Early loss of glutathione ‐s‐ transferase (GST) activity during diverse forms of acute renal tubular injury

• Published in: Physiological reports Vol. 10; no. 12; pp. e15352 - n/a
• Main Authors: Zager, Richard A., Johnson, Ali C. M.
• Format: Journal Article
• Language: English
• Published: Oxford John Wiley & Sons, Inc 01.06.2022; John Wiley and Sons Inc; Wiley
• Subjects: Abdomen; acute kidney injury; Animal models; Arachidonic acid; Cisplatin; Creatinine; Detoxification; Endotoxemia; Excretion; Fatty acids; Gene expression; Glutathione; Glycerol; GST inhibitors; GST isotypes; Ischemia; Isotypes; Kidneys; Original; oxidant stress; Oxidative stress; Physiology; Plasma; Protein folding; Proteins; Proteolysis; Reactive oxygen species; Reperfusion; Urine; Xenobiotics
• ISSN: 2051-817X
• DOI: 10.14814/phy2.15352

Glutathione‐S‐transferases (GSTs) are a diverse group of phase II detoxification enzymes which primarily evoke tissue protection via glutathione conjugation to xenobiotics and reactive oxygen species. Given their cytoprotective properties, potential changes in GST expression during AKI has pathophysiologic relevance. Hence, we evaluated total GST activity, and the mRNA responses of nine cytosolic GST isotypes (GST alpha1, kappa1, mu1/5, omega1, pi1 sigma1, theta1, zeta1 mRNAs), in five diverse mouse models of AKI (glycerol, ischemia/reperfusion; maleate, cisplatin, endotoxemia). Excepting endotoxemia, each AKI model significantly reduced GST activity (~35%) during both the AKI “initiation” (0‐4 h) and “maintenance” phases (18 or 72 h). During the AKI maintenance phase, increases in multiple GST mRNAs were observed. However, no improvement in GST activity resulted. Increased urinary GST excretion followed AKI induction. However, this could not explain the reduced renal GST activity given that it also fell in response to ex vivo renal ischemia (i.e., absent urinary excretion). GST alpha, a dominant proximal tubule GST isotype, manifested 5–10‐fold protein increases following AKI, arguing against GST proteolysis as the reason for the GST activity declines. Free fatty acids (FFAs) and lysophospholipids, which markedly accumulate during AKI, are known to bind to, and suppress, GST activity. Supporting this concept, arachidonic acid addition to renal cortical protein extracts caused rapid GST activity reductions. Based on these results, we conclude that diverse forms of AKI significantly reduce GST activity. This occurs despite increased GST transcription/translation and independent of urinary GST excretion. Injury‐induced generation of endogenous GST inhibitors, such as FFAs, appears to be a dominant cause. The paper demonstrates that an important 'self defense' group of anti‐oxidant enzymes, the glutathione‐S‐transferases (GSTs), have suppressed activity following diverse forms of AKI. Data are presented that this is due to enzyme inhibition which is induced by free fatty acids which markedly accumulate during AKI due to phospholipid hydrolysis and decreased mitochondrial consumption. Thus, this paper provides new insights into AKI pathogenesis.