MAPK8 and atrial fibrillation: In order to evaluate whether AF affects MAPK phosphorylation in LPS-treated RAW 264.7 macrophages, cells were pre-treated with AF prior to LPS stimulation and the phosphorylation of MAPKs p38, ERK, and JNK was analyzed As shown in Fig 6, AF showed no effect on the total expression level of p38, ERK, or JNK, but it specifically decreased the expression level of p-ERK in LPS-stimulated RAW264.7 cells; in other words, AF showed a preference for p-ERK, without affecting p-JNK or p-p38.