Abstract
Introduction:
Mitogen-activated protein kinases (MAPKs) are involved in T cell-mediated liver damage. However, the inhibitory mechanism(s) that controls T cell-mediated liver damage remains unknown.
Objectives:
We investigated whether Spred2 (Sprouty-related, EVH1 domain-containing protein 2) that negatively regulates ERK-MAPK pathway has a biological impact on T cell-mediated liver damage by using a murine model.
Methods:
We induced hepatotoxicity in genetically engineered mice by intravenously injecting Concanavalin A (Con A) and analyzed the mechanisms using serum chemistry, histology, ELISA, qRT-PCR, Western blotting and flow cytometry.
Results:
Spred2-deficient mice (Spred2-/-) developed more sever liver damage than wild-type (WT) mice with increased interferon-γ (IFNγ) production. Hepatic ERK phosphorylation was enhanced in Spred2-/- mice, and pretreatment of Spred2-/- mice with the MAPK/ERK inhibitor U0126 markedly inhibited the liver damage and reduced IFNγ production. Neutralization of IFNγ abolished the damage with decreased hepatic Stat1 activation in Spred2-/- mice. IFNγ was mainly produced from CD4+ and CD8+ T cells, and their depletion decreased liver damage and IFNγ production. Transplantation of CD4+ and/or CD8+ T cells from Spred2-/- mice into RAG1-/- mice deficient in both T and B cells caused more severe liver damage than those from WT mice. Hepatic expression of T cell attractants, CXCL9 and CXCL10, was augmented in Spred2-/- mice as compared to WT mice. Conversely, liver damage, IFNγ production and the recruitment of CD4+ and CD8+ T cells in livers after Con A challenge were lower in Spred2 transgenic mice, and Spred2-overexpressing CD4+ and CD8+ T cells produced lower levels of IFNγ than WT cells upon stimulation with Con A in vitro.
Conclusion:
We demonstrated, for the first time, that Spred2 functions as an endogenous regulator of T cell IFNγ production and Spred2-mediated inhibition of ERK-MAPK pathway may be an effective remedy for T cell-dependent liver damage.