Thalidomide blocking of particle-induced TNFalpha release in vitro

Tumor necrosis factor-alpha (TNFalpha) and interleukin-6 (IL-6), pleiotropic cytokines with osteotropic activities, are produced by multiple cells in the skeletal tissue, including macrophages and osteoblasts. They are thought to be pivotally involved in pathological bone resorption, such as that seen with aseptic loosening. Thalidomide is reported to have antiinflammatory, immunomodulatory effects in a number of inflammatory diseases. We investigated the effect of thalidomide on titanium (Ti) particle-induced TNFalpha and IL-6 production by both human macrophage U937 and osteoblast MG-63 cell lines. They were stimulated with 1 x 10(7) Ti particles/ml and treated simultaneously with or without various concentrations of thalidomide (from 2.5 ng/ml to 25 microg/ml) for 24, 48, or 72 h. Cell viability and proliferation were measured. TNFalpha and IL-6 in the supernatant of the culture media were also analyzed with an enzyme-linked immunosorbent assay. We found that with a concentration of thalidomide of less than 2.5 microg/ml the viability of the two cell lines did not differ significantly from that of controls treated simultaneously with 1 x 10(7) Ti particles/ml. Cell proliferation was inhibited to some extent when they were treated with thalidomide 2.5 microg/ml co-cultured with 1 x 10(7) Ti particles/ml. Thalidomide treatment was found to inhibit TNFalpha production in a dose-dependent manner in human macrophages exposed to Ti particles. At the clinically achievable drug dose of 2.5 microg/ml, 34.4% TNFalpha inhibition occurs. Thalidomide had no effect on IL-6 secretion in these cultures. These data support the idea that thalidomide may have potential for treating prosthetic loosening in humans.