Hypothetical molecular mechanisms by which local iron overload facilitates the development of venous leg ulcers and multiple sclerosis lesions

Abstract

This paper presents a hypothetical model of role for iron in the development of venous leg ulcers and multiple sclerosis. Elevated concentrations of iron were found in the skin affected by venous hypertension and also in the areas of brain with multiple sclerosis lesions. Individuals with hemochromatosis gene (HFE) mutations: C282Y and H63D, which result in a less efficient transport of iron by macrophages, are characterized by an increased risk for venous leg ulcer and multiple sclerosis. Multiple sclerosis is a T cell-mediated disease, and T cells probably participate in the development of venous ulcers. This deleterious role of ferric ions could be related to the regulation of T cell proliferation and apoptosis. Under normal conditions excessive accumulation of T cells cannot take place, because nitric oxide and interferon-gamma drive these cells toward apoptosis. However, in tissues with a high concentration of iron, T lymphocytes proliferate instead of undergoing apoptosis. This is possible due to the internalization of the INF-gammaR2 chain of the interferon-gamma receptor, the downregulation of inducible nitric oxide synthase expression in macrophages and the inactivation of the active site of caspases. Yet, it should be emphasized that this hypothesis does not claim for the increased concentration of iron as a direct causal factor for the development of venous ulcerations or multiple sclerosis, but rather, iron is a factor that modulates and exaggerates the autoimmune process. Iron chelators, administered systemically or locally, should potentially exhibit therapeutic and prophylactic activity against venous leg ulcers and multiple sclerosis.