Doxycycline inhibition of interleukin-1 in the corneal epithelium

PURPOSE. TO evaluate the effect of doxycycline on the regulation of interle ukin (IL)-1 expression and activity in human cultured corneal epithelium. METHODS. Human corneal limbal epithelium (HLE) was cultured from explants p repared from limbal rings of donor corneas. Primary cultured limbal epithel ial cells were treated with either 10 mu g/ml lipopolysaccharide (LPS), LPS with 10 mu g/ml doxycycline, or LPS with 0.1 mg/ml methylprednisolone OMP) for 24 hours. The intracellular and supernatant protein amounts of IL-1 al pha, the precursor and mature forms of IL-1 beta, IL-1 receptor antagonist (IL-1 RA), and the intracellular level of IL-1 beta-converting enzyme (TCE) were measured with enzyme-linked immunosorbent assays (ELISAs). Western bl ot analysis was performed to evaluate IL-1 RA protein, mRNA steady state am ounts were determined by RNase protection assay (RPA) for IL-1 alpha, IL-1 beta, IL-1 RA, and ICE. RESULTS. LPS increased the mRNA and protein amounts of intracellular and re leased IL-1 alpha, mature IL-1 beta, and IL-1 RA. Doxycycline inhibited the LPS-induced IL-1 beta increase in the mRNA and protein amounts in the corn eal epithelium and upregulated the expression of the anti-inflammatory IL-1 RA protein. In addition, doxycycline reduced the steady state level of the cellular ICE protein but did not affect the level of ICE transcripts. IL-1 beta secreted to the conditioned media of HLE was functionally active in i nducing matrix metalloproteinase (MMP)-1 and MMP-3 in cultured corneal fibr oblasts. Doxycycline significantly decreased IL-1 beta bioactivity in the s upernatants from LPS-treated corneal epithelial cultures. These effects wer e comparable to those induced by the corticosteroid, MP. CONCLUSIONS. Doxycycline can suppress the steady state amounts of mRNA and protein of IL-beta and decrease the bioactivity of this major inflammatory cytokine. These data may partially explain the clinically observed anti-inf lammatory properties of doxycycline. The observation that doxycycline was e qually potent as a corticosteroid, combined with the relative absence of ad verse effects, makes it a potent drug for a wide spectrum of ocular surface inflammatory diseases.