BACKGROUND Our previous study reports the causal role of high mobility group box 1 (HMGB1) in the development of depression; and we find glycyrrhizic acid (GZA) can be a potential treatment for major depressive disorder (MDD) considering its inhibition of HMGB1 activity. This study aims to further explore the exact cell types that release HMGB1 in the hippocampus METHODS: We detected the effects of microglia conditioned medium on primary astrocytes and neurons. The effects of minocycline on depressive-like behaviors were tested in BABLB/c mice after four weeks of chronic unpredictable mild stress (CUMS) exposure. Furthermore, the immunofluorescence (IF) assays, hematoxylin-eosin (HE) and TUNEL staining were used to observe hippocampal slices to evaluate the release of HMGB1. The cytoplasmic translocations of HMGB1 protein were assayed by western-blot RESULTS: Exposure to CUMS caused an active release of HMGB1 from microglia and neurons in the hippocampus. After minocycline administration for inhibiting the activation of microglia, both microglia and neurons reduced the release of HMGB1 and the protein level of central and peripheral HMGB1 recovered accordingly. Along with blocking the release of HMGB1, behavioral and cognitive deficits induced by CUMS were improved significantly by minocycline. In addition, the supernatant of primary microglia stimulated the secretion of HMGB1 in primary neurons, not in astrocytes, at 24 h after 4 h-LPS treatment CONCLUSION: All the evidence supported our hypotheses that microglia and neurons are the main cell sources of HMGB1 release under CUMS condition, and that the release of HMGB1 by microglia may play an important role in the development of depressive-like behavior.

中文翻译：

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米诺环素通过抑制小胶质细胞和神经元释放 HMGB1 来预防抑郁样行为

背景 我们之前的研究报告了高迁移率族框 1 (HMGB1) 在抑郁症发展中的因果作用；我们发现甘草酸 (GZA) 可以作为重度抑郁症 (MDD) 的潜在治疗方法，因为它可以抑制 HMGB1 的活性。本研究旨在进一步探索海马中释放 HMGB1 的确切细胞类型方法：我们检测了小胶质细胞条件培养基对原代星形胶质细胞和神经元的影响。在长期不可预测的轻度压力 (CUMS) 暴露 4 周后，在 BABLB/c 小鼠中测试了米诺环素对抑郁样行为的影响。此外，免疫荧光 (IF) 测定、苏木精-伊红 (HE) 和 TUNEL 染色用于观察海马切片以评估 HMGB1 的释放。通过蛋白质印迹分析 HMGB1 蛋白的细胞质易位 结果：暴露于 CUMS 导致 HMGB1 从海马中的小胶质细胞和神经元中主动释放。给予米诺环素抑制小胶质细胞活化后，小胶质细胞和神经元均减少HMGB1的释放，中枢和外周HMGB1的蛋白水平相应恢复。随着阻断 HMGB1 的释放，米诺环素显着改善了由 CUMS 引起的行为和认知缺陷。此外，在 LPS 处理 4 小时后 24 小时，原代小胶质细胞的上清液刺激原代神经元而非星形胶质细胞中 HMGB1 的分泌 结论：所有证据都支持我们的假设，即小胶质细胞和神经元是 HMGB1 释放的主要细胞来源在 CUMS 条件下，