The role of AGEs in aging: causation or correlation

Modification of extracellular matrix proteins by oxidants and electrophiles

The extracellular matrix (ECM) is critical to biological architecture and determines cellular properties, function and activity. In many situations it is highly abundant, with collagens and elastin being some of the most abundant proteins in mammals. The ECM comprises of multiple different protein species and sugar polymers, with both different isoforms and post-translational modifications (PTMs) providing a large variety of microenvironments that play a key role in determining tissue structure and health. A number of the PTMs (e.g. cross-links) present in the ECM are critical to integrity and function, whereas others are deleterious to both ECM structure and associated cells. Modifications induced by reactive oxidants and electrophiles have been reported to accumulate in some ECM with increasing age. This accumulation can be exacerbated by disease, and in particular those associated with acute or chronic inflammation, obesity and diabetes. This is likely to be due to higher fluxes of modifying agents in these conditions. In this focused review, the role and effects of oxidants and other electrophiles on ECM are discussed, with a particular focus on the artery wall and atherosclerotic cardiovascular disease. Modifications generated on ECM components are reviewed, together with the effects of these species on cellular properties including adhesion, proliferation, migration, viability, metabolic activity, gene expression and phenotype. Increasing data indicates that ECM modifications are both prevalent in human and mammalian tissues and play an important role in disease development and progression.

Stable, porous, light-emitting post-modification covalent organic frameworks conjugated molecularly imprinted polymers for selective detection of pyrraline in salami products

Molecular imprinting is one of the most frequently occurring post-modification in the preparation of covalent organic frameworks (COFs) to enhance selectivity and specificity. In this study, we prepared a 2D layer structure of methoxy-conjugated COFs with the modification of azide (4-azido-L-phenylalanine), named [4-ALP]0.17-COFs, which exhibited a large specific surface area of 827.6 m2/g, good stability of water, polar solvents, chemistry, and thermodynamics. Fluorescent COF nanosheets ([4-ALP]0.17-CONs) obtained by liquid-assisted ultrasonic stripping have excellent blue luminescence properties and ultra-high absolute fluorescence quantum yield of 33.34 %. The modifiable functional groups in the surface of [4-ALP]0.17-CONs interacted with the targets and functional monomers of molecularly imprinted polymers (MIPs) through hydrogen bonding interactions, to form the 3D holes with recognition sites. The quantitative detection of pyrraline (PRL) could be achieved in the concentration range of 0.05-4 μg/L with the LOD was 34.81 ng/L. The spiked recovery of PRL in meat products was 88.01-106.00 %. The [4-ALP]0.17-CONs@MIPs sensing system showed excellent stability, reliability, reusability, and practicability, promising its potential for targeted monitoring of trace molecules in real matrices.

Retinal Pigment Epithelium Pigment Granules: Norms, Age Relations and Pathology

The retinal pigment epithelium (RPE), which ensures the normal functioning of the neural retina, is a pigmented single-cell layer that separates the retina from the Bruch's membrane and the choroid. There are three main types of pigment granules in the RPE cells of the human eye: lipofuscin granules (LG) containing the fluorescent "age pigment" lipofuscin, melanoprotein granules (melanosomes, melanolysosomes) containing the screening pigment melanin and complex melanolipofuscin granules (MLG) containing both types of pigments simultaneously-melanin and lipofuscin. This review examines the functional role of pigment granules in the aging process and in the development of oxidative stress and associated pathologies in RPE cells. The focus is on the process of light-induced oxidative degradation of pigment granules caused by reactive oxygen species. The reasons leading to increased oxidative stress in RPE cells as a result of the oxidative degradation of pigment granules are considered. A mechanism is proposed to explain the phenomenon of age-related decline in melanin content in RPE cells. The essence of the mechanism is that when the lipofuscin part of the melanolipofuscin granule is exposed to light, reactive oxygen species are formed, which destroy the melanin part. As more melanolipofuscin granules are formed with age and the development of degenerative diseases, the melanin in pigmented epithelial cells ultimately disappears.

Effect of advanced glycation end-products in a wide range of medical problems including COVID-19

Glycation is a physiological process that determines the aging of the organism, while in states of metabolic disorders it is significantly intensified. High concentrations of compounds such as reducing sugars or reactive aldehydes derived from lipid oxidation, occurring for example in diabetes, atherosclerosis, dyslipidemia, obesity or metabolic syndrome, lead to increased glycation of proteins, lipids and nucleic acids. The level of advanced glycation end-products (AGEs) in the body depends on rapidity of their production and the rate of their removal by the urinary system. AGEs, accumulated in the extracellular matrix of the blood vessels and other organs, cause irreversible changes in the biochemical and biomechanical properties of tissues. As a consequence, micro- and macroangiopathies appear in the system, and may contribute to the organ failure, like kidneys and heart. Elevated levels of AGEs also increase the risk of Alzheimer's disease and various cancers. In this paper, we propose a new classification due to modified amino acid residues: arginyl-AGEs, monolysyl-AGEs and lysyl-arginyl-AGEs and dilysyl-AGEs. Furthermore, we describe in detail the effect of AGEs on the pathogenesis of metabolic and old age diseases, such as diabetic complications, atherosclerosis and neurodegenerative diseases. We summarize the currently available data on the diagnostic value of AGEs and present the AGEs as a therapeutic goal in a wide range of medical problems, including SARS-CoV-2 infection and so-called long COVID.

A revisiting of "the hallmarks of aging" in domestic dogs: current status of the literature

A progressive decline in biological function and fitness is, generally, how aging is defined. However, in 2013, a description on the "hallmarks of aging" in mammals was published, and within it, it described biological processes that are known to alter the aging phenotype. These include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication (inflammation), and changes within the microbiome. This mini-review provides a detailed account of the progress on each of these hallmarks of aging in the domestic dog within the last 5 years. Additionally, when there are gaps in the literature between other mammalian species and dogs, I highlight the aging biomarkers that may be missing for dogs as aging models. I also argue for the importance of dog aging studies to include several breeds of dogs at differing ages and for age corrections for breeds with differing mean lifespans throughout.

Effects of aging and diabetes on the deformation mechanisms and molecular structural characteristics of collagen fibrils under daily activity

Crosslinking plays an important role in collagen-based tissues since it affects mechanical behavior and tissue metabolism. Aging and diabetes affect the type and density of crosslinking, effectively altering tissue properties. However, most studies focus on these effects under large stress rather than daily activities. We focus on the deformation mechanisms and structural change at the binding sites for integrins, proteoglycans, and collagenase in collagen fibrils using a fully atomistic model. We show that high-connectivity enzymatic crosslinking (our "HC" model, representing normal tissues) and advanced-glycation end-products (our "Glucosepane" model, which increase in diabetes) result in uniform deformation under daily activity, but low-connectivity enzymatic crosslinking (our "LC" model, representing aging tissues) does not. In particular, the HC model displays more sliding, which may explain the ability of healthy tissues to absorb more strain energy. In contrast, AGEs induce instability in the structures near the binding sites, which would affect the tissue metabolism of the collagen molecule. Our results provide important insights into the molecular mechanisms of collagen and a possible explanation for the role of crosslinking in tissues undergoing daily activity.

Multiphoton imaging of the monosachharide induced formation of fluorescent advanced glycation end products in tissues

We studied the in vitro rate of fluorescent advanced glycation end products (fAGEs) formation with multiphoton microscopy in different porcine tissues (aorta, cornea, kidney, dermis, and tendon). These tissues were treated with d-glucose, d-galactose, and d-fructose, three primary monosaccharides found in human diets. We found that the use of d-fructose resulted in the highest glycation rate, followed by d-galactose and then d-glucose. Moreover, compared to non-collagen tissue constituents such as elastic fibers and cells, the rate of tissue glycation was consistently higher in collagen, suggesting that collagen is a more sensitive target for fAGE formation. However, we also found that collagen in different tissues exhibits different rates of fAGE formation, with slower rates observed in tightly packed tissues such as cornea and tendon. Our study suggests that for fAGE to be developed into a long-term glycemic biomarker, loosely organized collagen tissues located in the proximity of vasculature may be the best targets.

Role of advanced glycation end products in diabetic vascular injury: molecular mechanisms and therapeutic perspectives

BACKGROUND

In diabetic metabolic disorders, advanced glycation end products (AGEs) contribute significantly to the development of cardiovascular diseases (CVD).

AIMS

This comprehensive review aims to elucidate the molecular mechanisms underlying AGE-mediated vascular injury.

CONCLUSIONS

We discuss the formation and accumulation of AGEs, their interactions with cellular receptors, and the subsequent activation of signaling pathways leading to oxidative stress, inflammation, endothelial dysfunction, smooth muscle cell proliferation, extracellular matrix remodeling, and impaired angiogenesis. Moreover, we explore potential therapeutic strategies targeting AGEs and related pathways for CVD prevention and treatment in diabetic metabolic disorders. Finally, we address current challenges and future directions in the field, emphasizing the importance of understanding the molecular links between AGEs and vascular injury to improve patient outcomes.

Impacts of regular consumption of grapes on macular pigment accumulation in Singapore older adults: a randomized controlled trial

Background: Oxidative stress is a key risk factor for visual impairment and consuming dietary antioxidant-rich foods may help in managing visual impairments. However, a limited number of studies have investigated the effect of dietary antioxidant-rich food including grapes on eye health in older adults. Objectives: To assess the effects on macular pigment accumulation of regular consumption of grapes in Singapore older adults. Methods: This was a 16 week, double-blind, randomized, placebo-controlled trial. Thirty-four Singapore older adults were randomized into regularly consuming either 46 g day-1 of freeze-dried table grape powder (the intervention group) or the same amount of placebo powder (the control group). Macular pigment optical density (MPOD), skin carotenoid status, advanced glycation end product (AGEs) status and dietary lutein intake were assessed every 4 weeks, and plasma lutein concentration, total antioxidant capacity and total phenolic content were measured every 8 weeks. Results: A significant time effect (p = 0.007) was observed for MPOD, and this is largely attributed to the improvement in the MPOD for the intervention group, as a significant increase was observed only in this group (week 0: 0.56 ± 0.04 D.U.; week 16: 0.61 ± 0.04 D.U., p < 0.01). Additionally, a significant increase in plasma total antioxidant capacity (week 0: 0.26 ± 0.13 mM TEAC; week 16: 0.36 ± 0.20 mM TEAC, p < 0.01) and total phenolic content (week 0: 10.50 ± 0.44 mg L-1 GAE; week 16: 12.58 ± 0.55 mg L-1 GAE, p < 0.001) was observed for the intervention group only. In contrast, a significant increase in skin AGE status was observed in the control group (week 0: 2.47 ± 0.24; week 16: 2.99 ± 0.12, p < 0.05) while this was mitigated in the intervention group. There were no differences in dietary lutein intake, plasma lutein concentration and skin carotenoid status between groups throughout the study. Conclusions: Regular intake of grapes may improve eye health in Singapore older adults, specifically in augmenting MPOD, which can be explained by an increase in plasma total antioxidant capacity and phenolic content, and the downregulation of AGEs. This study was registered at clinicatrials.gov as NCT05064865.

Correlation between serum advanced glycation end products and dietary intake of advanced glycation end products estimated from home cooking and food frequency questionnaires

BACKGROUND & AIMS

To our knowledge the association between dietary advanced glycation end-products (dAGEs) and cardiometabolic disease is limited. Our aim was to examine the association between dAGEs and serum concentration of carboxymethyl-lysine (CML) or soluble receptor advanced glycation end-products (sRAGEs), and to assess the difference on dAGEs and circulating AGEs according to lifestyle and biochemical measures.

METHODS AND RESULTS

52 overweight or obese adults diagnosed with type 2 diabetes were included in this cross-sectional analysis. dAGEs were estimated from a Food Frequency Questionnaire (FFQ) or from a FFQ + Home Cooking Frequency Questionnaire (HCFQ). Serum concentrations of CML and sRAGEs were measured by ELISA. Correlation tests were used to analyze the association between dAGEs derived from the FFQ or FFQ + HCFQ and concentrations of CML or sRAGEs. Demographic characteristics, lifestyle factors and biochemical measures were analyzed according to sRAGEs and dAGEs using student t-test and ANCOVA. A significant inverse association was found between serum sRAGEs and dAGEs estimated using the FFQ + HCFQ (r = -0.36, p = 0.010), whereas no association was found for dAGEs derived from the FFQ alone. No association was observed between CML and dAGEs. dAGEs intake estimated from the FFQ + HCFQ was significantly higher among younger and male participants, and in those with higher BMI, higher Hb1Ac levels, longer time with type 2 diabetes, lower adherence to Mediterranean diet, and higher use of culinary techniques that generate more AGEs (all p values p < 0.05).

CONCLUSIONS

These results show knowledge on culinary techniques is relevant to derive the association between dAGEs intake and cardiometabolic risk factors.

Identification and quantification of protein nitration sites in human coronary artery smooth muscle cells in the absence and presence of peroxynitrous acid/peroxynitrite

Peroxynitrous acid/peroxynitrite (ONOOH/ONOO^-) is a powerful oxidizing/nitrating system formed at sites of inflammation, which can modify biological targets, and particularly proteins. Here, we show that multiple proteins from primary human coronary artery smooth muscle cells are nitrated, with LC-MS peptide mass mapping providing data on the sites and extents of changes on cellular and extracellular matrix (ECM) proteins. Evidence is presented for selective and specific nitrations at Tyr and Trp on 11 cellular proteins (out of 3668, including 205 ECM species) in the absence of added reagent ONOOH/ONOO^-, with this being consistent with low-level endogenous nitration. A number of these have key roles in cell signaling/sensing and protein turnover. With added ONOOH/ONOO^-, more proteins were modified (84 total; with 129 nitrated Tyr and 23 nitrated Trp, with multiple modifications on some proteins), with this occurring at the same and additional sites to endogenous modification. With low concentrations of ONOOH/ONOO^- (50 μM) nitration occurs on specific proteins at particular sites, and is not driven by protein or Tyr/Trp abundance, with modifications detected on some low abundance proteins. However, with higher ONOOH/ONOO^- concentrations (500 μM), modification is primarily driven by protein abundance. ECM species are major targets and over-represented in the pool of modified proteins, with fibronectin and thrombospondin-1 being particularly heavily modified (12 sites in each case). Both endogenous and exogenous nitration of cell- and ECM-derived species may have significant effects on cell and protein function, and potentially be involved in the development and exacerbation of diseases such as atherosclerosis.

LC-MS Profiling of Kakkonto and Identification of Ephedrine as a Key Component for Its Anti-Glycation Activity

A total of 147 oral Kampo prescriptions, which are used clinically in Japan, were evaluated for their anti-glycation activity. Kakkonto demonstrated significant anti-glycation activity, prompting further analysis of its chemical constituents using LC-MS, which revealed the presence of two alkaloids, fourteen flavonoids, two but-2-enolides, five monoterpenoids, and four triterpenoid glycosides. To identify the components responsible for its anti-glycation activity, the Kakkonto extract was reacted with glyceraldehyde (GA) or methylglyoxal (MGO) and analyzed using LC-MS. In LC-MS analysis of Kakkonto reacted with GA, the peak intensity of ephedrine was attenuated, and three products from ephedrine-scavenging GA were detected. Similarly, LC-MS analysis of Kakkonto reacted with MGO revealed two products from ephedrine reacting with MGO. These results indicated that ephedrine was responsible for the observed anti-glycation activity of Kakkonto. Ephedrae herba extract, which contains ephedrine, also showed strong anti-glycation activity, further supporting ephedrine's contribution to Kakkonto's reactive carbonyl species' scavenging ability and anti-glycation activity.

Skin Autofluorescence Mirrors Surrogate Parameters of Vascular Aging: An Enable Study

Advanced glycation end-products (AGEs) are implicated in vascular aging due to their pro-inflammatory properties. Skin autofluorescence (SAF) is a measure to estimate their deposition. It is an easily quantifiable marker that has been shown to correlate with cardiovascular risk and parameters of metabolic diseases. Herein, we compared skin autofluorescence with other techniques indicating increased cardiovascular diseases, namely, pulse wave velocity (PWVao) and intima–media thickness (IMT). We also studied the impacts of other parameters in deeply phenotyped cohorts of young, middle-aged, and older individuals. SAF, aortic PWVao, and IMT proved to be significantly correlated with each other and with age. However, based on a moderator analysis, we could not show that these associations were affected by age. Some specific parameters such as creatinine and CRP were found to be significantly associated with skin AGE values after adjusting for confounding variables. In conclusion, SAF is a simple screening tool for vascular health with comparable power to more elaborated technical tests.

Bone matrix quality in a developing high-fat diet mouse model is altered by RAGE deletion

Overweightness and obesity in adolescents are epidemics linked to chronic low-grade inflammation and elevated fracture risk. The increased fracture risk observed in overweight/obese adolescence contrasts the traditional concept that high body mass is protective against fracture, and thus highlights the need to determine why weight gain becomes detrimental to fracture during growth and maturity. The Receptor for Advanced Glycation End products (RAGE) is a central inflammatory regulator that can influence bone metabolism. It remains unknown how RAGE removal impacts skeletal fragility in overweightness/obesity, and whether increased fracture risk in adolescents could result from low-grade inflammation deteriorating bone quality. We characterized the multiscale structural, mechanical, and chemical properties of tibiae extracted from adolescent C57BL/6J (WT) and RAGE null (KO) mice fed either low-fat (LF) or high-fat (HF) diet for 12 weeks starting at 6 weeks of age using micro-computed tomography, strength, Raman spectroscopy, and nanoindentation. Overweight/obese WT HF mice possessed degraded mineral-crystal quality and increased matrix glycoxidation in the form of pentosidine and carboxymethyl-lysine, with HF diet in females only showing reduced cortical surface expansion and TMD independently of RAGE ablation. Furthermore, in contrast to males, HF diet in females led to more material damage and plastic deformation. RAGE KO mitigated glycoxidative matrix accumulation, preserved mineral quantity, and led to increased E/H ratio in females. Taken together, these results highlight the complex, multi-scale and sex-dependent relationships between bone quality and function under overweightness, and identifies RAGE-controlled glycoxidation as a target to potentially preserve matrix quality and mechanical integrity.

Accurate age estimation from blood samples of Han Chinese individuals using eight high-performance age-related CpG sites

Age-related CpG sites (AR-CpGs) are currently the most promising biomarkers for forensic age estimation. In our previous studies, we first validated the age correlation of seven reported AR-CpGs in blood samples of Chinese Han population. Subsequently, we screened some good age predictors from blood samples of Chinese Han population, and built pyrosequencing-based age prediction models. However, it is still important to select a set of high-performance AR-CpGs in a specific racial group and establish a simple and efficient method for accurate age estimation for forensic purpose. In this study, eight AR-CpGs, namely chr6: 11,044,628 (ELOVL2), cg06639320 (FHL2), chr1: 207,823,723 (C1orf132), cg19283806 (CCDC102B), cg14361627 (KLF14), cg17740900 (SYNE2), cg07553761 (TRIM59), and cg26947034, were selected based on our previous studies, and a multiplex methylation SNaPshot assay was developed to investigate DNA methylation levels at these AR-CpGs in 529 blood samples (aged 2-82 years) from Han Chinese population. All selected CpG sites showed strong age correlation with the correlation coefficient (r) from 0.8363 to 0.9251. Multiple linear regression (MLR) and support vector regression (SVR) age prediction models were simultaneously established to fit change characteristics of DNA methylation levels of eight AR-CpGs with the age in 374 donors' blood samples. The MLR model enabled age prediction with R² = 0.923, mean absolute error (MAE) = 3.52, while the SVR model enabled age prediction with R² = 0.935, MAE = 2.88. One hundred fifty-five independent samples were used as a validation set to test the two models' performance, and the prediction MAE for the validation set was 3.71 and 3.34 for the MLR and SVR models, respectively. For the MLR and SVR models, the correct prediction rate at ± 5 years reached a high level of 79.35% and 83.23%, respectively. In general, these statistical parameters indicated that the SVR model outperformed the MLR model in age prediction of the Han Chinese population. In addition, our method provides sufficient sensitivity in forensic applications and allows for 100% efficiency when examining bloodstains kept in room conditions for up to 43 days. These results indicate that our multiplex methylation SNaPshot assay is a reliable, effective, and accurate method for age prediction in blood samples from the Chinese Han population.

Pharmacological evaluation of bromelain in mouse model of Alzheimer's disease

The current study elucidates pharmacological evaluation of bromelain as a bioactive compound obtain from pineapple stem belongs to family Bromeliaceae in AlCl3 and D - galactose induced mice. In mice, co-administration of AlCl3 at dose 5 mg/kg b.w., via the oral route, and D - galactose at dose 60 mg/kg b.w., via intraperitoneal route for 90 days resulted in cognitive impairment, spatial learning, and memory deficits, as well as neurotoxicity. However, 30 consecutive days, treatments via an intraperitoneal route with bromelain low dose (Brm L) at dose 10 mg/kg b.w., bromelain high dose (Brm H) at dose 20 mg/kg b.w., donepezil (Dnpz) at dose 2 mg/kg b.w., and Brm L + Dnpz at doses 10, 2 mg/kg b.w. were considerably reversed the effect of AlCl3 and D - galactose induced AD mice. Consequences of behavioral parameters (Morris water maze, elevated plus maze and locomotor), biochemical estimation (MDA, GSH, SOD, CAT, Nitrite and AChE), and ELISA tests (mouse BACE, Aβ1 - 42, TNF-α, IL-6, and BDNF) confirmed significant (p < 0.05) neuroprotective effect of treatments in AlCl3 and D - galactose induced mice. Additionally, hematoxylin and eosin staining of the cerebral cortex and the hippocampus exposed eosinophilic lesions and hyperchromatic nuclei in AD mice, but these neurodegenerative effects were eliminated by Brm L, Brm H, Dnpz, and Brm L + Dnpz treatments. Thus, bromelain alone and in combination with donepezil prevent AlCl3 and D - galactose induced spatial learning and memory deficits, as well as cognitive impairment, by increasing cholinergic activity and synaptic plasticity, as well as reducing oxidative damage, neuroinflammation, Aβ 1-42 aggregations, and histopathological damage, according to our findings. The present study consequences indicate that bromelain alone and in combination with donepezil appears to have neuroprotective properties. Henceforward, this may be a promising treatment option for Alzheimer's disease.

Differences in advanced glycation endproducts (AGEs) in plasma from birds and mammals of different body sizes and ages

Birds and mammals provide a physiological paradox: similar-sized mammals live shorter lives than birds; yet, birds have higher blood glucose concentrations than mammals, and higher basal metabolic rates. We have previously shown that oxidative stress patterns between mammals and birds differ, so that birds, generally, have lower blood antioxidant capacity, and lower lipid peroxidation concentration. There is a close association between oxidative stress and the production of carbohydrate-based damaged biomolecules, Advanced Glycation End-products (AGEs). In mammals, AGEs can bind to their receptor (RAGE), which can lead to increases in reactive oxygen species (ROS) production, and can decrease antioxidant capacity. Here, we used plasma from birds and mammals to address whether blood plasma AGE-BSA concentration is associated with body mass and age in these two groups. We found a statistically significantly higher average concentrations of AGE-BSA in birds compared with mammals, and we found a significantly positive correlation between AGE-BSA and age in mammals, though, this correlation disappeared after phylogenetic correction. We propose that the higher AGE concentration in birds is mainly attributable to greater AGE-production due to elevated basal glucose concentrations and decreased AGE-clearance given differences in glomerular filtration rates in birds compared with mammals. Additionally, due to the potential lack of an AGE receptor in birds, AGE accumulation may not be closely linked to oxidative stress and therefore pose a lesser physiological challenge in birds compared to mammals.

Human Sensory Neuron-like Cells and Glycated Collagen Matrix as a Model for the Screening of Analgesic Compounds

Increased collagen-derived advanced glycation end-products (AGEs) are consistently related to painful diseases, including osteoarthritis, diabetic neuropathy, and neurodegenerative disorders. We have recently developed a model combining a two-dimensional glycated extracellular matrix (ECM-GC) and primary dorsal root ganglion (DRG) that mimicked a pro-nociceptive microenvironment. However, culturing primary cells is still a challenge for large-scale screening studies. Here, we characterized a new model using ECM-GC as a stimulus for human sensory-like neurons differentiated from SH-SY5Y cell lines to screen for analgesic compounds. First, we confirmed that the differentiation process induces the expression of neuron markers (MAP2, RBFOX3 (NeuN), and TUBB3 (β-III tubulin), as well as sensory neuron markers critical for pain sensation (TRPV1, SCN9A (Nav1.7), SCN10A (Nav1.8), and SCN11A (Nav1.9). Next, we showed that ECM-GC increased c-Fos expression in human sensory-like neurons, which is suggestive of neuronal activation. In addition, ECM-GC upregulated the expression of critical genes involved in pain, including SCN9A and TACR1. Of interest, ECM-GC induced substance P release, a neuropeptide widely involved in neuroinflammation and pain. Finally, morphine, the prototype opiate, decreased ECM-GC-induced substance P release. Together, our results suggest that we established a functional model that can be useful as a platform for screening candidates for the management of painful conditions.

Inhibitory Effects of Astaxanthin on CML-HSA-Induced Inflammatory and RANKL-Induced Osteoclastogenic Gene Expression in RAW 264.7 Cells

Objective: Elevated levels of serum N^ε-carboxymethyllysine (CML), a well-known advanced glycation end-product (AGE), were observed in patients with inflammation or osteoporosis. Astaxanthin was reported to possess anti-inflammatory and antioxidant effects. In the present study, we investigated the effects of commercially available dietary supplement AstaReal ACT^R (ASR) capsule content as astaxanthin on CML-HSA-induced inflammatory and receptor activator of nuclear factor-kappa-Β ligand (RANKL)-induced osteoclastogenic gene expression. Methods: RAW 264.7 murine macrophage cells were stimulated with CML-HSA to trigger inflammatory gene expression and treated with either a vehicle control or varied concentrations of astaxanthin. Inflammatory gene expression was measured using an enzyme-linked immunosorbent assay (ELISA) or qPCR. We triggered osteoclastogenesis using RANKL, and osteoclastogenic gene expression was measured through tartrate-resistant acid phosphatase (TRAP) activity, staining, immunofluorescence, and qPCR analyses. Results: CML-HSA showed a stimulatory effect on inflammatory gene expression, and astaxanthin reduced the expression by at least two-fold. The levels of autoinflammatory gene expression were reduced by astaxanthin. The RANKL-induced osteoclastogenesis was significantly inhibited by astaxanthin, with reductions in the activation of nuclear factor-κB (NF-κB), the expression of NFATc1 (nuclear factor of activated T cells 1), multinucleated cell formation, and the expression of mature osteoclast marker genes. Conclusion: Astaxanthin has potential as a remedy for CML-HSA-induced inflammation and RANKL-induced excessive bone loss.

Reversible processes in collagen dehydration: A molecular dynamics study

Collagen dehydration is an unavoidable damaging process that causes the lack of fibers' physical properties and it is usually irreversible. However, the identification of low hydration conditions that permit a recovering of initial collagen features after a rehydration treatment is particularly of interest. Monitoring structural changes by means of MD simulations, we investigated the hydration-dehydration-rehydration cycle of two microfibril models built on different fragments of the sequence of rat tail collagen type I. The microfibrils have different hydropathic features, to investigate the influence of amino acid composition on the whole process. We showed that with low hydration at a level corresponding to the first shell, microfibril gains in compactness and tubularity. Crucially, some water molecules remain trapped inside the fibrils, allowing, by rehydrating, a recovery of the initial collagen structural features. Water rearranges in cluster around the protein, and its first layer is more anchored to the surface. However, these changes in distribution and mobility in low hydration conditions get back with rehydration.

Role of Advanced Glycation End-Products and Other Ligands for AGE Receptors in Thyroid Cancer Progression

To date, thyroid cancers (TCs) remain a clinical challenge owing to their heterogeneous nature. The etiopathology of TCs is associated not only with genetic mutations or chromosomal rearrangements, but also non-genetic factors, such as oxidative-, nitrosative-, and carbonyl stress-related alterations in tumor environment. These factors, through leading to the activation of intracellular signaling pathways, induce tumor tissue proliferation. Interestingly, the incidence of TCs is often coexistent with various simultaneous mutations. Advanced glycation end-products (AGEs), their precursors and receptors (RAGEs), and other ligands for RAGEs are reported to have significant influence on carcinogenesis and TCs progression, inducing gene mutations, disturbances in histone methylation, and disorders in important carcinogenesis-related pathways, such as PI₃K/AKT/NF-kB, p21/MEK/MPAK, or JAK/STAT, RAS/ERK/p53, which induce synthesis of interleukins, growth factors, and cytokines, thus influencing metastasis, angiogenesis, and cancer proliferation. Precursors of AGE (such as methylglyoxal (MG)) and selected ligands for RAGEs: AS1004, AS1008, and HMGB1 may, in the future, become potential targets for TCs treatment, as low MG concentration is associated with less aggressive anaplastic thyroid cancer, whereas the administration of anti-RAGE antibodies inhibits the progression of papillary thyroid cancer and anaplastic thyroid cancer. This review is aimed at collecting the information on the role of compounds, engaged in glycation process, in the pathogenesis of TCs. Moreover, the utility of these compounds in the diagnosis and treatment of TCs is thoroughly discussed. Understanding the mechanism of action of these compounds on TCs pathogenesis and progression may potentially be the grounds for the development of new treatment strategies, aiming at quality-of-life improvements.

Protective Effects of Crocin Against Hepatic Damages in D-galactose Aging Model in Rats

Aging is a progressive process which is associated with liver dysfunction and it is due to oxidative stress, inflammation, and cell apoptosis. Long-term D-galactose (D-gal) administration is able to develop an aging model in animals. Crocin as a major active ingredient in saffron has shown anti-inflammatory and hepatoprotective effects via its antioxidant capacity. Thus, the aim of the present study was the assessment of crocin effects on hepatic and metabolic disorders induced by D-gal in rats. Aging model was induced in rats by 56-day administration of D-gal (400 mg/kg/day subcutaneously). Protective effects of different doses of crocin (7.5, 15 and 30 mg/kg/day) in concomitant with D-gal administration were evaluated. Malondialdehyde (MDA) and reduced glutathione (GSH) amounts were measured by means of their reaction, respectively, with thiobarbituric acid and 5,5'-Dithiobis (2-nitrobenzoic acid) (DTNB) under a specific condition. Cyclooxygenase-2 (COX-2), β-galactosidase, induced nitric oxide synthase (iNOS), and carboxymethyllysine (CML) levels were determined by western blotting method. Additionally, the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were measured in serum. D-gal administration significantly elevated ALT, AST, ALP levels, which were markedly inhibited by crocin administration. Crocin suppressed the overgeneration of lipid peroxidation products such as MDA. iNOS was elevated by D-gal administration and was returned to the normal extent by crocin. Therefore, Crocin as a powerful antioxidant and radical scavenger, totally exhibited hepatoprotective effects against D-gal-induced toxicity in rats.

Effects of High Intakes of Fructose and Galactose, with or without Added Fructooligosaccharides, on Metabolic Factors, Inflammation, and Gut Integrity in a Rat Model

SCOPE

A high fructose and galactose intake show adverse metabolic effects in animal models and in humans, but it is yet unknown if addition of fermentable dietary fiber can mitigate such effects. This study investigate the effects of high intakes of fructose and galactose, with/without added fructooligosaccharides (FOS), on metabolic factors, inflammation, and gut integrity markers in rats.

METHODS AND RESULTS

Rats (n = 6/group) receive different carbohydrates at isocaloric conditions for 12 weeks as follows: 1) starch (control), 2) fructose, 3) galactose, 4) starch + FOS (FOS control), 5) fructose + FOS, and 6) galactose + FOS, together with a high amount of n-6 polyunsaturated fatty acids (n-6 PUFA) in all diets except for in 7) starch + olive oil (negative control). The rats fed the galactose and galactose + FOS diets exhibit lower body weight than other groups. High-galactose diets has more pronounced effects on metabolic factors and gut permeability than high-fructose diets. High-fructose diets show less pronounced effect on these selected markers. No differences in inflammatory markers are detected for any of the diets.

CONCLUSIONS

The results suggest potential adverse effects of high galactose and fructose on metabolic factors and gut integrity markers, but not on inflammation. However, several mechanisms are at play, and general net effects are difficult to determine conclusively for the conditions tested.

Cross your heart? Collagen cross-links in cardiac health and disease

Extracellular matrix (ECM) remodeling occurs in response to various cardiac insults including infarction, pressure overload and dilated myopathies. Each type of remodeling necessitates distinct types of ECM turnover and deposition yet an increase in myocardial fibrillar collagen content is appreciated as a contributing feature to cardiac dysfunction in each of these pathologies. In addition, aging, is also associated with increases in cardiac collagen content. The importance of characterizing differences in ECM composition and processes used by cardiac fibroblasts in the assembly of fibrotic collagen accumulation is critical for the design of strategies to reduce and ultimately regress cardiac fibrosis. Collagen cross-linking is one factor that influences collagen deposition and insolubility with direct implications for tissue properties such as stiffness. In this review, three different types of collagen cross-links shown to be important in cardiac fibrosis will be discussed; those catalyzed by lysyl oxidases, those catalyzed by transglutaminases, and those that result from non-enzymatic modification by the addition of advanced glycation end products. Insight into cellular mechanisms that govern collagen cross-linking in the myocardium will provide novel pathways for exploring new treatments to treat diseases associated with cardiac fibrosis.

Sickle Cell Disease: Role of Oxidative Stress and Antioxidant Therapy

Sickle cell disease (SCD) is the most common hereditary disorder of hemoglobin (Hb), which affects approximately a million people worldwide. It is characterized by a single nucleotide substitution in the β-globin gene, leading to the production of abnormal sickle hemoglobin (HbS) with multi-system consequences. HbS polymerization is the primary event in SCD. Repeated polymerization and depolymerization of Hb causes oxidative stress that plays a key role in the pathophysiology of hemolysis, vessel occlusion and the following organ damage in sickle cell patients. For this reason, reactive oxidizing species and the (end)-products of their oxidative reactions have been proposed as markers of both tissue pro-oxidant status and disease severity. Although more studies are needed to clarify their role, antioxidant agents have been shown to be effective in reducing pathological consequences of the disease by preventing oxidative damage in SCD, i.e., by decreasing the oxidant formation or repairing the induced damage. An improved understanding of oxidative stress will lead to targeted antioxidant therapies that should prevent or delay the development of organ complications in this patient population.

Oxytocin promotes hepatic regeneration in elderly mice

Liver aging impairs the ability of hepatocyte regeneration. Recent studies have found that oxytocin (OT) plays an important role in promoting tissue repair and maintaining differentiation and regeneration of stem cells. Here, we reported that OT receptors, which are specifically located in hepatocytes, decrease with aging in human and mice. Interestingly, the level of serum OT also decline with age. Notably, OT promotes hepatocyte regeneration only in aged mice but not in young mice in vitro and in vivo. Further studies reveal that OT promotes autophagy in either AML12 mouse hepatocytes or aged mice after partial hepatectomy or with CCl4-induced acute liver injury. In conclusion, OT promotes liver regeneration, especially in aged mice, which may be achieved by promoting autophagy. All these results support the possibility of OT and its analog being a potent anti-aging drug and promote liver rejuvenation.

Plasma Concentration of Advanced Glycation End-Products From Wild Canids and Domestic Dogs Does Not Change With Age or Across Body Masses

Dogs provide a physiological paradox: In domestic dogs, small breeds live longer lives than large breed dogs. Comparatively, a wild canid can be a similar size than many large breed dogs and outlive their domestic cousin. We have previously shown that oxidative stress patterns between domestic and wild canids differ, so that wild canids invest in a robust antioxidant system across their lives; whereas domestic dogs tend to accumulate lipid damage with age. There is a close association between oxidative stress and the production of a carbohydrate based-damage, Advanced Glycation End-products (AGEs). AGEs can bind to their receptor (RAGE), which can lead to increases in reactive oxygen species (ROS) production, and decreases in antioxidant capacity. Here, I used plasma from wild and domestic canids to address whether blood plasma AGE-BSA concentration associated with body mass and age in domestic dogs; And whether AGE-BSA concentration patterns in blood plasma from wild canids are similar to those found in domestic dogs. I found no correlation between circulating AGE-BSA concentration and body size or age in either domestic dogs and wild canids. These data suggest that AGEs formation may be a conserved trait across the evolution of domesticated dogs from wild ancestors, in opposition to oxidative stress patterns between these two groups. And, that, in domestic dogs, lipid metabolism, rather than carbohydrate metabolism, may be upregulated to yield the previously found differences in circulating lipid damage across lifespan and body sizes.

MicroRNA-Mediated Gene Regulatory Mechanisms in Mammalian Female Reproductive Health

Mammalian reproductive health affects the entire reproductive cycle starting with the ovarian function through implantation and fetal growth. Various environmental and physiological factors contribute to disturbed reproductive health status leading to infertility problems in mammalian species. In the last couple of decades a significant number of studies have been conducted to investigate the transcriptome of reproductive tissues and organs in relation to the various reproductive health issues including endometritis, polycystic ovarian syndrome (PCOS), intrauterine growth restriction (IUGR), preeclampsia, and various age-associated reproductive disorders. Among others, the post-transcriptional regulation of genes by small noncoding miRNAs contributes to the observed transcriptome dysregulation associated with reproductive pathophysiological conditions. MicroRNAs as a class of non-coding RNAs are also known to be involved in various pathophysiological conditions either in cellular cytoplasm or they can be released to the extracellular fluid via membrane-bounded extracellular vesicles and proteins. The present review summarizes the cellular and extracellular miRNAs and their association with the etiology of major reproductive pathologies including PCOS, endometritis, IUGR and age-associated disorders in various mammalian species.

2,5-diketopiperazines mitigate the amount of advanced glycation end products accumulated with age in human dermal fibroblasts

OBJECTIVE

Glycation is a common non-enzymatic reaction between proteins and sugars, resulting in the formation of advanced glycation end products (AGEs) in the human body. As can be seen in diabetic patients, the accumulation of AGEs in the skin has aesthetic consequences (wrinkles, brown spots and yellowish complexion). Therefore, the objective of this work was to find compounds isolated from natural sources that could eliminate the final AGEs accumulated in the skin with ageing.

METHODS AND RESULTS

A preliminary screening performed on a bank of microbial extracts and pure compounds showed that 2,5-Diketopiperazines (DKPs), as well as the extract of Sphingobacterium sp (SNB-CN13), reduced the presence of AGEs in fibroblasts by -28% and -23%, respectively. In this article, we present the dereplication approach used to reveal the presence of 26 different DKPs in the crude extract of Sphingobacterium sp. Bioguided fractionation has led to the isolation of 12 of them, whose identity has been confirmed by HRMS and NMR. A green synthesis approach has been developed to synthesize 3 symmetrical DKPs. The biological activity of all DKPs was evaluated by the development of an in vitro test using immunocytochemistry to reveal the presence of AGE carboxymethyl-lysine in human dermal fibroblasts.

CONCLUSION

Our work shows for the first time that DKPs decrease the amount of carboxymethyl-lysine AGE in elderly human dermal fibroblasts grown in vitro. Therefore, diketopiperazines can be considered as compounds of interest for dermatological and cosmetic applications with an anti-ageing aim.

Glycation and Oxidative Stress Increase Autoantibodies in the Elderly

Aging causes gradual changes in free radicals, antioxidants, and immune-imbalance in the elderly. This study aims to understand links among aging, gluco-oxidative stress, and autoantibodies in asymptomatic individuals. In vitro glycation of human serum albumin (Gly-HSA) induces appreciable biochemical changes. Significant inhibition of advanced glycation end products (AGEs) formation was achieved using garlic extract (53.75%) and epigallocatechin-3-gallate from green tea (72.5%). Increased amounts of serum carbonyl content (2.42 ± 0.5) and pentosidine (0.0321 ± 0.0029) were detected in IV-S (S represent smokers) vs. IV group individuals. Direct binding ELISA results exhibited significantly high autoantibodies against Gly-HSA in group IV-S (0.55 ± 0.054; p < 0.001) and III-S (0.40 ± 0.044; p < 0.01) individuals as compared to the age matched subjects who were non-smokers (group IV and III). Moreover, high average percent inhibition (51.3 ± 4.1%) was obtained against Gly-HSA in IV-S group individuals. Apparent association constant was found to be high for serum immunoglobulin-G (IgG) from group IV-S (1.18 × 10⁻⁶ M) vs. serum IgG from IV group (3.32 × 10⁻⁷ M). Aging induced gluco-oxidative stress and AGEs formation may generate neo-epitopes on blood-proteins, contributing to production of autoantibodies in the elderly, especially smokers. Use of anti-glycation natural products may reduce age-related pathophysiological changes.

Oxidative stress in the retina and retinal pigment epithelium (RPE): Role of aging, and DJ-1

High levels of oxidative radicals generated by daily light exposure and high metabolic rate suggest that the antioxidant machinery of the retina and retinal pigment epithelium (RPE) is crucial for their survival. DJ-1 is a redox-sensitive protein that has been shown to have neuroprotective function in the brain in Parkinson's disease and other neurodegenerative diseases. Here, we analyzed the role of DJ-1 in the retina during oxidative stress and aging. We induced low-level oxidative stress in young (3-month-old) and old (15-month-old) C57BL/6J (WT) and DJ-1 knockout (KO) mice and evaluated effects in the RPE and retina. Absence of DJ-1 resulted in increased retinal dysfunction in response to low levels of oxidative stress. Our findings suggest that loss of DJ-1 affects the RPE antioxidant machinery, rendering it unable to combat and neutralize low-level oxidative stress, irrespective of age. Moreover, they draw a parallel to the retinal degeneration observed in AMD, where the occurrence of genetic variants may leave the retina and RPE unable to fight sustained, low-levels of oxidative stress.

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Antioxidants are upregulated in young DJ-1 KO RPE but downregulated in the retina.

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DJ-1 KO retinas are degenerated under low-level oxidative stress, regardless of age.

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Retinas of both young C57BL and DJ-1 KO were able to regulate antioxidant genes upon low-level oxidative stress.

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Retinas of both aged C57BL and DJ-1 KO were unable to regulate antioxidant genes upon low-level oxidative stress.

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RPE of aged C57BLl mice upregulated some antioxidant genes.

A Putative Prohibitin-Calcium Nexus in β-Cell Mitochondria and Diabetes

The role of mitochondria in apoptosis is well known; however, the mechanisms linking mitochondria to the proapoptotic effects of proinflammatory cytokines, hyperglycemia, and glucolipotoxicity are not completely understood. Complex Ca²⁺ signaling has emerged as a critical contributor to these proapoptotic effects and has gained significant attention in regulating the signaling processes of mitochondria. In pancreatic β-cells, Ca²⁺ plays an active role in β-cell function and survival. Prohibitin (PHB), a mitochondrial chaperone, is actively involved in maintaining the architecture of mitochondria. However, its possible interaction with Ca²⁺-activated signaling pathways has not been explored. The present review aims to examine potential crosstalk between Ca²⁺ signaling and PHB function in pancreatic β-cells. Moreover, this review will focus on the effects of cytokines and glucolipotoxicity on Ca²⁺ signaling and its possible interaction with PHB. Improved understanding of this important mitochondrial protein may aid in the design of more targeted drugs to identify specific pathways involved with stress-induced dysfunction in the β-cell.

Remodeling of the Basal Labyrinth of Retinal Pigment Epithelial Cells With Osmotic Challenge, Age, and Disease

Purpose

The basal surface of the retinal pigment epithelium (RPE) is folded into a complex basal labyrinth thought to facilitate solute and water transport. We aimed to analyze and define the structural organization of the basal labyrinth of the RPE to enable quantitative analysis of structural changes in age and disease and to better understand the relationship between basal labyrinth structure and efficiency of transepithelial transport.

Methods

Conventional transmission and serial block-face scanning electron microscopy and electron tomography were used to examine the structure of the basal labyrinth in mouse eyes of different ages and genotypes and with and without osmotic shock before fixation.

Results

We identified structurally distinct zones (stacked and ribbon-like) within the RPE basal labyrinth that are largely organelle free and cisternal elements that make contact with the endoplasmic reticulum (ER) and mitochondria. These zones are lost in a hierarchic fashion with age and prematurely in a model of the progressive retinal degenerative disease, choroideremia. Junctional complexes crosslink closely opposed infoldings. Spacing between the basal infoldings was affected by subtle osmotic changes while osmotic shock induced dramatic remodeling of the infoldings.

Conclusions

The basal labyrinth has complex but ordered structural elements that break down with age and in choroideremia. The geometry of these elements and site of contact with ER and mitochondria likely facilitate the ion transport that drives water transport across the basal RPE surface. Changes in structure in response to local osmotic variation may allow transport to be modulated in order to maintain RPE volume.

Clinical/Translational Aspects of Advanced Glycation End-Products

Advanced glycation end-products (AGEs) have been implicated in chronic hyperglycemia and age-related diseases. Endogenous AGEs produced by humans generate oxidative stress and activation of inflammatory signaling pathways via AGE-specific receptors. The present review summarizes current knowledge on the pathogenic role of AGEs in chronic noncommunicable diseases. Although correlations exist between glycation and the pathogenesis of these diseases, uncertainties remain in light of recurrent intervention failures of apparently promising animal models to be translated into clinically useful anti-AGE strategies. Future intervention of AGEs or their receptors should embrace more carefully executed clinical trials. Nevertheless, suppressing symptoms via lifetime drug application is unlikely to eliminate the burden of chronic diseases unless deep-rooted lifestyle issues that cause these diseases are simultaneously addressed.

Effect of N(Epsilon)-(carboxymethyl)lysine on Laboratory Parameters and Its Association with β S Haplotype in Children with Sickle Cell Anemia

The present study aimed to investigate the association of N^ε-carboxymethyllysine (CML) with laboratory parameters and β^S haplotypes in pediatric sickle cell anemia (SCA) patients with or without hydroxyurea (HU) therapy. We included 55 children with SCA (SCA_total), where 27 were on HU treatment (SCA-HU⁺) and 28 without HU treatment (SCA-HU⁻). Laboratory characteristics were determined using electronic methods while CML was measured using competitive ELISA. β^S haplotypes were determined by RFLP-PCR. Significant increases in MCV and MCH and significant decreases in leukocytes, eosinophils, basophils, atypical lymphocytes, lymphocytes, and monocytes were found in SCA-HU⁺ compared to SCA-HU⁻. SCA-HU⁺ presented significant reduction in aspartate transaminase and lactate dehydrogenase and increase in creatinine levels compared to SCA-HU⁻. CML levels were significantly higher in both SCA-HU⁺ and SCA-HU⁻ compared to the healthy control. In addition, a negative correlation was found between CML and alanine transaminase in SCA-HU⁺ and SCA_total (p < 0.01). A significant association was found between CML levels and β^S haplotypes. The results suggest that CML has a role to play in SCA complications, independent of HU therapy.

Flavonoids from Polyalthia longifolia prevents advanced glycation end products formation and protein oxidation aligned with fructose-induced protein glycation

Advanced glycation end products (AGEs) are reactive chemical entities formed by non-enzymatic reaction between reducing sugars and amino group of proteins. Enhanced accumulation of AGEs and associated protein oxidation contribute to pathogenesis of diabetes-associated complications. Here, we evaluated the inhibitory activity of flavonoid compounds isolated from the leaves of Polyalthia longifolia on formation of AGEs and protein oxidation. Antiglycation activity was determined by measuring the formation of AGE fluorescence intensity, Nε-(carboxymethyl) lysine, and level of fructosamine. Protein oxidation was examined using levels of protein carbonyls and thiol group. Compounds significantly (p < 0.001) restricted the formation of fluorescent AGEs in fructose- BSA and methylglyoxal-BSA systems. Furthermore, there was a decrease in levels of fructosamine and protein carbonyls, and elevation in level of thiol group in fructose-BSA in presence of flavonoids. In summary, flavonoids from Polyalthia longifolia inhibit fructose-mediated protein glycation and oxidation, and can be potential agent for preventing AGE-mediated diabetic complications.

Effects of sulforaphane on D-galactose-induced liver aging in rats: Role of keap-1/nrf-2 pathway

Aging; a biological phenomenon characterized by progressive decline in cellular functions, is considered as a major risk factor of various liver diseases that plays as an adverse prognostic role, thus increasing mortality rate. However, diet is the main environmental factor that has a major impact on the aging process whereas; sulforaphane (SFN), an isothiocyanate organosulfur compound in cruciferous vegetables, has been reported with myriad biological effects. In the present study, SFN antiaging properties were evaluated on D-galactose (D-Gal)-induced liver aging in rats. For this purpose, forty adult male Wistar rats were divided into five groups. All animals, except the normal control, were intraperitoneally injected with D-Gal (300 mg/kg/day for 5 days a week) for six consecutive weeks. In the hepatoprotective groups, animals received oral SFN (0.5, 1.0 and 2.0 mg/kg) for 6 weeks concurrently with D-GAL. SFN administration improved liver biomarkers through decreasing serum levels of AST, ALT, total and direct bilirubin when compared to D-Gal-aging group. SFN significantly increased hepatic GSH level as well as catalase and glutathione-S-transferase activities while counteracted the elevation in hepatic oxidative stress markers; MDA, NO and protein carbonyl in aged rats. SFN abrogated the dysregulation in hepatic Keap-1, Nrf-2 and HO-1and limited the elevation of TNF-α and TGF-β concentrations in aging liver. Histopathologically, SFN decreased the intensity of hepatic fibrous proliferation in D-Gal-induced aging. In conclusion, SFN has shown hepatic anti-aging potential through promoting the antioxidant machinery via regulating Keap-1, Nrf-2 and HO-1 and antioxidant enzyme activities as well as ameliorating oxidative stress, hampering the inflammatory cytokines; TNF-ɑ and TGF-β, and limiting hepatic fibrosis in a dose dependent manner.

GlyStruct: glycation prediction using structural properties of amino acid residues

Background

Glycation is a one of the post-translational modifications (PTM) where sugar molecules and residues in protein sequences are covalently bonded. It has become one of the clinically important PTM in recent times attributed to many chronic and age related complications. Being a non-enzymatic reaction, it is a great challenge when it comes to its prediction due to the lack of significant bias in the sequence motifs.

Results

We developed a classifier, GlyStruct based on support vector machine, to predict glycated and non-glycated lysine residues using structural properties of amino acid residues. The features used were secondary structure, accessible surface area and the local backbone torsion angles. For this work, a benchmark dataset was extracted containing 235 glycated and 303 non-glycated lysine residues. GlyStruct demonstrated improved performance of approximately 10% in comparison to benchmark method of Gly-PseAAC. The performance for GlyStruct on the metrics, sensitivity, specificity, accuracy and Mathew’s correlation coefficient were 0.7013, 0.7989, 0.7562, and 0.5065, respectively for 10-fold cross-validation.

Conclusion

Glycation has emerged to be one of the clinically important PTM of proteins in recent times. Therefore, the development of computational tools become necessary to predict glycation, which could help medical professionals administer drugs and manage patients more effectively. The proposed predictor manages to classify glycated and non-glycated lysine residues with promising results consistently on various cross-validation schemes and outperforms other state of the art methods.

Electronic supplementary material

The online version of this article (10.1186/s12859-018-2547-x) contains supplementary material, which is available to authorized users.

Protective effects of Aporosa octandra bark extract against D-galactose induced cognitive impairment and oxidative stress in mice

Aporosa octandra (Buch.-Ham. ex D.Don) Vickery is a native species of India. Different parts of the plant are used for the medicinal purpose by the tribal peoples of south-eastern part of India. However, the biological properties of A. octandra have not been studied well. The extracts obtained from the bark of A. octandra were evaluated to determine their protective effect on cognitive impairment and oxidative stress in mice induced by D-galactose using the standard protocol. Different dosages of extract AOE-4 (100, 200, and 300 mg/kg, p.o.) were administered to mice, which were previously treated for six weeks with D-galactose (100 mg/kg s.c.). The D-galactose-induced mice showed significantly impaired cognitive behavior, i.e., oxidative defense, compared to the sham group. Six weeks of treatment with A. octandra extract AOE-4 (100, 200 and 300 mg/kg, p.o.) considerably improved the cognitive behavior and oxidative impairment of mice compared to the control alone (D-galactose). For the phytochemical investigation, the bark of A. octandra was successively extracted with dichloromethane and methanol. The chemical constituents of A. octandra were isolated by multiple column chromatography and characterized by different spectral analyses. (R)-Coclaurine (AO-5), an alkaloid, was isolated along with two other compounds from the AOE-4 extract; three more compounds were also isolated from the AOE-1 extract of the bark of A. octandra. All the compounds were isolated for the first time from the bark of A. octandra, and their structures were established by detailed spectral studies. The structure of compound AO-5 was also investigated and confirmed by X-ray diffraction and DFT studies. This study highlights the protective effect of A. octandra bark extract against D-galactose-induced biochemically dysfunction in mice. (R)-Coclaurine (AO-5) was isolated as one of the major components of A. octandra bark from AOE-4 extract; this compound could be further evaluated for the development of new potential drug candidates.

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

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

The Role of Advanced Glycation End Products in Aging and Metabolic Diseases: Bridging Association and Causality

Accumulation of advanced glycation end products (AGEs) on nucleotides, lipids, and peptides/proteins are an inevitable component of the aging process in all eukaryotic organisms, including humans. To date, a substantial body of evidence shows that AGEs and their functionally compromised adducts are linked to and perhaps responsible for changes seen during aging and for the development of many age-related morbidities. However, much remains to be learned about the biology of AGE formation, causal nature of these associations, and whether new interventions might be developed that will prevent or reduce the negative impact of AGEs-related damage. To facilitate achieving these latter ends, we show how invertebrate models, notably Drosophila melanogaster and Caenorhabditis elegans, can be used to explore AGE-related pathways in depth and to identify and assess drugs that will mitigate against the detrimental effects of AGE-adduct development.

Calf melanin immunomodulates RPE cell attachment to extracellular matrix protein

PURPOSE

It is widely accepted that RPE melanin has a protective effect against oxidative damage in RPE cells. It is possible that an additional protective characteristic of melanin is the ability to modulate RPE cell immune response. In this study, in vitro modeling was used to probe the relationship between RPE pigmentation and immune response by monitoring IL-6 expression and secretion in calf melanin pigmented ARPE-19 cells seeded onto glycated extracellular matrix as a stressor.

METHODS

ARPE-19 cells were left unpigmented or were pigmented with either calf melanin or latex beads, and were then seeded onto RPE-derived extracellular matrix (ECM) or tissue culture-treated plates (no ECM). ECMs were modified by glycation. IL-6 expression was measured using qPCR and IL-6 secretion was determined using an ELISA, both at 30 min and 24 h after seeding. MTT assay was used to quantify cell attachment to glycated matrices 30 min after seeding. In unpigmented ARPE-19 cells, rate of cell attachment to substrate was monitored for 60 min after seeding using a hemacytometer to count unattached cells. Additionally, cell viability was evaluated using the Neutral Red assay 24 h after seeding.

RESULTS

A significant increase in IL-6 expression was observed in calf melanin pigmented cells versus latex bead and unpigmented controls (p < 0.0001) 30 min after seeding onto ECM. Twenty-four hours after seeding, a significant decrease in IL-6 expression was observed in calf melanin pigmented cells (p < 0.0001) versus controls, implicating down-regulation of the cytokine. Additionally, calf melanin pigmented cell populations showed significant increase in attachment compared to unpigmented controls on either no ECM or unmodified ECM.

CONCLUSIONS

Pigmentation of RPE cells with calf melanin resulted in significant changes in IL-6 expression regardless of ECM modification, in vitro. These findings suggest that melanin in the RPE may participate in immune response modulation in the retina with particular regard to cell attachment to protein substrates. The results of this study further implicate the role of chemical changes to melanin in regulating inflammation in retinal disease.