5 In fact, we were able to detect a larger amount of 2-OH-E+ by inhibiting SOD in our cells, and this suggests a significant selleckchem competition between the probe and SOD for the reaction with superoxide (unpublished observations, Reyes de Mochel and Choi, 2009). ROS/reactive nitrogen species thus generated would then cooperate with other Nox/Duox enzymes and other potential sources of ROS outside the nucleus to induce a chronic state of oxidative/nitrosative
stress during HCV infection. In this scheme, ROS generated by nuclear Nox4 and other extranuclear sources of ROS would form concentration gradients, the probability of their reacting with target molecules diminishing with increasing distance from their respective origin (Fig. 8D). Our discovery of nuclear Nox4 raises the question
of exactly where in the nucleus Nox4 is located and how HCV changes the location of Nox4 without affecting the location of Nox1. Nox family enzymes have multiple transmembrane domains selleck and are membrane-bound.6 In this respect, it may be important to note that the endoplasmic reticulum membrane is contiguous with the nuclear membrane. Also, the nucleoplasm is generally membrane-free, but intranuclear membrane structures have been reported,19 and Nox4 might be located within the inner or outer nuclear membrane or intranuclear cisternae of hepatocytes. If Nox4 is responsible
for peroxynitrite-dependent DNA damage, it is most likely located on the inner nuclear membrane or intranuclear membrane, with its active site facing the nucleoplasm. Notice that in our nuclear Nox activity assays, the nuclear pore was likely to allow NADPH, cytochrome c, and SOD to enter the nucleus. A detailed analysis of the subcellular MCE公司 location of Nox4 by electron microscopy is underway. With respect to the mechanism of increased nuclear localization of Nox4, HCV is known to induce severe membrane and nuclear alterations.20 Thus, the increased nuclear location of Nox4 might be a result of the virus modifying the cell for its replication. In addition, as some Nox4 could be found in the nucleus even without HCV (Fig. 5), nuclear Nox4 likely represents a normal cellular process that is enhanced by HCV. In this study, we focused primarily on 50- to 65-kDa Nox1/4 protein bands, which corresponded to the expected sizes of Nox1 and Nox4 proteins. The higher molecular weight bands, however, also increased with HCV and could be partly decreased with siRNAs (Figs. 3 and 4), and they might represent Nox protein complexes or posttranslationally modified Nox.9 Nox enzymes have been implicated in antimicrobial defense, toll-like receptor signaling, lung fibrosis, and cancers. H2O2 and Nox enzymes can also increase iron uptake and mediate many biological effects of TGFβ.