BTLA–HVEM Checkpoint Axis Regulates Hepatic Homeostasis and Inflammation in a ConA-Induced Hepatitis Model in Zebrafish

Abstract

The BTLA2HVEM checkpoint axis plays extensive roles in immunomodulation and diseases, including cancer and autoimmune disorders. However, the functions of this checkpoint axis in hepatitis remain limited. In this study, we explored the regulatory role of the Btla-Hvem axis in a ConA-induced hepatitis model in zebrafish. Results showed that Btla and Hvem were differentially expressed on intrahepatic Cd8 + T cells and hepatocytes. Knockdown of Btla or Hvem significantly promoted hepatic inflammation. Btla was highly expressed in Cd8 + T cells in healthy liver but was downregulated in inflamed liver, as evidenced by a disparate proportion of Cd8 + Btla + and Cd8 + Btla-T cells in individuals without or with ConA stimulation. Cd8 + Btla + T cells showed minimal cytotoxicity to hepatocytes, whereas Cd8 + Btla-T cells were strongly reactive. The depletion of Cd8 + Btla-T cells reduced hepatitis, whereas their transfer enhanced hepatic inflammation. These observations indicate that Btla endowed Cd8 + Btla + T cells with self-tolerance, thereby preventing them from attacking hepatocytes. Btla downregulation deprived this tolerization. Mechanistically, Btla-Hvem interaction contributed to Cd8 + Btla + T cell tolerization, which was impaired by Hvem knockdown but rescued by soluble Hvem protein administration. Notably, Light was markedly upregulated on Cd8 + Btla-T cells, accompanied by the transition of Cd8 + Btla + Lightto Cd8 + Btla-Light + T cells during hepatitis, which could be modulated by Cd4 + T cells. Light blockade attenuated hepatitis, thereby suggesting the positive role of Light in hepatic inflammation. These findings provide insights into a previously unrecognized Btla-Hvem-Light regulatory network in hepatic homeostasis and inflammation, thus adding a new potential therapeutic intervention for hepatitis.

Characterization of cGAS homologs in innate and adaptive mucosal immunities in zebrafish gives evolutionary insights into cGAS‐STING pathway

“…The eukaryotic expression vectors for Dr cGASa/b proteins with EGFP, Myc, Flag, and HA tags were constructed using pEGFP‐N1, pCMV‐N‐myc, pcDNA3.1‐EGFP‐Flag‐His, and pcDNA3.1‐EGFP‐HA‐His plasmids 31 . The point mutants of Dr cGASa/b prepared using a Quick Mutation Site‐Directed Mutagenesis Kit (Beyotime, Shanghai, China) were constructed into pcDNA3.1‐EGFP‐Flag‐His and pcDNA3.1‐EGFP‐HA‐His.…”

“…After washing with PBS, cells were permeabilized with 0.1% Triton X‐100, blocked with 5% normal goat serum, and incubated with primary Abs or unrelated control IgG and secondary Abs at 4°C for 1 hour. Gill tissues were fixed in 4% paraformaldehyde overnight, and the paraffin sections were prepared as described 31 . After dewaxing the paraffin and retrieving Ags, the sections were blocked with 5% normal goat serum and incubated with primary Abs at 4°C overnight.…”

Roles of BTLA in Immunity and Immune Disorders

“…In a Con A challenge model of acute hepatitis, BTLA -/- mice showed reduced survival and increased early secretion of serum cytokines, which was partly due to the negative regulation of NKT cells by BTLA ( 65 ). Moreover, Shi et al discovered that BTLA could induce the self-tolerance of CD8 + BTLA + T cells to reduce the attack on hepatocytes, thus regulating hepatic homeostasis in a Con A-induced hepatitis model in zebrafish ( 66 ).…”

Investigation of BTLA tagging variants with risk of esophagogastric junction adenocarcinoma

“…Recently, many investigations have focused on the relationship of BTLA with inflammation, autoimmune disease and cancer. Shi et al reported that BTLA-herpes virus entry mediator (HVEM) checkpoint axis might be implicated in the regulation of inflammation in liver [10]. A previous study indicated that the up-regulation of BTLA gene expression and soluble BTLA (sBTLA) was validated in thymoma-associated myasthenia gravis [11].…”