Adenine overload induces ferroptosis in human primary proximal tubular epithelial cells

  • Cell Death Dis. 2022 Feb 2;13(2):104. doi: 10.1038/s41419-022-04527-z.
Muhammad Ali Khan  1  2  3  4  5  6 ,  Purba Nag  3  4 ,  Anca Grivei  3  4 ,  Kurt T K Giuliani  2  3  4 ,  Xiangju Wang  3  4 ,  Vishal Diwan  1  7 ,  Wendy Hoy  1  7 ,  Helen Healy  1  3  4  7 ,  Glenda Gobe  1  2  5  7 ,  Andrew J Kassianos  8  9  10
Affiliations
  • 1. NHMRC CKD CRE (CKD.QLD), University of Queensland, Brisbane, Australia.
  • 2. School of Biomedical Sciences, Faculty of Medicine, University of Queensland, Brisbane, Australia.
  • 3. Conjoint Internal Medicine Laboratory, Chemical Pathology, Pathology Queensland, Brisbane, Australia.
  • 4. Kidney Health Service, Royal Brisbane and Women's Hospital, Brisbane, Australia.
  • 5. Kidney Disease Research Collaborative, Princess Alexandra Hospital and University of Queensland, Translational Research Institute, Brisbane, Australia.
  • 6. Department of Pharmacy, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj-8100, Dhaka, Bangladesh.
  • 7. Centre for Chronic Disease, Faculty of Medicine, University of Queensland, Brisbane, Australia.
  • 8. Conjoint Internal Medicine Laboratory, Chemical Pathology, Pathology Queensland, Brisbane, Australia. [email protected].
  • 9. Kidney Health Service, Royal Brisbane and Women's Hospital, Brisbane, Australia. [email protected].
  • 10. Centre for Chronic Disease, Faculty of Medicine, University of Queensland, Brisbane, Australia. [email protected].
PMID: 35110539 DOI: 10.1038/s41419-022-04527-z
Abstract

The pathogenesis of crystal nephropathy involves deposition of intratubular crystals, tubular obstruction and cell death. The deposition of 8-dihydroxyadenine (DHA) crystals within kidney tubules, for instance, is caused by a hereditary deficiency of adenine phosphoribosyl transferase in humans or adenine overload in preclinical models. However, the downstream pathobiological patterns of tubular cell attrition in adenine/DHA-induced nephropathy remain poorly understood. In this study, we investigated: (i) the modes of adenine-induced tubular cell death in an experimental rat model and in human primary proximal tubular epithelial cells (PTEC); and (ii) the therapeutic effect of the flavonoid baicalein as a novel cell death inhibitor. In a rat model of adenine diet-induced crystal nephropathy, significantly elevated levels of tubular iron deposition and lipid peroxidation (4-hydroxynonenal; 4-HNE) were detected. This phenotype is indicative of Ferroptosis, a novel form of regulated necrosis. In cultures of human primary PTEC, adenine overload-induced significantly increased mitochondrial superoxide levels, mitochondrial depolarisation, DNA damage and necrotic cell death compared with untreated PTEC. Molecular interrogation of adenine-stimulated PTEC revealed a significant reduction in the lipid repair enzyme Glutathione Peroxidase 4 (GPX4) and the significant increase in 4-HNE compared with untreated PTEC, supporting the concept of ferroptotic cell death. Moreover, baicalein treatment inhibited Ferroptosis in adenine-stimulated PTEC by selectively modulating the mitochondrial antioxidant enzyme superoxide dismutase 2 (SOD2) and thus, suppressing mitochondrial superoxide production and DNA damage. These data identify Ferroptosis as the primary pattern of PTEC necrosis in adenine-induced nephropathy and establish baicalein as a potential therapeutic tool for the clinical management of ferroptosis-associated crystal nephropathies (e.g., DHA nephropathy, oxalate nephropathy).

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