Vitamin C-induced increase of dermatan sulfate in cultured Hurler's fibroblasts

Oxidative Stress in Mucopolysaccharidoses: Pharmacological Implications

Although mucopolysaccharidoses (MPS) are caused by mutations in genes coding for enzymes responsible for degradation of glycosaminoglycans, storage of these compounds is crucial but is not the only pathomechanism of these severe, inherited metabolic diseases. Among various factors and processes influencing the course of MPS, oxidative stress appears to be a major one. Oxidative imbalance, occurring in MPS and resulting in increased levels of reactive oxidative species, causes damage of various biomolecules, leading to worsening of symptoms, especially in the central nervous system (but not restricted to this system). A few therapeutic options are available for some types of MPS, including enzyme replacement therapy and hematopoietic stem cell transplantation, however, none of them are fully effective in reducing all symptoms. A possibility that molecules with antioxidative activities might be useful accompanying drugs, administered together with other therapies, is discussed in light of the potential efficacy of MPS treatment.

The mucopolysaccharidoses (a review)

The mucopolysaccharidoses are a group of genetic diseases characterized by storage of incompletely degraded glycosaminoglycans. Such storage causes marked distortion of many tissues with consequent severe somatic changes and mental retardation. Storage of glycosaminoglycans results from markedly diminished activity of specific hydrolases requisite for the normal degradation of glycosaminoglycans. The specific enzymic defects have been identified in nine different diseases. In some cases evidence has been obtained indicating the existence of additional allelic diseases based on the same enzyme. The knowledge obtained from these studies has made prenatal diagnosis possible and has led to the possibility that therapy may be undertaken utilizing enzyme replacement.

Effect of ascorbic acid on arylsulfatase A and B activities in human chondrocyte cultures

Cultured normal human articular cartilage chondrocytes exhibited decreasing levels of arylsulfatase A and B activities when grown in the presence of increasing levels of ascorbic acid (0 to 90 mug/ml) in the media. That this was not a general effect on all lysosomal enzymes was supported by the increase in acid phosphatase activity and no change in beta-glucuronidase activity observed with increasing levels of vitamin C under identical culture conditions. No decrease in either arylsulfatase activity was observed when ascorbic acid was replaced by ascorbate-2-sulfate. Ascorbic acid did not inhibit either arylsulfatase activity when added directly to the assay mixture. These data, combined with results of mixing experiments, suggest that the effect of vitamin C is mediated through cellular factors produced in response to its inclusion in the growth media.

Biochemical studies on the sulphated glycosaminoglycan fraction of skin fibroblasts cultured from a patient with the Hurler syndrome

1. The metabolism of the sulphated glycosaminoglycan fraction in cultured skin fibroblasts derived from a patient with the Hurler syndrome and from a normal subject was studied. Two labelled precursors, Na(2) (35)SO(4) and d-[2-(3)H]glucose, were used and their intracellular fates during uptake and ;chase' periods were assessed after separation of sulphated glycosaminoglycans from hyaluronic acid. After 4 or 8h of exposure to culture medium containing both labels, [(35)S]sulphate incorporation into the sulphated glycosaminoglycan fraction was twofold greater in Hurler-syndrome cells than in normal cells. At the same time, the rate of incorporation of [(3)H]glucose into the sulphated glycosaminoglycan fraction was approximately the same for both cell types. Consequently, an increased (35)S/(3)H ratio (nmol of [(35)S]sulphate incorporated/nmol of [(3)H]glucose incorporated) was observed for Hurler-syndrome cells compared with normal cells. 2. The results of ;chase' experiments revealed that although the expected loss and relative retention of labelled sulphate occurred in the sulphated glycosaminoglycan fraction of normal and Hurler-syndrome cells, both cell types retained all of their radioactivity derived from [(3)H]glucose. 3. After 34h exposure to a ;corrective-factor' preparation from urine, the sulphated glycosaminoglycan content (as hexosamine and [(35)S]sulphate) of the Hurler-syndrome cells approached normal values. At the same time, there was an increase in specific radioactivity of ;corrected' Hurler-syndrome cells.

Urinary excretion of glycosaminoglycans in the various forms of gargoylism

The urinary excretion of glycosaminoglycans in 28 cases of gargoylism, embracing the Hurler, Hunter, Sanfilippo, Morquio, and Scheie syndromes (McKusick, 1966), has been examined using the cetylpyridinium chloride (CPC) turbidity test, the uronic acid/creatinine ratio, and the electrophoretic pattern of urine concentrates, as routine procedures. Ion-exchange column chromatographic techniques were also employed for the fractionation of glycosaminoglycans and aminosugars. Molecular weights were investigated by gel filtration and ultracentrifugation. The CPC turbidity test was positive in every case. The uronic acid/creatinine ratio provided a sensitive index of increased glycosaminoglycan excretion. Cases of the Hurler syndrome showed the highest, and cases of the Morquio and Scheie syndromes the lowest, ratios. A correlation was observed between the uronic acid/creatinine ratio and the clinical severity of the disease. Cellulose acetate electrophoresis differentiated clearly between the two major forms of gargoylism, the Hurler and Sanfilippo syndromes, but differentiation between the Hurler, Hunter, and Scheie syndromes was more difficult on electrophoretic data alone. Results obtained with cases diagnosed as the Morquio syndrome were disappointing. The existence of formes frustes of the Sanfilippo syndrome among the mentally subnormal is predicted. Errors caused by bacterial contamination of urine samples are emphasized. The atypical behaviour of urinary glycosaminoglycans in analytical procedures is discussed. Molecular weight studies suggested heterogeneity. The nature of the basic defect in gargoylism is discussed.

The effect of scurvy on glycosaminoglycans of granulation tissue and costal cartilage

1. The effect of ascorbic acid deficiency on glycosaminoglycans of granulation tissue and cartilage of guinea pigs was investigated by determination of the changes in the glucosamine and galactosamine contents 12 days after tendonectomy. 2. In normal granulation tissue, the glucosamine and galactosamine contents rose to a peak at 5 and 10 days respectively, whereas the hydroxyproline and proline contents continued to rise throughout the 20 days after tendonectomy. 3. The galactosamine in scorbutic granulation tissue, but not in that of pair-fed controls, decreased significantly in absolute amount and relatively to glucosamine, which remained practically unchanged; the cartilage galactosamine did not decrease during the 22 days of deficiency owing to the presence of excess of preformed galactosaminoglycans, which masked the small amount of newly formed glycosaminoglycans. 4. The chemical results were confirmed by radioactivity studies in vivo of incorporation of [U-(14)C]glucose into galactosamine and glucosamine of scorbutic granulation tissue and cartilage. The incorporation of (14)C into galactosamine decreased significantly in scurvy in both tissues. 5. The results indicated in both tissues a decreased formation of galactosamine during scurvy, although an increased degradation of polymerized glycosaminoglycans could not be entirely ruled out. It is concluded that, if lack of ascorbic acid causes an impaired galactosamine formation, the most likely position for the block may be in the UDP-N-acetylglucosamine 4-epimerase reaction.

Study of the Hurler syndrome using cell culture: definition of the biochemical phenotype and the effects of ascorbic acid on the mutant cell

Fibroblasts from patients with Hurler syndrome retain a distinctive biochemical phenotype when grown in culture which is characterized by increased synthesis of both nonsulfated and sulfated glycosaminoglycans. Ascorbic acid reinforces the phenotypic expression of the biochemical abnormality, producing not only increased synthesis of sulfated glycosaminoglycans, but selective retention of sulfated glycosaminoglycans within the cell. Although the synthesis of nonsulfated glycosaminoglycans is also increased, these compounds, particularly hyaluronic acid are not retained by the cell but are secreted into the medium. Analyses of urine from patients with Hurler syndrome show increased absolute concentrations of nonsulfated glycosaminoglycans in addition to the expected increase in sulfated glycosaminoglycans. This indicates that the biochemical phenotype as defined in cell culture is not an artifact of the experimental model but reflects the biochemical defect in the patient. Redefinition of the biochemical defect to include nonsulfated as well as sulfated glycosaminoglycans contradicts explanations of this disease which are based on a single structural gene mutation.