heparitin-sulfate and Pseudoxanthoma-Elasticum

A number of reports point to the presence of proteoglycans and/or glycosaminoglycans within elastic fibers in normal and in pathological conditions. We present data that heparan sulphate (HS)-containing proteoglycans are associated with normal elastic fibers in human dermis and that isolated HS chains interact in vitro with recombinant tropoelastin and with peptides encoded by distinct exons of the human tropoelastin gene (EDPs). By immunocytochemistry, HS chains were identified as associated with the amorphous elastin component in the human dermis and remained associated with the residual elastin in the partially degenerated fibers of old subjects. HS appeared particularly concentrated in the mineralization front of elastic fibers in the dermis of patients affected by pseudoxanthoma elasticum (PXE). In in vitro experiments, HS induced substantial changes in the coacervation temperature and in the aggregation properties of recombinant tropoelastin and of synthetic peptides (EDPs) corresponding to sequences encoded by exons 18, 20, 24 and 30 of the human tropoelastin gene. In particular, HS modified the coacervation temperature and favoured the aggregation into ordered structures of tropoelastin molecules and of EDPs 18, 20 and 24, but not of EDP30. These data strongly indicate that HS-elastin interactions may play a role in tissue elastin fibrogenesis as well as modulating elastin stability with time and in diseases.

Topics: Adult; Aged; Aged, 80 and over; Child; Dermis; Exons; Extracellular Matrix; Female; Heparitin Sulfate; Humans; Immunohistochemistry; In Vitro Techniques; Nephelometry and Turbidimetry; Peptides; Protein Binding; Protein Isoforms; Pseudoxanthoma Elasticum; Recombinant Proteins; Skin; Temperature; Time Factors; Tropoelastin

Pseudoxanthoma elasticum (PXE) is a hereditary connective tissue disease in which proteoglycans have altered properties. We investigated whether altered proteoglycan metabolism occurs in vivo and may be reflected in the urine of PXE individuals by analyzing the excreted polysaccharides.. We measured sulfated glycosaminoglycans in the urine of 10 PXE-affected patients, 12 healthy carriers, and 20 healthy controls by agarose gel electrophoresis. Chondroitin sulfate and heparan sulfate disaccharides were also quantified by treatment with specific lyases and separation of products by chromatography.. Total polysaccharides were 34% lower in the urine of PXE-affected patients and 17% lower in healthy carriers than in the control group. Chondroitin sulfate was significantly (P <0.01) decreased, and heparan sulfate was significantly increased. The ratio of chondroitin sulfate to heparan sulfate was 2.7 for PXE-affected patients, 2.3 for healthy carriers, and 10.7 for controls. In PXE-affected individuals and carriers, chondroitin sulfate contained more 4-sulfated disaccharide, less 6-sulfated disaccharide, and decreased nonsulfated disaccharide. Heparan sulfate from PXE-affected individuals and healthy carriers produced significantly less N-sulfated disaccharide and more disaccharide sulfated at the C-6 position with no significant abnormality of the nonsulfated disaccharide percentage and sulfates:disaccharide ratio.. The urinary data support the concept that the inherited defect of the ABCC6/MRP6 transporter in PXE alters metabolism of key polysaccharides. Structural analysis of urinary sulfated polyanions may be useful in the diagnosis of PXE.

Topics: Chondroitin Sulfates; Chromatography, High Pressure Liquid; Electrophoresis, Agar Gel; Glycosaminoglycans; Heparitin Sulfate; Humans; Pseudoxanthoma Elasticum