In vitro folate supplementation alleviates oxidative stress, mitochondria-associated death signalling and apoptosis induced by 7-ketocholesterol.
Folate has recently been proposed as a new antioxidant. Folate supplementation may have a protective effect in counteracting oxidant-induced apoptotic damage. The present studies were undertaken to examine whether there is a direct link between folate levels, antioxidant capability and reduced apoptotic damage. Using an in vitro cellular model of 7-ketocholesterol (KC)-induced apoptosis, U937 cells were pre-cultured with a folate-deficient medium supplemented with various levels of folate (2-1500 micromol/l) before treatment with 7-KC. Apoptotic markers, mitochondria-associated death signals and levels of reactive oxygen species were assayed. After treatment with 7-KC for 30 h, low and high levels of folate supplementation significantly (P<0.05) reduced nuclear DNA loss. Only high levels of folate supplementation (>1000 micromol/l) were effective in counteracting 7-KC-promoted apoptotic membrane phosphatidylserine exposure and DNA laddering. The attenuation of 7-KC-induced apoptotic damage by high-dose folate supplementation coincided with a partial normalization of mitochondria membrane potential dissipation, a suppression of cytochrome c release and an inhibition of procaspase 3 activation. The prevention of mitochondrial dysfunctions and apoptotic processes was associated with antioxidant actions of high-dose folate by a marked scavenging of intracellular superoxide. Collectively, our present results demonstrate that in vitro folate supplementation exerts differentially protective effects against 7-KC-induced damage. High-dose supplementation alleviates oxidative stress, mitochondria-associated death signalling and apoptosis induced by 7-KC. However, the in vivo relevance is not clear and requires further study.
Huang
R-F S
RF
Department of Nutrition and Food Sciences, Fu-Jen University, Hsin-Chuang, Taiwan, Republic of China. rweifen@mails.fju.edu.tw
Yaong
H-C
HC
Chen
S-C
SC
Lu
Y-F
YF
D000975:Antioxidants / Q000008:administration & dosage*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000633:toxicity; D004792:Enzyme Precursors / Q000378:metabolism; D005492:Folic Acid / Q000008:administration & dosage*; D006801:Humans; D007653:Ketocholesterols / Q000633:toxicity; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects* / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D017382:Reactive Oxygen Species / Q000032:analysis; D020298:U937 Cells / Q000187:drug effects
D000975:Antioxidants; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D007653:Ketocholesterols; D017382:Reactive Oxygen Species; D045304:Cytochromes c; D005492:Folic Acid; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C003001:7-ketocholesterol