Tyrosine mediated conformational change in bone morphogenetic protein – 2: Biophysical implications of protein – phytoestrogen interaction

Interaction between polydopamine-based IONPs and human serum albumin (HSA): a spectroscopic analysis with cytotoxicity impact

Iron oxide nanoparticles (IONPs) have been extensively explored in biomedicine, bio-sensing, hyperthermia, and drug/gene delivery, attributed to their versatile and tunable properties. However, owing to its numerous applications, the functionalization of IONPs with appropriate materials is in demand. To achieve optimal functionalization of IONPs, polydopamine (PDA) was utilized due to its ability to provide a superior functionalized surface, near-infrared light absorption, and adhesive nature to customize desired functionalized IONPs. This notion of involving PDA led to the successful synthesis of magnetite-PDA nanoparticles, where PDA is surface-coated on magnetite (Fe3O4@PDA). The Fe3O4@PDA nanoparticles were characterized using techniques like TEM, FESEM, PXRD, XPS, VSM, and FTIR, suggesting PDA's successful attachment with magnetite crystal structure retention. Human serum albumin (HSA), the predominant protein in blood plasma, interacts with the delivered nanoparticles. Therefore, we have employed various spectroscopic techniques, along with cytotoxicity, to inspect the effect of Fe3O4@PDA NPs on the stability and structure of HSA. The structural alterations were examined using circular dichroism (CD) and synchronous fluorescence spectroscopy (SFS). It has been observed that there are no structural perturbations in the secondary structure of the HSA protein after interaction with Fe3O4@PDA. Studies using steady-state fluorescence revealed that the inherent fluorescence intensities of HSA were suppressed after interaction with Fe3O4@PDA. In addition, temperature-dependent fluorescence measurements suggested that the type of quenching consists of both static and dynamic quenching simultaneously. A cytotoxicity study in Drosophila melanogaster larvae revealed no cytotoxic effects but did show a minor genotoxic effect only at higher concentrations.

Delineating the cascade of molecular events in protein aggregation triggered by Glyphosate, aminomethylphosphonic acid, and Roundup in serum albumins

The molecular basis of protein unfolding on exposure to the widely used herbicide, Glyphosate (GLY), its metabolite aminomethylphosphonic acid (AMPA), and the commercial formulation Roundup have been probed using human and bovine serum albumins (HSA and BSA). Protein solutions were exposed to chemical stress at set experimental conditions. The study proceeds with spectroscopic and imaging tools. Steady-state and time-resolved fluorescence (TRF) measurements indicated polarity changes with the possibility of forming a ground-state complex. Atomic force microscopy imaging results revealed the formation of fibrils from BSA and dimer, trimer, and tetramer forms of oligomers from HSA under the chemical stress of GLY. In the presence of AMPA, serum albumins (SAs) form a compact network of oligomers. The compact network of oligomers was transformed into fibrils for HSA with increasing concentrations of AMPA. In contrast, Roundup triggered the formation of amorphous aggregates from SAs. Analysis of the Raman amide I band of all aggregates showed a significant increase in antiparallel β-sheet fractions at the expense of α-helix. The highest percentage, 24.6%, of antiparallel β-sheet fractions was present in amorphous aggregate formed from HSA under the influence of Roundup. These results demonstrated protein unfolding, which led to the formation of oligomers and fibrils.

Chinese Ecliptae herba (Eclipta prostrata (L.) L.) extract and its component wedelolactone enhances osteoblastogenesis of bone marrow mesenchymal stem cells via targeting METTL3-mediated m6A RNA methylation

ETHNOPHARMACOLOGICAL RELEVANCE

Chinese Ecliptae herba (Eclipta prostrata (L.) L.) is an ethnomedicinal herb, which is used mainly to nourish kidney and thus strengthen bones according to traditional Chinese medicine theory. Pharmacological studies have supported the ethnomedicine use, showing that Ecliptae herba extract has an anti-osteoporotic effect in vivo and promoted osteoblast proliferation and activity in vitro. However, the molecular mechanism of Ecliptae herba on osteoblast differentiation from bone marrow mesenchymal stem cells (BMSC), the progenitors of osteoblasts, is still unclear.

AIM OF THE STUDY

N6-methyladenosine (m6A) mRNA epigenetic modification may play a key role in promoting osteoblastic differentiation, and thus treating osteoporosis. This study sought to assess the mechanism through which Eclipate herba and its component wedelolactone influence m6A modification during the process of osteoblastogenesis from BMSC.

MATERIAL AND METHODS

The alkaline phosphatase (ALP) and Alizarin red S (ARS) staining were applied to determine osteoblastogenesis from BMSC. Western blot and quantitative real-time PCR were performed. RNA sequencing analysis was used to determine the characteristics of m6A methylation. Stable knocking down of METTL3 using lentiviral-based shRNA was performed.

RESULTS

Upon 9 d treatment of BMSC with ethyl acetate extract of Ecliptae herba (MHL), ALP activity and ossification level increased in comparison with osteogenic medium (OS)-treated control. The expression of methyltransferase METTL3 and METTL14 was significantly increased, but WTAP expression had no change in response to MHL treatment. Knocking down of METTL3 resulted in a decrease in MHL-induced ALP activity, ossification level as well as mRNA expression of Osterix and Osteocalcin, two bone formation-related markers. The level of m6A increased when BMSC was treated with MHL for 9 d. RNA sequencing analysis indicated that MHL treatment altered mRNA m6A modification of genes associated with osteoblastogenesis. By kyoto encyclopedia of genes and genomes (KEGG) pathway analysis, HIF-1α, PI3K/Akt, and Hippo signaling pathways were enriched and associated with m6A modification. The expression of m6A-modified genes including HIF-1α, VEGF-A, and RASSF1, was upregulated by MHL, but the upregulation was reversed after METTL3 knockdown. Additionally, the enhanced expression of METTL3 was also observed after treatment with wedelolactone, a component from MHL.

CONCLUSIONS

These results suggested a previously uncharacterized mechanism of MHL and wedelolactone on osteoblastogenesis, by which METTL3-mediated m6A methylation is involved and thus contributes to the enhancement of osteoblastogenesis.

Exploring the interaction of myricetin with human alpha-2-macroglobulin: biophysical and in-silico analysis

Myricetin (MYR) is a bioactive secondary metabolite found in plants that is recognized for its nutraceutical value and is an essential constituent of various foods and beverages. It is reported to exhibit a plethora of activities, including antioxidant, antimicrobial, antidiabetic, anticancer, and anti-inflammatory. Alpha-2-macroglobulin (α2M) is a major plasma anti-proteinase that can inhibit proteinases of both human and non-human origin, regardless of their specificity and catalytic mechanism. Here, we explored the interaction of MYR-α2M using various biochemical and biophysical techniques. It was found that the interaction of MYR brings subtle change in its anti-proteolytic potential and thereby alters its structure and function, as can be seen from absorbance and fluorescence spectroscopy. UV spectroscopy of α2M in presence of MYR indicated the occurrence of hyperchromism, suggesting complex formation. Fluorescence spectroscopy reveals that MYR reduces the fluorescence intensity of native α2M with a shift in the wavelength maxima. At 318.15 K, MYR binds to α2M with a binding constant of 2.4 × 10³ M^-1, which indicates significant binding. The ΔG value was found to be - 7.56 kcal mol^-1 at 298.15 K, suggesting the interaction to be spontaneous and thermodynamically favorable. The secondary structure of α2M does not involve any major change as was confirmed by CD analysis. The molecular docking indicates that Asp-146, Ser-172, Glu-174, and Tyr-180 were the key residues involved in α2M-MYR complex formation. This study contributes to our understanding of the function and mechanism of protein and flavonoid binding by providing a molecular basis of the interaction between MYR and α2M.

Therapeutic application of quercetin in aging-related diseases: SIRT1 as a potential mechanism

Quercetin, a naturally non-toxic flavonoid within the safe dose range with antioxidant, anti-apoptotic and anti-inflammatory properties, plays an important role in the treatment of aging-related diseases. Sirtuin 1 (SIRT1), a member of NAD+-dependent deacetylase enzyme family, is extensively explored as a potential therapeutic target for attenuating aging-induced disorders. SIRT1 possess beneficial effects against aging-related diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), Depression, Osteoporosis, Myocardial ischemia (M/I) and reperfusion (MI/R), Atherosclerosis (AS), and Diabetes. Previous studies have reported that aging increases tissue susceptibility, whereas, SIRT1 regulates cellular senescence and multiple aging-related cellular processes, including SIRT1/Keap1/Nrf2/HO-1 and SIRTI/PI3K/Akt/GSK-3β mediated oxidative stress, SIRT1/NF-κB and SIRT1/NLRP3 regulated inflammatory response, SIRT1/PGC1α/eIF2α/ATF4/CHOP and SIRT1/PKD1/CREB controlled phosphorylation, SIRT1-PINK1-Parkin mediated mitochondrial damage, SIRT1/FoxO mediated autophagy, and SIRT1/FoxG1/CREB/BDNF/Trkβ-catenin mediated neuroprotective effects. In this review, we summarized the role of SIRT1 in the improvement of the attenuation effect of quercetin on aging-related diseases and the relationship between relevant signaling pathways regulated by SIRT1. Moreover, the functional regulation of quercetin in aging-related markers such as oxidative stress, inflammatory response, mitochondrial function, autophagy and apoptosis through SIRT1 was discussed. Finally, the prospects of an extracellular vesicles (EVs) as quercetin loading and delivery, and SIRT1-mediated EVs as signal carriers for treating aging-related diseases, as well as discussed the ferroptosis alleviation effects of quercetin to protect against aging-related disease via activating SIRT1. Generally, SIRT1 may serve as a promising therapeutic target in the treatment of aging-related diseases via inhibiting oxidative stress, reducing inflammatory responses, and restoring mitochondrial dysfunction.

Dietary mulberry-leaf flavonoids improve the eggshell quality of aged breeder hens

Eggshell quality is subject to a significant decline in the late laying period, which results in huge economic losses. The purpose of this study was to investigate the effects of dietary mulberry-leaf flavonoids (MF) on the eggshell quality of aged breeder hens. A total of 270 (60-week-old) Qiling breeder hens were randomly assigned to 3 treatments with supplemental dietary MF doses (0, 30, and 60 mg/kg). The results showed that dietary MF improved the eggshell thickness and strength, following the reduced broken egg ratio (P < 0.05). Histological analysis showed that dietary MF increased glandular density and luminal epithelium height in the shell gland (P < 0.05). MF treatment reduced the apoptotic index of the shell gland, following by improved antioxidant capacity (P < 0.05). The protein expression of Caspase 3 was down-regulated, and Nrf2 was up-regulated by dietary MF (P < 0.05). Furthermore, calcium (Ca) content in the serum and shell gland, as well as the activity of Ca²⁺-ATPase in the shell gland were increased by dietary MF (P < 0.05). Ca transport-related genes (ESRα, ESRβ, KCNA1, OPN, CABP-28K and CDH6) in the shell gland were upregulated by dietary MF treatment (P < 0.05). In conclusion, dietary MF could ameliorate the eggshell quality of aged hens by improving antioxidative capability and Ca deposition in the shell gland of uterus.

Exploring the chemistry behind protein-glycosaminoglycan conjugate: A steady-state and kinetic spectroscopy based approach

The impact of glycosaminoglycan (chondroitin sulphate, CS) on bone morphogenetic protein - 2 (BMP - 2) structure, stability (thermal and chemical), association kinetics and conformation was monitored by multiple spectroscopic techniques (UV-Visible, fluorescence and circular dichroism). The absorbance in peptide region and fluorescence intensity of BMP - 2 was quenched in presence of CS; thus, confirming the formation of a ground-state complex. As there was an increase in Stern-Volmer constant observed as a function of temperature, idea of dynamic quenching was established. However, the negligible changes in lifetime indicated static quenching; thus, making the process a combination of static-dynamic quenching. Basically, the protein - glycan interaction was driven by entropy of the system and mediated by hydrophobic interactions. Secondary structure (CD spectroscopy) of native protein was significantly affected (intensity became more negative) in presence of CS, thus, introducing more compactness in the protein. CS infused thermal and chemical stability into BMP - 2 via alteration in its conformation. The rate of association was inversely proportional to concentration of quencher (CS), which confirmed the correlation between large size (~ 5 times the size of protein) and structural complexity of CS with fewer binding sites present in BMP - 2. The rate of association in presence of urea, suggested a decrease in association rate as a function of urea concentration for 15 μM CS. Experimental evidences suggested an interaction between protein and glycan mediated by hydrophobic interactions, which deciphers structural, thermal and chemical stability into protein.