LSECtin attenuates hepatic Th17 expansion in a murine model of cirrhosis and signals through the LAG-3 receptor

Abstract Background and aims LSECtin downregulation during cirrhosis progression is associated with adaptive T cell expansion. We analyzed the molecular mechanism for LSECtin modulation of Th17 proliferation in an experimental cirrhosis model. Methods A transgenic mouse model of Clec4g/LSECtin overexpression (Clec4g KI) was subjected to CCl₄-induced cirrhosis. Cell death, liver function and inflammation markers (n=6/group) were evaluated. LSECtin-LAG3 signaling in Th17-differentiated spleen cells (n=5) and LAG3 expression in human cirrhotic livers (n=6) were also characterized. Results Densitometred LSECtin expression was significantly downregulated during cirrhosis in wildtype but not Clec4g-KI mice (0.6±0.2 vs 2.3±0.6 AU, p=0.001). LSECtin overexpression in cirrhotic mice resulted in less histological damage and improved liver enzyme levels (ALT: 152.7±66.3 vs 76.33±13.33U/L, p=0.004). Cell-death pathway analysis revealed no differences in apoptosis markers Casp3 and Casp8 but reduced levels of necroptotic intermediates Mlkl and Ripk3. LSECtin overexpression reduced hepatic leukocyte infiltration and enriched the differentiation from inflammatory Rorgt⁺/IL-17⁺ (2.4±0.8 vs 7.7±3.5%CD4⁺, p=0.043) to regulatory Foxp3⁺/IL-10⁺ cells (3.6±0.9 vs 1.2±0.7%CD4⁺, p=0.047) in cirrhotic animals. LSECtin interacted with LAG-3 on polarized spleen-derived CD4⁺ T cells, inhibiting Th17 differentiation (10.5±2.7 vs 6.6±2.1%CD4⁺, p=0.037) by suppressing Stat3 and Zap70 pathways. LSECtin didn't restrained the Th17 subset expansion during LAG3 blockade (6.6±2.1 vs 14.2±4.0%CD4⁺, p=0.005). Cirrhotic human livers showed increased LAG-3-expressing Th17 cells compared to controls (3.2±1.4 vs 0.1±0.1cells/mm², p=0.001). Conclusions We have established a valuable murine model of LSECtin overexpression to assess its impact on hepatic inflammation during cirrhosis. LAG-3 was identified as the molecular mechanism by which LSECtin attenuates Th17 differentiation. Given LSECtin capacity to modulate the Th profile and decrease pro-inflammatory cell death, liver-directed molecular approaches to restore its expression may be of therapeutic interest during cirrhosis.