Abstract
Abstract: :
Purpose: To determine if hypochlorite ion (OCl-) affects nuclear factor kappa B (NFΚB) dependent expression of interleukin 1 alpha (IL-1α) in cultured human corneal epithelial (HCE) cells. Methods: Cellular and nuclear extracts were prepared from HCE cells treated with NaOCl and subsequently stimulated with tumor necrosis factor α (TNFα). Time-dependent proteolysis of inhibitory protein kappa B α(IΚBα) and nuclear transfer of NFΚB in response to TNFα stimulation were estimated by Western blotting and gel shift assay, respectively. The degree of the transcription and translation of IL-1α was determined by semiquantitative RT-PCR and ELISA, respectively. Results: The concentration of ClO- was varied up to 2 mM to treat HCE cells for 10 min. A band shift of IΚBα was observed in Western blots when OCl- concentration was higher than 100 µM. This shifted band of IΚBα was not proteolysed for 30 min upon TNFα stimulation. Alkaline phosphatase treatment of cell lysate prior to electrophoresis did not return the shifted band to the original whereas methionine sulfoxide reductase A isolated from yeast did. Moreover, cell treatment with OCl- inhibited TNFα-induced nuclear transfer of NFΚB. Consequently, the transcription and translation of IL-1α were also suppressed. Conclusions: OCl- oxidizes IΚBα at a methionine residue and oxidized IΚBα increases resistance to proteolysis initiated by TNFα, resulting in inhibition of nuclear transfer of NFΚB and NFΚB-dependent expression of IL-1α. Because cornea epithelial cells are eventually exposed to OCl- secreted from neutrophils during inflammation and diffused from water in swimming pool, this interruption of NFΚB activation pathway may relate to self defense in the corneal epithelium.
Keywords: 372 cornea: epithelium • 437 inflammation • 581 signal transduction: pharmacology/physiology