Myeloid cannabinoid receptor CB1 deficiency confers atheroprotection in a sex-specific manner

Abstract Aim Cardiovascular diseases (CVDs) are the leading cause of death globally, claiming an estimated 17.9 million lives each year. A better understanding of the underlying chronic inflammatory disease mechanisms in atherosclerosis might help finding novel treatments and reduce CVD deaths. In particular, the cannabinoid receptor CB1 has been implicated in atherosclerosis, while its cell-specific effects in this disease are not well understood. Methods Myeloid Cnr1 (CB1 encoding gene) knockout mice were generated on apolipoprotein E deficiency (Apoe-/-) background by crossing CB1flox mice with transgenic mice carrying Cre under control of the lysozyme M (LysM) promoter for selective expression in myeloid cells. Age - and sex-matched groups were analyzed at baseline, 4 and 16 weeks Western diet (0,15% cholesterol). For in vitro experiments, murine bone marrow-derived macrophages (BMDM) were used. Results Male mice with myeloid-specific Cnr1 deficiency on atherogenic background developed smaller lesions and necrotic cores compared to controls, while only minor effects in females were observed. Male Cnr1 deficient mice had reduced arterial monocyte recruitment and macrophage proliferation with less inflammatory phenotype. The sex-specific differences were reproducible in vitro in BMDMs and blunted by female hormone estradiol treatment. Array-based kinase activity profiling of BMDMs stimulated with a synthetic CB1 agonist revealed a CB1-dependent regulation of p53 and cyclin-dependent kinases. Transcriptomic profiling via bulk RNA-sequencing of CB1 agonist-stimulated BMDMs further unveiled chromatin modifications, mRNA processing and mitochondrial respiration among the key processes affected by CB1 signaling, which was supported by metabolic flux assays. Chronic administration of the peripherally-restricted CB1 antagonist JD5037 inhibited plaque progression and macrophage proliferation, again only in male mice. Conclusion Impaired CB1 signaling in macrophages is atheroprotective by limiting their arterial recruitment, proliferation and inflammatory reprogramming. The biological effects of macrophage CB1 signaling seem to be more pronounced in male mice. This highlights the need to consider the biological sex as an important variable in preclinical studies.