Τετάρτη, 1 Μαΐου 2019

Aminoacids

Clinical significance of LOXL4 expression and features of LOXL4-associated protein–protein interaction network in esophageal squamous cell carcinoma

Abstract

Lysyl oxidase-like 4 (LOXL4), a member of the LOX family proteins, catalyzes oxidative deamination of lysine residues in collagen and elastin, which are responsible for maintaining extracellular matrix homeostasis. In this study, the mRNA expression of LOXL4 in seven esophageal squamous cell carcinoma (ESCC) cell lines and 15 ESCC pairs of clinical samples were examined. Furthermore, LOXL4 protein levels in the ESCC cell lines were determined using western blotting. With the use of immunofluorescence, LOXL4 was observed to be localized primarily in the cytoplasm, but was also present in the nucleus. In addition, the results indicated that the upregulated expression of LOXL4 was associated with poor survival in patients with ESCC even following curative resection (P = 0.010). Similar Kaplan–Meier estimator curves for proteins that interact with LOXL4, SUV39H1 (P = 0.014) and COL2A1 (P = 0.011), were plotted. The analyses based on the protein–protein interaction network depicted the expression of LOXL4 and its associated proteins as well as their functions, suggesting that LOXL4 and its associated proteins may serve a significant role in the development and progression of ESCC. In conclusion, the results of the present study suggest that LOXL4 is a potential biomarker for patients with ESCC, as well as SUV39H1 and COL2A1, and high expression levels of these genes are associated with poor prognosis in patients with ESCC.



Silver cluster–amino acid interactions: a quantum-chemical study

Abstract

Binding of silver ion (Ag+) and two atomic neutral silver cluster (Ag2) with a set of amino acids has been studied using Density Functional Theory (DFT) and ab initio MP2 method. We show that binding energy with Ag2 is higher for deprotonated anionic amino acids. Cysteine, aspartic acid, and tyrosine with deprotonated side chain exhibit the highest binding energy (Gbind) values among all the amino acids: − 30.1 kcal mol−1, − 30.7 kcal mol−1, and − 30.9 kcal mol−1, respectively. Binding energies of deprotonated cysteine, glutamic acid, tyrosine, and aspartic acid with silver ion Ag+ are reported here for the first time. Natural bond orbital (NBO) analysis has also been performed to calculate charge transfer, natural populations, occupancies, and Wiberg bond indices of the amino acid–Ag2 complexes. Atoms-in-molecules (AIM) theory was used to establish the nature of interactions. It was shown that, in most cases, the bonds between amino acid and Ag2 cluster are partially electrostatic and partially covalent.



Elevated circulating asymmetric dimethylarginine levels in rheumatoid arthritis: a systematic review and meta-analysis

Abstract

Rheumatoid arthritis (RA) patients have increased risk of cardiovascular disease (CVD) death. Elevated asymmetric dimethylarginine (ADMA) levels have been reported to be an independent predictor of CVD morbidity and mortality, however, the role of ADMA in RA remains undetermined. To derive a more accurate estimation on circulating ADMA levels in RA patients, a meta-analysis was performed. Embase, PubMed, and The Cochrane Library database (up to October 7 2018) were used to acquire published literatures. Heterogeneity test was performed by the Q statistic and quantified using I2. Publication bias was evaluated using a funnel plot and Egger's linear regression test. A total of 174 articles were identified, 16 studies with 1365 subjects (666 RA patients and 699 healthy individuals) were ultimately included. Plasma/serum ADMA levels appeared to be higher in RA patients than healthy controls (SMD = 0.84, 95% CI 0.32, 1.35). By assessing the BMI, age, disease duration and disease activity as subgroups, BMI ≥ 24 and BMI < 24 groups both showed elevated ADMA levels than controls, disease duration ≥ 8, age < 50 and disease activity ≥ 3.2 and < 5.1 group had a higher ADMA level than control groups. However, disease duration < 8, disease activity ≥ 5.1 and age ≥ 50 groups showed no difference between two groups. Circulating ADMA levels are higher in RA patients compared with healthy controls. In addition, ADMA levels are influenced by age, disease duration and disease activity.



Maternal l -proline supplementation during gestation alters amino acid and polyamine metabolism in the first generation female offspring of C57BL/6J mice

Abstract

We recently reported that dietary supplementation with l-proline (proline) during gestation improved embryonic survival in C57BL/6J mice. The objective of the present study was to test the hypothesis that the effect of maternal proline supplementation on embryonic survival can be carried forward to the first generation female offspring. In the F0 generation, pregnant dams were fed a purified diet supplemented with 0 (control) or 5 g proline/kg diet. The F1 female adult offsprings were bred to fertile males. Fetal survival at embryonic day (E)12.5 and reproductive outcomes at term birth were recorded. The concentrations of amino acids, ammonia, and urea in plasma and amniotic fluid, as well as concentrations of polyamines in placental tissues and amniotic fluid at E12.5 were determined. Results showed that the F1 generation female offspring from proline-supplemented dams had higher (P < 0.05) concentrations of glutamate and taurine in plasma; of putrescine and spermidine in placental tissues; and of glycine, taurine, and spermidine in amniotic fluid at E12.5, as compared with F1 generation female offsprings from dams without proline supplementation. Concentration of proline in the plasma of offspring mice from proline-supplemented dams were lower (P < 0.05), as compared with the control group. No differences in fetal survival, reproductive outcomes, or concentrations of ammonia and urea in plasma and amniotic fluid were observed between the two groups of F1 female offspring. Collectively, our results indicate that the benefits of maternal proline supplementation during gestation on improving embryonic survival and fetal growth in F0 females are not transmitted to their F1 generation females.



Comparative stability of ficin and papain in acidic conditions and the presence of ethanol

Abstract

Proteolytic enzymes are used for proteolysis and peptide synthesis which can be run in various conditions including low pH value and the presence of ethanol. The most common cysteine protease applied in acidic–alcoholic conditions is well-characterized papain. Ficin, which is closely related to papain in terms of proteolytic activity and substrate specificity, could potentially be applied in the alcoholic beverage industry and peptide synthesis. The aim of this study was to compare papain and ficin stability in process conditions. Comparative stability study showed that ficin as a mixture of different isoforms has a broader range of stability in respect of pH and cold storage stability, in comparison to papain. It retains about 70% of initial activity after 3-week cold storage at low pH and in the presence of ethanol. Unlike ficin, papain loses about 70% of initial activity in the same incubation period as it is more prone to non-native aggregation that was confirmed by FTIR analysis. The presence of multiple isoforms of ficin stabilizes the protease against cold denaturation and aggregation, making it more suitable for biotechnological and laboratory usage than single papain isoform. It is more cold-stable in alcoholic–acidic and acidic conditions suggesting possible replacement of papain with even lower enzyme concentration.



Computational characterization of structural and functional roles of DREB1A , DREB1B and DREB1C in enhancing cold tolerance in rice plant

Abstract

Rice serves as the major food for almost half of the world population. Because of its origin in the tropical and subtropical area, rice is more sensitive towards cold stress. Three homologs of DREB1, namely DREB1A, DREB1B and DREB1C are induced Queryduring cold stress and after binding with GCC-box in the promoter region of the target gene, they enhance cold tolerance in rice plants. Though the majority of DREBs bind GCC-box, the degree of activation varies among DREBs. The protein encoded via these three transcription factors contains a common domain, namely AP2/ERF. In silico method was utilised to predict 3D structure of each AP2/ERF domain. The molecular dynamic analysis suggests, under the normal environmental condition, in each AP2/ERF domain, a positive correlation exists between β-strands and the movement of C-α is constrained. However, during cold stress, when AP2/ERF domain binds with GCC-box present in the promoter region of the target gene, mean pressure of each three AP2/ERF domain gets lowered and final potential energy increases. A positive correlation between β-strands gets disrupted and C-α experiences random movement suggesting enhanced activity of DREB1A, DREB1B and DREB1C during cold stress and enhancement of cold tolerance in plants. Further, MM/PBSA calculations for protein–DNA affinities reveal that, due to lack of α2 in DREB1C, the binding affinity of GCC-box with AP2/ERF domain of DREB1A > DREB1B > DREB1C. Thus, due to a better binding affinity with GCC-box, DREB1A and DREB1B can be utilised in near future for increasing cold tolerance of rice plant and increasing yield.



The additive effect of type 2 diabetes on fibrinogen, von Willebrand factor, tryptophan and threonine in people living with HIV

Abstract

Chronic immune activation and ensuing inflammation that accompany HIV infection lead to adverse metabolic consequences and an increased risk of type 2 diabetes (T2D). We examined the additive effects of T2D on circulating biomarkers involved in inflammation, coagulation, and vascular function along with plasma amino acids in people living with HIV (PLWH). This cross-sectional study included PLWH with and without T2D (n = 32 total). Analyses involved a multiplex platform for circulating biomarkers and gas chromatography–vacuum ultraviolet spectroscopy for plasma amino acids. In PLWH and T2D, both fibrinogen (2.0 ± 0.6 vs 1.6 ± 0.4 µg/mL, p = 0.02) and von Willebrand factor (vWF) (40.8 ± 17.2 vs 26.7 ± 13.8 µg/mL, p = 0.02) were increased and tryptophan (47 ± 6 vs 53 ± 8 nmol/mL, p = 0.03) and threonine (102 ± 25 vs 125 ± 33 nmol/mL, p = 0.03) were decreased. Fibrinogen, as a biomarker of inflammation, and vWF, as a biomarker of endothelial dysfunction, are augmented by the combined effects of HIV and T2D and may contribute to the pathogenesis of T2D in PLWH. Chronic immune activation and inflammation compromise the integrity of the intestinal mucosa, which increases mucus production. Tryptophan metabolism is altered by a loss of intestinal membrane integrity and threonine is consumed in the production of mucus. Metabolic competition arising from increased protein synthesis in the setting of chronic inflammation along with the associated loss in intestinal membrane integrity may be a primary mechanism in the pathogenesis of T2D in PLWH and requires further investigation.



A novel comprehensive paradigm for the etiopathogenesis of multiple sclerosis: therapeutic approaches and future perspectives on its treatment

Abstract

It is well recognized that variation in the geographical distribution of prevalence of multiple sclerosis (MS) exists: increasing the latitude its prevalence increases as well, but the underlying causes of such dissimilarity still remained elusive as of today. Currently, the most accredited hypothesis is that the closer to the equator the more pronounced is the amount of sunlight which, in turn, increases the production of vitamin D. Cholecalciferol is indeed deficient in MS patients, but this factor does not explain by itself the etiopathogenesis of the disease. In the present study, to search for a pattern and provide a model of the disease's etiology consistent with this regional factor, as well with its changing ethnic, sex-ratio, lifestyle variations and the other unexplained aspects of MS, an extensive analysis of peer-reviewed literature and data was conducted. The arisen hypothesis was that, increasing the latitude, the factor that varies and can have the stronger effect on the human organism, is the continuous and ever-increasing diversity of the natural light–dark cycle. The consequent effort of the suprachiasmatic nucleus to entrain the organism's circadian rhythm affects the hypothalamic–pituitary–adrenal axis resulting in desynchronizing the central and peripheral circadian clocks and pathologizing the immunitary system. To verify such hypothesis, a theoretical framework of the etiopathogenesis, coherent with the gathered literature, was conceived and a demonstration to corroborate it was eventually devised and performed. The results underscored that people living in countries subjected to a further circadian disruptive factor, as daylight saving time, have a 6.35 times higher prevalence of MS than States placed on their same latitude that do not observe it, thus strongly supporting the hypothesis. As further reinforcement of the conclusions, it is worth mentioning that the levels of polyamines rise abruptly in autoimmune diseases. Moreover, among their numerous roles, these polycations participate to the regulation of the circadian clock so their sudden variation might disrupt it. Following these interesting findings, new perspectives in therapies are, therefore, proposed.



Carnosine's inhibitory effect on glioblastoma cell growth is independent of its cleavage

Abstract

The naturally occurring dipeptide carnosine (β-alanyl-l-histidine) inhibits the growth of tumor cells. As its component l-histidine mimics the effect, we investigated whether cleavage of carnosine is required for its antineoplastic effect. Using ten glioblastoma cell lines and cell cultures derived from 21 patients suffering from this malignant brain tumor, we determined cell viability under the influence of carnosine and l-histidine. Moreover, we determined expression of carnosinases, the intracellular release of l-histidine from carnosine, and whether inhibition of carnosine cleavage attenuates carnosine's antineoplastic effect. We observed a significantly higher response of the cells to l-histidine than to carnosine with regard to cell viability in all cultures. In addition, we detected protein and mRNA expression of carnosinases and a low but significant release of l-histidine in cells incubated in the presence of 50 mM carnosine (p < 0.05), which did not correlate with carnosine's effect on viability. Furthermore, the carnosinase 2 inhibitor bestatin did not attenuate carnosine's effect on viability. Interestingly, we measured a ~ 40-fold higher intracellular abundance of l-histidine in the presence of 25 mM extracellular l-histidine compared to the amount of l-histidine in the presence of 50 mM carnosine, both resulting in a comparable decrease in viability. In addition, we also examined the expression of pyruvate dehydrogenase kinase 4 mRNA, which was comparably influenced by l-histidine and carnosine, but did not correlate with effects on viability. In conclusion, we demonstrate that the antineoplastic effect of carnosine is independent of its cleavage.



Comparison between the effects of selenomethionine and S -adenosylmethionine in preventing cholestasis-induced rat liver damage

Abstract

We aimed to evaluate whether two methionine-related compounds, S-adenosylmethionine (SAM), and selenomethionine (SM), could lessen liver damage induced by regurgitated bile in a model of rat bile duct ligation (BDL). Hepatoprotective potentials of S-adenosylmethionine and selenomethionine were estimated based on the changes of serum liver damage parameters (aminotransferases, alkaline phosphatase, gamma-glutamyltranspeptidase and lactate dehydrogenase activity, and bilirubin concentration), tissue oxidative [xanthine oxidase (XO) and catalase activity, thiobarbituric acid reactive substances (TBARS) levels] and inflammatory [tumor necrosis factor-alfa (TNF-α) concentration] parameters, and morphological liver tissue alterations that follow cholestasis. The treatment regimens proved themselves able to prevent significant liver damage induced by cholestasis. Both SAM and SM decreased XO activity and TBARS levels and increased catalase activity, while only SM significantly reduced TNF-α concentration. Morphological changes related to bile-induced liver damage were also found to be partially diminished by SAM and SM. In view of the mechanisms of action of the two tested methionine-derived compounds, one might say that SM predominantly acted as an antioxidant, while SAM exerted its activity by potentially modulating different gene expression and protein structures. It is also worth mentioning that this is the first study (to the best of our knowledge) that dealt with the effects of SM on BDL-induced liver injury in rats and of the findings that speak favorably of this powerful antioxidant.



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