Betulinic acid derivatives can protect human Müller cells from glutamate-induced oxidative stress

YAP in development and disease: Navigating the regulatory landscape from retina to brain

The distinctive role of Yes-associated protein (YAP) in the nervous system has attracted widespread attention. This comprehensive review strategically uses the retina as a vantage point, embarking on an extensive exploration of YAP's multifaceted impact from the retina to the brain in development and pathology. Initially, we explore the crucial roles of YAP in embryonic and cerebral development. Our focus then shifts to retinal development, examining in detail YAP's regulatory influence on the development of retinal pigment epithelium (RPE) and retinal progenitor cells (RPCs), and its significant effects on the hierarchical structure and functionality of the retina. We also investigate the essential contributions of YAP in maintaining retinal homeostasis, highlighting its precise regulation of retinal cell proliferation and survival. In terms of retinal-related diseases, we explore the epigenetic connections and pathophysiological regulation of YAP in diabetic retinopathy (DR), glaucoma, and proliferative vitreoretinopathy (PVR). Lastly, we broaden our exploration from the retina to the brain, emphasizing the research paradigm of "retina: a window to the brain." Special focus is given to the emerging studies on YAP in brain disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD), underlining its potential therapeutic value in neurodegenerative disorders and neuroinflammation.

Ginkgo biloba extracts protect human retinal Müller glial cells from t-BHP induced oxidative damage by activating the AMPK-Nrf2-NQO-1 axis

OBJECTIVES

Retinal Müller glial cell loss is almost involved in all retinal diseases, especially diabetic retinopathy (DR). Oxidative stress significantly contributes to the development of Müller glial cell loss. Ginkgo biloba extracts (GBE) have been reported to possess antioxidant property, beneficial in treating human retinal diseases. However, little is known about its role in Müller glial cells. This study investigated the protective effect of GBE (prepared from ginkgo biloba dropping pills) in human Müller glial cells against tert-butyl hydroperoxide (t-BHP)-induced oxidative stress and its underlying molecular mechanism.

METHODS

MIO-M1 cells were pretreated with or without GBE prior to the exposure to t-BHP-induced oxidative stress. Cell viability, cell death profile and lipid peroxidation were subsequently assessed. Protein expression of the key anti-oxidative signalling factors were investigated.

KEY FINDINGS

We showed that GBE can effectively protect human MIO-M1 cells from t-BHP-induced oxidative injury by improving cell viability, reducing intracellular ROS accumulation and suppressing lipid peroxidation, which effect is likely mediated through activating AMPK-Nrf2-NQO-1 antioxidant respondent axis.

CONCLUSIONS

Our study is the first to reveal the great potentials of GBE in protecting human retinal Müller glial cell loss against oxidative stress. GBE might be used to prevent human retinal diseases particularly DR.

Ginkgo biloba extracts (GBE) protect human RPE cells from t-BHP-induced oxidative stress and necrosis by activating the Nrf2-mediated antioxidant defence

OBJECTIVES

Age-related macular degeneration (AMD) is a prevalent ocular disease. Dry AMD accounts for most cases of blindness associated with AMD but there are no treatments. Oxidative stress-induced damage to retinal pigment epithelial (RPE) cells is a major contributor to the pathogenesis of dry AMD. This study investigated the protective actions of Ginkgo biloba extracts (GBE) in human RPE cells subjected to tert-butyl hydroperoxide (t-BHP)-mediated oxidative stress.

METHODS

The human ARPE-19 cells were pre-treated with or without GBE before the exposure to t-BHP. Cell viability, cell death profile and lipid peroxidation were assessed. The findings were verified using human primary RPE cultures.

KEY FINDINGS

GBE pre-treatment prevented the increase in lipid peroxidation and necrosis/ferroptosis, and the concurrent viability decrease in RPE cells exposed to t-BHP. It enabled the pronounced activation of Nrf2 and its downstream genes. We found that ERK1/2 phosphorylation was increased to a similar extent by t-BHP and GBE.

CONCLUSION

This study revealed that GBE pre-treatment attenuates pro-oxidant stress and protects human RPE cells from oxidative injury by modulating ERK1/2-Nrf2 axis. These findings suggest that GBE has the potential to be developed as a agent that may be valuable in decreasing AMD progression.

Multitarget Activities of Müller Glial Cells and Low-Density Lipoprotein Receptor-Related Protein 1 in Proliferative Retinopathies

Müller glial cells (MGCs), the main glial component of the retina, play an active role in retinal homeostasis during development and pathological processes. They strongly monitor retinal environment and, in response to retinal imbalance, activate neuroprotective mechanisms mainly characterized by the increase of glial fibrillary acidic protein (GFAP). Under these circumstances, if homeostasis is not reestablished, the retina can be severely injured and GFAP contributes to neuronal degeneration, as they occur in several proliferative retinopathies such as diabetic retinopathy, sickle cell retinopathy and retinopathy of prematurity. In addition, MGCs have an active participation in inflammatory responses releasing proinflammatory mediators and metalloproteinases to the extracellular space and vitreous cavity. MGCs are also involved in the retinal neovascularization and matrix extracellular remodeling during the proliferative stage of retinopathies. Interestingly, low-density lipoprotein receptor-related protein 1 (LRP1) and its ligand α₂-macroglobulin (α₂M) are highly expressed in MGCs and they have been established to participate in multiple cellular and molecular activities with relevance in retinopathies. However, the exact mechanism of regulation of retinal LRP1 in MGCs is still unclear. Thus, the active participation of MGCs and LRP1 in these diseases, strongly supports the potential interest of them for the design of novel therapeutic approaches. In this review, we discuss the role of LRP1 in the multiple MGCs activities involved in the development and progression of proliferative retinopathies, identifying opportunities in the field that beg further research in this topic area.Summary StatementMGCs and LRP1 are active players in injured retinas, participating in key features such as gliosis and neurotoxicity, neovascularization, inflammation, and glucose control homeostasis during the progression of ischemic diseases, such as proliferative retinopathies.

The multi-kinase inhibitor afatinib serves as a novel candidate for the treatment of human uveal melanoma

PURPOSE

Uveal melanoma (UM) is the most common intraocular malignancy in adults with a poor prognosis and a high recurrence rate. Currently there is no effective treatment for UM. Multi-kinase inhibitors targeting dysregulated pro-tumorigenic signalling pathways have revolutionised anti-cancer treatment but, as yet, their efficacy in UM has not been established. Here, we identified the multi-kinase inhibitor afatinib as a highly effective agent that exerts anti-UM effects in in vitro, ex vivo and in vivo models.

METHODS

We assessed the anti-cancer effects of afatinib using cell viability, cell death and cell cycle assays in in vitro and ex vivo UM models. The signaling pathways involved in the anti-UM effects of afatinib were evaluated by Western blotting. The in vivo activity of afatinib was evaluated in UM xenograft models using tumour mass measurement, PET scan, immunohistochemical staining and TUNEL assays.

RESULTS

We found that afatinib reduced cell viability and activated apoptosis and cell cycle arrest in multiple established UM cell lines and in patient tumour-derived primary cell lines. Afatinib impaired cell migration and enhanced reproductive death in these UM cell models. Afatinib-induced cell death was accompanied by activation of STAT1 expression and downregulation of Bcl-xL and cyclin D1 expression, which control cell survival and cell cycle progression. Afatinib attenuated HER2-AKT/ERK/PI3K signalling in UM cell lines. Consistent with these observations, we found that afatinib suppressed tumour growth in UM xenografted mice.

CONCLUSION

Our data indicate that afatinib activates UM cell death and targets the HER2-mediated cascade, which modulates STAT1-Bcl-xL/cyclin D1 signalling. Thus, targeting HER2 with agents like afatinib may be a novel therapeutic strategy to treat UM and to prevent metastasis.

Compritol solid lipid nanoparticle formulations enhance the protective effect of betulinic acid derivatives in human Müller cells against oxidative injury

Müller cells maintain homeostatic functions in the retina. Their dysfunction leads to irreversible retinal diseases. Oxidative injury is a leading cause of retinal cytotoxicity. Our previous studies reported several betulinic acid (BA) derivatives can protect Müller cells from oxidative injury but achieving pharmacologically effective concentrations in the Müller cells could be a limitation. To optimise cellular delivery, we encapsulated the BA analogues H3, H5 and H7 into the clinically approved Compritol 888 and HD5 ATO solid lipid nanoparticles (SLNs) using the micro-emulsion method. The cytoprotective effects of these SLN-formulations were determined in human MIO-M1 cells. We found cytoprotection by H3 and H5 SLN-formulations was significantly enhanced, which was evident at concentrations much lower than those required with the free agents. Both SLN-formulations prolonged the duration of action of these agents. The most effective agent H5 delivered in 888 ATO SLNs attenuated glutamate-induced ROS formation and the associated necrosis in MIO-M1 cells. Overall, SLNs have emerged as promising delivery carriers for BA derivatives enhancing their protective effects against oxidative injury in human Müller cells. Our study is the first to show SLNs can be a viable route to delivery agents with improved efficacy and stability into human Müller cells favoring the treatment/prevention of retinal 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.

The anti-cancer effect of betulinic acid in u937 human leukemia cells is mediated through ROS-dependent cell cycle arrest and apoptosis

Although previous studies have shown anti-cancer activity of betulinic acid (BA), a pentacyclic triterpenoid, against various cancer lines, the underlying molecular mechanisms are not well elucidated. In this study, we evaluated the mechanisms involved in the anti-cancer efficacy of BA in U937 human myeloid leukemia cells. BA exerted a significant cytotoxic effect on U937 cells through blocking cell cycle arrest at the G2/M phase and inducing apoptosis, and that the intracellular reactive oxygen species (ROS) levels increased after treatment with BA. The down-regulation of cyclin A and cyclin B1, and up-regulation of cyclin-dependent kinase inhibitor p21WAF1/CIP1 revealed the G2/M phase arrest mechanism of BA. In addition, BA induced the cytosolic release of cytochrome c by reducing the mitochondrial membrane potential with an increasing Bax/Bcl-2 expression ratio. BA also increased the activity of caspase-9 and -3, and subsequent degradation of the poly (ADP-ribose) polymerase. However, quenching of ROS by N-acetyl-cysteine, an ROS scavenger, markedly abolished BA-induced G2/M arrest and apoptosis, indicating that the generation of ROS plays a key role in inhibiting the proliferation of U937 cells by BA treatment. Taken together, our results provide a mechanistic rationale that BA exhibits anti-cancer properties in U937 leukemia cells through ROS-dependent induction of cell cycle arrest at G2/M phase and apoptosis.

Outcome of Off-Label AREDS 2 Supplementation for the Treatment of Macular Degeneration in Non-Proliferative Idiopathic Type 2 Macular Telangiectasia

Purpose

To evaluate if off-label Age-Related Eye Disease Study 2 (AREDS2) supplementation prevents visual and anatomical deterioration in non-proliferative Idiopathic Macular Telangiectasia Type 2 (IMT2).

Patients and Methods

This is a single-center retrospective, comparative study of 82 IMT2 eyes treated with AREDS2 from January 1st, 2013 to January 1st, 2018. The study analysis consisted of a non-comparative arm, which included all AREDS2 eyes, and a comparative arm (27 AREDS2 and 42 untreated eyes) that only included eyes with complete follow-up data. Eyes were evaluated at baseline, 12 and 24 months. Better/worse eye sub-analysis was performed in the comparative study arm. Primary outcomes were best corrected visual acuity (BCVA) and optical coherence tomography (OCT) anatomical characteristics including largest cavitation diameter, central macular thickness (CMT), and length of ellipsoid zone (EZ) loss at 24 months.

Results

In the non-comparative arm, AREDS2 eyes showed stable BCVA (0.28 ± 0.18 logMAR at baseline vs 0.26 ± 0.19 logMAR at 24 months; p = 0.35) and OCT anatomical features after 24 months of supplementation. In the comparative arm, BCVA mean difference was greater for untreated eyes at 24 months (−0.09 ± 0.15 vs 0.03 ± 0.11 logMAR; p = <0.001). AREDS2 eyes had decreased cavitary diameter and EZ loss compared to untreated eyes at the study endpoint (p = 0.01 and p = 0.02, respectively). CMT remained stable for both cohorts throughout the study. For better/worse eye analysis, untreated eyes had worse BCVA at 24 months in both better and worse eyes (both p = 0.01). For anatomical outcomes, increases in both EZ loss (p = 0.04) and cavitary diameter (p = 0.001) among untreated eyes were only significant for eyes with worse baseline BCVA.

Conclusion

Our results suggest that off-label AREDS2 supplementation in non-proliferative IMT2 may prevent anatomical and visual deterioration in a subset of eyes.

Betulinic Acid Restricts Human Bladder Cancer Cell Proliferation In Vitro by Inducing Caspase-Dependent Cell Death and Cell Cycle Arrest, and Decreasing Metastatic Potential

Betulinic acid (BA) is a naturally occurring pentacyclic triterpenoid and generally found in the bark of birch trees (Betula sp.). Although several studies have been reported that BA has diverse biological activities, including anti-tumor effects, the underlying anti-cancer mechanism in bladder cancer cells is still lacking. Therefore, this study aims to investigate the anti-proliferative effect of BA in human bladder cancer cell lines T-24, UMUC-3, and 5637, and identify the underlying mechanism. Our results showed that BA induced cell death in bladder cancer cells and that are accompanied by apoptosis, necrosis, and cell cycle arrest. Furthermore, BA decreased the expression of cell cycle regulators, such as cyclin B1, cyclin A, cyclin-dependent kinase (Cdk) 2, cell division cycle (Cdc) 2, and Cdc25c. In addition, BA-induced apoptosis was associated with mitochondrial dysfunction that is caused by loss of mitochondrial membrane potential, which led to the activation of mitochondrial-mediated intrinsic pathway. BA up-regulated the expression of Bcl-2-accociated X protein (Bax) and cleaved poly-ADP ribose polymerase (PARP), and subsequently activated caspase-3, -8, and -9. However, pre-treatment of pan-caspase inhibitor markedly suppressed BA-induced apoptosis. Meanwhile, BA did not affect the levels of intracellular reactive oxygen species (ROS), indicating BA-mediated apoptosis was ROS-independent. Furthermore, we found that BA suppressed the wound healing and invasion ability, and decreased the expression of Snail and Slug in T24 and 5637 cells, and matrix metalloproteinase (MMP)-9 in UMUC-3 cells. Taken together, this is the first study showing that BA suppresses the proliferation of human bladder cancer cells, which is due to induction of apoptosis, necrosis, and cell cycle arrest, and decrease of migration and invasion. Furthermore, BA-induced apoptosis is regulated by caspase-dependent and ROS-independent pathways, and these results provide the underlying anti-proliferative molecular mechanism of BA in human bladder cancer cells.

Hyperglycemia-induced VEGF and ROS production in retinal cells is inhibited by the mTOR inhibitor, rapamycin

Determine the impact of the mTOR inhibitor, rapamycin, on the hyperglycemia-induced expression of vascular endothelial growth factor (VEGF) and the production of reactive oxygen species (ROS) in retinal cells. Rats made hyperglycemic for 8 weeks by streptozotocin, as well as control rats, received i.p. rapamycin (1 mg/kg) for 3 days prior to immunostaining of their retinas with anti-VEGF and anti-glial fibrillary acidic protein (GFAP) and measuring retinal protein levels of VEGF and GFAP by Western blotting. In other experiments, flow cytometry analysis of ethidium fluorescence determined intracellular ROS levels in the absence or presence of rapamycin (1 μM) under normoglycemic (5.5 mM) and hyperglycemic (25 mM) conditions in a rat retinal Müller cell line (TR-MUL5) and primary human retinal microvascular endothelial cells (HRMECs). In the diabetic retina, VEGF was elevated and colocalized with the glial marker, GFAP, whose level was also elevated. Treatment with rapamycin inhibited the diabetes-induced VEGF and GFAP increases. We also found that raising extracellular glucose from 5.5 mM to 25 mM resulted in significant rapamycin-sensitive increases in the ROS levels of TR-MUL5 cells and HRMECs. In rat retina, rapamycin attenuates the diabetes-induced VEGF overexpression, and in cultured Müller cells and HRMECs, inhibits the hyperglycemia-induced boost ROS.

Betulinic Acid Attenuates T-2-Toxin-Induced Testis Oxidative Damage Through Regulation of the JAK2/STAT3 Signaling Pathway in Mice

T-2 toxin is one of the most toxic type A trichothecene mycotoxins in nature, and it exhibits reproductive toxicity. Betulinic acid (BA) is a natural pentacyclic triterpene compound found in species of Betula, and it has been reported to have antioxidant activity. The aim of the present study was to investigate the protective effect of BA on T-2-toxin-induced testicular injury in mice and explore its molecular mechanism. Sixty adult male mice were randomly divided into groups. The mice were pretreated orally with BA (0.25, 0.5, and 1.0 mg/kg) daily for 14 days, and the T-2 toxin (4 mg/kg body weight) was administered via intraperitoneal injection to induce oxidative stress after the last administration of BA. BA pretreatment significantly increased the secreted levels of testosterone and sperm motility. Moreover, BA pretreatment significantly increased the total antioxidant capacity (T-AOC), the activity of SOD and CAT, and the content of GSH, and it reduced the content of MDA. Furthermore, BA relieved testicular injury and reduced the number of apoptotic cells, and it significantly decreased the protein expression of Janus kinase 2 (JAK2), signal transducers and activators of transcription 3 (STAT3), caspsae-3, and Bcl-2-associated X protein (Bax). BA also increased the expression of B-cell lymphoma-2 (Bcl-2). We suggest that BA reduced the oxidative damage induced by T-2 toxin, and that these protective effects may be partially mediated by the JAK2/STAT3 signaling pathway.