Palmitoylethanolamide counteracts substance P-induced mast cell activation in vitro by stimulating diacylglycerol lipase activity

Abstract

BackgroundPalmitoylethanolamide (PEA) is a pleiotropic endogenous lipid mediator currently used as a “dietary food for special medical purposes” against neuropathic pain and neuro-inflammatory conditions. Several mechanisms underlie PEA actions, among which the “entourage” effect, consisting of PEA potentiation of endocannabinoid signaling at either cannabinoid receptors or transient receptor potential vanilloid type-1 (TRPV1) channels. Here, we report novel molecular mechanisms through which PEA controls mast cell degranulation and substance P (SP)-induced histamine release in rat basophilic leukemia (RBL-2H3) cells, a mast cell model.MethodsRBL-2H3 cells stimulated with SP were treated with PEA in the presence and absence of a cannabinoid type-2 (CB2) receptor antagonist (AM630), or a diacylglycerol lipase (DAGL) enzyme inhibitor (OMDM188) to inhibit the biosynthesis of the endocannabinoid 2-arachidonoylglycerol (2-AG). The release of histamine was measured by ELISA and β-hexosaminidase release and toluidine blue staining were used as indices of degranulation. 2-AG levels were measured by LC-MS. The mRNA expression of proposed PEA targets (Cnr1, Cnr2, Trpv1, Ppara and Gpr55), and of PEA and endocannabinoid biosynthetic (Napepld, Dagla and Daglb) and catabolic (Faah, Naaa and Mgl) enzymes were also measured. The effects of PEA on the activity of DAGL-α or -β enzymes were assessed in COS-7 cells overexpressing the human recombinant enzyme or in RBL-2H3 cells, respectively.ResultsSP increased the number of degranulated RBL-2H3 cells and triggered the release of histamine. PEA counteracted these effects in a manner antagonized by AM630. PEA concomitantly increased the levels of 2-AG in SP-stimulated RBL-2H3 cells, and this effect was reversed by OMDM188. PEA significantly stimulated DAGL-α and -β activity and, consequently, 2-AG biosynthesis in cell-free systems. Co-treatment with PEA and 2-AG at per se ineffective concentrations downmodulated SP-induced release of histamine and degranulation, and this effect was reversed by OMDM188.ConclusionsActivation of CB2 underlies the inhibitory effects on SP-induced RBL-2H3 cell degranulation by PEA alone. We demonstrate for the first time that the effects in RBL-2H3 cells of PEA are due to the stimulation of 2-AG biosynthesis by DAGLs.

Palmitoylethanolamide: A Nutritional Approach to Keep Neuroinflammation within Physiological Boundaries—A Systematic Review

“…The mechanism through which PEA maintains the normal reactivity of mast cells and microglia/astrocytes in the peripheral and central nervous system respectively is historically known as autacoid local injury antagonism (ALIA) [ 139 , 140 , 141 ]. It is now acknowledged that ALIA depends on the ability of PEA to (i) indirectly interact with the type-1 (CB1) and type-2 (CB2) cannabinoid receptors [ 142 , 143 ], (ii) exert a positive allosteric modulation of the transient receptor potential vanilloid type-1 (TRPV1) [ 57 , 144 , 145 , 146 , 147 ], (iii) directly interact with the peroxisome proliferator-activated receptor-α (PPAR-α) [ 148 ] or with the orphan G-protein coupled receptor 55 (GPR55) [ 149 , 150 ]. The indirect interaction of PEA with specific receptors of the endocannabinoid and endovanilloid systems is well-known as the “entourage effect” [ 142 , 151 ].…”

“…The indirect interaction of PEA with specific receptors of the endocannabinoid and endovanilloid systems is well-known as the “entourage effect” [ 142 , 151 ]. By inhibiting the expression of the enzyme hydrolyzing the endocannabinoid anandamide (AEA) [ 142 ], or by stimulating the activity of the enzyme biosynthesizing the endocannabinoid 2-arachidonoylglycerol (2-AG) [ 143 ], PEA increases the endogenous levels of these lipid mediators and potentiates their actions at CB1, CB2, and TRPV1 receptors [ 57 , 142 , 143 , 145 , 146 ]. Nevertheless, it has also been demonstrated that PEA via direct interaction with PPAR-α receptors is capable to activate TRPV1 receptors [ 152 , 153 ], as well as to increase the expression of CB2 receptors [ 154 ].…”

“…PEA activates TRPV1 receptors [ 145 , 146 ] and increases the expression of CB2 receptors (orange arrows) via direct activation of PPAR-α receptors (blue arrow) [ 154 ]. PEA, through the stimulation of the activity of DAGL [ 143 ] or the inhibition of the expression of FAAH (yellow arrows) [ 142 ], increases the endogenous levels of 2-AG and AEA, respectively, which directly activate CB1, CB2, and TRPV1 receptors (“entourage effect”) (violet arrow) [ 57 , 142 , 143 , 145 , 146 ]. PEA, possibly through an allosteric modulation of TRPV1 receptors, potentiates the actions of AEA and 2-AG at TRPV1 receptors (“entourage effect”) [ 57 , 145 , 146 ].…”

Palmitoylethanolamide and Related ALIAmides: Prohomeostatic Lipid Compounds for Animal Health and Wellbeing

“…In particular, PEA can directly activate PPAR-α (peroxisome proliferator-activated receptor α) [ 85 ] or, more controversially, GPR55 (G-protein-coupled receptor 55) [ 86 ]. On the other hand, the activation of canonical cannabinoid receptors (i.e., Cannabinoid receptor (CB) type 1 CB1 and CB2) depends on the PEA-induced increase of endocannabinoids, like AEA or 2-AG [ 87 , 88 , 89 ]. The term “entourage effect” was coined to explain the aforementioned indirect effect of PEA on cannabinoid receptors, through the increased availability of endocannabinoid(s) [ 89 , 90 , 91 ].…”

Cannabinoid control of neurogenic inflammation

“…Mediators that promote endocannabinoid synthesis and inhibitors of endocannabinoid hydrolysis are also key modulators of neurogenic inflammation. For example, the endogenous lipid palmitoylethanolamide (PEA) promotes anandamide and 2-AG production by inhibiting fatty acid amide hydrolase and stimulating DAGL activity, respectively (DiMarzo et al, 2001;Petrosino et al, 2019). Treatment with palmitoylethanolamide attenuated SPinduced degranulation of RBL-2H cells(Petrosino et al, 2019), demonstrating that boosting endocannabinoid tone has the potential to reduce neurogenic inflammation.…”