Transforming Growth Factor β1-regulated Xylosyltransferase I Activity in Human Cardiac Fibroblasts and Its Impact for Myocardial Remodeling

Abstract

In cardiac fibrosis remodeling of the failing myocardium is associated with a complex reorganization of the extracellular matrix (ECM). Xylosyltransferase I and Xylosyltransferase II (XT-I and XT-II) are the key enzymes in proteoglycan biosynthesis, which are an important fraction of the ECM. XT-I was shown to be a measure for the proteoglycan biosynthesis rate and a biochemical fibrosis marker. Here, we investigated the XT-I and XT-II expression in cardiac fibroblasts and in patients with dilated cardiomyopathy and compared our findings with nonfailing donor hearts. We analyzed XT-I and XT-II expression and the glycosaminoglycan (GAG) content in human cardiac fibroblasts incubated with transforming growth factor (TGF)-␤ 1 or exposed to cyclic mechanical stretch. In vitro and in vivo no significant changes in the XT-II expression were detected. For XT-I we found an increased expression in parallel with an elevated chondroitin sulfate-GAG content after incubation with TGF-␤ 1 and after mechanical stretch. XT-I expression and subsequently increased levels of GAGs could be reduced with neutralizing anti-TGF-␤ 1 antibodies or by specific inhibition of the activin receptor-like kinase 5 or the p38 mitogen-activated protein kinase pathway. Usage of XT-I small interfering RNA could specifically block the increased XT-I expression under mechanical stress and resulted in a significantly reduced chondroitin sulfate-GAG content. In the left and right ventricular samples of dilated cardiomyopathy patients, our data show increased amounts of XT-I mRNA compared with nonfailing controls. Patients had raised levels of XT-I enzyme activity and an elevated proteoglycan content. Myocardial remodeling is characterized by increased XT-I expression and enhanced proteoglycan deposition. TGF-␤ 1 and mechanical stress induce XT-I expression in cardiac fibroblasts and have impact for ECM remodeling in the dilated heart. Specific blocking of XT-I expression confirmed that XT-I catalyzes a rate-limiting step during fibrotic GAG biosynthesis.

Myocardial Extracellular Matrix

“…79,80 Their importance is suggested by the increased expression of xylotransferase I, the enzyme responsible for attaching the GAG tertrasaccharide linker unit, and CS in patients with dilated cardiomyopathy. 75 This upregulation is also seen in fibroblasts stimulated with TGF-β or subjected to mechanical stress. 75 Some experimental studies support a potential role for GAGs in cardiac remodeling after MI, demonstrated by the increase of CS and DS expression in myocardial scars of dogs and rats.…”

“…cardiac remodeling, 75 more specifically in cardiac hypertrophy, 76 age-related degeneration of the myocardium, 77,78 and MI. 79,80 Their importance is suggested by the increased expression of xylotransferase I, the enzyme responsible for attaching the GAG tertrasaccharide linker unit, and CS in patients with dilated cardiomyopathy.…”

Heparin Cofactor II Protects Against Angiotensin II-Induced Cardiac Remodeling Via Attenuation of Oxidative Stress in Mice

“…Recent studies have shown that cardiac fibrosis is a process characterized by massive remodeling of the myocardial extracellular matrix and subsequent substitution of functional tissue by inelastic fibrotic tissue leading to failing heart. 27,28 Vanhoutte et al 29 demonstrated that syndecan-1, which is a transmembrane (type I) heparan sulfate proteoglycan and is a member of the syndecan proteoglycan family, plays a pivotal role in protection against exaggerated inflammation and adverse infarct healing after myocardial infarction in mice. Moreover, Hong et al 30 showed that supplementation with dermatan sulfate, a glycosaminoglycan, improved cardiac function and maintained viability of cardiac myocytes with complement activation.…”

Chondroitin sulfate expression predicts poor outcome in breast cancer

“…At a mechanistic level, TGF-β was shown to up-regulate xylosyltransferase-1, i.e. a rate-limiting enzyme that initiates CS attachment onto PG core protein (41) and GalNAc 4-O-sulfotransferase (42,43) that catalyzes one of the key steps in CS-56 epitope formation. Our group is currently investigating whether CS induction constitutes an important down-stream event of the TGF-β signalling pathway during epithelial-mesenchymal transition and cancer progression.…”