Elevation of endocannabinoids in the brain by synthetic cannabinoid JWH-018: mechanism and effect on learning and memory.

The impairment of learning and memory is a well-documented effect of both natural and synthetic cannabinoids. In the present study, we aimed to investigate the effect of acute administration of JWH-018, a synthetic cannabinoid, on the hippocampal metabolome to assess biochemical changes in vivo. JWH-018 elevated levels of the endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG). The increase of endocannabinoid levels in response to JWH-018 could be inhibited by co-administration of AM251, a CB1 receptor antagonist. Biochemical analyses revealed that this was the result of suppression of two hydrolases involved in endocannabinoid degradation (fatty acid amide hydrolase [FAAH] and monoacylglycerol lipase [MAGL]). Additionally, we showed that JWH-018 causes a reduction in the levels of brain-derived neurotrophic factor (BDNF), which is known to modulate synaptic plasticity and adaptive processes underlying learning and memory. The decrease of BDNF following JWH-018 treatment was also rescued by co-administration of AM251. As both endocannabinoids and BDNF have been shown to modulate learning and memory in the hippocampus, the alteration of their levels in response to JWH-018 may explain the contribution of synthetic cannabinoids to impairment of memory.

Characterization of a major secretory protein in the cane toad (Bufo marinus) choroid plexus as an amphibian lipocalin-type prostaglandin D synthase.

Here we report the enzymatic and ligand-binding properties of a major secretory protein in the choroid plexus of cane toad, Bufo marinus, whose protein is homologous with lipocalin-type prostaglandin (PG) D synthase (L-PGDS) and is recombinantly expressed in Xenopus A6 cells and Escherichia coli. The toad protein bound all-trans retinal, bile pigment, and thyroid hormones with high affinities (K(d)=0.17 to 2.00 microM). The toad protein also catalysed the L-PGDS activity, which was accelerated in the presence of GSH or DTT, similar to the mammalian enzyme. The K(m) value for PGH(2) (17 microM) of the toad protein was almost the same as that of rat L-PGDS (14 microM), whereas the turnover number (6 min(-1)) was approximately 28 fold lower than that of rat L-PGDS. Site-directed mutagenesis based on a modeled structure of the toad protein revealed that Cys(59) and Thr(61) residues were crucial for the PGDS activity. The quadruple Gly(39)Ser/Ala(75)Ser/Ser(140)Thr/Phe(142)Tyr mutant of the toad protein, resembling mouse L-PGDS, showed a 1.6 fold increase in the turnover number and a shift in the optimum pH for the PGDS activity from 9.0 to 8.5. Our results suggest that the toad protein is a prototype of L-PGDS with a highly functional ligand-binding pocket and yet with a primitive catalytic pocket.

First determination of the inhibitor complex structure of human hematopoietic prostaglandin D synthase.

Hematopoietic prostaglandin (PG) D synthase (H-PGDS) is responsible for the production of PGD(2) as an allergy or inflammation mediator in mast and Th2 cells. We determined the X-ray structure of human H-PGDS complexed with an inhibitor, 2-(2'-benzothiazolyl)-5-styryl-3-(4'-phthalhydrazidyl) tetrazolium chloride (BSPT) at 1.9 A resolution in the presence of Mg(2+). The styryl group of the inhibitor penetrated to the bottom of the active site cleft, and the tetrazole ring was stabilized by the stacking interaction with Trp104, inducing large movement around the alpha5-helix, which caused the space group of the complex crystal to change from P2(1) to P1 upon binding of BSPT. The phthalhydrazidyl group of BSPT exhibited steric hindrance due to the cofactor, glutathione (GSH), increasing the IC(50) value of BSPT for human H-PGDS from 36.2 micro M to 98.1 micro M upon binding of Mg(2+), because the K(m) value of GSH for human H-PGDS was decreased from 0.60 micro M in the presence of EDTA to 0.14 micro M in the presence of Mg(2+). We have to avoid steric hindrance of the GSH molecule that was stabilized by intracellular Mg(2+) in the mM range in the cytosol for further development of structure-based anti-allergic drugs.