Mechanisms of Dantrolene Neuroprotection in Alzheimer's Disease

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Abstract Coronavirus disease 2019 (COVID-19), a pandemic affecting millions of patients around the world, is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with no effective drug treatments. Both infection and transfection of virus in host cells require abnormally elevated Ca2+ concentrations in cytosol and endosome via overactivation of ryanodine receptors (RyRs) Ca2+ channel located on the membrane of the endoplasmic reticulum (ER). Dantrolene, an antagonist of RyRs, has been demonstrated to inhibit SARS- CoV-2-mediated host cell toxicity and damage. In the presence of RyRs overactivation and excessive and abnormal elevation of cytosolic and endosome Ca2+ concentrations, the spike proteins (S1, S2) of the virus play important roles in binding, fusion, and virus replication in the host cell, eventually leading to cell damage or death. Our long-term goal is to examine the efficacy and mechanisms of dantrolene to treat AD. The overall objective of this study is to investigate the effects and underlying mechanisms of dantrolene to protect against host cell damage or death induced by SARS-CoV-2 spike proteins-mediated overactivation of RyRs and associated Ca2+ dysregulation. Our central hypothesis supported by preliminary data is that dantrolene inhibits SARS-CoV-2 spike proteins-mediated cell damage by inhibiting the overactivation of RyRs and by restoring intracellular Ca2+ homeostasis in AD cells. We will test this hypothesis with the following specific aims. Specific Aim 1 (SA1). To determine the effects of dantrolene on SARS-CoV-2 spike (S) proteins-mediated Ca2+ dysregulation and cell damage by apoptosis in AD cells using induced pluripotent stem cells (iPSC), from skin fibroblasts of patients with either sporadic (SAD) or familial (FAD), and human neuroblastoma cells (SH-SY5Y), with knocked-in AD presenilin 1 mutation (M146L). Specific Aim 2 (SA2). To determine the effects and mechanisms of dantrolene on SARS-CoV-2 spike (S) proteins-mediated pathological pathways leading to host cell damage. We will examine the effects of S proteins on mitochondria oxygen consumption, ATP production, reactive oxygen species (ROS) production, ER stress, and cytokine release. We will correlate the results between SA1 and SA2. We expect that dantrolene will inhibit S proteins-mediated overactivation of RyRs and associated disruption of intracellular Ca2+ homeostasis and cell death by apoptosis.