Hyperphosphatemia induces protective autophagy in endothelial cells through the inhibition of Akt/mTOR signaling

Yu Juei Hsu, Shih Che Hsu, Shih Ming Huang, Herng Sheng Lee, Shih Hua Lin, Chien Sung Tsai, Chun Che Shih, Chih Yuan Lin

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Objective Hyperphosphatemia-induced endothelial dysfunction has been shown to play a pathogenic role in the development of atherosclerosis in chronic kidney disease (CKD) through unclear mechanisms. Emerging evidence indicates that autophagy is involved in the maintenance of normal cardiovascular function. However, it is unclear whether autophagy participates in the molecular mechanism underlying high phosphate (Pi)-induced endothelial dysfunction. Methods The autophagy activity was determined by the immunofluorescence staining of the expression of endothelial microtubule-associated protein 1 light chain 3 (LC3) in the 5/6 nephrectomy rat model of CKD and sham-operated control rats. The LC3-II/LC3-I ratio and the activation of the Akt/mammalian target of rapamycin (mTOR) signaling pathway were determined in cultured human microvascular endothelial cell (HMEC-1) endothelial cells that were exposed to a high concentration of Pi with or without the Pi influx blocker phosphonoformic acid, the autophagy inhibitor 3-methyladenine, and the autophagy inducer rapamycin. The impacts of autophagy on Pi-induced apoptotic damage were assessed by flow cytometry. Results The in vivo rat model of CKD revealed that hyperphosphatemia is associated with increased endothelial LC3 staining. The exposure of HMEC-1 cells to high Pi induced both dose-dependent and time-dependent increases in the LC3-II/LC3-I expression ratio accompanied by the inhibition of the Akt/mTOR signaling pathway. In HMEC-1 cells, high Pi-induced autophagy and the inhibition of Akt/mTOR signaling were reversed by phosphonoformic acid through the blockage of Pi influx. Apoptosis, characterized by the levels of cleaved caspase 3 and poly(ADP-ribose) polymerase, along with autophagy was induced by high Pi, and the inhibition of autophagy by 3-methyladenine significantly aggravated high Pi-induced apoptosis. The flow cytometry results confirmed that the blockage of autophagy promoted the apoptosis of endothelial cells. Conclusions Hyperphosphatemia induces endothelial autophagy, possibly through the inhibition of the Akt/mTOR signaling pathway, which may play a protective role against high Pi-induced apoptosis.

Original languageEnglish
Article number7384
Pages (from-to)210-221.e2
JournalJournal of Vascular Surgery
Volume62
Issue number1
DOIs
Publication statusPublished - Jul 1 2015
Externally publishedYes

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Hyperphosphatemia
Autophagy
Sirolimus
Endothelial Cells
Light
Chronic Renal Insufficiency
Apoptosis
Foscarnet
Flow Cytometry
Staining and Labeling
Microtubule-Associated Proteins
Poly(ADP-ribose) Polymerases
Nephrectomy
Caspase 3
Fluorescent Antibody Technique
Atherosclerosis
Phosphates

ASJC Scopus subject areas

  • Surgery
  • Cardiology and Cardiovascular Medicine

Cite this

Hsu, Y. J., Hsu, S. C., Huang, S. M., Lee, H. S., Lin, S. H., Tsai, C. S., ... Lin, C. Y. (2015). Hyperphosphatemia induces protective autophagy in endothelial cells through the inhibition of Akt/mTOR signaling. Journal of Vascular Surgery, 62(1), 210-221.e2. [7384]. https://doi.org/10.1016/j.jvs.2014.02.040

Hyperphosphatemia induces protective autophagy in endothelial cells through the inhibition of Akt/mTOR signaling. / Hsu, Yu Juei; Hsu, Shih Che; Huang, Shih Ming; Lee, Herng Sheng; Lin, Shih Hua; Tsai, Chien Sung; Shih, Chun Che; Lin, Chih Yuan.

In: Journal of Vascular Surgery, Vol. 62, No. 1, 7384, 01.07.2015, p. 210-221.e2.

Research output: Contribution to journalArticle

Hsu, Yu Juei ; Hsu, Shih Che ; Huang, Shih Ming ; Lee, Herng Sheng ; Lin, Shih Hua ; Tsai, Chien Sung ; Shih, Chun Che ; Lin, Chih Yuan. / Hyperphosphatemia induces protective autophagy in endothelial cells through the inhibition of Akt/mTOR signaling. In: Journal of Vascular Surgery. 2015 ; Vol. 62, No. 1. pp. 210-221.e2.
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abstract = "Objective Hyperphosphatemia-induced endothelial dysfunction has been shown to play a pathogenic role in the development of atherosclerosis in chronic kidney disease (CKD) through unclear mechanisms. Emerging evidence indicates that autophagy is involved in the maintenance of normal cardiovascular function. However, it is unclear whether autophagy participates in the molecular mechanism underlying high phosphate (Pi)-induced endothelial dysfunction. Methods The autophagy activity was determined by the immunofluorescence staining of the expression of endothelial microtubule-associated protein 1 light chain 3 (LC3) in the 5/6 nephrectomy rat model of CKD and sham-operated control rats. The LC3-II/LC3-I ratio and the activation of the Akt/mammalian target of rapamycin (mTOR) signaling pathway were determined in cultured human microvascular endothelial cell (HMEC-1) endothelial cells that were exposed to a high concentration of Pi with or without the Pi influx blocker phosphonoformic acid, the autophagy inhibitor 3-methyladenine, and the autophagy inducer rapamycin. The impacts of autophagy on Pi-induced apoptotic damage were assessed by flow cytometry. Results The in vivo rat model of CKD revealed that hyperphosphatemia is associated with increased endothelial LC3 staining. The exposure of HMEC-1 cells to high Pi induced both dose-dependent and time-dependent increases in the LC3-II/LC3-I expression ratio accompanied by the inhibition of the Akt/mTOR signaling pathway. In HMEC-1 cells, high Pi-induced autophagy and the inhibition of Akt/mTOR signaling were reversed by phosphonoformic acid through the blockage of Pi influx. Apoptosis, characterized by the levels of cleaved caspase 3 and poly(ADP-ribose) polymerase, along with autophagy was induced by high Pi, and the inhibition of autophagy by 3-methyladenine significantly aggravated high Pi-induced apoptosis. The flow cytometry results confirmed that the blockage of autophagy promoted the apoptosis of endothelial cells. Conclusions Hyperphosphatemia induces endothelial autophagy, possibly through the inhibition of the Akt/mTOR signaling pathway, which may play a protective role against high Pi-induced apoptosis.",
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AU - Lin, Shih Hua

AU - Tsai, Chien Sung

AU - Shih, Chun Che

AU - Lin, Chih Yuan

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N2 - Objective Hyperphosphatemia-induced endothelial dysfunction has been shown to play a pathogenic role in the development of atherosclerosis in chronic kidney disease (CKD) through unclear mechanisms. Emerging evidence indicates that autophagy is involved in the maintenance of normal cardiovascular function. However, it is unclear whether autophagy participates in the molecular mechanism underlying high phosphate (Pi)-induced endothelial dysfunction. Methods The autophagy activity was determined by the immunofluorescence staining of the expression of endothelial microtubule-associated protein 1 light chain 3 (LC3) in the 5/6 nephrectomy rat model of CKD and sham-operated control rats. The LC3-II/LC3-I ratio and the activation of the Akt/mammalian target of rapamycin (mTOR) signaling pathway were determined in cultured human microvascular endothelial cell (HMEC-1) endothelial cells that were exposed to a high concentration of Pi with or without the Pi influx blocker phosphonoformic acid, the autophagy inhibitor 3-methyladenine, and the autophagy inducer rapamycin. The impacts of autophagy on Pi-induced apoptotic damage were assessed by flow cytometry. Results The in vivo rat model of CKD revealed that hyperphosphatemia is associated with increased endothelial LC3 staining. The exposure of HMEC-1 cells to high Pi induced both dose-dependent and time-dependent increases in the LC3-II/LC3-I expression ratio accompanied by the inhibition of the Akt/mTOR signaling pathway. In HMEC-1 cells, high Pi-induced autophagy and the inhibition of Akt/mTOR signaling were reversed by phosphonoformic acid through the blockage of Pi influx. Apoptosis, characterized by the levels of cleaved caspase 3 and poly(ADP-ribose) polymerase, along with autophagy was induced by high Pi, and the inhibition of autophagy by 3-methyladenine significantly aggravated high Pi-induced apoptosis. The flow cytometry results confirmed that the blockage of autophagy promoted the apoptosis of endothelial cells. Conclusions Hyperphosphatemia induces endothelial autophagy, possibly through the inhibition of the Akt/mTOR signaling pathway, which may play a protective role against high Pi-induced apoptosis.

AB - Objective Hyperphosphatemia-induced endothelial dysfunction has been shown to play a pathogenic role in the development of atherosclerosis in chronic kidney disease (CKD) through unclear mechanisms. Emerging evidence indicates that autophagy is involved in the maintenance of normal cardiovascular function. However, it is unclear whether autophagy participates in the molecular mechanism underlying high phosphate (Pi)-induced endothelial dysfunction. Methods The autophagy activity was determined by the immunofluorescence staining of the expression of endothelial microtubule-associated protein 1 light chain 3 (LC3) in the 5/6 nephrectomy rat model of CKD and sham-operated control rats. The LC3-II/LC3-I ratio and the activation of the Akt/mammalian target of rapamycin (mTOR) signaling pathway were determined in cultured human microvascular endothelial cell (HMEC-1) endothelial cells that were exposed to a high concentration of Pi with or without the Pi influx blocker phosphonoformic acid, the autophagy inhibitor 3-methyladenine, and the autophagy inducer rapamycin. The impacts of autophagy on Pi-induced apoptotic damage were assessed by flow cytometry. Results The in vivo rat model of CKD revealed that hyperphosphatemia is associated with increased endothelial LC3 staining. The exposure of HMEC-1 cells to high Pi induced both dose-dependent and time-dependent increases in the LC3-II/LC3-I expression ratio accompanied by the inhibition of the Akt/mTOR signaling pathway. In HMEC-1 cells, high Pi-induced autophagy and the inhibition of Akt/mTOR signaling were reversed by phosphonoformic acid through the blockage of Pi influx. Apoptosis, characterized by the levels of cleaved caspase 3 and poly(ADP-ribose) polymerase, along with autophagy was induced by high Pi, and the inhibition of autophagy by 3-methyladenine significantly aggravated high Pi-induced apoptosis. The flow cytometry results confirmed that the blockage of autophagy promoted the apoptosis of endothelial cells. Conclusions Hyperphosphatemia induces endothelial autophagy, possibly through the inhibition of the Akt/mTOR signaling pathway, which may play a protective role against high Pi-induced apoptosis.

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