Nrf2 activation mediates tumor-specific hepatic stellate cells-induced DIgR2 expression in dendritic cells.

Yun-Hong Xia,Zhen Lu,Li-Xia Hu,Shou-Min Wang

doi:10.18632/aging.102554

Abstract

Our previous studies discovered that tumor-specific hepatic stellate cells (tHSCs) induced dendritic cell-derived immunoglobulin receptor 2 (DIgR2) expression in bone marrow-derived dendritic cells (mDCs), inhibiting splenic T cell activation. The current study aims to explore the underlying mechanism of DIgR2 expression by focusing on Nrf2 (nuclear-factor-E2-related factor 2) signaling. We show that tHSCs co-culture induced significant Nrf2 signaling activation in mDCs. The latter was evidenced by Nrf2-Keap1 disassociation, Nrf2 protein stabilization, accumulation and nuclear translocation. Expression of Nrf2-dependent genes, including heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO1), were detected in tHSCs-co-cultured mDCs. Importantly tHSCs-induced DIgR2 expression was blocked by Nrf2 shRNA or knockout (KO, by CRISPR/Cas9 method). Conversely, forced activation of Nrf2, by Keap1 shRNA or the Nrf2 activators (3H-1,2-dithiole-3-thione and MIND4-17), induced significant DIgR2 expression. tHSCs stimulation induced reactive oxygen species (ROS) production in mDCs. Conversely, ROS scavengers inhibited tHSCs-induced ROS production, Nrf2 activation and DIgR2 expression in mDCs. Significantly, tHSCs inhibited production of multiple cytokines (CD80, CD86 and IL-12) in mDCs, reversed by Nrf2 depletion. Moreover, Nrf2 shRNA or KO attenuated splenic T cell inhibition by tHSCs-stimulated mDCs. Together, we conclude that Nrf2 activation mediates tHSCs-induced DIgR2 expression in mDCs.

Highlights

Hepatocellular carcinoma (HCC) is a major health threat and a primary cause of cancer-associated human mortalities [1,2,3]
Using the H2DCFDA fluorescent dye assay, our results found that reactive oxygen species (ROS) levels were significantly increased in tumor-specific hepatic stellate cells (tHSCs)-stimulated marrow-derived dendritic cells (mDCs) (Figure 3A), where the H2DCFDA fluorescent intensity increased over five folds of control level (Figure 3A)
Since nuclear-factor-E2-related factor 2 (Nrf2) activation is required for derived immunoglobulin receptor 2 (DIgR2) expression, we proposed that Nrf2 depletion should abolish tHSCs-induced inhibition on cytokines in mDCs

Summary

Introduction

Hepatocellular carcinoma (HCC) is a major health threat and a primary cause of cancer-associated human mortalities [1,2,3]. Tumor immunity has become one research focus for HCC [7,8,9]. Dendritic cells (DCs) are antigen-presenting cells (APC) in tumor immunity, initiate key immune responses [10, 11]. Depletion or inhibition of DCs could lead to pro-cancer tumor environments [10, 11]. DIgR2, or dendritic cell-derived immunoglobulin receptor 2, is a member of IgSF inhibitory receptor, inhibiting DC-induced antigen-specific T-cell responses [12]. DCs-derived DIgR2 directly binds to T cells, suppressing T-cell-mediated tumor immunity [12]

Methods

Results

Conclusion