Abstract
KEY POINTS: Gene deletions of Zbp1, Ripk3, and Mlkl reduced severity of oxalate-induced AKI. Mice with mutation or deletion in the Z-nucleic acid sensing domain (Zα) of Z-DNA binding protein 1 were protected from AKI. Z-DNA binding protein 1 sensed mitochondrial Z-DNA through its Zα domain, recruited receptor-interacting protein kinase 3 through receptor-interacting protein homotypic interaction motif, and activated mixed lineage kinase domain-like to induce necroptosis. BACKGROUND: Calcium oxalate–induced acute kidney injury is a severe condition in which the kidneys suffer rapid damage due to the deposition of oxalate crystals. Known factors contributing to cell death induced by calcium oxalate include receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) protein–dependent necroptosis, as well as necrosis involving peptidylprolyl isomerase F–mediated mitochondrial permeability transition. However, the detailed molecular mechanisms linking mitochondrial dysfunction to RIPK3 activation are not fully understood. METHODS: Mice with gene knockout of Zbp1, Ripk3, or Mlkl and mice with mutations in the Z-nucleic acid sensing domain of Z-DNA binding protein 1 (ZBP1) or deletion of Zα1 were used in an oxalate-induced AKI model. Proximal renal tubule cells were isolated and cultured for further investigation. Human oxalate nephropathy biopsy samples were analyzed. RESULTS: Specific gene deletions of Zbp1, Ripk3, or Mlkl in proximal renal tubules significantly reduced the severity of oxalate-induced AKI by preventing necroptosis and subsequent inflammation. Notably, mice with mutations in the Z-nucleic acid sensing domain of ZBP1 or deletion of Zα1 were protected from AKI. In cultured proximal tubular cells, calcium oxalate damaged mitochondria, accompanied by an increase in Bax and a decrease in BCL2 and transcription factor A, mitochondrial (TFAM), leading to the release of mitochondrial Z-DNA. ZBP1 sensed this mitochondrial Z-DNA and then recruited RIPK3 through the receptor-interacting protein homotypic interaction motifs, which in turn activated MLKL through RIPK3 phosphorylation, leading to necroptosis and contributing to AKI. CONCLUSIONS: ZBP1 plays a critical role in sensing mitochondrial Z-DNA and initiating RIPK3/MLKL-mediated necroptosis, contributing to the development of oxalate-induced AKI.