Ciguatera poisoning: the role of high-voltage-activated and store-operated calcium channels in ciguatoxin-induced sensory effects

Introduction: Ciguatera fish poisoning (CFP), the most common seafood poisoning worldwide, is caused by the consumption of seafood contaminated with ciguatoxins (CTXs). Pruritus is one of the most distressing symptoms, associated with other cutaneous sensory disorders, including paresthesia and cold dysesthesia. No specific treatment exists. CTXs are known to primarily activate voltage-gated sodium channels, but the downstream molecular events that lead to sensory disturbances remain poorly defined. Peptidergic sensory neurons were recently identified as major players in CFP sensory disturbances. Methods: In this study, we examined the role of molecular actors in 2 effects induced by Pacific CTX-2 (P-CTX-2): the increase in cytosolic calcium levels in rat primary sensory neurons; and the release of the neuropeptide substance P (SP) in sensory neurons co-cultured with keratinocytes. Results: Our results (i) rule out the involvement of the Na+/Ca2+ exchanger (NCX) and the transient receptor potential channels transient receptor potential ankyrin 1 and and transient receptor potential vanilloid 1; (ii) show that N-type voltage-gated calcium (Cav) channels contribute to the initiation of the calcium signal elicited by P-CTX-2 in rat sensory neurons, while N-type and L-type Cav channels play equal parts in the SP release in the co-culture; and (iii) identify store-operated calcium entry supported by Orai calcium release-activated calcium modulator 1 (ORAI1) as a critical effector of the late phase of the calcium signal and the subsequent SP release elicited by P-CTX-2. Discussion: Our in vitro findings indicate that Cav and ORAI1 channels may be promising pharmacological targets for specifically relieving the sensory effects of CTXs.