Adelmidrol increases the endogenous concentrations of palmitoylethanolamide in canine keratinocytes and down-regulates an inflammatory reaction in an in vitro model of contact allergic dermatitis
Graphical Abstract
Introduction
Chronic allergic skin diseases represent a growing burden, and more than 20% of the animals are referred to a veterinary doctor for a dermatological problem (Hill et al., 2006). Although topical anti-inflammatory treatments are considered the reference standard for managing focal or multifocal skin lesions in atopic dermatitis (Olivry et al., 2010), only few alternatives to topical steroids are available. The search for valuable treatment options to be safely applied for long durations has recently focused on the cutaneous endocannabinoid system (Lambert, 2007, Biro et al, 2009, Kupczyk et al, 2009), including cannabinoid receptors, the endocannabinoids (anandamide and 2-arachidonoylglycerol), structurally similar bioactive amides (such as palmitoylethanolamide, PEA), and their biosynthetic and catabolic enzymes (Fezza and Maccarrone, 2014).
The main physiological function of the endocannabinoid system in the skin is to preserve the local homeostasis and the complex cellular dynamics (Biro et al., 2009). Recent studies have suggested the existence of the endocannabinoid system in the canine skin (Campora et al., 2012) and it has been shown that PEA concentrations in the skin change during canine atopic dermatitis (Abramo et al., 2014). Moreover, PEA was recently found to afford significant therapeutic benefit in dogs with experimental hypersensitivity (Cerrato et al., 2012a) and spontaneous atopic dermatitis (Noli et al., 2014).
Adelmidrol is an analogue of PEA. Unlike PEA, which is highly lipophilic, adelmidrol is suitable for topical application because it exhibits both hydrophilic and lipophilic features (Cerrato et al., 2012b). Adelmidrol is the di-ethanolamide derivative of azelaic acid, a natural substance, topically effective for human inflammatory skin disorders (Nazzaro-Porro, 1987) and able to modulate the inflammatory response in human keratinocytes (Mastrofrancesco et al., 2010).
Several mechanisms of action have been proposed for PEA (Petrosino et al., 2010a), including: (1) the direct stimulation of an as-yet uncharacterised cannabinoid type 2-like receptor (Conti et al, 2002, Farquhar-Smith, Rice, 2003); (2) an ‘entourage effect’ (Di Marzo et al, 2001, Petrosino et al, 2015); and (3) the direct stimulation of particular molecular targets (Lo Verme et al., 2005). By contrast, the mechanism of action of adelmidrol has been investigated only in part (De Filippis et al., 2009). Yet, topical application of adelmidrol alleviates chronic inflammatory skin conditions in both humans (Pulvirenti et al., 2007) and dogs (Mantis et al, 2007, Cerrato et al, 2012b, Fabbrini, Leone, 2013).
The aim of the present study was to investigate the mechanism(s) of action of adelmidrol and its potential effect in an in vitro model of contact allergic dermatitis (CAD).
Section snippets
Cell cultures and treatments
Canine keratinocytes, immortalised human keratinocytes (HaCaT) cells and human embryonic kidney (HEK)-293 cells, either wild-type (HEK-WT) or stably transfected with cDNA encoding for human recombinant N-acylethanolamine acid amidase (NAAA; HEK-NAAA), were cultured (Appendix: Supplementary material).
Keratinocytes (9 × 104 cells/cm2) were treated with adelmidrol (10 µM, Epitech Group) or vehicle (methanol 0.05%, Ctrl) for 24 h, or also with azelaic acid (10 µM) for 24 h (HaCaT), at 37 °C with 5%
Effect of adelmidrol on endocannabinoids and related compounds in keratinocytes
The concentrations of PEA and 2-AG were significantly increased in canine keratinocytes treated with adelmidrol (10 µM for 24 h) when compared to vehicle. No significant effect was observed on AEA and OEA (Fig. 1).
Adelmidrol (10 µM) also induced a significant increase in PEA concentrations in HaCaT cells after 24 h, without altering the concentrations of the other mediators (Fig. 2A). In HaCaT cells treated with azelaic acid (10 µM for 24 h), no significant effect on AEA, 2-AG, PEA and OEA
Discussion
The main findings of the present study are that adelmidrol increases PEA and 2-AG concentrations in canine keratinocytes and inhibits inflammatory response in keratinocytes. Since both PEA and 2-AG exert anti-inflammatory and anti-allergic effects in the skin (Karsak et al, 2007, Petrosino et al, 2010b, Cerrato et al, 2012a, Kendall, Nicolaou, 2013), these results suggest that adelmidrol potentiates an inherent cellular protective mechanism by increasing the availability of endogenous
Conclusions
Although the exact mechanism of action of adelmidrol is still not completely understood, our study has provided important new data. In particular, we have shown that adelmidrol: (1) increases PEA concentrations in canine and human keratinocytes (‘entourage effect’), this effect not being due to its hydrolysis to azelaic acid; (2) is not an inhibitor of NAAA and FAAH, although, under certain circumstances, it can modulate the expression of these two PEA catabolic enzymes and the biosynthetic
Conflict of interest statement
SP, MF and MA are employees of Epitech Group. MFdV is a scientific cofounder of and consultant for Innovet Italia. RV receives unrestricted research support from Epitech Group. None of the authors has any other financial or personal relationships that could inappropriately influence or bias the content of the paper.
Acknowledgments
This work was supported by Progetto Operativo Nazionale (PON01_02512) and by PO FESR 2007/20013 "BANDO PER LA REALIZZAZIONE DELLA RETE DELLE BIOTECNOLOGIE IN CAMPANIA" PROGETTO "Terapie Innovative di Malattie Infiammatorie croniche, metaboliche, Neoplastiche e Geriatriche - TIMING".
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2021, Otolaryngology Case ReportsCitation Excerpt :The association of Adelmidrol and Trans-traumatic acid thus determines a synergistic effect that favors the natural process of re-epithelialization [10,18]. The ability of Adelmidrol to control the inflammatory process, modulating mast cell degranulation through the increase of endogenous PEA levels [19,20], and the capacity of Trans-traumatic acid to stimulate keratinocytes convergence from the edges to the core lesion, allow a rapid healing process [23]. This study reports the cases of two patients whit persistent TMP, non-responder to systemic and topical therapies, successfully treated with a combination of Adelmidrol and Trans-traumatic acid (Nevamast® gel), without any adverse events.
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2019, Neurobiology of DiseaseCitation Excerpt :The PEA effect in increasing the 2-AG levels in healthy conditions was recently reported and associated to the PEA “entourage effect (Guida et al., 2015; Petrosino et al., 2016). The effect of PEA at increasing 2-AG level is unlikely associated with an inhibition of 2-AG metabolizing enzymes since: i) the time of the increase in 2-AG level is not compatible with transcriptional modulation (Petrosino et al., 2016), ii) monoacyglycerol lipase, the main enzyme degrading 2-AG (Blankman et al., 2007), is not inhibited by PEA, and iii) the inhibition of other hydrolases degrading 2-AG under certain circumstances, including FAAH (Goparaju et al., 1998), is denied by the lack of effect of PEA on AEA and PEA levels. The effect of PEA through other targets such as PPARα, GPR55 or GPR119 (Ryberg et al., 2007; Godlewski et al., 2009) is also unlikely since 2-AG increase is associated with Gq/11-coupled receptors and none of these receptors is associated with Gq/11.
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2016, Toxicology and Applied PharmacologyCitation Excerpt :As NM and SM are skin blistering agents, endocannabinoids are also likely to be generated in vesicant-induced blisters. N-acylethanolamines have been shown to suppress the release of the proinflammatory chemokines in poly-[I:C]-stimulated human keratinocytes (Petrosino et al., 2010, 2016). In human skin, endocannabinoid signaling has been shown to lead to suppression of mast cell maturation and activation, an important component of dermal inflammatory responses (Sugawara et al., 2012).