Cannabinoid CB1Receptors Are Localized in Striated Muscle Mitochondria and Regulate Mitochondrial Respiration.
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, CB1is mainly localized on presynaptic axon terminals but is also found on mitochondria (mtCB1), where it regulates cellular respiration and energy production. Likewise, CB1is 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 mtCB1in three different striated muscles. Immunoelectron microscopy for CB1was used in skeletal muscles (gastrocnemius and rectus abdominis) and myocardium from wild-type andCB1-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 CB1immunoparticles was about 60% in the gastrocnemius, 55% in the rectus abdominis and 78% in the myocardium. Importantly, the CB1immunolabeling pattern disappeared in muscles ofCB1-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 fromCB1-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 ofCB1-WT andCB1-KO.CB1-KO showed an increase in the gene expression ofEno3, Pkm2, andPdha1, suggesting an increased production of pyruvate. In contrast, no significant difference was observed in theSdhaandCox4i1expression, betweenCB1-WT andCB1-KO. In conclusion, CB1receptors in skeletal and myocardial muscles are predominantly localized in mitochondria. The activation of mtCB1receptors 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.
Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque CountryLeioa, Spain; Achucarro Basque Center for Neuroscience, Bizkaia Science and Technology ParkZamudio, Spain.
Juan
J
Mendizabal-Zubiaga
Group "Endocannabinoids and Neuroadaptation," NeuroCentre Magendie, Institut National de La Santé et de La Recherche Médicale, U81215Bordeaux, France; Group "Endocannabinoids and Neuroadaptation," NeuroCentre Magendie, Université de BordeauxBordeaux, France.
Su
S
Melser
Group "Endocannabinoids and Neuroadaptation," NeuroCentre Magendie, Institut National de La Santé et de La Recherche Médicale, U81215Bordeaux, France; Group "Endocannabinoids and Neuroadaptation," NeuroCentre Magendie, Université de BordeauxBordeaux, France.
Giovanni
G
Bénard
Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque CountryLeioa, Spain; Achucarro Basque Center for Neuroscience, Bizkaia Science and Technology ParkZamudio, Spain.
Almudena
A
Ramos
Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque CountryLeioa, Spain; Achucarro Basque Center for Neuroscience, Bizkaia Science and Technology ParkZamudio, Spain.
Leire
L
Reguero
Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga, Hospital Regional Universitario de Málaga Málaga, Spain.
Sergio
S
Arrabal
Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque CountryLeioa, Spain; Achucarro Basque Center for Neuroscience, Bizkaia Science and Technology ParkZamudio, Spain.
Izaskun
I
Elezgarai
Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque CountryLeioa, Spain; Achucarro Basque Center for Neuroscience, Bizkaia Science and Technology ParkZamudio, Spain.
Inmaculada
I
Gerrikagoitia
Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga, Hospital Regional Universitario de Málaga Málaga, Spain.
Juan
J
Suarez
Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga, Hospital Regional Universitario de Málaga Málaga, Spain.
Fernando
F
Rodríguez De Fonseca
Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque CountryLeioa, Spain; Achucarro Basque Center for Neuroscience, Bizkaia Science and Technology ParkZamudio, Spain.
Nagore
N
Puente
Group "Endocannabinoids and Neuroadaptation," NeuroCentre Magendie, Institut National de La Santé et de La Recherche Médicale, U81215Bordeaux, France; Group "Endocannabinoids and Neuroadaptation," NeuroCentre Magendie, Université de BordeauxBordeaux, France.
Giovanni
G
Marsicano
Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque CountryLeioa, Spain; Achucarro Basque Center for Neuroscience, Bizkaia Science and Technology ParkZamudio, Spain; Division of Medical Sciences, University of VictoriaVictoria, BC, Canada.
Pedro
P
Grandes
endocannabinoid system; immunocytochemistry; intracellular receptors; metabolism; mitochondrial respiration; striated muscle