Potential role for ET-2 acting through ETA receptors in experimental colitis in mice.

OBJECTIVE AND DESIGN: This study attempted to clarify the roles of endothelins and mechanisms associated with ETA/ETB receptors in mouse models of colitis. MATERIALS AND METHODS: Colitis was induced by intracolonic administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS, 1.5 mg/animal) or dextran sulfate sodium (DSS, 3%). After colitis establishment, mice received Atrasentan (ETA receptor antagonist, 10 mg/kg), A-192621 (ETB receptor antagonist, 20 mg/kg) or Dexamethasone (1 mg/kg) and several inflammatory parameters were assessed, as well as mRNA levels for ET-1, ET-2 and ET receptors. RESULTS: Atrasentan treatment ameliorates TNBS- and DSS-induced colitis. In the TNBS model was observed reduction in macroscopic and microscopic score, colon weight, neutrophil influx, IL-1ß, MIP-2 and keratinocyte chemoattractant (KC) levels, inhibition of adhesion molecules expression and restoration of IL-10 levels. However, A192621 treatment did not modify any parameter. ET-1 and ET-2 mRNA was decreased 24 h, but ET-2 mRNA was markedly increased at 48 h after TNBS. ET-2 was able to potentiate LPS-induced KC production in vitro. ETA and ETB receptors mRNA were increased at 24, 48 and 72 h after colitis induction. CONCLUSIONS: Atrasentan treatment was effective in reducing the severity of colitis in DSS- and TNBS-treated mice, suggesting that ETA receptors might be a potential target for inflammatory bowel diseases.

Gene expression of endothelin receptors in replaced rheumatic mitral stenotic valves / Expressão gênica de receptores de endotelina em valvas mitrais reumáticas estenóticas substituídas

OBJECTIVES: Rheumatic fever is a highly prevalent disease in Brazil, and it poses a major public health problem. It is the leading cause of acquired heart disease in childhood and adolescence. The aim of this study was to evaluate the gene expression of ET-3 and its receptors, in replaced rheumatic mitral valves. METHODS: We studied the gene expression of endothelin-3 (ET-3) and its receptors, endothelin receptor A and endothelin receptor B (ETr-A and ETr-B), in the rheumatic mitral valves of 17 patients who underwent valve replacement surgery. The samples also underwent a histological analysis. RESULTS: Our data showed that almost all patients, regardless of individual characteristics such as gender or age, expressed the endothelin receptor genes, but did not express the genes for ET-3. In quantitative analysis, the ETr-A/GAPDH mean ratio was 33.04 ± 18.09%; while the ETr-B/GAPDH mean ratio was 114.58 ± 42.30%. Regarding histopathological individual features, the frequency of fibrosis is 100%, 88.23% of mononuclear infiltrate, 52.94% of neovascularization, 58.82% of calcification and absence of ossification. CONCLUSION: The presence of receptors ETr-A and ETr-B in rheumatic mitral valves suggests its interaction with the system of circulating endothelins, particularly ETr-B (known for acting in the removal of excess endothelin) detected in a greater proportion, which could explain the lack of expression of endothelin in rheumatic mitral valve, process to be elucidated.

OBJETIVOS: A febre reumática é uma doença altamente prevalente no Brasil, e representa um importante problema de saúde pública. É a principal causa de cardiopatia adquirida na infância e adolescência. O objetivo deste estudo foi avaliar a expressão gênica de ET-3 e seus receptores, em valvas mitrais reumáticas substituídas. Métodos: Estudamos a expressão gênica de endotelina-3 (ET-3) e de seus receptores, receptor da endotelina A e receptor da endotelina B (ETr-A e ETr-B), nas valvas mitrais reumáticas de 17 pacientes que se submeteram à cirurgia de troca valvar. As amostras também foram submetidas à análise histológica. RESULTADOS: Nossos dados mostraram que praticamente todos os pacientes, independentemente de características individuais, como sexo ou idade, expressaram os genes de receptores de endotelina, porém não expressaram os genes para ET-3. Na análise quantitativa, a média da proporção ETr-A/GAPDH foi de 33,04 ± 18,09%; enquanto que a média da proporção ETr-B/GAPDH foi de 114,58 ± 42,30%. Em relação às características histopatológicas individuais, a frequência de fibrose foi de 100%, infiltrado mononuclear de 88,23%, neovascularização de 52,94%, calcificação de 58,82% e houve ausência de ossificação. CONCLUSÃO: A presença de receptores ETr-A e ETr-B em valvas mitrais reumáticas sugere sua interação com o sistema de endotelinas circulantes, particularmente ETr-B (reconhecido por atuar na remoção do excesso de endotelina), detectado em maior proporção, o que poderia explicar a ausência da expressão de endotelina em valva mitral reumática, processo a ser elucidado.

Endothelin and neonatal capsaicin regulate gastric resistance to injury in BDL rats.

AIM: To investigate the relationship between primary afferent neurons, endothelin (ET) and the role of its receptors on ethanol-induced gastric damage in cirrhotic rats. METHODS: Cirrhosis and portal hypertension were induced in rats by bile duct ligation (BDL) while controls had a sham operation. The association between ET and afferent neurons on the gastric mucosa was evaluated by capsaicin treatment in newborn rats, the use of ET agonists or antagonists, gastric ET-1 and -3 mRNA and synthetic capacity. Ethanol-induced damage was assessed using ex vivo gastric chamber experiments. Gastric blood flow was measured by laser-Doppler flowmetry. RESULTS: ET-3 and an ET(B) receptor antagonist significantly reduced the extent of ethanol-induced gastric damage in BDL rats. Gastric ET-1 and -3 levels were 30% higher in BDL rats compared to control rats. Capsaicin treatment restored the gastric resistance and blood flow responses to topical application of ethanol in BDL rats and ET-1 and -3 production to levels observed in controls. CONCLUSION: Our results suggest that the reduced resistance of the gastric mucosa of cirrhotic rats to ethanol-induced injury is a phenomenon modulated by ET through the ET(B) receptor and by sensory afferent neurons.

The kallikrein-kinin system in experimental Chagas disease: a paradigm to investigate the impact of inflammatory edema on GPCR-mediated pathways of host cell invasion by Trypanosoma cruzi.

Chronic chagasic myocarditis (CCM) depends on Trypanosoma cruzi persistence in the myocardium. Studies of the proteolytic mechanisms governing host/parasite balance in peripheral sites of T. cruzi infection revealed that tissue culture trypomastigotes (TCTs) elicit inflammatory edema and stimulate protective type-1 effector T cells through the activation of the kallikrein-kinin system. Molecular studies linked the proinflammatory phenotype of Dm28c TCTs to the synergistic activities of tGPI, a lipid anchor that functions as a Toll-like receptor 2 (TLR2) ligand, and cruzipain, a kinin-releasing cysteine protease. Analysis of the dynamics of inflammation revealed that TCTs activate innate sentinel cells via TLR2, releasing CXC chemokines, which in turn evoke neutrophil/CXCR2-dependent extravasation of plasma proteins, including high molecular weight kininogen (HK), in parasite-laden tissues. Further downstream, TCTs process surface bound HK, liberating lysyl-BK (LBK), which then propagates inflammatory edema via signaling of endothelial G-protein-coupled bradykinin B(2) receptors (BK(2)R). Dm28 TCTs take advantage of the transient availability of infection-promoting peptides (e.g., bradykinin and endothelins) in inflamed tissues to invade cardiovascular cells via interdependent signaling of BKRs and endothelin receptors (ETRs). Herein we present a space-filling model whereby ceramide-enriched endocytic vesicles generated by the sphingomyelinase pathway might incorporate BK(2)R and ETRs, which then trigger Ca(2+)-driven responses that optimize the housekeeping mechanism of plasma membrane repair from cell wounding. The hypothesis predicts that the NF-κB-inducible BKR (BK(1)R) may integrate the multimolecular signaling platforms forged by ceramide rafts, as the chronic myocarditis progresses. Exploited as gateways for parasite invasion, BK(2)R, BK(1)R, ET(A)R, ET(B)R, and other G protein-coupled receptor partners may enable persistent myocardial parasitism in the edematous tissues at expense of adverse cardiac remodeling.

Sistema endotelina / Endothelin system

La familia de las endotelinas (ET), está constituida por tres isoformas de 21 aminoácidos: endotelina-1 (ET-1), endotelina-2 (ET-2) y endotelina-3 (ET-3). Las ET son potentes agentes presores endógenos, secretadas por diferentes tejidos y células del organismo. De las tres isoformas, la ET-1 es sintetizada predominantemente por el endotelio vascular. La ET- 1 induce vasoconstricción, es proinflamatoria, profibrosis y tiene acción potencialmente mitógena. Es un importante factor en la regulación del tono vascular y participa en la remodelación vascular. Estos efectos son mediados a través de dos tipos de receptores, ET A y ET B. Los receptores ET A están localizados principalmente en el músculo liso vascular y son responsables de inducir la proliferación celular y vasoconstricción. Los receptores ET B están presentes en las células endoteliales y son mediadores de la relajación vascular por activación de la producción de óxido nítrico y prostaciclina, además, intervienen en la depuración de la ET-1. El sistema endotelina está involucrado esencialmente con la hipertensión arterial sistémica, hipertensión pulmonar, aterosclerosis, reestenosis coronaria, falla cardíaca, cardiomiopatías e insuficiencia renal.

The endothelins (ET S) family consists of three 21 aminoacid isoforms: endothelin-1 (ET-1), endothelin-2 (ET-2) and endothelin-3 (ET-3). ET S are very potent endogenous pressor agents, secreted by various cells and tissues in the human body. Of the three, endothelin-1 is the predominant isoform produced by the vascular endothelium. ET-1 induces vasoconstriction, is proinflammatory, profibrosis, and has mitogenic potential; it is also an important factor in the regulation of vascular tone and arterial vascular remodeling. These effects are mediated via two receptor types, ET A and ET B. ET A receptor is located mainly on vascular smooth muscle and is responsible for mediating vasoconstriction and proliferation. The ET B receptor is present predominantly on endothelial cells and mediates vasorelaxation for NO and prostacyclin release and also ET-1 clearance. The ET system is activated in essential hypertension, pulmonary hypertension, atherosclerosis, coronary restenosis, heart failure, idiopathic cardiomyopathy and renal failure.

Endothelin-1 immunoreactive in the plasma and follicular fluid of horses and cattle / Imunorreatividade para endotelina-1 no plasma e fluido folicular de eqüinos e bovinos

Endothelin-1, a recently isolated peptide, has been observed in different tissues and is involved in several reproductive functions. The objective of the present study was to determine the concentrations of immunoreactive endothelin-1 in the plasma of horses and cattle and in the follicular fluid of horses using a commercial radioimmunoassay kit. Mean immunoreactivity was 47.5%, the minimum detectable dose was 1 pg/tube and the interassay and intra-assay coefficients of variation were 2.36% and 7.26%, respectively. The parallelism between the standard curves and the curves determined with different volumes of plasma and follicular fluid validates the radioimmunoassay of endothelin-1 for these species. To our knowledge, this is the first report in the literature of detection of endothelin-1 in the plasma and follicular fluid of horses and in the plasma of cattle by radioimmunoassay. The present results suggest the use of the radioimmunoassay method employing commercial kits for the determination of endothelin-1 concentrations in horse and cattle plasma and horse follicular fluid because of its high sensitivity, accuracy and reproducibility, in order to study the multiple functions of endothelin-1 in these animals species, and especially in the endocrine-reproductive system.

A endotelina-1, um peptídeo isolado recentemente, tem sido observada em diferentes tecidos e está envolvida em várias funções reprodutivas. Propusemo-nos a determinar as concentrações da endotelina-1 por radioimunoensaio no plasma de eqüinos e bovinos e no fluido folicular de eqüinos. Foram testados 2 tipos de inibidores de degradação protéica no plasma e fluido folicular. A imunorreatividade média foi de 47,5%, a dose mínima detectável foi de 1 pg/tubo e o coeficiente de variação inter e intra-ensaio foi de 2,36% e 7,26%, respectivamente. O paralelismo entre a curva padrão e as curvas determinadas com diferentes volumes de plasma e fluido folicular valida o radioimunoensaio de endotelina-1 para estas espécies. Segundo nosso conhecimento, este é o primeiro relato de literatura que detecta por radioimunoensaio a endotelina-1 no plasma e fluido folicular de eqüinos e plasma de bovinos. Os resultados do presente trabalho sugerem a utilização do método de radioimunoensaio utilizando-se kits comerciais para a determinação das concentrações da endotelina-1 no plasma de eqüinos e bovinos e fluido folicular de eqüinos, pelo fato de este apresentar alta sensibilidade, precisão e reprodutibilidade, podendo assim ser utilizado no estudo de múltiplas funções da endotelina-1 nestas espécies animais e, em especial, no sistema endócrino-reprodutivo.