Evidence for the in vivo analgesic effect of carboxamido steroids via lipid rafts
Tünde Biró-Sütő1,2, Ádám Horváth1,2, Maja Payrits1,2, Éva Sághy1,2, Rita Skodáné Földes3, Eszter Szánti-Pintér3, Géza Makkai4, János Erostyák4, János Szolcsányi1,2, Zsuzsanna Helyes1,2, Éva Szőke1,2
1Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Pécs, Pécs; Hungary, 2Szentágothai Research Center, University of Pécs; Hungary, 3Institute of Chemistry, Deparment of Organic Chemistry, University of Pannonia, Veszprém; Hungary, 4Department of Experimental Physics, University of Pécs, Pécs; Hungary

Transient Receptor Potential ion channels, such as TRP Vanilloid 1 and Ankyrin 1 (TRPV1, TRPA1) are expressed in nociceptive primary sensory neurons. TRPV1 can be activated by capsaicin (CAPS), resiniferatoxin (RTX), low pH and noxious heat. Allyl-isothiocyanate (AITC) and formaldehyde activate TRPA1. Lipid rafts are liquid ordered plasma membran microdomains rich in cholesterol and sphingomyelin. We described that a carboxamido-steroid compound (C1) had an inhibitory effect on TRP ion channel activation through lipid raft disruption. The aim of this study is to examine the in vitro actions, and the analgesic effect of C1 in in vivo mouse models.

The effect of C1 was analysed on isolated trigeminal (TG) neurons by measuring agonist induced Ca2+-transients with ratiometric technique, and on receptor-expressing CHO cells by measuring 45Ca-uptake. We investigated the effect of C1 in RTX-, and formaldehyde-evoked hyperalgesia models. The analgesic effect of C1 was also measured in capsaicin-evoked acute nocifensive response („eye-wiping”) test. 

Our results show, that C1 treatment diminished the percentage of responsive cells, and the magnitude of Ca2+ transients in TG neurones, and decreased the 45Ca-uptake on receptor-expressing CHO cells. C1 treatment significantly reduced the RTX-induced thermal and mechanical hyperalgesia, the formaldehyde-evoked hyperalgesia and the number of capsaicin-evoked eye-wiping movements. 

Our results provide the first evidence that disruption of lipid rafts by C1 have an analgesic effect in in vivo mouse models. Our in vitro and in vivo findings suggest that the hydrofobic interactions between the TRP channel and lipid raft interfaces modulate the opening properties of these channels. 

Support: János Bolyai Fellowship, GINOP-2.3.2-15-2016-00048, GINOP-2.3.2-15-2016-00050, KTIA¬_NAP_ 20017-1.2.1-NKP -–2017-00002, EFOP-3.6.2-16-2017-00008, the ÚNKP-18-4 New National Excellence Program of the Ministry of Human Capacities

EVIDENCE FOR THE IN VIVO ANALGESIC EFFECT OF CARBOXAMIDO STEROIDS VIA LIPID RAFTS