UC Davis

Background & aims

The heterodimeric integrin receptor α₄β₇ regulates CD4 T cell recruitment to inflamed tissues, but its role in the pathogenesis of non-alcoholic steatohepatitis (NASH) is unknown. Herein, we examined the role of α₄β₇-mediated recruitment of CD4 T cells to the intestine and liver in NASH.

Methods

Male littermate F11r^+/+ (control) and junctional adhesion molecule A knockout F11r^-/- mice were fed a normal diet or a western diet (WD) for 8 weeks. Liver and intestinal tissues were analyzed by histology, quantitative reverse transcription PCR (qRT-PCR), 16s rRNA sequencing and flow cytometry. Colonic mucosa-associated microbiota were analyzed using 16s rRNA sequencing. Liver biopsies from patients with NASH were analyzed by confocal imaging and qRT-PCR.

Results

WD-fed knockout mice developed NASH and had increased hepatic and intestinal α₄β₇⁺ CD4 T cells relative to control mice who developed mild hepatic steatosis. The increase in α₄β₇⁺ CD4 T cells was associated with markedly higher expression of the α₄β₇ ligand mucosal addressin cell adhesion molecule 1 (MAdCAM-1) in the colonic mucosa and livers of WD-fed knockout mice. Elevated MAdCAM-1 expression correlated with increased mucosa-associated Proteobacteria in the WD-fed knockout mice. Antibiotics reduced MAdCAM-1 expression indicating that the diet-altered microbiota promoted colonic and hepatic MAdCAM-1 expression. α₄β₇ blockade in WD-fed knockout mice significantly decreased α₄β₇⁺ CD4 T cell recruitment to the intestine and liver, attenuated hepatic inflammation and fibrosis, and improved metabolic indices. MAdCAM-1 blockade also reduced hepatic inflammation and fibrosis in WD-fed knockout mice. Hepatic MAdCAM-1 expression was elevated in patients with NASH and correlated with higher expression of α₄ and β₇ integrins.

Conclusions

These findings establish α₄β₇/MAdCAM-1 as a critical axis regulating NASH development through colonic and hepatic CD4 T cell recruitment.

Lay summary

Non-alcoholic steatohepatitis (NASH) is an advanced and progressive form of non-alcoholic fatty liver disease (NAFLD), and despite its growing incidence no therapies currently exist to halt NAFLD progression. Herein, we show that blocking integrin receptor α₄β₇-mediated recruitment of CD4 T cells to the intestine and liver not only attenuates hepatic inflammation and fibrosis, but also improves metabolic derangements associated with NASH. These findings provide evidence for the potential therapeutic application of α₄β₇ antibody in the treatment of human NASH.