Binding of engeletin with bovine serum albumin: insights from spectroscopic investigations

Effects of Natural Products through Inhibiting Endoplasmic Reticulum Stress on Attenuation of Idiopathic Pulmonary Fibrosis

With ever-increasing intensive studies of idiopathic pulmonary fibrosis (IPF), significant progresses have been made. Endoplasmic reticulum stress (ERS)/unfolded protein reaction (UPR) is associated with the development and progression of IPF, and targeting ERS/UPR may be beneficial in the treatment of IPF. Natural product is a tremendous source of new drug discovery, and accumulating studies have reported that many natural products show potential therapeutic effects for IPF via modulating one or more branches of the ERS signaling pathway. Therefore, this review focuses on critical roles of ERS in IPF development, and summarizes herbal preparations and bioactive compounds which protect against IPF through regulating ERS.

Multispectroscopic and computational study of interaction of the bovine serum albumin with atropine and atropine-loaded chitosan nanoparticles (synthesized and characterized)

Two different systems of bovine serum albumin (BSA) were used for multiple spectroscopic and computational studies to determine interaction of BSA and atropine (Atrop), that is, BSA-Atrop system and Atrop-loaded chitosan nanoparticles (Atrop@CS NPs), that is, BSA-Atrop@CS NPs system. The study suggests that BSA-Atrop system and BSA-Atrop@CS NPs system involve non-fluorescent complexes of Ksv = 3.2 × 103 Lmol-1 and 3.1 × 104 Lmol-1, kq = 3.2 × 1011 Lmol-1 s-1 and 3.1 × 1012 Lmol-1 s-1, the binding constant Kb = 1.4 × 103 Lmol-1, 2.0 × 102 Lmol-1, respectively, and number of binding sites n ∼ 1 for both the systems. The negligible conformational changes induced in BSA were also observed. Synchronous fluorescence spectroscopic study revealed that more quenching occurred in intrinsic fluorescence of tryptophan (Trp, W) than that in tyrosine residue (Tyr, Y). UV-vis spectroscopic study verified the presence of static quenching from the presence of BSA-Atrop and BSA-Atrop@CS NPs complexes. CD spectra confirmed the conformational changes induced in BSA upon increment of concentrations of Atrop and Atrop@CS NPs separately into the constant concentration of BSA. The coherent observations from various spectroscopic studies were in agreement with those of computational study, showing BSA-Atrop complex formation and other related details. The hydrogen bonds (H-bonds), van der Walls (vdW) interactions and π -type of interactions were mainly involved in stabilization of the formed BSA-Atrop complex.Communicated by Ramaswamy H. Sarma.

Engeletin ameliorates sevoflurane-induced cognitive impairment by activating PPAR-gamma in neonatal mice

Sevoflurane (SEV) is a commonly used anesthetic in pediatric surgery. Recent studies reported that repeated use of SEV contributes to cognitive impairment. Engeletin has been discovered to exert anti-inflammatory effects in various diseases. However, the detailed roles and mechanisms of engeletin in SEV-induced cognitive dysfunction of neonatal mice remain unclear. In this study, C57BL/6 neonatal mice were randomly divided into Ctrl, SEV, SEV + Engeletin (10 mg /kg), SEV + Engeletin (20 mg/kg), and SEV + Engeletin (40 mg/kg) groups. The Morris water maze (MWM) test suggested that engeletin treatment significantly improved SEV-induced cognitive impairment in neonatal mice. Employing ELISA and Nissl staining analysis, engeletin reduced neuroinflammation and loss of nerve cells caused by SEV, respectively. The treatment of engeletin dramatically suppressed the activation of microglia and apoptosis induced by SEV in the hippocampus of neonatal mice. Furthermore, the inhibition of PPAR-γ obviously reversed the abovementioned effects of engeletin in the hippocampus of newborn mice. In conclusion, this study verified that engeletin notably ameliorated SEV-induced cognitive deficiencies in neonatal mice at least partially by mediating the expression of PPAR-γ.

Theoretical design for covering Engeletin with functionalized nanostructure-lipid carriers as neuroprotective agents against Huntington's disease via the nasal-brain route

Objective: To propose a theoretical formulation of engeletin-nanostructured lipid nanocarriers for improved delivery and increased bioavailability in treating Huntington's disease (HD). Methods: We conducted a literature review of the pathophysiology of HD and the limitations of currently available medications. We also reviewed the potential therapeutic benefits of engeletin, a flavanol glycoside, in treating HD through the Keap1/nrf2 pathway. We then proposed a theoretical formulation of engeletin-nanostructured lipid nanocarriers for improved delivery across the blood-brain barrier (BBB) and increased bioavailability. Results: HD is an autosomal dominant neurological illness caused by a repetition of the cytosine-adenine-guanine trinucleotide, producing a mutant protein called Huntingtin, which degenerates the brain's motor and cognitive functions. Excitotoxicity, mitochondrial dysfunction, oxidative stress, elevated concentration of ROS and RNS, neuroinflammation, and protein aggregation significantly impact HD development. Current therapeutic medications can postpone HD symptoms but have long-term adverse effects when used regularly. Herbal medications such as engeletin have drawn attention due to their minimal side effects. Engeletin has been shown to reduce mitochondrial dysfunction and suppress inflammation through the Keap1/NRF2 pathway. However, its limited solubility and permeability hinder it from reaching the target site. A theoretical formulation of engeletin-nanostructured lipid nanocarriers may allow for free transit over the BBB due to offering a similar composition to the natural lipids present in the body a lipid solubility and increase bioavailability, potentially leading to a cure or prevention of HD. Conclusion: The theoretical formulation of engeletin-nanostructured lipid nanocarriers has the potential to improve delivery and increase the bioavailability of engeletin in the treatment of HD, which may lead to a cure or prevention of this fatal illness.

Digital Database of Absorption Spectra of Diverse Flavonoids Enables Structural Comparisons and Quantitative Evaluations

Flavonoids play diverse roles in plants, comprise a non-negligible fraction of net primary photosynthetic production, and impart beneficial effects in human health from a plant-based diet. Absorption spectroscopy is an essential tool for quantitation of flavonoids isolated from complex plant extracts. The absorption spectra of flavonoids typically consist of two major bands, band I (300-380 nm) and band II (240-295 nm), where the former engenders a yellow color; in some flavonoids the absorption tails to 400-450 nm. The absorption spectra of 177 flavonoids and analogues of natural or synthetic origin have been assembled, including molar absorption coefficients (109 from the literature, 68 measured here). The spectral data are in digital form and can be viewed and accessed at http://www.photochemcad.com. The database enables comparison of the absorption spectral features of 12 distinct types of flavonoids including flavan-3-ols (e.g., catechin, epigallocatechin), flavanones (e.g., hesperidin, naringin), 3-hydroxyflavanones (e.g., taxifolin, silybin), isoflavones (e.g., daidzein, genistein), flavones (e.g., diosmin, luteolin), and flavonols (e.g., fisetin, myricetin). The structural features that give rise to shifts in wavelength and intensity are delineated. The availability of digital absorption spectra for diverse flavonoids facilitates analysis and quantitation of these valuable plant secondary metabolites. Four examples are provided of calculations─multicomponent analysis, solar ultraviolet photoprotection, sun protection factor (SPF), and Förster resonance energy transfer (FRET)─for which the spectra and accompanying molar absorption coefficients are sine qua non.

Engeletin ameliorates pulmonary fibrosis through endoplasmic reticulum stress depending on lnc949-mediated TGF-β1-Smad2/3 and JNK signalling pathways

CONTEXT

Pulmonary fibrosis (PF) is a highly heterogeneous and lethal pathological process having no effective drug. Engeletin exerts multiple biological activities including anti-inflammatory and lung repair. Whether engeletin has therapeutic effects on PF remains unclear.

OBJECTIVE

Examining effect and mechanism of engeletin on PF in vivo and in vitro.

MATERIALS AND METHODS

L929 cells (1 × 10⁶/well) were treated with TGF-β1 (5 ng/mL). Sixty male C57BL/6 mice were divided into three groups and given saline or single intratracheal instillation bleomycin (5 mg/kg) or both bleomycin and intraperitoneally injected engeletin (25 mg/kg).

RESULTS

Histological staining showed engeletin inhibited myofibrobasts activation and improved alveolar structure. Engeletin elevated forced vital capacity from 12 induced by bleomycin to 17. CCK-8 assay reported IC₅₀ value of engeletin was 270 μg/mL. Real-time cellular analysis showed engeletin reduced proliferation and migration of myofibroblasts by 2.5- and 2-fold. Engeletin blocked α-SMA, vimentin, and collagen expression. RNA sequencing revealed PERK-ATF4 signalling pathway relating to ER stress involved in anti-fibrotic function of engeletin. Engeletin reduced ATF4, CHOP and BIP expression. Chemical inhibitors of smad2/3- (SB431542) and JNK- (SP600125) signalling pathways blocked expression of long noncoding RNA (lncRNA) - lnc949. Engeletin inhibited phosphorylation of smad2/3 and JNK leading to lower level of lnc949. Knockdown lnc949 inhibited ATF4, CHOP and BIP expression.

CONCLUSIONS

We reported gene expression profiling of engeletin through RNA-seq; and identified lnc949-mediated TGF-β1-Smad2/3 and JNK were upstream signalling pathways of ER stress induced by engeletin. Our results showed engeletin remedies pulmonary fibrogenesis and may be a new drug candidate.

Analyzing organophosphate pesticide-serum albumin binding interaction: a combined STD NMR and molecular docking study

In Vitro analysis of the interaction of organophosphate pesticides (OP) with bovine serum albumin (BSA) is crucial to understand their potential effects at the molecular level. In this context, we have employed Saturation Transfer Difference (STD) NMR experiments in conjunction with molecular docking studies to unravel the binding interaction of the OP chlorpyrifos (CPF), diazinon (DZN) and parathion (PA) in solution. The relative STD (%) suggested the detailed epitope mapping of these OP with BSA while the concentration-dependent STD NMR studies were performed to obtain the complex dissociation constant (K_D) of the OP-BSA complexes; K_D=1.81 × 10^-4 M, 1.30 × 10^-3 M and 1.11 × 10^-3 M for CPF, DZN and PA were extracted respectively. Similar binding modes were identified for all the three OP using STD site-marker experiment. ITC experiments were performed as a complementary method that revealed a high binding affinity of OP-BSA complexes through non-covalent interaction. Molecular docking confirmed the possible interacting chemical groups of OP-BSA complexes. These significant results furnish valuable information about the toxicity risk of OP to proteins.Communicated by Ramaswamy H. Sarma.

In situ ultra-fast heat deposition does not perturb the structure of serum albumin

MnTPPS is a metallic water soluble porphyrin with high potential to be used as a contrast agent in photoacoustic tomography. In order to fully understand the interaction between MnTPPS and serum albumin and to investigate the effect of the light induced fast in situ heat deposition by MnTPPS in the protein, we performed several experimental studies using fluorescence and circular dichroism spectroscopies, as well as photoacoustic calorimetry. To identify the possible binding site(s) of the metalloporphyrin in serum albumin and to help interpret the spectroscopic results, a molecular docking exercise was also carried out. The fluorescence data indicate a 1 : 1 stoichiometry for the complex BSA : MnTPPS. The molecular docking results suggest one binding site at the subdomain IB of albumin, where Trp-134 is found, as the main binding site for MnTPPS. The CD data indicate no significant conformational changes of the BSA secondary structure upon MnTPPS binding and even after several minutes of laser excitation of MnTPPS. TR-PAC results show that the in situ heat deposition from MnTPPS does not cause any significant transient conformational change to the BSA structure. In conclusion, this work demonstrates that MnTPPS, in addition to the necessary physical and chemical properties to be used as a contrast agent in photoacoustic tomography, can be effectively carried by albumin and that in situ heat release following light absorption does not cause any significant damage to the protein structure.

Structural and Kinetic Visualization of the Protein Corona on Bioceramic Nanoparticles

Bioceramic nanoparticles exhibit excellent features that enable them to function as an ideal material for hard tissue engineering. However, to fully understand their behavior, it is of crucial importance to understand their behavior within the fluids of the human body. To achieve this goal, we have studied the interaction between hydroxyapatite nanorods (HA) and bovine serum albumin (BSA). First, we describe the surface morphology of the nanoparticle. Then, the main characteristics of the physiological interplay of BSA and the hydroxyapatite nanoparticle are presented by using a battery of techniques: ITC, zeta potential, UV-vis, fluorescence, and CD. Experimental data was analyzed by developing specific approaches to determining important parameters such as rates, affinities, and stochiometries of protein associated with the nanoparticles. ITC has been confirmed as a powerful technique for determining the affinity, binding, and thermodynamics of BSA-nanoparticle interactions. Careful quantitative assessment of the kinetic properties of the adsorption were revealed by UV-vis and fluorescence measurements. Finally, CD measurements highlight the important role of protein flexibility in these kinds of systems.

Determination and pharmacokinetics of engeletin in rat plasma by ultra-high performance liquid chromatography with tandem mass spectrometry

Engeletin, a bioactive flavonoid, has attracted much attention recently by virtue of its multiple biological (anti-diabetic and anti-inflammatory) activities. Despite signifying many therapeutic applications researches indicating quantification or pharmacokinetics of engeletin in biological matrix are still lacking. Here, a simple, sensitive, accurate and reliable ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) approach for the quantification of engeletin in rat plasma was developed and fully validated for the first time. Plasma samples were processed with acetonitrile by a single step protein precipitation and the separation was achieved on a ZORBAX Eclipse Plus C18 Rapid Resolution High Definition column with a gradient acetonitrile-water mobile phase. Quantification of engeletin was carried out by electrospray ionization tandem mass spectrometry in multiple reaction monitoring (MRM) mode with negative ionization. Results revealed that the approach was linearity from 5 to 5000ng/mL (r²=0.9937) and proved to be precise (better than 12.3%) and accurate (-3.3%-5.2%). The developed approach was successfully employed to pharmacokinetic study of engeletin following peroral and intravenous administration to rats. The results of pharmacokinetics demonstrated rapid engeletin absorption (T_max of 15min) after oral administration, extensive distribution after three different dosages and an absolute bioavailability of ∼1.53%. The developed method and pharmacokinetic data can provide a meaningful basis for further studies on engeletin.

Engeletin Alleviates Lipopolysaccharide-Induced Endometritis in Mice by Inhibiting TLR4-mediated NF-κB Activation

Engeletin (dihydrokaempferol 3-rhamnoside) is a flavanonol glycoside. It can be found in the skin of white grapes and white wine and is widely distributed in southeast Asia, and the leaves are used in a tea. Here, we explored the impact of engeletin against the inflammatory reaction in a lipopolysaccharide (LPS)-induced endometritis mouse model. Engeletin treatment significantly attenuated uterus damage and decreased myeloperoxidase activity. ELISA and qPCR assays showed that engeletin dose-dependently suppressed the expression of TNF-α, IL-1β, and IL-6. Molecular studies also demonstrated that the levels of iNOS, COX-2, and TLR4, along with their downstream molecules MyD88, IRAK1, TRAF6, and TAK1, were also suppressed by engeletin. In addition, engeletin treatment inhibited NF-κB signaling-pathway activation. Moreover, immunofluorescence analysis demonstrated that engeletin suppressed NF-κB-p65 nuclear translocation. These data indicated the protective action of engeletin against LPS-stimulated endometritis in mice via negative regulation of pro-inflammatory mediators via the TLR4-regulated NF-κB pathway.