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APP promotes osteoblast survival and bone formation by regulating mitochondrial function and preventing oxidative stress.

ABSTRACT: Amyloid precursor protein (APP) is ubiquitously expressed in various types of cells including bone cells. Mutations in App gene result in early-onset Alzheimer's disease (AD). However, little is known about its physiological function in bone homeostasis. Here, we provide evidence for APP's role in promoting bone formation. Mice that knocked out App gene (APP^-/-) exhibit osteoporotic-like deficit, including reduced trabecular and cortical bone mass. Such a deficit is likely due in large to a decrease in osteoblast (OB)-mediated bone formation, as little change in bone resorption was detected in the mutant mice. Further mechanical studies of APP^-/- OBs showed an impairment in mitochondrial function, accompanied with increased reactive oxygen species (ROS) and apoptosis. Intriguingly, these deficits, resemble to those in Tg2576 animal model of AD that expresses Swedish mutant APP (APPswe), were diminished by treatment with an anti-oxidant NAC (n-acetyl-l-cysteine), uncovering ROS as a critical underlying mechanism. Taken together, these results identify an unrecognized physiological function of APP in promoting OB survival and bone formation, implicate APPswe acting as a dominant negative factor, and reveal a potential clinical value of NAC in treatment of AD-associated osteoporotic deficits.

SUBMITTER: Pan JX

PROVIDER: S-EPMC6197195 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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APP promotes osteoblast survival and bone formation by regulating mitochondrial function and preventing oxidative stress.

Pan Jin-Xiu JX Tang Fulei F Xiong Fei F Xiong Lei L Zeng Peng P Wang Bo B Zhao Kai K Guo Haohan H Shun Cui C Xia Wen-Fang WF Mei Lin L Xiong Wen-Cheng WC

Cell death & disease 20181022 11

Amyloid precursor protein (APP) is ubiquitously expressed in various types of cells including bone cells. Mutations in App gene result in early-onset Alzheimer's disease (AD). However, little is known about its physiological function in bone homeostasis. Here, we provide evidence for APP's role in promoting bone formation. Mice that knocked out App gene (APP<sup>-/-</sup>) exhibit osteoporotic-like deficit, including reduced trabecular and cortical bone mass. Such a deficit is likely due in larg ...[more]

PMID: 30349052

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Project description:The Pacific oyster, Crassostrea gigas, is well-known as a nutritious food. Recently, we revealed that fermented extract of C. gigas (FO) inhibited ovariectomy-induced osteoporosis, resulting from suppression of osteoclastogenesis. However, since the beneficial effect of FO on osteogenesis is poorly understood, it was examined in mouse preosteoblast MC3T3-E1 cells, human osteosarcoma MG-63 osteoblast-like cells, and zebrafish larvae in this study. We found that FO increased mitochondrial activity from days 1 to 7; however, total cell number of MC3T3-E1 cells gradually decreased without any change in cell viability, which suggests that FO stimulates the differentiation of MC3T3-E1 cells. FO also promoted the expression of osteoblast marker genes, including runt-related transcription factor 2 (mRUNX2), alkaline phosphatase (mALP), collagen type I ?1 (mCol1?1), osteocalcin (mOCN), osterix (mOSX), bone morphogenetic protein 2 (mBMP2), and mBMP4 in MC3T3-E1 cells accompanied by a significant increase in ALP activity. FO also increased nuclear translocation of RUNX2 and OSX transcription factors, ALP activity, and calcification in vitro along with the upregulated expression of osteoblast-specific marker proteins such as RUNX2, ALP, Col1?1, OCN, OSX, and BMP4. Additionally, FO enhanced bone mineralization (calcein intensity) in zebrafish larvae at 9 days post-fertilization comparable to that in the ?-glycerophosphate (GP)-treated group. All the tested osteoblast marker genes, including zRUNX2a, zRUNX2b, zALP, zCol1a1, zOCN, zBMP2, and zBMP4, were also remarkably upregulated in the zebrafish larvae in response to FO. It also promoted tail fin regeneration in adult zebrafish as same as the GP-treated groups. Furthermore, not only FO positively regulate ?-catenin expression and Wnt/?-catenin luciferase activity, but pretreatment with a Wnt/?-catenin inhibitor (FH535) also significantly decreased FO-mediated bone mineralization in zebrafish larvae, which indicates that FO-induced osteogenesis depends on the Wnt/?-catenin pathway. Altogether, the current study suggests that the supplemental intake of FO has a beneficial effect on osteogenesis.

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APP promotes osteoblast survival and bone formation by regulating mitochondrial function and preventing oxidative stress.

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APP promotes osteoblast survival and bone formation by regulating mitochondrial function and preventing oxidative stress.

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