Deficiency for scavenger receptors Stabilin‐1 and Stabilin‐2 leads to age‐dependent renal and hepatic depositions of fasciclin domain proteins TGFBI and Periostin in mice

Abstract

Stabilin‐1 (Stab1) and Stabilin‐2 (Stab2) are two major scavenger receptors of liver sinusoidal endothelial cells that mediate removal of diverse molecules from the plasma. Double‐knockout mice (Stab‐DKO) develop impaired kidney function and a decreased lifespan, while single Stabilin deficiency or therapeutic inhibition ameliorates atherosclerosis and Stab1‐inhibition is subject of clinical trials in immuno‐oncology. Although POSTN and TFGBI have recently been described as novel Stabilin ligands, the dynamics and functional implications of these ligands have not been comprehensively studied. Immunofluorescence, Western Blotting and Simple Western™ as well as in situ hybridization (RNAScope™) and qRT‐PCR were used to analyze transcription levels and tissue distribution of POSTN and TGFBI in Stab‐KO mice. Stab‐POSTN‐Triple deficient mice were generated to assess kidney and liver fibrosis and function in young and aged mice. TGFBI and POSTN protein accumulated in liver tissue in Stab‐DKO mice and age‐dependent in glomeruli of Stabilin‐deficient mice despite unchanged transcriptional levels. Stab‐POSTN‐Triple KO mice showed glomerulofibrosis and a reduced lifespan comparable to Stab‐DKO mice. However, alterations of the glomerular diameter and vascular density were partially normalized in Stab‐POSTN‐Triple KO. TGFBI and POSTN are Stabilin‐ligands that are deposited in an age‐dependent manner in the kidneys and liver due to insufficient scavenging in the liver. Functionally, POSTN might partially contribute to the observed renal phenotype in Stab‐DKO mice. This study provides details on downstream effects how Stabilin dysfunction affects organ function on a molecular and functional level.

Association of Differentially Altered Liver Fibrosis with Deposition of TGFBi in Stabilin-Deficient Mice

“…Since TGFBi levels in the liver correlate with fibrosis in all our models and genotypes here, we hypothesize that the TGFBi protein in the liver we observed is not deposited as we previously hypothesized for high TGFBi and POSTN levels in glomeruli and liver tissue from Stab-DKO tissue [ 22 ]. Since no immunofluorescent signal was observed for POSTN, even in strongly fibrotic CDAA-fed livers, we hypothesize that POSTN positivity in Stab-DKO livers is indeed due to deposition from the plasma and fibrogenic stimuli alone are not sufficient to induce strong POSTN depositions as seen in Stab-DKO [ 22 ]. Correlation for POSTN and fibrosis was overall weaker than for TGFBi and fibrosis and did not reach significance in Stab2−/− mice, although TGFBi and POSTN levels correlated well overall, which is in line with previous findings [ 22 ].…”

“…Since our previous studies have shown that Stab1 and Stab2 can compensate each other to a certain degree, regarding scavenging of ligands like POSTN and TGFBi [ 8 , 22 ], we tested whether a pro-fibrotic stimulus adding on single Stabilin deficiency might trigger pronounced liver fibrosis and ligand deposition comparable to Stabilin-double-deficient mice. Interestingly, only a moderate pro-fibrotic stimulus with a MCD diet for two weeks showed differences between genotypes regarding overall fibrosis, which strongly mirrored baseline changes in fibrotic burden observed in each genotype.…”

“…Kidneys of Stab-DKO mice transplanted into WT mice showed an ameliorated progression of glomerular fibrosis, indicating that glomerulofibrotic nephropathy was probably caused by circulating blood factors in Stab-DKO mice [ 21 ]. Age-dependent depositions of direct Stabilin ligands TGFBi and POSTN in kidney and liver tissue of Stab-DKO mice may be detrimental to kidney function; although POSTN knockout from Stab-DKO mice did not show a completely rescued kidney function or lifespan, a slightly improved glomerular phenotype was observed [ 22 ]. Recently, we were able to show that genetic single Stabilin deficiency and anti-Stabilin antibody therapy in different atherosclerosis-prone mouse models ameliorate atherosclerosis, likely through altered immune cell activation mediated by a plasma proteome switch including TGFBi and POSTN [ 8 ].…”

TGFBI promotes proliferation and epithelial–mesenchymal transition in renal cell carcinoma through PI3K/AKT/mTOR/HIF-1α pathway

“…TGFBI plays a key role in the activation of PI3K/AKT/mTOR/ HIF-1α signaling pathway in RCC Previous literature has reported a close relationship between POSTN and TGFBI [19][20][21][22], We analyzed the correlation between TGFBI and POSTN at RNA, total protein, and phosphoprotein levels and found a positive correlation between the expression of the two (Fig. 6A), whereas previous studies have been performed on POSTN indicating the importance of the AKT/mTOR pathway in RCC [23] .…”

Highly oxidized albumin is cleared by liver sinusoidal endothelial cells via the receptors stabilin-1 and -2

“…KO models of stabilin-1 or -2 showed decreased atherosclerotic plaque formation under Western diet conditions or ApoE KO 38 , 39 —the effect was replicated using monoclonal antibodies and suggested as a therapy against atherosclerosis in prone individuals, as antibodies would likely not greatly interfere with liver endothelial scavenging 39 . Stabilin double KOs exhibit transforming growth factor beta induced protein (TGFBI) and Periostin (POSTN) deposition in liver and in glomeruli with age 40 . Even single KO models were found to have increased inappropriate deposition of connective tissue components, and showed more severe steatosis and fibrosis in induced models 41 .…”