CXCL8 and atrial fibrillation: In AF, the concentrations of MDK (approximately 2 ng/ml) and PTN (approximately 4.5 ng/ml) were substantially higher than the concentrations of other cytokines previously measured, including IL-6, IL-8, IL-10, IL-11, IL-15, TNF-α, TGF-β, and VEGF.