Annexin A1 treatment prevents the evolution to fibrosis of experimental nonalcoholic steatohepatitis

Abstract

Annexin A1 (AnxA1) is an important effector in the resolution of inflammation which is involved in modulating hepatic inflammation in nonalcoholic steatohepatitis (NASH). In this study we have investigated the possible effects of treatment with AnxA1 for counteracting the progression of experimental NASH. NASH was induced in C57BL/6 mice by feeding methionine-choline deficient (MCD) or Western diets and the animals were treated for 4-6 weeks with human recombinant AnxA1 (hrAnxA1; 1µg, daily IP) or saline once NASH was established. In both experimental models, treatment with hrAnxA1 improved parenchymal injury and lobular inflammation without interfering with the extension of steatosis. Furthermore, administration of hrAnxA1 significantly attenuated the hepatic expression of α1-procollagen and TGF-ß1 and reduced collagen deposition, as evaluated by collagen Sirius Red staining. Flow cytometry and immunohistochemistry showed that hrAnxA1 did not affect the liver recruitment of macrophages, but strongly interfered with the formation of crown-like macrophage aggregates and reduced their capacity of producing pro-fibrogenic mediators like osteopontin (OPN) and galectin-3 (Gal-3). This effect was related to an interference with the acquisition of a specific macrophage phenotype characterized by the expression of the Triggering Receptor Expressed on Myeloid cells 2 (TREM-2), CD9 and CD206, previously associated with NASH evolution to cirrhosis. Collectively, these results indicate that, beside ameliorating hepatic inflammation, AnxA1 is specifically effective in preventing NASH-associated fibrosis by interfering with macrophage pro-fibrogenic features. Such a novel function of AnxA1 gives the rational for the development of AnxA1 analogues for the therapeutic control of NASH evolution.

Modulating hepatic macrophages with annexin A1 in non-alcoholic steatohepatitis

“…Thus in a recent study, Gadipudi, Ramavath, Provera et al investigated how treating mice with NASH with recombinant human AnxA1 (hrAnxA1) would influence disease. Interestingly, they found that while this treatment had no effect on metabolic syndrome or hepatic steatosis, it did reduce liver inflammation and fibrosis in two different mouse models of NASH, suggesting this may be a relevant target for therapeutic intervention [ 9 ].…”

“…In the present study, NASH was first induced by feeding mice either a methionine and choline deficient diet for 4 weeks or a Western diet for 10 weeks and then continuing mice on the diets for an additional 4 or 6 weeks, respectively, in which the mice were treated 5 times per week with hrAnxA1 (intraperitoneal administration). This led to a reduction in the serum alanine aminotransferase levels (sALT) and ameliorated the global histological scoring for lobular inflammation [ 9 ]. Furthermore, collagen staining with Sirius Red shows a reduction of collagen deposition in mice treated with hrAnxA1, although no changes were detected in terms of steatosis and liver triglyceride content.…”

“…Furthermore, collagen staining with Sirius Red shows a reduction of collagen deposition in mice treated with hrAnxA1, although no changes were detected in terms of steatosis and liver triglyceride content. Similarly, body weight, liver weight and insulin resistance remain unchanged upon hrAnxA1 treatment [ 9 ]. In line with reduced inflammation and fibrosis, real-time PCRs (RT-PCRs) on total liver unveiled a reduction in expression of inflammatory markers such as TNFα, CCL2, IL-12p40, CD11b, Pro-Collagen-1α and TGFβ in mice treated with hrAnxA1, suggesting that hrAnxA1 administration is able to reduce hepatic inflammation and fibrosis during NASH progression [ 9 ].…”

“…Similarly, body weight, liver weight and insulin resistance remain unchanged upon hrAnxA1 treatment [ 9 ]. In line with reduced inflammation and fibrosis, real-time PCRs (RT-PCRs) on total liver unveiled a reduction in expression of inflammatory markers such as TNFα, CCL2, IL-12p40, CD11b, Pro-Collagen-1α and TGFβ in mice treated with hrAnxA1, suggesting that hrAnxA1 administration is able to reduce hepatic inflammation and fibrosis during NASH progression [ 9 ]. However, as these timepoints are still relatively early in the establishment of NASH and fibrosis in these models, it will be interesting to determine if similar results can be obtained when the hrAnxA1 treatment is started later, to better mimic a therapeutic intervention post diagnosis in the clinic.…”

“…With the aforementioned macrophage heterogeneity in mind, the authors performed RT-qPCRs on total livers of mice fed a WD for 16W and treated with hrAnxA1 during the last 6 weeks of diet. This analysis showed a reduced expression of LAM-specific markers such as Trem2 , Spp1 (Osteopontin) and Lgals3 (Galectin 3) and an increased expression of Cd163 [ 9 ], a marker of resident KCs [ 17 , 18 ], suggesting a switch in macrophage subsets present in the treated NASH livers. This finding was further corroborated by flow cytometry whereby TIM4 + macrophages were increased and TREM2 + macrophages were decreased, although whether all macrophages are captured in the F4/80 + CD11b + gate used here to define macrophages remains to be seen [ 9 ].…”