The mitochondrial permeability transition pore regulates endothelial bioenergetics and angiogenesis.
BACKGROUND
The mitochondrial permeability transition pore is a well-known initiator of cell death that is increasingly recognized as a physiological modulator of cellular metabolism.


OBJECTIVE
We sought to identify how the genetic deletion of a key regulatory subunit of the mitochondrial permeability transition pore, cyclophilin D (CypD), influenced endothelial metabolism and intracellular signaling.


RESULTS
In cultured primary human endothelial cells, genetic targeting of CypD using siRNA or shRNA resulted in a constitutive increase in mitochondrial matrix Ca(2+) and reduced nicotinamide adenine dinucleotide (NADH). Elevated matrix NADH, in turn, diminished the cytosolic NAD(+)/NADH ratio and triggered a subsequent downregulation of the NAD(+)-dependent deacetylase sirtuin 1 (SIRT1). Downstream of SIRT1, CypD-deficient endothelial cells exhibited reduced phosphatase and tensin homolog expression and a constitutive rise in the phosphorylation of angiogenic Akt. Similar changes in SIRT1, phosphatase and tensin homolog, and Akt were also noted in the aorta and lungs of CypD knockout mice. Functionally, CypD-deficient endothelial cells and aortic tissue from CypD knockout mice exhibited a dramatic increase in angiogenesis at baseline and when exposed to vascular endothelial growth factor. The NAD(+) precursor nicotinamide mononucleotide restored the cellular NAD(+)/NADH ratio and normalized the CypD-deficient phenotype. CypD knockout mice also presented accelerated wound healing and increased neovascularization on tissue injury as monitored by optical microangiography.


CONCLUSIONS
Our study reveals the importance of the mitochondrial permeability transition pore in the regulation of endothelial mitochondrial metabolism and vascular function. The mitochondrial regulation of SIRT1 has broad implications in the epigenetic regulation of endothelial phenotype.
From the Mitochondria and Metabolism Center, Departments of Anesthesiology and Pain Medicine (R.M., C.K.N., B.J.H.), Bioengineering (R.M., S.K., Z.Z., W.Q., R.K.W.), and Ophthalmology (R.K.W.), University of Washington, Seattle; and Department of General Surgery, University of Michigan, Ann Arbor (C.K.N.). bhawkins@uw.edu rmarcu@uw.edu.
Raluca
R
Marcu
From the Mitochondria and Metabolism Center, Departments of Anesthesiology and Pain Medicine (R.M., C.K.N., B.J.H.), Bioengineering (R.M., S.K., Z.Z., W.Q., R.K.W.), and Ophthalmology (R.K.W.), University of Washington, Seattle; and Department of General Surgery, University of Michigan, Ann Arbor (C.K.N.).
Surya
S
Kotha
From the Mitochondria and Metabolism Center, Departments of Anesthesiology and Pain Medicine (R.M., C.K.N., B.J.H.), Bioengineering (R.M., S.K., Z.Z., W.Q., R.K.W.), and Ophthalmology (R.K.W.), University of Washington, Seattle; and Department of General Surgery, University of Michigan, Ann Arbor (C.K.N.).
Zhongwei
Z
Zhi
From the Mitochondria and Metabolism Center, Departments of Anesthesiology and Pain Medicine (R.M., C.K.N., B.J.H.), Bioengineering (R.M., S.K., Z.Z., W.Q., R.K.W.), and Ophthalmology (R.K.W.), University of Washington, Seattle; and Department of General Surgery, University of Michigan, Ann Arbor (C.K.N.).
Wan
W
Qin
From the Mitochondria and Metabolism Center, Departments of Anesthesiology and Pain Medicine (R.M., C.K.N., B.J.H.), Bioengineering (R.M., S.K., Z.Z., W.Q., R.K.W.), and Ophthalmology (R.K.W.), University of Washington, Seattle; and Department of General Surgery, University of Michigan, Ann Arbor (C.K.N.).
Christopher K
CK
Neeley
From the Mitochondria and Metabolism Center, Departments of Anesthesiology and Pain Medicine (R.M., C.K.N., B.J.H.), Bioengineering (R.M., S.K., Z.Z., W.Q., R.K.W.), and Ophthalmology (R.K.W.), University of Washington, Seattle; and Department of General Surgery, University of Michigan, Ann Arbor (C.K.N.).
Ruikang K
RK
Wang
From the Mitochondria and Metabolism Center, Departments of Anesthesiology and Pain Medicine (R.M., C.K.N., B.J.H.), Bioengineering (R.M., S.K., Z.Z., W.Q., R.K.W.), and Ophthalmology (R.K.W.), University of Washington, Seattle; and Department of General Surgery, University of Michigan, Ann Arbor (C.K.N.).
Ying
Y
Zheng
From the Mitochondria and Metabolism Center, Departments of Anesthesiology and Pain Medicine (R.M., C.K.N., B.J.H.), Bioengineering (R.M., S.K., Z.Z., W.Q., R.K.W.), and Ophthalmology (R.K.W.), University of Washington, Seattle; and Department of General Surgery, University of Michigan, Ann Arbor (C.K.N.). bhawkins@uw.edu rmarcu@uw.edu.
Brian J
BJ
Hawkins
D000818:Animals; D002118:Calcium / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000172:deficiency / Q000235:genetics; D042783:Endothelial Cells / Q000378:metabolism*; D004734:Energy Metabolism; D005838:Genotype; D006801:Humans; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D009243:NAD / Q000378:metabolism; D018919:Neovascularization, Physiologic; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction; D056564:Sirtuin 1 / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D014945:Wound Healing
D000081406:Peptidyl-Prolyl Isomerase F; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; C000631446:PPIF protein, mouse; D009243:NAD; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D021983:Cyclophilins; D002118:Calcium
acetylation; angiogenesis effect; cyclophilin D; mitochondria