Contribution of superoxide to reduced antioxidant activity of glycoxidative serum albumin

Hyperglycemia increases oxidative stress in various tissues and leads to diabetic cardiovascular complication. Dyslipidemia, such as an increase in oxidized low-density lipoprotein (LDL), is well recognized in diabetic patients with hyperglycemia. However, the mechanism by which hyperglycemia causes the increased LDL oxidation remains unclear. Albumin is the most abundant protein in the circulation, and can function as an antioxidant. Therefore, we examined whether glycoxidative modification inhibits the antioxidant activity of albumin to LDL oxidation and clarified the mechanism by which this modification may suppress its antioxidant activity. Human serum albumin (HSA) was incubated in phosphate-buffered saline with and without glucose at 37°C for up to 8 weeks under aerobic conditions (referred to as glycoxidation (goHSA) and oxidation (oHSA), respectively). Metal chelator-treated, nonoxidative HSA (chHSA) and freshly prepared HSA (fHSA) were used as controls. N ^ε-(carboxymethyl)lysine (CML), a glycoxidative product, was determined by enzyme-linked immunosorbent assay. Oxidation was estimated by measuring the thiols of the HSA molecule. Copper-mediated oxidation of LDL was conducted in the presence or absence of modified HSAs at 37°C for 6 days. Malondialdehyde and negative charge of LDL were measured. To clarify the mechanism of reduced antioxidant activity of HSA, we examined firstly the binding activity of modified HSAs to copper, and secondly the effects of free radical scavengers on the formation of malondialdehyde. CML was formed in goHSA in a time- and concentration-dependent manner. Both goHSA and oHSA significantly decreased the contents of free thiol groups compared to ch- and fHSAs. The antioxidant activity of goHSA to LDL oxidation was the lowest among various modified HSAs. The oHSA showed a moderate decrease in antioxidant activity. The binding activity of go- and oHSAs to copper was lower than that of ch- and fHSAs. The formation of MDA from LDL oxidation in the presence of goHSA was completely inhibited by Tiron (1,2-dihydroxy-3,5-benzenedisulfonic acid) and superoxide dismutase. In contrast, catalase and mannitol had no effect. Our results indicate that in vitro glycoxidation of HSA induced a marked loss of antioxidant activity of this molecule to copper-mediated oxidation of LDL, which may be caused by the generation of superoxide. Received: December 17, 2001 / Accepted: June 28, 2002 Acknowledgments The authors thank Drs. Ryoji Nagai and Seikoh Horiuchi (Department of Biochemistry, Kumamoto University School of Medicine, Kumamoto, Japan) and Drs. Hiroyuki Itabe and Tatsuya Takano (Department of Microbiology and Molecular Pathology, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa, Japan) for kindly supplying antibodies. We also thank Associate Professor Takeo Yamaguchi (Department of Chemistry, Faculty of Science, Fukuoka University) for the ESR experiment and Miss Satoko Nagano for her excellent technical assistance. This work was supported by a Grant-in-Aid from the Ministry of Education, Science, Sports and Culture of Japan (No. 14570171) and in part by funds from the Central Research Institute of Fukuoka University (No. 016004). Correspondence to N. Sakata     

Retinyl palmitate reduces hepatic fibrosis in rats induced by dimethylnitrosamine or pig serum

Background/Aims: Lipid peroxidation has been found to be associated with Ito cell activation. Ito cells are the principal collagen-producing cells and the main storage sites of retinoids. However, the relationship between retinoids and hepatic fibrosis is complex. The aim of this study was to elucidate the role of retinoids as a fibrosuppressant: the effects of retinoids on hepatic fibrosis induced in rats by dimethylnitrosamine or pig serum, as well as on rat Ito cells in primary culture, were examined in order to assess the antioxidant activity of retinoids.Methods: Male Wistar rats were given a single injection of 40 mg/kg dimethylnitrosamine or 0.5 ml PS twice weekly for 10 weeks. In each model, rats were treated with retinyl palmitate for 2 weeks before hepatotoxin treatments or for the last 2 weeks of the treatments. The cumulative amount of retinyl palmitate administered in each experiment was 2, 10, or 20×10⁴ IU/rat.Results: Retinyl palmitate treatment before or after administration of dimethylnitrosamine or pig serum suppressed the induction of hepatic fibrosis, restored hepatic retinyl palmitate levels, prevented increases in hepatic levels of collagen and malondialdehyde, a product of lipid peroxidation, and prevented increases in deposition of type III collagen and the number of α-smooth muscle actin (α-SMA) positive-Ito cells in the liver. Retinyl palmitate supplementation resulted in a dose-dependent reduction of α-SMA expression and an oxidative burst in cultured Ito cells. In addition, retinyl palmitate inhibited Fe²⁺/adenosine 5′-diphosphate-induced lipid peroxidation in rat liver mitochondria and showed radical scavenging activity.Conclusions: These findings suggest that retinyl palmitate may suppress the induction of hepatic fibrosis, at least in part, by the inhibition of Ito cell activation through its antioxidant activity.     

Effects of Antioxidants Coenzyme Q10 and Lipoic Acid on Interleukin-1β-Mediated Inhibition of Glucose-Stimulated Insulin Release from Cultured Mouse Pancreatic Islets

During the development of the autoimmune disease, insulin-dependent diabetes mellitus (IDDM) islet cell death is thought to be mediated in part by oxygen and nitrogen free radicals and interleukin 1β (IL-1β), secreted by activated macrophages. Free radicals disrupt the homeostasis of biological systems by damaging major constituent molecules such as lipids, proteins, and DNA. Islet cells are quite susceptible to oxidative damage due to low levels of antioxidant enzymes involved in free radical consumption. If IDDM is associated with an imbalance of oxidative stresses and antioxidant responses in islet cells, then it may be possible to ameliorate disease by supplementating antioxidant defenses. In this study, the antioxidants coenzyme Q10 and lipoic acid were able to block IL-1β-mediated inhibition of glucose-stimulated insulin secretion from islet cells at 10^{? 12} M and 10^{? 9} M, respectively.     

Bottom-up analysis of emergent properties of N-acetylcysteine as an adjuvant therapy for COVID-19

N-acetylcysteine (NAC) is an abundantly available antioxidant with a wide range of antidotal properties currently best studied for its use in treating acetaminophen overdose. It has a robustly established safety profile with easily tolerated side effects and presents the Food and Drug Administration's approval for use in treating acetaminophen overdose patients. It has been proven efficacious in off-label uses, such as in respiratory diseases, heart disease, cancer, human immunodeficiency virus infection, and seasonal influenza. Clinical trials have recently shown that NAC's capacity to replenish glutathione stores may significantly improve coronavirus disease 2019 (COVID-19) outcomes, especially in high risk individuals. Interestingly, individuals with glucose 6-phosphate dehydrogenase deficiency have been shown to experience even greater benefit. The same study has concluded that NAC's ability to mitigate the impact of the cytokine storm and prevent elevation of liver enzymes, C-reactive protein, and ferritin is associated with higher success rates weaning from the ventilator and return to normal function in COVID-19 patients. Considering the background knowledge of biochemistry, current uses of NAC in clinical practice, and newly acquired evidence on its potential efficacy against COVID-19, it is worthwhile to investigate further whether this agent can be used as a treatment or adjuvant for COVID-19.     

酢浆草体外抗炎抗氧化检测方法的建立和优化

目的优化和建立酢浆草体外抗炎抗氧化活性的检测方法。方法建立抗氧化、蛋白酶活性抑制和蛋白变性抑制活性的检测方法。比较醇提水沉法和水提醇沉法、不同保存条件下药物的活性。结果优化检测方法后,不同浓度酢浆草样品的检测结果具有高度相关性,表明检测方法高度稳定且准确可靠。经醇提水沉法和水提醇沉法后,酢浆草的抗氧化活性为100%,蛋白变性抑制活性为90%,酶活性抑制活性为50%,两者出峰位置基本一致。醇提水沉法更易快速获得澄清的提取溶液。室温和4℃冷藏时,蛋白变性抑制成分第3天时均下降40%,第7天时下降至无活性;酶活性抑制成分在冷藏时下降比室温条件慢,在第7天时分别下降30%和60%;抗氧化成分在2种保存条件下均有较高活性。结论所建立的方法可用于体外检测酢浆草的抗炎活性。     

UPLC-QTOF-MS fingerprinting combined with chemometrics to assess the solvent extraction efficiency,phytochemical variation,and antioxidant activities of Beta vulgaris L.

Accurate assays of plant antioxidants and other phytochemicals require efficient extraction conditions and enable rigorous assessments of crop varieties and production systems. This study assessed the extraction of phytochemicals and antioxidants from conventionally or organically grown red and golden beets (Beta vulgaris L.), using twenty solvent (S1–S20) mixtures containing water, methanol, and ethanol alone or with acids (ascorbic, formic, acetic). Red beetroot extracted with methanol with or without acid had the highest betanin content (2791.0 μg/g and 8222.3 μg/g of fresh weight [FW], respectively) and golden beetroot extracted with methanol/ascorbic acid/water had the highest vulgaxanthin I (193.7 μg/g and 15.0 μg/g of FW, respectively). The radical-scavenging activity and total phenolics in beetroot extracts reflected the different extraction efficiency of each solvent. UHPLC-QTOF-MS was used to identify twenty-seven phytochemicals, including 23 betalains, 2 amino acids, and 2 phenolic acids. Chemometric approaches discriminated the beet varieties and different extracts within one variety based on the composition and abundance of the key phytochemicals. The red beetroot extracted with aqueous ethanol with or without acid (S5, S7, S8, S9), and golden beetroot extracted with methanol-containing solvents (S15 for conventionally and S20 for organically) had the highest levels of phytochemicals, suggesting that these conditions efficiently extract key phytochemicals.     

Sennoside A drug capped biogenic fabrication of silver nanoparticles and their antibacterial and antifungal activities

Sennoside A (dianthrone glycoside) shows laxative properties and used as a folk traditional medicine. Sennoside A capped silver nanoparticles (Ag/sennoside A) were synthesized at room temperature for the first time by using sennoside A as reducing and capping agent. UV–visible spectroscopic data reveals that the absorption peaks of pure sennoside A was appeared at 266, and 340 nm, which red shifted to 304, and 354 nm at higher sennoside A concentration. Upon addition of the Ag⁺ ions, an additional peak also observed at 398 nm, indicating the formation of spherical sennoside A capped silver nanoparticles (Ag/sennoside A). Cetyltrimethylammonium bromide (CTAB) was used a stabilizing agent to determine the role of cationic micelles on the nucleation and growth processes of Ag/sennoside A NPs formation. The 2,2-diphenyl-1-picrylhydrazyl nitrogen radical (DPPH^·), two bacteria strains (Staphylococcus aureus and Escherichia coli) and two yeast strains (Candida albicans ATCC 10231 and Candida parapsilosis ATCC 22019) were used to determine the antioxidant and antimicrobial properties of Ag/sennoside A NPs. In addition, Rhein-9-anthrone (4,5-dihydroxy-10-oxo-9H-anthracene-2-carboxylate) was isolated from the acidic hydrolysis of glycoside linkage of sennoside A and characterized. The antioxidant and antimicrobial activities of rhein-9-anthrone were also determined against DPPH radical, antibacterial and antifungal strains. The minimum inhibitory concentration was determined and discussed.     

Antioxidative effects of cysteamine,hyaluronan and fetuin on post‐thaw semen quality,DNA integrity and oxidative stress parameters in the Brown Swiss bull

The aim of this study was to compare the effectiveness of antioxidants including cysteamine (2.5, 7.5 mm ), hyaluronan (0.25, 1 mg ml^?1) and fetuin (5, 10 mg ml^?1) in the freezing of Brown Swiss bull semen. The best percentages of CASA motilities were achieved with 10 mg ml^?1 of fetuin and 2.5 mm of cysteamine. For sperm morphology, 10 mg ml^?1 of fetuin and 2.5 mm of cysteamine had better protective effects (P < 0.001). The results of hypo‐osmotic swelling test showed that the percentage values of membrane integrity in all the groups, excluding that supplemented with 5 mg ml^?1 of fetuin, were higher than those of the control group (P < 0.001). Results obtained for the DNA damage of sperm cells demonstrated that 0.25 mg ml^?1 of hyaluronan, and 2.5 and 7.5 mm of cysteamine led to lower rates of spermatozoa with damaged DNA, compared with the control group (P < 0.001). The maintenance of superoxide dismutase and glutathione peroxidase antioxidant activities following freeze‐thawing with 2.5 and 7.5 mm of cysteamine and 10 mg ml^?1 of fetuin was demonstrated to be at a higher level in comparison with the control group (P < 0.001). Malondialdehyde formation was found to be lower in the groups supplemented with 0.25 mg ml^?1 of hyaluronan and 7.5 mm of cysteamine after the freeze‐thawing process (P < 0.001).