Publications by authors named "Dat Da Ly"

4 Publications

  • Page 1 of 1

Ca-activated mitochondrial biogenesis and functions improve stem cell fate in Rg3-treated human mesenchymal stem cells.

Stem Cell Res Ther 2020 11 4;11(1):467. Epub 2020 Nov 4.

Mitohormesis Research Center, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, Gangwon-Do, 26426, Republic of Korea.

Although mitochondrial functions are essential for cell survival, their critical roles in stem cell fate, including proliferation, differentiation, and senescence, remain elusive. Ginsenoside Rg3 exhibits various biological activities and reportedly increases mitochondrial biogenesis and respiration. Herein, we observed that Rg3 increased proliferation and suppressed senescence of human bone marrow-derived mesenchymal stem cells. Osteogenic, but not adipogenic, differentiation was facilitated by Rg3 treatment. Rg3 suppressed reactive oxygen species production and upregulated mitochondrial biogenesis and antioxidant enzymes, including superoxide dismutase. Consistently, Rg3 strongly augmented basal and ATP synthesis-linked respiration with high spare respiratory capacity. Rg3 treatment elevated cytosolic Ca concentration contributing to mitochondrial activation. Reduction of intracellular or extracellular Ca levels strongly inhibited Rg3-induced activation of mitochondrial respiration and biogenesis. Taken together, Rg3 enhances capabilities of mitochondrial and antioxidant functions mainly through a Ca-dependent pathway, which improves the proliferation and differentiation potentials and prevents the senescence of human mesenchymal stem cells.
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http://dx.doi.org/10.1186/s13287-020-01974-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7640456PMC
November 2020

Oxidative stress by Ca overload is critical for phosphate-induced vascular calcification.

Am J Physiol Heart Circ Physiol 2020 12 23;319(6):H1302-H1312. Epub 2020 Oct 23.

Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Korea.

Hyperphosphatemia is the primary risk factor for vascular calcification, which is closely associated with cardiovascular morbidity and mortality. Recent evidence showed that oxidative stress by high inorganic phosphate (Pi) mediates calcific changes in vascular smooth muscle cells (VSMCs). However, intracellular signaling responsible for Pi-induced oxidative stress remains unclear. Here, we investigated molecular mechanisms of Pi-induced oxidative stress related with intracellular Ca ([Ca]) disturbance, which is critical for calcification of VSMCs. VSMCs isolated from rat thoracic aorta or A7r5 cells were incubated with high Pi-containing medium. Extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin were activated by high Pi that was required for vascular calcification. High Pi upregulated expressions of type III sodium-phosphate cotransporters PiT-1 and -2 and stimulated their trafficking to the plasma membrane. Interestingly, high Pi increased [Ca] exclusively dependent on extracellular Na and Ca as well as PiT-1/2 abundance. Furthermore, high-Pi induced plasma membrane depolarization mediated by PiT-1/2. Pretreatment with verapamil, as a voltage-gated Ca channel (VGCC) blocker, inhibited Pi-induced [Ca] elevation, oxidative stress, ERK activation, and osteogenic differentiation. These protective effects were reiterated by extracellular Ca-free condition, intracellular Ca chelation, or suppression of oxidative stress. Mitochondrial superoxide scavenger also effectively abrogated ERK activation and osteogenic differentiation of VSMCs by high Pi. Taking all these together, we suggest that high Pi activates depolarization-triggered Ca influx via VGCC, and subsequent [Ca] increase elicits oxidative stress and osteogenic differentiation. PiT-1/2 mediates Pi-induced [Ca] overload and oxidative stress but in turn, PiT-1/2 is upregulated by consequences of these alterations. The novel findings of this study are type III sodium-phosphate cotransporters PiT-1 and -2-dependent depolarization by high Pi, leading to Ca entry via voltage-gated Ca channels in vascular smooth muscle cells. Cytosolic Ca increase and subsequent oxidative stress are indispensable for osteogenic differentiation and calcification. In addition, plasmalemmal abundance of PiT-1/2 relies on Ca overload and oxidative stress, establishing a positive feedback loop. Identification of mechanistic components of a vicious cycle could provide novel therapeutic strategies against vascular calcification in hyperphosphatemic patients.
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http://dx.doi.org/10.1152/ajpheart.00305.2020DOI Listing
December 2020

Activation of ERK1/2-mTORC1-NOX4 mediates TGF-β1-induced epithelial-mesenchymal transition and fibrosis in retinal pigment epithelial cells.

Biochem Biophys Res Commun 2020 08 19;529(3):747-752. Epub 2020 Jul 19.

Department of Physiology, Republic of Korea; Mitohormesis Research Center, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea. Electronic address:

Transforming growth factor-β (TGF-β) plays a crucial role in the development of epithelial to mesenchymal transition (EMT) and fibrosis, particularly in an ocular disorder such as proliferative vitreoretinopathy (PVR). However, the key molecular mechanism underlying its pathogenesis remains unknown. In the present study, using cultured ARPE-19 cells, we determined that TGF-β initiates a signaling pathway through extracellular signal-regulated kinase (ERK)-mammalian target of rapamycin complex 1 (mTORC1) that stimulates trans-differentiation and fibrosis of retinal pigment epithelium. Blocking this pathway by a TGF-βRI, ERK or mTORC1 inhibitor protected cells from EMT and fibrotic protein expression. TGF-β1 treatment increased reactive oxygen species (ROS) via NOX4 upregulation, which acts downstream of ERK and mTORC1, as the ROS scavenger N-acetylcysteine and a pan-NADPH oxidase (NOX) inhibitor DPI dissipated excess ROS generation. TGF-β1-induced oxidative stress resulted in EMT and fibrotic changes, as NAC and DPI prevented α-SMA, Col4α3 expression and cell migration. All these inhibitors blocked the downstream pathway activation in addition to clearly preventing the activation of its upstream molecules, indicating the presence of a feedback loop system that may boost the upstream events. Furthermore, the FDA-approved drug trametinib (10 nM) blunted TGF-β1-induced mTORC1 activation and downstream pathogenic alterations through ERK1/2 inhibition, which opens a therapeutic avenue for the treatment of PVR in the future.
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http://dx.doi.org/10.1016/j.bbrc.2020.06.034DOI Listing
August 2020

Mitochondrial Ca Uptake Relieves Palmitate-Induced Cytosolic Ca Overload in MIN6 Cells.

Mol Cells 2020 01;43(1):66-75

Department of Physiology, Yonsei University Wonju College of Medicine, Wonju 26426, Korea.

Saturated fatty acids contribute to β-cell dysfunction in the onset of type 2 diabetes mellitus. Cellular responses to lipotoxicity include oxidative stress, endoplasmic reticulum (ER) stress, and blockage of autophagy. Palmitate induces ER Ca depletion followed by notable store-operated Ca entry. Subsequent elevation of cytosolic Ca2+ can activate undesirable signaling pathways culminating in cell death. Mitochondrial Ca2+ uniporter (MCU) is the major route for Ca2+ uptake into the matrix and couples metabolism with insulin secretion. However, it has been unclear whether mitochondrial Ca uptake plays a protective role or contributes to lipotoxicity. Here, we observed palmitate upregulated MCU protein expression in a mouse clonal β-cell, MIN6, under normal glucose, but not high glucose medium. Palmitate elevated baseline cytosolic Ca concentration ([Ca]) and reduced depolarization-triggered Ca influx likely due to the inactivation of voltage-gated Ca channels (VGCCs). Targeted reduction of MCU expression using RNA interference abolished mitochondrial superoxide production but exacerbated palmitate-induced [Ca] overload. Consequently, MCU knockdown aggravated blockage of autophagic degradation. In contrast, co-treatment with verapamil, a VGCC inhibitor, prevented palmitate-induced basal [Ca] elevation and defective [Ca] transients. Extracellular Ca chelation as well as VGCC inhibitors effectively rescued autophagy defects and cytotoxicity. These observations suggest enhanced mitochondrial Ca uptake via MCU upregulation is a mechanism by which pancreatic β-cells are able to alleviate cytosolic Ca overload and its detrimental consequences.
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http://dx.doi.org/10.14348/molcells.2019.0223DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6999716PMC
January 2020