Methylglyoxal-induced cytotoxicity in neonatal rat brain: a role for oxidative stress and MAP kinases

Depletion of MGO or Its Derivatives Ameliorate CUMS-Induced Neuroinflammation

Advanced glycation end products (AGEs) are a series of structurally complex and harmful compounds formed through the reaction between the carbonyl group of reducing sugars (such as glucose and fructose) and the free amino groups of proteins, lipids, or nucleic acids. Excessive accumulation of AGEs in the body can trigger oxidative stress, induce inflammatory responses, and contribute to the development of diabetes, atherosclerosis, and neurological disorders. Within the category of dicarbonyl compounds, methylglyoxal (MGO)-a byproduct resulting from glucose degradation-serves as a pivotal precursor in the formation of AGEs and the induction of neurotoxicity. Specifically, AGEs generated from MGO display significant cytotoxicity toward cells in the central nervous system. Therefore, we aimed to investigate the role of MGO-AGEs in neuroinflammation mediated by CUMS. Interestingly, we found that the overexpression of glyoxalase 1 (GLO1) reduced the levels of MGO in corticosterone-treated microglia, thereby alleviating the inflammatory response. Furthermore, overexpression of GLO1 in the hippocampus of chronically stressed mice reduced MGO levels, mitigating CUMS-induced neuroinflammation and cognitive impairment. Additionally, when using the receptor for advanced glycation end products (RAGE) inhibitor FPS-ZM1 in primary microglia cells, we observed that despite corticosterone-induced elevation of MGO, no significant inflammatory response occurred. This suggests that RAGE clearance can reduce MGO-AGE-mediated neurotoxicity. Subsequently, we used FPS-ZM1 to treat chronically stressed mice and found that it significantly ameliorated neuroinflammation and cognitive dysfunction. These results suggest that targeting MGO metabolism could serve as a therapeutic approach to manage neuroinflammation in stress-related mental disorders.

Characterization and In-vitro Study of Micro-encapsulation Chitosan Alginate of Single-bulb Garlic Extract

BACKGROUND

Single-bulb garlic extract (SBGE) contains more active compounds than regular garlic, but it is unstable and easily degraded in the digestive tract. SBGE is expected to be protected by microencapsulation chitosan-alginate (MCA).

OBJECTIVE

The present study aimed to characterize and assess the antioxidant activity, hemocompatibility, and toxicity of MCA-SBGE in 3T3-L1 cells.

METHODS

The research procedures consist of extraction of single bulb garlic, preparation of MCASBGE, Particle Size Analyzer (PSA), FTIR analysis, DPPH assay, hemocompatibility test, and MTT assay.

RESULTS

The average size of MCA-SGBE was 423.7 ± 2.8 nm, the polydispersity index (PdI) was 0.446 ± 0.022, and the zeta potential was -24.5 ± 0.4 mV. MCA-SGBE was spherical with a diameter range of 0.65-0.9 μm. A shift in absorption and addition of functional groups was found in SBGE after encapsulation. MCA-SBGE, at a concentration of 24 x 103 ppm, has higher antioxidants than SBGE. The hemocompatibility test shows the hemolysis of MCA-SBGE lower than SBGE. MCA-SBGE was not toxic to 3T3-L1 cells with cell viability percentage above 100% at all concentrations.

CONCLUSION

MCA-SBGE characterization has microparticle criteria with homogeneous PdI values, low particle stability, and spherical morphology. The results showed that SBGE and MCA-SBGE are nonhemolytic, compatible with red blood cells, and non-toxic to 3T3-L1 cells.

Dietary Methylglyoxal Exposure Induces Alzheimer's Disease by Promoting Amyloid β Accumulation and Disrupting Autophagy in Caenorhabditis elegans

Methylglyoxal (MG) is a precursor of advanced glycation end products usually generated during cooking. The high level of MG in the brain is correlated to the pathogenesis of Alzheimer's disease (AD). However, it is not clear if MG consumed through the diet can cause AD-related toxicity. Herein, the Caenorhabditis elegans (C. elegans) AD model was used to investigate the neurotoxicity after long-term MG exposure at dietary levels. The results showed that C. elegans locomotive behaviors were significantly decreased after 0.1, 0.5, and 1 mM MG exposure (p < 0.001). In amyloid β (Aβ)-expressing transgenic C. elegans strains, 0.5 mM MG significantly promoted Aβ accumulation by around 50% in day-8 CL2006 (p < 0.001), enhanced paralysis in CL4176 (p < 0.001) and CL2006 (p < 0.01), and made CL2355 around 17% more vulnerable to 5-HT, indicating impaired serotonin reuptake (p < 0.05). Additionally, 0.5 mM MG significantly increased the reactive oxygen species level (p < 0.001) by inhibiting the expression of stress-response genes including sod-3, gst-4, and hsp-16.2 in day-8 aged worms. Moreover, the autophagic pathway was disrupted through lgg-1, vps-34, and bec-1 expression after MG exposure and Aβ accumulation. Treatment with the citrus flavonoid nobiletin reduced the MG-induced toxicity (p < 0.001). Overall, these findings imply that it is possible to exacerbate AD pathogenesis by MG exposure through the diet.

Diabetes and Cognitive Impairment: A Role for Glucotoxicity and Dopaminergic Dysfunction

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by hyperglycemia, responsible for the onset of several long-term complications. Recent evidence suggests that cognitive dysfunction represents an emerging complication of DM, but the underlying molecular mechanisms are still obscure. Dopamine (DA), a neurotransmitter essentially known for its relevance in the regulation of behavior and movement, modulates cognitive function, too. Interestingly, alterations of the dopaminergic system have been observed in DM. This review aims to offer a comprehensive overview of the most relevant experimental results assessing DA’s role in cognitive function, highlighting the presence of dopaminergic dysfunction in DM and supporting a role for glucotoxicity in DM-associated dopaminergic dysfunction and cognitive impairment. Several studies confirm a role for DA in cognition both in animal models and in humans. Similarly, significant alterations of the dopaminergic system have been observed in animal models of experimental diabetes and in diabetic patients, too. Evidence is accumulating that advanced glycation end products (AGEs) and their precursor methylglyoxal (MGO) are associated with cognitive impairment and alterations of the dopaminergic system. Further research is needed to clarify the molecular mechanisms linking DM-associated dopaminergic dysfunction and cognitive impairment and to assess the deleterious impact of glucotoxicity.

Early AGEing and metabolic diseases: is perinatal exposure to glycotoxins programming for adult-life metabolic syndrome?

Perinatal early nutritional disorders are critical for the developmental origins of health and disease. Glycotoxins, or advanced glycation end-products, and their precursors such as the methylglyoxal, which are formed endogenously and commonly found in processed foods and infant formulas, may be associated with acute and long-term metabolic disorders. Besides general aspects of glycotoxins, such as their endogenous production, exogenous sources, and their role in the development of metabolic syndrome, we discuss in this review the sources of perinatal exposure to glycotoxins and their involvement in metabolic programming mechanisms. The role of perinatal glycotoxin exposure in the onset of insulin resistance, central nervous system development, cardiovascular diseases, and early aging also are discussed, as are possible interventions that may prevent or reduce such effects.

Curcumin Derivative Cur20 Attenuated Cerebral Ischemic Injury by Antioxidant Effect and HIF-1α/VEGF/TFEB-Activated Angiogenesis

In this paper, a curcumin derivative Cur20 was synthesized for better hydrolytic stability, which showed a higher angiogenic effect on zebrafish model than curcumin. In order to reveal the potential effects on neuroprotection, a mouse model of vascular dementia (VaD) induced by permanent right common carotid artery occlusion (rUCCAO) was established. After two weeks of curcumin administration, the cognitive function of mice was detected by Morris water maze and Y maze. The alteration on oxidative injuries and morphological damage were also analyzed by reactive oxygen species, superoxide dismutase, GSH, malondialdehyde tests, and Nissl stain on cortex/hippocampus. The angiogenesis and related signal factors were evaluated as well. The results showed that Cur20 significantly attenuated the cognitive dysfunction and histopathological changes of the VaD mice with enhanced antioxidant system and angiogenesis. In addition, primary rat brain microvessel endothelial cells (rBMECs) with oxygen glucose deprivation (OGD) were applied to further verify the possible mechanisms of Cur20-induced angiogenesis. The results demonstrated that the proliferation effect and the activation of pro-angiogenesis factors such as HIF-1α, VEGF, and TFEB might contribute to the protection of ischemic injury. Based on the above, our conclusion is that Cur20 can be considered as a promising therapeutic strategy for VaD.

Common Pathological Mechanisms and Risk Factors for Alzheimer's Disease and Type-2 Diabetes: Focus on Inflammation

BACKGROUND

Diabetes is considered as a risk factor for Alzheimer's Disease, but it is yet unclear whether this pathological link is reciprocal. Although Alzheimer's disease and diabetes appear as entirely different pathological entities affecting the Central Nervous System and a peripheral organ (pancreas), respectively, they share a common pathological core. Recent evidence suggests that in the pancreas in the case of diabetes, as in the brain for Alzheimer's Disease, the initial pathological event may be the accumulation of toxic proteins yielding amyloidosis. Moreover, in both pathologies, amyloidosis is likely responsible for local inflammation, which acts as a driving force for cell death and tissue degeneration. These pathological events are all inter-connected and establish a vicious cycle resulting in the progressive character of both pathologies.

OBJECTIVE

To address the literature supporting the hypothesis of a common pathological core for both diseases.

DISCUSSION

We will focus on the analogies and differences between the disease-related inflammatory changes in a peripheral organ, such as the pancreas, versus those observed in the brain. Recent evidence suggesting an impact of peripheral inflammation on neuroinflammation in Alzheimer's disease will be presented.

CONCLUSION

We propose that it is now necessary to consider whether neuroinflammation in Alzheimer's disease affects inflammation in the pancreas related to diabetes.

Cellular Signaling and Anti-Apoptotic Effects of Prolactin-Releasing Peptide and Its Analog on SH-SY5Y Cells

Prolactin-releasing peptide (PrRP), a natural ligand for the GPR10 receptor, is a neuropeptide with anorexigenic and antidiabetic properties. Due to its role in the regulation of food intake, PrRP is a potential drug for obesity treatment and associated type 2 diabetes mellitus (T2DM). Recently, the neuroprotective effects of lipidized PrRP analogs have been proven. In this study, we focused on the molecular mechanisms of action of natural PrRP31 and its lipidized analog palm¹¹-PrRP31 in the human neuroblastoma cell line SH-SY5Y to describe their cellular signaling and possible anti-apoptotic properties. PrRP31 significantly upregulated the phosphoinositide-3 kinase-protein kinase B/Akt (PI3K-PKB/Akt) and extracellular signal-regulated kinase/cAMP response element-binding protein (ERK-CREB) signaling pathways that promote metabolic cell survival and growth. In addition, we proved via protein kinase inhibitors that activation of signaling pathways is mediated specifically by PrRP31 and its palmitoylated analog. Furthermore, the potential neuroprotective properties were studied through activation of anti-apoptotic pathways of PrRP31 and palm¹¹-PrRP31 using the SH-SY5Y cell line and rat primary neuronal culture stressed with toxic methylglyoxal (MG). The results indicate increased viability of the cells treated with PrRP and palm¹¹-PrRP31 and a reduced degree of apoptosis induced by MG, suggesting their potential use in the treatment of neurological disorders.

Methylglyoxal, a Highly Reactive Dicarbonyl Compound, in Diabetes, Its Vascular Complications, and Other Age-Related Diseases

The formation and accumulation of methylglyoxal (MGO), a highly reactive dicarbonyl compound, has been implicated in the pathogenesis of type 2 diabetes, vascular complications of diabetes, and several other age-related chronic inflammatory diseases such as cardiovascular disease, cancer, and disorders of the central nervous system. MGO is mainly formed as a byproduct of glycolysis and, under physiological circumstances, detoxified by the glyoxalase system. MGO is the major precursor of nonenzymatic glycation of proteins and DNA, subsequently leading to the formation of advanced glycation end products (AGEs). MGO and MGO-derived AGEs can impact on organs and tissues affecting their functions and structure. In this review we summarize the formation of MGO, the detoxification of MGO by the glyoxalase system, and the biochemical pathways through which MGO is linked to the development of diabetes, vascular complications of diabetes, and other age-related diseases. Although interventions to treat MGO-associated complications are not yet available in the clinical setting, several strategies to lower MGO have been developed over the years. We will summarize several new directions to target MGO stress including glyoxalase inducers and MGO scavengers. Targeting MGO burden may provide new therapeutic applications to mitigate diseases in which MGO plays a crucial role.

Guaianolide sesquiterpene lactones and aporphine alkaloids from the stem bark of Guatteria friesiana

Three guaianolide sesquiterpenes, denoted guatterfriesols A-C, and four aporphine alkaloid derivatives were isolated from the stem bark of the Amazonian plant Guatteria friesiana. Thus far, sesquiterpene lactones have not been described in Annonaceae. Structures of the previously undescribed compounds were established by using 1D and 2D NMR spectroscopy in combination with MS. The absolute stereochemistry was assigned via NOE NMR experiments, ECD spectroscopy, and theoretical calculations using the TDDFT approach. Among the isolated compounds, the alkaloid guatterfriesidine showed anti-glycation activity by inhibiting the formation of advanced glycation end-products (AGEs) through the prevention of oxidation in both BSA/methylglyoxal and BSA/fructose systems.

Lespedeza bicolor ameliorates endothelial dysfunction induced by methylglyoxal glucotoxicity

BACKGROUND

Lespedeza species have been used as a traditional medicine to treat nephritis, azotemia, inflammation, energy depletion, diabetes, and diuresis.

PURPOSE

The purpose of this study is to screen the most potent Lespedeza species against methylglyoxal (MGO)-induced glucotoxicity, and to elucidate the mechanisms of action. Also, we will attempt to identify small chemical metabolites that might be responsible for such anti-glucotoxicity effects.

METHODS

Firstly, the protective effect of 26 different Lespedeza species against MGO-induced toxicity in human umbilical vein endothelial cells was investigated. The chemical metabolites of the most potent species (Lespedeza bicolor 1 (LB1) were identified by high pressure liquid chromatography quadrupole time-of-flight tandem mass spectrometry (HPLC-Q-TOF-MS/MS), then quantified by HPLC. The effects of LB1 on MGO-induced apoptosis were measured by annexin V-FITC staining and western blot. Inhibitory effects of LB1 on MGO-induced ROS generation, and effect of LB1 on advanced glycation end products (AGEs) inhibitor or a glycated cross-link breaker are also measured.

RESULTS

Among different Lespedeza species, LB1 extract was shown to reduce intracellular reactive oxidative species, exhibit anti-apoptotic effects, strongly inhibit all the mitogen-activated protein kinase signals, inhibit MGO-induced AGEs formation, and break down preformed AGEs. We tentatively identified 17 chemical constituents of LB1 by HPLC-Q-TOF-MS/MS. Among those, some components, such as genistein and quercetin, significantly reduced the AGEs formation and increased the AGEs-breaking activity, resulting in the reduction of glucotoxicity.

CONCLUSION

LB1 extract has shown to be effective in preventing or treating MGO-induced endothelial dysfunction.

Oligodendrocyte RasG12V expressed in its endogenous locus disrupts myelin structure through increased MAPK, nitric oxide, and notch signaling

Costello syndrome (CS) is a gain of function Rasopathy caused by heterozygous activating mutations in the HRAS gene. Patients show brain dysfunction that can include abnormal brain white matter. Transgenic activation of HRas in the entire mouse oligodendrocyte lineage resulted in myelin defects and behavioral abnormalities, suggesting roles for disrupted myelin in CS brain dysfunction. Here, we studied a mouse model in which the endogenous HRas gene is conditionally replaced by mutant HRasG12V in mature oligodendrocytes, to separate effects in mature myelinating cells from developmental events. Increased myelin thickness due to decompaction was detectable within one month of HRasG12V expression in the corpus callosum of adult mice. Increases in active ERK and Nitric Oxide (NO) were present in HRas mutants and inhibition of NO synthase (NOS) or MEK each partially rescued myelin decompaction. In addition, genetic or pharmacologic inhibition of Notch signaling improved myelin compaction. Complete rescue of myelin structure required dual drug treatments combining MAPK, NO, or Notch inhibition; with MEK + NOS blockade producing the most robust effect. We suggest that individual or concomitant blockade of these pathways in CS patients may improve aspects of brain function.

Luteolin, a natural flavonoid, inhibits methylglyoxal induced apoptosis via the mTOR/4E-BP1 signaling pathway

Methylglyoxal (MG) accumulation has been observed in human cerebrospinal fluid and body tissues under hyperglycaemic conditions. Recent research has demonstrated that MG-induces neuronal cell apoptosis, which promotes the development of diabetic encephalopathy. Our previous animal study has shown that luteolin, a natural flavonoid, attenuates diabetes-associated cognitive dysfunction. To further explore the neuroprotective properties of luteolin, we investigated the inhibitive effect of luteolin on MG-induced apoptosis in PC12 neuronal cells. We found that MG inhibited cell viability in a dose-dependent manner and induced apoptosis in PC12 cells. Pretreatment with Luteolin significantly elevated cell viability, reduced MG-induced apoptosis, inhibited the activation of the mTOR/4E-BP1 signaling pathway, and decreased pro-apoptotic proteins, Bax, Cytochrome C as well as caspase-3. Furthermore, we found that pretreatment with the mTOR inhibitor, rapamycin, significantly reduced the expression of the pro-apoptotic protein Bax. Therefore, these observations unambiguously suggest that the inhibitive effect of Luteolin against MG-induced apoptosis in PC12 cells is associated with inhibition of the mTOR/4E-BP1 signaling pathway.

(+)-Catechin prevents methylglyoxal-induced mitochondrial dysfunction and apoptosis in EA.hy926 cells

OBJECTIVE

To investigate whether (+)-catechin, a strong antioxidant, can prevent methylglyoxal (MGO)-induced cytotoxicity and its mechanism.

METHODS

Cytotoxicity, apoptosis, reactive oxygen species (ROS) generation, hydrogen peroxide (H₂O₂) formation, mitochondrial membrane potential (MMP) and mitochondrial morphology were measured in EA.hy926 cells.

RESULT

MGO (4 mM)-induced cytotoxicity was markedly inhibited by (+)-catechin (0.1-4 mM) in 24 h. 1 mM MGO-induced apoptotic cell death (44.7%) was significantly inhibited by 4 mM (+)-catechin (to 24.4%), 1 mM aminoguanidine (AG) (to 28.8%) or 4 mM N-acetylcysteine (NAC) (to 24.3%). (+)-Catechin (4 mM) or AG (4 mM) can inhibit the decrease of MMP induced by MGO (2-8 mM) in 3 h. (+)-Catechin (4 mM) or AG (4 mM) can inhibit MGO (4 mM)-induced mitochondrial swelling in 3 h. However, MGO (4 mM)-induced ROS and H₂O₂ generation was not prevented by (+)-catechin (4 mM).

CONCLUSIONS

(+)-Catechin prevents MGO-induced cytotoxicity in EA.Hy926 cells through inhibiting apoptosis and mitochondrial damage.

Methylglyoxal in Metabolic Disorders: Facts, Myths, and Promises

Glucose and fructose metabolism originates the highly reactive byproduct methylglyoxal (MG), which is a strong precursor of advanced glycation end products (AGE). The MG has been implicated in classical diabetic complications such as retinopathy, nephropathy, and neuropathy, but has also been recently associated with cardiovascular diseases and central nervous system disorders such as cerebrovascular diseases and dementia. Recent studies even suggested its involvement in insulin resistance and beta-cell dysfunction, contributing to the early development of type 2 diabetes and creating a vicious circle between glycation and hyperglycemia. Despite several drugs and natural compounds have been identified in the last years in order to scavenge MG and inhibit AGE formation, we are still far from having an effective strategy to prevent MG-induced mechanisms. This review summarizes the endogenous and exogenous sources of MG, also addressing the current controversy about the importance of exogenous MG sources. The mechanisms by which MG changes cell behavior and its involvement in type 2 diabetes development and complications and the pathophysiological implication are also summarized. Particular emphasis will be given to pathophysiological relevance of studies using higher MG doses, which may have produced biased results. Finally, we also overview the current knowledge about detoxification strategies, including modulation of endogenous enzymatic systems and exogenous compounds able to inhibit MG effects on biological systems.

Methylglyoxal-induced neuroinflammatory response in in vitro astrocytic cultures and hippocampus of experimental animals

Diabetes mellitus is characterized by chronic hyperglycemia and its diverse complications. Hyperglycemia is associated with inflammatory responses in different organs and diabetic patients have a higher risk of developing neurodegenerative disorders. Methylglyoxal is a reactive advanced glycation end product precursor that accumulates in diabetic patients. It induces various stress responses in the central nervous system and causes neuronal dysfunction. Astrocytes are actively involved in maintaining neuronal homeostasis and possibly play a role in protecting the brain against neurodegeneration. However it is not clear whether methylglyoxal exerts any adverse effects towards these astrocytes. In the present study we investigated the effects of methylglyoxal in astrocytic cultures and hippocampi of experimental animals. The cells from the astrocytic line DITNC1 were treated with methylglyoxal for 1 to 24 h. For the in vivo model, 3 months old C57BL/6 mice were treated with methylglyoxal solution for 6 weeks by intraperitoneal injection. Following the treatment, both astrocytes and hippocampi were harvested for MTT assay, Western blot and real time PCR analyses. We found that methylglyoxal induced astrogliosis in DITNC1 astrocytic cultures and C57BL/6 mice. Further, activation of the pro-inflammatory JNK signaling pathway and its downstream effectors c-Jun were observed. Furthermore, increased gene expression of pro-inflammatory cytokines and astrocytic markers were observed from real time PCR analyses. In addition, inhibition of JNK activities resulted in down-regulation of TNF-α gene expression in methylglyoxal treated astrocytes. Our results suggest that methylglyoxal may contribute to the progression of diabetes related neurodegeneration through JNK pathway activation in astrocytes and the subsequent neuroinflammatory responses in the central nervous system.

Methylglyoxal can mediate behavioral and neurochemical alterations in rat brain

Diabetes is associated with loss of cognitive function and increased risk for Alzheimer's disease (AD). Advanced glycation end products (AGEs) are elevated in diabetes and AD and have been suggested to act as mediators of the cognitive decline observed in these pathologies. Methylglyoxal (MG) is an extremely reactive carbonyl compound that propagates glycation reactions and is, therefore, able to generate AGEs. Herein, we evaluated persistent behavioral and biochemical parameters to explore the hypothesis that elevated exogenous MG concentrations, induced by intracerebroventricular (ICV) infusion, lead to cognitive decline in Wistar rats. A high and sustained administration of MG (3μmol/μL; subdivided into 6days) was found to decrease the recognition index of rats, as evaluated by the object-recognition test. However, MG was unable to impair learning-memory processes, as shown by the habituation in the open field (OF) and Y-maze tasks. Moreover, a single high dose of MG induced persistent alterations in anxiety-related behavior, diminishing the anxiety-like parameters evaluated in the OF test. Importantly, MG did not alter locomotion behavior in the different tasks performed. Our biochemical findings support the hypothesis that MG induces persistent alterations in the hippocampus, but not in the cortex, related to glyoxalase 1 activity, AGEs content and glutamate uptake. Glial fibrillary acidic protein and S100B content, as well as S100B secretion (astroglial-related parameters of brain injury), were not altered by ICV MG administration. Taken together, our data suggest that MG interferes directly in brain function and that the time and the levels of exogenous MG determine the different features that can be seen in diabetic patients.

Phycocyanin prevents methylglyoxal-induced mitochondrial-dependent apoptosis in INS-1 cells by Nrf2

Phycocyanin prevents mitochondrial-dependent apoptosis in methylgiyoxal-induced INS-1 cells by activating Nrf2.

Methylglyoxal Causes Cell Death in Neural Progenitor Cells and Impairs Adult Hippocampal Neurogenesis

Methylglyoxal (MG) is formed during normal metabolism by processes like glycolysis, lipid peroxidation, and threonine catabolism, and its accumulation is associated with various degenerative diseases, such as diabetes and arterial atherogenesis. Furthermore, MG has also been reported to have toxic effects on hippocampal neurons. However, these effects have not been studied in the context of neurogenesis. Here, we report that MG adversely affects hippocampal neurogenesis and induces neural progenitor cell (NPC) death. MG significantly reduced C17.2 NPC proliferation, and high concentration of MG (500 μM) induced cell death and elevated oxidative stress. Further, MG was found to activate the ERK signaling pathway, indicating elevated stress response. To determine the effects of MG in vivo, mice were administrated with vehicle or MG (0.5 or 1 % in drinking water) for 4 weeks. The numbers of BrdU-positive cells in hippocampi were significantly lower in MG-treated mice, indicating impaired neurogenesis, but MG did not induce neuronal damage or glial activations. Interestingly, MG reduced memory retention when administered to mice at 1 % but not at 0.5 %. In addition, the levels of hippocampal BDNF and synaptophysin were significantly lower in the hippocampi of mice treated with MG at 1 %. Collectively, our findings suggest MG could be harmful to NPCs and to hippocampal neurogenesis.

NMDA Receptors and Oxidative Stress Induced by the Major Metabolites Accumulating in HMG Lyase Deficiency Mediate Hypophosphorylation of Cytoskeletal Proteins in Brain From Adolescent Rats: Potential Mechanisms Contributing to the Neuropathology of This Disease

Neurological symptoms and cerebral abnormalities are commonly observed in patients with 3-hydroxy-3-methylglutaryl-CoA lyase (HMG lyase) deficiency, which is biochemically characterized by predominant tissue accumulation of 3-hydroxy-3-methylglutaric (HMG), 3-methylglutaric (MGA), and 3-methylglutaconic (MGT) acids. Since the pathogenesis of this disease is poorly known, the present study evaluated the effects of these compounds on the cytoskeleton phosphorylating system in rat brain. HMG, MGA, and MGT caused hypophosphorylation of glial fibrillary acidic protein (GFAP) and of the neurofilament subunits NFL, NFM, and NFH. HMG-induced hypophosphorylation was mediated by inhibiting the cAMP-dependent protein kinase (PKA) on Ser55 residue of NFL and c-Jun kinase (JNK) by acting on KSP repeats of NFM and NFH subunits. We also evidenced that the subunit NR2B of NMDA receptor and Ca(2+) was involved in HMG-elicited hypophosphorylation of cytoskeletal proteins. Furthermore, the antioxidants L-NAME and TROLOX fully prevented both the hypophosphorylation and the inhibition of PKA and JNK caused by HMG, suggesting that oxidative damage may underlie these effects. These findings indicate that the main metabolites accumulating in HMG lyase deficiency provoke hypophosphorylation of cytoskeleton neural proteins with the involvement of NMDA receptors, Ca(2+), and reactive species. It is presumed that these alterations may contribute to the neuropathology of this disease.

Dose-dependent effects of morphine exposure on mRNA and microRNA (miR) expression in hippocampus of stressed neonatal mice

Morphine is used to sedate critically ill infants to treat painful or stressful conditions associated with intensive care. Whether neonatal morphine exposure affects microRNA (miR) expression and thereby alters mRNA regulation is unknown. We tested the hypothesis that repeated morphine treatment in stress-exposed neonatal mice alters hippocampal mRNA and miR expression. C57BL/6 male mice were treated from postnatal day (P) 5 to P9 with morphine sulfate at 2 or 5 mg/kg ip twice daily and then exposed to stress consisting of hypoxia (100% N₂ 1 min and 100% O₂ 5 min) followed by 2h maternal separation. Control mice were untreated and dam-reared. mRNA and miR expression profiling was performed on hippocampal tissues at P9. Overall, 2 and 5 mg/kg morphine treatment altered expression of a total of 150 transcripts (>1.5 fold change, P<0.05) from which 100 unique mRNAs were recognized (21 genes were up- and 79 genes were down-regulated), and 5 mg/kg morphine affected 63 mRNAs exclusively. The most upregulated mRNAs were fidgetin, arginine vasopressin, and resistin-like alpha, and the most down-regulated were defensin beta 11, aquaporin 1, calmodulin-like 4, chloride intracellular channel 6, and claudin 2. Gene Set Enrichment Analysis revealed that morphine treatment affected pathways related to cell cycle, membrane function, signaling, metabolism, cell death, transcriptional regulation, and immune response. Morphine decreased expression of miR-204-5p, miR-455-3p, miR-448-5p, and miR-574-3p. Nine morphine-responsive mRNAs that are involved in neurodevelopment, neurotransmission, and inflammation are predicted targets of the aforementioned differentially expressed miRs. These data establish that morphine produces dose-dependent changes in both hippocampal mRNA and miR expression in stressed neonatal mice. If permanent, morphine–mediated neuroepigenetic effects may affect long-term hippocampal function, and this provides a mechanism for the neonatal morphine-related impairment of adult learning.

GIT2 Acts as a Systems-Level Coordinator of Neurometabolic Activity and Pathophysiological Aging

Aging represents one of the most complicated and highly integrated somatic processes. Healthy aging is suggested to rely upon the coherent regulation of hormonal and neuronal communication between the central nervous system and peripheral tissues. The hypothalamus is one of the main structures in the body responsible for sustaining an efficient interaction between energy balance and neurological activity and therefore likely coordinates multiple systems in the aging process. We previously identified, in hypothalamic and peripheral tissues, the G protein-coupled receptor kinase interacting protein 2 (GIT2) as a stress response and aging regulator. As metabolic status profoundly affects aging trajectories, we investigated the role of GIT2 in regulating metabolic activity. We found that genomic deletion of GIT2 alters hypothalamic transcriptomic signatures related to diabetes and metabolic pathways. Deletion of GIT2 reduced whole animal respiratory exchange ratios away from those related to primary glucose usage for energy homeostasis. GIT2 knockout (GIT2KO) mice demonstrated lower insulin secretion levels, disruption of pancreatic islet beta cell mass, elevated plasma glucose, and insulin resistance. High-dimensionality transcriptomic signatures from islets isolated from GIT2KO mice indicated a disruption of beta cell development. Additionally, GIT2 expression was prematurely elevated in pancreatic and hypothalamic tissues from diabetic-state mice (db/db), compared to age-matched wild type (WT) controls, further supporting the role of GIT2 in metabolic regulation and aging. We also found that the physical interaction of pancreatic GIT2 with the insulin receptor and insulin receptor substrate 2 was diminished in db/db mice compared to WT mice. Therefore, GIT2 appears to exert a multidimensional "keystone" role in regulating the aging process by coordinating somatic responses to energy deficits.

Dihydromyricetin ameliorates the oxidative stress response induced by methylglyoxal via the AMPK/GLUT4 signaling pathway in PC12 cells

Dihydromyricetin (DMY), the major bioactive flavonoid ingredient extracted from the leaves of Ampelopsis grossedentata (Hand.-Mazz) W.T. Wang, displays multiple pharmacological activities, including oxidation resistance, antitumor properties and free radical scavenging capacities. However, the role of DMY in methylglyoxal (MG)-induced diabetes-associated cognitive decline and its underlying molecular mechanisms are unclear. The aim of the present study was to evaluate the effects of DMY on oxidative stress and glucose transport activity in a MG-induced PC12 cell line and to explore the related mechanisms. The effects of DMY on cell survival and apoptosis were examined, and the dysregulation of intracellular Ca(2+) was determined. Oxidative stress was evaluated by monitoring ROS production and the glutathione to glutathione disulfide ratio. The effects of DMY on glucose metabolism were investigated using a fluorescently labeled deoxyglucose analog and by measuring ATP and lactate production. Western blot analysis was performed to examine the protein levels of glyoxalase I (Glo-1), glucose transporter 4 (GLUT4), AMP-activated protein kinase (AMPKα) and phosphorylated AMPKα (p-AMPKα). The results revealed that DMY suppressed cellular oxidative stress in PC12 cells and balanced glucose metabolism. Additionally, DMY reduced GLUT4 translocation dysfunction and increased Glo-1 and p-AMPKα expression. We found that DMY protected PC12 cells against MG-induced apoptosis and glycometabolic disorders, at least in part by restraining the hyperactivation of p-AMPK activity and normalizing the translocation of GLUT4 from the intracellular compartment, resulting in a balance in glucose uptake. This result indicates that DMY may serve as a novel and effective candidate agent to treat diabetic encephalopathy by reducing the toxicity of MG.

Protective effects of puerariae radix extract and its single compounds on methylglyoxal-induced apoptosis in human retinal pigment epithelial cells

ETHNOPHARMACOLOGICAL RELEVANCE

In Korea, Puerariae radix is a medicinal plant traditionally used to treat various diseases including diabetes mellitus. To provide pharmacological basis for Puerariae radix in the treatment of diabetes, we investigated the protective effects of the ethanolic extract and its single compounds on apoptosis associated with glycation in human retinal pigment epithelial (RPE) cells.

MATERIALS AND METHODS

In the present work, a quantified ethanolic extract or single compounds of Puerariae radix were selected to determine its anti-apoptotic effect in human RPE cells cultured with methylglyoxal (MG), which is a stimulator of glycation. To assess the protective effect of the extract or single compounds, the cytotoxicity assessment was performed using an MTT assay in the human RPE cells. Selected active compounds or extracts were tested by FACS analysis with annexin V staining for apoptosis.

RESULTS

Daidzein (1), daidzin (2), puerarin (3), 3'-hydroxy-daidzein 8-C-apiosyl (1→6) glucoside (4), and daidzein 8-C-apiosyl (1→6) glucoside (5), and pueroside B (6) were isolated from an ethanolic extract of Puerariae radix. MG-induced apoptosis was completely inhibited by Puerariae radix, ethanolic extract, and single compounds. Of the six major compounds, daidzin (2) and 3'-hydroxy-daidzein 8-C-apiosyl (1→6) glucoside (4) significantly inhibited MG-induced apoptosis.

CONCLUSION

Our results provide the first evidence that, due to its anti-glycation effect, Puerariae radix extract could inhibit MG-induced apoptosis in the cultured human RPE cells. These data suggest that Puerariae radix extract, especially its single compounds daidzin and 3'-hydroxy-daidzein 8-C-apiosyl (1→6) glucoside, has potential utility as a preventive agent for glycation-related diabetic retinopathy.

Role of methylglyoxal in Alzheimer's disease

Alzheimer's disease is the most common and lethal neurodegenerative disorder. The major hallmarks of Alzheimer's disease are extracellular aggregation of amyloid β peptides and, the presence of intracellular neurofibrillary tangles formed by precipitation/aggregation of hyperphosphorylated tau protein. The etiology of Alzheimer's disease is multifactorial and a full understanding of its pathogenesis remains elusive. Some years ago, it has been suggested that glycation may contribute to both extensive protein cross-linking and oxidative stress in Alzheimer's disease. Glycation is an endogenous process that leads to the production of a class of compounds known as advanced glycation end products (AGEs). Interestingly, increased levels of AGEs have been observed in brains of Alzheimer's disease patients. Methylglyoxal, a reactive intermediate of cellular metabolism, is the most potent precursor of AGEs and is strictly correlated with an increase of oxidative stress in Alzheimer's disease. Many studies are showing that methylglyoxal and methylglyoxal-derived AGEs play a key role in the etiopathogenesis of Alzheimer's disease.

Chemical composition, antioxidant and anti-AGEs activities of a French poplar type propolis

Accumulation in tissues and serum of advanced glycation end-products (AGEs) plays an important role in pathologies such as Alzheimer's disease or, in the event of complications of diabetes, atherosclerosis or renal failure. Therefore, there is a potential therapeutic interest in compounds able to lower intra and extracellular levels of AGEs. Among them, natural antioxidants (AO) with true anti-AGEs capabilities would represent good candidates for development. The purpose of this study was to evaluate the AO and anti-AGEs potential of a propolis batch and then to identify the main compounds responsible for these effects. In vivo, protein glycation and oxidative stress are closely related. Thus, AO and antiglycation activities were evaluated using both DPPH and ORAC assays, respectively, as well as a newly developed automated anti-AGEs test. Several propolis extracts exhibited very good AO and anti-AGEs activities, and a bioguided fractionation allowed us to identify pinobanksin-3-acetate as the most active component.

Methylglyoxal (MG) and cerebro-renal interaction: does long-term orally administered MG cause cognitive impairment in normal Sprague-Dawley rats?

Methylglyoxal (MG), one of the uremic toxins, is a highly reactive alpha-dicarbonyl compound. Recent clinical studies have demonstrated the close associations of cognitive impairment (CI) with plasma MG levels and presence of kidney dysfunction. Therefore, the present study aims to examine whether MG is a direct causative substance for CI development. Eight-week-old male Sprague-Dawley (SD) rats were divided into two groups: control (n = 9) and MG group (n = 10; 0.5% MG in drinking water), and fed a normal diet for 12 months. Cognitive function was evaluated by two behavioral tests (object exploration test and radial-arm maze test) in early (4–6 months of age) and late phase (7–12 months of age). Serum MG was significantly elevated in the MG group (495.8 ± 38.1 vs. 244.8 ± 28.2 nM; p < 0.001) at the end of study. The groups did not differ in cognitive function during the course of study. No time-course differences were found in oxidative stress markers between the two groups, while, antioxidants such as glutathione peroxidase and superoxide dismutase activities were significantly increased in the MG group compared to the control. Long-term MG administration to rats with normal kidney function did not cause CI. A counter-balanced activation of the systemic anti-oxidant system may offset the toxicity of MG in this model. Pathogenetic significance of MG for CI requires further investigation.

Uncoupling of eNOS contributes to redox-sensitive leukocyte recruitment and microvascular leakage elicited by methylglyoxal

Elevated levels of the glycolysis metabolite methylglyoxal (MG) have been implicated in impaired leukocyte-endothelial interactions and vascular complications in diabetes, putative mechanisms of which remain elusive. Uncoupling of endothelial nitric oxide synthase (eNOS) was shown to be involved in endothelial dysfunction in diabetes. Whether MG contributes to these effects has not been elucidated. By using intravital microscopy in vivo, we demonstrate that MG-triggered reduction in leukocyte rolling velocity and increases in rolling flux, adhesion, emigration and microvascular permeability were significantly abated by scavenging reactive oxygen species (ROS). In murine cremaster muscle, MG treatment reduced tetrahydrobiopterin (BH4)/total biopterin ratio, increased arginase expression and stimulated ROS and superoxide production. The latter was significantly blunted by ROS scavengers Tempol (300μM) or MnTBAP (300μM), by BH4 supplementation (100μM) or by NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME; 20μM). In these tissues and cultured murine and human primary endothelial cells, MG increased eNOS monomerization and decreased BH4/total biopterin ratio, effects that were significantly mitigated by supplementation of BH4 or its precursor sepiapterin but not by L-NAME or tetrahydroneopterin, indicative of MG-triggered eNOS uncoupling. MG treatment further decreased the expression of guanosine triphosphate cyclohydrolase I in murine primary endothelial cells. MG-induced leukocyte recruitment was significantly attenuated by supplementation of BH4 or sepiapterin or suppression of superoxide by L-NAME confirming the role of eNOS uncoupling in MG-elicited leukocyte recruitment. Together, our study uncovers eNOS uncoupling as a pivotal mechanism in MG-induced oxidative stress, microvascular hyperpermeability and leukocyte recruitment in vivo.

Carbonyl stress in aging process: role of vitamins and phytochemicals as redox regulators

There is a growing scientific agreement that the cellular redox regulators such as antioxidants, particularly the natural polyphenolic forms, may help lower the incidence of some pathologies, including metabolic diseases like diabetes and diabesity, cardiovascular and neurodegenerative abnormalities, and certain cancers or even have anti-aging properties. The recent researches indicate that the degree of metabolic modulation and adaptation response of cells to reductants as well as oxidants establish their survival and homeostasis, which is linked with very critical balance in imbalances in cellular redox capacity and signaling, and that might be an answer the questions why some antioxidants or phytochemicals potentially could do more harm than good, or why some proteins lose their function by increase interactions with glyco- and lipo-oxidation mediates in the cells (carbonyl stress). Nonetheless, pursue of healthy aging has led the use of antioxidants as a means to disrupt age-associated physiological dysfunctions, dysregulated metabolic processes or prevention of many age-related diseases. Although it is still early to define their exact clinical benefits for treating age-related disease, a diet rich in polyphenolic or other forms of antioxidants does seem to offer hope in delaying the onset of age-related disorders. It is now clear that any deficiency in antioxidant vitamins, inadequate enzymatic antioxidant defenses can distinctive for many age-related disease, and protein carbonylation can used as an indicator of oxidative stress associated diseases and aging status. This review examines antioxidant compounds and plant polyphenols as redox regulators in health, disease and aging processes with hope that a better understanding of the many mechanisms involved with these distinct compounds, which may lead to better health and novel treatment approaches for age-related diseases.

Nf1 loss and Ras hyperactivation in oligodendrocytes induce NOS-driven defects in myelin and vasculature

Patients with neurofibromatosis type 1 (NF1) and Costello syndrome Rasopathy have behavioral deficits. In NF1 patients, these may correlate with white matter enlargement and aberrant myelin. To model these features, we induced Nf1 loss or HRas hyperactivation in mouse oligodendrocytes. Enlarged brain white matter tracts correlated with myelin decompaction, downregulation of claudin-11, and mislocalization of connexin-32. Surprisingly, non-cell-autonomous defects in perivascular astrocytes and the blood-brain barrier (BBB) developed, implicating a soluble mediator. Nitric oxide (NO) can disrupt tight junctions and gap junctions, and NO and NO synthases (NOS1–NOS3) were upregulated in mutant white matter. Treating mice with the NOS inhibitor NG-nitro-L-arginine methyl ester or the antioxidant N-acetyl cysteine corrected cellular phenotypes. CNP-HRasG12V mice also displayed locomotor hyperactivity, which could be rescued by antioxidant treatment. We conclude that Nf1/Ras regulates oligodendrocyte NOS and that dysregulated NO signaling in oligodendrocytes can alter the surrounding vasculature. The data suggest that anti-oxidants may improve some behavioral deficits in Rasopathy patients.