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Nayak AP, An SS. Anxiolytics for Bronchodilation: Refinements to GABA A Agonists for Asthma Relief. Am J Respir Cell Mol Biol 2022; 67:419-420. [PMID: 35901197 PMCID: PMC9564927 DOI: 10.1165/rcmb.2022-0287ed] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Ajay P. Nayak
- Center for Translational Medicine,Department of MedicineThomas Jefferson UniversityPhiladelphia, Pennsylvania
| | - Steven S. An
- Rutgers Institute for Translational Medicine and ScienceNew Brunswick, New Jersey,Rutgers-Robert Wood Johnson Medical SchoolThe State University of New JerseyPiscataway, New Jersey
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Perez-Zoghbi JF, Sajorda DR, Webb DA, Arnold LA, Emala CW, Yocum GT. Imidazobenzodiazepine PI320 Relaxes Mouse Peripheral Airways by Inhibiting Calcium Mobilization. Am J Respir Cell Mol Biol 2022; 67:482-490. [PMID: 35776523 PMCID: PMC9564932 DOI: 10.1165/rcmb.2022-0084oc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Asthma is a common respiratory disease characterized, in part, by excessive airway smooth muscle (ASM) contraction (airway hyperresponsiveness). Various GABAAR (γ-aminobutyric acid type A receptor) activators, including benzodiazepines, relax ASM. The GABAAR is a ligand-operated Cl- channel best known for its role in inhibitory neurotransmission in the central nervous system. Although ASM cells express GABAARs, affording a seemingly logical site of action, the mechanism(s) by which GABAAR ligands relax ASM remains unclear. PI320, a novel imidazobenzodiazepine designed for tissue selectivity, is a promising asthma drug candidate. Here, we show that PI320 alleviates methacholine (MCh)-induced bronchoconstriction in vivo and relaxes peripheral airways preconstricted with MCh ex vivo using the forced oscillation technique and precision-cut lung slice experiments, respectively. Surprisingly, the peripheral airway relaxation demonstrated in precision-cut lung slices does not appear to be GABAAR-dependent, as it is not inhibited by the GABAAR antagonist picrotoxin or the benzodiazepine antagonist flumazenil. Furthermore, we demonstrate here that PI320 inhibits MCh-induced airway constriction in the absence of external Ca2, suggesting that PI320-mediated relaxation is not mediated by inhibition of Ca2+ influx in ASM. However, PI320 does inhibit MCh-induced intracellular Ca2+ oscillations in peripheral ASM, a key mediator of contraction that is dependent on sarcoplasmic reticulum Ca2+ mobilization. Furthermore, PI320 inhibits peripheral airway constriction induced by experimentally increasing the intracellular concentration of inositol triphosphate (IP3). These novel data suggest that PI320 relaxes murine peripheral airways by inhibiting intracellular Ca2+ mobilization in ASM, likely by inhibiting Ca2+ release through IP3Rs (IP3 receptors).
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Affiliation(s)
- Jose F. Perez-Zoghbi
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York; and
| | - Dannah Rae Sajorda
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York; and
| | - Daniel A. Webb
- Department of Chemistry and Biochemistry and,Milwaukee Institute for Drug Discovery, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin
| | - Leggy A. Arnold
- Department of Chemistry and Biochemistry and,Milwaukee Institute for Drug Discovery, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin
| | - Charles W. Emala
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York; and
| | - Gene T. Yocum
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York; and
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Sunny SK, Zhang H, Mzayek F, Relton CL, Ring S, Henderson AJ, Ewart S, Holloway JW, Arshad SH. Pre-adolescence DNA methylation is associated with lung function trajectories from pre-adolescence to adulthood. Clin Epigenetics 2021; 13:5. [PMID: 33407823 PMCID: PMC7789734 DOI: 10.1186/s13148-020-00992-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 12/15/2020] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND The pattern of lung function development from pre-adolescence to adulthood plays a significant role in the pathogenesis of respiratory diseases. Inconsistent findings in genetic studies on lung function trajectories, the importance of DNA methylation (DNA-M), and the critical role of adolescence in lung function development motivated the present study of pre-adolescent DNA-M with lung function trajectories. This study investigated epigenome-wide associations of DNA-M at cytosine-phosphate-guanine dinucleotide sites (CpGs) at childhood with lung function trajectories from childhood to young adulthood. METHODS DNA-M was measured in peripheral blood at age 10 years in the Isle of Wight (IOW) birth cohort. Spirometry was conducted at ages 10, 18, and 26 years. A training/testing-based method was used to screen CpGs. Multivariable logistic regressions were applied to assess the association of DNA-M with lung function trajectories from pre-adolescence to adulthood. To detect differentially methylated regions (DMRs) among CpGs, DMR enrichment analysis was conducted. Findings were further tested in the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort. Pathway analyses were performed on the mapped genes of the identified CpGs and DMRs. Biological relevance of the identified CpGs was assessed with gene expression. All analyses were stratified by sex. RESULTS High and low trajectories of FVC, FEV1, and FEV1/FVC in each sex were identified. At PBonferroni < 0.05, DNA-M at 96 distinct CpGs (41 in males) showed associations with FVC, FEV1, and FEV1/FVC trajectories in IOW cohort. These 95 CpGs (cg24000797 was disqualified) were further tested in ALSPAC; 44 CpGs (19 in males) of these 95 showed the same directions of association as in the IOW cohort; and three CpGs (two in males) were replicated. DNA-M at two and four CpGs showed significant associations with the corresponding gene expression in males and females, respectively. At PFDR < 0.05, 23 and 10 DMRs were identified in males and females, respectively. Pathways were identified; some of those were linked to lung function and chronic obstructive lung diseases. CONCLUSION The identified CpGs at pre-adolescence have the potential to serve as candidate markers for lung function trajectory prediction and chronic lung diseases.
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Affiliation(s)
- Shadia Khan Sunny
- Division of Epidemiology, Biostatistics, and Environmental Health Sciences, School of Public Health, University of Memphis, Memphis, TN 38152 USA
| | - Hongmei Zhang
- Division of Epidemiology, Biostatistics, and Environmental Health Sciences, School of Public Health, University of Memphis, Memphis, TN 38152 USA
| | - Fawaz Mzayek
- Division of Epidemiology, Biostatistics, and Environmental Health Sciences, School of Public Health, University of Memphis, Memphis, TN 38152 USA
| | - Caroline L. Relton
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, BS8 2BN UK
| | - Susan Ring
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, BS8 2BN UK
- Population Health Sciences, University of Bristol, Bristol, BS8 2BN UK
| | - A. John Henderson
- Population Health Sciences, University of Bristol, Bristol, BS8 2BN UK
| | - Susan Ewart
- Large Animal Clinical Sciences, Michigan State University, East Lansing, MI USA
| | - John W. Holloway
- Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, SO16 6YD UK
| | - S. Hasan Arshad
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, SO16 6YD UK
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD UK
- The David Hide Asthma and Allergy Research Centre, St Mary’s Hospital, Parkhurst Road, Newport, Isle of Wight, PO30 5TG UK
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Patel BS, Ravix J, Pabelick C, Prakash YS. Class C GPCRs in the airway. Curr Opin Pharmacol 2020; 51:19-28. [PMID: 32375079 DOI: 10.1016/j.coph.2020.04.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 03/17/2020] [Accepted: 04/02/2020] [Indexed: 02/07/2023]
Abstract
Understanding and targeting of GPCRs remain a critical aspect of airway pharmacology and therapeutics for diseases such as asthma or COPD. Most attention has been on the large Class A GPCRs towards improved bronchodilation and blunting of remodeling. Better known in the central or peripheral nervous system, there is increasing evidence that Class C GPCRs which include metabotropic glutamate and GABA receptors, the calcium sensing receptor, sweet/umami taste receptors and a number of orphan receptors, can contribute to airway structure and function. In this review, we will summarize current state of knowledge regarding the pharmacology of Class C GPCRs, their expression and potential functions in the airways, and the application of pharmacological agents targeting this group in the context of airway diseases.
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Affiliation(s)
- Brijeshkumar S Patel
- Department of Anesthesiologyand Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
| | - Jovanka Ravix
- Department of Anesthesiologyand Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
| | - Christina Pabelick
- Department of Anesthesiologyand Perioperative Medicine, Mayo Clinic, Rochester, MN, United States; Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
| | - Y S Prakash
- Department of Anesthesiologyand Perioperative Medicine, Mayo Clinic, Rochester, MN, United States; Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States.
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Regulation of Airway Smooth Muscle Contraction in Health and Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1124:381-422. [PMID: 31183836 DOI: 10.1007/978-981-13-5895-1_16] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Airway smooth muscle (ASM) extends from the trachea throughout the bronchial tree to the terminal bronchioles. In utero, spontaneous phasic contraction of fetal ASM is critical for normal lung development by regulating intraluminal fluid movement, ASM differentiation, and release of key growth factors. In contrast, phasic contraction appears to be absent in the adult lung, and regulation of tonic contraction and airflow is under neuronal and humoral control. Accumulating evidence suggests that changes in ASM responsiveness contribute to the pathophysiology of lung diseases with lifelong health impacts.Functional assessments of fetal and adult ASM and airways have defined pharmacological responses and signaling pathways that drive airway contraction and relaxation. Studies using precision-cut lung slices, in which contraction of intrapulmonary airways and ASM calcium signaling can be assessed simultaneously in situ, have been particularly informative. These combined approaches have defined the relative importance of calcium entry into ASM and calcium release from intracellular stores as drivers of spontaneous phasic contraction in utero and excitation-contraction coupling.Increased contractility of ASM in asthma contributes to airway hyperresponsiveness. Studies using animal models and human ASM and airways have characterized inflammatory and other mechanisms underlying increased reactivity to contractile agonists and reduced bronchodilator efficacy of β2-adrenoceptor agonists in severe diseases. Novel bronchodilators and the application of bronchial thermoplasty to ablate increased ASM within asthmatic airways have the potential to overcome limitations of current therapies. These approaches may directly limit excessive airway contraction to improve outcomes for difficult-to-control asthma and other chronic lung diseases.
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Prakash YS. Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease. Am J Physiol Lung Cell Mol Physiol 2016; 311:L1113-L1140. [PMID: 27742732 DOI: 10.1152/ajplung.00370.2016] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/06/2016] [Indexed: 12/15/2022] Open
Abstract
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.
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Affiliation(s)
- Y S Prakash
- Departments of Anesthesiology, and Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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Pera T, Penn RB. Bronchoprotection and bronchorelaxation in asthma: New targets, and new ways to target the old ones. Pharmacol Ther 2016; 164:82-96. [PMID: 27113408 PMCID: PMC4942340 DOI: 10.1016/j.pharmthera.2016.04.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 04/07/2016] [Indexed: 01/01/2023]
Abstract
Despite over 50years of inhaled beta-agonists and corticosteroids as the default management or rescue drugs for asthma, recent research suggests that new therapeutic options are likely to emerge. This belief stems from both an improved understanding of what causes and regulates airway smooth muscle (ASM) contraction, and the identification of new targets whose inhibition or activation can relax ASM. In this review we discuss the recent findings that provide new insight into ASM contractile regulation, a revolution in pharmacology that identifies new ways to "tune" G protein-coupled receptors to improve therapeutic efficacy, and the discovery of several novel targets/approaches capable of effecting bronchoprotection or bronchodilation.
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Affiliation(s)
- Tonio Pera
- Center for Translational Medicine and Jane and Leonard Korman Lung Center, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, United States.
| | - Raymond B Penn
- Center for Translational Medicine and Jane and Leonard Korman Lung Center, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, United States.
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Huang S, Mao J, Wei B, Pei G. The anti-spasticity drug baclofen alleviates collagen-induced arthritis and regulates dendritic cells. J Cell Physiol 2015; 230:1438-47. [PMID: 25556830 DOI: 10.1002/jcp.24884] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 12/05/2014] [Indexed: 12/27/2022]
Abstract
Baclofen is used clinically as a drug that treats spasticity, which is a syndrome characterized by excessive contraction of the muscles and hyperflexia in the central nervous system (CNS), by activating GABA(B) receptors (GABA(B)Rs). Baclofen was recently reported to desensitize chemokine receptors and to suppress inflammation through the activation of GABA(B)Rs. GABA(B)Rs are expressed in various immune cells, but the functions of these receptors in autoimmune diseases remain largely unknown. In this study, we investigated the effects of baclofen in murine collagen-induced arthritis (CIA). Oral administration of baclofen alleviated the clinical development of CIA, with a reduced number of IL-17-producing T helper 17 (T(H)17) cells. In addition, baclofen treatment suppressed dendritic cell (DC)-primed T(H)17 cell differentiation by reducing the production of IL-6 by DCs in vitro. Furthermore, the pharmacological and genetic blockade of GABA(B)Rs in DCs weakened the effects of baclofen, indicating that GABA(B)Rs are the molecular targets of baclofen on DCs. Thus, our findings revealed a potential role for baclofen in the treatment of CIA, as well as a previously unknown signaling pathway that regulates DC function.
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Affiliation(s)
- Shichao Huang
- State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Graduate School of the Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, P. R. China
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Jin S, Merchant ML, Ritzenthaler JD, McLeish KR, Lederer ED, Torres-Gonzalez E, Fraig M, Barati MT, Lentsch AB, Roman J, Klein JB, Rane MJ. Baclofen, a GABABR agonist, ameliorates immune-complex mediated acute lung injury by modulating pro-inflammatory mediators. PLoS One 2015; 10:e0121637. [PMID: 25848767 PMCID: PMC4388838 DOI: 10.1371/journal.pone.0121637] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 02/12/2015] [Indexed: 11/22/2022] Open
Abstract
Immune-complexes play an important role in the inflammatory diseases of the lung. Neutrophil activation mediates immune-complex (IC) deposition-induced acute lung injury (ALI). Components of gamma amino butyric acid (GABA) signaling, including GABA B receptor 2 (GABABR2), GAD65/67 and the GABA transporter, are present in the lungs and in the neutrophils. However, the role of pulmonary GABABR activation in the context of neutrophil-mediated ALI has not been determined. Thus, the objective of the current study was to determine whether administration of a GABABR agonist, baclofen would ameliorate or exacerbate ALI. We hypothesized that baclofen would regulate IC-induced ALI by preserving pulmonary GABABR expression. Rats were subjected to sham injury or IC-induced ALI and two hours later rats were treated intratracheally with saline or 1 mg/kg baclofen for 2 additional hours and sacrificed. ALI was assessed by vascular leakage, histology, TUNEL, and lung caspase-3 cleavage. ALI increased total protein, tumor necrosis factor α (TNF-α and interleukin-1 receptor associated protein (IL-1R AcP), in the bronchoalveolar lavage fluid (BALF). Moreover, ALI decreased lung GABABR2 expression, increased phospho-p38 MAPK, promoted IκB degradation and increased neutrophil influx in the lung. Administration of baclofen, after initiation of ALI, restored GABABR expression, which was inhibited in the presence of a GABABR antagonist, CGP52432. Baclofen administration activated pulmonary phospho-ERK and inhibited p38 MAPK phosphorylation and IκB degradation. Additionally, baclofen significantly inhibited pro-inflammatory TNF-α and IL-1βAcP release and promoted BAL neutrophil apoptosis. Protective effects of baclofen treatment on ALI were possibly mediated by inhibition of TNF-α- and IL-1β-mediated inflammatory signaling. Interestingly, GABABR2 expression was regulated in the type II pneumocytes in lung tissue sections from lung injured patients, further suggesting a physiological role for GABABR2 in the repair process of lung damage. GABABR2 agonists may play a potential therapeutic role in ALI.
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Affiliation(s)
- Shunying Jin
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Michael L. Merchant
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Jeffrey D. Ritzenthaler
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Kenneth R. McLeish
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
- Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, Kentucky, United States of America
- Robley Rex VA Medical Center, Zorn Avenue, Louisville, Kentucky, United States of America
| | - Eleanor D. Lederer
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
- Robley Rex VA Medical Center, Zorn Avenue, Louisville, Kentucky, United States of America
- Department of Physiology, University of Louisville, Louisville, Kentucky, United States of America
| | - Edilson Torres-Gonzalez
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Mostafa Fraig
- Department of Pathology, University of Louisville, Louisville, Kentucky, United States of America
| | - Michelle T. Barati
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Alex B. Lentsch
- Department of Surgery, University of Cincinnati, Cincinnati, OH, United States of America
| | - Jesse Roman
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
- Robley Rex VA Medical Center, Zorn Avenue, Louisville, Kentucky, United States of America
| | - Jon B. Klein
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
- Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, Kentucky, United States of America
- Robley Rex VA Medical Center, Zorn Avenue, Louisville, Kentucky, United States of America
| | - Madhavi J. Rane
- Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America
- Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, Kentucky, United States of America
- * E-mail:
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Wang XP, Cheng ZY, Schmid KL. GABAB receptors are expressed in human aortic smooth muscle cells and regulate the intracellular Ca(2+) concentration. Heart Vessels 2015; 30:249-57. [PMID: 24682435 DOI: 10.1007/s00380-014-0499-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 03/14/2014] [Indexed: 11/26/2022]
Abstract
The aim of this study was to investigate the expression of GABAB receptors, a subclass of receptors to the inhibitory neurotransmitter gamma-aminobutyric acid (GABAB), in human aortic smooth muscle cells (HASMCs), and to explore if altering receptor activation modified intracellular Ca(2+) concentration ([Ca(2+)]i) of HASMCs. Real-time PCR, western blots and immunofluorescence were used to determine the expression of GABABR1 and GABABR2 in cultured HASMCs. Immunohistochemistry was used to localize the two subunits in human left anterior descending artery (LAD). The effects of the GABAB receptor agonist baclofen on [Ca(2+)]i in cultured HASMCs were demonstrated using fluo-3. Both GABABR1 and GABABR2 mRNA and protein were identified in cultured HASMCs and antibody staining was also localized to smooth muscle cells of human LAD. 100 μM baclofen caused a transient increase of [Ca(2+)]i in cultured HASMCs regardless of whether Ca(2+) was added to the medium, and the effects were inhibited by pre-treatment with CGP46381 (selective GABAB receptor antagonist), pertussis toxin (a Gi/o protein inhibitor), and U73122 (a phospholipase C blocker). GABAB receptors are expressed in HASMCs and regulate the [Ca(2+)]i via a Gi/o-coupled receptor pathway and a phospholipase C activation pathway.
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MESH Headings
- Aorta/metabolism
- Calcium/metabolism
- Calcium Signaling/drug effects
- Cells, Cultured
- Enzyme Activation
- GABA Agonists/pharmacology
- GABA Antagonists/pharmacology
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Humans
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Receptors, GABA-B/drug effects
- Receptors, GABA-B/genetics
- Receptors, GABA-B/metabolism
- Type C Phospholipases/metabolism
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Affiliation(s)
- Xu-Ping Wang
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital, Shandong University, Jinan, Shandong, China
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Cytoskeletal rearrangement and Src and PI-3K-dependent Akt activation control GABA(B)R-mediated chemotaxis. Cell Signal 2015; 27:1178-1185. [PMID: 25725285 DOI: 10.1016/j.cellsig.2015.02.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 02/01/2015] [Accepted: 02/15/2015] [Indexed: 01/13/2023]
Abstract
The γ-amino butyric acid (GABA) type B receptors (GABA(B)R) function as chemoattractant receptors in response to GABA(B)R agonists in human neutrophils. The goal of this study was to define signaling mechanisms regulating GABA(B)R-mediated chemotaxis and cytoskeletal rearrangement. In a proteomic study we identified serine/threonine kinase Akt, tyrosine kinases Src and Pyk2, microtubule regulator kinesin and microtubule affinity-regulating kinase (MARK) co-immunoprecipitating with GABA(B)R. To define the contributions of these candidate signaling events in GABA(B)R-mediated chemotaxis, we used rat basophilic leukemic cells (RBL-2H3 cells) stably transfected with human GABA(B1b) and GABA(B2) receptors. The GABA(B)R agonist baclofen induced Akt phosphorylation and chemotaxis by binding to its specific GABA(B)R since pretreatment of cells with CGP52432, a GABA(B)R antagonist, blocked such effects. Moreover, baclofen induced Akt phosphorylation was shown to be dependent upon PI-3K and Src kinases. Baclofen failed to stimulate actin polymerization in suspended RBL cells unless exposed to a baclofen gradient. However, baclofen stimulated both actin and tubulin polymerization in adherent RBL-GABA(B)R cells. Blockade of actin and tubulin polymerization by treatment of cells with cytochalasin D or nocodazole respectively, abolished baclofen-mediated chemotaxis. Furthermore, baclofen stimulated Pyk2 and STAT3 phosphorylation, both known regulators of cell migration. In conclusion, GABA(B)R stimulation promotes chemotaxis in RBL cells which is dependent on signaling via PI3-K/Akt, Src kinases and on rearrangement of both microtubules and actin cytoskeleton. These data define mechanisms of GABA(B)R-mediated chemotaxis which may potentially be used to therapeutically regulate cellular response to injury and disease.
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12
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Cheng ZY, Wang XP, Schmid KL, Han XG. GABAB1 and GABAB2 receptor subunits co-expressed in cultured human RPE cells regulate intracellular Ca2+ via Gi/o-protein and phospholipase C pathways. Neuroscience 2014; 280:254-61. [PMID: 25241062 DOI: 10.1016/j.neuroscience.2014.09.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/10/2014] [Accepted: 09/10/2014] [Indexed: 11/26/2022]
Abstract
GABAB receptors associate with Gi/o-proteins that regulate voltage-gated Ca(2+) channels and thus the intracellular Ca(2+) concentration ([Ca(2+)]i), there is also reported cross-regulation of phospholipase C. These associations have been studied extensively in the brain and also shown to occur in non-neural cells (e.g. human airway smooth muscle). More recently GABAB receptors have been observed in chick retinal pigment epithelium (RPE). The aims were to investigate whether the GABAB receptor subunits, GABAB1 and GABAB2, are co-expressed in cultured human RPE cells, and then determine if the GABAB receptor similarly regulates the [Ca(2+)]i of RPE cells and if phospholipase C is involved. Human RPE cells were cultured from five donor eye cups. Evidence for GABAB1 and GABAB2 mRNAs and proteins in the RPE cell cultures was investigated using real time polymerase chain reaction, western blots and immunofluorescence. The effects of the GABAB receptor agonist baclofen, antagonist CGP46381, a Gi/o-protein inhibitor pertussis toxin, and the phospholipase C inhibitor U73122 on [Ca(2+)]i in cultured human RPE were demonstrated using Fluo-3. Both GABAB1 and GABAB2 mRNA and protein were identified in cell cultures of human RPE; antibody staining was co-localized to the cell membrane and cytoplasm. One-hundred micromolars of baclofen caused a transient increase in the [Ca(2+)]i of RPE cells regardless of whether Ca(2+) was added to the buffer. Baclofen-induced increases in the [Ca(2+)]i were attenuated by pre-treatment with CGP46381, pertussis toxin, and U73122. GABAB1 and GABAB2 are co-expressed in cell cultures of human RPE. GABAB receptors in RPE regulate the [Ca(2+)]i via a Gi/o-protein and phospholipase C pathway.
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Affiliation(s)
- Z-Y Cheng
- Department of Ophthalmology, Qilu Hospital, Shandong University, Jinan, Shandong 250012, China.
| | - X-P Wang
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital, Shandong University, Jinan, Shandong 250012, China
| | - K L Schmid
- School of Optometry and Vision Science, Faculty of Health, and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD 4059, Australia
| | - X-G Han
- Department of Ophthalmology, The Second Hospital, Jinan, Shandong 250001, China
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GABAB receptors expressed in human aortic endothelial cells mediate intracellular calcium concentration regulation and endothelial nitric oxide synthase translocation. BIOMED RESEARCH INTERNATIONAL 2014; 2014:871735. [PMID: 25114926 PMCID: PMC4119922 DOI: 10.1155/2014/871735] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 06/05/2014] [Accepted: 06/23/2014] [Indexed: 11/17/2022]
Abstract
GABAB receptors regulate the intracellular Ca2+ concentration ([Ca2+]i) in a number of cells (e.g., retina, airway epithelium and smooth muscle), but whether they are expressed in vascular endothelial cells and similarly regulate the [Ca2+]i is not known. The purpose of this study was to investigate the expression of GABAB receptors, a subclass of receptors to the inhibitory neurotransmitter γ-aminobutyric acid (GABA), in cultured human aortic endothelial cells (HAECs), and to explore if altering receptor activation modified [Ca2+]i and endothelial nitric oxide synthase (eNOS) translocation. Real-time PCR, western blots and immunofluorescence were used to determine the expression of GABAB1 and GABAB2 in cultured HAECs. The effects of GABAB receptors on [Ca2+]i in cultured HAECs were demonstrated using fluo-3. The influence of GABAB receptors on eNOS translocation was assessed by immunocytochemistry. Both GABAB1 and GABAB2 mRNA and protein were expressed in cultured HAECs, and the GABAB1 and GABAB2 proteins were colocated in the cell membrane and cytoplasm. One hundred μM baclofen caused a transient increase of [Ca2+]i and eNOS translocation in cultured HAECs, and the effects were attenuated by pretreatment with the selective GABAB receptor antagonists CGP46381 and CGP55845. GABAB receptors are expressed in HAECs and regulate the [Ca2+]i and eNOS translocation. Cultures of HAECs may be a useful in vitro model for the study of GABAB receptors and vascular biology.
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Prakash YS. Airway smooth muscle in airway reactivity and remodeling: what have we learned? Am J Physiol Lung Cell Mol Physiol 2013; 305:L912-33. [PMID: 24142517 PMCID: PMC3882535 DOI: 10.1152/ajplung.00259.2013] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 10/12/2013] [Indexed: 12/12/2022] Open
Abstract
It is now established that airway smooth muscle (ASM) has roles in determining airway structure and function, well beyond that as the major contractile element. Indeed, changes in ASM function are central to the manifestation of allergic, inflammatory, and fibrotic airway diseases in both children and adults, as well as to airway responses to local and environmental exposures. Emerging evidence points to novel signaling mechanisms within ASM cells of different species that serve to control diverse features, including 1) [Ca(2+)]i contractility and relaxation, 2) cell proliferation and apoptosis, 3) production and modulation of extracellular components, and 4) release of pro- vs. anti-inflammatory mediators and factors that regulate immunity as well as the function of other airway cell types, such as epithelium, fibroblasts, and nerves. These diverse effects of ASM "activity" result in modulation of bronchoconstriction vs. bronchodilation relevant to airway hyperresponsiveness, airway thickening, and fibrosis that influence compliance. This perspective highlights recent discoveries that reveal the central role of ASM in this regard and helps set the stage for future research toward understanding the pathways regulating ASM and, in turn, the influence of ASM on airway structure and function. Such exploration is key to development of novel therapeutic strategies that influence the pathophysiology of diseases such as asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis.
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Affiliation(s)
- Y S Prakash
- Dept. of Anesthesiology, Mayo Clinic, 4-184 W Jos SMH, 200 First St. SW, Rochester, MN 55905.
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Baclofen and other GABAB receptor agents are allosteric modulators of the CXCL12 chemokine receptor CXCR4. J Neurosci 2013; 33:11643-54. [PMID: 23843532 DOI: 10.1523/jneurosci.6070-11.2013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
CXCR4, a receptor for the chemokine CXCL12 (stromal-cell derived factor-1α), is a G-protein-coupled receptor (GPCR), expressed in the immune and CNS and integrally involved in various neurological disorders. The GABAB receptor is also a GPCR that mediates metabotropic action of the inhibitory neurotransmitter GABA and is located on neurons and immune cells as well. Using diverse approaches, we report novel interaction between GABAB receptor agents and CXCR4 and demonstrate allosteric binding of these agents to CXCR4. First, both GABAB antagonists and agonists block CXCL12-elicited chemotaxis in human breast cancer cells. Second, a GABAB antagonist blocks the potentiation by CXCL12 of high-threshold Ca(2+) channels in rat neurons. Third, electrophysiology in Xenopus oocytes and human embryonic kidney cell line 293 cells in which we coexpressed rat CXCR4 and the G-protein inward rectifier K(+) (GIRK) channel showed that GABAB antagonist and agonist modified CXCL12-evoked activation of GIRK channels. To investigate whether GABAB ligands bind to CXCR4, we expressed this receptor in heterologous systems lacking GABAB receptors and performed competition binding experiments. Our fluorescent resonance energy transfer experiments suggest that GABAB ligands do not bind CXCR4 at the CXCL12 binding pocket suggesting allosteric modulation, in accordance with our electrophysiology experiments. Finally, using backscattering interferometry and lipoparticles containing only the CXCR4 receptor, we quantified the binding affinity for the GABAB ligands, confirming a direct interaction with the CXCR4 receptor. The effect of GABAergic agents on CXCR4 suggests new therapeutic potentials for neurological and immune diseases.
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Quintas M, Neto JL, Pereira-Monteiro J, Barros J, Sequeiros J, Sousa A, Alonso I, Lemos C. Interaction between γ-aminobutyric acid A receptor genes: new evidence in migraine susceptibility. PLoS One 2013; 8:e74087. [PMID: 24040174 PMCID: PMC3764027 DOI: 10.1371/journal.pone.0074087] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 07/26/2013] [Indexed: 01/07/2023] Open
Abstract
Migraine is a common neurological episodic disorder with a female-to-male prevalence 3- to 4-fold higher, suggesting a possible X-linked genetic component. Our aims were to assess the role of common variants of gamma-aminobutyric acid A receptor (GABAAR) genes, located in the X-chromosome, in migraine susceptibility and the possible interaction between them. An association study with 188 unrelated cases and 286 migraine-free controls age- and ethnic matched was performed. Twenty-three tagging SNPs were selected in three genes (GABRE, GABRA3 and GABRQ). Allelic, genotypic and haplotypic frequencies were compared between cases and controls. We also focused on gene-gene interactions. The AT genotype of rs3810651 of GABRQ gene was associated with an increased risk for migraine (OR: 4.07; 95% CI: 1.71-9.73, p=0.002), while the CT genotype of rs3902802 (OR: 0.41; 95% CI: 0.21-0.78, p=0.006) and GA genotype of rs2131190 of GABRA3 gene (OR: 0.53; 95% CI: 0.32-0.88, p=0.013) seem to be protective factors. All associations were found in the female group and maintained significance after Bonferroni correction. We also found three nominal associations in the allelic analyses although there were no significant results in the haplotypic analyses. Strikingly, we found strong interactions between six SNPs encoding for different subunits of GABAAR, all significant after permutation correction. To our knowledge, we show for the first time, the putative involvement of polymorphisms in GABAAR genes in migraine susceptibility and more importantly we unraveled a role for novel gene-gene interactions opening new perspectives for the development of more effective treatments.
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Affiliation(s)
- Marlene Quintas
- UnIGENe IBMC – Instituto de Biologia Molecular Celular, Universidade do Porto, Porto, Portugal
| | - João Luís Neto
- UnIGENe IBMC – Instituto de Biologia Molecular Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - José Pereira-Monteiro
- UnIGENe IBMC – Instituto de Biologia Molecular Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
- Serviço de Neurologia, CHP-HSA, Centro Hospitalar do Porto, Hospital de Santo António. Abel Salazar, Porto, Portugal
| | - José Barros
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
- Serviço de Neurologia, CHP-HSA, Centro Hospitalar do Porto, Hospital de Santo António. Abel Salazar, Porto, Portugal
| | - Jorge Sequeiros
- UnIGENe IBMC – Instituto de Biologia Molecular Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Alda Sousa
- UnIGENe IBMC – Instituto de Biologia Molecular Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Isabel Alonso
- UnIGENe IBMC – Instituto de Biologia Molecular Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Carolina Lemos
- UnIGENe IBMC – Instituto de Biologia Molecular Celular, Universidade do Porto, Porto, Portugal
- ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
- * E-mail:
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Gallos G, Townsend E, Yim P, Virag L, Zhang Y, Xu D, Bacchetta M, Emala CW. Airway epithelium is a predominant source of endogenous airway GABA and contributes to relaxation of airway smooth muscle tone. Am J Physiol Lung Cell Mol Physiol 2012. [PMID: 23204068 DOI: 10.1152/ajplung.00274.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Chronic obstructive pulmonary disease and asthma are characterized by hyperreactive airway responses that predispose patients to episodes of acute airway constriction. Recent studies suggest a complex paradigm of GABAergic signaling in airways that involves GABA-mediated relaxation of airway smooth muscle. However, the cellular source of airway GABA and mechanisms regulating its release remain unknown. We questioned whether epithelium is a major source of GABA in the airway and whether the absence of epithelium-derived GABA contributes to greater airway smooth muscle force. Messenger RNA encoding glutamic acid decarboxylase (GAD) 65/67 was quantitatively measured in human airway epithelium and smooth muscle. HPLC quantified GABA levels in guinea pig tracheal ring segments under basal or stimulated conditions with or without epithelium. The role of endogenous GABA in the maintenance of an acetylcholine contraction in human airway and guinea pig airway smooth muscle was assessed in organ baths. A 37.5-fold greater amount of mRNA encoding GAD 67 was detected in human epithelium vs. airway smooth muscle cells. HPLC confirmed that guinea pig airways with intact epithelium have a higher constitutive elution of GABA under basal or KCl-depolarized conditions compared with epithelium-denuded airway rings. Inhibition of GABA transporters significantly suppressed KCl-mediated release of GABA from epithelium-intact airways, but tetrodotoxin was without effect. The presence of intact epithelium had a significant GABAergic-mediated prorelaxant effect on the maintenance of contractile tone. Airway epithelium is a predominant cellular source of endogenous GABA in the airway and contributes significant prorelaxant GABA effects on airway smooth muscle force.
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Affiliation(s)
- George Gallos
- Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, 622 W. 168 St., P&S Box 46, New York, NY 10032, USA.
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Determination of GABA(Aα1) and GABA (B1) receptor subunits expression in tissues of gilts during the late gestation. Mol Biol Rep 2012; 40:1377-84. [PMID: 23086273 DOI: 10.1007/s11033-012-2181-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Accepted: 10/08/2012] [Indexed: 10/27/2022]
Abstract
GABA(Aα1) and GABA(B1) receptor subunits are responsible for most behavioral, physiological and pharmacological effects of GABA receptors. We investigated the expression of GABA(Aα1) and GABA(B1) receptor subunits in different tissues of gilts during late pregnancy in hot summer. The mRNA abundance of GABA(Aα1) receptor subunit in different tissues of gilts at d 90 and d 110 of gestation was as follows: d 90: brain > lung > liver > ovary > spleen > kidney > heart; d 110: brain > lung > spleen > liver > ovary > kidney > heart. And, the mRNA abundance of GABA(B1) receptor subunit was as follows: d 90: spleen > lung > brain > kidney > ovary > liver > heart; d 110: spleen > lung > kidney > brain > ovary > liver > heart. The results in this trial indicated that the GABA(Aα1) receptor subunit was abundantly expressed in brain, while GABA(B1) receptor subunit was abundant in spleen and lung of gilts during late gestation. There were no gestation stage-dependent effects on GABA(Aα1) and GABA(B1) receptor subunits expression in all tissues.
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19
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Canning BJ, Mori N, Lehmann A. Antitussive effects of the peripherally restricted GABAB receptor agonist lesogaberan in guinea pigs: comparison to baclofen and other GABAB receptor-selective agonists. COUGH 2012; 8:7. [PMID: 23025757 PMCID: PMC3520872 DOI: 10.1186/1745-9974-8-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 09/07/2012] [Indexed: 12/17/2022]
Abstract
UNLABELLED BACKGROUND Gastroesophageal reflux disease (GERD) is a common cause of chronic cough. Both acid and nonacid reflux is thought to play a role in the initiation of coughing and cough hypersensitivity. The GABAB receptor agonist lesogaberan was developed as a peripherally restricted anti-reflux therapy that reduces the frequency of transient lower esophageal sphincter relaxations (TLESR; the major cause of reflux) in animals and in patients with GERD. GABAB receptor agonists have also been shown to possess antitussive effects in patients and in animals independent of their effects on TLESR, suggesting that lesogaberan may be a promising treatment for chronic cough. METHODS We have assessed the direct antitussive effects of lesogaberan (AZD3355). The effects of other GABAB receptor agonists were also determined. Coughing was evoked in awake guinea pigs using aerosol challenges with citric acid. RESULTS Lesogaberan dose-dependently inhibited citric acid evoked coughing in guinea pigs. Comparable effects of the GABAB receptor agonists baclofen and 3-aminopropylphosphinic acid (3-APPiA) on cough were also observed. Baclofen produced obvious signs of sedation and respiratory depression. By contrast, both lesogaberan and 3-APPiA (both inactivated centrally by GABA transporters) were devoid of sedative effects and did not alter respiratory rate. CONCLUSIONS Together, the data suggest that lesogaberan and related GABAB receptor agonists may hold promise as safe and effective antitussive agents largely devoid of CNS side effects.
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Affiliation(s)
- Brendan J Canning
- Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle, Baltimore, Maryland, 21224, USA.
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20
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Al-Wadei HAN, Ullah MF, Al-Wadei MH. Intercepting neoplastic progression in lung malignancies via the beta adrenergic (β-AR) pathway: implications for anti-cancer drug targets. Pharmacol Res 2012; 66:33-40. [PMID: 22487140 DOI: 10.1016/j.phrs.2012.03.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 03/12/2012] [Accepted: 03/18/2012] [Indexed: 11/27/2022]
Abstract
The understanding of signaling cascades involved in the induction, promotion, and progression of cancer, although advanced in recent years, is still incomplete. Tracing the imbalance of the impaired, physiologically-essential cellular signaling that drives the neoplastic process is a complex issue. This review discusses the role of the regulator of the fight or flight response, the beta-adrenergic signaling cascade, as a mediator of cancer growth and progression in in vitro and in vivo cancer models. We review a series of experiments from our own laboratory and those of others examining the contribution of this signaling network to lung and other human malignancies and thereby identifying potential targets for chemotherapeutic interventions. The stimulation of the β-adrenergic receptor by lifestyle and environmental factors, as well as a preexisting risk for neoplasm, activates downstream effector molecules (adenylyl cyclase/cAMP/PKA/CREB) concomitant to the transactivation of related pathways (EGFR) that lead to pro-oncogenic signaling; this β-adrenergic pathway thereby encourages cancer growth by evasion of apoptosis, invasion, angiogenesis, and metastasis. GABAergic signaling acts as an antagonist to the β-adrenergic cascade by intercepting adenylyl cyclase activation, and thereby neutralizing the pro-oncogenic effects of β-adrenergic stimulation. The regulation of cancer cell growth by neurobiological signals expands the possibilities for pharmacological interventions in cancer therapy.
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Affiliation(s)
- Hussein A N Al-Wadei
- Experimental Oncology Laboratory, Department of Biomedical and Diagnostic Sciences, University of Tennessee, Knoxville, TN 37996, USA.
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The potential use of GABAergic drugs in the treatment of asthma. Future Med Chem 2011; 3:145-7. [PMID: 21428808 DOI: 10.4155/fmc.10.297] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
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Mizuta K, Mizuta F, Xu D, Masaki E, Panettieri RA, Emala CW. Gi-coupled γ-aminobutyric acid-B receptors cross-regulate phospholipase C and calcium in airway smooth muscle. Am J Respir Cell Mol Biol 2011; 45:1232-8. [PMID: 21719794 DOI: 10.1165/rcmb.2011-0088oc] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
γ-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system, and exerts its actions via both ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. Although the functional expression of GABA(B) receptors coupled to the G(i) protein was reported for airway smooth muscle, the role of GABA(B) receptors in airway responsiveness remains unclear. We investigated whether G(i)-coupled GABA(B) receptors cross-regulate phospholipase C (PLC), an enzyme classically regulated by G(q)-coupled receptors in human airway smooth muscle cells. Both the GABA(B)-selective agonist baclofen and the endogenous ligand GABA significantly increased the synthesis of inositol phosphate, whereas GABA(A) receptor agonists, muscimol, and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol exerted no effect. The baclofen-induced synthesis of inositol phosphate and transient increases in [Ca(2+)](i) were blocked by CGP35348 and CGP55845 (selective GABA(B) antagonists), pertussis toxin (PTX, which inactivates the G(i) protein), gallein (a G(βγ) signaling inhibitor), U73122 (an inhibitor of PLC-β), and xestospongin C, an inositol 1,4,5-triphosphate receptor blocker. Baclofen also potentiated the bradykinin-induced synthesis of inositol phosphate and transient increases in [Ca(2+)](i), which were blocked by CGP35348 or PTX. Moreover, baclofen potentiated the substance P-induced contraction of airway smooth muscle in isolated guinea pig tracheal rings. In conclusion, the stimulation of GABA(B) receptors in human airway smooth muscle cells rapidly mobilizes intracellular Ca(2+) stores by the synthesis of inositol phosphate via the activation of PLC-β, which is stimulated by G(βγ) protein liberated from G(i) proteins coupled to GABA(B) receptors. Furthermore, crosstalk between GABA(B) receptors and G(q)-coupled receptors potentiates the synthesis of inositol phosphate, transient increases in [Ca(2+)](i), and smooth muscle contraction through G(i) proteins.
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Affiliation(s)
- Kentaro Mizuta
- Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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Lee M, Schwab C, McGeer PL. Astrocytes are GABAergic cells that modulate microglial activity. Glia 2011; 59:152-65. [PMID: 21046567 DOI: 10.1002/glia.21087] [Citation(s) in RCA: 228] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
GABA is assumed to function in brain only as an inhibitory neurotransmitter. Here we report a much broader CNS role. We show that human astrocytes are GABAergic cells, and that human microglia are GABAceptive cells. We show that in adult human brain tissue, astrocytes immunostain for the GABA synthesizing enzyme GAD 67, the GABA metabolizing enzyme GABA-T and the GABA(A) and GABA(B) receptors. The intensity of staining is comparable or greater to that observed for known inhibitory neurons. We show that cultured human astrocytes strongly express the mRNA and protein for GAD 67, as well as GABA-T, and the GABA(A) and GABA(B) receptors. We further show that cultured human microglia express the mRNA and protein for GABA-T, in addition to the GABA(A) and GABA(B) receptors characterizing them as GABAceptive cells. We demonstrate that GABA suppresses the reactive response of both astrocytes and microglia to the inflammatory stimulants lipopolysaccharide (LPS) and interferon-γ by inhibiting induction of inflammatory pathways mediated by NFκB and P38 MAP kinase. This results in a reduced release of the inflammatory cytokines TNFα and IL-6 and an attenuation of conditioned medium neurotoxicity toward neuroblastoma SH-SY5Y cells. These inhibitory reactions are partially mimicked by the GABA(A) receptor agonist muscimol and the GABA(B) receptor agonist baclofen, indicating that GABA can stimulate both types of receptors in astrocytes as well as microglia. We conclude that the antiinflammatory actions of GABA offer new therapeutic opportunities since agonists should enhance the effectiveness of other antiinflammatory agents that operate through non-GABA pathways.
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Affiliation(s)
- Moonhee Lee
- Kinsmen Laboratory of Neurological Research, University of British Columbia, Vancouver, BC, Canada
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Zaidi S, Gallos G, Yim PD, Xu D, Sonett JR, Panettieri RA, Gerthoffer W, Emala CW. Functional expression of γ-amino butyric acid transporter 2 in human and guinea pig airway epithelium and smooth muscle. Am J Respir Cell Mol Biol 2010; 45:332-9. [PMID: 21057105 DOI: 10.1165/rcmb.2010-0177oc] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
γ-Amino butyric acid (GABA) is a primary inhibitory neurotransmitter in the central nervous system, and is classically released by fusion of synaptic vesicles with the plasma membrane or by egress via GABA transporters (GATs). Recently, a GABAergic system comprised of GABA(A) and GABA(B) receptors has been identified on airway epithelial and smooth muscle cells that regulate mucus secretion and contractile tone of airway smooth muscle (ASM). In addition, the enzyme that synthesizes GABA, glutamic acid decarboxylase, has been identified in airway epithelial cells; however, the mechanism(s) by which this synthesized GABA is released from epithelial intracellular stores is unknown. We questioned whether any of the four known isoforms of GATs are functionally expressed in ASM or epithelial cells. We detected mRNA and protein expression of GAT2 and -4, and isoforms of glutamic acid decarboxylase in native and cultured human ASM and epithelial cells. In contrast, mRNA encoding vesicular GAT (VGAT), the neuronal GABA transporter, was not detected. Functional inhibition of (3)H-GABA uptake was demonstrated using GAT2 and GAT4/betaine-GABA transporter 1 (BGT1) inhibitors in both human ASM and epithelial cells. These results demonstrate that two isoforms of GATs, but not VGAT, are expressed in both airway epithelial and smooth muscle cells. They also provide a mechanism by which locally synthesized GABA can be released from these cells into the airway to activate GABA(A) channels and GABA(B) receptors, with subsequent autocrine and/or paracrine signaling effects on airway epithelium and ASM.
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Affiliation(s)
- Sarah Zaidi
- Department of Pediatrics, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA
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Wang G, Wang R, Ferris B, Salit J, Strulovici-Barel Y, Hackett NR, Crystal RG. Smoking-mediated up-regulation of GAD67 expression in the human airway epithelium. Respir Res 2010; 11:150. [PMID: 21034448 PMCID: PMC2988726 DOI: 10.1186/1465-9921-11-150] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 10/29/2010] [Indexed: 01/08/2023] Open
Abstract
Background The production of gamma-amino butyric acid (GABA) is dependent on glutamate decarboxylases (GAD65 and GAD67), the enzymes that catalyze the decarboxylation of glutamate to GABA. Based on studies suggesting a role of the airway epithelial GABAergic system in asthma-related mucus overproduction, we hypothesized that cigarette smoking, another disorder associated with increased mucus production, may modulate GABAergic system-related gene expression levels in the airway epithelium. Methods We assessed expression of the GABAergic system in human airway epithelium obtained using bronchoscopy to sample the epithelium and microarrays to evaluate gene expression. RT-PCR was used to confirm gene expression of GABAergic system gene in large and small airway epithelium from heathy nonsmokers and healthy smokers. The differences in the GABAergic system gene was further confirmed by TaqMan, immunohistochemistry and Western analysis. Results The data demonstrate there is a complete GABAergic system expressed in the large and small human airway epithelium, including glutamate decarboxylase, GABA receptors, transporters and catabolism enzymes. Interestingly, of the entire GABAergic system, smoking modified only the expression of GAD67, with marked up-regulation of GAD67 gene expression in both large (4.1-fold increase, p < 0.01) and small airway epithelium of healthy smokers (6.3-fold increase, p < 0.01). At the protein level, Western analysis confirmed the increased expression of GAD67 in airway epithelium of healthy smokers compared to healthy nonsmokers (p < 0.05). There was a significant positive correlation between GAD67 and MUC5AC gene expression in both large and small airway epithelium (p < 0.01), implying a link between GAD67 and mucin overproduction in association with smoking. Conclusions In the context that GAD67 is the rate limiting enzyme in GABA synthesis, the correlation of GAD67 gene expression with MUC5AC expressions suggests that the up-regulation of airway epithelium expression of GAD67 may contribute to the increase in mucus production observed in association with cigarette smoking. Trial registration NCT00224198; NCT00224185
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Affiliation(s)
- Guoqing Wang
- Department of Genetic Medicine, Weill Cornell Medical College, New York, New York, USA
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Endogenous gamma-aminobutyric acid modulates tonic guinea pig airway tone and propofol-induced airway smooth muscle relaxation. Anesthesiology 2009; 110:748-58. [PMID: 19322939 DOI: 10.1097/aln.0b013e31819c44e1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
BACKGROUND Emerging evidence indicates that an endogenous autocrine/paracrine system involving gamma-aminobutyric acid (GABA) is present in airways. GABAA channels, GABAB receptors, and the enzyme that synthesizes GABA have been identified in airway epithelium and smooth muscle. However, the endogenous ligand itself, GABA, has not been measured in airway tissues. The authors sought to demonstrate that GABA is released in response to contractile agonists and tonically contributes a prorelaxant component to contracted airway smooth muscle. METHODS The amount and cellular localization of GABA in upper guinea pig airways under resting and contracted tone was determined by high pressure liquid chromatography and immunohistochemistry, respectively. The contribution that endogenous GABA imparts on the maintenance of airway smooth muscle acetylcholine-induced contraction was assessed in intact guinea pig airway tracheal rings using selective GABAA antagonism (gabazine) under resting or acetylcholine-contracted conditions. The ability of an allosteric agent (propofol) to relax a substance P-induced relaxation in an endogenous GABA-dependent manner was assessed. RESULTS GABA levels increased and localized to airway smooth muscle after contractile stimuli in guinea pig upper airways. Acetylcholine-contracted guinea pig tracheal rings exhibited an increase in contracted force upon addition of the GABAA antagonist gabazine that was subsequently reversed by the addition of the GABAA agonist muscimol. Propofol dose-dependently relaxed a substance P contraction that was blocked by gabazine. CONCLUSION These studies demonstrate that GABA is endogenously present and increases after contractile stimuli in guinea pig upper airways and that endogenous GABA contributes a tonic prorelaxant component in the maintenance of airway smooth muscle tone.
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Abstract
Asthma often occurs as a result of immune-based inflammatory responses, which consequently cause pathological changes in airway structural cells. However, the underlying mechanisms of airway pathology in asthma are still not fully understood. Our recent studies revealed a critical role of gamma-aminobutyric acid (GABA) signalling pathway in the airway epithelium of allergic asthma through its ability to stimulate mucus production. This review briefly describes the GABAergic signalling system and its role in the regulation of mucus protein production in bronchial airway epithelial cells.
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Affiliation(s)
- W-Y Lu
- Departments of Anesthesia and Physiology, University of Toronto, ON, Canada.
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Gleason NR, Gallos G, Zhang Y, Emala CW. The GABAA agonist muscimol attenuates induced airway constriction in guinea pigs in vivo. J Appl Physiol (1985) 2009; 106:1257-63. [PMID: 19213928 DOI: 10.1152/japplphysiol.91314.2008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
GABA(A) channels are ubiquitously expressed on neuronal cells and act via an inward chloride current to hyperpolarize the cell membrane of mature neurons. Expression and function of GABA(A) channels on airway smooth muscle cells has been demonstrated in vitro. Airway smooth muscle cell membrane hyperpolarization contributes to relaxation. We hypothesized that muscimol, a selective GABA(A) agonist, could act on endogenous GABA(A) channels expressed on airway smooth muscle to attenuate induced increases in airway pressures in anesthetized guinea pigs in vivo. In an effort to localize muscimol's effect to GABA(A) channels expressed on airway smooth muscle, we pretreated guinea pigs with a selective GABA(A) antagonist (gabazine) or eliminated lung neural control from central parasympathetic, sympathetic, and nonadrenergic, noncholinergic (NANC) nerves before muscimol treatment. Pretreatment with intravenous muscimol alone attenuated intravenous histamine-, intravenous acetylcholine-, or vagal nerve-stimulated increases in peak pulmonary inflation pressure. Pretreatment with the GABA(A) antagonist gabazine blocked muscimol's effect. After the elimination of neural input to airway tone by central parasympathetic nerves, peripheral sympathetic nerves, and NANC nerves, intravenous muscimol retained its ability to block intravenous acetylcholine-induced increases in peak pulmonary inflation pressures. These findings demonstrate that the GABA(A) agonist muscimol acting specifically via GABA(A) channel activation attenuates airway constriction independently of neural contributions. These findings suggest that therapeutics directed at the airway smooth muscle GABA(A) channel may be a novel therapy for airway constriction following airway irritation and possibly more broadly in diseases such as asthma and chronic obstructive pulmonary disease.
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Affiliation(s)
- Neil R Gleason
- Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
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Gallos G, Gleason NR, Zhang Y, Pak SW, Sonett JR, Yang J, Emala CW. Activation of endogenous GABAA channels on airway smooth muscle potentiates isoproterenol-mediated relaxation. Am J Physiol Lung Cell Mol Physiol 2008; 295:L1040-7. [PMID: 18790991 DOI: 10.1152/ajplung.90330.2008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Reactive airway disease predisposes patients to episodes of acute smooth muscle mediated bronchoconstriction. We have for the first time recently demonstrated the expression and function of endogenous ionotropic GABA(A) channels on airway smooth muscle cells. We questioned whether endogenous GABA(A) channels on airway smooth muscle could augment beta-agonist-mediated relaxation. Guinea pig tracheal rings or human bronchial airway smooth muscles were equilibrated in organ baths with continuous digital tension recordings. After pretreatment with or without the selective GABA(A) antagonist gabazine (100 muM), airway muscle was contracted with acetylcholine or beta-ala neurokinin A, followed by relaxation induced by cumulatively increasing concentrations of isoproterenol (1 nM to 1 muM) in the absence or presence of the selective GABA(A) agonist muscimol (10-100 muM). In separate experiments, guinea pig tracheal rings were pretreated with the large conductance K(Ca) channel blocker iberiotoxin (100 nM) after an EC(50) contraction with acetylcholine but before cumulatively increasing concentrations of isoproterenol (1 nM to 1 uM) in the absence or presence of muscimol (100 uM). GABA(A) activation potentiated the relaxant effects of isoproterenol after an acetylcholine or tachykinin-induced contraction in guinea pig tracheal rings or an acetylcholine-induced contraction in human endobronchial smooth muscle. This muscimol-induced potentiation of relaxation was abolished by gabazine pretreatment but persisted after blockade of the maxi K(Ca) channel. Selective activation of endogenous GABA(A) receptors significantly augments beta-agonist-mediated relaxation of guinea pig and human airway smooth muscle, which may have important therapeutic implications for patients in severe bronchospasm.
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Affiliation(s)
- George Gallos
- Dept. of Anesthesiology, College of Physicians and Surgeons of Columbia Univ., 650 W. 168 St., P&S Box 46, New York, NY, USA.
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Mizuta K, Xu D, Pan Y, Comas G, Sonett JR, Zhang Y, Panettieri RA, Yang J, Emala CW. GABAA receptors are expressed and facilitate relaxation in airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 2008; 294:L1206-16. [PMID: 18408071 DOI: 10.1152/ajplung.00287.2007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system and exerts its actions via both ionotropic (GABA(A)) channels and metabotropic (GABA(B)) receptors. GABA(A) channels are ubiquitously expressed in neuronal tissues, and in mature neurons modulate an inward chloride current resulting in neuronal inhibition due to membrane hyperpolarization. In airway smooth muscle (ASM) cells, membrane hyperpolarization favors smooth muscle relaxation. Although GABA(A) channels and GABA(B) receptors have been functionally identified on peripheral nerves in the lung, GABA(A) channels have never been identified on ASM itself. We detected the mRNA encoding of the GABA(A) alpha(4)-, alpha(5)-, beta(3)-, delta-, gamma(1-3)-, pi-, and theta-subunits in total RNA isolated from native human and guinea pig ASM and from cultured human ASM cells. Selected immunoblots identified the GABA(A) alpha(4)-, alpha(5)-, beta(3)-, and gamma(2)-subunit proteins in native human and guinea pig ASM and cultured human ASM cells. The GABA(A) beta(3)-subunit protein was immunohistochemically localized to ASM in guinea pig tracheal rings. While muscimol, a specific GABA(A) channel agonist, did not affect the magnitude or the time to peak contractile effect of substance P, it directly concentration dependently relaxed a tachykinin-induced contraction in guinea pig tracheal rings, which was inhibited by the GABA(A)-selective antagonist gabazine. Muscimol also relaxed a contraction induced by an alternative contractile agonist histamine. These results demonstrate that functional GABA(A) channels are expressed on ASM and suggest a novel therapeutic target for the relaxation of ASM in diseases such as asthma and chronic obstructive lung disease.
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Affiliation(s)
- Kentaro Mizuta
- Deptartment of Anesthesiology, College of Physicians and Surgeons of Columbia University, 630 W. 168th St., P&S Box 46, New York, New York 10032, USA
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Mizuta K, Osawa Y, Mizuta F, Xu D, Emala CW. Functional expression of GABAB receptors in airway epithelium. Am J Respir Cell Mol Biol 2008; 39:296-304. [PMID: 18403780 DOI: 10.1165/rcmb.2007-0414oc] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system and exerts its actions via both ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. The GABA(B) receptor is a dimer composed of R1 and R2 components and classically couples to the heterotrimeric G(i) protein. In addition to their location on neurons, GABA and functional GABA(B) receptors have been detected in peripheral tissue such as airway smooth muscle. We questioned whether airway epithelium expresses receptors that could respond to GABA. We detected the mRNA encoding multiple-splice variants of the GABA(B)R1 and GABA(B)R2 in total RNA isolated from native human and guinea pig airway epithelium and human airway epithelial cell lines (BEAS-2B and H441). Immunoblots identified the GABA(B)R1 and GABA(B)R2 proteins in both guinea pig airway epithelium and BEAS-2B cells. The expression of GABA(B)R1 protein was immunohistochemically localized to basal mucin-secreting and ciliated columnar epithelial cells in guinea pig trachea. Baclofen inhibited adenylyl cyclase activity, induced ERK phosphorylation and cross-regulated phospholipase C, leading to increased inositol phosphates in BEAS-2B cells in a pertussis toxin-sensitive manner, implicating G(i) protein coupling. Thus, these receptors couple to G(i) and cross-regulate the phospholipase C/inositol phosphate pathway. The second messengers of these pathways, cyclic AMP and calcium, play pivotal roles in airway epithelial cell primary functions of mucus clearance. Furthermore, the enzyme that synthesizes GABA, glutamic acid decarboxylase (GAD65/67), was also localized to airway epithelium. GABA may modulate an uncharacterized signaling cascade via GABA(B) receptors coupled to G(i) protein in airway epithelium.
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Affiliation(s)
- Kentaro Mizuta
- Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA
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Regulation of heterotrimeric G protein signaling in airway smooth muscle. Ann Am Thorac Soc 2008; 5:47-57. [PMID: 18094084 DOI: 10.1513/pats.200705-054vs] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Heterotrimeric G proteins transduce signals from G protein-coupled receptors to regulate numerous signaling events and functions in airway smooth muscle (ASM). In this article, we detail the function and regulation of heterotrimeric G protein signaling in ASM. We further discuss recent advances in the development of experimental tools in the study of G protein signaling, and speculate how these tools might be used in therapeutic strategies that seek to mitigate bronchospasm and airway remodeling that occur in obstructive airway disease.
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Schuller HM, Al-Wadei HAN, Majidi M. Gamma-aminobutyric acid, a potential tumor suppressor for small airway-derived lung adenocarcinoma. Carcinogenesis 2008; 29:1979-85. [PMID: 18310090 PMCID: PMC2556972 DOI: 10.1093/carcin/bgn041] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Pulmonary adenocarcinoma (PAC) is the leading type of lung cancer in smokers and non-smokers that arises in most cases from small airway epithelial cells. PAC has a high mortality due to its aggressive behavior and resistance to cancer therapeutics. We have shown previously that the proliferation of human PAC cells NCI-H322 and immortalized human small airway epithelial cells HPL1D is stimulated by cyclic adenosine monophosphate (cAMP)/protein kinase A-dependent phosphorylation of cyclic adenosine monophosphate response element-binding (CREB) protein and transactivation of the epidermal growth factor receptor and that this pathway is activated by beta-1-adrenoreceptors (β1-ARs) and the non-genomic estrogen receptor beta. Our current in vitro studies with HPL1D and NCI-H322 cells showed that signaling via the gamma-amino butyric acid receptor (GABABR) strongly inhibited base level and isoproterenol-induced cAMP, p-CREB, cyclic adenosine monophosphate response element-luciferase activity and p-extracellular regulated kinase-1 (ERK1)/2 and effectively blocked DNA synthesis and cell migration. The inhibitory effects of gamma-amino butyric acid (GABA) were disinhibited by the GABABR antagonist CGP-35348 or GABABR knockdown. Immunohistochemical investigation of hamster lungs showed significant underexpression of GABA in animals with small airway-derived PACs induced by the nicotine-derived carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). These findings suggest that GABA may have tumor suppressor function in small airway epithelia and the PACs derived from them and that downregulation of GABA by NNK may contribute to the development of this cancer in smokers. Our findings suggest that marker-guided treatment with GABA or a GABABR agonist of individuals with downregulated pulmonary GABA may provide a novel targeted approach for the prevention of PAC in smokers.
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Affiliation(s)
- Hildegard M Schuller
- Experimental Oncology Laboratory, Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, TN 37996, USA.
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