XBP1 and acute kidney injury: XBP1 expression is remarkably high in various disorders, especially in the context of an activated UPR;33 for example, in renal disease progression,32  XBP1 activation is closely associated with the pathogenesis of kidney injury and with the transition from acute kidney injury to chronic kidney disease, which is marked by the up-regulation of fibrosis-associated genes and deposition of extracellular matrix.