Broad impact of deleting endogenous cannabinoid hydrolyzing enzymes and the CB1 cannabinoid receptor on the endogenous cannabinoid-related lipidome in eight regions of the mouse brain

Abstract

Background and purpose The enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) hydrolyze endogenous cannabinoids (eCBs), N-arachidonoyl ethanolamine (AEA) and 2-arachidonoyl glycerol (2-AG), respectively. These enzymes also metabolize eCB analogs such as lipoamines and 2-acyl glycerols, most of which are not ligands at CB1. To test the hypothesis that deleting eCB hydrolyzing enzymes and CB1 shifts lipid metabolism more broadly and impacts more families of eCB structural analogs, targeted lipidomics analyses were performed on FAAH KO, MAGL KO, and CB1 KO mice and compared to WT controls in 8 brain regions. Experimental approach Methanolic extracts of discrete brain regions (brainstem, cerebellum, cortex, hippocampus, hypothalamus, midbrain, striatum and thalamus) were partially purified on C-18 solid-phase extraction columns. Over 70 lipids per sample were then analyzed with HPLC/MS/MS. Key results AEA and 2-AG were unaffected throughout the brain in CB1 KO mice; however, there was an increase in the arachidonic acid (AA) metabolite, PGE2 in the majority of brain areas. By contrast, PGE2 and AA levels were significantly reduced throughout the brain in the MAGL KO corresponding to significant increases in 2-AG. No changes in AA or PGE2 were seen throughout in the FAAH KO brain, despite significant increases in AEA, suggesting AA liberated by FAAH does not contribute to steady state levels of AA or PGE2. Changes in the lipidome were not confined to the AA derivatives and showed regional variation in each of the eCB KO models. Conclusions and implications AEA and 2-AG hydrolyzing enzymes and the CB1 receptor link the eCB system to broader lipid signaling networks in contrasting ways, potentially altering neurotransmission and behavior independently of cannabinoid receptor signaling.

Positive Allosteric Modulation of Cannabinoid Receptor Type 1 Suppresses Pathological Pain Without Producing Tolerance or Dependence

“…By contrast, lipoxin A4 preferentially enhances anandamide but not 2-AG signaling(28). However, FAAH and MGL also degrade lipid mediators that do not bind to cannabinoid receptors(8, 12, 44). Sustained inhibition of MGL does not desensitize CB1 receptors in brain regions relevant to catalepsy (i.e.…”

“…Inhibitors of fatty-acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL), the major enzymes degrading anandamide and 2-AG, respectively, suppress pain in rodent models of traumatic nerve injury, toxic neuropathy(8, 9) and hyperglycemia(10) with efficacy comparable to or surpassing conventional treatments(9). However, FAAH and MGL degrade other lipids that do not bind to cannabinoid receptors(11, 12). Moreover, MGL inhibition can produce tolerance and CB1-dependent withdrawal (13, 14).…”

The monoacylglycerol lipase inhibitor KML29 with gabapentin synergistically produces analgesia in mice

“…Lipid extraction was performed on frozen spinal cord tissue as previously described (Leishman et al, ). In brief, frozen tissue underwent mechanical, methanolic extraction in the presence of deuterated standards, then partial purification on C18 columns (Agilent Technologies, Santa Clara, CA, USA).…”

Proteomics and Lipidomics in the Elucidation of Endocannabinoid Signaling in Healthy and Schizophrenia Brains

“…MAGL activity was lowest in the cerebellum, while the activity of DAGL‐α in that region was higher compared to the other regions, and FAAH was found to have the highest activity in the hippocampus and frontal cortex . Together, these findings point to the variability in the expression of endocannabinoid enzymes across different brain regions …”

“…Moreover, NAPE‐PLD‐knockout mice show lower levels of anandamide and other NAEs, such as prostaglandins . Thus, dysregulation of NAPE‐PLD may affect the brain through inflammatory processes .…”