Anti-Aging Effects of Polyoxometalates on Skin

Excessive reactive oxygen species (ROS) generation by inflammation and glycation contributes to various aging-related changes in the body. Therefore, inhibiting ROS production can prevent wrinkles, maculae, dullness, and slackness in skin. To assess the anti-aging effects of two polyoxometalates (PMs: VB2 and VB3) on skin, this study investigated whether they ameliorated the anti-aging responses of normal human dermal fibroblasts (NHDF) to oxidative stress due to ad-vanced glycation end products (AGEs) or H2O2 exposure. Compared with the mRNA expression levels of AGE receptors in cells exposed to AGEs alone, an additional treatment with VB2 or VB3 significantly increased the expression levels of FEEL-1, FEEL-2, and RAGE. Under AGE-induced stress conditions, the expression levels of five heat shock proteins were markedly increased by the VB treatments. Conversely, VBs suppressed the induction of cell death and intracellular ROS production. VBs also exerted prophylactic effects on these harmful events under stress conditions. Furthermore, VB treatments were found to prevent both the suppression of AQP-1/AQP-3 expression and the suppression of hyaluronan and elastin production induced via H2O2 exposure. These results show the potential of VB2 and VB3 as anti-aging agents.

Deletion of RAGE fails to prevent hepatosteatosis in obese mice due to impairment of other AGEs receptors and detoxifying systems

Advanced glycation endproducts (AGEs) are involved in several diseases, including NAFLD and NASH. RAGE is the main receptor mediating the pro-inflammatory signalling induced by AGEs. Therefore, targeting of RAGE has been proposed for prevention of chronic inflammatory diseases. However, the role of RAGE in the development of NAFLD and NASH remains poorly understood. We thus aimed to analyse the effect of obesity on AGEs accumulation, AGE-receptors and AGE-detoxification, and whether the absence of RAGE might improve hepatosteatosis and inflammation, by comparing the liver of lean control, obese (LeptrDb−/−) and obese RAGE-deficient (RAGE−/− LeptrDb−/−) mice. Obesity induced AGEs accumulation and RAGE expression with hepatosteatosis and inflammation in LeptrDb−/−, compared to lean controls. Despite the genetic deletion of RAGE in the LeptrDb−/− mice, high levels of intrahepatic AGEs were maintained accompanied by decreased expression of the protective AGE-receptor-1, impaired AGE-detoxifying system glyoxalase-1, and increased expression of the alternative AGE-receptor galectin-3. We also found sustained hepatosteatosis and inflammation as determined by persistent activation of the lipogenic SREBP1c and proinflammatory NLRP3 signalling pathways. Thus, RAGE targeting is not effective in the prevention of NAFLD in conditions of obesity, likely due to the direct liver specific crosstalk of RAGE with other AGE-receptors and AGE-detoxifying systems.

l-Theanine Ameliorates d-Galactose-Induced Brain Damage in Rats via Inhibiting AGE Formation and Regulating Sirtuin1 and BDNF Signaling Pathways

The maintenance of homeostasis is essential for mitigating stress and delaying degenerative diseases such as Alzheimer’s disease (AD). AD is generally defined as the abnormal production of β-amyloid (Aβ) and advanced glycation end products (AGEs). The effects of l-theanine on Aβ and AGE generation were investigated in this study. Decreased AGEs and Aβ1-42 levels were reflected by increased acetylcholine (ACh) concentration and acetylcholinesterase (AChE) activity inhibition compared to model rats. l-Theanine also inhibited nuclear factor-κB (p65) protein expression by activating sirtuin1 (SIRT1), reducing inflammatory factor expression, and downregulating the mRNA and protein expression of AGE receptors (RAGE). Superoxide dismutase 2 and catalase protein expressions were markedly upregulated by l-theanine, whereas oxidative stress-related injury was alleviated. The expression of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) was also found to be increased. H&E staining showed that the apoptosis of hippocampal neurons was mitigated by decreased Bax and cleaved-caspase-3 protein expression and the increase of Bcl-2 protein expression. Moreover, l-theanine increased the gene and protein expression of brain-derived neurotrophic factor (BDNF). These findings suggest that the potential preventive effects of l-theanine against AD may be attributed to its regulation of SIRT1 and BDNF proteins and its mitigation of AGEs/RAGE signaling pathways in the brain tissue of AD model rats.

Binding of CML-Modified as Well as Heat-Glycated β-lactoglobulin to Receptors for AGEs Is Determined by Charge and Hydrophobicity

Intake of dietary advanced glycation end products (AGEs) is associated with inflammation-related health problems. Nε-carboxymethyl lysine (CML) is one of the best characterised AGEs in processed food. AGEs have been described as ligands for receptors present on antigen presenting cells. However, changes in protein secondary and tertiary structure also induce binding to AGE receptors. We aimed to discriminate the role of different protein modifications in binding to AGE receptors. Therefore, β-lactoglobulin was chemically modified with glyoxylic acid to produce CML and compared to β-lactoglobulin glycated with lactose. Secondary structure was monitored with circular dichroism, while hydrophobicity and formation of β-sheet structures was measured with ANS-assay and ThT-assay, respectively. Aggregation was monitored using native-PAGE. Binding to sRAGE, CD36, and galectin-3 was measured using inhibition ELISA. Even though no changes in secondary structure were observed in all tested samples, binding to AGE receptors increased with CML concentration of CML-modified β-lactoglobulin. The negative charge of CML was a crucial determinant for the binding of protein bound CML, while binding of glycated BLG was determined by increasing hydrophobicity. This shows that sRAGE, galectin-3, and CD36 bind to protein bound CML and points out the role of negatively charged AGEs in binding to AGE receptors.

Inhibitory effect of black raspberry extract on AGE accumulation and degradation, and ROS production in HUVEC cells

Background: A critical event in age-related diseases involves the glycation of various proteins in the animal body to generate advanced glycation end products (AGEs). We have previously found that black raspberry extract (BRE) has effects on age-related diseases. From this observation, we expected that berry extracts, specifically BRE, would have positive effects on AGE-stimulated cell events that link to age-related diseases.Objective: To discuss the potency of berry extracts against diseases attributable to the AGE-dependent changes of cellular events, in this study, we examined the effects of berry extracts on the cellular events changed upon AGE stimulation of human umbilical vein endothelial cells (HUVECs) through AGE receptors.Methods: After HUVECs were incubated with AGE-BSA in the presence of serially diluted berry extracts, mRNA and protein levels of AGE receptors, intracellular AGE accumulation, and ROS production in the cell were determined by qRT-PCR and Western blotting, ELISA, and staining with the fluorescent probe, respectively.Results: Although concentration-dependent effects of berry extracts tested on mRNA levels of AGE receptors in HUVECs were not clear, mRNA level of the AGE receptor RAGE that is involved in the intracellular ROS production was increased by Blabina, which contains BRE, and the well-known anti-glycation compound aminoguanidine (AGD). In contrast, the protein expression level of RAGE was decreased by BRE and Blabina, but not by AGD. It was also found that BRE and Blabina suppressed AGE-BSA-stimulated ROS production in HUVECs. The extent of inhibition in the RAGE protein expression by BRE and Blabina was correlated well with the ROS generation measured in these samples.Conclusions: The results obtained in this study demonstrate that BRE has the most potent inhibitory effect on ROS accumulation in the cell, probably due to the suppression in the expression level of the RAGE protein. These observations suggest that black raspberry could be a potential nutraceutical to prevent various age-related diseases.Keywords: AGEs; RAGE; ROS; black raspberry; HUVECs.

Neural network modeling of multitarget RAGE inhibitory activity

Based on the methodology of artificial neural networks, models describing the dependence of the level of RAGE inhibitory activity on the affinity of compounds for target proteins of the RAGE-NF-kB signal pathway have been costructed. A validated database of the structures and activity levels of 183 known compounds, which were tested for RAGE inhibitory activity was formed. The analysis of the AGE-RAGE signaling pathways was carried out, 14 key RAGE-NF-kB signal pathway nodes were found, for which 34 relevant target proteins were identified. A database of 66 valid 3D models of 22 target proteins of the RAGE-NF-kB signal chain was compiled. Ensemble molecular docking of 3D models of 183 known RAGE inhibitors into sites of 66 valid 3D models of 22 relevant RAGE target proteins was performed and minimum docking energies for each compound were determined for each target. According to the method of artificial multilayer perceptron neural networks, classification models were constructed to predict level of RAGE inhibitory activity based on the calculated affinity of compounds for significant target proteins of the RAGE-NF-kB signaling chain. The prognostic ability of these models of RAGE-inhibitory activity was evaluated, the maximum accuracy according to ROC-analysis was 90% for a high level of activity. The sensitivity analysis of the developed multitarget models were carried out, the most significant targets of the RAGE-NF-kB signal transmission chain were determined. It was found that for high level of RAGE inhibitory activity, the most significant biotargets are not AGE receptors, but eight signaling kinases of the RAGE-NF-kB pathway and transcription factor NF-kB1. Thus, it is suggested that known compounds with high RAGE-inhibitory activity are preferential inhibitors of signal kinases.

Cardioprotective effect of pioglitazone in diabetic and non-diabetic rats subjected to acute myocardial infarction involves suppression of AGE-RAGE axis and inhibition of apoptosis

Insulin resistance increases risk of cardiovascular diseases. This work investigated the protective effect of pioglitazone on myocardial infarction (MI) in non-diabetic and diabetic rats, focusing on its role on advanced glycated endproducts (AGEs) and cardiac apoptotic machinery. Male rats were divided into 2 experiments: experiment I and II (non-diabetic and diabetic rats) were assigned as saline, MI (isoproterenol, 85 mg/kg, daily), and MI+pioglitazone (5, 10, and 20 mg/kg). Injection of isoproterenol in diabetic rats produced greater ECG disturbances compared to non-diabetic rats. Treatment with pioglitazone (5 mg/kg) reduced the infarct size and improved some ECG findings. Pioglitazone (10 mg/kg) enhanced ECG findings, improved the histopathological picture and downregulated apoptosis in cardiac tissues. Whereas the higher dose of pioglitazone (20 mg/kg) did not improve most of the measured parameters but rather worsened some of them, such as proapoptotic markers. Importantly, a positive correlation was found between serum AGEs and cardiac AGE receptors (RAGEs) versus caspase 3 expression in the two experiments. Therefore, the current effect of pioglitazone was, at least in part, mediated through downregulation of AGE-RAGE axis and inhibition of apoptosis. Consequently, these data suggest that pioglitazone, at optimized doses, may have utility in protection from acute MI.