Cannabidiol Impairs Glucagon Trafficking and Secretion Through the Lysosomal System in Murine αTC1-6 cells

Abstract

Glucagon secretion by pancreatic cells is regulated by nutrient, paracrine, and neural inputs, and emerging evidence suggests that the islet endocannabinoid system (ECS) may also regulate -cell function. While phytocannabinoids such as cannabidiol (CBD) have been shown to interact with the ECS, and negatively regulate insulin secretion from pancreatic {beta} cells, whether CBD alters cell function in ways that disrupt glucagon trafficking and secretion remains unclear. This study investigates how acute CBD exposure affects transcriptional and secretory networks governing cell function. Using the TC1-6 glucagon-secreting cell line, we exposed the cells to 0.3 and 3 M CBD for RT-qPCR analysis, 3 M CBD for bulk RNA sequencing, and 3 M CBD or its inactive metabolite 7-COOH-CBD for imaging and secretion experiments. Transcriptomic analysis revealed that treatment with CBD did not alter the expression of ECS receptors and enzymes. However, pathways involved in cellular excitability, peptide hormone trafficking, and secretion were significantly downregulated. Using confocal microscopy, we found that CBD exposure increased the colocalization of glucagon with LAMP1 (a lysosomal marker), and that CBD rerouted peripheral glucagon, and glucagon-containing lysosomes towards the intracellular region of the cell. In conjunction with these findings, we observed reduced glucose-stimulated glucagon secretion under high glucose conditions. Overall, our data supports a model in which acute CBD exposure downregulates processes governing cellular excitability and peptide secretion and negatively regulates glucagon trafficking and secretion by rerouting peripheral glucagon into lysosome-associated intracellular compartments in TC1-6 cells.