Functional interaction between nitric oxide-induced iron homeostasis and heme oxygenase-1 in immortalized and malignant oral keratinocytes.
Heme oxygenase-1 (HO-1) is involved in a variety of regulatory and protective cellular mechanisms as a stress-responsive protein. Whether HO-1 plays a protective role against NO-induced cytotoxicity in oral cancer cells has not yet been established. We used sodium nitroprusside (SNP) as a source of exogenous NO in studies of NO-induced cytotoxicity in immortalized (IHOK) and malignant oral keratinocytes (HN12). The roles of the caspase pathway, of regulatory proteins of iron metabolism (iron regulatory protein (IRP)1, IRP2, transferrin receptor (TfR), and ferritin), and of HO-1 in protection against NO-induced cytotoxicity were assessed. The SNP-induced growth inhibition and apoptosis of IHOK and HN12 cells was reduced by addition of ferric citrate (FC). At low concentrations (< 1 mM), SNP up-regulated cellular iron metabolism by increasing expression of IRP1, IRP2, and TfR, whereas at high concentrations (> 2 mM), SNP down-regulated expression of these proteins. A consistent correlation between decreased levels of IRP1, IRP2, and TfR and increased NO-induced cytotoxicity and apoptosis was observed. Addition of FC inhibited the NO-induced decrease in IRP1, IRP2, and TfR levels. Moreover, SNP increased the expression of HO-1 and ferritin in IHOK and HN12 cells in a concentration-dependent manner. NO-induced cytotoxicity was also inhibited by hemin (an HO-1 agonist) and was enhanced by zinc protoporphyrin IX (an HO-1 inhibitor). Based on these results, we conclude that HO-1 plays a major role in mediating cytoprotection and iron homeostasis against NO toxicity in immortalized and malignant oral keratinocytes.
Lee
Sun-Kyung
SK
Department of Oral and Maxillofacial Pathology, College of Dentistry, Wonkwang University, Iksan City, Jeonbuk 570-749, Republic of Korea.
Park
Dae-Yeol
DY
Lee
Hwa-Jeong
HJ
Lee
Jun
J
Choi
Moon-Ki
MK
Jeon
Byung-Hun
BH
Jun
Chang-Duk
CD
Lee
Suk-Keun
SK
Kim
Eun-Cheol
EC
D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D005290:Ferric Compounds / Q000494:pharmacology; D005293:Ferritins / Q000235:genetics; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D007501:Iron / Q000378:metabolism*; D035941:Iron Regulatory Protein 1 / Q000378:metabolism; D035942:Iron Regulatory Protein 2 / Q000378:metabolism; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism*; D009062:Mouth Neoplasms / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011990:Receptors, Transferrin / Q000235:genetics
D005290:Ferric Compounds; D020030:Nitric Oxide Donors; D012333:RNA, Messenger; D011990:Receptors, Transferrin; D009599:Nitroprusside; D009569:Nitric Oxide; C025314:ferric citrate; D005293:Ferritins; D007501:Iron; D052247:Nitric Oxide Synthase Type II; D051547:Heme Oxygenase-1; D035941:Iron Regulatory Protein 1; D035942:Iron Regulatory Protein 2