Rottlerin impairs the formation and maintenance of psychostimulant-supported memory.

RATIONALE AND OBJECTIVE: Since brain proteins such as protein kinase C (PKC), brain-derived neurotrophic factor (BDNF), and mammalian target of rapamycin (mTOR) are involved in the establishment and maintenance of psychostimulant memory, we sought to determine if systemic treatment with rottlerin, a natural compound affecting all these proteins, may modulate stimulant-supported memory. MATERIALS AND METHODS: Stimulant-induced conditioned place preference (CPP) was used in modeling stimulant-supported memory. RESULTS: Three cocaine (10 mg/kg; COC) or three methamphetamine (1 mg/kg; MA) conditioning trials reliably established the drug-induced CPP in male C57BL/6 mice. An intra-peritoneal rottlerin injection (5 mg/kg) at least 24 h prior to the first COC or first MA conditioning trial prevented the establishment of CPP. Following the establishment of the COC- or MA-induced CPP, saline conditioning trial was used to extinguish the CPP. Rottlerin (5 mg/kg, intra-peritoneal (i.p.)) administered 20 h prior to the first saline conditioning trial diminished subsequent drug- and stressor-primed reinstatement of the extinguished CPP. Rottlerin (5 mg/kg, i.p.) produced a fast-onset and long-lasting increase in hippocampal BDNF levels. However, treatment with a BDNF tropomyosin receptor kinase B (TrkB) receptor antagonist, K252a (5 µg/kg), did not affect rottlerin's suppressing effect on COC-induced CPP and treatment with 7,8-dihydroxyflavone (10 mg/kg x 6, 7,8-DHF), a selective TrkB agonist, prior to each conditioning trial did not affect COC-induced CPP. CONCLUSION: These results suggest that systemic rottlerin treatment may impair the formation of COC- and MA-supported memory. Importantly, such a treatment may advance our understanding of the underlying mechanism through which extinction training resulted in the "forgetting" of the COC- and MA-supported memory.

N-arachidonoyl glycine, an abundant endogenous lipid, potently drives directed cellular migration through GPR18, the putative abnormal cannabidiol receptor.

BACKGROUND: Microglia provide continuous immune surveillance of the CNS and upon activation rapidly change phenotype to express receptors that respond to chemoattractants during CNS damage or infection. These activated microglia undergo directed migration towards affected tissue. Importantly, the molecular species of chemoattractant encountered determines if microglia respond with pro- or anti-inflammatory behaviour, yet the signaling molecules that trigger migration remain poorly understood. The endogenous cannabinoid system regulates microglial migration via CB2 receptors and an as yet unidentified GPCR termed the 'abnormal cannabidiol' (Abn-CBD) receptor. Abn-CBD is a synthetic isomer of the phytocannabinoid cannabidiol (CBD) and is inactive at CB1 or CB2 receptors, but functions as a selective agonist at this Gi/o-coupled GPCR. N-arachidonoyl glycine (NAGly) is an endogenous metabolite of the endocannabinoid anandamide and acts as an efficacious agonist at GPR18. Here, we investigate the relationship between NAGly, Abn-CBD, the unidentified 'Abn-CBD' receptor, GPR18, and BV-2 microglial migration. RESULTS: Using Boyden chamber migration experiments, yellow tetrazolium (MTT) conversion, In-cell Western, qPCR and immunocytochemistry we show that NAGly, at sub-nanomolar concentrations, and Abn-CBD potently drive cellular migration in both BV-2 microglia and HEK293-GPR18 transfected cells, but neither induce migration in HEK-GPR55 or non-transfected HEK293 wildtype cells. Migration effects are blocked or attenuated in both systems by the 'Abn-CBD' receptor antagonist O-1918, and low efficacy agonists N-arachidonoyl-serine and cannabidiol. NAGly promotes proliferation and activation of MAP kinases in BV-2 microglia and HEK293-GPR18 cells at low nanomolar concentrations - cellular responses correlated with microglial migration. Additionally, BV-2 cells show GPR18 immunocytochemical staining and abundant GPR18 mRNA. qPCR demonstrates that primary microglia, likewise, express abundant amounts of GPR18 mRNA. CONCLUSIONS: NAGly is the most effective lipid recruiter of BV-2 microglia currently reported and its effects mimic those of Abn-CBD. The data generated from this study supports the hypothesis that GPR18 is the previously unidentified 'Abn-CBD' receptor. The marked potency of NAGly acting on GPR18 to elicit directed migration, proliferation and perhaps other MAPK-dependent phenomena advances our understanding of the lipid-based signaling mechanisms employed by the CNS to actively recruit microglia to sites of interest. It offers a novel research avenue for developing therapeutics to elicit a self-renewing population of neuroregenerative microglia, or alternatively, to prevent the accumulation of misdirected, pro-inflammatory microglia which contribute to and exacerbate neurodegenerative disease.

Novel endogenous N-acyl glycines identification and characterization.

Discovery of the endogenous cannabinoid and N-acyl amide, anandamide (N-arachidonoyl ethanolamine), paved the way for lipidomics discoveries in the growing family of N-acyl amides. Lipidomics is a field that is broadening our view of the molecular world to include a wide variety of endogenous lipid signaling molecules. Many of these lipids will undoubtedly provide new insights into old questions while others will provide broad platforms for new questions. J Michael Walker's last 8 years were dedicated to this search and he lived long enough to see 54 novel lipids isolated from biological tissues in his laboratory. Here, we summarize the biosynthesis, metabolism and biological activity of two of the family of N-acyl glycines, N-arachidonoyl glycine and N-palmitoyl glycine, and introduce four additional members: N-stearoyl glycine, N-linoleoyl glycine, N-oleoyl glycine, and N-docosahexaenoyl glycine. Each of these compounds is found throughout the body at differing levels suggesting region-specific functionality and at least four of the N-acyl glycines are regulated by the enzyme fatty acid amide hydrolase. The family of N-acyl glycines presented here is merely a sampling of what is to come in the continuing discovery of novel endogenous lipids.