Ginger (Zingiber officinale) phytochemicals-gingerenone-A and shogaol inhibit SaHPPK: molecular docking, molecular dynamics simulations and in vitro approaches.

BACKGROUND: Antibiotic resistance is a defense mechanism, harbored by pathogens to survive under unfavorable conditions. Among several antibiotic resistant microbial consortium, Staphylococcus aureus is one of the most havoc microorganisms. Staphylococcus aureus encodes a unique enzyme 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (SaHPPK), against which, none of existing antibiotics have been reported. METHODS: Computational approaches have been instrumental in designing and discovering new drugs for several diseases. The present study highlights the impact of ginger phytochemicals on Staphylococcus aureus SaHPPK. Herein, we have retrieved eight ginger phytochemicals from published literature and investigated their inhibitory interactions with SaHPPK. To authenticate our work, the investigation proceeds considering the known antibiotics alongside the phytochemicals. Molecular docking was performed employing GOLD and CDOCKER. The compounds with the highest dock score from both the docking programmes were tested for their inhibitory capability in vitro. The binding conformations that were seated within the binding pocket showing strong interactions with the active sites residues rendered by highest dock score were forwarded towards the molecular dynamic (MD) simulation analysis. RESULTS: Based on molecular dock scores, molecular interaction with catalytic active residues and MD simulations studies, two ginger phytochemicals, gingerenone-A and shogaol have been proposed as candidate inhibitors against Staphylococcus aureus. They have demonstrated higher dock scores than the known antibiotics and have represented interactions with the key residues within the active site. Furthermore, these compounds have rendered considerable inhibitory activity when tested in vitro. Additionally, their superiority was corroborated by stable MD results conducted for 100 ns employing GROMACS package. CONCLUSIONS: Finally, we suggest that gingerenone-A and shogaol may either be potential SaHPPK inhibitors or can be used as fundamental platforms for novel SaHPPK inhibitor development.

Inactivation of urease by catechol: Kinetics and structure.

Urease is a Ni(II)-containing enzyme that catalyzes the hydrolysis of urea to yield ammonia and carbamate at a rate 1015 times higher than the uncatalyzed reaction. Urease is a virulence factor of several human pathogens, in addition to decreasing the efficiency of soil organic nitrogen fertilization. Therefore, efficient urease inhibitors are actively sought. In this study, we describe a molecular characterization of the interaction between urease from Sporosarcina pasteurii (SPU) and Canavalia ensiformis (jack bean, JBU) with catechol, a model polyphenol. In particular, catechol irreversibly inactivates both SPU and JBU with a complex radical-based autocatalytic multistep mechanism. The crystal structure of the SPU-catechol complex, determined at 1.50Å resolution, reveals the structural details of the enzyme inhibition.

[Antagonism mechanism of gingerols against inflammatory effect of toxic raphides from Pinella pedatisecta].

This study was to investigate the mechanism of gingerols antagonizing the inflammatory effect of toxic raphides from Pinella pedatisecta. Mice peritonitis models induced by toxic raphides from P. pedatisecta were applied to observe the effect of gingerols on inflammatory mediators PGE2 in the exudates of abdominal inflammation in mice; rats peritoneal macrophage in vitro culture models were adopted to study the anti-inflammatory effects of gingerol against toxic raphides, with TNF-α and IL-1ß in supernatant as indexes. Scanning electron microscopy was used to observe the changes in surface morphology of macrophages treated by raphides and gingerols. Macrophages-neutrophils co-cultured models were used to study the antagonism of gingerols against the effect of toxic raphides' stimulation on neutrophils migration. Results showed that gingerols could significantly inhibit the production of PGE2 in the exudates of abdominal inflammation induced by toxic raphides from P. pedatisecta in mice. Gingerols could significantly inhibit the toxic raphides from P. pedatisecta to induce the release of inflammatory factors, with certain dose dependence. Scanning electron microscopy showed that gingerols could significantly inhibit phagocytosis of macrophages, cytomembrane injury, and neutrophils migration induced by toxic raphides from P. pedatisecta. The results showed that the antagonism mechanism of gingerols against the toxic raphides from P. pedatisecta may be associated with inhibiting the pro-inflammatory toxicity including macrophage activation, inflammatory factors release, and neutrophils migration.

Uncaria tomentosa extracts protect human erythrocyte catalase against damage induced by 2,4-D-Na and its metabolites.

The effect of ethanolic and aqueous extracts from leaves and bark of Uncaria tomentosa was studied, with particular attention to catalase activity (CAT - EC. 1.11.1.6). We observed that all tested extracts, at a concentration of 250 µg/mL were not toxic to erythrocyte catalase because they did not decreased its activity. Additionally, we investigated the protective effect of extracts on changes in CAT activity in the erythrocytes incubated with sodium salt of 2,4-dichlorophenoxyacetic acid (2,4-D-Na) and its metabolites i.e., 2,4-dichlorophenol (2,4-DCP) and catechol. Previous investigations showed that these chemicals decreased activity of erythrocyte catalase (Bukowska et al., 2000; Bukowska and Kowalska, 2004). The erythrocytes were divided into two portions. The first portion was incubated for 1 and 5h at 37°C with 2,4-D-Na, 2,4-DCP and catechol, and second portion was preincubated with extracts for 10 min and then incubated with xenobiotics for 1 and 5h. CAT activity was measured in the first and second portion of the erythrocytes. We found a protective effect of the extracts from U. tomentosa on the activity of catalase incubated with xenobiotics studied. Probably, phenolic compounds contained in U. tomentosa scavenged free radicals, and therefore protected active center (containing -SH groups) of catalase.

Catechol-O-methyltransferase in complex with substituted 3'-deoxyribose bisubstrate inhibitors.

The biological activity of catechol neurotransmitters such as dopamine in the synapse is modulated by transporters and enzymes. Catechol-O-methyltransferase (COMT; EC 2.1.1.6) inactivates neurotransmitters by catalyzing the transfer of a methyl group from S-adenosylmethionine to catechols in the presence of Mg²âº. This pathway also inactivates L-DOPA, the standard therapeutic for Parkinson's disease. Depletion of catechol neurotransmitters in the prefrontal cortex has been linked to schizophrenia. The inhibition of COMT therefore promises improvements in the treatment of these diseases. The concept of bisubstrate inhibitors for COMT has been described previously. Here, ribose-modified bisubstrate inhibitors were studied. Three high-resolution crystal structures of COMT in complex with novel ribose-modified bisubstrate inhibitors confirmed the predicted binding mode but displayed subtle alterations at the ribose-binding site. The high affinity of the inhibitors can be convincingly rationalized from the structures, which document the possibility of removing and/or replacing the ribose 3'-hydroxyl group and provide a framework for further inhibitor design.

[Prognostic value of circulating catestatin levels for in-hospital heart failure in patients with acute myocardial infarction].

OBJECTIVE: To determine whether circulating level of catestatin (CST) could provide prognostic information independently of conventional risk markers for the development of in-hospital heart failure in patients with ST-segment elevation myocardial infarction (STEMI). METHODS: The data of 120 STEMI patients (mean age: 61 years, 73% male) were collected from the Second Hospital of Shanxi Medical University and Taiyuan Central Hospital between November 2010 and September 2011.The patients were categorized into 4 groups according to CST (ng/L) quartile: ≤ 74.72, 74.73-79.67, 79.68 - 84.21 and ≥ 84.22 ng/L. Clinical features, therapeutic approaches were compared among groups. The patients were also grouped according to Killip class: Killip level I (n = 68), Killip level II (n = 23), Killip level III (n = 18), Killip level IV (n = 11). CST, NE and NT-proBNP were compared among groups. The Spearma rank correlation and multivariate logistic regression analysis were applied to determine the association between risk factors and in-hospital heart failure. Receiver-operator characteristic (ROC) curve was performed to evaluate the power of CST and NT-proBNP on predicting in-hospital heart failure. RESULTS: Gender, hospital days, past history of smoking, hypertension, myocardial infarction, CK-MB peak level, TnI peak level, heart rate, blood pressure, blood glucose, blood lipid levels on admission and early reperfusion therapy were similar among groups. Patients with higher CST values were more likely to be older, to have lower body mass index, to have higher white blood cell count, CysC, hs-CRP, NE, NT-proBNP, past history of angina, diabetes mellitus, being diuretic users, and to have a lower ejection fraction (all P < 0.05). Higher CST levels were also associated with increased risk of heart failure (P < 0.05). In proportion with the deterioration of the cardiac function, CST, NE, NT-proBNP concentration gradually increased (all P < 0.05). Spearman rank correlation analysis showed that the CST was negatively correlated with LVEF (r(s) = -0.923, P < 0.001) and positively correlated with NT-proBNP (r(s) = 0.884, P < 0.001). After multivariate adjustment, CST remained to be an independent risk factor for the development of in-hospital heart failure (OR = 1.125, 95%CI: 1.056 - 1.198;P < 0.001). The area under the ROC curve of CST and NT-proBNP was 0.777 and 0.874. Using CST = 77.29 ng/L as a cut-off value, the sensitivity was 92.8% and specificity was 70.6% for predicting the development of in-hospital heart failure. CONCLUSION: The plasma CST level is an independent predictor for the development of in-hospital heart failure in patients with STEMI.

Identification of COMT and ErmC inhibitors by using a microplate assay in combination with library focusing by virtual screening.

The paper describes a process of facilitated screening by using a combination of molecular modelling and a 96-well microplate assay for the identification of novel inhibitors of catechol-O-methyltransferase (COMT) and bacteria expressing ErmC. With the help of virtual screening the number of compounds processed in the in vitro screening assay was reduced from over 200,000 to 49. Out of the 49, two structurally very similar compounds were identified as confirmed hits with reasonable activity (IC50 values of 26 and 73 microM) and thus as potential core structures for further drug design and development.

Combinations of chlorocatechols and heavy metals cause DNA degradation in vitro but must not result in increased mutation rates in vivo.

Chlorocatechols introduced into the environment directly or as a result of degradation processes are highly toxic, particularly when combined with heavy metals. With in vitro DNA degradation assays, the high reactivity of chlorocatechols combined with heavy metals could be shown, whereby copper was shown to be more active than iron. Structure-activity analysis showed that the degradation potential of the chlorocatechols decreased with an increasing number of chloratoms. The addition of reactive oxygen species scavengers allowed the identification of hydrogen peroxide as an important agent leading to DNA damage in this reaction. The potential of other reactive compounds, however, can neither be determined nor excluded with this approach. Exposure of Escherichia coli and Salmonella typhimurium cultures to the same mixtures of chlorocatechols and copper surprisingly did not lead to an enhanced mutation rate. This phenomenon was explained by doing marker gene expression measurements and toxicity tests with E. coli mutants deficient in oxidative stress defense or DNA repair. In catechol-copper-exposed cultures an increased peroxide level could indeed be demonstrated, but the highly efficient defense and repair systems of E. coli avoid the phenotypical establishment of mutations. Increased mutation rates under chronic exposure, however, cannot be excluded.

Regulation of the contact sensitivity response to urushiol with anti-urushiol monoclonal antibody ALG 991.

The objective of the studies was to demonstrate that the contact sensitivity (CS) response to poison ivy/oak could be downregulated following treatment with a monoclonal antibody (mAb) reacting with the allergen urushiol. Conjugation of urushiol and its synthetic analogue 3-n-pentadecylcatechol (PDC) to N-acetylcysteine yielded hydrosoluble derivatives which induced humoral immune responses in BALB/c mice. Hybridomas secreting monoclonal antibodies (mAbs) reacting with urushiol and PDC were generated by fusion of B lymphocytes from immunized mice with mouse myeloma P3NS0 cells. The specificity of mAb ALG 991 (IgM isotype) was defined by inhibition of antibody binding by PDC analogues. This demonstrated that mAb ALG 991 reacted with the catechol moiety of urushiol, the region of the allergen being critically important in the induction of contact dermatitis. The CS response to urushiol in BALB/c mice was suppressed by stimulation with mAb ALG 991 and the role of sensitized T cells, including suppressor T cells, has been considered. Suppression of CS was most effective with low doses (1 microg) of mAb incorporated into a vaccine with Freund's adjuvant. This treatment suppressed CS responses in BALB/c mice already sensitized to urushiol.

Absence of evidence for a powerful tonic baroreflex-mediated inhibition on catechol activity in the rat rostral ventrolateral medulla: in vivo voltammetric evidence during sino-aortic deafferentation.

To test in a catechol-specific and dynamic manner for the existence of a powerful long-lasting inhibition arising from barosensitive afferents that depresses the activity of adrenergic neurons in the rostral ventrolateral medulla (RVLM), in vivo voltammetry was used before and after acute sino-aortic deafferentation. Rats were anaesthetized with pentobarbital or halothane and ventilated with a mixture of air and oxygen. Snares were inserted around the vagus, the glossopharyngeal and the superior laryngeal nerves. After placing the animal prone in the stereotaxic frame and stabilization at a high mean arterial pressure (MAP approximately 120 mmHg), the snares were rapidly closed to produce complete barodeafferentation, assessed by loss of heart rate responses and changes in renal nerve sympathetic activity in response to vasoactive agents. Recording of a catechol signal was maintained in the RVLM during deafferentation. Under pentobarbital-induced anaesthesia (n = 5), deafferentation did not lead to a significant change in the catechol signal within the deafferented group. Under halothane-induced anaesthesia and phenylephrine-induced high baseline pressure (n = 5), no changes in the catechol signal were observed upon deafferentation (not significant vs. sham animals: n = 5). This failure to demonstrate a major increase in catechol activity upon deafferentation does not fit with the hypothesis that a powerful tonic baroreflex-mediated inhibition depresses the activity of adrenergic RVLM barosensitive bulbospinal neurons, even when the baseline MAP is high. Rather, these data are compatible with weak or no inhibition of catechol activity by the baroreceptors and a nonessential role of adrenergic neurons within the baroreceptor reflex arc itself: the adrenergic neurons may not be in series within this arc but in parallel with the arc. This interpretation is in keeping with newer schemas of autonomic core circuitry that are devoid of adrenergic neurons.

Differential inhibition of DNA synthesis in human T cells by the cigarette tar components hydroquinone and catechol.

Hydroquinone (HQ), catechol, and phenol exist in microgram quantities in cigarette tar and represent the predominant form of human exposure to benzene. Exposure of human T lymphoblasts (HTL) in vitro to 50 microM HQ or 50 microM catechol decreased IL-2-dependent DNA synthesis and cell proliferation by >90% with no effect on cell viability. Phenol had no effect on HTL proliferation at concentrations up to 1 mm. The addition of HQ or catechol to proliferating HTL blocked 3H-TdR uptake by >90% within 2 hr without significantly affecting 3H-UR uptake, suggesting that both compounds inhibit a rate-limiting step in DNA synthesis. However, the effects of HQ and catechol appear to involve different mechanisms. Ferric chloride (FeCl3) reversed the inhibitory effect of catechol, but not HQ, corresponding with the known ability of catechol to chelate iron. HQ, but not catechol, caused a decrease in transferrin receptor (TfR, CD71) expression, comparable to the level observed in IL-2-starved cells. HQ also inhibited DNA synthesis in cultures of transformed Jurkat T lymphocytes, primary and transformed fibroblasts, and mink lung epithelial cells, indicating that its antiproliferative effect was not restricted to IL-2 mediated proliferation. However, DNA synthesis by primary lymphocytes was more sensitive to HQ (IC50 = 6 microM) than that of the transformed Jurkat T cell line (IC50 = 37 microM) or primary human fibroblasts (IC50 = 45 microM), suggesting that normal lymphocytes may be particularly sensitive to HQ. The effects of HQ and catechol on DNA synthesis could be partially reversed by a combination of adenosine deoxyribose and guanosine deoxyribose, suggesting that both compounds may inhibit ribonucleotide reductase.

Selective inhibition by E4080, a novel bradycardic agent, of positive chronotropic responses to norepinephrine in isolated dog hearts.

E4080, a novel bradycardic agent acts on various ionic currents including the hyperpolarization-activated inward current (I(f)), L-type Ca2+ current (ICa) and ATP-sensitive K+ (K+ATP) current in mammalian heart and vascular tissues. We thus investigated the chronotropic and inotropic effects of E4080 and its interaction with the positive cardiac responses to norepinephrine, 3-isobutyl-1-methyl-xanthine (IBMX) and Bay k 8644 in the isolated, blood-perfused dog right atria and left ventricles. E4080 (0.01-1 mumol) decreased the sinus rate and atrial and ventricular contractile forces in a dose-related manner. Glibenclamide (3 mumol) partly blocked the decrease in atrial force but not the decreases in sinus rate and ventricular force induced by E4080. Atropine (10 nmol) did not affect the negative cardiac responses to E4080. E4080 (0.01-1 mumol) inhibited the positive chronotropic responses to norepinephrine and IBMX dose dependently, but did not inhibit the positive inotropic ones in isolated atria. E4080 affected neither positive chronotropic nor inotropic responses to Bay k 8644. These results suggest that (1) the activation of K+ATP channels by E4080 is partly related to the decrease in atrial force but not the decreases in sinus rate and ventricular force, and (2) the selective inhibition of E4080 of the cyclic AMP-dependent positive chronotropic responses but not inotropic ones is probably due to the inhibition of I(f) rather than other properties, e.g., activation of K+ATP channels and inhibition of ICa in the dog heart.

Resonance Raman studies of pyrocatechase-inhibitor complexes.

The resonance Raman spectra of native pyrocatechase and its benzoate and phenolate complexes were investigated by using the available lines of an argon and a krypton laser. The data provide evidence for the presence of two distinct tyrosines coordinated to the active-site iron. The two tyrosines exhibit different upsilon CO values which show maximum resonance enhancements at different excitation wavelengths. Moreover, one tyrosine is more susceptible to changes in the active-site environment. Pyrocatechase is the only example thus far among iron-tyrosinate proteins where the tyrosines coordinating the iron are distinguishable.