Inhibition of interleukin-1 but not tumor necrosis factor suppresses neovascularization in rat models of corneal angiogenesis and adjuvant arthritis

Objective. To assess the capacities of the cytokine inhibitors interleukin-1 receptor antagonist (IL-1Ra; anakinra) and PEGylated soluble tumor necrosis factor receptor I (PEG sTNFR1; pegsunercept) to suppress neovascularization. Methods. A corneal angiogenesis assay was performed by implanting nylon discs impregnated with an angiogenic stimulator (basic fibroblast growth factor or vascular endothelial growth factor) into one cornea of female Sprague-Dawley rats. Animals were treated with IL-1Ra or PEG sTNFRI for 7 days, after which new vessels were quantified. In a parallel study, male Lewis rats with mycobacteria-induced adjuvant-induced arthritis were treated with IL-1Ra or PEG sTNFRI for 7 days beginning at disease onset, after which scores for inflammation and bone erosion as well as capillary counts were acquired from sections of arthritic hind paws. Results. Treatment with IL-1Ra yielded a dose-dependent reduction in growth factor-induced corneal angiogenesis, while PEG sTNFRI did not. IL-1Ra, but not PEG sTNFRI, significantly reduced the number of capillaries in arthritic paws, even though both anticytokines reduced inflammation and bone erosion to a similar degree. Conclusion. These data support a major role for IL-1, but not TNFalpha, in angiogenesis and suggest that an additional antiarthritic mechanism afforded by IL-1 inhibitors, but not anti-TNF agents, is the suppression of the angiogenic component of pannus.