N-nitroso-N-methylurea and N-nitroso-N-ethylurea induce upregulation of cellular NF-kappa B activity through protein kinase C-dependent pathway in human malignant keratinocytes.
The upregulatory mechanism of cellular NF-kappaB activity by carcinogens, N-nitroso-N-methylurea (NMU) and N-nitroso-N-ethylurea (NEU) in human malignant keratinocytes was investigated. To elucidate the role of protein kinase C (PKC) in the upregulation of NF-kappaB by NMU and NEU, two known PKC inhibitors, staurosporine and H-7 were studied. Treatment of cells with PKC inhibitors decreased NF-kappaB activity in a dose responsive manner at concentrations of 20 approximately 200 nM. Staurosporine (160 nM) and H-7 (200 nM) downregulated the cellular NF-kappaB activation up to 20 and 60% compared to the NF-kappaB activity that was upregulated by NMU (5 microM) and NEU (5 microM), respectively. These results indicated that the PKC activity was responsible for the upregulation of NF-kappaB activity. The level of phosphorylation of I-kappaBalpha, the predominant form of the I-kappaB family represented by NMU and NEU, was quantified. The relative amount of I-kappaBalpha phosphorylation (serines-32 and -36) determined using the cellular activation of signaling ELISA assay method showed that NMU (5 microM) and NEU (5 microM) increased the amount of I-kappaBalpha phosphorylation up to 17 and 10% compared to the control, respectively. The results demonstrate the upregulatory effect of NMU and NEU on cellular NF-kappaB activity in human keratinocytes via the protein kinase C-mediated pathway.
Moon
Ki-Young
KY
Department of Clinical Pathology, Gwangju Health College University, Gwangju 506-701, Korea. kmoon@ghc.ac.kr
D002273:Carcinogens / Q000494:pharmacology*; D002448:Cell Adhesion; D002452:Cell Count; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000633:toxicity; D004797:Enzyme-Linked Immunosorbent Assay; D005038:Ethylnitrosourea / Q000494:pharmacology*; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000201:enzymology*; D008770:Methylnitrosourea / Q000494:pharmacology*; D016328:NF-kappa B / Q000096:biosynthesis*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
D002273:Carcinogens; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D008770:Methylnitrosourea; D011493:Protein Kinase C; D005038:Ethylnitrosourea