Citations

Abstract Background Nicotinamide adenosine dinucleotide phosphate oxidases (NOX) play important roles in mediating stress-induced depression. Three NOX isotypes are expressed mainly in the brain: NOX2, NOX3 and NOX4. In this study, the expression and cellular sources of these NOX isoforms was investigated in the context of stress-induced depression. Methods Chronic restraint stress (CRS)-induced depressive-like behaviour and cognitive deficits were evaluated by tail suspension tests, forced swimming tests and the Morris water maze test. Hippocampal NOX expression was determined by immunofluorescence staining and western blotting. The hippocampal levels of the brain-derived neurotrophic factor (BDNF) mRNA were determined via quantitative real-time –polymerase chain reaction. Glucocorticoid levels in the hippocampus were measured using ELISA kits. Results In the mouse CRS model, a significant increase in NOX2 expression was observed in the hippocampus, whereas no significant changes in NOX3 and NOX4 expression were detected. Next, NOX2 expression was primarily localised to neurons (NeuN+) but not microglia (Iba-1+) or astrocytes (GFAP+). Treatment with gp91ds-tat, a specific NOX2 inhibitor, effectively mitigated the behavioural deficits induced by CRS. The decreased expression of the BDNF mRNA in the hippocampus of CRS mice was restored upon gp91ds-tat treatment. A positive correlation was identified between neuronal NOX2 expression and serum glucocorticoid levels. Conclusions Our study indicated that neuronal NOX2 may be a critical mediator of depression-like behaviours and spatial cognitive deficits in mice subjected to CRS. Blockade of NOX2 signalling may be a promising therapeutic strategy for depression.

Abstract Biomarkers are lacking for identifying the switch of transforming growth factor-beta (TGF-β) from tumor-suppressing to tumor-promoting. Mutated p53 (mp53) has been suggested to switch TGF-β to a tumor promoter. However, we found that mp53 does not always promote the oncogenic role of TGF-β. Here, we show that endogenous mp53 knockdown enhanced cell migration and phosphorylation of ERK in DU145 prostate cancer cells. Further, ectopic expression of mp53 in p53-null PC-3 prostate cancer cells enhanced Smad-dependent signaling, but inhibited TGF-β-induced cell migration by downregulating activated ERK. Reactivation of ERK by the expression of its activator, MEK-1, restored TGF-β-induced cell migration. Since TGF-β is known to activate MAPK/ERK pathway through direct phosphorylation of adaptor protein ShcA and MAPK/ERK signaling is pivotal to tumor progression, we investigated whether ShcA contributed to mp53-induced ERK inhibition and the conversion of TGF-β's role during carcinogenesis. We found that mp53 expression led to decrease of phosphorylated p52ShcA/ERK levels and increase of phosphorylated Smad levels in a panel of mp53-expressing cancer cell lines, and in mammary glands and tumors from mp53 knock-in mice. By manipulating ShcA levels to regulate ERK and Smad signaling in human untransformed and cancer cell lines, we show that TGF-β's role in regulating anchorage-dependent and -independent growth, and migration, can be shifted between growth suppression and migration promotion. Thus, our results, for the first time, suggest that mp53 disrupts ShcA's role in balancing Smad-dependent and -independent signaling activity of TGF-β and that ShcA/ERK signaling is a major pathway regulating the tumor-promoting activity of TGF-β. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1069. doi:1538-7445.AM2012-1069