Cutaneous TRPV4 Potentiates the Afferent Transmission of Electroacupuncture Stimulation

Electroacupuncture stimulation (ES) exerts therapeutic effects across various conditions, primarily by activating peripheral sensory nerves. The mechanosensitive ion channel transient receptor potential vanilloid 4 (TRPV4), expressed in peripheral non-neuronal cells, represents a potential molecular sensor for ES, yet its specific contribution to ES signal transmission remains unclear. In this study, we combined in vivo calcium imaging in transgenic mice with pharmacological interventions to investigate how cutaneous TRPV4 modulates afferent signaling at the lumbar 4 dorsal root ganglion (DRG) level. An ES intensity of 2 mA at the hindpaw activated more primary sensory and TRPV1-Cre-positive nociceptive neurons and evoked stronger calcium responses compared to 0.5 mA stimulation. Immunofluorescence analysis revealed TRPV4 expression in skin macrophages, but not in primary sensory neurons. To investigate the mechanistic link between ES and TRPV4, the response of primary sensory neurons to ES was assessed following the local activation or antagonism of cutaneous TRPV4. Intradermal injection of the TRPV4 agonist GSK1016790A increased the number of L4 DRG neurons exhibiting spontaneous calcium transients compared with vehicle controlswithout altering mean fluorescence intensityand produced a trend toward a greater proportion of neurons responding to ES alongside a significant enhancement in calcium transient intensity. Conversely, the TRPV4 antagonist GSK2193874 reduced the number of neurons showing basal calcium activity relative to vehicle and significantly attenuated ES-evoked calcium responses compared with the agonist group. These results demonstrate that non-neuronal TRPV4 in the skin potentiates afferent signaling during ES, underscoring a previously overlooked role for neuroimmune interaction in acupuncture signal initiation. These findings improve our understanding of how acupuncture initiates afferent signals at the cellular level and highlight cutaneous TRPV4 as a potential target for modulating ES-evoked afferent signaling.