AGEs Promote Oxidative Stress and Induce Apoptosis in Retinal Pigmented Epithelium Cells RAGE-dependently

Abnormal chenodexycholic acid metabolism programming promotes cartilage matrix degradation in male adult offspring rats induced by prenatal caffeine exposure

Epidemiological evidence links osteoarthritis to fetal origins. Our study shows prenatal caffeine exposure (PCE) in rats predisposes adult offspring to osteoarthritis, associated with elevated intrauterine glucocorticoid levels. Previous research indicates that chenodeoxycholic acid (CDCA), a bile acid, can slow osteoarthritis progression when administered intra-articularly. This study explored if disrupted bile acid metabolism in cartilage affects osteoarthritis risk in adult offspring with PCE. Our findings indicate that the expression of MMP3/MMP13 was upregulated, while endogenous CDCA levels were reduced in the cartilage of PCE-exposed offspring. Furthermore, we observed a persistent reduction in H3K27ac levels at the CYP7B1 promoter and its expression in the cartilage of PCE offspring from fetus to adulthood. Moreover, a sub-physiological level of CDCA promoted NF-κB phosphorylation and the expression of MMP3/MMP13 in chondrocytes in vitro. High levels of glucocorticoids reduced H3K27ac levels and CYP7B1 expression in the promoter region of CYP7B1 through the glucocorticoid receptor and histone deacetylase 4, consequently leading to decreased CDCA levels. In summary, our findings suggest that intrauterine low-expression programming of CYP7B1, induced by elevated glucocorticoid levels, reduces local CDCA levels in the cartilage of PCE offspring, ultimately leading to increased matrix degradation and susceptibility to osteoarthritis.

Protective effect of adiponectin on oxidative stress-induced ovarian granulosa cell senescence in geese

Geese are susceptible to oxidative stress during breeding, leading to senescence of granulosa cells (GCs) and reduced egg production. Adiponectin (ADPN) is a cytokine secreted by adipose tissue that functions to regulate metabolism and antioxidants. However, its role in the regulation of goose GCs is unclear. To investigate this, senescence in primary goose GCs was induced by D-gal and assessed via RT‒qPCR, senescence-associated β-galactosidase (SA-β-gal) staining, immunofluorescence, flow cytometry, and transcriptomics. The effect of ADPN on GC senescence was investigated by overexpressing and knocking down ADPN expression. The results showed that ADPN could alleviate oxidative stress and cell cycle arrest in GCs, reduce the expression of the senescence-associated secretory phenotype (SASP)-related genes IL-6 and IL-8, regulate the metabolic capacity of GCs, reduce the accumulation of SA-β-gal, maintain telomere length, and alleviate the senescence of GCs induced by D-gal. The RNA-seq results provided further evidence for the regulatory effect of ADPN on GC senescence. ADPN was shown to attenuate oxidative stress-induced GC senescence through the AGE (Advanced glycation end products)-RAGE (Receptor of advanced glycation end products) and NOD-like receptor pathways. These findings may contribute to the development of improved theoretical references for improving egg-laying performance and prolonging the service life of geese.

Methylglyoxal: A Key Factor for Diabetic Retinopathy and Its Effects on Retinal Damage

Background: Diabetic retinopathy is the most common retinal vascular disease, affecting the retina's blood vessels and causing chronic inflammation, oxidative stress, and, ultimately, vision loss. Diabetes-induced elevated glucose levels increase glycolysis, the main methylglyoxal (MGO) formation pathway. MGO is a highly reactive dicarbonyl and the most rapid glycation compound to form endogenous advanced glycation end products (AGEs). MGO can act both intra- and extracellularly by glycating molecules and activating the receptor for AGEs (RAGE) pathway. Conclusions: This review summarizes the sources of MGO formation and its actions on various cell pathways in retinal cells such as oxidative stress, glycation, autophagy, ER stress, and mitochondrial dysfunction. Finally, the detoxification of MGO by glyoxalases is discussed.

Glycative stress as a cause of macular degeneration

People are living longer and rates of age-related diseases such as age-related macular degeneration (AMD) are accelerating, placing enormous burdens on patients and health care systems. The quality of carbohydrate foods consumed by an individual impacts health. The glycemic index (GI) is a kinetic measure of the rate at which glucose arrives in the blood stream after consuming various carbohydrates. Consuming diets that favor slowly digested carbohydrates releases sugar into the bloodstream gradually after consuming a meal (low glycemic index). This is associated with reduced risk for major age-related diseases including AMD, cardiovascular disease, and diabetes. In comparison, consuming the same amounts of different carbohydrates in higher GI diets, releases glucose into the blood rapidly, causing glycative stress as well as accumulation of advanced glycation end products (AGEs). Such AGEs are cytotoxic by virtue of their forming abnormal proteins and protein aggregates, as well as inhibiting proteolytic and other protective pathways that might otherwise selectively recognize and remove toxic species. Using in vitro and animal models of glycative stress, we observed that consuming higher GI diets perturbs metabolism and the microbiome, resulting in a shift to more lipid-rich metabolomic profiles. Interactions between aging, diet, eye phenotypes and physiology were observed. A large body of laboratory animal and human clinical epidemiologic data indicates that consuming lower GI diets, or lower glycemia diets, is protective against features of early AMD (AMDf) in mice and AMD prevalence or AMD progression in humans. Drugs may be optimized to diminish the ravages of higher glycemic diets. Human trials are indicated to determine if AMD progression can be retarded using lower GI diets. Here we summarized the current knowledge regarding the pathological role of glycative stress in retinal dysfunction and how dietary strategies might diminish retinal disease.

ADPN Regulates Oxidative Stress-Induced Follicular Atresia in Geese by Modulating Granulosa Cell Apoptosis and Autophagy

Geese are susceptible to oxidative stress during reproduction, which can lead to follicular atresia and impact egg production. Follicular atresia is directly triggered by the apoptosis and autophagy of granulosa cells (GCs). Adiponectin (ADPN), which is secreted by adipose tissue, has good antioxidant and anti-apoptotic capacity, but its role in regulating the apoptosis of GCs in geese is unclear. To investigate this, this study examined the levels of oxidative stress, apoptosis, and autophagy in follicular tissues and GCs using RT-qPCR, Western blotting, immunofluorescence, flow cytometry, transcriptomics and other methods. Atretic follicles exhibited high levels of oxidative stress and apoptosis, and autophagic flux was obstructed. Stimulating GCs with H2O2 produced results similar to those of atretic follicles. The effects of ADPN overexpression and knockdown on oxidative stress, apoptosis and autophagy in GCs were investigated. ADPN was found to modulate autophagy and reduced oxidative stress and apoptosis in GCs, in addition to protecting them from H2O2-induced damage. These results may provide a reasonable reference for improving egg-laying performance of geese.

Dendrobium mixture ameliorates hepatic injury induced by insulin resistance in vitro and in vivo through the downregulation of AGE/RAGE/Akt signaling pathway

Dendrobium mixture (DM) is a patented Chinese herbal medicine which has been shown to ameliorate type 2 diabetes mellitus (T2DM) with non-alcoholic fatty liver disease (NAFLD) in vivo and in vitro. We aimed to investigate the underlying mechanism of DM as a therapeutic agent in attenuating liver steatosis in relation to type 2 diabetes mellitus (T2DM). DM (16.2 g/kg/d) was administered to db/db mice for 4 weeks. The db/m mice and db/db mice in the control and model groups were given normal saline. Additionally, DM (11.25 g/kg/d) was administered to Sprague-Dawley (SD) rats, and the serum was collected and used in an experiment involving palmitic acid (PA)-induced human liver HepG2 cells with abnormal lipid and glucose metabolism. In db/db mice, the administration of DM significantly alleviated liver steatosis, including histological damage and cell apoptosis. DM was found to prevent the upregulation of the RAGE and AKT1 proteins in liver tissues. The underlying mechanism of DM was further studied in PA-induced HepG2 cells. Post-DM administration serum from SD rats reduced lipid accumulation and regulated glucose metabolism in HepG2 cells. Consequently, it inhibited RAGE/AKT signaling and restored autophagy activity. The upregulated autophagy was associated with the mTOR-AMPK signaling pathway. Furthermore, post-DM administration serum reduced apoptosis of hepatocytes in PA-induced HepG2 cells. Our study supports the potential use of DM as a therapeutic agent for the treatment of NAFLD in T2DM. The mechanism underlying this therapeutic potential is associated with the downregulation of the AGE/RAGE/Akt signaling pathway.

Exploration of the Potential Mechanisms of Lingqihuangban Granule for Treating Diabetic Retinopathy Based on Network Pharmacology

BACKGROUND

The Lingqihuangban Granule (LQHBG), a remarkable Chinese herbal compound, has been used for decades to treat diabetic retinopathy (DR) in the Department of Ophthalmology, Shanghai General Hospital (National Clinical Research Center for Eye Diseases) with obvious effects. Through the method of network pharmacology, the present study constructed bioactive component-relative targets and protein-protein interaction network of the LQHBG and implemented gene function analysis and pathway enrichment of targets, discussing the mechanisms of traditional Chinese medicine LQHBG in treating DR.

MATERIALS AND METHODS

The bioactive ingredients of LQHBG were screened and obtained using TCMSP and ETCM databases, while the potential targets of bioactive ingredients were predicted by SwissTargetPrediction and ETCM databases. Compared with the disease target databases of TTD, Drugbank, OMIM and DisGeNET, the therapeutic targets of LQHBG for DR were extracted. Based on the DAVID platform, GO annotation and KEGG pathway analyses of key targets were explored, combined with the screening of core pathways on the Omicshare database and pathway annotation on the Reactome database.

RESULTS

A total of 357 bioactive components were screened from LQHBG, involving 86 possible targets of LQHBG treating DR. In the PPI network, INS and ALB were identified as key genes. The effective targets were enriched in multiple signaling pathways, such as PI3K/Akt and MAPK pathways.

CONCLUSION

This study revealed the possible targets and pathways of LQHBG treating DR, reflecting the characteristics of multicomponent, multitarget and multipathway treatment of a Chinese herbal compound, and provided new ideas for further discussion.

Silymarin reduces retinal microvascular damage in streptozotocin-induced diabetic rats

Diabetic retinopathy is a severe microvascular problem in diabetes mellitus. Silymarin is a flavonoid compound, and according to previous studies, it is a bioactive compound with potent antioxidant and anti-inflammatory properties. This investigation aims to peruse the impact of silymarin against diabetic retinopathy in streptozotocin (STZ)-provoked rats. Thirty-two adult male Wistar rats were randomly allocated into the control group, STZ group, STZ + silymarin (50 mg/kg), and STZ + silymarin (100 mg/kg). STZ rats received silymarin every day until 2 months after diabetes induction. The serum and retinal tissues were collected 2 months after silymarin treatment to determine biochemical and molecular analyses. Silymarin markedly lowered the serum glucose concentration in diabetic rats. Silymarin reduced the increased levels of advanced glycosylated end products (AGEs), the receptors for AGEs (RAGE), and reactive oxygen species (ROS) in diabetic rats. Silymarin also attenuated the phosphorylation of p38 MAP kinase and nuclear factor (NF)-κB p65 and diminished diabetes-induced overexpression of inflammatory cytokines, vascular endothelial growth factor (VEGF), adhesion molecules, and extracellular matrix proteins in STZ rats. Our data suggested that silymarin has protective effects against diabetic retinopathy, which might be related to the inhibition of the AGEs/RAGE axis and its antioxidant and anti-inflammatory activities.

Mechanisms of Qing-Gan Li-Shui Formulation in Ameliorating Primary Open Angle Glaucoma: An Analysis Based on Network Pharmacology

Objective

In this study, we investigated the mechanism of Qing-Gan Li-Shui formulation (QGLSF) in treating primary open glaucoma (POAG) by network pharmacology and in vitro experiments.

Methods

The active pharmaceutical ingredients (APIs) of GLQSF (prepared with Prunella vulgaris, Kudzu root, Plantago asiatica, and Lycium barbarum) were obtained from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) and Yet Another Traditional Chinese Medicine database (YATCM). The targets of POAG were screened out with GeneCards, OMIM, PharmGKB, Therapeutic Target Database (TTD), and DrugBank databases. The Venny platform was used to summarize the core targets. Topological analysis was performed using Cytoscape3.8.0. A protein-protein interaction network was plotted by STRING online. The key targets were subjected to GO and KEGG enrichment analyses. Finally, the effects of APIs were verified by a model of chloride hexahydrate (CoCl₂)-induced retinal ganglion cells-5 (RGC-5).

Results

The main APIs were selected as quercetin (Que) by network pharmacology. Nine clusters of QGLSF targets were obtained by the PPI network analysis, including AKT-1, TP53, and JUN. KEGG enrichment analysis showed that these targets were mainly involved in the AGE-RAGE signaling pathway. By in vitro experiments, Que promoted cell proliferation. The secretion of AKT-1, TP53, JUN, AGE, and RAGE in the cell culture supernatant decreased, as shown by ELISA. The mRNA levels of AKT-1, TP53, JUN, and RAGE decreased, as shown by RT-PCR. QGLSF may employ the AGE-RAGE signaling pathway to counter POAG.

Conclusion

This study preliminarily elucidates the efficacy and mechanism of QGLSF in the treatment of POAG.

Common pathways in dementia and diabetic retinopathy: understanding the mechanisms of diabetes-related cognitive decline

Type 2 diabetes (T2D) is associated with multiple comorbidities, including diabetic retinopathy (DR) and cognitive decline, and T2D patients have a significantly higher risk of developing Alzheimer's disease (AD). Both DR and AD are characterized by a number of pathological mechanisms that coalesce around the neurovascular unit, including neuroinflammation and degeneration, vascular degeneration, and glial activation. Chronic hyperglycemia and insulin resistance also play a significant role, leading to activation of pathological mechanisms such as increased oxidative stress and the accumulation of advanced glycation end-products (AGEs). Understanding these common pathways and the degree to which they occur simultaneously in the brain and retina during diabetes will provide avenues to identify T2D patients at risk of cognitive decline.

A Catecholaldehyde Metabolite of Norepinephrine Induces Myofibroblast Activation and Toxicity via the Receptor for Advanced Glycation Endproducts: Mitigating Role of l-Carnosine

Monoamine oxidase (MAO) is rapidly gaining appreciation for its pathophysiologic role in cardiac injury and failure. Oxidative deamination of norepinephrine by MAO generates H2O2 and the catecholaldehyde 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL), the latter of which is a highly potent and reactive electrophile that has been linked to cardiotoxicity. However, many questions remain as to whether catecholaldehydes regulate basic physiological processes in the myocardium and the pathways involved. Here, we examined the role of MAO-derived oxidative metabolites in mediating the activation of cardiac fibroblasts in response to norepinephrine. In neonatal murine cardiac fibroblasts, norepinephrine increased reactive oxygen species (ROS), accumulation of catechol-modified protein adducts, expression and secretion of collagens I/III, and other markers of profibrotic activation including STAT3 phosphorylation. These effects were attenuated with MAO inhibitors, the aldehyde-scavenging dipeptide l-carnosine, and FPS-ZM1, an antagonist for the receptor for advanced glycation endproducts (RAGE). Interestingly, treatment of cardiac fibroblasts with a low dose (1 μM) of DOPEGAL-modified albumin phenocopied many of the effects of norepinephrine and also induced an increase in RAGE expression. Higher doses (>10 μM) of DOPEGAL-modified albumin were determined to be toxic to cardiac fibroblasts in a RAGE-dependent manner, which was mitigated by l-carnosine. Collectively, these findings suggest that norepinephrine may influence extracellular matrix remodeling via an adrenergic-independent redox pathway in cardiac fibroblasts involving the MAO-mediated generation of ROS, catecholaldehydes, and RAGE. Furthermore, since elevations in the catecholaminergic tone and oxidative stress in heart disease are linked with cardiac fibrosis, this study illustrates novel drug targets that could potentially mitigate this serious disorder.

In Vitro Evaluation of the Toxicological Profile and Oxidative Stress of Relevant Diet-Related Advanced Glycation End Products and Related 1,2-Dicarbonyls

During food processing and storage, and in tissues and fluids under physiological conditions, the Maillard reaction occurs. During this reaction, reactive 1,2-dicarbonyl compounds arise as intermediates that undergo further reactions to form advanced glycation end products (AGEs). Diet is the primary source of exogenous AGEs. Endogenously formed AGEs have been proposed as a risk factor in the pathogenesis of diet-related diseases such as diabetes, insulin resistance, cardiovascular diseases, or chronic disease. AGEs may differently contribute to the diet-related exacerbation of oxidative stress, inflammation, and protein modifications. Here, to understand the contribution of each compound, we tested individually, for the first time, the effect of five 1,2-dicarbonyl compounds 3-deoxyglucosone (3-DG), 3-deoxygalactosone (3-DGal), 3,4-dideoxyglucosone-3-ene (3,4-DGE), glyoxal (GO), and methylglyoxal (MGO) and four different glycated amino acids N-ε-(carboxyethyl)lysine (CEL), N-ε-(carboxymethyl)lysine (CML), methylglyoxal-derived hydroimidazolone-1 (MG-H1), and pyrraline (Pyrr) in a cell line of human keratinocytes (HaCaT). We found that most of the glycated amino acids, i.e., CEL, CML, and MG-H1, did not show any cytotoxicity. At the same time, 1,2-dicarbonyl compounds 3-DGal, 3,4-DGE, GO, and MGO increased the production of reactive oxygen species and induced cell death. MGO induced cell death by apoptosis, whereas 3-DGal and 3,4-DGE induced nuclear translocation of the proinflammatory NF-κB transcription pathway, and the activation of the pyroptosis-related NLRP3 inflammasome cascade. Overall, these results demonstrate the higher toxic impact of 1,2-dicarbonyl compounds on mucosal epithelial cells when compared to glycated amino acids and the selective activation of intracellular signaling pathways involved in the crosstalk mechanisms linking oxidative stress to excessive inflammation.

Nerve Growth Factor Protects Retinal Ganglion Cells Related to Inhibiting Endoplasmic Reticulum Stress by Inhibiting IRE1-JNK-CHOP Signaling Pathway

BACKGROUND

Under various physiological conditions, endoplasmic reticulum stress can induce apoptotic cell death, leading to brain and retinal neuronal cell death, but the relations of ER stress-induced apoptosis and the nerve growth factor's therapeutic effect in Glaucoma optic neuropathy still unclear.

METHODS

An endoplasmic reticulum stress model was established in ganglion cells using TG, the endoplasmic reticulum stress inducer. MTT assay and flow cytometry were used to detect the protective effect of NGF on retinal ganglion cells. Western blot was used to detect apoptosis-related proteins Bcl-2, Bad and endoplasmic reticulum stress-related proteins GRP78, IRE1, JNK and CHOP.

RESULTS

MTT assay and flow cytometry showed NGF can protect the apoptosis of ganglion cells. Western blot analysis showed the level of pro-apoptotic protein Bad was decreased and anti-apoptotic protein Bcl-2 was increased after NGF treatment. Endoplasmic reticulum stress-induced proteins GRP78, IRE1, JNK and CHOP are counter- acted by NGF.

CONCLUSION

NGF protects retinal ganglion cells related to inhibiting endoplasmic reticulum stress by inhibiting IRE1-JNK-CHOP signaling pathway.

Glyoxalase System as a Therapeutic Target against Diabetic Retinopathy

Hyperglycemia, a defining characteristic of diabetes, combined with oxidative stress, results in the formation of advanced glycation end products (AGEs). AGEs are toxic compounds that have adverse effects on many tissues including the retina and lens. AGEs promote the formation of reactive oxygen species (ROS), which, in turn, boost the production of AGEs, resulting in positive feedback loops, a vicious cycle that compromises tissue fitness. Oxidative stress and the accumulation of AGEs are etiologically associated with the pathogenesis of multiple diseases including diabetic retinopathy (DR). DR is a devastating microvascular complication of diabetes mellitus and the leading cause of blindness in working-age adults. The onset and development of DR is multifactorial. Lowering AGEs accumulation may represent a potential therapeutic approach to slow this sight-threatening diabetic complication. To set DR in a physiological context, in this review we first describe relations between oxidative stress, formation of AGEs, and aging in several tissues of the eye, each of which is associated with a major age-related eye pathology. We summarize mechanisms of AGEs generation and anti-AGEs detoxifying systems. We specifically feature the potential of the glyoxalase system in the retina in the prevention of AGEs-associated damage linked to DR. We provide a comparative analysis of glyoxalase activity in different tissues from wild-type mice, supporting a major role for the glyoxalase system in the detoxification of AGEs in the retina, and present the manipulation of this system as a therapeutic strategy to prevent the onset of DR.

Exploring the Mechanism of Action Compound-Xueshuantong Capsule in Diabetic Retinopathy Treatment Based on Network Pharmacology

Materials and Methods

The components with oral bioavailability ≥30% and drug similarity ≥0.18 were screened by the Traditional Chinese Medicine System Pharmacology Database and Analysis Platform (TCMSP), and the effective grouping of Compound-Xueshuantong Capsule was obtained. At the same time, the targets of each drug active component in the Compound-Xueshuantong Capsule were obtained by searching the TCMSP. The effective components and targets of the Compound-Xueshuantong Capsule were annotated by the UniProt database, and the disease treatment targets were searched by the GeneCards database. The disease treatment target is intersected with the drug target and the Wayne diagram is drawn by VennDiagram. The active ingredient targets of the intersection and Compound-Xueshuantong Capsule were inputted into Cytoscape 3.7.2 software to construct the active ingredient-target-disease interaction network. The above targets were inputted into the String database for protein-protein interaction network prediction. Finally, by using the DAVID database, GO and KEGG enrichment analysis was carried out to reveal the potential signal pathway of the Compound-Xueshuantong Capsule in diabetic retinopathy treatment.

Results

93 active components of the Compound-Xueshuantong Capsule and 92 targets for treating diabetic retinopathy were screened. The main active components of the Compound-Xueshuantong Capsule in treating diabetic retinopathy were quercetin, luteolin, kaempferol, beta-sitosterol, isorhamnetin, and tanshinone IIa. The effect of the Compound-Xueshuantong Capsule on diabetic retinopathy may be related to IL6, EFGR, CASP3, and VEGFA. In addition, the treatment of diabetic retinopathy mainly involves in the regulation of nuclear receptors and transcription factors in vivo. The target of the Compound-Xueshuantong Capsule in diabetic retinopathy treatment is significantly enriched in the AGE-RAGE signal pathway, TNF signal pathway, HIF-1 signal pathway, and VEGF signal pathway in diabetic complications.

Conclusion

Compound-Xueshuantong Capsule can treat diabetic retinopathy through multitarget, multipathway, and multipathway regulation of the biomolecular network. The potential biological mechanism of the Compound-Xueshuantong Capsule in diabetic retinopathy treatment may be related to the AGE-RAGE signal pathway, TNF signal pathway, HIF-1 signal pathway, and VEGF signal pathway in diabetic complications, but these findings still need to be confirmed by further clinical research.

Redox Signaling and Advanced Glycation Endproducts (AGEs) in Diet-Related Diseases

Diets are currently characterized by elevated sugar intake, mainly due to the increased consumption of processed sweetened foods and drinks during the last 40 years. Diet is the main source of advanced glycation endproducts (AGEs). These are toxic compounds formed during the Maillard reaction, which takes place both in vivo, in tissues and fluids under physiological conditions, favored by sugar intake, and ex vivo during food preparation such as baking, cooking, frying or storage. Protein glycation occurs slowly and continuously through life, driving AGE accumulation in tissues during aging. For this reason, AGEs have been proposed as a risk factor in the pathogenesis of diet-related diseases such as diabetes, insulin resistance, cardiovascular diseases, kidney injury, and age-related and neurodegenerative diseases. AGEs are associated with an increase in oxidative stress since they mediate the production of reactive oxygen species (ROS), increasing the intracellular levels of hydrogen peroxide (H₂O₂), superoxide (O₂⁻), and nitric oxide (NO). The interaction of AGEs with the receptor for AGEs (RAGE) enhances oxidative stress through ROS production by NADPH oxidases inside the mitochondria. This affects mitochondrial function and ultimately influences cell metabolism under various pathological conditions. This short review will summarize all evidence that relates AGEs and ROS production, their relationship with diet-related diseases, as well as the latest research about the use of natural compounds with antioxidant properties to prevent the harmful effects of AGEs on health.

The Preventive Effect of Oxytocin on Retinopathy in Streptozotocin-Induced Diabetic Rats

Objectives:

The aim of this study was to investigate the impact of intravitreal and intraperitoneal use of oxytocin (OT) on retinopathy in streptozotocin-induced diabetic rats.

Materials and Methods:

Twenty-four 6-8-week-old adult male and female Sprague Dawley rats were used in the study. Diabetes was induced in the rats with a single injection of intraperitoneal streptozotocin. Diabetes was verified after 48 hours by measuring blood glucose levels of 260 mg/dl (14.4 mmol/L) or higher in diabetic rats. The rats were divided into 4 groups and treated as follows: intravitreal physiological saline group (0.01 mL saline weekly), intravitreal OT group (10 μU/μL OT weekly), intraperitoneal physiological saline group (1 mL daily), and intraperitoneal OT group (100 IU/kg OT daily). Hamilton syringes fitted with 27-gauge needles were used for intraperitoneal injections while 31-gauge needles were used for intravitreal injection. After 4 weeks of treatment the rats were euthanized to evaluate outer nuclear layer (ONL) thickness, vascular endothelial growth factor (VEGF) immunoexpression, and plasma VEGF levels from blood samples obtained by cardiac puncture.

Results:

Morphometric analysis of retinal cross-sections showed that intravitreal and intraperitoneal OT significantly increased ONL thickness compared to physiological saline-treated groups. Also, OT treatment significantly decreased VEGF protein expression compared with the physiological saline groups. Plasma VEGF level was significantly higher in the physiological saline treatment group compared to the OT treatment group.

Conclusion:

OT reduces diabetic retinopathy progression, particularly when administered intravitreally. To our knowledge, this is the first attempt to investigate the impact of OT on diabetic retinopathy and may provide a new area for further research.

Advanced glycation end products-related modulation of cathepsin L and NF-κB signalling effectors in retinal pigment epithelium lead to augmented response to TNFα

The retinal pigment epithelium (RPE) plays a central role in neuroretinal homoeostasis throughout life. Altered proteolysis and inflammatory processes involving RPE contribute to the pathophysiology of age‐related macular degeneration (AMD), but the link between these remains elusive. We report for the first time the effect of advanced glycation end products (AGE)—known to accumulate on the ageing RPE's underlying Bruch's membrane in situ—on both key lysosomal cathepsins and NF‐κB signalling in RPE. Cathepsin L activity and NF‐κB effector levels decreased significantly following 2‐week AGE exposure. Chemical cathepsin L inhibition also decreased total p65 protein levels, indicating that AGE‐related change of NF‐κB effectors in RPE cells may be modulated by cathepsin L. However, upon TNFα stimulation, AGE‐exposed cells had significantly higher ratio of phospho‐p65(Ser536)/total p65 compared to non‐AGEd controls, with an even higher fold increase than in the presence of cathepsin L inhibition alone. Increased proportion of active p65 indicates an AGE‐related activation of NF‐κB signalling in a higher proportion of cells and/or an enhanced response to TNFα. Thus, NF‐κB signalling modulation in the AGEd environment, partially regulated via cathepsin L, is employed by RPE cells as a protective (para‐inflammatory) mechanism but renders them more responsive to pro‐inflammatory stimuli.

RAGE-dependent mitochondria pathway: a novel target of silibinin against apoptosis of osteoblastic cells induced by advanced glycation end products

Advanced glycation end products (AGEs) can stimulate osteoblast apoptosis and have a critical role in the pathophysiology of diabetic osteoporosis. Mitochondrial abnormalities are closely related to osteoblast dysfunction. However, it remains unclear whether mitochondrial abnormalities are involved in AGE-induced osteoblastic cell apoptosis. Silibinin, a major flavonolignan compound of silimarin, has strong antioxidant and mitochondria-protective properties. In the present study, we explored the possible mitochondrial mechanisms underlying AGE-induced apoptosis of osteoblastic cells and the effect of silibinin on osteoblastic cell apoptosis. We demonstrated that mitochondrial abnormalities largely contributed to AGE-induced apoptosis of osteoblastic cells, as evidenced by enhanced mitochondrial oxidative stress, conspicuous reduction in mitochondrial membrane potential and adenosine triphosphate production, abnormal mitochondrial morphology, and altered mitochondrial dynamics. These AGE-induced mitochondrial abnormalities were mainly mediated by the receptor of AGEs (RAGE). In addition, we found that silibinin directly downregulated the expression of RAGE and modulated RAGE-mediated mitochondrial pathways, thereby preventing AGE-induced apoptosis of osteoblastic cells. This study not only provides a new insight into the mitochondrial mechanisms underlying AGE-induced osteoblastic cell apoptosis, but also lays a foundation for the clinical use of silibinin for the prevention or treatment of diabetic osteoporosis.

Molecular mechanism of the role of carbamyl erythropoietin in treating diabetic retinopathy rats

The aim of the present study was to investigate the therapeutic effects of carbamyl erythropoietin (CEPO) and safflor yellow (SY) in the treatment of rats with diabetic retinopathy (DR) as well as exploring the mechanism of action. Male SD rats were used to establish a diabetes model and streptozotocin-induced retinopathy was also performed in rats. A total of 126 rats with DR were obtained, and model rats were randomly divided into the model (n=42), experimental (n=42) and control (n=42) groups. The rats in the model group were injected with saline, the rats in the experimental group were treated with CEPO, and the rats in the control group were treated with SY. After treatment for 2 weeks, the retinas were harvested for quantitative analysis of the mRNA expression levels of angiogenesis-promoting and -inhibiting molecules, apoptosis-promoting and -inhibiting molecules, and oxidative stress pathway-related factors by Reverse transcription-quantitative PCR (RT-qPCR). No significant differences in expression levels of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), angiopoietin (Ang-1), tissue kallikrein (TKLK) and pigment epithelium-derived factor (PEDF) were observed between the experimental and model groups (P>0.05). The expression levels of apoptosis-promoting molecules Bcl-2 related X protein (Bax) and cysteine aspartate specific protease (caspase-3) mRNA in the retina of the experimental group was significantly lower than those in the control group (P<0.05). The expression levels of Bcl-2 and survivin mRNA were significantly higher in the experimental group than in the control group (P<0.05). The expression levels of the oxidative stress pathway nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H quinone dehydrogenase 1 (NQO1) mRNA were significantly higher in the experimental group than in the control group. Therefore, the therapeutic effects of CEPO in treating DR are better than those of SY. As a result, CEPO may inhibit apoptosis and oxidative stress damage of retinal tissue cells in DR rats without affecting angiogenesis.

Formula derived Maillard reaction products in post-weaning intrauterine growth-restricted piglets induce developmental programming of hepatic oxidative stress independently of microRNA-21 and microRNA-155

We recently reported augmentation of lipid peroxidation products in the liver of intrauterine growth-restricted (IUGR) piglets fed a high load of Maillard reaction products (MRPs) during suckling period. The underlying mechanisms of MRPs effects remain unknown. Here, we studied the long-term impact of MRPs exposure on liver oxidative status of IUGR juvenile pigs. Livers of 54-day-old pigs suckled with formula containing either a high (HHF, n=8) or a low (LHF: n=8) load of MRPs were analyzed for protein carbonylation levels , activities and messenger RNA (mRNA) expression of glutathione (GSH) and main antioxidant regulators of redox homeostasis [Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were measured. In addition, mRNA levels of miRNA-21 and miRNA-155 were measured. The liver of HHF group exhibited a high level of lipid peroxidation with significantly increased expression and activity of SOD. Further in liver of HHF group, CAT activity was decreased as compared with LHF group, though with comparable total protein carbonyl contents, GSH contents, and expression of GPx and microRNAs (miRNA-21 and miRNA-155). Our findings suggest that the potential mechanism of MRPs-mediated oxidative stress programming in liver of IUGR piglets may occur via impairment of antioxidant defenses.

Advanced Glycation End-Products Induce Apoptosis of Vascular Smooth Muscle Cells: A Mechanism for Vascular Calcification

Vascular calcification, especially medial artery calcification, is associated with cardiovascular death in patients with diabetes mellitus and chronic kidney disease (CKD). To determine the underlying mechanism of vascular calcification, we have demonstrated in our previous report that advanced glycation end-products (AGEs) stimulated calcium deposition in vascular smooth muscle cells (VSMCs) through excessive oxidative stress and phenotypic transition into osteoblastic cells. Since AGEs can induce apoptosis, in this study we investigated its role on VSMC apoptosis, focusing mainly on the underlying mechanisms. A rat VSMC line (A7r5) was cultured, and treated with glycolaldehyde-derived AGE-bovine serum albumin (AGE3-BSA). Apoptotic cells were identified by Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. To quantify apoptosis, an enzyme-linked immunosorbent assay (ELISA) for histone-complexed DNA fragments was employed. Real-time PCR was performed to determine the mRNA levels. Treatment of A7r5 cells with AGE3-BSA from 100 µg/mL concentration markedly increased apoptosis, which was suppressed by Nox inhibitors. AGE3-BSA significantly increased the mRNA expression of NAD(P)H oxidase components including Nox4 and p22^phox, and these findings were confirmed by protein levels using immunofluorescence. Dihydroethidisum assay showed that compared with cBSA, AGE3-BSA increased reactive oxygen species level in A7r5 cells. Furthermore, AGE3-induced apoptosis was significantly inhibited by siRNA-mediated knockdown of Nox4 or p22^phox. Double knockdown of Nox4 and p22^phox showed a similar inhibitory effect on apoptosis as single gene silencing. Thus, our results demonstrated that NAD(P)H oxidase-derived oxidative stress are involved in AGEs-induced apoptosis of VSMCs. These findings might be important to understand the pathogenesis of vascular calcification in diabetes and CKD.

Association of genetic variants in the receptor for advanced glycation end products gene with diabetic retinopathy: A meta-analysis

BACKGROUND

Diabetic retinopathy (DR) is a major sight-threatening diabetic complication. Previous studies have examined the association of DR with multiple genetic variants in the receptor for advanced glycation end products (RAGE) gene, with inconsistent results.

OBJECTIVE

To perform a systematic literature search and conduct meta-analyses to examine the association of genetic variants in RAGE with DR.

DATA SOURCES

PubMed, Cochrane Library, Embase, Google Scholar, and HuGE.

STUDY ELIGIBILITY CRITERIA AND PARTICIPANTS

Studies were on human subjects; the studies were case-control ones and included subjects who had DR and those who did not have DR; and the studies provided genotype data for genetic variants in RAGE, separately for subjects who had and did not have DR, or provided odds ratios (ORs) and the 95% confidence intervals (CIs), or provided sufficient data for the calculation of OR and the 95% CI.

STUDY APPRAISAL AND SYNTHESIS METHODS

We used OR as a measure of association, and used random-effects model in all the meta-analyses. Between-study heterogeneity was assessed using I, and publication bias was evaluated using Egger test.

RESULTS

A total of 13 studies met the eligibility criteria and were included in our analyses. We found that Gly82Ser was significantly associated with DR (OR = 2.40, 95% CI: 1.46-3.97; P = 0.001) using a recessive model. -374T/A also showed significant association with DR under a dominant model (OR = 1.21, 95% CI: 1.03-1.43; P = 0.023). We did not find a significant association of DR with other genetic variants in RAGE.

LIMITATIONS

The number of included studies is small for some genetic variants; duration of diabetes varied across studies; most studies were conducted in Asia; and it is not clear whether the observed association can be generalized to other ethnicities; and we could not control for other potential confounding factors.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

We found that Gly82Ser in RAGE showed significant association with DR. More studies with larger sample sizes that control for important risk factors, such as duration of diabetes, are needed to validate our findings.

Implications of the endogenous PPAR-gamma ligand, 15-deoxy-delta-12, 14-prostaglandin J2, in diabetic retinopathy

Diabetic retinopathy, a common secondary complication of diabetes mellitus, involves extensive damage to the retinal microvasculature. Retina, being a susceptible target, is highly prone to hyperglycemia-induced molecular damages. PPAR receptor, chiefly gamma subtype, mediates numerous responses related to glucose metabolism and hence is utilized, through its agonism, for the restoration of normal insulin sensitivity and glucose homeostasis in the body. Although a number of synthetic PPAR-gamma receptor agonists have been developed and are being employed for treatment purposes, the role of its endogenous ligand in the prevention of diabetic retinopathy is poorly acknowledged. Activation of PPAR-gamma receptor, via endogenous agents, provides a natural defensive shield against various hyperglycemia-induced pathological conditions. Although the biological levels of 15d-PGJ2 (an endogenous agonist of PPAR-gamma receptor) are found to be below the concentration required to trigger PPAR-gamma-mediated actions, employment of several advanced methods for the exogenous administration of this ligand might provide a beneficial option. Besides, 15d-PGJ2-induced defense is better than any of the newly developed alternative therapies, such as anti-inflammatory, anti-angiogenic or anti-apoptotic agents, of diabetic retinopathy, since it singularly provides, virtually, a complete protection package against all these pathological eventualities. Therefore, the physiology of this endogenous PPAR-gamma ligand might, possibly, be exploited to a great extent for the development of prophylactic agents, in order to restrict the progression of diabetic retinopathy.