缺氧对髓源性抑制细胞来源外泌体免疫抑制能力的影响

Effect of hypoxia on the immunosuppressive property of MDSC-derived exosomes

探讨在常氧(21%O_(2))和缺氧(1%O_(2))条件下,髓源性抑制细胞(myeloid-derived suppressor cell,MDSC)培养上清液中外泌体(exosome,Exo)的免疫抑制功能。该研究从小鼠结肠癌移植瘤模型的脾脏中磁珠分选MDSC,并在常氧和缺氧条件下自MDSC培养上清液中制备Exo。通过透射电子显微镜、流式粒径分析以及Western blotting特异性蛋白检测鉴定制备的MDSC来源外泌体((MDSC-derived exosome,MDSC-Exo)。将MDSC-Exo加至离体CD4^(+)T细胞和CD8^(+)T细胞增殖体系中后,相较于常氧条件下培养的MDSC,缺氧条件下的MDSC-Exo抑制CD4^(+)T细胞和CD8^(+)T细胞增殖的能力更强(均P<0.05)。同时,缺氧条件可以显著升高MDSC-Exo中精氨酸酶1(arginase 1,Arg-1)的水平(P<0.01),而这种作用会被干扰缺氧诱导因子1α(hypoxia-inducible factor 1α,HIF-1α)表达所抑制(P<0.01)。综上,缺氧可以使MDSC-Exo具有更强的免疫抑制功能,并且这种作用与HIF-1α介导的Arg-1的表达有关。

The study aims to compare the immunosuppressive property of exosome(Exo)isolated from myeloid-derived suppressor cell(MDSC)culture supernatant under normoxia(21%O_(2))and hypoxia(1%O_(2))conditions.MDSCs were isolated from the spleen of colon cancer-bearing mice by affinity magnetic beads and Exo was extracted from the supernatant of MDSC culture medium under normoxia and hypoxia conditions.The morphology and quality of the MDSC-derived exosome(MDSC-Exo)were identified by transmission electron microscopy,flow cytometric,and Western blotting.MDSC-Exo were added to CD4^(+)and CD8^(+)T cell cultures in vitro to test their effect on the proliferation of these cells.Compared to MDSC-Exo isolated from normal conditions,MDSC-Exo from hypoxia conditions inhibited both CD4^(+) and CD8^(+)T cell proliferation more effectively(both P<0.05).Meanwhile,hypoxia MDSC-Exo contained significantly increased arginase 1(Arg-1)(P<0.01),which was inhibited by the interference of hypoxia-inducible factor 1α(HIF-1α)(P<0.01).Taken together,hypoxia endows the MDSC-Exo with stronger immunosuppressive function and this property depends on the expression of Arg-1 mediated by HIF-1α.