Zhihua Yu

Targeted Inhibition of KCa3.1 Channel Attenuates Airway Inflammation and Remodeling in Allergic Asthma

KCa3.1 has been suggested to be involved in regulating cell activation, proliferation, and migration in multiple cell types, including airway inflammatory and structural cells. However, the contributions of KCa3.1 to airway inflammation and remodeling and subsequent airway hyperresponsiveness (AHR) in allergic asthma remain to be explored. The main purpose of this study was to elucidate the roles of KCa3.1 and the potential therapeutic value of KCa3.1 blockers in chronic allergic asthma. Using real-time PCR, Western blotting, or immunohistochemical analyses, we explored the precise role of KCa3.1 in the bronchi of allergic mice and asthmatic human bronchial smooth muscle cells (BSMCs). We found that KCa3.1 mRNA and protein expression were elevated in the bronchi of allergic mice, and double labeling revealed that up-regulation occurred primarily in airway smooth muscle cells. Triarylmethane (TRAM)-34, a KCa3.1 blocker, dose-dependently inhibited the generation and maintenance of the ovalbumin-induced airway inflammation associated with increased Th2-type cytokines and decreased Th1-type cytokine, as well as subepithelial extracellular matrix deposition, goblet-cell hyperplasia, and AHR in a murine model of asthma. Moreover, the pharmacological blockade and gene silencing of KCa3.1, which was evidently elevated after mitogen stimulation, suppressed asthmatic human BSMC proliferation and migration, and arrested the cell cycle at the G0/G1 phase. In addition, the KCa3.1 activator 1-ethylbenzimidazolinone-induced membrane hyperpolarization and intracellular calcium increase in asthmatic human BSMCs were attenuated by TRAM-34. We demonstrate for the first time an important role for KCa3.1 in the pathogenesis of airway inflammation and remodeling in allergic asthma, and we suggest that KCa3.1 blockers may represent a promising therapeutic strategy for asthma.

mAChRs activation induces epithelial-mesenchymal transition on lung epithelial cells

BackgroundEpithelial-mesenchymal transition (EMT) has been proposed as a mechanism in the progression of airway diseases and cancer. Here, we explored the role of acetylcholine (ACh) and the pathway involved in the process of EMT, as well as the effects of mAChRs antagonist.MethodsHuman lung epithelial cells were stimulated with carbachol, an analogue of ACh, and epithelial and mesenchymal marker proteins were evaluated using western blot and immunofluorescence analyses.ResultsDecreased E-cadherin expression and increased vimentin and α-SMA expression induced by TGF-β1 in alveolar epithelial cell (A549) were significantly abrogated by the non-selective mAChR antagonist atropine and enhanced by the acetylcholinesterase inhibitor physostigmine. An EMT event also occurred in response to physostigmine alone. Furthermore, ChAT express and ACh release by A549 cells were enhanced by TGF-β1. Interestingly, ACh analogue carbachol also induced EMT in A549 cells as well as in bronchial epithelial cells (16HBE) in a time- and concentration-dependent manner, the induction of carbachol was abrogated by selective antagonist of M1 (pirenzepine) and M3 (4-DAMP) mAChRs, but not by M2 (methoctramine) antagonist. Moreover, carbachol induced TGF-β1 production from A549 cells concomitantly with the EMT process. Carbachol-induced EMT occurred through phosphorylation of Smad2/3 and ERK, which was inhibited by pirenzepine and 4-DAMP.ConclusionsOur findings for the first time indicated that mAChR activation, perhaps via M1 and M3 mAChR, induced lung epithelial cells to undergo EMT and provided insights into novel therapeutic strategies for airway diseases in which lung remodeling occurs.

TNF-α-induced CXCL8 production by A549 cells: Involvement of the non-neuronal cholinergic system

It was recently suggested that the non-neuronal cholinergic system has a regulatory role in pulmonary inflammation. We investigated this systems involvement in the control of cytokine production by the A549 human alveolar epithelial cell line. CXCL8 and acetylcholine (ACh) concentrations were measured using ELISA and LC-MS/MS, respectively. The mRNA expression of muscarinic receptor (MR) subtypes was determined using RT-PCR. In A549 cells, TNF-α increased the release of CXCL8 and ACh and the expression of the subtype 3 MR (M3R). Furthermore, TNF-α-induced CXCL8 secretion was (i) inhibited by the MR antagonist tiotropium and the M3R antagonist 4-DAMP and (ii) enhanced by the M1/M3R agonist pilocarpine and the cholinesterase inhibitor physostigmine. Taken as a whole, these results suggest that ACh release by A549 cells enhances TNF-α-induced CXCL8 secretion through activation of the M3R. Western blot analysis revealed that pilocarpine and physostigmine enhanced the TNF-α-induced phosphorylation of ERK1/2 and p38 MAPK and the degradation of IκBα. Inhibition of these pathways with specific inhibitors abrogated the pilocarpine-induced CXCL8 release. Our results suggest that the TNF-α-induced secretion of CXCL8 in A549 cells is regulated by the release of ACh, the latters binding to the M3R and the downstream activation of NF-κB and the ERK1/2 and p38 MAPK signaling pathways. Our findings suggest that MR antagonists may have anti-inflammatory effects by preventing pro-inflammatory events driven by endogenous, non-neuronal ACh.

Up-regulation of KCa3.1 promotes human airway smooth muscle cell phenotypic modulation

Airway smooth muscle (ASM) cell phenotype modulation, characterized by reversible switching between contractile and proliferative phenotypes, is considered to contribute to proliferative diseases such as allergic asthma and chronic obstructive pulmonary disease (COPD). KCa3.1 has been suggested to be involved in regulating ASM cell activation, proliferation, and migration. However, little is known regarding the exact role of KCa3.1 in ASM cell phenotypic modulation. To elucidate the role of KCa3.1 in regulating ASM cell phenotypic modulation, we investigated the effects of KCa3.1 channels on ASM contractile marker protein expression, proliferation and migration of primary human bronchial smooth muscle (BSM) cells. We found that PDGF increased KCa3.1 channel expression in BSM cells with a concomitant marked decrease in the expression of contractile phenotypic marker proteins including smooth muscle myosin heavy chain (SMMHC), smooth muscle α-actin (α-SMA), myocardin and KCa1.1. These changes were significantly attenuated by the KCa3.1 blocker, TRAM-34, or gene silencing of KCa3.1. Pharmacological blockade or gene silencing of KCa3.1 also suppressed PDGF-induced human BSM cell migration and proliferation accompanied by a decrease in intracellular free Ca(2+) levels as a consequence of membrane depolarization, resulting in a reduction in cyclin D1 level and cell cycle arrest at G0-G1 phase. Additionally, PDGF-induced up-regulation of KCa3.1 and down-regulation of BSM contractile marker proteins were regulated by the ERK inhibitor U0126 and the AKT inhibitor LY294002. These findings highlight a novel role for the KCa3.1 channel in human BSM cell phenotypic modulation and provide a potential target for therapeutic intervention for proliferative airway diseases.

The newly identified K+ channel blocker talatisamine attenuates beta-amyloid oligomers induced neurotoxicity in cultured cortical neurons.

Loss of cytosolic K(+) through up-regulated delayed rectifier K(+) channels play an important role in beta-amyloid (Aβ) induced neurotoxicity. Potent K(+) channel blocker, particular specific for I(K) channels has been suggested as an attractive candidate for the treatment of Alzheimers disease (AD). Talatisamine is a novel I(K) channel blocker discovered by virtual screening and electrophysiological characterization. In the present study, we examined the neuroprotective effect of talatisamine against Aβ oligomers induced cytotoxicity in primarily cultured cortical neurons. The neurotoxicity related to K(+) loss caused by Aβ40 oligomers included enhanced I(K) density, increased cell membrane permeability, reduced cell viability, and impaired mitochondrial transmembrane potential. Decreased Bcl-2 and increased Bax level, activation of Caspase-3 and Caspase-9 were also observed after Aβ40 oligomers incubation. Talatisamine (120 μM) and TEA (5mM) inhibited the enhanced I(K) caused by Aβ40 oligomers, attenuated cytotoxicity of Aβ oligomers by restoring cell viability and suppressing K(+) loss related apoptotic response. Our results suggested that talatisamine may become a leading compound as I(K) channel blocker for neuroprotection.

Activation of the KCa3.1 channel contributes to traumatic scratch injury-induced reactive astrogliosis through the JNK/c-Jun signaling pathway.

Reactive astrogliosis is widely considered to contribute to pathogenic responses to stress and brain injury and to diseases as diverse as ischemia and neurodegeneration. We previously found that expression of the intermediate-conductance calcium-activated potassium channel (KCa3.1) involved in TGF-β-activated astrogliosis. In the present study, we investigated whether migration of cortical astrocytes following mechanical scratch injury involves the KCa3.1 channel, which contributes to Ca(2+)-mediated migration in other cells. We found that scratch injury increased the expression of KCa3.1 protein in reactive astrocytes. Application of the KCa3.1 blocker TRAM-34 decreased glial fibrillary acidic protein (GFAP) expression and slowed migration in a concentration-dependent manner. Application of the Ca(2+) chelators, EGTA and BAPTA-AM, also slowed the migration of astrocytes. Blockade or genetic deletion of KCa3.1 both slowed and dramatically reduced the scratch injuries induced the sharp rise in astrocytes Ca(2+) concentrations. The scratch injury-induced phosphorylation of JNK and c-Jun proteins was also attenuated both by blockade of KCa3.1 with TRAM-34 and in KCa3.1(-/-) astrocytes. Using KCa3.1 knockout mice, we further confirmed that deletion of KCa3.1 reduced expression of GFAP in an in vivo stab wound model. Taken together, our findings highlight a novel role for KCa3.1 in phenotypic modulation of reactive astrocytes and in astrocyte mobilization in response to mechanical stress, providing a potential target for therapeutic intervention in brain injuries.

KCa3.1 constitutes a pharmacological target for astrogliosis associated with Alzheimer's disease.

Alzheimers disease (AD) is the most common type of dementia and is characterized by a progression from decline of episodic memory to a global impairment of cognitive function. Astrogliosis is a hallmark feature of AD, and reactive gliosis has been considered as an important target for intervention in various neurological disorders. We previously found in astrocyte cultures that the expression of the intermediate conductance calcium-activated potassium channel KCa3.1 was increased in reactive astrocytes induced by TGF-β, while pharmacological blockade or genetic deletion of KCa3.1 attenuated astrogliosis. In this study, we sought to suppress reactive gliosis in the context of AD by inhibiting KCa3.1 and evaluate its effects on the cognitive impairment using murine animal models such as the senescence-accelerated mouse prone 8 (SAMP8) model that exhibits some AD-like symptoms. We found KCa3.1 expression was increased in reactive astrocytes as well as neurons in the brains of both SAMP8 mice and Alzheimers disease patients. Blockade of KCa3.1 with the selective inhibitor TRAM-34 in SAMP8 mice resulted in a decrease in astrogliosis as well as microglia activation, and moreover an attenuation of memory deficits. Using KCa3.1 knockout mice, we further confirmed that deletion of KCa3.1 reduced the activation of astrocytes and microglia, and rescued the memory loss induced by intrahippocampal Aβ1-42 peptide injection. We also found in astrocyte cultures that blockade of KCa3.1 or deletion of KCa3.1 suppressed Aβ oligomer-induced astrogliosis. Our data suggest that KCa3.1 inhibition might represent a promising therapeutic strategy for AD treatment.

The Potassium Channel KCa3.1 Represents a Valid Pharmacological Target for Astrogliosis-Induced Neuronal Impairment in a Mouse Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by progressive decline of cognitive function. Astrogliosis plays a critical role in AD by instigating neuroinflammation, which leads ultimately to cognition decline. We previously showed that the intermediate-conductance Ca2+-activated potassium channel (KCa3.1) is involved in astrogliosis-induced by TGF-β in vitro. In the present study, we investigated the contribution of KCa3.1 channels to astrogliosis-mediated neuroinflammation, using TgAPP/PS1 mice as a model for AD. We found that KCa3.1 expression was increased in reactive astrocytes as well as in neurons in the brains of both TgAPP/PS1 mice and AD patients. Pharmacological blockade of KCa3.1 significantly reduced astrogliosis, microglial activation, neuronal loss, and memory deficits. KCa3.1 blockade inhibited astrocyte activation and reduced brain levels of IL-1β, TNF-α, iNOS, and COX-2. Furthermore, we used primary co-cultures of cortical neurons and astrocytes to demonstrate an important role for KCa3.1 in the process of astrogliosis-induced neuroinflammatory responses during amyloid-β (Aβ)-induced neuronal loss. KCa3.1 was found to be involved in the Aβ-induced activated biochemical profile of reactive astrocytes, which included activation of JNK MAPK and production of reactive oxygen species. Pharmacological blockade of KCa3.1 attenuated Aβ-induced reactive astrocytes and indirect, astrogliosis-mediated damage to neurons. Our data clearly indicate a role for astrogliosis in AD pathogenesis and suggest that KCa3.1 inhibition might represent a good therapeutic target for the treatment of AD. Highlights: (1) Blockade of KCa3.1 in APP/PS1 transgenic mice attenuated astrogliosis and neuron loss, and an attenuation of memory deficits. (2) Blockade of KCa3.1 attenuated Aβ-induced indirect, astrogliosis-mediated damage to neurons in vitro via activation of JNK and ROS.

Carbocysteine restores steroid sensitivity by targeting histone deacetylase 2 in a thiol/GSH-dependent manner.

Steroid insensitivity is commonly observed in patients with chronic obstructive pulmonary disease. Here, we report the effects and mechanisms of carbocysteine (S-CMC), a mucolytic agent, in cellular and animal models of oxidative stress-mediated steroid insensitivity. The following results were obtained: oxidative stress induced higher levels of interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-α), which are insensitive to dexamethasone (DEX). The failure of DEX was improved by the addition of S-CMC by increasing histone deacetylase 2 (HDAC2) expression/activity. S-CMC also counteracted the oxidative stress-induced increase in reactive oxygen species (ROS) levels and decreases in glutathione (GSH) levels and superoxide dismutase (SOD) activity. Moreover, oxidative stress-induced events were decreased by the thiol-reducing agent dithiothreitol (DTT), enhanced by the thiol-oxidizing agent diamide, and the ability of DEX was strengthened by DTT. In addition, the oxidative stress-induced decrease in HDAC2 activity was counteracted by S-CMC by increasing thiol/GSH levels, which exhibited a direct interaction with HDAC2. S-CMC treatment increased HDAC2 recruitment and suppressed H4 acetylation of the IL-8 promoter, and this effect was further ablated by addition of buthionine sulfoximine, a specific inhibitor of GSH synthesis. Our results indicate that S-CMC restored steroid sensitivity by increasing HDAC2 expression/activity in a thiol/GSH-dependent manner and suggest that S-CMC may be useful in a combination therapy with glucocorticoids for treatment of steroid-insensitive pulmonary diseases.

A mucoactive drug carbocisteine ameliorates steroid resistance in rat COPD model

Steroid insensitivity has been commonly found in chronic obstructive pulmonary disease (COPD) patients, which is mediated by the reduction of histone deacetylase (HDAC) 2. Here we aimed to establish a steroid resistant model on experimental COPD rats and evaluate the effect of carbocisteine (S-CMC), a mucoactive drug. Exposure to cigarette smoke (CS) caused marked pathological features of COPD which are insensitive to DEX associated with the down-regulation of HDAC2 expression/activity. The DEX insensitivity observed in COPD featured rats was improved by S-CMC in the aspects of inhibiting chronic lung inflammation (total and differential inflammatory cell counts, inflammatory cytokines release and inflammatory cells infiltration); ameliorating airway remodeling (thickness of airway epithelium and smooth muscle, airway fibrosis, and the level of α-SMA and TGF-β1); improving emphysema (emphysema index D2, level of MMP-9 in BALF and the expression of alpha-1 antitrypsin) and preventing impairments of lung function (PEF, IP and IP-slope). Simultaneously, down-regulation of HDAC2 expression/activity was ameliorated by S-CMC treatment. These results indicate that the rat COPD model with steroid resistance was established by active smoking in a short time frame and demonstrate that the failure of steroid therapy can be restored by S-CMC accompanied by increasing HDAC2 expression/activity, providing additional evidence that S-CMC might be used for GC resistance in COPD.