Marine-Derived Leads as Anticancer Candidates by Disrupting Hypoxic Signaling through Hypoxia-Inducible Factors Inhibition.

The inadequate vascularization seen in fast-growing solid tumors gives rise to hypoxic areas, fostering specific changes in gene expression that bolster tumor cell survival and metastasis, ultimately leading to unfavorable clinical prognoses across different cancer types. Hypoxia-inducible factors (HIF-1 and HIF-2) emerge as druggable pivotal players orchestrating tumor metastasis and angiogenesis, thus positioning them as prime targets for cancer treatment. A range of HIF inhibitors, notably natural compounds originating from marine organisms, exhibit encouraging anticancer properties, underscoring their significance as promising therapeutic options. Bioprospection of the marine environment is now a well-settled approach to the discovery and development of anticancer agents that might have their medicinal chemistry developed into clinical candidates. However, despite the massive increase in the number of marine natural products classified as 'anticancer leads,' most of which correspond to general cytotoxic agents, and only a few have been characterized regarding their molecular targets and mechanisms of action. The current review presents a critical analysis of inhibitors of HIF-1 and HIF-2 and hypoxia-selective compounds that have been sourced from marine organisms and that might act as new chemotherapeutic candidates or serve as templates for the development of structurally similar derivatives with improved anticancer efficacy.

HIF-1 inhibitor-based one-stone-two-birds strategy for enhanced cancer chemodynamic-immunotherapy.

Based on its ability to induce strong immunogenic cell death (ICD), chemodynamic therapy (CDT) was elaborately designed to combine with immunotherapy for a synergistic anticancer effect. However, hypoxic cancer cells can adaptively regulate hypoxia-inducible factor-1 (HIF-1) pathways, leading to a reactive oxygen species (ROS)-homeostatic and immunosuppressive tumor microenvironment. Consequently, both ROS-dependent CDT efficacy and immunotherapy are largely diminished, further lowering their synergy. Here, a liposomal nanoformulation co-delivering a Fenton catalyst copper oleate and a HIF-1 inhibitor acriflavine (ACF) was reported for breast cancer treatment. Through in vitro and in vivo experiments, copper oleate-initiated CDT was proven to be reinforced by ACF through HIF-1-glutathione pathway inhibition, thus amplifying ICD for better immunotherapeutic outcomes. Meanwhile, ACF as an immunoadjuvant significantly reduced the levels of lactate and adenosine, and downregulated the expression of programmed death ligand-1 (PD-L1), thereby promoting the antitumor immune response in a CDT-independent manner. Hence, the "one stone" ACF was fully taken advantage of to enhance CDT and immunotherapy (two birds), both of which contributed to a better therapeutic outcome.

Repression of hypoxia-inducible factor-1 contributes to increased mitochondrial reactive oxygen species production in diabetes.

Background: Excessive production of mitochondrial reactive oxygen species (ROS) is a central mechanism for the development of diabetes complications. Recently, hypoxia has been identified to play an additional pathogenic role in diabetes. In this study, we hypothesized that ROS overproduction was secondary to the impaired responses to hypoxia due to the inhibition of hypoxia-inducible factor-1 (HIF-1) by hyperglycemia. Methods: The ROS levels were analyzed in the blood of healthy subjects and individuals with type 1 diabetes after exposure to hypoxia. The relation between HIF-1, glucose levels, ROS production and its functional consequences were analyzed in renal mIMCD-3 cells and in kidneys of mouse models of diabetes. Results: Exposure to hypoxia increased circulating ROS in subjects with diabetes, but not in subjects without diabetes. High glucose concentrations repressed HIF-1 both in hypoxic cells and in kidneys of animals with diabetes, through a HIF prolyl-hydroxylase (PHD)-dependent mechanism. The impaired HIF-1 signaling contributed to excess production of mitochondrial ROS through increased mitochondrial respiration that was mediated by Pyruvate dehydrogenase kinase 1 (PDK1). The restoration of HIF-1 function attenuated ROS overproduction despite persistent hyperglycemia, and conferred protection against apoptosis and renal injury in diabetes. Conclusions: We conclude that the repression of HIF-1 plays a central role in mitochondrial ROS overproduction in diabetes and is a potential therapeutic target for diabetic complications. These findings are timely since the first PHD inhibitor that can activate HIF-1 has been newly approved for clinical use. Funding: This work was supported by grants from the Swedish Research Council, Stockholm County Research Council, Stockholm Regional Research Foundation, Bert von Kantzows Foundation, Swedish Society of Medicine, Kung Gustaf V:s och Drottning Victorias Frimurarestifelse, Karolinska Institute's Research Foundations, Strategic Research Programme in Diabetes, and Erling-Persson Family Foundation for S-B.C.; grants from the Swedish Research Council and Swedish Heart and Lung Foundation for T.A.S.; and ERC consolidator grant for M.M.

Efficacy of marine biomolecules on angiogenesis by targeting hypoxia inducible factor/vascular endothelial growth factor signaling in zebrafish model.

Marine resources are notably explored for their unique biomolecules that have been designed to be drug targets for their immense potential against various pathologies. These biomolecules are mostly secondary metabolites from different species that include sponges, tunicates, echinoderms, ascidians, algae, and marine symbionts. Among the various biological activities of the marine biomolecules, antiangiogenic property has gained much significance in alternate therapy for treatment against cancer. Hypoxia inducible factor (HIF) and vascular endothelial growth factor (VEGF) are the prime signaling pathways related to angiogenesis that are exclusively designated as markers for critical selection of novel inhibitors. This is mainly due to their importance in tumor induction and regulatory control over other interlinked pathways involved in cancer. Small molecular drug screening using the zebrafish model has been an advantage in cancer research in recent times. This review addresses the importance of marine biomolecules and their antiangiogenic efficacy by targeting HIF/VEGF pathways experimented in the zebrafish model in the last decade. Thus, it would provide more clear insights into the role of biomolecules in alternative cancer therapy.

Contemporary Perspectives on the Warburg Effect Inhibition in Cancer Therapy.

In the 1920s, Otto Warburg observed the phenomenon of altered glucose metabolism in cancer cells. Although the initial hypothesis suggested that the alteration resulted from mitochondrial damage, multiple studies of the subject revealed a precise, multistage process rather than a random pattern. The phenomenon of aerobic glycolysis emerges not only from mitochondrial abnormalities common in cancer cells, but also results from metabolic reprogramming beneficial for their sustenance. The Warburg effect enables metabolic adaptation of cancer cells to grow and proliferate, simultaneously enabling their survival in hypoxic conditions. Altered glucose metabolism of cancer cells includes, inter alia, qualitative and quantitative changes within glucose transporters, enzymes of the glycolytic pathway, such as hexokinases and pyruvate kinase, hypoxia-inducible factor, monocarboxylate transporters, and lactate dehydrogenase. This review summarizes the current state of knowledge regarding inhibitors of cancer glucose metabolism with a focus on their clinical potential. The altered metabolic phenotype of cancer cells allows for targeting of specific mechanisms, which might improve conventional methods in anti-cancer therapy. However, several problems such as drug bioavailability, specificity, toxicity, the plasticity of cancer cells, and heterogeneity of cells in tumors have to be overcome when designing therapies based on compounds targeted in cancer cell energy metabolism.

Targeting hypoxia-inducible factor 1 (HIF-1) signaling with natural products toward cancer chemotherapy.

Tumor cells are often exposed to hypoxia because of the lower oxygen supply deep inside the tumor tissues. However, tumor cells survive in these severe conditions by adapting to hypoxic stress through the induction of hypoxia-inducible factor 1 (HIF-1) signaling. HIF-1 activation is responsible for the expression of numerous HIF-1 target genes, which are related to cell survival, proliferation, angiogenesis, invasion, metastasis, cancer stemness, and metabolic reprogramming. Therefore, HIF-1 is expected to be a potential pharmacological target for cancer therapy. Small molecules derived from natural products (microbial origin, plant-derived, or marine organisms) have been shown to have unique chemical structures and biological activities, including HIF-1 inhibition. Several studies identified HIF-1 inhibitors from natural products. In this review, we summarize the current HIF-1 signaling inhibitors originating from natural products with a variety of modes of action, mainly focusing on microbial metabolites.

Hypoxia-inducible factor-1: Regulatory mechanisms and drug development in stroke.

Stroke is an acute cerebrovascular disease caused by sudden rupture of blood vessels in the brain or blockage of blood vessels, which has now become one of the main causes of adult death. During stroke, hypoxia-inducible factor-1 (HIF-1), as an important regulator under hypoxia conditions, is involved in the pathological process of stroke by regulating multi-pathways, such as glucose metabolism, angiogenesis, erythropoiesis, cell survival. However, the roles of HIF-1 in stroke are still controversial, which are related with ischemic time and degree of ischemia. The regulatory mechanisms of HIF-1 in stroke include inflammation, autophagy, oxidative stress, apoptosis and energy metabolism. The potential drugs targeting HIF-1 have attracted more attention, such as HIF-1 inhibitors, HIF-1 stabilizers and natural products. Based on the role of HIF-1 in stroke, HIF-1 is expected to be a potential target for stroke treatment. Resolving when and what interventions for HIF-1 to take during stroke will provide novel strategies for stroke treatment.

Thymoquinone ameliorates acute kidney injury induced by renal ischemia-reperfusion / La timoquinona mejora la lesión renal aguda inducida por isquemia-reperfusión renal

SUMMARY: Renal ischemia-reperfusion injury (IRI)is an unavoidable consequence in renal transplantation and multiple clinical settings. A debate has been raised about the particular role of hypoxia-inducible factor (HF-1α) in the renal injury pathogenesis and the renal cortex ultrastructural alterations. Also, we investigated the antioxidant/anti-inflammatory effect of thymoquinone and its modulatory role on HIF-1α in protection against renal IRI.Adult male Wister albino rats were assigned into 3 groups (n=16); 1) Sham-operated, 2) IRI model and 3) renal IRI pre-treated with thymoquinone 10 mg.kg-1.day-1 (TQ-IRI) for 10 days and at the reperfusion onset. Following the operation, 8 rats from each group were euthanized after 3 hours and the remaining 8 rats at 24 hours. Renal injury was assessed by the increased blood urea nitrogen, creatinine level, and the EGTI histological injury scoreat both 3 and 24h. HIF-1α was upregulated (p<0.01) and was correlated with renal tissue reactive oxygen species (ROS) production and total oxidant capacity (TAC) consumption. Elevated inflammatory markers (NFkB, MCP-1 and VCAM-1) were associated with renal IRI.Thymoquinone treatment inhibited the accumulation of HIF-1α (p<0.01), reduced renal oxidation/inflammation process and markedly diminished renal injury.

RESUMEN: La lesión por isquemia-reperfusión renal (IRR) es una consecuencia inevitable en el trasplante renal como también en múltiples contextos clínicos. Se ha suscitado una discusión referente a la relación particular del factor inducible por hipoxia (HF- 1α) en la patogénesis de la lesión renal y las alteraciones ultraestructurales de la corteza renal. Además, investigamos el efecto antioxidante / antiinflamatorio de la timoquinona y su papel modulador sobre HIF-1α en la protección contra IRR. Se utilizaron ratas albinas Wister macho adultas divididas en 3 grupos (n = 16); 1) Intervención simulada, 2) modelo IRR y 3) IRR pretratado con timoquinona 10 mg/kg-1. día-1 (TQ-IRR) durante 10 días y al inicio de la reperfusión. Posterior a la operación, 8 ratas de cada grupo fueron sacrificadas después de 3 horas y las 8 ratas restantes a las 24 horas. La lesión renal se evaluó por el aumento de nitrógeno ureico en sangre, el nivel de creatinina y la puntuación de lesión histológica EGTI tanto a las 3 como a las 24 horas. HIF-1α se incrementó (p <0,01) y se correlacionó con la producción de especies de oxígeno reactivo (ROS) del tejido renal y el consumo de capacidad oxidante total. Los marcadores inflamatorios elevados (NFkB, MCP-1 y VCAM-1) se asociaron con IRR. El tratamiento con timoquinona inhibió la acumulación de HIF-1α (p <0,01), redujo el proceso de oxidación / inflamación renal y disminuyó notablemente la lesión renal.

HIF-1 Inhibitor YC-1 Reverses the Acquired Resistance of EGFR-Mutant HCC827 Cell Line with MET Amplification to Gefitinib.

BACKGROUND: Acquired resistance occurred in the majority of nonsmall cell lung cancer (NSCLC) patients receiving epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) therapy, and this may be related to the activation of the HIF-1 pathway. Therefore, we examined the influence of the hypoxia-inducible factor-1 (HIF-1) pathway inhibition on the sensitivity of HCC827 gefitinib-resistant (HCC827 GR) cells with MET amplification to gefitinib. METHODS: We established HCC827 GR cell line with MET amplification and set four groups with different treatment. An MTT assay, a colony formation analysis, and a wound healing assay were performed to determine the sensitivity change of HCC827 GR cells after different treatments. HIF-1α, p-EGFR, and p-Met levels were detected with western blot. Correlations among HIF-1α, p-EGFR, and p-Met levels of HCC827 GR cells with different treatments were analyzed with Pearson's correlation analysis. RESULTS: HIF-1 inhibitor YC-1 enhanced the sensitivity of HCC827 GR cells to gefitinib. p-Met level was correlated with HIF-1α level, while there was no correlation between p-Met level and p-EGFR level. CONCLUSION: HIF-1 inhibitor YC-1 is able to reverse the acquired resistance of HCC827 GR to gefitinib, and the regulation of the HIF-1 pathway on MET may be one of the mechanisms.

Inhibition of hypoxia inducible factor 1 by YC-1 attenuates tissue plasminogen activator induced hemorrhagic transformation by suppressing HMGB1/TLR4/NF-κB mediated neutrophil infiltration in thromboembolic stroke rats.

Hemorrhagic transformation (HT) is a frequent complication of ischemic stroke after thrombolytic therapy and seriously affects the prognosis of stroke. Due to the limited therapeutic window and hemorrhagic complications, tissue plasminogen activator (t-PA) is underutilized in acute ischemic stroke. Currently, there are no clinically effective drugs to decrease the incidence of t-PA-induced HT. Hypoxia-inducible factor 1 (HIF-1) is an important transcription factor that maintains oxygen homeostasis and mediates neuroinflammation under hypoxia. However, the effect of HIF-1 on t-PA-induced HT is not clear. The aim of this study was to investigate the role of HIF-1 in t-PA-induced HT by applying YC-1, an inhibitor of HIF-1. In the present study, we found that HIF-1 expression was significantly increased in ischemic brain tissue after delayed t-PA treatment and was mainly localized in neurons and endothelial cells. Inhibition of HIF-1 by YC-1 improved infarct volume and neurological deficits. YC-1 inhibited matrix metalloproteinase protein expression, increased tight junction protein expression, and ameliorated BBB disruption and the occurrence of HT. Furthermore, YC-1 suppressed the release of inflammatory factors, neutrophil infiltration and the activation of the HMGB1/TLR4/NF-κB signaling pathway. These results demonstrated that inhibition of HIF-1 could protect BBB integrity by suppressing HMGB1/TLR4/NF-κB-mediated neutrophil infiltration, thereby reducing the risk of t-PA-induced HT. Thus, HIF-1 may be a potential therapeutic target for t-PA-induced HT.

Non-classical cardenolides from Calotropis gigantea exhibit anticancer effect as HIF-1 inhibitors.

Six new non-classical cardenolides (1-6), and seventeen known ones (7-23) were isolated from Calotropis gigantea. All cardenolides showed inhibitory effect on hypoxia inducible factor-1 (HIF-1) transcriptional activity with IC50 of 8.85 nM-16.69 µM except 5 and 7. The novel 19-dihydrocalotoxin (1) exhibited a comparable HIF-1 inhibitory activity (IC50 of 139.57 nM) to digoxin (IC50 of 145.77 nM), a well-studied HIF-1 inhibitor, and 11, 12, 14, 16 and 19 presented 1.4-15.4 folds stronger HIF-1 inhibition than digoxin. 1 and 11 showed a dose-dependent inhibition on HIF-1α protein, which led to their HIF-1 suppressing effects. Compared with LO2 and H9c2 normal cell lines, both 1 and 11 showed selective cytotoxicity against various cancer cell lines including HCT116, HeLa, HepG2, A549, MCF-7, A2780 and MDA-MB-231. Moreover, a comprehensive structure-activity relationship was concluded for these non-classical cardenolides as HIF-1 inhibitors, which may shed some light on the rational design and development of cardenolide-based anticancer drugs.

Rosmarinic Acid Regulates Microglial M1/M2 Polarization via the PDPK1/Akt/HIF Pathway Under Conditions of Neuroinflammation.

Microglia are resident macrophage-like cells in the central nervous system (CNS). The induction of microglial activation dampens neuroinflammation-related diseases by promoting microglial (re)polarization to the anti-inflammatory (M2) phenotype and can serve as a potential therapeutic approach. Mitochondrial respiration and metabolic reprogramming are required for the anti-inflammatory response of M2 macrophages. However, whether these mitochondrial-dependent pathways are involved in microglial (re)polarization to the anti-inflammatory (M2) phenotype under conditions of lipopolysaccharide (LPS)-induced neuroinflammation remains unclear. Moreover, the mechanisms that coordinate mitochondrial respiration and the functional reprogramming of microglial cells have not been fully elucidated. Rosmarinic acid (RA) possesses antioxidative and anti-inflammatory activities, and we previously reported that RA markedly suppresses LPS-stimulated M1 microglial activation in mice. In this study, we found that RA suppresses M1 microglial polarization and promotes microglial polarization to the M2 phenotype under conditions of neuroinflammation. We identified an increase in mitochondrial respiration and found that metabolic reprogramming is required for the RA-mediated promotion of microglial polarization to the M2 phenotype under LPS-induced neuroinflammation conditions. Hypoxia-inducible factor (HIF) subunits are the key effector molecules responsible for the effects of RA on the restoration of mitochondrial function, metabolic reprogramming, and phenotypic polarization to M2 microglia. The phosphoinositide-dependent protein kinase 1 (PDPK1)/Akt/mTOR pathway is involved in the RA-mediated regulation of HIF expression and increase in M2 marker expression. We propose that the inhibition of PDPK1/Akt/HIFs by RA might be a potential therapeutic approach for inhibiting neuroinflammation through the regulation of microglial M1/M2 polarization. Graphical abstract Schematic of the mechanism through which RA suppresses LPS-induced neuroinflammation by promoting microglial polarization to the M2 phenotype via PDPK1/Akt/HIFs. The bold arrows indicate the direction of the effects of RA (i.e., inhibitory or promoting effects on cytokines or mediators).

A Fairy Chemical Suppresses Retinal Angiogenesis as a HIF Inhibitor.

Neovascular retinal degeneration is a leading cause of blindness in advanced countries. Anti-vascular endothelial growth factor (VEGF) drugs have been used for neovascular retinal diseases; however, anti-VEGF drugs may cause the development of chorioretinal atrophy in chronic therapy as they affect the physiological amount of VEGF needed for retinal homeostasis. Hypoxia-inducible factor (HIF) is a transcription factor inducing VEGF expression under hypoxic and other stress conditions. Previously, we demonstrated that HIF was involved with pathological retinal angiogenesis in murine models of oxygen-induced retinopathy (OIR), and pharmacological HIF inhibition prevented retinal neovascularization by reducing an ectopic amount of VEGF. Along with this, we attempted to find novel effective HIF inhibitors. Compounds originally isolated from mushroom-forming fungi were screened for prospective HIF inhibitors utilizing cell lines of 3T3, ARPE-19 and 661W. A murine OIR model was used to examine the anti-angiogenic effects of the compounds. As a result, 2-azahypoxanthine (AHX) showed an inhibitory effect on HIF activation and suppressed Vegf mRNA upregulation under CoCl2-induced pseudo-hypoxic conditions. Oral administration of AHX significantly suppressed retinal neovascular tufts in the OIR model. These data suggest that AHX could be a promising anti-angiogenic agent in retinal neovascularization by inhibiting HIF activation.

Effects of post-renal anemia treatment with the HIF-PHD inhibitor molidustat on adenine-induced renal anemia and kidney disease in mice.

The kidneys are the major organs for erythropoietin (EPO) production in adults, and thus, kidney damage results in reduced EPO levels and anemia. Inhibitors of Hypoxia-inducible factor-prolyl hydroxylase domain-containing protein (HIF-PHD) are awaited as new therapeutic options for renal anemia. It can be predicted that most patients who receive HIF-PHD inhibitors have renal dysfunction as a cause of anemia. Therefore, in the present study, we investigated the effects of the HIF-PHD inhibitor molidustat on anemia and renal dysfunction when initiated after the onset of renal anemia. Male C57BL/6J mice received adenine orally to induce nephropathy. After the onset of nephropathy, the mice were treated with either vehicle or molidustat. After 4 weeks of administration, vehicle-treated mice displayed significant anemia, and molidustat ameliorated this anemia. Vehicle-treated mice exhibited reduced creatinine clearance and body weight, increased blood urea nitrogen levels, histopathological changes, immune cell infiltration, and dehydration. Molidustat reversed immune cell infiltration, dehydration, and renal fibrosis without improving renal functional parameters. In conclusion, molidustat treatment initiated after the onset of nephropathy and renal anemia reversed anemia in mice. Molidustat improved some parameters of renal abnormality, but it did not restore renal function.

Hypoxia-inducible factors and innate immunity in liver cancer.

The liver has strong innate immunity to counteract pathogens from the gastrointestinal tract. During the development of liver cancer, which is typically driven by chronic inflammation, the composition and biological roles of the innate immune cells are extensively altered. Hypoxia is a common finding in all stages of liver cancer development. Hypoxia drives the stabilization of hypoxia-inducible factors (HIFs), which act as central regulators to dampen the innate immunity of liver cancer. HIF signaling in innate immune cells and liver cancer cells together favors the recruitment and maintenance of pro-tumorigenic immune cells and the inhibition of anti-tumorigenic immune cells, promoting immune evasion. HIFs represent attractive therapeutic targets to inhibit the formation of an immunosuppressive microenvironment and growth of liver cancer.

Sevoflurane inhibits neuronal apoptosis and expressions of HIF-1 and HSP70 in brain tissues of rats with cerebral ischemia/reperfusion injury.

OBJECTIVE: To observe the influences of sevoflurane on neuronal apoptosis and expressions of hypoxia-inducible factor 1 (HIF-1), and heat-shock protein 70 (HSP70) in brain tissues of rats with cerebral ischemia/reperfusion (I/R) injury. MATERIALS AND METHODS: A total of 60 Sprague-Dawley rats were selected and divided into sham-operation group (Sham group, n=20), cerebral I/R model group (Model group, n=20), and 3% sevoflurane treatment group (Sevoflurane group, n=20). The rats in each group received neurological scoring, and the blood and brain tissues were collected to detect the concentrations of serum K+, Na+ and glucose (Glu). Enzyme-linked immunosorbent assay (ELISA) was adopted to measure the levels of inflammatory factors [tumor necrosis factor-ß (TNF-ß) and interleukin-6 (IL-6)] and oxidative stress [catalase (CAT), malondialdehyde (MDA) and superoxide dismutase (SOD)]. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay was performed to determine the nerve cell apoptosis in the brain tissues. The gene and protein expressions of Caspase-3, HIF-1, and HSP70 in the brain tissues were measured via quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) and Western blotting. RESULTS: In Sevoflurane group, the content of serum Glu and Na+ was decreased markedly, that of K+ was increased notably, and the levels of TNF-ß, IL-1 and IL-6 were lowered remarkably compared with those in Model group (p<0.05). Moreover, the neurological score was reduced evidently (p<0.05). Model group had significantly strengthened the activity of MDA and CAT and decreased SOD content, while Sevoflurane group exhibited the opposite results. TUNEL staining showed that there were distinctly more apoptotic cells that were dominated by glial cells in Model group and fewer apoptotic cells in Sevoflurane group. It was indicated in gene assay that the messenger ribonucleic acid (mRNA) expression levels of HIF-1, HSP70, and Caspase-3 in Model group were remarkably higher than those in Sham group and Sevoflurane group (p<0.05). According to the results of Western blotting, the protein expressions of HIF-1 and HSP70 in Sevoflurane group were markedly lower than those in Model group. CONCLUSIONS: Sevoflurane can reduce the content of inflammatory factors, inhibit apoptosis, and reduce the expressions of HIF-1 and HSP70 in the case of cerebral I/R injury, thus exerting protective effects on rats with cerebral I/R injury.

Hypoxia-Inducible Factor Inhibitors Derived from Marine Products Suppress a Murine Model of Neovascular Retinopathy.

Neovascular retinal degenerative diseases are the leading causes of blindness in developed countries. Anti-vascular endothelial growth factor (VEGF) therapy is commonly used to treat these diseases currently. However, recent reports indicate that long term suppression of VEGF in the eye is associated with chorioretinal atrophy. Therefore, a physiological amount of VEGF is required for retinal homeostasis. Hypoxia-inducible factor (HIF) is a transcriptional factor upstream of VEGF. We previously reported that HIF regulated pathological angiogenesis in the retina of murine models of oxygen-induced retinopathy and laser-induced choroidal neovascularization. Most of the known HIF inhibitors are anti-cancer agents which may have systemic adverse effects in for clinical use; thus, there is a need for safer and less invasive HIF inhibitors. In this study, we screened marine products, especially fish ingredients, and found that six species of fish had HIF inhibitory effects. Among them, administration of Decapterus tabl ingredients significantly suppressed retinal neovascular tufts by inhibiting HIF expression in a murine oxygen-induced retinopathy model. These results indicate that particular fish ingredients can act as anti-angiogenic agents in retinal neovascularization diseases.

Design, Synthesis, and Conformation-Activity Study of Unnatural Bridged Bicyclic Depsipeptides as Highly Potent Hypoxia Inducible Factor-1 Inhibitors and Antitumor Agents.

By carrying out structural modifications based on the bicyclic peptide structure of echinomycin, we successfully synthesized various powerful antitumor derivatives. The ring conformation in the obtained compounds was restricted by cross-linking with an unnatural bond. The prepared derivatives were demonstrated to strongly suppress the hypoxia inducible factor (HIF)-1 transcriptional activation and hypoxia induction of HIF-1 protein expression. Particularly, alkene-bridged derivative 12 exhibited remarkably potent cytotoxicity (IC50 = 0.22 nM on the MCF-7 cell line) and HIF-1 inhibition (IC50 = 0.09 nM), which considerably exceeded those of echinomycin. Conformational analyses and molecular modeling studies revealed that the biological activities were enhanced following restriction of the conformation by cross-linking through a metabolically stable and rigid bridge bond. In addition, we proposed a new globular conformation stabilized by intramolecular π stacking that can contribute to the biological effects of bicyclic depsipeptides. The developments presented in the current study serve as a useful guide to expand the chemical space of peptides in drug discovery.

A lipophilic AIEgen for lipid droplet imaging and evaluation of the efficacy of HIF-1 targeting drugs.

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that mediates the cellular response to hypoxia. The upregulation of HIF-1 expression in hypoxic cells can induce the accumulation of lipid droplets (LDs), and the LD levels can in turn reflect the expression level of HIF-1. Herein, we report a LD-specific luminogen with aggregation-induced emission characteristics (AIEgen), and have explored its potential applications in the evaluation of the inhibitory efficacy of HIF-1 targeting drugs. Compared to Nile red, this AIEgen shows a larger Stokes shift, better photostability, a more sensitive response to changes in dye concentration and a broader quantitative range. We found that the AIEgen can be used for semi-quantifying LD levels in cancer cells under hypoxic conditions, and for evaluating the inhibitory efficacy of HIF-1 targeting drugs. This work provides a simple and cost-effective strategy for screening HIF-1-targeted drugs, which may also be an alternative for evaluating the drug efficacy of other LD-related diseases.

Hypoxia-inducible factor-prolyl hydroxylase inhibitor ameliorates myopathy in a mouse model of chronic kidney disease.

Muscle wasting and diminished physical performance contribute to the morbidity and mortality of chronic kidney disease (CKD), for which no curative therapy exists. Accumulating evidence indicates that impaired angiogenesis occurs in the muscles of CKD models. Therefore, proangiogenesis therapy is considered a potentially effective strategy for limiting CKD-associated myopathy. Hypoxia-inducible factor (HIF)-prolyl hydroxylase inhibitor (HIF-PHI) stabilizes HIF and enhances muscle angiogenesis during acute ischemia; however, little evidence was available from CKD models. Here, we assessed whether pharmacological activation of HIF by MK-8617 (MK), a novel orally active HIF-PHI, improves CKD-associated myopathy. Mice were divided into sham or CKD groups, and CKD mice were subdivided into CKD + vehicle or MK treatment groups (1.5, 5, or 12.5 mg/kg for 12 wk). In CKD mice, skeletal muscle mass, mitochondrial amount, and exercise capacity decreased compared with sham mice. Compared with the CKD + vehicle group, low (1.5 mg/kg) and medium (5 mg/kg) doses of MK, but not the high dose (12.5 mg/kg), significantly restored these changes and was accompanied by incremental increases in HIF-1α. Furthermore, increased capillary density and area were observed in a MK dose-dependent manner, which is likely related to an improved VEGF response in the skeletal muscle of CKD mice. In addition, macrophage and proinflammatory cytokines, including monocyte chemoattractant protein 1, TNF-α, and IL-6, significantly increased in the high-dose MK group. These results indicate that HIF-PHI provides a potential therapeutic strategy to improve CKD-associated myopathy.