Cognitive improvement via cortical cannabinoid receptors and choline-containing lipids.

Abstract

Recent research linking choline-containing lipids to degeneration of basal forebrain cholinergic neurons in neuropathological states illustrates the challenge of balancing lipid integrity with optimal acetylcholine levels, essential for memory preservation. The endocannabinoid system influences learning and memory processes regulated by cholinergic neurotransmission. Therefore, we hypothesised that activation of the endocannabinoid system may confer neuroprotection against cholinergic degeneration. We examined the neuroprotective potential of sub-chronic treatments with the cannabinoid agonist WIN55,212-2, using ex vivo organotypic tissue cultures including nucleus basalis magnocellularis and cortex and in vivo rat models of specific cholinergic damage induced by 192IgG-saporin. Levels of lipids, choline and acetylcholine were measured with histochemical and immunofluorescence assays, along with [35S]GTPγS autoradiography of cannabinoid and muscarinic GPCRs and MALDI-mass spectrometry imaging analysis. Learning and memory were assessed by the Barnes maze and the novel object recognition test in rats and in the 3xTg-AD mouse model. Degeneration, induced by 192IgG-saporin, of baso-cortical cholinergic pathways resulted in memory deficits and decreased cortical levels of lysophosphatidylcholines (LPC). WIN55,212-2 restored cortical cholinergic transmission and LPC levels via activation of cannabinoid receptors. This activation altered cortical lipid homeostasis mainly by reducing sphingomyelins in lesioned animals. These modifications were crucial for memory recovery. We hypothesise that WIN55,212-2 facilitates an alternative choline source by breaking down sphingomyelins, leading to elevated cortical acetylcholine levels and LPCs. These results imply that altering choline-containing lipids via activation of cannabinoid receptors presents a promising therapeutic approach for dementia linked to cholinergic dysfunction.