ABSTRACT
Alzheimer's disease (AD) is the most common cause of age-related neurodegeneration and cognitive decline. AD more commonly occurs in females than in males, so it is necessary to consider new treatments specifically targeting this population. The present study investigated the protective effects of Begacestat (γ-secretase inhibitor-953, GSI-953) and bone marrow-derived mesenchymal stem cells (BM-MSCs) during pregnancy on cognitive impairment in rat dams and neurodegeneration in offspring caused by the intracerebroventricular injection of Aß 25-35 before pregnancy. The performances of dams injected with amyloid-ß 25-35 (Aß 25-35) during behavioral tests were significantly impaired. The offspring of Aß 25-35-injected dams treated with BM-MSCs or GSI-953 showed a dramatically reduced number and size of activated microglial cells, enhancement in the processes length, and a decrease in the proinflammatory cytokine levels. Additionally, BM-MSC or GSI-953 therapy reduced Aß 25-35-induced increases in tau phosphorylation and amyloid precursor protein levels in the neonates' hippocampus and elevated the lower levels of glycogen synthase kinase-3 and brain-derived neurotrophic factor; moreover, reversed Aß 25-35-induced alterations in gene expression in the neonatal hippocampus. Finally, the treatments with BM-MSC or GSI-953 are globally beneficial against Aß 25-35-induced brain alterations, particularly by suppressing neural inflammation, inhibiting microglial cell activation, restoring developmental plasticity, and increasing neurotrophic signaling.
ABSTRACT
Alzheimer's disease (AD) is the most frequent cause of age-related neurodegeneration and ensuing cognitive impairment. Progressive deposition of extracellular amyloid beta (Aß) aggregates (plaques) and intracellular hyperphosphorylated Tau protein (p-Tau) are the core pathological markers of AD but may precede clinical symptoms by many years, presenting a therapeutic window of opportunity. Females are more frequently afflicted by AD than males, necessitating evaluation of novel treatments for the female population. The current study examined the protective efficacies of intravenous bone marrow-derived mesenchymal stem cells (BM-MSCs) and oral gamma-secretase inhibitor-953 (GSI-953) during pregnancy on cognitive impairment in rat dams and neurodegeneration in offspring induced by intracerebroventricular injection of Aß25-35 prior to pregnancy. The Aß25-35 (AD) group exhibited significant (P < 0.001) impairments in the Y-maze and novel object recognition test performance prior to conception. Histological analysis of the offspring cortex revealed substantial dendritic shrinkage and activation of microglial cells, while neurochemical analysis demonstrated significant increases in the proinflammatory cytokine interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α). In contrast, BM-MSC or GSI-953 treatment of dams following Aß25-35 injection significantly (P < 0.001) reduced the number and size of activated microglial cells, markedly increased dendrite length, and reversed proinflammatory cytokine elevations in offspring. Moreover, BM-MSC or GSI-953 treatment reversed the Aß25-35-induced amyloid precursor protein and p-Tau elevations in the offspring brain; these changes were accompanied by upregulation of the brain-derived neurotrophic factor and downregulation of glycogen synthase kinase-3ß in the serum and brain. Treatment with BM-MSCs or GSI-953 also reversed Aß25-35-induced elevations in different gene expressions in the neonatal cortex. Finally, treatment of dams with BM-MSCs or GSI-953 prevented the Aß25-35-induced disruption of newborn brain development. Thus, BM-MSC and GSI-953 treatments have broad-spectrum effects against Aß25-35-induced brain pathology, including the suppression of neural inflammation, restoration of developmental plasticity, and promotion of neurotrophic signaling.
