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Title: A study to investigate the involvement of Nadph Oxidase 5 (NOX5) in resveratrol (RSV) - induced reactive oxygen species (ROS) production in U937 cells
Keywords: Resveratrol, NOX5, ROS
Issue Date: 20-Jul-2010
Source: BHUVANESHWARI D/O SHUNMUGANATHAN (2010-07-20). A study to investigate the involvement of Nadph Oxidase 5 (NOX5) in resveratrol (RSV) - induced reactive oxygen species (ROS) production in U937 cells. ScholarBank@NUS Repository.
Abstract: ROS are oxygen - derived small molecules. The initial form of ROS is superoxide anion (O2 .- ) which is produced by the gain of electrons. Subsequent chemical reactions can lead to the formation of other forms of ROS species. NOX enzymes are one of the major sources of ROS. NOX5 belongs to the family of NOX enzymes. NOX5 differs from the other members of the NOX family in aspects as such as its mode of activation and biophysical structure. NOX5 comprises of 2 membrane-bound subunits namely gp91 and p22. It does not require the recruitment of cytosolic subunits, unlike its counterparts. The activity of NOX5 is regulated by elevations in cytosolic calcium levels and phosphorylation via kinases such as c- Abl (Abelson murine leukemia viral oncogene) and PKC. The N-terminus of NOX5 comprises EF-hands that serve as calcium binding domains. It has been established so far that NOX5 is a growth signalling oxidase and its expression is regulated via growth regulatory agonists/triggers/signals. NOX5 has been also shown to be expressed in a variety of tumour cell lines and is being explored as a cancer biomarker. RSV a naturally occurring phenolic phytoalexin is currently being employed as a `parent¿ compound in cancer drug development. It has been well-studied that RSV is a ROS-modulating compound. It can act as a pro/antioxidant depending on the concentration and cell line used. Previous studies have shown that, RSV is able to alter the expression and activity of other NOX isoforms is a range of cell lines. This study aimed to investigate the involvement of RSV-induced ROS production in regulating NOX5 expression in the U937 lymphoma cells. The initial part of the study involved analyzing the expression of NOX5 following RSV treatment. RSV was shown to increase NOX5 expression in U937 in a dose-dependent manner. A time course was also performed and it showed that NOX5 expression starts to increase as early as 2hr. ROS was being implicated as the possible factor involved in the regulation of NOX5 expression due to the nature of RSV. The pre-treatment of U937 with ROS scavengers prior to RSV treatment abrogated the increase in NOX5 expression. Further studies were performed and it showed ROS producing compounds such as DDC and H2O2 were able to increase NOX5 expression level. However, NO-producing compounds did not significantly alter the NOX5 expression level. CREB phosphorylation was observed post-RSV treatment and this was reversible via pre-incubation with Cyclosporin A. CREB phosphorylation levels were also observed to precede the increase NOX5 expression level. Thus CREB is being suggested as a possible transcription factor regulating NOX5 expression. This study highlights the role of ROS producing compound RSV in regulating the expression level of NOX5 in U937.
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