Introduction: Systemic inflammation induced by gut translocation of lipopolysaccharide (LPS), a major component of Gram-negative bacteria, in thalassemia with iron-overload worsens sepsis. However, the impact of (1→ 3)-β-D-glucan (BG), a major fungal molecule, in iron-overload thalassemia is still unclear. Hence, the influence of BG was explored in 1) iron-overload mice with sepsis induced by cecal ligation and puncture (CLP) surgery; and 2) in bone marrow-derived macrophages (BMMs).
Methods: The heterozygous β-globin-deficient mice, Hbb^th3/+ mice, were used as representative thalassemia (TH) mice. Iron overload was generated by 6 months of oral iron administration before CLP surgery- induced sepsis in TH mice and wild-type (WT) mice. Additionally, BMMs from both mouse strains were used to explore the impact of BG.
Results: Without sepsis, iron-overload TH mice demonstrated more severe intestinal mucosal injury (gut leakage) with higher LPS and BG in serum, from gut translocation, when compared with WT mice. With CLP in iron-overload mice, sepsis severity in TH mice was more severe than WT as determined by survival analysis, organ injury (kidney and liver), bacteremia, endotoxemia, gut leakage (FITC-dextran) and serum BG. Activation by LPS plus BG (LPS+BG) in BMMs and in peripheral blood-derived neutrophils (both WT and TH cells) demonstrated more prominent cytokine production when compared with LPS activation alone. In parallel, LPS+BG also prominently induced genes expression of M1 macrophage polarization (iNOS, TNF-α and IL-1β) in both WT and TH cells in comparison with LPS activation alone. In addition, LPS+BG activated macrophage cytokine production was enhanced by a high dose of ferric ion (800 mM), more predominantly in TH macrophages compared with WT cells. Moreover, LPS+BG induced higher glycolysis activity with similar respiratory capacity in RAW264.7 (a macrophage cell line) compared with LPS activation alone. These data support an additive pro-inflammatory effect of BG upon LPS.
Conclusion: The enhanced-severity of sepsis in iron-overload TH mice was due to 1) increased LPS and BG in serum from iron-induced gut-mucosal injury; and 2) the pro-inflammatory amplification by ferric ion on LPS+BG activation.

Keywords: thalassemia, iron overload, leaky-gut, sepsis


中文翻译：

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肠道易位的病原体相关分子可提高铁过载β-地中海贫血小鼠盲肠结扎和穿刺脓毒症的严重程度

简介：脂多糖 (LPS) 肠道易位引起的全身炎症，脂多糖 (LPS) 是革兰氏阴性菌的主要成分，在伴有铁过载的地中海贫血中会加重败血症。然而，主要真菌分子 (1→ 3)-β-D-葡聚糖 (BG) 在铁过载地中海贫血中的影响仍不清楚。因此，BG 对 1) 盲肠结扎和穿刺 (CLP) 手术致败血症的铁过载小鼠的影响进行了探讨；2) 在骨髓源性巨噬细胞 (BMM) 中。
方法：杂合β-珠蛋白缺陷小鼠，Hbb ^th3/+小鼠，被用作代表性的地中海贫血（TH）小鼠。在 TH 小鼠和野生型 (WT) 小鼠中，在 CLP 手术诱导的败血症之前 6 个月口服铁剂会产生铁过载。此外，来自两种小鼠品系的 BMM 被用于探索 BG 的影响。
结果：在没有败血症的情况下，与 WT 小鼠相比，铁过载 TH 小鼠表现出更严重的肠粘膜损伤（肠渗漏），血清中的 LPS 和 BG 更高，来自肠易位。通过生存分析、器官损伤（肾脏和肝脏）、菌血症、内毒素血症、肠渗漏（FITC-葡聚糖）和血清 BG 确定，在铁过载小鼠中使用 CLP，TH 小鼠的败血症严重程度比 WT 更严重。与单独的 LPS 激活相比，LPS 加 BG (LPS+BG) 在 BMM 和外周血衍生的中性粒细胞（WT 和 TH 细胞）中的激活表现出更显着的细胞因子产生。同时，LPS+BG 还显着诱导 M1 巨噬细胞极化的基因表达（iNOS、TNF-α和IL-1β) 在 WT 和 TH 细胞中与单独的 LPS 激活相比。此外，LPS+BG 激活的巨噬细胞细胞因子的产生被高剂量的铁离子 (800 mM) 增强，与 WT 细胞相比，在 TH 巨噬细胞中更明显。此外，与单独的 LPS 激活相比，LPS+BG 在 RAW264.7（一种巨噬细胞系）中诱导更高的糖酵解活性和相似的呼吸能力。这些数据支持 BG 对 LPS 的附加促炎作用。
结论：铁超负荷 TH 小鼠脓毒症严重程度的增加是由于 1）铁诱导的肠粘膜损伤血清中 LPS 和 BG 增加；2) 铁离子对 LPS+BG 活化的促炎放大作用。

关键词：地中海贫血，铁过载，肠漏，败血症