title: Downregulation of the CB1 cannabinoid receptor and related molecular elements of the endocannabinoid system in epileptic human hippocampus.
abstract: Endocannabinoid signaling is a key regulator of synaptic neurotransmission throughout the brain. Compelling evidence shows that its perturbation leads to development of epileptic seizures, thus indicating that endocannabinoids play an intrinsic protective role in suppressing pathologic neuronal excitability. To elucidate whether long-term reorganization of endocannabinoid signaling occurs in epileptic patients, we performed comparative expression profiling along with quantitative electron microscopic analysis in control (postmortem samples from subjects with no signs of neurological disorders) and epileptic (surgically removed from patients with intractable temporal lobe epilepsy) hippocampal tissue. Quantitative PCR measurements revealed that CB(1) cannabinoid receptor mRNA was downregulated to one-third of its control value in epileptic hippocampus. Likewise, the cannabinoid receptor-interacting protein-1a mRNA was decreased, whereas 1b isoform levels were unaltered. Expression of diacylglycerol lipase-alpha, an enzyme responsible for 2-arachidonoylglycerol synthesis, was also reduced by approximately 60%, whereas its related beta isoform levels were unchanged. Expression level of N-acyl-phosphatidylethanolamine-hydrolyzing phospholipase D and fatty acid amide hydrolase, metabolic enzymes of anandamide, and 2-arachidonoylglycerol's degrading enzyme monoacylglycerol lipase did not change. The density of CB(1) immunolabeling was also decreased in epileptic hippocampus, predominantly in the dentate gyrus, where quantitative electron microscopic analysis did not reveal changes in the ratio of CB(1)-positive GABAergic boutons, but uncovered robust reduction in the fraction of CB(1)-positive glutamatergic axon terminals. These findings show that a neuroprotective machinery involving endocannabinoids is impaired in epileptic human hippocampus and imply that downregulation of CB(1) receptors and related molecular components of the endocannabinoid system may facilitate the deleterious effects of increased network excitability.
authors: Institute of Experimental Medicine, Hungarian Academy of Sciences, H-1083 Budapest, Hungary.
authors: Anikó
authors: A
authors: Ludányi
authors: Loránd
authors: L
authors: Eross
authors: Sándor
authors: S
authors: Czirják
authors: János
authors: J
authors: Vajda
authors: Péter
authors: P
authors: Halász
authors: Masahiko
authors: M
authors: Watanabe
authors: Miklós
authors: M
authors: Palkovits
authors: Zsófia
authors: Z
authors: Maglóczky
authors: Tamás F
authors: TF
authors: Freund
authors: István
authors: I
authors: Katona
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D063385:Cannabinoid Receptor Modulators / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D016022:Case-Control Studies; D015536:Down-Regulation / Q000502:physiology*; D063388:Endocannabinoids; D004833:Epilepsy, Temporal Lobe / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006624:Hippocampus / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D060588:LIM Domain Proteins; D008297:Male; D016253:Microscopy, Immunoelectron / Q000379:methods; D008875:Middle Aged; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D011180:Postmortem Changes; D012333:RNA, Messenger / Q000378:metabolism; D043884:Receptor, Cannabinoid, CB1 / Q000235:genetics / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: C486181:CRIP1 protein, human; D063385:Cannabinoid Receptor Modulators; D002352:Carrier Proteins; D063388:Endocannabinoids; D060588:LIM Domain Proteins; D012333:RNA, Messenger; D043884:Receptor, Cannabinoid, CB1; D005680:gamma-Aminobutyric Acid