Laboratory of Clinical Science and Biomedicine, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka, Japan.
Laboratory for Animal Resource Development, RIKEN Center for Biosystems Dynamics Research, Japan.
Cardiovasc Res. 2019 Mar 15;115(4):765-775. doi: 10.1093/cvr/cvy254.
Accumulating evidence demonstrates that cardiomyocyte death contributes to the onset and progression of heart failure (HF) after myocardial injury. Recent studies revealed that immune/inflammatory reactions play important roles in cardiovascular diseases. However, it remains unclear whether immunosurveillance system, which eliminates cytopathic cells, including infected or malignant cancer cells, is involved in cardiomyocyte death, though cardiomyocytes are exposed to pathological stresses during post-infarct remodelling. The aim of this study is to clarify the pathophysiological significance of Natural Killer Group 2 member D (NKG2D)/NKG2D ligand (NKG2DL)-mediated cell death in HF after myocardial infarction (MI).
MI was generated by ligating left anterior descending artery in mice. The expression of NKG2D, NKG2DLs, especially Retinoic acid early induced transcript-1ɛ (Rae-1ɛ), perforin and granzyme B was concomitantly up-regulated after MI. Immunohistological analysis revealed that Rae-1 was expressed on the membranes of injured cardiomyocytes in the infarct and border area. The MI-induced increase of Rae-1 expression was suppressed in p53-/- mice and Rae-1 was induced by the overexpression of p53. We identified p53-binding sites in Rae-1ɛ gene promoter, by chromatin immunoprecipitation assay, indicating that Rae-1 expression was mediated partially through p53. Flow cytometric analysis indicated that NKG2D-expressing immune cells in the post-infarct myocardium were mainly γδT cells. The co-culture with γδT cells increased the frequency of apoptotic cells in the cultured cardiomyocytes. The blockade of NKG2D/NKG2DL interaction by intraperitoneal injection of anti-Rae-1ɛ antibody after MI reduced the frequency of apoptotic cardiomyocytes, accompanied by suppression of cardiac fibrosis, attenuating cardiac dysfunction. Finally, tamoxifen-inducible cardiomyocyte-specific Rae-1ɛ overexpressing mice exhibited the susceptibility to post-infarct remodelling with increased cardiomyocyte apoptosis and severer cardiac dysfunction.
The interaction between immune cells and cardiomyocytes via NKG2D/NKG2DL induces cardiomyocyte death, exacerbating cardiac remodelling after MI. The blockade of NKG2D/NKG2DL interaction could be a promising therapeutic strategy against HF.
越来越多的证据表明，心肌细胞死亡是心肌损伤后心力衰竭（HF）发生和进展的原因。最近的研究表明，免疫/炎症反应在心血管疾病中起着重要作用。然而，尽管在心肌梗死后重塑过程中心肌细胞会受到病理应激，但免疫监视系统（消除包括感染或恶性癌细胞在内的细胞病变细胞）是否参与心肌细胞死亡仍不清楚。本研究旨在阐明自然杀伤细胞组 2 成员 D（NKG2D）/NKG2D 配体（NKG2DL）介导的细胞死亡在心肌梗死后心力衰竭（HF）中的病理生理意义。
通过结扎小鼠左前降支动脉产生心肌梗死。NKG2D、NKG2DLs，特别是维甲酸早期诱导转录物 1ɛ（Rae-1ɛ）、穿孔素和颗粒酶 B 的表达在 MI 后同时上调。免疫组织化学分析显示，Rae-1 在梗死和边缘区受损心肌细胞的膜上表达。在 p53-/-小鼠中，MI 诱导的 Rae-1 表达增加受到抑制，并且 Rae-1 是由 p53 的过表达诱导的。通过染色质免疫沉淀测定，我们在 Rae-1ɛ基因启动子中鉴定出 p53 结合位点，表明 Rae-1 的表达部分通过 p53 介导。流式细胞术分析表明，心肌梗死后心肌中 NKG2D 表达的免疫细胞主要是γδT 细胞。与 γδT 细胞共培养可增加培养的心肌细胞中凋亡细胞的频率。MI 后腹腔注射抗 Rae-1ɛ 抗体阻断 NKG2D/NKG2DL 相互作用可降低凋亡心肌细胞的频率，同时抑制心肌纤维化，减轻心功能障碍。最后，他莫昔芬诱导的心肌细胞特异性 Rae-1ɛ过表达小鼠表现出对心肌梗死后重塑的易感性，导致心肌细胞凋亡增加和更严重的心功能障碍。
通过 NKG2D/NKG2DL，免疫细胞与心肌细胞相互作用诱导心肌细胞死亡，加剧 MI 后心脏重塑。阻断 NKG2D/NKG2DL 相互作用可能是一种有前途的 HF 治疗策略。
