Through the α1A adrenoceptor/p38/Smad3 signaling pathway, sympathetic overactivity promotes epithelial–mesenchymal transition (EMT) in renal epithelial cells and fibrosis, whereas α1A adrenoceptor inhibition may receive attention in the future owing to its potential effectiveness for the treatment of renal fibrosis [52]. Here, SMAD3 is linked to renal fibrosis.