Kidney transplantation recovers the reduction level of serum sulfatide in ESRD patients via processes correlated to oxidative stress and platelet count

Sulfatide is a major component of glycosphingolipids in lipoproteins. Recently, we reported that a low serum level of sulfatide in hemodialysis patients might be related to the high incidence of cardiovascular diseases. However, the serum kinetics of sulfatide in kidney disease patients and the function of endogenous serum sulfatide are still unclear. To obtain novel knowledge concerning these issues, we investigated the serum kinetics of sulfatide in 5 adult kidney transplant recipients. We also analyzed the correlated factors influencing the serum sulfatide level, using multiple regression analysis. Kidney transplantation caused a dramatic increase of serum sulfatide without an alteration of its composition in all recipients in a time-dependent manner; however, the recovery speed was slower than that of the improvement of kidney function and the serum sulfatide reached a nearly normal level after 1 year. Multiple regression analysis showed that the significant correlated factor influencing the serum sulfatide level was log duration (time parameter) throughout the observation period, and the correlated factors detected in the stable phase were the decrease of serum concentration of malondialdehyde (an oxidative stress marker) as well as the elevation of platelet count. The current study results demonstrated the gradual but reliable recovery of the serum sulfatide level in kidney transplant recipients for the first time, suggesting a close correlation between serum sulfatide and kidney function. The recovery of serum sulfatide might derive from the attenuation of systemic oxidative stress. The normal level of serum sulfatide in kidney transplant recipients might affect platelet function, and contribute to the reduction of cardiovascular disease incidence.ArticleGLYCOCONJUGATE JOURNAL. 28(3-4):125-135 (2011)journal articl

Acute kidney injury induced by protein-overload nephropathy down-regulates gene expression of hepatic cerebroside sulfotransferase in mice, resulting in reduction of liver and serum sulfatides

Sulfatides, possible antithrombotic factors belonging to sphingoglycolipids, are widely distributed in mammalian tissues and serum. We recently found that the level of serum sulfatides was significantly lower in hemodialysis patients than that in normal subjects, and that the m serum level closely correlated to the incidence of cardiovascular disease. These findings suggest a relationship between the level of serum sulfatides and kidney function; however, the molecular mechanism underlying this relationship remains unclear. In the present study, the influence of kidney dysfunction on the metabolism of sulfatides was examined using an established murine model of acute kidney injury, protein-overload nephropathy in mice. Protein-overload treatment caused severe proximal tubular injuries within 4 days, and this treatment obviously decreased both serum and hepatic sulfatide levels. The sphingoid composition of serum sulfatides was very similar to that of hepatic ones at each time point, suggesting that the serum sulfatide level is dependent on the hepatic secretory ability of sulfatides. The treatment also decreased hepatic expression of cerebroside sulfotransferase (CST), a key enzyme in sulfatide metabolism, while it scarcely influenced the expression of the other sulfatide-metabolizing enzymes, including arylsulfatase A, ceramide galactosyltransferase, and galactosylceramidase. Pro-inflammatory responses were not detected in the liver of these mice: however, potential oxidative stress was increased. These results suggest that down-regulation of hepatic CST expression, probably affected by oxidative stress from kidney injury, causes reduction in liver and serum sulfatide levels. This novel mechanism, indicating the crosstalk between kidney injury and specific liver function, may prove useful for helping to understand the situation where human hemodialysis patients have low levels of serum sulfatides.ArticleBIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS. 390(4):1382-1388 (2009)journal articl

Peroxisome proliferator-activated receptor alpha mediates enhancement of gene expression of cerebroside sulfotransferase in several murine organs

Sulfatides, 3-O-sulfogalactosylceramides, are known to have multifunctional properties. These molecules are distributed in various tissues of mammals, where they are synthesized from galactosylceramides by sulfation at C3 of the galactosyl residue. Although this reaction is specifically catalyzed by cerebroside sulfotransferase (CST), the mechanisms underlying the transcriptional regulation of this enzyme are not understood. With respect to this issue, we previously found potential sequences of peroxisome proliferator-activated receptor (PPAR) response element on upstream regions of the mouse CST gene and presumed the possible regulation by the nuclear receptor PPAR alpha. To confirm this hypothesis, we treated wild-type and Ppara-null mice with the specific PPAR alpha agonist fenofibrate and examined the amounts of sulfatides and CST gene expression in various tissues. Fenofibrate treatment increased sulfatides and CST mRNA levels in the kidney, heart, liver, and small intestine in a PPAR alpha-dependent manner. However, these effects of fenofibrate were absent in the brain or colon. Fenofibrate treatment did not affect the mRNA level of arylsulfatase A, which is the key enzyme for catalyzing desulfation of sulfatides, in any of these six tissues. Analyses of the DNA-binding activity and conventional gene expression targets of PPAR alpha has demonstrated that fenofibrate treatment activated PPAR alpha in the kidney, heart, liver, and small intestine but did not affect the brain or colon. These findings suggest that PPAR alpha activation induces CST gene expression and enhances sulfatide synthesis in mice, which suggests that PPAR alpha is a possible transcriptional regulator for the mouse CST gene.ArticleGLYCOCONJUGATE JOURNAL. 30(6):553-560 (2013)journal articl

Kidney dysfunction induced by protein overload nephropathy reduces serum sulfatide levels in mice

We recently proposed serum sulfatides as a novel biomarker for cardiovascular disease in patients with end-stage renal failure (ESRF), based on the possible antithrombotic properties of this molecule. In this earlier study, the level of serum sulfatides was gradually decreased in parallel with kidney dysfunction; however the precise mechanism underlying this decrease was unknown. The aim of the present study was to investigate the mechanism underlying the decrease in serum sulfatide levels caused by kidney dysfunction in an experimental animal model. To produce a kidney dysfunction animal model, we prepared a mouse model of protein overload nephropathy. Using high-throughput analysis combined with matrix-assisted laser desorption ionisation time-of-flight mass spectrometry, we measured the levels of sulfatides in the sera, livers, small intestines and kidneys of protein overload nephropathy mice. As the disease progressed, the levels of sulfatides in sera decreased. Also, the levels in livers and small intestines decreased in a similar manner to those in sera, to approximately 60% of the original levels. On the contrary, those in kidneys increased by approximately 1.4-fold. Our results indicate that kidney dysfunction affects the levels of sulfatides in lipoprotein-producing organs, such as livers and small intestines, and lowers the levels of sulfatides in sera.ArticleNEPHROLOGY. 14(7):658-662 (2009)journal articl

Kidney transplantation recovers the reduction level of serum sulfatide in ESRD patients via processes correlated to oxidative stress and platelet count

Sulfatide is a major component of glycosphingolipids in lipoproteins. Recently, we reported that a low serum level of sulfatide in hemodialysis patients might be related to the high incidence of cardiovascular diseases. However, the serum kinetics of sulfatide in kidney disease patients and the function of endogenous serum sulfatide are still unclear. To obtain novel knowledge concerning these issues, we investigated the serum kinetics of sulfatide in 5 adult kidney transplant recipients. We also analyzed the correlated factors influencing the serum sulfatide level, using multiple regression analysis. Kidney transplantation caused a dramatic increase of serum sulfatide without an alteration of its composition in all recipients in a time-dependent manner; however, the recovery speed was slower than that of the improvement of kidney function and the serum sulfatide reached a nearly normal level after 1 year. Multiple regression analysis showed that the significant correlated factor influencing the serum sulfatide level was log duration (time parameter) throughout the observation period, and the correlated factors detected in the stable phase were the decrease of serum concentration of malondialdehyde (an oxidative stress marker) as well as the elevation of platelet count. The current study results demonstrated the gradual but reliable recovery of the serum sulfatide level in kidney transplant recipients for the first time, suggesting a close correlation between serum sulfatide and kidney function. The recovery of serum sulfatide might derive from the attenuation of systemic oxidative stress. The normal level of serum sulfatide in kidney transplant recipients might affect platelet function, and contribute to the reduction of cardiovascular disease incidence.ArticleGLYCOCONJUGATE JOURNAL. 28(3-4):125-135 (2011)journal articl

Attenuation of Kidney Injuries Maintains Serum Sulfatide Levels Dependent on Hepatic Synthetic Ability: A Possible Involvement of Oxidative Stress

信州大学博士（医学）・学位論文・平成24年3月31日授与（甲第921号）・生暁娜Serum sulfatides are the major glycosphingolipids in lipoproteins. Although serum sulfatides are mainly synthesized and secreted by the liver, they are significantly decreased when the kidneys are impaired. Our recent experimental study using a murine protein-overload nephropathy model suggested a hypothetical mechanism whereby serum sulfatides were reduced due to kidney dysfunction. This was the result of decreased hepatic expression of a sulfatide synthetic enzyme, cerebroside sulfotransferase (CST), which is associated with systemic enhancement of oxidative stress. However, there is a possibility that the experimental process, protein-overload itself, directly affected the sulfatide metabolism and oxidative stress in the liver. To determine whether kidney dysfunction actually reduces the hepatic synthesis of sulfatides via oxidative stress, we examined sulfatide levels, the hepatic content of metabolic sulfatide enzymes, and the degree of oxidative stress in protein-overload mice subjected to renoprotective therapy using clofibrate, a representative hypolipidemic medicine. Protein-overload mice exhibited marked kidney injuries, enhancement of hepatic oxidative stress, decreased levels of serum and hepatic sulfatides, and decreased expression of hepatic CST. The clofibrate treatment attenuated kidney damage and hepatic oxidative stress while maintaining serum/hepatic sulfatide levels and hepatic CST content in the mice. Because clofibrate monotherapy without protein-overload treatment only minimally affected these hepatic parameters, the hepatic synthesis of sulfatides appeared to be strongly influenced by kidney dysfunction and subsequent oxidative stress. This study suggests that the crosstalk between kidney dysfunction and hepatic sulfatide metabolism is mediated by oxidative stress. These results should help to understand the phenomenon in patients with end-stage kidney disease.ArticleTOHOKU JOURNAL OF EXPERIMENTAL MEDICINE. 227(1):1-12 (2012)journal articl

High-resolution crystal structure of Arthrobacter aurescens chondroitin AC lyase: An enzyme-substrate complex defines the catalytic mechanism

Chondroitin lyases (EC 4.2.2.4 and EC 4.2.2.5) are glycosaminoglycan -degrading enzymes that act as eliminases. Chondroitin lyase AC from Arthrobacter, aurescens (ArthroAC) is known to act on chondroitin 4-sulfate and chondroitin 6-sulfate but not on dermatan sulfate. Like other chondroitin AC lyases, it is capable of cleaving hyaluronan. We have determined the three -dimensional crystal structure of ArthroAC in its native form as well as in complex with its substrates (chondroitin 4-sulfate tetrasaccharide, CStetra and hyaluronan tetrasaccharide) at resolution varying from 1.25 Angstrom to 1.9 Angstrom. The primary sequence of ArthroAC has not been previously determined but it was possible to determine the amino acid sequence of this enzyme from the high-resolution electron density maps and to confirm it by mass spectrometry. The enzyme -substrate complexes were obtained by soaking the substrate into the crystals for varying lengths of time (30 seconds to ten hours) and flash-cooling the crystals. The electron density map for crystals soaked in the substrate for as short as 30 seconds showed the substrate clearly and indicated that the ring of central glucuronic acid assumes a distorted boat conformation. This structure strongly supports the lytic mechanism where Tyr242 acts as a general base that abstracts the proton from the C5 position of glucuronic acid while Asn183 and His233 neutralize the charge on the glucuronate acidic group. Comparison of this structure with that of chondroitinase AC from Flavobacterium heparinum (FlavoAC) provides an explanation for the exolytic and endolytic mode of action of ArthroAC and FlavoAC, respectively. Crown Copyright (C) 2004 Published by Elsevier Ltd. All rights reservedPT: JournalIS: 0022-2836UD: 200415Pr\ufffdsentation non requise; en attente de brevet ( compagnie \ufffdtrang\ufffdre) 02.04.04 magNRC publication: Ye

High-resolution crystal structure of Arthrobacter aurescens chondroitin AC lyase: An enzyme-substrate complex defines the catalytic mechanism

Chondroitin lyases (EC 4.2.2.4 and EC 4.2.2.5) are glycosaminoglycan -degrading enzymes that act as eliminases. Chondroitin lyase AC from Arthrobacter, aurescens (ArthroAC) is known to act on chondroitin 4-sulfate and chondroitin 6-sulfate but not on dermatan sulfate. Like other chondroitin AC lyases, it is capable of cleaving hyaluronan. We have determined the three -dimensional crystal structure of ArthroAC in its native form as well as in complex with its substrates (chondroitin 4-sulfate tetrasaccharide, CStetra and hyaluronan tetrasaccharide) at resolution varying from 1.25 Angstrom to 1.9 Angstrom. The primary sequence of ArthroAC has not been previously determined but it was possible to determine the amino acid sequence of this enzyme from the high-resolution electron density maps and to confirm it by mass spectrometry. The enzyme -substrate complexes were obtained by soaking the substrate into the crystals for varying lengths of time (30 seconds to ten hours) and flash-cooling the crystals. The electron density map for crystals soaked in the substrate for as short as 30 seconds showed the substrate clearly and indicated that the ring of central glucuronic acid assumes a distorted boat conformation. This structure strongly supports the lytic mechanism where Tyr242 acts as a general base that abstracts the proton from the C5 position of glucuronic acid while Asn183 and His233 neutralize the charge on the glucuronate acidic group. Comparison of this structure with that of chondroitinase AC from Flavobacterium heparinum (FlavoAC) provides an explanation for the exolytic and endolytic mode of action of ArthroAC and FlavoAC, respectively. Crown Copyright (C) 2004 Published by Elsevier Ltd. All rights reservedPT: JournalIS: 0022-2836UD: 200415Pr\ufffdsentation non requise; en attente de brevet ( compagnie \ufffdtrang\ufffdre) 02.04.04 magNRC publication: Ye