The blood-brain barrier (BBB), which is formed by adherens and tight junctions (TJs) of endothelial cells, maintains homeostasis of the brain. Disrupted intracellular Ca 2ϩ homeostasis and breakdown of the BBB have been implicated in the pathogenesis of Alzheimer's disease (AD). The receptor for advanced glycation end products (RAGE) is known to interact with amyloid ␤-peptide (A␤) and mediate A␤ transport across the BBB, contributing to the deposition of A␤ in the brain. However, molecular mechanisms underlying A␤-RAGE interaction-induced alterations in the BBB have not been identified. We found that A␤ 1-42 induces enhanced permeability, disruption of zonula occludin-1 (ZO-1) expression in the plasma membrane, and increased intracellular calcium and matrix metalloproteinase (MMP) secretion in cultured endothelial cells. Neutralizing antibodies against RAGE and inhibitors of calcineurin and MMPs prevented A␤ 1-42 -induced changes in ZO-1, suggesting that A␤-RAGE interactions alter TJ proteins through the Ca 2ϩ -calcineurin pathway. Consistent with these in vitro findings, we found disrupted microvessels near A␤ plaque-deposited areas, elevated RAGE expression, and enhanced MMP secretion in microvessels of the brains of 5XFAD mice, an animal model for AD. We have identified a potential molecular pathway underlying A␤-RAGE interaction-induced breakage of BBB integrity. This pathway might play an important role in the pathogenesis of AD.

Blood-brain barrier (BBB) regulates transport of various molecules and maintains brain homeostasis. Perturbed intracellular Ca2+ homeostasis and BBB damage have been implicated in the pathogenesis of Alzheimer disease (AD). Although receptor for advanced glycation end products (RAGE) is known to mediate Aβ transcytosis across the BBB, molecular mechanisms underlying Aβ-RAGE interaction-induced BBB alterations are largely unknown. We found enhanced permeability, decreased zonula occludin-1 (ZO-1) expression and increased intracellular calcium and MMP secretion in endothelial cells exposed to Aβ1–42. Aβ-induced changes in ZO-1 were attenuated by neutralizing antibodies against RAGE and inhibitors of calcineurin (CaN) and MMPs, suggesting that Aβ-RAGE interactions disrupt tight junction proteins via the Ca2+-CaN pathway. We also found disrupted microvessels near Aβ plaque-deposited areas, elevated RAGE expression and enhanced MMP secretion in microvessels of the brains of 5XFAD mice, an animal model of AD. These results identify a potential molecular pathway underlying Aβ-RAGE interaction-induced breakage of BBB integrity.

One of the major hallmarks of Alzheimer's disease (AD) is the extracellular deposition of amyloid-β (Aβ) as senile plaques in specific brain regions. Clearly, an understanding of the cellular processes underlying Aβ deposition is a crucial issue in the field of AD research. Recent studies have found that accumulation of intraneuronal Aβ (iAβ) is associated with synaptic deficits, neuronal death, and cognitive dysfunction in AD patients. In this study, we found that Aβ deposits had several shapes and sizes, and that iAβ occurred before the formation of extracellular amyloid plaques in the subiculum of 5XFAD mice, an animal model of AD. We also observed pyroglutamate-modified Aβ (N3pE-Aβ), which has been suggested to be a seeding molecule for senile plaques, inside the Aβ plaques only after iAβ accumulation, which argues against its seeding role. In addition, we found that iAβ accumulates in calcium-binding protein (CBP)-free neurons, induces neuronal death, and then develops into senile plaques in 2-4-month-old 5XFAD mice. These findings suggest that N3pE-Aβ-independent accumulation of Aβ in CBP-free neurons might be an early process that triggers neuronal damage and senile plaque formation in AD patients. Our results provide new insights into several long-standing gaps in AD research, namely how Aβ plaques are formed, what happens to iAβ and how Aβ causes selective neuronal loss in AD patients.

The evidence of strong pathological associations between type 2 diabetes and Alzheimer's disease (AD) has increased in recent years. Contrary to suggestions that anti-diabetes drugs may have potential for treating AD, we demonstrate here that the insulin sensitizing anti-diabetes drug metformin (Glucophage®) increased the generation of amyloid-β (Aβ), one of the major pathological hallmarks of AD, by promoting β- and γ-secretase-mediated cleavage of amyloid-β protein precursor (AβPP) in SH-SY5Y cells. In addition, we show that metformin caused autophagosome accumulation in Tg6799 AD model mice. Extremely high γ-secretase activity was also detected in autophagic vacuoles, apparently a novel site of Aβ peptide generation. Together, these data suggest that metformin-induced accumulation of autophagosomes resulted in increased γ-secretase activity and Aβ generation. Additional experiments indicated that metformin increased phosphorylation of AMP-activated protein kinase, which activates autophagy by suppressing mammalian target of rapamycin (mTOR). The suppression of mTOR then induces the abnormal accumulation of autophagosomes. We conclude that metformin, an anti-diabetes drug, may exacerbate AD pathogenesis by promoting amyloidogenic AβPP processing in autophagosomes.

To ascertain the properties of human dental stem cells, various postnatal human stem cells were isolated from extracted human teeth and jawbones. Isolated dental stem cells were plated until losing their ‘stemness’ and were evaluated for their proliferation rate, colony forming efficiency, and expression of a specific stem cell marker. These dental stem cells have the potential to proliferate for more than 10 passages, except for the maxillary bone marrow stem cells (MXBMSCs). In particular, stem cells obtained from the periapical follicle (PAFSCs) were definitely superior to the other dental stem cells in proliferation, colony forming efficiency and expression of specific stem cells marker.