Acetyl-11-keto-β-boswellic acid reduces retinal angiogenesis in a mouse model of oxygen-induced retinopathy

Development of coumarin and procaine linked hybrid molecules as a novel class of SHP1 fluorescent activators

The development of small fluorescent organic molecules used in bioimaging experiment has boomed the progress of molecular and cellular biology, providing new and efficient tools to elucidate a myriad of cellular and multicellular processes. In this work, a class of fluorescent activators against SHP1 was designed and synthesized for the first time. The representative compound 3n showed activating effect against SHP1 with EC50 of 17.66 ± 1.48 μM and a fluorescence quantum yield of 0.521 in DMSO. Meanwhile, 3n showed good selectivity for SHP1, inhibited the proliferation of SU-DHL-2 cells and OCI-Ly10 cells with IC50 of 8.66 ± 1.26 μM and 9.16 ± 0.53 μM and exhibited potential for cellular imaging on human breast cancer cells.

Natural Products in the Treatment of Retinopathy of Prematurity: Exploring Therapeutic Potentials

Retinopathy of prematurity (ROP) is a vascular disorder affecting the retinas of preterm infants. This condition arises when preterm infants in incubators are exposed to high oxygen levels, leading to oxidative stress, inflammatory responses, and a downregulation of vascular endothelial growth factors, which causes the loss of retinal microvascular capillaries. Upon returning to room air, the upregulation of vascular growth factors results in abnormal vascular growth of retinal endothelial cells. Without appropriate intervention, ROP can progress to blindness. The prevalence of ROP has risen, making it a significant cause of childhood blindness. Current treatments, such as laser therapy and various pharmacologic approaches, are limited by their potential for severe adverse effects. Therefore, a deeper understanding of ROP's pathophysiology and the development of innovative treatments are imperative. Natural products from plants, fungi, bacteria, and marine organisms have shown promise in treating various diseases and have gained attention in ROP research due to their minimal side effects and wide-ranging beneficial properties. This review discusses the roles and mechanisms of natural products that hold potential as therapeutic agents in ROP management.

Boswellia serrata Enhances Passive Range-of-Motion Exercises in Radiation-Induced Trismus: A Case Report

Trismus is a common, extremely detrimental side effect following definitive radiotherapy for head and neck malignancies. Existing therapeutic modalities (active and passive range-of-motion exercises and systemic therapies) offer only modest, slow improvements in jaw opening; thus, there is a need for additional treatment options. Boswellia serrata (BS) ("Indian frankincense") is a tree native to West Asia and North Africa that produces resin-containing "boswellic" acids. These have been shown to have in vitro and in vivo anti-inflammatory effects and have previously been found to be an effective treatment for asthma, colitis, arthritis, and post-radiation edema. Herein we report the case of a 54-year-old male with severe post-radiation trismus who experienced a dramatic resolution with BS/Therabite® combination therapy. His trismus improved from 6 mm to 45 mm over 10 weeks (0.46 mm/day), far exceeding previous rates of improvement documented in the literature. There were no ill effects. Given the dearth of effective treatments for post-radiation trismus, BS is a promising agent deserving of further study.

Three Major Causes of Metabolic Retinal Degenerations and Three Ways to Avoid Them

An imbalance of homeostasis in the retina leads to neuron loss and this eventually results in a deterioration of vision. If the stress threshold is exceeded, different protective/survival mechanisms are activated. Numerous key molecular actors contribute to prevalent metabolically induced retinal diseases-the three major challenges are age-related alterations, diabetic retinopathy and glaucoma. These diseases have complex dysregulation of glucose-, lipid-, amino acid or purine metabolism. In this review, we summarize current knowledge on possible ways of preventing or circumventing retinal degeneration by available methods. We intend to provide a unified background, common prevention and treatment rationale for these disorders and identify the mechanisms through which these actions protect the retina. We suggest a role for herbal medicines, internal neuroprotective substances and synthetic drugs targeting four processes: parainflammation and/or glial cell activation, ischemia and related reactive oxygen species and vascular endothelial growth factor accumulation, apoptosis and/or autophagy of nerve cells and an elevation of ocular perfusion pressure and/or intraocular pressure. We conclude that in order to achieve substantial preventive or therapeutic effects, at least two of the mentioned pathways should be targeted synergistically. A repositioning of some drugs is considered to use them for the cure of the other related conditions.

Synthesis and Biological Evaluation of 3-Amino-4,4-Dimethyl Lithocholic Acid Derivatives as Novel, Selective, and Cellularly Active Allosteric SHP1 Activators

Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP1), a non-receptor member of the protein tyrosine phosphatase (PTP) family, negatively regulates several signaling pathways that are responsible for pathological cell processes in cancers. In this study, we report a series of 3-amino-4,4-dimethyl lithocholic acid derivatives as SHP1 activators. The most potent compounds, 5az-ba, showed low micromolar activating effects (EC50: 1.54–2.10 μM) for SHP1, with 7.63–8.79-fold maximum activation and significant selectivity over the closest homologue Src homology 2 domain-containing protein tyrosine phosphatase 2 (SHP2) (>32-fold). 5az-ba showed potent anti-tumor effects with IC50 values of 1.65–5.51 μM against leukemia and lung cancer cells. A new allosteric mechanism of SHP1 activation, whereby small molecules bind to a central allosteric pocket and stabilize the active conformation of SHP1, was proposed. The activation mechanism was consistent with the structure–activity relationship (SAR) data. This study demonstrates that 3-amino-4,4-dimethyl lithocholic acid derivatives can be selective SHP1 activators with potent cellular efficacy.

Anatomical and Functional Effects of Oral Administration of Curcuma Longa and Boswellia Serrata Combination in Patients with Treatment-Naïve Diabetic Macular Edema

Anti-vascular endothelial growth factor nowdays represents the standard of care for diabetic macular edema (DME). Nevertheless, the burden of injections worldwide has created tremendous stress on the healthcare system during the COVID-19 pandemic. The aim of this study was to investigate the effects of the oral administration of Curcuma longa and Boswellia serrata (Retimix®) in patients with non-proliferative diabetic retinopathy (DR) and treatment-naïve DME < 400 μm, managed during the COVID-19 pandemic. In this retrospective study, patients were enrolled and divided into two groups, one undergoing observation (Group A, n 12) and one receiving one sachet a day of Retimix® (Group B, n 49). Best-corrected visual acuity (BCVA) and central macular thickness (CMT) measured by spectral-domain optical coherence tomography were performed at baseline, then at one and six months. A mixed-design ANOVA was calculated to determine whether the change in CMT and BCVA over time differed according to the consumption of Retimix®. The interaction between time and treatment was significant, with F (1.032, 102.168) = 14.416; η2 = 0.127; p < 0.001, indicating that the change in terms of CMT and BCVA over time among groups was significantly different. In conclusion, our results show the efficacy of Curcuma longa and Boswellia serrata in patients with non-proliferative DR and treatment-naïve DME in maintaining baseline CMT and BCVA values over time.

Acetyl-11-Keto-Beta Boswellic Acid (AKBA) Protects Lens Epithelial Cells Against H2O2-Induced Oxidative Injury and Attenuates Cataract Progression by Activating Keap1/Nrf2/HO-1 Signaling

Age-related cataract (ARC) is one of the leading blinding eye diseases worldwide. Chronic oxidative stress and the apoptosis of human lens epithelial cells (HLECs) have been suggested to be the mechanism underlying cataract formation. Acetyl-11-keto-β-boswellic acid (AKBA) is a pentacyclic triterpene with antioxidative and antiapoptotic effects. In this study, we investigated the potential effects of AKBA on oxidative-induced HLECs injury and cataract formation. H₂O₂ was used to simulate HLECs oxidative injury in vitro, and Na₂SeO₃ was applied to establish an in vivo cataract model. In our current study, a cell counting kit-8 (CCK-8) assay was performed to evaluate the effects of H₂O₂ and AKBA on cell viability in vitro. Intracellular reactive oxygen species (ROS) levels were measured with the ROS assay to verify the antioxidant capacity of AKBA. Apoptotic cells were detected and measured by TUNEL staining and flow cytometry, and quantitative real-time (qRT)-PCR and Western blotting were applied to examine the transcription and expression of apoptosis-related proteins. Furthermore, immunofluorescence staining was performed to locate factor-erythroid 2-related factor 2 (Nrf2), and the protein levels of Nrf2, kelch-like ECH-associated protein 1 (Keap1) and heme oxygenase-1 (HO-1) were determined by Western blotting. Finally, we observed the degree of lens opacity and performed hematoxylin-eosin (H&E) staining to assess the protective effect of AKBA on cataract formation in vivo. AKBA increased HLECs viability under H₂O₂ stimulation, decreased intracellular ROS levels and alleviated the cell apoptosis rate in vitro. AKBA significantly decreased the expression of caspase-3 and Bax and increased the content of Bcl-2. The results of immunofluorescence and immunohistochemical staining proved that the expression and nuclear translocation of Nrf2 were activated with AKBA treatment in vivo and in vitro. Moreover, computational docking results showed that AKBA could bind specifically to the predicted Keap1/Nrf2 binding sites. After AKBA activation, Nrf2 dissociates from the Nrf2/Keap1 complex, translocates into the nucleus, and subsequently promotes HO-1 expression. In addition, AKBA attenuated lens opacity in selenite-induced cataracts. Overall, these findings indicated that AKBA alleviated oxidative injury and cataract formation by activating the Keap1/Nrf2/HO-1 cascade. Therefore, our current study highlights that AKBA may serve as a promising treatment for ARC progression.

The Biological Activity of 3-O-Acetyl-11-keto-β-Boswellic Acid in Nervous System Diseases

Frankincense is a hard gelatinous resin exuded by Boswellia serrata. It contains a complex array of components, of which acetyl-11-keto-beta-boswellic acid (AKBA), a pentacyclic triterpenoid of the resin class, is the main active component. AKBA has a variety of physiological actions, including anti-infection, anti-tumor, and antioxidant effects. The use of AKBA for the treatment of mental diseases has been documented as early as ancient Greece. Recent studies have found that AKBA has anti-aging and other neurological effects, suggesting its potential for the treatment of neurological diseases. This review focuses on nervous system-related diseases, summarizes the functions and mechanisms of AKBA in promoting nerve repair and regeneration after injury, protecting against ischemic brain injury and aging, inhibiting neuroinflammation, ameliorating memory deficits, and alleviating neurotoxicity, as well as having anti-glioma effects and relieving brain edema. The mechanisms by which AKBA functions in different diseases and the relationships between dosage and biological effects are discussed in depth with the aim of increasing understanding of AKBA and guiding its use for the treatment of nervous system diseases.

The Potential Application of Pentacyclic Triterpenoids in the Prevention and Treatment of Retinal Diseases

Retinal diseases are a leading cause of impaired vision and blindness but some lack effective treatments. New therapies are required urgently to better manage retinal diseases. Natural pentacyclic triterpenoids and their derivatives have a wide range of activities, including antioxidative, anti-inflammatory, cytoprotective, neuroprotective, and antiangiogenic properties. Pentacyclic triterpenoids have great potential in preventing and/or treating retinal pathologies. The pharmacological effects of pentacyclic triterpenoids are often mediated through the modulation of signalling pathways, including nuclear factor erythroid-2 related factor 2, high-mobility group box protein 1, 11β-hydroxysteroid dehydrogenase type 1, and Src homology region 2 domain-containing phosphatase-1. This review summarizes recent in vitro and in vivo evidence for the pharmacological potential of pentacyclic triterpenoids in the prevention and treatment of retinal diseases. The present literature supports the further development of pentacyclic triterpenoids. Future research should now attempt to improve the efficacy and pharmacokinetic behaviour of the agents, possibly by the use of medicinal chemistry and targeted drug delivery strategies.

Haem relieves hyperoxia-mediated inhibition of HMEC-1 cell proliferation, migration and angiogenesis by inhibiting BACH1 expression

Background

Hyperoxia-mediated inhibition of vascular endothelial growth factor (VEGF) in the retina is the main cause of impeded angiogenesis during phase I retinopathy of prematurity (ROP). Human retinal angiogenesis involves the proliferation, migration and vessel-forming ability of microvascular endothelial cells. Previous studies have confirmed that BTB and CNC homology l (BACH1) can inhibit VEGF and angiogenesis, while haem can specifically degrade BACH1. However, the effect of haem on endothelial cells and ROP remains unknown.

Methods

In this report, we established a model of the relative hyperoxia of phase I ROP by subjecting human microvascular endothelial cells (HMEC-1) to 40% hyperoxia. Haem was added, and its effects on the growth and viability of HMEC-1 cells were evaluated. Cell counting kit 8 (CCK8) and 5-ethynyl-2′-deox-yuridine (EdU) assays were used to detect proliferation, whereas a wound healing assay and Matrigel cultures were used to detect the migration and vessel-forming ability, respectively. Western blot (WB) and immunofluorescence (IF) assays were used to detect the relative protein levels of BACH1 and VEGF.

Results

HMEC-1 cells could absorb extracellular haem under normoxic or hyperoxic conditions. The proliferation, migration and angiogenesis abilities of HMEC-1 cells were inhibited under hyperoxia. Moderate levels of haem can promote endothelial cell proliferation, while 20 μM haem could inhibit BACH1 expression, promote VEGF expression, and relieve the inhibition of proliferation, migration and angiogenesis in HMEC-1 cells induced by hyperoxia.

Conclusions

Haem (20 μM) can relieve hyperoxia-induced inhibition of VEGF activity in HMEC-1 cells by inhibiting BACH1 and may be a potential medicine for overcoming stunted retinal angiogenesis induced by relative hyperoxia in phase I ROP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-01866-x.

Association of the Somatostatin Analog Octreotide With Magnetic Nanoparticles for Intraocular Delivery: A Possible Approach for the Treatment of Diabetic Retinopathy

The somatostatin analog octreotide (OCT) displays important neuroprotective and anti-angiogenic properties that could make it an interesting candidate to treat diabetic retinopathy (DR). Unfortunately, systemic drug administration is hindered by severe side effects, therefore topical administration routes are preferable. However, drug delivery through eye drops may be difficult due to ocular barriers and, in the long term, could induce ocular damage. On the other hand, intraocular injections must be repeated to maintain drug concentration, and this may cause severe damage to the eye. To decrease injection frequency, long-term release and reduced biodegradation could be obtained by binding the drug to biodegradable polymeric nanoparticles. In the present study, we made a preparation of OCT bound to magnetic nanoparticles (MNP-OCT) and tested its possible use as an OCT delivery system to treat retinal pathologies such as DR. In particular, in vitro, ex vivo, and in vivo experimental models of the mammalian retina were used to investigate the possible toxicity of MNPs, possible effects of the binding to MNPs on OCT bioactivity, and the localization of MNP-OCT in the retina after intraocular injection. The results showed that, both in human retinal endothelial cells (HRECs) and in mouse retinal explants, MNPs were not toxic and the binding with MNPs did not influence OCT antiangiogenic or antiapoptotic activity. Rather, effects of MNP-OCT were observed at concentrations up to 100-fold (in HRECs) or 10-fold (in mouse retinal explants) lower compared to OCT, indicating that OCT bioactivity was enhanced in MNP-OCT. MNP-OCT in mouse retinas in vivo after intraocular delivery were initially localized mainly to the outer retina, at the level of the retinal pigment epithelium, while after 5 days they were observed throughout the retinal thickness. These observations demonstrate that MNP-OCT may be used as an OCT intraocular delivery system that may ensure OCT localization to the retina and enhanced OCT bioactivity. Further studies will be necessary to determine the OCT release rate in the retina and the persistence of drug effects in the long period.

Advanced glycation end products induce immature angiogenesis in in vivo and ex vivo mouse models

Proliferative diabetic retinopathy (PDR) is a progressive disease predominantly involving pathological angiogenesis and is characterized by the development of immature, fragile, and easily hemorrhagic new vessels. Advanced glycation end products (AGEs) and the receptor for AGEs (RAGE) play important roles in the progression of diabetic retinopathy. Our previous studies demonstrated that AGEs promoted HUVEC angiogenesis by inducing moesin phosphorylation via RhoA/Rho-associated protein kinase (ROCK) pathway. The aim of this study was to further confirm AGE-induced angiogenesis in vivo and the involvement of RAGE, ROCK, and moesin phosphorylation in this process. We performed the study in an AGE-treated mouse model with various angiogenesis assays in multiple in vivo and ex vivo models. The results demonstrated that AGEs promoted significant neovascularization in whole mount retina and mouse aortic ring of adult and postnatal mice and in Matrigel plug as well, which were consistently accompanied by increased moesin phosphorylation. The increase of AGE-evoked neovascularization and moesin phosphorylation were both attenuated by RAGE knockout or ROCK inhibitor Y27632 administration in mice. We also revealed the pathological characteristics of AGE-promoted angiogenesis by demonstrating the decrease of pericyte coverage and the disarranged endothelial alignment in microvessels. In conclusion, this study provides in vivo evidences that AGEs induce immature angiogenesis by binding to RAGE, activating the RhoA/ROCK signal pathway and inducing moesin phosphorylation.NEW & NOTEWORTHY Advanced glycation end product (AGE)-induced formation of neovessels and phosphorylation of moesin in retina and aortic ring required AGE receptors. AGEs increased neovessels and the phosphorylation of moesin in retina and aortic ring via RhoA/ROCK pathway. AGE-induced immature angiogenesis in AGE-treated mouse retina and aortic ring. The AGE-RAGE axis and moesin could be candidate targets for overcoming relative diseases.

Induction of developmental toxicity and cardiotoxicity in zebrafish embryos/larvae by acetyl-11-keto-β-boswellic acid (AKBA) through oxidative stress

Acetyl-11-keto-β-boswellic acid (AKBA), a triterpenoid from Boswellia serrate, is regarded as an angiogenesis inhibitor. However, its toxicity is unknown. The aim of this study was to examine its developmental toxicity and cardiotoxicity. A developmental toxicity assay in zebrafish embryos/larvae from 4 to 96 hours post-fertilization (hpf) was performed and a cardiotoxicity assay was designed from 48 to 72 hpf. Markers of oxidative stress and related genes were selected to access the possible mechanisms. According to the results, AKBA induced pericardium edema, yolk-sac edema, abnormal melanin, spinal curvature, hatching inhibition and shortened body length. Further, increased SV-BA distance, reduced heart rate, increased pericardium area and decreased blood flow velocity were detected in AKBA treated groups. The inhibition of cardiac progenitor gene expression, such as Nkx2.5 and Gata4, may be related to cardiotoxicity. The activities of antioxidant enzymes were decreased and the content of MDA was increased. In addition, AKBA treatment decreased the expression levels of Mn-Sod, Cat, and Gpx. These results suggested that AKBA induced developmental toxicity and cardiotoxicity through oxidative stress. As far as we know, this is the first report on the toxicity of AKBA. It reminds us to pay attention to developmental toxicity and cardiotoxicity of AKBA.

Nutraceuticals and "Repurposed" Drugs of Phytochemical Origin in Prevention and Interception of Chronic Degenerative Diseases and Cancer

BACKGROUND

Chronic, degenerative diseases are often characterized by inflammation and aberrant angiogenesis. For these pathologies, including rheumatoid arthritis, cardiovascular and autoimmune diseases, cancer, diabetes, and obesity, current therapies have limited efficacy.

OBJECTIVES

The validation of novel (chemo)preventive and interceptive approaches, and the use of new or repurposed agents, alone or in combination with registered drugs, are urgently required.

RESULTS

Phytochemicals (triterpenoids, flavonoids, retinoids) and their derivatives, nonsteroidal anti-inflammatory drugs (aspirin) as well as biguanides (metformin and phenformin) originally developed from phytochemical backbones, are multi-target agents showing antiangiogenic and anti-anti-inflammatory proprieties. Many of them target AMPK and metabolic pathways such as the mTOR axis. We summarize the beneficial effects of several compounds in conferring protection and supporting therapy, and as a paradigm, we present data on terpenoids & biquanides on beer hop xanthohumol and hydroxytryrosol from olive mill waste waters.

CONCLUSIONS

These molecules could be employed for combinatorial chemoprevention and interception approaches or chemoprevention/therapy regimens for cancer and other chronic complex diseases.

Nutraceuticals for the Treatment of Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus and is characterized by degeneration of retinal neurons and neoangiogenesis, causing a severe threat to vision. Nowadays, the principal treatment options for DR are laser photocoagulation, vitreoretinal surgery, or intravitreal injection of drugs targeting vascular endothelial growth factor. However, these treatments only act at advanced stages of DR, have short term efficacy, and cause side effects. Treatment with nutraceuticals (foods providing medical or health benefits) at early stages of DR may represent a reasonable alternative to act upstream of the disease, preventing its progression. In particular, in vitro and in vivo studies have revealed that a variety of nutraceuticals have significant antioxidant and anti-inflammatory properties that may inhibit the early diabetes-driven molecular mechanisms that induce DR, reducing both the neural and vascular damage typical of DR. Although most studies are limited to animal models and there is the problem of low bioavailability for many nutraceuticals, the use of these compounds may represent a natural alternative method to standard DR treatments.

Anti-Inflammatory Activity of Boswellia serrata Extracts: An In Vitro Study on Porcine Aortic Endothelial Cells

This study is aimed at investigating the cytotoxicity, anti-inflammatory, and angiogenic activities of two Boswellia serrata extracts on primary culture of porcine aortic endothelial cells (pAECs). Chemical characterization of a dry extract (extract A) and a hydroenzymatic extract (extract G) of B. serrata was performed by HPLC using pure boswellic acids (BAs) as standard. In cultured pAECs, extract G improved cell viability, following LPS challenge, in a dose-dependent manner and did not show any toxic effect. On the other hand, extract A was toxic at higher doses and restored pAEC viability after LPS challenge only at lower doses. Pure BAs, used at the same concentrations as those determined in the phytoextracts, did not contrast LPS-induced cytotoxicity. Extract A showed proangiogenic properties at the lowest dose, and the same result was observed using pure AKBA at the corresponding concentration, whereas extract G did not show any effect on the migration capacity of endothelial cells. In conclusion, an anti-inflammatory activity of B. serrata extracts on endothelial cells was reported, though cytotoxicity or proliferative stimulation can occur instead of a protective effect, depending on the dose and the formulation.

Mature and progenitor endothelial cells perform angiogenesis also under protease inhibition: the amoeboid angiogenesis

Background

Controlling vascular growth is a challenging aim for the inhibition of tumor growth and metastasis. The amoeboid and mesenchymal types of invasiveness are two modes of migration interchangeable in cancer cells: the Rac-dependent mesenchymal migration requires the activity of proteases; the Rho-ROCK-dependent amoeboid motility is protease-independent and has never been described in endothelial cells.

Methods

A cocktail of physiologic inhibitors (Ph-C) of serine-proteases, metallo-proteases and cysteine-proteases, mimicking the physiological environment that cells encounter during their migration within the angiogenesis sites was used to induce amoeboid style migration of Endothelial colony forming cells (ECFCs) and mature endothelial cells (ECs). To evaluate the mesenchymal-ameboid transition RhoA and Rac1 activation assays were performed along with immunofluorescence analysis of proteins involved in cytoskeleton organization. Cell invasion was studied in Boyden chambers and Matrigel plug assay for the in vivo angiogenesis.

Results

In the present study we showed in both ECFCs and ECs, a decrease of activated Rac1 and an increase of activated RhoA upon shifting of cells to the amoeboid conditions. In presence of Ph-C inhibitors both cell lines acquired a round morphology and Matrigel invasion was greatly enhanced with respect to that observed in the absence of protease inhibition. We also observed that the urokinase-plasminogen-activator (uPAR) receptor silencing and uPAR-integrin uncoupling with the M25 peptide abolished both mesenchymal and amoeboid angiogenesis of ECFCs and ECs in vitro and in vivo, indicating a role of the uPAR-integrin-actin axis in the regulation of amoeboid angiogenesis. Furthermore, under amoeboid conditions endothelial cells seem to be indifferent to VEGF stimulation, which induces an amoeboid signaling pattern also in mesenchymal conditions.

Conclusion

Here we first provide a data set disclosing that endothelial cells can move and differentiate into vascular structures in vitro and in vivo also in the absence of proteases activity, performing a new type of neovascularization: the “amoeboid angiogenesis”. uPAR is indispensable for ECs and ECFCs to perform an efficient amoeboid angiogenesis. Therefore, uPAR silencing or the block of its integrin-interaction, together with standard treatment against VEGF, could be a possible solution for angiogenesis inhibition.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0742-2) contains supplementary material, which is available to authorized users.

The Beta Adrenergic Receptor Blocker Propranolol Counteracts Retinal Dysfunction in a Mouse Model of Oxygen Induced Retinopathy: Restoring the Balance between Apoptosis and Autophagy

In a mouse model of oxygen induced retinopathy (OIR), beta adrenergic receptor (BAR) blockade has been shown to recover hypoxia-associated retinal damages. Although the adrenergic signaling is an important regulator of apoptotic and autophagic processes, the role of BARs in retinal cell death remains to be elucidated. The present study was aimed at investigating whether ameliorative effects of BAR blockers may occur through their coordinated action on apoptosis and autophagy. To this aim, retinas from control and OIR mice untreated or treated with propranolol, a non-selective BAR1/2 blocker, were characterized in terms of expression and localization of apoptosis and autophagy markers. The effects of propranolol on autophagy signaling were also evaluated and specific autophagy modulators were used to get functional information on the autophagic effects of BAR antagonism. Finally, propranolol effects on neurodegenerative processes were associated to an electrophysiological investigation of retinal function by recording electroretinogram (ERG). We found that retinas of OIR mice are characterized by increased apoptosis and decreased autophagy, while propranolol reduces apoptosis and stimulates autophagy. In particular, propranolol triggers autophagosome formation in bipolar, amacrine and ganglion cells that are committed to die by apoptosis in response to hypoxia. Also our data argue that propranolol, through the inhibition of the Akt-mammalian target of rapamycin pathway, activates autophagy which decreases retinal cell death. At the functional level, propranolol recovers dysfunctional ERG by recovering the amplitude of a- and b-waves, and oscillatory potentials, thus indicating an efficient restoring of retinal transduction. Overall, our results demonstrate that BAR1/2 are key regulators of retinal apoptosis/autophagy, and that BAR1/2 blockade leads to autophagy-mediated neuroprotection. Reinstating the balance between apoptotic and autophagic machines may therefore be viewed as a future goal in the treatment of retinopathies.

In vitro and in vivo inhibition of proangiogenic retinal phenotype by an antisense oligonucleotide downregulating uPAR expression

Neoangiogenesis is the main pathogenic event involved in a variety of retinal diseases. It has been recently demonstrated that inhibiting the urokinase-type plasminogen activator receptor (uPAR) results in reduced angiogenesis in a mouse model of oxygen-induced retinopathy (OIR), establishing uPAR as a therapeutic target in proliferative retinopathies. Here, we evaluated in cultured human retinal endothelial cells (HRECs) and in OIR mice the potential of a specific antisense oligodeoxyribonucleotide (ASO) in blocking the synthesis of uPAR and in providing antiangiogenic effects. uPAR expression in HRECs was inhibited by lipofection with the phosphorotioated 5'-CGGCGGGTGACCCATGTG-3' ASO-uPAR, complementary to the initial translation site of uPAR mRNA. Inhibition of uPAR expression via ASO-uPAR was evaluated in HRECs by analyzing VEGF-induced tube formation and migration. In addition, the well-established and reproducible murine OIR model was used to induce retinal neovascularization in vivo. OIR mice were injected intraperitoneally with ASO-uPAR and retinopathy was evaluated considering the extent of the avascular area in the central retina and neovascular tuft formation. The ASO-uPAR specifically decreased uPAR mRNA and protein levels in HRECs and mitigated VEGF-induced tube formation and cell migration. Noteworthy, in OIR mice ASO-uPAR administration reduced both the avascular area and the formation of neovascular tufts. In conclusion, although the extrapolation of these experimental findings to the clinic is not straightforward, ASO-uPAR may be considered a potential therapeutic tool for treatment of proliferative retinal diseases.