https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/j.febslet.2008.04.057

The antioxidant properties of serum albumin

Improvements in health care and lifestyle have led to an elevated lifespan and increased focus on age-associated diseases, such as neurodegeneration, cardiovascular disease, frailty and arteriosclerosis. In all these chronic diseases protein, lipid or nucleic acid modifications are involved, including cross-linked and non-degradable aggregates, such as advanced glycation end products (AGEs). Formation of endogenous or uptake of dietary AGEs can lead to further protein modifications and activation of several inflammatory signaling pathways. This review will give an overview of the most prominent AGE-mediated signaling cascades, AGE receptor interactions, prevention of AGE formation and the impact of AGEs during pathophysiological processes.

Role of advanced glycation end products in cellular signaling

Diabetic retinopathy (DR) and diabetic macular edema (DME) are leading causes of blindness in the working-age population of most developed countries. The increasing number of individuals with diabetes worldwide suggests that DR and DME will continue to be major contributors to vision loss and associated functional impairment for years to come. Early detection of retinopathy in individuals with diabetes is critical in preventing visual loss, but current methods of screening fail to identify a sizable number of high-risk patients. The control of diabetes-associated metabolic abnormalities (i.e., hyperglycemia, hyperlipidemia, and hypertension) is also important in preserving visual function because these conditions have been identified as risk factors for both the development and progression of DR/DME. The currently available interventions for DR/DME, laser photocoagulation and vitrectomy, only target advanced stages of disease. Several biochemical mechanisms, including protein kinase C-beta activation, increased vascular endothelial growth factor production, oxidative stress, and accumulation of intracellular sorbitol and advanced glycosylation end products, may contribute to the vascular disruptions that characterize DR/DME. The inhibition of these pathways holds the promise of intervention for DR at earlier non-sight-threatening stages. To implement new therapies effectively, more individuals will need to be screened for DR/DME at earlier stages-a process requiring both improved technology and interdisciplinary cooperation among physicians caring for patients with diabetes.

https://care.diabetesjournals.org/content/diacare/26/9/2653.full.pdf

Diabetic Retinopathy and Diabetic Macular Edema: Pathophysiology, screening, and novel therapies

https://www.newtricious.nl/sites/default/files/DHA%20EFSA.pdf

The role of omega-3 long-chain polyunsaturated fatty acids in health and disease of the retina.

In this work we advance the hypothesis that omega-3 (omega-3) long-chain polyunsaturated fatty acids (LCPUFAs) exhibit cytoprotective and cytotherapeutic actions contributing to a number of anti-angiogenic and neuroprotective mechanisms within the retina. omega-3 LCPUFAs may modulate metabolic processes and attenuate effects of environmental exposures that activate molecules implicated in pathogenesis of vasoproliferative and neurodegenerative retinal diseases. These processes and exposures include ischemia, chronic light exposure, oxidative stress, inflammation, cellular signaling mechanisms, and aging. A number of bioactive molecules within the retina affect, and are effected by such conditions. These molecules operate within complex systems and include compounds classified as eicosanoids, angiogenic factors, matrix metalloproteinases, reactive oxygen species, cyclic nucleotides, neurotransmitters and neuromodulators, pro-inflammatory and immunoregulatory cytokines, and inflammatory phospholipids. We discuss the relationship of LCPUFAs with these bioactivators and bioactive compounds in the context of three blinding retinal diseases of public health significance that exhibit both vascular and neural pathology. How is omega-3 LCPUFA status related to retinal structure and function? Docosahexaenoic acid (DHA), a major dietary omega-3 LCPUFA, is also a major structural lipid of retinal photoreceptor outer segment membranes. Biophysical and biochemical properties of DHA may affect photoreceptor membrane function by altering permeability, fluidity, thickness, and lipid phase properties. Tissue DHA status affects retinal cell signaling mechanisms involved in phototransduction. DHA may operate in signaling cascades to enhance activation of membrane-bound retinal proteins and may also be involved in rhodopsin regeneration. Tissue DHA insufficiency is associated with alterations in retinal function. Visual processing deficits have been ameliorated with DHA supplementation in some cases. What evidence exists to suggest that LCPUFAs modulate factors and processes implicated in diseases of the vascular and neural retina? Tissue status of LCPUFAs is modifiable by and dependent upon dietary intake. Certain LCPUFAs are selectively accreted and efficiently conserved within the neural retina. On the most basic level, omega-3 LCPUFAs influence retinal cell gene expression, cellular differentiation, and cellular survival. DHA activates a number of nuclear hormone receptors that operate as transcription factors for molecules that modulate reduction-oxidation-sensitive and proinflammatory genes; these include the peroxisome proliferator-activated receptor-alpha (PPAR-alpha) and the retinoid X receptor. In the case of PPAR-alpha, this action is thought to prevent endothelial cell dysfunction and vascular remodeling through inhibition of: vascular smooth muscle cell proliferation, inducible nitric oxide synthase production, interleukin-1 induced cyclooxygenase (COX)-2 production, and thrombin-induced endothelin 1 production. Research on model systems demonstrates that omega-3 LCPUFAs also have the capacity to affect production and activation of angiogenic growth factors, arachidonic acid (AA)-based vasoregulatory eicosanoids, and MMPs. Eicosapentaenoic acid (EPA), a substrate for DHA, is the parent fatty acid for a family of eicosanoids that have the potential to affect AA-derived eicosanoids implicated in abnormal retinal neovascularization, vascular permeability, and inflammation. EPA depresses vascular endothelial growth factor (VEGF)-specific tyrosine kinase receptor activation and expression. VEGF plays an essential role in induction of: endothelial cell migration and proliferation, microvascular permeability, endothelial cell release of metalloproteinases and interstitial collagenases, and endothelial cell tube formation. The mechanism of VEGF receptor down-regulation is believed to occur at the tyrosine kinase nuclear factor-kappa B (NFkappaB). NFkappaB is a nuclear transcription factor that up-regulates COX-2 expression, intracellular adhesion molecule, thrombin, and nitric oxide synthase. All four factors are associated with vascular instability. COX-2 drives conversion of AA to a number angiogenic and proinflammatory eicosanoids. Our general conclusion is that there is consistent evidence to suggest that omega-3 LCPUFAs may act in a protective role against ischemia-, light-, oxygen-, inflammatory-, and age-associated pathology of the vascular and neural retina.

Integrated Systems Approach to Study the Role of Omega-3 Long-Chain Polyunsaturated Fatty Acids in Health and Disease of the Retina

Reaction of Metformin with Dicarbonyl Compounds. Possible Implication in the Inhibition of Advanced Glycation End Product Formation

Advanced glycation end-products induce apoptosis of bovine retinal pericytes in culture: involvement of diacylglycerol/ceramide production and oxidative stress induction

One of the earliest changes observed in retinal microvessels in diabetic retinopathy is the selective loss of intramural pericytes. We tested the hypothesis that AGE might be involved in the disappearance of retinal pericytes by apoptosis and further investigated the signaling pathway leading to cell death. Chronic exposure of pericytes to methylglyoxal-modified bovine serum albumin (AGE-BSA) (3 M) leads to a 3-fold increase of apoptosis (8.9 1.1%), associated with an increase in cellular ceramide (185 12%) and diacylglycerol (194 9%) levels. Ceramide formation was almost inhibited (95%) by an acidic sphingomyelinase inhibitor, desipramine (0.3 M). Dual inhibition of ceramide (95%) and diacylglycerol (80%) production was observed with a phosphatidylcholine-phospholipase C inhibitor, D609 (9.4 M). Taken together, these results suggest activation of phosphatidylcholine-phospholipase C coupled to acidic sphingomyelinase. However, both inhibitors only partially protected pericytes against apoptosis, suggesting another apoptotic pathway independent of diacylglycerol/ceramide production. Treatments with various antioxidants completely inhibited pericyte apoptosis, suggesting oxidative stress induction during this apoptotic process. Inhibition of diacylglycerol/ceramide production by N-acetyl-L-cysteine suggests that oxidative stress acts upstream of the two metabolic pathways. AGE treated with metal chelators were also able to induce pericyte apoptosis, suggesting a specific effect of AGE on intracellular oxidative stress independent of redox-active metal ions bound to AGE. In conclusion, these results identify new biochemical targets involved in pericyte loss, which can provide new therapeutic perspectives in diabetic retinopathy. © 2002 Elsevier Science Inc. Keywords—Diabetic retinopathy, Pericyte, Advanced glycation end-products, Apoptosis, Ceramides, Oxidative stress,

Original Contribution ADVANCED GLYCATION END-PRODUCTS INDUCE APOPTOSIS OF BOVINE RETINAL PERICYTES IN CULTURE: INVOLVEMENT OF DIACYLGLYCEROL/CERAMIDE PRODUCTION AND OXIDATIVE STRESS INDUCTION

Marc Lecomte

Papers

Reaction of Metformin with Dicarbonyl Compounds. Possible Implication in the Inhibition of Advanced Glycation End Product Formation

Advanced glycation end-products induce apoptosis of bovine retinal pericytes in culture: involvement of diacylglycerol/ceramide production and oxidative stress induction

Original Contribution ADVANCED GLYCATION END-PRODUCTS INDUCE APOPTOSIS OF BOVINE RETINAL PERICYTES IN CULTURE: INVOLVEMENT OF DIACYLGLYCEROL/CERAMIDE PRODUCTION AND OXIDATIVE STRESS INDUCTION

Modification of Enzymatic Antioxidants in Retinal Microvascular Cells by Glucose or Advanced Glycation End Products

Albumin antioxidant capacity is modified by methylglyoxal.