Macrophage-inflammatory protein-3α/CCL-20 is transcriptionally induced by the iron chelator desferrioxamine in human mononuclear phagocytes through nuclear factor (NF)-κB

Abstract

Alterations in iron availability can trigger pro-inflammatory signals in various cell types. We demonstrate that desferrioxamine (DFX), an iron chelator used in clinics for the treatment of iron overload, neoplasias, and Alzheimer disease, stimulates the expression and secretion of CCL20, a chemoattractant for immature dendritic cells, activated/memory T lymphocytes, and naive B cells, in primary human monocytes and monocyte-derived macrophages. Iron chelation was part of the mechanism by which DFX induced CCL20, because addition of iron sulfate counteracted its stimulatory effects. Functional studies of the CCL20 promoter, using a series of 5′-deleted and mutated reporter constructs, demonstrated that CCL20 mRNA induction was dependent on gene transcription activation and mediated by the NF-κB pathway. The NF-κB element located at position −92/−82 of the CCL20 promoter was required for gene transactivation by DFX because: (i) transcription was abrogated by a 3 bp mutation of the NF-κB-binding motif; (ii) treatment with DFX increased specific NF-κB binding to this sequence. Nuclear translocation of both NF-κBp65 and NF-κBp50 family members was increased in response to DFX and associated with I-κBα degradation, suggesting a role for these subunits in CCL20 promoter transactivation. In conclusion, this study provides the first evidence that iron chelation can transcriptionally induce CCL20 in mononuclear phagocytes and identify the NF-κB binding site as a regulatory sequence of the CCL20 promoter that is activated by iron deprivation. These results add new insights into our understanding of the mechanisms by which iron perturbations affect mononuclear phagocyte immune functions and regulate inflammatory responses.