Possible role of endostatin in the antiangiogenic therapy of diabetic retinopathy

Diabetic retinopathy: emerging concepts of current and potential therapy

Diabetic retinopathy (DR) is one of the leading causes of permanent central blindness worldwide. Despite the complexity and inadequate understanding of DR pathogenesis, many of the underlying pathways are currently partially understood and may offer potential targets for future treatments. Anti-VEGF medications are currently the main medication for this problem. This article provides an overview of the established pharmacological treatments and those that are being developed to cure DR. We firstly reviewed the widely utilized approaches including pan-retinal photocoagulation therapy, anti-VEGF therapy, corticosteroid therapy, and surgical management of DR. Next, we discussed the mechanisms of action and prospective benefits of novel candidate medications. Current management are far from being a perfect treatment for DR, despite mild-term favorable efficiency and safety profiles. Pharmacological research should work toward developing longer-lasting treatments or new drug delivery systems, as well as on identifying new molecular targets in the pathogenetical mechanism for DR. In order to find a treatment that is specifically designed for each patient, it is also necessary to properly characterize patients, taking into account elements like hereditary factors and intraretinal neovascularization stages for effective utilization of drugs. The current and potential approaches for diabetic retinopathy. Image was constructed using Biorender.com.

Possible Role of Wnt Signaling Pathway in Diabetic Retinopathy

The core of impaired vision in working people suffering from insulin-dependent and noninsulin- dependent diabetes mellitus is diabetic retinopathy (DR). The Wnt Protein Ligands family influences various processes; this ensures the cells are able to interact and co-ordinate various mobile functions, including cell growth, division, survival, apoptosis, migration, and cell destiny. The extracellular Wnt signal activates other signals. It is seen that Wnt pathways play an important role in inflammation, oxidative stress, and angiogenesis. It has been illustrated that the canonically preserved Wnt signaling system has a vital role in the homeostasis of adulthood. Developmental disorders in each of these stages will lead to serious eye problems and eventually blindness. There is, therefore, a need to specifically organize and regulate the growth of ocular tissues. In tissue specification and polarities, axonal exhaust, and maintenance of cells, especially in the central nervous system, Wnt/frizzled pathways play an important role. Thus, Wnt route antagonists may act as have been possible therapeutic options in DR by inhibiting aberrant Wnt signals. Elaborative and continued research in this area will help in the advancement of current knowledge in the field of DR, and eventually, this can lead to the development of new therapeutic approaches.

The role of Optical Coherence Tomography Angiography to detect early microvascular changes in Diabetic Retinopathy: a systematic review

PURPOSE

To evaluate quantitative parafoveal microvascular changes using Optical Coherence Tomography Angiography (OCTA) by comparing the area of foveal avascular zone (FAZ) and vessel density (VD) between nondiabetic controls and patients with different levels of Diabetic Retinopathy (DR).

METHODS

A systematic review was performed according to the recommendations of the "Cochrane Handbook for Systematic Reviews of Interventions" and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Three electronic databases including PubMed, Web of Science and Cochrane Library were systematically retrieved by using key terms with Boolean operators. The data extracted from each study included: first author, year of publication, study design, sample size and participant characteristics (mean age, type of diabetes mellitus and mean duration of diabetic disease). Outcome variables included: VD and area of FAZ, in superficial and deep capillary plexuses of parafovea.

RESULTS

355 articles were identified from our search of databases and 10 studies were included in this systematic review. Patients with diabetes with or without clinical signs of DR have a significantly enlarged area of FAZ and decreased parafoveal VD compared to healthy controls, as well as an association between these microvascular changes and worsening DR.

CONCLUSION

OCTA can provide valuable information about early and subtle microvascular changes of parafoveal capillary plexuses in patients with diabetes and can identify preclinical DR before the manifestation of clinically apparent retinopathy. The non-invasive nature of OCTA allows routine imaging of the retinal vasculature, so this approach may be a promising tool for screening programmes of DR.

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.

Anti-angiogenic activity and safety of intraocular application of triterpenes

PURPOSE

Assessment of the anti-angiogenic activity and the safety of ophthalmic use of four pentacyclic triterpenes (friedelin, friedelinol, lupenone, and lupeol).

METHODS

Triterpenes cytotoxicity (5-640 µmol L^-1) was examined in ARPE-19 cells by sulforhodamine B colorimetric method, and the anti-angiogenic activity (50-1000 µmol L^-1) was evaluated in the chorioallantoic membrane model. Full-field electroretinography and histological analysis were performed to evaluate intraocular effects of these four triterpenes (at 100 or 500 μmol L^-1) in eyes of Wistar rats, for 15 days.

RESULTS

In the cytotoxicity assay, friedelin and friedelinol were not able to drastically reduce cell growth. A dose-dependent response was observed in groups exposed to lupeol or lupenone. During the chorioallantoic membrane assay, friedelinol at 500 μmol L^-1 reduced the vascularity in 26%; lupeol and lupenone showed promising anti-angiogenic activity, reducing three parameters: vascularized area (> 30%), number of junctions (> 20%), and vessel length (> 15%). According to the electroretinographic and histologic findings, triterpenes at 100 µmol L^-1 or lupenone at 500 µmol L^-1 did not induce any transient or permanent disturbance in retinal structure or functioning.

CONCLUSIONS

Triterpenes at 100 µmol L^-1 or lupenone at 500 µmol L^-1 were considered safe for potential ophthalmic use.

Engineered nanomedicines for tumor vasculature blockade therapy

Tumor vasculature blockade therapy (TVBT), including angiogenesis inhibition, vascular disruption, and vascular infarction, provides a promising treatment modality for solid tumors. However, low selectivity, drug resistance, and possible severe side effects have limited the clinical transformation of TVBT. Engineered nanoparticles offer potential solutions, including prolonged circulation time, targeted transportation, and controlled release of TVBT agents. Moreover, engineered nanomedicines provide a promising combination platform of TVBT with chemotherapy, radiotherapy, photodynamic therapy, photothermal therapy, ultrasound therapy, and gene therapy. In this article, we offer a comprehensive summary of the current progress of engineered nanomedicines for TVBT and also discuss current deficiencies and future directions for TVBT development. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Consumption of Cooked Common Beans or Saponins Could Reduce the Risk of Diabetic Complications

Several risks for diseases, such as atherosclerosis, renal diseases, and diabetes, have inextricably been linked with obesity. Nowadays, this health-risk-laden disease is being managed with assorted types of drugs, some of which guarantee modest benefits. The chronic inflammatory effect of obesity has a negative effect in insulin signaling, a situation attributable to insulin resistance that culminates in high blood sugar inputs seen in diseases such as type 2 diabetes and metabolic syndrome. Food such as beans with different bioactive compounds could reduce the risk of diabetic complications. Demand for bean products is growing because of its robust contents of several health-promoting components, eg, saponins. Saponins are characterized by containing lower glucose and cholesterol levels and have been doted with antioxidant activities, as well as anti-inflammatory and anti-diabetic effects. In this writing, the attributes of saponins in providing substantial health and nutritional benefits in humans, as well as in improving and ameliorating diabetic complications, were reviewed.

Schizandrin A Protects Human Retinal Pigment Epithelial Cell Line ARPE-19 against HG-Induced Cell Injury by Regulation of miR-145

Diabetic retinopathy (DR) is a serious complication of diabetes, which is the main cause of blindness among adults. Traditional Chinese medicines (TCMs) have been proven to delay the development of DR. Nonetheless, the effect of Schizandrin A (SchA) on DR remains uninvestigated. The present study aimed to probe the protective effect of SchA on high-glucose (HG)-induced injury in ARPE-19 cells. We observed that SchA accelerated cell proliferation, prohibited apoptosis, and restrained pro-inflammatory cytokines (monocyte chemoattractant protein-1 [MCP-1], interleukin-6 [IL-6], and tumor necrosis factor alpha [TNF-α]) and reactive oxygen species (ROS) level in HG-stimulated cells. Additionally, miR-145 expression was upregulated in HG and SchA co-treated cells, and miR-145 inhibition reversed the protective effect of SchA on HG-managed ARPE-19 cells. Interestingly, downregulated myeloid differentiation factor 88 (MyD88) was found in HG and SchA co-treated cells, and upregulation of MyD88 was observed in miR-145 inhibitor-transfected cells. Additionally, SchA hindered nuclear factor κB (NF-κB) and p38 mitogen-activated protein kinase (p38MAPK) signaling pathways in HG-treated ARPE-19 cells. The findings validated that SchA could protect ARPE-19 cells from HG-induced cell injury by regulation of miR-145.

Antiangiogenic properties of nanoparticles: a systematic review

Nanoparticles appear to be one of the most promising agents that offer efficacy in angiogenesis-related disease therapy. The objective of this research is to systematically review studies that have probed into the effect of nanoparticles on angiogenesis. Selected inclusion criteria were used to extract articles, references that were cited in the initial search were sought to identify more potential articles, and articles that did not meet the inclusion criteria and duplicates were discarded. The spherical shape was shown to be the most common shape employed to investigate the role of nanoparticles in angiogenesis therapy. The size of nanoparticles appears to play a crucial role for efficacy on angiogenesis, in which 20 nm emerged as the preferred size. Gold nanoparticles exhibit the most promise as an antiangiogenesis agent, and the toxicity was adjustable based on the dosages applied.

Quality, bioactivity study, and preclinical acute toxicity, safety pharmacology evaluation of PEGylated recombinant human endostatin (M2 ES)

Endostar, a potent endogenous antiangiogenic factor, is wildly used in clinics. However, it was easily degraded by enzymes and rapidly cleared by the kidneys. To overcome these shortcomings, PEGylated recombinant human endostatin was developed. In this study, the purity of M₂ ES was evaluated by silver stain and reversed-phase high-performance liquid chromatography. Ultraviolet spectrum was used to examine the structural of M₂ ES and endostar. The bioactivity and antitumor efficacy of M₂ ES were evaluated using an in vitro endothelial cell migration model and athymic nude mouse xenograft model of a heterogeneous lung adenocarcinoma, respectively. A preclinical study was performed to evaluate the acute toxicity and safety pharmacology in rhesus monkeys. The purity of M₂ ES was more than 98%; PEG modification has no effect on endostatin structure. Compared with the control group, M₂ ES dramatically retards endothelial cell migration and tumor growth. After intravenous (IV) infusions of M₂ ES at a dose level of three and 75 mg/kg in rhesus monkeys, there was no observable serious adverse event in both acute toxicity and safety pharmacology study. On the basis of the quality and bioactivity study data of M₂ ES and the absence of serious side effect in rhesus monkeys, M₂ ES was authorized to initiate a phase I clinical trial.

Fragments generated upon extracellular matrix remodeling: Biological regulators and potential drugs

The remodeling of the extracellular matrix (ECM) by several protease families releases a number of bioactive fragments, which regulate numerous biological processes such as autophagy, angiogenesis, adipogenesis, fibrosis, tumor growth, metastasis and wound healing. We review here the proteases which generate bioactive ECM fragments, their ECM substrates, the major bioactive ECM fragments, together with their biological properties and their receptors. The translation of ECM fragments into drugs is challenging and would take advantage of an integrative approach to optimize the design of pre-clinical and clinical studies. This could be done by building the contextualized interaction network of the ECM fragment repertoire including their parent proteins, remodeling proteinases, and their receptors, and by using mathematical disease models.

Canonical Wnt signaling in diabetic retinopathy

Diabetic retinopathy (DR) is a common eye complication of diabetes, and the pathogenic mechanism of DR is still under investigation. The canonical Wnt signaling pathway is an evolutionarily conserved pathway that plays fundamental roles in embryogenesis and adult tissue homeostasis. Wnt signaling regulates expression of multiple genes that control retinal development and eye organogenesis, and dysregulated Wnt signaling plays pathophysiological roles in many ocular diseases, including DR. This review highlights recent progress in studies of Wnt signaling in DR. We discuss Wnt signaling regulation in the retina and dysregulation of Wnt signaling associated with ocular diseases with an emphasis on DR. We also discuss the therapeutic potential of modulating Wnt signaling in DR. Continued studies in this field will advance our current understanding on DR and contribute to the development of new treatments.

Omega-3 fatty acids in prevention of diabetic retinopathy

OBJECTIVES

To review the competence of Omega-3 fatty acids in restricting the progression, thereby leading to prevention of diabetic retinopathy.

KEY FINDINGS

Owing to their anti-inflammatory and anti-angiogenic properties, Omega-3 fatty acids alleviate major aetiological agents. These fatty acids are renowned for their beneficial effects in various cardiovascular and other disorders; however, their potential to prevent the progression of diabetic retinopathy remains least explored.

SUMMARY

Utilizing this potential, we may develop effective prophylactic agents which markedly inhibit the advent of retinal angiogenesis and prevent the apoptosis of retinal endothelial and neuronal cells, thereby averting retinal degeneration, hence safeguarding diabetic patients from this sight-threatening complication.

Potential of angiotensin II receptor blockers in the treatment of diabetic retinopathy

Impairments in renin-angiotensin-aldosterone system during diabetes mellitus, leading to its dysfunction, have been known since a decade. Hyperglycemia induces several pathological alterations which upregulate this system, accounting for overexpression of its downstream signaling molecules, amongst which angiotensin II (Ang II) and aldosterone hold prime pathological notoriety. Although it is well known that elevated plasma levels of Ang II play a crucial role in the pathophysiology of type-II diabetic mellitus, by inducing and aggravating insulin resistance, it is not quite much known that it equally elevates the possibility/risk of development of diabetic complications. Also, amongst the various diabetic complications, the effects of Ang II upregulation are more widely acknowledged in studies concerning the pathophysiology of diabetic nephropathy; however, its role in exacerbating diabetic retinopathy has not received much attention. Ang II, indeed, plays a detrimental role in the progression of diabetic retinopathy by augmenting the principal events involved in its pathogenesis, namely oxidative stress, angiogenesis and inflammation. The utility of angiotensin receptor blockers has shown positive results in research studies and hence, might potentially provide a novel adjuvant therapy for treating this complication and preventing the associated vision-loss in diabetic patients.

Chinese herbal drugs for the treatment of diabetic retinopathy

Objectives

To explore the various pharmacological actions and the molecular mechanisms behind them by which Chinese herbs tend to lower the risk of developing microvascular diabetic complications in retina and prevent its further progression.

Key findings

Several Chinese herbs, indeed, elicit potent anti-inflammatory, antioxidant, anti-angiogenic, anti-apoptotic, peroxisome proliferator-activated receptor-gamma receptor agonistic, platelet-activating factor antagonistic, aldose reductase inhibitory and various other beneficial pharmacological activities, required to counteract the pathological conditions prevalent in retina during diabetes.

Summary

Chinese herbs can potentially be used for the treatment/prevention of diabetic retinopathy owing to the virtue of numerous properties by which they alleviate several hyperglycaemia-induced pathological occurrences in retina. This would provide a natural and safe therapy for diabetic retinopathy, which currently is clinically limited to destructive techniques like laser photocoagulation and vitrectomy.

Proposed mechanisms of Terminalia catappa in hyperglycaemia and associated diabetic complications

Objectives

Terminalia catappa has shown potent antidiabetic activity in the past; however, the exact molecular mechanisms by which it acts have not been elucidated. This review aims at exploring several hypotheses which have been proposed to explain its mechanism of action, including reduction in oxidative stress, inflammation, angiogenesis, lipid profile correction and direct hypoglycaemic actions.

Methods

A thorough review of all the articles, research as well as reviews, available regarding the concerned topic was performed. MEDLINE databases were searched using keywords (and their combinations), such as T. catappa, renin oxidative stress, inflammation, angiogenesis, diabetic retinopathy, α-glucosidase and α-amylase, among several others. English-language articles were preferably selected.

Key findings

Apart from metabolic dysfunctions, several hyperglycaemia-induced pathological conditions come into scene as the after-effects of diabetes. These mainly include inflammation, oxidative stress, angiogenesis and lipid profile alteration, which ultimately result in vascular endothelial dysfunction, hepatic steatosis, lipid peroxidation and apoptosis of endothelial, hepatic and neuronal cells. Terminalia catappa effectively attenuates the progression of diabetic retinopathy and shows significant hypoglycaemic actions. The mechanisms behind these effects were explained.

Conclusion

Terminalia catappa may provide an effective natural product to treat hyperglycaemia and prevent subsequent diabetic complications.

Biglycan potentially regulates angiogenesis during fracture repair by altering expression and function of endostatin

The small proteoglycan biglycan (Bgn) is highly expressed in the organic matrix of bone and plays a role in bone formation. Previous work implicated Bgn in vessel growth during bone healing [1]. By infusing barium sulfate (BaSO4) into WT and Bgn-deficient mice we discovered the positive effect of Bgn in modulating angiogenesis during fracture healing. Using micro-computed tomography angiography we found significant differences in the vessel size and volume among other parameters. To further understand the mechanistic basis for this, we explored the relationship between Bgn and the anti-angiogenic protein endostatin. Immunohistochemistry (IHC) showed co-localization of Bgn and endostatin in regions of bone formation, with increased endostatin staining in Bgn-KO compared to WT at 14days post-fracture. To further elucidate the relationship between Bgn and endostatin, an endothelial cell tube formation assay was used. This study showed that endothelial cells treated with endostatin had significantly decreased vessel length and vessel branches compared to untreated cells, while cells treated with endostatin and Bgn at a 1:1M ratio had vessel length and vessel branches comparable to untreated cells. This indicated that Bgn was able to mitigate the inhibitory effect of endostatin on endothelial cell growth. In summary, these results suggest that Bgn is needed for proper blood vessel formation during fracture healing, and one mechanism by which Bgn impacts angiogenesis is through inhibition of endostatin.