Copper and iron in nutritional immunity

本提案的目的是阐明含铜蛋白的铁氧化酶，铜蓝蛋白，调节对细菌感染的营养免疫的机制。迫切需要了解营养稳态的机制，以开发更有效的治疗和疗法。营养免疫描述了在微生物感染期间改变宿主金属离子稳态的机制。营养免疫的一个重要方面是通过低铁血症（低血浆铁水平）阻止细菌病原体的铁。低铁血症由肽激素铁调素调节，其通过诱导肝细胞、肠细胞和巨噬细胞中的铁输出蛋白铁转运蛋白的降解来限制铁输出到血浆中。营养免疫的另一个机制涉及高铜血症（高血浆铜水平）。这一过程通过血浆铜蓝蛋白的肝分泌增加而发生，血浆铜蓝蛋白是一种携带铁氧化酶的铜，含有血浆中的大部分铜。铜被认为有助于通过先天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。尽管其在60多年前被鉴定为急性期蛋白，但在感染期间对铜蓝蛋白的需求仍然未知。作为一种铁氧化酶，铜蓝蛋白通过膜铁转运蛋白促进铁输出，然而，由于膜铁转运蛋白降解，在感染期间这种功能是不必要的。因此，很可能铜蓝蛋白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细菌病原体鼠伤寒沙门氏菌和金黄色葡萄球菌的全身感染高度敏感。此外，发现铜蓝蛋白敲除小鼠在用Toll样受体（TLR）的细菌配体攻击时表现出促炎细胞因子的血清水平降低，这突出了铜蓝蛋白在TLR信号传导中的可能作用。在这个建议中，生化和遗传学的方法将被用来了解铜蓝蛋白的营养免疫的贡献。AIM 1测试了铁和铜对铜蓝蛋白基因敲除小鼠对感染的超敏反应的作用。目的2旨在了解铜蓝蛋白在巨噬细胞TLR信号转导中的作用。目的3研究铜蓝蛋白在巨噬细胞或肝细胞中的表达是否是宿主免疫所必需的.

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.