Future perspective: immunomodulatory therapy for autoimmune hepatitis

Deletion of the C6orf120 gene with unknown function ameliorates autoimmune hepatitis induced by concanavalin A

The present study was conducted to characterize the C6orf120 gene, by using C6orf120 gene-deleted rats (C6orf120^-/-), to determine its role in the development and severity of autoimmune hepatitis induced by concanavalin A (Con A), as well as the underlying mechanisms. We found that following Con A injection, C6orf120^-/- rats were less susceptible to developing autoimmune hepatitis with low levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) post challenge. Additionally, C6orf120 deficiency increased the frequency of cluster of differentiation (CD)4⁺ CD25⁺ Forkhead box P3⁺ regulatory T cells (Tregs) among intrahepatic lymphocytes, splenocytes, peripheral blood mononuclear cells, and CD4⁺ T in vitro. Moreover, C6orf120 deficiency downregulated interleukin (IL)-1β, IL-6, tumor necrosis factor alpha-α, interferon-γ and IL-17a secretion in the plasma and liver tissues. Our results indicated that the C6orf120 gene-deleted rats were less susceptible to Con A-induced autoimmune hepatitis, which may be partly related to the increased frequency of Tregs and inhibited secretion of inflammatory cytokines.

Activated farnesoid X receptor attenuates apoptosis and liver injury in autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease associated with interface hepatitis, the presence of autoantibodies, regulatory T-cell dysfunction and raised plasma liver enzyme levels. The present study assessed the hepatoprotective and antiapoptotic role of farnesoid X receptor (FXR) in AIH. A mouse model of AIH was induced by treatment with concanavalin A (ConA). The FXR agonist, chenodeoxycholic acid (CDCA), was administered to mice exhibiting ConA-induced liver injury and a normal control. Blood samples were obtained to detect the levels of aminotransferases and inflammatory cytokines. Liver specimens were collected, and hematoxylin-eosin staining was used for histopathological examination and detection. Apoptosis was evaluated using the terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling (TUNEL) method. The expression levels of apoptosis-associated genes and proteins were determined by reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. The results demonstrated that FXR was downregulated at the mRNA and protein level in the liver specimens of mice induced with ConA-induced hepatitis. Increased levels of aminotransferases and inflammatory cytokines, including interferon-γ, tumor necrosis factor-α, interleukin (IL)-4 and IL-2, were detected in ConA-treated mice. The mice pretreated with the FXR agonist, CDCA, were more resistant to ConA hepatitis, as indicated by reduced levels of alanine transaminase/aspartate aminotransferase and aminotransferases. The activation of FXR ameliorated hepatocyte apoptosis, as demonstrated by TUNEL analysis and downregulation of the Fas/Fas ligand, tumor necrosis factor-related apoptosis-inducing ligand and caspase-3. Taken together, FXR activation ameliorated liver injury and suppressed inflammatory cytokines in ConA-induced hepatitis. FXR, therefore, exerts a protective role against ConA-induced apoptosis.

Medullary thymic epithelial cells and central tolerance in autoimmune hepatitis development: novel perspective from a new mouse model

Autoimmune hepatitis (AIH) is an immune-mediated disorder that affects the liver parenchyma. Diagnosis usually occurs at the later stages of the disease, complicating efforts towards understanding the causes of disease development. While animal models are useful for studying the etiology of autoimmune disorders, most of the existing animal models of AIH do not recapitulate the chronic course of the human condition. In addition, approaches to mimic AIH-associated liver inflammation have instead led to liver tolerance, consistent with the high tolerogenic capacity of the liver. Recently, we described a new mouse model that exhibited spontaneous and chronic liver inflammation that recapitulated the known histopathological and immunological parameters of AIH. The approach involved liver-extrinsic genetic engineering that interfered with the induction of T-cell tolerance in the thymus, the very process thought to inhibit AIH induction by liver-specific expression of exogenous antigens. The mutation led to depletion of specialized thymic epithelial cells that present self-antigens and eliminate autoreactive T-cells before they exit the thymus. Based on our findings, which are summarized below, we believe that this mouse model represents a relevant experimental tool towards elucidating the cellular and molecular aspects of AIH development and developing novel therapeutic strategies for treating this disease.