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Alzheimer's disease (AD) is characterized by enhanced ␤-amyloid peptide (␤A) deposition along with glial activation in senile plaques, selective neuronal loss, and cognitive deficits. Cannabinoids are neuroprotective agents against excitotoxicity in vitro and acute brain damage in vivo. This background prompted us to study the localization, expression, and function of cannabinoid receptors in AD and the possible protective role of cannabinoids after ␤A treatment, both in vivo and in vitro. Here, we show that senile plaques in AD patients express cannabinoid receptors CB 1 and CB 2 , together with markers of microglial activation, and that CB 1 -positive neurons, present in high numbers in control cases, are greatly reduced in areas of microglial activation. In pharmacological experiments, we found that G-protein coupling and CB 1 receptor protein expression are markedly decreased in AD brains. Additionally, in AD brains, protein nitration is increased, and, more specifically, CB 1 and CB 2 proteins show enhanced nitration. Intracerebroventricular administration of the synthetic cannabinoid WIN55,212-2 to rats prevent ␤A-induced microglial activation, cognitive impairment, and loss of neuronal markers. Cannabinoids (HU-210, WIN55,212-2, and JWH-133) block ␤A-induced activation of cultured microglial cells, as judged by mitochondrial activity, cell morphology, and tumor necrosis factor-␣ release; these effects are independent of the antioxidant action of cannabinoid compounds and are also exerted by a CB 2 -selective agonist. Moreover, cannabinoids abrogate microglia-mediated neurotoxicity after ␤A addition to rat cortical cocultures. Our results indicate that cannabinoid receptors are important in the pathology of AD and that cannabinoids succeed in preventing the neurodegenerative process occurring in the disease.

Autophagy can promote cell survival or cell death, but the molecular basis underlying its dual role in cancer remains obscure. Here we demonstrate that Δ 9 -tetrahydrocannabinol (THC), the main active component of marijuana, induces human glioma cell death through stimulation of autophagy. Our data indicate that THC induced ceramide accumulation and eukaryotic translation initiation factor 2α (eIF2α) phosphorylation and thereby activated an ER stress response that promoted autophagy via tribbles homolog 3-dependent (TRB3-dependent) inhibition of the Akt/mammalian target of rapamycin complex 1 (mTORC1) axis. We also showed that autophagy is upstream of apoptosis in cannabinoid-induced human and mouse cancer cell death and that activation of this pathway was necessary for the antitumor action of cannabinoids in vivo. These findings describe a mechanism by which THC can promote the autophagic death of human and mouse cancer cells and provide evidence that cannabinoid administration may be an effective therapeutic strategy for targeting human cancers. IntroductionMacro-autophagy, hereafter referred to as "autophagy," is a highly conserved cellular process in which cytoplasmic materials - including organelles - are sequestered into double-membrane vesicles called autophagosomes and delivered to lysosomes for degradation or recycling (1). In many cellular settings, triggering of autophagy relies on the inhibition of mammalian target of rapamycin complex 1 (mTORC1), an event that promotes the activation (de-inhibition) of several autophagy proteins (Atgs) involved in the initial phase of membrane isolation (1). Enlargement of this complex to form the autophagosome requires the participation of 2 ubiquitin-like conjugation systems. One involves the conjugation of ATG12 to ATG5 and the other of phosphatidylethanolamine to LC3/ATG8 (1). The final outcome of the activation of the autophagy program is highly dependent on the cellular context and the strength and duration of the stress-inducing signals (2-5). Thus, besides its role in cellular homeostasis, autophagy can be a form of programmed cell death, designated "type II programmed cell death," or play a cytoprotective role, for example in situations

One of the most exciting areas of current research in the cannabinoid field is the study of the potential application of these compounds as antitumoral drugs. Here, we describe the signaling pathway that mediates cannabinoid-induced apoptosis of tumor cells. By using a wide array of experimental approaches, we identify the stress-regulated protein p8 (also designated as candidate of metastasis 1) as an essential mediator of cannabinoid antitumoral action and show that p8 upregulation is dependent on de novo-synthesized ceramide. We also observe that p8 mediates its apoptotic effect via upregulation of the endoplasmic reticulum stress-related genes ATF-4, CHOP, and TRB3. Activation of this pathway may constitute a potential therapeutic strategy for inhibiting tumor growth.

Amides of fatty acids with ethanolamine (FAE) are biologically active lipids that participate in a variety of biological functions, including the regulation of feeding. The polyunsaturated FAE anandamide (arachidonoylethanolamide) increases food intake by activating G proteincoupled cannabinoid receptors. On the other hand, the monounsaturated FAE oleoylethanolamide (OEA) reduces feeding and body weight gain by activating the nuclear receptor PPAR-␣ (peroxisome proliferator-activated receptor ␣). In the present report, we examined whether OEA can also influence energy utilization. OEA (1-20 M) stimulated glycerol and fatty acid release from freshly dissociated rat adipocytes in a concentration-dependent and structurally selective manner. Under the same conditions, OEA had no effect on glucose uptake or oxidation. OEA enhanced fatty acid oxidation in skeletal muscle strips, dissociated hepatocytes, and primary cardiomyocyte cultures. Administration of OEA in vivo (5 mg kg ؊1 , intraperitoneally) produced lipolysis in both rats and wild-type mice, but not in mice in which PPAR-␣ had been deleted by homologous recombination (PPAR-␣ ؊/؊ ). Likewise, OEA was unable to enhance lipolysis in adipocytes or stimulate fatty acid oxidation in skeletal muscle strips isolated from PPAR-␣ mice. The synthetic PPAR-␣ agonist Wy-14643 produced similar effects, which also were dependent on the presence of PPAR-␣. Subchronic treatment with OEA reduced body weight gain and triacylglycerol content in liver and adipose tissue of dietinduced obese rats and wild-type mice, but not in obese PPAR-␣ ؊/؊ mice. The results suggest that OEA stimulates fat utilization through activation of PPAR-␣ and that this effect may contribute to its anti-obesity actions.Amides of long-chain fatty acids with ethanolamine (FAE) 1 are a family of lipid mediators produced through the concerted action of two enzymes present in mammalian cells: N-acyltransferase, which transfers a fatty acid from the sn-1 position of a donor phospholipid to the free amine in phosphatidylethanolamine, producing N-acyl-phosphatidylethanolamine; and phospholipase D, which converts N-acyl-phosphatidylethanolamine to FAE (1, 2). The FAE are hydrolyzed intracellularly to fatty acids and ethanolamine by the action of fatty acid amide hydrolase enzymes (3)(4)(5).Although the FAE were first described four decades ago (6), they did not attract much attention until the discovery that a polyunsaturated member of this family, anandamide (arachidonoylethanolamide), is an endogenous ligand for cannabinoid receptors, G protein-coupled receptors targeted by the marijuana constituent ⌬ 9 -tetrahydrocannabinol (7). Anandamide is now established as a brain endocannabinoid messenger (8) and multiple roles for other FAE have also been proposed (9 -11). One emerging function of these lipid mediators is the regulation of feeding behavior. Anandamide causes overeating in rats because of its ability to activate cannabinoid receptors (12). This action is of therapeutic relevance: cannabinoid agonists su...