Autoimmune hepatitis and pregnancy: considerations for the clinician

Tipping the balance in autoimmunity: are regulatory t cells the cause, the cure, or both?

Regulatory T cells (Tregs) are a specialized subgroup of T-cell lymphocytes that is crucial for maintaining immune homeostasis and preventing excessive immune responses. Depending on their differentiation route, Tregs can be subdivided into thymically derived Tregs (tTregs) and peripherally induced Tregs (pTregs), which originate from conventional T cells after extrathymic differentiation at peripheral sites. Although the regulatory attributes of tTregs and pTregs partially overlap, their modes of action, protein expression profiles, and functional stability exhibit specific characteristics unique to each subset. Over the last few years, our knowledge of Treg differentiation, maturation, plasticity, and correlations between their phenotypes and functions has increased. Genetic and functional studies in patients with numeric and functional Treg deficiencies have contributed to our mechanistic understanding of immune dysregulation and autoimmune pathologies. This review provides an overview of our current knowledge of Treg biology, discusses monogenetic Treg pathologies and explores the role of Tregs in various other autoimmune disorders. Additionally, we discuss novel approaches that explore Tregs as targets or agents of innovative treatment options.

zVAD alleviates experimental autoimmune hepatitis in mice by increasing the sensitivity of macrophage to TNFR1-dependent necroptosis

BACKGROUND & AIMS

Autoimmune hepatitis (AIH) is characterized by hepatocyte destruction, leading to lymphocyte and macrophage accumulation in the liver. Macrophages are key drivers of AIH. A membrane-permeable pan-caspase inhibitor, Z-Val-Ala-DL-Asp-fluoromethylketone (zVAD), induces macrophage necroptosis in response to certain stimuli. However, the function of zVAD in the pathogenesis of autoimmune hepatitis remains elusive. In this study, we aimed to evaluate the effect and explore the underlying mechanisms of zVAD against AIH.

METHODS

Murine acute autoimmune liver injury was established by concanavalin A (ConA) injection. Bone marrow-derived macrophages (BMDMs) were used in adoptive cell transfer experiments. The mechanism of action of zVAD was examined using macrophage cell lines and BMDMs. Phosphorylation of mixed lineage kinase domain-like proteins was used as a marker of necroptosis.

RESULTS

Treatment with zVAD increased necroptosis, reduced inflammatory cytokine production, and alleviated liver injury in a ConA-induced liver injury mouse model. Regardless of zVAD treatment, macrophage deletion resulted in reduced neutrophil accumulation and relieved ConA-induced liver injury. In vitro studies have shown that zVAD pretreatment promotes lipopolysaccharide-induced macrophage necroptosis and leads to reduced pro-inflammatory cytokine and chemokine secretion. Transferring zVAD-pretreated BMDMs in mice notably reduced ConA-associated liver inflammation and injury, resulting in lower mortality than that observed after transferring normal BMDMs. Mechanistically, zVAD treatment increased the expression of tumour necrosis factor receptor (TNFR)-1 and interleukin (IL)-10 in macrophages. TNFR1 expression decreased upon transfection with IL-10-specific small interfering RNAs and blocking of TNFR1 decreased macrophage necroptosis.

CONCLUSIONS

We found that zVAD alleviated ConA-induced liver injury by increasing the sensitivity of macrophages to necroptosis via IL-10-induced TNFR1 expression. This study provides new insights into the treatment of autoimmune hepatitis via zVAD-induced macrophage necroptosis.