Downregulated VISTA enhances Th17 differentiation and aggravates inflammation in patients with acute-on-chronic liver failure

Taraxasterol protects against acetaminophen-induced hepatotoxicity by reducing liver inflammatory response and ameliorating oxidative stress in mice

Acute liver failure is mainly caused by the overdose of acetaminophen (APAP) globally. The traditional Chinese medicinal (TCM) herb, Taraxacum, contains Taraxasterol (TAX) as one of the active components. It is a pentacyclic-triterpene compound isolated from this herb. Present work aimed to investigate the in vitro and in vivo protection effect of TAX in APAP-induced acute liver injury, and determine the potential regulatory mechamisms. The liver injury caused by APAP is attenuated by TAX, as shown by the alleviated pathological changes of mice liver and the reduced serological indexes. TAX evidently controlled the oxidative stress and liver inflammation in mice liver. In vitro studies found that TAX reversed the decrease in LO2 cell viability induced by APAP, and protected LO2 cells from APAP-induced injury. In addition, TAX reduced the secretion of inflammatory factors in RAW264.7 macrophages as induced via APAP. Besides, TAX inhibited oxidative stress in LO2 cells induced by APAP in vitro. Noteworthy, TAX enhanced protein and mRNA expressions of Nrf2 in vivo, and knockdown of Nrf2 by using adeno-associated virus (AAV)-Nrf2-KO attenuated inhibitory impact of TAX in acute liver injury induced by APAP. Also, AAV-NRF2-KO weakened the inhibitory impact of TAX against APAP-triggered liver inflammation and oxidative stress of mice liver. Moreover, TAX activated the Nrf2 signaling in APAP-induced LO2 cells, as shown by the increased nuclear Nrf2 expression together with downstream HO-1 expression in vitro. Inhibition of Nrf2 by using ML-385, anNrf2inhibitor, weakened the inhibitory effect of TAX against APAP-induced oxidative stress and cell injury in LO2 cells. Moreover, inhibition of Nrf2 attenuated anti-inflammatory effect of TAX for APAP-induced RAW264.7 cells. Collectively, TAX could protect against APAP-triggered hepatotoxicitythrough suppression of liver oxidative stress and inflammatory response in mice.

VISTA Deficiency Exacerbates the Development of Pulmonary Fibrosis by Promoting Th17 Differentiation

Background

Interstitial lung disease (ILD), characterized by pulmonary fibrosis (PF), represents the end-stage of various ILDs. The immune system plays an important role in the pathogenesis of PF. V-domain immunoglobulin suppressor of T-cell activation (VISTA) is an immune checkpoint with immune suppressive functions. However, its specific role in the development of PF and the underlying mechanisms remain to be elucidated.

Methods

We assessed the expression of VISTA in CD4 T cells from patients with connective tissue disease-related interstitial lung disease (CTD-ILD). Spleen cells from wild-type (WT) or Vsir -/- mice were isolated and induced for cell differentiation in vitro. Additionally, primary lung fibroblasts were isolated and treated with interleukin-17A (IL-17A). Mice were challenged with bleomycin (BLM) following VISTA blockade or Vsir knockout. Moreover, WT or Vsir -/- CD4 T cells were transferred into Rag1 -/- mice, which were then challenged with BLM.

Results

VISTA expression was decreased in CD4 T cells from patients with CTD-ILD. Vsir deficiency augmented T-helper 17 (Th17) cell differentiation in vitro. Furthermore, IL-17A enhanced the production of inflammatory cytokines, as well as the differentiation and migration of lung fibroblasts. Both VISTA blockade and knockout of Vsir increased the percentage of IL-17A-producing Th17 cells and promoted BLM-induced PF. In addition, mice receiving Vsir -/- CD4 T cells exhibited a higher percentage of Th17 cells and more severe PF compared to those receiving WT CD4 T cells.

Conclusion

These findings demonstrate the significant role of VISTA in modulating the development of PF by controlling Th17 cell differentiation. These insights suggest that targeting VISTA could be a promising therapeutic strategy for PF.

Expression and function of VISTA on myeloid cells

V-domain containing Ig Suppressor of T cell Activation (VISTA) is predominantly expressed on myeloid cells and functions as a ligand/receptor/soluble molecule. In inflammatory responses and immune responses, VISTA regulates multiple functions of myeloid cells, such as chemotaxis, phagocytosis, T cell activation. Since inflammation and immune responses are critical in many diseases, VISTA is a promising therapeutic target. In this review, we will describe the expression and function of VISTA on different myeloid cells, including neutrophils, monocytes, macrophages, dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs). In addition, we will discuss whether the functions of VISTA on these cells impact the disease processing.

Imatinib and M351-0056 enhance the function of VISTA and ameliorate the development of SLE via IFN-I and noncanonical NF-κB pathway

V-domain immunoglobulin suppressor of T-cell activation (VISTA), an important negative checkpoint protein, participates in immunoregulation. Systemic lupus erythematosus (SLE) is an autoimmune disease in which patients exhibit high levels of autoantibodies and multi-organ tissue injury, primarily involving the kidney and skin. In wild-type (WT) mice and Vsir-/- mice with pristane-induced lupus-like disease, we found that VISTA deficiency exacerbated the lupus-like disease in mice, possibly through aberrant activation of type I interferon (IFN-I) signaling, CD4+ T cell, and noncanonical nuclear factor-κB (NF-κB) pathway. Surface plasmon resonance results showed that imatinib, an FDA-approved tyrosine kinase inhibitor, may have a high affinity for human VISTA-ECD with a KD value of 0.2009 μM. The biological activities of imatinib and VISTA agonist M351-0056 were studied in monocytes and T cells and in lupus-like disease murine model of chronic graft-versus-host disease (cGVHD) and lupus-prone MRL/lpr mice. VISTA small-molecule agonist reduced the cytokine production of peripheral blood mononuclear cells (PBMCs) and Jurkat cells and inhibited PBMCs proliferation. Moreover, they attenuated the levels of autoantibodies, renal injury, inflammatory cytokines, chemokines, and immune cell expansion in the cGVHD mouse model and MRL/lpr mice. Our findings also demonstrated that VISTA small-molecule agonist ameliorated the development of SLE through improving aberrantly activated IFN-I signaling and noncanonical NF-κB pathway. In conclusion, VISTA has a protective effect on the development and progression of SLE. VISTA agonist M351-0056 and imatinib have been firstly demonstrated to attenuate SLE, suggesting interventions to enhance VISTA function may be effective in treating SLE. VISTA deficiency exacerbates pristane-induced lupus-like disease in mice by promoting activation of the IFN-I and noncanonical NF-κB pathway. Imatinib was screened as a small-molecule VISTA agonist by molecular docking, SPR, and cellular level experiments. VISTA agonists (M351-0056 and imatinib) alleviated lupus-like disease progression in the cGVHD mouse model and MRL/lpr mice by inhibiting activation of IFN-I and noncanonical NF-κB pathway.