Study Title:

Quercetin Reduces Oxidative Stress of Cold Virus

Study Abstract

Background. Infection of the airway epithelium with rhinovirus (RV), the virus responsible for the majority of common colds, promotes secondary bacterial infection. Previously, we showed that RV disrupts barrier function, as evidenced by reduced transepithelial resistance (TER), and facilitates bacterial transmigration across polarized airway epithelial cells. Disruption of barrier function by RV is associated with dissociation of zona occludins (ZO)-1 from the tight junction complex; however, the underlying biochemical mechanisms are not known. Since RV has been shown to induce oxidative stress in infected cells, we hypothesized that RV-induced oxidative stress contributes to the observed tight junction breakdown.

Methods. Human bronchial airway (16HBE14o-) epithelial cells grown as polarized monolayers were infected apically with RV39. After 1 h, infection media was replaced with fresh media in the presence or absence of selected chemical inhibitors (see below), and incubated for an additional 23 h. TER was measured using a voltmeter. Tyrosine phosphorylation of ZO-1 and Rac1 activation were determined by pull-down assays.

Results. RV infection induced expression of NADPH oxidase (NOX)-1 and stimulated Rac1 and NADPH oxidase activity. Chemical inhibitors of NOX, diphenyleneiodonium (DPI), and Rac1, NSC23766 reversed RV-induced reductions in TER. Poly I:C treatment also reduced the TER and DPI reversed this effect. ROS scavenger, n-propylgallate; PI3-kinase inhibitor, LY294002; a plant flavonoid, quercetin which functions both as ROS scavenger and PI3-kinase inhibitor; MMP inhibitor, O-phenanthroline; EGFR inhibitor AG1458; and the Src tyrosine kinase inhibitor, PP2 also inhibited the RV-induced reduction in TER. Further, RV-infection caused tyrosine phosphorylation of ZO-1, which was inhibited by DPI and PP2. Conclusions. We conclude that activation of Rac-1 dependent NADPH oxidase is required for RV-induced tyrosine phosphorylation of ZO-1 and reduced barrier function. We speculate tha

t RV infection induces the activation of a Src/PI 3-kinase/Rac1 signaling complex, leading to the generation of reactive oxygen, tyrosine phosphorylation of ZO-1 and dissociation of ZO-1 from the tight junction complex.

Study Information

A. Comstock, BS, A. Chattoraj, MS, S. Ganesan, PhD, S. Chattoraj, MS, M.B. Hershenson, MD, U. Sajjan, PhD
Oxidative Stress Induced by Rhinovirus Plays a Role in the Disruption of Epithelial Barrier Function
American Thoracic Society May 2010 annual International Conference in New Orleans.
2010 May
Ann Arbor, MI/US

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