n-oleoylethanolamine and Glioblastoma

Primary astrocytomas of grade 3 or 4 according to the classification system of the World Health Organization (high-grade astrocytomas or HGAs) are preponderant among adults and are almost invariably fatal despite the use of multimodal therapy. Here we show that the juvenile brain has an endogenous defense mechanism against HGAs. Neural precursor cells (NPCs) migrate to HGAs, reduce glioma expansion and prolong survival time by releasing endovanilloids that activate the vanilloid receptor (transient receptor potential vanilloid subfamily member-1 or TRPV1) on HGA cells. TRPV1 is highly expressed in tumor and weakly expressed in tumor-free brain. TRPV1 stimulation triggers tumor cell death through the branch of the endoplasmic reticulum stress pathway that is controlled by activating transcription factor-3 (ATF3). The antitumorigenic response of NPCs is lost with aging. NPC-mediated tumor suppression can be mimicked in the adult brain by systemic administration of the synthetic vanilloid arvanil, suggesting that TRPV1 agonists have potential as new HGA therapeutics.

Topics: Aging; Amides; Amidohydrolases; Animals; Antineoplastic Agents; Apoptosis; Arachidonic Acids; Brain; Brain Neoplasms; Capsaicin; Cell Movement; Culture Media, Conditioned; Dopamine; Endocannabinoids; Ethanolamines; Female; Gene Expression Regulation, Neoplastic; Glioblastoma; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, SCID; Neoplasm Proteins; Neural Stem Cells; Oleic Acids; Palmitic Acids; Polyunsaturated Alkamides; Real-Time Polymerase Chain Reaction; RNA, Small Interfering; TRPV Cation Channels; Tumor Cells, Cultured

Although the p53 tumor-suppressor gene product plays a critical role in apoptotic cell death induced by DNA-damaging chemotherapeutic agents, human glioma cells with functional p53 were more resistant to gamma-radiation than those with mutant p53. U-87 MG cells with wild-type p53 were resistant to gamma-radiation. U87-W E6 cells that lost functional p53, by the expression of type 16 human papillomavirus E6 oncoprotein, became susceptible to radiation-induced apoptosis. The formation of ceramide by acid sphingomyelinase (A-SMase), but not by neutral sphingomyelinase, was associated with p53-independent apoptosis. SR33557 (2-isopropyl-1-(4-[3-N-methyl-N-(3,4-dimethoxybphenethyl)amino]propyloxy)benzene-sulfonyl) indolizine, an inhibitor of A-SMase, suppressed radiation-induced apoptotic cell death. In contrast, radiation-induced A-SMase activation was blocked in glioma cells with endogenous functional p53. The expression of acid ceramidase was induced by gamma-radiation, and was more evident in cells with functional p53. N-oleoylethanolamine, which is known to inhibit ceramidase activity, unexpectedly downregulated acid ceramidase and accelerated radiation-induced apoptosis in U87-W E6 cells. Moreover, cells with functional p53 could be sensitized to gamma-radiation by N-oleoylethanolamine, which suppressed radiation-induced acid ceramidase expression and then enhanced ceramide formation. Sensitization to gamma-radiation was also observed in U87-MG cells depleted of functional p53 by retroviral expression of small interfering RNA. These results indicate that ceramide may function as a mediator of p53-independent apoptosis in human glioma cells in response to gamma-radiation, and suggest that p53-dependent expression of acid ceramidase and blockage of A-SMase activation play pivotal roles in protection from gamma-radiation of cells with endogenous functional p53.

Topics: Apoptosis; Ceramides; DNA-Binding Proteins; Endocannabinoids; Enzyme Activation; Enzyme Inhibitors; Ethanolamines; Galactosylgalactosylglucosylceramidase; Gamma Rays; Glioblastoma; Humans; Oleic Acids; Oncogene Proteins, Viral; RNA, Small Interfering; Sphingomyelin Phosphodiesterase; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Endocannabinoids are lipid mediators thought to modulate central and peripheral neural functions. We report here gas chromatography-electron impact mass spectrometry analysis of human brain, showing that lipid extracts contain anandamide and 2-arachidonoylglycerol (2-AG), the most active endocannabinoids known to date. Human brain also contained the endocannabinoid-like compounds N-oleoylethanolamine, N-palmitoylethanolamine and N-stearoylethanolamine. Anandamide and 2-AG (0.16 +/- 0.05 and 0.10 +/- 0.05 nmol/mg protein, respectively) represented 7.7% and 4.8% of total endocannabinoid-like compounds, respectively. N-Palmitoyethanolamine was the most abundant (50%), followed by N-oleoyl (23.6%) and N-stearoyl (13.9%) ethanolamines. A similar composition in endocannabinoid-like compounds was found in human neuroblastoma CHP100 and lymphoma U937 cells, and also in rat brain. Remarkably, human meningioma specimens showed an approximately six-fold smaller content of all N-acylethanolamines, but not of 2-AG, and a similar decrease was observed in a human glioblastoma. These ex vivo results fully support the purported roles of endocannabinoids in the nervous system.

Topics: Amides; Animals; Arachidonic Acids; Brain Chemistry; Brain Neoplasms; Cannabinoid Receptor Modulators; Cannabinoids; Endocannabinoids; Ethanolamines; Gas Chromatography-Mass Spectrometry; Glioblastoma; Glycerides; Humans; Lymphoma; Meningioma; Neuroblastoma; Oleic Acids; Palmitic Acids; Polyunsaturated Alkamides; Rats; Rats, Wistar; Reference Values; Stearic Acids; Tumor Cells, Cultured; U937 Cells