The endocannabinoid 2-arachidonoylglicerol decreases calcium induced cytochrome c release from liver mitochondria

Abstract

2-Arachidonoylglicerol (2-AG) is an endocannabinoid that mimics the pharmacological effects of Δ⁹ tetrahydrocannabinol, the psychoactive component of the plant Cannabis sativa. It is present in many mammalian tissues, such as brain, liver, spleen, heart and kidney, where it exerts different biological effects either receptor mediated or independently of receptor activation. This work analyzes the effects of 2-AG on liver mitochondrial functions. It is shown that 2-AG causes a relevant decrease of calcium induced cyclosporine A sensitive cytochrome c release from mitochondria, a process representing an early event of the apoptotic program. Cyclosporin sensitive matrix swelling and ROS production measured under the same conditions are, on the contrary, almost unaffected or even enhanced, respectively, by 2-AG. Furthemore, 2-AG is found to stimulate resting state succinate oxidase activity and to inhibit oligomycin sensitive F₀F₁ ATP synthase activity. All these effects are apparently associated with 2-AG dependent alteration in the fluidity of the mitochondrial membranes, which was measured as generalized polarization of laurdan fluorescence.

The endocannabinoid system in guarding against fear, anxiety and stress

“…Mitochondria, which are the main cellular ‘power plants’ producing the large majority of ATP, are therefore crucial for efficient brain function, including the regulation of mood and anxiety 142 . The ability of cannabinoids to control mitochondrial activity was first reported in the 1970s 143 and is now thought to be a potentially important way in which eCBs influence cellular and brain functions 144,145 . Recently, the presence of functional CB1R at mitochondrial membranes was demonstrated by different groups 146,147 (see REFS 148,149 for methodological discussions).…”

Mitochondria: a possible nexus for the regulation of energy homeostasis by the endocannabinoid system?

“…In contrast, AEA has been shown to reduce intracellular calcium concentrations by suppressing Na ϩ /Ca 2ϩ exchanger current in rat cardiac myocytes (74). Interestingly, AEA and 2-AG have also been reported to reduce Ca 2ϩ dependent release of cytochrome c, a mobile electron transport protein, which, when released from mitochondria, can result in mitochondrial swelling and caspase-dependent apoptosis (20,159). It is important to note that a functional distinction may exist between the effects of more subtle increases in intracellular calcium that can promote improvements in mitochondrial respiratory activity, in contrast to mitochondrial calcium overload, which has been reported to reduce mitochondrial electron flow and augment mitochondrial dysfunction (130).…”

“…Citations refer to studies performed using the compounds listed in order to elucidate the role of the endocannabinoid system in regulating energy metabolism and/or mitochondrial function. cells and/or isolated mitochondria to cannabinoid receptor ligands has been shown to convey deleterious effects on mitochondrial integrity, oxidative phosphorylation, and ATP production (4,122,123,159). For example, studies performed in isolated rat liver mitochondria show that both AEA and 2-AG inhibit ATP synthesis at the level of F 0 /F 1 ATP synthase when applied at low micromolar concentrations (4,158,159).…”

“…cells and/or isolated mitochondria to cannabinoid receptor ligands has been shown to convey deleterious effects on mitochondrial integrity, oxidative phosphorylation, and ATP production (4,122,123,159). For example, studies performed in isolated rat liver mitochondria show that both AEA and 2-AG inhibit ATP synthesis at the level of F 0 /F 1 ATP synthase when applied at low micromolar concentrations (4,158,159). In addition, the Cannabis sativa (marijuana)-derived cannabinoid ⌬9-THC, and the synthetic cannabinoid HU210 (a mixed CB1R/CB2R agonist), have also been shown to impair mitochondrial respiratory function by reducing oxygen consumption and mitochondrial membrane potential (4).…”

“…However, whether ROS derived from mitochondria or from an alternative subcellular source is responsible for perturbing mitochondrial respiratory function by the ECS remains unclear. In addition, insulin resistance has also been associated with an increase in mitochondrial ROS emission, but whether this occurs as a result of enhanced ECS activity remains unknown, although, somewhat paradoxically, ECS stimulation has been shown to decrease proton motive force in mitochondria (4,59,95,158,159). Indeed, it may be the case that the combined effect of enhanced ROS production alongside increased ceramide generation and/or calcium overload may collectively contribute toward an overall reduction in mitochondrial oxidative capacity and/or insulin sensitivity in response to ECS hyperactivation (18,130).…”