Endothelial progenitor cells (EPCs) home from the bone marrow to the site of tissue regeneration and sustain neovascularization after acute vascular injury and upon the angiogenic switch in solid tumors. Therefore, they represent a suitable tool for cell-based therapy (CBT) in regenerative medicine and provide a novel promising target in the fight against cancer. Intracellular Ca2+ signals regulate numerous endothelial functions, such as proliferation and tubulogenesis. The growth of endothelial colony forming cells (ECFCs), which are EPCs capable of acquiring a mature endothelial phenotype, is governed by store-dependent Ca2+ entry (SOCE). This study aimed at investigating the nature and the role of VEGF-elicited Ca2+ signals in ECFCs. VEGF induced asynchronous Ca2+ oscillations, whose latency, amplitude, and frequency were correlated to the growth factor dose. Removal of external Ca2+ (0Ca2+) and SOCE inhibition with N-(4-[3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl]phenyl)-4-methyl-1,2,3-thiadiazole-5-carboxamide (BTP-2) reduced the duration of the oscillatory signal. Blockade of phospholipase C-γ with U73122, emptying the inositol-1,4,5-trisphosphate (InsP3)-sensitive Ca2+ pools with cyclopiazonic acid (CPA), and inhibition of InsP3 receptors with 2-APB prevented the Ca2+ response to VEGF. VEGF-induced ECFC proliferation and tubulogenesis were inhibited by the Ca2+-chelant, BAPTA, and BTP-2. NF-κB activation by VEGF was impaired by BAPTA, BTP-2, and its selective blocker, thymoquinone. Thymoquinone, in turn, suppressed VEGF-dependent ECFC proliferation and tubulogenesis. These data indicate that VEGF-induced Ca2+ oscillations require the interplay between InsP3-dependent Ca2+ release and SOCE, and promote ECFC growth and tubulogenesis by engaging NF-κB. This novel signaling pathway might be exploited to enhance the outcome of CBT and chemotherapy.

BackgroundEndothelial progenitor cells (EPCs) may be recruited from bone marrow to sustain tumor vascularisation and promote the metastatic switch. Understanding the molecular mechanisms driving EPC proliferation and tubulogenesis could outline novel targets for alternative anti-angiogenic treatments. Store-operated Ca2+ entry (SOCE), which is activated by a depletion of the intracellular Ca2+ pool, regulates the growth of human EPCs, where is mediated by the interaction between the endoplasmic reticulum Ca2+-sensor, Stim1, and the plasmalemmal Ca2+ channel, Orai1. As oncogenesis may be associated to the capability of tumor cells to grow independently on Ca2+ influx, it is important to assess whether SOCE regulates EPC-dependent angiogenesis also in tumor patients.Methodology/Principal FindingsThe present study employed Ca2+ imaging, recombinant sub-membranal and mitochondrial aequorin, real-time polymerase chain reaction, gene silencing techniques and western blot analysis to investigate the expression and the role of SOCE in EPCs isolated from peripheral blood of patients affected by renal cellular carcinoma (RCC; RCC-EPCs) as compared to control EPCs (N-EPCs). SOCE, activated by either pharmacological (i.e. cyclopiazonic acid) or physiological (i.e. ATP) stimulation, was significantly higher in RCC-EPCs and was selectively sensitive to BTP-2, and to the trivalent cations, La3+ and Gd3+. Furthermore, 2-APB enhanced thapsigargin-evoked SOCE at low concentrations, whereas higher doses caused SOCE inhibition. Conversely, the anti-angiogenic drug, carboxyamidotriazole (CAI), blocked both SOCE and the intracellular Ca2+ release. SOCE was associated to the over-expression of Orai1, Stim1, and transient receptor potential channel 1 (TRPC1) at both mRNA and protein level The intracellular Ca2+ buffer, BAPTA, BTP-2, and CAI inhibited RCC-EPC proliferation and tubulogenesis. The genetic suppression of Stim1, Orai1, and TRPC1 blocked CPA-evoked SOCE in RCC-EPCs.ConclusionsSOCE is remodelled in EPCs from RCC patients and stands out as a novel molecular target to interfere with RCC vascularisation due to its ability to control proliferation and tubulogenesis.

A quarter of patients with essential thrombocythemia or primary myelofibrosis carry a driver mutation of CALR, the calreticulin gene. A 52-bp deletion (type 1) and a 5-bp insertion (type 2 mutation) are the most frequent variants. These indels might differentially impair the calcium binding activity of mutant calreticulin. We studied the relationship between mutation subtype and biological/clinical features of the disease. Thirty-two different types of CALR variants were identified in 311 patients. Based on their predicted effect on calreticulin C-terminal, mutations were classified as: (i) type 1-like (65%); (ii) type 2-like (32%); and (iii) other types (3%). Corresponding CALR mutants had significantly different estimated isoelectric points. Patients with type 1 mutation, but not those with type 2, showed abnormal cytosolic calcium signals in cultured megakaryocytes. Type 1-like mutations were mainly associated with a myelofibrosis phenotype and a significantly higher risk of myelofibrotic transformation in essential thrombocythemia. Type 2-like CALR mutations were preferentially associated with an essential thrombocythemia phenotype, low risk of thrombosis despite very-high platelet counts and indolent clinical course. Thus, mutation subtype contributes to determining clinical phenotype and outcomes in CALR-mutant myeloproliferative neoplasms. CALR variants that markedly impair the calcium binding activity of mutant calreticulin are mainly associated with a myelofibrosis phenotype.

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.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells following binding with the cell surface ACE2 receptors, thereby leading to coronavirus disease 2019 (COVID-19). SARS-CoV-2 causes viral pneumonia with additional extrapulmonary manifestations and major complications, including acute myocardial injury, arrhythmia, and shock mainly in elderly patients. Furthermore, patients with existing cardiovascular comorbidities, such as hypertension and coronary heart disease, have a worse clinical outcome following contraction of the viral illness. A striking feature of COVID-19 pandemics is the high incidence of fatalities in advanced aged patients: this might be due to the prevalence of frailty and cardiovascular disease increase with age due to endothelial dysfunction and loss of endogenous cardioprotective mechanisms. Although experimental evidence on this topic is still at its infancy, the aim of this position paper is to hypothesize and discuss more suggestive cellular and molecular mechanisms whereby SARS-CoV-2 may lead to detrimental consequences to the cardiovascular system. We will focus on aging, cytokine storm, NLRP3/inflammasome, hypoxemia, and air pollution, which is an emerging cardiovascular risk factor associated with rapid urbanization and globalization. We will finally discuss the impact of clinically available CV drugs on the clinical course of COVID-19 patients. Understanding the role played by SARS-CoV2