Ryanodine Receptors Are Expressed in Epidermal Keratinocytes and Associated with Keratinocyte Differentiation and Epidermal Permeability Barrier Homeostasis

Activation of ryanodine-sensitive calcium store drives pseudo-allergic dermatitis via Mas-related G protein-coupled receptor X2 in mast cells

Mast cell (MC) activation is implicated in the pathogenesis of multiple immunodysregulatory skin disorders. Activation of an IgE-independent pseudo-allergic route has been recently found to be mainly mediated via Mas-Related G protein-coupled receptor X2 (MRGPRX2). Ryanodine receptor (RYR) regulates intracellular calcium liberation. Calcium mobilization is critical in the regulation of MC functional programs. However, the role of RYR in MRGPRX2-mediated pseudo-allergic skin reaction has not been fully addressed. To study the role of RYR in vivo, we established a murine skin pseudo-allergic reaction model. RYR inhibitor attenuated MRGPRX2 ligand substance P (SP)-induced vascular permeability and neutrophil recruitment. Then, we confirmed the role of RYR in an MC line (LAD2 cells) and primary human skin-derived MCs. In LAD2 cells, RYR inhibitor pretreatment dampened MC degranulation (detected by β-hexosaminidase retlease), calcium mobilization, IL-13, TNF-α, CCL-1, CCL-2 mRNA, and protein expression activated by MRGPRX2 ligands, namely, compound 48/80 (c48/80) and SP. Moreover, the inhibition effect of c48/80 by RYR inhibitor was verified in skin MCs. After the confirmation of RYR2 and RYR3 expression, the isoforms were silenced by siRNA-mediated knockdown. MRGPRX2-induced LAD2 cell exocytosis and cytokine generation were substantially inhibited by RYR3 knockdown, while RYR2 had less contribution. Collectively, our finding suggests that RYR activation contributes to MRGPRX2-triggered pseudo-allergic dermatitis, and provides a potential approach for MRGPRX2-mediated disorders.

Distinct sets of olfactory receptors highly expressed in different human tissues evaluated by meta-transcriptome analysis: Association of OR10A6 in skin with keratinization

Olfactory receptors (ORs) are expressed in many tissues and have multiple functions. However, most studies have focused on individual ORs. Here, we aimed to conduct a comprehensive meta-transcriptome analysis of OR gene expression in human tissues by using open-source tools to search a large, publicly available genotype-tissue expression (GTEx) data set. Analysis of RNA-seq data from GTEx revealed that OR expression patterns were tissue-dependent, and we identified distinct sets of ORs that were highly expressed in 12 tissues, involving 97 ORs in total. Among them, OR5P2, OR5P3 and OR10A6 were associated with skin. We further examined the roles of these ORs in skin by performing weighted gene correlation network analysis (WGCNA) and c3net analysis. WGCNA suggested that the three ORs are involved in epidermal differentiation and water-impermeable barrier homeostasis, and OR10A6 showed the largest gene sub-network in the c3net network. Immunocytochemical examination of human skin keratinocytes revealed a sparse expression pattern of OR10A6, suggesting that it is not uniformly distributed among all keratinocytes. An OR10A6 agonist, 3-phenylpropyl propionate (3PPP), transiently increased intracellular Ca²⁺ concentration and increased cornified envelope (CE) production in cultured keratinocytes. Knock-down of OR10A6 diminished the effect of 3PPP. Overall, integration of meta-transcriptome analysis and functional analysis uncovered distinct expression patterns of ORs in various human tissues, providing basic data for future studies of the biological functions of highly expressed ORs in individual tissues. Our results further suggest that expression of OR10A6 in skin is related to epidermal differentiation, and OR10A6 may be a potential target for modulation of keratinization.

Signaling pathways in cutaneous wound healing

Wound healing is a very complex process, where variety of different pathways is activated, depending on the phase of healing. Improper or interrupted healing might result in development of chronic wounds. Therefore, novel approaches based on detailed knowledge of signalling pathways that are activated during acute or chronic cutaneous wound healing enables quicker and more effective healing. This review outlined new possibilities of cutaneous wound healing by modulation of some signalling molecules, e.g., gasotransmitters, or calcium. Special focus is given to gasotransmitters, since these bioactive signalling molecules that can freely diffuse into the cell and exert antioxidative effects. Calcium is an important booster of immune system and it can significantly contribute to healing process. Special interest is given to chronic wounds caused by diabetes mellitus and overcoming problems with the inflammation.

Structural Insight Into Ryanodine Receptor Channelopathies

The ryanodine receptors (RyRs) are large cation-selective ligand-gated channels that are expressed in the sarcoplasmic reticulum (SR) membrane. They mediate the controlled release of Ca²⁺ from SR and play an important role in many cellular processes. The mutations in RyRs are associated with several skeletal muscle and cardiac conditions, including malignant hyperthermia (MH), central core disease (CCD), catecholaminergic polymorphic ventricular tachycardia (CPVT), and arrhythmogenic right ventricular dysplasia (ARVD). Recent breakthroughs in structural biology including cryo-electron microscopy (EM) and X-ray crystallography allowed the determination of a number of near-atomic structures of RyRs, including wildtype and mutant structures as well as the structures in complex with different modulating molecules. This allows us to comprehend the physiological gating and regulatory mechanisms of RyRs and the underlying pathological mechanisms of the disease-causing mutations. In this review, based on the insights gained from the available high-resolution structures of RyRs, we address several questions: 1) what are the gating mechanisms of different RyR isoforms; 2) how RyRs are regulated by multiple channel modulators, including ions, small molecules, and regulatory proteins; 3) how do disease-causing mutations affect the structure and function of RyRs; 4) how can these structural information aid in the diagnosis of the related diseases and the development of pharmacological therapies.

Calcium Channels: Noteworthy Regulators and Therapeutic Targets in Dermatological Diseases

Dysfunctional skin barrier and impaired skin homeostasis may lead to or aggravate a series of dermatologic diseases. A large variety of biological events and bioactive molecules are involved in the process of skin wound healing and functional recovery. Calcium ions (Ca²⁺) released from intracellular stores as well as influx through plasma membrane are essential to skin function. Growing evidence suggests that calcium influx is mainly regulated by calcium-sensing receptors and channels, including voltage-gated, transient potential receptor, store-operated, and receptor-operated calcium channels, which not only maintain cellular Ca²⁺ homeostasis, but also participate in cell proliferation and skin cell homeostasis through Ca²⁺-sensitive proteins such as calmodulin (CaM). Furthermore, distinct types of Ca²⁺ channels not merely work separately, they may work concertedly to regulate cell function. In this review, we discussed different calcium-sensing receptors and channels, including voltage-gated, transient receptor potential, store-operated, and receptor-operated calcium channels, particularly focusing on their regulatory functions and inherent interactions as well as calcium channels-related reagents and drugs, which is expected to bridge basic research and clinical applications in dermatologic diseases.

Study of Carnosine's effect on nude mice skin to prevent UV-A damage

The skin is an important barrier against external attacks from bacteria, radicals, or radiations. UV-A radiations cause significant impairment of this barrier, inducing inflammation, oxidative stress, and wrinkle formation, thereby promoting photoaging. Previous studies reported that carnosine, a potent antioxidant, and carbonyl scavenger agent, may prevent photoaging features in the skin of hairless mice exposed to UV-A radiations. In the present study, we used a quantitative proteomic approach to analyze the changes evoked by carnosine in the skin proteome of hairless mice exposed to UV-A. This approach allowed to quantify more than 2480 proteins, among them consistent differences were observed for 89 proteins in UV-A exposed vs control unexposed skins, and 252 proteins in UV-A-exposed skin preventively treated by carnosine (UVAC) vs UV-A. Several functional pathways were altered in the skins of UV-A exposed hairless mice, including the integrin-linked kinase, calcium signaling, fibrogenesis, cell migration and filament formation. An impairment of mitochondrial function and metabolism was observed, with an up-regulation of cytochrome C oxidase 6B1 and NADH: ubiquinone oxidoreductase S8. Skins pre-treated by carnosine were prevented from UV-A induced proteome alterations. In conclusion, our study emphasizes the potency of a proteomic approach to identify the consequences of UV radiations in the skins, and points out the capacity of carnosine to prevent the alterations of skin proteome evoked by UV-A.

Proteomic analysis of bone marrow-derived mesenchymal stem cell extracellular vesicles from healthy donors: implications for proliferation, angiogenesis, Wnt signaling, and the basement membrane

Background

Bone marrow-derived mesenchymal stem cells (BM-MSCs) have shown therapeutic potential in various in vitro and in vivo studies in cutaneous wound healing. Furthermore, there are ubiquitous studies highlighting the pro-regenerative effects of BM-MSC extracellular vesicles (BM-MSC EVs). The similarities and differences in BM-MSC EV cargo among potential healthy donors are not well understood. Variation in EV protein cargo is important to understand, as it may be useful in identifying potential therapeutic applications in clinical trials. We hypothesized that the donors would share both important similarities and differences in cargo relating to cell proliferation, angiogenesis, Wnt signaling, and basement membrane formation—processes shown to be critical for effective cutaneous wound healing.

Methods

We harvested BM-MSC EVs from four healthy human donors who underwent strict screening for whole bone marrow donation and further Good Manufacturing Practices-grade cell culture expansion for candidate usage in clinical trials. BM-MSC EV protein cargo was determined via mass spectrometry and Proteome Discoverer software. Corresponding proteomic networks were analyzed via the UniProt Consortium and STRING consortium databases.

Results

More than 3000 proteins were identified in each of the donors, sharing > 600 proteins among all donors. Despite inter-donor variation in protein identities, there were striking similarities in numbers of proteins per biological functional category. In terms of biologic function, the proteins were most associated with transport of ions and proteins, transcription, and the cell cycle, relating to cell proliferation. The donors shared essential cargo relating to angiogenesis, Wnt signaling, and basement membrane formation—essential processes in modulating cutaneous wound repair.

Conclusions

Healthy donors of BM-MSC EVs contain important similarities and differences among protein cargo that may play important roles in their pro-regenerative functions. Further studies are needed to correlate proteomic signatures to functional outcomes in cutaneous repair.

From Orai to E-Cadherin: Subversion of Calcium Trafficking in Cancer to Drive Proliferation, Anoikis-Resistance, and Metastasis

The common currency of epithelial differentiation and homeostasis is calcium, stored primarily in the endoplasmic reticulum, rationed according to need, and replenished from the extracellular milieu via store-operated calcium entry (SOCE). This currency is disbursed by the IP3 receptor in response to diverse extracellular signals. The rate of release is governed by regulators of proliferation, autophagy, survival, and programmed cell death, the strength of the signal leading to different outcomes. Intracellular calcium acts chiefly through intermediates such as calmodulin that regulates growth factor receptors such as epidermal growth factor receptor (EGFR), actin polymerization, and adherens junction assembly and maintenance. Here we review this machinery and its role in differentiation, then consider how cancer cells subvert it to license proliferation, resist anoikis, and enable metastasis, either by modulating the level of intracellular calcium or its downstream targets or effectors such as EGFR, E-cadherin, IQGAP1, TMEM16A, CLCA2, and TRPA1. Implications are considered for the roles of E-cadherin and growth factor receptors in circulating tumor cells and metastasis. The discovery of novel, cell type-specific modulators and effectors of calcium signaling offers new possibilities for cancer chemotherapy.

ER stress induced by ER calcium depletion and UVB irradiation regulates tight junction barrier integrity in human keratinocytes

BACKGROUND

Endoplasmic reticulum (ER) calcium depletion-induced ER stress is a crucial signal for keratinocyte differentiation and barrier homeostasis, but its effects on the epidermal tight junction (TJ) have not been characterized. Ultraviolet B (UVB) causes ER calcium release in keratinocytes and disrupts epidermal TJ, however, the involvement of ER stress in the UVB-induced TJ alterations remains unknown.

OBJECTIVES

To investigate the effect of ER stress by pharmacological ER calcium depletion or UVB on the TJ integrity in normal human epidermal keratinocytes (NHEK).

METHODS

NHEK were exposed to ER calcium pump inhibitor thapsigargin (Tg) or UVB. ER stress markers and TJ molecules expression, TJ and F-actin structures, and TJ barrier function were analyzed.

RESULTS

Tg or UVB exposure dose-dependently triggered unfolded protein response (UPR) in NHEK. Low dose Tg induced the IRE1α-XBP1 pathway and strengthened TJ barrier. Contrary, high dose Tg activated PERK phosphorylation and disrupted TJ by F-actin disorganization. UVB disrupted TJ and F-actin structures dose dependently. IRE1α RNase inhibition induced or exacerbated TJ and F-actin disruption in the presence of low dose Tg or UVB. High dose Tg increased RhoA activity. 4-PBA or Rho kinase (ROCK) inhibitor partially prevented the disruption of TJ and F-actin following high dose Tg or UVB.

CONCLUSIONS

ER stress has bimodal effects on the epidermal TJ depending on its intensity. The IRE1α pathway is critical for the maintenance of TJ integrity during mild ER stress. Severe ER stress-induced UPR or ROCK signalling mediates the disruption of TJ through cytoskeletal disorganization during severe ER stress.

Somatic mutations and promotor methylation of the ryanodine receptor 2 is a common event in the pathogenesis of head and neck cancer

Genomic sequencing projects unraveled the mutational landscape of head and neck squamous cell carcinoma (HNSCC) and provided a comprehensive catalog of somatic mutations. However, the limited number of significant cancer-related genes obtained so far only partially explains the biological complexity of HNSCC and hampers the development of novel diagnostic biomarkers and therapeutic targets. We pursued a multiscale omics approach based on whole-exome sequencing, global DNA methylation and gene expression profiling data derived from tumor samples of the HIPO-HNC cohort (n = 87), and confirmed new findings with datasets from The Cancer Genome Atlas (TCGA). Promoter methylation was confirmed by MassARRAY analysis and protein expression was assessed by immunohistochemistry and immunofluorescence staining. We discovered a set of cancer-related genes with frequent somatic mutations and high frequency of promoter methylation. This included the ryanodine receptor 2 (RYR2), which showed variable promoter methylation and expression in both tumor samples and cell lines. Immunohistochemical staining of tissue sections unraveled a gradual loss of RYR2 expression from normal mucosa via dysplastic lesion to invasive cancer and indicated that reduced RYR2 expression in adjacent tissue and precancerous lesions might serve as risk factor for unfavorable prognosis and upcoming malignant conversion. In summary, our data indicate that impaired RYR2 function by either somatic mutation or epigenetic silencing is a common event in HNSCC pathogenesis. Detection of RYR2 expression and/or promoter methylation might enable risk assessment for malignant conversion of dysplastic lesions.

A novel target for the promotion of dermal wound healing: Ryanodine receptors

Ryanodine receptors have an important role in the regulation of intracellular calcium levels in the nervous system and muscle. It has been described that ryanodine receptors influence keratinocyte differentiation and barrier homeostasis. Our goal was to examine the role of ryanodine receptors in the healing of full-thickness dermal wounds by means of in vitro and in vivo methods. The effect of ryanodine receptors on wound healing, microcirculation and inflammation was assessed in an in vivo mouse wound healing model, using skin fold chambers in the dorsal region, and in HaCaT cell scratch wound assay in vitro. SKH-1 mice were subjected to sterile saline (n = 36) or ryanodine receptor agonist 4-chloro-m-cresol (0.5 mM) (n = 42) or ryanodine receptor antagonist dantrolene (100 μM) (n = 42). Application of ryanodine receptor agonist 4-chloro-m-cresol did not influence the studied parameters significantly, whereas ryanodine receptor antagonist dantrolene accelerated the wound closure. Inhibition of the calcium channel also increased the vessel diameters in the wound edges during the process of healing and increased the blood flow in the capillaries at all times of measurement. Furthermore, application of dantrolene decreased xanthine-oxidoreductase activity during the inflammatory phase of wound healing. Inhibition of ryanodine receptor-mediated effects positively influence wound healing. Thus, dantrolene may be of therapeutic potential in the treatment of wounds.

Genome-wide Target Enrichment-aided Chip Design: a 66 K SNP Chip for Cashmere Goat

Compared with the commercially available single nucleotide polymorphism (SNP) chip based on the Bead Chip technology, the solution hybrid selection (SHS)-based target enrichment SNP chip is not only design-flexible, but also cost-effective for genotype sequencing. In this study, we propose to design an animal SNP chip using the SHS-based target enrichment strategy for the first time. As an update to the international collaboration on goat research, a 66 K SNP chip for cashmere goat was created from the whole-genome sequencing data of 73 individuals. Verification of this 66 K SNP chip with the whole-genome sequencing data of 436 cashmere goats showed that the SNP call rates was between 95.3% and 99.8%. The average sequencing depth for target SNPs were 40X. The capture regions were shown to be 200 bp that flank target SNPs. This chip was further tested in a genome-wide association analysis of cashmere fineness (fiber diameter). Several top hit loci were found marginally associated with signaling pathways involved in hair growth. These results demonstrate that the 66 K SNP chip is a useful tool in the genomic analyses of cashmere goats. The successful chip design shows that the SHS-based target enrichment strategy could be applied to SNP chip design in other species.

Endoplasmic Reticulum Calcium Regulates Epidermal Barrier Response and Desmosomal Structure

Ca(2+) fluxes direct keratinocyte differentiation, cell-to-cell adhesion, migration, and epidermal barrier homeostasis. We previously showed that intracellular Ca(2+) stores constitute a major portion of the calcium gradient especially in the stratum granulosum. Loss of the calcium gradient triggers epidermal barrier homeostatic responses. In this report, using unfixed ex vivo epidermis and human epidermal equivalents we show that endoplasmic reticulum (ER) Ca(2+) is released in response to barrier perturbation, and that this release constitutes the major shift in epidermal Ca(2+) seen after barrier perturbation. We find that ER Ca(2+) release correlates with a transient increase in extracellular Ca(2+). Lastly, we show that ER calcium release resulting from barrier perturbation triggers transient desmosomal remodeling, seen as an increase in extracellular space and a loss of the desmosomal intercellular midline. Topical application of thapsigargin, which inhibits the ER Ca(2+) ATPase activity without compromising barrier integrity, also leads to desmosomal remodeling and loss of the midline structure. These experiments establish the ER Ca(2+) store as a master regulator of the Ca(2+) gradient response to epidermal barrier perturbation, and suggest that ER Ca(2+) homeostasis also modulates normal desmosomal reorganization, both at rest and after acute barrier perturbation.

Calcium signaling in skeletal muscle development, maintenance and regeneration

Skeletal muscle-specific stem cells are pivotal for tissue development and regeneration. Muscle plasticity, inherent in these processes, is also essential for daily life activities. Great advances and efforts have been made in understanding the function of the skeletal muscle-dedicated stem cells, called muscle satellite cells, and the specific signaling mechanisms that activate them for recruitment in the repair of the injured muscle. Elucidating these signaling mechanisms may contribute to devising therapies for muscular injury or disease. Here we review the studies that have contributed to our understanding of how calcium signaling regulates skeletal muscle development, homeostasis and regeneration, with a focus on the calcium dynamics and calcium-dependent effectors that participate in these processes.

Frontiers in epidermal barrier homeostasis--an approach to mathematical modelling of epidermal calcium dynamics

Intact epidermal barrier function is crucial for survival and is associated with the presence of gradients of both calcium ion concentration and electric potential. Although many molecules, including ion channels and pumps, are known to contribute to maintenance of these gradients, the mechanisms involved in epidermal calcium ion dynamics have not been clarified. We have established that a variety of neurotransmitters and their receptors, originally found in the brain, are expressed in keratinocytes and are also associated with barrier homeostasis. Moreover, keratinocytes and neurons show some similarities of electrochemical behaviour. As mathematical modelling and computer simulation have been employed to understand electrochemical phenomena in brain science, we considered that a similar approach might be applicable to describe the dynamics of epidermal electrochemical phenomena associated with barrier homeostasis. Such methodology would also be potentially useful to address a number of difficult problems in clinical dermatology, such as ageing and itching. Although this work is at a very early stage, in this essay, we discuss the background to our approach and we present some preliminary results of simulation of barrier recovery.

Effects of CaMKII-mediated phosphorylation of ryanodine receptor type 2 on islet calcium handling, insulin secretion, and glucose tolerance

Altered insulin secretion contributes to the pathogenesis of type 2 diabetes. This alteration is correlated with altered intracellular Ca²⁺-handling in pancreatic β cells. Insulin secretion is triggered by elevation in cytoplasmic Ca²⁺ concentration ([Ca²⁺]_cyt) of β cells. This elevation in [Ca²⁺]_cyt leads to activation of Ca²⁺/calmodulin-dependent protein kinase II (CAMKII), which, in turn, controls multiple aspects of insulin secretion. CaMKII is known to phosphorylate ryanodine receptor 2 (RyR2), an intracellular Ca²⁺-release channel implicated in Ca²⁺-dependent steps of insulin secretion. Our data show that RyR2 is CaMKII phosphorylated in a pancreatic β-cell line in a glucose-sensitive manner. However, it is not clear whether any change in CaMKII-mediated phosphorylation underlies abnormal RyR2 function in β cells and whether such a change contributes to alterations in insulin secretion. Therefore, knock-in mice with a mutation in RyR2 that mimics its constitutive CaMKII phosphorylation, RyR2-S2814D, were studied. This mutation led to a gain-of-function defect in RyR2 indicated by increased basal RyR2-mediated Ca²⁺ leak in islets of these mice. This chronic in vivo defect in RyR2 resulted in basal hyperinsulinemia. In addition, S2814D mice also developed glucose intolerance, impaired glucose-stimulated insulin secretion and lowered [Ca²⁺]_cyt transients, which are hallmarks of pre-diabetes. The glucose-sensitive Ca²⁺ pool in islets from S2814D mice was also reduced. These observations were supported by immunohistochemical analyses of islets in diabetic human and mouse pancreata that revealed significantly enhanced CaMKII phosphorylation of RyR2 in type 2 diabetes. Together, these studies implicate that the chronic gain-of-function defect in RyR2 due to CaMKII hyperphosphorylation is a novel mechanism that contributes to pathogenesis of type 2 diabetes.

Differential effects of arsenic on calcium signaling in primary keratinocytes and malignant (HSC-1) cells

Arsenic is highly toxic to living cells, especially skin, and skin cancer is induced by drinking water containing arsenic. The molecular mechanisms of arsenic-induced cancer, however, are not well understood. To examine the initial processes in the development of arsenic-induced cancer, we analyzed calcium signaling at an early stage of arsenic treatment of human primary cells and compared the effects with those observed with arsenic treatment in carcinoma-derived cells. We found that arsenic inhibited inositol trisphosphate receptor (IP3R) function in the endoplasmic reticulum by inducing phosphorylation, which led to decreased intracellular calcium levels. Blockade of IP3R phosphorylation by the serine/threonine protein kinase Akt inhibitor wortmannin rescued calcium signaling. In contrast, arsenic treatment of cells derived from a carcinoma (human squamous carcinoma; HSC-1) for 1h had no obvious effect. Taken together, these results suggest that arsenic-induced reduction in calcium signaling is one of the initial mechanisms underlying the malignant transformation in the development of skin cancer.

Oxytocin is expressed in epidermal keratinocytes and released upon stimulation with adenosine 5'-[γ-thio]triphosphate in vitro

Oxytocin is a neuropeptide produced primarily in the hypothalamus and is best known for its roles in parturition and lactation. It also influences behaviour, memory and mental state. Recent studies have suggested a variety of roles for oxytocin in peripheral tissues, including skin. Here we show that oxytocin is expressed in human skin. Immunohistochemical studies showed that oxytocin and its carrier protein, neurophysin I, are predominantly localized in epidermis. RT-PCR confirmed the expression of oxytocin in both skin and cultured epidermal keratinocytes. We also show that oxytocin is released from keratinocytes after application of adenosine 5'-[γ-thio]triphosphate (ATPγS, a stable analogue of ATP) in a dose-dependent manner. The ATPγS-induced oxytocin release was inhibited by removal of extracellular calcium, or by the P2X receptor antagonist 2',3'-O-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate (TNP-ATP). These results suggest that oxytocin is produced in human epidermal keratinocytes and is released in response to calcium influx via P2X receptors.