Copper and iron in nutritional immunity

这项建议的目的是阐明铜氧化铁酶，铜蓝蛋白，通过其调节细菌感染的营养免疫的机制。迫切需要了解营养动态平衡的机制，以便开发更有效的治疗方法和疗法。营养免疫描述了微生物感染期间改变宿主金属离子动态平衡的机制。营养免疫的一个重要方面是通过低铁血症(低血浆铁水平)来阻止细菌病原体的铁。低铁血症是由多肽激素海普西丁调节的，它通过诱导肝细胞、肠细胞和巨噬细胞中铁出口蛋白的降解来限制铁向血浆的输出。营养免疫的另一种机制涉及高铜(高血浆铜水平)。这一过程是通过增加肝脏铜蓝蛋白的分泌而发生的，铜蓝蛋白是一种携带铜的铁氧化物酶，含有血浆中的大部分铜。铜被认为有助于通过天然免疫系统的巨噬细胞杀死细菌病原体，然而，铜蓝蛋白在这一过程中的作用尚不清楚。尽管铜蓝蛋白在60多年前就被确定为急性时相蛋白，但在感染过程中对铜蓝蛋白的需求仍然未知。铜蓝蛋白作为一种铁氧合酶，通过铁蛋白促进铁的输出，但由于铁蛋白的降解，在感染过程中这一功能是不必要的。因此，铜蓝蛋白很可能在感染过程中具有替代功能。初步结果表明，铜蓝蛋白基因敲除小鼠对鼠伤寒沙门氏菌和金黄色葡萄球菌的全身性感染高度敏感。此外，铜蓝蛋白基因敲除小鼠被Toll样受体(TLRs)的细菌配体攻击时，发现血清促炎细胞因子水平降低，这突显了铜蓝蛋白在TLR信号转导中的可能作用。在这项提案中，将使用生化和遗传学方法来了解铜蓝蛋白对营养免疫的贡献。AIM1测试铁和铜在铜蓝蛋白缺失小鼠对感染超敏反应中的作用。目的2研究铜蓝蛋白在巨噬细胞TLR信号转导中的作用。目的3研究宿主免疫是否需要巨噬细胞或肝细胞表达铜蓝蛋白。

The objective of this proposal is to elucidate the mechanisms by which the copper­containing ferroxidase, ceruloplasmin, regulates nutritional immunity against bacterial infection. There is an urgent need to understand mechanisms of nutrient homeostasis in order to develop more effective treatments and therapies. Nutritional immunity describes mechanisms that alter host metal ion homeostasis during microbial infection. An important aspect of nutritional immunity is iron withholding from bacterial pathogens via hypoferremia (low plasma iron levels). Hypoferremia is regulated by peptide hormone, hepcidin, which restricts iron export into the plasma by inducing the degradation of the iron exporter, ferroportin in hepatocytes, enterocytes and macrophages. Another mechanism of nutritional immunity involves hypercupremia (high plasma copper levels). This process occurs via increased hepatic secretion of ceruloplasmin, a copper carrying ferroxidase that contains the majority of copper in the plasma. Copper is thought to facilitate killing of bacterial pathogens via macrophages of the innate immune system, however, the role of ceruloplasmin in this process is unknown. Despite its identification as an acute phase protein more than 60 years ago, the requirement for ceruloplasmin during infection remains unknown. As a ferroxidase, ceruloplasmin facilitates iron export via ferroportin, however, this function is unnecessary during infection due to ferroportin degradation. Thus, it is likely that ceruloplasmin has alternative functions during infection. Preliminary results demonstrate that ceruloplasmin knockout mice are highly susceptible to systemic infection by the bacterial pathogens Salmonella typhimurium and Staphylococcus aureus. In addition, ceruloplasmin knockout mice were found to exhibit reduced serum levels of proinflammatory cytokines when challenged with bacterial ligands to Toll­like receptors (TLRs), highlighting a possible role for ceruloplasmin in TLR signaling. In this proposal, biochemical and genetic approaches will be used to understand the contribution of ceruloplasmin to nutritional immunity. AIM1 tests the role of iron and copper on hypersensitivity of ceruloplasmin-­null mice to infection. AIM 2 seeks to understand the role of ceruloplasmin in TLR signaling within macrophages. AIM 3 investigates whether macrophage or hepatocyte expression of ceruloplasmin is required for host immunity.