Diabetic Retinopathy: Vascular and Inflammatory Disease

Treatment of diabetic retinopathy with herbs for tonifying kidney and activating blood circulation: A review of pharmacological studies

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic retinopathy (DR) is a prevalent microvascular complication of diabetes. Chinese medicine believes that kidney deficiency and blood stasis are significant pathogenesis of DR. A characteristic therapeutic approach for this pathogenesis is the kidney-tonifying and blood-activating method. By literature retrieval from several databases, we methodically summarized the commonly used kidney-tonifying and blood-activating herbs for treating DR, including Lycii Fructus, Rehmanniane Radix Praeparata, and Corni Fructus with the function of nourishing kidney; Salvia Miltiorrhizae Radix et Rhizoma with the function of enhancing blood circulation; Rehmanniae Radix with the function of nourishing kidney yin; and Astragali Radix with the function of tonifying qi. It has been demonstrated that these Chinese herbs described above, by tonifying the kidney and activating blood circulation, significantly improve the course of DR.

AIM OF THE STUDY

Through literature research, to gain a thorough comprehension of the pathogenesis of DR. Simultaneously, through the traditional application analysis, modern pharmacology research and network pharmacology analysis of kidney-tonifying and blood-activating herbs, to review the effectiveness and advantages of kidney-tonifying and blood-activating herbs in treating DR comprehensively.

MATERIALS AND METHODS

PubMed, the China National Knowledge Infrastructure (CNKI), and Wanfang Data were used to filter the most popular herbs for tonifying kidney and activating blood in the treatment of DR. The search terms were "diabetic retinopathy" and "tonifying kidney and activating blood". Mostly from 2000 to 2023. Network pharmacology was applied to examine the key active components and forecast the mechanisms of kidney-tonifying and blood-activating herbs in the treatment of DR.

RESULTS

Kidney deficiency and blood stasis are the pathogenesis of DR, and the pathogenesis is linked to oxidative stress, inflammation, hypoxia, and hyperglycemia. Scientific data and network pharmacology analysis have demonstrated the benefit of tonifying kidney and activating blood herbs in treating DR through several channels, multiple components, and multiple targets.

CONCLUSIONS

This review first presents useful information for subsequent research into the material foundation and pharmacodynamics of herbs for tonifying kidney and activating blood, and offers fresh insights into the treatment of DR.

Multiplatform tear proteomic profiling reveals novel non-invasive biomarkers for diabetic retinopathy

OBJECTIVES

To investigate a comprehensive proteomic profile of the tear fluid in patients with diabetic retinopathy (DR) and further define non-invasive biomarkers.

METHODS

A cross-sectional, multicentre study that includes 46 patients with DR, 28 patients with diabetes mellitus (DM), and 30 healthy controls (HC). Tear samples were collected with Schirmer strips. As for the discovery set, data-independent acquisition mass spectrometry was used to characterize the tear proteomic profile. Differentially expressed proteins between groups were identified, with gene ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes enrichment analysis further developed. Classifying performance of biomarkers for distinguishing DR from DM was compared by the combination of three machine-learning algorithms. The selected biomarker panel was tested in the validation cohort using parallel reaction monitoring mass spectrometry.

RESULTS

Among 3364 proteins quantified, 235 and 88 differentially expressed proteins were identified for DR when compared to HC and DM, respectively, which were fundamentally related to retina homeostasis, inflammation and immunity, oxidative stress, angiogenesis and coagulation, metabolism, and cellular adhesion processes. The biomarker panel consisting of NAD-dependent protein deacetylase sirtuin-2 (SIR2), amine oxidase [flavin-containing] B (AOFB), and U8 snoRNA-decapping enzyme (NUD16) exhibited the best diagnostic performance in discriminating DR from DM, with AUCs of 0.933 and 0.881 in the discovery and validation set, respectively.

CONCLUSIONS

Tear protein dysregulation is comprehensively revealed to be associated with DR onset. The combination of tear SIR2, AOFB, and NUD16 can be a novel potential approach for non-invasive detection or pre-screening of DR.

CLINICAL TRIAL REGISTRATION

Chinese Clinical Trial Registry Identifier: ChiCTR2100054263. https://www.chictr.org.cn/showproj.html?proj=143177 . Date of registration: 2021/12/12.

Immunomodulatory effects of Kaempferol on microglial and Macrophage cells during the progression of diabetic retinopathy

BACKGROUND

Diabetic retinopathy (DR) stands as a prevalent secondary complication of diabetes, notably Type 1 Diabetes Mellitus (T1D), characterized by immune system involvement potentially impacting the retinal immune response mediated by microglia. Early stages of DR witness blood-retinal barrier permeabilization, facilitating peripheral immune cell interaction with the retinal immune system. Kaempferol (Kae), known for its potent anti-inflammatory activity, presents a promising avenue in DR treatment by targeting the immune mechanisms underlying its onset and progression. Our investigation delves into the molecular intricacies of innate immune cell interaction during DR progression and the attenuation of inflammatory processes pivotal to its pathology.

METHODS

Employing in vitro studies, we exposed HAPI microglial and J774.A1 macrophage cells to pro-inflammatory stimuli in the presence or absence of Kae. Ex vivo and in vivo experiments utilized BB rats, a T1D animal model. Retinal explants from BB rats were cultured with Kae, while intraperitoneal Kae injections were administered to BB rats for 15 days. Quantitative PCR, Western blotting, immunofluorescence, and Spectral Domain - Optical Coherence Tomography (SD-OCT) facilitated survival assessment, cellular signaling analysis, and inflammatory marker determination.

RESULTS

Results demonstrate Kae significantly mitigates inflammatory processes across in vitro, ex vivo, and in vivo DR models, primarily targeting immune cell responses. Kae administration notably inhibits proinflammatory responses during DR progression while promoting an anti-inflammatory milieu, chiefly through microglia-mediated synthesis of Arginase-1 and Hemeoxygenase-1(HO-1). In vivo, Kae administration effectively preserves retinal integrity amid DR progression.

CONCLUSIONS

Our findings elucidate the interplay between retinal and systemic immune cells in DR progression, underscoring a differential treatment response predominantly orchestrated by microglia's anti-inflammatory action. Kae treatment induces a phenotypic and functional shift in immune cells, delaying DR progression, thereby spotlighting microglial cells as a promising therapeutic target in DR management.

Identification of biomarkers associated with ferroptosis in diabetic retinopathy based on WGCNA and machine learning

Objective: Diabetic retinopathy (DR) is a chronic progressive eye disease that affects millions of diabetic patients worldwide, and ferroptosis may contribute to the underlying mechanisms of DR. The main objective of this work is to explore key genes associated with ferroptosis in DR and to determine their feasibility as diagnostic markers. Methods: WGCNA identify the most relevant signature modules in DR. Machine learning methods were used to de-screen the feature genes. ssGSEA calculated the scoring of immune cells in the DR versus control samples and compared the associations with the core genes by Spearman correlation. Results: We identified 2,897 differential genes in DR versus normal samples. WGCNA found tan module to have the highest correlation with DR patients. Finally, 20 intersecting genes were obtained from differential genes, tan module and iron death genes, which were screened by LASSO and SVM-RFE method, and together identified 6 genes as potential diagnostic markers. qPCR verified the expression and ROC curves confirmed the diagnostic accuracy of the 6 genes. In addition, our ssGSEA scoring identified these 6 core genes as closely associated with immune infiltrating cells. Conclusion: In conclusion, we analyzed for the first time the potential link of iron death in the pathogenesis of DR. This has important implications for future studies of iron death-mediated pro-inflammatory immune mechanisms.

The role of inflammation in central serous chorioretinopathy: From mechanisms to therapeutic prospects

Central serous chorioretinopathy (CSC) is a leading cause of permanent vision loss, ranking fourth among macular diseases, trailing only age-related macular degeneration, diabetic retinopathy, and retinal vein obstruction. While mounting evidence implicates inflammation as a pivotal factor in the onset and advancement of CSC, the specific pathophysiological process and molecular mechanisms underlying inflammation remain incompletely understood. A complex network of cytokines, chemokines, and adhesion molecules interplay to trigger inflammatory and pathological cascades, highlighting the need for a comprehensive comprehension of the inflammation-related mechanisms behind CSC progression. In this piece, we examine the existing comprehension of CSC's pathology and pathogenesis. Additionally, we present an overview of the mechanisms underlying the onset and progression of CSC inflammation, followed by a thorough analysis and discussion of the potential of targeted inflammatory intervention for both preventing and treating CSC.

Systemic immune-inflammation index, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio in patients with type 2 diabetes at different stages of diabetic retinopathy

AIM

To investigate systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) levels in patients with type 2 diabetes at different stages of diabetic retinopathy (DR).

METHODS

This retrospective study included 141 patients with type 2 diabetes mellitus (DM): 45 without diabetic retinopathy (NDR), 47 with non-proliferative diabetic retinopathy (NPDR), and 49 with proliferative diabetic retinopathy (PDR). Complete blood counts were obtained, and NLR, PLR, and SII were calculated. The study analysed the ability of inflammatory markers to predict DR using receiver operating characteristic (ROC) curves. The relationships between DR stages and SII, PLR, and NLP were assessed using multivariate logistic regression.

RESULTS

The average NLR, PLR, and SII were higher in the PDR group than in the NPDR group (P=0.011, 0.043, 0.009, respectively); higher in the NPDR group than in the NDR group (P<0.001 for all); and higher in the PDR group than in the NDR group (P<0.001 for all). In the ROC curve analysis, the NLR, PLR, and SII were significant predictors of DR (P<0.001 for all). The highest area under the curve (AUC) was for the PLR (0.929 for PLR, 0.925 for SII, and 0.821 for NLR). Multivariate regression analysis indicated that NLR, PLR, and SII were statistically significantly positive and independent predictors for the DR stages in patients with DM [odds ratio (OR)=1.122, 95% confidence interval (CI): 0.200-2.043, P<0.05; OR=0.038, 95%CI: 0.018-0.058, P<0.05; OR=0.007, 95%CI: 0.001-0.01, P<0.05, respectively).

CONCLUSION

The NLR, PLR, and SII may be used as predictors of DR.

CD200R promotes high glucose-induced oxidative stress and damage in human retinal pigment epithelial cells by activating the mTOR signaling pathway

Diabetic retinopathy (DR) is established as the primary cause of visual impairment and preventable blindness, posing significant social and economic burdens on healthcare systems worldwide. Oxidative stress has been identified as a major contributor to DR, yet the precise role of the transmembrane glycoprotein CD200R in this context remains elusive. We studied human retinal pigment epithelia ARPE-19 cells to investigate the role of CD200R in high-glucose (HG) induced oxidative stress. Under HG conditions, we found a significant increase in CD200R expression in a time-dependent pattern. Conversely, knockdown of CD200R effectively alleviated oxidative stress and restored cell viability in HG-treated ARPE-19 cells, a phenomenon corroborated by the addition of a reactive oxygen species (ROS) scavenger. Exploration of the AKT/mTOR signaling pathway confirmed its mediating role regarding CD200R knockdown suppression of the expression of key proteins induced by HG conditions. Additionally, we found that the inhibition of mTOR signaling with Rapamycin effectively countered HG-induced oxidative stress in ARPE-19 cells, suggesting a promising therapeutic target against oxidative stress in the context of DR. This study establishes the crucial role of CD200R in HG-induced oxidative stress and identifies potential therapeutic avenues for the treatment of DR.

Effects of Diabetes Mellitus on Corneal Immune Cell Activation and the Development of Keratopathy

Diabetes mellitus (DM) is one of the most prevalent diseases globally, and its prevalence is rapidly increasing. Most patients with a long-term history of DM present with some degree of keratopathy (DK). Despite its high incidence, the underlying inflammatory mechanism of DK has not been elucidated yet. For further insights into the underlying immunopathologic processes, we utilized streptozotocin-induced mice to model type 1 DM (T1D) and B6.Cg-Lepob/J mice to model type 2 DM (T2D). We evaluated the animals for the development of clinical manifestations of DK. Four weeks post-induction, the total frequencies of corneal CD45+CD11b+Ly-6G- myeloid cells, with enhanced gene and protein expression levels for the proinflammatory cytokines TNF-α and IL-1β, were higher in both T1D and T2D animals. Additionally, the frequencies of myeloid cells/mm2 in the sub-basal neural plexus (SBNP) were significantly higher in T1D and T2D compared to non-diabetic mice. DK clinical manifestations were observed four weeks post-induction, including significantly lower tear production, corneal sensitivity, and epitheliopathy. Nerve density in the SBNP and intraepithelial terminal endings per 40x field were lower in both models compared to the normal controls. The findings of this study indicate that DM alters the immune quiescent state of the cornea during disease onset, which may be associated with the progressive development of the clinical manifestations of DK.

Dapagliflozin ameliorated retinal vascular permeability in diabetic retinopathy rats by suppressing inflammatory factors

BACKGROUND

Diabetic retinopathy is a common microvascular complication of diabetes and one of the major causes of blindness in the working-age population. Emerging evidence has elucidated that inflammation drives the key mechanism of diabetes-mediated retinal disturbance. As a new therapeutic drug targeting diabetes, whether dapagliflozin could improve vascular permeability from the perspective of anti-inflammatory effect need to be further explored.

METHODS

Type 2 diabetic retinopathy rat model was established and confirmed by fundus fluorescein angiography (FFA). ELISA detected level of plasma inflammatory factors and C-peptide. HE staining, immunohistochemistry and western blot detected histopathology changes of retina, expression of retinal inflammatory factors and tight junction proteins.

RESULTS

Dapagliflozin exhibited hypoglycemic effect comparable to insulin, but did not affect body weight. By inhibiting expression of inflammatory factors (NLRP3, Caspase-1, IL-18, NF-κB) in diabetic retina and plasma, dapagliflozin reduced damage of retinal tight junction proteins and improved retinal vascular permeability. The anti-inflammatory effect of dapagliflozin was superior to insulin.

CONCLUSIONS

Dapagliflozin improved retinal vascular permeability by reducing diabetic retinal and plasma inflammatory factors. The anti-inflammatory mechanism of dapagliflozin is independent of hypoglycemic effect and superior to insulin.

Fetuin-B Overexpression Promotes Inflammation in Diabetic Retinopathy Through Activating Microglia and the NF-κB Signaling Pathway

PURPOSE

To investigate the expression, source, role, and mechanism of Fetuin-B (FETUB) in diabetic retinopathy (DR).

METHODS

ELISA and immunofluorescence were used to analyze the concentration of FETUB in plasma, aqueous fluid, and tissue specimens of patients with DR and healthy controls. Immunofluorescence, q-PCR, and western blotting were used to examine the expression of FETUB in DR mice and cells cultured with different concentrations of glucose. BV2 microglia cell line and DR mice were treated using FETUB recombination protein and FETUB shRNA to explore the function of FETUB in DR by q-PCR, western blotting, and immunofluorescence.

RESULTS

FETUB concentrations in plasma, aqueous fluid, and tissue specimens were significantly increased in DR patients. The mice in DR group had a higher concentration of FETUB in the retina and liver tissues than those in the control group, and the expression of FETUB was increased in both ARPE19 and BV2 cells under a high-glucose environment. The ratio of p-P65 (Phospho-P65)/P65 and the expression levels of TNF-α, VEGF, and ionized calcium binding adaptor molecule (IBA)-1 were increased in BV2 cells cultured with FETUB recombinant protein, while they were decreased in BV2 cells transfected with FETUB shRNA. Immunofluorescence staining showed that there were more IBA-1+ activated microglia in the retinas of the FETUB recombination protein group than in the retinas of the DR group, and there were fewer IBA-1+ activated microglia in the retinas of the FETUB shRNA group than in the retinas of the DR group.

CONCLUSIONS

FETUB sourced from endocrine, autocrine, and paracrine pathways could promote inflammation in DR by activating the NF-κB pathway and microglia.

Panax notoginseng saponins alleviate diabetic retinopathy by inhibiting retinal inflammation: Association with the NF-κB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic retinopathy (DR) is a neurovascular disease that causes blindness in adults and is the most serious and common complication of diabetes mellitus. Retinal inflammation is an early stage of DR, and it is believed to play a crucial role in the development of DR. Panax notoginseng saponins (PNS) are the major active constituent in the main root of P. notoginseng, and they exhibit various biological activities, including anti-inflammatory, antioxidant, neuroprotective, and immunomodulatory functions. However, the protective effects and underlying mechanisms of PNS against DR remain unclear.

AIM OF THE STUDY

This study aimed to investigate the alleviation effects of PNS on DR and the mechanisms involved. Furthermore, it intended to explore the major components that exert efficacy in vivo.

MATERIALS AND METHODS

Streptozotocin (STZ) was administered intraperitoneally to Sprague Dawley rats, and PNS was administered orally for 1 month after 2 months of STZ injection. The morphological structure of the retina and retinal acellular capillaries were assessed via hematoxylin and eosin (H&E) staining assay. The disruption of the blood-retinal barrier (BRB) was detected through Evans blue dye leakage assay, and retinal leukocyte adhesion was achieved via fluorescein isothiocyanate-coupled concanavalin A lectin labeling assay. Immunofluorescence staining and Western blot assays were conducted to detect the expression of tight junction proteins, adhesion molecules, and the ionized calcium-binding adapter molecule-1 (Iba-1) in the retina. Enzyme-linked immunosorbent assay was performed to detect the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β in serum. In addition, the protein expression levels of nuclear factor (NF)-κB p65, phosphorylated IκB kinase (p-IKK), phosphorylated NF-κB inhibitor (p-IκB), and phosphorylated NF-κB p65 (p-p65) were measured using Western blot assay. The ocular tissue distribution of PNS in normal and diabetic rats was determined through ultra-performance liquid chromatography-tandem mass spectrometry. The in vitro anti-inflammatory effects of PNS, notoginsenoside (NGR1), ginsenoside Rg1, Re, Rb1, and Rd (GRg1, GRe, GRb1, and GRd) were evaluated on human Müller (MIO-M1) cells.

RESULTS

PNS increased the reduction in retinal inner nuclear layer thickness, reduced the increase in retinal acellular capillaries, and attenuated elevated BRB disruption by upregulating the decrease in protein expression of claudin-1 and occludin. Furthermore, PNS significantly abrogated microglial cell activation and reversed the increase in leukocyte adhesion by downregulating the increase in the protein expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. Moreover, PNS reduced the elevated levels of TNF-α, IL-6, and IL-1β in serum and inhibited the increased protein expression of p-IKK, p-IκB, and p-p65, and the nuclear translocation of p65. The tissue distribution results revealed that NGR1, GRg1, GRe, GRb1, and GRd were detected in the ocular tissue, while GRg1 and GRb1 were found at the highest levels compared with the other components. The cellular results showed that PNS, NGR1, GRg1, GRe, GRb1, and GRd suppressed the development of cellular inflammatory responses by inhibiting the activation of the NF-κB signaling pathway in MIO-M1 cells and that their anti-inflammatory effects were comparable.

CONCLUSION

PNS suppressed retinal inflammation by inhibiting the activation of the NF-κB signaling pathway, alleviating DR. GRg1 and GRb1 may be the primary components that exert anti-inflammatory effects in vivo.

Andrographis Paniculata (Burm. F.) Flavonoid Compound and Prevention of Diabetic Retinopathy

Purpose

To explore the effect of the flavonoid compounds of Andrographis paniculata by evaluating the glycemic profile, oxidative process, and inflammatory values in rats with diabetic retinopathy (DR).

Methods

An extract of A. paniculata was macerated with ethanol which yielded flavonoid compounds. Streptozotocin was utilized to induce diabetes mellitus in male Wistar rats. Vucetic's methods were used to evaluate the retinal vessel diameters. Antioxidant parameters and inflammatory cytokines were assessed in retinal tissue.

Results

A funduscopic examination revealed some alterations in the retinal veins. In comparison to the DR group with no treatment, the diameter of the retinal vessels in the DR group that was treated with the flavonoid component of the A. paniculata extract (FAP) at doses of 20 and 40 mg/kg body weight (BW) was significantly smaller (P < 0.05). The DR treatment groups administered with FAP at doses of 20 and 40 mg/kg BW had a greater ability to reduce TNF-alpha and VEGF levels as compared to the DR rats without treatment (P < 0.05), Glutathione, superoxide dismutase (SOD), and catalase levels were increased after receiving FAP at doses of 20 and 40 mg/kg BW (P < 0.05).

Conclusion

Administration of doses of 20 and 40 mg/kg BW of the A. paniculata's flavonoid compoundsimproved DR in rats via retinal vessel diameter reduction, TNF-α and VEGF level reduction, and increasing antioxidants, SOD, catalase, and glutathione.

Recent Updates on Nanocarriers for Drug Delivery in Posterior Segment Diseases with Emphasis on Diabetic Retinopathy

In recent years, various conventional formulations have been used for the treatment and/or management of ocular medical conditions. Diabetic retinopathy, a microvascular disease of the retina, remains the leading cause of visual disability in patients with diabetes. Currently, for treating diabetic retinopathy, only intraocular, intravitreal, periocular injections, and laser photocoagulation are widely used. Frequent administration of these drugs by injections may lead to serious complications, including retinal detachment and endophthalmitis. Although conventional ophthalmic formulations like eye drops, ointments, and suspensions are available globally, these formulations fail to achieve optimum drug therapeutic profile due to immediate nasolacrimal drainage, rapid tearing, and systemic tearing toxicity of the drugs. To achieve better therapeutic outcomes with prolonged release of the therapeutic agents, nano-drug delivery materials have been investigated. These nanocarriers include nanoparticles, solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), dendrimers, nanofibers, in-situ gel, vesicular carriers, niosomes, and mucoadhesive systems, among others. The nanocarriers carry the potential benefits of site-specific delivery and controlled and sustained drug release profile. In the present article, various nanomaterials explored for treating diabetic retinopathy are reviewed.

Association of altered fibrinogen indexes levels as a potential biomarker in determining the possible onset of diabetic retinopathy

Research suggests that fibrinogen was related to diabetic retinopathy (DR). Then, the relationship between functional indices of fibrinogen and detailed staging of DR has not been explored. Type 2 diabetic and healthy control subjects (n = 960) were recruited in a cross-sectional study. Participants with type 2 diabetes mellitus were categorized into five stages according to their fundus lesions, and fibrinogen (Fib) and its functional indices (angle α and k value) were measured. The angle α levels increased in diabetic subjects with retinopathy compared with those without, and it was significantly elevated early in retinopathy. In contrast, the k value levels slightly decreased. Despite observing an increase in angle α levels and a decrease in k value levels during the later stages of retinopathy compared to the earlier stages, there was no statistically significant difference in the later stages. The association of the angle α and k value with DR was independent of the hyperglycaemic state and other potential confounders (OR = 1.672, 95% CI 1.489-1.876, P < 0.01; OR = 0.013, 95% CI 0.004-0.041, P < 0.01). The angle α levels and k value levels were closely correlated with retinopathy (r = 0.593, P < 0.00; r = - 0.646, P < 0.01). The ROC curve indicated that the diagnostic value of angle α and k value were (AUC = 0.897, P < 0.001; AUC = 0.859, P < 0.001). Fibrinogen function indexes, such as angle α and k value, may be valuable for the early diagnosis of DR but do not directly assess the severity of DR.

Tyrosine Kinase Inhibitors and their role in treating neovascular age-related macular degeneration and diabetic macular oedema

The advent of intravitreal anti-VEGF injections has revolutionised the treatment of both neovascular age-related macular degeneration (nAMD or wet AMD) and diabetic macular oedema (DMO). Despite their efficacy, anti-VEGF injections precipitate significant treatment burden for patients, caregivers and healthcare systems due to the high frequency of injections required to sustain treatment benefit. Therefore, there remains an unmet need for lower-burden therapies. Tyrosine kinase inhibitors (TKI) are a novel class of drugs that may have considerable potential in addressing this issue. This review will summarise and discuss the results of various pilot studies and clinical trials exploring the role of TKIs in treatment of nAMD and DMO, highlighting promising candidates and possible challenges in developments.

Subconjunctival therapy by cubic liquid crystalline nanoparticles to deliver Triamcinolone acetonide for the management of diabetic Retinopathy: In vivo evidences

The expression of inflammatory markers and vascular endothelial growth factor (VEGF) was found to be upregulated in various posterior ocular disorders, including diabetic retinopathy (DR). Effective delivery of therapeutic agents to the retina poses a significant challenge in ophthalmic drug delivery due to biological ocular barriers. Triamcinolone acetonide (TA) was selected as the model corticosteroid drug targeting cytokines and VEGF in DR. However, despite TA's low molecular weight and hydrophobicity, which enable it to bypass the conjunctival epithelial barrier, it doesn't efficiently exert its effect at the target site. Nanocarriers have emerged as a solution to enhance drug delivery to the retina and improve bioavailability. This study aimed to compare the effects of Triamcinolone-loaded cubic liquid crystalline nanoparticles (TA-cubic LCNPs) and TA-Suspension in an experimental DR model administered via the subconjunctival (SCJ) route. The results demonstrated that TA-cubic LCNPs enhanced TA periocular delivery efficacy by reducing inflammatory and VEGF markers through the advanced glycation end products (AGE)/protein kinase C pathway. They were identified as promising nano-carriers, exhibiting potential for targeted delivery to the retina.

27‑Gauge vitrectomy vs. 25‑gauge vitrectomy in the management of proliferative diabetic retinopathy with preoperative intravitreal injection of conbercept

Small-gauge vitrectomy has become popular due to its notable advantages, including less trauma, shortened convalescence and improved manoeuvrability. The aim of the present study was to compare the surgical outcomes of 27-gauge (27-G) vitrectomy with those of 25-gauge (25-G) vitrectomy in the management of proliferative diabetic retinopathy (PDR) with preoperative intravitreal injection of conbercept. The data of 48 consecutive patients with PDR (48 eyes) were retrospectively collected. The patients underwent conbercept intravitreal injection and pars plana vitrectomy with a 27-G group (23 eyes) or 25-G group (25 eyes) vitrectomy system. The operating time, suturing rate, endodiathermy rate, postoperative best-corrected visual acuity (BCVA), intraocular pressure (IOP) and complications were recorded. The mean postoperative BCVA at final follow-up was significantly improved compared with that at the baseline in both groups (P<0.001 for both). The differences in the mean BCVA changes between the two groups were not significant (P>0.99), and no differences were observed in the final central foveal thickness (P=0.51) between the two groups. The final IOP remained stable compared with that at the baseline in the 27-G group (P=0.36) and the 25-G group (P=0.05). The suturing rate was significantly decreased in the 27-G group compared with the 25-G group (P=0.04). There were no significant differences between the two groups in terms of the operating time (P=0.18), rate of endodiathermy use (P>0.99), iatrogenic retinal breaks (P=0.42) or postoperative recurrent vitreous haemorrhage (P>0.99). In addition, no case of ocular hypotony was observed in either group. In conclusion, 27-G vitrectomy was as efficient and safe as 25-G vitrectomy in the management of PDR in terms of operating time and complications. With reference to the literature, preoperative conbercept injection appears to assist in decreasing the incidence of intraoperative and postoperative complications.

LncRNA SNHG4 sponges miR-200b to inhibit cell apoptosis in diabetic retinopathy

This study aimed to investigate the role of long non-coding RNA (lncRNA) small nucleolar RNA host gene 4 (SNHG4) in diabetic retinopathy (DR). We found that SNHG4 was downregulated in DR. SNHG4 could directly interact with miR-200b, while overexpression of miR-200b did not affect the expression of SNHG4 in human retinal pigment epithelial cells ARPE-19. In contrast, overexpression of SNHG4 led to the upregulation of oxidation resistance 1 (Oxr1), a target of miR-200b. Cell apoptosis analysis showed that overexpression of miR-200b increased the apoptotic rate of ARPE-19 cells under high glucose treatment. Oxr1 and SNHG4 played opposite roles and reduced the effects of overexpression of miR-200b. In conclusion, SNHG4 may sponge miR-200b to inhibit cell apoptosis in DR by upregulating Oxr1.

Senescent Cells: Dual Implications on the Retinal Vascular System

Cellular senescence, a state of permanent cell cycle arrest in response to endogenous and exogenous stimuli, triggers a series of gradual alterations in structure, metabolism, and function, as well as inflammatory gene expression that nurtures a low-grade proinflammatory milieu in human tissue. A growing body of evidence indicates an accumulation of senescent neurons and blood vessels in response to stress and aging in the retina. Prolonged accumulation of senescent cells and long-term activation of stress signaling responses may lead to multiple chronic diseases, tissue dysfunction, and age-related pathologies by exposing neighboring cells to the heightened pathological senescence-associated secretory phenotype (SASP). However, the ultimate impacts of cellular senescence on the retinal vasculopathies and retinal vascular development remain ill-defined. In this review, we first summarize the molecular players and fundamental mechanisms driving cellular senescence, as well as the beneficial implications of senescent cells in driving vital physiological processes such as embryogenesis, wound healing, and tissue regeneration. Then, the dual implications of senescent cells on the growth, hemostasis, and remodeling of retinal blood vessels are described to document how senescent cells contribute to both retinal vascular development and the severity of proliferative retinopathies. Finally, we discuss the two main senotherapeutic strategies-senolytics and senomorphics-that are being considered to safely interfere with the detrimental effects of cellular senescence.

Pseudophakic macular edema in nondiabetic and diabetic patients without diabetic retinopathy treated with intravitreal dexamethasone implant

BACKGROUND

The purpose of this study was to compare the impact of intravitreal dexamethasone (DEX) implant during a 12-month period in nondiabetic and diabetic patients without diabetic retinopathy (DR) as a treatment for refractory pseudophakic cystoid macular edema (PCME) following prior treatment with topical nepafenac 0.1% and prednisolone 1%.

METHODS

Forty-two consecutive medical records of patients diagnosed with PCME after uneventful cataract surgery were included. The outcomes measured included best corrected visual acuity (BCVA) and central foveal thickness (CFT). Linear regression analysis was statistically applied.

RESULTS

Following topical treatment, nondiabetic and diabetic subjects presented a mean ± SD gain of - 0.11 ± 0.11 and - 0.18 ± 0.11 BCVA logMAR and a CFT reduction of - 43.42 ± 53.66 µm and - 58.76 ± 36.28 µm, respectively. The mean BCVA gain at month 12 subsequent to DEX implantation was - 0.35 ± 0.17 in nondiabetic (p < 0.001) and - 0.55 ± 0.26 in diabetic patients (p < 0.001), with CFT reductions of - 195.71 ± 93.23 µm (p < 0.001) and - 260.81 ± 198.69 µm (p < 0.001), respectively. Patients who responded with better VA after topical treatment presented better visual outcomes at month 12 following DEX implantation (r2 = 0.46; rho = - 0.71, p < 0.01).

CONCLUSION

Nondiabetic and diabetic patients without DR demonstrated similar results after DEX implant after combined topical therapy, suggesting that selected diabetic patients may have a response comparable to that of nondiabetic patients with PCME.

The impact of donor diabetes on corneal transplant immunity

Corneal transplantation is the most common form of solid tissue grafting, with an approximately 80% to 90% success rate. However, success rates may decline when donor tissues are derived from patients with a history of diabetes mellitus (DM). To evaluate the underlying immunopathologic processes that cause graft rejection, we used streptozotocin-induced type 1 DM (DM1) and transgenic Lepob/ob type 2 DM (DM2) diabetic murine models as donors and nondiabetic BALB/c as recipients. DM resulted in an increased frequency of corneal antigen-presenting cells (APCs) with an acquired immunostimulatory phenotype. Following transplantation, recipients that received either type of diabetic graft showed increased APC migration and T helper type 1 alloreactive cells, impaired functional regulatory T cells, and graft survival. Insulin treatment in streptozotocin-induced diabetic mice led to an increased tolerogenic profile of graft APC, lower T helper type 1 sensitization, and a higher frequency of functional regulatory T cells with high suppressive capacity, reflected in increased graft survival. We conclude that both DM1 and DM2 in donors can impact corneal APC functional phenotype, rendering the tissue more immunogenic and thereby increasing the risk of graft failure.

IL-33 regulates Müller cell-mediated retinal inflammation and neurodegeneration in diabetic retinopathy

Diabetic retinopathy (DR) is characterised by dysfunction of the retinal neurovascular unit, leading to visual impairment and blindness. Müller cells are key components of the retinal neurovascular unit and diabetes has a detrimental impact on these glial cells, triggering progressive neurovascular pathology of DR. Amongst many factors expressed by Müller cells, interleukin-33 (IL-33) has an established immunomodulatory role, and we investigated the role of endogenous IL-33 in DR. The expression of IL-33 in Müller cells increased during diabetes. Wild-type and Il33-/- mice developed equivalent levels of hyperglycaemia and weight loss following streptozotocin-induced diabetes. Electroretinogram a- and b-wave amplitudes, neuroretina thickness, and the numbers of cone photoreceptors and ganglion cells were significantly reduced in Il33-/- diabetic mice compared with those in wild-type counterparts. The Il33-/- diabetic retina also exhibited microglial activation, sustained gliosis, and upregulation of pro-inflammatory cytokines and neurotrophins. Primary Müller cells from Il33-/- mice expressed significantly lower levels of neurotransmitter-related genes (Glul and Slc1a3) and neurotrophin genes (Cntf, Lif, Igf1 and Ngf) under high-glucose conditions. Our results suggest that deletion of IL-33 promotes inflammation and neurodegeneration in DR, and that this cytokine is critical for regulation of glutamate metabolism, neurotransmitter recycling and neurotrophin secretion by Müller cells.

The Value of White Cell Inflammatory Biomarkers as Potential Predictors for Diabetic Retinopathy in Type 2 Diabetes Mellitus (T2DM)

The pathogenesis of diabetic retinopathy is still challenging, with recent evidence proving the key role of inflammation in the damage of the retinal neurovascular unit. This study aims to investigate the predictive value of the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte (PLR), lymphocyte-to-monocyte ratio (LMR), and systemic inflammation index (SII) for diabetic retinopathy (DR) and its severity. We performed a retrospective study on 129 T2DM patients, divided into three groups: without retinopathy (NDR), non-proliferative DR (NPDR), and proliferative DR (PDR). NLR, MLR, and SII were significantly higher in the PDR group when compared to NDR and NPDR (3.2 ± 1.6 vs. 2.4 ± 0.9 and 2.4 ± 1.1; p = 0.005; 0.376 ± 0.216 vs. 0.269 ± 0.083 and 0.275 ± 0.111, p = 0.001; 754.4 ± 514.4 vs. 551.5 ± 215.1 and 560.3 ± 248.6, p = 0.013, respectively). PDR was correlated with serum creatinine (OR: 2.551), NLR (OR: 1.645), MPV (OR: 1.41), and duration of diabetes (OR: 1.301). Logistic regression analysis identified three predictive models with very good discrimination power for PDR (AUC ROC of 0.803, 0.809, and 0.830, respectively): combining duration of diabetes with NLR, MLR, and, respectively, PLR, MPV, and serum creatinine. NLR, MPV, SII, and LMR were associated with PDR and could be useful when integrated into comprehensive risk prediction models.

Klotho: A new therapeutic target in diabetic retinopathy?

Klotho (Kl) is considered an antiaging gene, mainly for the inhibition of the insulin-like growth factor-1 signaling. Kl exists as full-length transmembrane, which acts as co-receptor for fibroblast growth factor receptor, and in soluble forms (sKl). The sKl may exert pleiotropic effects on organs and tissues by regulating several pathways involved in the pathogenesis of diseases associated with oxidative and inflammatory state. In diabetic Patients, serum levels of Kl are significantly decreased compared to healthy subjects, and are related to duration of diabetes. In diabetic retinopathy (DR), one of the most common microvascular complications of type 2 diabetes, serum Kl levels are negatively correlated with progression of the disease. A lot of evidences showed that Kl regulates several mechanisms involved in maintaining homeostasis and functions of retinal cells, including phagocytosis, calcium signaling, secretion of vascular endothelial growth factor A (VEGF-A), maintenance of redox status, and melanin biosynthesis. Experimental data have been shown that Kl exerts positive effects on several mechanisms involved in onset and progression of DR. In particular, treatment with Kl: (1) Prevents apoptosis induced by oxidative stress in human retinal endothelial cells and in retinal pigment epithelium (RPE) cells; (2) reduces secretion of VEGF-A by RPE cells; and (3) decreases subretinal fibrosis and preserves autophagic activity. Therefore, Kl may become a novel biomarker and a good candidate for the treatment of DR.

In Vitro Evaluation of Apoptosis, Inflammation, Angiogenesis, and Neuroprotection Gene Expression in Retinal Pigmented Epithelial Cell Treated with Interferon α-2b

Angiogenesis, retinal neuropathy, and inflammation are the main molecular features of diabetic retinopathy (DR) and should be taken into consideration for potential treatment approaches. Retinal pigmented epithelial (RPE) cells play a major role in DR progression. This study evaluated the in vitro effect of interferon (IFN) α-2b on the expression of genes involved in apoptosis, inflammation, neuroprotection, and angiogenesis in RPE cells. RPE cells were cocultured with IFN α-2b at 2 doses (500 and 1,000 IU) and treatment periods (24 and 48 h). The quantitative relative expression of genes (BCL-2, BAX, BDNF, VEGF, and IL-1b) was evaluated in the treated versus control cells through real-time polymerase chain reaction (PCR). The result of this study demonstrated that IFN treatment at 1,000 IU (48 h) led to significant upregulation of BCL-2, BAX, BDNF, and IL-1b; however, the BCL-2/BAX ratio was not statistically altered from 1:1, in any of the treatment patterns. We also showed that VEGF expression was downregulated in RPE cells treated with 500 IU for 24 h. It can be concluded that IFN α-2b was safe (BCL-2/BAX ∼1:1) and enhanced neuroprotection at 1,000 IU (48 h); however-at the same time-IFN α-2b induced inflammation in RPE cells. Moreover, the antiangiogenic effect of IFN α-2b was solely observed in RPE cells treated with 500 IU (24 h). It seems that IFN α-2b in lower doses and short duration exerts antiangiogenic effects and in higher doses and longer duration has neuroprotective and inflammatory effects. Hence, appropriate concentration and duration of treatment, according to the type and stage of the disease, should be considered to achieve success in IFN therapy.

Tocotrienol-rich fraction reduces retinal inflammation and angiogenesis in rats with streptozotocin-induced diabetes

BACKGROUND

Diabetic retinopathy (DR) is the second commonest microvascular complication of diabetes mellitus. It is characterized by chronic inflammation and angiogenesis. Palm oil-derived tocotrienol-rich fraction (TRF), a substance with anti-inflammatory and anti-angiogenic properties, may provide protection against DR development. Therefore, in this study, we investigated the effect of TRF on retinal vascular and morphological changes in diabetic rats. The effects of TRF on the retinal expression of inflammatory and angiogenic markers were also studied in the streptozotocin (STZ)-induced diabetic rats.

METHODS

Male Sprague Dawley rats weighing 200-250 g were grouped into normal rats (N) and diabetic rats. Diabetes was induced by intraperitoneal injection of streptozotocin (55 mg/kg body weight) whereas N similarly received citrate buffer. STZ-injected rats with blood glucose of more than 20 mmol/L were considered diabetic and were divided into vehicle-treated (DV) and TRF-treated (DT) groups. N and DV received vehicle, whereas DT received TRF (100 mg/kg body weight) via oral gavage once daily for 12 weeks. Fundus images were captured at week 0 (baseline), week 6 and week 12 post-STZ induction to estimate vascular diameters. At the end of experimental period, rats were euthanized, and retinal tissues were collected for morphometric analysis and measurement of NFκB, phospho-NFκB (Ser536), HIF-1α using immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA). Retinal inflammatory and angiogenic cytokines expression were measured by ELISA and real-time quantitative PCR.

RESULTS

TRF preserved the retinal layer thickness (GCL, IPL, INL and OR; p < 0.05) and retinal venous diameter (p < 0.001). TRF also lowered the retinal NFκB activation (p < 0.05) as well as expressions of IL-1β, IL-6, TNF-α, IFN-γ, iNOS and MCP-1 (p < 0.05) compared to vehicle-treated diabetic rats. Moreover, TRF also reduced retinal expression of VEGF (p < 0.001), IGF-1 (p < 0.001) and HIF-1α (p < 0.05) compared to vehicle-treated rats with diabetes.

CONCLUSION

Oral TRF provided protection against retinal inflammation and angiogenesis in rats with STZ-induced diabetes by suppressing the expression of the markers of retinal inflammation and angiogenesis.

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

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

Elucidating glial responses to products of diabetes-associated systemic dyshomeostasis

Diabetic retinopathy (DR) is a leading cause of blindness in working age adults. DR has non-proliferative stages, characterized in part by retinal neuroinflammation and ischemia, and proliferative stages, characterized by retinal angiogenesis. Several systemic factors, including poor glycemic control, hypertension, and hyperlipidemia, increase the risk of DR progression to vision-threatening stages. Identification of cellular or molecular targets in early DR events could allow more prompt interventions pre-empting DR progression to vision-threatening stages. Glia mediate homeostasis and repair. They contribute to immune surveillance and defense, cytokine and growth factor production and secretion, ion and neurotransmitter balance, neuroprotection, and, potentially, regeneration. Therefore, it is likely that glia orchestrate events throughout the development and progression of retinopathy. Understanding glial responses to products of diabetes-associated systemic dyshomeostasis may reveal novel insights into the pathophysiology of DR and guide the development of novel therapies for this potentially blinding condition. In this article, first, we review normal glial functions and their putative roles in the development of DR. We then describe glial transcriptome alterations in response to systemic circulating factors that are upregulated in patients with diabetes and diabetes-related comorbidities; namely glucose in hyperglycemia, angiotensin II in hypertension, and the free fatty acid palmitic acid in hyperlipidemia. Finally, we discuss potential benefits and challenges associated with studying glia as targets of DR therapeutic interventions. In vitro stimulation of glia with glucose, angiotensin II and palmitic acid suggests that: 1) astrocytes may be more responsive than other glia to these products of systemic dyshomeostasis; 2) the effects of hyperglycemia on glia are likely to be largely osmotic; 3) fatty acid accumulation may compound DR pathophysiology by promoting predominantly proinflammatory and proangiogenic transcriptional alterations of macro and microglia; and 4) cell-targeted therapies may offer safer and more effective avenues for DR treatment as they may circumvent the complication of pleiotropism in retinal cell responses. Although several molecules previously implicated in DR pathophysiology are validated in this review, some less explored molecules emerge as potential therapeutic targets. Whereas much is known regarding glial cell activation, future studies characterizing the role of glia in DR and how their activation is regulated and sustained (independently or as part of retinal cell networks) may help elucidate mechanisms of DR pathogenesis and identify novel drug targets for this blinding disease.

MicroRNA-21: A critical underestimated molecule in diabetic retinopathy

Diabetes mellitus (DM) has grown in attention in recent years as a result of its debilitating complications and chronic disabilities. Diabetic retinopathy (DR) is a chronic microvascular complication of DM and is considered as the primary reason for blindness in adults. Early diagnosis of diabetes complications along with targeted therapy options are critical in avoiding morbidity and mortality associated with complications of diabetes. miR-21 is an important and widely studied non-coding-RNA (ncRNA) with considerable roles in various pathologic conditions including diabetic complications. miR-21 is one of the most elevated miRNAs in response to hyperglycemia and its role in angiogenesis is a major culprit of a wide range of disorders including DR. The main role of miR-21 in DR pathophysiology is believed to be through regulating angiogenesis in retina. This article aims to outline miR-21 biogenesis and distribution in human body along with discussions about its role in DR pathogenesis and its biomarker value in order to facilitate understanding of the new characteristics of miR-21 in DR management.

JP1, a polypeptide specifically targeting integrin αVβ3, ameliorates choroidal neovascularization and diabetic retinopathy in mice

Anti-vascular endothelial growth factor (VEGF) drugs have revolutionized the treatment of neovascular eye diseases, but responses are incomplete in some patients. Recent evidence shows that integrins are involved in the pathogenesis of neovascular age-related macular degeneration and diabetic retinopathy. JP1, derived from an optimized seven-amino-acid fragment of JWA protein, is a polypeptide specifically targeting integrin αVβ3. In this study we evaluated the efficacy of JP1 on laser-induced choroidal neovascularization (CNV) and retinal vascular leakage. CNV mice received a single intravitreal (IVT) injection of JP1 (10, 20, 40 µg) or ranibizumab (RBZ, 10 µg). We showed that JP1 injection dose-dependently inhibited laser-induced CNV; the effect of RBZ was comparable to that of 20 µg JP1; a combined IVT injection of JP1 (20 μg) and RBZ (5 μg) exerted a synergistic effect on CNV. In the 3rd month after streptozotocin injection, diabetic mice receiving IVT injection of JP1 (40 µg) or RBZ (10 µg) once a week for 4 weeks showed significantly suppressed retinal vascular leakage. In both in vivo and in vitro experiments, JP1 counteracted oxidative stress and inflammation via inhibiting ROS/NF-κB signaling in microglial cells, and angiogenesis via modulating MEK1/2-SP1-integrin αVβ3 and TRIM25-SP1-MMP2 axes in vascular endothelial cells. In addition, intraperitoneal injection of JP1 (1, 5 or 10 mg) once every other day for 3 times also dose-dependently inhibited CNV. After intraperitoneal injection of FITC-labeled JP1 (FITC-JP1) or FITC in laser-induced CNV mice, the fluorescence intensity in the CNV lesion was markedly increased in FITC-JP1 group, compared with that in FITC group, confirming that JP1 could penetrate the blood-retinal barrier to target CNV lesion. We conclude that JP1 can be used to design novel CNV-targeting therapeutic agents that may replace current invasive intraocular injections.

Association between Systemic Factors and Vitreous Fluid Cytokines in Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is a vision-threatening complication of diabetes mellitus (DM). Systemic and intraocular factors are intricately related to PDR, and vitreous fluid (VF) cytokines are representative intraocular biomarkers. However, the associations between systemic factors and VF cytokines and their influence on PDR pathology are unclear. This study aimed to examine the correlation between systemic factors and VF cytokines and analyze their contributions to the pathology of PDR using multivariate analyses. We conducted a retrospective observational study on 26 PDR eyes of 25 patients with type 2 DM, and 30 eyes of 30 patients with idiopathic macular hole or epiretinal membrane as controls. Fifteen systemic and laboratory tests including blood pressure (BP) and body mass index (BMI), and 27 cytokines in VF were analyzed. BP and BMI correlated positively with VF levels of IL-6 and IP-10 in PDR patients, while no significant correlation was found between systemic factors and VF cytokines in controls. MCP-1 and VEGF-A in VF separately clustered with different systemic factors in controls, but these cytokines lost the property similarity with systemic factors and acquired property similarity with each other in PDR. Systemic factors contributed to only 10.4%, whereas VF cytokines contributed to 42.3% out of 52.7% variance of the whole PDR dataset. Our results suggest that intraocular factors play a major role in the pathology of PDR, whereas systemic factors may have limited effects, and that BP and BMI control in PDR could be useful interventions to improve intraocular immune condition.

Neutrophil–lymphocyte ratio as a reliable marker to predict pre-clinical retinopathy among type 2 diabetic patients

Background

Diabetic retinopathy is now recognized as a neurovascular in lieu of a microvascular complication. Visual evoked potentials (VEPs) are greatly valuable in detecting early diabetic retinal functional changes before the occurrence of structural damage. Low-grade inflammation plays a fundamental part in the development and progression of retinopathy in diabetics. Detecting diabetic patients with early retinopathy before the occurrence of clinical symptoms provides a window of opportunity to ensure the best prognosis for these eyes. Neutrophil–lymphocyte ratio (NLR) has recently been introduced as a novel marker of inflammation in various diseases. Indeed, the presence of a cheap, available, and reliable marker of inflammation that is capable to detect pre-clinical diabetic retinopathy (P-DR) is crucial for early intervention to retard the progression of ocular damage. As far as we know no previous studies investigated the role of NLR in the detection of P-DR. The aim of this study was to investigate the quality of prediction of NLR in detecting pre-clinical retinopathy in type 2 diabetic patients.

Results

In this case–control study, VEPs results showed a significant delay in P100 latencies of the patients’ group compared to the control group. According to the VEPs results, the patient group was further subdivided into two: diabetic with VEPs changes (a group with P-DR) and diabetic without VEPs changes. NLR was significantly elevated in patients with P-DR (p < 0.001). NLR cut-off point ≥ 1.97 is able to predict P-DR with 89.29% sensitivity and 84.37% specificity. Linear regression model revealed that NLR is the only independent factor that predicts P-DR. (odds ratio 3.312; 95% confidence interval 1.262–8.696, p = 0.015*.

Conclusions

Visual evoked potentials have an important role to evaluate the visual pathway in diabetics and to diagnose pre-clinical diabetic retinopathy before the occurrence of structural damage. Neutrophil–lymphocyte ratio is a reliable marker for the detection of pre-clinical diabetic retinopathy with good sensitivity (89.29%) and specificity (84.37%). Finding a reliable available laboratory test to predict P-DR could be of help to save diabetic patients from serious ocular complications.

Lactucaxanthin Regulates the Cascade of Retinal Oxidative Stress, Endoplasmic Reticulum Stress and Inflammatory Signaling in Diabetic Rats

PURPOSE

The purpose of this study is to investigate the protective mechanism of lactucaxanthin against retinal angiogenesis in diabetic retinopathy.

METHODS

Streptozotocin-induced diabetic rats were orally gavaged with either lactucaxanthin or lutein (n=12/group) for 8 weeks. Serum and retina collected from euthanized rats were subjected to assess oxidative stress, ER stress and inflammatory response.

RESULTS

Lactucaxanthin administration was found to lower oxidative stress markers (protein carbonylation and lipid peroxidation) by augmenting antioxidant activity expression and ameliorated VEGF-A levels in diabetic group. Likewise, it suppressed the expression of ER stress (ATF4, ATF6, and XBP1), and inflammatory (TNF-α, IL-6, NF-κB, and ICAM-1) markers in diabetic retina. In addition, lactucaxanthin improved glucose tolerance and lipid profile under diabetic condition and suppressed the crosstalk between OS, ER stress, and inflammation.

CONCLUSION

Lactucaxanthin could be used as a promising therapeutic bioactive for treating DR condition, and retinal angiogenesis.

EXPERT OPINION

Limitation of the study includes the sample size and the duration of treatment. Despite these limitations, this study has revealed the potential of lactucaxanthin in treating eye related diabetic complications. To validate the results obtained from this study, clinical study must be performed to understand the relative benefit of lactucaxanthin in DR treatment.

miRNA-124 Prevents Rat Diabetic Retinopathy by Inhibiting the Microglial Inflammatory Response

Diabetic retinopathy (DR) is characterized by vasoregression and glial activation. miRNA-124 (miR-124) reduces retinal microglial activation and alleviates vasoregression in a neurodegenerative rat model. Our aim was to determine whether miR-124 affects vascular and neural damage in the early diabetic retina. Diabetes was induced in 8-week-old Wistar rats by streptozotocin (STZ) injection. At 16 and 20 weeks, the diabetic rats were intravitreally injected with miR-124 mimic, and retinae were analyzed at 24 weeks. Microvascular damage was identified by evaluating pericyte loss and acellular capillary (AC) formation. Müller glial activation was assessed by glial fibrillary acidic protein (GFAP) immunofluorescence staining. Microglial activation was determined by immunofluorescent staining of ionized calcium-binding adaptor molecule 1 (Iba1) in whole mount retinae. The neuroretinal function was assessed by electroretinography. The expression of inflammation-associated genes was evaluated by qRT-PCR. A wound healing assay was performed to quantitate the mobility of microglial cells. The results showed that miR-124 treatment alleviated diabetic vasoregression by reducing AC formation and pericyte loss. miR-124 blunted Müller glial- and microglial activation in diabetic retinae and ameliorated neuroretinal function. The retinal expression of inflammatory factors including Tnf-α, Il-1β, Cd74, Ccl2, Ccl3, Vcam1, Tgf-β1, Arg1, and Il-10 was reduced by miR-124 administration. The elevated mobility of microglia upon high glucose exposure was normalized by miR-124. The expression of the transcription factor PU.1 and lipid raft protein Flot1 was downregulated by miR-124. In rat DR, miR-124 prevents vasoregression and glial activation, improves neuroretinal function, and modulates microglial activation and inflammatory responses.

The Correlation between Waist Circumference and the Pro-Inflammatory Adipokines in Diabetic Retinopathy of Type 2 Diabetes Patients

Central obesity is one of the major risk factors for type 2 diabetes mellitus (DM), and the most common complication of DM is diabetic retinopathy. However, the exact relationship between obesity and DR remains unknown. In this study, we evaluate the effect of obesity on DR by comparing the aqueous humor-derived adipokines. For the analysis, 37 DR patients and 29 non-DR-patients participated. To evaluate the obesity of the patients, body mass index (BMI) and waist circumference (WC) were used. By comparing the concentrations of adipokines obtained from the aqueous humor of the two groups, the relationship between DR and adipokines was analyzed. In addition, by analyzing the correlation between obesity and adipokines in patients, the relationship between central obesity and DR was finally confirmed. The WC was significantly higher in patients than in the non-patient group. The concentrations of all adipokines compared in this study were significantly higher in the DR group than in the non-DM group (p < 0.05). Among them, adiponectin, leptin, TNF-α, Factor D (adipsin), lipocalin-2 (NGAL), Serpin E1 (PAI-1), and CXCL8 (IL-8) were confirmed to have a positive correlation with central obesity (defined as WC). These findings suggest that central obesity is strongly associated with the risk of DR.

Identification of immune associated potential molecular targets in proliferative diabetic retinopathy

BACKGROUND

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes and causes of blindness in developed countries. Our study was designed to identify immune-related genes involved in the progression of proliferative diabetic retinopathy (PDR).

METHODS

The "GSE102485" dataset of neovascular membrane samples (NVMs) from type 1 and 2 diabetes mellitus patients was downloaded from the Gene Expression Omnibus database. Functional enrichment analyses, protein-protein interaction network (PPI) construction, and module analysis of immune pathways in NVMs and controls were conducted via Gene Set Enrichment Analysis and Metascape.

RESULTS

The significantly upregulated hallmark gene sets in DR2 and DR1 groups were involved in five immune pathways. Only CCR4, CXCR6, C3AR1, LPAR1, C5AR1, and P2RY14 were not previously reported in the context of PDR molecular pathophysiology. Except for P2RY14, all of the above were upregulated in retinal samples from experimental diabetes mouse models and human retina microvascular endothelial cells (HRMECs) treated with high glucose (HG) by quantitative Real Time Polymerase Chain Reaction (qRT-PCR).

CONCLUSION

The genes identified herein provide insight into immune-related differential gene expression during DR progression.

Associations between Visual Acuity and Cognitive Decline in Older Adulthood: A 9-Year Longitudinal Study

OBJECTIVE

Emerging evidence suggests low vision may be a modifiable risk factor for cognitive decline. We examined effects of baseline visual acuity (VA) on level of, and change in, cognitive test performance over 9 years.

METHOD

A population-based sample of 1,621 participants (average age 77 years) completed a comprehensive neuropsychological evaluation and VA testing at baseline and reassessed at nine subsequent annual visits. Linear regression modeled the association between baseline VA and concurrent cognitive test performance. Joint modeling of a longitudinal sub-model and a survival sub-model to adjust for attrition were used to examine associations between baseline VA and repeated cognitive test performance over time.

RESULTS

Better baseline VA was associated cross-sectionally with younger age, male sex, greater than high school education, and higher baseline neuropsychological test scores on both vision-dependent (B coefficient range -0.163 to -0.375, p = .006 to <.001) and vision-independent tests (-0.187 to -0.215, p = .003 to .002). In longitudinal modeling, better baseline VA was associated with slower decline in vision-dependent tests (B coefficient range -0.092 to 0.111, p = .005 to <.001) and vision-independent tests (-0.107 to 0.067, p = .007 to <.001).

CONCLUSIONS

Higher VA is associated with higher concurrent cognitive abilities and slower rates of decline over 9 years in both vision-dependent and vision-independent tests of memory, language, and executive functioning. Findings are consistent with emerging literature supporting vision impairment in aging as a potentially modifiable risk factor for cognitive decline. Clinicians should encourage patient utilization of vision assessment and correction with the added aim of protecting cognition.

Protective Effect of Pioglitazone on Retinal Ganglion Cells in an Experimental Mouse Model of Ischemic Optic Neuropathy

The aim was to assess the protective effect of pioglitazone (PGZ) on retinal ganglion cells (RGCs) after anterior ischemic optic neuropathy (AION) in diabetic and non-diabetic mice. Adult C57BL/6 mice with induced diabetes were divided into three groups: group 1: oral PGZ (20 mg/kg) in 0.1% dimethyl sulfoxide (DMSO) for 4 weeks; group 2: oral PGZ (10 mg/kg) in 0.1% DMSO for 4 weeks; and group 3: oral DMSO only for 4 weeks (control group). Two weeks after treatment, AION was induced through photochemical thrombosis. For non-diabetic mice, adult C57BL/6 mice were divided into four groups after AION was induced: group 1: oral DMSO for 4 weeks; group 2: oral PGZ (20 mg/kg) in 0.1% DMSO for 4 weeks; group 3: oral PGZ (20 mg/kg) in 0.1% DMSO + peritoneal injection of GW9662 (one kind of PPAR-γ inhibitor) (1 mg/kg) for 4 weeks; group 4: peritoneal injection of GW9662 (1 mg/kg) for 4 weeks; One week after the induction of AION in diabetic mice, apoptosis in RGCs was much lower in group 1 (8.0 ± 4.9 cells/field) than in group 2 (24.0 ± 11.5 cells/field) and 3 (25.0 ± 7.7 cells/field). Furthermore, microglial cell infiltration in the retina (group 1: 2.0 ± 2.6 cells/field; group 2: 15.6 ± 3.5 cells/field; and group 3: 14.8 ± 7.5 cells/field) and retinal thinning (group 1: 6.7 ± 5.7 μm; group 2: 12.8 ± 6.1 μm; and group 3: 15.8 ± 5.8 μm) were also lower in group 1 than in the other two groups. In non-diabetic mice, preserved Brn3A⁺ cells were significantly greater in group 2 (2382 ± 140 Brn3A+ cells/mm², n = 7) than in group 1 (1920 ± 228 Brn3A+ cells/mm²; p = 0.03, n = 4), group 3 (1938 ± 213 Brn3A+ cells/mm²; p = 0.002, n = 4), and group 4 (2138 ± 126 Brn3A+ cells/mm²; p = 0.03, n = 4), respectively; PGZ confers protection to RGCs from damage caused by ischemic optic neuropathy in diabetic and non-diabetic mice.

The role of inflammation in immune system of diabetic retinopathy: Molecular mechanisms, pathogenetic role and therapeutic implications

Diabetic retinopathy is one of the most common complications of diabetes mellitus and the leading cause of low vision and blindness worldwide. Mounting evidence demonstrates that inflammation is a key mechanism driving diabetes-associated retinal disturbance, yet the pathophysiological process and molecular mechanisms of inflammation underlying diabetic retinopathy are not fully understood. Cytokines, chemokines, and adhesion molecules interact with each other to form a complex molecular network that propagates the inflammatory and pathological cascade of diabetic retinopathy. Therefore, it is important to understand and elucidate inflammation-related mechanisms behind diabetic retinopathy progression. Here, we review the current understanding of the pathology and pathogenesis of inflammation in diabetic retinopathy. In addition, we also summarize the relevant clinical trials to further suggest inflammation-targeted therapeutics for prevention and management of diabetic retinopathy.

Molecular mechanism of VEGF and its role in pathological angiogenesis

Over the last seven decades, a significant scientific contribution took place in the delineation of the implications of vascular endothelial-derived growth factor (VEGF) in the processes of angiogenesis. Under pathological conditions, mainly in response to hypoxia or ischemia, elevated VEGF levels promote vascular damage and the growth of abnormal blood vessels. Indeed, the development of VEGF biology has revolutionized our understanding of its role in pathological conditions. Hence, targeting VEGF or VEGF-mediated molecular pathways could be an excellent therapeutic strategy for managing cancers and intraocular neovascular disorders. Although anti-VEGF therapies, such as monoclonal antibodies and small-molecule tyrosine kinase inhibitors, have limited clinical efficacy, they can still significantly improve the overall survival rate. This thus demands further investigation through the development of alternative strategies in the management of VEGF-mediated pathological angiogenesis. This review article focuses on the recent developments toward the delineation of the functional biology of VEGF and the role of anti-VEGF strategies in the management of tumor and eye pathologies. Moreover, therapeutic angiogenesis, an exciting frontier for the treatment of ischemic disorders, is highlighted in this review, including wound healing.

Deferoxamine/magnesium modified β-tricalcium phosphate promotes the bone regeneration in osteoporotic rats

Recently, Deferoxamine (DFO) and magnesium (Mg) have been identified as critical factors for angiogenesis and bone formation. However, in current research studies, there is a lack of focus on whether DFO plus Mg can affect the regeneration of β-tricalcium phosphate (β-TCP) in osteoporosis and through what biological mechanisms. Therefore, the present work was aimed to preparation and evaluate the effect of Deferoxamine/magnesium modified β-tricalcium phosphate promotes (DFO/Mg-TCP) in ovariectomized rats model and preliminary exploration of possible mechanisms. The MC3T3-E1 cells were co-cultured with the exudate of DFO/Mg-TCP and induced to osteogenesis, and the cell viability, osteogenic activity were observed by Cell Counting Kit-8(CCK-8), Alkaline Phosphatase (ALP) staining, Alizarin Red Staining (RES) and Western Blot. In vitro experiments, CCK-8, ALP and ARS staining results show that the mineralization and osteogenic activity of MC3T3-E1increased significantly after intervention by DFO/Mg-TCP, as well as a higher levels of protein expressions including VEGF, OC, Runx-2 and HIF-1α. In vivo experiment, Micro-CT and Histological analysis evaluation show that DFO/Mg-TCP treatment presented the stronger effect on bone regeneration, bone mineralization and biomaterial degradation, when compared with OVX+Mg-TCP group and OVX+TCP group, as well as a higher VEGF, OC, Runx-2 and HIF-1α gene expression. The present study indicates that treatment with DFO/Mg-TCP was associated with increased regeneration by enhancing the function of osteoblasts in an OVX rat.

The role of the mTOR pathway in diabetic retinopathy

The retina, the part of the eye, translates the light signal into an electric current that can be sent to the brain as visual information. To achieve this, the retina requires fine-tuned vascularization for its energy supply. Diabetic retinopathy (DR) causes alterations in the eye vascularization that reduce the oxygen supply with consequent retinal neurodegeneration. During DR, the mammalian target of rapamycin (mTOR) pathway seems to coordinate retinal neurodegeneration with multiple anabolic and catabolic processes, such as autophagy, oxidative stress, cell death, and the release of pro-inflammatory cytokines, which are closely related to chronic hyperglycemia. This review outlines the normal anatomy of the retina and how hyperglycemia can be involved in the neurodegeneration underlying this disease through over activation or inhibition of the mTOR pathway.

m6A transferase METTL3 regulates endothelial-mesenchymal transition in diabetic retinopathy via lncRNA SNHG7/KHSRP/MKL1 axis

Diabetic retinopathy is one of the microvascular complications in diabetic patients and the leading cause of blindness worldwide. The levels of METTL3, lncRNA SNHG7, KHSRP, MKL1, endothelial and mesenchymal markers were determined by RT-qPCR or western blot assays in vitro and in vivo. H&E staining was used to observe the retinal structure in a mouse model of DR. The expression levels of METTL3 and SNHG7 were significantly downregulated in DR patients, DR mice and high glucose-induced HRMECs cells. Notably, METTL3 installed the m6A modification and enhanced the stability of SNHG7. Besides, METTL3 inhibited HRMECs EndoMT by promoting the expression of SNHG7. Additionally, SNHG7 was found to weaken MKL1 mRNA stability by binding to the RNA-binding protein KHSRP. Furthermore, we verified that METTL3 regulated EndoMT in DR through the SNHG7/MKL1 axis. We conclude that METTL3 regulates endothelial-mesenchymal transition in DR via the SNHG7/KHSRP/MKL1 axis, providing a new target for DR treatment.

Lower hydration status increased diabetic retinopathy among middle-aged adults and older adults: Results from NHANES 2005-2008

Background

Diabetic retinopathy (DR) is a common complication of diabetic patients. Retinal physiological function is affected by hydration status. We aimed to explore the association between hydration status and DR.

Methods

National Health and Nutrition Examination Survey (NHANES) 2005-2008 was used to perform this cross-sectional study. Serum osmolality was used to assess hydration status for all participants and calculated osmolality was evaluated for only older people. DR and its severity were evaluated and graded into mild non-proliferative retinopathy, moderate/severe non-proliferative retinopathy, and proliferative diabetic retinopathy by the Early Treatment for Diabetic Retinopathy Study protocol and NHANES Digital Grading Protocol. Fully adjusted multivariable logistic regression models were used by SAS OnDemand for Academics.

Results

Among the 5,220 United States adults aged 40 or older, compared with the lowest osmolality group, participants with the highest quartile of serum osmolarity had higher odds of DR (OR: 1.371, 95% CI: 1.001-1.876). For participants with DR, the adjusted OR (95 % CI) of moderate/severe non-proliferative retinopathy and proliferative diabetic retinopathy in the higher serum osmolarity group was 2.119 (1.200-3.741) and 7.001 (3.175-15.438), respectively. Furthermore, in older people, higher calculated osmolarity was significantly associated with increased occurrence of DR (OR: 2.039, 95% CI: 1.305-3.186).

Conclusions

Adults with lower hydration status had higher risk of DR, moderate/severe non-proliferative retinopathy, and proliferative diabetic retinopathy. Dehydration in older adults, classified by calculated osmolality, is associated with a higher rate of DR. There was consistent trend in the results between the two methods.

Changes in Tear Proteomic Profile in Ocular Diseases

The search for proteomic biomarkers in ocular disease is one of the most important research directions in recent years. Reliable biomarkers can be an immense adjuvant for both diagnostic and therapeutic approaches. There is no more readily available ocular tissue for proteomic analysis than tear film, which makes an interesting target for the biomarker search. Tear film is a complex fluid consisting of a superficial lipid layer, which covers the aqueous-mucous layer. Its complexity makes it a perfect candidate for all the "omics" approaches. Glaucoma, cataract, age-related macular degeneration, and other diseases are commonly thought to have a multifactorial background. Currently, no reliable non-invasive tests are available that would help physicians with screening and further patient management. The aim of the study is to present modern methods of measuring biomarkers in tears, with particular emphasis on spectrometric methods, and to discuss their diagnostic and therapeutic usefulness.

Reducing Akt2 in retinal pigment epithelial cells causes a compensatory increase in Akt1 and attenuates diabetic retinopathy

The retinal pigment epithelium (RPE) plays an important role in the development of diabetic retinopathy (DR), a leading cause of blindness worldwide. Here we set out to explore the role of Akt2 signaling-integral to both RPE homeostasis and glucose metabolism-to DR. Using human tissue and genetically manipulated mice (including RPE-specific conditional knockout (cKO) and knock-in (KI) mice), we investigate whether Akts in the RPE influences DR in models of diabetic eye disease. We found that Akt1 and Akt2 activities were reciprocally regulated in the RPE of DR donor tissue and diabetic mice. Akt2 cKO attenuated diabetes-induced retinal abnormalities through a compensatory upregulation of phospho-Akt1 leading to an inhibition of vascular injury, inflammatory cytokine release, and infiltration of immune cells mediated by the GSK3β/NF-κB signaling pathway; overexpression of Akt2 has no effect. We propose that targeting Akt1 activity in the RPE may be a novel therapy for treating DR.