Endothelial cells are key regulators of transendothelial migration and their secretion of chemokines and expression of adhesion molecules facilitates lymphocyte entry into tissues. Previously, we demonstrated that Tregs can reduce transendothelial migration of T cells into tumors by decreasing endothelial CXCL10 secretion, but the mechanism by which this occurs is still not known. In this study, we aimed to define how Tregs decrease transendothelial migration into tumors. mRNA sequencing of intestinal tumor endothelial cells from Treg depleted mice identified neutral sphingomyelinase 2 (nSMase2) as a gene downregulated in the presence of Tregs. nSMase2 is expressed in human umbilical vein endothelial cells (HUVECs) and was decreased after coculture with Tregs. Furthermore, blocking of nSMase2 activity in vitro decreased VCAM1, CX3CL1, and CXCL10 expression in HUVECs, mirroring the same decrease found in Treg cocultures. In the APC^min/+ mouse model of intestinal cancer, nSMase2 is lower in tumor endothelial cells than in unaffected small intestine and chronic treatment with a nSMase2 inhibitor suppressed the increased migration that is otherwise seen in the absence of Tregs. We conclude that nSMase2 is an important mediator in endothelial cells supporting transendothelial migration, which may be targeted by Tregs to reduce T-cell migration into tumors.

中文翻译：

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调节性 T 细胞减少内皮中性鞘磷脂酶 2 以防止 T 细胞迁移到肿瘤中

内皮细胞是跨内皮迁移的关键调节剂，它们分泌趋化因子和表达粘附分子促进淋巴细胞进入组织。以前，我们证明 Tregs 可以通过减少内皮 CXCL10 分泌来减少 T 细胞向肿瘤的跨内皮迁移，但发生这种情况的机制尚不清楚。在这项研究中，我们旨在确定 Tregs 如何减少跨内皮迁移到肿瘤中。来自 Treg 耗竭小鼠的肠肿瘤内皮细胞的 mRNA 测序将中性鞘磷脂酶 2 (nSMase2) 鉴定为在 Treg 存在下下调的基因。nSMase2 在人脐静脉内皮细胞 (HUVEC) 中表达，并在与 Treg 共培养后降低。此外，在体外阻断 nSMase2 活性降低 HUVEC 中 VCAM1、CX3CL1 和 CXCL10 的表达，反映了在 Treg 共培养物中发现的相同降低。在肠癌的 APC ^min/+小鼠模型中，肿瘤内皮细胞中的 nSMase2 低于未受影响的小肠，并且用 nSMase2 抑制剂长期治疗抑制了在没有 Tregs 的情况下增加的迁移。我们得出结论，nSMase2 是内皮细胞中支持跨内皮迁移的重要介质，Treg 可能会靶向其以减少 T 细胞迁移到肿瘤中。