Non-selective cation channels mediate chloroquine-induced relaxation in precontracted mouse airway smooth muscle

Cellular mechanism underlying the facilitation of contractile response induced by IL-25 in mouse tracheal smooth muscle

Asthma is a common heterogeneous respiratory disease characterized by airway inflammation and airway hyperresponsiveness (AHR) which is associated with abnormality in smooth muscle contractility. The epithelial cell-derived cytokine IL-25 is implicated in type 2 immune pathology including asthma, whereas the underlying mechanisms have not been fully elucidated. This study aims to investigate the effects of IL-25 on mouse tracheal smooth muscle contractility and elucidate the cellular mechanisms. Incubation with IL-25 augmented the contraction of mouse tracheal smooth muscles, which could be suppressed by the L-type voltage-dependent Ca²⁺ channel (L-VDCC) blocker nifedipine. Furthermore, IL-25 enhanced the cytosolic Ca²⁺ signals and triggered up-regulation of α1C L-VDCC (Ca_V1.2) in primary cultured mouse tracheal smooth muscle cells. Knocking down IL-17RA/IL-17RB receptors or inhibiting the transforming growth factor-β-activated kinase 1 (TAK1)-tumor progression locus 2 (TPL2)-MAPK kinase 1/2 (MEK1/2)-ERK1/2-activating protein-1 (AP-1) signaling pathways suppressed the IL-25-elicited up-regulation of Ca_V1.2 and hyperreactivity in tracheal smooth muscles. Moreover, inhibition of TPL2, ERK1/2 or L-VDCC alleviated the AHR symptom induced by IL-25 in a murine model. This study revealed that IL-25 potentiated the contraction of tracheal smooth muscle and evoked AHR via activation of TPL2-ERK1/2-Ca_V1.2 signaling, providing novel targets for the treatment of asthma with a high-IL-25 phenotype.

Relaxation Effect of Schisandra Chinensis Lignans on the Isolated Tracheal Smooth Muscle in Rats and Its Mechanism

Schisandra chinensis (S. chinensis) is one of the core drugs used for relieving cough and asthma in traditional Chinese medicine. However, there are few basic studies on the treatment of respiratory diseases with S. chinensis in modern pharmacology, and the material basis and mechanism of its antiasthmatic effect are still unclear. Lignans are the main active components of S. chinensis. The aim of this study was to observe the relaxation effect of S. chinensis lignans (SCL) on the tracheal smooth muscle of rats by in vitro tracheal perfusion experiments, and to explore the mechanism by preincubation with L-type calcium channel blocker verapamil, four potassium channel blockers glibenclamide, tetraethylamine, 4-aminopyridine and barium chloride (BaCl₂), β-adrenoceptor blocker propranolol, nitric oxide synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME), and the cyclooxygenase inhibitor indomethacin, respectively. The results showed that SCL (0.25-1.75 mg/mL) reduced the contraction of isolated tracheal smooth muscle induced by acetylcholine, the preincubation with verapamil and glibenclamide could attenuate the relaxation effect, whereas propranolol, 4-aminopyridine, BaCl₂, tetraethylamine, L-NAME, and indomethacin had no such effect. These results suggest that SCL has a significant relaxation effect on the isolated tracheal smooth muscle of rats, and the mechanism may be related to the inhibition of extracellular calcium influx and intracellular calcium release from the sarcoplasmic reticulum, as well as the activation of ATP-sensitive potassium channels. These findings may provide a pharmacological basis for the traditional use of S. chinensis to treat asthma.

Coptisine, a protoberberine alkaloid, relaxes mouse airway smooth muscle via blockade of VDLCCs and NSCCs

Background/Aims: Recently, effective and purified ingredients of traditional Chinese medicine (TCM) were extracted to play crucial roles in the treatment of pulmonary diseases. Our previous research focused on TCM drug screening aimed at abnormal airway muscle contraction during respiratory diseases. Coptisine, an effective ingredient extracted from bitter herbs has shown a series of antioxidant, antibacterial, cardioprotective and neuroprotective pharmacological properties. In the current study, we questioned whether coptisine could also participate in asthma treatment through relaxing abnormal contracted mouse airway smooth muscle (ASM). The present study aimed to characterize the relaxant effects of coptisine on mouse ASM and uncover the underlying molecular mechanisms. Methods: To investigate the role of coptisine on pre-contracted mouse ASM, a series of biological techniques, including force measurement and patch-clamp experiments were employed. Results: Coptisine was found to inhibit high K⁺ or acetylcholine chloride (ACh)-induced pre-contracted mouse tracheal rings in a dose-dependent manner. Further research demonstrated that the coptisine-induced mouse ASM relaxation was mediated by alteration of calcium mobilization via voltage-dependent L-type Ca²⁺ channels (VDLCCs) and non-selective cation channels (NSCCs). Conclusion: Our data showed that mouse ASM could be relaxed by coptisine via altering the intracellular Ca²⁺ concentration through blocking VDLCCs and NSCCs, which suggested that this pharmacological active constituent might be classified as a potential new drug for the treatment of abnormal airway muscle contraction.

Research progress in the mechanism of calcium ion on contraction and relaxation of airway smooth muscle cells

lntracellular calcium ion is the key secondary messenger system of the cellular processes in airway smooth muscle cells(ASMc). The treatment and regulation of Ca²⁺ in airway smooth muscle (ASM) is, in part, to associated with many airway diseases such as asthma, COPD and pulmonary fibrosis. The mechanism of contraction and relaxation of ASM is a concerned aspect in airway diseases. This review emphasizes established and recent discoveries whice show the research progress of Ca²⁺ on cell contraction and relaxation in ASM in recent years, to provide theoretical support and new targets for clinical prevention and treatment of perioperative bronchospasm and variousrespiratory related diseases.

Folium Sennae and emodin reverse airway smooth muscle contraction

The objective of this project was to find a bronchodilatory compound from herbs and clarify the mechanism. We found that the ethanol extract of Folium Sennae (EEFS) can relax airway smooth muscle (ASM). EEFS inhibited ASM contraction, induced by acetylcholine, in mouse tracheal rings and lung slices. High-performance liquid chromatography assay showed that EEFS contained emodin. Emodin had a similar reversal action. Acetylcholine-evoked contraction was also partially reduced by nifedipine (a selective inhibitor of L-type voltage-dependent Ca²⁺ channels, LVDCCs), YM-58483 (a selective inhibitor of store-operated Ca²⁺ entry, SOCE), as well as Y-27632 (an inhibitor of Rho-associated protein kinase). In addition, LVDCC- and SOCE-mediated currents and cytosolic Ca²⁺ elevations were inhibited by emodin. Emodin reversed acetylcholine-caused increases in phosphorylation of myosin phosphatase target subunit 1. Furthermore, emodin, in vivo, inhibited acetylcholine-induced respiratory system resistance in mice. These results indicate that EEFS-induced relaxation results from emodin inhibiting LVDCC, SOCE, and Ca²⁺ sensitization. These findings suggest that Folium Sennae and emodin may be new sources of bronchodilators.

Sanguinarine Rapidly Relaxes Rat Airway Smooth Muscle Cells Dependent on TAS2R Signaling

Excessive contraction of airway smooth muscle cells (ASMCs) is a hallmark feature of asthma. Intriguing, the activation of bitter taste receptor (TAS2R) in ASMCs can relax ASMCs. However, there is a lack of potent TAS2R agonists that can be used in asthma therapies since those tested agonists cannot relax ASMCs at the dose below a few hundred micromolar. Considering that sanguinarine (SA) is a bitter substance often used in small doses for the treatment of asthma in folk medicine, the present study was to determine the rapid relaxation effect of SA on ASMCs and to reveal the underlying mechanisms associated with TAS2R signaling. Here, cell stiffness, traction force, calcium signaling, cAMP levels, and the mRNA expression were evaluated by using optical magnetic twisting cytometry, traction force microscopy, Fluo-4/AM labeling, enzyme-linked immunosorbent assay (ELISA), and quantitative (q)RT-PCR, respectively. We found that 0.5 µM SA immediately decreased cell stiffness and traction force, which is comparable with the effect of 5 µM isoproterenol. In addition, 0.5 µM SA immediately increased intracellular free calcium concentration ([Ca²⁺]_i) and decreased the mRNA expression of contractile proteins such as calponin and α-smooth muscle actin after the treatment for 24 h. Furthermore, SA-mediated decrease in cell stiffness/traction force and increase in [Ca²⁺]_i were significantly blunted by inhibiting the TAS2Rs signaling. These findings establish the rapid relaxation effect of SA at low concentration (<1 µM) on cultured ASMCs depending on TAS2R signaling, indicating that SA might be developed as a useful bronchodilator in asthma therapy.

Paracetamol inhibits Ca2+ permeant ion channels and Ca2+ sensitization resulting in relaxation of precontracted airway smooth muscle

The purpose of this study was to screen a bronchodilator from old drugs and elucidate the underlying mechanism. Paracetamol (acetaminophen) is a widely used analgesic and antipyretic drug. It has been reported that it inhibits the generation of prostaglandin and histamine, which play roles in asthma. These findings led us to explore whether paracetamol could be a potential bronchodilator. Paracetamol inhibited high K⁺- and acetylcholine (ACH)-induced precontraction of mouse tracheal and bronchial smooth muscles. Moreover, the ACH-induced contraction was partially inhibited by nifedipine (selective blocker of LVDCCs), YM-58483 (selective inhibitor of store-operated Ca²⁺ entry (SOCE), canonical transient receptor potential 3 (TRPC3) and TRPC5 channels) and Y-27632 (selective blocker of ROCK, a linker of the Ca²⁺ sensitization pathway). In single airway smooth muscle cells, paracetamol blocked the currents sensitive to nifedipine and YM-58483, and inhibited intracellular Ca²⁺ increases. In addition, paracetamol inhibited ACH-induced phosphorylation of myosin phosphatase target subunit 1 (MYPT1, another linker of the Ca²⁺ sensitization pathway). Finally, in vivo paracetamol inhibited ACH-induced increases of mouse respirator system resistance. Collectively, we conclude that paracetamol inhibits ASM contraction through blocking LVDCCs, SOCE and/or TRPC3 and/or TRPC5 channels, and Ca²⁺ sensitization. These results suggest that paracetamol might be a new bronchodilator.

Relaxant Action of Diclofenac Sodium on Mouse Airway Smooth Muscle

Diclofenac sodium (DCF) is a nonsteroidal anti-inflammatory drug (NSAID) and is widely used as an analgesic and anti-inflammatory agent. Herein, we found that DCF could relax high K+ (80 mM K+)-/ACh-precontracted tracheal rings (TRs) in mice. This study aimed to elucidate the underlying mechanisms of DCF-induced relaxations. The effects of DCF on airway smooth muscle (ASM) cells were explored using multiple biophysiological techniques, such as isometric tension measurement and patch-clamping experiments. Both high K+- and ACh-evoked contraction of TRs in mice were relaxed by DCF in a dose-dependent manner. The results of isometric tension and patch-clamping experiments demonstrated that DCF-induced relaxation in ASM cells was mediated by cytosolic free Ca2+, which was decreased via inhibition of voltage-dependent L-type Ca2+ channels (VDLCCs), nonselective cation channels (NSCCs), and Na+/Ca2+ exchange. Meanwhile, DCF also enhanced large conductance Ca2+ activated K+ (BK) channels, which led to the relaxation of ASMs. Our data demonstrated that DCF relaxed ASMs by decreasing the intracellular Ca2+ concentration via inhibition of Ca2+ influx and Na+/Ca2+ exchange. Meanwhile, the enhanced BK channels also played a role in DCF-induced relaxation in ASMs. These results suggest that DCF is a potential candidate for antibronchospasmic drugs used in treating respiratory diseases such as asthma and chronic obstructive pulmonary disease.

Azithromycin inhibits muscarinic 2 receptor-activated and voltage-activated Ca2+ permeant ion channels and Ca2+ sensitization, relaxing airway smooth muscle contraction

Azithromycin (AZM) has been used for the treatment of asthma and chronic obstructive pulmonary disease (COPD); however, the effects and underlying mechanisms of AZM remain largely unknown. The effects of AZM on airway smooth muscles (ASMs) and the underlying mechanisms were studied using isometric muscle force measurements, the examination of lung slices, imaging, and patch-clamp techniques. AZM completely inhibited acetylcholine (ACH)-induced precontraction of ASMs in animals (mice, guinea pigs, and rabbits) and humans. Two other macrolide antibiotics, roxithromycin and Klaricid, displayed a decreased inhibitory activity, and the aminoglycoside antibiotics penicillin and streptomycin did not have an inhibitory effect. Precontractions were partially inhibited by nifedipine (selective inhibitor of L-type voltage-dependent Ca²⁺ channels (LVDCCs)), Pyr3 (selective inhibitor of TRPC3 and/or STIM/Orai channels, which are nonselective cation channels (NSCCs)), and Y-27632 (selective inhibitor of Rho-associated kinase (ROCK)). Moreover, LVDCC- and NSCC-mediated currents were inhibited by AZM, and the latter were suppressed by the muscarinic (M) 2 receptor inhibitor methoctramine. AZM inhibited LVDCC Ca²⁺ permeant ion channels, M2 receptors, and TRPC3 and/or STIM/Orai, which decreased cytosolic Ca²⁺ concentrations and led to muscle relaxation. This relaxation was also enhanced by the inhibition of Ca²⁺ sensitization. Therefore, AZM has potential as a novel and potent bronchodilator. The findings of this study improve the understanding of the effects of AZM on asthma and COPD.

Semen cassiae Extract Inhibits Contraction of Airway Smooth Muscle

β₂-adrenoceptor agonists are commonly used as bronchodilators to treat obstructive lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), however, they induce severe side effects. Therefore, developing new bronchodilators is essential. Herbal plants were extracted and the extracts’ effect on airway smooth muscle (ASM) precontraction was assessed. The ethyl alcohol extract of semen cassiae (EESC) was extracted from Semen cassia. The effects of EESC on the ACh- and 80 mM K⁺-induced sustained precontraction in mouse and human ASM were evaluated. Ca²⁺ permeant ion channel currents and intracellular Ca²⁺ concentration were measured. HPLC analysis was employed to determine which compound was responsible for the EESC-induced relaxation. The EESC reversibly inhibited the ACh- and 80 mM K⁺-induced precontraction. The sustained precontraction depends on Ca²⁺ influx, and it was mediated by voltage-dependent L-type Ca²⁺ channels (LVDCCs), store-operated channels (SOCs), TRPC3/STIM/Orai channels. These channels were inhibited by aurantio-obtusin, one component of EESC. When aurantio-obtusin removed, EESC’s action disappeared. In addition, aurantio-obtusin inhibited the precontraction of mouse and human ASM and intracellular Ca²⁺ increases. These results indicate that Semen cassia-contained aurantio-obtusin inhibits sustained precontraction of ASM via inhibiting Ca²⁺-permeant ion channels, thereby, which could be used to develop new bronchodilators.

Polygonum aviculare L. extract and quercetin attenuate contraction in airway smooth muscle

Because of the serious side effects of the currently used bronchodilators, new compounds with similar functions must be developed. We screened several herbs and found that Polygonum aviculare L. contains ingredients that inhibit the precontraction of mouse and human airway smooth muscle (ASM). High K⁺-induced precontraction in ASM was completely inhibited by nifedipine, a selective blocker of L-type voltage-dependent Ca²⁺ channels (LVDCCs). However, nifedipine only partially reduced the precontraction induced by acetylcholine chloride (ACH). Additionally, the ACH-induced precontraction was partly reduced by pyrazole-3 (Pyr3), a selective blocker of TRPC3 and stromal interaction molecule (STIM)/Orai channels. These channel-mediated currents were inhibited by the compounds present in P. aviculare extracts, suggesting that this inhibition was mediated by LVDCCs, TRPC3 and/or STIM/Orai channels. Moreover, these channel-mediated currents were inhibited by quercetin, which is present in P. aviculare extracts. Furthermore, quercetin inhibited ACH-induced precontraction in ASM. Overall, our data indicate that the ethyl acetate fraction of P. aviculare and quercetin can inhibit Ca²⁺-permeant LVDCCs, TRPC3 and STIM/Orai channels, which inhibits the precontraction of ASM. These findings suggest that P. aviculare could be used to develop new bronchodilators to treat obstructive lung diseases such as asthma and chronic obstructive pulmonary disease.

Activation of bitter taste receptors (tas2rs) relaxes detrusor smooth muscle and suppresses overactive bladder symptoms

Bitter taste receptors (TAS2Rs) are traditionally thought to be expressed exclusively on the taste buds of the tongue. However, accumulating evidence has indicated that this receptor family performs non-gustatory functions outside the mouth in addition to taste. Here, we examined the role of TAS2Rs in human and mouse detrusor smooth muscle (DSM). We showed that mRNA for various TAS2R subtypes was expressed in both human and mouse detrusor smooth muscle (DSM) at distinct levels. Chloroquine (CLQ), an agonist for TAS2Rs, concentration-dependently relaxed carbachol- and KCl-induced contractions of human DSM strips. Moreover, 100 μM of CLQ significantly inhibited spontaneous and electrical field stimulation (EFS)-induced contractions of human DSM strips. After a slight contraction, CLQ (1 mM) entirely relaxed carbachol-induced contraction of mouse DSM strips. Furthermore, denatonium and quinine concentration-dependently decreased carbachol-induced contractions of mouse DSM strips. Finally, we demonstrated that CLQ treatment significantly suppressed the overactive bladder (OAB) symptoms of mice with partial bladder outlet obstruction (PBOO). In conclusion, we for the first time provide evidence of the existence of TAS2Rs in the urinary DSM and demonstrate that TAS2Rs may represent a potential target for OAB. These findings open a new approach to develop drugs for OAB in the future.

Chloroform Extract of Artemisia annua L. Relaxes Mouse Airway Smooth Muscle

Artemisia annua L. belongs to the Asteraceae family, which is indigenous to China. It has valuable pharmacological properties, such as antimalarial, anti-inflammatory, and anticancer properties. However, whether it possesses antiasthma properties is unknown. In the current study, chloroform extract of Artemisia annua L. (CEAA) was prepared, and we found that CEAA completely eliminated acetylcholine (ACh) or high K⁺-elicited (80 mM) contractions of mouse tracheal rings (TRs). Patch-clamp technique and ion channel blockers were employed to explore the underlying mechanisms of the relaxant effect of CEAA. In whole-cell current recording, CEAA almost fully abolished voltage-dependent Ca²⁺ channel (VDCC) currents and markedly enhanced large conductance Ca²⁺-activated K⁺ (BK) channel currents on airway smooth muscle cells (ASMCs). In single channel current recording, CEAA increased the opening probability but had no effect on the single channel conductance of BK channels. However, under paxilline-preincubated (a selective BK channel blocker) conditions, CEAA only slightly increased BK channel currents. These results indicate that CEAA may contain active components with potent antiasthma activity. The abolished VDCCs by CEAA may mainly contribute to the underlying mechanism through which it acts as an effective antiasthmatic compound, but the enhanced BK currents might play a less important role in the antiasthmatic effects.

Chloroquine is a potent pulmonary vasodilator that attenuates hypoxia-induced pulmonary hypertension

BACKGROUND AND PURPOSE

Sustained pulmonary vasoconstriction and excessive pulmonary vascular remodelling are two major causes of elevated pulmonary vascular resistance in patients with pulmonary arterial hypertension. The purpose of this study was to investigate whether chloroquine induced relaxation in the pulmonary artery (PA) and attenuates hypoxia-induced pulmonary hypertension (HPH).

EXPERIMENTAL APPROACH

Isometric tension was measured in rat PA rings pre-constricted with phenylephrine or high K⁺ solution. PA pressure was measured in mouse isolated, perfused and ventilated lungs. Fura-2 fluorescence microscopy was used to measure cytosolic free Ca²⁺ concentration levels in PA smooth muscle cells (PASMCs). Patch-clamp experiments were performed to assess the activity of voltage-dependent Ca²⁺ channels (VDCCs) in PASMC. Rats exposed to hypoxia (10% O₂ ) for 3 weeks were used as the model of HPH or Sugen5416/hypoxia (SuHx) for in vivo experiments.

KEY RESULTS

Chloroquine attenuated agonist-induced and high K⁺ -induced contraction in isolated rat PA. Pretreatment with l-NAME or indomethacin and functional removal of endothelium failed to inhibit chloroquine-induced PA relaxation. In PASMC, extracellular application of chloroquine attenuated store-operated Ca²⁺ entry and ATP-induced Ca²⁺ entry. Furthermore, chloroquine also inhibited whole-cell Ba²⁺ currents through VDCC in PASMC. In vivo experiments demonstrated that chloroquine treatment ameliorated the HPH and SuHx models.

CONCLUSIONS AND IMPLICATIONS

Chloroquine is a potent pulmonary vasodilator that may directly or indirectly block VDCC, store-operated Ca²⁺ channels and receptor-operated Ca²⁺ channels in PASMC. The therapeutic potential of chloroquine in pulmonary hypertension is probably due to the combination of its vasodilator, anti-proliferative and anti-autophagic effects.

Distinct Effects of Ca2+ Sparks on Cerebral Artery and Airway Smooth Muscle Cell Tone in Mice and Humans

The effects of Ca²⁺ sparks on cerebral artery smooth muscle cells (CASMCs) and airway smooth muscle cells (ASMCs) tone, as well as the underlying mechanisms, are not clear. In this investigation, we elucidated the underlying mechanisms of the distinct effects of Ca²⁺ sparks on cerebral artery smooth muscle cells (CASMCs) and airway smooth muscle cells (ASMCs) tone. In CASMCs, owing to the functional loss of Ca²⁺-activated Cl^- (Clca) channels, Ca²⁺ sparks activated large-conductance Ca²⁺-activated K⁺ channels (BKs), resulting in a decreases in tone against a spontaneous depolarization-caused high tone in the resting state. In ASMCs, Ca²⁺ sparks induced relaxation through BKs and contraction via Clca channels. However, the integrated result was contraction because Ca²⁺ sparks activated BKs prior to Clca channels and Clca channels-induced depolarization was larger than BKs-caused hyperpolarization. However, the effects of Ca²⁺ sparks on both cell types were determined by L-type voltage-dependent Ca²⁺ channels (LVDCCs). In addition, compared with ASMCs, CASMCs had great and higher amplitude Ca²⁺ sparks, a higher density of BKs, and higher Ca²⁺ and voltage sensitivity of BKs. These differences enhanced the ability of Ca²⁺ sparks to decrease CASMC and to increase ASMC tone. The higher Ca²⁺ and voltage sensitivity of BKs in CASMCs than ASMCs were determined by the β1 subunits. Moreover, Ca²⁺ sparks showed the similar effects on human CASMC and ASMC tone. In conclusions, Ca²⁺ sparks decrease CASMC tone and increase ASMC tone, mediated by BKs and Clca channels, respectively, and finally determined by LVDCCs.

Bitter taste receptors as targets for tocolytics in preterm labor therapy

Preterm birth (PTB) is the leading cause of neonatal mortality and morbidity, with few prevention and treatment options. Uterine contraction is a central feature of PTB, so gaining new insights into the mechanisms of this contraction and consequently identifying novel targets for tocolytics are essential for more successful management of PTB. Here we report that myometrial cells from human and mouse express bitter taste receptors (TAS2Rs) and their canonical signaling components (i.e., G-protein gustducin and phospholipase C β2). Bitter tastants can completely relax myometrium precontracted by different uterotonics. In isolated single mouse myometrial cells, a phenotypical bitter tastant (chloroquine, ChQ) reverses the rise in intracellular Ca2+ concentration ([Ca2+]i) and cell shortening induced by uterotonics, and this reversal effect is inhibited by pertussis toxin and by genetic deletion of α-gustducin. In human myometrial cells, knockdown of TAS2R14 but not TAS2R10 inhibits ChQ's reversal effect on an oxytocin-induced rise in [Ca2+]i Finally, ChQ prevents mouse PTBs induced by bacterial endotoxin LPS or progesterone receptor antagonist mifepristone more often than current commonly used tocolytics, and this prevention is largely lost in α-gustducin-knockout mice. Collectively, our results reveal that activation of the canonical TAS2R signaling system in myometrial cells produces profound relaxation of myometrium precontracted by a broad spectrum of contractile agonists, and that targeting TAS2Rs is an attractive approach to developing effective tocolytics for PTB management.-Zheng, K., Lu, P., Delpapa, E., Bellve, K., Deng, R., Condon, J. C., Fogarty, K., Lifshitz, L. M., Simas, T. A. M., Shi, F., ZhuGe, R. Bitter taste receptors as targets for tocolytics in preterm labor therapy.

Hypertonic saline inhibits airway smooth muscle contraction by inhibiting Ca2+ sensitization

The effects of hypertonic solution on airway smooth muscle (ASM) contraction and the underlying mechanisms are largely unknown. We found that hypertonic saline (HS) inhibited acetylcholine (ACh)-induced contraction of ASM from the mouse trachea and human bronchi. In single mouse ASM cells (ASMCs), ACh induced an increase in intracellular Ca²⁺ that was further enhanced by 5% NaCl, indicating that the HS-induced inhibition of ASM contraction was not mediated by a decrease in cytosolic Ca²⁺ . The Rho-associated kinase (ROCK) inhibitor Y-27632 relaxed ACh-induced precontraction of mouse tracheal rings. However, such inhibition was not observed after the relaxation induced by 5% NaCl. Moreover, the incubation of mouse tracheal rings with 5% NaCl decreased ACh-induced phosphorylation of myosin light chain 20 and myosin phosphatase target subunit 1. These data indicate that HS inhibits the contraction of ASM by inhibiting Ca²⁺ sensitization, not by decreasing intracellular Ca²⁺ .

Chloroquine inhibits Ca2+ permeable ion channels-mediated Ca2+ signaling in primary B lymphocytes

BACKGROUND

Chloroquine, a bitter tastant, inhibits Ca²⁺ signaling, resulting in suppression of B cell activation; however, the inhibitory mechanism remains unclear.

RESULTS

In this study, thapsigargin (TG), but not caffeine, induced sustained intracellular Ca²⁺ increases in mouse splenic primary B lymphocytes, which were markedly inhibited by chloroquine. Under Ca²⁺-free conditions, TG elicited transient Ca²⁺ increases, which additionally elevated upon the restoration of 2 mM Ca²⁺. The former were from release of intracellular Ca²⁺ store and the latter from Ca²⁺ influx. TG-induced release was inhibited by 2-APB (an inhibitor of inositol-3-phosphate receptors, IP₃Rs) and chloroquine, and TG-caused influx was inhibited by pyrazole (Pyr3, an inhibitor of transient receptor potential C3 (TRPC3) and stromal interaction molecule (STIM)/Orai channels) and chloroquine. Moreover, chloroquine also blocked Ca²⁺ increases induced by the engagement of B cell receptor (BCR) with anti-IgM.

CONCLUSIONS

These results indicate that chloroquine inhibits Ca²⁺ elevations in splenic B cells through inhibiting Ca²⁺ permeable IP₃R and TRPC3 and/or STIM/Orai channels. These findings suggest that chloroquine would be a potent immunosuppressant.

Nelumbo nucifera leaves extracts inhibit mouse airway smooth muscle contraction

Background

Alkaloids extracted from lotus leaves (AELL) can relax vascular smooth muscle. However, whether AELL has a similar relaxant role on airway smooth muscle (ASM) remains unknown. This study aimed to explore the relaxant property of AELL on ASM and the underlying mechanism.

Methods

Alkaloids were extracted from dried lotus leaves using the high temperature rotary evaporation extraction method. The effects of AELL on mouse ASM tension were studied using force measuring and patch-clamp techniques.

Results

It was found that AELL inhibited the high K⁺ or acetylcholine chloride (ACh)-induced precontraction of mouse tracheal rings by 64.8 ± 2.9%, or 48.8 ± 4.7%, respectively. The inhibition was statistically significant and performed in a dose-dependent manner. Furthermore, AELL-induced smooth muscle relaxation was partially mediated by blocking voltage-dependent Ca²⁺ channels (VDCC) and non-selective cation channels (NSCC).

Conclusion

AELL, which plays a relaxant role in ASM, might be a new complementary treatment to treat abnormal contractions of the trachea and asthma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1674-7) contains supplementary material, which is available to authorized users.

Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease

Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.

Cortex phellodendri Extract Relaxes Airway Smooth Muscle

Cortex phellodendri is used to reduce fever and remove dampness and toxin. Berberine is an active ingredient of C. phellodendri. Berberine from Argemone ochroleuca can relax airway smooth muscle (ASM); however, whether the nonberberine component of C. phellodendri has similar relaxant action was unclear. An n-butyl alcohol extract of C. phellodendri (NBAECP, nonberberine component) was prepared, which completely inhibits high K⁺- and acetylcholine- (ACH-) induced precontraction of airway smooth muscle in tracheal rings and lung slices from control and asthmatic mice, respectively. The contraction induced by high K⁺ was also blocked by nifedipine, a selective blocker of L-type Ca²⁺ channels. The ACH-induced contraction was partially inhibited by nifedipine and pyrazole 3, an inhibitor of TRPC3 and STIM/Orai channels. Taken together, our data demonstrate that NBAECP can relax ASM by inhibiting L-type Ca²⁺ channels and TRPC3 and/or STIM/Orai channels, suggesting that NBAECP could be developed to a new drug for relieving bronchospasm.

The pharmacology of bitter taste receptors and their role in human airways

The receptors involved in bitter taste perception (bitter taste receptors--T2Rs) constitute a family of G-protein-coupled receptors, of which around 29 subtypes have been identified in humans. T2R expression was initially thought to be confined to the oral cavity but has recently been described in a range of other tissues (such as the heart, gut, nasal cavity and lungs) and cell types (chemosensory, smooth muscle, endothelial, epithelial and inflammatory cells). Although it is still not clear whether endogenous T2R agonists exist, the T2R receptors recognize many natural and synthetic compounds, such as the acyl-homoserine lactones produced by bacteria, caffeine, chloroquine, and erythromycin. In the upper airways, T2Rs are involved in neurogenic inflammation and bacterial clearance. Their known effects in the lungs are exerted at three different levels. Firstly, T2R agonists increase the beating frequency of cilia on epithelial cells. Secondly, the T2Rs induce bronchial smooth muscle cells to relax. Thirdly, the T2R receptors expressed on immune cells (such as macrophages and mast cells) modulate production of pro-inflammatory mediators. Furthermore, T2R agonists are effective in inhibiting lung inflammation or smooth muscle contraction in ex vivo and asthma animal models, and are known to be involved in bacterial killing in the nasal cavity and enhancing lung function in humans. This review focuses on the pharmacology and physiological functions of T2R receptors in the upper and lower airways. It presents recently acquired knowledge suggesting that T2Rs may become valuable drug targets in the treatment of diseases such as asthma and chronic rhinosinusitis.

Involvement of large-conductance Ca2+-activated K+ channels in chloroquine-induced force alterations in pre-contracted airway smooth muscle

The participation of large-conductance Ca²⁺ activated K⁺ channels (BKs) in chloroquine (chloro)-induced relaxation of precontracted airway smooth muscle (ASM) is currently undefined. In this study we found that iberiotoxin (IbTx, a selective inhibitor of BKs) and chloro both completely blocked spontaneous transient outward currents (STOCs) in single mouse tracheal smooth muscle cells, which suggests that chloro might block BKs. We further found that chloro inhibited Ca²⁺ sparks and caffeine-induced global Ca²⁺ increases. Moreover, chloro can directly block single BK currents completely from the intracellular side and partially from the extracellular side. All these data indicate that the chloro-induced inhibition of STOCs is due to the blockade of chloro on both BKs and ryanodine receptors (RyRs). We also found that low concentrations of chloro resulted in additional contractions in tracheal rings that were precontracted by acetylcholine (ACH). Increases in chloro concentration reversed the contractile actions to relaxations. In the presence of IbTx or paxilline (pax), BK blockers, chloro-induced contractions were inhibited, although the high concentrations of chloro-induced relaxations were not affected. Taken together, our results indicate that chloro blocks BKs and RyRs, resulting in abolishment of STOCs and occurrence of contraction, the latter will counteract the relaxations induced by high concentrations of chloro.

Relaxant action of plumula nelumbinis extract on mouse airway smooth muscle

The traditional herb Plumula Nelumbinis is widely used in the world because it has many biological activities, such as anti-inflammation, antioxidant, antihypertension, and butyrylcholinesterase inhibition. However, the action of Plumula Nelumbinis on airway smooth muscle (ASM) relaxation has not been investigated. A chloroform extract of Plumula Nelumbinis (CEPN) was prepared, which completely inhibited precontraction induced by high K⁺ in a concentration-dependent manner in mouse tracheal rings, but it had no effect on resting tension. CEPN also blocked voltage-dependent L-type Ca²⁺ channel- (VDCC-) mediated currents. In addition, ACh-induced precontraction was also completely blocked by CEPN and partially inhibited by nifedipine or pyrazole 3. Besides, CEPN partially reduced ACh-activated nonselective cation channel (NSCC) currents. Taken together, our data demonstrate that CEPN blocked VDCC and NSCC to inhibit Ca²⁺ influx, resulting in relaxation of precontracted ASM. This finding indicates that CEPN would be a candidate of new potent bronchodilators.