Estrogen prevents high-glucose-induced damage of retinal ganglion cells via mitochondrial pathway

Sex differences in the development of experimental diabetic retinopathy

This study aimed to characterize the role of female sex in the pathogenesis of diabetic retinopathy. In the retinae of female Ins2Akita-diabetic mice (F-IA), ovariectomized female Ins2Akita-diabetic mice (F-IA/OVX), male Ins2Akita-diabetic mice (M-IA), and female STZ-diabetic mice (F-STZ), the formation of reactive metabolites and post-translational modifications, damage to the neurovascular unit, and expression of cellular stress response genes were analyzed. Compared to the male diabetic retina, the concentrations of the glycation adduct fructosyl-lysine, the Maillard product 3-deoxyglucosone, and the reactive metabolite methylglyoxal were significantly reduced in females. In females, there was also less evidence of diabetic damage to the neurovascular unit, as shown by decreased pericyte loss and reduced microglial activation. In the male diabetic retina, the expression of several members of the crystallin gene family (Cryab, Cryaa, Crybb2, Crybb1, and Cryba4) was increased. Clinical data from type 1 diabetic females showed that premenopausal women had a significantly lower prevalence of diabetic retinopathy compared to postmenopausal women stratified for disease duration and glycemic control. These data emphasize the importance of estradiol in protecting the diabetic retina and highlight the pathogenic relevance of sex in diabetic retinopathy.

Type 2 Diabetes Mellitus Prevalence and Associated Risk Factors in Postmenopausal Women

Introduction Type 2 diabetes mellitus (T2DM) is the most common problem in postmenopausal women. This study aimed to find out the prevalence of T2DM and its risk factors in postmenopausal women. Methods The study is a population-based cross-sectional study. Anthropometric measurements, blood pressure, and biochemical measurements of 2295 postmenopausal women up to the age of 55 years were taken following face-to-face interviews. Odds ratio was used to find out the role of risk factors associated with T2DM. Results Prevalence of T2DM was reported to be 15.51%. Significant contribution of waist circumference (WC) followed by body mass index (BMI), total cholesterol (TC), and triglycerides (p<0.05) was noted in increasing the risk of T2DM. No association was found between T2DM and hypertension (p>0.05). Conclusion A high prevalence of T2DM was reported in postmenopausal women. Higher levels of BMI, WC, TC, and triglycerides were found to be the major risk factors for T2DM.

Insights into the liver-eyes connections, from epidemiological, mechanical studies to clinical translation

Maintenance of internal homeostasis is a sophisticated process, during which almost all organs get involved. Liver plays a central role in metabolism and involves in endocrine, immunity, detoxification and storage, and therefore it communicates with distant organs through such mechanisms to regulate pathophysiological processes. Dysfunctional liver is often accompanied by pathological phenotypes of distant organs, including the eyes. Many reviews have focused on crosstalk between the liver and gut, the liver and brain, the liver and heart, the liver and kidney, but with no attention paid to the liver and eyes. In this review, we summarized intimate connections between the liver and the eyes from three aspects. Epidemiologically, we suggest liver-related, potential, protective and risk factors for typical eye disease as well as eye indicators connected with liver status. For molecular mechanism aspect, we elaborate their inter-organ crosstalk from metabolism (glucose, lipid, proteins, vitamin, and mineral), detoxification (ammonia and bilirubin), and immunity (complement and inflammation regulation) aspect. In clinical application part, we emphasize the latest advances in utilizing the liver-eye axis in disease diagnosis and therapy, involving artificial intelligence-deep learning-based novel diagnostic tools for detecting liver disease and adeno-associated viral vector-based gene therapy method for curing blinding eye disease. We aim to focus on and provide novel insights into liver and eyes communications and help resolve existed clinically significant issues.

Etiology of Idiopathic Macular Holes in the Light of Estrogen Hormone

The aim of this review was to identify a new potential explanation for the development of macular holes in relation to the female sex and to explain the possible underlying pathways. This approach was based on the evaluation of anatomical, physiological, and morphological analyses currently available in the literature. The findings showed that estrogen exerts a protective effect on the neuroretina and may influence Müller and cone cells. Both cell types are responsible for the building of the fovea structure. However, this protection may be lost due to the sudden decrease in estrogen levels during menopause. In conclusion, the fovea cones, through its sensitivity to estrogen and high energy consumption, may be very vulnerable to damage caused by a sudden changes in the concentration of estrogen in menopausal females. Such changes may result in cone degeneration, and thus a destroyed structure of the fovea, and may lead to the development of a hole in the fovea, as in the case of macular holes. This review revealed that under the decreasing influence of estrogen may cones play a key role with regard to the etiology of the development of macular holes. This aspect may be of strategic importance in prophylactic therapy for the prevention of the development of macular holes in premenopausal females or after ocular trauma.

Relationship Between Estimated Glucose Disposal Rate and Type 2 Diabetic Retinopathy

PURPOSE

To investigate the association between diabetic retinopathy (DR), DR intensity, and estimated glucose disposal rate (eGDR) in individuals with type 2 diabetes mellitus (T2DM).

PATIENTS AND METHODS

This study comprised 1762 T2DM patients who were admitted between January and December, 2021. Overall, the DR was identified in 430 patients. Based on the eGDR, the participants were divided into four study groups. One-way analysis of variance was used to compare the groups. The correlations between eGDR and DR risk, eGDR, and DR severity were analyzed using regression analysis. Furthermore, these relationships were analyzed in different sex groups.

RESULTS

Patients with T2DM had a 19.75% (348/1762) DR detection rate, whereas those with DR had a 22.41% (78/348) proliferative DR detection rate. The DR group had substantially reduced levels of eGDR compared with the non-DR group. Multivariate logistic regression analysis demonstrated that reduced eGDR was an independent risk factor for DR, after adjusting for confounding variables. eGDR correlated significantly with proliferative DR in women but not in men.

CONCLUSION

In Chinese individuals with T2DM, lower eGDR was independently associated with a higher risk of DR.

Research Progress on Mitochondrial Dysfunction in Diabetic Retinopathy

Diabetic Retinopathy (DR) is one of the most important microvascular complications of diabetes mellitus, which can lead to blindness in severe cases. Mitochondria are energy-producing organelles in eukaryotic cells, which participate in metabolism and signal transduction, and regulate cell growth, differentiation, aging, and death. Metabolic changes of retinal cells and epigenetic changes of mitochondria-related genes under high glucose can lead to mitochondrial dysfunction and induce mitochondrial pathway apoptosis. In addition, mitophagy and mitochondrial dynamics also change adaptively. These mechanisms may be related to the occurrence and progression of DR, and also provide valuable clues for the prevention and treatment of DR. This article reviews the mechanism of DR induced by mitochondrial dysfunction, and the prospects for related treatment.

Relationship between renal and liver function with diabetic retinopathy in patients with type 2 diabetes mellitus: a study based on cross-sectional data

This study aims to explore the relationship between abnormal renal- and liver-function and diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (T2DM). A total of 994 T2DM patients who received inpatient treatment in the Endocrinology Department of Henan Province People’s Hospital were included in the study. Logistic regression was performed to identify the relationship between abnormal renal and liver function with DR. Receiver operator characteristic analysis was performed to explore the efficacy of risk factors in predicting DR. Higher urine albumin [OR(95%CI) = 3.344(1.921–5.822), P < 0.001] and urine albumin/creatinine ratio [OR (95%CI) = 2.901(1.911–5.822), P < 0.001] were closely related to the occurrence of DR. People with low TP had a 1.624-times higher risk (95%CI: 1.008–2.617) of developing DR than those with normal total protein (P = 0.046). The more risk factors that are present, the greater the risk of DR. For every one-point incremental increase in the risk-factor score, the risk of DR increased by 31.0% (P < 0.001). The area under receiver operating curve of risk-factor score was 0.839 (0.812, 0.866), with a sensitivity of 81.9% and a specificity of 74.8%. The risk of developing DR increased with an increased risk-factor score. These findings are potentially valuable for DR screening and early diagnosis in patients with T2DM.

Genetic variation reveals the influence of steroid hormones on the risk of retinal neurodegenerative diseases

It is difficult to get evidence from randomized trials of a causal relationship between steroid hormones produced by the adrenal gland and gonad and retinal neurodegenerative disorders (RND). In this study, genetic variations of aldosterone (Aldo), androstenedione (A4), progesterone (P4), hydroxyprogesterone (17-OHP), and testosterone/17β-estradiol (T/E2) were obtained from genome-wide association studies as instrumental variables. Mendelian randomization (MR) analysis was used to assess the impact on the risk of RND, including glaucoma (8,591 cases and 210,201 controls), diabetic retinopathy (DR, 14,584 cases and 202,082 controls) and age-related macular degeneration (AMD, 14,034 cases and 91,214 controls). As the main method, inverse variance weighted results suggest that the increased glaucoma risk was affected by T/E2 (OR = 1.11, 95% CI, 1.01-1.22, P = 0.03), which was further validated by other methods (P_WM = 0.03, P_MLE = 0.03, P_{MR-RAPS =} 0.03). In the replicated stage, the causal relationship between T/E2 and glaucoma was verified based on the MRC-IEU consortium (P = 0.04). No impact of Aldo, A4, P4, 17-OHP, and T/E2 was observed for the risk of DR (P > 0.05) and AMD (P > 0.05). The heterogeneity test (P > 0.05) and pleiotropy test (P > 0.05) verified the robustness of the results. Our results suggest that T/E2 has a suggestive effect on the glaucoma risk. However, the genetic evidence based on a large sample does not support the effect of steroid hormones on DR and AMD risk. Further studies are vital to assess the possibility of steroid hormones as targets for prevention and treatment.

Comparison of Glaucoma-Relevant Transcriptomic Datasets Identifies Novel Drug Targets for Retinal Ganglion Cell Neuroprotection

Glaucoma is a leading cause of blindness and is characterized by the progressive dysfunction and irreversible death of retinal ganglion cells. We aimed to identify shared differentially expressed genes (DE genes) between different glaucoma relevant models of retinal ganglion cell injury using existing RNA-sequencing data, thereby discovering targets for neuroprotective therapies. A comparison of DE genes from publicly available transcriptomic datasets identified 12 shared DE genes. The Comparative Toxicogenomics Database (CTD) was screened for compounds targeting a significant proportion of the identified DE genes. Forty compounds were identified in the CTD that interact with >50% of these shared DE genes. We next validated this approach by testing select compounds for an effect on retinal ganglion cell survival using a mouse retinal explant model. Folic acid, genistein, SB-431542, valproic acid, and WY-14643 (pirinixic acid) were tested. Folic acid, valproic acid, and WY-14643 demonstrated significant protection against retinal ganglion cell death in this model. The increasing prevalence of open access-omics data presents a resource to discover targets for future therapeutic investigation.

Serum progesterone and retinopathy in male patients with type 2 diabetes: A cross-sectional study

AIMS/INTRODUCTION

The aim of this study was to investigate the relationship between serum progesterone (P) and retinopathy in male patients with type 2 diabetes mellitus, and to investigate whether P is associated with its progression.

MATERIALS AND METHODS

A total of 1,376 male participants with type 2 diabetes mellitus were recruited from Affiliated Hospital of Medical College Qingdao University (Qingdao, China). Through logistic regression analysis after adjusting the potential confounding variation, the odds ratio (OR) and the corresponding 95% confidence interval related to the quartiles of progesterone were obtained.

RESULTS

According to the quartiles of P levels, the prevalence rate of diabetic retinopathy (DR) in the last quartile is obviously greater to other quartiles (52.5-34.9%, 31.9%, 37.5%, P < 0.001). Compared with those in the first quartile, the prevalence of DR for the last quartile had an OR of 1.85 in the non-proliferative diabetic retinopathy group, while the OR was 8.35 in the proliferative diabetic retinopathy group (P < 0.001, unadjusted model). When adjusted for age, body mass index, duration of type 2 diabetes mellitus, glycated hemoglobin, blood pressure and other variables, the ORs for DR in the fourth quartile were 2.13 (95% confidence interval 1.49-3.06) in the non-proliferative diabetic retinopathy group and 8.44 (95% confidence interval 2.69-26.43) in the proliferative diabetic retinopathy group (P < 0.001). The positive association between P and DR risk was independent in adjusted logistic regression.

CONCLUSIONS

High levels of serum progesterone are significantly associated with DR in male hospitalized patients. This could mean that a higher P level in men is a potential clinical factor to identify DR, and the causality remains to be further explored.

Antioxidants for the Treatment of Retinal Disease: Summary of Recent Evidence

Retinal tissue is prone to oxidant burden and oxidative stress secondary to the generation of reactive oxygen species from high metabolic demand. The formation of reactive oxygen species occurs primarily from the mitochondrial respiratory chain as well as several enzymatic and oxidation reactions that occur in the neurosensory retina and retinal pigment epithelium. This oxidative stress has been implicated in the pathogenesis of several retinal diseases and the role of antioxidants as a therapeutic treatment shows promise in slowing the progression of certain diseases. The aim of this narrative review is to describe the mechanisms of retinal oxidative stress and summarize the current available evidence for antioxidants as a treatment for vitreoretinal disorders.

Level of hormones in menopause in relation to diabetic retinopathy among type 2 diabetic women

Hormonal transition among middle-aged women with type 2 diabetes may exert an impact in the development of diabetic retinopathy (DR). In this cross-sectional study, we aimed to assess the levels of estradiol, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in the presence of DR and their relationship with risk factors for DR among pre- and post-menopausal women with type 2 diabetes. Serum levels of estradiol, FSH, and LH were measured using the immunoassay technique. All statistical analysis was performed using SPSS software. From the 255 participants, diabetes duration-matched, 35 premenopausal, and 57 postmenopausal women were selected for analysis. The levels of estradiol, LH, and FSH were found to be similar in participants with and without DR among pre- and post-menopausal women with diabetes. Estradiol level was not found to be related with the risk factors of DR among women with type 2 diabetes. In conclusion, female sex hormone, estradiol is not related to the presence of DR. Further prospective studies are necessary to reveal the mechanistic role of this hormone in the development of DR.

Association of menopause and type 2 diabetes mellitus

OBJECTIVE

Limited information is available on the direct effect of menopause and risk of type 2 diabetes mellitus (T2DM) among women with different metabolic types. We aimed to investigate whether menopause is a direct risk factor for T2DM.

METHODS

In this population-based cross-sectional study, women were recruited from a rural area of China from July to August 2013 and July to August 2014. Multivariate logistic regression analysis yielded adjusted odds ratios (ORs) and 95% CIs. Mediation analysis was performed to examine the contribution of age to menopause status-related T2DM.

RESULTS

We included 8,191 women (median age 56, interquartile range 47-65). The prevalence of T2DM was 13.22%. Risk of T2DM was increased with postmenopause versus premenopause status after adjustment (adjusted OR [aOR] = 1.90, 95% CI = 1.51-2.37), with the strongest association between postmenopause status and T2DM among women with body mass index (BMI) <24.0 kg/m (aOR, 3.25; 95% CI, 1.98-5.32). Risk of T2DM was increased with postmenopause status interacting with BMI, hypertension, triglycerides level, and waist circumference. On mediation analysis, age partially mediated the menopause status-T2DM association (indirect effect: OR = 1.27, 95% CI = 1.13-1.46; direct effect: OR = 1.88, 95% CI = 1.49-2.36).

CONCLUSIONS

The prevalence of T2DM is high among women, and postmenopause status might be a stable and significant risk factor for T2DM; especially, postmenopausal women with normal weight should not be ignored in addressing the risk.

n-3 Fatty Acid and Its Metabolite 18-HEPE Ameliorate Retinal Neuronal Cell Dysfunction by Enhancing Müller BDNF in Diabetic Retinopathy

Diabetic retinopathy (DR) is a widespread vision-threatening disease, and neuroretinal abnormality should be considered as an important problem. Brain-derived neurotrophic factor (BDNF) has recently been considered as a possible treatment to prevent DR-induced neuroretinal damage, but how BDNF is upregulated in DR remains unclear. We found an increase in hydrogen peroxide (H₂O₂) in the vitreous of patients with DR. We confirmed that human retinal endothelial cells secreted H₂O₂ by high glucose, and H₂O₂ reduced cell viability of MIO-M1, Müller glia cell line, PC12D, and the neuronal cell line and lowered BDNF expression in MIO-M1, whereas BDNF administration recovered PC12D cell viability. Streptozocin-induced diabetic rats showed reduced BDNF, which is mainly expressed in the Müller glia cell. Oral intake of eicosapentaenoic acid ethyl ester (EPA-E) ameliorated BDNF reduction and oscillatory potentials (OPs) in electroretinography (ERG) in DR. Mass spectrometry revealed an increase in several EPA metabolites in the eyes of EPA-E-fed rats. In particular, an EPA metabolite, 18-hydroxyeicosapentaenoic acid (18-HEPE), induced BDNF upregulation in Müller glia cells and recovery of OPs in ERG. Our results indicated diabetes-induced oxidative stress attenuates neuroretinal function, but oral EPA-E intake prevents retinal neurodegeneration via BDNF in Müller glia cells by increasing 18-HEPE in the early stages of DR.

Females with Type 2 Diabetes Mellitus Are Prone to Diabetic Retinopathy: A Twelve-Province Cross-Sectional Study in China

AIMS

To investigate the distribution of diabetic retinopathy (DR) by sex in patients with type 2 diabetes mellitus (T2DM) in a twelve-province cross-sectional study in China.

METHODS

Patients with T2DM, whose ages were ≥18 years, were recruited from 76 cities/counties in 12 provinces in mainland China between January 2015 and December 2018. All participants received a standardized interview, eye examinations, and digital fundus photography. The presence and severity of DR were diagnosed and classified by retina specialists according to the DR domestic typing method.

RESULTS

A total of 12,766 participants (5963 males and 6803 females) were eligible for this study. The total prevalence of DR was 30.1%. Females exhibited a significantly higher prevalence of DR than males (31.1% vs. 29.0%, P = 0.011). A multivariate logistic regression analysis confirmed that female sex was an independent predictor for a higher prevalence of DR after adjusting for age, the duration of diabetes, economic status, and the presence of hypertension (OR: 1.096, 95% CI: 1.013-1.186, P = 0.023). Even after stratification by the diabetic duration, age, and economic status, female sex was still independently associated with the presence of DR in patients whose T2DM history was more than 10 years, whose ages were over 60 years, or who were in a relatively intermediate economic area.

CONCLUSION

Females had a higher prevalence of DR than males in T2DM patients with a diabetic history of more than 10 years, ages over 60 years, or a relatively intermediate economic status.

The Role of Endogenous Neuroprotective Mechanisms in the Prevention of Retinal Ganglion Cells Degeneration

Retinal neurons are not able to undergo spontaneous regeneration in response to damage. A variety of stressors, i.e., UV radiation, high temperature, ischemia, allergens, and others, induce reactive oxygen species production, resulting in consecutive alteration of stress-response gene expression and finally can lead to cell apoptosis. Neurons have developed their own endogenous cellular protective systems. Some of them are preventing cell death and others are allowing functional recovery after injury. The high efficiency of these mechanisms is crucial for cell survival. In this review we focus on the contribution of the most recently studied endogenous neuroprotective factors involved in retinal ganglion cell (RGC) survival, among which, neurotrophic factors and their signaling pathways, processes regulating the redox status, and different pathways regulating cell death are the most important. Additionally, we summarize currently ongoing clinical trials for therapies for RGC degeneration and optic neuropathies, including glaucoma. Knowledge of the endogenous cellular protective mechanisms may help in the development of effective therapies and potential novel therapeutic targets in order to achieve progress in the treatment of retinal and optic nerve diseases.

Reactive Oxygen Species-Mediated Damage of Retinal Neurons: Drug Development Targets for Therapies of Chronic Neurodegeneration of the Retina

The significance of oxidative stress in the development of chronic neurodegenerative diseases of the retina has become increasingly apparent in recent years. Reactive oxygen species (ROS) are free radicals produced at low levels as a result of normal cellular metabolism that are ultimately metabolized and detoxified by endogenous and exogenous mechanisms. In the presence of oxidative cellular stress, ROS are produced in excess, resulting in cellular injury and death and ultimately leading to tissue and organ dysfunction. Recent studies have investigated the role of excess ROS in the pathogenesis and development of chronic neurodegenerative diseases of the retina including glaucoma, diabetic retinopathy, and age-related macular degeneration. Findings from these studies are promising insofar as they provide clear rationales for innovative treatment and prevention strategies of these prevalent and disabling diseases where currently therapeutic options are limited. Here, we briefly outline recent developments that have contributed to our understanding of the role of ROS in the pathogenesis of chronic neurodegenerative diseases of the retina. We then examine and analyze the peer-reviewed evidence in support of ROS as targets for therapy development in the area of chronic neurodegeneration of the retina.

High glucose levels impact visual response properties of retinal ganglion cells in C57 mice-An in vitro physiological study

This study investigated visual response properties of retinal ganglion cells (RGCs) under high glucose levels. Extracellular single-unit responses of RGCs from mouse retinas were recorded. And the eyecup was prepared as a flat mount in a recording chamber and superfused with Ames medium. The averaged RF size of the ON RGCs (34.1±2.9, n=14) was significantly smaller than the OFF RGCs under the HG (49.3±0.3, n=12) (P<0.0001) conditions. The same reduction pattern was also observed in the osmotic control group (HM) between ON and OFF RGCs (P<0.0001). The averaged luminance threshold (LT) of ON RGCs increased significantly under HG or HM (HG: P<0.0001; HM: P<0.0002). OFF RGCs exhibited a similar response pattern under the same conditions (HG: P<0.01; HM: P<0.0002). The averaged contrast gain of ON cells was significantly lower than that of OFF cells with the HM treatment (P<0.015, unpaired Student's t test). The averaged contrast gain of ON cells was significantly higher than OFF cells with the HG treatment (P<0.0001). The present results suggest that HG reduced receptive field center size, suppressed luminance threshold, and attenuated contrast gain of RGCs. The impact of HG on ON and OFF RGCs may be mediated via different mechanisms.

The impact of combined oral contraceptives on ocular tissues: a review of ocular effects

The aim of this manuscript is to review the action and adverse effects of combined oral contraceptives (COCs) on ocular tissues. The percentage of unwanted pregnancies and the subsequent abortions make contraception crucial worldwide. Over 100 million women around the world use common contraceptive methods, including intrauterine devices, combined estrogen and progestin oral contraceptives, as well as progestin only preparations (oral contraceptives, implants or injections). COCs are widely used for contraception, but they are also indicated in menorrhagia, endometriosis, acne and hirsutism, fibroid uterus and premenstrual syndrome. However, they have been associated with high rates of cardiovascular events, venous thromboembolic disease, ischemic strokes and breast cancer. The incidence of COCs-related ocular complications is estimated to be 1 in 230 000, including dry eye symptoms, corneal edema, lens opacities and retinal neuro-ophthalmologic or vascular complications. We may infer that the serious ocular complications of COCs can be prevented by eliminating the estrogen dosage and choosing third-generation progestins. In any case, doctors should take into consideration the systemic and ocular history of the patients before selecting any method of contraception.

Crocin protects retinal ganglion cells against H2O2-induced damage through the mitochondrial pathway and activation of NF-κB

Glaucoma is a degenerative nerve disorder that results in irreversible blindness. It has been reported that the apoptosis of retinal ganglion cells (RGCs) is a hallmark of glaucoma. Oxidative stress is one of the major factors that cause apoptosis of RGCs. Crocin has many beneficial effects, including antioxidant and anti-apoptotic actions. However, the mechanism by which crocin protects against oxidative stress‑induced damage to RGCs remains unclear. The present study aimed to investigate the mechanism by which crocin protects RGC-5 cells against H2O2-induced damage. H2O2 was used to establish a model of oxidative stress injury in RGC-5 cells to mimic the development of glaucoma in vitro. Different concentrations (0.1 and 1 µM) of crocin were added to test whether crocin was capable of protecting RGCs from H2O2-induced damage. WST-1, lactic dehydrogenase (LDH) release and Annexin V/FITC assays were then performed. Levels of reactive oxygen species (ROS) were detected using a ROS assay kit, mitochondrial membrane potential (ΔΨm) was analyzed by JC-1 staining, caspase-3 activity was examined using a Caspase-3 assay kit, and the protein levels of Bax, Bcl-1 and cytochrome c were measured using western blot analysis. In addition, the protein level of phosphorylated nuclear factor-κB (p-NF-κB) p65 was also evaluated using western blot analysis. The results showed that crocin protected RGC-5 cells from apoptosis, decreased LDH release and enhanced cell viability. Additional experiments demonstrated that crocin decreased ROS levels, increased ΔΨm, downregulated the protein expression of Bax and cytochrome c, promoted Bcl-2 protein expression and activated NF-κB. Taken together, the findings of this study indicate that crocin prevented H2O2‑induced damage to RGCs through the mitochondrial pathway and activation of NF-κB.

HMGB-1 as a Potential Target for the Treatment of Diabetic Retinopathy

Background

Diabetic retinopathy (DR) is one of the most important complications of diabetes mellitus (DM) and is the leading cause of blindness in diabetic patients. Recent studies showed that as important inflammatory mediators, high mobility group box 1 (HMGB-1) is associated with diabetic peripheral neuropathy and can participate in the occurrence and development of DR. This study explored HMGB-1 as a therapeutic target for DR treatment through observing its role in retinal ganglion cells (GRCs) in a high glucose environment.

Material/Methods

RGCs were randomly divided into 3 groups: the normal control group, the high glucose group, and the siRNA HMGB-1 group. Real-time PCR was used to detect HMGB-1 mRNA expression. ELISA was used to test HMGB-1 protein expression in the supernatant. MTT assay was performed to determine cell proliferation. Real-time PCR and Western blotting were used to analyze TLR4 and NF-κB expression.

Results

HMGB-1 mRNA was up-regulated (P=0.015) and protein secretion increased (P=0.022) in the high glucose environment. RGCs survival decreased (P=0.026), while TLR4 and NF-κB mRNA (P=0.009 and P=0.017, respectively) and protein expression increased significantly (P=0.041 and P=0.024, respectively). SiRNA HMGB-1 transfection obviously inhibited HMGB-1 mRNA expression (P=0.032), reduced HMGB-1 secretion (P=0.012), and decreased TLR4 and NF-κB mRNA (P=0.033 and P=0.024, respectively) and protein expression (P=0.032; P=0.027, respectively). Compared with the high glucose group, the RGCs survival rate increased significantly (P=0.037).

Conclusions

As a therapeutic target, HMGB-1 can inhibit inflammation and promote RGCs survival to delay DR progress through the HMGB-1-TLR4-NF-κB signaling pathway.

Natural compounds and retinal ganglion cell neuroprotection

Glaucoma, the second leading cause of blindness in the world, is a chronic optic neuropathy often associated with increased intraocular pressure and characterized by progressive retinal ganglion cell (RGC) axons degeneration and death leading to typical optic nerve head damage and distinctive visual field defects. Although the pathogenesis of glaucoma is still largely unknown, it is hypothesized that RCGs become damaged through various insults/mechanisms, including ischemia, oxidative stress, excitotoxicity, defective axonal transport, trophic factor withdrawal, and neuroinflammation. In this review, we summarize the potential benefits of several natural compounds for RGCs neuroprotection.