Anionic linear aliphatic surfactants activate TRPV1: A possible endpoint for estimation of detergent induced eye nociception?

The transient receptor potential vanilloid type 1 (TRPV1) has been reported as one of the key components in the pain pathway. Activation of the receptor causes a Ca2+ influx in sensory C-fibres with secondary effects leading to neurogenic inflammation in the surrounding tissue. We have earlier reported specific activation of TRPV1 by surfactant-containing hygiene products. We have continued this project by investigating activation of the TRPV1 by shampoo and soap ingredients in low concentrations measured as intracellular Ca2+ influxes in stably TRPV1-expressing neuroblastoma SH-SY5Y cells. As a TRPV1 specific control, the TRPV1 antagonist capsazepine was used. The response was quantified as the product induced Ca2+ influx during 2 min in relation to the maximum response induced by the TRPV1 agonist capsaicin. The results show that anionic alkyl linear surfactant ingredients such as sodium lauryl sulphate, sodium laureth sulphate, ammonium lauryl sulphate, sodium C12-15 pareth sulphate and N-lauroylsarcosine concentration-dependently induced Ca2+ influx that could be addressed to TRPV1. The cationic surfactants benzalkonium chloride and cetylpyridinium chloride induced a Ca2+ influx that was not TRPV1 mediated as well as the zwitterionic surfactant cocamidopropyl betaine, the non-linear anionic surfactant sodium deoxycholate and the non-ionic surfactant Triton-X. These results reveal a new mechanistic pathway for surfactant-induced nociception.