HMGB1 regulates the activation of dendritic cells and CD4+ T cell responses through the modulation of autophagy in bleomycin-induced pulmonary fibrosis.

Background: The role of HMGB1 in inflammation and autophagy has garnered increasing attention; however, its impact on the activation of dendritic cells (DCs) and autophagy remains unclear. This study aims to explore the effects of HMGB1 on DC activation, autophagy, and its influence on CD4+ T cell responses in a bleomycin-induced pulmonary fibrosis (PF) mouse model.

Methods: Thirty mice were randomly divided into control and model groups. The model group was established by intratracheal injection of bleomycin to induce PF. Flow cytometry was used to detect DC surface markers, and western blot was employed to assess the expression of autophagy-related protein LC3. Lung DCs and peripheral blood CD14+ monocytes were sorted using magnetic beads and differentiated into M0-DCs, which were then subjected to HMGB1 stimulation experiments to assess activation and cytokine secretion. HMGB1-stimulated or untreated M0-DCs were co-cultured with CFSE-labeled naive CD4+ T cells to evaluate T cell proliferation and differentiation. The effects of HMGB1 on DCs activation, cytokine secretion, and autophagy-related protein expression were assessed after treatment with autophagy regulators.

Results: The model group showed significantly elevated levels of HMGB1 in serum and lung tissues, accompanied by upregulated activation markers of DCs and increased expression of autophagy-related protein LC3. HMGB1 stimulation significantly enhanced the activation of M0-DCs and the secretion of pro-inflammatory cytokines, promoting the proliferation of CD4+ T cells and their differentiation into Th1 and Th17 subsets. Rapamycin, which enhances autophagy, potentiated HMGB1-mediated DC activation, while 3-MA, which inhibits autophagy, suppressed the effects of HMGB1, further influencing CD4+ T cell differentiation.

Conclusion: HMGB1 modulates DC autophagy, thereby affecting their activation and immune responses of CD4+ T cells in bleomycin-induced PF. Targeting HMGB1 and the autophagy pathway may provide new strategies for the treatment of PF.