Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church St. SE, Minneapolis, MN, 55455, USA.
Institute of Biomaterials and, Bioengineering, Tokyo Medical and Dental University (TMDU), 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo, 01-0062, Japan.
Cell Commun Signal. 2021 Jun 30;19(1):69. doi: 10.1186/s12964-021-00751-w.
Intercellular communications are important for maintaining normal physiological processes. An important intercellular communication is mediated by the exchange of membrane-enclosed extracellular vesicles. Among various vesicles, exosomes can be detected in a wide variety of biological systems, but the regulation and biological implication of exosome secretion/uptake remains largely unclear.
Cellular retinoic acid (RA) binding protein 1 (Crabp1) knockout (CKO) mice were used for in vivo studies. Extracellular exosomes were monitored in CKO mice and relevant cell cultures including embryonic stem cell (CJ7), macrophage (Raw 264.7) and hippocampal cell (HT22) using Western blot and flow cytometry. Receptor Interacting Protein 140 (RIP140) was depleted by Crispr/Cas9-mediated gene editing. Anti-inflammatory maker was analyzed using qRT-PCR. Clinical relevance was accessed by mining multiple clinical datasets.
This study uncovers Crabp1 as a negative regulator of exosome secretion from neurons. Specifically, RIP140, a pro-inflammatory regulator, can be transferred from neurons, via Crabp1-regulated exosome secretion, into macrophages to promote their inflammatory polarization. Consistently, CKO mice, defected in the negative control of exosome secretion, have significantly elevated RIP140-containing exosomes in their blood and cerebrospinal fluid, and exhibit an increased vulnerability to systemic inflammation. Clinical relevance of this pathway is supported by patients' data of multiple inflammatory diseases. Further, the action of Crabp1 in regulating exosome secretion involves its ligand and is mediated by its downstream target, the MAPK signaling pathway.
This study presents the first evidence for the regulation of exosome secretion, which mediates intercellular communication, by RA-Crabp1 signaling. This novel mechanism can contribute to the control of systemic inflammation by transferring an inflammatory regulator, RIP140, between cells. This represents a new mechanism of vitamin A action that can modulate the homeostasis of system-wide innate immunity without involving gene regulation. Video Abstract.
细胞间通讯对于维持正常生理过程至关重要。一种重要的细胞间通讯是通过膜封闭的细胞外囊泡的交换来介导的。在各种囊泡中，外泌体可以在广泛的生物系统中检测到，但外泌体分泌/摄取的调节和生物学意义在很大程度上仍不清楚。
使用细胞视黄酸（RA）结合蛋白 1（Crabp1）敲除（CKO）小鼠进行体内研究。使用 Western blot 和流式细胞术监测 CKO 小鼠以及相关细胞培养物中的细胞外外泌体，包括胚胎干细胞（CJ7）、巨噬细胞（Raw 264.7）和海马细胞（HT22）。用 Crispr/Cas9 介导的基因编辑耗竭受体相互作用蛋白 140（RIP140）。使用 qRT-PCR 分析抗炎标志物。通过挖掘多个临床数据集评估临床相关性。
这项研究揭示了 Crabp1 是神经元来源的外泌体分泌的负调控因子。具体来说，RIP140 是一种促炎调节剂，可通过 Crabp1 调节的外泌体分泌从神经元转移到巨噬细胞中，促进其炎症极化。一致地，在缺乏外泌体分泌负调控的 CKO 小鼠中，其血液和脑脊液中的 RIP140 含量显著升高，并表现出对全身炎症的易感性增加。该通路的临床相关性得到了多个炎症性疾病患者数据的支持。此外，Crabp1 调节外泌体分泌的作用涉及其配体，并通过其下游靶标 MAPK 信号通路介导。
本研究首次证明了 RA-Crabp1 信号转导调节外泌体分泌，从而介导细胞间通讯。这种新机制可以通过细胞间转移促炎调节剂 RIP140 来控制全身炎症。这代表了维生素 A 作用的一种新机制，可调节全身性固有免疫的内稳状态，而不涉及基因调控。
