[What is the Initiating Reaction for the Lipid Radical Chain Reaction System That Can Induce Ferroptotic Cell Death at the Lower Oxygen Content?]

The neural cell death in cerebral infarction is suggested to be ferroptosis-like cell death, involving the participation of 15-lipoxygenase (15-LOx). Ferroptosis is induced by lipid radical species generated through the one-electron reduction of lipid hydroperoxides, and it has been shown to propagate intracellularly and intercellularly. At lower oxygen concentration, it appeared that both regiospecificity and stereospecificity of conjugated diene moiety in lipoxygenase-catalysed lipid hydroperoxidation are drastically lost. As a result, in the reaction with linoleic acid, the linoleate 9-peroxyl radical-ferrous lipoxygenase complex dissolves into the linoleate 9-peroxyl radical and ferrous 15-lipoxygenase. Subsequently, the ferrous 15-lipoxygenase then undergoes one-electron reduction of 13-hydroperoxy octadecadienoic acid, generating an alkoxyl radical (pseudoperoxidase reaction). A part of the produced lipid alkoxyl radicals undergoes cleavage of C-C bonds, liberating small molecular hydrocarbon radicals. Particularly, in ω-3 polyunsaturated fatty acids, which are abundant in the vascular and nervous systems, the liberation of small molecular hydrocarbon radicals was more pronounced compared to ω-6 polyunsaturated fatty acids. The involvement of these small molecular hydrocarbon radicals in the propagation of membrane lipid damage is suggested.

Quantitative Assessment of the Post-translational Modifications of Human Serum Albumin by Dimethyl Trisulfide

Some bacteria, such as Fusobacterium nucleatum, act as dimethyl trisulfide (DMTS) producers in the host in vivo. DMTS acts as a sulfane sulfur donor and chemically modifies the sulfhydryl groups. This study explored the post-translational modifications of human serum albumin using DMTS. Quantitative assessments were conducted on mixed disulfides of mercaptoalbumin with mercaptomethane (Alb-SS-CH3) and albumin hydropersulfide (Alb-SSH) as post-translationally modified species. The hydropersulfide group was alkylated with iodoacetamide, resulting in the formation of an albumin-mercaptoacetamide mixed disulfide. The mixed disulfides were subsequently reduced with tris(2-carboxyethyl)phosphine, and the liberated mercaptomethane and mercaptoacetamide were fluorescently labeled with 4-fluoro-7-sulfamoylbenzofurazan (ABD-F). Quantification was performed using HPLC with fluorescence detection. Using this methodology, we examined the formation of Alb-SS-CH3 and Alb-SSH via the reaction between 4% human serum albumin and DMTS at 10-100 µM concentrations. Approximately two molecules of Alb-SS-CH3 and one molecule of Alb-SSH were generated from one DMTS molecule. Moreover, hydrogen sulfide was identified as an intermediate, suggesting its generation and subsequent reaction with intraprotein disulfide bonds, leading to the production of Alb-SSH. These results suggest the production of DMTS in humans in vivo should be involved in the elevation of Alb-SS-CH3 and Alb-SSH contents in plasma samples.

Isomerization of Oxidized Linoleate Metabolites with trans/cis Conjugated Diene Moiety to Those with trans/trans One in the Lipoxygenase/Linoleate/Hydrogen Polysulfide System

Endogenous hydrogen polysulfides are radical scavengers, and the resulting thiyl radical may catalyze isomerization of the cis-double bond to a trans-double bond. This study examined whether oxidized linoleate species with trans/trans-conjugated diene moieties were generated in the 15-lipoxygenase/linoleate/hydrogen polysulfide system at a lower oxygen content. When 40 µL of 0.1 M phosphate buffer (pH 7.4) containing 1.0 mM linoleate, 1.0 µM soybean 15-lipoxygenase, and 100 µM sodium trisulfide was placed in a 0.6 mL polypropylene microtube for 1 h at 25 °C, the proportion of (E/E)-oxo-octadecadienoic acids (OxoODEs) content to the total OxoODEs content was estimated to be more than 80% (mol/mol). OxoODEs are generated through the pseudoperoxidase reaction of ferrous 15-lipoxygenase with hydroperoxy octadecadienoic acids (HpODEs), which are produced by the lipoxygenase reaction of ferric 15-lipoxygenase. The content of OxoODEs was positively correlated with the content of 9-HpODEs, indicating that 9-HpODEs production is involved in converting ferric 15-lipoxygenase to ferrous 15-lipoxygenase. Furthermore, when 40 µL of 0.1 M phosphate buffer (pH 7.4) containing 1.0 mM linoleate, 1.0 µM soybean 15-lipoxygenase, 100 µM sodium trisulfide, and nitroxyl radical (carbon-centered radical-trapping agent, 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-N-oxyl (CmΔP)) was incubated in a 0.6 mL polypropylene microtube at room temperature, CmΔP-(E/Z)-ODEs were isomerized to CmΔP-(E/E)-ODEs in a time-dependent manner and this isomerization was inhibited by a radical scavenger, Trolox. The results indicate that thiyl radicals derived from hydrogen polysulfides isomerize trans/cis conjugated diene moiety to the trans/trans moiety.

2,2,6,6-Tetramethylpiperidine-1-oxyl acts as a volatile inhibitor of ferroptosis and neurological injury

Ferroptosis, a type of oxidative stress cell death, has been implicated in cell injury in several diseases, and treatments with specific inhibitors have been shown to protect cells and tissues. Here we demonstrated that a treatment with the nitroxide radical, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), prevented the ferroptotic cell death in an airborne manner. Other TEMPO derivatives and lipophilic antioxidants, such as Trolox and ferrostatin-1, also prevented cell death induced by erastin and RSL3; however, only TEMPO exhibited inhibitory activity from a physically distant location. TEMPO vaporized without decomposing, and then dissolved again into a nearby water solution. Volatilized TEMPO inhibited glutamate-induced cell death in mouse hippocampal cell lines, and also reduced neuronal cell death in a mouse ischemia model. These results suggest that TEMPO is a unique cell protective agent that acts in a volatility-mediated manner.

Simple and sensitive quantification of glutathione hydropersulfide alkylated using iodoacetamide by high-performance liquid chromatography with post-column derivatization

A novel analytical method was developed for the quantification of glutathione hydropersulfide (G-SSH) in biological samples by high-performance liquid chromatography (HPLC) with post-column derivatization. G-SSH was treated with iodoacetamide as an alkylating agent for 5 min at 37 °C, and the resultant acetamide-labeled G-SSH (G-SS-acetamide) was subjected to HPLC. After separation on a reversed-phase column, G-SS-acetamide was quantified by detection using a post-column reaction with orthophthalaldehyde under alkaline conditions. The standard G-SS-acetamide was synthesized through the S-S exchange reaction between oxidized glutathione and 2-mercaptoacetamide. It should be noted that some types of alkylating agents, including N-ethylmaleimide and monobromobimane, cleave the polysulfide chains of polysulfides that consist of glutathione, resulting in the production of alkylated G-SSHs. We confirmed that iodoacetamide did not enhance the cleavage of acetamide-labeled glutathione trihydropersulfide (G-SSS-acetamide). The lowest quantification limit was estimated to be 25 nM for G-SS-acetamide. This method can be useful for studying the dynamics of sulfane sulfur in glutathione-containing matrices.

Botanical sulfane sulfur donors inhibit ferroptotic cell death caused by the depletion of cysteine

Inhibitors against cystine-glutamate antiporter, including erastin, elicit ferroptotic cell death. The erastin-induced ferroptotic cell death appears to be caused by cysteine as well as glutathione depletion. Cysteine is an essential substrate for sulfane sulfur producing systems in cells, generating persulfides that function as intracellular antioxidants and intermediates in iron-sulfur cluster production. Therefore, we examined whether botanical sulfane sulfur donors such as diallyl trisulfide (DATS) and dimethyl trisulfide (DMTS) prevent ferroptotic cell death in HT1080 cells treated with erastin. As a result, DMTS (20 μM) and DATS (10 μM) rescued the erastin-treated HT1080 cells by 69.6% and 91.6%, respectively. Furthermore, DMTS-containing squeeze of cabbage (2.0 g/L) and DATS-containing squeeze of garlic (0.07 g/L) rescued the erastin-treated HT1080 cells by 76.5% and almost 100%, respectively. In conclusion, the ingestion of trisulfides may bring about increased resistance to ferroptotic cell death in vivo.

Lipoxygenase-mediated generation of lipid peroxides enhances ferroptosis induced by erastin and RSL3

In cancer cells the small compounds erastin and RSL3 promote a novel type of cell death called ferroptosis, which requires iron-dependent accumulation of lipid reactive oxygen species. Here we assessed the contribution of lipid peroxidation activity of lipoxygenases (LOX) to ferroptosis in oncogenic Ras-expressing cancer cells. Several 12/15-LOX inhibitors prevented cell death induced by erastin and RSL3. Furthermore, siRNA-mediated silencing of ALOX15 significantly decreased both erastin-induced and RSL3-induced ferroptotic cell death, whereas exogenous overexpression of ALOX15 enhanced the effect of these compounds. Immunofluorescence analyses revealed that the ALOX15 protein consistently localizes to cell membrane during the course of ferroptosis. Importantly, treatments of cells with ALOX15-activating compounds accelerated cell death at low, but not high doses of erastin and RSL3. These observations suggest that tumor ferroptosis is promoted by LOX-catalyzed lipid hydroperoxide generation in cellular membranes.

Involvement of lysosomal storage-induced p38 MAP kinase activation in the overproduction of nitric oxide by microglia in cathepsin D-deficient mice

Nitric oxide (NO) and peroxynitrite, which are produced by activated microglia, are responsible for accelerated neurodegeneration in cathepsin D-deficient (CD-/-) mice. To elucidate the mechanisms by which microglia are initially activated in CD-/- mice, we analyzed the possible relationship between lysosomal storage and microglial activation. In CD-/- mice, the microglial NO-generating activity that was closely associated with the induction of inducible NO synthase and the cationic amino acid transporter-2 (CAT-2) coincided well with the lysosomal storage of subunit c of mitochondrial F0F1ATPase and the formation of ceroid/lipofuscin. Furthermore, activated microglia, which are often accumulating subunit c and ceroid/lipofuscin, showed proliferation activity and an activation of p38 mitogen-activated protein (MAP) kinase. In the primary cultured microglia, pepstatin A was found to enhance the generation of NO and superoxide anion radicals. In these pepstatin A-treated microglia, both an increased generation of the intracellular reactive oxygen species (ROS) and an activation of p38 MAP kinase were observed. These results suggest that the ceroid/lipofuscin which form in microglia activate the p38 MAP kinase cascade through the increased intracellular generation of ROS in CD-/- mice. The activated p38 MAP kinase cascade then promotes the expression of iNOS and CAT-2, thereby inducing the overproduction of NO.

Regulation of S-thiolation and S-nitrosylation in the thiol/nitric oxide system by radical scavengers

Nitric oxide (NO) is a possible agent, which induces crosslinking among molecules containing sulfhydryl groups. However, the S-thiolation is essentially accompanied by S-nitrosylation. In the present study, we evaluated radical scavengers as a regulator for S-thiolation and S-nitrosylation by NO released from NO-generator, 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1-triazene (P-NONOate). When glutathione was incubated with P-NONOate in 4% (vol/vol) O(2)-saturated buffer solution (pH 7.4) in the presence of nitrone spin-trapping agent, 5,5'-dimethyl-1-pyroline-N-oxide (DMPO), the prevention of S-thiolation and the promotion of S-nitrosylation were observed. The DMPO adduct was identified to be thiyl radical-DMPO adduct via ESR study. In contrast, nitroxyl radical, radical scavenger against oxygen-centered radicals, promoted the S-thiolation but prevented S-nitrosylation. Nitronyl nitroxide, radical scavenger against nitric oxide, can convert nitric oxide into nitrogen dioxide in the O(2)-independent manner. In the presence of nitronyl nitroxide in the thiol/P-NONOate system, S-thiolation was remarkably enhanced up to 60% (mol/mol) of sulfhydryl groups. However, nitronyl nitroxide at enough content (>or=1.0 mM) almost completely prevented S-nitrosylation, whereas nitronyl nitroxide at comparatively lower content (0.5 mM) contrarily enhanced the S-nitrosylation. Based on these facts, it appeared to be possible to consequently regulate S-thiolation and S-nitrosylation through controlling the thiyl radical chain reaction by radical scavengers.

Immunohistochemical localization of d-alanine to β-cells in rat pancreas

A mouse monoclonal antibody against D-alanine (D-Ala) has been raised and the immunohistochemical localization of this D-amino acids in the rat pancreas is visualized. The obtained anti-D-Ala monoclonal antibody has no significant cross-reactivity to all proteinogenic L-amino acids and their D-enantiomers. Using this antibody, immunohistochemical staining was performed on the pancreas, and specific staining for d-Ala has been observed only in the Langerhans islets. To identify the types of D-Ala-immunopositive cells, double staining was carried out with antibodies against D-Ala and pancreatic hormones. Similar immunostaining patterns have been observed for D-Ala and insulin, while D-Ala is hardly co-localized with other hormones (glucagon, somatostatin, and pancreatic polypeptide). These results indicate for the first time that D-Ala is localized to insulin producing beta-cells in mammalian pancreas, suggesting that this D-amino acid would be involved in the regulation of the blood glucose level.

Feedback activation of ferrous 5-lipoxygenase during leukotriene synthesis by coexisting linoleic acid

Ferrous lipoxygenases seem to be activated through a feedback control mechanism via FA hydroperoxides generated from PUFAs by partially existing ferric lipoxygenases. However, during leukotriene synthesis, feedback activation of ferrous 5-lipoxygenase in the presence of arachidonic acid (AA) was not observed. In the present study, we examined the feedback activation of ferrous 5-lipoxygenase in the 5-lipoxygenase/AA system in the presence of linoleic aicd (LA), which is a predominant component of membrane phospholipids. When potato 5-lipoxygenase was incubated with AA and LA in the presence of nitroxyl radical, 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrroline-N-oxyl (CmDeltaP), one-electron redox cycle reaction between ferric and ferrous 5-lipoxygenase was detected. For each revolution of the cycle, one molecule of PUFA and one molecule of its hydroperoxide were converted into PUFA-allyl radical-CmDeltaP adduct ([PUFA-H].-CmDeltaP) and PUFA-epoxyallyl radical-CmDeltaP adduct ([PUFA-H+O].-CmDeltaP), respectively. The ratios, [AA-H].-CmDeltaP/[LA-H].-CmDeltaP and [AA-H+O].-CmDeltaP/[LA-H+O].-CmDeltaP, were estimated to be 1.7 and 0.13, respectively. These facts indicate that ferrous 5-lipoxygenase is activated through feedback control in the presence of LA, and that resulting ferric 5-lipoxygenase catalyzes the stoichiometric synthesis of leukotrienes from AA. In conclusion, the biosynthesis of leukotrienes is remarkably efficient.

Intramolecular rearrangement of linolenate peroxyl radicals in lipoxygenase reactions at lower oxygen content

Variation of tissue oxygen content is thought to be a possible factor in determining the structural diversity of hydroperoxy fatty acids. In the present study, we evaluated the structural diversity of intermediate carbon-centered radicals at lower oxygen content. When the buffered solution (pH 7.4) containing 1.0 mM alpha-linolenic acid, 1.0 muM soybean 15-lipoxygenase, and 1.0 mM nitroxyl radical [3-carbamoyl-2,2,5,5-tetramethyl-3-pyrroline-N-oxyl (CmDeltaP)], which selectively traps carbon-centered radicals, was incubated in a sealed vial, the generation of linolenate hydroperoxide was completed within 1 min. In the subsequent reaction at lower oxygen content, the production of the [LnA-H+O(2)].-CmDeltaP adduct was ascertained by liquid chromatography tandem mass spectrometry with precursor ion scanning. Furthermore, HPLC analysis with photodiode array detection showed that the adduct exhibits an absorption maximum at 278 nm, indicating a conjugated triene moiety. On the basis of these facts, the structure of the adduct was speculated to be C(2)H(5)-CH(CmDeltaP)-CH = CH-CH = CH-CH = CH-CH(OOH) -C(7)H(14)-COOH. We proposed a possible reaction pathway as follows: a linolenate 9-peroxyl radical generated in the lipoxygenase reaction might be converted into C(2)H(5)-.CH-CH = CH-CH = CH-CH = CH-CH(OOH) -C(7)H(14)-COOH through an intramolecular rearrangement. This intermediate radical may give rise to hydroperoxy fatty acids with structural diversity.

Radical scavenger can scavenge lipid allyl radicals complexed with lipoxygenase at lower oxygen content

Lipoxygenases have been proposed to be a possible factor that is responsible for the pathology of certain diseases, including ischaemic injury. In the peroxidation process of linoleic acid by lipoxygenase, the E,Z-linoleate allyl radical-lipoxygenase complex seems to be generated as an intermediate. In the present study, we evaluated whether E,Z-linoleate allyl radicals on the enzyme are scavenged by radical scavengers. Linoleic acid, the content of which was greater than the dissolved oxygen content, was treated with soya bean lipoxygenase-1 (ferric form) in the presence of radical scavenger, CmP (3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl). The reaction rate between oxygen and lipid allyl radical is comparatively faster than that between CmP and lipid allyl radical. Therefore a reaction between linoleate allyl radical and CmP was not observed while the dioxygenation of linoleic acid was ongoing. After the dissolved oxygen was depleted, CmP stoichiometrically trapped linoleate-allyl radicals. Accompanied by this one-electron redox reaction, the resulting ferrous lipoxygenase was re-oxidized to the ferric form by hydroperoxylinoleate. Through the adduct assay via LC (liquid chromatography)-MS/MS (tandem MS), four E,Z-linoleate allyl radical-CmP adducts corresponding to regio- and diastereo-isomers were detected in the linoleate/lipoxygenase system, whereas E,E-linoleate allyl radical-CmP adducts were not detected at all. If E,Z-linoleate allyl radical is liberated from the enzyme, the E/Z-isomer has to reach equilibrium with the thermodynamically favoured E/E-isomer. These data suggested that the E,Z-linoleate allyl radicals were not liberated from the active site of lipoxygenase before being trapped by CmP. Consequently, we concluded that the lipid allyl radicals complexed with lipoxygenase could be scavenged by radical scavengers at lower oxygen content.

Quantification of lipid alkyl radicals trapped with nitroxyl radical via HPLC with postcolumn thermal decomposition

Lipid alkyl radicals generated from polyunsaturated fatty acids via chemical or enzymatic H-abstraction have been a pathologically important target to quantify. In the present study, we established a novel method for the quantification of lipid alkyl radicals via nitroxyl radical spin-trapping. These labile lipid alkyl radicals were converted into nitroxyl radical-lipid alkyl radical adducts using 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrroline-N-oxyl (CmdeltaP) (a partition coefficient between octanol and water is approximately 3) as a spin-trapping agent. The resulting CmdeltaP-lipid alkyl radical adducts were determined by HPLC with postcolumn online thermal decomposition, in which the adducts were degraded into nitroxyl radicals by heating at 100 degrees C for 2 min. The resulting nitroxyl radicals were selectively and sensitively detected by electrochemical detection. With the present method, we, for the first time, determined the lipid alkyl radicals generated from linoleic acid, linolenic acid, and arachidonic acid via soybean lipoxygenase-1 or the radical initiator 2,2'-azobis(2,4-dimethyl-valeronitrile).

Confirmation of superoxide generation via xanthine oxidase in streptozotocin-induced diabetic mice

Reactive oxygen species (ROS) may play key roles in vascular inflammation and atherogenesis in patients with diabetes. In this study, xanthine oxidase (XO) system was examined as a potential source of superoxide in mice with streptozotocin (STZ)-induced experimental diabetes. Plasma XO activity increased 3-fold in diabetic mice (50 +/- 33 microU/ml) 2 weeks after the onset of diabetes, as compared with non-diabetic control mice (15 +/- 6 microU/ml). In vivo superoxide generation in diabetic mice was evaluated by an in vivo electron spin resonance (ESR)/spin probe method. Superoxide generation was significantly enhanced in diabetic mice, and the enhancement was restored by the administration of superoxide dismutase (SOD) and 4,5-dihydroxy-1,3-benzene disulfonic acid (Tiron), which was reported to scavenge superoxide. Pretreatment of diabetic mice with XO inhibitors, allopurinol and its active metabolite oxipurinol, normalized the increased superoxide generation. In addition, there was a correlation (r = 0.78) between the level of plasma XO activity and the relative degree of superoxide generation in diabetic and non-diabetic mice. Hence, the results of this study strongly suggest that superoxide should be generated through the increased XO seen in the diabetic model mice, which may be involved in the pathogenesis of diabetic vascular complications.

Association between the expression of inducible nitric oxide synthase by chondrocytes and its nitric oxide-generating activity in adjuvant arthritis in rats

Inducible nitric oxide synthase (iNOS) is one of the clinical targets in rheumatoid arthritis. Synoviocytes, macrophages, and chondrocytes in the joints of patients with rheumatoid arthritis appear to express iNOS, but the contribution of iNOS molecules to rheumatoid arthritis is not yet clear. This study used adjuvant-induced arthritis in rats as a model to examine the association between the iNOS expression and its activity in rheumatoid arthritis. In adjuvant-injected rats, arthritic changes in the paw were first observed between days 10 and 12. NO-generation activity was precisely determined by combining an electron spin resonance/nitric oxide (NO)-trapping method with the method of standard addition using an NO generator, and we found that the activity in the joint samples was extremely high on day 10. The administration of S-(2-aminoethyl)isothiourea, a selective iNOS inhibitor, from day 0 to day 10, effectively reduced the paw swelling. Immunohistological studies showed that chondrocytes expressed iNOS on days 7-14 and that nitrotyrosine residues, a footprint of NO generation, were produced on day 10. This indicates that NO generation by iNOS induced in chondrocytes is a key event in the induction of adjuvant arthritis.

Quantitative and qualitative alterations of chondroitin/dermatan sulfates accompanied with development of tubulointerstitial nephritis

Quantitative and qualitative alterations of renal oversulfated chondroitin/dermatan sulfates (C/DSs) accompanied by the development of tubulointerstitial nephritis were examined. The rat model with unilateral ureteral obstruction (UUO) is a suitable model for study of renal interstitial fibrosis, and was utilized in the present study. Cortical regions of serial sections of UUO kidney and sham-operated kidney on glass slides were processed using a small surgical knife under dark field microscopy. Oversulfated C/DSs in tissue sections on a glass slide were degraded to unsaturated disaccharides using chondroitinase ABC and ACII digestion in the presence of bacterial collagenase. The resulting unsaturated disaccharides were subsequently determined by HPLC. These in situ investigations yielded the following results: (1) marked increases in oversulfated C/DSs content and decreases in the oversulfation degree of C/DSs were observed in fibrous lesions, compared to non-fibrous lesions, and (2) iduronic acid content in C/DSs in fibrous lesions was significantly lower than that in non-fibrous lesions. These findings indicate that oversulfated C/DSs with low-iduronic acid content represent a potential marker for tubulointerstitial nephritis.

Development of rapid in vitro assay for oxidative liver injury and its application to 230 chemicals

Water environments are thought to be polluted with thousands of synthetic chemicals and biproducts involving persistent organic pollutants and endocrine disrupters, and their human and ecological impacts are causing serious anxiety. Many bioassays have been undertaken to evaluate the hazardous impacts of toxic chemicals dissolved in water. Reactive Oxygen Species (ROS) are well known to be involved in the toxicity of various chemicals. ROS are mostly generated in liver and cause oxidative damage to DNA, lipids and proteins, resulting in the failure of cellular functions. In order to develop an in vitro bioassay system to estimate ROS induced liver toxicity by chemicals, we investigated the lipid peroxidation, liver cell injury, and genotoxicity using the human hepatocellular carcinoma cell line, Hep-G2 (ATCC HB 8065), and applied it to 230 chemicals.

1,25-Dihydroxyvitamin D(3) prevents the conversion of adipose tissue into fibrous tissue in skin exposed to chronic UV irradiation

The hormonally active form of vitamin D (1,25(OH)2D3) is known to be a physiological regulator of the proliferation and differentiation of skin cells including keratinocytes, fibroblasts, and adipocytes. In the present study, the efficacy of 1,25(OH)2D3 on the conversion of adipose tissue to fibrous tissue in photodamaged skin was investigated in a murine animal model. Groups of hairless mice were exposed to solar-simulating UV irradiation (lambdamax, 352 nm; UV distribution: 300-310 nm, 0.9%; 310-320 nm, 2.0%; 320-420 nm, 97.1%) for 20 weeks at a dose of 10.8 J/cm2 five times weekly on weekdays. At the end of 20 weeks irradiation, wrinkling in the dorsal skin was induced. The histological and biochemical studies indicated that UV irradiation caused a disappearance of adipocytes and concomitant accumulation of the extracellular matrix components (fibrosis), including collagen, hyaluronan, and chondroitin/dermatan, which are synthesized by fibroblasts. Application of 1,25(OH)2D3 on the dorsal skin prior to UV irradiation dramatically prevented both the disappearance of adipocytes and the accumulation of extracellular matrix components in the lower dermis, resulting in antiwrinkling. These findings indicate that 1,25(OH)2D3 prevents the UV-induced abnormal differentiation and proliferation of adipocytes and fibroblasts, which arise from a common progenitor, mesenchymal cells.

Prevention of the photodamage in the hairless mouse dorsal skin by kojic acid as an iron chelator

Kojic acid, a fungal metabolic product, has been used as a skin-depigmenting agent in skin care products marketed in Japan. Iron in the skin is known to be involved in wrinkling as a result of chronic photodamage. Kojic acid was expected to have anti-wrinkling activity, since it possesses iron-chelating activity. We now evaluated the anti-wrinkling activity of kojic acid by using hairless mice exposed to chronic solar-simulating ultraviolet (UV) irradiation as model animal. At the end of a 20-week irradiation period, topical application of kojic acid before UV irradiation was observed to dramatically prevent: (1) the wrinkling, (2) hyperplasia of the epidermis, (3) fibrosis of the lower dermis, and (4) the increase of extracellular matrix components in the upper dermis. These findings indicate that kojic acid is a typical agent preventing wrinkling of the skin due to chronic photodamage.

Structural characteristics of oversulfated chondroitin/dermatan sulfates in the fibrous lesions of the liver with cirrhosis

The structural characteristics of oversulfated chondroitin/dermatan sulfates (C/DSs) in the fibrous lesions of the rat liver with cirrhosis were examined. Long-Evans Cinnamon rats were subjected to the present study as the model animals with cirrhosis. The serial polyester wax sections of liver with cirrhosis were processed into the fibrous lesions and the nonfibrous lesions. The oversulfated C/DSs in the tissue sections on a glass slide were degraded to unsaturated disaccharides by chondroitinase ABC and ACII digestion in the presence of bacterial collagenase. Subsequently, the resulting unsaturated disaccharides were determined by the reversed-phase ion-pair high-performance liquid chromatography with fluorometric postcolumn derivatization using 2-cyanoacetamide as a reagent. Through these in situ investigations, we found some facts as follows: (i) in the fibrous lesion, the remarkable increase of the oversulfated C/DSs content and the decrease of the oversulfation degree of the C/DSs were observed compared with those in the nonfibrous lesion, (ii) the proportion of the iduronic acid content in the C/DSs in the fibrous lesion was significantly low compared with that in the nonfibrous lesion, and (iii) in the nonfibrous lesion close to the fibrous lesion, both quantitative and qualitative alterations of C/DSs were not observed at all. These findings indicate that the oversulfated C/DSs with low iduronic acid content are possible marker for the fibrogenesis of liver with cirrhosis.

Quantitative alterations of hyaluronan and dermatan sulfate in the hairless mouse dorsal skin exposed to chronic UV irradiation

The quantitative alterations of hyaluronan and dermatan sulfate in the upper dermis (fibrous tissue) and the lower dermis (adipose tissue) of the hairless mouse skin chronically exposed to the UV irradiation as solar-simulating irradiation (lambda(max) 352 nm, UV distribution: 300-310 nm, 0.9%; 310-320 nm, 2.0%; 320-420 nm, 97.1%) were evaluated. Hyaluronan and dermatan sulfate contents in each part of dermis were determined as follows: skin sections on a glass slide prepared by histological technique were processed into the upper dermis and the lower dermis with a small surgical knife, and treated with chondroitinase ABC and ACII in the presence of bacterial collagenase. The resulting unsaturated disaccharides were determined by HPLC method. By applying this method to the UV-irradiated hairless mouse skin, it was found that the chronic UV irradiation increased dermatan sulfate in the upper dermis, whereas an increase of hyaluronan content was not statistically significant. In the lower dermis, on the contrary, both hyaluronan and dermatan sulfate contents remarkably increased as compared with the control mice. Furthermore, the histological study showed the accumulation of the collagen fibers in the lower dermis of the UV-irradiated hairless mouse skin following the disappearance of adipocytes. These findings indicate that the increases of glycosaminoglycan contents in the UV-irradiated skin are related to the accumulation of the extracellular matrix components in the lower dermis.

Quantification of hyaluronan and chondroitin/dermatan sulfates in the tissue sections on glass slides

The method for the determination of hyaluronan and chondroitin/dermatan sulfates in the tissue sections on a glass slide, which were prepared by histological technique, was established by applying to porcine skin. The degradation of these glycosaminoglycans to the unsaturated disaccharides in porcine skin sections on a glass slide was achieved by chondroitinase ABC and ACII in the presence of highly purified bacterial collagenase. Subsequently, the resulting unsaturated disaccharides were determined by HPLC with fluorometric postcolumn derivatization using 2-cyanoacetamide as a reagent. So far, the determination of the glycosaminoglycans in the tissues has taken up more than 5 days, whereas the determination of the glycosaminoglycans in the frozen sections by the present method was completed within a day. In addition, applications of the present method to the serial polyester wax sections processed with a small surgical knife made it possible to determine the glycosaminoglycans in a local part in the tissue section. The present method should open a way for the clinical analysis of glycosaminoglycans in the pathological tissue samples.

Alterations of hairless mouse skin exposed to chronic UV irradiation and its prevention by hydrocortisone

Ultraviolet-induced alterations of skin were investigated in a murine animal model. Groups of hairless mice were exposed to UV (black light, lambda max 352 nm; UV distribution: 300-310 nm, 0.9%; 310-320 nm, 2.0%; 320-420 nm, 97.1%) for 20 weeks at a dose of 16.3 J/cm2 five times weekly on weekdays. At the end of 20 weeks irradiation, the dorsal skins were biochemically and histologically examined. Ultraviolet caused remarkable increases in amounts of hyaluronan, chondroitin sulfates and dermatan sulfates in skin (microgram/cm2). Interestingly, a significant change in a collagen content (hydroxyproline, microgram/g of dry powder) caused by UV irradiation was not observed, whereas the amount of collagen (hydroxyproline, microgram/cm2) increased remarkably. Histologically, no distinguishable thickening was observed in both upper dermis and lower dermis, but thickening of the epidermis was observed. Furthermore, the histological study indicated that UV irradiation caused a disappearance of crowds of adipocytes, alternative appearance of numerous fibroblasts and accumulation of collagen bundles and hyaluronan in lower dermis. Hydrocortisone, an anti-inflammatory agent, prevented both the fibrosis of lower dermis and the accumulation of the extracellular matrix components. Based on these results, it seems reasonable that UV penetrates into the lower dermis and causes fibrosis there, resulting from the inflammatory responses.

Enzymatic method for the simultaneous determination of hyaluronan and chondroitin sulfates using high-performance liquid chromatography

A chromatographic method for the simultaneous determination of hyaluronan and chondroitin sulfates was examined. Hyaluronan differs from chondroitin sulfates in the susceptibility to chondroitinase ABC under alkaline conditions. When hyaluronan and chondroitin sulfates were treated with chondroitinase ABC in the buffered solution (pH 9.1), chondroitin sulfates were selectively degraded to the unsaturated disaccharides, whereas hyaluronan was not. Subsequently, hyaluronan in the reaction mixture was digested to the unsaturated tetrasaccharide and hexasaccharide at pH 6.0 by Streptomyces hyaluronidase in the presence of zinc ion (inhibitor for chondroitinase ABC). The separation of the resulting unsaturated disaccharides from chondroitin sulfates and the unsaturated oligosaccharides from hyaluronan was achieved by a reversed-phase ion-pair HPLC. The structural polydispersities of hyaluronan and chondroitin sulfates in the molecular weight, the sulfation position, or the components of uronic acid did not affect their determination. The usefulness of the present method was proved by application to the porcine skin samples.

Degradation of dehydroascorbate to 2,3-diketogulonate in blood circulation

In our previous paper (Biochim. Biophys. Acta 1379 (1998) 257-263), we demonstrated that bicarbonate promotes a cleavage of lactone ring of dehydroascorbate (DHA) on the basis of in vitro experiments. In the present study, we examined the degradation of DHA in blood circulation in vivo by using a high-performance liquid chromatographic method for the determination of ascorbate (AsA), DHA and 2,3-diketogulonate (2,3-DKG), which required no pretreatment of biological fluids. When DHA was intravenously administered to rats, a rapid disappearance of DHA (t1/2 < 1 min) and a concomitant appearance of 2,3-DKG in blood circulation were observed. Approximately 90% of the administered DHA were excreted into urine as resulting 2,3-DKG (55%) and AsA (31%), respectively. Furthermore, we elucidated that rat plasma lacks an enzyme having an aldonolactonase-like activity. The result of the present study suggests that this DHA disappearance is a function of both a chemical degradation to 2,3-DKG and a reduction to AsA.

Quantification of carbamylated dehydroascorbate derivative produced from cyanate and dehydroascorbate

We established a high-performance liquid chromatographic method for separating and quantifying carbamylated dehydroascorbate derivative (CDA), a reaction product of cyanate with dehydroascorbate. The separation of CDA from interfering substances was achieved by anion-exchange HPLC using a TSK gel SAX (250x4.6 mm I.D.) column and 0.12 M NaCl eluent. The detection of CDA was achieved through two steps: (1) degradation of CDA to cyanate and amino compounds in alkaline solution, and (2) detection of these products by an indophenol reaction. For the processing of plasma and urine samples, anion-exchange solid-phase extraction was used. The detection limit for quantitative determination was 0.1 microM CDA (S/N=3). The linear range found applying the optimized conditions was 0.2 to 200 microM. The intra- and inter-day assay precision (R.S.D.) of CDA (10 microM) were 4.8 and 7.2% for rat plasma, and 4.0 and 4.9% for rat urine, respectively. The usefulness of the present method was proved by the application to plasma and urine samples. The study of the biokinetics of CDA in rats revealed that the elimination of CDA is due to urinary excretion.

Evaluation of an acidic deproteinization for the measurement of ascorbate and dehydroascorbate in plasma samples

The most popular pretreatment method of plasma samples for the measurement of ascorbate (AsA) and dehydroascorbate (DHA) has been an acidic deproteinization via metaphosphoric acid or trichloroacetic acid. In general, DHA is absent in plasma samples prepared from human blood in a conventional manner. However, when these plasma samples were subjected to acidic deproteinization, DHA was detected in the acidified sample solutions. In the present study, we demonstrate that the oxidation of AsA to DHA in the solutions was promoted by at least two mechanisms, one involving catalysis by ferric ion released from transferrin, and the other involving catalysis by plasma hemoglobin. In the acidified transferrin solution by trichloroacetic acid, an oxidation of AsA to DHA proceeded with standing time, whereas the oxidation was not observed in that by metaphosphoric acid. This oxidation appeared to be catalyzed by ferric ion released from transferrin. In contrast, plasma hemoglobin functioned as a catalyst for AsA oxidation in both metaphosphoric acid and trichloroacetic acid solutions. Therefore, DHA content in the trichloroacetic acid-treated plasma sample was markedly higher than that in the metaphosphoric acid-treated one. These results suggest that DHA detected in acidified plasma samples is an artifact resulting from AsA oxidation.

Evaluation of an acidic deproteinization for the measurement of ascorbate and dehydroascorbate in plasma samples

The most popular pretreatment method of plasma samples for the measurement of ascorbate (AsA) and dehydroascorbate (DHA) has been an acidic deproteinization via metaphosphoric acid or trichloroacetic acid. In general, DHA is absent in plasma samples prepared from human blood in a conventional manner. However, when these plasma samples were subjected to acidic deproteinization, DHA was detected in the acidified sample solutions. In the present study, we demonstrate that the oxidation of AsA to DHA in the solutions was promoted by at least two mechanisms, one involving catalysis by ferric ion released from transferrin, and the other involving catalysis by plasma hemoglobin. In the acidified transferrin solution by trichloroacetic acid, an oxidation of AsA to DHA proceeded with standing time, whereas the oxidation was not observed in that by metaphosphoric acid. This oxidation appeared to be catalyzed by ferric ion released from transferrin. In contrast, plasma hemoglobin functioned as a catalyst for AsA oxidation in both metaphosphoric acid and trichloroacetic acid solutions. Therefore, DHA content in the trichloroacetic acid-treated plasma sample was markedly higher than that in the metaphosphoric acid-treated one. These results suggest that DHA detected in acidified plasma samples is an artifact resulting from AsA oxidation.

Bicarbonate promotes a cleavage of lactone ring of dehydroascorbate

The half-life of dehydroascorbate (DHA) in human plasma is only a few minutes. This DHA disappearance is caused by a cleavage of lactone ring. Similarly, when DHA was incubated in Dulbecco's modified Eagle's medium (D-MEM), which stood in atmosphere of 5% CO2-95% air, the rapid transformation of DHA into 2,3-diketogulonate (2,3-DKG) is also observed. These observations suggest that both human plasma and D-MEM contain a common component, which promotes the hydrolysis of DHA. In the present study, this component was identified to be bicarbonate which acts as a general base catalyst. Direct evidence for this mechanism was obtained as follows: (1) significant hydrolysis of DHA in the bicarbonate-free D-MEM (pH 7.40) was not observed; (2) hydrolysis of DHA in Tris-HCl buffer at constant pH (7.4) increases with increasing bicarbonate concentration; and (3) significant hydrolysis of DHA in the decarbonated ultrafiltrate of plasma was not observed. These results suggest that DHA hydrolysis may be controlled by the variation of CO2 pressure in circulating blood.

[Activation of skin cells by inorganic compounds]

It has been known that the stimulation of skin cells by physiologically active substances is accompanied by the quantitative and qualitative alterations of the glycosaminoglycans (GAGs) in skin. This phenomenon make it possible to evaluate the activity of test substances for the stimulation of skin cells. The purpose of our study is to elucidate the effectiveness of inorganic compounds for the stimulation of skin cells. (1) The cultured skin cells including keratinocytes and fibroblasts, (2) the cultured model skin constituted of collagen gel, fibroblasts and keratinocytes, and (3) the mouse damaged skin were used in the present study. The results obtained from these studies demonstrate that inorganic substances commonly have a possibility to activate cyclic AMP-dependent protein kinase (A-kinase), and the A-kinase activation results in an increase in GAGs. These findings brought the scientific basis for the effectiveness of the Japanese traditional balneotherapy for damaged skin.

Cyanate causes depletion of ascorbate in organisms

Ascorbate-dehydroascorbate redox cycle plays a key role in protecting organisms from an excess of oxidants. Recently, we found a novel reaction of dehydroascorbate with cyanate under the conditions of neutral pH and ordinary temperature. In this report, we demonstrated that through this irreversible reaction, cyanate causes the depletion of ascorbate in the matrix, where the ascorbate-dehydroascorbate redox cycle revolves. When the leaves of weed (Erigeron canadensis) were soaked in sodium cyanate solution generally used as a herbicide, the depletion of ascorbate as well as dehydroascorbate in them was observed, followed by the change in color from green to brown. These results suggest that a possible way of cyanate toxicity is to inflict oxidative stress on organisms.

Structural differences and the presence of unsubstituted amino groups in heparan sulphates from different tissues and species

This study presents a comparison of heparan sulphate chains isolated from various porcine and bovine tissues. 1H-NMR spectroscopy (500 MHz) was applied for structural and compositional studies on intact heparan sulphate chains. After enzymic digestion of heparan sulphate using heparin lyase I (EC 4.2.2.7) II and III (EC 4.2.2.8), the compositions of unsaturated disaccharides obtained were determined by analytical capillary electrophoresis. Correlations between the N-sulphated glucosamine residues and O-sulphation and between iduronic acid content and total sulphation were discovered using the data obtained by NMR and disaccharide analysis. Heparan sulphate chains could be classified into two groups based on the sulphation degree and the iduronic acid content. Heparan sulphate chains with a high degree of sulphation possessed also a significant number of iduronic acid residues and were isolated exclusively from porcine brain, liver and kidney medulla. The presence and amount of N-unsubstituted glucosamine residues (GlcNp) was established in all of the heparan sulphates examined. The structural context in which this residue occurs was demonstrated to be: high sulphation domain --> 4)-beta-D-GlcAp-(1 --> 4)-alpha-D-GlcNp-(1 --> 4)-beta-D-GlcAp-(1 --> low sulphation domain (where GlcNp is 2-amino-2-deoxyglucopyranose, and GlcAp is glucopyranosyluronic acid), based on the isolation and characterization of a novel, heparin lyase III-derived, GlcNp containing tetrasaccharide and hexasaccharide. The results presented suggest that structural differences may play a role in important biological events controlled by heparan sulphate in different tissues.

Measurement of ascorbate and dehydroascorbate contents in biological fluids

Instabilities of ascorbate and dehydroascorbate throughout sample processing are clearly a significant aspect of quantifying of them. Contents of ascorbate in biological fluids decrease with measurable oxidation occurring within minutes to hours. Similarly, dehydroascorbate disappears with chemical or enzymatic degradation within minutes. The half-life of dehydroascorbate in human heparinized plasma was approximately 2 min. These results indicated that the amount of dehydroascorbate present in sample solutions is a function of both the oxidation of ascorbate and the degradation of dehydroascorbate during the processing of biological fluids. To quantify ascorbate and dehydroascorbate concentrations in biological fluids including circulating blood plasma and urine, we established a high-performance liquid chromatographic method, which requires no pretreatment of sample solutions.

Simultaneous determination of dermatan sulfate and oversulfated dermatan sulfate in plasma by high-performance liquid chromatography with postcolumn fluorescence derivatization

A chemical method for the determination of dermatan sulfate (DS) and oversulfated dermatan sulfate has been developed and applied to the pharmacokinetic study of these polysaccharides in experimental animals. The analytical procedure includes a simple preparation step of administered DS and oversulfated DS from blood plasma, HPLC for the separation and detection of DS and oversulfated DS using an Asahipak NH2P-50 column, fluorometric reaction of the polysaccharides with guanidine in a strong alkaline medium. DS and oversulfated DS were extracted from plasma by treating it with proteinase to remove plasma proteins and recovered with endogenous plasma glycosaminoglycans by ethanol precipitation. Finally, DS and oversulfated DS were analyzed by fluorometric HPLC. The detection limits of DS and oversulfated DS were 10 and 20 ng, respectively. Furthermore, we demonstrated that artificial oversulfation of DS increased its biological half-life after intravenous administration to rats.

Compositional analysis of hyaluronan, chondroitin sulfate and dermatan sulfate: HPLC of disaccharides produced from the glycosaminoglycans by solvolysis

An ion-exchange high-performance liquid chromatography procedure was developed for analysis of mixtures of N-acetyldermosine, N-acetylchondrosine and N-acetylhyalobiuronic acid produced quantitatively by heating dermatan sulfate, chondroitin sulfate and hyaluronan in dimethyl sulfoxide (DMSO) containing 0.1% (v/v) H20 at 80 degrees C for 48 h. These disaccharides were eluted from a TSK gel SAX column using 0.1 M acetic acid containing KCl, and detected fluorometrically by post column derivatization. The eluate was mixed with 2-cyanoacetamide solution and alkaline solution, and heated at 110 degrees C for 4 min. The resultant compounds were detected fluorometrically (Ex. 335 nm and Em. 390 nm). The usefulness and practicality of the present method were verified by applications to the determination of glycosaminoglycans in tissues.

High-performance liquid chromatographic analysis of glycosaminoglycan-derived oligosaccharides

High-performance liquid chromatography of glycosaminoglycan (GAG)-derived oligosaccharides has been employed for the structural analysis and measurement of hyaluronan, chondroitin sulphate, dermatan sulphate, keratan sulphate, heparan sulphate and heparin. Recent developments in the separation and detection of unsaturated disaccharides and oligosaccharides derived from GAGs by enzymatic or chemical degradation are reviewed.

Determination of a depolymerized holothurian glycosaminoglycan in plasma after intravenous administration by postcolumn HPLC

Depolymerized holothurian glycosaminoglycan (DHG) produced artificially from sea cucumber has an anticoagulant and antithrombotic activity. In the present study, we attempted to determine the plasma level of DHG using a chemical procedure. A general method for determination of chondroitin sulfates by forming unsaturated disaccharides with chondroitinase digestion was difficult to apply to DHG, because it was resistant to any chondroitinase digestion. We therefore developed a highly sensitive postcolumn HPLC method for determination of intact DHG. DHG was applied to Asahipak NH2P-50, an amino-bonded column, eluted by alkaline solution and then detected with arginine under a strong alkaline condition as a postcolumn reagent. The limit of detection for DHG was 10 ng. The present method was applicable to the determination of DHG in plasma after intravenous administration.

CD44 can mediate the adhesion of platelets to hyaluronan

CD44 represents a family of glycoproteins that are present on the surfaces of some types of lymphocytes, macrophages, and epithelial cells. In the present study, we have found that CD44 is also present on murine megakaryocytes and peripheral blood platelets as judged by immunohistochemical staining. Western blotting of platelet proteins indicated that this CD44 was predominantly of the 85-kD form. This form of CD44 also had the capacity to bind hyaluronan, because detergent extracts of platelets as well as intact platelets could bind soluble [3H]hyaluronan, and this property was blocked by antibodies directed against CD44. More importantly, isolated platelets could attach to the hyaluronan-containing extracellular matrix produced by cultured rat fibrosarcoma cells. This attachment took place in the absence of divalent cations and could be blocked by pretreating the rat fibrosarcoma cells with hyaluronidase or by the addition of an antibody to CD44. These results suggested that CD44 was responsible for the attachment of platelets to hyaluronan. Histochemical staining also showed that hyaluronan was present immediately beneath the endothelial cells of many blood vessels of various tissues, such as the dermis, lamina propria of the intestinal tract, the lungs, and the pericardium. Thus, it is possible that CD44 plays an important role in the attachment of platelets to the surface of exposed connective tissue after injury to endothelial cells.

Structural diversity of mammalian hepatic dermatan sulfates

Dermatan sulfate-proteoglycans (DS-PGs) were extracted from rabbit, rat and bovine defatted livers by magnesium chloride extraction and DEAE-cellulose chromatography, and then submitted successively to Asahipak GS-520 gel filtration chromatography, Asahipak ES-502N anion exchange chromatography, and cellulose acetate membrane electrophoresis. The disaccharide composition of the glycosaminoglycan chains was determined by differential digestion by chondroitinase ABC, AC, ACII and/or B followed by HPLC for analysis of the resulting unsaturated disaccharides. The hepatic dermatan sulfate chains contained disulfated disaccharide units; Di-diSB and Di-diSE. The hepatic DS-PGs were divided into two groups; Di-diSE-poor DS-PGs and Di-diSE-rich DS-PGs. The iduronic acid content of Di-diSE-poor dermatan sulfate chains was higher than that of Di-diSE-rich ones.

Separation and characterization of dermatan sulfate in normal human urine

Dermatan sulfate excreted in normal human urine was isolated and characterized by TLC and cellulose acetate strip electrophoresis after cetylpyridinium chloride precipitation and pronase digestion. In these separation methods, dermatan sulfate and chondroitin sulfate were extracted and then monitored by sensitive HPLC methods with post column fluorometric derivatization coupled with chondroitinase ABC, ACII and B digestion. From the results, we demonstrated that human urinary dermatan sulfate contains iduronic acid as its major uronic acid (80-90% of total uronic acid), and is composed mainly of repeated mono-sulfated disaccharide units [Di-4S (structure shown in Fig. 1), 89%] and small numbers of di-sulfated disaccharide units (Di-diSB, 7% and Di-diSE, 1%).