Genetic deletion of Fatty Acid Amide Hydrolase results in improved long-term outcome in chronic autoimmune encephalitis

The enzyme Fatty Acid Amide Hydrolase (FAAH) is a key regulator of the endogenous levels of a family of biologically active lipid mediators, the fatty acid amides. These include anandamide, oleoyl ethanolamide and palmitoyl ethanolamide, and their effects are mediated by a variety of downstream targets including cannabinoid receptors and peroxisome proliferator-activated receptors (PPARs). Activation of both of these may have anti-inflammatory and neuroprotective effects. Levels of all three mediators are low in normal nervous tissue, but substantially elevated in mice lacking FAAH as a result of genetic deletion. There is a long anecdotal history of cannabis use by patients suffering from multiple sclerosis, and preclinical studies have indicated beneficial effects of cannabinoid receptor stimulation on both long-term outcome and acute muscle spasm in rodent models of multiple sclerosis (experimental autoimmune encephalitis; EAE). Thus far no report has appeared on the effect of inhibition of FAAH on the progression of EAE. Using a chronic mouse EAE model, we present data indicating that mice lacking FAAH experience an initial inflammatory phase of EAE similar in severity to wild type controls, but exhibited a more substantial clinical remission compared to wild type mice.