Daldipyrenones A-C: Caged [6,6,6,6,6] Polyketides Derived from an Endolichenic Fungus Daldinia pyrenaica 047188.

Daldipyrenones A-C (1-3), three unprecedented caged xanthone [6,6,6,6,6] polyketides featuring a spiro-azaphilone unit, were discovered from an endolichenic fungus, Daldinia pyrenaica 047188. The structures of 1-3 were determined by using spectroscopic analysis and chemical derivatization. Daldipyrenones are likely derived by combining a chromane biosynthesis intermediate, 1-(2,6-dihydroxyphenyl)but-2-en-2-one, and a spiro-azaphilone, pestafolide A, via radical coupling or Michael addition to form a bicyclo[2.2.2]octane ring. Genome sequencing of the strain revealed two separate biosynthetic gene clusters responsible for forming two biosynthetic intermediates, suggesting a proposed biosynthetic pathway. Daldipyrenone A (1) exhibited significant antimelanogenic activity with lower EC50's than positive controls and moderate adiponectin-secretion promoting activity.

Prenylated Chrysin Derivatives as Partial PPARγ Agonists with Adiponectin Secretion-Inducing Activity.

Decreased circulating adiponectin levels are associated with an increased risk of human metabolic diseases. The chemical-mediated upregulation of adiponectin biosynthesis has been proposed as a novel therapeutic approach to managing hypoadiponectinemia-associated diseases. In preliminary screening, the natural flavonoid chrysin (1) exhibited adiponectin secretion-inducing activity during adipogenesis in human bone marrow mesenchymal stem cells (hBM-MSCs). Here, we provide the 7-prenylated chrysin derivatives, chrysin 5-benzyl-7-prenylether compound 10 and chrysin 5,7-diprenylether compound 11, with the improved pharmacological profile compared with chrysin (1). Nuclear receptor binding and ligand-induced coactivator recruitment assays revealed that compounds 10 and 11 functioned as peroxisome proliferator-activated receptor (PPAR)γ partial agonists. These findings were supported by molecular docking simulation, followed by experimental validation. Notably, compound 11 showed PPARγ binding affinity as potent as that of the PPARγ agonists pioglitazone and telmisartan. This study presents a novel PPARγ partial agonist pharmacophore and suggests that prenylated chrysin derivatives have therapeutic potential in various human diseases associated with hypoadiponectinemia.

In vitro and in vivo suppression of SARS-CoV-2 replication by a modified, short, cell-penetrating peptide targeting the C-terminal domain of the viral spike protein.

Peptides are promising therapeutic agents for COVID-19 because of their specificity, easy synthesis, and ability to be fine-tuned. We previously demonstrated that a cell-permeable peptide corresponding to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Spike C-terminal domain (CD) inhibits the interaction between viral spike and nucleocapsid proteins that results in SARS-CoV-2 replication in vitro. Here, we used docking studies to design R-t-Spike CD(D), a more potent short cell-penetrating peptide composed of all D-form amino acids and evaluated its inhibitory effect against the replication of SARS-CoV-2 S clade and other variants. R-t-Spike CD(D) was internalized into Vero cells and Calu-3 cells and suppressed the replication of SARS-CoV-2 S clade, delta variant, and omicron variant with higher potency than the original peptide. In hemizygous K18-hACE2 mice, intratracheal administration of R-t-Spike CD(D) effectively delivered the peptide to the trachea and lungs, whereas intranasal administration delivered the peptide mostly to the upper respiratory system and stomach, and a small amount to the lungs. Administration by either route reduced viral loads in mouse lungs and turbinates. Furthermore, intranasally administered R-t-Spike CD(D) mitigated pathological change in the lungs and increased the survival of mice after infection with the SARS-CoV-2 S clade or delta variant. Our data suggest that R-t-Spike CD(D) has potential as a therapeutic agent against SARS-CoV-2 infection.

Structure-Activity Relationships of Truncated 1'-Homologated Carbaadenosine Derivatives as New PPARγ/δ Ligands: A Study on Sugar Puckering Affecting Binding to PPARs.

Peroxisome proliferator-activated receptors (PPARs) are associated with the regulation of metabolic homeostasis. Based on a previous report that 1'-homologated 4'-thionucleoside acts as a dual PPARγ/δ modulator, carbocyclic nucleosides 2-5 with various sugar conformations were synthesized to determine whether sugar puckering affects binding to PPARs. (S)-conformer 2 was synthesized using Charette asymmetric cyclopropanation, whereas (N)-conformer 3 was synthesized using stereoselective Simmons-Smith cyclopropanation. All synthesized nucleosides did not exhibit binding affinity to PPARα but exhibited significant binding affinities to PPARγ/δ. The binding affinity of final nucleosides to PPARγ did not differ significantly based on their conformation, but their affinity to PPARδ depended greatly on their conformation, correlated with adiponectin production. (N)-conformer 3h was discovered to be the most potent PPARδ antagonist with good adiponectin production, which exhibited the most effective activity in inhibiting the mRNA levels of LPS-induced IL-1ß expression in RAW 264.7 macrophages, implicating its anti-inflammatory activity.

Computational Prediction of the Phenotypic Effect of Flavonoids on Adiponectin Biosynthesis.

In silico machine learning applications for phenotype-based screening have primarily been limited due to the lack of machine-readable data related to disease phenotypes. Adiponectin, a nuclear receptor (NR)-regulated adipocytokine, is relatively downregulated in human metabolic diseases. Here, we present a machine-learning model to predict the adiponectin-secretion-promoting activity of flavonoid-associated phytochemicals (FAPs). We modeled a structure-activity relationship between the chemical similarity of FAPs and their bioactivities using a random forest-based classifier, which provided the NR activity of each FAP as a probability. To link the classifier-predicted NR activity to the phenotype, we next designed a single-cell transcriptomics-based multiple linear regression model to generate the relative adiponectin score (RAS) of FAPs. In experimental validation, estimated RAS values of FAPs isolated from Scutellaria baicalensis exhibited a significant correlation with their adiponectin-secretion-promoting activity. The combined cheminformatics and bioinformatics approach enables the computational reconstruction of phenotype-based screening systems.

Discovery of PPARγ and glucocorticoid receptor dual agonists to promote the adiponectin and leptin biosynthesis in human bone marrow mesenchymal stem cells.

Adiponectin and leptin are major adipocytokines that control crosstalk between adipose tissue and other organ systems. Hypoadiponectinemia and hypoleptinemia are associated with human metabolic diseases. Compounds with adipocytokine biosynthesis-stimulating activities could be developed as therapeutics against diverse metabolic conditions. In phenotypic screening with human bone marrow mesenchymal stem cells (hBM-MSCs), (E)-4-hydroxy-3-(3-(4-hydroxy-3-methoxyphenyl)acryloyl)-6-methyl-2H-pyran-2-one (1) was identified to increase adiponectin biosynthesis during adipogenesis and simultaneously to stimulate leptin production. Using the compound 1 structure, the structure-activity relationship study was performed to discover more potent compounds stimulating both adiponectin and leptin production. (E)-3-(3-(2-fluoropyridin-4-yl)acryloyl)-4-hydroxy-6-methyl-2H-pyran-2-one (11) exhibited the most potent adiponectin (EC50, 2.87 µM) and leptin (EC50, 2.82 µM) biosynthesis-stimulating activities in hBM-MSCs. In a target identification study, compound 11 was characterized as a dual modulator binding to both peroxisome proliferator-activated receptor (PPAR) γ and glucocorticoid receptor (GR). This study provides a novel pharmacophore for PPARγ/GR dual modulators with therapeutic potential against human metabolic diseases.

Macakurzin C Derivatives as a Novel Pharmacophore for Pan-Peroxisome Proliferator-Activated Receptor Modulator.

The natural flavonoid macakurzin C (1) exhibited adiponectin biosynthesis-inducing activity during adipogenesis in human bone marrow mesenchymal stem cells and its molecular mechanism was directly associated with a pan-peroxisome proliferator-activated receptor (PPAR) modulator affecting all three PPAR subtypes α, γ, and δ. In this study, increases in adiponectin biosynthesis-inducing activity by macakurzin C derivatives (2-7) were studied. The most potent adiponectin biosynthesis-inducing compound 6, macakurzin C 3,5-dimethylether, was elucidated as a dual PPARα/γ modulator. Compound 6 may exhibit the most potent activity because of the antagonistic relationship between PPARδ and PPARγ. Docking studies revealed that the O-methylation of macakurzin C to generate compound 6 significantly disrupted PPARδ binding. Compound 6 has therapeutic potential in hypoadiponectinemia-related metabolic diseases.

Sunscreen filter octocrylene is a potential obesogen by acting as a PPARγ partial agonist.

Octocrylene (OC) is an extensively prescribed organic ultraviolet B filter used in sunscreen products. Due to its extensive use, a significant level of OC is detected in marine and freshwater environments. Notably, the bioaccumulation of OC in aquatic biota may affect human health. In this study, the effect of OC on metabolism was investigated using the adipogenesis model of human bone marrow mesenchymal stem cells (hBM-MSCs). OC promoted adiponectin production during adipogenesis in hBM-MSCs compared to the vehicle-treated control (EC50, 29.6 µM). In target identification, OC directly bound to peroxisome proliferator-activated receptor (PPAR) γ (Ki, 37.8 µM). OC-bound PPARγ also significantly recruited nuclear receptor coactivator proteins SRC-1 (EC50, 54.1 µM) and SRC-2 (EC50, 58.6 µM). In the molecular docking simulation study, the optimal ligand-binding mode of OC suggested that OC is a PPARγ partial agonist. A competitive analysis with a PPARγ full agonist pioglitazone revealed that OC acted as a PPARγ partial agonist. OC altered the gene transcription profile of lipid-metabolism associated enzymes in normal human keratinocytes, primarily exposed human cells after the application of sunscreens. In conclusion, OC is a potential metabolic disrupting obesogen.

Galangin 3-benzyl-5-methylether derivatives function as an adiponectin synthesis-promoting peroxisome proliferator-activated receptor γ partial agonist.

The upregulation of adiponectin production has been suggested as a novel strategy for the treatment of metabolic diseases. Galangin, a natural flavonoid, exhibited adiponectin synthesis-promoting activity during adipogenesis in human bone marrow mesenchymal stem cells. In target identification, galangin bound both peroxisome proliferator-activated receptor (PPAR) γ and estrogen receptor (ER) ß. Novel galangin derivatives were synthesized to improve adiponectin synthesis-promoting compounds by increasing the PPARγ activity of galangin and reducing its ERß activity, because PPARγ functions can be inhibited by ERß. Three galangin 3-benzyl-5-methylether derivatives significantly promoted adiponectin production by 2.88-, 4.47-, and 2.76-fold, respectively, compared to the effect of galangin. The most potent compound, galangin 3-benzyl-5,7-dimethylether, selectively bound to PPARγ (Ki, 1.7 µM), whereas it did not bind to ERß. Galangin 3-benzyl-5,7-dimethylether was identified as a PPARγ partial agonist in docking and pharmacological competition studies, suggesting that it may have diverse therapeutic potential in a variety of metabolic diseases.

Salicinoyl Quinic Acids and Their Prostaglandin E2 Production Inhibitory Activities from the Fruits of Casearia grewiifolia.

Phytochemical investigation on the dried fruits of Casearia grewiifolia led to the identification of 10 new salicinoyl quinic acid derivatives (1-10), a new benzoyl quinic acid (11), and two known compounds (12 and 13). The structures of the new compounds were elucidated by interpreting 1D and 2D NMR spectroscopic data including HMBC and EXSIDE along with a chemical method for sugar unit analysis. All isolates were evaluated for their inhibitory activities against prostaglandin E2 (PGE2) production in ultraviolet B (UVB)-irradiated HaCat keratinocytes. Of the isolates tested, compounds 6 and 12 were found to inhibit PGE2 production with IC50 values of 20.5 and 28.8 µM, respectively.

Psammocindoles A-C: Isolation, Synthesis, and Bioactivity of Indole-γ-lactams from the Sponge Psammocinia vermis.

Psammocindoles A-C (1-3), a new class of indole alkaloids, were isolated from a Psammocinia vermis sponge. By combined spectroscopic analyses, the structures of these compounds were determined to be the indole-γ-lactams derived from three amino acid residues. In addition, an enantiomer psammocindole D (4), and the N-lactam isomers isopsammocindoles A-D (5-8) were also synthesized. These natural products and synthetic analogues were found to significantly stimulate adiponectin secretion in human bone marrow mesenchymal stem cells.

Hypoxia Suppresses Spontaneous Mineralization and Osteogenic Differentiation of Mesenchymal Stem Cells via IGFBP3 Up-Regulation.

Hypoxia has diverse stimulatory effects on human adipose-derived stem cells (ASCs). In the present study, we investigated whether hypoxic culture conditions (2% O2) suppress spontaneous mineralization and osteogenic differentiation of ASCs. We also investigated signaling pathways and molecular mechanisms involved in this process. We found that hypoxia suppressed spontaneous mineralization and osteogenic differentiation of ASCs, and up-regulated mRNA and protein expression of Insulin-like growth factor binding proteins (IGFBPs) in ASCs. Although treatment with recombinant IGFBPs did not affect osteogenic differentiation of ASCs, siRNA-mediated inhibition of IGFBP3 attenuated hypoxia-suppressed osteogenic differentiation of ASCs. In contrast, overexpression of IGFBP3 via lentiviral vectors inhibited ASC osteogenic differentiation. These results indicate that hypoxia suppresses spontaneous mineralization and osteogenic differentiation of ASCs via intracellular IGFBP3 up-regulation. We determined that reactive oxygen species (ROS) generation followed by activation of the MAPK and PI3K/Akt pathways play pivotal roles in IGFBP3 expression under hypoxia. For example, ROS scavengers and inhibitors for MAPK and PI3K/Akt pathways attenuated the hypoxia-induced IGFBP3 expression. Inhibition of Elk1 and NF-κB through siRNA transfection also led to down-regulation of IGFBP3 mRNA expression. We next addressed the proliferative potential of ASCs with overexpressed IGFBP3, but IGFBP3 overexpression reduced the proliferation of ASCs. In addition, hypoxia reduced the osteogenic differentiation of bone marrow-derived clonal mesenchymal stem cells. Collectively, our results indicate that hypoxia suppresses the osteogenic differentiation of mesenchymal stem cells via IGFBP3 up-regulation.