Andrographolide attenuates choroidal neovascularization by inhibiting the HIF-1α/VEGF signaling pathway

Natural products for the treatment of age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a chronic retinal disease that significantly influences the vision of the elderly.

PURPOSE

There is no effective treatment and prevention method. The pathogenic process behind AMD is complex, including oxidative stress, inflammation, and neovascularization. It has been demonstrated that several natural products can be used to manage AMD, but systematic summaries are lacking.

STUDY DESIGN AND METHODS

PubMed, Web of Science, and ClinicalTrials.gov were searched using the keywords "Biological Products" AND "Macular Degeneration" for studies published within the last decade until May 2023 to summarize the latest findings on the prevention and treatment of age-related macular degeneration through the herbal medicines and functional foods.

RESULTS

The eligible studies were screened, and the relevant information about the therapeutic action and mechanism of natural products used to treat AMD was extracted. Our findings demonstrate that natural substances, including retinol, phenols, and other natural products, prevent the development of new blood vessels and protect the retina from oxidative stress in cells and animal models. However, they have barely been examined in clinical studies.

CONCLUSION

Natural products could be highly prospective candidate drugs used to treat AMD, and further preclinical and clinical research is required to validate it to control the disease.

Inhibition of hypoxia-inducible factors suppresses subretinal fibrosis

Age-related macular degeneration (AMD) is a common cause of vision loss. The aggressive form of AMD is associated with ocular neovascularization and subretinal fibrosis, representing a responsive outcome against neovascularization mediated by epithelial-mesenchymal transition of retinal pigment epithelium (RPE) cells. A failure of the current treatment (anti-vascular endothelial growth factor therapy) has also been attributed to the progression of subretinal fibrosis. Hypoxia-inducible factors (HIFs) increase gene expressions to promote fibrosis and neovascularization. HIFs act as a central pathway in the pathogenesis of AMD. HIF inhibitors may suppress ocular neovascularization. Nonetheless, further investigation is required to unravel the aspects of subretinal fibrosis. In this study, we used RPE-specific HIFs or von Hippel-Lindau (VHL, a regulator of HIFs) conditional knockout (cKO) mice, along with pharmacological HIF inhibitors, to demonstrate the suppression of subretinal fibrosis. Fibrosis was suppressed by treatments of HIF inhibitors, and similar suppressive effects were detected in RPE-specific Hif1a/Hif2a- and Hif1a-cKO mice. Promotive effects were observed in RPE-specific Vhl-cKO mice, where fibrosis-mediated pathologic processes were evident. Marine products' extracts and their component taurine suppressed fibrosis as HIF inhibitors. Our study shows critical roles of HIFs in the progression of fibrosis, linking them to the potential development of therapeutics for AMD.

Pharmacological regulation of HIF-1α, RGC death, and glaucoma

Hypoxia can regulate oxygen-sensitive pathways that could be neuroprotective to compensate for the detrimental effects of low oxygen. However, prolonged hypoxia can activate neurodegenerative pathways. HIF-1α is upregulated/stabilized in hypoxic conditions, promoting alteration of gene expression, and ultimately leading to cell-death. Therefore, regulation of HIF-1α expression pharmacologically is a vital approach to mitigate cell death. In this review, we provide information showing the role of HIF-1α and its associated pathways in ocular retinopathies. We also discuss the beneficial roles of HIF-1α inhibitor, KC7F2, in ocular pathologies. Finally, we provided our own data demonstrating RGC neuroprotection by KC7F2 in glaucomatous animals.

Phytochemicals Showing Antiangiogenic Effect in Pre-clinical Models and their Potential as an Alternative to Existing Therapeutics

Angiogenesis, the formation of new blood vessels from a pre-existing vascular network, is an important hallmark of several pathological conditions, such as tumor growth and metastasis, proliferative retinopathies, including proliferative diabetic retinopathy and retinopathy of prematurity, age-related macular degeneration, rheumatoid arthritis, psoriasis, and endometriosis. Putting a halt to pathology-driven angiogenesis is considered an important therapeutic strategy to slow down or reduce the severity of pathological disorders. Considering the attrition rate of synthetic antiangiogenic compounds from the lab to reaching the market due to severe side effects, several compounds of natural origin are being explored for their antiangiogenic properties. Employing pre-clinical models for the evaluation of novel antiangiogenic compounds is a promising strategy for rapid screening of antiangiogenic compounds. These studies use a spectrum of angiogenic model systems that include HUVEC two-dimensional culture, nude mice, chick chorioallantoic membrane, transgenic zebrafish, and dorsal aorta from rats and chicks, depending upon available resources. The present article emphasizes the antiangiogenic activity of the phytochemicals shown to exhibit antiangiogenic behavior in these well-defined existing angiogenic models and highlights key molecular targets. Different models help to get a quick understanding of the efficacy and therapeutics mechanism of emerging lead molecules. The inherent variability in assays and corresponding different phytochemicals tested in each study prevent their immediate utilization in clinical studies. This review will discuss phytochemicals discovered using suitable preclinical antiangiogenic models, along with a special mention of leads that have entered clinical evaluation.

Honokiol Attenuates Choroidal Neovascularization by Inhibiting the Hypoxia-Inducible Factor-α/Vascular Endothelial Growth Factor Axis via Nuclear Transcription Factor-Kappa B Activation

PURPOSE

Honokiol is a lignan isolated from Magnolia officinalis and exhibits anti-angiogenic properties. This study was conducted to investigate the role of honokiol in choroidal neovascularization.

METHODS

C57BL/6 mice were treated with honokiol at 10-20 mg/kg by daily intraperitoneal injection from day 1 to 6 after laser photocoagulation. ARPE-19 cells were cultured under hypoxic conditions with or without the presence of honokiol. After laser photocoagulation and honokiol treatment, hematoxylin and eosin staining, immunofluorescence and fundus fluorescein angiography were used to analyze the effect of honokiol on choroidal neovascularization formation. Quantitative real-time PCR, western blot, enzyme-linked immunosorbent assay, immunofluorescence, luciferase assay, and chromatin immunoprecipitation were performed to explore the mechanism of honokiol in the pathological process of choroidal neovascularization. Finally, the role of honokiol on the human choroidal vascular endothelial cells was detected by using 5-ethynyl-20-deoxyuridine assay, Transwell and Tube formation assays.

RESULTS

The results of hematoxylin and eosin staining and immunofluorescence suggested that honokiol reduced the thickness, length, and area of choroidal neovascularization lesions in laser-induced choroidal neovascularization mouse model. Fundus fluorescein angiography showed that choroidal neovascularization leakage was reduced in honokiol group and the concentration of 20 mg/kg showed better effects. Mechanism studies have shown that honokiol exerted inhibitory effects on choroidal neovascularization by inactivating hypoxia-inducible factor-1α/vascular endothelial growth factor axis through the nuclear transcription factor-kappa B signaling pathway. The same results were obtained in ARPE-19 cells under hypoxic conditions. Furthermore, the conditional medium of retinal pigmented epithelial cells promoted the proliferation, migration, and tube formation of human choroidal vascular endothelial cells, while honokiol reversed these.

CONCLUSION

We demonstrated that honokiol attenuated choroidal neovascularization formation by inactivating the hypoxia-inducible factor-1α/vascular endothelial growth factor axis through nuclear transcription factor-kappa B signaling pathway.

Andrographolide inhibits the proliferation and migration of vascular smooth muscle cells via PI3K/AKT signaling pathway and amino acid metabolism to prevent intimal hyperplasia

Andrographolide (AGP) exerts pharmacological effects when used for the treatment of cardiovascular disease, but the molecular mechanisms underlying its inhibitory effects on the proliferation and migration of vascular smooth muscle cells (VSMCs) and intimal hyperplasia (IH) are unknown. The proliferation and migration of VSMCs treated with AGP were examined using the CCK-8, flow cytometry, and wound healing assays. Expression levels of proteins related to cell proliferation and apoptosis were quantified. Multi-omics analysis with RNA-seq and metabolome was used to explore the potential molecular mechanism of AGP treatment. Additionally, an in vivo model was established through ligation of the left common carotid artery to identify the therapeutic potential of AGP in IH. Molecular docking and western blotting were performed to verify the mechanism discovered with multi-omics analysis. The results showed that AGP inhibited the proliferation and migration of cultured VSMCs in a dose-dependent manner and alleviated IH-related vascular stenosis. AGP significantly downregulated the protein levels of CDK1, CCND1, and BCL2 and upregulated the protein level of BAX. Gene expression profiles showed a total of 3,298 differentially expressed genes (DEGs) after AGP treatment, of which 1,709 DEGs had upregulated expression and 1,589 DEGs had downregulated expression. KEGG enrichment analysis highlighted the PI3K/AKT signaling pathway, verified with the detection of the activation of PI3K and AKT phosphorylation. Further GO enrichment combined with metabolomics analysis showed that AGP inhibition in cultured VSMCs involved the amino acid metabolic process, and the expression levels of the two key factors PRDM16 and EZH2, identified with PPI and docking analysis, were significantly inhibited by AGP treatment. In conclusion, our study showed that AGP inhibited VSMCs proliferation and migration by suppressing the PI3K/AKT signaling pathway and amino acid metabolism, which, in turn, improved IH.

Exploring the synergistic pharmacological mechanism of Huoxiang Drink against irritable bowel syndrome by integrated data mining and network pharmacology

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder, characterized by abdominal pain, bloating, and changes in bowel habits. Huoxiang Drink (HD), derived from traditional Chinese medicine, has been reported to effectively treat digestive disorders caused by external cold and internal dampness. However, the pharmaceutical targets and mechanisms for HD against IBS remain unclear. Data mining, bioinformatics analysis, and network pharmacology were employed to explore the potential pharmacological mechanisms of HD against IBS. In this study, we screened 50 core targets to investigate the pharmacological mechanisms of HD against IBS. Enrichment analysis revealed that HD may participate in various signaling pathways, especially the inflammation-related tumor necrosis factor, signaling pathway and hypoxia-inducible factor signaling pathway. Molecular docking results confirmed that MOL000098 (Quercetin), MOL000006 (Luteolin), MOL005828 (Nobiletin), MOL005916 (Irisolidone), and MOL004328 (Naringenin), as key active ingredients in HD, bound to core targets (tumor protein P53, tumor necrosis factor, matrix metalloproteinases 9, and vascular endothelial growth factor-A) for topical treatment of IBS. This study suggested that HD offered a potential therapeutic strategy against IBS. Our findings may facilitate the efficient screening of active ingredients in HD and provide a theoretical basis for further validating the clinical therapeutic effects of HD on treating IBS.

Neovascular Progression and Retinal Dysfunction in the Laser-Induced Choroidal Neovascularization Mouse Model

The mouse model of laser-induced choroidal neovascularization (LI-CNV) has been widely used to study neovascular age-related macular degeneration; however, it still lacks a comprehensive characterization. Here, CNV was induced in the eyes of 12-week-old C57BL/6J male mice by argon laser irradiation. We studied the CNV lesion progression of an LI-CNV mouse cohort by using multimodal imaging (color fundus, optical coherence tomography (OCT), and fluorescence angiography, focal electroretinography features for 14 days, and related cytokines, angiogenic factors, and reactive gliosis for 5 days. CNV lesions involving the rupture of the Bruch's membrane were confirmed using funduscopy and OCT after laser photocoagulation. During the initial stage, from the CNV induction until day 7, CNV lesions presented leakage observed by using fluorescence angiography and a typical hyperreflective area with cell infiltration, subretinal leakage, and degeneration of photoreceptors observed through OCT. This correlated with decreased retinal responses to light. Moreover, inflammatory and angiogenic markers were reduced to basal levels in the first 5 days of CNV progression. In contrast, reactive gliosis and the VEGF expression in retinal sections were sustained, with infiltration of endothelial cells in the subretinal space. In the second stage, between days 7 and 14 post-induction, we observed stabilization of the CNV lesions, a hyperfluorescent area corresponding to the formation of fibrosis, and a partial rescue of retinal function. These findings suggest that the LI-CNV lesion development goes through an acute phase during the first seven days following induction, and then the CNV lesion stabilizes. According to these results, this model is suitable for screening anti-inflammatory and anti-angiogenic drugs in the early stages of LI-CNV. At the same time, it is more convenient for screening anti-fibrotic compounds in the later stages.

Hypoxia: syndicating triple negative breast cancer against various therapeutic regimens

Triple-negative breast cancer (TNBC) is one of the deadliest subtypes of breast cancer (BC) for its high aggressiveness, heterogeneity, and hypoxic nature. Based on biological and clinical observations the TNBC related mortality is very high worldwide. Emerging studies have clearly demonstrated that hypoxia regulates the critical metabolic, developmental, and survival pathways in TNBC, which include glycolysis and angiogenesis. Alterations to these pathways accelerate the cancer stem cells (CSCs) enrichment and immune escape, which further lead to tumor invasion, migration, and metastasis. Beside this, hypoxia also manipulates the epigenetic plasticity and DNA damage response (DDR) to syndicate TNBC survival and its progression. Hypoxia fundamentally creates the low oxygen condition responsible for the alteration in Hypoxia-Inducible Factor-1alpha (HIF-1α) signaling within the tumor microenvironment, allowing tumors to survive and making them resistant to various therapies. Therefore, there is an urgent need for society to establish target-based therapies that overcome the resistance and limitations of the current treatment plan for TNBC. In this review article, we have thoroughly discussed the plausible significance of HIF-1α as a target in various therapeutic regimens such as chemotherapy, radiotherapy, immunotherapy, anti-angiogenic therapy, adjuvant therapy photodynamic therapy, adoptive cell therapy, combination therapies, antibody drug conjugates and cancer vaccines. Further, we also reviewed here the intrinsic mechanism and existing issues in targeting HIF-1α while improvising the current therapeutic strategies. This review highlights and discusses the future perspectives and the major alternatives to overcome TNBC resistance by targeting hypoxia-induced signaling.

Application and mechanism of anti-VEGF drugs in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. The incidence rate increases with age in people over 50 years of age. With the advent of China’s aging society, the number of patients is increasing year by year. Although researchers have done a lot of basic research and clinical research on the pathogenesis and treatment of AMD in recent years, the pathogenesis of AMD is still controversialdue to the complexity of the disease itself. AMD is the primary cause of blindness in the elderly over 50 years old. It is characterized by the formation of choroidal neovascularization (CNV) and the over secretion of vascular endothelial growth factor (VEGF) as its main mechanism, which can eventually lead to vision loss or blindness. The occurrence and development of AMD is an extremely complex process, in which a large number of regulatory factors and cytokines are involved. Most of the existing treatments are for its concomitant CNV. Targeted VEGF drugs for neovascularization, such as Lucentis and Aflibercept, are the first-line drugs for AMD. Their application has greatly reduced the blinding rate of patients. However, there are still some patients who have no response to treatment or cannot maintain their vision after long-term treatment. Frequent injection also increases the risk of complications and economic burden. In order to further improve the quality of life and long-term prognosis of AMD patients, a variety of new treatmentshave been or will be applied in clinic, including combined treatment with the same or different targets to improve the curative effect, change or simplify the mode of medication, inhibit VEGF receptor tyrosine protein kinase and so on. This article provides a brief review of the research progress of anti-VEGF drugs and their mechanisms for the treatment of AMD, it is expected to provide a better treatment plan for AMD treatment.

Targeting HIF-1α by Natural and Synthetic Compounds: A Promising Approach for Anti-Cancer Therapeutics Development

Advancement in novel target detection using improved molecular cancer biology has opened up new avenues for promising anti-cancer drug development. In the past two decades, the mechanism of tumor hypoxia has become more understandable with the discovery of hypoxia-inducible factor-1α (HIF-1α). It is a major transcriptional regulator that coordinates the activity of various transcription factors and their downstream molecules involved in tumorigenesis. HIF-1α not only plays a crucial role in the adaptation of tumor cells to hypoxia but also regulates different biological processes, including cell proliferation, survival, cellular metabolism, angiogenesis, metastasis, cancer stem cell maintenance, and propagation. Therefore, HIF-1α overexpression is strongly associated with poor prognosis in patients with different solid cancers. Hence, pharmacological targeting of HIF-1α has been considered to be a novel cancer therapeutic strategy in recent years. In this review, we provide brief descriptions of natural and synthetic compounds as HIF-1α inhibitors that have the potential to accelerate anticancer drug discovery. This review also introduces the mode of action of these compounds for a better understanding of the chemical leads, which could be useful as cancer therapeutics in the future.

Andrographolide: A review of its pharmacology, pharmacokinetics, toxicity and clinical trials and pharmaceutical researches

Andrographis paniculata (Burm. f.) Wall. ex Nees, a renowned herb medicine in China, is broadly utilized in traditional Chinese medicine (TCM) for the treatment of cold and fever, sore throat, sore tongue, snake bite with its excellent functions of clearing heat and toxin, cooling blood and detumescence from times immemorial. Modern pharmacological research corroborates that andrographolide, the major ingredient in this traditional herb, is the fundamental material basis for its efficacy. As the main component of Andrographis paniculata (Burm. f.) Wall. ex Nees, andrographolide reveals numerous therapeutic actions, such as antiinflammatory, antioxidant, anticancer, antimicrobial, antihyperglycemic and so on. However, there are scarcely systematic summaries on the specific mechanism of disease treatment and pharmacokinetics. Moreover, it is also found that it possesses easily ignored security issues in clinical application, such as nephrotoxicity and reproductive toxicity. Thereby it should be kept a lookout over in clinical. Besides, the relationship between the efficacy and security issues of andrographolide should be investigated and evaluated scientifically. In this review, special emphasis is given to andrographolide, a multifunctional natural terpenoids, including its pharmacology, pharmacokinetics, toxicity and pharmaceutical researches. A brief overview of its clinical trials is also presented. This review intends to systematically and comprehensively summarize the current researches of andrographolide, which is of great significance for the development of andrographolide clinical products. Noteworthy, those un-cracked issues such as specific pharmacological mechanisms, security issues, as well as the bottleneck in clinical transformation, which detailed exploration and excavation are still not to be ignored before achieving integration into clinical practice. In addition, given that current extensive clinical data do not have sufficient rigor and documented details, more high-quality investigations in this field are needed to validate the efficacy and/or safety of many herbal products.

Amelioration of diabetic retinopathy in db/db mice by treatment with different proportional three active ingredients from Tibetan medicine Berberis dictyophylla F

ETHNOPHARMACOLOGICAL RELEVANCE

Berberis dictyophylla F., a famous Tibetan medicine, has been used to prevent and treat diabetic retinopathy (DR) for thousands of years in clinic. However, its underlying mechanisms remain unclear.

AIM OF THE STUDY

The present study was designed to probe the synergistic protection and involved mechanisms of berberine, magnoflorine and berbamine from Berberis dictyophylla F. on the spontaneous retinal damage of db/db mice.

MATERIALS AND METHODS

The 14-week spontaneous model of DR in db/db mice were randomly divided into eight groups: model group, calcium dobesilate (CaDob, 0.23 g/kg) group and groups 1-6 (different proportional three active ingredients from Berberis dictyophylla F.). All mice were intragastrically administrated for a continuous 12 weeks. Body weight and fasting blood glucose (FBG) were recorded and measured. Hematoxylin-eosin and periodic acid-Schiff (PAS) stainings were employed to evaluate the pathological changes and abnormal angiogenesis of the retina. ELISA was performed to assess the levels of IL-6, HIF-1α and VEGF in the serum. Immunofluorescent staining was applied to detect the protein levels of CD31, VEGF, p-p38, p-JNK, p-ERK and NF-κB in retina. In addition, mRNA expression levels of VEGF, Bax and Bcl-2 in the retina were monitored by qRT-PCR analysis.

RESULTS

Treatment with different proportional three active ingredients exerted no significant effect on the weight, but decreased the FBG, increased the number of retinal ganglionic cells and restored internal limiting membrane. The results of PAS staining demonstrated that the drug treatment decreased the ratio of endothelial cells to pericytes while thinned the basal membrane of retinal vessels. Moreover, these different proportional active ingredients can markedly downregulate the protein levels of retinal CD31 and VEGF, and serum HIF-1α and VEGF. The gene expression of retinal VEGF was also suppressed. The levels of retinal p-p38, p-JNK and p-ERK proteins were decreased by drug treatment. Finally, drug treatment reversed the proinflammatory factors of retinal NF-κB and serum IL-6, and proapoptotic Bax gene expression, while increased antiapoptotic Bcl-2 gene expression.

CONCLUSIONS

These results indicated that DR in db/db mice can be ameliorated by treatment with different proportional three active ingredients from Berberis dictyophylla F. The potential vascular protection mechanisms may be involved in inhibiting the phosphorylation of the MAPK signaling pathway, thus decreasing inflammatory and apoptotic events.