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

BACKGROUND & 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 CCl(4)-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 livers of human individuals with cirrhosis (n = 6) were also characterized. RESULTS: Densitometred LSECtin expression was significantly downregulated during cirrhosis in wild-type 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 (alanine aminotransferase: 152.7 ± 66.3 vs. 76.33 ± 13.33 U/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 did not restrain the Th17 subset expansion during LAG3 blockade (6.6 ± 2.1 vs. 14.2 ± 4.0% CD4(+), p = 0.005). Livers of human individuals with cirrhosis showed increased LAG-3-expressing Th17 cells compared with controls (3.2 ± 1.4 vs. 0.1 ± 0.1 cells/mm(2), 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 proinflammatory cell death, liver-directed molecular approaches to restore its expression may be of therapeutic interest during cirrhosis. IMPACT AND IMPLICATIONS: LSECtin downregulation is associated with the expansion of Th17 cell subpopulation during cirrhosis. Findings highlight the crucial role of LSECtin in regulating immune responses and mitigating liver damage in cirrhosis. Restoring LSECtin expression through targeted liver-directed molecular interventions may be of therapeutic relevance in cirrhosis.