Gut leakage enhances sepsis susceptibility in iron-overloaded beta-thalassemia mice through macrophage hyperinflammatory responses.

摘要

Iron overload induces intestinal-permeability defect (gut leakage), and gut translocation of organismal molecules might enhance systemic inflammation and sepsis severity in patients with thalassemia (Thal). Hence, iron administration in Hbb~th3/+ mice, heterozygous beta-globin-deficient Thal mice, was explored. Oral iron administration induced more severe secondary hemochromatosis and gut leakage in Thal mice compared with wild-type (WT) mice. Gut leakage was determined by 1) FITC-dextran assay, 2) spontaneous serum elevation of endotoxin (LPS) and (1->3)-beta-D-grucan (BG), molecular structures of gut-organisms, and 3) reduction of tight-junction molecules with increased enterocyte apoptosis (activated caspase-3) by immunofluo-rescent staining. Iron overload also enhanced serum cytokines and increased Bacteroides spp. (gram-negative bacteria) in feces as analyzed by microbiome analysis. LPS injection in iron-overloaded Thal mice produced higher mortality and prominent cytokine responses. Additionally, stimulation with LPS plus iron in macrophage from Thal mice induced higher cytokines production with lower beta-globin gene expression compared with WT. Furthermore, possible gut leakage as determined by elevated LPS or BG ( >60 pg/mL) in serum without systemic infection was demonstrated in 18 out of 41 patients with beta-thalassemia major. Finally, enhanced LPS-induced cytokine responses of mononuclear cells from these patients compared with cells from healthy volunteers were demonstrated. In conclusion, oral iron administration in Thal mice induced more severe gut leakage and increased fecal gram-negative bacteria, resulting in higher levels of endotoxemia and serum inflammatory cytokines compared with WT. Preexisting hyperinflammatory cytokines in iron-overloaded Thal enhanced susceptibility toward infection.