RESUMO
Ouabain, an organic compound with the ability to strengthen the contraction of the heart muscle, was originally derived from plants. It has been observed that certain mammalian species, including humans, naturally produce ouabain, leading to its classification as a new type of hormone. When ouabain binds to Na+/K+-ATPase, it elicits various physiological effects, although these effects are not well characterized. Previous studies have demonstrated that ouabain, within the concentration range found naturally in the body (10 nmol/L), affects the polarity of epithelial cells and their intercellular contacts, such as tight junctions, adherens junctions, and gap junctional communication. This is achieved by activating signaling pathways involving cSrc and Erk1/2. To further investigate the effects of ouabain within the hormonally relevant concentration range (10 nmol/L), mRNA-seq, a high-throughput sequencing technique, was employed to identify differentially expressed transcripts. The discovery that the transcript encoding MYO9A was among the genes affected prompted an exploration of whether RhoA and its downstream effector ROCK were involved in the signaling pathways through which ouabain influences cell-to-cell contacts in epithelial cells. Supporting this hypothesis, this study reveals the following: (1) Ouabain increases the activation of RhoA. (2) Treatment with inhibitors of RhoA activation (Y27) and ROCK (C3) eliminates the enhancing effect of ouabain on the tight junction seal and intercellular communication via gap junctions. These findings further support the notion that ouabain acts as a hormone to emphasize the epithelial phenotype.
RESUMO
Ouabain is a cardiac glycoside, initially isolated from plants, and currently thought to be a hormone since some mammals synthesize it endogenously. It has been shown that in epithelial cells, it induces changes in properties and components related to apical-basolateral polarity and cell-cell contacts. In this work, we used a whole-cell patch clamp to test whether ouabain affects the properties of the voltage-gated potassium currents (Ik) of epithelial cells (MDCK). We found that: (1) in cells arranged as mature monolayers, ouabain induced changes in the properties of Ik; (2) it also accelerated the recovery of Ik in cells previously trypsinized and re-seeded at confluence; (3) in cell-cell contact-lacking cells, ouabain did not produce a significant change; (4) Na+/K+ ATPase might be the receptor that mediates the effect of ouabain on Ik; (5) the ouabain-induced changes in Ik required the synthesis of new nucleotides and proteins, as well as Golgi processing and exocytosis, as evidenced by treatment with drugs inhibiting those processes; and (5) the signaling cascade included the participation of cSrC, PI3K, Erk1/2, NF-κB and ß-catenin. These results reveal a new role for ouabain as a modulator of the expression of voltage-gated potassium channels, which require cells to be in contact with themselves.
Assuntos
Ouabaína , Canais de Potássio de Abertura Dependente da Tensão da Membrana , Animais , Ouabaína/farmacologia , Potássio/metabolismo , Canais de Potássio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Células Epiteliais/metabolismo , Mamíferos/metabolismoRESUMO
Prostaglandins are a group of lipids that produce diverse physiological and pathological effects. Among them, prostaglandin E2 (PGE2) stands out for the wide variety of functions in which it participates. To date, there is little information about the influence of PGE2 on gap junctional intercellular communication (GJIC) in any type of tissue, including epithelia. In this work, we set out to determine whether PGE2 influences GJIC in epithelial cells (MDCK cells). To this end, we performed dye (Lucifer yellow) transfer assays to compare GJIC of MDCK cells treated with PGE2 and untreated cells. Our results indicated that (1) PGE2 induces a statistically significant increase in GJIC from 100 nM and from 15 min after its addition to the medium, (2) such effect does not require the synthesis of new mRNA or proteins subunits but rather trafficking of subunits already synthesized, and (3) such effect is mediated by the E2 receptor, which, in turn, triggers a signaling pathway that includes activation of adenylyl cyclase and protein kinase A (PKA). These results widen the knowledge regarding modulation of gap junctional intercellular communication by prostaglandins.
Assuntos
Comunicação Celular/efeitos dos fármacos , Dinoprostona/farmacologia , Células Epiteliais/efeitos dos fármacos , Junções Comunicantes/efeitos dos fármacos , Adenilil Ciclases/metabolismo , Animais , AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Cães , Relação Dose-Resposta a Droga , Células Epiteliais/citologia , Células Epiteliais/metabolismo , Junções Comunicantes/metabolismo , Células Madin Darby de Rim Canino , Receptores de Prostaglandina E Subtipo EP2/metabolismo , Transdução de Sinais/efeitos dos fármacos , Fatores de TempoRESUMO
Cannabidiol (CBD) has been used to treat a variety of cancers and inflammatory conditions with controversial results. In previous work, we have shown that breast cancer MCF-7 cells, selected by their response to inflammatory IL-1ß cytokine, acquire a malignant phenotype (6D cells) through an epithelial-mesenchymal transition (EMT). We evaluated CBD as a potential inhibitor of this transition and inducer of reversion to a non-invasive phenotype. It decreased 6D cell viability, downregulating expression of receptor CB1. The CBD blocked migration and progression of the IL-1ß-induced signaling pathway IL-1ß/IL-1RI/ß-catenin, the driver of EMT. Cannabidiol reestablished the epithelial organization lost by dispersion of the cells and re-localized E-cadherin and ß-catenin at the adherens junctions. It also prevented ß-catenin nuclear translocation and decreased over-expression of genes for ∆Np63α, BIRC3, and ID1 proteins, induced by IL-1ß for acquisition of malignant features. Cannabidiol inhibited the protein kinase B (AKT) activation, a crucial effector in the IL-1ß/IL-1RI/ß-catenin pathway, indicating that at this point there is crosstalk between IL-1ß and CBD signaling which results in phenotype reversion. Our 6D cell system allowed step-by-step analysis of the phenotype transition and better understanding of mechanisms by which CBD blocks and reverts the effects of inflammatory IL-1ß in the EMT.
Assuntos
Neoplasias da Mama/metabolismo , Canabidiol/farmacologia , Citocinas/metabolismo , Interleucina-1beta/metabolismo , Neoplasias da Mama/genética , Caderinas/metabolismo , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Regulação para Baixo , Transição Epitelial-Mesenquimal/efeitos dos fármacos , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Células MCF-7 , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais , Cicatrização , beta Catenina/metabolismoRESUMO
BACKGROUND/AIMS: Ouabain, a well-known plant-derived toxin, is also a hormone found in mammals at nanomolar levels that binds to a site located in the a-subunit of Naâº,Kâº-ATPase. Our main goal was to understand the physiological roles of ouabain. Previously, we found that ouabain increases the degree of tight junction sealing, GAP junction-mediated communication and ciliogenesis. Considering our previous results, we investigated the effect of ouabain on adherens junctions. METHODS: We used immunofluorescence and immunoblot methods to measure the effect of 10 nM ouabain on the cellular and nuclear content of E-cadherin, ß-catenin and γ-catenin in cultured monolayers of Marin Darby canine renal cells (MDCK). We also studied the effect of ouabain on adherens junction biogenesis through sequential Ca²âº removal and replenishment. Then, we investigated whether c-Src and ERK1/2 kinases are involved in these responses. RESULTS: Ouabain enhanced the cellular content of the adherens junction proteins E-cadherin, ß-catenin and γ-catenin and displaced ß-catenin and γ-catenin from the plasma membrane into the nucleus. Ouabain also increased the expression levels of E-cadherin and ß-catenin in the plasma membrane after Ca²âº replenishment. These effects on adherens junctions were sensitive to PP2 and PD98059, suggesting that they depend on c-Src and ERK1/2 signaling. The translocation of ß-catenin and γ-catenin into the nucleus was specific because ouabain did not change the localization of the tight junction proteins ZO-1 and ZO-2. Moreover, in ouabain-resistant MDCK cells, which express a Naâº,Kâº-ATPase α1-subunit with low affinity for ouabain, this hormone was unable to regulate adherens junctions, indicating that the ouabain receptor that regulates adherens junctions is Naâº,Kâº-ATPase. CONCLUSION: Ouabain (10 nM) upregulated adherens junctions. This novel result supports the proposition that one of the physiological roles of this hormone is the modulation of cell contacts.
Assuntos
Junções Aderentes/efeitos dos fármacos , Ouabaína/farmacologia , Junções Aderentes/metabolismo , Animais , Proteína Tirosina Quinase CSK , Caderinas/metabolismo , Cálcio/metabolismo , Núcleo Celular/metabolismo , Cães , Células Madin Darby de Rim Canino , Microscopia de Fluorescência , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Transdução de Sinais/efeitos dos fármacos , ATPase Trocadora de Sódio-Potássio/metabolismo , beta Catenina/metabolismo , gama Catenina/metabolismo , Quinases da Família src/metabolismoRESUMO
Cardiac glycosides are a group of compounds widely known for their action in cardiac tissue, some of which have been found to be endogenously produced (ECG). We have previously studied the effect of ouabain, an endogenous cardiac glycoside, on the physiology of epithelial cells, and we have shown that in concentrations in the nanomolar range, it affects key properties of epithelial cells, such as tight junction, apical basolateral polarization, gap junctional intercellular communication (GJIC), and adherent junctions. In this work, we study the influence of digoxin and marinobufagenin, two other endogenously expressed cardiac glycosides, on GJIC as well as the degree of transepithelial tightness due to tight junction integrity (TJ). We evaluated GJIC by dye transfer assays and tight junction integrity by transepithelial electrical resistance (TER) measurements, as well as immunohistochemistry and western blot assays of expression of claudins 2 and 4. We found that both digoxin and marinobufagenin improve GJIC and significantly enhance the tightness of the tight junctions, as evaluated from TER measurements. Immunofluorescence assays show that both compounds promote enhanced basolateral localization of claudin-4 but not claudin 2, while densitometric analysis of western blot assays indicate a significantly increased expression of claudin 4. These changes, induced by digoxin and marinobufagenin on GJIC and TER, were not observed on MDCK-R, a modified MDCK cell line that has a genetically induced insensitive α1 subunit, indicating that Na-K-ATPase acts as a receptor mediating the actions of both ECG. Plus, the fact that the effect of both cardiac glycosides was suppressed by incubation with PP2, an inhibitor of c-Src kinase, PD98059, an inhibitor of mitogen extracellular kinase-1 and Y-27632, a selective inhibitor of ROCK, and a Rho-associated protein kinase, indicate altogether that the signaling pathways involved include c-Src and ERK1/2, as well as Rho-ROCK. These results widen and strengthen our general hypothesis that a very important physiological role of ECG is the control of the epithelial phenotype and the regulation of cell-cell contacts.
RESUMO
Inflammation and oxidative stress play major roles in endothelial dysfunction, and are key factors in the progression of cardiovascular diseases. The aim of this study was to evaluate in vitro the effect of three subfractions (SFs) from the Cucumis sativus aqueous fraction to reduce inflammatory factors and oxidative stress induced by angiotensin II (Ang II) in human microvascular endothelial cells-1 (HMEC-1) cells. The cells were cultured with different concentrations of Ang II and 0.08 or 10 µg/mL of SF1, SF2, or SF3, or 10 µmol of losartan as a control. IL-6 (Interleukin 6) concentration was quantified. To identify the most effective SF combinations, HMEC-1 cells were cultured as described above in the presence of four combinations of SF1 and SF3. Then, the effects of the most effective combination on the expression of adhesion molecules, the production of reactive oxygen species (ROS), and the bioavailability of nitric oxide (NO) were evaluated. Finally, a mass spectrometry analysis was performed. Both SF1 and SF3 subfractions decreased the induction of IL-6 by Ang II, and C4 (SF1 and SF3, 10 µg/mL each) was the most effective combination to inhibit the production of IL-6. Additionally, C4 prevented the expression of adhesion molecules, reduced the production of ROS, and increased the bioavailability of NO. Glycine, arginine, asparagine, lysine, and aspartic acid were the main components of both subfractions. These results demonstrate that C4 has anti-inflammatory and antioxidant effects.
Assuntos
Aminoácidos/farmacologia , Angiotensina II/toxicidade , Anti-Inflamatórios/farmacologia , Antioxidantes/farmacologia , Cucumis sativus , Células Endoteliais/efeitos dos fármacos , Inflamação/prevenção & controle , Estresse Oxidativo/efeitos dos fármacos , Extratos Vegetais/farmacologia , Aminoácidos/isolamento & purificação , Anti-Inflamatórios/isolamento & purificação , Antioxidantes/isolamento & purificação , Moléculas de Adesão Celular/metabolismo , Linhagem Celular , Cucumis sativus/química , Relação Dose-Resposta a Droga , Células Endoteliais/metabolismo , Humanos , Inflamação/induzido quimicamente , Inflamação/metabolismo , Mediadores da Inflamação/metabolismo , Interleucina-6/metabolismo , Óxido Nítrico/metabolismo , Fitoterapia , Extratos Vegetais/isolamento & purificação , Plantas Medicinais , Espécies Reativas de Oxigênio/metabolismoRESUMO
In addition to being a very well-known ion pump, Na(+), K(+)-ATPase is a cell-cell adhesion molecule and the receptor of digitalis, which transduces regulatory signals for cell adhesion, growth, apoptosis, motility and differentiation. Prolonged ouabain (OUA) blockage of activity of Na(+), K(+)-ATPase leads to cell detachment from one another and from substrates. Here, we investigated the cellular mechanisms involved in tight junction (TJ) disassembly upon exposure to toxic levels of OUA (≥300 nM) in epithelial renal canine cells (MDCK). OUA induces a progressive decrease in the transepithelial electrical resistance (TER); inhibitors of the epidermal growth factor receptor (EGFR, PD153035), cSrc (SU6656 and PP2) and ERK1/2 kinases (PD98059) delay this decrease. We have determined that the TER decrease depends upon internalization and degradation of the TJs proteins claudin (CLDN) 2, CLDN-4, occludin (OCLN) and zonula occludens-1 (ZO-1). OUA-induced degradation of proteins is either sensitive (CLDN-4, OCLN and ZO-1) or insensitive (CLDN-2) to ERK1/2 inhibition. In agreement with the protein degradation findings, OUA decreases the cellular content of ZO-1 and CLDN-2 mRNAs but surprisingly, increases the mRNA of CLDN-4 and OCLN. Changes in the mRNA levels are sensitive (CLDN-4, OCLN and ZO-1) or insensitive (CLDN-2) to ERK1/2 inhibition as well. Thus, toxic levels of OUA activate the EGFR-cSrc-ERK1/2 pathway to induce endocytosis, internalization and degradation of TJ proteins. We also observed decreases in the levels of CLDN-2 protein and mRNA, which were independent of the EGFR-cSrc-ERK1/2 pathway.
Assuntos
Endocitose/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Ouabaína/farmacologia , Proteólise/efeitos dos fármacos , Proteínas de Junções Íntimas/metabolismo , Animais , Células Cultivadas , Cães , Células Madin Darby de Rim CaninoRESUMO
The exchange of substances between higher organisms and the environment occurs across transporting epithelia whose basic features are tight junctions (TJs) that seal the intercellular space, and polarity, which enables cells to transport substances vectorially. In a previous study, we demonstrated that 10 nM ouabain modulates TJs, and we now show that it controls polarity as well. We gauge polarity through the development of a cilium at the apical domain of Madin-Darby canine kidney cells (MDCK, epithelial dog kidney). Ouabain accelerates ciliogenesis in an ERK1/2-dependent manner. Claudin-2, a molecule responsible for the Na(+) and H(2)O permeability of the TJs, is also present at the cilium, as it colocalizes and coprecipitates with acetylated α-tubulin. Ouabain modulates claudin-2 localization at the cilium through ERK1/2. Comparing wild-type and ouabain-resistant MDCK cells, we show that ouabain acts through Na(+),K(+)-ATPase. Taken together, our previous and present results support the possibility that ouabain constitutes a hormone that modulates the transporting epithelial phenotype, thereby playing a crucial role in metazoan life.
Assuntos
Cílios/metabolismo , Células Epiteliais/metabolismo , Ouabaína/química , Animais , Caderinas/metabolismo , Adesão Celular , Comunicação Celular , Linhagem Celular , Proliferação de Células , Claudinas/metabolismo , Cães , Imunoprecipitação , Espectroscopia de Ressonância Magnética/métodos , Ouabaína/farmacologia , ATPase Trocadora de Sódio-Potássio/metabolismo , Esteroides/metabolismo , Junções Íntimas , Fatores de TempoRESUMO
Epithelial cells treated with high concentrations of ouabain (e.g., 1 microM) retrieve molecules involved in cell contacts from the plasma membrane and detach from one another and their substrates. On the basis of this observation, we suggested that ouabain might also modulate cell contacts at low, nontoxic levels (10 or 50 nM). To test this possibility, we analyzed its effect on a particular type of cell-cell contact: the tight junction (TJ). We demonstrate that at concentrations that neither inhibit K(+) pumping nor disturb the K(+) balance of the cell, ouabain modulates the degree of sealing of the TJ as measured by transepithelial electrical resistance (TER) and the flux of neutral 3 kDa dextran (J(DEX)). This modulation is accompanied by changes in the levels and distribution patterns of claudins 1, 2, and 4. Interestingly, changes in TER, J(DEX), and claudins behavior are mediated through signal pathways containing ERK1/2 and c-Src, which have distinct effects on each physiological parameter and claudin type. These observations support the theory that at low concentrations, ouabain acts as a modulator of cell-cell contacts.