TNF and atrial fibrillation: Next, to investigate further the involvement of MAPKs, we cultured H2O2-treated or BSO-treated AF cells with MAPK signaling inhibitors, including p38 inhibitor (SB203580), JNK inhibitor (SP600125), and ERK inhibitor (PD98059), and assessed the mRNA expression of COX-2, TNFα, and MMP-3 by real time RT-PCR analysis.