ABSTRACT

Background: The macrophage is an innate immune defense cell involved in pathogen recognition and clearance.

Aim: In view of the diversity of the macrophage phenotype and function, the present study investigated how Enterococcus faecalis infection affects the differentiation, phenotype and cytokine profile of macrophages.

Methods: Murine bone marrow-derived stem cells were co-cultured with E. faecalis before and after differentiation. Macrophage M0 polarization towards M1 or M2 was initiated at day 6 by addition of LPS and INF-γ, or IL-4 and IL-13, respectively.

Results: E. faecalis did not inhibit macrophage differentiation and were identified within macrophages. Viability of the macrophages infected with E. faecalis prior to differentiation was enhanced, evidenced by apoptosis inhibition, as was expression of CD38 and IRF5 proteins, indicators of M1-like polarization. These M1-like macrophages expressed an aberrant cytokine mRNA profile, with reduction in inflammatory cytokines IL-1β and IL-12 and increase in regulatory cytokine IL-10. No changes in TNF-α or TGF-β1 were detected, compared with the control groups. This atypical M1-like phenotype was retained even upon stimulation with growth factors that normally trigger their development into M2 macrophages.

Conclusions: These findings suggested that E. faecalis infection of bone marrow-derived stem cells during differentiation into macrophages induces an atypical M1-like phenotype associated with intracellular bacterial survival.

摘要

背景：巨噬细胞是一种参与病原体识别和清除的先天免疫防御细胞。

目的：鉴于巨噬细胞表型和功能的多样性，本研究探讨粪肠球菌感染如何影响巨噬细胞的分化、表型和细胞因子谱。

方法：小鼠骨髓来源的干细胞在分化前后与粪肠球菌共培养。通过分别添加 LPS 和 INF-γ 或 IL-4 和 IL-13 在第 6 天开始巨噬细胞 M0 向 M1 或 M2 极化。

结果：粪肠球菌不抑制巨噬细胞分化，并且在巨噬细胞内被鉴定。细胞凋亡抑制证明了在分化前感染粪肠球菌的巨噬细胞的活力增强，CD38 和 IRF5 蛋白的表达也是 M1 样极化的指标。这些 M1 样巨噬细胞表达异常的细胞因子 mRNA 谱，炎症细胞因子 IL-1β 和 IL-12 减少，调节细胞因子 IL-10 增加。与对照组相比，未检测到 TNF-α 或 TGF-β1 的变化。这种非典型的 M1 样表型即使在用通常触发其发育成 M2 巨噬细胞的生长因子刺激后也得以保留。

结论：这些研究结果表明，粪肠球菌感染骨髓来源的干细胞在分化为巨噬细胞期间诱导了与细胞内细菌存活相关的非典型 M1 样表型。