TGFB1 and renal fibrosis: Furthermore, inhibition of ER stress by 4-PBA reduced the activity of the main element of renal fibrosis: transforming growth factor-beta (TGF-β), in addition to the chemical chaperone mimicking an ER chaperone in the kidneys and significantly reducing GRP78, important in its role in activation of transmembrane ER stress sensors and pro-apoptotic CHOP expression in a rat unilateral ureteral obstruction (UUO) model of renal fibrosis (Liu et al., 2016).