XBP1 and acute kidney injury: Perturbations of kidney cells in AKI resulted in the accumulation of unfolded and misfolded proteins in the ER, leading to UPR or ER stress.27 Firstly, we evaluated ER stress in kidney tissues by the expression of three UPR‐related proteins, XBP1, p‐PERK and ATF4, which were highly expressed in cisplatin‐injured kidney tissues by immunofluorescence staining.