Novel heme-binding component in the serum of the channel catfish (Ictalurus punctatus)

The serum of the channel catfish (Ictalurus punctatus) was examined for heme- and hemoglobin-binding proteins. Electrophoretic mobility retardation assays failed to detect a hemoglobin-binding material similar to mammalian haptoglobin; however, a heme-binding component (not previously described) was identified in catfish seru. The heme-binding component was purified by gel filtration chromatography; electrophoretic analyses suggested it to be composed of two polypeptide subunits of molecular masses about 115 and 98 kDa. This composition is inconsistent with hemopexin, the known heme-binding serum protein of mammals. Although it was not fully saturated with heme, the catfish component contained detectable heme in normal sera. When complexed by the binding material, heme was used as an iron source by isolates of the bacterial Gram-negative genusAeromonas; the capacity of other bacteria to use the complex was not tested. The physiological function of the catfish heme-binding serum protein is presently not clear.     

触珠蛋白研究进展

触珠蛋白是一种酸性糖蛋白,属急性期反应蛋白之一,由于所含轻链类型的不同,触珠蛋白具有遗传多态性,触珠蛋白的合成和降解主要在肝脏进行,并受细胞因子、前列腺素、激素等的调节,触珠蛋白具有广泛的生物学功能,可能是一种重要的调节蛋白.     

Quantitative analysis of site-specific N-glycans on sera haptoglobin βchain in liver diseases

The site-specific characterization of N-glycans in glycopro- teins with the potential of clinical application is important. In our previous report, the overall N-glycans of sera haptoglobin （Hp） β chain were found to be different in liver diseases. Hp β chain contains four potential sites of N-glycosylation. In this study, we investigated the potential change of N-glycans on Hp β chain in a site-specific fashion. Sera Hp β chain in healthy individuals as well as patients with hepatitis B virus （HBV）, liver cirrhosis （LC） and hepatocellular carcinoma （HCC） were purified, digested and subjected to liquid chromatography-electro- spray ionization-higher energy collision dissociation mass spectrometry, which allowed identification and structure determination of the glycopeptide, as well as the relative quantification of glycans present on each glycopeptide. The quantitative results revealed that the sialylation of NLFLN207HSEN211 ATAK and the fucosylated structure at all glycopeptides increased significantly in LC and HCC patients compared with those in HBV patients and healthy individuals. A set of different N-glycan patterns of Hp β chain in various liver diseases has been determined. Thus, the sialylated and fucosylated glycoforms of Hp β chain might be related to early hepatocarcinogenesis and also might be useful as novel differential markers for LC and HCC patients.     

Haptoglobin glycoforms in a case of carbohydrate-deficient glycoprotein syndrome

Alterations in haptoglobin (Hp) glycosylation were examined in the plasma of the first patient with carbohydrate-deficient glycoprotein syndrome (CDGS) who was described in Poland. Hp concentration in the CDGS patient plasma was low (240mg/l) and the Hp phenotype was shown to be 2-2. Three glycoforms of the Hp subunit were observed in SDS-PAGE in CDGS. The densitometric analysis and molecular weight determinations suggested that 50% of glycoforms were fully glycosylated; 30% contained three out of four and 20% only two out of four glycan units compared to those that are present in Hp derived from healthy people. Results with lectins (concanavalin A and Sambucus nigra, Maackia amurensis and Alleuria aurantia agglutinins) indicate that all three glycoforms of subunit of CDGS-Hp contained biantennary complex glycans terminated with 2,6 bound sialic acid, but without fucose or 2,3 linked sialic acid. Hp glycosylation abnormalities described in this work suggest that this case was a type I carbohydrate-deficient glycoprotein syndrome.     

Status and metabolism of iron in elite sportsmen during a period of professional competition

The aim of this study was to determine the effect of both acute exercise and maintained training during a period of competition (3 mo, at the start of the season) on iron metabolism in sportsmen on a professional volleyball team. Twelve sportsmen volunteered for this study. The exercise test was performed on a mechanically braked Monark cycle ergometer and consisted of a triangular progressive test. Three blood samples were obtained in each test: at rest, just after exercise, and after recovery. The following hematological parameters were determined: red blood count (RBC), hemoglobin (Hb) and hematocrit (Hto), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), total proteins (TP), serum iron (Fe) and total iron-binding capacity (TIBC), ferritin (FER), transferrin (TRF), haptoglobin (HPT), and serum cortisol (COR) concentrations. We have found changes in hematological and biochemical variables related to Fe metabolism during the study. The changes observed could be the result of hemoconcentration processes after exercise and, at least in part, to physical stress and muscular damage. We conclude that athletes, after a period of adaptation, with a good plan of work/recovery series, undergo a biological redistribution on hematological and biochemical parameters concerning Fe metabolism during the training and competition period. Also, daily Fe supplementation could restore and mask the true repercussions of maintained training observed in other sports.     

Reproducible and sensitive determination of charged oligosaccharides from haptoglobin by PNGase F digestion and HPAEC/PAD analysis: glycan composition varies with disease

Many studies have reported changes in the carbohydrate structure of serum glycoproteins in disease, but this information is often of limited value for understanding disease mechanisms because it is obtained with simple and/or indirect methodologies that determine only one structural feature. On the other hand, more detailed carbohydrate methodologies are time-consuming and require a lot of purified material. Using haptoglobin (Hp) as a model protein, a new procedure was devised that determined the oligosaccharide composition of very small amounts of Hp in a relatively short time. The Hp was purified by batch affinity-chromatography, oligosaccharides were removed with PNGase F, and the oligosaccharide composition of charged species was determined using HPAEC/PAD (Dionex carbohydrate analyser). The method was applied to the analysis of Hp from eight healthy individuals and 37 patients with different inflammatory diseases or cancers. Twenty-seven oligosaccharides were consistently detected, but the majority could not be identified. However, by calculating retention times relative to the sialylated biantennary peak (Neu5Ac2-3/6Gal1-4GlcNAc1-2Man1-6(Neu5Ac2-3/6 Gal1-4GlcNAc1-2Man1-3)Man1-4GlcNAc1-4GlcNAc) it was possible to compare profiles quantitatively. Although no peak was identified as disease-specific, characteristic and reproducible profiles were obtained. Particularly striking were reductions in the major peaks in Crohn's disease, rheumatoid arthritis, stomach cancer, accompanied by increases in unidentified peaks. Previous studies suggested that many of the unknown peaks were due to increased sialylation and fucosylation. Only small changes in patterns were observed for breast and ovarian cancer. The new procedure will be very useful in the characterization of oligosaccharide composition of glycoproteins in clinical specimens.     

Multiple immunoreactive forms of calcitonin in human plasma

Purified rabbit serum haptoglobin was partially characterized, and it was found that the hemoglobin-binding property and subunit structure were similar to those of human type 1-1, swine, canine, and equine haptoglobins. However, rabbit haptoglobin was dissociated into subunits and few intermediates only in the presence of urea or sodium dodecyl sulfate without reduction. Thus the absence of interchain disulfide bonds in rabbit haptoglobin is unique among many animal haptoglobins.     

The enzyme lecithin‐cholesterol acyltransferase esterifies cerebrosterol and limits the toxic effect of this oxysterol on SH‐SY5Y cells

Cholesterol is mostly removed from the CNS by its conversion to cerebrosterol (24(S)‐hydroxycholesterol, 24(S)OH‐C), which is transported to the circulation for bile formation in liver. A neurotoxic role of this oxysterol was previously demonstrated in cell culture. Here, we provide evidence that the enzyme lecithin‐cholesterol acyltransferase, long known to esterify cholesterol, also produces monoesters of 24(S)OH‐C. Proteoliposomes containing apolipoprotein A‐I or apolipoprotein E were used to stimulate the enzyme activity and entrap the formed esters. Proteoliposomes with apolipoprotein A‐I were found to be more active than those with apolipoprotein E in stimulating the production of oxysteryl esters. Cholesterol and 24(S)OH‐C were found to compete for enzyme activity. High levels of haptoglobin, as those circulating during the acute inflammatory phase, inhibited 24(S)OH‐C esterification. When highly neurotoxic 24(S)OH‐C was treated with enzyme and proteoliposomes before incubation with differentiated SH‐SY5Y cells, the neuron survival improved. The esters of 24(S)OH‐C, embedded into proteoliposomes by the enzyme and isolated from unesterified 24(S)OH‐C by gel filtration chromatography, did not enter the neurons in culture. These results suggest that the enzyme, in the presence of the apolipoproteins, converts 24(S)OH‐C into esters restricted to the extracellular environment, thus preventing or limiting oxysterol‐induced neurotoxic injuries to neurons in culture.

     

Vitamin E in the prevention of cardiovascular disease: the importance of proper patient selection

Vitamin E is a naturally occurring fat-soluble antioxidant which has been proposed as a treatment for both primary and secondary protection against cardiovascular (CV) events. Promising data from observational epidemiological studies associating higher vitamin E dietary intake with lower risk of CV events have not been validated in randomized controlled clinical trials assessing the effect of vitamin E on CV outcomes. While the pendulum of medical opinion has swung to suggest that high dose vitamin E supplements have no place in the treatment and prevention of CV disease, new data is emerging that allows identification of a specific target population for this treatment, namely patients with diabetes mellitus and the haptoglobin genotype 2-2. This review details the scientific basis and clinical evidence related to the effect of vitamin E on CV outcomes, and the importance of proper patient selection in gaining therapeutic benefit from this intervention.