Adenosine triphosphate regulates NADPH oxidase activity leading to hydrogen peroxide production and COX-2/PGE(2) expression in A549 cells

Dept. of Pharmacology, College of Medicine, Chang Gung Univ., Kwei-San, Tao-Yuan, Taiwan.
AJP Lung Cellular and Molecular Physiology (Impact Factor: 4.08). 07/2012; 303(5):L401-12. DOI: 10.1152/ajplung.00090.2012
Source: PubMed


Non-small cell lung carcinoma (NSCLC) accounts for most of all lung cancers, which is the leading cause of mortality in human beings. High level of cyclooxygenase-2 (COX-2) is one of the features of NSCLC and related to the low survival rate of NSCLC. However, whether extracellular nucleotides releasing from stressed resident tissues contributes to the expression of COX-2 remains unclear. Here, we showed that stimulation of A549 cells by adenosine 5'-O-(3-thiotriphosphate) (ATPγS) led to an increase in COX-2 gene expression and prostaglandin E(2) (PGE(2)) synthesis, revealed by Western blotting, RT-PCR, promoter assay, and enzyme-linked immunosorbent assay. In addition, ATPγS induced intracellular reactive oxygen species (ROS) generation through the activation of NADPH oxidase. The increase of ROS level resulted in activation of the c-Src/epidermal growth factor receptor (EGFR)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/nuclear factor (NF)-κB cascade. We also found that activated Akt was translocated into the nucleus and recruited with NF-κB and p300 to form a complex. Thus, activation of p300 modulated the acetylation of histone H4 via the NADPH oxidase/c-Src/EGFR/PI3K/Akt/NF-κB cascade stimulated by ATPγS. Our results are the first to show a novel role of NADPH oxidase-dependent Akt/p65/p300 complex formation that plays a key role in regulating COX-2/PGE(2) expression in ATPγS-treated A549 cells. Taken together, we demonstrated that ATPγS stimulated activation of NADPH oxidase, resulting in generation of ROS, which then activated the downstream c-Src/EGFR/PI3K/Akt/NF-κB/p300 cascade to regulate the expression of COX-2 and synthesis of PGE(2) in A549 cells. Understanding the regulation of COX-2 expression and PGE(2) release by ATPγS on A549 cells may provide potential therapeutic targets of NSCLC.

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    • "COX-1 is constitutively expressed in most tissues and considered to be the " housekeeping " isoform that produces PGs which are required for maintenance of normal cell and organ function. In contrast, COX-2 is primarily an inducible isoform whose expression can be upregulated in many cell types by cytokines, mitogens, and endotoxin [3] [4]. It is highly expressed in inflamed tissues and believed to produce PGs involved in inflammatory processes [33]. "
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