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Y. Kondo, T. Adachi, K. Fukuda, T. Nishida; Suppression by IKK-2 Inhibitor of IL-1-Induced Collagen Degradation by Corneal Fibroblasts. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4819.
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We previously reported that interleukin (IL)-1 secreted by neutrophils augments collagen degradation by corneal fibroblasts through a stimulatory effect on matrix metalloproteinase (MMP) synthesis. We also revealed the central role of nuclear factor (NF)-ΚB, which regulate the expression of many inflammatory genes, including MMP, on the IL-1-induced collagen degradation by fibroblasts. NF-ΚB is held inactive in the cytoplasm, bound to I-ΚB. The removal of I-ΚB, via the actions of I-ΚB kinase-2 (IKK-2), allows NF-ΚB to enter the nucleus. To determine the impact of inhibiting IKK-2 selectively, we investigated the effects of IKK-2 inhibitor on collagen degradation by three-dimensionally cultured corneal fibroblasts in collagen gel.
Rabbit corneal fibroblasts were cultured in type I collagen gels three-dimensionally with IKK-2 inhibitor in the absence or presence of IL-1β. After acid-heat hydrolysis of culture supernatants, the amount of hydroxyproline was measured spectrometrically. The amount of MMP released into the culture medium was determined by immunoblot analysis and gelatin zymography, and the intracellular abundance of MMP mRNA was quantitated by reverse transcription and real-time polymerase chain reaction analysis. The phosphorylation and degradation of I-ΚBα and the subcellular localization of NF-ΚB were examined by immunoblot and immunocytochemistry analyses, respectively.
IL-1β-induced collagen degradation by corneal fibroblasts was significantly suppressed by the addition of IKK-2 inhibitor in a dose- and time-dependent manner. IKK-2 inhibitor reduced the increased expression of MMP-1, -3, and -9 by these cells both at the protein and mRNA levels. IKK-2 inhibitor suppressed the degradation and phosphorylation of I-ΚBα, and the translocation of NF-ΚB from the cytoplasm to the nucleus of corneal fibroblasts.
IKK-2 inhibitor attenuated the IL-1β-induced collagen degradation by corneal fibroblasts through the suppression of MMP synthesis by these cells.
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