Nonstructural 3 protein of hepatitis C virus triggers an oxidative burst in human monocytes via activation of NADPH oxidase

It has been shown that oxidative stress occurs in chronic hepatitis C. Rele ase of reactive oxygen species (ROS) from sequestered phagocytes and activa ted resident macrophages represents the predominant component of oxidative stress in the liver. However, little is known about the ability of the mono cyte to produce ROS in response to protein of hepatitis C virus. In this st udy, we investigated the ROS production in human monocytes stimulated by se veral viral proteins of hepatitis C virus. Human monocytes from healthy blo od donors were incubated with recombinant viral protein: Core, NS3, NS4, an d NS5. ROS production was measured by chemiluminescence. Only NS3 triggered ROS production in human monocytes. Generated ROS were mainly the anion sup eroxide. NS3 also induced a rapid and transient increase in intracellular c alcium concentration measured by a video digital microscopy technique. By u sing different metabolic inhibitors, we showed that ROS production requires calcium influx, tyrosine kinases, and the stress-activated protein kinase, p38. The study of p47(PHOX) phosphorylation and translocation showed that NADPH oxidase was activated and involved in ROS production induced by NS3. In a second experiment, NS3 inhibited the oxidative burst induced by phorbo l 12-myristate 13-acetate. These results indicate that NS3 activates NADPH oxidase and modulates ROS production, which may be involved in the natural history of hepatitis C infection.