CB2 receptor-mediated effects of pro-inflammatory macrophages influence survival of cardiomyocytes

• Published in: Life sciences (1973) 2015-10, Vol.138, p.18-28
• Main Authors: Heinemann, Jan C., Duerr, Georg D., Keppel, Katharina, Breitbach, Martin, Fleischmann, Bernd K., Zimmer, Andreas, Wehner, Sven, Welz, Armin, Dewald, Oliver
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - genetics; Cannabinoid Receptor Agonists - pharmacology; Cardiomyocytes; CB2 receptor; Cell Movement - drug effects; Cell Survival - drug effects; Coculture Techniques; Endocannabinoids; Inflammation; Inflammation - pathology; Interferon-gamma - pharmacology; Macrophages; Macrophages - drug effects; Mice; Mice, Knockout; Myocytes, Cardiac - drug effects; Primary Cell Culture; Receptor, Cannabinoid, CB2 - drug effects; Receptor, Cannabinoid, CB2 - genetics; Tumor Necrosis Factor-alpha - biosynthesis
• ISSN: 0024-3205; 1879-0631
• DOI: 10.1016/j.lfs.2014.11.027

The endocannabinoid system and cannabinoid receptor 2 (CB2 receptor) have been associated with modulation of inflammatory response and myocardial adaptation after ischemic injury. In order to elucidate CB2 receptor-related effects during cellular interactions, we investigated cardiomyocyte survival and macrophage function in vitro. Murine embryonic (eCM) and adult (CM) cardiomyocytes, murine macrophages (MO), and their subtypes M1 (M1-MO) and M2 (M2-MO) were derived from wildtype- (WT) and CB2 receptor-deficient (Cnr2−/−) mice. Cells were cultured separately or in co-culture under normoxia or hypoxia (2% O2) and pro-inflammatory stimulation using interferon (IFN)γ. Besides immunohistochemistry, we also measured mRNA expression (Taqman®) and performed FACS-analysis of cardiomyocytes. Macrophage migration was assessed using Boyden chamber assay. We found a significant induction of CB2 receptor mRNA and protein in murine eCM as well as M1- and M2-MO in vitro following cultivation under hypoxia or stimulation with IFNγ. A significantly higher amount of apoptotic Cnr2−/−-CMs was found after incubation under hypoxia when compared to WT-CMs. We observed a significantly stronger migration potential in Cnr2−/−-M1-MOs towards the supernatant of apoptotic CM, than in corresponding WT-cells. Co-culture revealed a significantly higher loss of eCMs and induction of their apoptosis after cultivation with Cnr2−/−-M1-MOs. Production of TNF-α in M1-MOs was dependent on CB2 receptor stimulation by anandamide. Our data provide novel insights into CB2 receptor-mediated protection of cardiomyocytes during hypoxia and pro-inflammatory stimulation. We show CB2 receptor-dependent effects on migration and function of M1-MOs in interaction with cardiomyocytes, thereby influencing their survival.