Although children born with severe homocystinurea (i.e.
cystathionine beta synthase homozygote knockout, CBS-/-) develop deleterious vascular complications with structural malformation and do not live past teenage, the heterozygote (CBS-/+) lives with apparently normal phenotype. Interestingly, this differential role of CBS expression in
vascular remodeling is unclear.
Peroxisome proliferator activated receptor gamma (PPARγ) is nuclear
transcription factor that mitigates vascular complications. The hypothesis was that
homocysteine (Hcy) decreased
thioredoxin (Trx),
peroxiredoxin (Prx), increased
NADPH oxidase (NOX1), mitochondrial
nitric oxide synthase (mtNOS) activity and
reactive oxygen species (ROS) in mitochondria in a CBS gene dose-dependent manner. ROS transduced
matrix metalloproteinase (
MMP) activation causing thickening (
fibrosis) of the basement membrane, rendering ineffective
endothelial nitric oxide synthase (eNOS) and promoted endothelial-smooth muscle disconnection/uncoupling by antagonizing PPARγ. Wild type (WT-CBS+/+), CBS-/+ and CBS -/- mice were treated with or without
ciglitazone (CZ, a PPARγ agonist) in food at birth. Aortic nuclear PPARγ expression was measured by EMSA. Aortic mtNOS activity and ROS production was measured using NO- and H(2)O(2)-electrodes, respectively. Aorta was analyzed for Trx, Prx, by Western blot, and PCR.
MMP activity was by in situ zymography. Aortic function was measured in tissue myobath. The results suggested 90% morbidity in CBS-/- allele at 12 wks. However, treatment with the PPARγ agonist, CZ significantly reduced the morbidity to 20%. In addition, CZ restored the PPARγ activity in CBS-/+ and -/- mice to normal levels. The oxidative stress was alleviated by CZ treatment. In situ labeling with mito-tracker suggests co-localization of ROS with mitochondrial mitophagy. The mtNOS activity was increased in HHcy compared to WT. The data support the notion that Hcy decreases redoxins, increases mtNOS activity and ROS/
oxidase in mitochondrial mitophagy in a gene dose-dependent manner of CBS. ROS transduces
MMP activation, rendering ineffective eNOS and promotes endothelial-smooth muscle disconnection/uncoupling by antagonizing PPARγ. We suggest that the children born with severe ho-mocystineurea may do better if treated with PPARγ agonist.