Identifying points of control in inflammation isNAAA ͉ oleoylethanolamide ͉ PPAR-␣

Cannabinoid receptors and their endogenous ligands have been recently identified in the brain as potent inhibitors of neurotransmitter release. Here we show that, in a rat model of Parkinson's disease induced by unilateral nigral lesion with 6-hydroxydopamine (6-OHDA), the striatal levels of anandamide, but not that of the other endocannabinoid 2-arachidonoylglycerol, were increased. Moreover, we observed a decreased activity of the anandamide membrane transporter (AMT) and of the anandamide hydrolase [fatty acid amide hydrolase (FAAH)], whereas the binding of anandamide to cannabinoid receptors was unaffected. Spontaneous glutamatergic activity recorded from striatal spiny neurons was higher in 6-OHDA-lesioned rats. Inhibition of AMT by N-(4-hydroxyphenyl)-arachidonoylamide (AM-404) or by VDM11, or stimulation of the cannabinoid CB1 receptor by HU-210 reduced glutamatergic spontaneous activity in both naive and 6-OHDA-lesioned animals to a similar extent. Conversely, the FAAH inhibitors phenylmethylsulfonyl fluoride and methyl-arachidonoyl fluorophosphonate were much more effective in 6-OHDA-lesioned animals. The present study shows that inhibition of anandamide hydrolysis might represent a possible target to decrease the abnormal cortical glutamatergic drive in Parkinson's disease.

Several G protein-coupled receptors function within lipid rafts plasma membrane microdomains, which may be important in limiting signal transduction. Here we show that treatment of rat C6 glioma cells with the raft disruptor methyl-␤-cyclodextrin (MCD) doubles the binding efficiency (i.e. the ratio between maximum binding and dissociation constant) of type-1 cannabinoid receptors (CB1R), which belong to the rhodopsin family of G protein-coupled receptors. In parallel, activation of CB1R by the endogenous agonist anandamide (AEA) leads to ϳ3-fold higher [35 S]GTP␥S binding in MCD-treated cells than in controls, and CB1R-dependent signaling via adenylate cyclase, and p42/p44 MAPK is almost doubled by MCD. Unlike CB1R, the other AEAbinding receptor TRPV1, the AEA synthetase NAPE-PLD, and the AEA hydrolase FAAH are not modulated by MCD, whereas the activity of the AEA membrane transporter (AMT) is reduced to ϳ50% of the controls. We also show that MCD reduces dose-dependently AEAinduced apoptosis in C6 cells but not in human CHP100 neuroblastoma cells, which mirror the endocannabinoid system of C6 cells but are devoid of CB1R. MCD reduces also cytochrome c release from mitochondria of C6 cells, and this effect is CB1R-dependent and partly mediated by activation of p42/p44 MAPK. Altogether, the present data suggest that lipid rafts control CB1R binding and signaling, and that CB1R activation underlies the protective effect of MCD against apoptosis.Anandamide (arachidonoylethanolamide, AEA) 1 belongs to a group of endogenous lipids, which include amides, esters, and ethers of long chain polyunsaturated fatty acids, collectively termed endocannabinoids (1, 2). It binds to type-1 and type-2 cannabinoid receptors (CB1R and CB2R), thus playing many actions in the central nervous system (3) and in the periphery (4). The activities of AEA at CB receptors are terminated by cellular uptake through an AEA membrane transporter (AMT) (5), followed by hydrolysis to ethanolamine and arachidonic acid by the fatty acid amide hydrolase (FAAH) (6, 7). The checkpoint in AEA synthesis is the N-acyl-phosphatidylethanolamines (NAPE)-hydrolyzing phospholipase D (NAPE-PLD), which releases on demand AEA from membrane NAPEs (8).Together with AEA and congeners like 2-arachidonoylglycerol (2-AG), N-arachidonoyldopamine, noladin ether, and virodhamine, these proteins form the endocannabinoid system (2).One activity of AEA that has attracted growing interest is its ability to induce programmed cell death (apoptosis) in neuronal and peripheral cells (9), with therapeutic potential in cancer (10) and neurodegenerative diseases (11)(12)(13)(14). In a previous study we have shown that the pro-apoptotic activity of AEA occurs through activation of type 1 vanilloid receptors (now called transient receptor potential channel vanilloid receptor subunit 1, TRPV1), which are six transmembrane-spanning proteins with intracellular N and C termini (15). In fact, we have shown that AEA is a physiological agonist of TRPV1 (16), and thus can be also considered a ...