Kinin B2-Receptor in human iPSC differentiation into cardiomyocytes / Receptor B2 de cininas na diferenciação de iPSC humanas em cardiomiócitos

Cardiovascular diseases are responsible for almost one third of all global deaths yearly, and therefore are largely studied. Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CM) have emerged as an exciting technology for cardiac disease modelling and personalised therapy. Nevertheless, issues concerning functional and molecular maturation are still faced. In addition to this, differentiation protocols generally yield a heterogeneous mixed population comprised of nodal, atrial and ventricular-like subtypes, being unsuitable for therapeutic purposes. Bradykinin (BK) is a vasoactive peptide which exerts important physiological roles in the cardiovascular system, having been previously described as important for cellular, keratinocyte and skeletal muscle differentiation. This project performed in cooperation with PluriCell Biotech, a startup specialized in the production and differentiation of hiPSC-CM, has sought (1) characterizing gene and protein expression of molecular markers of maturation and of subtype specification throughout of differentiation; (2) Assessing the electrical functionality of hiPSC-CM through the characterization of subtype-specific action potentials (APs) and (3) Investigating whether the progress of hiPSCCM maturation is regulated by BK through kinin-B2 receptors (B2R). Our results have validated the model that proposes a developmental-dependent switch between skeletal (ssTnI) and cardiac (cTnI) isoforms of troponin I as differentiation progresses, at least to some extent. Furthermore, prolonged time in culture has resulted in higher levels of expression of the ventricular marker MLC2v and in increased rates of ventricular-like action APs. Electrophysiological analysis of hiPSC-CM reveals a mixed population with AP morphologies correspondent to nodal, atrial and ventricular subtypes, all showing pronounced automaticity as well as other features of immature cardiomyocytes, such as low amplitude and depolarization velocity. Such findings are coherent with those from other groups who have attempted to differentiate mature native-like cardiac cells from pluripotent stem cells sources, without fully succeeding. After showing that differentiating hiPSC-CM express a functional and responsive B2R, the receptor was subjected to chronic activation with 10µM BK and 1µM BK or inhibition with 5µM Firazyr+BK. Even though B2R modulation has not interfered negatively with differentiation yields nor cell morphology, analysis of gene andprotein expression of ssTnI or cTnI and of the ventricular marker MLC2v, have revealed no significant results in comparison to untreated controls. This suggests that BK does not interfere on hiPSC-CM maturation nor subtype specification, although we cannot rule out that it could be leading to other unexplored effects. We recommend a closer look into which intracellular signalling pathways become active upon B2R stimulation in hiPSC-CM, in order to narrow down cellular processes for further investigation

Doenças cardiovasculares são responsáveis por quase um terço de todas as mortes globais anualmente, e por isto o sistema cardiovascular é amplamente estudado. Cardiomiócitos derivados a partir de células-tronco pluripotentes induzidas humanas (hiPSCCM) emergiram como uma promissora tecnologia para modelagem de doenças cardíacas e terapia personalizada. No entanto, desafios acerca de sua maturação funcional e molecular ainda são enfrentados. Além disso, protocolos de diferenciação geralmente levam à obtenção de populações heterogêneas contendo células com fenótipos similares aos de cardiomiócitos nodais, atriais e ventriculares sendo, portanto, inapropriadas para fins terapêuticos. A bradicinina (BK) é um peptídio vasoativo que exerce importantes papeis fisiológicos no sistema cardiovascular, além de ter sido previamente descrita como importante para a diferenciação neuronal, de queratinócitos e de músculo esquelético. Este projeto foi realizado em colaboração com a empresa PluriCell Biotech, uma startup especializada na produção e diferenciação de hiPSC-CM, e buscou (1) caracterizar a expressão gênica e proteíca de marcadores moleculares de maturação e de especificação de subtipos cardíacos durante a diferenciação; (2) avaliar a funcionalidade elétrica de hiPSC-CM por meio da caracterização de seus potenciais de ação (PAs) e (3) Investigar se o progresso da diferenciação de hiPSCCM é regulado por bradicinina por meio do receptor B2 (B2R). Nossos resultados validaram o modelo que propõe um switch na expressão das isoformas funcionais de troponina I esquelética (ssTnI) e cardíaca (cTnI), durante o desenvolvimento e diferenciação celular, pelo menos parcialmente. Além disso, tempo prolongado em cultura resultou em maiores níveis de expressão do marcador ventricular MLC2v, assim como maiores frequências de PAs com morfologias similares a de cardiomiócitos ventriculares. Análise eletrofisiológica de hiPSCCM revelam a existência de uma população mista contendo PAs correspondentes aos subtipos nodais, atriais e ventriculares, assim como pronunciada automaticidade e outros atributos típicos de cardiomiócitos imaturos, como baixa amplitude e devagar velocidade de despolarização. Estes resultados são coerentes com os de outros grupos que ainda não foram totalmente bem-sucedidos em diferenciar células cardíacas maduras similares acardiomiócitos nativos a partir de células-troncos pluripotentes. Após mostrar que as hiPSCCM expressam receptores B2 funcionais e responsivos, submetemos o receptor a uma ativação crônica com BK 10µM e BK 1µM ou inibição crônica com Firazyr 5µM + BK. Apesar da modulação do B2R não ter interferido de forma negativa no rendimento da diferenciação ou na morfologia celular, análise de expressão gênica e proteica de ssTnI e cTnI e do marcador ventricular MLC2v não revelou resultados significativos em comparação aos controles não-tratados. Isto sugere que a BK não interfere na maturação e especificação de subtipos cardíacos em hiPSC-CM, apesar de não podermos ignorar o fato de que ela poderia estar desencadeando outros efeitos inexplorados. Nós recomendamos um estudo mais aprofundado acerca de quais vias de sinalização se tornam ativas após estimulação do receptor B2 em hiPSC-CM, com o objetivo de afunilar quais processos celulares poderiam ser investigados em uma próxima etapa deste estudo

The role of bradykinin in lung ischemia-reperfusion injury in a rat lung transplantation model

ABSTRACT PURPOSE: To investigate the role of bradykinin in a rat lung transplantation (LTx) model and preliminarily discuss the relationship between bradykinin and CD26/DPP-4. METHODS: Rats were randomly divided into four groups: Control (CON), Sham, low potassium dextranglucose (LPD), and AB192 (n=15/group). Orthotopic single LTx was performed in the LPD and AB192 groups. The donor lungs were flush-perfused and preserved with low potassium dextranglucose (LPD) or LPD+CD26/DPP-4 catalytic inhibitor (AB192). LTx was performed after 18 h cold ischemia time and harvested two days post-LTx. Blood gas analysis (PO2), wet/dry weight ratio (W/D), myeloperoxidase activity (MPO), and lipid peroxidation (MDA) were analyzed at 48 hr after transplantation. Immunohistochemical (IHC) analysis was performed in the same sample and validated by Western-Blot. RESULTS: Compared to the LPD group, the AB192 group showed higher PO2, lower W/D ratio, and decreased MPO and MDA. IHC studies showed strong bradykinin β2 receptor (B2R) staining in the LPD group, especially in inflammatory cells, alveolar macrophages, and respiratory epithelial cells. Expression of B2R by Western-Blot was significantly different between the AB192 and LPD groups. CONCLUSION: Bradykinin may be a competitive substrate of DPP-4, and decreased bradykinin levels may enhance protective effects against ischemia/reperfusion injury during LTx.

Substâncias vasoativas e a modulaçäo do sistema microvascular hepático / Vasoactive substances and the modulation of the hepatic microvascular system

Objetivo. Revisão da filogênese e ontogênese hepáticas, do sistema microvascular hepático e da modulação do tônus deste sistema vascular por diferentes substâncias vasoativas. Método. Levantamento de artigos por meio do sistema Medline e consulta a livros-texto. Resultado. Foram selecionados 52 trabalhos publicados entre 1949, dos quais retiramos as informações a respeito de filogênese e ontogênese hepáticas, sistema microvascular hepático e mecanismos de controle do tônus vascular hepático. Conclusão. O fígado possui sistema vascular altamente especializado na promoção de mecanismos de troca entre hepatócitos e sangue. Diferentes fatores atuam continuamente sobre estruturas contrácteis deste sistema vascular adequando a perfusão do tecido hepático às necessidades homeostáticas de cada momento. O fígado é órgão eminentemente mantenedor do meio interno.

Role of bradykinin in postprandial hypotension in humans

A transient significant decrease in mean arterial blood pressure (MAP) from 107 + ou - 3 to 98 + ou - 3 mmHg (P<0.05) was observed in elderly (59-69 years of age), healthy volunteers 25-30 min following ingestion of a test meal. In young volunteers (22-34 years of age), a postprandial decrease of MAP from 88 + ou - 3 to 83 + ou - 4 mmHg was also noted but it was not statistically significant. A 40 per cent decrease in bradykinin (BK) content of circulatory high molecular weight kininogen had previously been observed in human subjects given the same test meal. We presently demonstrate by specific ELISA that the stable pentapeptide metabolite (1-5 BK) of BK increases from 2.5 + ou - 1.0 to 11.0 + ou - 2.5 pg/ml plasma (P<0.05) in elderly volunteers and from 2.0 + ou - 1.0 to 10.3 + ou - 3.2 pg/ml plasma (P<0.05) in young volunteers 3 h following food intake. This result suggests that ingestion of food stimulates BK release from kininogen in normal man. Postprandial splanchnic vasodilatation, demonstrated by a decrease of plasma half-life of intravenously administered indocyanine green (ICG), a marker of mesenteric blood flow to the liver, from 4.4 + ou - 0.4 to 3.0 + ou - 0.1 min (P<0.05) in young volunteers and from 5.2 + ou - 1.0 to 4.0 + ou - 0.5 min (P<0.05) in elderly volunteers, accompanied BK release. The participation of BK in this response was investigated in subjects given the BK-potentiating drug captopril prior to food intake. Postprandial decreases of ICG half-lives were not changed by this treatment in either young or elderly subjects, a result which may indicate that BK released following food intake plays no role in postprandial splanchnic vasodilatation in normal man.

La glucosa en conjunto con péptidos derivados de cininógenos podrían actuar desde el aparato digestivo como bloqueadores de la acción diurética-natriurética del péptido natriurético auricular / Glucose in conjunction with peptides derived from kininogens might act from digestive tract as blockers of ANP mediated diuresis-natriuresis

This paper describes long term research efforts wich have lead: 1) to the identification of peptides present in pepsanurin, a peptidic fraction obtained by pepsin hydrolisis of plasma globulins that inhibits the renal excretory action of atrial natriuretic peptide (ANP) and 2) to the discovery of an unexpected role of glucose, as a requisite, for these inhibitory effects. The active peptides identified in pepsanurin are derived from plasma kininogens, substrates of the kallikrein-kinin system. Pro-kinins of 15, 16 and 18 aminoacids, and bradykinin itself, block ANP-induced diuresis and natriuresis when injected iv, ip or into, the duodenal lumen of anesthetized rats in picomol doses. Furthermore, a novel 20 aminoacids fragment derived from kininogen dominium-1, named PU-D1, is the most potent and longer lasting blocker of ANP renal effects. The anti-ANP effects of those peptides are prevented by B2- kinin receptor antagonists. The inhibition of ANP by kinins and PU-D1 was evident only in rats infused with isotonic glucose; whereas the excretory effect of ANP was not affected in fasted rats not infused, or infused with saline. These findings provide evidence that glucose facilitates liquid retention through a kinin-mediated inhibition of ANP excretory action that may be related to the prandial cycle