Systemic C-peptide supplementation ameliorates retinal neurodegeneration by inhibiting VEGF-induced pathological events in diabetes.

Diabetic retinopathy (DR) is caused by retinal vascular dysfunction and neurodegeneration. Intraocular delivery of C-peptide has been shown to be beneficial against hyperglycemia-induced microvascular leakage in the retina of diabetes; however, the effect of C-peptide on diabetes-induced retinal neurodegeneration remains unknown. Moreover, extraocular C-peptide replacement therapy against DR to avoid various adverse effects caused by intravitreal injections has not been studied. Here, we demonstrate that systemic C-peptide supplementation using osmotic pumps or biopolymer-conjugated C-peptide hydrogels ameliorates neurodegeneration by inhibiting vascular endothelial growth factor-induced pathological events, but not hyperglycemia-induced vascular endothelial growth factor expression, in the retinas of diabetic mice. C-peptide inhibited hyperglycemia-induced activation of macroglial and microglial cells, downregulation of glutamate aspartate transporter 1 expression, neuronal apoptosis, and histopathological changes by a mechanism involving reactive oxygen species generation in the retinas of diabetic mice, but transglutaminase 2, which is involved in retinal vascular leakage, is not associated with these pathological events. Overall, our findings suggest that systemic C-peptide supplementation alleviates hyperglycemia-induced retinal neurodegeneration by inhibiting a pathological mechanism, involving reactive oxygen species, but not transglutaminase 2, in diabetes.

Norterpene Cyclic Peroxides from the Marine Sponge Diacarnus spinipoculum, Inhibitors of Transient Receptor Potential Ankyrin 1.

Bioassay-guided isolation of the extract from the marine sponge Diacarnus spinipoculum showing inhibitory activity against human transient receptor potential ankyrin 1 (hTRPA1) resulted in the isolation of 12 norditerpene cyclic peroxides (1-12) and eight norsesterterpene cyclic peroxides (13-20). Among these, 10 (5-7, 11, 12, 16-20) are unprecedented analogs. Compounds with either a hydroxy (5, 11) or a methoxy (6, 12) group attached to the cyclohexanone moiety were obtained as epimeric mixtures at C-11, while compounds 4, 6, 10, and 12 are likely the artifacts of isolation. The absolute configurations of the new compounds were established based on an NMR-based empirical method and comparison of specific rotation values. Mosher ester analysis revealed the absolute configurations of compounds 17-20. The inhibitory activity of the isolated compounds against hTRPA1 varied significantly depending on their structures, with the norsesterterpenoid 19 displaying the most potent activity (IC50 2.0 µM).

Halenaquinol Blocks Staphylococcal Protein A Anchoring on Cell Wall Surface by Inhibiting Sortase A in Staphylococcus aureus.

Sortase A (SrtA) is a cysteine transpeptidase that binds to the periplasmic membrane and plays a crucial role in attaching surface proteins, including staphylococcal protein A (SpA), to the peptidoglycan cell wall. Six pentacyclic polyketides (1-6) were isolated from the marine sponge Xestospongia sp., and their structures were elucidated using spectroscopic techniques and by comparing them to previously reported data. Among them, halenaquinol (2) was found to be the most potent SrtA inhibitor, with an IC50 of 13.94 µM (4.66 µg/mL). Semi-quantitative reverse transcription PCR data suggest that halenaquinol does not inhibit the transcription of srtA and spA, while Western blot analysis and immunofluorescence microscopy images suggest that it blocks the cell wall surface anchoring of SpA by inhibiting the activity of SrtA. The onset and magnitude of the inhibition of SpA anchoring on the cell wall surface in S. aureus that has been treated with halenaquinol at a value 8× that of the IC50 of SrtA are comparable to those for an srtA-deletion mutant. These findings contribute to the understanding of the mechanism by which marine-derived pentacyclic polyketides inhibit SrtA, highlighting their potential as anti-infective agents targeting S. aureus virulence.

Dopamine ameliorates hyperglycemic memory-induced microvascular dysfunction in diabetic retinopathy.

Dopamine is a neurotransmitter that mediates visual function in the retina and diabetic retinopathy (DR) is the most common microvascular complication of diabetes and the leading cause of blindness; however, the role of dopamine in retinal vascular dysfunction in DR remains unclear. Here, we report a mechanism of hyperglycemic memory (HGM)-induced retinal microvascular dysfunction and the protective effect of dopamine against the HGM-induced retinal microvascular leakage and abnormalities. We found that HGM induced persistent oxidative stress, mitochondrial membrane potential collapse and fission, and adherens junction disassembly and subsequent vascular leakage after blood glucose normalization in the mouse retinas. These persistent hyperglycemic stresses were inhibited by dopamine treatment in human retinal endothelial cells and by intravitreal injection of levodopa in the retinas of HGM mice. Moreover, levodopa supplementation ameliorated HGM-induced pericyte degeneration, acellular capillary and pericyte ghost generation, and endothelial apoptosis in the mouse retinas. Our findings suggest that dopamine alleviates HGM-induced retinal microvascular leakage and abnormalities by inhibiting persistent oxidative stress and mitochondrial dysfunction.

Coscinoderines A-J: Trisubstituted Pyridinium-Containing Norterpenoids Isolated from Coscinoderma bakusi, a Tropical Marine Sponge.

Ten new norterpene alkaloids, coscinoderines A-J (1-10), were isolated from the marine sponge Coscinoderma bakusi. Each coscinoderine contains a 1,2,5-trisubstituted pyridinium moiety bearing a terpene unit at the C-2 position. Their structures were elucidated by analysis of NMR and HRMS data, and the absolute stereochemistry of 4 with a 2-methylbutyl group attached to the nitrogen was determined from a comparison of the calculated and measured ECD spectra. The isolation of coscinoderines expands the repertoire of pyridinium alkaloids isolated from marine sponges.

Bottom-up Solution Synthesis of Graphene Nanoribbons with Precisely Engineered Nanopores.

The incorporation of nanopores into graphene nanostructures has been demonstrated as an efficient tool in tuning their band gaps and electronic structures. However, precisely embedding the uniform nanopores into graphene nanoribbons (GNRs) at the atomic level remains underdeveloped especially for in-solution synthesis due to the lack of efficient synthetic strategies. Herein we report the first case of solution-synthesized porous GNR (pGNR) with a fully conjugated backbone via the efficient Scholl reaction of tailor-made polyphenylene precursor (P1) bearing pre-installed hexagonal nanopores. The resultant pGNR features periodic subnanometer pores with a uniform diameter of 0.6 nm and an adjacent-pores-distance of 1.7 nm. To solidify our design strategy, two porous model compounds (1 a, 1 b) containing the same pore size as the shortcuts of pGNR, are successfully synthesized. The chemical structure and photophysical properties of pGNR are investigated by various spectroscopic analyses. Notably, the embedded periodic nanopores largely reduce the π-conjugation degree and alleviate the inter-ribbon π-π interactions, compared to the nonporous GNRs with similar widths, affording pGNR with a notably enlarged band gap and enhanced liquid-phase processability.

Scalarane Sesterterpenoids Isolated from the Marine Sponge Hyrtios erectus and their Cytotoxicity.

Eighteen scalarane sesterterpenoids (1-18), including eight new derivatives (1-8), were isolated from the sponge Hyrtios erectus (family Thorectidae), the extract of which showed cytotoxicity against the HeLa and MCF-7 cell lines. Of the new derivatives, six compounds (1-6) were found to contain a γ-hydroxybutenolide moiety capable of reversible stereoinversion at the hydroxylated carbon center. Under the influence of other adjacent functional groups, each derivative exhibited a different stereochemical behavior, which was fully deduced by ROESY experiments. All the isolated compounds were examined for their cytotoxicity by MTS assay using staurosporine as a positive control (IC50 0.18 and 0.13 µΜ against HeLa and MCF-7 cells, respectively), and they were found to show weak growth inhibitory activities against HeLa and MCF-7 cells, with a minimal IC50 value of 20.0 µΜ. The compounds containing a γ-hydroxybutenolide moiety (1-3, 10, 12) showed cytotoxicity, with IC50 values ranging from 24.3 to 29.9 µΜ, and the most potent derivative was heteronemin (16). Although the cytotoxicities of isolated compounds were insufficient to discuss the structure-activity relationship, this research could contribute to expanding the structural diversity of scalaranes and understanding the stereochemical behavior of γ-hydroxybutenolides.

Midazolam Ameliorates Hyperglycemia-Induced Glomerular Endothelial Dysfunction by Inhibiting Transglutaminase 2 in Diabetes.

Midazolam is an anesthetic widely used for anxiolysis and sedation; however, to date, a possible role for midazolam in diabetic kidney disease remains unknown. Here, we investigated the effect of midazolam on hyperglycemia-induced glomerular endothelial dysfunction and elucidated its mechanism of action in kidneys of diabetic mice and human glomerular microvascular endothelial cells (HGECs). We found that, in diabetic mice, subcutaneous midazolam treatment for 6 weeks attenuated hyperglycemia-induced elevation in urine albumin/creatinine ratios. It also ameliorated hyperglycemia-induced adherens junction disruption and subsequent microvascular leakage in glomeruli of diabetic mice. In HGECs, midazolam suppressed high glucose-induced vascular endothelial-cadherin disruption and endothelial cell permeability via inhibition of intracellular Ca2+ elevation and subsequent generation of reactive oxygen species (ROS) and transglutaminase 2 (TGase2) activation. Notably, midazolam also suppressed hyperglycemia-induced ROS generation and TGase2 activation in glomeruli of diabetic mice and markedly improved pathological alterations in glomerular ultrastructure in these animals. Analysis of kidneys from diabetic Tgm2-/- mice further revealed that TGase2 played a critical role in microvascular leakage. Overall, our findings indicate that midazolam ameliorates hyperglycemia-induced glomerular endothelial dysfunction by inhibiting ROS-mediated activation of TGase2.

Secondary Metabolites from the Marine Sponges of the Genus Petrosia: A Literature Review of 43 Years of Research.

Sponges are prolific sources of various natural products that have provided the chemical scaffolds for new drugs. The sponges of the genus Petrosia inhabit various regions and contain a variety of biologically active natural products such as polyacetylenes, sterols, meroterpenoids, and alkaloids. This review aims to provide a comprehensive summary of the chemical structures and biological activities of Petrosia metabolites covering a period of more than four decades (between 1978 and 2020). It is also described in this review that the major groups of metabolites from members of the genus Petrosia differed with latitude. The polyacetylenes were identified to be the most predominant metabolites in Petrosia sponges in temperate regions, while tropical Petrosia species were sources of a greater variety of metabolites, such as meroterpenoids, sterols, polyacetylenes, and alkaloids.

A Novel Agarase, Gaa16B, Isolated from the Marine Bacterium Gilvimarinus agarilyticus JEA5, and the Moisturizing Effect of Its Partial Hydrolysis Products.

We recently identified a ß-agarase, Gaa16B, in the marine bacterium Gilvimarinus agarilyticus JEA5. Gaa16B, belonging to the glycoside hydrolase 16 family of ß-agarases, shows less than 70.9% amino acid similarity with previously characterized agarases. Recombinant Gaa16B lacking the carbohydrate-binding region (rGaa16Bc) was overexpressed in Escherichia coli and purified. Activity assays revealed the optimal temperature and pH of rGaa16Bc to be 55 ∘C and pH 6-7, respectively, and the protein was highly stable at 55 ∘C for 90 min. Additionally, rGaa16Bc activity was strongly enhanced (2.3-fold) in the presence of 2.5 mM MnCl2. The Km and Vmax of rGaa16Bc for agarose were 6.4 mg/mL and 953 U/mg, respectively. Thin-layer chromatography analysis revealed that rGaa16Bc can hydrolyze agarose into neoagarotetraose and neoagarobiose. Partial hydrolysis products (PHPs) of rGaa16Bc had an average molecular weight of 88-102 kDa and exhibited > 60% hyaluronidase inhibition activity at a concentration of 1 mg/mL, whereas the completely hydrolyzed product (CHP) showed no hyaluronidase at the same concentration. The biochemical properties of Gaa16B suggest that it could be useful for producing functional neoagaro-oligosaccharides. Additionally, the PHP of rGaa16Bc may be useful in promoting its utilization, which is limited due to the gel strength of agar.

Aptamer-Based Field-Effect Transistor for Detection of Avian Influenza Virus in Chicken Serum.

Early diagnosis of the highly pathogenic H5N1 avian influenza virus (AIV) is significant for preventing and controlling a global pandemic. However, there is no existing electrical biosensor for detecting biomarkers for AIV in clinically relevant samples such as chicken serum. Herein, we report the first use of an aptamer-functionalized field-effect transistor (FET) as a label-free sensor for AIV detection in chicken serum. A DNA aptamer is employed as a sensitive and selective receptor for hemagglutinin (HA) protein, which is a biomarker for AIVs. This aptamer is immobilized on a gold microelectrode that is connected to the gate of a reusable FET transducer. The specific binding of the target protein results in a change in the surface potential, which generates a signal response of the FET transducer. We hypothesize that a conformational change in the DNA aptamer upon specific binding of HA protein may alter the surface potential. The signal of the aptamer-based FET biosensor increased linearly with the increase in the logarithm of HA protein concentration in a dynamic range of 10 pM to 10 nM with a detection limit of 5.9 pM. The selectivity of the biosensor for HA protein was confirmed by employing relevant interfering proteins. The proposed biosensor was successfully applied to the selective detection of HA protein in a chicken serum sample. Owing to its simple and low-cost architecture, portability, and sensitivity, the aptamer-based FET biosensor has potential as a point-of-care diagnosis of H5N1 AIVs in clinical samples.

Unique cartilage matrix-associated protein inhibits the migratory and invasive potential of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) that lacks expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) is a breast cancer subtype with very aggressive metastasis and poor prognosis. Unique cartilage matrix-associated protein (UCMA) is a vitamin K-dependent protein (VKDP) with a high-density γ-carboxyglutamic acid (Gla) domain due to the action of vitamin K. UCMA promotes osteoblast differentiation and mineral deposition in bone and suppresses calcification in vessels. However, correlation between UCMA and TNBC is unknown. This study investigated the inhibitory effect of UCMA on TNBC cell in vitro migration, invasion, and colony formation in addition to in vivo tumorigenesis. Cell migration and invasion significantly decreased in Ucma-overexpressing MDA-MB-231 and 4T1 cells compared to the mock control cells. Also, colony formation and the number of colonies significantly decreased in Ucma-overexpressing MDA-MB-231 and 4T1 cells. These results indicate that UCMA significantly inhibits the migration, invasion, and colony formation of TNBC cells. In an in vivo xenograft mouse model, tumor growth significantly decreased in mice bearing Ucma-overexpressing TNBC cells compared to the mock control cells, indicating that UCMA reduced in vivo tumor growth, similar to the inhibitory role of UCMA in vitro. Survival analysis using publicly available database showed that high UCMA expression significantly correlated with favorable relapse-free survival in TNBC patients compared to those with the other VKDPs, matrix Gla protein (MGP) and osteocalcin (OCN). Collectively, this study suggests that UCMA is a promising new therapeutic agent for TNBC.

Activity-expression profiling of glucose-6-phosphate dehydrogenase in tissues of normal and diabetic mice.

Glucose-6-phosphate dehydrogenase (G6PD) plays a principal role in the regulation of oxidative stress by modulating the nicotinamide adenine dinucleotide phosphate pool and is expected to be associated with metabolic diseases such as diabetes mellitus (DM). However, it is unclear whether hyperglycemia increases G6PD activity levels in DM because suitable assays for quantifying the activity in a high-throughput manner are lacking. Using liquid droplet arrays tailored to analyze tissue lysates, we performed G6PD activity profiling in eight tissues of normal and diabetic mice: brain, heart, kidney, liver, lung, muscle, spleen, and thyroid. Diabetic mice exhibited significantly higher G6PD activities in the kidney, liver, spleen, and thyroid than normal mice; no significant difference was found in the brain, heart, lung, or muscle. We also performed G6PD expression profiling in the eight tissues using Western blot analysis. Diabetic mice showed significantly elevated G6PD expression levels in the kidney, lung, spleen, and thyroid compared with normal mice; no significant difference was found in the brain, heart, liver, or muscle. An analysis of G6PD activity-expression profiles demonstrated tissue-specific changes in response to hyperglycemia. Thus, our approach would be helpful for understanding the role of G6PD in tissue-based pathogenesis of diabetic complications.

Proinsulin C-peptide prevents hyperglycemia-induced vascular leakage and metastasis of melanoma cells in the lungs of diabetic mice.

C-peptide has a beneficial effect against diabetic complications, but its role in hyperglycemia-induced metastasis is unknown. We investigated hyperglycemia-mediated pulmonary vascular leakage and metastasis and C-peptide inhibition of these molecular events using human pulmonary microvascular endothelial cells (HPMVECs) and streptozotocin-induced diabetic mice. VEGF, which is elevated in the lungs of diabetic mice, activated transglutaminase 2 (TGase2) in HPMVECs by sequential elevation of intracellular Ca2+ and reactive oxygen species (ROS) levels. VEGF also induced vascular endothelial (VE)-cadherin disruption and increased the permeability of endothelial cells, both of which were prevented by the TGase inhibitors monodansylcadaverine and cystamine or TGM2-specific small interfering RNA. C-peptide prevented VEGF-induced VE-cadherin disruption and endothelial cell permeability through inhibiting ROS-mediated activation of TGase2. C-peptide supplementation inhibited hyperglycemia-induced ROS generation and TGase2 activation and prevented vascular leakage and metastasis in the lungs of diabetic mice. The role of TGase2 in hyperglycemia-induced pulmonary vascular leakage and metastasis was further demonstrated in diabetic Tgm2-/- mice. These findings demonstrate that hyperglycemia induces metastasis, and C-peptide prevents the hyperglycemia-induced metastasis in the lungs of diabetic mice by inhibiting VEGF-induced TGase2 activation and subsequent vascular leakage.-Jeon, H.-Y., Lee, Y.-J., Kim, Y.-S., Kim, S.-Y., Han, E.-T., Park, W. S., Hong, S.-H., Kim, Y.-M., Ha, K.-S. Proinsulin C-peptide prevents hyperglycemia-induced vascular leakage and metastasis of melanoma cells in the lungs of diabetic mice.

The vicious cycle between transglutaminase 2 and reactive oxygen species in hyperglycemic memory-induced endothelial dysfunction.

Clinical trials suggested that the vascular system can remember episodes of poor glycemic control through a phenomenon known as hyperglycemic memory (HGM). HGM is associated with long-term diabetic vascular complications in type 1 and type 2 diabetes, although the molecular mechanism of that association is not clearly understood. We hypothesized that transglutaminase 2 (TGase2) and intracellular reactive oxygen species (ROS) play a key role in HGM-induced vascular dysfunction. We found that hyperglycemia induced persistent oxidative stress, expression of inflammatory adhesion molecules, and apoptosis in the aortic endothelium of HGM mice whose blood glucose levels had been normalized by insulin supplementation. TGase2 activation and ROS generation were in a vicious cycle in the aortic endothelium of HGM mice and also in human aortic endothelial cells after glucose normalization, which played a key role in the sustained expression of inflammatory adhesion molecules and apoptosis. Our findings suggest that the TGase2-ROS vicious cycle plays an important role in HGM-induced endothelial dysfunction.-Lee, J.-Y., Lee, Y.-J., Jeon, H.-Y., Han, E.-T., Park, W. S., Hong, S.-H., Kim, Y.-M., Ha, K.-S. The vicious cycle between transglutaminase 2 and reactive oxygen species in hyperglycemic memory-induced endothelial dysfunction.

Enantioselective total synthesis of (+)-ieodomycin A, (+)-ieodomycin B, and their three stereoisomers.

We describe a divergent and enantioselective total synthesis of (+)-ieodomycin A and (+)-ieodomycin B with three stereoisomers. The main advantage of the present synthesis is the late-stage elaboration of the side chain, which would afford a wide range of structurally diverse analogs with interesting bioactivities.

Therapeutic Potential of (-)-Agelamide D, a Diterpene Alkaloid from the Marine Sponge Agelas sp., as a Natural Radiosensitizer in Hepatocellular Carcinoma Models.

Radiation therapy (RT) is an effective local treatment for unresectable hepatocellular carcinoma (HCC), but there are currently no predictive biomarkers to guide treatment decision for RT or adjuvant systemic drugs to be combined with RT for HCC patients. Previously, we reported that extracts of the marine sponge Agelas sp. may contain a natural radiosensitizer for HCC treatment. In this study, we isolated (-)-agelamide D from Agelas extract and investigated the mechanism underlying its radiosensitization. (-)-Agelamide D enhanced radiation sensitivity of Hep3B cells with decreased clonogenic survival and increased apoptotic cell death. Furthermore, (-)-agelamide D increased the expression of protein kinase RNA-like endoplasmic reticulum kinase/inositol-requiring enzyme 1α/activating transcription factor 4 (PERK/eIF2α/ATF4), a key pathway of the unfolded protein response (UPR) in multiple HCC cell lines, and augmented radiation-induced UPR signaling. In vivo xenograft experiments confirmed that (-)-agelamide D enhanced tumor growth inhibition by radiation without systemic toxicity. Immunohistochemistry results showed that (-)-agelamide D further increased radiation-induced ATF4 expression and apoptotic cell death, which was consistent with our in vitro finding. Collectively, our results provide preclinical evidence that the use of UPR inducers such as (-)-agelamide D may enhance the efficacy of RT in HCC management.

Oxygenated Theonellastrols: Interpretation of Unusual Chemical Behaviors Using Quantum Mechanical Calculations and Stereochemical Reassignment of 7α-Hydroxytheonellasterol.

A total of eight new oxygenated 4-exo-methylene sterols, 1-8, together with one artifact 9 and six known sterols 11-16, were isolated from the marine sponge Theonella swinhoei collected from the Bohol province in Philippines. Structures of sterols 1-8 were determined from 1D and 2D NMR data. Among the sterols, 8α-hydroxytheonellasterol (4) spontaneously underwent an allylic 1,3-hydroxyl shift to produce 15α-hydroxytheonellasterol (9) as an artifact; this was rationalized by quantum mechanical calculations of the transition state. In addition, the 1,2-epoxy alcohol subunit of 8α-hydroxy-14,15-ß-epoxytheonellasterol (5) was assigned using the Gauge-Independent Atomic Orbital (GIAO) NMR chemical shift calculations and subsequent DP4+ analysis. Finally, comparison of the 13C chemical shifts of isolated 7α-hydroxytheonellasterol (6) with the reported values revealed significant discrepancies at C-6, C-7, C-8, and C-14, leading to reassignment of the C-7 stereochemistry in the known structure.

Enhanced Power Conversion Efficiency of Dye-Sensitized Solar Cells by Band Edge Shift of TiO2 Photoanode.

By simple soaking titanium dioxide (TiO2) films in an aqueous Na2S solution, we could prepare surface-modified photoanodes for application to dye-sensitized solar cells (DSSCs). An improvement in both the open-circuit voltage (Voc) and the fill factor (FF) was observed in the DSSC with the 5 min-soaked photoanode, compared with those of the control cell without any modification. The UV-visible absorbance spectra, UPS valence band spectra, and dark current measurements revealed that the Na2S modification led to the formation of anions on the TiO2 surface, and thereby shifted the conduction band edge of TiO2 in the negative (upward) direction, inducing an increase of 29 mV in the Voc. It was also found that the increased FF value in the surface-treated device was attributed to an elevation in the shunt resistance.

Unique cartilage matrix-associated protein regulates fibrillin-2 expression and directly interacts with fibrillin-2 protein independent of calcium binding.

Unique cartilage matrix-associated protein (UCMA) is a secretory γ-carboxyglutamate (Gla) containing protein that is mainly expressed in the cartilage. Ucma, a downstream gene of both Runx2 and Osterix, has recently been described to promote osteoblast differentiation and matrix mineralization. However, till date, no studies have focused on the role of downstream target genes of Ucma in osteogenesis. Here, by Affymetrix GeneChip microarray analysis, we determined 45 differentially expressed genes in response to Ucma stable overexpression or knockdown in osteoblast cells, which provided insight into molecular mechanisms underlying osteoblast differentiation. In particular, we showed that fibrillin-2 (FBN2) expression was proportional to Ucma expression in osteoblasts as validated by quantitative PCR. We also showed that even though Gla-containing UCMA and calcium-binding EGF-like domain-containing FBN2 are known to have a high affinity for calcium, FBN2 whose expression was regulated by UCMA directly interacted with the UCMA protein, independent of calcium.