Background:Immune checkpoint inhibitor (ICI) therapy is often accompanied by immune-related pathology, with an increasing occurrence of high-risk ICI-related myocarditis. Understanding the mechanisms involved in this side effect could enable the development of management strategies. In mouse models, immune checkpoints, such as PD-1 (programmed cell death protein 1), control the threshold of self-antigen responses directed against cardiac TnI (troponin I). We aimed to identify how the immunoproteasome, the main proteolytic machinery in immune cells harboring 3 distinct protease activities in the LMP2 (low-molecular-weight protein 2), LMP7 (low-molecular-weight protein 7), and MECL1 (multicatalytic endopeptidase complex subunit 1) subunit, affects TnI-directed autoimmune pathology of the heart.Methods:TnI-directed autoimmune myocarditis (TnI-AM), a CD4⁺ T-cell–mediated disease, was induced in mice lacking all 3 immunoproteasome subunits (triple-ip^−/−) or lacking either the gene encoding LMP2 and LMP7 by immunization with a cardiac TnI peptide. Alternatively, before induction of TnI-AM or after establishment of autoimmune myocarditis, mice were treated with the immunoproteasome inhibitor ONX 0914. Immune parameters defining heart-specific autoimmunity were investigated in experimental TnI-AM and in 2 cases of ICI-related myocarditis.Results:All immunoproteasome-deficient strains showed mitigated autoimmune-related cardiac pathology with less inflammation, lower proinflammatory and chemotactic cytokines, less interleukin-17 production, and reduced fibrosis formation. Protection from TnI-directed autoimmune heart pathology with improved cardiac function in LMP7^−/− mice involved a changed balance between effector and regulatory CD4⁺ T cells in the spleen, with CD4⁺ T cells from LMP7^−/− mice showing a higher expression of inhibitory PD-1 molecules. Blocked immunoproteasome proteolysis, by treatment of TLR2 (Toll-like receptor 2)–engaged and TLR7 (Toll-like receptor 7)/TLR8 (Toll-like receptor 8)–engaged CD14⁺ monocytes with ONX 0914, diminished proinflammatory cytokine responses, thereby reducing the boost for the expansion of self-reactive CD4⁺ T cells. Correspondingly, in mice, ONX 0914 treatment reversed cardiac autoimmune pathology, preventing the induction and progression of TnI-AM when self-reactive CD4⁺ T cells were primed. The autoimmune signature during experimental TnI-AM, with high immunoproteasome expression, immunoglobulin G deposition, interleukin-17 production in heart tissue, and TnI-directed humoral autoimmune responses, was also present in 2 cases of ICI-related myocarditis, demonstrating the activation of heart-specific autoimmune reactions by ICI therapy.Conclusions:By reversing heart-specific autoimmune responses, immunoproteasome inhibitors applied to a mouse model demonstrate their potential to aid in the management of autoimmune myocarditis in humans, possibly including patients with ICI-related heart-specific autoimmunity.

中文翻译：

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免疫蛋白酶体抑制剂和基因消融减轻的自身免疫相关心肌炎动物模型中的心脏特异性免疫反应。

背景：免疫检查点抑制剂（ICI）治疗常伴有免疫相关病理，高危 ICI 相关心肌炎的发生率越来越高。了解这种副作用所涉及的机制可以促进管理策略的发展。在小鼠模型中，免疫检查点，如 PD-1（程序性细胞死亡蛋白 1），控制针对心脏 TnI（肌钙蛋白 I）的自身抗原反应的阈值。我们旨在确定免疫蛋白酶体（免疫细胞中的主要蛋白水解机制）如何在 LMP2（低分子量蛋白 2）、LMP7（低分子量蛋白 7）和 MECL1（多催化内肽酶复合物）中具有 3 种不同的蛋白酶活性亚基 1) 亚基，影响心脏的 TnI 导向的自身免疫病理学。方法：TnI 导向的自身免疫性心肌炎 (TnI-AM)，⁺ T 细胞介导的疾病，在缺乏所有 3 个免疫蛋白酶体亚基（triple-ip ^-/-）的小鼠中诱导) 或通过用心脏 TnI 肽免疫而缺乏编码 LMP2 和 LMP7 的基因。或者，在诱导 TnI-AM 之前或建立自身免疫性心肌炎之后，用免疫蛋白酶体抑制剂 ONX 0914 治疗小鼠。在实验性 TnI-AM 和 2 例 ICI 相关心肌炎中研究了定义心脏特异性自身免疫的免疫参数。 ：所有免疫蛋白酶体缺陷菌株均表现出减轻的自身免疫相关心脏病变，炎症较少，促炎和趋化细胞因子较低，白细胞介素 17 产生较少，纤维化形成减少。在 LMP7 ^-/-小鼠中通过改善心脏功能保护免受 TnI 导向的自身免疫性心脏病病理，涉及效应子和调节性 CD4 ⁺之间的平衡改变脾脏中的T 细胞，来自 LMP7 ^{- /-}小鼠的CD4 ⁺ T 细胞显示出更高的抑制性 PD-1 分子表达。通过用 ONX 0914处理 TLR2（Toll 样受体 2）参与和 TLR7（Toll 样受体 7）/TLR8（Toll 样受体 8）参与的 CD14 ⁺单核细胞，阻断免疫蛋白酶体蛋白水解，减少促炎细胞因子反应，从而减少自我反应性 CD4 ⁺ T 细胞扩增的促进作用。相应地，在小鼠中，ONX 0914 治疗逆转了心脏自身免疫病理，阻止了自身反应性 CD4 ⁺时 TnI-AM 的诱导和进展T细胞被引发。实验性 TnI-AM 期间的自身免疫特征，具有高免疫蛋白酶体表达、免疫球蛋白 G 沉积、心脏组织中白细胞介素 17 的产生以及 TnI 导向的体液自身免疫反应，也存在于 2 例 ICI 相关心肌炎中，证明了ICI 治疗引起的心脏特异性自身免疫反应。 结论：通过逆转心脏特异性自身免疫反应，应用于小鼠模型的免疫蛋白酶体抑制剂证明了它们有助于治疗人类自身免疫性心肌炎的潜力，可能包括患有 ICI 相关心脏特异性的患者自身免疫。