Department of Immunology, Instituto de Microbiologia Paulo de Goes, Universidade Federal do Rio de Janeiro, Brazil.
FIOCRUZ, Rio de Janeiro, Brazil.
Curr Drug Targets. 2019;20(8):871-878. doi: 10.2174/1389450120666181217095323.
Vitamin A and its derivatives (retinoids) act as potent regulators in many aspects of mammalian reproduction, development, repair, and maintenance of differentiated tissue functioning. Unlike other vitamins, Vitamin A and retinoids, which have hormonal actions, present significant toxicity, which plays roles in clinically relevant situations, such as hypervitaminosis A and retinoic acid ("differentiation") syndrome. Although clinical presentation is conspicuous in states of insufficient or excessive Vitamin A and retinoid concentration, equally relevant effects on host resistance to specific infectious agents, and in the general maintenance of immune homeostasis, may go unnoticed, because their expression requires either pathogen exposure or the presence of inflammatory co-morbidities. There is a vast literature on the roles played by retinoids in the maintenance of a tolerogenic, noninflammatory environment in the gut mucosa, which is considered by many investigators representative of a general role played by retinoids as anti-inflammatory hormones elsewhere. However, in the gut mucosa itself, as well as in the bone marrow and inflammatory sites, context determines whether one observes an anti-inflammatory or proinflammatory action of retinoids. Both interactions between specialized cell populations, and interactions between retinoids and other classes of mediators/regulators, such as cytokines and glucocorticoid hormones, must be considered as important factors contributing to this overall context. We review evidence from recent studies on mucosal immunity, granulocyte biology and respiratory allergy models, highlighting the relevance of these variables as well as their possible contributions to the observed outcomes.
维生素 A 及其衍生物（视黄醇）在哺乳动物生殖、发育、修复和分化组织功能维持的许多方面发挥着强有力的调节作用。与其他具有激素作用的维生素不同，维生素 A 和视黄醇具有显著的毒性，在临床相关情况下（如维生素 A 过多症和维甲酸“分化”综合征）发挥作用。尽管在维生素 A 和视黄醇浓度不足或过量的情况下，临床表现明显，但对宿主对特定感染性病原体的抵抗力以及对一般免疫稳态的维持的同等相关影响可能未被注意到，因为它们的表达需要病原体暴露或存在炎症合并症。关于视黄醇在维持肠道黏膜的耐受性、非炎症环境中的作用，有大量文献记载，许多研究人员认为这代表了视黄醇作为其他部位抗炎激素的一般作用。然而，在肠道黏膜本身以及骨髓和炎症部位，视黄醇的抗炎或促炎作用取决于具体情况。专门细胞群体之间的相互作用以及视黄醇与其他类别的介质/调节剂（如细胞因子和糖皮质激素）之间的相互作用，都必须被视为促成这种整体情况的重要因素。我们回顾了黏膜免疫、粒细胞生物学和呼吸道过敏模型的最新研究证据，强调了这些变量的相关性及其对观察结果的可能贡献。
