Endothelial progenitor cells (EPCs) may be recruited from the bone marrow to sites of tissue regeneration to sustain neovascularization and reendothelialization after acute vascular injury. This feature makes them particularly suitable for cell-based therapy. In mature endothelium, store-operated Ca(2+) entry (SOCE) is activated following emptying of inositol-1,4,5-trisphosphate-sensitive stores, and controls a wide number of functions, including proliferation, nitric oxide synthesis, and vascular permeability. The present work aimed at investigating SOCE expression in EPCs harvested from both peripheral blood (PB-EPCs) and umbilical cord blood (UCB-EPCs) by employing both Ca(2+) imaging and molecular biology techniques. SOCE was induced upon either pharmacological (ie, cyclopiazonic acid) or physiological (ie, ATP) depletion of the intracellular Ca(2+) pool. Further, store-dependent Ca(2+) entry was inhibited by the SOCE inhibitor, N-(4-[3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl]phenyl)-4-methyl-1,2,3-thiadiazole-5-carboxamide (BTP-2). Real-time reverse transcription-polymerase chain reaction and western blot analyses showed that both PB-EPCs and UCB-EPCs express all the molecular candidates to mediate SOCE in differentiated cells, including TRPC1, TRPC4, Orai1, and Stim1. Moreover, pharmacological maneuvers demonstrated that, as well as in differentiated endothelial cells, the signal transduction pathway leading to depletion of the intracellular Ca(2+) pool impinged on the phospholipase C/inositol-1,4,5-trisphosphate pathway. Finally, blockage of SOCE with BTP-2 impaired PB-EPC proliferation. These findings provide the first evidence that EPCs express SOCE, which might thus be regarded as a novel target to enhance the regenerative outcome of cell-based therapy.

The Na(+)-K(+)-ATPase (NKA) differs from most other ion transporters, not only in its capacity to maintain a steep electrochemical gradient across the plasma membrane, but also as a receptor for a family of cardiotonic steroids, to which ouabain belongs. Studies from many groups, performed during the last 15 years, have demonstrated that ouabain, a member of the cardiotonic steroid family, can activate a network of signaling molecules, and that NKA will also serve as a signal transducer that can provide a feedback loop between NKA and the mitochondria. This brief review summarizes the current knowledge and controversies with regard to the understanding of NKA signaling.

No abstract

Background information. Celiac disease is a chronic inflammatory disorder of the small bowel induced in genetically susceptible subjects by gluten ingestion. Diarrhoea, weight loss and malabsorption represent the major clinical presentation of the disease. Here we examined the possible alteration in the expression and localization of water channels [AQPs (aquaporins)] and some solute transporters in duodenal mucosa of celiac disease patients. Duodenal biopsies from untreated celiacs, treated celiacs, healthy controls and disease controls were considered in the present study. The expressions of some AQPs and transporter mRNAs in human duodenal biopsies were determined by semi‐quantitative RT—PCR (reverse transcription PCR) and real‐time RT—PCR. The localization of AQPs 3, 7 and 10 and of SGLT1 (Na+/glucose co‐transporter 1), PEPT1 (H+/oligopeptide transporter 1) and NHE3 (Na+/H+ exchanger 3) was evaluated by immunohistochemistry. Results. AQPs 3, 7, 10 and 11, SGLT, PEPT and NHE, CFTR (cystic fibrosis transmembrane conductance regulator) and NKCC (Na‐K‐2Cl co‐transporter) mRNAs were expressed in duodenal biopsies of healthy controls, treated celiac patients and disease controls. The expression of transcripts was virtually absent in duodenal biopsies of untreated celiac disease patients except for CFTR and NKCC. In healthy controls, immunohistochemistry revealed a labelling in the apical membrane of surface epithelial cells of the duodenum. The immunolabelling was heavily reduced or absent in untreated celiac patients, while it was normal in patients consuming a gluten‐free diet for at least 12 months. Conclusions. Our results indicate that the main routes for water and solute absorption are deficient in celiac disease and may play a role in the onset of malabsorption symptoms.

The pumping function of NKA is essential for the regulation of cell ionic content, pH and for maintaining resting membrane potential. NKA is a heterotrimeric protein complex consisting of a large catalytic a subunit, a heavily glycosylated b subunit and a tissue-specific regulatory subunit belonging to the FXYD proteins family. In mammals, there are four a subunits, three b subunits and seven FXYD [4].The cardiotonic steroids (CTS) are highly specific NKA ligands that bind to all catalytic a-isoforms [5,6]. The CTS consist of a steroid core with a lactone ring and a sugar moiety. The CTS can be divided into two families, the cardenolides, to which ouabain and digoxin belong and the bufadienolides, to which marinobufagenin belongs. Ouabain, digoxin and marinobufagenin have been identified in human plasma. The cardenolides have a five-membered lactone ring and the bufadienolides a six-membered lactone ring. Ouabain, which is perhaps the best studied CTS, binds to the a subunit on the extracellular side in the cavity in the transmembrane domain at the interface created by six transmembrane segments aM1-6. Its lactone ring is buried within the transmembrane domain and

Our data suggest that the rs1333049 polymorphism at 9p21.3 may influence successful human longevity, possibly by modulating the risk of age-related disorders.

No abstract

Ouabain is a cardiotonic steroid with a history of medical uses. It acts as a ligand to the ubiquitous ion pump Na+,K+‐ATPase which it inhibits at high concentrations. At lower concentrations it triggers calcium oscillations and activation of MAP kinases, stimulates cell proliferation as well as adhesion and acts anti‐apoptotic. In light of this, it has been proposed that the pump may have a dual function as a signaling transducer. To investigate this, we have analyzed the phosphoproteome of COS‐7 kidney cells after treatment with sub‐saturating levels (100 nM) of ouabain, which were high enough to induce Ca2+ oscillations but below those needed to modulate the ion pumping function of Na+,K+‐ATPase. Gene ontology analysis was performed to find distinct cellular processes regulated by ouabain after 10 and 20 min of treatment in the phopshoproteomic analysis. The analysis revealed 2580 ouabain‐regulated phosphorylation sites, many of which were associated with cell adhesion and proliferation. Two of the regulated phospho‐proteins were the inositol triphosphoate receptor (InsP3) and stromal interaction molecule (STIM), both of which are essential for ouabain‐induced calcium oscillations. We used siRNA and Western blotting for target confirmation. One confirmed target, calcium/calmodulin‐dependent protein kinase II gamma (CAMK2γ), were shown to be involved in the anti‐apoptotic effect of ouabain; siRNA silencing of CaMK2γ in primary renal cells eliminates the protective effect of ouabain against apoptosis induced by either serum starvation or glucose. In conclusion, our findings support a role for Na+,K+‐ATPase as a signal transducer that serves to protect cell and tissue integrity. Support or Funding Information This study was supported by the Swedish Research Council and Erling‐Persson Family Foundation. D.S. is supported by a Novo Nordisk postdoctoral fellowship run in partnership with Karolinska Institutet. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.