Interplay between transglutaminases and heparan sulphate in progressive renal scarring

Transglutaminase-2 (TG2) is a new anti-fibrotic target for chronic kidney disease, for its role in altering the extracellular homeostatic balance leading to excessive build-up of matrix in kidney. However, there is no confirmation that TG2 is the only transglutaminase involved, neither there are strategies to control its action specifically over that of the conserved family-members. In this study, we have profiled transglutaminase isozymes in the rat subtotal nephrectomy (SNx) model of progressive renal scarring. All transglutaminases increased post-SNx peaking at loss of renal function but TG2 was the predominant enzyme. Upon SNx, extracellular TG2 deposited in the tubulointerstitium and peri-glomerulus via binding to heparan sulphate (HS) chains of proteoglycans and co-associated with syndecan-4. Extracellular TG2 was sufficient to activate transforming growth factor-β1 in tubular epithelial cells, and this process occurred in a HS-dependent way, in keeping with TG2-affinity for HS. Analysis of heparin binding of the main transglutaminases revealed that although the interaction between TG1 and HS is strong, the conformational heparin binding site of TG2 is not conserved, suggesting that TG2 has a unique interaction with HS within the family. Our data provides a rationale for a novel anti-fibrotic strategy specifically targeting the conformation-dependent TG2-epitope interacting with HS

Activities of glutamate dehydrogenase and aspartate and alanine aminotransferases in freshwater snails Helisoma duryi and Lymnaea natalensis exposed to copper.

In this paper we investigate the potential of glutamate dehydrogenase (GDH) and aspartate and alanine aminotransferases (AST and ALT) as biomarkers of water pollution due to copper in the freshwater snails Helisoma duryi and Lymnaea natalensis. Snails were dosed with copper(II) ion concentrations of 0.01, 0.1 and 1 mg kg(-1) breeding water for a period of 96 h, after which those surviving were shelled. The copper content in the breeding water, in whole snail tissue and in the snail shells was determined at the end of the period of exposure. For enzyme determinations, whole snail tissue was first homogenized and fractionated by centrifugation at 500 g to remove the nuclei. The resulting supernatant was then centrifuged at 10,000 g to give a pellet fraction representing the mitochondrial fraction and a supernatant representing the cytosolic fraction. Copper was very toxic to both snail species at concentrations above 0.2 mg l(-1), with only 3% of the Helisoma and 12% of the Lymnaea surviving at concentrations of approximately 1 mg l(-1). The copper content in the shells and tissues of snails rose with increasing copper concentration in the breeding water, and was 2.1- to 4.9-fold in snails exposed to copper ion at a dose of 1 mg kg(-1) water compared with undosed snails. Similarly, the activities of GDH and AST rose by up to 4.7-fold in the homogenate and the mitochondrial and cytosolic fractions with increasing concentrations of copper. These activities, however, fell at copper concentrations of approximately 1 mg l(-1), which coincided with massive death of snails. Mitochondrial ALT disappeared at copper ion concentrations of approximately 0.2 mg l(-1) for Lymnaea and 1 mg l(-1) for Helisoma, possibly indicating mitochondrial degeneration. These results show that GDH, AST and ALT have the potential to be biomarkers of sublethal copper pollution in these two snail species, since their activities were significantly altered by low copper concentrations.,Sida/SAREC Water Projec

Effects Of Exposure To Lead And Zinc On Antioxidant Enzyme Activity In Lymnaea Natalensis And Helisoma Duryi.

Presented at the Biochemistry and Molecular Biology Society Conference held at the University of Zimbabwe in October 2002,Metals such as Zinc (Zn) are is found in high concentrations in mine drainage, while lead, as tetra-ethyl lead in petrol, causes contamination of water, soil and air can lead to severe health consequences. Zinc has been shown to reduce the efficiency of oxygen transport across the gill membrane of fish, as well as the respiration and ammonia excretion rates of freshwater shrimp. Molluscs have been shown to accumulate a wide variety of pollutants and have, in some instances, proposed as indicators of environmental pollution by metals. The effect of lead (Pb) and Zn on the antioxidant enzymes (AOE's) of two aquatic snail species, namely Lymnaea natalensis and Helisoma duryi was studied with a view to developing a biomarker of freshwater metal pollution. Adult snails reared in the laboratory were exposed daily for three days to 0.01 ppm, 0.1 ppm and 1.0 ppm of either Pb or Zn S-9 fractions were prepared form whole snails. The S-9 fractions were used to measure the activity of AOE's such as DT-diaphorase, catalase and glutathione-S-transferase as well as reduced glutathione (GSH) and the product of lipid peroxidation, malondialdehyde (MDA). Lead exposure tended to increase enzymatic activity several fold. Significant changes were observed after exposure to 0.01 ppm and 0.1 ppm in L. natalensis. Zinc also increased activity of the enzymes but to a lesser extent. Levels of markers of oxidative stress, MDA and glutathione GSH were also altered, with MDA generally decreased in L. natalensis. In H duryimetal exposure resulted in an increased GSH levels when exposed to 0.1 ppm and 1.0 ppm of Pb as well as by all three concentrations of Zn but not in a dose dependent manner. In H duryi, but not L. natalensis metal exposure resulted in an increased (up to 75'7'0) MDA level. Our data suggest that antioxidant status, as a result of exposure to heavy metals in aquatic snails metals is not altered in a dose dependent or manner and is also species specific. Thus, the alterations in AOE's using either L. natalensisor H duryi, are not sufficiently reliable to develop a biomarker of heavy metal pollution in aquatic systems.,Biochemistry and Molecular Biology Societ