Lymphtoxin beta receptor-Ig protects from T-cell-mediated liver injury in mice through blocking LIGHT/HVEM signaling

LIGHT is a member of the TNF superfamily, which is transiently expressed on the surface of activated T lymphocytes and immature dendritic cells. Its known receptors are herpesvirus entry mediator (HVEM) prominently in T lymphocytes, and lymphtoxin beta receptor (LTbetaR) in stromal cells or nonlymphoid hematopoietic cells. Previous studies have shown that overexpression of LIGHT on T cells could lead to autoimmune reaction including lymphocytes activation, inflammation, and tissue destruction. To address the role of LIGHT/HVEM signaling in autoimmune hepatitis, an experimental colitis model induced by intravenous administration of concanavalin A (ConA) was given a soluble LTbetaR-Ig fusion protein as a competitive inhibitor of LIGHT/HVEM pathway. Marked elevation of LIGHT expression was detected in isolate intrahepatic leukocytes (IHLs) of the experimental animal. Treatment with LTbetaR-Ig significantly attenuated the progression and histological manifestations of the hepatic inflammation and reduced the production of inflammatory cytokines including TNF-alpha, IFN-gamma. Moreover, LTbetaR-Ig treatment significantly down-regulated LIGHT expression, leading to reduced lymphocytes (particularly CD4+ T cells), infiltrating into the hepatic inflammation and inhibited NF-kappaB activation and expression. We postulated that blockade of LIGHT/HVEM signaling by LTbetaR-Ig may ameliorate hepatitis by down-regulating LIGHT expression, and therefore we envision that LTbetaR-Ig would prove to a promising strategy for the clinical treatment of human autoimmune hepatitis.