AA-I = aristolochic acid I; AAN = aristolochic acid nephropathy; CKD = chronic kidney disease; Col = collagen; ECM = extracellular matrix; EMT = epithelial-mesenchymal transition; IS = indoxyl sulfate; PCS = p-cresyl sulfate; PE = propolis extract; SMA = smooth muscle actin; TGF-β = transforming growth factor-β; TIF = tubulointerstitial fibrosis. The gene discussed is TGFB1; the disease is Balkan nephropathy.