Abstract
Acupoints are the initiation sites for acupuncture analgesic signals, where adenosine signaling plays a crucial role. A comprehensive understanding of this matter will guide clinicians to optimize acupuncture manipulations to improve acupuncture effectiveness. Recently, keratinocyte Piezo1 channels and cascade ATP release are independently unveiled to be essential for the skin tactile sensation. Thus, we aimed to investigate whether keratinocyte Piezo1-mediated ATP release, in orchestration with CD39, contributed to this initiation mechanism via producing adenosine. 20-min needling was administered at the unilateral ST36 acupoint on the acute ankle arthritis rats. The pain thresholds in the affected hindpaws were determined. Interstitial ATP and adenosine were extracted with microdialysis and assessed by luciferase-luciferin and HPLC, respectively. To simulate needling stimulation, keratinocyte HaCaT cells were subjected to hypotonic shock. ATP release and live calcium imaging were conducted. Immunofluorescence labeling showed the presence of Piezo1 and CD39 on keratinocytes. Acupuncture led to a prompt analgesic effect, as well as a temporary accumulation of ATP and adenosine. Activating adenosine A1 receptors, promoting ATP release by activating Piezo1, or facilitating ATP hydrolysis by potentiating CD39 achieved anti-nociceptive effects. Conversely, altering these modulations in the opposite direction reversed the subsequent effects of acupuncture. Needling-induced accumulation of interstitial ATP parallelly changed with these modulations. Hypotonic shock led to ATP release and [Ca(2+)](i) rise in HaCaT, which were impeded by introducing siRNA-Piezo1, or replicated by agonism at Piezo1. These findings suggest that keratinocyte Piezo1 and CD39 co-mediated ATP mobilization at acupoints contributes to the initiation signals of acupuncture analgesia via triggering adenosine signaling. SECTION: Physical/Mental practices (acupuncture). TAXONOMY CLASSIFICATION BY EVISE: pain and analgesia.