Endothelial 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 Ca(2+) entry (SOCE), which is activated by a depletion of the intracellular Ca(2+) pool, regulates the growth of human EPCs, where is mediated by the interaction between the endoplasmic reticulum Ca(2+)-sensor, Stim1, and the plasmalemmal Ca(2+) channel, Orai1. As oncogenesis may be associated to the capability of tumor cells to grow independently on Ca(2+) influx, it is important to assess whether SOCE regulates EPC-dependent angiogenesis also in tumor patients.
The present study employed Ca(2+) 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, La(3+) and Gd(3+). 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 Ca(2+) 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 Ca(2+) 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.
SOCE 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.
Platelet release by megakaryocytes is regulated by a concert of environmental and autocrine factors. We previously showed that constitutively released adenosine diphosphate by human megakaryocytes ...leads to platelet production. Here we show that adenosine diphosphate elicits, in human megakaryocytes, an increase in cytosolic calcium concentration, followed by a plateau, which is lowered in the absence of extracellular calcium, suggesting the involvement of Store-Operated Calcium Entry. Indeed, we demonstrate that megakaryocytes express the major candidates to mediate Store-Operated Calcium Entry, stromal interaction molecule 1, Orai1 and canonical transient receptor potential 1, which are activated upon either pharmacological or physiological depletion of the intracellular calcium pool. This mechanism is inhibited by phospholipase C or inositol-3-phosphate receptor inhibitors and by a specific calcium entry blocker. Studies on megakaryocyte behavior, on extracellular matrix proteins that support proplatelet extension, show that calcium mobilization from intracellular stores activates signaling cascades that trigger megakaryocyte adhesion and proplatelet formation, and promotes extracellular calcium entry which is primarily involved in the regulation of the contractile force responsible for megakaryocyte motility. These findings provide the first evidence that both calcium mobilization from intracellular stores and extracellular calcium entry specifically regulate human megakaryocyte functions.
The term "angiogenic switch" describes one of the earlier events of tumorigenesis, that occurs when the balance between pro-and anti-angiogenic factors shifts towards a pro-angiogenic outcome. This ...leads to the transition from a microscopic indolent lesion to a macroscopic and vascularised primary tumor, that may eventually metastasize and spread to distant sites. The molecular mechanisms underlying such a critical step in the carcinogenetic process have been extensively investigated. Both local endothelial cells (ECs) and endothelial progenitor cells (EPCs), recruited from bone marrow, have been implicated in the angiogenic switch, which is ultimately triggered by a plethora of growth factors released by cancer cells, pivotal among which is vascular endothelial growth factor (VEGF); indeed, VEGF both activates ECs nearby the growing tumor, and leads to EPC mobilization into the circulation. In kidney, in particular, the frequent mutation of the Von Hippel Lindau tumor suppressor gene leads to an overproduction of pro-angiogenic factors which makes this neoplasm quite sensitive to antiangiogenic drugs. However, it is now evident that the use of VEGF(Rs) inhibitors in everyday clinical practice is not as effective as observed in murine models. The investigation of alternative signaling pathways involved in the angiogenic switch is, therefore, imperative in order to induce tumor regression whereby preventing harmful drawback consequences. Ca(2+) entry across the plasma membrane has long been known to stimulate mature ECs to undergo angiogenesis. Recent work from several groups worldwide has then outlined that members of the Transient Receptor Potential (TRP) super-family of cationic channels and Orai1 provide the pathway for such proangiogenic Ca(2+) signal. In addition, Canonical TRP 1 (TRPC1) and Orai1 channels control proliferation and tubulogenesis in both normal EPCs and EPCs isolated from peripheral blood of tumor patients. As a consequence, TRP channels and Orai1 might serve as novel molecular targets to develop alternative and more effective strategies of angiogenesis inhibition.
An increase in the frequency of circulating endothelial colony forming cells (ECFCs), the only subset of endothelial progenitor cells (EPCs) truly belonging to the endothelial phenotype, occurs in ...patients affected by primary myelofibrosis (PMF). Herein, they might contribute to the enhanced neovascularisation of fibrotic bone marrow and spleen. Store-operated Ca2+ entry (SOCE) activated by the depletion of the inositol-1,4,5-trisphosphate (InsP3)-sensitive Ca2+ store drives proliferation in ECFCs isolated from both healthy donors (N-ECFCs) and subjects suffering from renal cellular carcinoma (RCC-ECFCs). SOCE is up-regulated in RCC-ECFCs due to the over-expression of its underlying molecular components, namely Stim1, Orai1, and TRPC1.
We utilized Ca2+ imaging, real-time polymerase chain reaction, western blot analysis and functional assays to evaluate molecular structure and the functional role of SOCE in ECFCs derived from PMF patients (PMF-ECFCs). SOCE, induced by either pharmacological (i.e. cyclopiazonic acid or CPA) or physiological (i.e. ATP) stimulation, was significantly higher in PMF-ECFCs. ATP-induced SOCE was inhibited upon blockade of the phospholipase C/InsP3 signalling pathway with U73111 and 2-APB. The higher amplitude of SOCE was associated to the over-expression of the transcripts encoding for Stim2, Orai2-3, and TRPC1. Conversely, immunoblotting revealed that Stim2 levels remained constant as compared to N-ECFCs, while Stim1, Orai1, Orai3, TRPC1 and TRPC4 proteins were over-expressed in PMF-ECFCs. ATP-induced SOCE was inhibited by BTP-2 and low micromolar La3+ and Gd3+, while CPA-elicited SOCE was insensitive to Gd3+. Finally, BTP-2 and La3+ weakly blocked PMF-ECFC proliferation, while Gd3+ was ineffective.
Two distinct signalling pathways mediate SOCE in PMF-ECFCs; one is activated by passive store depletion and is Gd3+-resistant, while the other one is regulated by the InsP3-sensitive Ca2+ pool and is inhibited by Gd3+. Unlike N- and RCC-ECFCs, the InsP3-dependent SOCE does not drive PMF-ECFC proliferation.
Endothelial colony-forming cells (ECFCs) are the only endothelial progenitor cells (EPCs) that are capable of acquiring a mature endothelial phenotype. ECFCs are mainly mobilized from bone marrow to ...promote vascularization and represent a promising tool for cell-based therapy of severe ischemic diseases. Vascular endothelial growth factor (VEGF) stimulates the proliferation of peripheral blood-derived ECFCs (PB-ECFCs) through oscillations in intracellular Ca(2+) concentration (Ca(2+)i). VEGF-induced Ca(2+) spikes are driven by the interplay between inositol-1,4,5-trisphosphate (InsP3)-dependent Ca(2+) release and store-operated Ca(2+) entry (SOCE). The therapeutic potential of umbilical cord blood-derived ECFCs (UCB-ECFCs) has also been shown in recent studies. However, VEGF-induced proliferation of UCB-ECFCs is faster compared with their peripheral counterpart. Unlike PB-ECFCs, UCB-ECFCs express canonical transient receptor potential channel 3 (TRPC3) that mediates diacylglycerol-dependent Ca(2+) entry. The present study aimed at investigating whether the higher proliferative potential of UCB-ECFCs was associated to any difference in the molecular underpinnings of their Ca(2+) response to VEGF. We found that VEGF induces oscillations in Ca(2+)i that are patterned by the interaction between InsP3-dependent Ca(2+) release and SOCE. Unlike PB-ECFCs, VEGF-evoked Ca(2+) oscillations do not arise in the absence of extracellular Ca(2+) entry and after pharmacological (with Pyr3 and flufenamic acid) and genetic (by employing selective small interference RNA) suppression of TRPC3. VEGF-induced UCB-ECFC proliferation is abrogated on inhibition of the intracellular Ca(2+) spikes. Therefore, the Ca(2+) response to VEGF in UCB-ECFCs is shaped by a different Ca(2+) machinery as compared with PB-ECFCs, and TRPC3 stands out as a promising target in EPC-based treatment of ischemic pathologies.
The functional relevance of nitric oxide (NO) in the cardiovascular system is well established since the end of the 80', when it was firstly proposed as a key controller of vasodilation. More recent ...evidences, still debated and partly conflicting, point to a role of NO in the angiogenic progression. On the other hand hydrogen sulfide is a new entry as a gasotransmitter in the cardiovascular system. The variety of its biological functions seems to grow day after day. The first to be described is surely its reversible and poisoning binding of the cytochrome c oxidase that leads to impairment of the respiratory chain in mitochondria. However, sub-toxic concentrations have been later proved to be essential to maintain fundamental physiological functions in several tissues. The basal production of H2S is determined by the activity of, at least, three constitutively expressed enzymes (CBS, CSE, and 3-MPT) with tissue specificity for CBS and CSE in the central nervous and cardiovascular system, respectively. The assumption of a pivotal role of H2S in regulating physiological function is supported by the demonstration that reduced production of this gaseous molecule by CSE induces hypertension in mice. The increasing number of studies showing the regulatory functions of H2S reveals that maintaining the normal blood pressure levels is only one of its multiple biological actions. In this review, we would like to explore the recent literature on NO and H2S roles on cardiovascular system and to elucidate potential outcomes in the use of pharmacological drugs interfering with their metabolism.
Hydrogen sulphide (H2S) is a recently discovered gasotransmitter that may regulate a growing number of endothelial functions, including nitric oxide (NO) release, proliferation, adhesion and ...migration, which are the key steps of angiogenesis. The mechanism whereby H2S impacts on endothelial physiology is still unclear: however, the aforementioned processes are driven by an increase in intracellular Ca2+ concentration (Ca2+i). In the present study, we exploited the excised rat aorta to gain insights into the regulation of Ca2+i by H2S within in situ endothelial cells (ECs). Sodium hydrosulphide (NaHS), a H2S donor, caused an elevation in Ca2+i, which disappeared in absence of extracellular Ca2+. NaHSinduced Ca2+ inflow was sensitive to high doses of Gd3+, but not BTP-2. Inhibition of the reverse-mode of the Na+-Ca2+ exchanger (NCX), with KB-R7943 or upon removal of extracellular Na+, abrogated the Ca2+ response to NaHS. Moreover, NaHS-elicited Ca2+ entry was significantly reduced by TEA and glybenclamide, which hinted at the involvement of ATP-dependent K+ (KATP) channels. Conversely, NaHS-evoked Ca2+ signal was not affected by the reducing agent, dithiothreitol. Acute addition of NaHS hindered both Ca2+ release and Ca2+ entry induced by ATP, a physiological agonist of ECs. Consistently, inhibition of endogenous H2S synthesis with DL-propargylglycine impaired ATP-induced Ca2+ inflow, whereas it did not affect Ca2+ mobilization. These data provide the first evidence that H2S may stimulate Ca2+ influx into ECs by recruiting the reverse-mode of NCX and KATP channels. In addition, they show that such gasotransmitter may modulate the Ca2+ signals elicited by physiological stimuli in intact endothelium.
Beractant, a natural surfactant, induces an antifibrogenic phenotype and apoptosis in normal human lung fibroblasts (NHLF). As intracellular Ca2+ signalling has been related to programmed cell death, ...we aimed to assess the effect of beractant on intracellular Ca2+ concentration (Ca2+i) in NHLF in vitro. Cultured NHLF were loaded with Fura-2 AM (3 μM) and Ca2+ signals were recorded by microfluorimetric techniques. Beractant causes a concentration-dependent increase in Ca2+i with a EC50 of 0.82 μg/ml. The application of beractant, at a concentration of 500 μg/ml, which has been shown to exert an apoptotic effect in human fibroblasts, elicited different patterns of Ca2+ signals in NHLF: a) a single Ca2+ spike which could be followed by b) Ca2+ oscillations, c) a sustained Ca2+ plateau or d) a sustained plateau overlapped by Ca2+ oscillations. The amplitude and pattern of Ca2+ transients evoked by beractant were dependent on the resting Ca2+i. Pharmacological manipulation revealed that beractant activates a Ca2+ signal through Ca2+ release from intracellular stores mediated by phospholipase Cβ (PLCβ), Ca2+ release from inositol 1,4,5-trisphosphate receptors (IP3Rs) and Ca2+ influx via a store-operated pathway. Moreover, beractant-induced Ca2+ release was abolished by preventing membrane depolarization upon removal of extracellular Na+ and Ca2+. Finally, the inhibition of store-operated channels prevented beractant-induced NHLF apoptosis and downregulation of α1(I) procollagen expression. Therefore, beractant utilizes SOCE to exert its pro-apoptotic and antifibrinogenic effect on NHLF.
To compare the prediction of hip fracture risk of several bone ultrasounds (QUS), 7062 Swiss women ≥70 years of age were measured with three QUSs (two of the heel, one of the phalanges). Heel QUSs ...were both predictive of hip fracture risk, whereas the phalanges QUS was not.
Introduction: As the number of hip fracture is expected to increase during these next decades, it is important to develop strategies to detect subjects at risk. Quantitative bone ultrasound (QUS), an ionizing radiation‐free method, which is transportable, could be interesting for this purpose.
Materials and Methods: The Swiss Evaluation of the Methods of Measurement of Osteoporotic Fracture Risk (SEMOF) study is a multicenter cohort study, which compared three QUSs for the assessment of hip fracture risk in a sample of 7609 elderly ambulatory women ≥70 years of age. Two QUSs measured the heel (Achilles+; GE‐Lunar and Sahara; Hologic), and one measured the heel (DBM Sonic 1200; IGEA). The Cox proportional hazards regression was used to estimate the hazard of the first hip fracture, adjusted for age, BMI, and center, and the area under the ROC curves were calculated to compare the devices and their parameters.
Results: From the 7609 women who were included in the study, 7062 women 75.2 ± 3.1 (SD) years of age were prospectively followed for 2.9 ± 0.8 years. Eighty women reported a hip fracture. A decrease by 1 SD of the QUS variables corresponded to an increase of the hip fracture risk from 2.3 (95% CI, 1.7, 3.1) to 2.6 (95% CI, 1.9, 3.4) for the three variables of Achilles+ and from 2.2 (95% CI, 1.7, 3.0) to 2.4 (95% CI, 1.8, 3.2) for the three variables of Sahara. Risk gradients did not differ significantly among the variables of the two heel QUS devices. On the other hand, the phalanges QUS (DBM Sonic 1200) was not predictive of hip fracture risk, with an adjusted hazard risk of 1.2 (95% CI, 0.9, 1.5), even after reanalysis of the digitalized data and using different cut‐off levels (1700 or 1570 m/s).
Conclusions: In this elderly women population, heel QUS devices were both predictive of hip fracture risk, whereas the phalanges QUS device was not.
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