The isoflavone genistein inhibits LPS-stimulated TNFalpha, but not IL-6 expression in monocytes from hemodialysis patients and healthy subjects.

BACKGROUND: Whole blood and peripheral blood mononuclear cells from hemodialysis (HD) patients show increased production and secretion of inflammatory cytokines. We determined the contribution of blood monocytes to the production of inflammatory cytokines in whole blood from HD patients.

METHODS: Whole blood and isolated mononuclear cells from HD patients and healthy control subjects were preincubated with the isoflavone genistein and stimulated with LPS. TNFalpha, IL-6 and IL-10 formation in the whole blood was measured with ELISA and intracellular cytokine formation in CD 14-positive monocytes was determined by flow cytometry.

RESULTS: Unstimulated blood levels of TNFalpha, IL-6 and IL-10 were significantly elevated in HD patients compared to controls, but intracellular monocyte content of these cytokines was identical between groups. LPS induced a robust TNFalpha response in both whole blood and monocytes, and TNFalpha formation was 2.3-fold higher in blood from HD patients compared to controls. A similar trend was observed in monocytes. Conversely, LPS stimulation increased IL-6 levels >1000-fold in whole blood, albeit without a noticeable difference between groups. Only minor increases in monocyte IL-6 content were observed. The isoflavone genistein did not inhibit IL-6 formation and did not alter basal TNFalpha levels, but genistein selectively blocked LPS-induced TNFalpha formation in whole blood and monocytes from both groups.

CONCLUSION: Intracellular levels of TNFalpha, IL-6 and IL-10 in monocytes are indistinguishable between HD patients and healthy controls. However, monocytes from HD patients are selectively primed for enhanced TNFalpha secretion in response to LPS. The selective inhibition of monocyte TNFalpha production by genistein may explain the anti-inflammatory action of this phytochemical observed in vivo.