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Nature Metabolism Nov 2019Senescence is a cellular stress response that results in the stable arrest of old, damaged or preneoplastic cells. Oncogene-induced senescence is tumor suppressive but...
Senescence is a cellular stress response that results in the stable arrest of old, damaged or preneoplastic cells. Oncogene-induced senescence is tumor suppressive but can also exacerbate tumorigenesis through the secretion of pro-inflammatory factors from senescent cells. Drugs that selectively kill senescent cells, termed senolytics, have proved beneficial in animal models of many age-associated diseases. Here, we show that the cardiac glycoside, ouabain, is a senolytic agent with broad activity. Senescent cells are sensitized to ouabain-induced apoptosis, a process mediated in part by induction of the pro-apoptotic Bcl2-family protein NOXA. We show that cardiac glycosides synergize with anti-cancer drugs to kill tumor cells and eliminate senescent cells that accumulate after irradiation or in old mice. Ouabain also eliminates senescent preneoplastic cells. Our findings suggest that cardiac glycosides may be effective anti-cancer drugs by acting through multiple mechanism. Given the broad range of senescent cells targeted by cardiac glycosides their use against age-related diseases warrants further exploration.
Topics: Animals; Antineoplastic Agents; Apoptosis; Cardiac Glycosides; Cellular Senescence; Humans; Mice; Ouabain; Quercetin; Rats
PubMed: 31799499
DOI: 10.1038/s42255-019-0122-z -
Annals of the Rheumatic Diseases Apr 2022Dysregulated chondrocyte metabolism is closely associated with the pathogenesis of osteoarthritis (OA). Suppressing chondrocyte catabolism to restore cartilage...
OBJECTIVES
Dysregulated chondrocyte metabolism is closely associated with the pathogenesis of osteoarthritis (OA). Suppressing chondrocyte catabolism to restore cartilage homeostasis has been extensively explored, whereas far less effort has been invested toward enhancing chondrocyte anabolism. This study aimed to repurpose clinically approved drugs as potential stimulators of chondrocyte anabolism in treating OA.
METHODS
Screening of a Food and Drug Administration-approved drug library; Assays for examining the chondroprotective effects of digoxin in vitro; Assays for defining the therapeutic effects of digoxin using a surgically-induced OA model; A propensity-score matched cohort study using The Health Improvement Network to examine the relationship between digoxin use and the risk of joint OA-associated replacement among patients with atrial fibrillation; identification and characterisation of the binding of digoxin to low-density lipoprotein receptor-related protein 4 (LRP4); various assays, including use of CRISPR-Cas9 genome editing to delete LRP4 in human chondrocytes, for examining the dependence on LRP4 of digoxin regulation of chondrocytes.
RESULTS
Serial screenings led to the identification of ouabain and digoxin as stimulators of chondrocyte differentiation and anabolism. Ouabain and digoxin protected against OA and relieved OA-associated pain. The cohort study of 56 794 patients revealed that digoxin use was associated with reduced risk of OA-associated joint replacement. LRP4 was isolated as a novel target of digoxin, and deletion of LRP4 abolished digoxin's regulations of chondrocytes.
CONCLUSIONS
These findings not only provide new insights into the understanding of digoxin's chondroprotective action and underlying mechanisms, but also present new evidence for repurposing digoxin for OA.
Topics: Cartilage, Articular; Chondrocytes; Cohort Studies; Digoxin; Drug Repositioning; Humans; LDL-Receptor Related Proteins; Osteoarthritis; Ouabain
PubMed: 34853001
DOI: 10.1136/annrheumdis-2021-221380 -
Toxins May 2021Cardiac glycosides (CGs), toxins well-known for numerous human and cattle poisoning, are natural compounds, the biosynthesis of which occurs in various plants and... (Review)
Review
Cardiac glycosides (CGs), toxins well-known for numerous human and cattle poisoning, are natural compounds, the biosynthesis of which occurs in various plants and animals as a self-protective mechanism to prevent grazing and predation. Interestingly, some insect species can take advantage of the CG's toxicity and by absorbing them, they are also protected from predation. The mechanism of action of CG's toxicity is inhibition of Na/K-ATPase (the sodium-potassium pump, NKA), which disrupts the ionic homeostasis leading to elevated Ca concentration resulting in cell death. Thus, NKA serves as a molecular target for CGs (although it is not the only one) and even though CGs are toxic for humans and some animals, they can also be used as remedies for various diseases, such as cardiovascular ones, and possibly cancer. Although the anticancer mechanism of CGs has not been fully elucidated, yet, it is thought to be connected with the second role of NKA being a receptor that can induce several cell signaling cascades and even serve as a growth factor and, thus, inhibit cancer cell proliferation at low nontoxic concentrations. These growth inhibitory effects are often observed only in cancer cells, thereby, offering a possibility for CGs to be repositioned for cancer treatment serving not only as chemotherapeutic agents but also as immunogenic cell death triggers. Therefore, here, we report on CG's chemical structures, production optimization, and biological activity with possible use in cancer therapy, as well as, discuss their antiviral potential which was discovered quite recently. Special attention has been devoted to digitoxin, digoxin, and ouabain.
Topics: Animals; Antineoplastic Agents; Cardiac Glycosides; Cattle; Digitoxin; Digoxin; Humans; Molecular Targeted Therapy; Neoplasms; Ouabain; Sodium-Potassium-Exchanging ATPase
PubMed: 34064873
DOI: 10.3390/toxins13050344 -
Cell Communication and Signaling : CCS Oct 2023Acute myeloid leukemia (AML) is an aggressive hematologic malignancy characterized by an accumulation of immature leukemic myeloblasts initiating from leukemic stem...
BACKGROUND
Acute myeloid leukemia (AML) is an aggressive hematologic malignancy characterized by an accumulation of immature leukemic myeloblasts initiating from leukemic stem cells (LSCs)-the subpopulation that is also considered the root cause of chemotherapy resistance. Repurposing cardiac glycosides to treat cancers has gained increasing attention and supporting evidence, but how cardiac glycosides effectively target LSCs, e.g., whether it involves cell differentiation, remains largely unexplored.
METHODS
Digoxin, a user-designed digitoxigenin-α-L-rhamnoside (D6-MA), and ouabain were tested against various human AML-derived cells with different maturation phenotypes. Herein, we established two study models to specifically determine the effects of cardiac glycosides on LSC death and differentiation-one allowed change in dynamics of LSCs and leukemic progenitor cells (LPCs), while another maintained their undifferentiated status. Regulatory mechanisms underlying cardiac glycoside-induced cytotoxicity were investigated and linked to cell cycle distribution and apoptotic machinery.
RESULTS
Primitive AML cells containing CD34 LSCs/LPCs were very responsive to nanomolar concentrations of cardiac glycosides, with ouabain showing the greatest efficiency. Ouabain preferentially induces caspase-dependent apoptosis in LSCs, independent of its cell differentiation status, as evidenced by (i) the tremendous induction of apoptosis by ouabain in AML cells that acquired less than 15% differentiation and (ii) the higher rate of apoptosis in enriched LSCs than in LPCs. We sorted LSCs and LPCs according to their cell cycle distribution into G0/G1, S, and G2/M cells and revealed that G0/G1 cells in LSCs, which was its major subpopulation, were the top ouabain responders, indicating that the difference in ouabain sensitivity between LSCs and LPCs involved both distinct cell cycle distribution and intrinsic apoptosis regulatory mechanisms. Further, Mcl-1 and c-Myc, which were differentially expressed in LSCs and LPCs, were found to be the key apoptosis mediators that determined ouabain sensitivity in AML cells. Ouabain induces a more rapid loss of Mcl-1 and c-Myc in LSCs than in LPCs via the mechanisms that in part involve an inhibition of Mcl-1 protein synthesis and an induction of c-Myc degradation.
CONCLUSIONS
Our data provide new insight for repurposing cardiac glycosides for the treatment of relapsed/refractory AML through targeting LSCs via distinct cell cycle and apoptosis machinery. Video Abstract.
Topics: Humans; Cardiac Glycosides; Ouabain; Myeloid Cell Leukemia Sequence 1 Protein; Leukemia, Myeloid, Acute; Cell Differentiation; Stem Cells; Neoplastic Stem Cells; Apoptosis
PubMed: 37828578
DOI: 10.1186/s12964-023-01317-8 -
Hypertension (Dallas, Tex. : 1979) Sep 2016In this brief article, we summarize recent reports about endogenous ouabain (EO), a cardiotonic steroid (CTS). This includes analysis of mammalian EO, the discovery of... (Review)
Review
In this brief article, we summarize recent reports about endogenous ouabain (EO), a cardiotonic steroid (CTS). This includes analysis of mammalian EO, the discovery of EO isomers, regulation of intracellular signaling by EO, and the roles of EO in hypertension, pregnancy, and heart and kidney diseases. Novel ouabain-resistant mice that elucidate the key roles of α2 Na pumps and their CTS binding site are also discussed.
Topics: Adrenal Cortex; Animals; Blood Pressure Determination; Cardiovascular Diseases; Female; Humans; Hypertension; Kidney Diseases; Male; Mice; Needs Assessment; Ouabain; Sodium-Potassium-Exchanging ATPase
PubMed: 27456525
DOI: 10.1161/HYPERTENSIONAHA.116.06599 -
Bulletin of Experimental Biology and... Mar 2023The effects of cardiotonic steroids (ouabain and digoxin) on the bone formation were studied using the organotypic tissue culture in combination with confocal...
The effects of cardiotonic steroids (ouabain and digoxin) on the bone formation were studied using the organotypic tissue culture in combination with confocal microscopy. The expression of α- and α-isoforms of Na,K-ATPase was detected in cells of the bone tissue of 12-day-old chicken embryos. Ouabain in a concentrations 10 M (comparable with its endogenous concentration) can modulate transducer function of Na,K-ATPase and control the growth and proliferation bone tissue cells. Unlike ouabain, digoxin is not involved in the regulation of bone tissue growth in a 12-day-old chicken embryo.
Topics: Animals; Chick Embryo; Ouabain; Sodium-Potassium-Exchanging ATPase; Digoxin; Protein Isoforms; Sodium; Bone Remodeling
PubMed: 37046115
DOI: 10.1007/s10517-023-05768-4 -
Current Opinion in Nephrology and... Mar 2017Primary hypertension is characterized by Na excess and K deficit in the body, which together are key to its pathogenesis. These derangements work jointly in the brain... (Review)
Review
PURPOSE OF REVIEW
Primary hypertension is characterized by Na excess and K deficit in the body, which together are key to its pathogenesis. These derangements work jointly in the brain and the peripheral vascular wall to establish hypertension. In this review, we highlight recent evidence describing the central mechanisms through which Na surfeit and K deficit enhance sympathetic nerve activity, thereby raising peripheral vascular resistance and generating hypertension.
RECENT FINDINGS
Animal studies point to a small increase in plasma and cerebrospinal fluid (CSF) [Na], a small decrease in CSF [K], and increased levels of circulating angiotensin II, aldosterone, and endogenous ouabain as the central signals evoking hypertension. These signals are detected by circumventricular organ sensors in the forebrain, and are then relayed to hypothalamic nuclei, which project angiotensinergic effector pathways to brainstem nuclei and spinal preganglionic neurons, triggering increased sympathetic nerve activity and hypertension. These central processes depend on a noncirculating (brain) renin-angiotensin-aldosterone system, local production of endogenous ouabain, and increased oxidative stress.
SUMMARY
Recent insights into the mechanisms mediating the central effects of Na excess and K deficit on raising sympathetic activity might pave the way for novel approaches to preventing and treating hypertensive disorders.
Topics: Aldosterone; Angiotensin II; Animals; Brain; Humans; Hypertension; Ouabain; Oxidative Stress; Potassium; Renin-Angiotensin System; Sodium; Sympathetic Nervous System; Vascular Resistance
PubMed: 27906749
DOI: 10.1097/MNH.0000000000000301 -
International Journal of Molecular... Jun 2024The sodium pump, or Na/K-ATPase (NKA), is an essential enzyme found in the plasma membrane of all animal cells. Its primary role is to transport sodium (Na) and... (Review)
Review
The sodium pump, or Na/K-ATPase (NKA), is an essential enzyme found in the plasma membrane of all animal cells. Its primary role is to transport sodium (Na) and potassium (K) ions across the cell membrane, using energy from ATP hydrolysis. This transport creates and maintains an electrochemical gradient, which is crucial for various cellular processes, including cell volume regulation, electrical excitability, and secondary active transport. Although the role of NKA as a pump was discovered and demonstrated several decades ago, it remains the subject of intense research. Current studies aim to delve deeper into several aspects of this molecular entity, such as describing its structure and mode of operation in atomic detail, understanding its molecular and functional diversity, and examining the consequences of its malfunction due to structural alterations. Additionally, researchers are investigating the effects of various substances that amplify or decrease its pumping activity. Beyond its role as a pump, growing evidence indicates that in various cell types, NKA also functions as a receptor for cardiac glycosides like ouabain. This receptor activity triggers the activation of various signaling pathways, producing significant morphological and physiological effects. In this report, we present the results of a comprehensive review of the most outstanding studies of the past five years. We highlight the progress made regarding this new concept of NKA and the various cardiac glycosides that influence it. Furthermore, we emphasize NKA's role in epithelial physiology, particularly its function as a receptor for cardiac glycosides that trigger intracellular signals regulating cell-cell contacts, proliferation, differentiation, and adhesion. We also analyze the role of NKA β-subunits as cell adhesion molecules in glia and epithelial cells.
Topics: Sodium-Potassium-Exchanging ATPase; Animals; Humans; Cell Membrane; Signal Transduction; Ouabain; Cardiac Glycosides; Sodium
PubMed: 38892309
DOI: 10.3390/ijms25116122 -
International Immunopharmacology Aug 2022Ouabain, an inhibitor of Na+/K+-ATPase, is a type of endogenous hormone synthesized in the adrenal cortex and hypothalamus. Previous studies found that ouabain potently...
OBJECTIVE
Ouabain, an inhibitor of Na+/K+-ATPase, is a type of endogenous hormone synthesized in the adrenal cortex and hypothalamus. Previous studies found that ouabain potently inhibited acute inflammatory reactions such as type 2 inflammation and regulated immunological processes. In this study, we aimed to investigate ouabain effect on allergic asthma.
METHODS
BALB/c mice were submitted to chronic airway allergic inflammation induced by an ovalbumin (OVA) protocol. The animals were treated with ouabain or standard drug, budesonide. The following parameters were evaluated: cell migration, cytokine profile, IgE levels, lung histological modifications and MAPK activation.
RESULTS
At first, it was observed that ouabain reduced OVA-induced cell migration into the lung, observed by bronchoalveolar lavage fluid (BALF) cell counting and lung histological analysis (HE stain). Additionally, ouabain negatively modulated alarmins (IL-33 and TSLP), Th2 high cytokines levels (IL-1β and IL-4) and tissue remodeling markers such as TNF-α and TGF-β. Treatment with ouabain also reduced OVA-specific IgE titers in BALF and serum, respectively, when compared to the OVA group. Lung histological parameters, including collagen deposition and mucus production induced by OVA were also attenuated by ouabain treatment. Finally, our results showed that p38 mitogen-activated protein kinase (MAPK) signaling pathways were suppressed by ouabain in this model. All these parameters were reduced by budesonide, a steroidal anti-inflammatory standard drug.
CONCLUSION
These data together suggest that, in addition to its acute anti-inflammatory action, ouabain is also able to modulate allergic asthma.
Topics: Airway Remodeling; Animals; Anti-Inflammatory Agents; Asthma; Bronchoalveolar Lavage Fluid; Budesonide; Cytokines; Disease Models, Animal; Immunoglobulin E; Inflammation; Lung; Mice; Mice, Inbred BALB C; Ouabain; Ovalbumin
PubMed: 35504206
DOI: 10.1016/j.intimp.2022.108808 -
American Journal of Physiology. Cell... Apr 2024Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the... (Review)
Review
Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na/Ca exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.
Topics: Humans; Rats; Animals; Ouabain; Sodium-Potassium-Exchanging ATPase; Ligands; Digoxin; Cardiotonic Agents; Hypertension; Heart Failure; Enzyme Inhibitors; Calcium Signaling; Binding Sites
PubMed: 38223926
DOI: 10.1152/ajpcell.00273.2023