Investigation into the role of TRPV4 in chronic respiratory diseases

Asthma and COPD are respiratory diseases with ever-increasing global prevalence that represent a social and economic burden for industrialised and developing countries. There is a desperate need for effective, novel therapy to treat these patients. Our preliminary preclinical data suggests that TRPV4 channel blockers could represent a novel class of disease modifying compounds, especially in patients with asthma and COPD. Recent evidence suggests that TRPV4 could play a prominent role in idiopathic pulmonary fibrosis (IPF). The central aim of this collaborative studentship is to confirm the published finding with superior pharmacological tools and to investigate the mechanism involved.
Previous studies in our laboratory suggest that TRPV4-induced effects are mediated via ATP and the activation of purinoceptors. For example, TRPV4-induced airway sensory nerve activation involves the release of ATP (via the pannexin channel) which then acts on P2X3; in TRPV4-induced airway smooth muscle contraction it appears that ATP acts on P2X4 channels to drive the response; in COPD-like models P2X7 channels are important and in allergic models the pannexin 1 channel is key to the asthma phenotype. Thus we speculate that this ATP-axis is central to the apparent role of TRPV4 in IPF, indeed this agreement is supported by the fact that airway ATP levels are increased in this patient group.
Study plan:
In vitro systems - cultured primary human and mouse (use of GM cells and for translation to in vivo model systems) airway fibroblasts exposed to appropriate stimulus (i.e. TGFb) to switch to disease relevant myofibroblasts. Determine the impact of TRPV4 ligands or compare cells from wild type and TRPV4 -/- mice lungs on the switch (as determined by measuring end points such as increases in collagen or ASM alpha actin at the mRNA (via TaqMan RT-PCR) and protein (via western analysis) level). Determine the role of the ATP-purine axis in the cell system using assays (ATP assay and expression of purinergic receptors), inhibitors (i.e. ATP chelator/breakdown enzyme), blockers (non-specific and specific purinergic ligands) and cells from GM mice (i.e. pannexin 1 -/-).
In vivo systems - use pharmacological tools or GM mice to study the role of the TRPV4-ATP axis in IPF model systems (i.e. using bleomycin or specific mediator)
Clinical samples - ATP levels in airway and TRPV4/purinergic receptor expression
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(mRNA and protein) in fibroblasts/myofibroblasts from non-diseased and IPF lungs and lung biopsies. Effect of TRPV4-ATP blockers on cultured primary myofibroblasts from IPF lungs.
Through the collaboration this plan will determine for the first time the role of the TRPV4-ATP axis in IPF using robust, established systems and primary cells/clinical samples obtained by Dr Maher with the appropriate ethics approval and consents. The project will provide evidence for the development of TRPV4/ATP axis modulators for the treatment of IPF and other lung diseases.