CCL2 and atrial fibrillation: In another study, Wiet et al. found that healthy AF conditioned medium obtained from AF cultures could inhibit mast cell activation by downregulating its expression of vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF)-α, interleukin (IL)-1β and chemokine (C-C motif) ligand 2 (CCL2/MCP-1), and inhibit mast cell induced angiogenesis 26.