Anti-Inflammatory Effects of Alphitolic Acid Isolated from Agrimonia coreana Nakai Extracts Are Mediated via the Inhibition of ICRAC Activity in T Cells

Agrimonia pilosa Ledeb., an important medicinal herb in traditional East Asian medicine, is primarily used to treat abdominal pain, dysentery, and hemostasis. There are ten other reported species of Agrimonia plants, including Agrimonia coreana Nakai-a naturally growing species in South Korea-and Agrimonia eupatoria Linn. Although recent studies have isolated numerous active constituents and investigated their effects, the medicinal utility of this herb is not yet fully explored. Through patch-clamp recording, a previous study reported that Agrimonia plant extracts inhibit the function of Ca2+ release-activated Ca2+ channels (CRACs). Herein, we aimed to identify and isolate the main compounds in A. coreana responsible for CRAC inhibition while assessing the anti-inflammatory effects mediated by this inhibition. We demonstrated for the first time that alphitolic acid isolated from A. coreana has a dose-dependent inhibitory effect on CRAC activity and, thus, an inhibitory effect on intracellular calcium increase. Furthermore, analysis of human CD4+ T cell proliferation via the carboxyfluorescein diacetate succinimidyl ester method revealed that alphitolic acid inhibited T cell proliferation in a concentration-dependent manner. Our findings provide a theoretical basis for the potential therapeutic use of alphitolic acid in the treatment of inflammatory diseases.

In-vitro and in-vivo anti-allergic effects of magnolol on allergic rhinitis via inhibition of ORAI1 and ANO1 channels

ETHNOPHARMACOLOGICAL RELEVANCE

Flos Magnoliae (the dried flower buds of Magnolia biondii Pamp, FM) is a known herbal traditional medicine used for the symptomatic relief of nasal congestion and rhinorrhea caused by rhinitis and sinusitis. Magnolol, a neolignan from the magnolia family, is a secondary metabolite known to have anti-allergic and anti-inflammatory effects. However, the underlying mechanisms and therapeutic effect of magnolol in the treatment of allergic rhinitis (AR) remain elusive.

AIMS OF THE STUDY

Anoctamin 1 (ANO1), a calcium-activated anion channel, mediates mucus and electrolyte secretion in nasal airway epithelial cells, whereas calcium release-activated calcium channel protein 1 (ORAI1) participates in the activation of T-lymphocytes and mast cells. The aim of our study is to understand the mechanisms of action of magnolol against AR, i.e., whether it acts through the modulation of ANO1 and ORAI1 channels that are expressed in nasal epithelial cells and T-lymphocytes, respectively.

MATERIALS AND METHODS

Whole-cell patch clamp was used to record the activity of ORAI1 and ANO1 ion channels in ORAI1 or ANO1 overexpressed HEK293T cells, while the Ussing chamber apparatus was used to measure electrolyte transport via the epithelium, in Calu-3 cells cultured in an air-liquid interface. Additionally, calcium imaging of Jurkat T-lymphocytes was used to assess changes in the intracellular calcium concentration. Magnolol toxicity was assessed using the CCK-8 assay, and its effect on T-lymphocyte proliferation was measured by labeling human primary T-lymphocytes with carboxyfluorescein succinimidyl ester. Finally, OVA-induced Balb/c mice were employed to evaluate the effect of magnolol on nasal symptoms, as well as cytokine and eosinophil infiltration in AR.

RESULTS

Magnolol inhibits ORAI1 and ANO1 channels in a concentration-dependent manner. Magnolol (30 μM) inhibits anti-CD3 induced cellular proliferation and production of IL-2 via ORAI1 channels in T-lymphocytes. Further, ATP-induced electrolyte transport mediated by ANO1 channels is significantly inhibited by magnolol in IL-4 sensitized Calu-3 cells. Notably, 300 μM magnolol significantly attenuates cytokine and eosinophil infiltration, thus alleviating AR symptoms in mice OVA-induced AR.

CONCLUSION

Magnolol may be a promising therapeutic agent for the treatment and prevention of AR.

Inhibitory effects of α-Mangostin on T cell cytokine secretion via ORAI1 calcium channel and K+ channels inhibition

Background

As one of the main components of mangosteen (Garcinia mangostana), a tropical fruit, α-mangostin has been reported to have numerous pharmacological benefits such as anti-cancer, anti-inflammatory, and anti-allergic effects through various mechanisms of action. The effects of α-mangostin on intracellular signaling proteins is well studied, but the effects of α-mangostin on ion channels and its physiological effects in immune cells are unknown. Generation of intracellular calcium signaling is a fundamental step for T cell receptor stimulation. This signaling is mediated not only by the ORAI1 calcium channel, but also by potassium ion channels, which provide the electrical driving forces for generating sufficient calcium ion influx. This study investigated whether α-mangosteen suppress T cell stimulation by inhibiting ORAI1 and two kinds of potassium channels (K_v1.3 and K_Ca3.1), which are normally expressed in human T cells.

Methods

This study analyzed the inhibitory effect of α-mangostin on immune cell activity via inhibition of calcium and potassium ion channels expressed in immune cells.

Results

α-mangostin inhibited ORAI1 in a concentration-dependent manner, and the IC₅₀ value was 1.27 ± 1.144 µM. K_v1.3 was suppressed by 41.38 ± 6.191% at 3 µM, and K_Ca3.1 was suppressed by 51.16 ± 5.385% at 3 µM. To measure the inhibition of cytokine secretion by immune cells, Jurkat T cells were stimulated to induce IL-2 secretion, and α-mangostin was found to inhibit it. This study demonstrated the anti-inflammatory effect of α-mangostin, the main component of mangosteen, through the regulation of calcium signals.

Gardenia jasminoides extract and its constituent, genipin, inhibit activation of CD3/CD28 co-stimulated CD4+ T cells via ORAI1 channel

Gardenia jasminoides (GJ) is a widely used herbal medicine with anti-inflammatory properties, but its effects on the ORAI1 channel, which is important in generating intracellular calcium signaling for T cell activation, remain unknown. In this study, we investigated whether 70% ethanolic GJ extract (GJ_EtOH) and its subsequent fractions inhibit ORAI1 and determined which constituents contributed to this effect. Whole-cell patch clamp analysis revealed that GJ_EtOH (64.7% ± 3.83% inhibition at 0.1 mg/ml) and all its fractions showed inhibitory effects on the ORAI1 channel. Among the GJ fractions, the hexane fraction (GJ_HEX, 66.8% ± 9.95% at 0.1 mg/ml) had the most potent inhibitory effects in hORAI1-hSTIM1 co-transfected HEK293T cells. Chemical constituent analysis revealed that the strong ORAI1 inhibitory effect of GJ_HEX was due to linoleic acid, and in other fractions, we found that genipin inhibited ORAI1. Genipin significantly inhibited I_ORAI1 and interleukin-2 production in CD3/CD28-stimulated Jurkat T lymphocytes by 35.9% ± 3.02% and 54.7% ± 1.32% at 30 μM, respectively. Furthermore, the same genipin concentration inhibited the proliferation of human primary CD4⁺ T lymphocytes stimulated with CD3/CD28 antibodies by 54.9% ± 8.22%, as evaluated by carboxyfluorescein succinimidyl ester assay. Our findings suggest that genipin may be one of the active components of GJ responsible for T cell suppression, which is partially mediated by activation of the ORAI1 channel. This study helps us understand the mechanisms of GJ in the treatment of inflammatory diseases.

Flos Magnoliae and its Constituent Linoleic Acid Suppress T Lymphocyte Activation via Store-Operated Calcium Entry

Intracellular calcium signaling is crucial for type 2 helper T cell and mast cell activation, which is essential for allergic inflammation. It is initiated by antigen-mediated receptor stimulation that triggers store-operated calcium entry (SOCE) via ORAI1 calcium channel. Flos Magnoliae (FM) is widely used to treat allergic diseases such as allergic rhinitis and asthma. Although many studies have reported that FM regulates intracellular calcium signaling, research on the exact type of calcium channel modulated by FM is scarce. Therefore, we hypothesized that the anti-allergic effects of FM might result from ORAI1 inhibition in T cells. We investigated whether a 70% ethanolic extract of FM (FMEtOH) and its constituents inhibit ORAI1 channel activity and subsequent T cell activation. We performed conventional whole-cell patch clamp studies in hSTIM1 and hORAI1-overexpressing HEK293T cells (HEKORAI1). Intracellular calcium concentration was determined using Fura-2 dye and cytokine production measurement in Jurkat T lymphocytes. FM_EtOH (0.03 mg/mL) and its fractions, especially hexane fraction (FM_Hex, 0.01 mg/mL), significantly inhibited SOCE and IL-2 cytokine production in Jurkat T lymphocytes. GC/MS analysis showed linoleic acid (LA) as the major component of FM_Hex. FM_Hex at 0.01 mg/mL (equivalent to 10 μM LA) inhibited not only SOCE but also IL-2 production, as well as CD3/CD28 receptor co-stimulation induced calcium signaling in Jurkat T lymphocytes. FM_EtOH and LA suppressed CD4+ T lymphocyte activation, at least in part, by inhibiting ISOCE. Thus, ISOCE inhibition may be a potential strategy to inhibit immune responses in inflammation.

Mitochondrial dysfunction reduces the activity of KIR2.1 K+ channel in myoblasts via impaired oxidative phosphorylation

Myoblast fusion depends on mitochondrial integrity and intracellular Ca²⁺ signaling regulated by various ion channels. In this study, we investigated the ionic currents associated with [Ca²⁺]_i regulation in normal and mitochondrial DNA-depleted (ρ0) L6 myoblasts. The ρ0 myoblasts showed impaired myotube formation. The inwardly rectifying K⁺ current (I_Kir) was largely decreased with reduced expression of KIR2.1, whereas the voltage-operated Ca²⁺ channel and Ca²⁺-activated K⁺ channel currents were intact. Sustained inhibition of mitochondrial electron transport by antimycin A treatment (24 h) also decreased the I_Kir. The ρ0 myoblasts showed depolarized resting membrane potential and higher basal [Ca²⁺]_i. Our results demonstrated the specific downregulation of I_Kir by dysfunctional mitochondria. The resultant depolarization and altered Ca²⁺ signaling might be associated with impaired myoblast fusion in ρ0 myoblasts.

Spirodela polyrhiza and its Chemical Constituent Vitexin Exert Anti-Allergic Effect via ORAI1 Channel Inhibition

Intracellular calcium signaling cascades are integral to early and late allergic responses involving mast cell degranulation and type 2 helper T cell activation, respectively. Both the responses are accompanied by the movement of calcium through the calcium release-activated calcium (CRAC) channel, encoded by the ORAI1 gene. Spirodela polyrhiza (L.) Schleid (SP) has anti-inflammatory and anti-allergic effects, but its effect on calcium signaling has not been reported. This study investigated whether a 30% ethanolic SP extract (SP_EtOH) and its constituents can reduce CRAC currents ([Formula: see text]), and thus inhibit mast cell degranulation and T cell activation. In Jurkat T lymphocytes, we found that 3[Formula: see text]mg/mL SP_EtOH inhibited the [Formula: see text] by [Formula: see text]%, whereas one of its constituents vitexin (100[Formula: see text][Formula: see text]M) inhibited the [Formula: see text] by [Formula: see text]%. Furthermore, in the RBL-2H3 mast cell, the [Formula: see text] was inhibited by 3[Formula: see text]mg/mL SP_EtOH ([Formula: see text]%) and 100[Formula: see text][Formula: see text]M vitexin ([Formula: see text]%). Investigation of human primary T cell proliferation induced by co-stimulation with antibodies to cluster of differentiation 3 and 28, and of RBL-2H3 mast cell degranulation following IgE-antigen complex stimulation revealed that 100[Formula: see text][Formula: see text]M vitexin inhibited both T-cell proliferation (by [Formula: see text]%) and mast cell degranulation (by [Formula: see text]%). These effects were concentration-dependent, and no cytotoxicity was observed. Our findings suggest that vitexin is a promising candidate compound for the development of therapeutic agents to prevent and treat allergic diseases.

Flos Magnoliae Inhibits Chloride Secretion via ANO1 Inhibition in Calu-3 Cells

Flos Magnoliae (FM, Chinese name: Xin-yi) is an oriental medicinal herb commonly used for symptomatic relief from allergic rhinitis, sinusitis, and headache, including in traditional Chinese and Korean medicine formulations. FM inhibits histamine release from mast cells and cytokine secretion from T cells. However, the mechanism of action of FM on the anoctamin-1 (ANO1) ion channel, which is responsible for nasal hypersecretion in allergic rhinitis, has not been elucidated. Therefore, in this study, we investigated the effect of a 30% ethanolic extract of FM (FM_EtOH) and its chemical constituents on ANO1 activity. We used high-performance liquid chromatography analysis to identify five major chemical constituents of FM_EtOH: vanillic acid, tiliroside, eudesmin, magnolin, and fargesin. Using a conventional whole-cell patch clamp method, we found that FM_EtOH (30, 100, and 300[Formula: see text][Formula: see text]g/mL) and its chemical constituent tiliroside inhibited ANO1 activity in ANO1-overexpressing HEK293T cells. In addition, we found that the treatment of the airway epithelial cell line Calu-3 with interleukin 4 significantly increased Ca[Formula: see text] activated Cl[Formula: see text] current (I_CaCC), but not cystic fibrosis transmembrane conductance regulator (CFTR)-mediated chloride current (I_CFTR). FM_EtOH and tiliroside specifically inhibited I_CaCC. Thus, in this study, we identified a novel mechanism underlying the alleviation of allergic rhinitis by FM_EtOH. Our results indicate that FM_EtOH and its chemical constituent tiliroside are promising and potent agents for the prevention and treatment of allergic rhinitis.

Enhanced expression of glutamate decarboxylase 65 improves symptoms of rat parkinsonian models

In this study, we report the amelioration of parkinsonian symptoms in rat Parkinson's disease (PD) models, as a result of the expression of glutamate decarboxylase (GAD) 65 with a modified cytomegalovirus (CMV) promoter. The transfer of the gene for gamma-amino butryic acid (GAD), the rate-limiting enzyme in gama-amino butrylic acid (GABA) production, has been investigated as a means to increase inhibitory synaptic activity. Electrophysiological evidence suggests that the transfer of the GAD65 gene to the subthalamic nucleus (STN) can change the excitatory output of this nucleus to inhibitory output. Our in vitro results also demonstrated higher GAD65 expression in cells transfected with the JDK promoter, as compared to cells transfected with the CMV promoter. Also, a rat PD model in which recombinant adeno-associated virus-2 (rAAV2)-JDK-GAD65 was delivered into the STN exhibited significant behavioral improvements, as compared to the saline-injected group. Interestingly, we observed that these behavioral improvements were more obvious in rat PD models in which rAAV2-JDK-GAD65 was injected into the STN than in rat PD models in which rAAV2-CMV-GAD65 was injected into the STN. Moreover, according to electrophysiological data, the rAAV2-JDK-GAD65-injected group exhibited more constant improvements in firing rates than did the rAAV2-CMV-GAD65-injected group. These data indicate that the JDK promoter, when coupled with GAD65 expression, is more effective with regard to parkinsonian symptoms than is the CMV promoter.