Coordinated time-dependent modulation of AMPK/Akt/mTOR signaling and autophagy controls osteogenic differentiation of human mesenchymal stem cells

Cui

et al. 2014

Cell Physiol Biochem

Background: Arterial calcification is a major event in the progression of atherosclerosis. It is reported that statins exhibit various protective effects against vascular smooth muscle cell (VSMC) inflammation and proliferation in cardiovascular remodeling. Although statins counteract atherosclerosis, the molecular mechanisms of statins on the calcium release from VSMCs have not been clearly elucidated. Methods: Calcium content of VSMCs was measured using enzyme-linked immunosorbent assay (ELISA). The expression of proteins involved in cellular transdifferentiation was analyzed by western blot. Cell autophagy was measured by fluorescence microscopic analysis for acridine orange staining and transmission electron microscopy analysis. The autophagic inhibitors (3-MA, chloroquine, NH₄Cl and bafilomycin A1) and β-catenin inhibitor JW74 were used to assess the effects of atorvastatin on autophagy and the involvement of β-catenin on cell calcification respectively. Furthermore, cell transfection was performed to overexpress β-catenin. Results: In VSMCs, atorvastatin significantly suppressed transforming growth factor-β1 (TGF-β1)-stimulated calcification, accompanied by the induction of autophagy. Downregulation of autophagy with autophagic inhibitors significantly suppressed the inhibitory effect of atorvastatin on cell calcification. Moreover, the beneficial effect of atorvastatin on calcification and autophagy was reversed by β-catenin overexpression. Conversely, JW74 supplement enhanced this effect. Conclusion: These data demonstrated that atorvastatin protect VSMC from TGF-β1-stimulated calcification by inducing autophagy through suppression of the β-catenin pathway, identifying autophagy induction might be a therapeutic strategy for use in vascular calcification.

Section: Resultsmentioning

confidence: 99%

Atorvastatin Protects Vascular Smooth Muscle Cells From TGF-�1-Stimulated Calcification by Inducing Autophagy via Suppression of the �-Catenin Pathway

Cui

et al. 2014

Cell Physiol Biochem

“…*P<0.05; **P<0.01 eATP treatment was coordinated with AMPK activation and mTOR antagonization. mTOR is a validated downstream target of AMPK, and the AMPK/mTOR axis not only participates in regulation of intracellular metabolism, but also is involved in signaling network controlling proliferation, survival, and cell death [28][29][30][31]. However, this is the first report to show their effect on eATP-induced signaling transduction in anchorage-dependent and anchorage-independent hepatoma cells.…”

Section: Discussionmentioning

confidence: 80%

High dose of extracellular ATP switched autophagy to apoptosis in anchorage-dependent and anchorage-independent hepatoma cells

Wei

Zhang

Xing

et al. 2013

Purinergic Signalling

Extracellular adenosine triphosphate (eATP) transduces purinergic signal and plays an important regulatory role in many biological processes, including tumor cell growth and cell death. A large amount of eATP exists in the fast-growing tumor center and inflammatory tumor microenvironment. Tumor cells could acquire anoikis resistance and anchorage independence in tumor microenvironment and further cause metastatic lesion. Whether such a high amount of eATP has any effect on the anchored and nonanchored tumor cells in tumor microenvironment has not been elucidated and is investigated in this study. Our data showed that autophagy helped hepatoma cells to maintain survival under the treatment of no more than 1 mM of eATP. Only when eATP concentration reached a relatively high level (2.5 mM), cell organelle could not be further maintained by autophagy, and apoptosis and cell death occurred. In hepatoma cells under treatment of 2.5 mM of eATP, an AMP-activated protein kinase (AMPK) pathway was dramatically activated while mTOR signaling pathway was suppressed in coordination with apoptosis. Further investigation showed that the AMPK/mTOR axis played a key role in tipping the balance between autophagy-mediated cell survival and apoptosis-induced cell death under the treatment of eATP. This work provides evidence to explain how hepatoma cells escape from eATP-induced cytotoxicity as well as offers an important clue to consider effective manipulation of cancer.

“…Pantovic et al showed that human dental pulp mesenchymal stem cells differentiate via AMPK-induced autophagy and Akt activity to osteoblasts [84].…”

Section: Discussionmentioning

confidence: 99%

Ti-SLActive and TiZr-SLActive Dental Implant Surfaces Promote Fast Osteoblast Differentiation

et al. 2017

A primary goal in modern surface modification technology of dental implants is to achieve biocompatible surfaces with rapid but controlled healing which also allow health and longevity of implants. In order to realize all, understanding of osseointegration phenomena is crucial. Although Ti-SLA, Ti-SLActive and TiZr-SLActive surfaces have been successfully used in clinical implantology and were shown to notably reduce the primary healing time, available in vitro studies are sparse and do not concern or explore the mechanism(s) involved in human osteoblast behavior on these surfaces. Ti-SLA, Ti-SLActive, TiZr-SLActive, Ti cp, Ticer and Cercon surfaces were used. Osteoblast proliferation, cell cluster formation, morphological changes, induction of autophagy, nitric oxide (NO), reactive oxygen species/reactive nitrogen species (ROS/RNS) formation, osteocalcin (OC), bone sialoprotein (BSP) and collagen type I (Col-1) affected by various surfaces were analyzed. These surfaces induced formation of mature osteoblasts caused by elevated oxidative stress (ROS) followed by overexpression of osteoblast maturation key molecule (NO), with different intensity however. These mature osteoblasts induced upregulation of OC, BSP and Col-1, activating PI3/Akt signalling pathway resulting in autophagy, known as an important process in differentiation of osteoblast cells. Additional distinctive subpopulation identified on Ticer, Ti-SLA (after 5 days), Ti-SLActive and TiZr-SLActive surfaces (after 2 days) were forming cell clusters, essential for bone noduli formation and mineralisation. The results suggest that Ti-and TiZr-SLActive possess advanced properties in comparison with Ticer and Ti-SLA manifested as accelerated osteoblast differentiation. These effects could explain already known fast osseointegration of these surfaces in vivo.