MAPK8 and atrial fibrillation: Our findings revealed that phosphorylation of p38 MAPK appeared after 60 min of AOPPs stimulation, while ERK phosphorylation appeared 5 min after AOPPs stimulation, and JNK phosphorylation similarly began to rise 5 min after AOPPs stimulation, while AF cells stimulated with RSA for 60 min showed a slight rise in JNK phosphorylation (Figs. 5A, 5B and 5C).