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

Functional lipid diversity and novel oxylipin identification for interspecies differentiation and nutritional assessment of commercial seahorse (Hippocampus) using untargeted and targeted lipidomics

Interspecific lipidological variations in seahorse (Hippocampus), as a functional food resource, profoundly influences its bioefficacy. This study employed untargeted and targeted lipidomics to comprehensively analyse and identify previously uncharacterized lipids in four commercial seahorses. A total of 41 lipid subclasses were discerned, encompassing 1114 and 1219 distinct lipid molecular species in positive and negative ion modes, respectively. Significant interspecific differences were observed in fatty acyls, glycerolipids, phospholipids, saccharolipids, sphingolipids, and sterol lipids across various detection modalities. Triacylglycerols and sphingolipids were dominant lipids in four seahorses. Additionally, 58 oxylipins derived from n-3/n-6 polyunsaturated fatty acids were identified and characterized within seahorses for the first time. Notably, the lined seahorse exhibited a remarkable enrichment in docosahexaenoic acid-derived oxylipins, underscoring its potential as valuable sources of functional lipids. Conclusively, these bioactive lipid profiles were proposed as potential biomarkers for distinguishing different seahorse species and substantiating nutritional values based on multivariate statistical analysis.

A Cell Autonomous Free fatty acid receptor 4 - ChemR23 Signaling Cascade Protects Cardiac Myocytes from Ischemic Injury

Acute myocardial infarction (AMI) causes ischemic damage and cardiac remodeling that ultimately progresses into ischemic cardiomyopathy (ICM). Coronary revascularization reduces morbidity and mortality from an MI, however, reperfusion also induces oxidative stress that drives cardiac myocyte (CM) dysfunction and ICM. Oxidative stress in CMs leads to reactive oxygen species (ROS) production and mitochondrial damage. Free fatty acid receptor 4 (Ffar4) is a GPCR for long chain fatty acids (FA) that is expressed in multiple cell types including CMs. We have recently shown that CM-specific overexpression of Ffar4 protects the heart from systolic dysfunction in the context of ischemic injury. Mechanistically, in CMs, Ffar4 increases the levels of 18-hydroxyeicosapentaenoic acid (18-HEPE), an eicosapentaenoic acid (EPA)-derived, cardioprotective oxylipin (oxidatively modified FA). 18-HEPE is the precursor for resolvin E1 (RvE1), a cardioprotective, specialized pro-resolving mediator (SPM) that activates the GPCR ChemR23. We hypothesize Ffar4 in CMs protects the heart from oxidative stress and ischemic injury through activation of a CM-autonomous, Ffar4-ChemR23 cardioprotective signaling pathway. Here, we developed an in vitro hypoxia reoxygenation (H/R) model (3 hours of hypoxia, 17 hours of reoxygenation) in adult CMs as a model for ischemic injury. In adult CMs subjected to H/R, TUG-891, an Ffar4 agonist, attenuated ROS generation and TUG-891, 18-HEPE, and RvE1 protected CMs from H/R-induced cell death. More importantly, we found that the ChemR23 antagonist α-NETA prevented TUG-891 cytoprotection in adult CMs subjected to H/R, demonstrating that ChemR23 is required for Ffar4 cardioprotection. In summary, our data demonstrate co-expression of Ffar4 and ChemR23 in the same CM, that Ffar4, 18-HEPE, and RvE1 attenuate H/R-induced CM death, and that ChemR23 is required for Ffar4 cardioprotection in H/R support a CM-autonomous Ffar4-ChemR23 cardioprotective signaling pathway.

The profile of oxidative stress markers (arachidonic and linoleic acid derivatives) in patients with benign prostatic hyperplasia in relation to metabolic syndrome

So far, it has been proven that benign prostatic hyperplasia (BPH) is strongly associated with inflammation resulting from, i.a. the presence of infectious agent, autoimmune disease, aging process and lipid disorders associated with metabolic syndrome (MetS). We analyzed the association between serum eicosanoides (HETE, HODE, lipoxins, prostaglandin, and leucotrien) in aging man with benign prostatic hyperplasia (BPH) and healthy controls. The study involved 219 men (with BPH, n = 144; healthy controls, n = 75). We assessed the content arachidonic and linoleic acid derivatives in the serum samples of the study participants using liquid chromatography (HPLC). The levels of: RvE1 (p < 0.001); LXA4 5S,6R,15R (p = 0.001); 10S,17R-DiDHA (p < 0.001); MaR1 (p = 0.002); 9S-HODE (p < 0.05); 15S-HETE (p < 0.05); 12S-HETE (p < 0.001); 5-oxoETE (p < 0.05) and 5-HETE (p < 0.001) were significantly higher in patients with BPH than in the control group. PGE2 (p = 0.007), LTB4 (p < 0.001), and 18RS-HEPE (p < 0.001) were significantly higher in control group. We also analyzed the relationship between LXA4 5S,6R,15R serum levels of oxidative stress markers and concomitance of MetS. We noticed a relationship between levels and MetS (F1216 = 6.114965, p = 0.01). Our research results suggest that pro-inflammatory mediators and suppressors of inflammation are involved in the development of BPH, but their exact contribution has yet to be investigated.

Correlation between omega-3 intake and the incidence of diabetic retinopathy based on NHANES from 2005 to 2008

AIMS

To identify correlations between omega-3 intake and incidence of diabetic retinopathy (DR).

METHODS

This was a cross-sectional study using data from participants over age 40 in the National Health and Nutrition Examination Survey (NHANES) 2005-2008. Metrics included participants' intake of omega-3 fatty acids, specifically three types of representative polyunsaturated fatty acids, DR prevalence, and demographic characteristics. Multiple logistic regression models were used to assess the relationship between omega-3 intake and DR.

RESULTS

Of the 1243 participants included in this study, omega-3 intake was lower in patients with DR relative to those without DR. Of the three polyunsaturated fatty acids within the omega-3 fatty acid family that we focused on, participants without DR consumed more docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) than those with DR. In contrast, there was no significant difference in the intake of eicosapentaenoic acid (EPA). Higher omega-3 intake was associated with a decreased risk of DR. In a crude model, the odds ratio (OR) was 0.548 (95% CI 0.315, 0.951; p = 0.033). In the fully adjusted model of omega-3 (model II), the adjusted OR was 0.525 (95% CI 0.306, 0.901; p = 0.021). DPA and DHA were also associated with a decreased risk of DR. In the full adjustment model (model II) of DPA and DHA, the adjusted ORs were 0.0002 (95% CI 0.000, 0.166; p = 0.014) and 0.293 (95% CI 0.105, 0.819; p = 0.020). Subgroup analysis showed that the protective effect of omega-3 against DR was more significant in younger patients (p value = 0.015).

CONCLUSIONS

In this cross-sectional study of the U.S. general population, we found that increased intake of omega-3 and its components, specifically DPA and DHA were negatively associated with DR incidence. This suggests that omega-3 may be a potential protective factor for DR and may help to prevent or delay the onset and progression of DR.

Knockdown of thioredoxin interacting protein in Müller cells attenuates photoreceptor apoptosis in streptozotocin-induced diabetic mouse model

We explored the effect of inhibition of thioredoxin interacting protein (Txnip) on neuroprotection in Müller cells under high glucose. Wild-type (WT) and Txnip knockout (Txnip-/-) mice were used to establish a streptozotocin (STZ)-induced diabetes model and a Müller cells high glucose model. We detected BDNF expression and PI3K/AKT/CREB pathway activation levels in the retina and Müller cells of each group in vivo and in vitro experiments. The Txnip-/- STZ group showed higher expression of BDNF and phosphorylation of PI3K/AKT/CREB in retina, and less retinal photoreceptor apoptosis was observed in Txnip-/- diabetic group than in WT. After using an inhibitor of PI3K signaling pathway, BDNF expression was reduced; In vitro co-cultured with Müller cells in different groups, 661 W cells showed different situations, Txnip-/- Müller cells maximum downregulated Cleaved-caspase 3 expression in 661 W, accompanied by an increase in Bcl-2/Bax ratio. These findings indicate that inhibiting endogenous Txnip in mouse Müller cells can promote their expression and secretion of BDNF, thereby reducing HG induced photoreceptor apoptosis and having important neuroprotective effects on DR. The regulation of BDNF expression by Txnip may be achieved by activating the PI3K/AKT/CREB pathway. This study suggests that regulating Txnip may be a potential target for DR treatment.

Myricanol improves metabolic profiles in dexamethasone induced lipid and protein metabolism disorders in mice

Myricanol (MY) is one of the main active components from bark of Myrica Rubra. It is demonstrated that MY rescues dexamethasone (DEX)-induced muscle dysfunction via activating silent information regulator 1 (SIRT1) and increasing adenosine 5'-monophosphate-activated protein kinase (AMPK) phosphorylation. Since SIRT1 and AMPK are widely involved in the metabolism of nutrients, we speculated that MY may exert beneficial effects on DEX-induced metabolic disorders. This study for the first time applied widely targeted metabolomics to investigate the beneficial effects of MY on glucose, lipids, and protein metabolism in DEX-induced metabolic abnormality in mice. The results showed that MY significantly reversed DEX-induced soleus and gastrocnemius muscle weight loss, muscle fiber damage, and muscle strength loss. MY alleviated DEX-induced metabolic disorders by increasing SIRT1 and glucose transporter type 4 (GLUT4) expressions. Additionally, myricanol prevented muscle cell apoptosis and atrophy by inhibiting caspase 3 cleavages and muscle ring-finger protein-1 (MuRF1) expression. Metabolomics showed that MY treatment reversed the serum content of carnitine ph-C1, palmitoleic acid, PS (16:0_17:0), PC (14:0_20:5), PE (P-18:1_16:1), Cer (t18:2/38:1(2OH)), four amino acids and their metabolites, and 16 glycerolipids in DEX mice. Kyoto encyclopedia of genes and genomes (KEGG) and metabolic set enrichment analysis (MSEA) analysis revealed that MY mainly affected metabolic pathways, glycerolipid metabolism, lipolysis, fat digestion and absorption, lipid and atherosclerosis, and cholesterol metabolism pathways through regulation of metabolites involved in glutathione, butanoate, vitamin B6, glycine, serine and threonine, arachidonic acid, and riboflavin metabolism. Collectively, MY can be used as an attractive therapeutic agent for DEX-induced metabolic abnormalities.

Eurycomanone from Eurycoma longifolia Jack upregulates neurotrophin-3 gene expression in retinal Müller cells in vitro

Photoreceptor degeneration decreases light sensitivity and leads to vision loss and various retinal diseases. Neurotrophin-3, originating from Müller glial cells in the retina, plays a key role in protecting photoreceptors from damage induced by light or hypoxia. This neuroprotective approach is important because there are no established methods to regenerate lost photoreceptors. Dietary supplements are one of the useful methods for improving eye health. Eurycoma longifolia (E. longifolia) Jack, which is native to the tropical forest of Malaysia and other Southeast Asian countries, exhibits several medicinal properties. In the present study, we demonstrated that the water extract of E. longifolia roots enhanced neurotrophin-3 gene expression in primary rat Müller cells. Using a stepwise bioassay-guided fractionation and purification of E. longifolia root extracts, we isolated the active compound underlying neurotrophin-3 gene-enhancing activities. Mass spectrometry and nuclear magnetic resonance spectral data identified the compound as eurycomanone. This study provides evidence for the efficacy of E. longifolia and eurycomanone in enhancing neurotrophin-3 expression in Müller cells in vitro. Although the biological significance of this effect and its underlying mechanism remain to be elucidated, this study suggests that E. longifolia may be promising for improving eye health and must be further investigated.

Ferric particle-assisted LDI-MS platform for metabolic fingerprinting of diabetic retinopathy

OBJECTIVES

To explore the metabolic fingerprints of diabetic retinopathy (DR) in individuals with type 2 diabetes using a newly-developed laser desorption/ionization mass spectrometry (LDI-MS) platform assisted by ferric particles.

METHODS

Metabolic fingerprinting was performed using a ferric particle-assisted LDI-MS platform. A nested population-based case-control study was performed on 216 DR cases and 216 control individuals with type 2 diabetes.

RESULTS

DR cases and control individuals with type 2 diabetes were comparable for a list of clinical factors. The newly-developed LDI-MS platform allowed us to draw the blueprint of plasma metabolic fingerprints from participants with and without DR. The neural network afforded diagnostic performance with an average area under curve value of 0.928 for discovery cohort and 0.905 for validation cohort (95 % confidence interval: 0.902-0.954 and 0.845-0.965, respectively). Tandem MS and Fourier transform ion cyclotron resonance MS with ultrahigh resolution identified seven specific metabolites that were significantly associated with DR in fully adjusted models. Of these metabolites, dihydrobiopterin, phosphoserine, N-arachidonoylglycine, and 3-methylhistamine levels in plasma were first reported to show the associations.

CONCLUSIONS

This work advances the design of metabolic analysis for DR and holds the potential to promise as an efficient tool for clinical management of DR.

Recent advances in the treatment and delivery system of diabetic retinopathy

Diabetic retinopathy (DR) is a highly tissue-specific neurovascular complication of type 1 and type 2 diabetes mellitus and is among the leading causes of blindness worldwide. Pathophysiological changes in DR encompass neurodegeneration, inflammation, and oxidative stress. Current treatments for DR, including anti-vascular endothelial growth factor, steroids, laser photocoagulation, and vitrectomy have limitations and adverse reactions, necessitating the exploration of novel treatment strategies. This review aims to summarize the current pathophysiology, therapeutic approaches, and available drug-delivery methods for treating DR, and discuss their respective development potentials. Recent research indicates the efficacy of novel receptor inhibitors and agonists, such as aldose reductase inhibitors, angiotensin-converting enzyme inhibitors, peroxisome proliferator-activated receptor alpha agonists, and novel drugs in delaying DR. Furthermore, with continuous advancements in nanotechnology, a new form of drug delivery has been developed that can address certain limitations of clinical drug therapy, such as low solubility and poor penetration. This review serves as a theoretical foundation for future research on DR treatment. While highlighting promising therapeutic targets, it underscores the need for continuous exploration to enhance our understanding of DR pathogenesis. The limitations of current treatments and the potential for future advancements emphasize the importance of ongoing research in this field.

Compound Danshen dripping pills prevent early diabetic retinopathy: roles of vascular protection and neuroprotection

Introduction: Diabetic retinopathy (DR) represents a major cause of adult blindness, and early discovery has led to significant increase in the number of patients with DR. The drugs currently used for treatment, such as ranibizumab, mainly focus on the middle and late periods of DR, and thus do not meet the clinical need. Here, the potential mechanisms by which compound Danshen Dripping Pills (CDDP) might protect against early DR were investigated. Methods: Db/db mice were used to establish a DR model. The initial weights and HbA1c levels of the mice were monitored, and retinal pathology was assessed by hematoxylin-eosin (HE) staining. The vascular permeability of the retina and thickness of each retinal layer were measured, and electroretinogram were performed together with fundus fluorescein angiography and optical coherence tomography. The levels of inflammatory factors were examined in retinal tissue, as well as those of intercellular adhesion molecule 1 (ICAM-1), IL-6, and monocyte chemoattractant protein 1 (MCP-1) in the serum using ELISA. Immunohistochemistry was used to evaluate levels of vascular endothelial growth factor (VEGF), B-cell lymphoma 2 (Bcl-2), and Bclassociated X protein (Bax). Retinal cell injury and apoptosis were examined by TdT-mediated dUTP Nick End Labeling (TUNEL) assays. Results: The data showed that CDDP significantly improved cellular disarrangement. Imaging data indicated that CDDP could reduce vascular permeability and the amplitude of oscillatory potentials (OPs), and restore the thickness of the ganglion cell layer. Moreover, CDDP reduced the expression levels of inflammatory factors in both the retina and serum. Conclusion: These findings strongly suggest that CDDP prevents early DR through vascular and neuroprotection.

Glial cells as a promising therapeutic target of glaucoma: beyond the IOP

Glial cells, a type of non-neuronal cell found in the central nervous system (CNS), play a critical role in maintaining homeostasis and regulating CNS functions. Recent advancements in technology have paved the way for new therapeutic strategies in the fight against glaucoma. While intraocular pressure (IOP) is the most well-known modifiable risk factor, a significant number of glaucoma patients have normal IOP levels. Because glaucoma is a complex, multifactorial disease influenced by various factors that contribute to its onset and progression, it is imperative that we consider factors beyond IOP to effectively prevent or slow down the disease's advancement. In the realm of CNS neurodegenerative diseases, glial cells have emerged as key players due to their pivotal roles in initiating and hastening disease progression. The inhibition of dysregulated glial function holds the potential to protect neurons and restore brain function. Consequently, glial cells represent an enticing therapeutic candidate for glaucoma, even though the majority of glaucoma research has historically concentrated solely on retinal ganglion cells (RGCs). In addition to the neuroprotection of RGCs, the proper regulation of glial cell function can also facilitate structural and functional recovery in the retina. In this review, we offer an overview of recent advancements in understanding the non-cell-autonomous mechanisms underlying the pathogenesis of glaucoma. Furthermore, state-of-the-art technologies have opened up possibilities for regenerating the optic nerve, which was previously believed to be incapable of regeneration. We will also delve into the potential roles of glial cells in the regeneration of the optic nerve and the restoration of visual function.

Enhanced Production of EPA-Derived Anti-Inflammatory Metabolites after Oral Administration of a Novel Self-Emulsifying Highly Purified EPA Ethyl Ester Formulation (MND-2119)

AIMS

MND-2119 is a novel once-daily dose self-emulsifying formulation of highly purified eicosapentaenoic acid ethyl ester (EPA-E) and is approved as an antihyperlipidemia agent in Japan. It has improved absorption and achieves higher plasma EPA concentrations at Cmax than conventional EPA-E. In the JELIS trial, concomitant use of EPA-E with statin therapy significantly reduced atherosclerotic cardiovascular disease (ASCVD) risks. As a potential mechanism of action of EPA, endogenous formation of EPA-derived anti-inflammatory metabolites is receiving greater attention. This study aims to investigate the endogenous formation of EPA-derived anti-inflammatory metabolites following single and multiple administrations of MND-2119.

METHODS

Healthy adult male subjects were randomly assigned to a nonintervention (control) group, MND-2119 2-g/day group, MND-2119 4-g/day group, or EPA-E 1.8-g/day group for 7 days (N=8 per group). Plasma fatty acids and EPA-derived metabolites were evaluated. Peripheral blood neutrophils were isolated, and the production of EPA-derived metabolites from in vitro stimulated neutrophils was evaluated.

RESULTS

After single and multiple administrations of MND-2119 2 g/day, there were significant increases in plasma EPA concentration, 18-hydroxyeicosapentaenoic acid (18-HEPE), and 17,18-epoxyeicosatetraenoic acid compared with those of EPA-E 1.8 g/day. They were further increased with MND-2119 4 g/day administration. In neutrophils, the EPA concentration in the MND-2119 2-g/day group was significantly higher compared with that in the EPA-E 1.8-g/day group after multiple administration, and 18-HEPE production was positively correlated with EPA concentration. No safety issues were noted.

CONCLUSIONS

These results demonstrate that MND-2119 increases the plasma and cellular concentrations of EPA and EPA-derived metabolites to a greater extent than conventional EPA-E formulations.

Retinal ferroptosis as a critical mechanism for the induction of retinochoroiditis during ocular toxoplasmosis

Toxoplasmosis is a major infectious disease, affecting approximately one-third of the world's population; its main clinical manifestation, ocular toxoplasmosis (OT), is a severe sight-threatening disease. Nevertheless, the diagnosis of OT is based on clinical findings, which needs improvement, even with biochemical tests, such as polymerase chain reaction and antibody detections. Furthermore, the efficacy of OT-targeted treatment is limited; thus, additional measures for diagnosis and treatments are needed. Here, we for the first time report a significantly reduced iron concentration in the vitreous humor (VH) of human patients infected with OT. To obtain further insights into molecular mechanisms, we established a mouse model of T. gondii infection, in which intravitreally injected tracer 57Fe, was accumulated in the neurosensory retina. T. gondii-infected eyes showed increased lipid peroxidation, reduction of glutathione peroxidase-4 expression and mitochondrial deformity in the photoreceptor as cristae loss. These findings strongly suggest the involvement of ferroptotic process in the photoreceptor of OT. In addition, deferiprone, an FDA-approved iron chelator, reduced the iron uptake but also ameliorated toxoplasma-induced retinochoroiditis by reducing retinal inflammation. In conclusion, the iron levels in the VH could serve as diagnostic markers and iron chelators as potential treatments for OT.

Evaluating fine changes in visual function of diabetic eyes using spatial-sweep steady-state pattern electroretinography

The visual function of diabetic eyes was assessed to evaluate spatial-sweep steady-state pattern electroretinography (swpPERG) as a potential high-sensitivity analysis method. Data from 24 control eyes, 28 diabetic eyes without diabetic retinopathy (DR), and 30 diabetic eyes with DR (all with best-corrected visual acuity [BCVA] better than logMAR 0.05; median age, 51) in response to spatial-patterned and contrast-reversed stimuli of sizes 1 (thickest) to 6 were converted into the frequency domain using a Fourier transform and expressed as signal-to-noise ratios (SNRs). SNRs of diabetic eyes, both with and without DR, were lower than those of controls (P < 0.05), and those of DR eyes were lower than those of diabetic eyes without DR (P < 0.05). The SNRs were correlated with ganglion cell layer volume measured using optical coherence tomography (OCT) and foveal vascular length density at the superficial retinal layer measured using OCT angiography (P < 0.05 or < 0.01, according to stimulus size). Therefore, swpPERG SNRs could detect fine reductions in visual function in diabetic eyes and were particularly low in DR eyes. Moreover, SNRs were correlated with inner retinal morphological changes in diabetic eyes, both with and without DR. swpPERG may therefore be useful for detecting fine fluctuations in visual function in diabetic eyes.

SRY-box transcription factor 9 modulates Müller cell gliosis in diabetic retinopathy by upregulating TXNIP transcription

Diabetic retinopathy (DR), a common complication of diabetes, involves excessive proliferation and inflammation of Muller cells and ultimately leads to vision loss and blindness. SRY-box transcription factor 9 (SOX9) has been reported to be highly expressed in Müller cells in light-induced retinal damage rats, but the functional role of SOX9 in DR remains unclear. To explore this issue, the DR rat model was successfully constructed via injection with streptozotocin (65 mg/kg) and the retinal thicknesses and blood glucose levels were evaluated. Müller cells were treated with 25 mmol/l glucose to create a cell model in vitro. The results indicated that SOX9 expression was significantly increased in DR rat retinas and in Müller cells stimulated with a high glucose (HG) concentration. HG treatment promoted the proliferation and migration capabilities of Müller cells, whereas SOX9 knockdown reversed those behaviors. Moreover, SOX9 knockdown provided protection against an HG-induced inflammatory response, as evidenced by reduced tumor necrosis factor-α, IL-1β, and IL-6 levels in serum and decreased NLRP3 inflammasome activation. Notably, SOX9 acted as a transcription factor that positively regulated thioredoxin-interacting protein (TXNIP), a positive regulator of Müller cells gliosis under HG conditions. A dual-luciferase assay demonstrated that SOX9 could enhance TXNIP expression at the transcriptional level through binding to the promoter of TXNIP. Moreover, TXNIP overexpression restored the effects caused by SOX9 silencing. In conclusion, these findings demonstrate that SOX9 may accelerate the progression of DR by promoting glial cell proliferation, metastasis, and inflammation, which involves the transcriptional regulation of TXNIP, providing new theoretical fundamentals for DR therapy.

Current advancements and future perspectives of long noncoding RNAs in lipid metabolism and signaling

BACKGROUND

The investigation of lncRNAs has provided a novel perspective for elucidating mechanisms underlying diverse physiological and pathological processes. Compelling evidence has revealed an intrinsic link between lncRNAs and lipid metabolism, demonstrating that lncRNAs-induced disruption of lipid metabolism and signaling contribute to the development of multiple cancers and some other diseases, including obesity, fatty liver disease, and cardiovascular disease.

AIMOF REVIEW

The current review summarizes the recent advances in basic research about lipid metabolism and lipid signaling-related lncRNAs. Meanwhile, the potential and challenges of targeting lncRNA for the therapy of cancers and other lipid metabolism-related diseases are also discussed.

KEY SCIENTIFIC CONCEPT OF REVIEW

Compared with the substantial number of lncRNA loci, we still know little about the role of lncRNAs in metabolism. A more comprehensive understanding of the function and mechanism of lncRNAs may provide a new standpoint for the study of lipid metabolism and signaling. Developing lncRNA-based therapeutic approaches is an effective strategy for lipid metabolism-related diseases.

Current Treatments for Diabetic Macular Edema

Diabetic retinopathy is a major retinal disorder and a leading cause of blindness. Diabetic macular edema (DME) is an ocular complication in patients with diabetes, and it can impair vision significantly. DME is a disorder of the neurovascular system, and it causes obstructions of the retinal capillaries, damage of the blood vessels, and hyperpermeability due to the expression and action of vascular endothelial growth factor (VEGF). These changes result in hemorrhages and leakages of the serous components of blood that result in failures of the neurovascular units (NVUs). Persistent edema of the retina around the macula causes damage to the neural cells that constitute the NVUs resulting in diabetic neuropathy of the retina and a reduction in vision quality. The macular edema and NVU disorders can be monitored by optical coherence tomography (OCT). Neuronal cell death and axonal degeneration are irreversible, and their development can result in permanent visual loss. Treating the edema before these changes are detected in the OCT images is necessary for neuroprotection and maintenance of good vision. This review describes the effective treatments for the macular edema that are therefore neuroprotective.

Prevention of progressive hearing loss in a mouse model of diabetes by oral intake of eicosapentaenoic acid ethyl ester

BACKGROUND

The prevalence of hearing impairment in patients with diabetes was significantly higher, and the development of preventive methods is desirable.

AIMS/OBJECTIVES

This study examined the effects of eicosapentaenoic acid (EPA) administration on the prevention of early hearing loss in diabetic mice.

MATERIALS AND METHODS

Tsumura, Suzuki, Obese Diabetes (TSOD) mice were used as a model of diabetes and Tsumura, Suzuki, Non Obesity (TSNO) mice were used as controls. The animals were divided into three groups: the TSNO group and the TSOD (EPA-) group (provided sunflower oil), and the TSOD (EPA+) group (provided EPA). Auditory brainstem responses (ABRs) were measured and the cochlea was evaluated histologically.

RESULTS

The TSOD (EPA+) group showed a lower tendency to increase thresholds than the TSOD (EPA-) group. The TSOD (EPA+) group had a significantly lower ABR threshold than the TSOD (EPA-) group from 11 to 14 months of age at 4 kHz. Narrowing of the capillary lumens in the stria vascularis and thickening of the vessel wall in the modiolus were observed in the TSOD (EPA-) group.

CONCLUSIONS AND SIGNIFICANCE

It was suggested that the suppression of cochlear vascular atherosclerosis by EPA administration in TSOD mice suppressed early age-related hearing loss.

Neuroprotective Effect of Ponicidin Alleviating the Diabetic Cognitive Impairment: Regulation of Gut Microbiota

Cognitive impairment is a major complication of diabetes mellitus, which is caused by constitutive hyperglycaemia. Ponicidin is a diterpenoid isolated from a Chinese traditional herb (Rabdosia rubescens) and demonstrates the various pharmacological effects. The goal of this study was to scrutinise the neuroprotective effect of ponicidin against diabetic nephropathy (DN) induced by streptozotocin (STZ). Intraperitoneal administration of STZ (55 mg/kg) was used for the induction of diabetes and rats were received oral administration of ponicidin (5, 10 and 15 mg/kg) until 28 days. The body weight, food intake, water intake and blood glucose level were assessed at regular time interval. Plasma insulin level, antioxidant, inflammatory cytokines, apoptosis marker and faecal gut microbiota compositions were estimated. DN-induced group rats revealed the augmented glucose level, water intake, food intake and reduced body weight. Ponicidin significantly (P < 0.001) repressed the glucose level and water food intake and improved the body weight and plasma insulin. Ponicidin significantly (P < 0.001) repressed the malonaldehyde (MDA) level and boosted the level of glutathione (GSH), glutathione reductase (GR) and superoxide dismutase (SOD) in the brain and serum level. Ponicidin significantly (P < 0.001) repressed the level of interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) and enhanced the level of interleukin-4 (IL-4), interleukin-10 (IL-10) in the brain and serum level. DN group rats exhibited the enhanced relative abundance of Firmicutes, along with enhancing the Firmicutes/Bacteroidetes ratio and repressing the Bacteroidetes relative abundance. Ponicidin effectually restored the relative abundance of Allobaculum, Lactobacillus and Ruminococcus genera. Our findings clearly demonstrated that ponicidin has a neuroprotective effect against diabetic cognitive impairment through modulating the gut microbiome.

RNA Foci Formation in a Retinal Glial Model for Spinocerebellar Ataxia Type 7

Spinocerebellar ataxia type 7 (SCA7) is a neurodegenerative disorder characterized by cerebellar ataxia and retinopathy. SCA7 is caused by a CAG expansion in the ATXN7 gene, which results in an extended polyglutamine (polyQ) tract in the encoded protein, the ataxin-7. PolyQ expanded ataxin-7 elicits neurodegeneration in cerebellar Purkinje cells, however, its impact on the SCA7-associated retinopathy remains to be addressed. Since Müller glial cells play an essential role in retinal homeostasis, we generate an inducible model for SCA7, based on the glial Müller MIO-M1 cell line. The SCA7 pathogenesis has been explained by a protein gain-of-function mechanism, however, the contribution of the mutant RNA to the disease cannot be excluded. In this direction, we found nuclear and cytoplasmic foci containing mutant RNA accompanied by subtle alternative splicing defects in MIO-M1 cells. RNA foci were also observed in cells from different lineages, including peripheral mononuclear leukocytes derived from SCA7 patient, suggesting that this molecular mark could be used as a blood biomarker for SCA7. Collectively, our data showed that our glial cell model exhibits the molecular features of SCA7, which makes it a suitable model to study the RNA toxicity mechanisms, as well as to explore therapeutic strategies aiming to alleviate glial dysfunction.

FX5, a non-steroidal glucocorticoid receptor antagonist, ameliorates diabetic cognitive impairment in mice

Diabetic cognitive impairment (DCI) is a common diabetic complication characterized by learning and memory deficits. In diabetic patients, hyperactivated hypothalamic-pituitary-adrenal (HPA) axis leads to abnormal increase of glucocorticoids (GCs), which causes the damage of hippocampal neurons and cognitive impairment. In this study we investigated the cognition-improving effects of a non-steroidal glucocorticoid receptor (GR) antagonist 5-chloro-N-[4-chloro-3-(trifluoromethyl) phenyl]thiophene-2-sulfonamide (FX5) in diabetic mice. Four weeks after T1DM or T2DM was induced, the mice were administered FX5 (20, 40 mg·kg-1·d-1, i.g.) for 8 weeks. Cognitive impairment was assessed in open field test, novel object recognition test, Y-maze test, and Morris water maze test. We showed that FX5 administration significantly ameliorated the cognitive impairments in both type 1 and 2 diabetic mice. Similar cognitive improvement was observed in diabetic mice following brain GR-specific knockdown by injecting AAV-si-GR. Moreover, AAV-si-GR injection occluded the cognition-improving effects of FX5, suggesting that FX5 functioning as a non-steroidal GR antagonist. In PA-treated primary neurons (as DCI model in vitro), we demonstrated that FX5 (2, 5, 10 μM) dose-dependently ameliorated synaptic impairment via upregulating GR/BDNF/TrkB/CREB pathway, protected against neuronal apoptosis through repressing GR/PI3K/AKT/GSK3β-mediated tauopathy and subsequent endoplasmic reticulum stress. In LPS-treated primary microglia, FX5 dose-dependently inhibited inflammation through GR/NF-κB/NLRP3/ASC/Caspase-1 pathway. These beneficial effects were also observed in the hippocampus of diabetic mice following FX5 administration. Collectively, we have elucidated the mechanisms underlying the beneficial effects of non-steroidal GR antagonist FX5 on DCI and highlighted the potential of FX5 in the treatment of the disease.

Norepinephrine Inhibits Lipopolysaccharide-Stimulated TNF-α but Not Oxylipin Induction in n-3/n-6 PUFA-Enriched Cultures of Circumventricular Organs

Sensory circumventricular organs (sCVOs) are pivotal brain structures involved in immune-to-brain communication with a leaky blood-brain barrier that detect circulating mediators such as lipopolysaccharide (LPS). Here, we aimed to investigate the potential of sCVOs to produce n-3 and n-6 oxylipins after LPS-stimulation. Moreover, we investigated if norepinephrine (NE) co-treatment can alter cytokine- and oxylipin-release. Thus, we stimulated rat primary neuroglial sCVO cultures under n-3- or n-6-enriched conditions with LPS or saline combined with NE or vehicle. Supernatants were assessed for cytokines by bioassays and oxylipins by HPLC-MS/MS. Expression of signaling pathways and enzymes were analyzed by RT-PCR. Tumor necrosis factor (TNF)α bioactivity and signaling, IL-10 expression, and cyclooxygenase (COX)2 were increased, epoxide hydroxylase (Ephx)2 was reduced, and lipoxygenase 15-(LOX) was not changed by LPS stimulation. Moreover, LPS induced increased levels of several n-6-derived oxylipins, including the COX-2 metabolite 15d-prostaglandin-J2 or the Ephx2 metabolite 14,15-DHET. For n-3-derived oxylipins, some were down- and some were upregulated, including 15-LOX-derived neuroprotectin D1 and 18-HEPE, known for their anti-inflammatory potential. While the LPS-induced increase in TNFα levels was significantly reduced by NE, oxylipins were not significantly altered by NE or changes in TNFα levels. In conclusion, LPS-induced oxylipins may play an important functional role in sCVOs for immune-to-brain communication.

LncRNA MALAT1 aggravates the retinal angiogenesis via miR-320a/HIF-1α axis in diabetic retinopathy

Diabetic retinopathy (DR) is one of the most serious microvascular complications of diabetes and an important cause of blindness in adults. In previous study, we found that miR-320a alleviated the damage of muller cells in DR. In this study, we mainly explored the mechanism of lncRNA MALAT1 on retinal angiogenesis in DR by regulating miR-320a/HIF-1α. The expression of MALAT1 and miR-320a was detected by RT-qPCR, and the expression of HIF-1α was detected by Western blot. The superoxide anion level, invasion, angiogenesis, and vascular permeability of mouse retinal microvascular endothelial cells (MRMECs) co-cultured with muller cells were evaluated by dihydroethidium, transwell, angiogenesis and immunofluorescence assay. In order to analyze the targeting relationship between miR-320a and MALAT1 or HIF-1α, we performed dual luciferase reporter gene, fluorescence in situ hybridization (FISH), RNA immunoprecipitation (RIP) and RNA pulldown experiments. The results should that MALAT1 and HIF-1α were highly expressed and miR-320a was low expressed in high glucose (HG)-induced muller cells, and MALAT1 could competitively bind with HIF-1α. Knocking down miR-320a inhibited MRMECs invasion angiogenesis, and vascular permeability by targeting miR-320a. Overexpression of miR-320a down regulated HIF-1α and inhibited the invasion, angiogenesis, and vascular permeability of MRMECs. In conclusion, MALAT1 inhibits HIF-1α expression and MRMECs angiogenesis in DR through spongy miR-320a.

Human Umbilical Cord Blood-Derived CD133+CD34+ Cells Protect Retinal Endothelial Cells and Ganglion Cells in X-Irradiated Rats through Angioprotective and Neurotrophic Factors

Radiation retinopathy (RR) is a common complication following radiation therapy of globe, head, and neck malignancies, and is characterized by microangiopathy, neuroretinopathy, and the irreversible loss of visual function. To date, there is no effective treatment for RR. Stem cells have been clinically used to treat retinal degeneration. CD133+CD34+ cells from human umbilical cord blood (hUCB-CD133+CD34+ cells), a subpopulation of hematopoietic stem cells, were applied to determine their protective efficacy on irradiated rat retinas. After X-ray irradiation on the retinas, rats were intravitreally injected with hUCB-CD133+CD34+ cells. Transplantation of hUCB-CD133+CD34+ cells prevented retinal dysfunction 2 weeks post-operation and lasted at least 8 weeks. CD133+CD34+ cells were distributed along the retinal vessel and migrated to the ganglion cell layer. Moreover, grafted CD133+CD34+ cells reduced the apoptosis of endothelial and ganglion cells in irradiated rats and increased the number of survived CD31+ retinal endothelial cells and Brn3a+ ganglion cells at 2 and 4 weeks, respectively, post-operation. Co-culturing of CD133+CD34+ cells or supernatants with irradiated human retinal microvascular endothelial cells (hRECs) in vitro, confirmed that CD133+CD34+ cells ameliorated hREC apoptosis caused by irradiation. Mechanistically, we found that angioprotective mediators and neurotrophic factors were secreted by CD133+CD34+ cells, which might attenuate irradiation-induced injury of retinal endothelial cells and ganglion cells. hUCB-CD133+CD34+ cell transplantation, as a novel treatment, protects retinal endothelial and ganglion cells of X-irradiated rat retinas, possibly through angioprotective and neurotrophic factors.

The gut microbiota in retinal diseases

The gut microbiota is a complex ecosystem that inhabits the gastrointestinal tract and consists of archaea, fungi, viruses, and bacteria, with bacteria being dominant. From birth onwards, it coevolves dynamically together with the host. The composition of the gut microbiota is under the influence of a complex interplay between both host and environmental factors. Scientific advances in the past few decades have shown that it is essential in maintaining homeostasis and tipping the balance between health and disease. In addition to its role in food digestion, the gut microbiota is implicated in regulating multiple physiological processes in the host gut mucosa and in distant organs such as the brain. Persistent imbalance between gut microbial communities, termed "dysbiosis," has been associated with several inflammatory and metabolic diseases as well as with central nervous system disorders. In this review, we present the state of the art of current knowledge on an emerging concept, the microbiota-retina axis, and the potential role of its disturbance in the development of retinopathies. We also describe several microbiota-targeting strategies that could constitute preventive and therapeutic tools for retinopathies.

The Pathogenesis and Therapeutic Approaches of Diabetic Neuropathy in the Retina

Diabetic retinopathy is a major retinal disease and a leading cause of blindness in the world. Diabetic retinopathy is a neurovascular disease that is associated with disturbances of the interdependent relationship of cells composed of the neurovascular units, i.e., neurons, glial cells, and vascular cells. An impairment of these neurovascular units causes both neuronal and vascular abnormalities in diabetic retinopathy. More specifically, neuronal abnormalities including neuronal cell death and axon degeneration are irreversible changes that are directly related to the vision reduction in diabetic patients. Thus, establishment of neuroprotective and regenerative therapies for diabetic neuropathy in the retina is an emergent task for preventing the blindness of patients with diabetic retinopathy. This review focuses on the pathogenesis of the neuronal abnormalities in diabetic retina including glial abnormalities, neuronal cell death, and axon degeneration. The possible molecular cell death pathways and intrinsic survival and regenerative pathways are also described. In addition, therapeutic approaches for diabetic neuropathy in the retina both in vitro and in vivo are presented. This review should be helpful for providing clues to overcome the barriers for establishing neuroprotection and regeneration of diabetic neuropathy in the retina.

Apocynin ameliorates NADPH oxidase 4 (NOX4) induced oxidative damage in the hypoxic human retinal Müller cells and diabetic rat retina

NADPH oxidase (NOX) is a main producers of reactive oxygen species (ROS) that may contribute to the early pathogenesis of diabetic retinopathy (DR). ROS has harmful effects on endogenous neuro-survival factors brain-derived neurotrophic factor (BDNF) and sirtuin 1 (SIRT1) are necessary for the growth and survival of the retina. The role of NOX isoforms NOX4 in triggering ROS in DR is not clear. Here we determine the protective effects of a plant-derived NOX inhibitor apocynin (APO) on NOX4-induced ROS production which may contribute to the depletion of survival factors BDNF/SIRT1 or cell death in the diabetic retinas. Human retinal Müller glial cells (MGCs) were treated with hypoxia mimetic agent cobalt chloride (CoCl₂) in the absence or presence of APO. Molecular analysis demonstrates that NOX4 is upregulated in CoCl₂-treated MGCs and in the diabetic retinas. Increased NOX4 was accompanied by the downregulation of BDNF/SIRT1 expression or in the activation of apoptotic marker caspase-3. Whereas, APO treatment downregulates NOX4 and subsequently upregulates BDNF/SIRT1 or alleviate caspase-3 expression. Accordingly, in the diabetic retina we found a positive correlation in NOX4 vs ROS (p = 0.025; R² = 0.488) and caspase-3 vs ROS (p = 0.04; R² = 0.428); whereas a negative correlation in BDNF vs ROS (p = 0.009; R² = 0.596) and SIRT1 vs ROS (p = 0.0003; R² = 0.817) respectively. Taken together, NOX4-derived ROS could be a main contributor in downregulating BDNF/SIRT1 expression or in the activation of caspase-3. Whereas, APO treatment may minimize the deleterious effects occurring due to hyperglycemia and/or diabetic mimic hypoxic condition in early pathogenesis of DR.

The innate immune system in diabetic retinopathy

The prevalence of diabetes has been rising steadily in the past half-century, along with the burden of its associated complications, including diabetic retinopathy (DR). DR is currently the most common cause of vision loss in working-age adults in the United States. Historically, DR has been diagnosed and classified clinically based on what is visible by fundoscopy; that is vasculature alterations. However, recent technological advances have confirmed pathology of the neuroretina prior to any detectable vascular changes. These, coupled with molecular studies, and the positive impact of anti-inflammatory therapeutics in DR patients have highlighted the central involvement of the innate immune system. Reminiscent of the systemic impact of diabetes, immune dysregulation has become increasingly identified as a key element of the pathophysiology of DR by interfering with normal homeostatic systems. This review uses the growing body of literature across various model systems to demonstrate the clear involvement of all three pillars of the immune system: immune-competent cells, mediators, and the complement system. It also demonstrates how the relative contribution of each of these requires more extensive analysis, including in human tissues over the continuum of disease progression. Finally, although this review demonstrates how the complex interactions of the immune system pose many more questions than answers, the intimately connected nature of the three pillars of the immune system may also point to possible new targets to reverse or even halt reverse retinopathy.

Acrolein: A Potential Mediator of Oxidative Damage in Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of vision loss among working-age adults. Extensive evidences have documented that oxidative stress mediates a critical role in the pathogenesis of DR. Acrolein, a product of polyamines oxidation and lipid peroxidation, has been demonstrated to be involved in the pathogenesis of various human diseases. Acrolein’s harmful effects are mediated through multiple mechanisms, including DNA damage, inflammation, ROS formation, protein adduction, membrane disruption, endoplasmic reticulum stress, and mitochondrial dysfunction. Recent investigations have reported the involvement of acrolein in the pathogenesis of DR. These studies have shown a detrimental effect of acrolein on the retinal neurovascular unit under diabetic conditions. The current review summarizes the existing literature on the sources of acrolein, the impact of acrolein in the generation of oxidative damage in the diabetic retina, and the mechanisms of acrolein action in the pathogenesis of DR. The possible therapeutic interventions such as the use of polyamine oxidase inhibitors, agents with antioxidant properties, and acrolein scavengers to reduce acrolein toxicity are also discussed.

Effect of Periodontal Disease on Diabetic Retinopathy in Type 2 Diabetic Patients: A Cross-sectional Pilot Study

Both periodontal disease and diabetes are common chronic inflammatory diseases. One of the major problems with type 2 diabetes is that unregulated blood glucose levels damage the vascular endothelium and cause complications. A bidirectional relationship between periodontal disease and diabetic complications has been reported previously. However, whether periodontal disease affects the presence of diabetic complications has not been clarified. Therefore, we examined the effect of the periodontal disease status on diabetic complications in patients with type 2 diabetes. Periodontal doctors examined the periodontal disease status of 104 type 2 diabetic patients who visited a private diabetes medical clinic once a month between 2016 and 2018. The subject's diabetic status was obtained from their medical records. Bayesian network analysis showed that bleeding on probing directly influenced the presence of diabetic retinopathy in type 2 diabetes patients. In addition, bleeding on probing was higher in the diabetic retinopathy group (n = 36) than in the group without diabetic retinopathy (n = 68, p = 0.006, Welch's t-test). Bleeding on probing represents gingival inflammation, which might affect the presence of diabetic retinopathy in type 2 diabetes patients who regularly visit diabetic clinics.

Protective Effects and Molecular Signaling of n-3 Fatty Acids on Oxidative Stress and Inflammation in Retinal Diseases

Oxidative stress and inflammation play crucial roles in the development and progression of retinal diseases. Retinal damage by various etiologies can result in retinopathy of prematurity (ROP), diabetic retinopathy (DR), and age-related macular degeneration (AMD). n-3 fatty acids are essential fatty acids and are necessary for homeostasis. They are important retinal membrane components and are involved in energy storage. n-3 fatty acids also have antioxidant and anti-inflammatory properties, and their suppressive effects against ROP, DR, and AMD have been previously evaluated. α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and their metabolites have been shown to alleviate retinal oxidative stress and inflammation involving various biological signaling pathways. In this review, we summarize the current understanding of the n-3 fatty acids effects on the mechanisms of these retinal diseases and how they exert their therapeutic effects, focusing on ALA, EPA, DHA, and their metabolites. This knowledge may provide new remedial strategies for n-3 fatty acids in the prevention and treatment of retinal diseases associated with oxidative stress and inflammation.

Melatonin exerts neuroprotective effects by inhibiting neuronal pyroptosis and autophagy in STZ-induced diabetic mice

Diabetes mellitus (DM) patients are at a higher risk of developing brain injury characterized by neuronal death. Melatonin, a hormone produced by the pineal gland, exerts neuroprotective effects against brain damage. However, the effect of melatonin on diabetes-induced brain injury has not been elucidated. This study was to evaluate the role of melatonin against neuronal death in DM and to elucidate the underlying mechanisms. Herein, we found that melatonin administration significantly alleviated the neuronal death in both streptozotocin (STZ)-induced diabetic mice and high glucose (HG)-treated neuronal cells. Melatonin inhibited neuronal pyroptosis and excessive autophagy, as evidenced by decreased levels of NLRP3, cleaved caspase-1, GSDMD-N, IL-1β, LC3, Beclin1, and ATG12 both in vivo and in vitro. MicroRNA-214-3p (miR-214-3p) was decreased in DM mice and HG-treated cells, and such a downregulation was corrected by melatonin, which was accompanied by repression of caspase-1 and ATG12. Furthermore, downregulation of miR-214-3p abrogated the anti-pyroptotic and anti-autophagic actions of melatonin in vitro. Our results indicate that melatonin exhibits a neuroprotective effect by inhibiting neuronal pyroptosis and excessive autophagy through modulating the miR-214-3p/caspase-1 and miR-214-3p/ATG12 axes, respectively, and it might be a potential agent for the treatment of brain damage in the setting of DM.

Oxidative Stress and Vascular Dysfunction in the Retina: Therapeutic Strategies

Many retinal diseases, such as diabetic retinopathy, glaucoma, and age-related macular (AMD) degeneration, are associated with elevated reactive oxygen species (ROS) levels. ROS are important intracellular signaling molecules that regulate numerous physiological actions, including vascular reactivity and neuron function. However, excessive ROS formation has been linked to vascular endothelial dysfunction, neuron degeneration, and inflammation in the retina. ROS can directly modify cellular molecules and impair their function. Moreover, ROS can stimulate the production of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) causing inflammation and cell death. However, there are various compounds with direct or indirect antioxidant activity that have been used to reduce ROS accumulation in animal models and humans. In this review, we report on the physiological and pathophysiological role of ROS in the retina with a special focus on the vascular system. Moreover, we present therapeutic approaches for individual retinal diseases targeting retinal signaling pathways involving ROS.

Lipid Signaling in Ocular Neovascularization

Vasculogenesis and angiogenesis play a crucial role in embryonic development. Pathological neovascularization in ocular tissues can lead to vision-threatening vascular diseases, including proliferative diabetic retinopathy, retinal vein occlusion, retinopathy of prematurity, choroidal neovascularization, and corneal neovascularization. Neovascularization involves various cellular processes and signaling pathways and is regulated by angiogenic factors such as vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF). Modulating these circuits may represent a promising strategy to treat ocular neovascular diseases. Lipid mediators derived from membrane lipids are abundantly present in most tissues and exert a wide range of biological functions by regulating various signaling pathways. In particular, glycerophospholipids, sphingolipids, and polyunsaturated fatty acids exert potent pro-angiogenic or anti-angiogenic effects, according to the findings of numerous preclinical and clinical studies. In this review, we summarize the current knowledge regarding the regulation of ocular neovascularization by lipid mediators and their metabolites. A better understanding of the effects of lipid signaling in neovascularization may provide novel therapeutic strategies to treat ocular neovascular diseases and other human disorders.

Leukotriene B4 receptors as therapeutic targets for ophthalmic diseases

Leukotriene B₄ (LTB₄) is an inflammatory lipid mediator produced from arachidonic acid by multiple reactions catalyzed by two enzymes 5-lipoxygenase (5-LOX) and LTA₄ hydrolase (LTA₄H). The two receptors for LTB₄ have been identified: a high-affinity receptor, BLT1, and a low-affinity receptor, BLT2. Our group identified 12(S)-hydroxy-5Z,8E,10E-heptadecatrienoic acid (12-HHT) as a high-affinity BLT2 ligand. Numerous studies have revealed critical roles for LTB₄ and its receptors in various systemic diseases. Recently, we also reported the roles of LTB₄, BLT1 and BLT2 in the murine ophthalmic disease models of mice including cornea wound, allergic conjunctivitis, and age-related macular degeneration. Moreover, other groups revealed the evidence of the ocular function of LTB₄. In the present review, we introduce the roles of LTB₄ and its receptors both in ophthalmic diseases and systemic inflammatory diseases. LTB₄ and its receptors are putative novel therapeutic targets for systemic and ophthalmic diseases.

Recent Developments in Diabetic Retinal Neurodegeneration: A Literature Review

Neurodegeneration plays a significant role in the complex pathology of diabetic retinopathy. Evidence suggests the onset of neurodegeneration occurs early on in the disease, and so a greater understanding of the process is essential for prompt detection and targeted therapies. Neurodegeneration is a common pathway of assorted processes, including activation of inflammatory pathways, reduction of neuroprotective factors, DNA damage, and apoptosis. Oxidative stress and formation of advanced glycation end products amplify these processes and are elevated in the setting of hyperglycemia, hyperlipidemia, and glucose variability. These key pathophysiologic mechanisms are discussed, as well as diagnostic modalities and novel therapeutic avenues, with an emphasis on recent discoveries. The aim of this article is to highlight the crucial role of neurodegeneration in diabetic retinopathy and to review the molecular basis for this neuronal dysfunction, its diagnostic features, and the progress currently made in relevant therapeutic interventions.