NOX1/nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase promotes proliferation of stellate cells and aggravates liver fibrosis induced by bile duct ligation.

Abstract

UNLABELLED:

Among multiple isoforms of nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase expressed in the liver, the phagocytic NOX2 isoform in hepatic stellate cells (HSCs) has been demonstrated to play a key role in liver fibrogenesis. The aim of this study was to clarify the role of NOX1, a nonphagocytic form of NADPH oxidase, in the development of fibrosis using Nox1-deficient mice (Nox1KO). Liver injury and fibrosis were induced by bile duct ligation (BDL) and carbon tetrachloride in Nox1KO and wildtype littermate mice (WT). Primary HSCs were isolated to characterize the NOX1-induced signaling cascade involved in liver fibrogenesis. Following BDL, a time-dependent increase in NOX1 messenger RNA (mRNA) was demonstrated in WT liver. Compared with those in WT, levels of collagen-1α mRNA and hydroxyproline were significantly suppressed in Nox1KO with a reduced number of activated HSCs and less severe fibrotic lesions. The expression levels of α-smooth muscle actin, a marker of HSCs activation, were similar in cultured HSCs isolated from both genotypes. However, cell proliferation was significantly attenuated in HSCs isolated from Nox1KO. In these cells, the expression of p27(kip1) , a cell cycle suppressor, was significantly up-regulated. Concomitantly, a significant reduction in phosphorylated forms of Akt and forkhead box O (FOXO) 4, a downstream effector of Akt that regulates the transcription of p27(kip1) gene, was demonstrated in Nox1KO. Finally, the level of the oxidized inactivated form of phosphatase and tensin homolog (PTEN), a negative regulator of PI3K/Akt pathway, was significantly attenuated in HSCs of Nox1KO.

CONCLUSION:

These findings indicate that reactive oxygen species derived from NOX1/NADPH oxidase oxidize and inactivate PTEN to positively regulate the Akt/FOXO4/p27(kip1) signaling pathway. NOX1 may thus promote proliferation of HSCs and accelerate the development of fibrosis following BDL-induced liver injury.

• Authors: Wenhao Cui, Kuniharu Matsuno, Kazumi Iwata, Masakazu Ibi, Misaki Matsumoto, Jia Zhang, Kai Zhu, Masato Katsuyama, Natalie J Torok, Chihiro Yabe-Nishimura
• Journal: Hepatology (Baltimore, Md.) (Hepatology) Vol. 54 Issue 3 Pg. 949-58 (Sep 02 2011) ISSN: 1527-3350 [Electronic] United States
• PMID: 21618578 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 American Association for the Study of Liver Diseases.

Chemical References

• Cdkn1b protein, mouse
• Cell Cycle Proteins
• Forkhead Transcription Factors
• FoxO4 protein, mouse
• Reactive Oxygen Species
• Cyclin-Dependent Kinase Inhibitor p27
• NADP
• Carbon Tetrachloride
• NADH, NADPH Oxidoreductases
• NADPH Oxidase 1
• NOX1 protein, mouse
• Proto-Oncogene Proteins c-akt
• PTEN Phosphohydrolase
• Pten protein, mouse

Topics

• Animals
• Carbon Tetrachloride (toxicity)
• Cell Cycle Proteins
• Cell Proliferation
• Cells, Cultured
• Cyclin-Dependent Kinase Inhibitor p27 (physiology)
• Forkhead Transcription Factors (physiology)
• Hepatic Stellate Cells (pathology)
• Ligation
• Liver Cirrhosis, Experimental (etiology, pathology)
• Mice
• NADH, NADPH Oxidoreductases (physiology)
• NADP (physiology)
• NADPH Oxidase 1
• PTEN Phosphohydrolase (physiology)
• Proto-Oncogene Proteins c-akt (physiology)
• Reactive Oxygen Species (metabolism)
• Signal Transduction (physiology)