Anandamide endocannabinoids

Endocannabinoids are endogenous mediators acting via the binding to, and activation of, cannabinoid receptors, CBX and CB2 [1]. iV-arachidonoy 1-ethanol-amine (AEA, anandamide) and 2-arachidonoyl-glycerol (2-AG) (Fig. 1) are the two most studied endocannabinoids. In the nervous system, endocannabinoids act as... 

Endocannabinoids. Figure 1 Chemical structures of the two most studied endocannabinoids, anandamide and 2-arachidonoylglycerol, of Cannabis sativa psychoactive principle, A9-tetrahydrocannabinol, and of the CB-i receptor antagonist/inverse agonist, rimonabant. 

The development of SAR for endocannabinoid-derived structures has primarily focused on the anandamide skeleton (1) with a large number of publications addressing the requirements for activity and stability of this scaffold. More recently, some SAR has begun to emerge for the other end-ocannabinoids, in particular 2-AG (2). The following discussion will focus on highlighting some of the main features that contribute to affinity and/or stability each endocannabinoid will be treated separately. A number of detailed reviews on this subject have been published [142-146]. 

In addition to anandamide, several other endogenous polyunsaturated fatty acid derivatives were also found to act as cannabimimetics. They are all now collectively referred to as endocannabinoids. Soon after the discovery of anandamide, two more fatty acid ethanolamides were isolated and found to bind to CB1 preparations with affinities similar to that of anandamide (anandamide CB1 binding affinity K = 39.2 nM, according to Hanus et al., 1993). These were the homo-y-linolenylethanol-amide (CB1 K[ = 53.4 nM) and 7,10,13,16-docosatetraenylethanolamide (CB1 K[ = 34.4 nM) (Fig. 2). All three V-acylethanolamide endocannabinoids were found to be CB1 agonists in the MVD test (Pertwee, 1994). 

Later 2-AG was also found in the brain (Stella, 1997) and spleen (Di Marzo, 1998). It was shown to be released in a calcium-dependent manner, reaching concentrations 170 times higher than that of anandamide in the brain (Stella, 1997). Like the other endocannabinoids, 2-AG was shown to produce the typical tetrad of cannabimimetic behavioral effects and inhibit electrically evoked contractions of mouse MVD (Mechoulam, 1995a). 

All the foregoing pharmacological effects of anandamide, in conjunction with the well-documented existence of specific systems for its biosynthesis, catabolism, and cellular reuptake to be discussed shortly, suggest that anandamide is indeed the endogenous cannabinoid ligand. The other two less studied A -acylethanolamide endocannabinoids and also 2-AG may serve similar functions. The differential roles of each of these four endocannabinoids are still unclear. 

Immediately after synthesis, endocannabinoids are released in the extracellular space, where they then act on the same or neighboring cells as autocrine or paracrine mediators (Di Marzo, 1999). Experimental evidence thus far indicates that anandamide and 2-AG, unlike other classical neurotransmitters, are not stored in vesicles. First, anandamide basal concentrations are extremely low (5-10 pmol/g), 100 to 10,000 times lower than those of classical neurotransmitters (Cadas, 1997). Second, stimulus-dependent anandamide release is linked with de novo NAPE and... 

With the discovery of anandamide and 2-arachidonyl glycerol as two new families of endocannabinoids, cannabinoid research has taken major... 

Mulet, X. and Drummond, C.J. (2011) Anandamide andanalogous endocannabinoids a lipid self-assembly study. Soft Matter, 7, 5319—5328. 

Anandamide One of the endogenous ligands, or endocannabinoids, which is active at cannabinoid receptors. 

A competitive version of ABPP identifies the target(s) and assesses the selectivity of an enzyme inhibitor in biological systems by gauging how well the inhibitor slows the enzyme s reaction with an ABP. For example, fluorophosphonate ABP 3 was used to profile the selectivity of fatty acid amide hydrolase (FAAH) inhibitors within the serine hydrolase superfamily [27] (FAAH hydrolyzes endocannabinoids such as anandamide). Serine hydrolases that exhibited reduced labeling by the probe in the presence of inhibitor were scored as targets of the inhibitor. Urea FAAH inhibitors exemplified by PF-3845 (5) that covalently modify the active-site serine nucleophile of FAAH were found to be exquisitely selective for FAAH in brain and liver... 

Endocannabinoids are endogenous ligands for the CB1 receptor. The best established are anandamide (N-arachidonoylethanolamine) and 2-AG (2-arachidonoyl-glycerol). Others may also exist. Pathways involved in the formation and inactivation of anandamide and 2-AG are shown in Figure 56-6. Some steps in their formation are Ca2+-dependent. This explains the ability of neuronal depolarization, which increases postsynaptic intracellular Ca2+ levels, to stimulate endocannabinoid formation and release. Some neurotransmitter receptors (e.g. the D2 dopamine receptor) also stimulate endocannabinoid formation, probably by modulating postsynaptic Ca2+ levels or signaling pathways (e.g. PLC) that regulate endocannabinoid formation. 

Anandamide may reduce pain by a peripheral action, by acting on CB 1-like receptors located outside the CNS (Calignano et al. 1998). Palmitylethanolamide (PEA) is an endocannabinoid that is coreleased with anandamide and activates peripheral CB2 receptors. When the two are administered together, they show a 100-fold synergistic effect on analgesic measures. Measurements of anandamide and PEA levels in the skin show that there are sufficient amounts to create tonic activation of local cannabinoid receptors. Thus, endocannabinoids may tonically inhibit cutaneous pain. 

Our research group expected that additional polyunsaturated fatty acid ethanolamides may be present in the brain. We also identified in porcine brain another two putative endocannabinoids, namely homo-y-linoleoylethanolamide (K = 53.4 5-5 nM) and 7,10,13,16-docosatetraenoylethanolamide (K = 34.4 3.2 nM). The isolation of these two compounds as constituents of porcine brain that bind to the cannabinoid receptor demonstrated that anandamide is not the sole representative of this class of potential mediators. 

Endocannabinoids Widely distributed CB1 Anandamide, 2- arachidonyglycerol Rimonabant Inhibitory (presynaptic) -r Ca2+ conductance, i cAMP... 

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