Inhibition of Protein Aggregation: Supramolecular Assemblies of Arginine Hold the Key

BACKGROUND: Aggregation of unfolded proteins occurs mainly through the exposed hydrophobic surfaces. Any mechanism of inhibition of this aggregation should explain the prevention of these hydrophobic interactions. Though arginine is prevalently used as an aggregation suppressor, its mechanism of action is not clearly understood. We propose a mechanism based on the hydrophobic interactions of arginine. METHODOLOGY: We have analyzed arginine solution for its hydrotropic effect by pyrene solubility and the presence of hydrophobic environment by 1-anilino-8-naphthalene sulfonic acid fluorescence. Mass spectroscopic analyses show that arginine forms molecular clusters in the gas phase and the cluster composition is dependent on the solution conditions. Light scattering studies indicate that arginine exists as clusters in solution. In the presence of arginine, the reverse phase chromatographic elution profile of Alzheimer's amyloid beta 1-42 (Abeta(1-42)) peptide is modified. Changes in the hydrodynamic volume of Abeta(1-42) in the presence of arginine measured by size exclusion chromatography show that arginine binds to Abeta(1-42). Arginine increases the solubility of Abeta(1-42) peptide in aqueous medium. It decreases the aggregation of Abeta(1-42) as observed by atomic force microscopy. CONCLUSIONS: Based on our experimental results we propose that molecular clusters of arginine in aqueous solutions display a hydrophobic surface by the alignment of its three methylene groups. The hydrophobic surfaces present on the proteins interact with the hydrophobic surface presented by the arginine clusters. The masking of hydrophobic surface inhibits protein-protein aggregation. This mechanism is also responsible for the hydrotropic effect of arginine on various compounds. It is also explained why other amino acids fail to inhibit the protein aggregation

The Competence of 7,8-Diacetoxy-4-Methylcoumarinand other Polyphenolic Acetates in Mitigating the Oxidative Stress and their Role in Angiogenesis.

The potential role of polyphenolic acetate (PA) in causing diverse biological and pharmacological actions has been well studied in our laboratory. Our investigations, for the first time, established the role of calreticulin transacetylase (CRTAase) in catalyzing the acetylation of nitric oxide synthase (NOS) by Pas leading to robust activation of NOS. 7, 8-Diacetoxy-4-methylcoumarin (DAMC) and other acetoxycoumarins augmented the expression of thioredoxin (TRX) and vascular endothelial growth factor (VEGF) in human peripheral blood mononuclear cells (PBMCs). These findings substantiated our earlier observations that DAMC was a superb inducer of angiogenesis. The enhanced expression of thioredoxin reductase (TRXR) and diminished expression of thioredoxin interacting protein (TRXIP) leading to increased expression and activity of TRX in PBMCs due to the action of DAMC was revealed by real time RT-PCR analysis. The possible activation of TRX due to acetylation was confirmed by the fact that TRX activity of PBMCs was enhanced by variousacetoxycoumarins in tune with their affinities to CRTAase as substrates. DAMC caused enhanced production of NO by way of acetylation of NOS as mentioned above and thereby acted as an inducer of VEGF. Real time RT-PCR and VEGF ELISA results also revealed the overexpression of TRX. DAMC and other PAs were found to reduce the oxidative stress in cells as proved by significant reduction of intracellular ROS levels. Thus, the crucial role of TRX in DAMC-induced angiogenesis with the involvement of VEGF was established

The competence of 7,8-diacetoxy-4-methylcoumarin and other polyphenolic acetates in mitigating the oxidative stress and their role in angiogenesis

The potential role of polyphenolic acetate (PA) in causing diverse biological and pharmacological actions has been well studied in our laboratory. Our investigations, for the first time, established the role of calreticulin transacetylase (CRTAase) in catalyzing the acetylation of nitric oxide synthase (NOS) by Pas leading to robust activation of NOS. 7, 8-Diacetoxy-4-methylcoumarin (DAMC) and other acetoxycoumarins augmented the expression of thioredoxin (TRX) and vascular endothelial growth factor (VEGF) in human peripheral blood mononuclear cells (PBMCs). These findings substantiated our earlier observations that DAMC was a superb inducer of angiogenesis. The enhanced expression of thioredoxin reductase (TRXR) and diminished expression of thioredoxin interacting protein (TRXIP) leading to increased expression and activity of TRX in PBMCs due to the action of DAMC was revealed by real time RT-PCR analysis. The possible activation of TRX due to acetylation was confirmed by the fact that TRX activity of PBMCs was enhanced by variousacetoxycoumarins in tune with their affinities to CRTAase as substrates. DAMC caused enhanced production of NO by way of acetylation of NOS as mentioned above and thereby acted as an inducer of VEGF. Real time RT-PCR and VEGF ELISA results also revealed the overexpression of TRX. DAMC and other PAs were found to reduce the oxidative stress in cells as proved by significant reduction of intracellular ROS levels. Thus, the crucial role of TRX in DAMC-induced angiogenesis with the involvement of VEGF was established

Machine Learning From Quantitative Coronary Computed Tomography Angiography Predicts Fractional Flow Reserve-Defined Ischemia and Impaired Myocardial Blood Flow

Background: A pathophysiological interplay exists between plaque morphology and coronary physiology. Machine learning (ML) is increasingly being applied to coronary computed tomography angiography (CCTA) for cardiovascular risk stratification. We sought to assess the performance of a ML score integrating CCTA-based quantitative plaque features for predicting vessel-specific ischemia by invasive fractional flow reserve (FFR) and impaired myocardial blood flow (MBF) by positron emission tomography (PET). Methods: This post-hoc analysis of the PACIFIC trial (Prospective Comparison of Cardiac Positron Emission Tomography/Computed Tomography [CT]‚ Single Photon Emission Computed Tomography/CT Perfusion Imaging and CT Coronary Angiography with Invasive Coronary Angiography) included 208 patients with suspected coronary artery disease who prospectively underwent CCTA‚ [ 15O]H 2O PET, and invasive FFR. Plaque quantification from CCTA was performed using semiautomated software. An ML algorithm trained on the prospective NXT trial (484 vessels) was used to develop a ML score for the prediction of ischemia (FFR≤0.80), which was then evaluated in 581 vessels from the PACIFIC trial. Thereafter, the ML score was applied for predicting impaired hyperemic MBF (≤2.30 mL/min per g) from corresponding PET scans. The performance of the ML score was compared with CCTA reads and noninvasive FFR derived from CCTA (FFR CT). Results: One hundred thirty-nine (23.9%) vessels had FFR-defined ischemia, and 195 (33.6%) vessels had impaired hyperemic MBF. For the prediction of FFR-defined ischemia, the ML score yielded an area under the receiver-operating characteristic curve of 0.92, which was significantly higher than that of visual stenosis grade (0.84; P<0.001) and comparable with that of FFR CT(0.93; P=0.34). Quantitative percent diameter stenosis and low-density noncalcified plaque volume had the greatest ML feature importance for predicting FFR-defined ischemia. When applied for impaired MBF prediction, the ML score exhibited an area under the receiver-operating characteristic curve of 0.80; significantly higher than visual stenosis grade (area under the receiver-operating characteristic curve 0.74; P=0.02) and comparable with FFR CT(area under the receiver-operating characteristic curve 0.77; P=0.16)

Impact of soil fertility management practices on the nutritional quality of Soybean (Glycine max (l.) Merr.) varieties grown in Eastern Zambia

Open Access Journal; Published online: 26 Sept 2019Zambia has three primary agro-ecological regions, with each region having specific ecological characteristics. Region II agro-ecological zone of Zambia has low nutrient reserves and poor water holding capacity due to moderately leached clayey to loamy soil; this has led to low soybean productivity. Soil fertility management (ISFM) strategies such as the use of inorganic fertilizers and the use of inoculants of rhizobia have been introduced and promoted among small-scale farmers in Eastern Province. Two soybean varieties (Lukanga and Kafue) were used for this study and 96 samples from on-farm soil fertility management trials in Chipata, and Petauke districts were collected for the determinations of nutritional and anti-nutritional properties. The proximate analysis of Chipata samples showed that the ash content 5.10‒6.23%, fat content 17.71‒25.57%, protein content 27.73‒37.11%, amylose content 1.26‒4.56 %, sugar content 6.75‒9.62%, and starch content 4.00‒18.57%, while anti-nutritional properties ranged between 3.07 and 8.21% for phytate and 1.42‒3.35% for tannin. With Petauke, the ash content 3.32‒6.8 %, fat content 19.16‒26.85%, protein content 27.68‒35.62%, amylose 2.00‒4.37%, sugar content 6.23‒9.76%, and starch content 5.70‒18.63%. Phytate and tannin contents were 3.37‒7.90% and 0.14‒3.32%, respectively. The highest protein content was found at the level of 37.11% in Kafue with 40kg P/ha and inoculant, and the least was 27.73% for Lukanga without inputs in Chipata while in Petauke, Lukanga with 40 P/ha and inoculant had the highest protein content of 35.62% and the least was 27.68% for Lukanga with inoculant. The co-application of rhizobia inoculant and P nutrient increased phytate, and tannin content significantly (P < 0.05)

Normalization of deranged signal transduction in lymphocytes of COPD patients by the novel calcium channel blocker H-DHPM

Investigations on the role of intracellular Ca(2+) ion concentration in the mechanism of development of COPD in smokers and non-smokers were carried out. The intracellular Ca(2+) levels were found to be increased in human lymphocytes in patients with COPD as compared to non-smokers and smokers without COPD. The investigations reveal an association in altered intracellular Ca(2+) regulation in lymphocytes and severity of COPD, by means of significant activation of Protein kinase C and inducible nitric oxide synthase (iNOS). The effect of a novel calcium channel blocker ethyl 4-(4'-heptanoyloxyphenyl)-6-methyl-3,4-dihydropyrimidin-2-one-5-carboxylate (H-DHPM) as a potential candidate for the treatment of COPD was also investigated. H-DHPM treated cells showed a decrease in intracellular Ca(2+) level as compared to the control cells. Molecular studies were carried out to evaluate the expression profile of NOS isoforms in human lymphocytes and it was shown that H-DHPM decreases the increased iNOS in COPD along with reestablishing the normal levels of endothelial nitric oxide synthase (eNOS). The results of H-DHPM were comparable with those of Amlodipine, a known calcium channel blocker. Calcium channel blocker H-DHPM proves to be a potential candidate for the treatment of COPD and further clinical studies are required to prove its role in the treatment of pulmonary hypertension (PH). (C) 2011 Elsevier Masson SAS. All rights reserved