Tumour necrosis factor alpha and its promoter polymorphisms' role in the phenotypic expression of hemochromatosis

The majority of hemochromatosis patients are homozygous for the HFE-C282Y mutation. However, less than half of C282Y homozygous subjects identified by population screening studies actually develop the disease. The cytokine TNF-alpha is implicated in the regulation of iron metabolism at different levels. Our aim was to study the role of TNF-alpha and its promoter polymorphisms in the phenotypic expression of hemochromatosis in individuals with and without the C282Y mutation.

We studied 4 groups of 10 subjects each: (1) C282Y homozygotes without clinical hemochromatosis; (2) C282Y homozygotes with hemochromatosis; (3) secondary hemochromatosis (without C282Y mutation); and (4) controls. Groups were age-matched and sex-matched. Peripheral blood mononuclear cells (PBMC) were stimulated with lipopolysaccharide (LPS) and the release of TNF-alpha was measured. Additionally, the G/A polymorphisms at position -238 and -308 of the TNF-alpha, gene were determined by PCR and RFLP analysis in 178 hemochromatosis patients and 41 controls.

TNF-alpha production from PBMC at 8 and 24 h after increasing concentrations of LPS stimulation were similar in the four groups. The prevalence of TNF-alpha polymorphisms was similar in patients and controls. The prevalences of cirrhosis, siderosis, median s-ferritin and median ALT values were similar in patients with and without the TNF-alpha polymorphisms.

Neither TNF-alpha, released from PBMC nor the presence of TNF-alpha polymorphisms seem to be associated with disease manifestation in hemochromatosis.