Immune cell mechanisms of Bacillus anthracis sepsis

总结 细菌性脓毒症是一种严重且难以治疗的疾病，其死亡率很高，部分原因是最初的过度活动 先天免疫，随后是免疫抑制，使宿主易受新的感染。吸入 炭疽是与生物恐怖主义有关的炭疽杆菌孢子释放的已知和预期结果， 不可避免地导致败血症和高死亡率而不进行早期干预。抗炎脓毒症治疗 在小鼠中开发的基因在人类中失败了，这表明对基因突变的分子机制的理解的提高， Ba脓毒症中需要人免疫细胞参与。我们中心之前的工作表明， 炎症和脓毒症的病理学由于从死亡细胞释放的升高的循环核小体而恶化。 凋亡细胞的清除是由巨噬细胞通过巨噬细胞增多过程介导的。一个主要的网站， 脓毒症中淋巴细胞凋亡发生在次级淋巴器官中。组织巨噬细胞的分泌功能 这些淋巴器官可能对脓毒症期间凋亡淋巴细胞的清除至关重要。我们的初步数据 表明Ba及其毒素损害人单核细胞衍生巨噬细胞吞噬功能，尽管其机制 还不清楚在目标1中，我们将测试Ba及其毒素抑制人组织巨噬细胞的假设， 通过降低巨噬细胞机制的表达和损害巨噬细胞受体信号传导来抑制巨噬细胞。 广泛的淋巴细胞凋亡也有助于免疫抑制，脓毒症后的主要并发症 生存长期免疫抑制与低反应性T细胞的积累相关， 疲劳的标志，表明参与表观遗传变化。我们的初步数据显示 在Ba诱导的脓毒症的灵长类动物模型中，淋巴细胞减少症和携带耗竭标志物的T细胞。在目标2中，我们将 检验活Ba及其毒素促进T淋巴细胞凋亡和耗竭的假设， 败血症后表观遗传学变化导致的免疫抑制T细胞表型脂质激活核 受体如过氧化物酶体增殖物激活受体（PPARs）和肝X受体（LXRs）响应于 脂质通过增加凋亡细胞机制的转录而使凋亡细胞凋亡。然而，很少有研究 已经评估了PPAR或LXR活性对人组织巨噬细胞基因表达或淋巴细胞的影响 凋亡这些受体的合成激动剂在糖尿病和复发性中风中显示出有效性， 据我们所知，已有研究使用这类调节剂治疗人或灵长类动物的脓毒症。在目标3中，我们 测试这一假设，合成的激动剂的过氧化物酶体增殖物激活受体和LXR脂质激活的核受体可以减轻 Ba及其毒素在脓毒症期间对巨噬细胞和T细胞的负面影响。这些研究的结果 将导致更好地了解急性病理学和随后的免疫抑制机制， 脓毒症，并可能加速发展新的治疗策略，用于治疗脓毒症患者。

Summary Bacterial sepsis is a serious and difficult-to-treat condition with high mortality in part due to initial overactive innate immunity followed by immunosuppression that leaves the host vulnerable to new infections. Inhalational anthrax, a known and expected outcome of bioterrorism-related release of Bacillus anthracis (Ba) spores, inevitably leads to sepsis and high mortality without early intervention. Anti-inflammatory sepsis therapies developed in mice have failed in humans, indicating that improved understanding of molecular mechanisms of human immune cell involvement in Ba sepsis is needed. Prior work in our center showed that unchecked inflammation and sepsis pathology is worsened by elevated circulating nucleosomes released from dying cells. Clearance of apoptotic cells is mediated by macrophages via the process of efferocytosis. A major site of lymphocyte apoptosis in sepsis is in secondary lymphoid organs. Efferocytic function by tissue macrophages in these lymphoid organs is likely crucial for apoptotic lymphocyte clearance during sepsis. Our preliminary data show that Ba and its toxins impair human monocyte-derived macrophage efferocytosis, although the mechanism is unclear. In Aim 1, we will test the hypothesis that Ba and its toxins inhibit human tissue macrophage efferocytosis by decreasing expression of efferocytic machinery and impairing efferocytic receptor signaling. Extensive lymphocyte apoptosis also contributes to immunosuppression, a major complication following sepsis survival. Long term immunosuppression correlates with the accumulation of hyporesponsive T cells bearing markers of exhaustion, suggesting the involvement of epigenetic changes. Our preliminary data show lymphopenia and T cells bearing exhaustion markers in a primate model of Ba induced sepsis. In Aim 2, we will test the hypothesis that live Ba and its toxins promote T lymphocyte apoptosis and exhaustion, leading to immunosuppressed T cell phenotypes enforced by epigenetic changes after sepsis. Lipid-activated nuclear receptors such as peroxisome proliferator activated receptors (PPARs) and liver X receptors (LXRs) respond to lipids of efferocytosed apoptotic cells by increasing transcription of efferocytic machinery. However, few studies have assessed the impact of PPAR or LXR activity on human tissue macrophage gene expression or lymphocyte apoptosis. Synthetic agonists of these receptors have shown efficacy in diabetes and recurrent stroke but no studies to our knowledge have used such modulators to treat sepsis in humans or primates. In Aim 3, we will test the hypothesis that synthetic agonists of PPAR and LXR lipid-activated nuclear receptors can mitigate negative impacts of Ba and its toxins on macrophages and T cells during sepsis. The results of these studies will lead to a better understanding of mechanisms of acute pathology and subsequent immunosuppression in sepsis and may accelerate the development of new therapeutic strategies for the treatment of septic patients.