angiogenin and Acute-Kidney-Injury

The ribonuclease angiogenin is a component of the mammalian stress response that is secreted by renal epithelial cells on activation of the inositol-requiring enzyme 1α (IRE1α)-active spliced X-box binding protein 1 (sXBP1) axis and instrumental to the adaptation to AKI associated with endoplasmic reticulum stress. To determine whether the amount of angiogenin in urine of individuals with a kidney injury reflects the magnitude of the lesions and provides information on the risk of organ failure, we examined individuals referred for a kidney injury and determined the biochemical characteristics of urinary angiogenin and its diagnostic and prognostic values. Urinary angiogenin did not correlate with the urinary concentrations of high molecular weight proteins and correlated only weakly with low molecular weight proteins, suggestive of tubular production. In a cohort of 242 kidney transplant recipients with acute allograft dysfunction, higher urinary angiogenin concentrations at the time of the biopsy associated with worse renal function and higher proteinuria but did not correlate with histologic lesions as defined in the Banff classification. Kidney transplant recipients with urinary angiogenin amounts in the highest 50% had a risk of graft failure 3.59 times as high (95% confidence interval, 1.12 to 15.94) as that of patients with amounts in the lowest 50%. Finally, the amount of urinary angiogenin reflected the activity of the IRE1α-XBP1 axis in allografts. Our approach identified urinary angiogenin as a noninvasive indicator of the extent of tissue damage, independent of the histologic lesions, and a risk predictor of kidney allograft failure.

Topics: Acute Kidney Injury; Female; Humans; Male; Middle Aged; Ribonuclease, Pancreatic; Severity of Illness Index

Endoplasmic reticulum (ER) stress is involved in the pathophysiology of kidney disease and aging, but the molecular bases underlying the biologic outcomes on the evolution of renal disease remain mostly unknown. Angiogenin (ANG) is a ribonuclease that promotes cellular adaptation under stress but its contribution to ER stress signaling remains elusive. In this study, we investigated the ANG-mediated contribution to the signaling and biologic outcomes of ER stress in kidney injury. ANG expression was significantly higher in samples from injured human kidneys than in samples from normal human kidneys, and in mouse and rat kidneys, ANG expression was specifically induced under ER stress. In human renal epithelial cells, ER stress induced ANG expression in a manner dependent on the activity of transcription factor XBP1, and ANG promoted cellular adaptation to ER stress through induction of stress granules and inhibition of translation. Moreover, the severity of renal lesions induced by ER stress was dramatically greater in ANG knockout mice (Ang(-/-)) mice than in wild-type mice. These results indicate that ANG is a critical mediator of tissue adaptation to kidney injury and reveal a physiologically relevant ER stress-mediated adaptive translational control mechanism.

Topics: Acute Kidney Injury; Adaptation, Physiological; Animals; Apoptosis; Cells, Cultured; DNA-Binding Proteins; Endoplasmic Reticulum Stress; Endoribonucleases; Epithelial Cells; Gene Silencing; Humans; Kidney; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Poly(ADP-ribose) Polymerases; Protein Biosynthesis; Protein Serine-Threonine Kinases; Rats; Rats, Sprague-Dawley; Regulatory Factor X Transcription Factors; Ribonuclease, Pancreatic; Signal Transduction; Transcription Factors; Transcription, Genetic; Tunicamycin; X-Box Binding Protein 1