NAD(P)H oxidase plays a crucial role in PDGF-induced proliferation of hepatic stellate cells

Abstract

The proliferation of hepatic stellate cells (HSCs) is a critical step in hepatic fibrogenesis. Platelet‐derived growth factor (PDGF) is the most potent mitogen for HSCs. We investigated the role of nonphagocytic NAD(P)H oxidase–derived reactive oxygen species (ROS) in PDGF‐induced HSC proliferation. The human HSC line, LI‐90 cells, murine primary‐cultured HSCs, and PDGF‐BB were used in this study. We examined the mechanism of PDGF‐BB‐induced HSC proliferation in relation to the role of a ROS scavenger and diphenylene iodonium, an inhibitor of NAD(P)H oxidase. We also measured ROS production with the aid of chemiluminescence. We showed that PDGF‐BB induced proliferation of HSCs through the intracellular production of ROS. We also demonstrated that HSCs expressed key components of nonphagocytic NAD(P)H oxidase (p22phox, gp91phox, p47phox, and p67phox) at both the messenger RNA and protein levels. Diphenylene iodonium suppressed PDGF‐BB–induced ROS production and HSC proliferation. Coincubation of H2O2 and PDGF‐BB restored the proliferation of HSCs that was inhibited by diphenylene iodonium pretreatment. Phosphorylation of the mitogen‐activated protein kinase (MAPK) family constitutes a signal transduction pathway of cell proliferation. Our data demonstrate that NAD(P)H oxidase–derived ROS induce HSC proliferation mainly through the phosphorylation of p38 MAPK. Moreover, an in vivo hepatic fibrosis model also supported the critical role of NAD(P)H oxidase in the activation and proliferation of HSCs. In conclusion, NAD(P)H oxidase is expressed in HSCs and produces ROS via activation of NAD(P)H oxidase in response to PDGF‐BB. ROS further induce HSC proliferation through the phosphorylation of p38 MAPK. (HEPATOLOGY 2005;41:1272–1281.)

TNF-α-induced up-regulation of intercellular adhesion molecule-1 is regulated by a Rac-ROS-dependent cascade in human airway epithelial cells

“…Recently, however, NADPH-oxidase (Nox) has received a lot of interest as source of ROS in cellular signaling and these Nox-derived ROS are suggested to act as specific signaling mediators in various non-phagocytic cells (Vaquero et al, 2004;Adachi et al, 2005). Although upstream regulatory mechanism for Nox activation has not been understood yet, Rac was suggested to be a crucial component for full activation of Nox (Mizrahi et al, 2005), in accordance with our observation that Rac is associated with NADPH oxidase-like flavoenzyme-derived ROS generation ( Figure 4A).…”

Inhibition of platelet‐derived growth factor‐induced mesangial cell proliferation by cyclooxygenase‐2 overexpression is abolished through reactive oxygen species

“…Moreover, catalase and NADPH oxidase could probably be influenced by COX-2 because increased catalase activity blocked PDGF-induced processes [19] and NADPH oxidase plays a crucial role in PDGF-induced proliferation in other cell systems [23].…”

Role of free radicals in liver diseases

“…High levels of ROS, from phagocytic cells, such as Kupffer cells (KC), protect the organism from external pathogens; however, lower amounts of ROS mainly from HSC actively participate in the regulation of intracellular signaling [25,27]. Platelet-derived growth factor (PDGF) is the most potent mitogen of HSC and is, therefore, likely to be an important mediator during liver fibrogenesis [28].…”

“…Platelet-derived growth factor (PDGF) is the most potent mitogen of HSC and is, therefore, likely to be an important mediator during liver fibrogenesis [28]. Interestingly, NAD(P)H is expressed in HSC and produce ROS, which, in turn, induces the production of PDGF; again, this molecule increases mitosis of HSC [27]. These results strongly suggest that ROS play an important role in fibrogenesis increasing PDGF throughout.…”