide (NO) during I/R. Anesthetized pigs were subjected to 45-min ligation of the left anterior descending coronary artery (LAD) followed by 4 h of reperfusion. Vehicle (n = 7), the ET(A)-receptor antagonist LU 135252 (LU; 0.1 mg/kg, n = 7), the combination of LU and the NO precursor L-arginine (15 mg/kg, n = 7; LU + L-arg), the NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA; 0.2 mg/kg, n = 6), or the combination of LU and L-NMMA (LU + L-NMMA; n = 6) were injected into the LAD during the last 10 min of ischemia and the first 5 min of reperfusion. There were no significant differences in coronary flow, pulmonary capillary wedge pressure, mean arterial pressure, or heart rate between the groups before ischemia or at the end of reperfusion. The area at risk was similar in all five groups. The infarct size of the vehicle group was 79 +/- 6% of the area at risk. LU and LU + L-arginine (L-arg) reduced the infarct size to 39 +/- 6% and 35 +/- 8%, respectively (p < 0.001 vs. vehicle). L-NMMA completely prevented the infarct-limiting effect of LU. Thus the infarct size in the LU + L-NMMA group was 83 +/- 4% (p < 0.001 vs. LU alone); L-NMMA did not affect infarct size per se (79 +/- 4%). ET immunoreactivity increased threefold in the I/R myocardium of the vehicle group. The increase in ET immunoreactivity was significantly attenuated in the LU and LU + L-arg groups (p < 0.001), but not in the groups given L-NMMA or LU + L-NMMA. In conclusion, ET(A)-receptor blockade results in cardioprotection and attenuation of the increase in myocardial ET levels after I/R. Both effects were inhibited by NO synthase blockade, suggesting that they are dependent on maintained production of NO.

The endothelin system in normal human colon

Endothelin (ET)-1 is a potent vasoconstrictor and mitogenic peptide that has a variety of biological effects in noncardiovascular tissues. The precise cellular distribution of the ET-1 system in the wall of the normal human colon was studied to identify the physiological role of ET in the gut. In situ hybridization revealed ET-converting enzyme-1 (ECE-1) mRNA in all vessels, the colon epithelium, and macrophages. Prepro-ET-1 (PPET-1) mRNA had a similar distribution except for a scattered signal in mucosal microvessels. ET(A) and ET(B) receptor mRNAs were mainly in the lamina propria, pericryptal myofibroblasts, microvessels, and mononuclear cells, with ET(A) mRNA more abundant than ET(B) mRNA. (125)I-ET-1 binding showed ET(B) along the crypts and in nerve fibers descending from the ganglionic plexus that contained PPET-1, ECE-1, and ET(B) transcripts, whereas glia contained ET(A) receptors. The finding of the entire ET system in the normal mucosa suggests its implication in some characteristic functions of the colon and its secretion as both a neuroactive and a vasoactive peptide.

Local neurohumoral regulation in the transition to isolated diastolic heart failure in hypertensive heart disease: absence of AT1 receptor downregulation and 'overdrive' of the endothelin system

OBJECTIVE

Although isolated diastolic heart failure with preserved left ventricular (LV) systolic function frequently occurs, regulation of local neurohumoral factors in the transition from diastolic dysfunction without signs of heart failure to diastolic failure, a target for therapeutic strategy, remains to be clarified, partly because of a lack of animal models. Our laboratory recently demonstrated that Dahl-Iwai salt-sensitive (Dahl-S) rats fed on a high-salt diet since 7 weeks of age develop hypertension followed by compensated LV hypertrophy at 13 weeks and transition to isolated diastolic heart failure at 19 weeks.

METHODS

Gene expression of the components of the renin-angiotensin system, endothelin (ET) system and natriuretic peptide system in the left ventricle was investigated in the transition to isolated diastolic heart failure in this model.

RESULTS

The compensated ventricular hypertrophy was associated with slight increases in angiotensin-converting enzyme (ACE) and angiotensin II type-1a (AT1a) receptor mRNA levels. Although preproET-1 (ppET-1) and ET-converting enzyme-1 (ECE-1) mRNA levels were not increased, mRNA levels of ET type-A (ETA) and ET type-B (ETB) receptors were increased. Atrial natriuretic peptide (ANP) mRNA level increased, but not brain natriuretic peptide (BNP) mRNA level. At the decompensated failing stage (at 19 weeks), ACE mRNA level further increased without downregulation of ATla receptor mRNA level. The mRNA levels of ppET-1 and ECE-1 increased with persistent upregulation of mRNA levels of ETA and ETB receptors, and immunohistochemical staining for ET-1 was found at endothelial cells and myocytes. BNP mRNA level increased with a further increase in ANP mRNA level.

CONCLUSIONS

The transition to isolated diastolic heart failure in hypertrophied hearts was associated with preserved gene expression of the renin-angiotensin system and 'overdrive' of gene expression of the ET system. BNP gene expression is likely to be activated by the progression of diastolic failure rather than by LV hypertrophy alone.

Regulation of ET: pulmonary release of ET contributes to increased plasma ET levels and vasoconstriction in CHF

Endothelin (ET) contributes to the increased systemic vascular resistance and elevated cardiac filling pressures seen in congestive heart failure (CHF). We investigated to what extent ET-mediated vasoconstriction in CHF occurs through an endocrine action of elevated plasma ET or by an autocrine/paracrine mechanism related to induction of vascular ET gene expression. Three weeks of pacing (225 beats/min) induced a marked release of ET-1 from the pulmonary circulation with a sixfold elevation of arterial plasma ET in CHF pigs compared with sham-operated pigs. Arterial plasma ET was the strongest and only independent predictor of systemic vascular resistance. In contrast, vascular preproET-1 and ET-receptor mRNA expression were unaltered or decreased in CHF pigs and did not correlate with indexes of vascular tone. However, myocardial preproET-1 mRNA expression increased twofold in CHF pigs. PreproET-2 and preproET-3 mRNAs were not detectable in cardiovascular tissues. In conclusion, plasma ET was markedly increased because of an augmented release from the pulmonary circulation during CHF, and arterial plasma ET correlated with systemic vascular resistance. The absence of ET induction in the peripheral vasculature suggests that ET increases vascular tone during CHF by an endocrine, not an autocrine/paracrine, mechanism.

ET(B) receptor blockade potentiates the pressor response to big endothelin-1 but not big endothelin-2 in the anesthetized rabbit

The precursor of endothelin-1, big endothelin-1, is considered to be a more reliable marker of systemic production of vasoactive peptide. However, it is largely unclear whether ET(B) receptor-dependent clearance and endothelium-derived relaxing factors affect the precursor in a similar manner to mature ET-1. These ET(B)-dependent modulations of big ET-1 and big ET-2 pressor properties were therefore studied in the anesthetized rabbit. When injected into the left cardiac ventricle, ET-1 and ET-2 (0.01 to 1 nmol/kg) each induced biphasic responses (a depressor followed by a pressor response), whereas big ET-1 and big ET-2 (0.1 to 3 nmol/kg) caused only protracted pressor responses. The highest dose of big ET-1 caused significantly greater responses than ET-1, ET-2, or big ET-2. A selective ET(A) receptor antagonist, BQ-123 (1 mg/kg), markedly reduced pressor responses to all 4 peptides, whereas blockade of ET(B) receptors with BQ-788 (0.25 mg/kg) sharply potentiated the responses to ET-1, ET-2, and big ET-1, but not to big ET-2. Indomethacin (10 mg/kg) sharply potentiated the pressor response to ET-1 (1 nmol/kg), but not big ET-1, at all time points. In control animals, ET-1, but not big ET-1, also triggered an indomethacin-sensitive increase in circulating prostacyclin. Finally, systemically administered big ET-1, but not big ET-2, induced a phosphoramidon-sensitive increase in plasma IR-ET. Our results suggest a significant limiting role of ET(B) receptors on pressor responses to big ET-1. In contrast, the same receptor entities do not modulate the hemodynamic properties of the ET-2 precursor, given that, unlike big ET-1, it is poorly converted in the pulmonary or systemic circulation in anesthetized rabbits.

Salivary endothelin concentrations in the assessment of chronic heart failure

We have shown that salivary endothelin concentrations are raised in patients with chronic heart failure and indicate progression of disease severity through each New York Heart Association Functional Class. Furthermore, endothelin concentrations in saliva seem to discriminate between controls and patients with mild symptoms of chronic heart failure.

Potential role of endothelin and nitric oxide in physiology and pathophysiology of the lower urinary tract

Endothelium-derived vasoactive mediators (endothelin-1 with its vasoconstrictive and mitogenic properties and nitric oxide with its vasodilatory and antiproliferative properties) play an important role in the regulation of vascular smooth muscle tone and cellular proliferation. Several recent studies have now demonstrated the presence of these vasoactive agents in the urinary tract where they are thought to play a prominent role in urinary tract physiology and disease. This article reviews the synthesis, localisation and actions of endothelin and nitric oxide in the lower urinary tract and examines the possible role of these mediators in disease.

[Study on endothlin and its gene expression in splanchnic vessels in cirrhotic rats]

OBJECTIVE

To investigate the role of endothelin(ET) in the pathogenesis of portal hypertension, ET-1 level and its gene expression in splanchnic vessels from cirrhotic rats were observed.

METHODS

ET levels of both plasma and vascular tissues were determined by radioimmunoassay. ET mRNA in vascular tissues was probed with RT-PCR technique expressed as optical density(OD) value from image analysis.

RESULTS

ET peptide and mRNA in PV and SMA vessels were all significantly higher in cirrhotic rats than those in normal rats, while in cirrhotic rats, ET and its gene expression of PV was dramatically higher than that of SMA(P < 0.05). In addition, the positive correlation was observed in difference between PV and SMA in ET concentration with portal pressure(r = 0.737, P < 0.01).

CONCLUSION

ET may be involved in the mechanisms of the formation of portal hypertension mainly due to constructing portal vein, increasing portal flow resistance.

Neuronal nitric oxide synthase (nNOS) expression in the epithelial neuroendocrine cell system and nerve fibers in the gill of the catfish, Heteropneustes fossilis

We studied immunohistochemically the localization of neuronal nitric oxide synthase (nNOS) in gills of an Indian catfish species, Heteropneustes fossilis. It is shown that most of the epithelial neuroendocrine cells that are present in gill filaments and lamellae stained positively. Co-localization of nNOS and endothelin was also shown in neuroendocrine cells. A dense plexus of nNOS-containing nerve fibers was present beneath the gill epithelium, associated with efferent filament arteries and the basal side of neuroendocrine cells. nNOS immunopositive neurons were not found in gill areas. nNOS immunopositive neuroendocrine cells appeared to differ from neuroepithelial cells in gills of various teleost species, which are considered as oxygen-sensitive receptors and are present in the distal halves of gill filaments. Other types of neuroendocrine cells have been identified previously in other areas of gills using antibodies to serotonin and endothelin peptides. These cell types are likely to be involved in chemical regulation of the physiology of gill cells. In relation to the function of the other cell types, our data on nNOS localization suggest that NO is a wide-spread transmitter in the gill of the Indian catfish. It may play a role both in the local regulation of vascular tone and in inhibitory innervation of the gill.

Cardiac endothelin and big endothelin in right-heart hypertrophy due to monocrotaline-induced pulmonary hypertension in rat

OBJECTIVE

Recent observations suggest the existence of a myocardial endothelin (ET) system and its possible involvement in left-ventricular myocardial hypertrophy and failure. However, nothing is known about the role of myocardial ET in right-ventricular hypertrophy.

METHODS

Rats (80-100 g) were given an intraperitoneal injection of saline (controls) or monocrotaline (50 mg/kg) resulting in pulmonary hypertension-induced myocardial hypertrophy (n = 11 in both groups). After 10 weeks, the animals were sacrificed and hearts perfused in vitro to determine levels of big ET-1 and ET-1 in coronary effluent, interstitial fluid and ventricular tissue homogenates; plasma levels were also determined.

RESULTS

In monocrotaline-treated animals, weights of right ventricles were 1.5 and of right atria 1.8-fold higher than in controls (p < 0.05), indicating substantial right-ventricular hypertrophy as also evident from greatly increased myocardial production of atrial natriuretic peptide. Left-ventricular weights were not different. Release of big ET-1 in coronary effluent, and of ET-1 in coronary effluent and interstitial transudate were similar in control and hypertrophic hearts (p > 0.05). Disruption of endothelium with collagenase reduced release of both peptides close to zero, indicating endothelial (not myocardial) origin of the peptides. Levels of big ET-1 and ET-1 were similar in left ventricles of both experimental groups, but lower in right ventricles of hypertrophic than control hearts (p < 0.05), reflecting increased tissue mass rather than reduced peptide production. On the other hand, plasma levels of both peptides and of ANP were twofold and levels of angiotensin II 1.3-fold higher in rats with right-heart hypertrophy than in controls (p < 0.05 in each case).

CONCLUSION

These data do not support a role for local cardiac ET-1 and/or big ET-1 in right-ventricular hypertrophy, but point to blood-borne endothelins as possible mediators.