Published online May 14, 2023. doi: 10.3748/wjg.v29.i18.2798
Peer-review started: December 13, 2022
First decision: February 23, 2023
Revised: March 8, 2023
Accepted: April 10, 2023
Article in press: April 10, 2023
Published online: May 14, 2023
Processing time: 148 Days and 21.6 Hours
Hepatic fibrosis is a serious condition, and the development of hepatic fibrosis can lead to a series of complications. However, the pathogenesis of hepatic fibrosis remains unclear, and effective therapy options are still lacking. Our group identified hepatitis C virus nonstructural protein 3-transactivated protein 1 (NS3TP1) by suppressive subtractive hybridization and bioinformatics analysis, but its role in diseases including hepatic fibrosis remains undefined. Therefore, additional studies on the function of NS3TP1 in hepatic fibrosis are urgently needed to provide new targets for treatment.
To elucidate the mechanism of NS3TP1 in hepatic fibrosis and the regulatory effects of calcitriol on NS3TP1.
Twenty-four male C57BL/6 mice were randomized and separated into three groups, comprising the normal, fibrosis, and calcitriol treatment groups, and liver fibrosis was modeled by carbon tetrachloride (CCl4). To evaluate the level of hepatic fibrosis in every group, serological and pathological examinations of the liver were conducted. TGF-β1 was administered to boost the in vitro cultivation of LX-2 cells. NS3TP1, α-smooth muscle actin (α-SMA), collagen I, and collagen III in every group were examined using a Western blot and real-time quantitative polymerase chain reaction. The activity of the transforming growth factor beta 1 (TGFβ1)/Smad3 and NF-κB signaling pathways in each group of cells transfected with pcDNA-NS3TP1 or siRNA-NS3TP1 was detected. The statistical analysis of the data was performed using the Student’s t test.
NS3TP1 promoted the activation, proliferation, and differentiation of hepatic stellate cells (HSCs) and enhanced hepatic fibrosis via the TGFβ1/Smad3 and NF-κB signaling pathways, as evidenced by the presence of α-SMA, collagen I, collagen III, p-smad3, and p-p65 in LX-2 cells, which were upregulated after NS3TP1 overexpression and downregulated after NS3TP1 interference. The proliferation of HSCs was lowered after NS3TP1 interference and elevated after NS3TP1 overexpression, as shown by the luciferase assay. NS3TP1 inhibited the apoptosis of HSCs. Moreover, both Smad3 and p65 could bind to NS3TP1, and p65 increased the promoter activity of NS3TP1, while NS3TP1 increased the promoter activity of TGFβ1 receptor I, as indicated by coimmunoprecipitation and luciferase assay results. Both in vivo and in vitro, treatment with calcitriol dramatically reduced the expression of NS3TP1. Calcitriol therapy-controlled HSCs activation, proliferation, and differentiation and substantially suppressed CCl4-induced hepatic fibrosis in mice. Furthermore, calcitriol modulated the activities of the above signaling pathways via downregulation of NS3TP1.
Our results suggest that calcitriol may be employed as an adjuvant therapy for hepatic fibrosis and that NS3TP1 is a unique, prospective therapeutic target in hepatic fibrosis.
Core Tip: We proved that hepatitis C virus nonstructural protein 3-transactivated protein 1 (NS3TP1) promoted hepatic fibrosis via the transforming growth factor beta 1/Smad3 and NF-κB signaling pathways. Calcitriol attenuates liver fibrosis through NS3TP1-mediated above both signaling pathways. These novel findings profoundly expand our knowledge about the mechanisms underlying the role and function of NS3TP1 in hepatic fibrosis. The relationship between NS3TP1 and liver fibrosis was discussed for the first time and provided a foundation for research related to liver fibrosis by targeting NS3TP1. We first showed that calcitriol alleviated hepatic fibrosis through the above signaling pathways via NS3TP1.