Biology subjects

Paine, L. W.

Publications and source records attributed to Paine, L. W..

3 recordsLinked to original sources

bioRxiv2024

TRPV4 stimulates colonic afferents through mucosal release of ATP and glutamate

Background and PurposeAbdominal 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 ApproachChanges 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 Ca2+ imaging when cultured alone or co-cultured with colonic mucosal cells. Key ResultsThe 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 Ca2+ to GSK1016790A compared to neurons cultured alone. Conclusions and ImplicationsOur 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 SummaryWhat is already known? O_LIActivation of TRPV4 causes visceral hypersensitivity via the stimulation of colonic afferents. C_LI What does this study add? O_LITRPV4-mediated colonic afferent activation is dependent on mucosal release of ATP and glutamate. C_LI What is the clinical significance? O_LIMucosal TRPV4-mediated colonic afferent activation provides a gut restricted target for treating abdominal pain. C_LI

pharmacology and toxicology↗

bioRxiv2023

GPR35 inhibits TRPA1-mediated colonic afferent hypersensitivity through suppression of Substance P release

The development of non-opioid analgesics for the treatment of chronic abdominal pain is a pressing area of unmet clinical need. To address this, we examined the expression of Gi/o-coupled receptors in colonic sensory neurons, which, like opioid receptors, have the potential to inhibit nociceptor activation due to their inhibitory G protein coupling. This led to the identification of the orphan receptor GPR35 as a visceral analgesic drug target due to its marked co-expression with TRPA1, a mediator of noxious mechanotransduction in the bowel. Consistent with in silico docking studies which identified binding sites for the mast cell stabiliser cromolyn and phosphodiesterase inhibitor zaprinast at GPR35, we demonstrated, using GPR35 knockout mice, that the antinociceptive effects of these drugs on TRPA1-mediated colonic nociceptor activation and mechanosensitisation were GPR35-dependent. Further work showed these antinociceptive effects occurred through the inhibition of substance P (SP) release. This confirmed both the pronociceptive effect of SP on colonic afferents, and the contribution of SP to TRPA1-mediated colonic nociceptor activation and sensitisation. We also found that TRPA1-induced contraction of the colon was mediated by SP signalling and could be inhibited by cromolyn in a GPR35-dependent manner. Our data identify GPR35, through its inhibition of SP-mediated colonic contractility and nociceptor activation and sensitisation, as a putative mechanism for the reported clinical efficacy of cromolyn in the treatment of irritable bowel syndrome. These findings highlight the potential utility of GPR35 agonists to deliver non-opioid analgesia for the treatment of abdominal pain associated with gastrointestinal diseases such as irritable bowel syndrome and inflammatory bowel disease.

physiology↗

bioRxiv2023

Digging deeper into pain - an ethological behavior assay correlating well-being in mice with human pain experience.

The pressing need for safer, more efficacious analgesics is felt worldwide. Pre-clinical tests in animal models of painful conditions represent one of the earliest checkpoints novel therapeutics must negotiate before consideration for human use. Traditionally, the pain status of laboratory animals has been inferred from evoked nociceptive assays which measure their responses to noxious stimuli. The disconnect between how pain is tested in laboratory animals and how it is experienced by humans may in part explain the shortcomings of current pain medications and highlights a need for refinement. Here, we survey human chronic pain patients who assert that everyday aspects of life, such as cleaning and leaving the house, are affected by their on-going level of pain. Accordingly, we test the impact of painful conditions on an ethological behavior of mice, digging. Stable digging behavior was observed over time in naive mice of both sexes. By contrast, deficits in digging were seen following acute knee inflammation. The analgesia conferred by meloxicam and gabapentin was compared in the monosodium iodoacetate knee osteoarthritis model, meloxicam more effectively ameliorating digging deficits, in line with human patients finding meloxicam more effective. Lastly, in a visceral pain model, the decrease in digging behavior correlated with the extent of disease. Ultimately, we make a case for adopting ethological assays, such as digging, in studies of pain in laboratory animals, which we believe to be more representative of the human experience of pain and thus valuable in assessing clinical potential of novel analgesics in animals.

neuroscience↗