Epigenetic drug control of Clec4g/LSECtin expression reduces fibrosis burden in cirrhosis

Background: Liver and lymph node endothelial cell C-type lectin (LSECtin) loss in liver sinusoidal endothelial cells (LSECs) during cirrhosis favors hepatic pro-inflammatory T-cell infiltration. We characterize histone protein post-translational modifications and DNA methylation in LSECs that may control LSECtin expression and evaluate methyltransferase inhibitors' capacity to retrieve LSECtin. Methods: DNA-methylation levels and histone post-translational modifications were studied by methylation array and ChIP-Seq experiments carried out on LSECs isolated by FACS from control and cirrhotic mice. Immortalized LSECs were treated with epigenetic effector inhibitory drugs (OTS186935-Suv39h2i, UNC0642-G9a/Glpi, UNC1999-EZH2/1i, 5-Aza-2’-deoxycitidine-DNMTi), alone and with IL-4, an LSECtin expression inducer. Drugs with regulatory potential were tested in vivo. LSECtin gene and protein expression, lymphocyte differentiation, and Th17-subpopulation proliferation were studied. Results: H3K9me3 and H3K27Me3 were reduced in LSECs of cirrhotic versus control mice. Suv39h2 and Ezh2/1 methyltransferase inhibitors OTS186935 and UNC1999, respectively, reduced Clec4g /LSECtin expression in immortalized LSECs. Murine primary LSECs showed H3K27me3 and H3K9me3 significantly enriched (controls) and reduced (cirrhotics) regions located upstream of the Clec4g promoter. OTS186935 and UNC1999 treated immortalized LSECs reduced H3K9me3 and H3K27me3 enrichment in these regions. Clec4g /LSECtin expression was also controlled by DNA methylation, as confirmed by Clec4g /LSECtin induction after 5-Aza-2’-deoxycitidine-DNMTi treatment in vitro and in vivo. Epigenetic drugs induced LSECtin in LSECs, contracted the hepatic Th17 compartment, attenuated hepatic structural damage, and improved liver function in cirrhosis. Conclusion: H3K9me3 and H3K27me3, and DNA-methylation regulate Clec4g expression in LSECs during cirrhosis. Inhibitory epigenetic-enzyme drugs increase Clec4g /LSECtin expression and provide evidence on relevant genomic regions for Clec4g reprogramming. The LSECtin-modulated hepatic Th17 compartment is contracted in cirrhosis by targeting these modifications.