Sustained expression of NADPH oxidase 4 by p38 MAPK-Akt signaling potentiates radiation-induced differentiation of lung fibroblasts

Abstract

Radiation-induced fibrosis (RIF) is a long-term adverse effect of curative radiotherapy; however, the distinct molecular mechanisms of RIF in neighboring normal tissue are not fully understood. We investigated the mechanisms underlying radiation-induced fibroblast differentiation into myofibroblasts. Lung fibroblasts produced reactive oxygen species (ROS) immediately after irradiation, the level of which remained increased for 24 h. The NADPH oxidase inhibitor, diphenyleneiodonium (DPI), suppressed ROS production and significantly decreased the radiation-induced expression of alpha-smooth muscle actin (alpha-SMA) and fibronectin (FN). The mRNA and protein expression of Nox4 was increased by radiation, and siRNA knockdown of Nox4 reduced alpha-SMA and FN levels. Increased phosphorylation of p38MAPK, Erk, and PI3k/Akt was observed after irradiation. Inhibitors of p38 MAPK and Akt, but not of Erk, reduced radiation-induced fibroblast differentiation and Nox4 expression. Notably, DPI partially decreased phosphorylation of p38MAPK and Akt, suggesting that p38MAPK, Akt, and Nox4 may cooperate in a positive feedback loop. Nox4 expression was also increased during bleomycin-induced fibroblast differentiation, and downregulation of Nox4 reduced alpha-SMA levels and extracellular matrix (ECM) accumulation. These results demonstrate that interfering Nox4 activation can be a potential strategy to disrupt fibrotic process.

O-linked β-N-acetylglucosamine supports p38 MAPK activation by high glucose in glomerular mesangial cells

“…O-GlcNAc may influence the expression or function of a variety of proteins involved in high-glucose-induced ROS production. On the other hand, it is equally plausible that much of this effect of OGT shRNA on ROS is secondary to inactivation of p38, which can phosphorylate the NADPH oxidase subunit p47 phox (57) and upregulate the expression of the NADPH oxidase Nox4 (54). Reinforcing this view, the p38 inhibitor SB-203580 has been shown to block high-glucose-induced increases in ROS in mesangial cells (60).…”

NADPH oxidase subunit 4 mediates cycling hypoxia-promoted radiation resistance in glioblastoma multiforme

“…As expected, our results confirmed that intracerebral glioblastoma-bearing mice receiving Nox4 knockdown result in an improved overall therapeutic efficiency in radiotherapy. Although we did not investigate the effect of this therapeutic approach on normal tissues, recent studies highlight that radiation induces chronic oxidative stress in rat brain microvascular endothelial cells [44], murine hematopoietic stem cells [45], and human lung fibroblast cells [46], at least in part via up-regulation of Nox4 that leads to the induction of brain and bone marrow injury or fibrosis. Therefore, treatment via Nox4 inhibition may be a good clinical practice to block cycling hypoxia-mediated tumor radioresistance and prevent radiation-induced normal tissue injury in the radiotherapy of GBM.…”

Glycated human serum albumin induces NF-κB activation and endothelial nitric oxide synthase uncoupling in human umbilical vein endothelial cells

“…4 been associated with the expression and activity of NADPH oxidase (Pedruzzi, E. et al 2004;Anrather, J. et al 2006;Manea, A. et al 2008;Manea, A. et al 2010;Park, S. et al 2010). …”

“…However, the molecular signalling pathways activated by glycated albumin leading to these effects are still unclear, although some hypotheses can be suggested based on previous data: indeed, transcription factors like NF-κB and AP-1, which are the final step of signalling pathways mediated by kinases like MEK 1/2 and PI3K (Higai, K. et al 2006;Manea, A. et al 2008; Manea, A. et al 2010;Park, S. et al 2010). Moreover, these pathways have also A C C E P T E D M A N U S C R I P T…”