Peroxynitrite Enhances Interleukin-10 Reduction in the Release of Neutrophil Chemotactic Activity

Peroxynitrite, formed by nitric oxide and superoxide, has been shown to nitrate and reduce the function of proinflammatory proteins such as interleukin (IL)-8, monocyte chemoattractant protein-1, and eotaxin, but in contrast, to enhance the function of the anti-inflammatory cytokine IL-10 in reducing IL-1 release from blood monocytes. However, the effect of nitrated IL-10 on release of proinflammatory cytokines from lung epithelial cells is unknown. We hypothesized that peroxynitrite would enhance the capacity of human IL-10 to reduce inflammatory mediators released by epithelial cells. To test this hypothesis, recombinant human IL-10 was evaluated for its capacity to attenuate the release of neutrophil chemotactic activity and IL-8 from a human epithelial cell line in response to IL-1 beta and tumor necrosis factor-alpha. Neutrophil chemotactic activity and IL-8 in lung epithelial culture supernatant fluids were significantly lower after culture with nitrated human IL-10 compared with non-nitrated human IL-10 controls (P < 0.05). Consistent with these results, nitrated human IL-10 attenuated IL-8 mRNA expression more than non-nitrated human IL-10 controls (P < 0.05). These data demonstrate that peroxynitrite exposed human IL-10 has enhanced anti-inflammatory activity and suggest that nitration may play a critical role in the regulation of inflammation within the lower respiratory tract.