Cannabinoid CB1 Receptors Are Localized in Striated Muscle Mitochondria and Regulate Mitochondrial Respiration

Abstract

The cannabinoid type 1 (CB1) receptor is widely distributed in the brain and peripheral organs where it regulates cellular functions and metabolism. In the brain, CB1 is mainly localized on presynaptic axon terminals but is also found on mitochondria (mtCB1), where it regulates cellular respiration and energy production. Likewise, CB1 is localized on muscle mitochondria, but very little is known about it. The aim of this study was to further investigate in detail the distribution and functional role of mtCB1 in three different striated muscles. Immunoelectron microscopy for CB1 was used in skeletal muscles (gastrocnemius and rectus abdominis) and myocardium from wild-type and CB1-KO mice. Functional assessments were performed in mitochondria purified from the heart of the mice and the mitochondrial oxygen consumption upon application of different acute delta-9-tetrahydrocannabinol (Δ9-THC) concentrations (100 nM or 200 nM) was monitored. About 26% of the mitochondrial profiles in gastrocnemius, 22% in the rectus abdominis and 17% in the myocardium expressed CB1. Furthermore, the proportion of mtCB1 versus total CB1 immunoparticles was about 60% in the gastrocnemius, 55% in the rectus abdominis and 78% in the myocardium. Importantly, the CB1 immunolabeling pattern disappeared in muscles of CB1-KO mice. Functionally, acute 100 nM or 200 nM THC treatment specifically decreased mitochondria coupled respiration between 12 and 15% in wild-type isolated mitochondria of myocardial muscles but no significant difference was noticed between THC treated and vehicle in mitochondria isolated from CB1-KO heart. Furthermore, gene expression of key enzymes involved in pyruvate synthesis, tricarboxylic acid (TCA) cycle and mitochondrial respiratory chain was evaluated in the striated muscle of CB1-WT and CB1-KO. CB1-KO showed an increase in the gene expression of Eno3, Pkm2, and Pdha1, suggesting an increased production of pyruvate. In contrast, no significant difference was observed in the Sdha and Cox4i1 expression, between CB1-WT and CB1-KO. In conclusion, CB1 receptors in skeletal and myocardial muscles are predominantly localized in mitochondria. The activation of mtCB1 receptors may participate in the mitochondrial regulation of the oxidative activity probably through the relevant enzymes implicated in the pyruvate metabolism, a main substrate for TCA activity.

Localization of the cannabinoid type‐1 receptor in subcellular astrocyte compartments of mutant mouse hippocampus

“…We estimated that 10%–15% of the total CB 1 receptor labeling in the hippocampus is localized at mitochondrial membranes (Bénard et al, ; Bonilla‐Del Río et al, ; Hebert‐Chatelain et al, ), and this percentage is increased in muscle and heart (Mendizabal‐Zubiaga et al, ). Yet, about 22% of the mitochondrial sections in axon terminals and somatodendritic domains contain CB 1 receptors (Hebert‐Chatelain et al, a,b).…”

“…The endocannabinoid (eCB) system is composed of the seven‐transmembrane G protein coupled cannabinoid type‐1 (CB 1 ) receptor and other receptors (including CB 2 receptors), their endogenous lipid ligands (endocannabinoids) and the proteins involved in synthesis, transport and degradation of the endocannabinoids (Katona & Freund, ; Lutz, Marsicano, Maldonado, & Hillard, ; Pertwee, ; Piomelli, ). This system is widely distributed in the central and peripheral nervous system (Katona & Freund, ; Lu & Mackie, ), and also in peripheral organs (Piazza, Cota, & Marsicano, ), where the CB 1 receptors are also localized in mitochondria of striated and heart muscles (Mendizabal‐Zubiaga et al, ). The eCB system regulates brain functions by acting on different cell types and cellular compartments (Busquets‐Garcia, Bains, & Marsicano, ; Gutiérrez‐Rodríguez et al, ; Katona & Freund, ; Lu & Mackie, ).…”

“…The CB 1 receptor-mediated astrocyte functions are highly dependent on the CB 1 receptor distribution in astrocytes relative to close neuronal compartments, particularly at synapses (Bonilla-Del Río et al, 2017). However, the low CB 1 receptor expression in astrocytes (Bosier et al, 2013;Han et al, 2012;Kov acs et al, 2017;Rodriguez, Mackie, & Pickel, 2001) and mitochondria (B enard et al, 2012;Hebert-Chatelain et al, 2014a;2016) constrains a consolidated picture of the subcellular CB 1 receptor distribution in the astroglial compartments that holds the anatomical substrate for a functional interaction with the nearby synapses under normal or pathological conditions (Bonilla-Del Río et al, 2017). Yet, whether intracellular CB 1 receptors exist in astroglial mitochondria has remained unknown.…”

Cannabinoid‐1 receptor regulates mitochondrial dynamics and function in renal proximal tubular cells

“…In fact, 30% of neuronal mitochondria carry CB 1 Rs (mtCB 1 R), and both Δ 9 ‐THC and eCBs suppress electron transport complex I activity and respiration in isolated mitochondria, probably by reducing cAMP levels and PKA activity . Since this initial discovery, others have suggested the presence of CB 1 Rs in the mitochondria of different organs . Whether cannabinoids also modulate mitochondrial dynamics via a direct effect on mtCB 1 R in RPTCs remains to be determined, and we are currently conducting studies to elucidate this phenomenon.…”

THC Treatment Alters Glutamate Receptor Gene Expression in Human Stem Cell-Derived Neurons

“…Evidence from neuron subtype-specific deletions suggests that CB1R may have different functions and pharmacological properties in different cell types (reviewed in [17]) and that its subcellular localization may mediate distinct signaling [18,19]. Endocannabinoids play critical roles during fetal brain development, being involved in neuronal differentiation, survival and the regulation of neurotransmitter systems [20,21,22].…”