Store-Operated Ca2+ Release-Activated Ca2+ Channels Regulate PAR2-Activated Ca2+ Signaling and Cytokine Production in Airway Epithelial Cells

IL-37 protects against house dust mite-induced airway inflammation and airway epithelial barrier dysfunction via inhibiting store-operated calcium entry

BACKGROUND

Airway epithelial barrier dysfunction has been proved to contribute to the development of type 2 inflammation of asthma. Interleukin (IL)-37 is a negative regulator of immune responses and allergic airway inflammation. However, whether IL-37 has any effect on airway epithelial barrier has been unknown.

METHODS

We evaluated the role of IL-37 in both mouse model and cultured 16HBE cells. Histology and ELISA assays were used to evaluate airway inflammation. FITC-dextran permeability assay was used to evaluate the airway epithelial barrier function. Immunofluorescence, western blot and quantitative Real-Time PCR (RT-PCR) were used to evaluate the distribution and expression of tight junction proteins. RT-PCR and Ca2+ fluorescence measurement were used to evaluate the mRNA expression and activity of store-operated calcium entry (SOCE).

RESULTS

IL-37 inhibited house dust mite (HDM)-induced airway inflammation and decreased the levels of IgE in serum and type 2 cytokines in bronchoalveolar lavage fluid (BALF) compared to asthmatic mice. IL-37 protected against HDM-induced airway epithelial barrier dysfunction, including reduced leakage of FITC-dextran, enhanced expression of TJ proteins, and restored the membrane distribution of TJ proteins. Moreover, IL-37 decreased the level of IL-33 in the BALF of asthmatic mice and the supernatants of HDM-treated 16HBE cells. IL-37 decreased the peak level of Ca2+ fluorescence induced by thapsigargin and HDM, and inhibited the mRNA expression of Orai1, suggesting an inhibiting effect of IL-37 on SOCE in airway epithelial cells.

CONCLUSION

IL-37 plays a protective role in airway inflammation and HDM-induced airway epithelial barrier dysfunction by inhibiting SOCE.

Akt activator SC79 stimulates antibacterial nitric oxide generation in human nasal epithelial cells in vitro

BACKGROUND

The role of Akt in nasal immunity is unstudied. Akt phosphorylates and activates endothelial nitric oxide synthase (eNOS) expressed in epithelial ciliated cells. Nitric oxide (NO) production by ciliated cells can have antibacterial and antiviral effects. Increasing nasal NO may be a useful antipathogen strategy in chronic rhinosinusitis (CRS). We previously showed that small-molecule Akt activator SC79 induces nasal cell NO production and suppresses IL-8 via the transcription factor Nrf-2. We hypothesized that SC79 NO production may additionally have antibacterial effects.

METHODS

NO production was measured using fluorescent dye DAF-FM. We tested effects of SC79 during co-culture of Pseudomonas aeruginosa with primary nasal epithelial cells, using CFU counting and live-dead staining to quantify bacterial killing. Pharmacology determined the mechanism of SC79-induced NO production and tested dependence on Akt.

RESULTS

SC79 induced dose-dependent, Akt-dependent NO production in nasal epithelial cells. The NO production required eNOS and Akt. The NO released into the airway surface liquid killed P. aeruginosa. No toxicity (LDH release) or inflammatory effects (IL8 transcription) were observed over 24 h.

CONCLUSIONS

Together, these data suggest multiple immune pathways are stimulated by SC79, with antipathogen effects. This in vitro pilot study suggests that a small-molecule Akt activator may have clinical utility in CRS or respiratory other infection settings, warranting future in vivo studies.

Calcium Signaling in Airway Epithelial Cells: Current Understanding and Implications for Inflammatory Airway Disease

Airway epithelial cells play an indispensable role in protecting the lung from inhaled pathogens and allergens by releasing an array of mediators that orchestrate inflammatory and immune responses when confronted with harmful environmental triggers. While this process is undoubtedly important for containing the effects of various harmful insults, dysregulation of the inflammatory response can cause lung diseases including asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis. A key cellular mechanism that underlies the inflammatory responses in the airway is calcium signaling, which stimulates the production and release of chemokines, cytokines, and prostaglandins from the airway epithelium. In this review, we discuss the role of major Ca2+ signaling pathways found in airway epithelial cells and their contributions to airway inflammation, mucociliary clearance, and surfactant production. We highlight the importance of store-operated Ca2+ entry as a major signaling hub in these processes and discuss therapeutic implications of targeting Ca2+ signaling for airway inflammation.

House dust mite allergens induce Ca2+ signalling and alarmin responses in asthma airway epithelial cells

Type 2 inflammation in asthma develops with exposure to stimuli to include inhaled allergens from house dust mites (HDM). Features include mucus hypersecretion and the formation of pro-secretory ion transport characterised by elevated basal Cl- current. Studies using human sinonasal epithelial cells treated with HDM extract report a higher protease activated receptor-2 (PAR-2) agonist-induced calcium mobilisation that may be related to airway sensitisation by allergen-associated proteases. Herein, this study aimed to investigate the effect of HDM on Ca2+ signalling and inflammatory responses in asthmatic airway epithelial cells. Primary bronchial epithelial cells (hPBECs) from asthma donors cultured at air-liquid interface were used to assess electrophysiological, Ca2+ signalling and inflammatory responses. Differences were observed regarding Ca2+ signalling in response to PAR-2 agonist 2-Furoyl-LIGRLO-amide (2-FLI), and equivalent short-circuit current (Ieq) in response to trypsin and 2-FLI, in ALI-asthma and healthy hPBECs. HDM treatment led to increased levels of intracellular cations (Ca2+, Na+) and significantly reduced the 2-FLI-induced change of Ieq in asthma cells. Apical HDM-induced Ca2+ mobilisation was found to mainly involve the activation of PAR-2 and PAR-4-associated store-operated Ca2+ influx and TRPV1. In contrast, PAR-2, PAR-4 antagonists and TRPV1 antagonist only showed slight impact on basolateral HDM-induced Ca2+ mobilisation. HDM trypsin-like serine proteases were the main components leading to non-amiloride sensitive Ieq and also increased interleukin-33 (IL-33) and thymic stromal lymphopoietin (TSLP) from asthma hPBECs. These studies add further insight into the complex mechanisms associated with HDM-induced alterations in cell signalling and their relevance to pathological changes within asthma.

Keratinocytes coordinate inflammatory responses and regulate development of secondary lymphedema

Epidermal changes are histological hallmarks of secondary lymphedema, but it is unknown if keratinocytes contribute to its pathophysiology. Using clinical lymphedema specimens and mouse models, we show that keratinocytes play a primary role in lymphedema development by producing T-helper 2 (Th2) -inducing cytokines. Specifically, we find that keratinocyte proliferation and expression of protease-activated receptor 2 (PAR2) are early responses following lymphatic injury and regulate the expression of Th2-inducing cytokines, migration of Langerhans cells, and skin infiltration of Th2-differentiated T cells. Furthermore, inhibition of PAR2 activation with a small molecule inhibitor or the proliferation inhibitor teriflunomide (TF) prevents activation of keratinocytes stimulated with lymphedema fluid. Finally, topical TF is highly effective for decreasing swelling, fibrosis, and inflammation in a preclinical mouse model. Our findings suggest that lymphedema is a chronic inflammatory skin disease, and topically targeting keratinocyte activation may be a clinically effective therapy for this condition.

Chlamydia trachomatis suppresses host cell store-operated Ca2+ entry and inhibits NFAT/calcineurin signaling

The obligate intracellular bacterium, Chlamydia trachomatis, replicates within a parasitophorous vacuole termed an inclusion. During development, host proteins critical for regulating intracellular calcium (Ca²⁺) homeostasis interact with the inclusion membrane. The inclusion membrane protein, MrcA, interacts with the inositol-trisphosphate receptor (IP₃R), an ER cationic channel that conducts Ca²⁺. Stromal interaction molecule 1 (STIM1), an ER transmembrane protein important for regulating store-operated Ca²⁺ entry (SOCE), localizes to the inclusion membrane via an uncharacterized interaction. We therefore examined Ca²⁺ mobilization in C. trachomatis infected cells. Utilizing a variety of Ca²⁺ indicators to assess changes in cytosolic Ca²⁺ concentration, we demonstrate that C. trachomatis impairs host cell SOCE. Ca²⁺ regulates many cellular signaling pathways. We find that the SOCE-dependent NFAT/calcineurin signaling pathway is impaired in C. trachomatis infected HeLa cells and likely has major implications on host cell physiology as it relates to C. trachomatis pathogenesis.

Distinct roles of ORAI1 in T cell-mediated allergic airway inflammation and immunity to influenza A virus infection

T cell activation and function depend on Ca2+ signals mediated by store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ (CRAC) channels formed by ORAI1 proteins. We here investigated how SOCE controls T cell function in pulmonary inflammation during a T helper 1 (TH1) cell-mediated response to influenza A virus (IAV) infection and TH2 cell-mediated allergic airway inflammation. T cell-specific deletion of Orai1 did not exacerbate pulmonary inflammation and viral burdens following IAV infection but protected mice from house dust mite-induced allergic airway inflammation. ORAI1 controlled the expression of genes including p53 and E2F transcription factors that regulate the cell cycle in TH2 cells in response to allergen stimulation and the expression of transcription factors and cytokines that regulate TH2 cell function. Systemic application of a CRAC channel blocker suppressed allergic airway inflammation without compromising immunity to IAV infection, suggesting that inhibition of SOCE is a potential treatment for allergic airway disease.

The airway smooth muscle sodium/calcium exchanger NCLX is critical for airway remodeling and hyperresponsiveness in asthma

The structural changes of airway smooth muscle (ASM) that characterize airway remodeling (AR) are crucial to the pathogenesis of asthma. During AR, ASM cells dedifferentiate from a quiescent to a proliferative, migratory, and secretory phenotype. Calcium (Ca²⁺) is a ubiquitous second messenger that regulates many cellular processes, including proliferation, migration, contraction, and metabolism. Furthermore, mitochondria have emerged as major Ca²⁺ signaling organelles that buffer Ca²⁺ through uptake by the mitochondrial Ca²⁺ uniporter and extrude it through the Na⁺/Ca²⁺ exchanger (NCLX/Slc8b1). Here, we show using mitochondrial Ca²⁺-sensitive dyes that NCLX only partially contributes to mitochondrial Ca²⁺ extrusion in ASM cells. Yet, NCLX is necessary for ASM cell proliferation and migration. Through cellular imaging, RNA-Seq, and biochemical assays, we demonstrate that NCLX regulates these processes by preventing mitochondrial Ca²⁺ overload and supporting store-operated Ca²⁺ entry, activation of Ca²⁺/calmodulin-dependent kinase II, and transcriptional and metabolic reprogramming. Using small animal respiratory mechanic measurements and immunohistochemistry, we show that smooth muscle-specific NCLX KO mice are protected against AR, fibrosis, and hyperresponsiveness in an experimental model of asthma. Our findings support NCLX as a potential therapeutic target in the treatment of asthma.

Extracellular Nucleotides and Histamine Suppress TLR3- and RIG-I-Mediated Release of Antiviral IFNs from Human Airway Epithelial Cells

Respiratory viruses stimulate the release of antiviral IFNs from the airway epithelium. Previous studies have shown that asthmatic patients show diminished release of type I and type III IFNs from bronchial epithelia. However, the mechanism of this suppression is not understood. In this study, we report that extracellular nucleotides and histamine, which are elevated in asthmatic airways, strongly inhibit release of type I and type III IFNs from human bronchial airway epithelial cells (AECs). Specifically, ATP, UTP, and histamine all inhibited the release of type I and type III IFNs from AECs induced by activation of TLR3, retinoic acid-inducible gene I (RIG-I), or cyclic GMP-AMP synthase-STING. This inhibition was at least partly mediated by Gq signaling through purinergic P2Y2 and H1 receptors, but it did not involve store-operated calcium entry. Pharmacological blockade of protein kinase C partially reversed inhibition of IFN production. Conversely, direct activation of protein kinase C with phorbol esters strongly inhibited TLR3- and RIG-I-mediated IFN production. Inhibition of type I and type III IFNs by ATP, UTP, histamine, and the proteinase-activated receptor 2 (PAR2) receptor agonist SLIGKV also occurred in differentiated AECs grown at an air-liquid interface, indicating that the suppression is conserved following mucociliary differentiation. Importantly, histamine and, more strikingly, ATP inhibited type I IFN release from human airway cells infected with live influenza A virus or rhinovirus 1B. These results reveal an important role for extracellular nucleotides and histamine in attenuating the induction of type I and III IFNs from AECs and help explain the molecular basis of the suppression of IFN responses in asthmatic patients.

Nicotinic Acid Adenine Dinucleotide Phosphate Induces Intracellular Ca2+ Signalling and Stimulates Proliferation in Human Cardiac Mesenchymal Stromal Cells

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a newly discovered second messenger that gates two pore channels 1 (TPC1) and 2 (TPC2) to elicit endo-lysosomal (EL) Ca²⁺ release. NAADP-induced lysosomal Ca²⁺ release may be amplified by the endoplasmic reticulum (ER) through the Ca²⁺-induced Ca²⁺ release (CICR) mechanism. NAADP-induced intracellular Ca²⁺ signals were shown to modulate a growing number of functions in the cardiovascular system, but their occurrence and role in cardiac mesenchymal stromal cells (C-MSCs) is still unknown. Herein, we found that exogenous delivery of NAADP-AM induced a robust Ca²⁺ signal that was abolished by disrupting the lysosomal Ca²⁺ store with Gly-Phe β-naphthylamide, nigericin, and bafilomycin A1, and blocking TPC1 and TPC2, that are both expressed at protein level in C-MSCs. Furthermore, NAADP-induced EL Ca²⁺ release resulted in the Ca²⁺-dependent recruitment of ER-embedded InsP₃Rs and SOCE activation. Transmission electron microscopy revealed clearly visible membrane contact sites between lysosome and ER membranes, which are predicted to provide the sub-cellular framework for lysosomal Ca²⁺ to recruit ER-embedded InsP₃Rs through CICR. NAADP-induced EL Ca²⁺ mobilization via EL TPC was found to trigger the intracellular Ca²⁺ signals whereby Fetal Bovine Serum (FBS) induces C-MSC proliferation. Furthermore, NAADP-evoked Ca²⁺ release was required to mediate FBS-induced extracellular signal-regulated kinase (ERK), but not Akt, phosphorylation in C-MSCs. These finding support the notion that NAADP-induced TPC activation could be targeted to boost proliferation in C-MSCs and pave the way for future studies assessing whether aberrant NAADP signaling in C-MSCs could be involved in cardiac disorders.

Impact of Air Pollution in Airway Diseases: Role of the Epithelial Cells (Cell Models and Biomarkers)

Biomedical research is multidisciplinary and often uses integrated approaches performing different experimental models with complementary functions. This approach is important to understand the pathogenetic mechanisms concerning the effects of environmental pollution on human health. The biological activity of the substances is investigated at least to three levels using molecular, cellular, and human tissue models. Each of these is able to give specific answers to experimental problems. A scientific approach, using biological methods (wet lab), cell cultures (cell lines or primary), isolated organs (three-dimensional cell cultures of primary epithelial cells), and animal organisms, including the human body, aimed to understand the effects of air pollution on the onset of diseases of the respiratory system. Biological methods are divided into three complementary models: in vitro, ex vivo, and in vivo. In vitro experiments do not require the use of whole organisms (in vivo study), while ex vivo experiments use isolated organs or parts of organs. The concept of complementarity and the informatic support are useful tools to organize, analyze, and interpret experimental data, with the aim of discussing scientific notions with objectivity and rationality in biology and medicine. In this scenario, the integrated and complementary use of different experimental models is important to obtain useful and global information that allows us to identify the effect of inhaled pollutants on the incidence of respiratory diseases in the exposed population. In this review, we focused our attention on the impact of air pollution in airway diseases with a rapid and descriptive analysis on the role of epithelium and on the experimental cell models useful to study the effect of toxicants on epithelial cells.

Transmembrane serine protease 2 is a prognostic factor for lung adenocarcinoma

Transmembrane serine protease 2 (TMPRSS2) has been intensively investigated during the current Sars-CoV-2 pandemic as a virus activating protease. Furthermore, TMPRSS2 is an oncogenic gene associated with several cancer entities. Co-expression of TMPRSS2 and serpin family A member 1 (SERPINA1) (encoding alpha-1-antitrypsin; AAT) has been reported in the human lung. Recently, AAT was identified as a novel TMPRSS2 inhibitor. We previously reported that lower SERPINA1 expression in tumor tissues and higher levels of plasma AAT are associated with worse survival of patients with non-small cell lung cancer (NSCLC). In the present study, we sought to examine TMPRSS2 and SERPINA1/AAT expression in tumor and adjacent lung tissues from 347 NSCLC patients. Based on clinical data and gene expression analysis, we performed Cox regression for the survival analysis, and correlated TMPRSS2 and AAT protein levels in tissue samples by immunohistochemical and western blot analyses. We found that lower TMPRSS2 expression in tumor compared to adjacent non-tumor tissues is linked to a poor overall survival in patients with adenocarcinoma (ADC) and those who are current smokers. IHC staining of TMPRSS2 validated our findings in regard to overall survival while we did not observe a correlation with AAT staining. Based on western blot analyses, we found only a slight negative correlation between full-length TMPRSS2 and AAT in non-tumor tissues, which seems to be related to smoking status. Taken together, we demonstrated that TMPRSS2 is a prognostic factor in patients with lung ADC; however, a link between AAT and TMPRSS2 proteins warrants further investigation.

STIM1 is a core trigger of airway smooth muscle remodeling and hyperresponsiveness in asthma

Stromal-interacting molecule 1 (STIM1) proteins are essential for the function of store-operated Ca²⁺ entry (SOCE). Using transcriptomics, metabolomics, imaging, and inducible smooth muscle–specific STIM1 knockout mice expressing genetically encoded Ca²⁺ sensors, we reveal a crucial function of STIM1 in airway remodeling and airway hyperresponsiveness in asthma. STIM1-mediated Ca²⁺ oscillations in airway smooth muscle (ASM) cells are critical for ASM remodeling through metabolic and transcriptional reprogramming and cytokine secretion, including IL-6. These effects are driven by Ca²⁺-dependent activation of the transcription factor isoform NFAT4 specifically in ASM. Our data provide evidence that ASM STIM1 and SOCE are central triggers of asthma manifestations and advocate for the future use of STIM1 as a molecular target in asthma therapy.

Airway remodeling and airway hyperresponsiveness are central drivers of asthma severity. Airway remodeling is a structural change involving the dedifferentiation of airway smooth muscle (ASM) cells from a quiescent to a proliferative and secretory phenotype. Here, we show up-regulation of the endoplasmic reticulum Ca²⁺ sensor stromal-interacting molecule 1 (STIM1) in ASM of asthmatic mice. STIM1 is required for metabolic and transcriptional reprogramming that supports airway remodeling, including ASM proliferation, migration, secretion of cytokines and extracellular matrix, enhanced mitochondrial mass, and increased oxidative phosphorylation and glycolytic flux. Mechanistically, STIM1-mediated Ca²⁺ influx is critical for the activation of nuclear factor of activated T cells 4 and subsequent interleukin-6 secretion and transcription of pro-remodeling transcription factors, growth factors, surface receptors, and asthma-associated proteins. STIM1 drives airway hyperresponsiveness in asthmatic mice through enhanced frequency and amplitude of ASM cytosolic Ca²⁺ oscillations. Our data advocates for ASM STIM1 as a target for asthma therapy.

Differential Regulation of ATP- and UTP-Evoked Prostaglandin E2 and IL-6 Production from Human Airway Epithelial Cells

The airway epithelial cells (AECs) lining the conducting passageways of the lung secrete a variety of immunomodulatory factors. Among these, PGE2 limits lung inflammation and promotes bronchodilation. By contrast, IL-6 drives intense airway inflammation, remodeling, and fibrosis. The signaling that differentiates the production of these opposing mediators is not understood. In this study, we find that the production of PGE2 and IL-6 following stimulation of human AECs by the damage-associated molecular pattern extracellular ATP shares a common requirement for Ca2+ release-activated Ca2+ (CRAC) channels. ATP-mediated synthesis of PGE2 required activation of metabotropic P2Y2 receptors and CRAC channel-mediated cytosolic phospholipase A2 signaling. By contrast, ATP-evoked synthesis of IL-6 occurred via activation of ionotropic P2X receptors and CRAC channel-mediated calcineurin/NFAT signaling. In contrast to ATP, which elicited the production of both PGE2 and IL-6, the uridine nucleotide, UTP, stimulated PGE2 but not IL-6 production. These results reveal that human AECs employ unique receptor-specific signaling mechanisms with CRAC channels as a signaling nexus to regulate release of opposing immunomodulatory mediators. Collectively, our results identify P2Y2 receptors, CRAC channels, and P2X receptors as potential intervention targets for airway diseases.

Indomethacin Treatment Post-irradiation Improves Mouse Parotid Salivary Gland Function via Modulation of Prostaglandin E2 Signaling

Annually, >600,000 new cases of head and neck cancer (HNC) are diagnosed worldwide with primary treatment being surgery and radiotherapy. During ionizing radiation (IR) treatment of HNC, healthy salivary glands are collaterally damaged, leading to loss of function that severely diminishes the quality of life for patients due to increased health complications, including oral infections and sores, cavities, and malnutrition, among others. Therapies for salivary hypofunction are ineffective and largely palliative, indicating a need for further research to uncover effective approaches to prevent or restore loss of salivary gland function following radiotherapy. Previous work in our lab implicated prostaglandin E₂ (PGE₂) as an inflammatory mediator whose release from radiation-exposed cells promotes salivary gland damage and loss of function. Deletion of the P2X7 purinergic receptor for extracellular ATP reduces PGE₂ secretion in irradiated primary parotid gland cells, and salivary gland function is enhanced in irradiated P2X7R^-/- mice compared to wild-type mice. However, the role of PGE₂ signaling in irradiated salivary glands is unclear and understanding the mechanism of PGE₂ action is a goal of this study. Results show that treatment of irradiated mice with the non-steroidal anti-inflammatory drug (NSAID) indomethacin, which reduces PGE₂ production via inhibition of cyclooxygenase-1 (COX-1), improves salivary gland function compared to irradiated vehicle-treated mice. To define the signaling pathway whereby PGE₂ induces salivary gland dysfunction, primary parotid gland cells treated with PGE₂ have increased c-Jun N-terminal Kinase (JNK) activation and cell proliferation and reduced amylase levels and store-operated calcium entry (SOCE). The in vivo effects of blocking PGE₂ production were also examined and irradiated mice receiving indomethacin injections have reduced JNK activity at 8 days post-irradiation and reduced proliferation and increased amylase levels at day 30, as compared to irradiated mice without indomethacin. Combined, these data suggest a mechanism whereby irradiation-induced PGE₂ signaling to JNK blocks critical steps in saliva secretion manifested by a decrease in the quality (diminished amylase) and quantity (loss of calcium channel activity) of saliva, that can be restored with indomethacin. These findings encourage further attempts evaluating indomethacin as a viable therapeutic option to prevent damage to salivary glands caused by irradiation of HNC in humans.

Orai1 Channel Regulates Human-Activated Pancreatic Stellate Cell Proliferation and TGFβ1 Secretion through the AKT Signaling Pathway

Simple Summary

Activated pancreatic stellate cells (aPSCs), the main source of cancer-associated fibroblasts in pancreatic ductal adenocarcinoma (PDAC), are well known as the key actor of the abundant fibrotic stroma development surrounding the tumor cells. In permanent communication with the tumor cells, they enhance PDAC early spreading and limit the drug delivery. However, the understanding of PSC activation mechanisms and the associated signaling pathways is still incomplete. In this study, we aimed to evaluate the role of Ca²⁺, and Orai1 Ca²⁺ channels, in two main PSC activation processes: cell proliferation and cytokine secretion. Indeed, Ca²⁺ is a versatile second messenger implicated in the regulation of numerous biological processes. We believe that a better comprehension of PSC Ca²⁺ -dependent activation mechanisms will bring up new crucial PDAC early prognostic markers or new targeting approaches in PDAC treatment.

Abstract

Activated pancreatic stellate cells (aPSCs), the crucial mediator of pancreatic desmoplasia, are characterized, among others, by high proliferative potential and abundant transforming growth factor _β1 (TGF_β1) secretion. Over the past years, the involvement of Ca²⁺ channels in PSC pathophysiology has attracted great interest in pancreatic cancer research. We, thus, aimed to investigate the role of the Orai1 Ca²⁺ channel in these two PSC activation processes. Using the siRNA approach, we invalided Orai1 expression and assessed the channel functionality by Ca²⁺ imaging, the effect on aPSC proliferation, and TGF_β1 secretion. We demonstrated the functional expression of the Orai1 channel in human aPSCs and its implication in the store-operated Ca²⁺ entry (SOCE). Orai1 silencing led to a decrease in aPSC proliferation, TGF_β1 secretion, and AKT activation. Interestingly, TGF_β1 induced a higher SOCE response by increasing Orai1 mRNAs and proteins and promoted both AKT phosphorylation and cell proliferation, abolished by Orai1 silencing. Together, our results highlight the role of Orai1-mediated Ca²⁺ entry in human aPSC pathophysiology by controlling cell proliferation and TGF_β1 secretion through the AKT signaling pathway. Moreover, we showed a TGF_β1-induced autocrine positive feedback loop by promoting the Orai1/AKT-dependent proliferation via the stimulation of Orai1 expression and function.

Cellular and mitochondrial calcium communication in obstructive lung disorders

Calcium (Ca²⁺) signalling is well known to dictate cellular functioning and fate. In recent years, the accumulation of Ca²⁺ in the mitochondria has emerged as an important factor in Chronic Respiratory Diseases (CRD) such as Asthma and Chronic Obstructive Pulmonary Disease (COPD). Various reports underline an aberrant increase in the intracellular Ca²⁺, leading to mitochondrial ROS generation, and further activation of the apoptotic pathway in these diseases. Mitochondria contribute to Ca²⁺ buffering which in turn regulates mitochondrial metabolism and ATP production. Disruption of this Ca²⁺ balance leads to impaired cellular processes like apoptosis or necrosis and thus contributes to the pathophysiology of airway diseases. This review highlights the key role of cytoplasmic and mitochondrial Ca²⁺ signalling in regulating CRD, such as asthma and COPD. A better understanding of the dysregulation of mitochondrial Ca²⁺ homeostasis in these diseases could provide cues for the development of advanced therapeutic interventions in these diseases.

Orai1 Channels Are Essential for Amplification of Glutamate-Evoked Ca2+ Signals in Dendritic Spines to Regulate Working and Associative Memory

Store-operated Orai1 calcium channels function as highly Ca²⁺-selective ion channels and are broadly expressed in many tissues including the central nervous system, but their contributions to cognitive processing are largely unknown. Here, we report that many measures of synaptic, cellular, and behavioral models of learning are markedly attenuated in mice lacking Orai1 in forebrain excitatory neurons. Results with focal glutamate uncaging in hippocampal neurons support an essential role of Orai1 channels in amplifying NMDA-receptor-induced dendritic Ca²⁺ transients that drive activity-dependent spine morphogenesis and long-term potentiation at Schaffer collateral-CA1 synapses. Consistent with these signaling roles, mice lacking Orai1 in pyramidal neurons (but not interneurons) exhibit striking deficits in working and associative memory tasks. These findings identify Orai1 channels as essential regulators of dendritic spine Ca²⁺ signaling, synaptic plasticity, and cognition.

The PAR2 inhibitor I-287 selectively targets Gαq and Gα12/13 signaling and has anti-inflammatory effects

Protease-activated receptor-2 (PAR2) is involved in inflammatory responses and pain, therefore representing a promising therapeutic target for the treatment of immune-mediated inflammatory diseases. However, as for other GPCRs, PAR2 can activate multiple signaling pathways and those involved in inflammatory responses remain poorly defined. Here, we describe a new selective and potent PAR2 inhibitor (I-287) that shows functional selectivity by acting as a negative allosteric regulator on Gα_q and Gα_12/13 activity and their downstream effectors, while having no effect on G_i/o signaling and βarrestin2 engagement. Such selective inhibition of only a subset of the pathways engaged by PAR2 was found to be sufficient to block inflammation in vivo. In addition to unraveling the PAR2 signaling pathways involved in the pro-inflammatory response, our study opens the path toward the development of new functionally selective drugs with reduced liabilities that could arise from blocking all the signaling activities controlled by the receptor.

Avet et al. characterize I-287, an inhibitor to protease-activated receptor 2 using BRET-assays. They find that I-287 selectively inhibits Gα_q and Gα_12/13 without affecting the activation of G_i/o or the recruitment of βarrestin2 and that it blocks inflammation in vitro and in vivo.

Store-Operated Ca2+ Channels: Mechanism, Function, Pharmacology, and Therapeutic Targets

Calcium (Ca²⁺) release-activated Ca²⁺ (CRAC) channels are a major route for Ca²⁺ entry in eukaryotic cells. These channels are store operated, opening when the endoplasmic reticulum (ER) is depleted of Ca²⁺, and are composed of the ER Ca²⁺ sensor protein STIM and the pore-forming plasma membrane subunit Orai. Recent years have heralded major strides in our understanding of the structure, gating, and function of the channels. Loss-of-function and gain-of-function mutants combined with RNAi knockdown strategies have revealed important roles for the channel in numerous human diseases, making the channel a clinically relevant target. Drugs targeting the channels generally lack specificity or exhibit poor efficacy in animal models. However, the landscape is changing, and CRAC channel blockers are now entering clinical trials. Here, we describe the key molecular and biological features of CRAC channels, consider various diseases associated with aberrant channel activity, and discuss targeting of the channels from a therapeutic perspective.

Effect of chitinase-3-like protein 1 on glucose metabolism: In vitro skeletal muscle and human genetic association study

We investigated the effect of chitinase-3-like protein 1 (CHI3L1) on glucose metabolism and its underlying mechanisms in skeletal muscle cells, and evaluated whether the observed effects are relevant in humans. CHI3L1 was associated with increased glucose uptake in skeletal muscles in an AMP-activated protein kinase (AMPK)-dependent manner, and with increased intracellular calcium levels via PAR2. The improvement in glucose metabolism observed in an intraperitoneal glucose tolerance test on male C57BL/6J mice supported this association. Inhibition of the CaMKK was associated with suppression of CHI3L1-mediated glucose uptake. Additionally, CHI3L1 was found to influence glucose uptake through the PI3K/AKT pathway. Results suggested that CHI3L1 stimulated the phosphorylation of AS160 and p38 MAPK downstream of AMPK and AKT, and the resultant GLUT4 translocation. In primary myoblast cells, stimulation of AMPK and AKT was observed in response to CHI3L1, underscoring the biological relevance of CHI3L1. CHI3L1 levels were elevated in cells under conditions that mimic exercise in vitro and in exercised mice in vivo, indicating that CHI3L1 is secreted during muscle contraction. Finally, similar associations between CHI3L1 and metabolic parameters were observed in humans alongside genotype associations between CHI3L1 and diabetes at the population level. CHI3L1 may be a potential therapeutic target for the treatment of diabetes.

PAR2-Mediated cAMP Generation Suppresses TRPV4-Dependent Ca2+ Signaling in Alveolar Macrophages to Resolve TLR4-Induced Inflammation

Alveolar macrophages (AMs), upon sensing pathogens, trigger host defense by activating toll-like receptor 4 (TLR4), but the counterbalancing mechanisms that deactivate AM inflammatory signaling and prevent lethal edema, the hallmark of acute lung injury (ALI), remain unknown. Here, we demonstrate the essential role of AM protease-activating receptor 2 (PAR2) in rapidly suppressing inflammation to prevent long-lasting injury. We show that thrombin, released during TLR4-induced lung injury, directly activates PAR2 to generate cAMP, which abolishes Ca²⁺ entry through the TRPV4 channel. Deletion of PAR2 and thus the accompanying cAMP generation augments Ca²⁺ entry via TRPV4, causing sustained activation of the transcription factor NFAT to produce long-lasting TLR4-mediated inflammatory lung injury. Rescuing thrombin-sensitive PAR2 expression or blocking TRPV4 activity in PAR2-null AMs restores their capacity to resolve inflammation and reverse lung injury. Thus, activation of the thrombin-induced PAR2-cAMP cascade in AMs suppresses TLR4 inflammatory signaling to reinstate tissue integrity.

Could Inflammaging and Its Sequelae Be Prevented or Mitigated?

Aged humans display a chronic and low-grade inflammation, termed “inflammaging”, which has been potentially linked to the subsequent development of some aging-associated systemic disorders, including type 2 diabetes, atherosclerotic cardiovascular disease, Alzheimer’s disease and obesity. Though the origin of aging-associated systemic inflammation is uncertain, epidemiological studies show that inflammatory dermatoses (psoriasis and eczema) are risk factors for some aging-associated systemic disorders, such as type 2 diabetes and atherosclerotic cardiovascular disease. Moreover, recent studies demonstrate that epidermal dysfunction in aged skin not only causes cutaneous inflammation, but also a subsequent increase in circulating levels of proinflammatory cytokines, suggesting that the skin could be a major contributor to inflammaging. This hypothesis is further supported by reductions in circulating levels of proinflammatory cytokines in both aged humans and murine, following improvements in epidermal function with topical emollients. Therefore, correction of epidermal dysfunction could be a novel approach for the prevention and mitigation of certain inflammation-associated chronic disorders in aged humans.

Expression Suppression and Activity Inhibition of TRPM7 Regulate Cytokine Production and Multiple Organ Dysfunction Syndrome During Endotoxemia: a New Target for Sepsis

BACKGROUND

Main pathological features detected during sepsis and endotoxemia include over-secretion of pro-inflammatory cytokines and multiorgan dysfunction syndrome (MODS). Unfortunately, current clinical efforts to treat sepsis are unsatisfactory, and mortality remains high. Interestingly, transient receptor potential (TRP) melastatin 7 (TRPM7) ion channel controlling Ca2+ and Mg2+ permeability is involved in cytokine production and inflammatory response. Furthermore, TRPM7 downregulation has been shown to alleviate local symptoms in some models of sepsis, but its effects at a systemic level remain to be explored.

OBJECTIVE

To test whether TRPM7 mediates cytokine production and MODS during endotoxemia.

METHODS

Endotoxemic and sham-endotoxemic rats were subjected to pharmacological inhibition of TRPM7 using carvacrol, or to expression suppression by adenovirus delivery of shRNA (AdVshTRPM7). Then, cytokine and MODS levels in the blood were measured.

RESULTS

Inhibition of TRPM7 with carvacrol and suppression with AdVshTRPM7 were both efficient in inhibiting the over-secretion of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-12, in endotoxemic rats, without inducing downregulation in blood levels of antiinflammatory cytokines IL-10 and IL-4. Additionally, the use of carvacrol and AdVshTRPM7 significantly prevented liver and pancreas dysfunction, altered metabolic function, and hypoglycemia, induced by endotoxemia. Furthermore, muscle mass wasting and cardiac muscle damage were also significantly reduced by the use of carvacrol and AdVshTRPM7 in endotoxemic rats.

CONCLUSION

Our results indicate TRPM7 ion channel as a key protein regulating inflammatory responses and MODS during sepsis. Moreover, TRPM7 appears as a novel molecular target for the management of sepsis.

Gene expression of TMEM178, which encodes a negative regulator of NFATc1, decreases with the progression of asthma severity

In two independent microarray studies involving primary airway epithelial cells, the relative gene expression of TMEM178 decreases with the progression of asthma severity. Our manuscript creates a paradigm for future studies dissecting the role of Tmem178 in the pathogenesis of severe asthma.

Dust mite-derived Der f 3 activates a pro-inflammatory program in airway epithelial cells via PAR-1 and PAR-2

Protease activity of allergens has been suggested to be involved in the pathogenesis of allergic diseases. The major allergen Der f 3 from Dermatophagoides farinae harbors serine protease activity, but its immunopathogenesis remains unclear. This study aims to explore the effect of Der f 3 on the airway epithelial barrier and on the molecular pathways by which Der f 3 induces inflammation. RNA-seq was performed to identify differentially expressed genes in bronchial airway epithelial cells (AEC) between native Der f 3 and heat-inactivated (H) Der f 3, coupled with real-time PCR (RT-PCR) and ELISA for validation. Unlike other protease allergens such as that induce Th2-promoting alarmins (IL-25, IL-33, TSLP) in AECs, Der f 3 induced pro-inflammatory cytokines and chemokines including IL-6, IL-8 and GM-CSF, which are known to promote Th17 response. These pro-inflammatory mediators were induced by Der f 3 via the MAPK and NF-κB pathways as well as the store-operated calcium signaling. Gene silencing with small interfering RNA in A549 and BEAS-2B cells indicated that activation of AECs by Der f 3 was mainly dependent on protease-activated receptor 2 (PAR-2), while PAR-1 was also required for the full activation of AECs. Double knock-down of PAR-1 and PAR-2 largely impaired Der f 3-inducecd IL-8 production and subsequent signaling pathways. Our data suggest that Der f 3 induces pro-inflammatory mediators in human epithelial cell lines via the PARs-MAPK-NF-κB axis. Our results provide a molecular mechanism by which Der f 3 may trigger the Th17-skewed allergic response toward house dust mites.

Metformin Targets Mitochondrial Electron Transport to Reduce Air-Pollution-Induced Thrombosis

Urban particulate matter air pollution induces the release of pro-inflammatory cytokines including interleukin-6 (IL-6) from alveolar macrophages, resulting in an increase in thrombosis. Here, we report that metformin provides protection in this murine model. Treatment of mice with metformin or exposure of murine or human alveolar macrophages to metformin prevented the particulate matter-induced generation of complex III mitochondrial reactive oxygen species, which were necessary for the opening of calcium release-activated channels (CRAC) and release of IL-6. Targeted genetic deletion of electron transport or CRAC channels in alveolar macrophages in mice prevented particulate matter-induced acceleration of arterial thrombosis. These findings suggest metformin as a potential therapy to prevent some of the premature deaths attributable to air pollution exposure worldwide.

Differential bronchial epithelial response regulated by ΔNp63: a functional understanding of the epithelial shedding found in asthma

Bronchial epithelial cells serve as a physical barrier at the forefront of the immune system. Barrier disruption and an excessive immune response of the bronchial epithelium contribute to the pathophysiology of asthma, a chronic bronchial inflammatory disease. The purpose of this study was to investigate the functional significance of ΔNp63, a p53-like transcription factor expressed by the basal bronchial epithelium. The immunohistochemical expression profile of ΔNp63 was evaluated in human bronchial tissue derived from asthma patients. The role of ΔNp63 in apoptosis inhibition and production of soluble mediators was investigated in vitro with cultured BEAS-2B bronchial epithelial cells using molecular biological analysis. In healthy bronchial tissue, ΔNp63-positive basal epithelial cells were covered with differentiated ΔNp63-negative cells but in the asthmatic airway, ΔNp63-positive cells were directly exposed to the bronchial lumen due to severe epithelial shedding. ΔNp63 regulated bronchial apoptosis in response to Toll-like receptor 3 stimulation. On the other hand, expression of ΔNp63 was modulated by stimulation with trypsin and SLIGKV, protease-activated receptor 2 ligands. Further phenotypic analysis revealed that ΔNp63 controlled the transcriptional expression and protein release of some epithelium-derived proinflammatory cytokines and endogenous protease inhibitors. We conclude that ΔNp63 modulates the bronchial epithelial response to viral infection. At the same time, ΔNp63 expression is influenced by proteases, which are abundant in house dust mites. Therefore, the ΔNp63 axis would be intimately involved in these two major triggers of asthma exacerbations, viral infection and protease overload.

Human airway trypsin-like protease enhances interleukin-8 synthesis in bronchial epithelial cells by activating protease-activated receptor 2

Human airway trypsin-like protease (HAT) localizes at human bronchial epithelial cells (HBECs). HAT enhanced release of interleukin-8 (IL-8) from HBECs at 10-100 mU/mL and the enhanced release was almost completely abolished by 50 μM leupeptin, a serine protease inhibitor. Previous reports suggested that HAT displays its physiological functions via protease-activated receptor 2 (PAR2). In the present study, we examined the mechanism whereby HAT upregulates IL-8 synthesis in HBECs with a focus on PAR2. Northern blot analysis revealed that HAT enhanced IL-8 mRNA expression at concentrations of 10-100 mU/mL. PAR2 activating peptide (PAR2 AP) also enhanced IL-8 release and IL-8 mRNA expression in HBECs at 50-1,000 μM at similar levels as HAT. Knockdown of PAR2 mRNA by siRNA methods showed that PAR2 mRNA expression was significantly depressed in primary HBECs, and both HAT- and PAR2 AP-induced IL-8 mRNA elevation was significantly depressed in PAR2 siRNA-transfected HBECs. Additionally, HAT cleaved the PAR2 activating site (R³⁶-S³⁷ bond) of synthetic PAR2 N-terminal peptide. These results indicate that HAT stimulates IL-8 synthesis in airway epithelial cells via PAR2 and could help to amplify inflammation in chronic respiratory tract disease.

Protease-activated receptor 2 activates CRAC-mediated Ca2+ influx to cause prostate smooth muscle contraction

Protease activated receptor 2 (PAR2) is a G-protein coupled receptor that contributes to prostate fibrosis and lower urinary tract symptoms (LUTS). In addition to fibrosis, aberrant smooth muscle tone in the prostate has been hypothesized to play a role. We therefore examined PAR2 expression in primary human prostate smooth muscle cells (PSMC) and studied the downstream signaling effects of PAR2 activation. Signaling pathways involved in the process were assessed using the PAR2 activating peptide SLIGKV-NH2. We show that PAR2 is expressed in PSMC and that PAR2 activation mediates a biphasic elevation in intracellular Ca²⁺ and phosphorylation of myosin light chain 20 (MLC20), causing cellular contraction as assessed in a gel contraction assay. Intracellular Ca²⁺ flux was inhibited by a phosphoinositide hydrolysis inhibitor, U73122, showing a requirement for phospholipase C β (PLCβ) activation. PSMC expressed mRNA for L-type voltage dependent Ca²⁺ channels (VDCC) as well as Ca²⁺ release activated channels (CRAC), a hitherto unreported finding. Secondary intracellular Ca²⁺ oscillations were abrogated only by BTP2, the CRAC channel inhibitor, but not by nifedipine, an inhibitor of VDCC. These data suggest that, PAR2 activation and subsequent Ca²⁺ entry through CRAC channels are important mechanisms in prostate smooth muscle contraction.

M1 Macrophage Polarization Is Dependent on TRPC1-Mediated Calcium Entry

Macrophage plasticity is essential for innate immunity, but in-depth signaling mechanism(s) regulating their functional phenotypes are ill-defined. Here we report that interferon (IFN) γ priming of naive macrophages induces store-mediated Ca²⁺ entry and inhibition of Ca²⁺ entry impairs polarization to M1 inflammatory phenotype. In vitro and in vivo functional analyses revealed ORAI1 to be a primary contributor to basal Ca²⁺ influx in macrophages, whereas IFNγ-induced Ca²⁺ influx was mediated by TRPC1. Deficiency of TRPC1 displayed abrogated IFNγ-induced M1 inflammatory mediators in macrophages. In a preclinical model of peritonitis by Klebsiella pneumoniae infection, macrophages showed increased Ca²⁺ influx, which was TRPC1 dependent. Macrophages from infected TRPC1^−/− mice showed inhibited expression of M1-associated signature molecules. Furthermore, in human patients with systemic inflammatory response syndrome, the level of TRPC1 expression in circulating macrophages directly correlated with M1 inflammatory mediators. Overall, TRPC1-mediated Ca²⁺ influx is essential for the induction/shaping of macrophage polarization to M1 inflammatory phenotype.

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TRPC1 mediates sterile or infection-induced Ca²⁺ influx and M1 phenotype in macrophages

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ORAI1 mediates the basal Ca²⁺ influx in macrophages

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In patients with SIRS, the TRPC1 level correlates with M1 inflammatory mediators in macrophages

Interleukin-33 is activated by allergen- and necrosis-associated proteolytic activities to regulate its alarmin activity during epithelial damage

Interleukin (IL)-33 is an IL-1 family alarmin released from damaged epithelial and endothelial barriers to elicit immune responses and allergic inflammation via its receptor ST2. Serine proteases released from neutrophils, mast cells and cytotoxic lymphocytes have been proposed to process the N-terminus of IL-33 to enhance its activity. Here we report that processing of full length IL-33 can occur in mice deficient in these immune cell protease activities. We sought alternative mechanisms for the proteolytic activation of IL-33 and discovered that exogenous allergen proteases and endogenous calpains, from damaged airway epithelial cells, can process full length IL-33 and increase its alarmin activity up to ~60-fold. Processed forms of IL-33 of apparent molecular weights ~18, 20, 22 and 23 kDa, were detected in human lungs consistent with some, but not all, proposed processing sites. Furthermore, allergen proteases degraded processed forms of IL-33 after cysteine residue oxidation. We suggest that IL-33 can sense the proteolytic and oxidative microenvironment during tissue injury that facilitate its rapid activation and inactivation to regulate the duration of its alarmin function.

Store-operated Ca2+ channels in airway epithelial cell function and implications for asthma

The epithelial cells of the lung are at the interface of a host and its environment and are therefore directly exposed to the inhaled air-borne particles. Rather than serving as a simple physical barrier, airway epithelia detect allergens and other irritants and then help organize the subsequent immune response through release of a plethora of secreted signals. Many of these signals are generated in response to opening of store-operated Ca²⁺ channels in the plasma membrane. In this review, we describe the properties of airway store-operated channels and their role in regulating airway epithelial cell function.

This article is part of the themed issue ‘Evolution brings Ca²⁺ and ATP together to control life and death’.

Protease-activated receptor 2 activates airway apical membrane chloride permeability and increases ciliary beating

Mucociliary clearance, driven by the engine of ciliary beating, is the primary physical airway defense against inhaled pathogens and irritants. A better understanding of the regulation of ciliary beating and mucociliary transport is necessary for identifying new receptor targets to stimulate improved clearance in airway diseases, such as cystic fibrosis and chronic rhinosinusitis. In this study, we examined the protease-activated receptor (PAR)-2, a GPCR previously shown to regulate airway cell cytokine and mucus secretion, and transepithelial Cl^- current. PAR-2 is activated by proteases secreted by airway neutrophils and pathogens. We cultured various airway cell lines, primary human and mouse sinonasal cells, and human bronchial cells at air-liquid interface and examined them using molecular biology, biochemistry, and live-cell imaging. We found that PAR-2 is expressed basolaterally, where it stimulates both intracellular Ca²⁺ release and Ca²⁺ influx, which activates low-level nitric oxide production, increases apical membrane Cl^- permeability ∼3-5-fold, and increases ciliary beating ∼20-50%. No molecular or functional evidence of PAR-4 was observed. These data suggest a novel and previously overlooked role of PAR-2 in airway physiology, adding to our understanding of the role of this receptor in airway Ca²⁺ signaling and innate immunity.-McMahon, D. B., Workman, A. D., Kohanski, M. A., Carey, R. M., Freund, J. R., Hariri, B. M., Chen, B., Doghramji, L. J., Adappa, N. D., Palmer, J. N., Kennedy, D. W., Lee, R. J. Protease-activated receptor 2 activates airway apical membrane chloride permeability and increases ciliary beating.

ORAI2 modulates store-operated calcium entry and T cell-mediated immunity

Store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ (CRAC) channels is critical for lymphocyte function and immune responses. CRAC channels are hexamers of ORAI proteins that form the channel pore, but the contributions of individual ORAI homologues to CRAC channel function are not well understood. Here we show that deletion of Orai1 reduces, whereas deletion of Orai2 increases, SOCE in mouse T cells. These distinct effects are due to the ability of ORAI2 to form heteromeric channels with ORAI1 and to attenuate CRAC channel function. The combined deletion of Orai1 and Orai2 abolishes SOCE and strongly impairs T cell function. In vivo, Orai1/Orai2 double-deficient mice have impaired T cell-dependent antiviral immune responses, and are protected from T cell-mediated autoimmunity and alloimmunity in models of colitis and graft-versus-host disease. Our study demonstrates that ORAI1 and ORAI2 form heteromeric CRAC channels, in which ORAI2 fine-tunes the magnitude of SOCE to modulate immune responses.

Protective Roles for RGS2 in a Mouse Model of House Dust Mite-Induced Airway Inflammation

The GTPase-accelerating protein, regulator of G-protein signalling 2 (RGS2) reduces signalling from G-protein-coupled receptors (GPCRs) that signal via Gαq. In humans, RGS2 expression is up-regulated by inhaled corticosteroids (ICSs) and long-acting β2-adrenoceptor agonists (LABAs) such that synergy is produced in combination. This may contribute to the superior clinical efficacy of ICS/LABA therapy in asthma relative to ICS alone. In a murine model of house dust mite (HDM)-induced airways inflammation, three weeks of intranasal HDM (25 μg, 3×/week) reduced lung function and induced granulocytic airways inflammation. Compared to wild type animals, Rgs2-/- mice showed airways hyperresponsiveness (increased airways resistance and reduced compliance). While HDM increased pulmonary inflammation observed on hematoxylin and eosin-stained sections, there was no difference between wild type and Rgs2-/- animals. HDM-induced mucus hypersecretion was also unaffected by RGS2 deficiency. However, inflammatory cell counts in the bronchoalveolar lavage fluid of Rgs2-/- animals were significantly increased (57%) compared to wild type animals and this correlated with increased granulocyte (neutrophil and eosinophil) numbers. Likewise, cytokine and chemokine (IL4, IL17, IL5, LIF, IL6, CSF3, CXCLl, CXCL10 and CXCL11) release was increased by HDM exposure. Compared to wild type, Rgs2-/- animals showed a trend towards increased expression for many cytokines/chemokines, with CCL3, CCL11, CXCL9 and CXCL10 being significantly enhanced. As RGS2 expression was unaffected by HDM exposure, these data indicate that RGS2 exerts tonic bronchoprotection in HDM-induced airways inflammation. Modest anti-inflammatory and anti-remodelling roles for RGS2 are also suggested. If translatable to humans, therapies that maximize RGS2 expression may prove advantageous.

Tight junctions in pulmonary epithelia during lung inflammation

Inflammatory lung diseases like asthma bronchiale, chronic obstructive pulmonary disease and allergic airway inflammation are widespread public diseases that constitute an enormous burden to the health systems. Mainly classified as inflammatory diseases, the treatment focuses on strategies interfering with local inflammatory responses by the immune system. Inflammatory lung diseases predispose patients to severe lung failures like alveolar oedema, respiratory distress syndrome and acute lung injury. These life-threatening syndromes are caused by increased permeability of the alveolar and airway epithelium and exudate formation. However, the mechanism underlying epithelium barrier breakdown in the lung during inflammation is elusive. This review emphasises the role of the tight junction of the airway epithelium as the predominating structure conferring epithelial tightness and preventing exudate formation and the impact of inflammatory perturbations on their function.

Immunomodulatory effect of APS and PSP is mediated by Ca2+-cAMP and TLR4/NF-κB signaling pathway in macrophage

OBJECTIVE

This study is to investigate the role of second messengers and TLR4/NF-κB signaling pathway in the immunomodulatory activities of Astragalus polysaccharide (APS) and Polysaccharopeptide (PSP) in macrophages.

METHODS

RAW 264.7 macrophage cells were treated with APS, PSP, lipopolysaccharide (LPS), or NiCl₂. Power-spectral method was used to detect protein kinase C (PKC) and Griess reaction to detect nitric oxide (NO). ELISA was conducted to detect cyclic adenosine monophosphate (cAMP), diglycerides (DAG), inositol 1, 4, 5-triphosphate (IP3), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Confocal laser scanning microscopy was performed to detect calcium level. qRT-PCR and Western blot was used to detect mRNA and protein expression of NF-κB.

RESULTS

APS and PSP significantly increased the concentrations of intracellular second messengers (NO, cAMP, DAG, IP3, Ca²⁺) and the activity of PKC in macrophages (p<0.05).The intracellular NF-κB mRNA and protein levels were significantly increased in macrophages treated by APS and PSP (p<0.05), whereas those were significantly decreased after NiCl₂ incubation (p<0.05). Similarly, the secretion of TNF-α and IL-6 were significantly decreased by the treatment of NiCl₂.

CONCLUSION

Our findings strongly suggest that Ca²⁺-cAMP and TLR4/NF-κB signaling pathways are, at least partly, involved in APS and PSP mediated immunomodulatory activities in macrophages.

Allergens stimulate store-operated calcium entry and cytokine production in airway epithelial cells

Aberrant immune responses to environmental allergens including insect allergens from house dust mites and cockroaches contribute to allergic inflammatory diseases such as asthma in susceptible individuals. Airway epithelial cells (AECs) play a critical role in this process by sensing the proteolytic activity of allergens via protease-activated receptors (PAR2) to initiate inflammatory and immune responses in the airway. Elevation of cytosolic Ca²⁺ is an important signaling event in this process, yet the fundamental mechanism by which allergens induce Ca²⁺ elevations in AECs remains poorly understood. Here we find that extracts from dust mite and cockroach induce sustained Ca²⁺ elevations in AECs through the activation of Ca²⁺ release-activated Ca²⁺ (CRAC) channels encoded by Orai1 and STIM1. CRAC channel activation occurs, at least in part, through allergen mediated stimulation of PAR2 receptors. The ensuing Ca²⁺ entry then activates NFAT/calcineurin signaling to induce transcriptional production of the proinflammatory cytokines IL-6 and IL-8. These findings highlight a key role for CRAC channels as regulators of allergen induced inflammatory responses in the airway.

The role of Ca(2+) mediated signaling pathways on the effect of taurine against Streptococcus uberis infection

To provide insight into the mechanisms of taurine attenuation of pro-inflammatory response in mouse mammary epithelial cell line (EpH4-Ev, purchased by ATCC, USA) after Streptococcus uberis (S. uberis, 0140J) challenge, we infected MECs with S. uberis (2.5×10(7)cfumL(-1), MOI=10) for 3h and quantified changes in TLR-2 and calcium (Ca(2+)) mediated signaling pathways. The results indicate that S. uberis infection significantly increases the expression of TLR-2, intracellular Ca(2+) levels, PLC-γ1 and PKC-α, the activities of transcription factors NF-κB and NFAT, and related cytokines (TNF-α, IL-1β, IL-6, G-CSF, IL-2, KC, IL-15, FasL, MCP-1, and LIX) in culture supernatants. Taurine administration downregulated all these indices, the activities of NF-κB and NFAT. Cytokine secretions were similar using special PKC inhibitor Go 6983 and NFAT inhibitor VIVIT. Our data indicate that S. uberis infection induces pro-inflammatory response of MECs through a TLR-2 mediated signaling pathway. In addition, taurine can prevent MEC damage by affecting both PLC-γ1-Ca(2+)-PKC-α-NF-κB and PLC-γ1-Ca(2+)-NFATs signaling pathways. This is the first report to demonstrate the mechanisms of taurine attenuated pro-inflammatory response in MECs after S. uberis challenge.

Regulation of neurogenesis by calcium signaling

Calcium (Ca(2+)) signaling has essential roles in the development of the nervous system from neural induction to the proliferation, migration, and differentiation of neural cells. Ca(2+) signaling pathways are shaped by interactions among metabotropic signaling cascades, intracellular Ca(2+) stores, ion channels, and a multitude of downstream effector proteins that activate specific genetic programs. The temporal and spatial dynamics of Ca(2+) signals are widely presumed to control the highly diverse yet specific genetic programs that establish the complex structures of the adult nervous system. Progress in the last two decades has led to significant advances in our understanding of the functional architecture of Ca(2+) signaling networks involved in neurogenesis. In this review, we assess the literature on the molecular and functional organization of Ca(2+) signaling networks in the developing nervous system and its impact on neural induction, gene expression, proliferation, migration, and differentiation. Particular emphasis is placed on the growing evidence for the involvement of store-operated Ca(2+) release-activated Ca(2+) (CRAC) channels in these processes.

Inhibition of Orai1 Store-Operated Calcium Channel Prevents Foam Cell Formation and Atherosclerosis

OBJECTIVE

To determine the role of orai1 store-operated Ca(2+) entry in foam cell formation and atherogenesis.

APPROACH AND RESULTS

Acute administration of oxidized low-density lipoprotein (oxLDL) activates an orai1-dependent Ca(2+) entry in macrophages. Chelation of intracellular Ca(2+), inhibition of orai1 store-operated Ca(2+) entry, or knockdown of orai1 dramatically inhibited oxLDL-induced upregulation of scavenger receptor A, uptake of modified LDL, and foam cell formation. Orai1-dependent Ca(2+) entry induces scavenger receptor A expression and foam cell formation through activation of calcineurin but not calmodulin kinase II. Activation of nuclear factor of activated T cells is not involved in calcineurin signaling to foam cell formation. However, oxLDL dephosohorylates and activates apoptosis signal-regulating kinase 1 in macrophages. Orai1 knockdown prevents oxLDL-induced apoptosis signal-regulating kinase 1 activation. Knockdown of apoptosis signal-regulating kinase 1, or inhibition of its downstream effectors, JNK and p38 mitogen-activated protein kinase, reduces scavenger receptor A expression and foam cell formation. Notably, orai1 expression is increased in atherosclerotic plaques of apolipoprotein E(-/-) mice fed with high-cholesterol diet. Knockdown of orai1 with adenovirus harboring orai1 siRNA or inhibition of orai1 Ca(2+) entry with SKF96365 for 4 weeks dramatically inhibits atherosclerotic plaque development in high-cholesterol diet feeding apolipoprotein E(-/-) mice. In addition, inhibition of orai1 Ca(2+) entry prevents macrophage apoptosis in atherosclerotic plaque. Moreover, the expression of inflammatory genes in atherosclerotic lesions and the infiltration of myeloid cells into the aortic sinus plaques are decreased after blocking orai1 signaling.

CONCLUSIONS

Orai1-dependent Ca(2+) entry promotes atherogenesis possibly by promoting foam cell formation and vascular inflammation, rendering orai1 Ca(2+) channel a potential therapeutic target against atherosclerosis.