What controls calcium homeostasis in human airway smooth muscle?

Lead Research Organisation: University of Nottingham
Department Name: Therapeutics

Abstract

Asthma is a major cause of lost working days in the UK: currently, according to Asthma UK 5.2 million are taking asthma treatment. The majority of symptoms are caused by narrowing of the airways. A major component of airway narrowing is due to contraction of the muscle (called airway smooth muscle) in the airway wall. This contraction is due to calcium release within the muscle cell or entry of calcium into the muscle cell. The mechanisms underlying these responses are poorly understood. This project will systematically define the important pathways and signalling molecules responsible for these processes. By defining these mechanisms, it should be feasible to design new treatments for asthma. We will also gain a fuller understanding of the mechanisms underlying the development of asthma.

Technical Summary

Short term changes in the calibre of the human airway are primarily influenced by the tone of the airway smooth muscle (ASM) bundles found in the airway wall. Contraction of ASM produces bronchoconstriction. In contrast relaxation produces bronchodilation, a response which underlies the mechanism of action of beta2 adrenoceptor agonists, the most widely used agents for symptom relief in asthma and COPD. Thus understanding the mechanisms underlying contraction and relaxation of the ASM cell is critical to the study of the pathophysiology of airway disease. Recent studies including those by the applicant using siRNA and other approaches has led to the recognition of Ca2+ homeostasis being fundamental to these processes. The hypotheses to be examined in this programme of work are therefore as follow:

(i) contraction of airway smooth muscle (ASM) is dependent upon Ca2+ entry via both receptor and store dependent pathways
(ii) signalling of Ca2+ entry into ASM following store depletion is mediated by STIM1 and Orai1 induced activation of as yet undefined Ca2+ entry channels
(iii) agonist induced Ca2+ entry is dependent in part on store dependent pathways but also involves separate, receptor activated pathways, involving trp channels and related homologues
(iv) using a systematic siRNA based approach in a range of physiologically relevant model systems including human primary cultured cell and lung slice models these pathways can be defined
To address the role of these pathways in ASM contraction, we will (i) delineate Ca2+ entry pathways in primary cultured human ASM cells using both measurement of intracellular Ca2+ and electrophysiological (patch clamp) approaches, and (ii) delineate the contribution of these pathways to ASM contraction using lung slice preparations from murine and human lung to simultaneously monitor ASM Ca2+ oscillations and contractile responses. Inhibition of components potentially important in contractile signalling will be achieved by use of selective antagonists (where available), siRNA approaches using a panel of characterised siRNA species we are developing and with which we have undertaken preliminary proof of principle work, and exploratory screening using two siRNA libraries targeted at ion channels and Ca2+ signalling pathways.

Publications

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Billington CK (2013) cAMP regulation of airway smooth muscle function. in Pulmonary pharmacology & therapeutics

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Brook BS (2010) A biomechanical model of agonist-initiated contraction in the asthmatic airway. in Respiratory physiology & neurobiology

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Peel SE (2008) ORAI and store-operated calcium influx in human airway smooth muscle cells. in American journal of respiratory cell and molecular biology

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Singh SR (2010) Can lineage-specific markers be identified to characterize mesenchyme-derived cell populations in the human airways? in American journal of physiology. Lung cellular and molecular physiology

 
Description NC3Rs consultation on animal models and lung disease
Geographic Reach Asia 
Policy Influence Type Participation in a national consultation
 
Description GSK research collaboration
Amount £1,000,000 (GBP)
Organisation GlaxoSmithKline (GSK) 
Sector Private
Country Global
Start 12/2017 
End 12/2020
 
Description industry collaboration,
Amount £180,000 (GBP)
Organisation Boehringer Ingelheim 
Sector Private
Country Germany
Start 11/2016 
End 10/2017
 
Description University of Bonn 
Organisation University of Bonn
Country Germany 
Sector Academic/University 
PI Contribution functional work in human lung tissue
Collaborator Contribution Animal models
Impact Paper in Science Translational Medicine, ongoing work. Multidiscplinary (pharmaceutical sciences, life sciences, clinical)
Start Year 2015
 
Description University of nottingham Mathematical modelling group 
Organisation University of Nottingham
Department School of Mathematical Sciences Nottingham
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaboration on paper (listed above) resulting in new investigator grant to Dr B Brook.
Collaborator Contribution Provision of in vitro model system to allow modelling work to be validated
Impact See above: recently awarded NRC NIRG to Dr Brook.
Start Year 2009
 
Description functional genetics of COPD 
Organisation Pfizer Ltd
Country United Kingdom 
Sector Private 
PI Contribution Methods developed during this grant have led (in conjunction with work on population genetics) to a funded research collaboration with Pfizer (value ~ £380k)
Collaborator Contribution access to novel agents
Impact none yet (about to commence)
Start Year 2010