TRPV4 stimulates colonic afferents through mucosal release of ATP and glutamate
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Background and Purpose
Abdominal pain is a leading cause of morbidity for people living with gastrointestinal disease. While the vanilloid transient receptor potential 4 (TRPV4) ion channel has been implicated in the pathogenesis of abdominal pain, the relative paucity of TRPV4 expression in colon-projecting sensory neurons suggests that non-neuronal cells may also contribute to TRPV4-mediated nociceptor stimulation.
Experimental Approach
Changes in murine colonic afferent activity were examined using ex vivo electrophysiology in tissues with the gut mucosa present or removed. ATP and glutamate release were measured by bioluminescence assay from human colon organoid cultures and mouse colon. Dorsal root ganglion sensory neuron activity was evaluated by Ca 2+ imaging when cultured alone or co-cultured with colonic mucosal cells.
Key Results
The TRPV4 agonist GSK1016790A elicited a robust increase in murine colonic afferent activity, which was abolished by removal of the gut mucosa. GSK1016790A promoted ATP and glutamate release from human colon organoid cultures and mouse colon. Inhibition of ATP degradation in mouse colon enhanced the afferent response to GSK1016790A. Pre-treatment with purinoreceptor or glutamate receptor antagonists attenuated and abolished the response to GSK1016790A when given alone or in combination, respectively. Sensory neurons co-cultured with colonic mucosal cells produced a marked increase in intracellular Ca 2+ to GSK1016790A compared to neurons cultured alone.
Conclusions and Implications
Our data indicate that mucosal release of ATP and glutamate is responsible for the stimulation of colonic afferents following TRPV4 activation. These findings highlight an opportunity to target the gut mucosa for the development of new visceral analgesics.
Bullet Point Summary
What is already known?
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Activation of TRPV4 causes visceral hypersensitivity via the stimulation of colonic afferents.
What does this study add?
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TRPV4-mediated colonic afferent activation is dependent on mucosal release of ATP and glutamate.
What is the clinical significance?
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Mucosal TRPV4-mediated colonic afferent activation provides a gut restricted target for treating abdominal pain.
