Developing Topics.

Abstract

We hypothesized that lithium inhibits critical upper stream Ca2+ dysregulation via inhibition of methyl-D-aspartate (NMDARs) and/or InsP3 (InsP3Rs) receptors and downstream mitochondria dysfunction and cell death in a cell model of sporadic Alzheimer's Disease (SAD). Induced pluripotent stem cells (iPSCs) were derived from the skin fibroblasts of a SAD patient with parental ApoE4/E4, and then gene-edited to isogenic ApoE3/E3 cells as control. Cells were cultured with mTeSR1 plus medium on Matrigel-coated plates, differentiated to NPC by Dual-SMAD inhibition. Mitochondrial function and cell viability of both ApoE4/E4 vs. ApoE3/E3 iPSCs were determined using MTT reduction assay. Cells were pretreated with lithium and then challenged with glutamate for 24 hrs. Calcium concentration in cytosol space ([Ca2+]c) was measured using jellyfish-specific photo protein aequorin-based probes or microscopy Fura-2 dye. Mitochondria oxygen consumption rate (OCR) and ATP production were measured using the Seahorse ® Mito Stress Assay. Compared to ApoE3/E3 cells, ApoE4/E4 cells have significantly decreased cell viability, which could be inhibited by lithium at clinically low concentrations. ApoE4/E4 iPSCs had significantly increased baseline levels of [Ca2+]c and a significantly higher elevation of [Ca2+]c after glutamate treatment than its isogenic ApoE3/E3 iPSCs. Lithium at a clinical concentration (1mM) significantly inhibited the pathological elevation of baseline [Ca2+]c in ApoE4/E4 iPSCs. Lithium-inhibited mitochondria proton leak as an indicator of cell damage induced by glutamate (15mM) in ApoE4/E4 iPSCs. Glutamate induced mitochondrial and cell damage dose-dependently. Lithium at a clinically low concentration (0.25mM) significantly inhibited glutamate (15mM)-induced mitochondria and cell damage in ApoE4/E4 iPSCs. Glutamate treatment for 24 hours significantly inhibited the proliferation of NPCs derived from SAD iPSCs with parental ApoE4/E4 and isogenic E3/E3. Lithium (1mM) significantly inhibited the glutamate-mediated impairment of ApoE3/E3 NPCs proliferation. Our results suggest that ApoE4 plays an important role in critical upstream Ca2+ dysregulation and downstream mitochondrial dysfunction and cell damage, particularly under the stress of glutamate excitotoxicity. Lithium at clinically low concentrations ameliorated critical Ca2+ dysregulation and AD pathologies, warranting further studies to repurpose lithium as future effective drug for AD treatment.