2-Arachidonoylglycerol

2-AG is produced on demand from arachidonic acid-containing phospholipids. The major pathway involves phospholipase C (PLC) cleaving phosphatidylinositol 4,5-bisphosphate to diacylglycerol (DAG), which is then converted to 2-AG by diacylglycerol lipase (DAGL) α and β.¹ Alternative routes include the hydrolysis of lysophosphatidylinositol by lyso-PLC. Degradation is primarily mediated by monoacylglycerol lipase (MAGL), which accounts for about 85% of 2-AG hydrolysis in the brain; the remaining activity is attributed to ABHD6 and ABHD12.² This rapid turnover allows precise temporal control of signaling.

2-AG acts as a retrograde messenger at synapses: postsynaptic neurons synthesize it upon depolarization, and it diffuses backward to activate presynaptic CB1 receptors, suppressing neurotransmitter release.³ This mechanism underlies forms of short-term and long-term synaptic plasticity, including depolarization-induced suppression of inhibition (DSI) and excitation (DSE). Beyond the nervous system, 2-AG modulates immune cell function, pain perception, and appetite. It also influences neuroinflammation and has been implicated in the pathophysiology of multiple sclerosis, epilepsy, and anxiety disorders.⁴

Because 2-AG is a full agonist at CB1 and CB2 receptors, its pharmacological manipulation holds therapeutic promise. Inhibitors of MAGL, such as JZL184, elevate endogenous 2-AG levels and produce analgesic, anxiolytic, and anti-inflammatory effects in animal models.⁵ Conversely, DAGL inhibitors reduce 2-AG production and have been explored for conditions like epilepsy and neuropathic pain. However, chronic MAGL inhibition leads to CB1 receptor desensitization and potential adverse effects, highlighting the need for balanced approaches. 2-AG itself is unstable and rapidly metabolized, limiting its direct use as a drug.

2-AG was first identified in the gut in 1995, but its role as a brain endocannabinoid was established later by Mechoulam's group.⁶ Unlike anandamide, 2-AG is a full agonist at both CB1 and CB2 receptors, and its brain concentrations are roughly 170-fold higher than anandamide's. 2-AG also serves as a precursor for prostaglandins via cyclooxygenase-2 (COX-2), linking endocannabinoid and eicosanoid pathways. In the immune system, 2-AG is produced by macrophages and platelets, influencing inflammation and thrombosis. Additionally, 2-AG has been detected in breast milk, suggesting a role in neonatal development.⁷

Endocannabinoid

An endogenous lipid that activates cannabinoid receptors.

CB1 receptor

A G protein-coupled receptor primarily expressed in the central nervous system.

CB2 receptor

A G protein-coupled receptor mainly found on immune cells.

Retrograde signaling

A process where a signal travels from the postsynaptic neuron back to the presynaptic terminal.

Monoacylglycerol lipase (MAGL)

The principal enzyme that degrades 2-AG.