Transient Receptor Potential (TRP) cation as the TRP Vanilloid 1 and TRP Ankyrin 1 channels (TRPV1 and TRPA1) are nocisensors playing important role to trigger pain. These cation channels serve as thermosensors and are suitable to be activated also by several exogenous and endogenous chemical ligands. Capsaicin activates TRPV1, allyl-isothiocyanate (AITC) and formaldehyde activate TRPA1 receptors. Lipid rafts are plasma membrane microdomains rich in cholesterol and sphingomyelin. Sphingomyelinase (SMase) decreases membrane sphingomyelin by hydrolization. Our aim was to examine its in vitro actions on TRP channels, and the potential analgesic effect of SMase in in vivo mouse models.
The effect of SMase was analysed on TRPV1- or TRPA1-expressing CHO cells by measuring 45Ca-uptake and on isolated trigeminal (TG) neurones by measuring Ca2+ transients with ratiometric technique. Mechanonociceptive and thermonociceptive thresholds of the animals in RTX-induced thermal, and mechanical hyperalgesia, and formaldehyde-evoked hyperalgesia model were measured. The analgesic effect of SMase was measured in capsaicin-evoked acute nocifensive response test.
It has been revealed that intracellular Ca2+ enhancement evoked by capsaicin (TRPV1), AITC and formaldehyde (TRPA1) was inhibited after SMase incubation in TG neurons and receptor-expressing cells. In vivo the SMase treatment significantly diminished the RTX-induced thermal, and mechanical hyperalgesia, the formaldehyde-evoked hyperalgesia and the capsaicin-evoked nocifensive reaction.
Our in vitro and in vivo results suggest that the hydrophobic interactions between the TRP channel and lipid raft interfaces modulate the channel opening. Targeting this interaction might be a tool for drug developmental purposes.
Support: János Bolyai Fellowship, KTIA_NAP_ 20017-1.2.1-NKP -2017-00002, GINOP-2.3.2-15-2016-00050, EFOP-3.6.2-16-2017-00008, 20765/3/2018 FEKUTSTRAT

IN VITRO AND IN VIVO EVIDENCE FOR THE ROLE OF SPHINGOMYELIN AND LIPID RAFTS IN CA2+-GATING OF THE TRANSIENT RECEPTOR POTENTIAL CHANNELS IN SENSORY NEURONS