Maimaitijiang Alimujiang, Huang Qingyu, Wu Yurong, Sun Shengjia, Chen Qiying
Department of Cardiology, Huashan Hospital, Fudan University, Shanghai, China.
Cytojournal. 2024 Nov 28;21:58. doi: 10.25259/Cytojournal_32_2024. eCollection 2024.
Macrophages perform vital functions in cardiac remodeling after myocardial infarction (MI). Transglutaminase 2 (TG2) participates in fibrosis. Nevertheless, the role of TG2 in MI and mechanisms underlying macrophage polarization are unclear. This study aimed to discover the functions and possible mechanisms of TG2 in MI.
C57BL/6 mice were classified into three groups (six mice per group): Sham, MI, and MI+GK921 groups. GK921 acts as a TG2 inhibitor. Cardiac function, myocardial cell apoptosis, fibrosis, and macrophage phenotype in mouse experiments were detected through echocardiography, terminal deoxynucleotidyl transferase dUTP nick end labeling, Masson staining, immunofluorescence, and flow cytometry, respectively. The study involved the treatment of mouse cardiac fibroblasts isolated from mice with transforming growth factor β1 (TGF-β1) and evaluation of fibrosis through the detection of the expressions of fibrosis-associated proteins using Western blot. Bone marrow-derived macrophages (BMDMs) obtained from mice were triggered by interleukin (IL)-4, and the type of macrophages was determined through flow cytometry.
In experiments, GK921 substantially improved cardiac injury and fibrosis, induced M2 macrophage polarization, and suppressed the TGF-β1/small mother against decapentaplegic 3 (Smad3) pathway in MI mice. Moreover, TG2 knockdown considerably decreased the expressions of fibrosis-associated proteins in TGF-β1-triggered mouse cardiac fibroblasts, which indicates the repressive effect of TG2 knockdown on fibrosis. In addition, the inhibition effect of TG2 downregulation on the TGF-β1/Smad3 pathway was proven in TGF-β1-treated mouse cardiac fibroblasts . Moreover, TG2 inhibition remarkably increased M2 macrophage polarization in IL-4-induced BMDMs.
TG2 inhibition facilitated M2 macrophage polarization to provide protection against MI-caused cardiac fibrosis in mice, and these effects may be attained through modulation of the TGF-β1/Smad3 pathway.
巨噬细胞在心肌梗死（MI）后的心脏重塑中发挥着重要作用。转谷氨酰胺酶2（TG2）参与纤维化过程。然而，TG2在MI中的作用以及巨噬细胞极化的潜在机制尚不清楚。本研究旨在探讨TG2在MI中的功能及可能机制。
将C57BL/6小鼠分为三组（每组6只）：假手术组、MI组和MI+GK921组。GK921作为TG2抑制剂。分别通过超声心动图、末端脱氧核苷酸转移酶介导的dUTP缺口末端标记法、Masson染色、免疫荧光和流式细胞术检测小鼠实验中的心脏功能、心肌细胞凋亡、纤维化和巨噬细胞表型。本研究涉及用转化生长因子β1（TGF-β1）处理从小鼠分离的心脏成纤维细胞，并通过蛋白质免疫印迹法检测纤维化相关蛋白的表达来评估纤维化。从小鼠获得的骨髓来源巨噬细胞（BMDMs）用白细胞介素（IL）-4刺激，通过流式细胞术确定巨噬细胞类型。
实验中，GK921显著改善了MI小鼠的心脏损伤和纤维化，诱导了M2巨噬细胞极化，并抑制了TGF-β1/小母细胞抗五体不全蛋白3（Smad3）通路。此外，敲低TG2显著降低了TGF-β1刺激的小鼠心脏成纤维细胞中纤维化相关蛋白的表达，这表明敲低TG2对纤维化有抑制作用。此外，在TGF-β1处理的小鼠心脏成纤维细胞中证实了下调TG2对TGF-β1/Smad3通路的抑制作用。此外，抑制TG2显著增加了IL-4诱导的BMDMs中M2巨噬细胞极化。
抑制TG2促进M2巨噬细胞极化，为小鼠MI所致心脏纤维化提供保护，这些作用可能是通过调节TGF-β1/Smad3通路实现的。
