Antisense inhibition of silica-induced tumor necrosis factor in alveolar macrophages

Tumor necrosis factor-alpha (TNF alpha) has been shown to play an important role in the pathogenesis of silicotic fibrosis, In this study, antisense oligonucleotides targeted to TNF alpha mRNA were used to inhibit silica-induced TNF alpha gene expression in alveolar macrophages. To achieve macrophage-specific oligonucleotide delivery, a molecular conjugate consisting of mannosylated polylysine that exploits endocytosis via the macrophage mannose receptor was used. Complexes were formed between the mannosylated polylysine and oligonucleotides and added to the cells in the presence of silica, Enzyme-linked immunoadsorbent assay showed that the complex consisting of the conjugate and antisense oligomer effectively inhibited TNF alpha production, whereas the oligomer alone had much less effect. Reverse transcriptase-polymerase chain reaction analysis revealed that the reduction in TNF alpha secretion was associated with specific ablation of targeted TNF alpha mRNA. The conjugate alone or conjugate complexed with inverted or sense sequence oligonucleotide had no effect. The promoting effect of the conjugate on antisense activity was shown to be due to enhanced cellular uptake of the oligomer via mannose receptor-mediated endocytosis. Cells lacking mannose receptors showed no susceptibility to the conjugate treatment. These results indicate that effective and selective inhibition of macrophage TNF alpha expression can be achieved using the antisense mannosylated polylysine system.