Hyperuricemia increases susceptibility to chronic kidney injury exacerbation via autophagic flux blockade-mediated ammonia death pathway

Schematic diagram illustrating how hyperuricemia exacerbates chronic kidney injury through an autophagy flux blockade-mediated ammonia-induced metabolic death pathway. MSU crystals and a hyperuricemic diet induce renal glutaminolysis disorder, leading to mitochondrial ammonia overload and damage. RHCG protein-mediated ammonia translocation into lysosomes causes lysosomal alkalinization and hydrolase inactivation. This results in accumulation of undigested autophagosomes and autolysosomes, impairing clearance of damaged mitochondria. Ultimately, metabolic waste accumulation and ATP depletion drive cell death. • Ammonia overload triggers lysosomal alkalinization in hyperuricemic nephropathy. • HN accelerates renal glutamine catabolism, generating excess ammonia. • Mitochondrial ammonia retention impairs autophagic flux and mitochondrial clearance. • Ammonia induced cell death mechanism was found in HN. Ammonia (NH 3 ), a core toxic byproduct of amino acid metabolism in the body, poses a severe threat to cell survival when its homeostasis is disrupted. Maintaining low systemic ammonia concentrations is crucial. Under physiological conditions, the kidneys regulate ammonia metabolism precisely through glutaminase (GLS1)- mediated ammonia production and the urea cycle, ensuring efficient detoxification. Hyperuricemic nephropathy (HN), a common complication of hyperuricemia, impairs patient health significantly. However, whether and how ammonia toxicity triggers cell death under this pathological condition remains unclear. Here, we demonstrated that HN promoted ammonia-dependent cell death by blocking autophagic flux, revealing a novel mechanism of HN injury. In vivo and in vitro models were used to evaluate the lysosome mitochondria damage and autophagic flux arrest mechanism caused by ammonia metabolism disorder through ultrastructural analysis, fluorescent probe and autophagic flux detection, and the causal association was verified by ammonia scavengers and gene intervention. Mechanistically, chronic hyperuricemic stress accelerates renal glutaminolysis to mitigate injury and generate sufficient ATP, resulting in excessive mitochondrial ammonia production. The ammonia accumulated undergoes RHCG-dependent transmembrane transport, causing lysosomal alkalinization and dysfunction, further resulting in mitochondrial ammonia retention and swelling. This ultimately inhibited autolysosomal disassembly, which impaired the clearance of damaged mitochondria and constitutes autophagic flux blockade, consequently driving cell death. These findings identified a distinct form of cell death in HN, mechanistically divergent from previously known mechanisms such as apoptosis or pyroptosis. It redefined HN pathogenesis through a metabolic lens, identifying druggable targets to mitigate renal damage in hyperuricemic patients.