BRCA1 shields vascular smooth muscle cells from oxidative stress.
BACKGROUND
Excessive production of reactive oxygen species (ROS), in part via upregulation of DNA damage pathways, is a central mechanism governing pathologic activation of vascular smooth muscle cells (VSMCs). We hypothesized that the breast cancer 1, early onset (BRCA1) gene that is involved in cellular resistance to DNA damage limits ROS production and oxidative stress in VSMCs.


METHODS
We evaluated basal and H2O2-stimulated expression of BRCA1 in human aortic smooth muscle cells (HASMCs). In vitro gain-of-function experiments were performed in BRCA1 adenovirus (Ad-BRCA1)-transfected HASMCs. ROS production and expression of Nox1 and its key regulatory subunit p47phox, key components of the ROS-generating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system, were evaluated. In vivo gain-of-function experiments were performed in spontaneously hypertensive (SHR) rats treated with Ad-BRCA1 (5 × 10(10) IU/rat). Blood pressure, vascular ROS generation, Nox1, and p47phox expression were measured.


RESULTS
BRCA1 was constitutively expressed in murine, rat, and human smooth muscle cells (SMCs). H2O2 significantly reduced BRCA1 expression with a resultant increase in ROS generation. BRCA1-overexpressing HASMCs were protected against H2O2-induced ROS generation, in part, via downregulation of the ROS-producing NADPH oxidase subunits Nox1 and p47phox. Ad-BRCA1 treatment in SHR rats was associated with a sustained increase in aortic BRCA1 expression, lower aortic ROS production, reduced γH2A.X levels, greater RAD51 foci, and decreases in blood pressure.


CONCLUSIONS
BRCA1 is a novel and previously unrecognized target that may shield VSMCs from oxidative stress by inhibiting NADPH Nox1-dependent ROS production. Gene- and/or cell-based approaches that improve BRCA1 bioavailability may represent a new approach in the treatment of diverse vascular diseases associated with an aberrant VSMC phenotype.
Division of Cardiac Surgery, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
Fina
F
Lovren
Division of Cardiac Surgery, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
Yi
Y
Pan
Division of Cardiac Surgery, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
Adrian
A
Quan
Division of Cardiac Surgery, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
Krishna K
KK
Singh
Division of Cardiac Surgery, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
Rishad
R
Khan
University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
Nandini
N
Gupta
Division of Medicine & Hematology-Oncology, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada; Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
Christine
C
Brezden-Masley
Division of Cardiac Surgery, St. Michael's Hospital, Toronto, Ontario, Canada; Division of Endocrinology & Metabolism, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
Hwee
H
Teoh
Division of Vascular & Endovascular Surgery, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada; Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
Mark D
MD
Wheatcroft
Division of Vascular & Endovascular Surgery, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada; Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
Mohammed
M
Al-Omran
Division of Cardiac Surgery, St. Michael's Hospital, Toronto, Ontario, Canada; Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada; Department of Surgery, University of Toronto, Toronto, Ontario, Canada. Electronic address: vermasu@smh.ca.
Subodh
S
Verma
D000818:Animals; D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism*; D001794:Blood Pressure; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D015316:Genetic Therapy / Q000379:methods; D006657:Histones / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006973:Hypertension / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology / Q000628:therapy; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D000074624:NADPH Oxidase 1; D019255:NADPH Oxidases / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D010750:Phosphoproteins / Q000378:metabolism; D051135:Rad51 Recombinase / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014162:Transfection
D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D006657:Histones; D016877:Oxidants; D010750:Phosphoproteins; D017382:Reactive Oxygen Species; C577575:gamma-H2AX protein, rat; D006861:Hydrogen Peroxide; D009247:NADH, NADPH Oxidoreductases; D000074624:NADPH Oxidase 1; D019255:NADPH Oxidases; C402799:NOX1 protein, human; C000614711:NOX1 protein, mouse; C000614712:NOX1 protein, rat; C060505:neutrophil cytosolic factor 1; D051135:Rad51 Recombinase; C495155:Rad51 protein, rat