Dantrolene Ameliorates Impaired Neurogenesis and Synaptogenesis in Induced Pluripotent Stem Cell Lines Derived from Patients with Alzheimer's Disease

Background: Overactivation of ryanodine receptors and the resulting impaired calcium homeostasis contribute to Alzheimer's disease-related pathophysiology. This study hypothesized that exposing neuronal progenitors derived from induced pluripotent stems cells of patients with Alzheimer's disease to dantrolene will increase survival, proliferation, neurogenesis, and synaptogenesis. Methods: Induced pluripotent stem cells obtained from skin fibroblast of healthy subjects and patients with familial and sporadic Alzheimer's disease were used. Biochemical and immunohistochemical methods were applied to determine the effects of dantrolene on the viability, proliferation, differentiation, and calcium dynamics of these cells. Results: Dantrolene promoted cell viability and proliferation in these two cell lines. Compared with the control, differentiation into basal forebrain cholinergic neurons significantly decreased by 10.7% (32.9 +/- 3.6% vs. 22.2 +/- 2.6%, N = 5, P = 0.004) and 9.2% (32.9 +/- 3.6% vs. 23.7 +/- 3.1%, N = 5, P = 0.017) in cell lines from sporadic and familial Alzheimer's patients, respectively, which were abolished by dantrolene. Synapse density was significantly decreased in cortical neurons generated from stem cells of sporadic Alzheimer's disease by 58.2% (237.0 +/- 28.4 vs. 99.0 +/- 16.6 arbitrary units, N = 4, P = 0.001) or familial Alzheimer's disease by 52.3% (237.0 +/- 28.4 vs.113.0 +/- 34.9 vs. arbitrary units, N = 5, P = 0.001), which was inhibited by dantrolene in the familial cell line. Compared with the control, adenosine triphosphate (30 mu M) significantly increased higher peak elevation of cytosolic calcium concentrations in the cell line from sporadic Alzheimer's patients (84.1 +/- 27.0% vs. 140.4 +/- 40.2%, N = 5, P = 0.049), which was abolished by the pretreatment of dantrolene. Dantrolene inhibited the decrease of lysosomal vacuolar-type H+-ATPase and the impairment of autophagy activity in these two cell lines from Alzheimer's disease patients. Conclusions: Dantrolene ameliorated the impairment of neurogenesis and synaptogenesis, in association with restoring intracellular Ca2+ homeostasis and physiologic autophagy, cell survival, and proliferation in induced pluripotent stem cells and their derived neurons from sporadic and familial Alzheimer's disease patients.