Orai1 and Orai3 act through distinct signalling axes to promote stemness and tumorigenicity of breast cancer stem cells.

BACKGROUND: One of major challenges in breast tumor therapy is the existence of breast cancer stem cells (BCSCs). BCSCs are a small subpopulation of tumor cells that exhibit characteristics of stem cells. BCSCs are responsible for progression, recurrence, chemoresistance and metastasis of breast cancer. Ca2+ signalling plays an important role in diverse processes in cancer development. However, the role of Ca2+ signalling in BCSCs is still poorly understood. METHODS: A highly effective 3D soft fibrin gel system was used to enrich BCSC-like cells from ER+ breast cancer lines MCF7 and MDA-MB-415. We then investigated the role of two Ca2+-permeable ion channels Orai1 and Orai3 in the growth and stemness of BCSC-like cells in vitro, and tumorigenicity in female NOD/SCID mice in vivo. RESULTS: Orai1 RNA silencing and pharmacological inhibition reduced the growth of BCSC-like cells in tumor spheroids, decreased the expression levels of BCSC markers, and reduced the growth of tumor xenografts in NOD/SCID mice. Orai3 RNA silencing also had similar inhibitory effect on the growth and stemness of BCSC-like cells in vitro, and tumor xenograft growth in vivo. Mechanistically, Orai1 and SPCA2 mediate store-operated Ca2+ entry. Knockdown of Orai1 or SPCA2 inhibited glycolysis pathway, whereas knockdown of Orai3 or STIM1 had no effect on glycolysis. CONCLUSION: We found that Orai1 interacts with SPCA2 to mediate store-independent Ca2+ entry, subsequently promoting the growth and tumorigenicity of BCSC-like cells via glycolysis pathway. In contrast, Orai3 and STIM1 mediate store-operated Ca2+ entry, promoting the growth and tumorigenicity of BCSC-like cells via a glycolysis-independent pathway. Together, our study uncovered a well-orchestrated mechanism through which two Ca2+ entry pathways act through distinct signalling axes to finely control the growth and tumorigenicity of BCSCs.

Septin regulation of Orai-mediated Ca2+ entry - a novel target for neurodegeneration.

Aberrant Ca2+ signaling is an early hallmark of multiple neurodegenerative syndromes including Alzheimer's and Parkinson's disease (AD and PD) as well as classes of rare genetic disorders such as Spinocebellar Ataxias. Therapeutic strategies that target aberrant Ca2+ signals whilst allowing normal neuronal Ca2+ signals have been a challenge. In a recent study Princen et al., performed a screen in the tauP301L cell model of AD for drugs that could specifically ameliorate the excess Ca2+ entry observed. They identified a class of compounds referred to as ReS19-T that interact with Septins, previously identified as regulators of the Store-operated Ca2+ entry channel Orai. Drug treatment of the cellular model, a mouse model and human iPSC derived neurons alleviate cellular and systemic deficits associated with tauP301L. Comparison of Septin filament architecture in disease conditions with and without the drug treatment indicate that excess Ca2+ entry is a consequence of abnormal Septin filament architecture resulting in aberrant ER-PM contacts. The importance of membrane contacts for maintaining precise cellular signaling has been recognized previously. However, the molecular mechanism by which Septin filaments organize the ER-PM junctions to regulate Ca2+ entry through Orai remains to be fully understood.

Exploring potential ion channel targets for rheumatoid arthritis: combination of network analysis and gene expression analysis.

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the synovial membrane that leads to the destruction of cartilage and bone. Currently, pharmacological targeting of ion channels is being increasingly recognized as an attractive and feasible strategy for the treatment of RA. The present work employs a network analysis approach to predict the most promising ion channel target for potential RA-treating drugs. A protein-protein interaction map was generated for 343 genes associated with inflammation in RA and ion channel genes using Search Tool for the Retrieval of Interacting Genes and visualized using Cytoscape. Based on the betweenness centrality and traffic values as key topological parameters, 17 hub nodes were identified, including FOS (9800.85), tumor necrosis factor (3654.60), TGFB1 (3305.75), and VEGFA (3052.88). The backbone network constructed with these 17 hub genes was intensely analyzed to identify the most promising ion channel target using network analyzer. Calcium permeating ion channels, especially store-operated calcium entry channels, and their associated regulatory proteins were found to highly interact with RA inflammatory hub genes. This significant ion channel target for RA identified by theoretical and statistical studies was further validated by a pilot case-control gene expression study. Experimental verification of the above findings in 75 RA cases and 25 controls showed increased ORAI1 expression. Thus, with a combination of network analysis approach and gene expression studies, we have explored potential targets for RA treatment.

Interstitial cell of Cajal-like cells (ICC-LC) exhibit dynamic spontaneous activity but are not functionally innervated in mouse urethra.

Urethral smooth muscle cells (USMC) contract to occlude the internal urethral sphincter during bladder filling. Interstitial cells also exist in urethral smooth muscles and are hypothesized to influence USMC behaviours and neural responses. These cells are similar to Kit+ interstitial cells of Cajal (ICC), which are gastrointestinal pacemakers and neuroeffectors. Isolated urethral ICC-like cells (ICC-LC) exhibit spontaneous intracellular Ca2+ signalling behaviours that suggest these cells may serve as pacemakers or neuromodulators similar to ICC in the gut, although observation and direct stimulation of ICC-LC within intact urethral tissues is lacking. We used mice with cell-specific expression of the Ca2+ indicator, GCaMP6f, driven off the endogenous promoter for Kit (Kit-GCaMP6f mice) to identify ICC-LC in situ within urethra muscles and to characterize spontaneous and nerve-evoked Ca2+ signalling. ICC-LC generated Ca2+ waves spontaneously that propagated on average 40.1 ± 0.7 µm, with varying amplitudes, durations, and spatial spread. These events originated from multiple firing sites in cells and the activity between sites was not coordinated. ICC-LC in urethra formed clusters but not interconnected networks. No evidence for entrainment of Ca2+ signalling between ICC-LC was obtained. Ca2+ events in ICC-LC were unaffected by nifedipine but were abolished by cyclopiazonic acid and decreased by an antagonist of Orai Ca2+ channels (GSK-7975A). Phenylephrine increased Ca2+ event frequency but a nitric oxide donor (DEA-NONOate) had no effect. Electrical field stimulation (EFS, 10 Hz) of intrinsic nerves, which evoked contractions of urethral rings and increased Ca2+ event firing in USMC, failed to evoke responses in ICC-LC. Our data suggest that urethral ICC-LC are spontaneously active but are not regulated by autonomic neurons.

Targeting calciumopathy for neuroprotection: focus on calcium channels Cav1, Orai1 and P2X7.

As the uncontrolled entry of calcium ions (Ca2+) through plasmalemmal calcium channels is a cell death trigger, the conjecture is here raised that mitigating such an excess of Ca2+ entry should rescue from death the vulnerable neurons in neurodegenerative diseases (NDDs). However, this supposition has failed in some clinical trials (CTs). Thus, a recent CT tested whether isradipine, a blocker of the Cav1 subtype of voltage-operated calcium channels (VOCCs), exerted a benefit in patients with Parkinson's disease (PD); however, outcomes were negative. This is one more of the hundreds of CTs done under the principle of one-drug-one-target, that have failed in Alzheimer's disease (AD) and other NDDs during the last three decades. As there are myriad calcium channels to let Ca2+ ions gain the cell cytosol, it seems reasonable to predict that blockade of Ca2+ entry through a single channel may not be capable of preventing the Ca2+ flood of cells by the uncontrolled Ca2+ entry. Furthermore, as Ca2+ signaling is involved in the regulation of myriad functions in different cell types, it seems also reasonable to guess that a therapy should be more efficient by targeting different cells with various drugs. Here, we propose to mitigate Ca2+ entry by the simultaneous partial blockade of three quite different subtypes of plasmalemmal calcium channels that is, the Cav1 subtype of VOCCs, the Orai1 store-operated calcium channel (SOCC), and the purinergic P2X7 calcium channel. All three channels are expressed in both microglia and neurons. Thus, by targeting the three channels with a combination of three drug blockers we expect favorable changes in some of the pathogenic features of NDDs, namely (i) to mitigate Ca2+ entry into microglia; (ii) to decrease the Ca2+-dependent microglia activation; (iii) to decrease the sustained neuroinflammation; (iv) to decrease the uncontrolled Ca2+ entry into neurons; (v) to rescue vulnerable neurons from death; and (vi) to delay disease progression. In this review we discuss the arguments underlying our triad hypothesis in the sense that the combination of three repositioned medicines targeting Cav1, Orai1, and P2X7 calcium channels could boost neuroprotection and delay the progression of AD and other NDDs.

Combination of the CRAC Channel Inhibitor CM4620 and Galactose as a Potential Therapy for Acute Pancreatitis.

Acute pancreatitis (AP) is a life-threatening inflammatory disease with no specific therapy. Excessive cytoplasmic Ca2+ elevation and intracellular ATP depletion are responsible for the initiation of AP. Inhibition of Ca2+ release-activated Ca2+ (CRAC) channels has been proposed as a potential treatment, and currently, a novel selective CRAC channel inhibitor CM4620 (Auxora, CalciMedica) is in Phase 2b human trials. While CM4620 is on track to become the first effective treatment for AP, it does not produce complete protection in animal models. Recently, an alternative approach has suggested reducing ATP depletion with a natural carbohydrate galactose. Here, we have investigated the possibility of using the smallest effective concentration of CM4620 in combination with galactose. Protective effects of CM4620, in the range of 1-100 n m, have been studied against necrosis induced by bile acids, palmitoleic acid, or l-asparaginase. CM4620 markedly protected against necrosis induced by bile acids or asparaginase starting from 50 n m and palmitoleic acid starting from 1 n m. Combining CM4620 and galactose (1 m m) significantly reduced the extent of necrosis to near-control levels. In the palmitoleic acid-alcohol-induced experimental mouse model of AP, CM4620 at a concentration of 0.1 mg/kg alone significantly reduced edema, necrosis, inflammation, and the total histopathological score. A combination of 0.1 mg/kg CM4620 with galactose (100 m m) significantly reduced further necrosis, inflammation, and histopathological score. Our data show that CM4620 can be used at much lower concentrations than reported previously, reducing potential side effects. The novel combination of CM4620 with galactose synergistically targets complementary pathological mechanisms of AP.

ER and SOCE Ca2+ signals are not required for directed cell migration in human iPSC-derived microglia.

The central nervous system (CNS) is constantly surveilled by microglia, highly motile and dynamic cells deputed to act as the first line of immune defense in the brain and spinal cord. Alterations in the homeostasis of the CNS are detected by microglia that respond by extending their processes or - following major injuries - by migrating toward the affected area. Understanding the mechanisms controlling directed cell migration of microglia is crucial to dissect their responses to neuroinflammation and injury. We used a combination of pharmacological and genetic approaches to explore the involvement of calcium (Ca2+) signaling in the directed migration of human induced pluripotent stem cell (iPSC)-derived microglia challenged with a purinergic stimulus. This approach mimics cues originating from injury of the CNS. Unexpectedly, simultaneous imaging of microglia migration and intracellular Ca2+ changes revealed that this phenomenon does not require Ca2+ signals generated from the endoplasmic reticulum (ER) and store-operated Ca2+ entry (SOCE) pathways. Instead, we find evidence that human microglial chemotaxis to purinergic signals is mediated by cyclic AMP in a Ca2+-independent manner. These results challenge prevailing notions, with important implications in neurological conditions characterized by perturbation in Ca2+ homeostasis.

Loss of Calpain 3 dysregulates store-operated calcium entry and its exercise response in mice.

Limb-Girdle Muscular Dystrophy R1/2A (LGMD R1/2A) is caused by mutations in the CAPN3 gene encoding Calpain 3, a skeletal-muscle specific, Ca2+-dependent protease. Localization of Calpain 3 within the triad suggests it contributes to Ca2+ homeostasis. Through live-cell Ca2+ measurements, muscle mechanics, immunofluorescence, and electron microscopy (EM) in Capn3 deficient (C3KO) and wild-type (WT) mice, we determined whether loss of Calpain 3 altered Store-Operated Calcium Entry (SOCE) activity. Direct Ca2+ influx measurements revealed loss of Capn3 elicits elevated resting SOCE and increased resting cytosolic Ca2+, supported by high incidence of calcium entry units (CEUs) observed by EM. C3KO and WT mice were subjected to a single bout of treadmill running to elicit SOCE. Within 1HR post-treadmill running, C3KO mice exhibited diminished force production in extensor digitorum longus muscles and a greater decay of Ca2+ transients in flexor digitorum brevis muscle fibers during repetitive stimulation. Striking evidence for impaired exercise-induced SOCE activation in C3KO mice included poor colocalization of key SOCE proteins, stromal-interacting molecule 1 (STIM1) and ORAI1, combined with disappearance of CEUs in C3KO muscles. These results demonstrate that Calpain 3 is a key regulator of SOCE in skeletal muscle and identify SOCE dysregulation as a contributing factor to LGMD R1/2A pathology.

STIM1: A new player in nuclear dynamics? Lessons learnt from tubular aggregate myopathy.

Two recent papers have highlighted that STIM1, a key component of Store-operated Ca2+-entry, is able to translocate to the nucleus and participate in nuclear Ca2+-handling and in DNA repair. These finding opens new avenues on the role that this Ca2+-sensing protein may have in health and disease.

STIM1, ORAI1, and KDM2B in circulating tumor cells (CTCs) isolated from prostate cancer patients.

Introduction: Previous publications have shown that STIM1, ORAI1, and KDM2B, are implicated in Ca2+ signaling and are highly expressed in various cancer subtypes including prostate cancer. They play multiple roles in cancer cell migration, invasion, and metastasis. In the current study we investigated the expression of the above biomarkers in circulating tumor cells from patients with metastatic prostate cancer. Methods: Thirty-two patients were enrolled in this study and CTCs' isolation was performed with Ficoll density gradient. Two different triple immunofluorescence stainings were conducted with the following combination of antibodies: CK/KDM2B/CD45 and CK/STIM1/ORAI1. Slides were analyzed using VyCAP microscopy technology. Results: CTC-positive patients were detected in 41% for (CK/KDM2B/CD45) staining and in 56% for (CK/STIM1/ORAI1) staining. The (CK+/KDM2B+/CD45-) and the (CK+/STIM1+/ORAI1+) were the most frequent phenotypes as they were detected in 85% and 94% of the CTC-positive patients, respectively. Furthermore, the expression of ORAI1 and STIM1 in patients' PBMCs was very low exhibiting them as interesting specific biomarkers for CTC detection. The (CK+/STIM1+/ORAI1+) phenotype was correlated to bone metastasis (p = 0.034), while the (CK+/STIM1+/ORAI1-) to disease relapse (p = 0.049). Discussion: STIM1, ORAI1, and KDM2B were overexpressed in CTCs from patients with metastatic prostate cancer. STIM1 and ORAI1 expression was related to disease recurrence and bone metastasis. Further investigation of these biomarkers in a larger cohort of patients will clarify their clinical significance for prostate cancer patients.

Calcium channel signalling at neuronal endoplasmic reticulum-plasma membrane junctions.

Neurons are highly specialised cells that need to relay information over long distances and integrate signals from thousands of synaptic inputs. The complexity of neuronal function is evident in the morphology of their plasma membrane (PM), by far the most intricate of all cell types. Yet, within the neuron lies an organelle whose architecture adds another level to this morphological sophistication - the endoplasmic reticulum (ER). Neuronal ER is abundant in the cell body and extends to distant axonal terminals and postsynaptic dendritic spines. It also adopts specialised structures like the spine apparatus in the postsynapse and the cisternal organelle in the axon initial segment. At membrane contact sites (MCSs) between the ER and the PM, the two membranes come in close proximity to create hubs of lipid exchange and Ca2+ signalling called ER-PM junctions. The development of electron and light microscopy techniques extended our knowledge on the physiological relevance of ER-PM MCSs. Equally important was the identification of ER and PM partners that interact in these junctions, most notably the STIM-ORAI and VAP-Kv2.1 pairs. The physiological functions of ER-PM junctions in neurons are being increasingly explored, but their molecular composition and the role in the dynamics of Ca2+ signalling are less clear. This review aims to outline the current state of research on the topic of neuronal ER-PM contacts. Specifically, we will summarise the involvement of different classes of Ca2+ channels in these junctions, discuss their role in neuronal development and neuropathology and propose directions for further research.

STIM1-dependent store-operated calcium entry mediates sex differences in macrophage chemotaxis and monocyte recruitment.

Infiltration of monocyte-derived cells to sites of infection and injury is greater in males than in females, due in part, to increased chemotaxis, the process of directed cell movement toward a chemical signal. The mechanisms governing sexual dimorphism in chemotaxis are not known. We hypothesized a role for the store-operated calcium entry (SOCE) pathway in regulating chemotaxis by modulating leading and trailing edge membrane dynamics. We measured the chemotactic response of bone marrow-derived macrophages migrating toward complement component 5a (C5a). Chemotactic ability was dependent on sex and inflammatory phenotype (M0, M1, and M2), and correlated with SOCE. Notably, females exhibited a significantly lower magnitude of SOCE than males. When we knocked out the SOCE gene, stromal interaction molecule 1 (STIM1), it eliminated SOCE and equalized chemotaxis across both sexes. Analysis of membrane dynamics at the leading and trailing edges showed that STIM1 influences chemotaxis by facilitating retraction of the trailing edge. Using BTP2 to pharmacologically inhibit SOCE mirrored the effects of STIM1 knockout, demonstrating a central role of STIM/Orai-mediated calcium signaling. Importantly, by monitoring the recruitment of adoptively transferred monocytes in an in vivo model of peritonitis, we show that increased infiltration of male monocytes during infection is dependent on STIM1. These data support a model in which STIM1-dependent SOCE is necessary and sufficient for mediating the sex difference in monocyte recruitment and macrophage chemotactic ability by regulating trailing edge dynamics.

Essential role of N-terminal SAM regions in STIM1 multimerization and function.

The single-pass transmembrane protein Stromal Interaction Molecule 1 (STIM1), located in the endoplasmic reticulum (ER) membrane, possesses two main functions: It senses the ER-Ca2+ concentration and directly binds to the store-operated Ca2+ channel Orai1 for its activation when Ca2+ recedes. At high resting ER-Ca2+ concentration, the ER-luminal STIM1 domain is kept monomeric but undergoes di/multimerization once stores are depleted. Luminal STIM1 multimerization is essential to unleash the STIM C-terminal binding site for Orai1 channels. However, structural basis of the luminal association sites has so far been elusive. Here, we employed molecular dynamics (MD) simulations and identified two essential di/multimerization segments, the α7 and the adjacent region near the α9-helix in the sterile alpha motif (SAM) domain. Based on MD results, we targeted the two STIM1 SAM domains by engineering point mutations. These mutations interfered with higher-order multimerization of ER-luminal fragments in biochemical assays and puncta formation in live-cell experiments upon Ca2+ store depletion. The STIM1 multimerization impeded mutants significantly reduced Ca2+ entry via Orai1, decreasing the Ca2+ oscillation frequency as well as store-operated Ca2+ entry. Combination of the ER-luminal STIM1 multimerization mutations with gain of function mutations and coexpression of Orai1 partially ameliorated functional defects. Our data point to a hydrophobicity-driven binding within the ER-luminal STIM1 multimer that needs to switch between resting monomeric and activated multimeric state. Altogether, these data reveal that interactions between SAM domains of STIM1 monomers are critical for multimerization and activation of the protein.

Regulation of T Lymphocyte Functions through Calcium Signaling Modulation by Nootkatone.

Recent advancements in understanding the intricate molecular mechanisms underlying immunological responses have underscored the critical involvement of ion channels in regulating calcium influx, particularly in inflammation. Nootkatone, a natural sesquiterpenoid found in Alpinia oxyphylla and various citrus species, has gained attention for its diverse pharmacological properties, including anti-inflammatory effects. This study aimed to elucidate the potential of nootkatone in modulating ion channels associated with calcium signaling, particularly CRAC, KV1.3, and KCa3.1 channels, which play pivotal roles in immune cell activation and proliferation. Using electrophysiological techniques, we demonstrated the inhibitory effects of nootkatone on CRAC, KV1.3, and KCa3.1 channels in HEK293T cells overexpressing respective channel proteins. Nootkatone exhibited dose-dependent inhibition of channel currents, with IC50 values determined for each channel. Nootkatone treatment did not significantly affect cell viability, indicating its potential safety for therapeutic applications. Furthermore, we observed that nootkatone treatment attenuated calcium influx through activated CRAC channels and showed anti-proliferative effects, suggesting its role in regulating inflammatory T cell activation. These findings highlight the potential of nootkatone as a natural compound for modulating calcium signaling pathways by targeting related key ion channels and it holds promise as a novel therapeutic agent for inflammatory disorders.

The A-kinase anchoring protein Yotiao decrease the ER calcium content by inhibiting the store operated calcium entry.

The meticulous regulation of ER calcium (Ca2+) homeostasis is indispensable for the proper functioning of numerous cellular processes. Disrupted ER Ca2+ balance is implicated in diverse diseases, underscoring the need for a systematic exploration of its regulatory factors in cells. Our recent genomic-scale screen identified a scaffolding protein A-kinase anchoring protein 9 (AKAP9) as a regulator of ER Ca2+ levels, but the underlying molecular mechanisms remain elusive. Here, we reveal that Yotiao, the smallest splicing variant of AKAP9 decreased ER Ca2+ content in animal cells. Additional testing using a combination of Yotiao truncations, knock-out cells and pharmacological tools revealed that, Yotiao does not require most of its interactors, including type 1 inositol 1,4,5-trisphosphate receptors (IP3R1), protein kinase A (PKA), protein phosphatase 1 (PP1), adenylyl cyclase type 2 (AC2) and so on, to reduce ER Ca2+ levels. However, adenylyl cyclase type 9 (AC9), which is known to increases its cAMP generation upon interaction with Yotiao for the modulation of potassium channels, plays an essential role for Yotiao's ER-Ca2+-lowering effect. Mechanistically, Yotiao may work through AC9 to act on Orai1-C terminus and suppress store operated Ca2+ entry, resulting in reduced ER Ca2+ levels. These findings not only enhance our comprehension of the interplay between Yotiao and AC9 but also contribute to a more intricate understanding of the finely tuned mechanisms governing ER Ca2+ homeostasis.

Role of KDM2B epigenetic factor in regulating calcium signaling in prostate cancer cells.

KDM2B, a histone lysine demethylase, is expressed in a plethora of cancers. Earlier studies from our group, have showcased that overexpression of KDM2B in the human prostate cancer cell line DU-145 is associated with cell adhesion, actin reorganization, and improved cancer cell migration. In addition, we have previously examined changes of cytosolic Ca2+, regulated by the pore-forming proteins ORAI and the Ca2+ sensing stromal interaction molecules (STIM), via store-operated Ca2+ entry (SOCE) in wild-type DU-145. This study sought to evaluate the impact of KDM2B overexpression on the expression of key molecules (SGK1, Nhe1, Orai1, Stim1) and SOCE. Furthermore, this is the first study to evaluate KDM2B expression in circulating tumor cells (CTCs) from patients with prostate cancer. mRNA levels for SGK1, Nhe1, Orai1, and Stim1 were quantified by RT-PCR. Calcium signals were measured in KDM2B-overexpressing DU-145 cells, loaded with Fura-2. Blood samples from 22 prostate cancer cases were scrutinized for KDM2B expression using immunofluorescence staining and the VyCAP system. KDM2B overexpression in DU-145 cells increased Orai1, Stim1, and Nhe1 mRNA levels and significantly decreased Ca2+ release. KDM2B expression was examined in 22 prostate cancer patients. CTCs were identified in 45 % of these patients. 80 % of the cytokeratin (CK)-positive patients and 63 % of the total examined CTCs exhibited the (CK + KDM2B + CD45-) phenotype. To conclude, this study is the first to report increased expression of KDM2B in CTCs from patients with prostate cancer, bridging in vitro and preclinical assessments on the potentially crucial role of KDM2B on migration, invasiveness, and ultimately metastasis in prostate cancer.

Sodium Houttuyfonate Alleviates MCT-induced Pulmonary Hypertension by Regulating Orai1 and Orai2.

Elevated intracellular Ca2+ concentration ([Ca2+]i) is a key trigger for pulmonary arterial smooth muscle cell (PASMC) proliferation and contributes greatly to pulmonary hypertension (PH). Extracellular Ca2+ influx via a store-operated Ca2+ channel (SOCC), termed store-operated Ca2+ entry (SOCE), is a crucial mechanism for [Ca2+]i elevation in PASMCs. Calcium release-activated calcium modulator (Orai) proteins, consisting of three members (Orai1-3), are the main components of SOCC. Sodium houttuyfonate (SH) is a product of the addition reaction of sodium bisulfite and houttuynin and has antibacterial, anti-inflammatory, and other properties. In this study, we assessed the contributions of Orai proteins to MCT-enhanced SOCE, [Ca2+]i, and cell proliferation in PASMCs and determined the effect of SH on MCT-PH and the underlying mechanism, focusing on Orai proteins, SOCE, and [Ca2+]i in PASMCs. Our results showed that 1) Orai1 and Orai2 were selectively upregulated in the distal pulmonary arteries (PAs) and the PASMCs of MCT-PH rats. 2) Knockdown of Orai1 or Orai2 reduced SOCE, [Ca2+]i, and cell proliferation without affecting their expression in PASMCs in MCT-PH rats. 3) SH significantly normalized the characteristic parameters in a dose-dependent manner in the MCT-PH rat model. 4) SH decreased MCT-enhanced SOCE, [Ca2+]i and PASMC proliferation via Orai1 or Orai2. These results indicate that SH likely exerts its protective role in MCT-PH by inhibiting the Orai1,2-SOCE-[Ca2+]i signaling pathway.

Deletion of myeloid-specific Orai1 calcium channel does not affect pancreatic tissue damage in experimental acute pancreatitis.

BACKGROUND: Store-operated Ca2+ entry (SOCE) mediated by ORAI1 channel plays a crucial role in acute pancreatitis (AP). Macrophage is an important regulator in amplifying pancreatic tissue damage, but little is known about the role of ORAI1 in macrophages. In this study, we examined the effects of macrophage-specific ORAI1 on pancreatic tissue damage in AP. METHOD: Myeloid-specific Orai1 deficient mice was generated by crossing a LysM-Cre mouse line with Orai1f/f mice. Bone marrow-derived macrophages (BMDMs) were isolated, cultured, and stimulated to induce M1 or M2 macrophage polarization. Intracellular Ca2+ signals were measured by time-lapse confocal microscope imaging, with a Ca2+ indicator (Fluo 4). Experimental AP was induced by hourly intraperitoneal injections of caerulein or retrograde biliopancreatic infusion of sodium taurocholate. Pancreatic tissue damage was assessed by histopathological scoring and immunostaining. Sepsis was induced by intraperitoneal injection of lipopolysaccharide; organ damage and serum pro-inflammatory cytokines were measured. RESULT: Myeloid-specific Orai1 deletion exhibited minimal effect on SOCE in M0 macrophages and promoted M2 macrophage polarization ex vivo. Myeloid-specific Orai1 deletion did not affect pancreatic tissue damage, nor neutrophil or macrophage infiltration in two models of AP. Similarly, myeloid-specific Orai1 deletion did not influence overall survival rate in a model of sepsis, nor lung, kidney, and liver damage; while serum pro-inflammatory cytokines, including IL-6, TNF-α, and IL-1ß were higher in Orai1ΔLysM mice, but were largely reduced in mice with Orai1 inhibitor. CONCLUSION: Our data suggest that ORAI1 may not be a predominant SOCE channel in macrophages and play a limited role in mediating pancreatic tissue damage in AP.

Quercetin and Kaempferol inhibit HMC-1 activation via SOCE/NFATc2 signaling and suppress hippocampal mast cell activation in lipopolysaccharide-induced depressive mice.

OBJECTIVE AND DESIGN: Mast cells (MCs), as the fastest immune responders, play a critical role in the progression of neuroinflammation-related diseases, especially in depression. Quercetin (Que) and kaempferol (Kae), as two major diet-derived flavonoids, inhibit MC activation and exhibit significant antidepressant effect due to their anti-inflammatory capacity. The study aimed to explore the mechanisms of inhibitory effect of Que and Kae on MC activation, and whether Que and Kae suppress hippocampal mast cell activation in LPS-induced depressive mice. SUBJECTS AND TREATMENT: In vitro assays, human mast cells (HMC-1) were pretreated with Que or Kae for 1 h, then stimulated by phorbol 12-myristate 13-acetate (PMA) and 2,5-di-t-butyl-1,4-benzohydroquinone (tBHQ) for 3 h or 12 h. In vivo assays, Que or Kae was administered by oral gavage once daily for 14 days and then lipopolysaccharide (LPS) intraperitoneally injection to induce depressive behaviors. METHODS: The secretion and expression of TNF-α were determined by ELISA and Western blotting. The nuclear factor of activated T cells (NFAT) transcriptional activity was measured in HMC-1 stably expressing NFAT luciferase reporter gene. Nuclear translocation of NFATc2 was detected by nuclear protein extraction and also was fluorescently detected in HMC-1 stably expressing eGFP-NFATc2. We used Ca2+ imaging to evaluate changes of store-operated calcium entry (SOCE) in HMC-1 stably expressing fluorescent Ca2+ indicator jGCamP7s. Molecular docking was used to assess interaction between the Que or Kae and calcium release-activated calcium modulator (ORAI). The  hippocampal mast cell accumulation and activation  were detected by toluidine blue staining and immunohistochemistry with ß-tryptase. RESULTS: In vitro assays of HMC-1 activated by PtBHQ (PMA and tBHQ), Que and Kae significantly decreased expression and secretion of TNF-α. Moreover, NFAT transcriptional activity and nuclear translocation of NFATc2 were remarkably inhibited by Que and Kae. In addition, the Ca2+ influx mediated by SOCE was suppressed by Que, Kae and the YM58483 (ORAI inhibitor), respectively. Importantly, the combination of YM58483 with Que or Kae had no additive effect on the inhibition of SOCE. The molecular docking also showed that Que and Kae both exhibit high binding affinities with ORAI at the same binding site as YM58483. In vivo assays, Que and Kae significantly reversed LPS-induced depression-like behaviors in mice, and inhibited hippocampal mast cell activation  in LPS-induced depressive mice. CONCLUSIONS: Our results indicated that suppression of SOCE/NFATc2 pathway-mediated by ORAI channels may be the mechanism of inhibitory effect of Que and Kae on MC activation, and also suggested Que and Kae may exert the antidepressant effect through suppressing hippocampal mast cell activation.