Epigenetic regulation of C-Kitlo FcɛR1a+ mast cells by cannabidiol during staphylococcal enterotoxin B-induced liver injury

Abstract

Abstract Although recent studies have established cannabidiol (CBD) as a potent anti-inflammatory agent, the mechanisms governing these processes remain unclear. Our previous research demonstrated that CBD treatment induced expansion of CD11b+Gr-1+MDSC in the peritoneum, which suppressed T cell functions leading to attenuation of staphylococcal enterotoxin B (SEB)-mediated liver inflammation in mice. Using the same model, we characterize the effects of CBD administration in the liver. Briefly, mice were injected intraperitoneally (I.P.) with 50mg/kg of CBD for 4 days (d), followed by SEB challenge on d 3. Flow cytometry analysis revealed a significant reduction in Vβ8+ CD8+ T cells. In agreement with our earlier findings, mice treated with CBD displayed robust expansion of Gr-1+ MDSC in the liver, which was primarily comprised of Ly6CHI MHCIILO leukocytes. As mast cells have been found to play a role in CBD-mediated induction of MDSC via increased peroxisome proliferator-activated receptor gamma (PPARγ) signaling, we examined changes to liver mast cell populations. We discovered two distinct subsets of mast cells, C-KithiFcɛR1a+ and C-Kitlo FcɛR1a+present in the liver. CBD treatment promoted expansion of the C-Kitlo FcɛR1a+ subset. Analysis by miRNA microarray displayed enrichment of miRNAs targeting mast cell growth factor, KIT ligand (KITLG), and significant downregulation of miR-217-5p, which is conserved for the co-activator of PPARγ (PPARγC1A). Increased gene expression of PPARγ was confirmed by single-cell RNA sequencing (sc-RNAseq). Taken together, our results identify CBD induced epigenetic reduction of C-Kit expression and KITLG signaling in mast cells to favor PPARγ signaling as a novel anti-inflammatory mechanism.