Effect of a chondroitin sulfate chain linked to the bikunin core peptide on gene expression in lipopolysaccharide-treated uterine cervical fibroblasts

Bikunin is a proteoglycan with a core protein and a low sulfated chondroitin 4-sulfate (Ch4S) chain. This chain has low 4-sulfated glucuronic acid-<i>N</i>-acetylgalactosamine (GlcUAβ1-3GalNAcβ1-4) repeating disaccharide units, and is covalently linked to the core protein through a glucuronic acid-galactose-galactose-xylose-serine the linkage tetrasaccharide (GlcUAβ1-3Galβ1-3Galβ1-4Xylβ1-<i>O</i>-Ser¹⁰). The linkage tetrasaccharide is sometimes complexly modified by phosphorylation on Xyl, sulfation on Gal, fucosylation on Xyl, or sialylation on Gal, or combinations of them. Bikunin is used in obstetrics to prevent preterm birth caused by bacterial infection inflammation in Japan. However, the role of the Ch4S chain in the anti-inflammatory action of bikunin has not been fully clarified. To investigate this role, the Ch4S chain was enzymatically removed resulting in a remaining hexasaccharide linkage (GlcUAβ1-3GalNAcβ1-4GlcUAβ1-3Galβ1-3Galβ1-4Xylβ1-<i>O</i>-Ser¹⁰) attached to the core peptide. The effects of exogenous bikunin or Ch4S-deficient bikunin on gene expression in lipopolysaccharide (LPS)-treated uterine cervical fibroblasts were comprehensively analyzed by DNA microarray. The expression of IL-8, an inflammation marker in this inflammatory model culture, was upregulated by LPS and the upregulation was inhibited by addition of bikunin together with LPS. Increased expression of genes, related to inflammation or collagen, by LPS was also suppressed by bikunin at the same time point. Ch4S-deficient bikunin did not show significant suppression compared to original bikunin, suggesting that the Ch4S structure of bikunin is important for the suppression of the inflammatory response induced by LPS.