Intestinal decontamination inhibits TLR4 dependent fibronectin-mediated cross-talk between stellate cells and endothelial cells in liver fibrosis in mice

Abstract

Background/Aims Liver fibrosis is associated with angiogenesis and leads to portal hypertension. Certain antibiotics reduce complications of liver failure in humans, however, effect of antibiotics on the pathologic alterations of the disease are not fully understood. The aim of this study was to test whether the non-absorbable antibiotic rifaximin could attenuate fibrosis progression and portal hypertension in vivo, and explore potential mechanisms in vitro. Methods Effect of rifaximin on portal pressure, fibrosis, and angiogenesis was examined in wild type and toll like receptor 4 (TLR4) mutant mice after bile duct ligation (BDL). In vitro studies were carried out to evaluate the effect of the bacterial product and TLR agonist, lipopolysaccharide (LPS) on paracrine interactions between hepatic stellate cells (HSC) and liver endothelial cells (LEC) that lead to fibrosis and portal hypertension. Results Portal pressure, fibrosis, and angiogenesis were significantly lower in BDL mice receiving rifaximin compared to BDL mice receiving vehicle. Studies in TLR4 mutant mice confirmed that the effect of rifaximin was dependent on LPS/TLR4 pathway. Fibronectin (FN) was increased in BDL liver and was reduced by rifaximin administration and thus was explored further in vitro as a potential mediator of paracrine interactions of HSC and LEC. In vitro, LPS promoted FN production from HSC. Furthermore, HSC-derived FN promoted LEC migration and angiogenesis. Conclusion These studies expand our understanding of the relationship of intestinal microbiota with fibrosis development by identifying FN as a TLR4 dependent mediator of the matrix and vascular changes that characterize cirrhosis.

Exosome Adherence and Internalization by Hepatic Stellate Cells Triggers Sphingosine 1-Phosphate-dependent Migration

“…We hypothesized that adhesion between exosomes and HSC may require ligand/receptor interactions to facilitate chemotactic signaling. FN is a glycoprotein of the extracellular matrix that is secreted by EC during liver fibrosis (27,(35)(36)(37)42). Indeed, exosomes contained FN, as detected by FN immunogold labeling (Fig.…”

“…SK1 is an enzyme that produces the HSC chemotactic factor S1P. Additionally, active SK1 enzyme has been detected in the extracellular environment, although not specifically within an exosome fraction (24,25,27,(35)(36)(37). We therefore focused on SK1-derived S1P as a potential pathway relevant to our model of EC-HSC interaction.…”

Origins of Portal Hypertension in Nonalcoholic Fatty Liver Disease

“…However, there is increasing evidence that the vicious cycle of gut-liver dysfunction can be interrupted by manipulating the gut microbiota. Intestinal decontamination by rifaximin in mice following bile duct ligation reduces liver fibrosis, angiogenesis, and PHT in association with diminished activation of the LPS/TLR4 pathway and fibronectin production, which is limiting the cross talk between HSCs and LSECs [69]. Thus, modulation of the gut-liver axis may prove to be a helpful strategy for preventing and managing NAFLDassociated PHT [70,71].…”

“…Additional agents with impact on HSC activation and contractility include mitochondrial antioxidants [95,96], renin-angiotensin system inhibitors [97], and relaxin [98]. Finally, selective Experimental Intestinal decontamination by rifaximin blocks TLR4-mediated activation of HSCs and modulates FXR signaling by changing intestinal bile acid composition associated with reduced fibrosis, angiogenesis, and PVP in experimental PHT [69] beta3 receptor agonists induce relaxation of HSCs via cAMP accumulation and Rho-kinase inhibition with no effect on normal PVP, indicating that these drugs primarily target the dynamic components of IHVR [99,100]. FXR has recently become a major pharmacological target in NAFLD owing to its complex role in bile acid and lipid metabolism, inflammation, and fibrosis [101].…”

Hepatic sinusoids in liver injury, inflammation, and fibrosis: new pathophysiological insights

“…Bacterially derived lipopolysaccharides (LPS) bind to their receptor TLR-4 expressed on SEC, inducing injury and inflammation [11]. Interestingly, recent studies have shown that LPS can also induce fibrosis-associated angiogenesis by interacting with TLR-4, highlighting the role of SEC in the so-called gut-liver axis [12,13].…”