VCP/p97 mediates nuclear targeting of non-ER-imported prion protein to maintain proteostasis.

Mistargeting of secretory proteins in the cytosol can trigger their aggregation and subsequent proteostasis decline. We have identified a VCP/p97-dependent pathway that directs non-ER-imported prion protein (PrP) into the nucleus to prevent the formation of toxic aggregates in the cytosol. Upon impaired translocation into the ER, PrP interacts with VCP/p97, which facilitates nuclear import mediated by importin-ß. Notably, the cytosolic interaction of PrP with VCP/p97 and its nuclear import are independent of ubiquitination. In vitro experiments revealed that VCP/p97 binds non-ubiquitinated PrP and prevents its aggregation. Inhibiting binding of PrP to VCP/p97, or transient proteotoxic stress, promotes the formation of self-perpetuating and partially proteinase resistant PrP aggregates in the cytosol, which compromised cellular proteostasis and disrupted further nuclear targeting of PrP. In the nucleus, RNAs keep PrP in a soluble and non-toxic conformation. Our study revealed a novel ubiquitin-independent role of VCP/p97 in the nuclear targeting of non-imported secretory proteins and highlights the impact of the chemical milieu in triggering protein misfolding.

Chemical Genetics in C. elegans Identifies Anticancer Mycotoxins Chaetocin and Chetomin as Potent Inducers of a Nuclear Metal Homeostasis Response.

C. elegans numr-1/2 (nuclear-localized metal-responsive) is an identical gene pair encoding a nuclear protein previously shown to be activated by cadmium and disruption of the integrator RNA metabolism complex. We took a chemical genetic approach to further characterize regulation of this novel metal response by screening 41,716 compounds and extracts for numr-1p::GFP activation. The most potent activator was chaetocin, a fungal 3,6-epidithiodiketopiperazine (ETP) with promising anticancer activity. Chaetocin activates numr-1/2 strongly in the alimentary canal but is distinct from metal exposure, because it represses canonical cadmium-responsive metallothionine genes. Chaetocin has diverse targets in cancer cells including thioredoxin reductase, histone lysine methyltransferase, and acetyltransferase p300/CBP; further work is needed to identify the mechanism in C. elegans as genetic disruption and RNAi screening of homologues did not induce numr-1/2 in the alimentary canal and chaetocin did not affect markers of integrator dysfunction. We demonstrate that disulfides in chaetocin and chetomin, a dimeric ETP analog, are required to induce numr-1/2. ETP monomer gliotoxin, despite possessing a disulfide linkage, had almost no effect on numr-1/2, suggesting a dimer requirement. Chetomin inhibits C. elegans growth at low micromolar levels, and loss of numr-1/2 increases sensitivity; C. elegans and Chaetomiaceae fungi inhabit similar environments raising the possibility that numr-1/2 functions as a defense mechanism. There is no direct orthologue of numr-1/2 in humans, but RNaseq suggests that chaetocin affects expression of cellular processes linked to stress response and metal homeostasis in colorectal cancer cells. Our results reveal interactions between metal response gene regulation and ETPs and identify a potential mechanism of resistance to this versatile class of preclinical compounds.

Epigenetic small-molecule screen for inhibition and reversal of acinar ductal metaplasia in mouse pancreatic organoids.

Background: Acinar ductal metaplasia (ADM) is among the earliest initiating events in pancreatic ductal adenocarcinoma (PDAC) development. Methods: We developed a novel morphology-based screen using organoids from wildtype and p48Cre/+ (Cre) mice to discover epigenetic modulators that inhibit or reverse pancreatic ADM more effectively than the broad-spectrum HDAC inhibitor trichostatin A (TSA). Results: Of the 144 compounds screened, nine hits and two additional natural product HDAC inhibitors were validated by dose-response analysis. The class I HDAC inhibitors apicidin and FK228, and the histone methyltransferase inhibitor chaetocin demonstrated pronounced ADM inhibition and reversal without inducing significant cytotoxicity at 1 µM. Thioester prodrug class I HDAC inhibitor largazole attenuated ADM while its disulfide homodimer was effective in both ADM inhibition and reversal. Prioritized compounds were validated for ADM reversal in p48Cre/+; LSL-KrasG12D/+ (KC) mouse organoids using both morphological and molecular endpoints. Molecular index analysis of ADM reversal in KC mouse organoids demonstrated improved activity compared to TSA. Improved prodrug stability translated into a stronger phenotypic and molecular response. RNA-sequencing indicated that angiotensinogen was the top inhibited pathway during ADM reversal. Conclusion: Our findings demonstrate a unique epigenetic mechanism and suggest that the phenotypic screen developed here may be applied to discover potential treatments for PDAC.

Biosynthesis of Dolastatin 10 in Marine Cyanobacteria, a Prototype for Multiple Approved Cancer Drugs.

Dolastatin 10, a potent tubulin-targeting marine anticancer natural product, provided the basis for the development of six FDA-approved antibody-drug conjugates. Through the screening of cyanobacterial Caldora penicillata environmental DNA libraries and metagenome sequencing, we identified its biosynthetic gene cluster. Functional prediction of 10 enzymes encoded in the 39 kb cluster supports the dolastatin 10 biosynthesis. The nonheme diiron monooxygenase DolJ was biochemically characterized to mediate the terminal thiazole formation in dolastatin 10.

Epigenetic Small-Molecule Screen for Inhibition and Reversal of Acinar Ductal Metaplasia in Mouse Pancreatic Organoids.

Background: Acinar ductal metaplasia (ADM) is among the earliest initiating events in pancreatic ductal adenocarcinoma (PDAC) development. Methods: We developed a novel morphology-based screen using organoids from wildtype and p48 Cre/+ (Cre) mice to discover epigenetic modulators that inhibit or reverse pancreatic ADM more effectively than the broad-spectrum HDAC inhibitor trichostatin A (TSA). Results: Of the 144 compounds screened, nine hits and two additional natural product HDAC inhibitors were validated by dose-response analysis. The class I HDAC inhibitors apicidin and FK228, and the histone methyltransferase inhibitor chaetocin demonstrated pronounced ADM inhibition and reversal without inducing significant cytotoxicity at 1 µM. Thioester prodrug class I HDAC inhibitor largazole attenuated ADM while its disulfide homodimer was effective in both ADM inhibition and reversal. Prioritized compounds were validated for ADM reversal in p48 Cre/+ ;LSL-Kras G12D/+ (KC) mouse organoids using both morphological and molecular endpoints. Molecular index analysis of ADM reversal in KC mouse organoids demonstrated improved activity compared to TSA. Improved prodrug stability translated into a stronger phenotypic and molecular response. RNA-sequencing indicated that angiotensinogen was the top inhibited pathway during ADM reversal. Conclusion: Our findings demonstrate a unique epigenetic mechanism and suggest that the phenotypic screen developed here may be applied to discover potential treatments for PDAC.

Triazolothiadiazine derivative positively modulates CXCR4 signaling and improves diabetic wound healing.

Development of specific therapies that target and accelerate diabetic wound repair is an urgent need to alleviate pain and suffering and the huge socioeconomic burden of this debilitating disease. C-X-C Motif Chemokine Ligand 12 (CXCL12) also know an stromal cell-derived factor 1α (SDF-1α) is a chemokine that binds the CXC chemokine receptor type 4 (CXCR4) and activates downstream signaling resulting in recruitment of hematopoietic cells to locations of tissue injury and promotes tissue repair. In diabetes, low expression of CXCL12 correlates with impaired wound healing. Activation of CXCR4 receptor signaling with agonists or positive allosteric modulators (PAMs) provides a potential for small molecule therapeutic discovery and development. We recently reported high throughput screening and identification of the CXCR4 partial agonist UCUF-728, characterization of in vitro activity and reduced wound closure time in diabetic mice at 100 µM as a proof-of-concept study. We report here, the discovery of a second chemical scaffold demonstrating increased agonist potency and represented by thiadiazine derivative, UCUF-965. UCUF-965 is a potent partial agonist of ß-arrestin recruitment in CXCR4 receptor overexpressing cell line. Furthermore, UCUF-965 potentiates the CXCL12 maximal response in cAMP signaling pathway, activates CXCL12 stimulated migration in lymphoblast cells and modulates the levels of specific microRNA involved in the complex wound repair process, specifically in mouse fibroblasts. Our results indicate that UCUF-965 acts as a PAM agonist of the CXCR4 receptor. Furthermore, UCUF-965 enhanced angiogenesis markers and reduced wound healing time by 36% at 10.0 µM in diabetic mice models compared to untreated control.

Heterologous Production of the C33-C45 Polyketide Fragment of Anticancer Apratoxins in a Cyanobacterial Host.

A polyketide synthase subcluster of cytotoxic apratoxin A was isolated from a Moorena bouillonii environmental DNA library and engineered with a thioesterase II domain for heterologous expression in the filamentous cyanobacterium Anabaena sp. PCC7120. Further engineering with a rhamnose-inducible promoter led to the production of (2R,3R,5R,7R)-3,7-dihydroxy-2,5,8,8-tetramethylnonanoic acid, a stereogenically rich chiral building block that is important to the efficient synthesis of apratoxin analogues, representing the first synthetic biology attempt for this type of polyketide fragment.

Sec61 Inhibitor Apratoxin S4 Potently Inhibits SARS-CoV-2 and Exhibits Broad-Spectrum Antiviral Activity.

There is a pressing need for host-directed therapeutics that elicit broad-spectrum antiviral activities to potentially address current and future viral pandemics. Apratoxin S4 (Apra S4) is a potent Sec61 inhibitor that prevents cotranslational translocation of secretory proteins into the endoplasmic reticulum (ER), leading to anticancer and antiangiogenic activity both in vitro and in vivo. Since Sec61 has been shown to be an essential host factor for viral proteostasis, we tested Apra S4 in cellular models of viral infection, including SARS-CoV-2, influenza A virus, and flaviviruses (Zika, West Nile, and Dengue virus). Apra S4 inhibited viral replication in a concentration-dependent manner and had high potency particularly against SARS-CoV-2 and influenza A virus, with subnanomolar activity in human cells. Characterization studies focused on SARS-CoV-2 revealed that Apra S4 impacted a post-entry stage of the viral life-cycle. Transmission electron microscopy revealed that Apra S4 blocked formation of stacked double-membrane vesicles, the sites of viral replication. Apra S4 reduced dsRNA formation and prevented viral protein production and trafficking of secretory proteins, especially the spike protein. Given the potent and broad-spectrum activity of Apra S4, further preclinical evaluation of Apra S4 and other Sec61 inhibitors as antivirals is warranted.

Discovery, Synthesis, and Biological Evaluation of Anaenamides C and D from a New Marine Cyanobacterium, Hormoscilla sp.

Our ongoing efforts to explore the chemical space associated with marine cyanobacteria from coral reefs of Guam have yielded two new members of the anaenamide family of natural products, anaenamides C (3) and D (4). These compounds were isolated from a novel Hormoscilla sp. (VPG16-58). Our phylogenetic profiling (16S rDNA) of this cyanobacterium indicated that VPG16-58 is taxonomically distinct from the previously reported producer of the anaephenes, VPG16-59 (Hormoscilla sp.), and other previously documented species of the genus Hormoscilla. The planar structures of 3 and 4 were determined via spectroscopic methods, and absolute configurations of the α-hydroxy acids were assigned by enantioselective HPLC analysis. To address the requirement for sufficient material for testing, we first adapted our published linear synthetic approach for 1 and 2 to generate anaenoic acid (7), which served as a point for diversification, providing the primary amides 3 and 4 from synthetic intermediates 5 and 6, respectively. The compounds were then tested for effects on HCT116 colon cancer cell viability and in an ARE-luciferase reporter gene assay for Nrf2 modulation using HEK293 human embryonic kidney cells. Our findings indicate that, in contrast to cytotoxic methyl esters 1 and 2, the primary amides 3 and 4 activate the Nrf2 pathway at noncytotoxic concentrations. Overall, our data suggest that the anaenamide scaffold is tunable to produce differential biological outcomes.

Inhibition of cotranslational translocation by apratoxin S4: Effects on oncogenic receptor tyrosine kinases and the fate of transmembrane proteins produced in the cytoplasm.

Receptor tyrosine kinases (RTKs) have become major targets for anticancer therapy. However, resistance and signaling pathway redundancy has been problematic. The marine-derived apratoxins act complementary to direct kinase inhibitors by downregulating the levels of multiple of these receptors and additionally prevent the secretion of growth factors that act on these receptors by targeting Sec61α, therefore interfering with cotranslational translocation. We have profiled the synthetic, natural product-inspired apratoxin S4 against panels of cancer cells characterized by differential sensitivity to RTK inhibitors due to receptor mutations, oncogenic KRAS mutations, or activation of compensatory pathways. Apratoxin S4 was active at low-nanomolar to sub-nanomolar concentrations against panels of lung, head and neck, bladder, and pancreatic cancer cells, concomitant with the downregulation of levels of several RTKs, including EGFR, MET and others. However, the requisite concentration to inhibit certain receptors varied, suggesting some differential substrate selectivity in cellular settings. This selectivity was most pronounced in breast cancer cells, where apratoxin S4 selectively targeted HER3 over HER2 and showed greater activity against ER+ and triple negative breast cancer cells than HER2+ cancer cells. Depending on the breast cancer subtype, apratoxin S4 differentially downregulated transmembrane protein CDCP1, which is linked to metastasis and invasion in breast cancer and modulates EGFR activity. We followed the fate of CDCP1 through proteomics and found that nonglycosylated CDCP1 associates with chaperone HSP70 and HUWE1 that functions as an E3 ubiquitin ligase and presumably targets CDCP1, as well as potentially other substrates inhibited by apratoxins, for proteasomal degradation. By preventing cotranslational translocation of VEGF and other proangiogenic factors as well as VEGFR2 and other receptors, apratoxins also possess antiangiogenic activity, which was validated in endothelial cells where downregulation of VEGFR2 was observed, extending the therapeutic scope to angiogenic diseases.

Largazole Inhibits Ocular Angiogenesis by Modulating the Expression of VEGFR2 and p21.

Ocular angiogenic diseases, characterized by abnormal blood vessel formation in the eye, are the leading cause of blindness. Although Anti-VEGF therapy is the first-line treatment in the market, a substantial number of patients are refractory to it or may develop resistance over time. As uncontrolled proliferation of vascular endothelial cells is one of the characteristic features of pathological neovascularization, we aimed to investigate the role of the class I histone deacetylase (HDAC) inhibitor Largazole, a cyclodepsipeptide from a marine cyanobacterium, in ocular angiogenesis. Our study showed that Largazole strongly inhibits retinal vascular endothelial cell viability, proliferation, and the ability to form tube-like structures. Largazole strongly inhibits the vessel outgrowth from choroidal explants in choroid sprouting assay while it does not affect the quiescent choroidal vasculature. Largazole also inhibits vessel outgrowth from metatarsal bones in metatarsal sprouting assay without affecting pericytes coverage. We further demonstrated a cooperative effect between Largazole and an approved anti-VEGF drug, Alflibercept. Mechanistically, Largazole strongly inhibits the expression of VEGFR2 and leads to an increased expression of cell cycle inhibitor, p21. Taken together, our study provides compelling evidence on the anti-angiogenic role of Largazole that exerts its function through mediating different signaling pathways.

Gatorbulin-1, a distinct cyclodepsipeptide chemotype, targets a seventh tubulin pharmacological site.

Tubulin-targeted chemotherapy has proven to be a successful and wide spectrum strategy against solid and liquid malignancies. Therefore, new ways to modulate this essential protein could lead to new antitumoral pharmacological approaches. Currently known tubulin agents bind to six distinct sites at α/ß-tubulin either promoting microtubule stabilization or depolymerization. We have discovered a seventh binding site at the tubulin intradimer interface where a novel microtubule-destabilizing cyclodepsipeptide, termed gatorbulin-1 (GB1), binds. GB1 has a unique chemotype produced by a marine cyanobacterium. We have elucidated this dual, chemical and mechanistic, novelty through multidimensional characterization, starting with bioactivity-guided natural product isolation and multinuclei NMR-based structure determination, revealing the modified pentapeptide with a functionally critical hydroxamate group; and validation by total synthesis. We have investigated the pharmacology using isogenic cancer cell screening, cellular profiling, and complementary phenotypic assays, and unveiled the underlying molecular mechanism by in vitro biochemical studies and high-resolution structural determination of the α/ß-tubulin-GB1 complex.

Bifunctional Doscadenamides Activate Quorum Sensing in Gram-Negative Bacteria and Synergize with TRAIL to Induce Apoptosis in Cancer Cells.

New cyanobacteria-derived bifunctional analogues of doscadenamide A, a LasR-dependent quorum sensing (QS) activator in Pseudomonas aeruginosa, characterized by dual acylation of the pyrrolinone core structure and the pendant side chain primary amine to form an imide/amide hybrid are reported. The identities of doscadenamides B-J were confirmed through total synthesis and a strategic focused library with different acylation and unsaturation patterns was created. Key molecular interactions for binding with LasR and a functional response through mutation studies coupled with molecular docking were identified. The structure-activity relationships (SARs) were probed in various Gram-negative bacteria, including P. aeruginosa and Vibrio harveyi, indicating that the pyrrolinone-N acyl chain is critical for full agonist activity, while the other acyl chain is dispensable or can result in antagonist activity, depending on the bacterial system. Since homoserine lactone (HSL) quorum sensing activators have been shown to act in synergy with TRAIL to induce apoptosis in cancer cells, selected doscadenamides were tested in orthogonal eukaryotic screening systems. The most potent QS agonists, doscadenamides S10-S12, along with doscadenamides F and S4 with partial or complete saturation of the acyl side chains, exhibited the most pronounced synergistic effects with TRAIL in triple negative MDA-MB-231 breast cancer cells. The overall correlation of the SAR with respect to prokaryotic and eukaryotic targets may hint at coevolutionary processes and intriguing host-bacteria relationships. The doscadenamide scaffold represents a non-HSL template for combination therapy with TRAIL pathway stimulators.

Correlation between physical exercise,screen time and mental sub-health among Chinese adolescents / 中国学校卫生

Objective@#To understand the relationships between video time, exercise time and the mental sub-health of Chinese adolescents, and to assist the development of Chinese adolescents’ mental health.@*Methods@#In this study, 16 545 adolescents aged 13-22 years in six administrative regions of China were surveyed using an adolescent sub-health multi-dimensional assessment questionnaire (MSQA), and daily physical exercise time, video screen time and other indicators were recorded. Binary Logistic regression analysis was used to understand adolescents’ mental sub-health and the correlation between video time and exercise time.@*Results@#Detection rate of mental sub-health status in adolescents with video time ≤2 h/d was lower than that of adolescents with video time >2 h/d(19.1%，22.1%), and the detection rate of adolescents with exercise time ≤60 min/d(22.1%，17.7%) was higher than that of adolescents with exercise time >60 min/d. These differences were statistically significant (χ2=14.47, 6.97, P<0.05). Binary Logistic regression analysis showed that the risk of mental sub-health status for Chinese adolescents whose screen time was more than 2 h/d was 1.20 times that of those with screen time ≤2 h/d, and the difference was statistically significant (P<0.01). The risk of mental sub-health for students whose exercise time was > 60 min/d was 0.86 times that of students who exercised ≤ 60 min/d, and the difference was statistically significant (P<0.05).@*Conclusion@#Screen time >2 h/d and exercise time <60 min/d were negative factors leading to mental sub-health symptoms in Chinese adolescents.It is proposed to jointly promote the healthy adolescent development through health education,as well as positive family and social environment.

Ahp-Cyclodepsipeptides as tunable inhibitors of human neutrophil elastase and kallikrein 7: Total synthesis of tutuilamide A, serine protease selectivity profile and comparison with lyngbyastatin 7.

We describe the total synthesis of tutuilamide A, a potent porcine pancreatic elastase (PPE) inhibitor and a representative member of the 3-amino-6-hydroxy-2-piperidone (Ahp) cyclodepsipeptide family, isolated from marine cyanobacteria. The Ahp unit serves as a pharmacophore and the adjacent 2-amino-2-butenoic acid (Abu) is a main driver of the selectivity among serine proteases. We adapted our previous convergent strategy to generate the macrocycle, common with lyngbyastatin 7 and related elastase inhibitors, and then appended the tutuilamide A-specific side chain bearing a vinyl chloride. Tutuilamide A and lyngbyastatin 7 were evaluated side by side for the inhibition of the disease-relevant human neutrophil elastase (HNE). Tutuilamide A and lyngbyastatin 7 were approximately equipotent against HNE, while tutuilamide A was previously shown to be more active against PPE compared with lyngbyastatin 7, further demonstrating that the side chain provides opportunities to not only modulate potency but also selectivity among proteases of the same function from different organisms. Profiling of tutuilamide A against mainly human serine proteases revealed high selectivity for HNE (IC50 0.73 nM) and pleiotropic activity against kallikrein 7 (KLK7, IC50 5.0 nM), without affecting other kallikreins, similarly to lyngbyastatin 7 (IC50 0.85 nM for HNE and 3.1 nM for KLK7). A comprehensive molecular docking study for elastases and KLK7 afforded deeper insight into the intricate differences between inhibitor interactions with HNE and PPE, accounting for the differential activities for both compounds. The synthesis and molecular studies serve as a proof-of-concept that the macrocyclic scaffold can be diversified to fine-tune the activity of serine protease inhibitors.

Largazole is a Brain-Penetrant Class I HDAC Inhibitor with Extended Applicability to Glioblastoma and CNS Diseases.

Largazole is a potent class I selective histone deacetylase inhibitor prodrug with anticancer activity against solid tumors in preclinical models. Largazole possesses in vitro activity against glioblastoma multiforme (GBM) cells and sufficiently crosses the blood-brain barrier based on measurement of the active species, largazole thiol, to achieve therapeutically relevant concentrations in the mouse brain. The effective dose resulted in pronounced functional responses on the transcript level based on RNA sequencing and quantitative polymerase chain reaction after reverse transcription (RT-qPCR), revealing desirable expression changes of genes related to neuroprotection, including Bdnf and Pax6 upregulation, extending the applicability of largazole to the treatment of brain cancer and neurodegenerative disorders. The largazole-induced modulation of Pax6 unifies both activities, since Pax6 expression suppresses GBM proliferation and invasion and inversely correlates with GBM tumor grade, while it is also implicated in neurogenesis, neuronal plasticity, and cognitive ability. Our results suggest that largazole could be repurposed for diseases of the brain.

Discovery, Total Synthesis, and SAR of Anaenamides A and B: Anticancer Cyanobacterial Depsipeptides with a Chlorinated Pharmacophore.

New modified depsipeptides and geometric isomers, termed anaenamides A (1a) and B (1b), along with the presumptive biosynthetic intermediate, anaenoic acid (2), were discovered from a marine cyanobacterium from Guam. Structures were confirmed by total synthesis. The alkylsalicylic acid fragment and the C-terminal α-chlorinated α,ß-unsaturated ester are novelties in cyanobacterial natural products. Cancer cell viability assays indicated that the C-terminal unit serves as the pharmacophore and that the double-bond geometry impacts the cytotoxicity.

Seaweed natural products modify the host inflammatory response via Nrf2 signaling and alter colon microbiota composition and gene expression.

Seaweeds are an important component of human diets, especially in Asia and the Pacific islands, and have shown chemopreventive as well as anti-inflammatory properties. However, structural characterization and mechanistic insight of seaweed components responsible for their biological activities are lacking. We isolated cymopol and related natural products from the marine green alga Cymopolia barbata and demonstrated their function as activators of transcription factor Nrf2-mediated antioxidant response to increase the cellular antioxidant status. We probed the reactivity of the bioactivation product of cymopol, cymopol quinone, which was able to modify various cysteine residues of Nrf2's cytoplasmic repressor protein Keap1. The observed adducts are reflective of the polypharmacology at the level of natural product, due to multiple electrophilic centers, and at the amino acid level of the cysteine-rich target protein Keap1. The non-polar C. barbata extract and its major active component cymopol, reduced inflammatory gene transcription in vitro in macrophages and mouse embryonic fibroblasts in an Nrf2-dependent manner. Cymopol-containing extracts attenuated neutrophil migration in a zebrafish tail wound model. RNA-seq analysis of colonic tissues of mice exposed to non-polar extract or cymopol showed an antioxidant and anti-inflammatory response, with more pronounced effects exhibited by the extract. Cymopolia extract reduced DSS-induced colitis as measured by fecal lipocalin concentration. RNA-seq showed that mucosal-associated bacterial composition and transcriptional profile in large intestines were beneficially altered to varying degrees in mice treated with either the extract or cymopol. We conclude that seaweed-derived compounds, especially cymopol, alter Nrf2-mediated host and microbial gene expression, thereby providing polypharmacological effects.

Discovery and Total Synthesis of Doscadenamide A: A Quorum Sensing Signaling Molecule from a Marine Cyanobacterium.

Quorum sensing (QS) plays a critical role in the regulation of bacterial pathogenesis. Doscadenamide A (1a) was isolated from a marine cyanobacterium, its structure elucidated by NMR, and its activity linked to QS induction. The total synthesis of 1a was developed, and the absolute configuration confirmed through comparison of the isolated natural product with synthetic diastereomers. Our preliminary investigation indicated that 1a could activate QS signaling in a LasR-dependent manner.

Apratoxin S4 Inspired by a Marine Natural Product, a New Treatment Option for Ocular Angiogenic Diseases.

Purpose: Abnormal blood vessel formation is a defining feature of many blinding eye diseases. Targeting abnormal angiogenesis by inhibiting VEGF has revolutionized the treatment of many ocular angiogenic diseases over the last decade. However, a substantial number of patients are refractory to anti-VEGF treatment or may develop resistance over time. The objective of this study was to determine the efficacy and the mechanism of action of Apratoxin S4 in ocular angiogenesis. Methods: Retinal vascular cell proliferation, migration, and the ability to form tube-like structure were studied in vitro. Ex vivo aortic ring, choroid, and metatarsal assays were used to study Apratoxin S4's impact on vessel outgrowth in a multicellular environment. Apratoxin S4 was also tested in mouse models of oxygen-induced retinopathy (OIR) and laser-induced choroidal neovascularization (CNV), and in a rabbit model of persistent retinal neovascularization (PRNV). Western blot and ELISA were used to determine the expression of key angiogenic regulators after Apratoxin S4 treatment. Results: Apratoxin S4 strongly inhibits retinal vascular cell activation by suppressing multiple angiogenic pathways. VEGF-activated vascular cells and angiogenic vessels are more susceptible to Apratoxin S4 treatment than quiescent vascular cells and vessels. Both intraperitoneal and intravitreal delivery of Apratoxin S4 are able to impede ocular neovascularization in vivo. Apratoxin S4 specifically attenuates pathological ocular angiogenesis and exhibits a combinatorial inhibitory effect with standard-of-care VEGF inhibitor drug (aflibercept). Conclusions: Apratoxin S4 is a potent antiangiogenic drug that inhibits the activation of retinal endothelial cells and pericytes through mediating multiple angiogenic pathways.