Simultaneous Inhibition of Glycolysis and Oxidative Phosphorylation Triggers a Multi-Fold Increase in Secretion of Exosomes: Possible Role of 2′3′-cAMP

Abstract

Exosome secretion by cells is a complex, poorly understood process. Studies of exosomes would be facilitated by a method for increasing their production and release. Here, we present a method for stimulating the secretion of exosomes. Cultured cells were treated or not with sodium iodoacetate (IAA; glycolysis inhibitor) plus 2,4-dinitrophenol (DNP; oxidative phosphorylation inhibitor). Exosomes were isolated by size-exclusion chromatography and their morphology, size, concentration, cargo components and functional activity were compared. IAA/DNP treatment (up to 10 µM each) was non-toxic and resulted in a 3 to 16-fold increase in exosome secretion. Exosomes from IAA/DNP-treated or untreated cells had similar biological properties and functional effects on endothelial cells (SVEC4-10). IAA/DNP increased exosome secretion from mouse organ cultures, and in vivo injections enhanced the levels of circulating exosomes. IAA/DNP decreased ATP levels (p < 0.05) in cells. A cell membrane-permeable form of 2′,3′-cAMP and 3′-AMP mimicked the potentiating effects of IAA/DNP on exosome secretion. In cells lacking 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase; an enzyme that metabolizes 2′,3′-cAMP into 2′- and 3′-AMP), effects of IAA/DNP on exosome secretion were enhanced. The IAA/DNP combination is a powerful stimulator of exosome secretion, and these stimulatory effects are, in part, mediated by intracellular 2′,3′-cAMP.