Does inflammation increase hepcidin and lower serum iron?

Systemic iron balance is regulated by a protective cellular pathway during inflammatory stress, redirecting iron away from circulation.

Inflammatory induction of hepcidin

• Inflammatory stimuli trigger the secretion of interleukin-6 (IL-6) by immune cells.
• IL-6 activates the JAK-STAT3 signaling pathway (via JAK1/JAK2/TYK2), causing phosphorylated STAT3 to translocate to the nucleus and bind the HAMP promoter at a conserved motif (-64/-72 bp) to drive hepcidin transcription.
• This inflammatory upregulation requires cooperative crosstalk with the bone morphogenetic protein (BMP)-SMAD pathway, specifically involving SMAD4.

Mechanistic restriction of iron release

• Elevated circulating hepcidin targets ferroportin, the sole cellular iron exporter present on macrophages, enterocytes, and hepatocytes.
• The C-terminal tail of hepcidin physically occludes the iron transport pore, immediately blocking iron efflux.
• This binding triggers the phosphorylation, polyubiquitination, and clathrin-dependent endocytosis of ferroportin, leading to its lysosomal degradation and intracellular iron sequestration.

Systemic consequences on serum iron

• Because the body depends on continuous iron mobilization from dietary absorption and recycled red blood cells, removing active surface ferroportin rapidly restricts iron entry into the plasma.
• This cellular restriction causes a profound decrease in serum iron levels and transferrin saturation within hours, causing acute hypoferremia and potentially leading to anemia of inflammation.

Bottom line

• Inflammation directly lowers serum iron levels by triggering an IL-6/JAK-STAT3 cascade that transcriptionally upregulates hepcidin, which then binds, occludes, and degrades the cellular exporter ferroportin to sequester iron within tissues.