Dual Pathogenic Mechanisms in Lysinuric Protein Intolerance: Interplay Between Hyperammonemia and Cellular Metabolic Dysregulation in Astrocyte Injury.

BACKGROUND:Lysinuric protein intolerance (LPI) is a rare genetic disorder characterized by an inherited defect in cationic amino acid transport caused by pathogenic variants in the SLC7A7 gene. While LPI causes systemic complications, the underlying cellular mechanisms remain poorly understood. This study investigated the cellular characteristics of LPI, focusing on intracellular metabolite profiles and astrocyte response to hyperammonemia. OBJECTIVES:To examine intracellular metabolite changes in LPI patients and to evaluate the response of patient-derived astrocytes to ammonia exposure. METHODS:Peripheral blood mononuclear cells (PBMCs) from three LPI patients and three healthy controls were analyzed for intracellular metabolite profiles using capillary electrophoresis-fourier transform mass spectrometry. Induced pluripotent stem cells were generated from a patient's PBMCs and differentiated into astrocytes. We evaluated LPI-astrocytes and their response to ammonia treatment by RNA sequencing, gene expression profiling, and cell viability assays. RESULTS:Metabolite analysis revealed significant intracellular metabolite imbalances in LPI patients, with increases of 21 metabolites including 11 amino acids. LPI-astrocytes exhibited distinct cellular characteristics regarding altered gene expression and enhanced cell cycle progression. When exposed to ammonia, the astrocytes demonstrated markedly lower cell viability and increased reactive oxygen species (ROS) production compared to control astrocytes. N-acetylcysteine supplementation significantly ameliorated ammonia-induced cytotoxicity. CONCLUSIONS:SLC7A7 dysfunction leads to intracellular metabolite disturbances and an increase in vulnerability to ammonia toxicity through ROS production of astrocyte, suggesting hyperammonemia and amino acid deficiencies as potential therapeutic targets in LPI patient care.