Niclosamide alleviates pathological angiogenesis in hepatopulmonary syndrome by inhibiting S100A4 expression

To investigate the effects of niclosamide on S100A4 expression and pathological angiogenesis of hepatopulmonary syndrome（HPS）in rats.

Thirty male SD rats were randomly divided into control group（Sham group, n=6）, common bile duct ligation（CBDL）group（n=18）and niclosamide treatment group（NIC group, n=6）. The rats of the NIC group were gavaged with niclosamide suspension for 1 week since the first day of the third week after modelling, and the rats were dissected at the end of the fifth week to assess the pathological changes and disease progression of liver and lung tissues by HE and Masson staining. Immunofluorescence assay was used to detect the location and intensity of S100A4 and CD31 expression in the lung of rats. The expression of S100A4 at mRNA and protein levels was detected using qPCR and Western blotting. Pulmonary microvascular endothelial cells（PMVECs）were treated with small interfering RNA（siRNA）serum of HPS rats and nichosamide, respectively, and their effects on cell migration and tube-forming abilities were observed.

Both mRNA and protein expression of S100A4 in lung tissue of the CBDL group rats were increased with disease progression, and the expression levels were higher than those in the Sham group（P<0.000 1）; The lung mRNA and protein levels of S100A4 were lower in the NIC group than the CBDL group at the 5th week, but still higher than those in the Sham group. After knockdown of S100A4 using siRNA in PMVECs, the migration and tube-forming abilities were reduced when compared with the NC group（P<0.000 1）. HE staining displayed that pulmonary pathological changes were milder in the NIC group than the CBDL group at the 5th week, while no such effect was found in the liver tissues. Masson staining showed that hepatic fibrosis was not obviously ameliorated in the NIC group. The migration and tube-forming abilities of the cells was significantly increased in the CBDL group after the 5 weeks of serum stimulation compared to the Sham rats, while niclosamide treatment reversed this phenomenon（P<0.000 1）.

S100A4 can accelerate the progression of HPS by promoting pulmonary micro-angiogenesis in HPS rats, and niclosamide inhibits the expression of S100A4 in the lung and thus delays the progression of HPS.