SMAD2 and atrial fibrillation: Ang II infusion activates several signaling pathways including AKT/mTOR, TGF-β/Smad2/3, and NF-κB through Ang II type receptor (AT1R), causing hypertrophy, fibrosis, inflammation, and oxidative stress, finally leading to cardiac hypertrophy and AF (Li et al., 2018; Cao et al., 2019).