NO-induced downregulation of HSP10 and HSP60 expression in the postischemic brain.
Heat shock protein 60 (HSP60) and HSP10 are mitochondrial chaperonin proteins and are responsible for the folding of newly imported proteins and 13 polypeptides encoded by mitochondrial DNA. The expressions of HSP60 and HSP10 are regulated simultaneously because these genes are localized head to head on chromosome, separated by a bidirectional promoter, which harbors heat shock element (HSE), CHOP, STAT3, and SP1 binding sites. In the present study, we show that the expressions of HSP60 and HSP10 in the brain after middle cerebral artery occlusion (MCAO) are induced significantly. Interestingly, the expressions of HSP60 and HSP10 were further upregulated by the administration of aminoguanidine (AG), an inhibitor of the inducible nitric oxide synthase (iNOS), which is known to reduce ischemic damage in an animal model after MCAO. The results obtained in the present study suggest that HSP10 and HSP60 are induced in the postischemic brain, yet are downregulated by NO generated from 12 hr after MCAO/reperfusion. The downregulation of HSP60 and HSP10 by NO were confirmed in vitro, wherein HSP10 and SHP60 expressions were increased by treatment of LPS and IFN gamma (LPS/INF gamma) in C6 astroglioma cells and further upregulated by NMMA, another iNOS inhibitor. Reporter gene analysis combined with deletion and mutation studies showed that STAT3 binding site in the bidirectional promoter is responsible for LPS/INF gamma-induced upregulation and for downregulation by NO. Our results indicated that NO suppresses HSP60 and HSP10 inductions in the postischemic brain by suppressing STAT3 binding to its recognition site.
Kim
Seung-Woo
SW
Department of Anatomy and Center for Advanced Medical Education (BK21 project), Inha University School of Medicine, Inchon, Korea.
Lee
Ja-Kyeong
JK
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D045744:Cell Line, Tumor; D018835:Chaperonin 10 / Q000235:genetics / Q000378:metabolism*; D018834:Chaperonin 60 / Q000235:genetics / Q000378:metabolism*; D004347:Drug Interactions; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D005910:Glioma / Q000473:pathology; D020244:Infarction, Middle Cerebral Artery / Q000188:drug therapy / Q000473:pathology*; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D050791:STAT Transcription Factors / Q000378:metabolism; D013997:Time Factors; D014162:Transfection / Q000379:methods
D018835:Chaperonin 10; D018834:Chaperonin 60; D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D050791:STAT Transcription Factors; D009569:Nitric Oxide; D007371:Interferon-gamma