Department of Thoracic Surgery, Renmin Hospital of Wuhan University, Wuhan, China.
Department of Cardiovascular Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Cell Signal. 2023 Sep;109:110783. doi: 10.1016/j.cellsig.2023.110783. Epub 2023 Jun 24.
Acute allograft rejection remains a major obstacle after heart transplantation, and CD4+ T cells play a crucial role in allograft rejection. Upregulation of Nr4A1 could regulate CD4+ T-cell function and alleviate allograft rejection. However, the regulatory mechanism of Nr4A1 in allograft rejection remains elusive.
BALB/c mouse hearts were transplanted into WT C57BL/6 mice, and dynamic detection of the changes in Nr4A1 expression revealed that Nr4A1 was regulated posttranscriptionally after heart transplantation. Potential upstream miRNAs of Nr4A1 were screened, and the transfection of cells with these miRNA mimics/inhibitors and dual-luciferase reporter experiments were performed to clarify the regulatory mechanism of miRNAs on Nr4A1 expression. The miRNA agomiR/antagomiR was applied in vivo to validate the role of the corresponding miRNA in heart transplantation. Finally, Nr4A1 knockout mice and an adoptive T-cell cotransfer model were used to confirm the specific effects of miRNA.
The expression of Nr4A1 protein (rather than mRNA) exhibited a trend of initially increasing and then decreasing rapidly, and this phenomenon could not be reversed by lysosomal or proteasomal inhibitors. The miRNA let-7a directly binds to the Nr4A1 3'UTR and posttranscriptionally regulates Nr4A1 expression. The let-7a antagomiR prolonged allograft survival and regulated CD4+ T-cell function by upregulating Nr4A1 protein expression in CD4+ T cells.
This study confirmed that let-7a is a potential target for interfering with Nr4A1 expression in CD4+ T cells and preventing the pathological progression of cardiac allograft rejection.
急性移植物排斥反应仍是心脏移植后的主要障碍，CD4+T 细胞在移植物排斥反应中起关键作用。Nr4A1 的上调可调节 CD4+T 细胞功能并减轻移植物排斥反应。然而，Nr4A1 在移植物排斥反应中的调节机制仍不清楚。
BALB/c 小鼠心脏移植到 WT C57BL/6 小鼠中，动态检测 Nr4A1 表达的变化，发现 Nr4A1 在心脏移植后受转录后调控。筛选 Nr4A1 的潜在上游 miRNA，用这些 miRNA 模拟物/抑制剂转染细胞，并进行双荧光素酶报告实验，阐明 miRNA 对 Nr4A1 表达的调节机制。将 miRNA agomiR/antagomiR 应用于体内，验证相应 miRNA 在心脏移植中的作用。最后，使用 Nr4A1 敲除小鼠和过继性 T 细胞共转染模型，确认 miRNA 的特定作用。
Nr4A1 蛋白（而非 mRNA）的表达呈先增后迅速下降的趋势，且这种现象不能被溶酶体或蛋白酶体抑制剂逆转。miRNA let-7a 直接结合 Nr4A1 3'UTR，并通过上调 CD4+T 细胞中 Nr4A1 蛋白表达来对 Nr4A1 进行转录后调节。let-7a 拮抗物通过上调 CD4+T 细胞中 Nr4A1 蛋白表达延长移植物存活并调节 CD4+T 细胞功能。
本研究证实，let-7a 是一种潜在的干扰 CD4+T 细胞中 Nr4A1 表达并阻止心脏移植物排斥反应病理进展的靶标。
