Endothelin and endothelin receptors A and B in the human testis

Endothelin-1 induces changes in the expression levels of steroidogenic enzymes and increases androgen receptor and testosterone production in the PC3 prostate cancer cell line

Endothelin-1 (ET-1) is involved in the regulation of steroidogenesis. Additionally, patients with castration-resistant prostate cancer (PCa) have a higher ET-1 plasma concentration than those with localized PCa and healthy individuals. The aim of the present study was to evaluate the effect of ET-1 on steroidogenesis enzymes, androgen receptor (AR) and testosterone (T) production in PCa cells. The expression levels of endothelin receptors in prostate tissue from patients with localized PCa by immunohistochemistry, and those in LNCaP and PC3 cells were determined reverse transcription-quantitative PCR (RT-qPCR) and western blotting. Furthermore, the expression levels of ET-1 were determined in LNCaP and PC3 cells by RT-qPCR and western blotting. The ET-1 receptor activation was evaluated by intracellular calcium measurement, the expression levels of AR and enzymes participating in steroidogenesis [cytochrome P450 family 11 subfamily A member 1 (CyP11A1), cytochrome P450 family 17 subfamily A member 1, aldo-keto reductase family member C2 and 3β-hydroxysteroid dehydrogenase/isomerase 2 (3β HSD2)] were determined by western blotting and T concentration was determined by ELISA using PC3 cells. The present results revealed higher expression levels of endothelin A receptor (ET_AR) in tissues obtained from samples of patients with PCa with a low Gleason Score. No changes were identified for endothelin B receptor (ET_BR). PC3 cells expressed higher levels of ET-1 and ET_AR, while LNCaP cells exhibited higher expression levels of ET_BR. Blocking of ET_AR and endothelin B receptor decreased the expression levels of CyP11A1 and 3β HSD2 enzymes and AR in PC3 cells, as well as T secretion. These findings suggested that ET-1 has a potential role in modulating the intratumoral steroidogenesis pathway and might have relevance as a possible therapeutic target.

The Pluripotent Microvascular Pericytes Are the Adult Stem Cells Even in the Testis

The pericytes of the testis are part of the omnipresent population of pericytes in the vertebrate body and are the only true pluripotent adult stem cells able to produce structures typical for the tree primitive germ layers: ectoderm, mesoderm, and endoderm. They originate very early in the embryogenesis from the pluripotent epiblast. The pericytes become disseminated through the whole vertebrate organism by the growing and differentiating blood vessels where they remain in specialized periendothelial vascular niches as resting pluripotent adult stem cells for tissue generation, maintenance, repair, and regeneration. The pericytes are also the ancestors of the perivascular multipotent stromal cells (MSCs). The variable appearance of the pericytes and their progeny reflects the plasticity under the influence of their own epigenetic and the local environmental factors of the host organ. In the testis the pericytes are the ancestors of the neuroendocrine Leydig cells. After activation the pericytes start to proliferate, migrate, and build transit-amplifying cells that transdifferentiate into multipotent stromal cells. These represent progenitors for a number of different cell types in an organ. Finally, it becomes evident that the pericytes are a brilliant achievement of the biological nature aiming to supply every organ with an omnipresent population of pluripotent adult stem cells. Their fascinating features are prerequisites for future therapy concepts supporting cell systems of organs.

Therapeutic potential of endothelin receptor antagonism in kidney disease

Our growing understanding of the role of the endothelin (ET) system in renal physiology and pathophysiology is from emerging studies of renal disease in animal models and humans. ET receptor antagonists reduce blood pressure and proteinuria in chronic kidney disease and cause regression of renal injury in animals. However, the therapeutic potential of ET receptor antagonism has not been fully explored and clinical studies have been largely limited to patients with diabetic nephropathy. There remains a need for more work in nondiabetic chronic kidney disease, end-stage renal disease (patients requiring maintenance dialysis and those with a functioning kidney transplant), ischemia reperfusion injury, and sickle cell disease. The current review summarizes the most recent advances in both preclinical and clinical studies of ET receptor antagonists in the field of kidney disease.

Generation and characterization of an endothelin-2 iCre mouse

A novel transgenic mouse line that expresses codon-improved Cre recombinase (iCre) under regulation of the Endothelin-2 gene (edn2) promoter was developed for the conditional deletion of genes in Endothelin-2 lineage cells and for the spatial and temporal localization of Endothelin-2 expression. Endothelin-2 (EDN2, ET-2, previously VIC) is a transcriptionally regulated 21 amino acid peptide implicated in vascular homeostasis, and more recently in female reproduction, gastrointestinal function, immunology, and cancer pathogenesis that acts through membrane receptors and G-protein signaling. A cassette (edn2-iCre) was constructed that contained iCre, a polyadenylation sequence, and a neomycin selection marker in front of the endogenous start codon of the edn2 gene in a mouse genome BAC clone. The cassette was introduced into the C57BL/6 genome by pronuclear injection, and two lines of edn2-iCre positive mice were produced. The edn2-iCre mice were bred with ROSA26-lacZ and Ai9 reporter mice to visualize areas of functional iCre expression. Strong expression was seen in the periovulatory ovary, stomach and small intestine, and colon. Uniquely, we report punctate expression in the corneal epithelium, the liver, the lung, the pituitary, the uterus, and the heart. In the embryo, expression is localized in developing hair follicles and the dermis. Therefore, edn2-iCre mice will serve as a novel line for conditional gene deletion in these tissues.

Microcirculatory effects of selective endothelin-A receptor antagonism in testicular torsion

PURPOSE

Testicular torsion without timely intervention causes incurable damage to the testis. We examined the causative role of microcirculatory injury in torsion induced testicular damage with particular regard to endothelin-A receptor activation.

MATERIALS AND METHODS

The microcirculatory consequences of testicular torsion were assessed in the presence or absence of endothelin-A receptor antagonism in rats. Microcirculatory perfusion changes (red blood cell velocity and pulsatile flow pattern alterations) were examined by an orthogonal polarization spectral imaging technique. Microcirculatory inflammatory alterations were assessed by fluorescence intravital video microscopy after 60-minute torsion followed by 240-minute reperfusion. As a specific endothelin-A receptor inhibitor, the antisense homology box derived peptide ETR-p1/fl was applied 10 minutes before reperfusion. Tissue accumulation of leukocytes was estimated by myeloperoxidase activity in tissue biopsies taken at the end of the 4-hour reperfusion period. In further experiments testicular weight as a marker of permanent damage was evaluated 45 days after torsion.

RESULTS

The physiological pulsatile flow pattern ceased in the initial phase of reperfusion while leukocyte-endothelial interactions increased throughout the examined reperfusion period. Endothelin-A receptor antagonism caused earlier return of pulsatile flow and recovery of red blood cell velocity, and alleviated microcirculatory inflammatory reactions and atrophy.

CONCLUSIONS

Results suggest a pathophysiological role of endothelin-A receptor activation in the pathogenesis of testicular torsion. This effect is related to deterioration in testicular perfusion and activation of microcirculatory inflammatory reactions.

Role of angiotensin and endothelin in testicular ischemia reperfusion injury

OBJECTIVES

To determine whether angiotensin and endothelin have any role in testicular ischemia reperfusion injury by investigating the effects of the angiotensin converting enzyme inhibitor enalapril, selective non-peptide angiotensin-II type I blocker losartan and dual endothelin receptor blocker bosentan.

METHODS

Rats were anesthetized with thiopental sodium (50 mg/kg i.p.) before the operation. The left testicular artery and vein of rats were occluded for 1 h; before the bilateral orchiectomy, the organ was allowed to reperfuse for 3 h or 24 h. Enalapril (20 mg/kg i.p.), losartan (30 mg/kg i.p.), bosentan (10 mg/kg i.p.) or vehicle (saline) were given 30 min before reperfusion. Malondialdehyde level was measured in testicular tissue after 3 h of reperfusion. Histological examination was carried out after 24 h of reperfusion.

RESULTS

Ischemia reperfusion caused a significant increase in malondialdehyde level of ipsilateral testis, and histopathological injury in both ipsilateral and contralateral testes. Enalapril, losartan and bosentan treatments prevented the ischemia reperfusion-induced augmentation in malondialdehyde levels. Only bosentan treatment ameloriated ischemia reperfusion-induced histopathological alterations.

CONCLUSIONS

Endothelin might play a more important role in pathogenesis of testicular ischemia reperfusion injury when compared with angiotensin.

Ontogeny of gonadal sex steroids

Sex steroids are crucial hormones for the proper development and function of the body; they regulate sexual differentiation, the secondary sex characteristics, and sexual behaviour patterns. Gonads are the major sources of sex steroids, although adrenal cortex, placenta, and to a lesser extent other tissues contribute to their production in adult life and at various phases of development. Steroidogenesis of gonadal sex hormones is by definition sexually dimorphic, and involves differences not only in hormonal action but also in regulation and temporal patterns of production. This review focuses on the ontogeny and developmental regulation of steroid hormones in the gonads, with an attempt to detail these processes in humans.

Regulation of the gonadal transcriptome during sex determination and testis morphogenesis: comparative candidate genes

Gene expression profiles during sex determination and gonadal differentiation were investigated to identify new potential regulatory factors. Embryonic day 13 (E13), E14, and E16 rat testes and ovaries were used for microarray analysis, as well as E13 testis organ cultures that undergo testis morphogenesis and develop seminiferous cords in vitro. A list of 109 genes resulted from a selective analysis for genes present in male gonadal development and with a 1.5-fold change in expression between E13 and E16. Characterization of these 109 genes potentially important for testis development revealed that cytoskeletal-associated proteins, extracellular matrix factors, and signaling factors were highly represented. Throughout the developmental period (E13-E16), sex-enriched transcripts were more prevalent in the male with 34 of the 109 genes having testis-enriched expression during sex determination. In ovaries, the total number of transcripts with a 1.5-fold change in expression between E13 and E16 was similar to the testis, but none of those genes were both ovary enriched and regulated during the developmental period. Genes conserved in sex determination were identified by comparing changing transcripts in the rat analysis herein, to transcripts altered in previously published mouse studies of gonadal sex determination. A comparison of changing mouse and rat transcripts identified 43 genes with species conservation in sex determination and testis development. Profiles of gene expression during E13-E16 rat testis and ovary development are presented and candidate genes for involvement in sex determination and testis differentiation are identified. Analysis of cellular pathways did not reveal any specific pathways involving multiple candidate genes. However, the genes and gene network identified influence numerous cellular processes with cellular differentiation, proliferation, focal contact, RNA localization, and development being predominant.

Effects of CPU 86017 (chlorobenzyltetrahydroberberine chloride) and its enantiomers on thyrotoxicosis-induced overactive endothelin-1 system and oxidative stress in rat testes

OBJECTIVES

To study the effects of CPU 86017, a berberine derivative, and its four enantiomers on thyrotoxicosis-induced oxidative stress and the excessive endothelin-1 system in rat testes.

METHODS

Adult male SD rats were given high-dose L-thyroxin (0.2 mg/kg subcutaneously) once daily for 10 days to develop thyrotoxicosis. Subsets of the rats were treated with CPU 86017 or its four enantiomers (SR, SS, RS, and RR) once daily from day 6 to day 10. The alterations of redox, nitric oxide synthase, and endothelin-1 system in testes were examined by spectrophotometry and reverse transcriptase-polymerase chain reaction assay.

RESULTS

After 10 days of high-dose L-thyroxin administration, increased mRNA expression of prepro-endothelin-1 and endothelin-converting enzyme was observed in the rat testes, accompanied by an elevated inducible nitric oxide synthase activity and oxidative stress. CPU 86017 and its enantiomer SR significantly improved these abnormalities.

CONCLUSIONS

High-dose L-thyroxin results in an overactive endothelin-1 system and oxidative stress in adult rat testis. CPU 86017 and its enantiomer SR suppressed the excessive ET-1 system by improving oxidative stress, and SR exhibited more potent efficacy than CPU 86017 and other enantiomers.

Transgenic mice over-expressing endothelin-1 in testis transactivated by a Cre/loxP system showed decreased testicular capillary blood flow

It is generally believed that too high or low levels of endothelin-1 (ET-1), a strong vasoconstrictor, may be detrimental to animals. Therefore, in order to understand the in vivo function of ET-1, we used a conditional transgenic approach, Cre/loxP recombination system, to generate transgenic mice that over-express ET-1 in a tissue-specific manner. In such a strategy a single transgenic mouse line, ELSE, was initially generated where a general promoter, human elongation factor 1alpha (hEF1alpha) promoter, was used to drive the expression of a loxP-flanked sequence containing the lacZ reporter gene and a STOP cassette before the ET-1 cDNA, the recombinational competency of which was confirmed in an Escherichia coli test system. In ELSE mice, expression of the reporter lacZ was limited to spermatozoa and spermatogonia as well as Sertoli, Leydig and endothelial cells in the testis, thus confirming the suitability of these mice for the generation of testes-limited ET-1 expression. To generate transgenic progeny with ET-1 over-expression in the testis (successful recombination, ELSE/ELT), ELSE mice were mated with EIIa-cre mice expressing Cre recombinase in pre-implantation mouse embryos. These ELSE/ELT mice exhibiting testis-specific ET-1 over-expression had normal reproductive function and showed no obvious alterations in gross testicular morphology. Although over-expression of ET-1 leads to reduction of testicular blood flow, young adult ELSE/ELT mice showed no obvious signs of inflammation, fibrosis or abnormal proliferation of cells in the testes of young ELSE/ELT mice by histochemical analyses.

Localization of endothelin receptor subtype-A in the testis of rats, dogs, and monkeys

In order to evaluate the physiological roles of the testicular endothelin (Edn) signaling via Edn receptor subtype-A (Ednra) in mammals, the localization of Ednra was investigated by in situ hybridization and immunohistochemistry in the testis of rats, dogs, and monkeys. For in situ hybridization, a rat Ednra RNA probe which is highly homologous to the subcloned canine and monkey Ednra (88.7% and 87.9% identical, respectively) was used. Both Ednra mRNA and protein were detected in interstitial cells and cells in the basal compartment of the seminiferous tubules, mainly Sertoli cells, as well as spermatogonia and some early spermatocytes, but not spermatids. The localization pattern of Ednra was exhibited in a same manner among species, indicating that the physiological role of Edn signaling throughout Ednra was maintained in the mammalian testis.

Cell biology of Leydig cells in the testis

This article reviews results on differentiation, structure, and regulation of Leydig cells in the testes of rodents and men. Two different populations-fetal and adult Leydig cells-can be recognized in rodents. The cells in these two populations are different in ultrastructure, life span, capacity for androgen synthesis, and mechanisms of regulation. A brief survey on the origin, ontogenesis, characterization of precursors, ultrastructure, and functional markers of fetal and adult Leydig cells is presented, followed by an analysis of genes in Leydig cells and the role of luteinizing hormone and its receptor, steroidogenic acute regulatory protein, hydroxysteroid dehydrogenases, androgen and its receptor, anti-Müllerian hormone, estrogens, and thyroid hormones. Various growth factors modulate Leydig cell differentiation, regeneration, and steroidogenic capacity, for example, interleukin 1alpha, transforming growth factor beta, inhibin, insulin-like growth factors I and II, vascular endothelial growth factor, and relaxin-like growth factor. Retinol and retinoic acid increase basal testosterone secretion in adult Leydig cells, but decrease it in fetal Leydig cells. Resident macrophages in the interstitial tissue of the testis are important for differentiation and function of Leydig cells. Apoptosis of Leydig cells is involved in the regulation of Leydig cell number and can be induced by cytotoxins. Characteristics of aging Leydig cells in rodents seem to be species specific. 11beta-hydroxysteroid dehydrogenase protects testosterone synthesis in the Leydig cells of stressed rats. Last, the following aspects of human Leydig cells are briefly described: origin, differentiation, triphasic development, aging changes, pathological changes, and gene mutations leading to infertility.

Increased plasma endothelin levels in patients with male hypogonadism

Endothelin has various paracrine and endocrine effects on the male reproductive system. Testosterone is probably responsible for the higher endothelin levels in males. In addition, there is much ambiguity about the relationship between gonadotrophic hormones and endothelin. In order to study in more detail the relationship of endothelin with the hypothalamo-pituitary-gonadal axis in the male, we investigated 18 male patients with various forms of hypogonadism (seven with hypergonadotrophic hypogonadism and 11 with hypogonadotrophic hypogonadism). Eight age-matched healthy males served as controls. The basal endothelin levels in patients with hypogonadism (0.95 +/- 0.53 fmol ml(-1)) were significantly higher than those of the controls (0.54 +/- 0.06 fmol ml(-1); P < 0.05). Males with hypergonadotrophic hypogonadism had significantly increased endothelin concentrations (1.05 +/- 0.57 fmol ml(-1); P < 0.05), whereas those with hypogonadotrophic hypogonadism (0.89 +/- 0.53 fmol ml(-1)) had nonsignificantly (P > 0.05) elevated levels. No significant correlation was found between plasma endothelin levels and gonadotrophin, prolactin and testosterone concentrations. The results of this study suggest that plasma endothelin levels are increased in males with hypogonadism.

New strategies in anti-vascular cancer therapy

Angiogenesis is a critical step in the progression of tumours from dormancy to a clinical relevant cancer. Inhibition of this process is one of the most promising new anti-cancer strategies. To develop new drugs that interfere with the cascade of events required for the formation of new blood vessels, insight into this process is essential. Here, we discuss the molecular basis of angiogenesis and the concepts of vascular targeting. Furthermore new strategies will be discussed to discover surface markers on endothelial cells that confer sufficient specificity for targeted intervention in the tumour vasculature.