muramidase and baicalein

More than 20 human diseases involve the fibrillation of a specific protein/peptide which forms pathological deposits at various sites. Hereditary lysozyme amyloidosis is a systemic disorder which mostly affects liver, spleen and kidney. This conformational disorder is featured by lysozyme fibril formation. In vivo lysozyme fibrillation was simulated under in vitro conditions using a strong denaturant GdHCl at 3 M concentration. Sharp decline in the ANS fluorescence intensity compared to the partially unfolded states, almost 20-fold increase in ThT fluorescence intensity, increase in absorbance at 450 nm suggesting turbidity, negative ellipticity peak in the far-UVCD at 217 nm, red shift of 50 nm compared to the native state in Congo red assay and appearance of a network of long rope-like fibrils in transmission electron microscope (TEM) analysis suggested HEWL fibrillation. Anti-fibrillation potency of baicalein against the preformed fibrils of HEWL was investigated following ThT assay in which there was a dose-dependent decrease in ThT fluorescence intensity compared to the fibrillar state of HEWL with the maximum effect observed at 150-μM baicalein concentration, loss of negative ellipticity peak in the far-UVCD region, dip in the Rayleigh scattering intensity and absorbance at 350 and 450 nm, respectively, together with a reduction in the density of fibrillar structure in TEM imaging. Thus, it could be suggested that baicalein could prove to be a positive therapeutics for hereditary human lysozyme amyloidosis.

Topics: Animals; Antioxidants; Drug Discovery; Flavanones; Models, Molecular; Molecular Conformation; Molecular Docking Simulation; Molecular Dynamics Simulation; Muramidase; Polyphenols; Protein Binding; Structure-Activity Relationship

The interaction mechanism of baicalein and lysozyme (Lys) has been characterized by fluorescence, synchronous fluorescence, ultraviolet-vis absorbance, and three-dimensional (3D) fluorescence. The structural characteristics of baicalein and Lys were probed, and their binding affinities were determined under different pH conditions (pH 7.4, 4.5, and 2.5). The results showed that the binding abilities of the drug to Lys increased under lower pH conditions (pH 4.5 and 2.5) due to the alterations of the protein secondary and tertiary structures or the structural change of baicalein. The effect of baicalein on the conformation of Lys was analyzed using UV, synchronous fluorescence and three-dimensional (3D) fluorescence under different pH conditions. These results indicate that the binding of baicalein to Lys causes apparent change in the secondary and tertiary structure of Lys. In the presence of Cu(2+), the decrease of the binding constant in buffer solution of pH 2.5 may result from the competition of the metal ion and baicalein binding to Lys. In addition, the presence of Cu(2+) increased the binding constants of baicalein-Lys complex under higher pH conditions (pH 7.4 and 4.5). The possible site of binding of baicalein to Lys has been proposed to explain these observations.

Topics: Binding Sites; Flavanones; Hydrogen-Ion Concentration; Metals; Muramidase; Protein Binding; Protein Structure, Tertiary; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet

The interactions of baicalein, baicalin and scutellarin with lysozyme (LYSO) were studied by fluorescence and UV spectroscopy. The results showed that all the three flavones can quench the fluorescence of LYSO via static quenching with the distance between the donor and acceptor less than 7 nm. The hydroxyl at B-ring gave flavones an advantage to binding with LYSO. Electrostatic forces played a major role in stabilizing baicalein-LYSO complex and baicalin-LYSO complex, whereas hydrophobic interactions in scutellarin-LYSO. Furthermore, the presence of pantothenic acid can increase the binding constant and the number of binding sites between flavones and LYSO.

Topics: Animals; Anti-Infective Agents; Apigenin; Chickens; Enzyme Inhibitors; Flavanones; Flavonoids; Glucuronates; Muramidase; Pantothenic Acid; Protein Binding; Spectrometry, Fluorescence

Studies were made on the effects of baicalein (5,6,7-trihydroxyflavone) on leukotrienes B4 and C4 biosyntheses and degranulation induced by calcium ionophore A23187 (A23187) in human polymorphonuclear leukocytes. Baicalein inhibited A23187-induced biosynthesis of leukotrienes B4 and C4 in human polymorphonuclear leukocytes. The concentration of baicalein required for 50% inhibition (IC50) of leukotrienes B4 and C4 formations was 1.46.10(-6) and 6.00.10(-7) M, respectively, using 1.0 microgram/ml of A23187. In addition, baicalein dose-dependently inhibited beta-glucuronidase and lysozyme releases induced by A23187, leukotriene B4 plus cytochalasin B and platelet-activating factor plus cytochalasin B. Furthermore, baicalein was found to inhibit dose-dependently Ca2+ uptake into the cells and Ca2+ mobilization from the intracellular stores.

Topics: Calcimycin; Calcium; Cyclic AMP; Cytochalasin B; Dose-Response Relationship, Drug; Flavanones; Flavonoids; Glucuronidase; Humans; Muramidase; Neutrophils; Platelet Activating Factor; SRS-A