Role Of Ouabain Research Articles

ROSTAFUROXIN RESTORES THE INCREASED PERIVASCULAR INNERVATION IN RESISTANCE ARTERIES OF HYPERTENSIVE RATS

Objective: Ouabain (OUA) inhibiting Na+, K+-ATPase (NKA) activity modulates neurotransmitter release from perivascular innervation (PVI). However, the role of OUA on PVI through NKA/cSRC signalosome pathway is unknown. Thus, we investigated the role of rostafuroxin (ROSTA) treatment, an OUA signalosome pathway antagonist, on PVI of mesenteric resistance arteries (MRAs) from deoxycorticosterone acetate-salt (DOCA-salt) hypertensive rats, mainly on sympathetic and nitrergic PVI participation. Design and method: Five-week after DOCA-salt treatment, rats were allocated into two groups: DOCA-salt treated with ROSTA (1 mg/kg per day gavage, 3 weeks) or vehicle. Male, Wistar rats uninephrectomized were used as normal control (NC). Systolic blood pressure (SBP) was measured weekly by tail-cuff method. Electric field stimulation (EFS), noradrenaline (NA) and sodium nitroprusside (SNP) response-curves were evaluated in isolated MRA without endothelium. Results: ROSTA treatment decreased SBP (42%) compared to DOCA-salt. EFS induced contractile response in MRAs of all groups, while this response was higher in DOCA-salt compared to NC or ROSTA group. EFS-induced contraction was reduced in the presence of alfa-adrenoceptor antagonist (phentolamine, PNT) in all groups, whereas this contractile response was blocked by the association between PNT and suramin (P2-purinergic receptor antagonist) only in NC and ROSTA groups. L-NAME enhanced the contraction induced by EFS; however, this effect was smaller in DOCA-salt rings compared to NC and ROSTA. EFS-induced contraction was abolished in MRAs preincubated with tetrodotoxin (voltage-dependent sodium channel blocker). On the other hand, concentration–response curves to exogenous NA and SNP were unmodified among groups. Conclusions: ROSTA treatment was able to reduce perivascular sympathetic innervation and to increase nitrergic innervation on the contractile response to EFS in MRAs of DOCA-salt rats. These modifications might contribute to the beneficial effects of OUA/NKA/cSRC pathway antagonism on volume-dependent hypertension.

Novel role of ouabain as a cystogenic factor in autosomal dominant polycystic kidney disease

The classic role of the Na-K-ATPase is that of a primary active transporter that utilizes cell energy to establish and maintain transmembrane Na(+) and K(+) gradients to preserve cell osmotic stability, support cell excitability, and drive secondary active transport. Recent studies have revealed that Na-K-ATPase located within cholesterol-containing lipid rafts serves as a receptor for cardiotonic steroids, including ouabain. Traditionally, ouabain was viewed as a toxin produced only in plants, and it was used in relatively high concentrations to experimentally block the pumping action of the Na-K-ATPase. However, the new and unexpected role of the Na-K-ATPase as a signal transducer revealed a novel facet for ouabain in the regulation of a myriad of cell functions, including cell proliferation, hypertrophy, apoptosis, mobility, and metabolism. The seminal discovery that ouabain is endogenously produced in mammals and circulates in plasma has fueled the interest in this endogenous molecule as a potentially important hormone in normal physiology and disease. In this article, we review the role of the Na-K-ATPase as an ion transporter in the kidney, the experimental evidence for ouabain as a circulating hormone, the function of the Na-K-ATPase as a signal transducer that mediates ouabain's effects, and novel results for ouabain-induced Na-K-ATPase signaling in cystogenesis of autosomal dominant polycystic kidney disease.

Abstract 3335: Ouabain, a cardiac glycoside, inhibits the Fanconi Anemia-BRCA pathway activated by DNA crosslinking agents.

Abstract Most cancer therapies, including conventional chemotherapy and radiotherapy, are based on DNA damage-induced tumor cell death. In tumor cells, cellular DNA repair machinery can decrease anticancer drug efficacy and induce drug resistance. The DNA repair pathway has been an emerging target for development of anticancer drugs. DNA intercrosslinking, one of the most severe forms of DNA damage which are caused by anticancer drugs, such as cisplatin and mitomycin C (MMC), could activate the Fanconi anemia (FA)-BRCA DNA repair pathway. Inhibition of the FA-BRCA pathway can enhance the cytotoxic effects of anticancer drugs which induce DNA crosslinking and can reduce anticancer drug resistance. To find FA-BRCA pathway inhibitory small molecules, we established a cell-based high-content screening method for detecting the FA-BRCA pathway by measuring ubiquitinated FANCD2 foci on DNA lesions after immunofluorescence staining and then we applied our method to chemical screening. Using commercial LOPAC1280 chemical library screening, ouabain was identified as a competent FA-BRCA pathway inhibitory molecule. Ouabain, a member of the cardiac glycoside family and an endogenous mammalian hormone, binds to and inhibits the plasma membrane protein Na+/K+-ATPase and has been used for the treatment of heart disease for many years. We observed that ouabain, as well as its cardiac glycoside family members―digitoxin and digoxin―reduced monoubiquitination of FANCD2, inhibited ubiquitinated FANCD2 foci formation on DNA lesions and abrogated cell cycle arrest induced by MMC treatment. These inhibitory activities of the FA-BRCA pathway were independent of the cellular Ca++ ion increase or the drug uptake-inhibition effect which is known to be a function of ouabain. Furthermore, we found that ouabain potentiated cytotoxic effects of MMC in tumor cells. Taken together, we identified an additional role of ouabain as a FA-BRCA pathway inhibitor which has chemosensitization activity. The results of this study suggest that ouabain may serve as a chemosensitizer to anticancer drugs which induce DNA crosslinking. Citation Format: Mihwa Hwang, Dong Wha Jun, Hyun Jung Kim, Soo Kyung Hwang, Chang-Hun Lee, Sunshin Kim. Ouabain, a cardiac glycoside, inhibits the Fanconi Anemia-BRCA pathway activated by DNA crosslinking agents. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3335. doi:10.1158/1538-7445.AM2013-3335

Role of ouabain and diuretics on sodium, potassium and chloride retention in perfused rat kidney

1. 1. A novel in situ kidney perfusion technique is described in Sprague-Dawley rats. The procedure involves retrograde perfusion from the renal veins via the kidneys, and then through the renal arteries and dorsal aorta. 2. 2. Ouabain (15 mM) in perfusate increased Na retention by 92%, decreased K. retention by 53% and produced no effect on Cl retention. 3. 3. Ethacrynic acid (1 mM) in perfusate decreased Na retention by 52%, increased K retention by 105% and decreased Cl retention by 27%. 4. 4. Furosemide (1.5 mM) in perfusate decreased Na retention by 52%, increased K retention by 47% and decreased Cl retention by 56%. 5. 5. The Na-K-ATPase pump localized at the peritubular side of the proximal tubule cell is ouabain sensitive and Mg dependent. 6. 6. An Na-K pump responsible for Na influx and K efflux exists at the luminal side of the proximal tubule cell and is ethacrynic acid and furosemide sensitive.

Studies on (Na+K+)-activated ATPase XVII. Effect of ouabain and erythrophleine on potassium concentration and membrane potential of frog sartorius muscle

Abstract 1. 1. The effect of ouabain and erythrophleine on K + , Na + and Cl − concentrations and membrane potential in frog sartorius muscle was studied in view of reports that changes in internal ionic concentrations would not be concerned in the effect of ouabain on membrane potential. 2. 2. The two drugs each caused a decrease in membrane potential and K + concentration. The observed change in potential agreed with the expected change calculated from the decrease in K + concentration. 3. 3. There was also an uptake of Na + , larger than the loss of K + , and an uptake of Cl − equivalent to the excess Na + uptake, as well as an uptake of water sufficient to make the entering NaCl solution isotonic. 4. 4. The results are in quantitative as well as qualitative agreement with a role of ouabain- and erythrophleine-sensitive (Na + K + )-activated ATPase in the cation transport of frog sartorius muscle.

The role of ouabain in myocardial insufficiency during anesthesia and surgery ∗

The pathogenesis of myocardial insufficiency during anesthesia and surgery is shown to be related to alterations in effective circulating blood volume as well as the directly depressant effects of anesthetic drugs on the myocardium. Stress is laid upon considering myocardial insufficiency in any differential diagnosis of the cause of hypotension in an anesthetized subject. A rational method for treating this state with ouabain, relating the known pharmacology of the drug to known pathologic changes in “shock” states, is presented. The key to these concepts is found in presently available knowledge of the effects of drugs on energy release mechanisms of the myocardium.