BRUSSELS/LONDON – Scientists have identified a key mechanism regulating the brain’s response to itching, revealing the crucial role of the TRPV4 ion channel. Research indicates that without this channel, the signal informing the brain when scratching has provided sufficient relief is diminished, potentially leading to chronic, excessive scratching.
The discovery, presented at the 70th Annual Meeting of the Biophysical Society in San Francisco, offers potential recent avenues for treating chronic itch conditions like eczema and psoriasis. Researchers at the University of Louvain in Brussels, led by Professor Roberta Gualdani, found that TRPV4 functions as a biological “brake” on scratching behavior.
The study, conducted on mice, demonstrated that mice lacking the TRPV4 channel scratched for significantly longer durations than those with a functioning channel, despite not necessarily scratching more frequently. This suggests that TRPV4 is essential for signaling itch relief and terminating scratching episodes. According to research published in PubMed, keratinocytes in human psoriasis skin exhibit high TRPV4 expression.
TRPV4 appears to have a dual function in itch regulation. It triggers itch sensations in skin cells, but simultaneously works to limit scratching in sensory neurons known as Aβ-LTMRs. This dual role explains why mice without the channel experience prolonged scratching when they do scratch – the signal to stop is absent. The research detailed in The Journal of Investigative Dermatology shows that blocking TRPV4 with an antagonist effectively prevented the progression of psoriasis-like dermatitis in mice.
Researchers found that TRPV4 mediates the release of adenosine triphosphate (ATP) from keratinocytes and increases the secretion of neuropeptides, ultimately activating and amplifying IL-23/Th17 responses, which are key drivers of psoriasis. Suppressing TRPV4 activity significantly reduced ATP release in both human and mouse keratinocytes in vitro, according to published findings.
The findings suggest that targeting TRPV4 could lead to the development of new medications that specifically control itch without disrupting the neuronal mechanisms responsible for stopping scratching. A broad blockade of the channel could potentially be counterproductive, highlighting the need for precise therapeutic interventions. Further research is needed to determine the optimal approach for modulating TRPV4 activity in humans.
The study likewise revealed that TRPV4 is expressed in neurons typically associated with touch, further solidifying their role in regulating the duration of itch relief. This discovery could pave the way for more targeted treatments for individuals suffering from chronic itch, according to Professor Gualdani’s team.
