Toll-Like Receptor 2–Mediated Intestinal Injury and Enteric Tumor Necrosis Factor Receptor I Contribute to Liver Fibrosis in Mice

doi:10.1053/j.gastro.2012.07.099

Gastroenterology

Volume 143, Issue 5, November 2012, Pages 1330-1340.e1

https://doi.org/10.1053/j.gastro.2012.07.099 Get rights and content

Background & Aims

Progression of liver fibrosis in experimental models depends on gut-derived bacterial products, but little is known about mechanisms of disruption of the mucosal barrier or translocation. We used a mouse model of cholestatic liver disease to investigate mechanisms of intestinal barrier disruption following liver injury.

Methods

Liver fibrosis and bacterial translocation were assessed in Toll-like receptor 2 (TLR2)-deficient and tumor necrosis factor receptor I (TNFRI)-deficient mice subjected to bile duct ligation. Epithelial and lamina propria cells were isolated and analyzed by immunoblot analyses and flow cytometry. We analyzed bone marrow chimeras and mice with a conditional gain-of-function allele for the TNFRI receptor. By crossing TNFRI^{flxneo/flxneo} mice with mice that expressed the VillinCre transgene specifically in intestinal epithelial cells, we created mice that express functional TNFRI specifically on intestinal epithelial cells (VillinCreTNFRI^{flxneo/flxneo} mice).

Results

Following bile duct ligation, TLR2-deficient mice had less liver fibrosis and intestinal translocation of bacteria and bacterial products than wild-type mice. Mice with hematopoietic cells that did not express TLR2 also had reduced bacterial translocation, indicating that TLR2 expression by hematopoietic cells regulates intestinal barrier function. The number of TLR2⁺ monocytes that produce tumor necrosis factor α increased in the intestinal lamina propria of wild-type mice following bile duct ligation; bacterial translocation was facilitated by TNFRI-mediated signals on intestinal epithelial cells.

Conclusions

Intestinal inflammation and bacterial translocation contribute to liver fibrosis via TLR2 signaling on monocytes in the lamina propria and TNFRI signaling on intestinal epithelial cells in mice. Therefore, enteric TNFRI is an important mediator of cholestatic liver fibrosis.

Section snippets

Animal Models of Liver Disease

TNFRI^−/−¹¹ and transgenic mice expressing green fluorescent protein (GFP) under the control of a β-actin promoter⁶ have been described. TNFRI^{flxneo/flxneo12} and VillinCreTNFRI^{flxneo/flxneo13} were kindly provided by Drs Manolis Roulis and George Kollias (Biomedical Sciences Research Center “Alexander Fleming,” Vari, Greece), and littermates were used for the experiments. TLR2-deficient mice that were originally purchased from Jackson Laboratory (Bar Harbor, ME) were rederived by cesarean section

TLR2-Deficient Mice Are Protected From Cholestatic Liver Fibrosis

TLR2 is the receptor for products from gram-positive bacteria such as peptidoglycan. Conflicting results about the importance of TLR2 in experimental liver injury and fibrosis have been reported. Although one study reported increased survival and protection from liver injury of TLR2-deficient mice following bile duct ligation for up to 30 days,¹⁹ another report showed no difference in bile duct ligation–induced liver fibrosis.⁶ Because the phenotype in experimental disease models changes with

Discussion

Bacterial translocation is a well-characterized phenomenon in patients with liver disease.⁴ Although experimental studies suggest that progression of liver disease, particularly progression of fibrosis, is dependent on gut-derived bacterial products,6, 8, 9, 10 the molecular mechanisms leading to a leaky gut barrier are unknown. Our study provides important insights into changes of the intestinal barrier function associated with cholestatic liver injury that result in bacterial translocation

Acknowledgments

The authors thank Dr Keiko Iwaisako for assistance with intestinal loops; Drs Jerrold Turner, Alan Hofmann, and Reiner Wiest for helpful discussion; and the Flow Cytometry Research Core Facility of the VA San Diego Healthcare System, the San Diego Center for AIDS Research (AI 36214), and the VA Research Center for AIDS & HIV Infection.

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: Conflicts of interest The authors disclose no conflicts.

: Funding Supported in part by National Institutes of Health grants K08 DK081830 and R01 AA020703 (to B.S.), the UCSD Digestive Diseases Research Development Center (DK080506 to B.S.), and the AGA Fellowship to Faculty Transition Award (to B.S.).

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Original ResearchBasic and Translational—LiverToll-Like Receptor 2–Mediated Intestinal Injury and Enteric Tumor Necrosis Factor Receptor I Contribute to Liver Fibrosis in Mice

Background & Aims

Methods

Results

Conclusions

Section snippets

Animal Models of Liver Disease

TLR2-Deficient Mice Are Protected From Cholestatic Liver Fibrosis

Discussion

Acknowledgments

J Hepatol

Gastroenterology

J Hepatol

Gastroenterology

J Hepatol

Biochem Biophys Res Commun

Immunity

Curr Biol

Gastroenterology

Gastroenterology

Lab Invest

Toxicol Appl Pharmacol

Cytokine

J Hepatol

Deaths: final data for 2004

Natl Vital Stat Rep

TLR4 enhances TGF-beta signaling and hepatic fibrosis

Nat Med

The critical role of toll-like receptor (TLR) 4 in alcoholic liver disease is independent of the common TLR adapter MyD88

Hepatology

Original Research
Basic and Translational—Liver
Toll-Like Receptor 2–Mediated Intestinal Injury and Enteric Tumor Necrosis Factor Receptor I Contribute to Liver Fibrosis in Mice