Immune cells and microbiota response to iron starvation

Metal ions are essential for life on Earth, mostly as crucial components of all living organisms; indeed, they are necessary for bioenergetics functions as crucial redox catalysts. Due to the essential role of iron in biological processes, body iron content is finely regulated and is the battlefield of a tug-of-war between the host and the microbiota. Iron availability in the intestinal lumen could prevent or promote intestinal dysbiosis, although current data do not provide a definitive response. Recent data demonstrated that nutritional derived polyphenols explicit their anti-inflammatory functions sequestrating iron from immune cells. Here, we discuss whether nutritional iron chelators could be able to change the gut microbiota composition and prevent the intestinal dysbiosis associated with intestinal chronic inflammatory syndromes. Iron is lost by cellular exfoliation and occasional bleeding; it is absorbed from nutritional components. Heme is the most important source of dietary iron, while non-heme iron can be absorbed only in the duodenum and the beginning of the jejunum in pH permissive (acid) conditions. Western diets often contain large quantities of foods characterized by a high heme-iron content like meat, fish, and poultry, and small quantities of non-heme-iron content like vegetables, fruits, and nuts. Furthermore, nutritional substances can affect iron absorption: ascorbic acid is an efficient enhancer of non-heme-iron absorption, vice versa, phytic acid is known to be among the major iron absorption inhibitors, and iron-chelating substances like quercetin inhibit its absorption, likely due to loss of chelated-iron solubility. Iron deficiency is the most common cause of anemia worldwide and one of the most common complications observed in inflammatory bowel disease (IBD) patients due to gastrointestinal hemorrhages. In IBD patients, the guidelines for the management of iron deficiency are not entirely satisfactory because following oral iron supplementation patients sometimes report worsening of the IBD symptoms (1). Interestingly, iron supplemented diets can also show protective effects in dextran sodium sulfate (DSS)-induced colitis models. Constante et al. demonstrated that iron formulation dramatically changed the outcome of the DSS-induced colitis, as oral supplementation with ferrous bisglycinate but not ferric ethylenediaminetetraacetic acid enhanced the beneficial action of probiotics (2).