Nicotinamide adenine dinucleotide phosphate oxidase in experimental liver fibrosis: GKT137831 as a novel potential therapeutic agent

Abstract

Background & Aims NADPH oxidase (NOX) generates reactive oxygen species (ROS) in hepatic stellate cells (HSCs) during liver fibrosis. In response to fibrogenic agonists, such as angiotensin II (Ang II), the NOX1 components form an active complex including Rac1. Superoxide dismutase 1 (SOD1) interacts with the NOX-Rac1 complex to stimulate NOX activity. NOX4 is also induced in activated HSCs/myofibroblast by increased gene expression. Here, we investigate the role of an enhanced activity SOD1 G37R mutation (SODmu) and the effects of GKT137831, a dual NOX1/4 inhibitor, on HSCs and liver fibrosis. Methods To induce liver fibrosis, wild-type (WT) and SOD1mu mice were treated with carbon tetrachloride (CCl4) or bile duct ligation (BDL). Then, to address the role of NOX-SOD1-mediated ROS production in HSC activation and liver fibrosis, mice were treated with a NOX1/4 inhibitor. Fibrosis and ROS generation was assessed by histology and measurement of TBARS and NOX related genes. Primary cultured HSCs isolated from WT, SODmu, and NOX1 knock-out (KO) mice were assessed for ROS production, Rac1 activity, and NOX gene expression. Results Liver fibrosis was increased in SOD1mu mice, and ROS production and Rac1 activity were increased in SOD1mu HSCs. The NOX1/4 inhibitor GKT137831 attenuated liver fibrosis and ROS production in both SOD1mu and WT mice as well as mRNA expression of fibrotic and NOX genes. Treatment with GKT137831 suppressed ROS production and NOX and fibrotic gene expression, but not Rac1 activity, in SOD1mut and WT HSCs. Both Ang II and TGFb upregulated NOX4, but AngII required NOX1. Conclusions SOD1mu induces excessive NOX1 activation through Rac1 in HSCs, causing enhanced NOX4 upregulation, ROS generation, and liver fibrosis. Treatment targeting NOX1/4 may be a new therapy for liver fibrosis.

Genetic Targeting or Pharmacologic Inhibition of NADPH Oxidase Nox4 Provides Renoprotection in Long-Term Diabetic Nephropathy

“…It has been shown to provide endorgan protective effects, albeit in the liver. 22,52 Importantly, in our study, treatment of diabetic ApoE 2 / 2 mice with GKT137831 mimicked the effects of Nox4 deletion on glomerular injury, albuminuria, ROS production, ECM accumulation, and macrophage infiltration. Thus, the renoprotective effects of GKT137831 are likely to be mediated by Nox4 rather than Nox1 inhibition.…”

“…In addition, the genetic deletion studies were complemented by a pharmacologic intervention study using the currently most specific Nox inhibitor, GKT137831. 22 Key findings in the in vivo studies were confirmed in vitro using human podocytes.…”

NADPH oxidase 4 represents a potential target for the treatment of osteoporosis

“…These results suggest that bone loss could be attenuated by the inhibition of NOX4. NOX4 inhibitors 13 are currently in preclinical testing and could represent a novel class of future osteoporosis drugs. Although several different anti-osteoporotic agents have been developed such as the gold standard bisphosphonates, there is a need for effective new treatment strategies.…”

The Nox4 Inhibitor GKT137831 Attenuates Hypoxia-Induced Pulmonary Vascular Cell Proliferation

“…GKT137831 is a weak inhibitor of Nox2 in cell-free assays and did not significantly inhibit neutrophil oxidative burst. GKT137831 had no radical scavenging or antioxidant activity and did not show significant in vitro offtarget inhibition of 170 different proteins, indicating high Nox specificity (21,22).…”

“…The current study used GKT137831, a recently described pyrazolopyridinedione derivative that inhibits Nox4 and Nox1 (21), to further examine the role of Nox4 in hypoxia-induced alterations in pulmonary vascular cell proliferation and PH. GKT137831 [2-(2-…”