Cannabinoids act via cell surface G protein-coupled receptors (CB(1) and CB(2)) and the ion channel receptor TRPV1. Evidence has now emerged suggesting that an additional target is the peroxisome proliferator-activated receptor (PPAR) family of nuclear receptors. There are three PPAR subtypes alpha, delta (also known as beta) and gamma, which regulate cell differentiation, metabolism and immune function. The major endocannabinoids, anandamide and 2-arachidonoylglycerol, and ajulemic acid, a structural analogue of the phytocannabinoid Delta(9)-tetrahydrocannabinol (THC), have anti-inflammatory properties mediated by PPARgamma. Other cannabinoids which activate PPARgamma include N-arachidonoyl-dopamine, THC, cannabidiol, HU210, WIN55212-2 and CP55940. The endogenous acylethanolamines, oleoylethanolamide and palmitoylethanolamide regulate feeding and body weight, stimulate fat utilization and have neuroprotective effects mediated through PPARalpha. Other endocannabinoids that activate PPARalpha include anandamide, virodhamine and noladin ether. There is, as yet, little direct evidence for interactions of cannabinoids with PPARdelta. There is a convergence of effects of cannabinoids, acting via cell surface and nuclear receptors, on immune cell function which provides promise for the targeted therapy of a variety of immune, particularly neuroinflammatory, diseases.
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