Calcitriol ameliorates the progression of hepatic fibrosis through autophagy-related gene 16-like 1-mediated autophagy.

BACKGROUND: Calcitriol has the potential to counteract fibrotic diseases beyond its classical action of maintaining calcium and bone metabolism; however, its functional mechanism remains unknown. Autophagy-related gene 16-like 1 (Atg16l1) is one of the genes related to autophagy and is involved in protecting against fibrotic diseases. The present study aimed to explore the contribution of autophagy to the inhibition of calcitriol-induced hepatic fibrosis, as well as its potential molecular mechanism. METHODS: Carbon tetrachloride (Ccl4)-treated mice were established as hepatic fibrosis models and received calcitriol treatment for 6 weeks. Quantification of Sirius red staining and measurement of key fibrotic markers (collagen-1 and α-SMA) was performed to detect hepatic fibrosis. Chloroquine (CQ) treatment was used to observe autophagic flux, and 3-methyladenine (3-MA) was used to inhibit autophagy. Furthermore, the effects of calcitriol on transforming growth factor ß1 (TGFß1)-stimulated primary hepatic stellate cells (HSCs) were detected. Downregulation of Atg16l1 or vitamin D receptor (VDR) in LX-2 cells was used to explore the mechanism of action of calcitriol in fibrosis and autophagy. Additionally, the electrophoretic mobility shift assay (EMSA) was used to investigate the interactions between VDR and ATG16L1. RESULTS: Calcitriol increased the expression of VDR and ATG16L1, enhanced autophagy and attenuated hepatic fibrosis. 3-MA treatment and VDR silencing abolished the protective effects of calcitriol against fibrosis. Calcitriol-induced anti-fibrosis effects were blocked by ATG16L1 suppression. Furthermore, VDR bound to the ATG16L1 promoter and downregulation of VDR decreased the expression of ATG16L1 in LX-2 cells. CONCLUSION: Calcitriol mitigates hepatic fibrosis partly through ATG16L1-mediated autophagy.

Establishment of a Functional Cell Line Expressing both Subunits of H1a and H2c of Human Hepatocyte Surface Molecule ASGPR / 华中科技大学学报（医学）（英德文版）

To better understand the effect of a new split variant of human asialoglycoprotein receptor (ASGPR Hlb) on ASGPR ligands' binding ability, we established a functional cell line which expresses ASGPR. The full lengths of ASGPRH 1 a and H2c fragments from human liver were amplified by reverse transcript PCR (RT-PCR) and inserted into eukaryotic expression vector plRES2EGFP,pCDNA3.1 (Zeo+) respectively. The recombinants were co-transfected into HeLa cells. After selection by using Neocin and Zeocin, a stably transfected cell line was established, which was designated 4-1-6. The transcription and expression of ASGPRHla and H2c in 4-1-6 were confirmed by RT-PCR,Western blotting and immunofluorescence. The endocytosis function of the artificial "ASGPR" on the surface of 4-1-6 was tested by FACS. It was found that the cell line 4-1-6 could bind ASGPR natural ligand molecular asialo-orosomucoid (ASOR). After the eukaryotic plasmid H lb/pCDNA3.1 (neo)was transfected into cell line 4-1-6, Hlb did not down-regulate the ligand binding ability of ASGPR.The eukaryotic expression plasmid Hlb/pcDNA3.1 (neo) and H2c/pcDNA3.1 (neo) were co-transfected transiently into Hela cell. Neither single Hlb nor Hlb and H2c could bind ASOR. In conclusion, a functional cell line of human asialoglycoprotein receptor (ASGPR) which expresses both Hla and H2c stably was established. The new split variant Hlb has no effect on ASGPR binding to ASOR. ASGPRHlb alone can't bind to ASOR, it yet can't form functional complex with ASGPRH2c.