Mitigation of GI-ARS by Lactobacillus species

大规模辐射事故引起的公众辐射暴露是一个日益引起全球关注的问题。胃肠 急性放射综合征（GI-ARS）与高发病率和死亡率相关。然而，FDA- 用于GI-ARS的批准的治疗剂是不可用的。因此，概述辐射损伤的机制， 制定有针对性的医疗对策（MCM）是一个高度优先事项。肠道微生物组高度 易受电离辐射影响，微生物组的改变是发病机制的主要因素 关于GI-ARS这一领域的差距是辐射引起肠道生态失调的确切机制 微生物群及其对辐射损伤的影响的定义很差。我们研究的长期目标是 确定肠道中对辐射敏感的微生物群，并开发针对肠道微生物群的MCMs， 辐射损伤我们的初步研究已经确定：1）干酪乳杆菌和植物乳杆菌减轻 辐射诱导的上皮紧密连接（TJ）破坏和屏障功能障碍， 机制等2)潘氏细胞α-防御素的耗竭在辐射损伤机制中起着关键作用， 导致微生物群生态失调。3)照射后24小时喂饲L. casei和L. plantarum 减轻辐射诱导的α-防御素耗竭、微生物群生态失调、肠道屏障功能障碍、内毒素血症， 和全身性炎症。这些发现构成了科学前提，并支持了中心假设， “L. casei和L.植物通过逆转肠道微生物群的生态失调协同减轻GI-ARS， 上皮屏障功能障碍，导致内毒素血症和全身炎症的减弱。我们 将通过确定1）L.植物减轻辐射诱导的上皮TJ破坏 通过EGFR介导的c-Jun N-末端激酶-2（JNK 2）/c-Src/蛋白酪氨酸磷酸化的抑制，2）L. 酪蛋白减轻放射诱导的肌动蛋白细胞骨架重塑和粘膜屏障功能障碍， 3）L. casei和L.植物协同减轻 辐射诱导的肠屏障功能障碍; 4）辐射下调肠潘氏细胞α-防御素 通过HDAC 3介导的组蛋白去乙酰化，5）HDAC 3和α-防御素下调在 辐射诱导的肠道微生物群生态失调，6）L. casei和L.植物，和他们的3 KDF馏分减轻 辐射诱导的HDAC 3表达、α-防御素耗竭和肠道微生物群生态失调，7） 最低有效剂量L.干酪湖（L. casei）8）测定植物提取物和3 KDF组分的含量， 理想的时间窗口的有效性L。干酪湖（L. casei）植物提取物和3 KDF级分，和9）测定植物提取物的总含量。 最有效剂量L. casei和L. plantarum，以及提高存活率的理想时间窗 致死剂量照射后。完成这个项目将建立一个显着的因果关系，肠道 乳酸菌耗竭与辐射损伤。此外，这些研究将验证基于乳酸杆菌的 益生菌疗法作为动物规则指导下GI-ARS的新型微生物组靶向MCM。

Public radiation exposure due to large-scale radiation incidents is a rising global concern. Gastrointestinal Acute Radiation Syndrome (GI-ARS) is associated with high morbidity and mortality. However, FDA- approved therapeutics for GI-ARS are unavailable. Therefore, outlining the mechanisms of radiation injury to develop targeted medical countermeasures (MCMs) is a high priority. The gut microbiome is highly susceptible to ionizing radiation, and an altered microbiome is a major contributing factor in the pathogenesis of GI-ARS. The gap in this field is that the precise mechanisms by which radiation causes dysbiosis of gut microbiota and its impact on radiation injury are poorly defined. The long-term goal of our research is to identify the radiation-sensitive microbiota in the gut and develop gut microbiome-targeted MCMs to mitigate radiation injury. Our preliminary studies have identified that: 1) Lactobacillus casei and plantarum mitigate radiation-induced epithelial tight junction (TJ) disruption and barrier dysfunction by distinct cellular mechanisms. 2) Depletion of Paneth cell α-defensins plays a pivotal role in the mechanism of radiation- induced microbiota dysbiosis. 3) When administered in diet 24 hours after irradiation, L. casei and L. plantarum mitigate radiation-induced α-defensin depletion, microbiota dysbiosis, gut barrier dysfunction, endotoxemia, and systemic inflammation. These findings form the scientific premise and support the central hypothesis that “L. casei and L. plantarum synergistically mitigate GI-ARS by reversing dysbiosis of gut microbiota and epithelial barrier dysfunction, leading to attenuation of endotoxemia and systemic inflammation.” We will test this hypothesis by determining that 1) L. plantarum mitigates radiation-induced epithelial TJ disruption by EGFR-mediated inhibition of c-Jun N-terminal kinase-2 (JNK2)/c-Src/protein tyrosine phosphorylation, 2) L. casei mitigates radiation-induced remodeling of the actin cytoskeleton and mucosal barrier dysfunction in the intestinal epithelium by a PKC-dependent mechanism, 3) L. casei and L. plantarum synergistically mitigate radiation-induced intestinal barrier dysfunction, 4) Radiation downregulates intestinal Paneth cell α-defensins by HDAC3-mediated histone deacetylation, 5) HDAC3 and α-defensin downregulation play crucial roles in radiation-induced dysbiosis of gut microbiota, 6) L. casei and L. plantarum, and their 3KDF fractions mitigate radiation-induced HDAC3 expression, α-defensin depletion, and gut microbiota dysbiosis, 7) Identifying the lowest effective doses of L. casei, L. plantarum, and 3KDF fractions for mitigating GI-ARS, 8) Determining the ideal time window for the effectiveness of L. casei, L. plantarum, and 3KDF fractions, and 9) Determining the most effective doses of L. casei and L. plantarum, and the ideal time window for increasing the survival rate after lethal dose irradiation. Completing this project will establish a significant causative relation of intestinal Lactobacillus depletion with radiation injury. Furthermore, these studies will validate Lactobacillus-based probiotic therapy as a novel microbiome-targeted MCM for GI-ARS under the Animal-Rule guidance.