Inhibition of mitochondrial cytochrome c release and suppression of caspases by gamma-tocotrienol prevent apoptosis and delay aging in stress-induced premature senescence of skin fibroblasts.
In this study, we determined the molecular mechanism of γ-tocotrienol (GTT) in preventing cellular aging by focusing on its anti-apoptotic effect in stress-induced premature senescence (SIPS) model of human diploid fibroblasts (HDFs). Results obtained showed that SIPS exhibited senescent-phenotypic characteristic, increased expression of senescence-associated β-galactosidase (SA β-gal) and promoted G(0)/G(1) cell cycle arrest accompanied by shortening of telomere length with decreased telomerase activity. Both SIPS and senescent HDFs shared similar apoptotic changes such as increased Annexin V-FITC positive cells, increased cytochrome c release and increased activation of caspase-9 and caspase-3 (P < 0.05). GTT treatment resulted in a significant reduction of Annexin V-FITC positive cells, inhibited cytochrome c release and decreased activation of caspase-9 and caspase-3 (P < 0.05). Gene expression analysis showed that GTT treatment down regulated BAX mRNA, up-regulated BCL2A1 mRNA and decreased the ratio of Bax/Bcl-2 protein expression (P < 0.05) in SIPS. These findings suggested that GTT inhibits apoptosis by modulating the upstream apoptosis cascade, causing the inhibition of cytochrome c release from the mitochondria with concomitant suppression of caspase-9 and caspase-3 activation. In conclusion, GTT delays cellular senescence of human diploid fibroblasts through the inhibition of intrinsic mitochondria-mediated pathway which involved the regulation of pro- and anti-apoptotic genes and proteins.
Department of Biochemistry, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia. suzanamakpol@yahoo.com
Suzana
S
Makpol
Norhazira
N
Abdul Rahim
Chua Kien
CK
Hui
Wan Zurinah Wan
WZ
Ngah
D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D015139:Blotting, Southern; D020169:Caspases / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D048430:Cell Shape / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects*; D002839:Chromans / Q000494:pharmacology*; D045304:Cytochromes c / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012867:Skin / Q000473:pathology; D013312:Stress, Physiological / Q000187:drug effects; D019098:Telomerase / Q000378:metabolism; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000494:pharmacology; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D017304:Annexin A5; D002839:Chromans; D051028:bcl-2-Associated X Protein; D014810:Vitamin E; C013649:plastochromanol 8; D045304:Cytochromes c; D019098:Telomerase; D020169:Caspases; D016650:Fluorescein-5-isothiocyanate