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Mediators of Inflammation
Volume 10 (2001), Issue 4, Pages 209-215
http://dx.doi.org/10.1080/09629350120080401

Diphenyleneiodonium inhibits NF-κB activation and iNOS expression induced by IL-1β: involvement of reactive oxygen species

1Faculty of Pharmacy, Department of Zoology, University of Coimbra, Rua do Norte, Coimbra 3000–295, Portugal
2Centre for Neurosciences of Coimbra, Department of Zoology, University of Coimbra, Rua do Norte, Coimbra 3000–295, Portugal

Copyright © 2001 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Aims: In this work, we studied the mechanisms by which diphenyleneiodonium chloride (DPI) inhibits nitric oxide (NO) synthesis induced by the pro-inflammatory cytokine interleukin-1β (IL-1) in bovine articular chondrocytes. To achieve this, we evaluated the ability of DPI to inhibit the expression and activity of the inducible isoform of the NO synthase (iNOS) induced by IL-1. We also studied the ability of DPI to prevent IL-1-induced NF-κB activation and reactive oxygen species (ROS) production.

Results: Northern and Western blot analysis, respectively, showed that DPI dose-dependently inhibited IL-1-induced iNOS mRNA and protein synthesis in primary cultures of bovine articular chondrocytes. DPI effectively inhibited NO production (IC50 = 0.03 Ī 0.004 μ M), as evaluated by the method of Griess. Nuclear factor-kappa B (NF- κB) activation, as evaluated by electrophoretic mobility shift assay, was inhibited by DPI (1-10 μ M) in a dose-dependent manner. IL-1-induced ROS production, as evaluated by measurement of dichlorofluorescein fluorescence, was inhibited by DPI at concentrations that also prevented NF-κB activation and iNOS expression.

Conclusions: DPI inhibits IL-1-induced NO production in chondrocytes by two distinct mechanisms: (i) by inhibiting NOS activity, and (ii) by preventing iNOS expression through the blockade of NF-κB activation. These results also support the involvement of reactive oxygen species in IL-1-induced NF-κB activation and expression of NF-κB-dependent genes, such as iNOS.