Redox Factor-1 Inhibits Cyclooxygenase-2 Expression via Inhibiting of p38 MAPK in the A549 Cells

In this study, we evaluated the role of apurinic/apyrimidinic endonuclease1/redox factor-1 (Ref-1) on the tumor necrosis factor-alpha (TNF-alpha) induced cyclooxygenase-2 (COX-2) expression using A549 lung adenocarcinoma cells. TNF-alpha induced the expression of COX-2 in A549 cells, but did not induce BEAS-2B expression. The expression of COX-2 in A549 cells was TNF-alpha dose-dependent (5~100 ng/ml). TNF-alpha-stimulated A549 cells evidenced increased Ref-1 expression in a dose-dependent manner. The adenoviral transfection of cells with AdRef-1 inhibited TNF-alpha-induced COX-2 expression relative to that seen in the control cells (Ad beta gal). Pretreatment with 10 micrometer of SB203580 suppressed TNF-alpha-induced COX-2 expression, thereby suggesting that p38 MAPK might be involved in COX-2 expression in A549 cells. The phosphorylation of p38 MAPK was increased significantly after 5 minutes of treatment with TNF-alpha, reaching a maximum level at 10 min which persisted for up to 60 min. However, p38MAPK phosphorylation was markedly suppressed in the Ref-1-overexpressed A549 cells. Taken together, our results appear to indicate that Ref-1 negatively regulates COX-2 expression in response to cytokine stimulation via the inhibition of p38 MAPK phosphorylation. In the lung cancer cell lines, Ref-1 may be involved as an important negative regulator of inflammatory gene expression.

Alteration of Apurinic/Apyrimidinic Endonuclease-1/Redox Factor-1 in Human Non-small Cell Lung Cancer / 대한흉부외과학회지

BACKGROUND: An imbalance between oxidants and antioxidants leads to oxidative stress, and this has been proposed to play an important role in the pathogenesis of lung neoplasm. Apurinic/apyrimidinic endonuclease-1/redox factor-1 (APE/ref-1) is a multifunctional protein involved in DNA base excision repair and the redox regulation of many transcription factors. However, the alteration of the expressed levels of APE/ref-1 in non-small cell lung cancer is unknown. MATERIAL AND METHOD: Forty-nine patients with surgically resected non-small cell lung cancer (NSCLC) were included in this study. Immunohistochemical staining with APE/ref-1 antibodies was performed, and their expressions were analyzed via Western blotting for specific antibodies. RESULT: APE/ref-1 was localized at the nucleus and mainly in the non-tumor region of the NSCLC tissue specimens; it was expressed in the cytoplasm and nucleus of the NSCLC. The nuclear and cytoplasmic expressions of APE/ref-1 in lung cancers were markedly up-regulated in the NSCLC, and this was correlated with the clinical stage. Catalase, as first-line antioxidant defense, was dramatically decreased in the NSCLC. CONCLUSION: Taken together, our results suggest that APE/ref-1, and especially cytoplasmic APE/ref-1, was upregulated in the lung cancer regions, and this may contribute to the compensatory defense system against oxidative stress. A low expression of catalase might have fundamental effects on the extracellular redox state of lung tumors, along with the potential consequences for the tumors.

p66shc Adaptor Protein Suppresses the Activation of Endothelial Nitric Oxide Synthase in Mouse Embryonic Fibroblasts

Among the Shc proteins, p66shc is known to be related to oxidative stress responses and regulation of the production of reactive oxygen species (ROS). The present study was undertaken to investigate the role of p66shc on endothelial nitric oxide synthase (eNOS) activity in the mouse embryonic fibroblasts (MEFs). When wild type (WT) or p66shc (-/-) MEFs were transfected with full length of eNOS cDNA, the expression and activity of eNOS protein were higher in the p66shc (-/-) MEFs. These phenomena were reversed by reconstitution of p66shc cDNA transfection in the p66shc (-/-) MEFs. The basal superoxide production in the p66shc (-/-) MEFs was not significantly different from that of WT of MEFs. However, superoxide production induced by NADPH in the p66shc (-/-) MEF was lesser than that in WT MEFs. When compared with WT MEFs, cell lysate of p66shc (-/-) MEFs showed significantly increased H-ras activity without change of endogenous H-ras expression. Our findings suggest the pivotal role of p66shc adaptor protein played in inhibition of endothelial nitric oxide production via modulation of the expression and/or activity of eNOS protein.

NADPH Oxidase and Mitochondrial ROS are Involved in the TNF-alpha-induced Vascular Cell Adhesion Molecule-1 and Monocyte Adhesion in Cultured Endothelial Cells

Atherosclerosis is considered as a chronic inflammatory process. However, the nature of the oxidant signaling that regulates monocyte adhesion and its underlying mechanism is poorly understood. We investigated the role of reactive oxygen species on the vascular cell adhesion molecule-1 (VCAM-1) and monocyte adhesion in the cultured endothelial cells. TNF-alpha at a range of 1~30 ng/ml induced VCAM-1 expression dose-dependently. BCECF-AM-labeled U937 cells firmly adhered on the surface of endothelial cells when the endothelial cells were incubated with TNF-alpha (15 ng/ml). Ten micromol/L of SB203580, an inhibitor of p38 MAPK, significantly reduced TNF-alpha-induced VCAM-1 expression, compared to the JNK inhibitor (40micromol/L of SP60015) or ERK inhibitor (40micrommol/L of U0126). Also, SB203580 significantly inhibited TNF-alpha-induced monocyte adhesion in HUVEC. Superoxide production was minimal in the basal condition, however, treatment of TNF-alpha induced superoxide production in the dihydroethidine-loaded endothelial cells. Diphenyleneiodonium (DPI, 10micromol/L), an inhibitor of NADPH oxidase, and rotenone (1micromol/L), an inhibitor of mitochondrial complex I inhibited TNF-alpha-induced superoxide production, VCAM-1 expression and monocyte adhesion in the endothelial cells. Taken together, our data suggest that NADPH oxidase and mitochondrial ROS were involved in TNF-alpha-induced VCAM-1 and monocyte adhesion in the endothelial cells.