Impact of salt exposure on N-acetylgalactosamine-4-sulfatase (arylsulfatase B) activity, glycosaminoglycans, kininogen, and bradykinin

N-acetylgalactosamine-4-sulfatase (Arylsulfatase B; ARSB) is the enzyme that removes sulfate groups from the N-acetylgalactosamine-4-sulfate residue at the non-reducing end of chondroitin-4-sulfate (C4S) and dermatan sulfate (DS). Previous studies demonstrated reduction in cell-bound high molecular weight kininogen in normal rat kidney (NRK) epithelial cells when chondroitin-4-sulfate content was reduced following overexpression of ARSB activity, and chondroitinase ABC produced similar decline in cell-bound kininogen. Reduction in the cell-bound kininogen was associated with increase in secreted bradykinin. In this report, we extend the in vitro findings to in vivo models, and present findings in Dahl salt-sensitive (SS) rats exposed to high (SSH) and low salt (SSL) diets. In the renal tissue of the SSH rats, ARSB activity was significantly less than in the SSL rats, and chondroitin-4-sulfate and total sulfated glycosaminoglycan content were significantly greater. Disaccharide analysis confirmed marked increase in C4S disaccharides in the renal tissue of the SSH rats. In contrast, unsulfated, hyaluronan-derived disaccharides were increased in the rats on the low salt diet. In the SSH rats, with lower ARSB activity and higher C4S levels, cell-bound, high-molecular weight kininogen was greater and urinary bradykinin was lower. ARSB activity in renal tissue and NRK cells declined when exogenous chloride concentration was increased in vitro. The impact of high chloride exposure in vivo on ARSB, chondroitin-4-sulfation, and C4S-kininogen binding provides a mechanism that links dietary salt intake with bradykinin secretion and may be a factor in blood pressure regulation.     

Feline arylsulfatase B (ARSB): isolation and expression of the cDNA, comparison with human ARSB, and gene localization to feline chromosome A1.

Arylsulfatase B (ARSB) is the lysosomal enzyme that catalyzes the hydrolysis of 4-sulfate groups from N-acetylgalactosamine 4-sulfate moieties on the glycosaminoglycans, dermatan sulfate and chondroitin sulfate A. In man, a deficiency of this enzymatic activity causes the lysosomal storage disorder, Maroteaux-Lamy disease (mucopolysaccharidosis Type VI; MPS VI). MPS VI in Siamese cats also has been described, and the comparative pathologic and biochemical abnormalities of the human and feline disorders have been well characterized. The present study describes the isolation and expression of cDNAs encoding feline ARSB and the assignment of the feline ARSB gene to feline chromosome A1. The full-length feline ARSB cDNA sequence is 1939 bp, including 3 and 328 bp of 5' and 3' untranslated sequences, respectively, and a 1608-bp open reading frame encoding 535 amino acids. The predicted human and feline ARSB proteins are 91% identical and 94% similar. However, despite this high homology, the predicted feline ARSB polypeptide has nine cysteine residues, while the human enzyme has eight. The presence of the extra cysteine residue at position 451 in the feline enzyme may explain why feline ARSB is a homodimer and the human enzyme is a monomer. To facilitate comparative structure/function studies of the human and feline enzymes and to initiate somatic gene therapy trials in the MPS VI cats, a full-length feline ARSB cDNA was reconstructed from a 1440-bp partial cDNA and an ARSB fragment amplified from feline first-strand cDNA by the polymerase chain reaction. The functional integrity of this cDNA was demonstrated by transient expression in human embryonic kidney cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Extra-Lysosomal Localization of Arylsulfatase B in Human Colonic Epithelium

The enzyme arylsulfatase B (N-acetylgalactosamine-4-sulfatase; ARSB; ASB) removes 4-sulfate groups from the sulfated glycosaminoglycans (sGAG) chondroitin-4-sulfate (C4S) and dermatan sulfate (DS). Inborn deficiency of ARSB leads to the lysosomal storage disease mucopolysaccharidosis VI, characterized by accumulation of sGAG in vital organs, disruption of normal physiological processes, severe morbidity, and premature death. Recent published work demonstrated extra-lysosomal localization with nuclear and cell membrane ARSB observed in bronchial and colonic epithelial cells, cerebrovascular cells, and hepatic cells. In this report, the authors present ARSB immunostaining in a colonic microarray and show differences in distribution, intensity, and pattern of ARSB staining among normal colon, adenomas, and adenocarcinomas. Distinctive, intense luminal membrane staining was present in the normal epithelial cells but reduced in the malignancies and less in the grade 3 than in the grade 1 adenocarcinomas. In the normal cores, a distinctive pattern of intense cytoplasmic positivity at the luminal surface was followed by reduced staining deeper in the crypts. ARSB enzymatic activity was significantly greater in normal than in malignant tissue. These study findings affirm extra-lysosomal localization of ARSB and suggest that altered ARSB immunostaining and reduced activity may be useful indicators of malignant transformation in human colonic tissue.     

小鼠毛囊不同生长周期中MITF下游色素相关基因的定位表达及相关性分析

小眼畸形转录因子（MITF）不仅是黑色素细胞发育、增殖和存活的必要调节因子,而且对调节相关酶和黑素体蛋白表达来确保黑色素产生具有至关重要的作用。MITF下游色素相关基因在小鼠毛囊生长周期中的表达及相关性仍有待研究。HE染色结果表明不同毛囊时期的小鼠毛囊呈现典型的组织形态学结构;免疫组织化学显示,MITF、GPNMB、OA1、TYR、TYRP2在不同毛囊生长周期中的毛基质及内外毛根鞘均有不同程度的阳性表达。黑色素测定结果表明,在毛囊生长初期和中期,碱性可溶性总黑色素（ASM）、真黑素（EM）以及褐黑素（PM）相对含量高于毛囊生长末期。蛋白免疫印迹结果表明,MITF、GPNMB、OA1、TYR、TYRP2在毛囊生长初期和中期蛋白质相对水平明显高于毛囊生长末期。实时荧光定量PCR结果表明, MITF、GPNMB、OA1、TYR、TYRP2、PMEL在毛囊生长初期和中期,mRNA相对表达量显著高于毛囊生长末期。在不同毛囊生长周期小鼠皮肤的MITF下游色素相关基因表达存在显著差异,表明上述因子在维持黑色素细胞色素生成是不可或缺的因素。     

Tyrosine phosphatase SHP2 regulates the expression of acyl-CoA synthetase ACSL4

Acyl-CoA synthetase 4 (ACSL4) is implicated in fatty acid metabolism with marked preference for arachidonic acid (AA). ACSL4 plays crucial roles in physiological functions such as steroid synthesis and in pathological processes such as tumorigenesis. However, factors regulating ACSL4 mRNA and/or protein levels are not fully described. Because ACSL4 protein expression requires tyrosine phosphatase activity, in this study we aimed to identify the tyrosine phosphatase involved in ACSL4 expression. NSC87877, a specific inhibitor of the tyrosine phosphatase SHP2, reduced ACSL4 protein levels in ACSL4-rich breast cancer cells and steroidogenic cells. Indeed, overexpression of an active form of SHP2 increased ACSL4 protein levels in MA-10 Leydig steroidogenic cells. SHP2 has to be activated through a cAMP-dependent pathway to exert its effect on ACSL4. The effects could be specifically attributed to SHP2 because knockdown of the phosphatase reduced ACSL4 mRNA and protein levels. Through the action on ACSL4 protein levels, SHP2 affected AA-CoA production and metabolism and, finally, the steroidogenic capacity of MA-10 cells: overexpression (or knockdown) of SHP2 led to increased (or decreased) steroid production. We describe for the first time the involvement of SHP2 activity in the regulation of the expression of the fatty acid-metabolizing enzyme ACSL4.     

Molecular signature of kappa-carrageenan mimics chondroitin-4-sulfate and dermatan sulfate and enables interaction with arylsulfatase B

The common food additive kappa-carrageenan (κ-CGN) is a sulfated polysaccharide that resembles chondroitin-4-sulfate (C4S) and dermatan sulfate (DS). All have a sulfate group on C4 of a glycoside (galactose for CGN and N-acetylgalactosamine for C4S), and the sulfate-bearing glycoside is linked in a β-1,4-configuration to an unsulfated, six-carbon sugar (galactose for CGN, glucuronate for C4S and iduronate for DS). The enzyme arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfate) is the highly selective enzyme that removes the four-sulfate group from the nonreducing terminus of C4S and DS, thereby regulating subsequent degradation. In this report, κ-CGN is shown to be a substrate for recombinant human ARSB (rhARSB). Sulfate was generated from both C4S and κ-CGN following incubation with rhARSB. Exposure of human colonic epithelial cells to κ-CGN, but not to C4S, produced reactive oxygen species (ROS) and increased interleukin (IL)-8 secretion. The ROS production from κ-CGN was reduced by exposure to rhARSB, but increased by competition from C4S or DS, but not from chondroitin-6-sulfate. Prior treatment of either lambda- or iota-CGN with rhARSB had no impact on ROS, IL-8 or inorganic sulfate production, demonstrating a specific effect of the molecular configuration of κ-CGN. By mimicry of C4S and DS and by interaction with ARSB, κ-CGN can directly interfere with the normal cellular functions of C4S, DS and ARSB. Since C4S and DS are present in high concentration in tissues, the impact of κ-CGN exposure may be due to some extent to interference with the normal biological functions of ARSB, C4S and DS.     

Reptin regulates insulin‐stimulated Akt phosphorylation in hepatocellular carcinoma via the regulation of SHP‐1/PTPN6

Hepatocellular carcinoma (HCC) is the main primary cancer of the liver. Many studies have shown that insulin resistance is a risk factor for HCC. We previously discovered the overexpression and oncogenic role of the Reptin/RUVBL2 ATPase in HCC. Here, we found that Reptin silencing enhanced insulin sensitivity in 2 HCC cell lines, as shown by a large potentiation of insulin‐induced AKT phosphorylation on Ser473 and Thr308, and of downstream signalling. Reptin silencing did not affect the tyrosine phosphorylation of the insulin receptor nor of IRS1, but it enhanced the tyrosine phosphorylation of the p85 subunit of PI3K. The expression of the SHP‐1/PTPN6 phosphatase, which dephosphorylates p85, was reduced after Reptin depletion. Forced expression of SHP‐1 restored a normal AKT phosphorylation after insulin treatment in cells where Reptin was silenced, demonstrating that the downregulation of SHP1 is mechanistically linked to increased Akt phosphorylation. In conclusion, we have uncovered a new function for Reptin in regulating insulin signalling in HCC cells via the regulation of SHP‐1 expression. We suggest that the regulation of insulin sensitivity by Reptin contributes to its oncogenic action in the liver.     

Arylsulfatase B Improves Locomotor Function after Mouse Spinal Cord Injury

Bacterial chondroitinase ABC (ChaseABC) has been used to remove the inhibitory chondroitin sulfate chains from chondroitin sulfate proteoglycans to improve regeneration after rodent spinal cord injury. We hypothesized that the mammalian enzyme arylsulfatase B (ARSB) would also enhance recovery after mouse spinal cord injury. Application of the mammalian enzyme would be an attractive alternative to ChaseABC because of its more robust chemical stability and reduced immunogenicity. A one-time injection of human ARSB into injured mouse spinal cord eliminated immunoreactivity for chondroitin sulfates within five days, and up to 9 weeks after injury. After a moderate spinal cord injury, we observed improvements of locomotor recovery assessed by the Basso Mouse Scale (BMS) in ARSB treated mice, compared to the buffer-treated control group, at 6 weeks after injection. After a severe spinal cord injury, mice injected with equivalent units of ARSB or ChaseABC improved similarly and both groups achieved significantly more locomotor recovery than the buffer-treated control mice. Serotonin and tyrosine hydroxylase immunoreactive axons were more extensively present in mouse spinal cords treated with ARSB and ChaseABC, and the immunoreactive axons penetrated further beyond the injury site in ARSB or ChaseABC treated mice than in control mice. These results indicate that mammalian ARSB improves functional recovery after CNS injury. The structural/molecular mechanisms underlying the observed functional improvement remain to be elucidated.     

Integrin β4 attenuates SHP‐2 and MAPK signaling and reduces human lung endothelial inflammatory responses

We previously identified the marked upregulation of integrin β4 in human lung endothelial cells (EC) treated with simvastatin, an HMG coA‐reductase inhibitor with vascular‐protective and anti‐inflammatory properties in murine models of acute lung injury (ALI). We now investigate the role of integrin β4 as a novel mediator of vascular inflammatory responses with a focus on mitogen‐activated protein kinases (MAPK) signaling and the downstream expression of the inflammatory cytokines (IL‐6 and IL‐8) essential for the full elaboration of inflammatory lung injury. Silencing of integrin β4 (siITGB4) in human lung EC resulted in significant increases in both basal and LPS‐induced phosphorylation of ERK 1/2, JNK, and p38 MAPK, consistent with robust integrin β4 regulation of MAPK activation. In addition, siITB4 increased both basal and LPS‐induced expression of IL‐6 and IL‐8 mRNA and protein secretion into the media. We next observed that integrin β4 silencing increased basal and LPS‐induced phosphorylation of SHP‐2, a protein tyrosine phosphatase known to modulate MAPK signaling. In contrast, inhibition of SHP‐2 enzymatic activity (sodium stibogluconate) abrogated the increased ERK phosphorylation associated with integrin β4 silencing in LPS‐treated EC and attenuated the increases in levels of IL‐6 and IL‐8 in integrin‐β4‐silenced EC. These findings highlight a novel negative regulatory role for integrin β4 in EC inflammatory responses involving SHP‐2‐mediated MAPK signaling. Upregulation of integrin β4 may represent an important element of the anti‐inflammatory and vascular‐protective properties of statins and provides a novel strategy to limit inflammatory vascular syndromes. J. Cell. Biochem. 110: 718–724, 2010. © 2010 Wiley‐Liss, Inc.     

Selective hydrolysis of chondroitin sulfates by hyaluronidase

Chondroitin 4-sulfate and chondroitin 6-sulfate were incubated with testicular hyaluronidase in the presence of excess beta-glucuronidase. The beta-glucuronidase caused rapid removal of the nonreducing terminal beta-D-glucuronosyl residues from the oligosaccharides formed by the action of the hyaluronidase, destroying the oligosaccharide acceptors required for the transglycosylation activity of hyaluronidase and releasing free D-glucuronic acid at a rate that was equal to the rate of the hyaluronidase-catalyzed hydrolysis. When hyaluronidase was assayed at 37 degrees C in the presence of 0.05 M NaCl, 0.05 M Na2SO4, and 0.1 M sodium acetate at pH 5, chondroitin 4-sulfate was hydrolyzed at 1.5 times the rate found for chondroitin 6-sulfate. When hyaluronidase was assayed at 45 degrees C in 0.06 M sodium acetate at pH 6, chondroitin 4-sulfate was hydrolyzed at 8 times the rate observed for chondroitin 6-sulfate. Under the pH5 conditions, the chondroitin 4-sulfate was converted to a mixture of tri- and pentasaccharides, while the chondroitin 6-sulfate was converted primarily to a mixture of penta- and heptasaccharides, with only a small amount of trisaccharide. Under the pH 6 conditions, the chondroitin 4-sulfate was converted to a mixture of penta- and heptasaccharides, with only a small amount of trisaccharide, but the products from chondroitin 6-sulfate were a mixture of oligosaccharides ranging in degree of polymerization from 7 to 25 monosaccharides per oligosaccharide. End-group analyses of the products formed at pH 6 showed that both substrates were cleaved preferentially at the glycosidic bonds of the 4-sulfated disaccharides.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distinct effects of N-acetylgalactosamine-4-sulfatase and galactose-6-sulfatase expression on chondroitin sulfates

The sulfatase enzymes, N-acetylgalactosamine-4-sulfatase (arylsulfatase B (ASB)) and galactose-6-sulfatase (GALNS) hydrolyze sulfate groups of CS. Deficiencies of ASB and GALNS are associated with the mucopolysaccharidoses. To determine if expression of ASB and GALNS impacts on glycosaminoglycans (GAGs) and proteoglycans beyond their association with the mucopolysaccharidoses, we modified the expression of ASB and GALNS by overexpression and by silencing with small interference RNA in MCF-7 cells. Content of total sulfated GAG (sGAG), chondroitin 4-sulfate (C4S), and total chondroitin sulfates (CSs) was measured following immunoprecipitation with C4S and CS antibodies and treatment with chondroitinase ABC. Following silencing of ASB or GALNS, total sGAG, C4S, and CS increased significantly. Following overexpression of ASB or GALNS, total sGAG, C4S, and CS declined significantly. Measurements following chondroitinase ABC treatment of the cell lysates demonstrated no change in the content of the other sGAG, including heparin, heparan sulfate, dermatan sulfate, and keratan sulfate. Following overexpression of ASB and immunoprecipitation with C4S antibody, virtually no sGAG was detectable. Total sGAG content increased to 23.39 (+/-1.06) microg/mg of protein from baseline of 12.47 (+/-0.68) microg/mg of protein following ASB silencing. mRNA expression of core proteins of the CS-containing proteoglycans, syndecan-1 and decorin, was significantly up-regulated following overexpression of ASB and GALNS. Soluble syndecan-1 protein increased following increases in ASB and GALNS and reduced following silencing, inversely to changes in CS. These findings demonstrate that modification of expression of the lysosomal sulfatases ASB and GALNS regulates the content of CSs.     

Epitope-specific changes in chondroitin sulfate/dermatan sulfate proteoglycans as markers in the lymphopoietic and granulopoietic compartments of developing bursae of Fabricius

The types and distributions of chondroitin sulfate proteoglycans within developing chick bursae of Fabricius were determined by indirect immunocytochemical analyses using mAb specific for chondroitin/dermatan sulfate epitopes. Analyses obtained from the use of well characterized mAb known to specifically identify chondroitin 4- and dermatan sulfates (antibody 2B6) and chondroitin 6-sulfate (antibody 3B3) were compared with those obtained from two additional mAb raised against chick chondroitin sulfates proteoglycans derived from hemopoietic tissue. The results indicate that chondroitin sulfate compositions of the adjacent lymphopoietic and granulopoietic compartments differ. Chondroitin 6-sulfate, notably absent from lymphopoietic regions, is a major chondroitin sulfate species in granulopoietic regions of day 13 bursae. Moreover, chondroitin 6-sulfate disappears from the granulopoietic compartment in a time course that corresponds to the decline in granulopoietic activity. Simultaneously, there is an apparent increase in chondroitin sulfates associated with developing medullary regions of lymphoid follicles. The content of chondroitin 4-/dermatan sulfates and, most significantly, of chondroitin/dermatan sulfates identified by antibodies raised against chick proteoglycans, increases within developing follicles. As a consequence, by day 18 of incubation, immunostained follicles become clearly demarcated from the connective tissue of the tunica propria. This study provides evidence that chondroitin sulfates are constituents of both lymphopoietic and granulopoietic microenvironments and that subtle changes occur within these proteoglycan structures during bursal development. These developmental changes in chondroitin sulfate compositions are consistent with these molecules playing a functional role in hemopoiesis.     

Arylsulfatase B regulates interaction of chondroitin-4-sulfate and kininogen in renal epithelial cells

The enzyme arylsulfatase B (N-acetylgalactosamine 4-sulfatase; ASB; ARSB), which removes 4-sulfate groups from the nonreducing end of chondroitin-4-sulfate (C4S;CSA) and dermatan sulfate, has cellular effects, beyond those associated with the lysosomal storage disease mucopolysaccharidosis VI. Previously, reduced ASB activity was reported in cystic fibrosis patients and in malignant human mammary epithelial cell lines in tissue culture compared to normal cells. ASB silencing and overexpression were associated with alterations in syndecan-1 and decorin expression in MCF-7 cells and in IL-8 secretion in human bronchial epithelial cells. In this report, we present the role of ASB in the regulation of the kininogen–bradykinin axis owing to its effect on chondroitin-4-sulfation and the interaction of C4S with kininogen. Silencing or overexpression of ASB in normal rat kidney epithelial cells in tissue culture modified the content of total sulfated glycosaminoglycans (sGAGs), C4S, kininogen, and bradykinin in spent media and cell lysates. Treatment of the cultured cells with chondroitinase ABC also increased the secretion of bradykinin into the spent media and reduced the C4S-associated kininogen. When ASB was overexpressed, the cellular kininogen that associated with C4S declined, suggesting a vital role for chondroitin-4-sulfation in regulating the kininogen–C4S interaction. These findings suggest that ASB, owing to its effect on chondroitin-4-sulfation, may impact on the kininogen–bradykinin axis and, thereby, may influence blood pressure.Because ASB activity is influenced by several ions, including chloride and phosphate, ASB activity may provide a link between salt responsiveness and the bradykinin-associated mechanism of blood pressure regulation.