Guest guest Posted February 15, 2001 Report Share Posted February 15, 2001 Before confusion sets in I better clarify: I am not a Doctor. DMSO= Dimethyl-Sulfoxide and DMSA= Dimercaptosuccinic Acid, it is not just the similarity between the names that makes me ask, DMSO is an oxidized sulfur compound that is fairly inexpensive and does seem to be associated with Mercury detox pathways. It is also used as a sequestrant in Secretin trans-dermal patches. On its own it seems to have a variety of uses but no FDA approval. I understand that the Mercury toxicity we are finding is due to a defect in Sulfur handling and that Metallothioneins may well be compromised. Does anyone know more about DMSO or even Genestein which I have read increases Metallothionein and decreases angiogenesis (new blood vessels to tumours)? Well worth a visit to http://www.melisa.org/nl2099.html may be a bit heavy-going for some. I think that some of the problem emanates from Delta-Aminolevulinic-acid-(ALA)-dehydratase being extremely susceptible to lead etc. inhibition, it is a -SH containing enzyme and it's substrate is found in increased proportion in urine of lead poisoned people. This enzyme is instrumental in Heme synthesis and also Chlorophyll & Porphyrins, the irony it seems is that the very detoxification pathway for heavy metals is in fact blocked by heavy metals. Another consequence of a failure in this respect is that the Cytochromes will be compromised, it is the absence of cytochrome activity I suspect is largely responsible for I-A-G in the urine of so many Autistic people (but that is another story). Any ideas? Jon. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted February 15, 2001 Report Share Posted February 15, 2001 Many people speculate on what causes mercury tox. The theory that mercury tox is due to a defect of sulfur handling has been conclusively proven incorrect. DMSO is not useful in mercury detoxification. Andy > Before confusion sets in I better clarify: I am not a Doctor. DMSO= Dimethyl-Sulfoxide and DMSA= Dimercaptosuccinic Acid, it is not just the similarity between the names that makes me ask, DMSO is an oxidized sulfur compound that is fairly inexpensive and does seem to be associated with Mercury detox pathways. It is also used as a sequestrant in Secretin trans-dermal patches. On its own it seems to have a variety of uses but no FDA approval. I understand that the Mercury toxicity we are finding is due to a defect in Sulfur handling and that Metallothioneins may well be compromised. Does anyone know more about DMSO or even Genestein which I have read increases Metallothionein and decreases angiogenesis (new blood vessels to tumours)? > > Well worth a visit to http://www.melisa.org/nl2099.html may be a bit heavy-going for some. > > I think that some of the problem emanates from Delta-Aminolevulinic-acid-(ALA)-dehydratase being extremely susceptible to lead etc. inhibition, it is a -SH containing enzyme and it's substrate is found in increased proportion in urine of lead poisoned people. This enzyme is instrumental in Heme synthesis and also Chlorophyll & Porphyrins, the irony it seems is that the very detoxification pathway for heavy metals is in fact blocked by heavy metals. Another consequence of a failure in this respect is that the Cytochromes will be compromised, it is the absence of cytochrome activity I suspect is largely responsible for I-A-G in the urine of so many Autistic people (but that is another story). > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted February 15, 2001 Report Share Posted February 15, 2001 Andy, At 2/15/2001 +000006:36 AM, you wrote: >Many people speculate on what causes mercury tox. The theory that >mercury tox is due to a defect of sulfur handling has been >conclusively proven incorrect. I'd love to know which studies were supposed to have proven that conclusion. I have yet to see any study on mercury (and I have looked!) that has been conducted by someone with a sufficient knowledge of sugar and lipid chemistry, and on the sulfation of sugars and lipids, and their regulation, their role in endocytosis and their ability to chelate metals. Unless detox questions were asked in that context, it means that the right issues have not been asked relative to sulfur chemistry's role in mercury detox. (see articles below) The molecules that have not been investigated properly govern the traffic that approaches the cell, even " remotely " from the cell, in what is called the glycocalyx, and that also cover the cell membrane. A completely different experimental approach would be required to examine this issue than has been used before: requiring techniques that are from the field of glycobiology, and are not familiar to most biologists and chemists whose training circles around protein issues. These techniques were discussed in my lecture at the Autism 2000 Congress in Glasgow last May. Andy, the involvement of these molecules, already recognized as chelators of mercury's closest physiological " kin " , would have a LOT BETTER CHANCE at explaining things like the fact that it took about 2 solid months before any symptoms showed up in the professor who spilled dimethyl mercury on her hand. Think about this. Certainly her enzymes would have been inhibited by the higher amounts in her system that were there at first, but she must have had some form of biological protection that eventually ran out. After two months of no problems at all, she began losing weight during the third month after her accident. (Sulfation has a LOT to do with cachexia.) Only after that did neurological symptoms appear, and she got scared and went to the doctor at that point. Only then did she start getting exogenous chelation, and it did not help her at all, even though it was getting mercury out. She went into a coma within the next few weeks: AFTER chelation, and AFTER most of the initial toxic load had left her system. The declines in this toxicity was demonstrated in hair samples that were able to chronicle the declines week by week since the accident. What was happening with her sulfate chemistry in the meantime? No one asked, and they certainly did not treat that issue. She died not too long after that. That is just one example, but a potent one. I would recommend reading that study to listmates, and ask whether existing models really explain the course of her troubles. The most compelling reason to suspect sulfation's role in heavy metal toxicity in autism is the very different response to mercury toxicity that exists between boys and girls, demonstrated experimentally time and again. Sulfotransferase expression is vastly different between boys and girls because the expression of these enzymes is regulated by the sex hormones. This difference in expression constructs lifelong differences in the sulfation of the brain and changes brain structure and function. This leads to the sexual differences that determine the way that men and women differ in the way they think and regulate issues of chemistry, but it affects differences all over the body as well. Present models cannot account for the differences in mercury toxicity between male and female and they don't even try to, which is troublesome, and certainly should help us realize the lack of completeness in current models. Shouldn't we pay attention to data that is bound to be particularly relevant to autism because those sex ratios are preserved in the incidence of autism? A recent study has demonstrated a problem with sulfotransferase activity that affected 92% of those with low-functioning autism with a significance of P<.00002. There is no way this data is irrelevant! The exposure to mercury that most of our children had is likely to be much less than what happened to the lady at Dartmouth, but she probably had a healthy sulfate chemistry to start out with. That would not have been the case for any infant exposed to mercury and may especially not have been the case in our kids, who became injured more by this exposure than most infants. Whatever sulfate status they had before mercury exposure would likely have gotten worse after mercury, because sulfate transport across membranes has been shown experimentally to be thoroughly blocked by mercury, and the most important sulfate transporters are likely to be those in the kidneys. Chelation may restore the retention of sulfate in these children in their kidneys, and help them function better, but they may do better still if efforts were made to restore sulfate on the supply side. The kidneys are where most of the toxicity is likely to collect, because the kidneys are the body's main filters, and are themselves completely dependent on sulfate to do their job properly. (see article below) 23: Biopolymers 1992 Jun;32(6):597-619 Heavy metal binding to heparin disaccharides. II. First evidence for zinc chelation. Whitfield DM, Sarkar B Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada. To map out the heavy metal binding sites of iduronic acid containing oligosaccharides isolated from human kidneys, we studied Zn(II) binding by nuclear magnetic resonance (NMR) and molecular modeling to two disaccharides isolated after nitrous acid depolymerization of heparin and two synthetic disaccharides representative of the heparin structure, namely, IdopA2S (alpha 1,4)AnManOH, 1 alpha, IdopA2S (alpha 1,4)AnManOH6S, 1b, IdopA2S-(alpha 1,4)GlcNS alpha Me, 2a, and IdopA2S (alpha 1,4)GlcNS6S alpha Me, 2b (see previous article in this series). A conformational analysis of the metal free and metal bound solutions was made by comparing calculated [(NOE)]s, [T1]s, and [J]s to experimental values. The 1C4, 4C1, and 2S0 conformations of the L-idopyranosiduronate ring and the 4E and 4T3 of the anhydro-D-mannitol ring are evaluated as are rotations about the C5-C6 hydroxymethylene of the AnManOH(6S) or GlcNS (6S) residues. The NOE between IdopA2S H1 and H3 and the known NOE between H2 and H5, as well as the T1 of IdopA2S H3, are introduced as NMR observables sensitive to the IdopA2S ring conformation. Similarly, a NOE between IdopA2S H5 and AnManOH(6S) or GlcNS(6S) H3 was observed that directly restricts the allowed interglycosidic conformational space. For all disaccharides, the Zn(II) bound spectral data are consistent with models in which these motions are partially " frozen " such that the 1C4 conformation of the IdopA2S is stabilized along with the 4T3 conformation of the AnManOH(6S) ring. The interglycosidic conformation is also stabilized in one of two minima. Electrostatic potential energy calculations gave the best overall agreement with experiment and suggest metal binding conformations with the carboxylate and ring oxygen of the IdopA2S residues (1C4 conformation) and either O3 of the GlcNS(6S) residues or the sulfate oxygens of the 6-sulphate for 2b providing additional chelating sites. These chelation models concur with the observation of marked 13C and 1H NMR chemical shifts for the IdopA2S resonances and of GlcNS H3 for 2 alpha and GlcNS6S C6 for 2b. This study of model compounds implicates the IdopA2S(alpha 1,4)GlcNS6S group as part of the heavy metal binding site in biologically important acidic oligosaccharides such as heparin. PMID: 1643265 Biochem J 1992 Aug 1;285 ( Pt 3):857-62 Characterization of proteoglycan degradation by calpain. Suzuki K, Shimizu K, Hamamoto T, Nakagawa Y, Murachi T, Yamamuro T Department of Orthopedic Surgery, Faculty of Medicine, Kyoto University, Japan. .....Ca(2+)-dependent proteoglycan degradation was unique in that proteoglycans adsorb large amounts of Ca2+ ions rapidly before activation of calpain II: 1 mg of pig cartilage proteoglycan monomer adsorbed 1.3-1.6 mu equiv. of Ca2+ ions before activation of calpain II, which corresponds to half the sum of anion groups in glycosaminoglycan side chains. This adsorption of Ca2+ was lost after solvolysis of proteoglycan monomer with methanol/50 mM-HCl, which was used to desulphate glycosaminoglycans. Therefore cartilage proteoglycans are not merely the substrates of proteolysis, but they may regulate the activation of Ca(2+)-dependent enzymes including calpains through tight chelation of Ca2+ ions between glycosaminoglycan side chains. PMID: 1497624 24: Biopolymers 1992 Jun;32(6):585-96 Heavy metal binding to heparin disaccharides. I. Iduronic acid is the main binding site. Whitfield DM, Choay J, Sarkar B Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada. As model compounds for Ni(II)-binding heparin-like compounds isolated from human kidneys (Templeton, D.M. & Sarkar, B. (1985) Biochem. J. 230 35-42.), we investigated two disaccharides--4-O-(2-O-sulfo-alpha-L-idopyranosyluronic acid)-2,5-anhydro- D-mannitol, disodium salt (1a), and 4-O-(2-O-sulfo-alpha-L-idopyranosyluronic acid)-6-O- sulfo-2,5-anhydro-D-mannitol, trisodium salt (1b)--that were isolated from heparin after nitrous acid hydrolysis and reduction. The monosulfate (1a) was active whereas the disulfate (1b) was inactive in a high-performance liquid chromatography (HPLC) binding assay with the tracer ions 63Ni(II) 54Mn(II), 65Zn(II), and 109Cd(II). This result is in accord with the isolation of two 67Cu(II) and 63Ni(II) binding fractions from a complete pool of nitrous-acid-derived heparin disaccharides using sulfate gradients and a MonoQ anion exchange column on an FPLC system. One was identified as compound (1a) and the other as a tetrasulfated trisaccharide by high resolution FAB-MS, NMR and HPLC-PAD. Similarly, two synthetic disaccharides-methyl, 2-O-sulfo-4-O-(alpha-L-idopyranosyluronic acid)-2-deoxy-2-sulfamide-alpha-D-glucosamine, trisodium salt [idopA2S(alpha 1,4)GlcNS alpha Me, 2a], and 2-O-sulfo-4-O-(alpha-L-idopyranosyluronic acid)-2-deoxy-2-sulfamide-6-O-sulfo- alpha-D-glucosamine, tetrasodium salt [idopA2S (alpha 1,4)GlcNS6S alpha Me, 2b]--were shown to bind tracer amounts of 63Ni and 67Cu using chromatographic assays. Subsequently, 1H NMR titrations of 1a, 1b, 2a, and 2b with Zn (OAc)2 were analyzed to yield 1:1 Zn(II)-binding constants of 472 +/- 59, 698 +/- 120, 8,758 +/- 2,237 and 20,100 +/- 5,598 M-1, respectively. The values for 2a and 2b suggest chelation. It is suggested that the idopyranosiduronic acid residue is the major metal binding site. NMR evidence for this hypothesis comes from marked 1H and 13C chemical shift changes to the iduronic acid resonances after addition of diamagnetic Zn(II) ions. PMID: 1643264 Kidney Int 2000 Feb;57(2):385-400 Glomerular heparan sulfate alterations: mechanisms and relevance for proteinuria. Raats CJ, Van Den Born J, Berden JH Division of Nephrology, University Hospital St. Radboud, Nijmegen, The Netherlands. Heparan sulfate (HS) is the anionic polysaccharide side chain of HS proteoglycans (HSPGs) present in basement membranes, in extracellular matrix, and on cell surfaces. Recently, agrin was identified as a major HSPG present in the glomerular basement membrane (GBM). An increased permeability of the GBM for proteins after digestion of HS by heparitinase or after antibody binding to HS demonstrated the importance of HS for the permselective properties of the GBM. With recently developed antibodies directed against the GBM HSPG (agrin) core protein and the HS side chain, we demonstrated a decrease in HS staining in the GBM in different human proteinuric glomerulopathies, such as systemic lupus erythematosus (SLE), minimal change disease, membranous glomerulonephritis, and diabetic nephropathy, whereas the staining of the agrin core protein remained unaltered. This suggested changes in the HS side chains of HSPG in proteinuric glomerular diseases. To gain more insight into the mechanisms responsible for this observation, we studied GBM HS(PG) expression in experimental models of proteinuria. Similar HS changes were found in murine lupus nephritis, adriamycin nephropathy, and active Heymann nephritis. In these models, an inverse correlation was found between HS staining in the GBM and proteinuria. From these investigations, four new and different mechanisms have emerged. First, in lupus nephritis, HS was found to be masked by nucleosomes complexed to antinuclear autoantibodies. This masking was due to the binding of cationic moieties on the N-terminal parts of the core histones to anionic determinants in HS. Second, in adriamycin nephropathy, glomerular HS was depolymerized by reactive oxygen species (ROS), mainly hydroxyl radicals, which could be prevented by scavengers both in vitro (exposure of HS to ROS) and in vivo. Third, in vivo renal perfusion of purified elastase led to a decrease of HS in the GBM caused by proteolytic cleavage of the agrin core protein near the attachment sites of HS by the HS-bound enzyme. Fourth, in streptozotocin-induced diabetic nephropathy and during culture of glomerular cells under high glucose conditions, evidence was obtained that hyperglycemia led to a down-regulation of HS synthesis, accompanied by a reduction in the degree of HS sulfation. Publication Types: Review Review, tutorial PMID: 10652015 Quote Link to comment Share on other sites More sharing options...
Guest guest Posted February 21, 2001 Report Share Posted February 21, 2001 , May I ask what you meant by saying: " Chelation may restore the retention of sulfate in these children in their kidneys, and help them function better, but they may do better still if efforts were made to restore sulfate on the supply side. " Are you referring to chelating kids taking glucosamine sulfate? or using epsom salts (on skin)? How would they do better....in language, articulation, handling stress? Thanks so much. Aly Re: [ ] Re: DMSA & DMSO ? not the same but DMSO seems to have the makings of a good Chelator. > Andy, > > At 2/15/2001 +000006:36 AM, you wrote: > >Many people speculate on what causes mercury tox. The theory that > >mercury tox is due to a defect of sulfur handling has been > >conclusively proven incorrect. > > I'd love to know which studies were supposed to have proven that conclusion. > > I have yet to see any study on mercury (and I have looked!) that has been > conducted by someone with a sufficient knowledge of sugar and lipid > chemistry, and on the sulfation of sugars and lipids, and their regulation, > their role in endocytosis and their ability to chelate metals. Unless > detox questions were asked in that context, it means that the right issues > have not been asked relative to sulfur chemistry's role in mercury > detox. (see articles below) > > The molecules that have not been investigated properly govern the traffic > that approaches the cell, even " remotely " from the cell, in what is called > the glycocalyx, and that also cover the cell membrane. A completely > different experimental approach would be required to examine this issue > than has been used before: requiring techniques that are from the field of > glycobiology, and are not familiar to most biologists and chemists whose > training circles around protein issues. These techniques were discussed in > my lecture at the Autism 2000 Congress in Glasgow last May. > > Andy, the involvement of these molecules, already recognized as chelators > of mercury's closest physiological " kin " , would have a LOT BETTER CHANCE at > explaining things like the fact that it took about 2 solid months before > any symptoms showed up in the professor who spilled dimethyl mercury on her > hand. > > Think about this. Certainly her enzymes would have been inhibited by the > higher amounts in her system that were there at first, but she must have > had some form of biological protection that eventually ran out. After two > months of no problems at all, she began losing weight during the third > month after her accident. (Sulfation has a LOT to do with cachexia.) > > Only after that did neurological symptoms appear, and she got scared and > went to the doctor at that point. Only then did she start getting > exogenous chelation, and it did not help her at all, even though it was > getting mercury out. She went into a coma within the next few weeks: AFTER > chelation, and AFTER most of the initial toxic load had left her > system. The declines in this toxicity was demonstrated in hair samples > that were able to chronicle the declines week by week since the accident. > > What was happening with her sulfate chemistry in the meantime? No one > asked, and they certainly did not treat that issue. She died not too long > after that. That is just one example, but a potent one. I would recommend > reading that study to listmates, and ask whether existing models really > explain the course of her troubles. > > The most compelling reason to suspect sulfation's role in heavy metal > toxicity in autism is the very different response to mercury toxicity that > exists between boys and girls, demonstrated experimentally time and again. > > Sulfotransferase expression is vastly different between boys and girls > because the expression of these enzymes is regulated by the sex hormones. > This difference in expression constructs lifelong differences in the > sulfation of the brain and changes brain structure and function. This > leads to the sexual differences that determine the way that men and women > differ in the way they think and regulate issues of chemistry, but it > affects differences all over the body as well. > > Present models cannot account for the differences in mercury toxicity > between male and female and they don't even try to, which is troublesome, > and certainly should help us realize the lack of completeness in current > models. Shouldn't we pay attention to data that is bound to be > particularly relevant to autism because those sex ratios are preserved in > the incidence of autism? > > A recent study has demonstrated a problem with sulfotransferase activity > that affected 92% of those with low-functioning autism with a significance > of P<.00002. There is no way this data is irrelevant! > > The exposure to mercury that most of our children had is likely to be much > less than what happened to the lady at Dartmouth, but she probably had a > healthy sulfate chemistry to start out with. That would not have been the > case for any infant exposed to mercury and may especially not have been the > case in our kids, who became injured more by this exposure than most infants. > > Whatever sulfate status they had before mercury exposure would likely have > gotten worse after mercury, because sulfate transport across membranes has > been shown experimentally to be thoroughly blocked by mercury, and the most > important sulfate transporters are likely to be those in the > kidneys. Chelation may restore the retention of sulfate in these children > in their kidneys, and help them function better, but they may do better > still if efforts were made to restore sulfate on the supply side. > > The kidneys are where most of the toxicity is likely to collect, because > the kidneys are the body's main filters, and are themselves completely > dependent on sulfate to do their job properly. (see article below) > > > > 23: Biopolymers 1992 Jun;32(6):597-619 > > Heavy metal binding to heparin disaccharides. II. First evidence for zinc > chelation. > > Whitfield DM, Sarkar B > > Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada. > > To map out the heavy metal binding sites of iduronic acid containing > oligosaccharides isolated from human kidneys, we studied Zn(II) binding by > nuclear magnetic resonance (NMR) and molecular modeling to two disaccharides > isolated after nitrous acid depolymerization of heparin and two synthetic > disaccharides representative of the heparin structure, namely, IdopA2S (alpha > 1,4)AnManOH, 1 alpha, IdopA2S (alpha 1,4)AnManOH6S, 1b, IdopA2S-(alpha > 1,4)GlcNS > alpha Me, 2a, and IdopA2S (alpha 1,4)GlcNS6S alpha Me, 2b (see previous article > in this series). A conformational analysis of the metal free and metal bound > solutions was made by comparing calculated [(NOE)]s, [T1]s, and [J]s to > experimental values. The 1C4, 4C1, and 2S0 conformations of the > L-idopyranosiduronate ring and the 4E and 4T3 of the anhydro-D-mannitol > ring are > evaluated as are rotations about the C5-C6 hydroxymethylene of the AnManOH(6S) > or GlcNS (6S) residues. The NOE between IdopA2S H1 and H3 and the known NOE > between H2 and H5, as well as the T1 of IdopA2S H3, are introduced as NMR > observables sensitive to the IdopA2S ring conformation. Similarly, a NOE > between > IdopA2S H5 and AnManOH(6S) or GlcNS(6S) H3 was observed that directly restricts > the allowed interglycosidic conformational space. For all disaccharides, the > Zn(II) bound spectral data are consistent with models in which these > motions are > partially " frozen " such that the 1C4 conformation of the IdopA2S is stabilized > along with the 4T3 conformation of the AnManOH(6S) ring. The interglycosidic > conformation is also stabilized in one of two minima. Electrostatic potential > energy calculations gave the best overall agreement with experiment and suggest > metal binding conformations with the carboxylate and ring oxygen of the IdopA2S > residues (1C4 conformation) and either O3 of the GlcNS(6S) residues or the > sulfate oxygens of the 6-sulphate for 2b providing additional chelating sites. > These chelation models concur with the observation of marked 13C and 1H NMR > chemical shifts for the IdopA2S resonances and of GlcNS H3 for 2 alpha and > GlcNS6S C6 for 2b. This study of model compounds implicates the IdopA2S(alpha > 1,4)GlcNS6S group as part of the heavy metal binding site in biologically > important acidic oligosaccharides such as heparin. > > PMID: 1643265 > > Biochem J 1992 Aug 1;285 ( Pt 3):857-62 > > Characterization of proteoglycan degradation by calpain. > > Suzuki K, Shimizu K, Hamamoto T, Nakagawa Y, Murachi T, Yamamuro T > > Department of Orthopedic Surgery, Faculty of Medicine, Kyoto University, Japan. > > ....Ca(2+)-dependent proteoglycan degradation was unique in that proteoglycans > adsorb large amounts of Ca2+ ions rapidly before activation of calpain II: 1 mg > of pig cartilage proteoglycan monomer adsorbed 1.3-1.6 mu equiv. of Ca2+ ions > before activation of calpain II, which corresponds to half the sum of anion > groups in glycosaminoglycan side chains. This adsorption of Ca2+ was lost after > solvolysis of proteoglycan monomer with methanol/50 mM-HCl, which was used to > desulphate glycosaminoglycans. Therefore cartilage proteoglycans are not merely > the substrates of proteolysis, but they may regulate the activation of > Ca(2+)-dependent enzymes including calpains through tight chelation of Ca2+ > ions > between glycosaminoglycan side chains. > > PMID: 1497624 > > > 24: Biopolymers 1992 Jun;32(6):585-96 > > Heavy metal binding to heparin disaccharides. I. Iduronic acid is the main > binding site. > > Whitfield DM, Choay J, Sarkar B > > Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada. > > As model compounds for Ni(II)-binding heparin-like compounds isolated from > human > kidneys (Templeton, D.M. & Sarkar, B. (1985) Biochem. J. 230 35-42.), we > investigated two disaccharides--4-O-(2-O-sulfo-alpha-L-idopyranosyluronic > acid)-2,5-anhydro- D-mannitol, disodium salt (1a), and > 4-O-(2-O-sulfo-alpha-L-idopyranosyluronic acid)-6-O- > sulfo-2,5-anhydro-D-mannitol, trisodium salt (1b)--that were isolated from > heparin after nitrous acid hydrolysis and reduction. The monosulfate (1a) was > active whereas the disulfate (1b) was inactive in a high-performance liquid > chromatography (HPLC) binding assay with the tracer ions 63Ni(II) 54Mn(II), > 65Zn(II), and 109Cd(II). This result is in accord with the isolation of two > 67Cu(II) and 63Ni(II) binding fractions from a complete pool of > nitrous-acid-derived heparin disaccharides using sulfate gradients and a MonoQ > anion exchange column on an FPLC system. One was identified as compound > (1a) and > the other as a tetrasulfated trisaccharide by high resolution FAB-MS, NMR and > HPLC-PAD. Similarly, two synthetic disaccharides-methyl, > 2-O-sulfo-4-O-(alpha-L-idopyranosyluronic > acid)-2-deoxy-2-sulfamide-alpha-D-glucosamine, trisodium salt [idopA2S(alpha > 1,4)GlcNS alpha Me, 2a], and 2-O-sulfo-4-O-(alpha-L-idopyranosyluronic > acid)-2-deoxy-2-sulfamide-6-O-sulfo- alpha-D-glucosamine, tetrasodium salt > [idopA2S (alpha 1,4)GlcNS6S alpha Me, 2b]--were shown to bind tracer amounts of > 63Ni and 67Cu using chromatographic assays. Subsequently, 1H NMR titrations of > 1a, 1b, 2a, and 2b with Zn (OAc)2 were analyzed to yield 1:1 Zn(II)-binding > constants of 472 +/- 59, 698 +/- 120, 8,758 +/- 2,237 and 20,100 +/- 5,598 M-1, > respectively. The values for 2a and 2b suggest chelation. It is suggested that > the idopyranosiduronic acid residue is the major metal binding site. NMR > evidence for this hypothesis comes from marked 1H and 13C chemical shift > changes > to the iduronic acid resonances after addition of diamagnetic Zn(II) ions. > > PMID: 1643264 > > Kidney Int 2000 Feb;57(2):385-400 > > Glomerular heparan sulfate alterations: mechanisms and relevance for > proteinuria. > > Raats CJ, Van Den Born J, Berden JH > > Division of Nephrology, University Hospital St. Radboud, Nijmegen, The > Netherlands. > > Heparan sulfate (HS) is the anionic polysaccharide side chain of HS > proteoglycans (HSPGs) present in basement membranes, in extracellular matrix, > and on cell surfaces. Recently, agrin was identified as a major HSPG present in > the glomerular basement membrane (GBM). An increased permeability of the > GBM for > proteins after digestion of HS by heparitinase or after antibody binding to HS > demonstrated the importance of HS for the permselective properties of the GBM. > With recently developed antibodies directed against the GBM HSPG (agrin) core > protein and the HS side chain, we demonstrated a decrease in HS staining in the > GBM in different human proteinuric glomerulopathies, such as systemic lupus > erythematosus (SLE), minimal change disease, membranous glomerulonephritis, and > diabetic nephropathy, whereas the staining of the agrin core protein remained > unaltered. This suggested changes in the HS side chains of HSPG in proteinuric > glomerular diseases. To gain more insight into the mechanisms responsible for > this observation, we studied GBM HS(PG) expression in experimental models of > proteinuria. Similar HS changes were found in murine lupus nephritis, > adriamycin > nephropathy, and active Heymann nephritis. In these models, an inverse > correlation was found between HS staining in the GBM and proteinuria. From > these > investigations, four new and different mechanisms have emerged. First, in lupus > nephritis, HS was found to be masked by nucleosomes complexed to antinuclear > autoantibodies. This masking was due to the binding of cationic moieties on the > N-terminal parts of the core histones to anionic determinants in HS. Secon d, in > adriamycin nephropathy, glomerular HS was depolymerized by reactive oxygen > species (ROS), mainly hydroxyl radicals, which could be prevented by scavengers > both in vitro (exposure of HS to ROS) and in vivo. Third, in vivo renal > perfusion of purified elastase led to a decrease of HS in the GBM caused by > proteolytic cleavage of the agrin core protein near the attachment sites of HS > by the HS-bound enzyme. Fourth, in streptozotocin-induced diabetic nephropathy > and during culture of glomerular cells under high glucose conditions, evidence > was obtained that hyperglycemia led to a down-regulation of HS synthesis, > accompanied by a reduction in the degree of HS sulfation. > > Publication Types: > Review > Review, tutorial > > PMID: 10652015 > > > > > > > Quote Link to comment Share on other sites More sharing options...
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