Glycyrrhizin protects against sodium iodate-induced RPE and retinal injury though activation of AKT and Nrf2/HO-1 pathway

Myricetin inhibits 4 T1 breast tumor growth in mice via induction of Nrf-2/GPX4 pathway-mediated Ferroptosis

Ferroptosis is a recently identified form of programmed cell death that is iron-dependent and closely involved in the pathogenesis of breast cancer. Past studies have identified myricetin as being able to inhibit breast cancer growth through its targeting of apoptotic mechanisms, but the precise mechanisms whereby it exerts its antitumoral effects in breast cancer remain to be characterized in detail. Here, the effects of myricetin on the induction of ferroptosis in breast cancer cells were investigated. It was found that myricetin was able to significantly inhibit 4 T1 tumor cell viability and colony forming activity, increasing the level of MDA, Fe2+, and ROS within these cells. From a mechanistic perspective, myricetin was found to induce ferroptotic 4 T1 cell death via downregulating Nrf-2 and GPX4. In vivo experimentation demonstrated that myricetin treatment was sufficient to reduce the growth of subcutaneous breast tumors in female mice as evidenced by decreases in tumor weight and volume, while significantly inhibiting Nrf-2 and GPX4 expression within the tumors of treated mice. Myricetin is capable of readily suppressing breast tumor growth in mice via the induction of ferroptotic activity through the Nrf-2/GPX4 pathway. Myricetin may thus offer utility as a therapeutic agent for the management of breast cancer in clinical settings.

The significance of precisely regulating heme oxygenase-1 expression: Another avenue for treating age-related ocular disease?

Aging entails the deterioration of the body's organs, including overall damages at both the genetic and cellular levels. The prevalence of age-related ocular disease such as macular degeneration, dry eye diseases, glaucoma and cataracts is increasing as the world's population ages, imposing a considerable economic burden on individuals and society. The development of age-related ocular disease is predominantly triggered by oxidative stress and chronic inflammatory reaction. Heme oxygenase-1 (HO-1) is a crucial antioxidant that mediates the degradative process of endogenous iron protoporphyrin heme. It catalyzes the rate-limiting step of the heme degradation reaction, and releases the metabolites such as carbon monoxide (CO), ferrous, and biliverdin (BV). The potent scavenging activity of these metabolites can help to defend against peroxides, peroxynitrite, hydroxyl, and superoxide radicals. Other than directly decomposing endogenous oxidizing substances (hemoglobin), HO-1 is also a critical regulator of inflammatory cells and tissue damage, exerting its anti-inflammation activity through regulating complex inflammatory networks. Therefore, promoting HO-1 expression may act as a promising therapeutic strategy for the age-related ocular disease. However, emerging evidences suggest that the overexpression of HO-1 significantly contributes to ferroptosis due to its dual nature. Surplus HO-1 leads to excessive Fe2+ and reactive oxygen species, thereby causing lipid peroxidation and ferroptosis. In this review, we elucidate the role of HO-1 in countering age-related disease, and summarize recent pharmacological trials that targeting HO-1 for disease management. Further refinements of the knowledge would position HO-1 as a novel therapeutic target for age-related ocular disease.

Protective effects of triptolide against oxidative stress in retinal pigment epithelium cells via the PI3K/AKT/Nrf2 pathway: a network pharmacological method and experimental validation

PURPOSE

Among aging adults, age-related macular degeneration (AMD), is a prevalent cause of blindness. Nevertheless, its progression may be halted by antioxidation in retinal pigment epithelium (RPE). The primary effective constituent of Tripterygium wilfordii Hook. F., triptolide (TP), has demonstrated anti-inflammatory, antiproliferative, and antioxidant properties. The mechanics of the protective effect of triptolide against the oxidative damage in retinal pigment epithelial (RPE) were assessed in this study.

METHODS

ARPE-19 cells were pretreated with TP, and then exposed to sodium iodate (SI). First, cell viability was assessed using CCK-8. Subsequently, we measured indicators for cell oxidation including reactive oxygen species (ROS), catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA). Then, we used network pharmacological analysis and molecular docking to explore the signaling pathway of TP. Last, we used western blot, ELISA, and immunofluorescence assays to clarify the potential mechanistic pathways.

RESULTS

The network pharmacology data suggested that TP may inhibit AMD by regulating the PI3K/Akt signaling pathway. Experimental results showed that the potential mechanism is that it regulates the PI3K/Akt pathway and promotes Nrf2 phosphorylation and activation, thereby raising the level of antioxidant factors (HO-1, NQO1) and reducing the generation of ROS, which inhibit oxidative damage.

CONCLUSION

Our findings suggested that the effect of TP on SI-exposed RPE cells principally relies on the regulation of oxidative stress through the PI3K/Akt/Nrf2 signaling pathway.

N-Acetylserotonin Alleviates Retinal Autophagy via TrkB/AKT/Nrf2 Signaling Pathway in Retinal Ischemia-Reperfusion Injury Rats

INTRODUCTION

The objective of this study was to investigate the impact of N-acetylserotonin (NAS) on the autophagy of retinal cells in rats with retinal ischemia-reperfusion injury (RIRI) and to explore the mechanisms by which NAS administration can alleviate RIRI through the tropomyosin-related kinase receptor B (TrkB)/protein kinase B (Akt)/nuclear factor erythroid-derived factor 2-related factor (Nrf2) signaling pathway.

METHODS

Healthy adult male rats were randomly assigned to four groups: sham, RIRI, RIRI+NAS, and RIRI+NAS+ANA-12. The RIRI group was induced by elevating intraocular pressure, and changes in retinal structure and edema were assessed using H&E staining. The RIRI+NAS and RIRI+NAS+ANA-12 groups received intraperitoneal injections of NAS before and after modeling. The RIRI+NAS+ANA-12 group was also administered ANA-12, a TrkB antagonist. Immunohistochemical staining and Western blot analysis were used to evaluate phosphorylated TrkB (p-TrkB), phosphorylated Akt (p-Akt), Nrf2, sequestosome 1 (P62), and microtubule-associated protein 1 light chain 3 (LC3-II) levels in the retinas of each group. Electroretinogram was recorded to detect retinal function in each group of rats 24 h after modeling.

RESULTS

The RIRI+NAS group had a thinner retina and more retinal ganglion cells (RGCs) than RIRI and RIRI+NAS+ANA-12 groups (p < 0.05). Immunohistochemical staining and Western blot results showed that p-TrkB, p-Akt, n-Nrf2, and P62 levels in the RIRI+NAS group were higher compared with those in RIRI and RIRI+NAS+ANA-12 groups (p < 0.05). Also, lower LC3-II levels were observed in the RIRI+NAS group compared with that in RIRI and RIRI+NAS+ANA-12 groups (p < 0.05). Electroretinogram recording results showed that 24 h after retinal ischemia-reperfusion, the magnitude of b-wave changes was attenuated in the RIRI+NAS group compared with the RIRI group (p < 0.05).

CONCLUSION

The administration of NAS activates the TrkB/Akt/Nrf2 signaling pathway, reduces autophagy, alleviates retinal edema, promotes the survival of retinal ganglion cells (RGCs), and provides neuroprotection against retinal injury.

Paraoxonase 2 Deficiency Causes Mitochondrial Dysfunction in Retinal Pigment Epithelial Cells and Retinal Degeneration in Mice

Although AMD is a complex disease, oxidative stress is a crucial contributor to its development, especially in view of the higher oxygen demand of the retina. Paraoxonase 2 (PON2) is a ubiquitously and constitutively expressed antioxidant protein that is found intracellularly associated with mitochondrial membranes and modulates mitochondrial ROS production and function. The contribution of PON2 to AMD has not been studied to date. In this study, we examined the role of PON2 in AMD utilizing both in vitro and in vivo models of AMD with emphasis on mitochondrial function. Mitochondrial localization and regulation of PON2 following oxidative stress were determined in human primary cultured retinal pigment epithelium (hRPE) cells. PON2 was knocked down in RPE cells using siRNA and mitochondrial bioenergetics were measured. To investigate the function of PON2 in the retina, WT and PON2-deficient mice were administered NaIO3 (20 mg/kg) intravenously; fundus imaging, optical coherence tomography (OCT), electroretinography (ERG) were conducted; and retinal thickness and cell death were measured and quantified. In hRPE, mitochondrial localization of PON2 increased markedly with stress. Moreover, a time-dependent regulation of PON2 was observed following oxidative stress, with an initial significant increase in expression followed by a significant decrease. Mitochondrial bioenergetic parameters (basal respiration, ATP production, spare respiratory capacity, and maximal respiration) showed a significant decrease with oxidative stress, which was further exacerbated in the absence of PON2. NaIO3 treatment caused significant retinal degeneration, retinal thinning, and reduced rod and cone function in PON2-deficient mice when compared to WT mice. The apoptotic cells and active caspase 3 significantly increased in PON2-deficient mice treated with NaIO3, when compared to WT mice. Our investigation demonstrates that deficiency of PON2 results in RPE mitochondrial dysfunction and a decline in retinal function. These findings imply that PON2 may have a beneficial role in retinal pathophysiology and is worthy of further investigation.

Artesunate alleviates intestinal ischemia/reperfusion induced acute lung injury via up-regulating AKT and HO-1 signal pathway in mice

Acute Lung injury (ALI) is a common complication following intestinal ischemia/reperfusion (II/R) injury that can lead to acute respiratory distress syndrome (ARDS) a fatal illness for there is no specific therapy. The semisynthetic artemisinin Artesunate (Art) extracted from Artemisia annua has been found lots of pharmaceutical effects such as anti-malaria, anti-inflammatory, and anti-apoptosis. This study aimed to investigate the effect of Artesunate on intestinal ischemia/reperfusion and the mechanism of how Artesunate works in mice. To establish the II/R model, the C57BL/c mice were subjected to occlude superior mesenteric artery (SMA) for 45 min and 120 min reperfusion, and the lung tissue was collected for examination. Severe lung injury occurred during the II/R, meanwhile Art pretreatment decreased the lung injury score, wet/dry ratio, the level of MDA, MPO, IL-1β, TNFα, CXCL1, MCP-1, the TUNEL-positive cells, Bax and Cleaved-Caspase3 protein expression obviously, and increased the activity of SOD and the expression of Bcl-2. In addition, the protein of P-AKT and HO-1 were upregulated during the Art pretreatment. Then the AKT inhibitor Triciribin and HO-1 inhibitor Tin-protoporphyrin IX were administered which reversed the protein expression of apoptosis, AKT and HO-1. Our study suggests that Art mitigated the II/R induced acute lung injury by targeting the oxidative stress, inflammatory response and apoptosis which is associated with the activating of AKT and HO-1, providing novel insights into the therapeutic candidate for the treatment of II/R induced acute lung injury.

Glycyrrhizin protects against particulate matter-induced lung injury via regulation of endoplasmic reticulum stress and NLRP3 inflammasome-mediated pyroptosis through Nrf2/HO-1/NQO1 signaling pathway

Particulate matter (PM) is a major environmental pollutant that contributes considerably to deaths worldwide. The pathogenesis of PM-induced lung injury (PILI) is far from elucidated and warrants effective intervention. An effective component of licorice, glycyrrhizin (GL), has been the subject of much research due to its anti-inflammatory and anti-oxidative capabilities. Although preventive properties of GL are well-known, the precise mechanism of GL in PILI has not yet been investigated. A mouse model of PILI was used to examine the protective effects of GL in vivo, and a human bronchial epithelial cells (HBECs) model was used in vitro. In order to determine whether GL mitigates PILI, its effects on endoplasmic reticulum (ER) stress, NLRP3 inflammasome-mediated pyroptosis and the oxidative response were examined. According to the findings, GL reduced PILI and activate anti-oxidative Nrf2/HO-1/NQO1 signaling in mice. Notably, the effect of GL on PM-induced ER stress and NLRP3 inflammasome-mediated pyroptosis was significantly attenuated by the Nrf2 inhibitor ML385. The data suggest that via the anti-oxidative Nrf2 signaling, GL may reduce oxidative stress-mediated ER stress and NLRP3 inflammasome-mediated pyroptosis. Therefore, GL may serve as a promising treatment for PILI.

Role of circular RNA and its delivery strategies to cancer - An overview

With the passage of years and the progress of research on ribonucleic acids, the range of forms in which these molecules have been observed grows. One of them, discovered relatively recently, is circular RNA - covalently closed circles (circRNA). In recent years, there has been a huge increase in the interest of researchers in this group of molecules. It entailed a significant increase in the state of knowledge about them, which in turn caused a dramatic change in their perception. Rather than seeing circular RNAs as curiosities that represent a minor information noise in a cell or a result of RNA misprocessing, they came to be regarded as a common, essential, and potentially extremely useful group of molecules. Nevertheless, the current state of the art of circRNA is full of white cards. A lot of valuable information has been obtained from high-throughput methods to study whole transcriptomes, but many issues related to circular RNAs still need to be clarified. Presumably, each answer obtained will raise several new questions. However, circRNAs have a wealth of potential applications, including therapeutic applications.

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.

Melatonin inhibits NaIO3-induced ARPE-19 cell apoptosis via suppression of HIF-1α/BNIP3-LC3B/mitophagy signaling

Background

Age-related macular degeneration (AMD) leads to gradual central vision loss and eventual irreversible blindness. Melatonin, an endogenous hormone, exhibits anti-inflammatory and antitumor effects; however, the role it plays in AMD remains unclear. Herein, we investigated the anti-AMD molecular mechanism of melatonin after sodium iodate (NaIO3) treatment of ARPE-19 cells in vitro and in animal models with the goal of improving the therapeutic effect.

Results

The in vitro results showed that melatonin protected against NaIO₃-induced cell viability decline, mitochondrial dysfunction and apoptosis in ARPE-19 cells, and melatonin also alleviated NaIO₃-induced reactive oxygen species (ROS) production, mitochondrial dysfunction and mitophagy activation. Melatonin reduced NaIO₃-induced mitophagy activation through HIF-1α-targeted BNIP3/LC3B transcription, whereas ROS inhibition realized with N-acetylcysteine (NAC, a ROS inhibitor) combined with melatonin reduced the effect of NaIO₃ on mitophagy. An animal model of AMD was established to confirm the in vitro data. Mouse tail vein injection of NaIO₃ and melatonin was associated with enhanced repair of retinal layers within 7 days, as observed by optical coherence tomography (OCT) and hematoxylin and eosin (H&E) staining. A reduction in BNIP3 and HIF-1α levels, as determined by immunohistochemistry (IHC) assay, was also observed.

Conclusions

These results indicate that melatonin attenuated NaIO₃-induced mitophagy of ARPE-19 cells via reduction in ROS-mediated HIF-1α targeted BNIP3/LC3B signaling in vitro and in vivo. Melatonin may be a potential therapeutic drug in the treatment of AMD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00879-3.

Neighborhood-based inference and restricted Boltzmann machine for microbe and drug associations prediction

Background

Efficient identification of microbe-drug associations is critical for drug development and solving problem of antimicrobial resistance. Traditional wet-lab method requires a lot of money and labor in identifying potential microbe-drug associations. With development of machine learning and publication of large amounts of biological data, computational methods become feasible.

Methods

In this article, we proposed a computational model of neighborhood-based inference (NI) and restricted Boltzmann machine (RBM) to predict potential microbe-drug association (NIRBMMDA) by using integrated microbe similarity, integrated drug similarity and known microbe-drug associations. First, NI was used to obtain a score matrix of potential microbe-drug associations by using different thresholds to find similar neighbors for drug or microbe. Second, RBM was employed to obtain another score matrix of potential microbe-drug associations based on contrastive divergence algorithm and sigmoid function. Because generalization ability of individual method is poor, we used an ensemble learning to integrate two score matrices for predicting potential microbe-drug associations more accurately. In particular, NI can fully utilize similar (neighbor) information of drug or microbe and RBM can learn potential probability distribution hid in known microbe-drug associations. Moreover, ensemble learning was used to integrate individual predictor for obtaining a stronger predictor.

Results

In global leave-one-out cross validation (LOOCV), NIRBMMDA gained the area under the receiver operating characteristics curve (AUC) of 0.8666, 0.9413 and 0.9557 for datasets of DrugVirus, MDAD and aBiofilm, respectively. In local LOOCV, AUCs of 0.8512, 0.9204 and 0.9414 were obtained for NIRBMMDA based on datasets of DrugVirus, MDAD and aBiofilm, respectively. For five-fold cross validation, NIRBMMDA acquired AUC and standard deviation of 0.8569 ± -0.0027, 0.9248 ± -0.0014 and 0.9369 ± -0.0020 on the basis of datasets of DrugVirus, MDAD and aBiofilm, respectively. Moreover, case study for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) showed that 13 out of the top 20 predicted drugs were verified by searching literature. The other two case studies indicated that 17 and 17 out of the top 20 predicted microbes for the drug of ciprofloxacin and minocycline were confirmed by identifying published literature, respectively.

Glycyrrhiza uralensis promote the metabolism of toxic components of Aconitum carmichaeli by CYP3A and alleviate the development of chronic heart failure

Aconitum, as "the first drug of choice for invigorating Yang and saving lives", has been widely used for the treatment of heart failure. However, toxic components of Aconitum can easily lead to serious arrhythmia, even death (Y. CT., 2009; Zhang XM., 2018). In this study, a High Performance Liquid Chromatography (HPLC) method for the determination of aconitine (AC), mesaconitine (MA) and hypaconitine (HA) was established; The effect of Glycyrrhiza on CYP3A1 / 2 mRNA expression was detected by RT-PCR; SD rats were given Aconitum and compatibility of Glycyrrhizae and Aconitum by gavage respectively, the blood concentration of toxic components were determined by LC-MS / MS; The CHF rat model was established by intraperitoneal injection of adriamycin (2.5 mg / kg), and were randomly divided into model, Aconitum, the compatibility of Glycyrrhizae and Aconitum and Captopril group, 5 mice/group. After 4 weeks of gavage, the corresponding indexes were detected by ELISA and HPLC. The results showed that Ketoconazole significantly inhibited the metabolites of AC, MA and HA; Glycyrrhiza induced CYP3A gene expression; The level of ALD in the compatibility of Glycyrrhizae and Aconitum group was significantly lower than that in Aconitum group. After intervention with the compatibility of Glycyrrhizae and Aconitum, ATP increased, ADP decreased significantly. In conclusion, we found Glycyrrhiza promoted the metabolism of toxic components of Aconitum by up regulating the expression of CYP3A, and reduced the content of BNP, Ang II and ALD, improved the energy metabolism disorder of myocardium, alleviated the development of CHF.

Ming-Mu-Di-Huang-Pill Activates SQSTM1 via AMPK-Mediated Autophagic KEAP1 Degradation and Protects RPE Cells from Oxidative Damage

Oxidative stress and diminished autophagy in the retinal pigment epithelium (RPE) play crucial roles in the pathogenesis of age-related macular degeneration (AMD). Enhancing autophagy has recently been identified as an important strategy to protect RPE cells from oxidative damage. Ming-Mu-Di-Huang-Pill (MMDH pill) is a traditional herbal medicine used to treat AMD, and its molecular mechanism is not well understood. The aim of the present study was to investigate whether the MMDH pill relieved acute oxidative damage by activating autophagy in an in vitro and in vivo model of sodium iodate (NaIO3). The results showed that NaIO3 induced cell death and inhibited proliferation. The MMDH pill increased cell viability, restored the activities of antioxidant enzymes, and reduced reactive oxygen species (ROS) fluorescence intensity. The MMDH pill mediated Kelch-like ECH-associated protein 1 (Keap1) degradation and decreased oxidative damage, which was blocked in autophagy inhibitor (chloroquine) or sequestosome-1 (SQSTM1) siRNA-treated RPE cells. Furthermore, we indicated that the MMDH pill could promote adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and autophagy adaptor-SQSTM1 expression, which could stimulate autophagic degradation of Keap1. In addition, the MMDH pill increased nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nuclear translocation in a SQSTM1-dependent manner and induced the expression of the downstream antioxidant factors heme oxygenase-1 (HO-1) and nicotinamide adenine dinucleotide phosphate quinone dehydrogenase 1 (NQO1). In conclusion, MMDH pill plays a protective role in relieving NaIO3-induced oxidative stress by activating the AMPK/SQSTM1/Keap1 pathway. The MMDH pill may be useful to treat AMD by maintaining redox homeostasis and autophagy.

5,8-Dihydroxy-4 ′ , 7-dimethoxyflavone Attenuates TNF-α-Induced Expression of Vascular Cell Adhesion Molecule-1 through EGFR/PKCα/PI3K/Akt/Sp1-Dependent Induction of Heme Oxygenase-1 in Human Cardiac Fibroblasts

Recently, we found that 5,8-dihydroxy-4 ${}^{\text{’}}$ ,7-dimethoxyflavone (DDF) upregulated the expression of heme oxygenase (HO)-1 via p38 mitogen-activated protein kinase/nuclear factor-erythroid factor 2-related factor 2 (MAPK/Nrf2) pathway in human cardiac fibroblasts (HCFs). However, the alternative processes by which DDF induces the upregulation of HO-1 expression are unknown. Activation of epidermal growth factor receptor (EGFR), phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), and protein kinase C (PKC)α may initiate specificity protein (Sp)1 activity, which has been reported to induce expression of antioxidant molecules. Thus, we explored whether these components are engaged in DDF-induced HO-1 upregulation in HCFs. Western blotting, promoter-reporter analyses, and real-time polymerase chain reactions were adopted to measure HO-1 and vascular cell adhesion molecule (VCAM)-1 expressions in HCFs. Respective small interfering (si)RNAs and pharmacological inhibitors were employed to investigate the signaling components engaged in DDF-induced HO-1 upregulation. The chromatin immunoprecipitation assay was conducted to detect the binding interaction of Sp1 and antioxidant response elements (ARE) on the promoter of HO-1. An adhesion assay of THP-1 monocyte was undertaken to examine the functional effect of HO-1 on tumor necrosis factor (TNF)-α-induced VCAM-1 expression. DDF stimulated the EGFR/PKCα/PI3K/Akt pathway leading to activation of Sp1 in HCFs. The roles of these protein kinases in HO-1 induction were ensured by transfection with their respective siRNAs. Chromatin immunoprecipitation assays revealed the interaction between Sp1 and the binding site of proximal ARE on the HO-1 promoter, which was abolished by glutathione, AG1478, Gö6976, LY294002, or mithramycin A. HO-1 expression enhanced by DDF abolished the monocyte adherence to HCFs and VCAM-1 expression induced by TNF-α. Pretreatment with an inhibitor of HO-1: zinc protoporphyrin IX reversed these inhibitory effects of HO-1. We concluded that DDF-induced HO-1 expression was mediated via an EGFR/PKCα/PI3K/Akt-dependent Sp1 pathway and attenuated the responses of inflammation in HCFs.

Discovering the Potential of Natural Antioxidants in Age-Related Macular Degeneration: A Review

Age-related macular degeneration (AMD) is a multifactorial disease associated with anatomical changes in the inner retina. Despite tremendous advances in clinical care, there is currently no cure for AMD. This review aims to evaluate the published literature on the therapeutic roles of natural antioxidants in AMD. A literature search of PubMed, Web of Science and Google Scholar for peer-reviewed articles published between 1 January 2011 and 31 October 2021 was undertaken. A total of 82 preclinical and 18 clinical studies were eligible for inclusion in this review. We identified active compounds, carotenoids, extracts and polysaccharides, flavonoids, formulations, vitamins and whole foods with potential therapeutic roles in AMD. We evaluated the integral cellular signaling pathways including the activation of antioxidant pathways and angiogenesis pathways orchestrating their mode of action. In conclusion, we examined the therapeutic roles of natural antioxidants in AMD which warrant further study for application in clinical practice. Our current understanding is that natural antioxidants have the potential to improve or halt the progression of AMD, and tailoring therapeutics to the specific disease stages may be the key to preventing irreversible vision loss.

Electrophysiologic and Morphologic Strain Differences in a Low-Dose NaIO3-Induced Retinal Pigment Epithelium Damage Model

Purpose

We aimed to explore differences in the NaIO₃-elicited responses of retinal pigment epithelium (RPE) and other retinal cells associated with mouse strains and dosing regimens.

Methods

One dose of NaIO₃ at 10 or 15 mg/kg was given intravenously to adult male C57BL/6J and 129/SV-E mice. Control animals were injected with PBS. Morphologic and functional changes were characterized by spectral domain optical coherence tomography, electroretinography, histologic, and immunofluorescence techniques.

Results

Injection with 10 mg/kg of NaIO₃ did not cause consistent RPE or retinal changes in either strain. Administration of 15 mg/kg of NaIO₃ initially induced a large transient increase in scotopic electroretinography a-, b-, and c-wave amplitudes within 12 hours of injection, followed by progressive structural and functional degradation at 3 days after injection in C57BL/6J mice and at 1 week after injection in 129/SV-E mice. RPE cell loss occurred in a large posterior-central lesion with a ring-like transition zone of abnormally shaped cells starting 12 hours after NaIO₃ treatment.

Conclusions

NaIO₃ effects depended on the timing, dosage, and mouse strain. The RPE in the periphery was spared from damage compared with the central RPE. The large transient increase in the electroretinography was remarkable.

Translational Relevance

This study is a phase T1 translational research study focusing on the development and validation of a mouse model of RPE damage. It provides a detailed foundation for future research, informing choices of mouse strain, dosage, and time points to establish NaIO₃-induced RPE damage.

Natural Anti-Inflammatory Compounds as Drug Candidates for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) represents chronic recurrent intestinal inflammation resulting from various factors. Crohn’s disease (CD) and ulcerative colitis (UC) have been identified as the two major types of IBD. Currently, most of the drugs for IBD used commonly in the clinic have adverse reactions, and only a few drugs present long-lasting treatment effects. Moreover, issues of drug resistance and disease recurrence are frequent and difficult to resolve. Together, these issues cause difficulties in treating patients with IBD. Therefore, the development of novel therapeutic agents for the prevention and treatment of IBD is of significance. In this context, research on natural compounds exhibiting anti-inflammatory activity could be a novel approach to developing effective therapeutic strategies for IBD. Phytochemicals such as astragalus polysaccharide (APS), quercetin, limonin, ginsenoside Rd, luteolin, kaempferol, and icariin are reported to be effective in IBD treatment. In brief, natural compounds with anti-inflammatory activities are considered important candidate drugs for IBD treatment. The present review discusses the potential of certain natural compounds and their synthetic derivatives in the prevention and treatment of IBD.

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.

IL-33trap-mediated IL-33 neutralization does not exacerbate choroidal neovascularization, but fails to protect against retinal degeneration in a dry age-related macular degeneration model

The progressive and sight-threatening disease, age-related macular degeneration (AMD), is a growing public health concern due to ageing demographics, with the highest unmet medical need for the advanced stage of dry AMD, geographic atrophy. The pathogenesis underlying AMD is driven by a complex interplay of genetic and environmental factors. There is ample evidence that inflammation is strongly involved in AMD development. Interleukin-33 (IL-33) has been proposed to be critically involved in retinal degeneration, but a protective role in eye pathophysiology was also demonstrated. The current study investigated the therapeutic potential of IL-33trap, a novel IL-33-neutralizing biologic, in dry AMD/geographic atrophy and, based on controversial data regarding the protective versus detrimental functions of IL-33 in neovascularization, evaluated the risk of progression to wet AMD by IL-33 neutralization. Repeated intravitreal (IVT) injections of IL-33trap in the mouse laser-induced choroidal neovascularization model did not exacerbate neovascularization or leakage, while it significantly inhibited inflammatory cell infiltration in the retinal pigment epithelium and choroid. On the contrary, IVT treatment with IL-33trap significantly induced retinal inflammation and could not prevent retinopathy induction in the mouse sodium iodate (NaIO₃) model. Overall, these data suggest a complex and dichotomous role of IL-33 in eye pathology and indicate that IL-33 neutralization is not able to prevent onset and progression of dry AMD pathogenesis.

New insights into oxidative stress and immune mechanisms involved in age-related macular degeneration tackled by novel therapies

The prevalence of age-related macular degeneration (AMD) has increased in the last years. Although anti-VEGF agents have improved the prognosis of exudative AMD, dry AMD has still devastating effects on elderly people vision. Oxidative stress and inflammation are mechanisms involved in AMD pathogenesis and its progression. Molecular pathways involving epidermal growth factor receptor (EGFR), bone morphogenetic protein (BMP4) and the nuclear erythroid related factor 2 (Nrf2) are behind oxidative stress in AMD due to their participation in antioxidant cellular pathways. As a consequence of the disbalance produced in the antioxidant mechanisms, there is an activation of innate and adaptative immune response with cell recruitment, changes in complement factors expression, and modification of cellular milieu. Different therapies are being studied to treat dry AMD based on the possible effects on antioxidant molecular pathways or their action on the immune response. There is a wide range of treatments presented in this review, from natural antioxidant compounds to cell and gene therapy, based on their mechanisms. Finally, we hypothesize that alpha-1-antitrypsin (AAT), an anti-inflammatory and immunomodulatory molecule that can also modulate antioxidant cellular defenses, could be a good candidate for testing in AMD. This article is part of the special ssue on 'The Quest for Disease-Modifying Therapies for Neurodegenerative Disorders'.

Glabridin Attenuates the Retinal Degeneration Induced by Sodium Iodate In Vitro and In Vivo

Background

Age-related macular degeneration (AMD) is one of the major causes of blindness in the elderly over the age of 60. AMD is divided into dry AMD and wet AMD. Although there are certain treatment methods for wet age-related macular degeneration (AMD), there are no effective treatments for dry AMD yet, and finding new drugs or treatment methods for dry AMD has become a priority. For this purpose, this study explored Glabridin (Glab), an isoflavane found in the root extract of licorice, which has never been investigated in relation to eye diseases.

Purpose

To investigate the effect of Glab on the sodium iodate (NaIO₃) induced retinal degeneration in vitro and in vivo.

Methods

In vitro, cell viability and cytotoxicity were tested with methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay among the groups of ARPE-19 cells. The cell apoptosis was tested with Hoechst 33342 staining and flow cytometry. The level of Reactive oxygen species (ROS) was measured to check the effect on oxidative stress. The protein expressions of phosphorylation of ERK1/2 and p38 were detected by Western blotting. In vivo, C57BL/6J mice were pretreated with Glab intraperitoneally for one week and continued for 4 weeks. NaIO₃ was given to mice through tail vein intravenous injection after 1 week of Glab administration. The retinas of mice were monitored by Optical coherence tomography (OCT) and electroretinography (ERG) at 1w, 2w, 3w, and 4w, respectively, followed by H&E staining.

Results

In vitro, the Glab protected the retinal pigment epithelial (RPE) cells against oxidative stress and apoptosis by inhibiting phosphorylation of ERK1/2 and the p38 MAPK pathway. In vivo, Glab significantly prevented retinal damage by stopping the progression of retinal degeneration and reducing the formation of deposits on the RPE layer induced by NaIO₃. According to the findings of electroretinogram (ERG), Glab helped to maintain the normal function of the retina.

Conclusion

Glabridin has a protective effect against retinal degeneration. It is suggested that Glab be further investigated for the treatment of retinal degeneration diseases.

Mechanisms of mitochondrial dysfunction and their impact on age-related macular degeneration

Oxidative stress-induced damage to the retinal pigment epithelium (RPE) is considered to be a key factor in age-related macular degeneration (AMD) pathology. RPE cells are constantly exposed to oxidative stress that may lead to the accumulation of damaged cellular proteins, lipids, nucleic acids, and cellular organelles, including mitochondria. The ubiquitin-proteasome and the lysosomal/autophagy pathways are the two major proteolytic systems to remove damaged proteins and organelles. There is increasing evidence that proteostasis is disturbed in RPE as evidenced by lysosomal lipofuscin and extracellular drusen accumulation in AMD. Nuclear factor-erythroid 2-related factor-2 (NFE2L2) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) are master transcription factors in the regulation of antioxidant enzymes, clearance systems, and biogenesis of mitochondria. The precise cause of RPE degeneration and the onset and progression of AMD are not fully understood. However, mitochondria dysfunction, increased reactive oxygen species (ROS) production, and mitochondrial DNA (mtDNA) damage are observed together with increased protein aggregation and inflammation in AMD. In contrast, functional mitochondria prevent RPE cells damage and suppress inflammation. Here, we will discuss the role of mitochondria in RPE degeneration and AMD pathology focused on mtDNA damage and repair, autophagy/mitophagy signaling, and regulation of inflammation. Mitochondria are putative therapeutic targets to prevent or treat AMD.

Different Effects of Metformin and A769662 on Sodium Iodate-Induced Cytotoxicity in Retinal Pigment Epithelial Cells: Distinct Actions on Mitochondrial Fission and Respiration

Oxidative stress-associated retinal pigment epithelium (RPE) cell death is critically implicated in the pathogenesis of visual dysfunction and blindness of retinal degenerative diseases. Sodium iodate (NaIO₃) is an oxidative retinotoxin and causes RPE damage. Previously, we found that NaIO₃ can induce human ARPE-19 cell death via inducing mitochondrial fission and mitochondrial dysfunction. Although metformin has been demonstrated to benefit several diseases possibly via AMP-activated protein kinase (AMPK) activation, it remains unknown how AMPK affects retinopathy in NaIO₃ model. Therefore, in this study, we compared the effects of metformin and AMPK activator A769662 on NaIO₃-induced cellular stress and toxicity. We found that A769662 can protect cells against NaIO₃-induced cytotoxicity, while metformin exerts an enhancement in cell death. The mitochondrial reactive oxygen species (ROS) production as well as mitochondrial membrane potential loss induced by NaIO₃ were not altered by both agents. In addition, NaIO₃-induced cytosolic ROS production, possibly from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation and counteracting cell death, was not altered by A769662 and metformin. Notably, NaIO₃-induced mitochondrial fission and inhibition of mitochondrial respiration for ATP turnover were reversed by A769662 but not by metformin. In agreement with the changes on mitochondrial morphology, the ERK-Akt signal axis dependent Drp-1 phosphorylation at S616 (an index of mitochondrial fission) under NaIO₃ treatment was blocked by A769662, but not by metformin. In summary, NaIO₃-induced cell death in ARPE cells primarily comes from mitochondrial dysfunction due to dramatic fission and inhibition of mitochondrial respiration. AMPK activation can exert a protection by restoring mitochondrial respiration and inhibition of ERK/Akt/Drp-1 phosphorylation, leading to a reduction in mitochondrial fission. However, inhibition of respiratory complex I by metformin might deteriorate mitochondrial dysfunction and cell death under NaIO₃ stress.

Glycyrrhizin: An alternative drug for the treatment of COVID-19 infection and the associated respiratory syndrome?

Safe and efficient drugs to combat the current COVID-19 pandemic are urgently needed. In this context, we have analyzed the anti-coronavirus potential of the natural product glycyrrhizic acid (GLR), a drug used to treat liver diseases (including viral hepatitis) and specific cutaneous inflammation (such as atopic dermatitis) in some countries. The properties of GLR and its primary active metabolite glycyrrhetinic acid are presented and discussed. GLR has shown activities against different viruses, including SARS-associated Human and animal coronaviruses. GLR is a non-hemolytic saponin and a potent immuno-active anti-inflammatory agent which displays both cytoplasmic and membrane effects. At the membrane level, GLR induces cholesterol-dependent disorganization of lipid rafts which are important for the entry of coronavirus into cells. At the intracellular and circulating levels, GLR can trap the high mobility group box 1 protein and thus blocks the alarmin functions of HMGB1. We used molecular docking to characterize further and discuss both the cholesterol- and HMG box-binding functions of GLR. The membrane and cytoplasmic effects of GLR, coupled with its long-established medical use as a relatively safe drug, make GLR a good candidate to be tested against the SARS-CoV-2 coronavirus, alone and in combination with other drugs. The rational supporting combinations with (hydroxy)chloroquine and tenofovir (two drugs active against SARS-CoV-2) is also discussed. Based on this analysis, we conclude that GLR should be further considered and rapidly evaluated for the treatment of patients with COVID-19.

Potential Protective and Therapeutic Roles of the Nrf2 Pathway in Ocular Diseases: An Update

Nuclear factor- (erythroid-derived 2-) like 2 (Nrf2) is a regulator of many processes of life, and it plays an important role in antioxidant, anti-inflammatory, and antifibrotic responses and in cancer. This review is focused on the potential mechanism of Nrf2 in the occurrence and development of ocular diseases. Also, several Nrf2 inducers, including noncoding RNAs and exogenous compounds, which control the expression of Nrf2 through different pathways, are discussed in ocular disease models and ocular cells, protecting them from dysfunctional changes. Therefore, Nrf2 might be a potential target of protecting ocular cells from various stresses and preventing ocular diseases.

Glycyrrhizin protects against sodium iodate-induced RPE and retinal injury though activation of AKT and Nrf2/HO-1 pathway

Glycyrrhizin is a bioactive triterpenoid saponin extracted from a traditional Chinese medicinal herb, glycyrrhiza, and has been reported to protect the organs such as liver and heart from injuries. However, there is no report about the effects of glycyrrhizin on atrophic age‐related macular degeneration (AMD). This study investigated the effects of glycyrrhizin on retinal pigment epithelium (RPE) in vitro and retina of mice in vivo treated with sodium iodate (SI). Glycyrrhizin significantly inhibited SI‐induced reactive oxygen species (ROS), and decreased apoptosis of RPE in vitro. The underlying mechanisms included increased phosphorylation of Akt, and increased expression of nuclear factor erythroid 2‐related factor2 (Nrf‐2) and HO‐1, thereby protecting RPE from SI‐induced ROS and apoptosis. Furthermore, glycyrrhizin significantly decreased the apoptosis of retinal cells in vivo, resulting in the inhibition of thinning of retina, decreasing the number of drusen and improving the function of retina. These findings suggested that glycyrrhizin may be a potential candidate for the treatment of atrophic AMD in clinical practice.