The studies of the effect of gaseous nitrogen oxides (NOx) on tumor promotion and malignant progression

• Main Authors: Jing-Hsien, 陳璟賢
• Other Authors: 王朝鐘
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/00421412260448601045

博士 === 中山醫學大學 === 生化暨生物科技研究所 === 94 === Part 1 Nitrogen oxides (NOx) are important indoor and outdoor air pollutants. Many studies have indicated that NOx gas causes lung tissue damage by its oxidation properties and its free radicals. In a previous study we demonstrated that NOx gas induced proliferation of human lung .broblast MRC-5 cells. In this study we show that NOx gas stimulates MRC-5 cell proliferation by Rb (retinoblastoma) phosphorylation via activation of cyclin-cell division protein kinase (cdk) complexes. Western blot and immunoprecipitation data showed that NOx gas increased the expressions of cyclinA/cdk2, cyclinD1/cdk4, and cyclinE/cdk2 complexes in the cells at 9 h after treatment. The levels of phospho-Rb were also increased and cdk inhibitors (CKIs) p27 and p16 were apparently decreased. These data suggested that NOx gas stimulates cell-cycle progression by Rb phosphorylation via activation of cyclin-cdk complexes and inhibition of CKIs. In conclusion, the NOx-gas that induced lung .broblast cell proliferation by stimulation of cellcycle progression may contribute to lung .brosis by NOx pollutants. Part 2 Benzo[a]pyrene (B[a]P) present in environmental pollution and cigarette smoke. B[a]P has been shown to induce apoptosis in hepatoma cells, human B cells, human ectocervical cells , macrophages and rat lungs. Nitrogen oxides (NOx) are other important indoor and outdoor air pollutants. Many studies have indicated that NOx gas causes lung tissue damage by its oxidative properties and its free-radicals. In our previous study we demonstrated that NOx gas induced proliferation of human lung fibroblast MRC-5 cells. In this study we showed that NOx gas inhibits B[a]P induced MRC-5 cells apoptosis by cell cycle analysis. Western blot data revealed that NOx gas increased the expressions of antiapoptosis proteins (Bcl-2 and Mcl-1) and decreased the expression of apoptosis proteins (Bax, t-Bid, cytochrome c, FasL and caspases) after B[a]P treatment. We further clarified that B[a]P induced MRC-5 cell apoptosis via JNK1/FasL and JNK1/p53 signals. In conclusion, NOx gas inhibited B[a]P-induced MRC-5 cells apoptosis via inhibition of JNK1 apoptosis pathway and induction of Bcl-2 and Mcl-1 antiapoptosis pathway. Part 3 Nitric oxide (NO), a short-lived radical molecule was considered as an environmental pollutant. Recent studies have demonstrated the biological importance of the interaction of NOx with proteins (1,2). Muller et al. provide evidences that peroxynitrite is formed in aqueous cigarette smoke fractions (3,4). Peroxynitrite, a reaction product of superoxide and nitric oxide, has been implicated in neurotoxicity (5,6), endothelial injury (7) and lipid peroxidative damage (8). Although much work has been performed characterizing the peroxynitrite, there is considerably less data on the cause of lung cancer exposure of NOx. In our previous study, we found that NOx caused DNA damage by the formation of 8-NO2-guanine in MRC-5 cells (9). We also provide evidences to suggest that stimulation of iNOS and accumulation of P53 by NOx gas in MRC-5 cells, we also found that gaseous NOx as a tumor promoter characterized by stimulation of cell proliferation (10) and inflammation via activation of Cyclin/CDK and increase phosphorylation of Rb (11) and gaseous NOx could repressed Benzo[a]pyrene induced MRC-5 cells apoptosis via inhibiting JNK1 signals (12). The present and future work, we designed to study the role of NOx on the tumor promotion via against carcinogens- mediated apoptosis and the role of NOx on the tumor metastasis and angiogenesis. Furthermore, we used A549 cells that exposed to NOx to study the role NOx in lung cancer metastasis and angiogenesis. The results of these studies may be used to firstly demonstrate the tumor promoting effect of NOx from air pollutant or cigarette on lung pathogenesis and tumor metastasis induction, respectively. Moreover, the results also explored that the NOx induced cell proliferation and blocked carcinogens-mediated apoptosis and NOx induced tumor metastasis, invasion and angiogenesis which may contribute to the lung pathogenic process, respectively.