Antagonistic crosstalk between NF-κB and SIRT1 in the regulation of inflammation and metabolic disorders

The silent information regulator 1 (Sirt1) is a positive regulator of the Notch pathway in Drosophila

The silent information regulator 1 (Sirt1) has been shown to have negative effects on the Notch pathway in several contexts. We bring evidence that Sirt1 has a positive effect on Notch activation in Drosophila, in the context of sensory organ precursor specification and during wing development. The phenotype of Sirt1 mutant resembles weak Notch loss-of-function phenotypes, and genetic interactions of Sirt1 with the components of the Notch pathway also suggest a positive role for Sirt1 in Notch signalling. Sirt1 is necessary for the efficient activation of enhancer of split [E(spl)] genes by Notch in S2N cells. Additionally, the Notch-dependent response of several E(spl) genes is sensitive to metabolic stress caused by 2-deoxy-d-glucose treatment, in a Sirt1-dependent manner. We found Sirt1 associated with several proteins involved in Notch repression as well as activation, including the cofactor exchange factor Ebi (TBL1), the RLAF/LAF histone chaperone complex and the Tip60 acetylation complex. Moreover, Sirt1 participates in the deacetylation of the CSL transcription factor Suppressor of Hairless. The role of Sirt1 in Notch signalling is, therefore, more complex than previously recognized, and its diverse effects may be explained by a plethora of Sirt1 substrates involved in the regulation of Notch signalling.

Role of nutraceutical SIRT1 modulators in AMPK and mTOR pathway: Evidence of a synergistic effect

OBJECTIVE

The aim of this study was to evaluate the effect of different natural substances on SIRT1 expression and on AMPK and mTOR phosphorylation. Moreover, we investigated the presence of a synergistic effect between the substances.

METHODS

Human cervical carcinoma cells were seeded in 12-well plates, then incubated with the nine tested substances (resveratrol, quercetin, berberine, catechin, tyrosol, ferulic acid, niclosamide, curcumin, and malvidin) at different concentrations and left in incubation for 3, 6, and 24 h. The targeting proteins' expression and phosphorylation were evaluated by immunoblotting, and cytotoxicity tests were performed by CellTiter-Blue Cell Viability Assay.

RESULTS

No statistically significant decrease (P > 0.05) in the number of viable cells was found. The expression of SIRT1 was significantly increased in all experimental groups compared with the control group (P < 0.001). Instead, the simultaneous administration involved a significant and synergistic increase in the expression of SIRT1 for some but not all of the tested compounds. Finally, the individual administration of berberine, quercetin, ferulic acid, and tyrosol resulted in a statistically significant increase in AMPK activation and mTOR inhibition, whereas their associated administration did not reveal a synergistic effect.

CONCLUSIONS

Our results provide evidence that all compounds have the potential to stimulate SIRT1 and sustain the stimulating action of resveratrol on SIRT1, already widely reported in the literature. In this regard, we confirm the interaction of these substances also with the pathway of AMPK and mTOR, in support of the studies that highlight the importance of SIRT1/AMPK and mTOR pathway in many diseases.

Melatonin modulates neonatal brain inflammation through endoplasmic reticulum stress, autophagy, and miR-34a/silent information regulator 1 pathway

Maternal infection/inflammation represents one of the most important factors involved in the etiology of brain injury in newborns. We investigated the modulating effect of prenatal melatonin on the neonatal brain inflammation process resulting from maternal intraperitoneal (i.p.) lipopolysaccharide (LPS) injections. LPS (300 μg/kg) was administered to pregnant rats at gestational days 19 and 20. Melatonin (5 mg/kg) was administered i.p. at the same time as LPS. Melatonin counteracted the LPS sensitization to a second ibotenate-induced excitotoxic insult performed on postnatal day (PND) 4. As melatonin succeeded in reducing microglial activation in neonatal brain at PND1, pathways previously implicated in brain inflammation regulation, such as endoplasmic reticulum (ER) stress, autophagy and silent information regulator 1 (SIRT1), a melatonin target, were assessed at the same time-point in our experimental groups. Results showed that maternal LPS administrations resulted in an increase in CHOP and Hsp70 protein expression and eIF2α phosphorylation, indicative of activation of the unfolded protein response consequent to ER stress, and a slighter decrease in the autophagy process, determined by reduced lipidated LC3 and increased p62 expression. LPS-induced inflammation also reduced brain SIRT1 expression and affected the expression of miR-34a, miR146a, and miR-126. All these effects were blocked by melatonin. Cleaved-caspase-3 apoptosis pathway did not seem to be implicated in the noxious effect of LPS on the PND1 brain. We conclude that melatonin is effective in reducing maternal LPS-induced neonatal inflammation and related brain injury. Its role as a prophylactic/therapeutic drug deserves to be investigated by clinical studies.

Metabolism and acetylation in innate immune cell function and fate

Innate immunity is the first line of defense against invading pathogens. Changes in both metabolism and chromatin accessibility contribute to the shaping of these innate immune responses, and we are beginning to appreciate that cross-talk between these two systems plays an important role in determining innate immune cell differentiation and function. In this review we focus on acetylation, a post-translational modification important for both regulating chromatin accessibility by modulating histone function, and for functional regulation of non-histone proteins, which has many links to both immune signaling and metabolism. We discuss the interactions between metabolism and acetylation, including the requirement for metabolic intermediates as substrates and co-factors for acetylation, and the regulation of metabolic proteins and enzymes by acetylation. Here we highlight recent findings, which demonstrate the role that the metabolism-acetylation axis has in coordinating the responses of innate immune cells to the availability of nutrients and the microenvironment.

Molecular Mechanisms of Latent Inflammation in Metabolic Syndrome. Possible Role of Sirtuins and Peroxisome Proliferator-Activated Receptor Type γ

The problem of metabolic syndrome is one of the most important in medicine today. The main hazard of metabolic syndrome is development of latent inflammation in adipose tissue, which promotes atherosclerosis, non-alcoholic fatty liver disease, myocarditis, and a number of other illnesses. Therefore, understanding of molecular mechanisms of latent inflammation in adipose tissue is very important for treatment of metabolic syndrome. Three main components that arise during hypertrophy and hyperplasia of adipocytes underlie such inflammation: endoplasmic reticulum stress, oxidative stress, and hypoxia. Each of these components mediates activation in different ways of the key factor of inflammation - NF-κB. For metabolic syndrome therapy, it is suggested to influence a number of inflammatory signaling components by activating other cell factors to suppress development of inflammation. Such potential factors are peroxisome proliferator-activated receptors type γ that suppress transcription factor NF-κB through direct contact or via kinase of a NF-κB inhibitor (IKK), and also the antiinflammatory transcription factor AP-1. Other possible targets are type 3 NAD+-dependent histone deacetylases (sirtuins). There are mutually antagonistic relationships between NF-κB and sirtuin type 1 that prevent development of inflammation in metabolic syndrome. Moreover, sirtuin type 1 inhibits the antiinflammatory transcription factor AP-1. Study of the influence of these factors on the relationship between macrophages and adipocytes, macrophages, and adipose tissue-derived stromal cells can help to understand mechanisms of signaling and development of latent inflammation in metabolic syndrome.

The Tumor Microenvironment Represses T Cell Mitochondrial Biogenesis to Drive Intratumoral T Cell Metabolic Insufficiency and Dysfunction

Although tumor-specific T cells recognize cancer cells, they are often rendered dysfunctional due to an immunosuppressive microenvironment. Here we showed that T cells demonstrated persistent loss of mitochondrial function and mass when infiltrating murine and human tumors, an effect specific to the tumor microenvironment and not merely caused by activation. Tumor-infiltrating T cells showed a progressive loss of PPAR-gamma coactivator 1α (PGC1α), which programs mitochondrial biogenesis, induced by chronic Akt signaling in tumor-specific T cells. Reprogramming tumor-specific T cells through enforced expression of PGC1α resulted in superior intratumoral metabolic and effector function. Our data support a model in which signals in the tumor microenvironment repress T cell oxidative metabolism, resulting in effector cells with metabolic needs that cannot be met. Our studies also suggest that modulation or reprogramming of the altered metabolism of tumor-infiltrating T cells might represent a potential strategy to reinvigorate dysfunctional T cells for cancer treatment.

SIRT1 and SIRT7 expression in adipose tissues of obese and normal-weight individuals is regulated by microRNAs but not by methylation status

BACKGROUND/OBJECTIVE

Given their importance in the regulation of metabolism, sirtuins (SIRTs) constitute promising subjects of research on the pathogenesis of obesity and the metabolic syndrome. The aim of this study was to assess whether obesity in humans is associated with changes in the expression of SIRT genes in adipose tissue and whether epigenetic mechanisms, DNA methylation and microRNA (miRNA) interference, mediate in this phenomenon.

SUBJECTS/METHODS

The expression of SIRTs and of SIRT1 and SIRT7 mRNA-interacting miRNAs was evaluated by real-time PCR in visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) of 58 obese (body mass index (BMI) >40 kg m^-2) and 31 normal-weight (BMI 20-24.9 kg m^-2) individuals. The methylation status of SIRTs was studied by the methylation-sensitive digestion/real-time PCR method.

RESULTS

SIRT1 mRNA levels were lower in adipose tissues of obese patients than of normal-weight controls (VAT: P=0.0002, SAT: P=0.008). In contrast, expression of SIRT7 was higher in adipose tissues of obese patients than in the control group (VAT: P=0.001, SAT: P=0.008). The mean methylation of the SIRT1 and SIRT7 CpG islands was similar in tissues with high and low expression of these genes, and there was no correlation between the level of expression and the level of methylation. On the other hand, expression of SIRT1 in VAT of obese subjects correlated negatively with the expression of miR-22-3p (P<0.0001, r_s=-0.514), miR-34a-5p (P=0.01, r_s=-0.326) and miR-181a-3p (P<0.0001, r_s=-0.536). In turn, expression of SIRT7 in VAT of slim individuals correlated negatively with the expression of miR-125a-5p (P=0.003, r_s=-0.562) and miR-125b-5p (P=0.018, r_s=-0.460).

CONCLUSIONS

We observed obesity-associated downregulation of SIRT1 and upregulation of SIRT7 mRNA levels that were not associated with the methylation status of their promoters. We found a negative correlation between mRNA levels of SIRT1 in VAT of obese individuals and SIRT7 in VAT of the normal-weight subjects and expression of the relevant miRNAs.

Platelet-Rich Plasma Activates Proinflammatory Signaling Pathways and Induces Oxidative Stress in Tendon Fibroblasts

BACKGROUND

Tendon injuries are one of the most common musculoskeletal conditions in active patients. Platelet-rich plasma (PRP) has shown some promise in the treatment of tendon disorders, but little is known as to the mechanisms by which PRP can improve tendon regeneration. PRP contains numerous different growth factors and cytokines that activate various cellular signaling cascades, but it has been difficult to determine precisely which signaling pathways and cellular responses are activated after PRP treatment. Additionally, macrophages play an important role in modulating tendon regeneration, but the influence of PRP on determining whether macrophages assume a proinflammatory or anti-inflammatory phenotype remains unknown.

PURPOSE

To use genome-wide expression profiling, bioinformatics, and protein analysis to determine the cellular pathways activated in fibroblasts treated with PRP. The effect of PRP on macrophage polarization was also evaluated.

STUDY DESIGN

Controlled laboratory study.

METHODS

Tendon fibroblasts or macrophages from rats were cultured and treated with either platelet-poor plasma (PPP) or PRP. RNA or protein was isolated from cells and analyzed using microarrays, quantitative polymerase chain reaction, immunoblotting, or bioinformatics techniques.

RESULTS

Pathway analysis determined that the most highly induced signaling pathways in PRP-treated tendon fibroblasts were TNFα and NFκB pathways. PRP also downregulated the expression of extracellular matrix genes and induced the expression of autophagy-related genes and reactive oxygen species (ROS) genes and protein markers in tendon fibroblasts. PRP failed to have a major effect on markers of macrophage polarization.

CONCLUSION

PRP induces an inflammatory response in tendon fibroblasts, which leads to the formation of ROS and the activation of oxidative stress pathways. PRP does not appear to significantly modulate macrophage polarization.

CLINICAL RELEVANCE

PRP might act by inducing a transient inflammatory event, which could then trigger a tissue regeneration response.

Nicotinamide phosphoribosyltransferase (Nampt) in carcinogenesis: new clinical opportunities

INTRODUCTION

Nicotinamide phosphoribosyltransferase (Nampt) is the rate-limiting enzyme that catalyzes the first step in the mammalian nicotinamide adenine dinucleotide (NAD) salvage pathway. Aberrant NAD metabolism was associated with oncogenic signal transduction, suggesting the critical roles of Nampt in tumorigenesis and metastasis. Additionally, Nampt can be secreted out of the cell, and this extracellular form of Nampt (eNampt) was shown to induce inflammation and angiogenesis due to its cytokine activity, which may also be involved in carcinogenesis.

AREAS COVERED

This article reviews recent advances in the studies of Nampt in carcinogenesis, with a special highlight on Nampt inhibitors and future clinical application, including cancer diagnosis, prognosis and therapy. Expert commentary: Nampt not only maintains the balance of cellular metabolism, but also has a profound influence on multiple aspects of carcinogenesis. Therefore, elucidation of these mechanisms opens the door for future clinical applications targeting this protein. Additional studies are needed to address important questions including the relationship between extracellular Nampt and carcinogenesis.

Metabolic profiling distinguishes three subtypes of Alzheimer's disease

The cause of Alzheimer's disease is incompletely defined, and no truly effective therapy exists. However, multiple studies have implicated metabolic abnormalities such as insulin resistance, hormonal deficiencies, and hyperhomocysteinemia. Optimizing metabolic parameters in a comprehensive way has yielded cognitive improvement, both in symptomatic and asymptomatic individuals. Therefore, expanding the standard laboratory evaluation in patients with dementia may be revealing. Here I report that metabolic profiling reveals three Alzheimer's disease subtypes. The first is inflammatory, in which markers such as hs-CRP and globulin:albumin ratio are increased. The second type is non-inflammatory, in which these markers are not increased, but other metabolic abnormalities are present. The third type is a very distinctive clinical entity that affects relatively young individuals, extends beyond the typical Alzheimer's disease initial distribution to affect the cortex widely, is characterized by early non-amnestic features such as dyscalculia and aphasia, is often misdiagnosed or labeled atypical Alzheimer's disease, typically affects ApoE4-negative individuals, and is associated with striking zinc deficiency. Given the involvement of zinc in multiple Alzheimer's-related metabolic processes, such as insulin resistance, chronic inflammation, ADAM10 proteolytic activity, and hormonal signaling, this syndrome of Alzheimer's-plus with low zinc (APLZ) warrants further metabolic, genetic, and epigenetic characterization.

Mitochondrial function in hypoxic ischemic injury and influence of aging

Mitochondria are a major target in hypoxic/ischemic injury. Mitochondrial impairment increases with age leading to dysregulation of molecular pathways linked to mitochondria. The perturbation of mitochondrial homeostasis and cellular energetics worsens outcome following hypoxic-ischemic insults in elderly individuals. In response to acute injury conditions, cellular machinery relies on rapid adaptations by modulating posttranslational modifications. Therefore, post-translational regulation of molecular mediators such as hypoxia-inducible factor 1α (HIF-1α), peroxisome proliferator-activated receptor γ coactivator α (PGC-1α), c-MYC, SIRT1 and AMPK play a critical role in the control of the glycolytic-mitochondrial energy axis in response to hypoxic-ischemic conditions. The deficiency of oxygen and nutrients leads to decreased energetic reliance on mitochondria, promoting glycolysis. The combination of pseudohypoxia, declining autophagy, and dysregulation of stress responses with aging adds to impaired host response to hypoxic-ischemic injury. Furthermore, intermitochondrial signal propagation and tissue wide oscillations in mitochondrial metabolism in response to oxidative stress are emerging as vital to cellular energetics. Recently reported intercellular transport of mitochondria through tunneling nanotubes also play a role in the response to and treatments for ischemic injury. In this review we attempt to provide an overview of some of the molecular mechanisms and potential therapies involved in the alteration of cellular energetics with aging and injury with a neurobiological perspective.

Inhibition of Extracellular Calcium Influx Results in Enhanced IL-12 Production in LPS-Treated Murine Macrophages by Downregulation of the CaMKKβ-AMPK-SIRT1 Signaling Pathway

Activated macrophages are the primary sources of IL-12, a key cytokine bridging innate and adaptive immunity. However, macrophages produce low amounts of IL-12 upon stimulation and the underlying regulatory mechanism remains unclear. In this study, we found a new calcium-dependent mechanism that controlled IL-12 production in LPS-treated murine macrophages. First, LPS was demonstrated to induce extracellular calcium entry in murine peritoneal macrophages and inhibition of calcium influx resulted in marked enhancement in IL-12 production. Then, withdrawal of extracellular calcium was found to suppress CaMKKβ and AMPK activation triggered by LPS while chemical inhibition or genetic knockdown of these two kinases augmented LPS induced IL-12 production. AMPK activation increased the NAD⁺/NADH ratio and activated Sirtuin 1 (SIRT1), a NAD⁺-dependent deacetylating enzyme and negative regulator of inflammation. Chemical inhibitor or siRNA of SIRT1 enhanced IL-12 release while its agonist suppressed IL-12 production. Finally, it was found that SIRT1 selectively affected the transcriptional activity of NF-κB which thereby inhibited IL-12 production. Overall, our study demonstrates a new role of transmembrane calcium mobilization in immunity modulation such that inhibition of calcium influx leads to impaired activation of CaMKKβ-AMPK-SIRT1 signaling pathway which lifts restriction on NF-κB activation and results in enhanced IL-12 production.

Direct Transcriptional Effects of Apolipoprotein E

A major unanswered question in biology and medicine is the mechanism by which the product of the apolipoprotein E ε4 allele, the lipid-binding protein apolipoprotein E4 (ApoE4), plays a pivotal role in processes as disparate as Alzheimer's disease (AD; in which it is the single most important genetic risk factor), atherosclerotic cardiovascular disease, Lewy body dementia, hominid evolution, and inflammation. Using a combination of neural cell lines, skin fibroblasts from AD patients, and ApoE targeted replacement mouse brains, we show in the present report that ApoE4 undergoes nuclear translocation, binds double-stranded DNA with high affinity (low nanomolar), and functions as a transcription factor. Using chromatin immunoprecipitation and high-throughput DNA sequencing, our results indicate that the ApoE4 DNA binding sites include ∼1700 gene promoter regions. The genes associated with these promoters provide new insight into the mechanism by which AD risk is conferred by ApoE4, because they include genes associated with trophic support, programmed cell death, microtubule disassembly, synaptic function, aging, and insulin resistance, all processes that have been implicated in AD pathogenesis. Significance statement: This study shows for the first time that apolipoprotein E4 binds DNA with high affinity and that its binding sites include 1700 promoter regions that include genes associated with neurotrophins, programmed cell death, synaptic function, sirtuins and aging, and insulin resistance, all processes that have been implicated in Alzheimer's disease pathogenesis.

Dynamic self-guiding analysis of Alzheimer's disease

We applied a self-guiding evolutionary algorithm to initiate the synthesis of the Alzheimer's disease-related data and literature. A protein interaction network associated with amyloid-beta precursor protein (APP) and a seed model that treats Alzheimer's disease as progressive dysregulation of APP-associated signaling were used as dynamic “guides” and structural “filters” in the recursive search, analysis, and assimilation of data to drive the evolution of the seed model in size, detail, and complexity. Analysis of data and literature across sub-disciplines and system-scale discovery platforms suggests a key role of dynamic cytoskeletal connectivity in the stability, plasticity, and performance of multicellular networks and architectures. Chronic impairment and/or dysregulation of cell adhesions/synapses, cytoskeletal networks, and/or reversible epithelial-to-mesenchymal-like transitions, which enable and mediate the stable and coherent yet dynamic and reconfigurable multicellular architectures, may lead to the emergence and persistence of the disordered, wound-like pockets/microenvironments of chronically disconnected cells. Such wound-like microenvironments support and are supported by pro-inflammatory, pro-secretion, de-differentiated cellular phenotypes with altered metabolism and signaling. The co-evolution of wound-like microenvironments and their inhabitants may lead to the selection and stabilization of degenerated cellular phenotypes, via acquisition of epigenetic modifications and mutations, which eventually result in degenerative disorders such as cancer and Alzheimer's disease.

Polyunsaturated fatty acid induces cardioprotection against ischemia-reperfusion through the inhibition of NF-kappaB and induction of Nrf2

The mechanistic evidence to support the cardioprotective effects of polyunsaturated fatty acids (PUFA) are controversial. The aim was to test cardioprotective mechanisms induced by PUFA supplementation against cardiac ischemia-reperfusion (IR) injury. Ten-week-old male Wistar rats (225 ± 14 g, n = 14) were divided in two groups: rats without supplementation ( n = 7) and a PUFA group, supplemented by PUFA (0.6 g/kg/day; DHA:EPA = 3:1) for eight weeks ( n = 7). Hearts were perfused with Krebs-Henseleit buffer for 20 min (control conditions); others were subjected to control conditions, 30 min of global ischemia and 120 min of reperfusion (IR group). Infarct size (IS) and left ventricular developed pressure (LVDP) were measured at 120 min of reperfusion. Oxidative stress biomarkers (TBARS, total carbonyls), antioxidant status (CAT, catalase; SOD, superoxide dismutase; GSH-Px, glutathione peroxidase activity and GSH/GSSG ratio), myeloperoxidase activity, ATP levels and nuclear transcription factor erythroid 2-related factor 2 (Nrf2) and nuclear factor kappaB (NF-κB) were determined in both experimental conditions. At the end of reperfusion, hearts supplemented with PUFA showed lower IS and a higher LVDP compared with the nonsupplemented rats. Hearts in the group supplemented with PUFA showed lower levels of oxidative stress markers and higher antioxidant activity, decreased MPO activity and NF-κB and Nrf2 activation compared with the nonsupplemented group. Cardioprotective effects of PUFA are exerted through induction of anti-inflammatory and antioxidant mechanism at tissue level.

Resveratrol attenuates 4-hydroxy-2-hexenal-induced oxidative stress in mouse cortical collecting duct cells

Resveratrol (RSV) may provide numerous protective eff ects against chronic inflammatory diseases. Due to local hypoxia and hypertonicity, the renal medulla is subject to extreme oxidative stress, and aldehyde products formed during lipid peroxidation, such as 4-hydroxy-2-hexenal (HHE), might be responsible for tubular injury. This study aimed at investigating the eff ects of RSV on renal and its signaling mechanisms. While HHE treatment resulted in decreased expression of Sirt1, AQP2, and nuclear factor erythroid 2-related factor 2 (Nrf2), mouse cortical collecting duct cells (M1) cells treated with HHE exhibited increased activation of p38 MAPK, extracellular signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and increased expression of NOX4, p47^phox, Kelch ECH associating protein 1 (Keap1) and COX2. HHE treatment also induced NF-κB activation by promoting IκB-α degradation. Meanwhile, the observed increases in nuclear NF-κB, NOX4, p47^phox, and COX2 expression were attenuated by treatment with Bay 117082, N-acetyl-l-cysteine (NAC), or RSV. Our findings indicate that RSV inhibits the expression of inflammatory proteins and the production of reactive oxygen species in M1 cells by inhibiting NF-κB activation.

Diabetic retinopathy and transcriptional regulation of a small molecular weight G-Protein, Rac1

In diabetic retinopathy, increased cytosolic reactive oxygen species, produced by NADPH oxidase (Nox), damage mitochondria, and this accelerates apoptosis of retinal capillary cells, resulting in the histopathology. Activation of Nox2 is mediated by a small molecular weight GTPase, Rac1, and retinal Rac1 is activated in diabetes. Our goal is to investigate the molecular mechanism responsible for transcriptional activation of Rac1 in the development of diabetic retinopathy. Using retinal microvessels, the site of histopathology associated with diabetic retinopathy, from streptozotocin-induced diabetic rats, we investigated the binding of the nuclear transcriptional factor-kB (NF-kB) at Rac1 promoter. Since activation of NF-kB is regulated by its acetylation-deacetylation, the role of acetylation in Rac1 transcription was confirmed in the retina from diabetic mice overexpressing a deacetylase, Sirtuin 1. Diabetes increased the binding of p65 subunit of NF-kB at the Rac1 promoter. Overexpression of Sirtuin 1 prevented hyper-acetylation of p65, decreased its binding at the Rac1 promoter and ameliorated Rac1-Nox2 mediated mitochondrial damage. Thus, in diabetes Rac1 transcriptional activation in the retina is mediated by acetylation of NF-kB, and modulation of acetylation during the early stages of diabetic retinopathy has potential to inhibit/retard its development.

Inhibition of BET bromodomains alleviates inflammation in human RPE cells

Bromodomain-containing proteins are vital for controlling the expression of many pro-inflammatory genes. Consequently, compounds capable of inhibiting specific bromodomain-facilitated protein-protein interactions would be predicted to alleviate inflammation, making them valuable agents in the treatment of diseases caused by dysregulated inflammation, such as age-related macular degeneration. Here, we assessed the ability of known inhibitors JQ-1, PFI-1, and IBET-151 to protect from the inflammation and cell death caused by etoposide exposure in the human retinal pigment epithelial cell line, ARPE-19. The potential anti-inflammatory effects of the bromodomain inhibitors were assessed by ELISA (enzyme-linked immunosorbent assay) profiling. The involvement of NF-κB and SIRT1 in inflammatory signaling was monitored by ELISA and western blotting. Furthermore, SIRT1 was knocked down using a specific siRNA or inhibited by EX-527 to elucidate its role in the inflammatory reaction. The bromodomain inhibitors effectively decreased etoposide-induced release of IL-6 and IL-8. This anti-inflammatory effect was not related to SIRT1 activity, although all bromodomain inhibitors decreased the extent of acetylation of p53 at the SIRT1 deacetylation site. Overall, since bromodomain inhibitors display anti-inflammatory properties in human retinal pigment epithelial cells, these compounds may represent a new way of alleviating the inflammation underlying the onset of age-related macular degeneration.

Sir2 Acts through Hepatocyte Nuclear Factor 4 to maintain insulin Signaling and Metabolic Homeostasis in Drosophila

SIRT1 is a member of the sirtuin family of NAD+-dependent deacetylases, which couple cellular metabolism to systemic physiology. Although studies in mouse models have defined a central role for SIRT1 in maintaining metabolic health, the molecular mechanisms remain unclear. Here we show that loss of the Drosophila SIRT1 homolog sir2 leads to the age-progressive onset of hyperglycemia, obesity, glucose intolerance, and insulin resistance. Tissue-specific functional studies show that Sir2 is both necessary and sufficient in the fat body (analogous to the mammalian liver) to maintain glucose homeostasis and peripheral insulin sensitivity. Transcriptional profiling of sir2 mutants by RNA-seq revealed a major overlap with genes regulated by the nuclear receptor Hepatocyte Nuclear Factor 4 (HNF4). Consistent with this, Drosophila HNF4 mutants display diabetic phenotypes similar to those of sir2 mutants, and protein levels for dHNF4 are reduced in sir2 mutant animals. We show that Sir2 exerts these effects by deacetylating and stabilizing dHNF4 through protein interactions. Increasing dHNF4 expression in sir2 mutants is sufficient to rescue their insulin signaling defects, defining this nuclear receptor as an important downstream effector of Sir2 signaling. This study demonstrates that the key metabolic activities of SIRT1 have been conserved through evolution, provides a genetic model for functional studies of phenotypes related to type 2 diabetes, and establishes HNF4 as a critical downstream target by which Sir2 maintains metabolic health.

Anti-Apoptotic and Pro-Survival Effect of Alpinate Oxyphyllae Fructus (AOF) in a d-Galactose-Induced Aging Heart

Aging, a natural biological/physiological phenomenon, is accelerated by reactive oxygen species (ROS) accumulation and identified by a progressive decrease in physiological function. Several studies have shown a positive relationship between aging and chronic heart failure (HF). Cardiac apoptosis was found in age-related diseases. We used a traditional Chinese medicine, Alpinate Oxyphyllae Fructus (AOF), to evaluate its effect on cardiac anti-apoptosis and pro-survival. Male eight-week-old Sprague–Dawley (SD) rats were segregated into five groups: normal control group (NC), d-Galactose-Induced aging group (Aging), and AOF of 50 (AL (AOF low)), 100 (AM (AOF medium)), 150 (AH (AOF high)) mg/kg/day. After eight weeks, hearts were measured by an Hematoxylin–Eosin (H&E) stain, Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-assays and Western blotting. The experimental results show that the cardiomyocyte apoptotic pathway protein expression increased in the d-Galactose-Induced aging groups, with dose-dependent inhibition in the AOF treatment group (AL, AM, and AH). Moreover, the expression of the pro-survival p-Akt (protein kinase B (Akt)), Bcl-2 (B-cell lymphoma 2), anti-apoptotic protein (Bcl-xL) protein decreased significantly in the d-Galactose-induced aging group, with increased performance in the AOF treatment group with levels of p-IGFIR and p-PI3K (Phosphatidylinositol-3′ kinase (PI3K)) to increase by dosage and compensatory performance. On the other hand, the protein of the Sirtuin 1 (SIRT1) pathway expression decreased in the aging groups and showed improvement in the AOF treatment group. Our results suggest that AOF strongly works against ROS-induced aging heart problems.

Short-term exposure to a diet high in fat and sugar, or liquid sugar, selectively impairs hippocampal-dependent memory, with differential impacts on inflammation

Chronic high-energy diets are known to induce obesity and impair memory; these changes have been associated with inflammation in brain areas crucial for memory. In this study, we investigated whether inflammation could also be related to diet-induced memory deficits, prior to obesity. We exposed rats to chow, chow supplemented with a 10% sucrose solution (Sugar) or a diet high in fat and sugar (Caf+Sugar) and assessed hippocampal-dependent and perirhinal-dependent memory at 1 week. Both high-energy diet groups displayed similar, selective hippocampal-dependent memory deficits despite the Caf+Sugar rats consuming 4-5 times more energy, and weighing significantly more than the other groups. Extreme weight gain and excessive energy intake are therefore not necessary for deficits in memory. Weight gain across the diet period however, was correlated with the memory deficits, even in the Chow rats. The Sugar rats had elevated expression of a number of inflammatory genes in the hippocampus and WAT compared to Chow and Caf+Sugar rats but not in the perirhinal cortex or hypothalamus. Blood glucose concentrations were also elevated in the Sugar rats, and were correlated with the hippocampal inflammatory markers. Together, these results indicate that liquid sugar can rapidly elevate markers of central and peripheral inflammation, in association with hyperglycemia, and this may be related to the memory deficits in the Sugar rats.

SIRT1 alleviates senescence of degenerative human intervertebral disc cartilage endo-plate cells via the p53/p21 pathway

Cartilage end plates (CEP) degeneration plays an integral role in intervertebral disc (IVD) degeneration resulting from nutrient diffusion disorders. Although cell senescence resulting from oxidative stress is known to contribute to degeneration, no studies concerning the role of senescence in CEP degeneration have been conducted. SIRT1 is a longevity gene that plays a pivotal role in many cellular functions, including cell senescence. Therefore, the aim of this study was to investigate whether senescence is more prominent in human degenerative CEP and whether SIRT1-regulated CEP cells senescence in degenerative IVD as well as identify the signaling pathways that control that cell fate decision. In this study, the cell senescence phenotype was found to be more prominent in the CEP cells obtained from disc degenerative disease (DDD) patients than in the CEP cells obtained from age-matched lumbar vertebral fractures (LVF) patients. In addition, the results indicated that p53/p21 pathway plays an important role in the senescence of CEP cells in vivo and vitro. Furthermore, SIRT1 was found to be capable of alleviating the oxidative stress-induced senescence of CEP cells in humans via p53/p21 pathway. Thus, the information presented in this study could be used to further investigate the underlying mechanisms of CEP.

The emerging role of fibroblast growth factor 21 in diabetic nephropathy

Diabetic nephropathy (DN), an important cause of end-stage renal diseases, brings about great social and economic burden. Due to the variable pathological changes and clinical course, the prognosis of DN is very difficult to predict. DN is also usually associated with enhanced genomic damage and cellular injury. Fibroblast growth factor 21 (FGF21), a nutritionally regulated hormone secreted mainly by the liver, plays a critical role in metabolism. Administration of FGF21 decreases blood glucose, triglyceride, and cholesterol levels, and improves insulin sensitivity, which is closely associated with the development and progression of glomerular diseases. In addition, FGF21 level was associated with renal function. However, the precise role of FGF21 in DN remains unclear. This review will give a comprehensive understanding of the underlying role of FGF21 and its possible interaction with other molecules in DN.

AMPK-Activated Protein Kinase Suppresses Ccr2 Expression by Inhibiting the NF-κB Pathway in RAW264.7 Macrophages

C-C chemokine receptor 2 (Ccr2) is a key pro-inflammatory marker of classic (M1) macrophage activation. Although Ccr2 is known to be expressed both constitutively and inductively, the full regulatory mechanism of its expression remains unclear. AMP-activated protein kinase (AMPK) is not only a master regulator of energy homeostasis but also a central regulator of inflammation. In this study, we sought to assess AMPK's role in regulating RAW264.7 macrophage Ccr2 protein levels in resting (M0) or LPS-induced M1 states. In both M0 and M1 RAW264.7 macrophages, knockdown of the AMPKα1 subunit by siRNA led to increased Ccr2 levels whereas pharmacologic (A769662) activation of AMPK, attenuated LPS-induced increases in Ccr2 expression in an AMPK dependent fashion. The increases in Ccr2 levels by AMPK downregulation were partially reversed by NF-κB inhibition whereas TNF-a inhibition had minimal effects. Our results indicate that AMPK is a negative regulator of Ccr2 expression in RAW264.7 macrophages, and that the mechanism of action of AMPK inhibition of Ccr2 is mediated, in part, through the NF-κB pathway.

Hydrogen Sulfide Attenuates Inflammatory Hepcidin by Reducing IL-6 Secretion and Promoting SIRT1-Mediated STAT3 Deacetylation

AIMS

Anemia of inflammation is quite prevalent in hospitalized patients with poor prognosis. Concerns about the effectiveness and safety of iron supplementation have arisen, driving the demand for alternative therapies. Induction of hepatic hepcidin, the master hormone of iron homeostasis, causes anemia under inflammatory conditions. Previous studies indicated that hydrogen sulfide (H2S), the third gasotransmitter and a well-known regulator of inflammation, may inhibit the secretion of inflammatory cytokines. We thus investigated the effect of H2S on inflammatory hepcidin induction.

RESULTS

H2S suppressed lipopolysaccharide (LPS)-induced hepcidin production and regulated iron homeostasis in mice by decreasing serum interleukin-6 (IL-6) and Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) activation; similar results were obtained in Huh7 cells exposed to conditioned medium from LPS-challenged THP-1 macrophages. Intriguingly, we found H2S also attenuated hepcidin levels in Huh7 cells and mouse primary hepatocytes in a sirtuin 1 (SIRT1)-dependent manner. By promoting SIRT1 expression and stabilizing SIRT1-STAT3 interactions, H2S ameliorated IL-6-induced STAT3 acetylation, resulting in reduced hepcidin production. Inhibition and silencing of SIRT1 diminished H2S-mediated suppression of hepcidin, as opposed to SIRT1 activation and overexpression. Consistent results were observed in vivo. Furthermore, knockout of cystathionine γ-lyase (CSE), an endogenous H2S synthase, exaggerated inflammatory hepcidin expression in mice.

INNOVATION

For the first time, we elucidated the effects and possible mechanisms of H2S on inflammatory hepcidin and established a novel regulatory link between SIRT1 and hepcidin.

CONCLUSION

Our work demonstrates that H2S attenuates inflammation-induced hepatic hepcidin via multipathways and suggests new treatment strategies for anemia of inflammation.

The Interplay of Reactive Oxygen Species, Hypoxia, Inflammation, and Sirtuins in Cancer Initiation and Progression

The presence of ROS is a constant feature in living cells metabolizing O2. ROS concentration and compartmentation determine their physiological or pathological effects. ROS overproduction is a feature of cancer cells and plays several roles during the natural history of malignant tumor. ROS continuously contribute to each step of cancerogenesis, from the initiation to the malignant progression, acting directly or indirectly. In this review, we will (a) underline the role of ROS in the pathway leading a normal cell to tumor transformation and progression, (b) define the multiple roles of ROS during the natural history of a tumor, (c) conciliate many conflicting data about harmful or beneficial effects of ROS, (d) rethink the importance of oncogene and tumor suppressor gene mutations in relation to the malignant progression, and (e) collocate all the cancer hallmarks in a mechanistic sequence which could represent a "physiological" response to the initial growth of a transformed stem/pluripotent cell, defining also the role of ROS in each hallmark. We will provide a simplified sketch about the relationships between ROS and cancer. The attention will be focused on the contribution of ROS to the signaling of HIF, NFκB, and Sirtuins as a leitmotif of cancer initiation and progression.

The peroxisome proliferator-activated receptor γ agonist pioglitazone prevents NF-κB activation in cisplatin nephrotoxicity through the reduction of p65 acetylation via the AMPK-SIRT1/p300 pathway

The thiazolidinedione pioglitazone, which is also a PPAR-γ agonist, now is widely used in patients with hypercholesterolemia and hypertriglyceridemia. NF-κB is a ubiquitously expressed transcription factor controlling the expression of numerous genes involved in inflammation. The aim of the present study was to evaluate whether the activation of PPAR-γ attenuates the cisplatin-induced NF-κB activation in cisplatin nephrotoxicity. The results showed that the PPAR-γ agonist pioglitazone decreased the expression of NF-κB p65 transcription target genes (e.g., IL-6, IL-1β, and TNF-α) and inhibited histological injury and inflammatory cells infiltration in cisplatin nephrotoxicity. The suppression of NF-κB activity following pioglitazone treatment inhibited the cisplatin-induced IκB-α degredation and NF-κB p65 subunit translocation. Translocation of the NF-κB p65 subunit depends on p65 acetylation, which primarily regulated by SIRT1 or p300. Notably, AMP kinase (AMPK) activation not only decreased the phosphorylation, activation and p65 interaction of p300 but also increased SIRT1 expression, activation and p65 binding, thus leading to a significant reduction in p65 acetylation. Interestingly, the reduction of IL-6, TNF-α and IL-1β, the inhibition of histological injury and the inflammatory cells infiltration following pioglitazone treatment in cisplatin nephrotoxicity were attenuated after treatment with the PPAR-γ antagonist GW9662. These results suggest that the PPAR-γ agonist pioglitazone prevents NF-κB activation in cisplatin nephrotoxicity through a reduction in p65 acetylation via the AMPK-SIRT1/p300 pathway.

Models and Methods to Investigate Acute Stress Responses in Cattle

There is a growing appreciation within the livestock industry and throughout society that animal stress is an important issue that must be addressed. With implications for animal health, well-being, and productivity, minimizing animal stress through improved animal management procedures and/or selective breeding is becoming a priority. Effective management of stress, however, depends on the ability to identify and quantify the effects of various stressors and determine if individual or combined stressors have distinct biological effects. Furthermore, it is critical to determine the duration of stress-induced biological effects if we are to understand how stress alters animal production and disease susceptibility. Common stress models used to evaluate both psychological and physical stressors in cattle are reviewed. We identify some of the major gaps in our knowledge regarding responses to specific stressors and propose more integrated methodologies and approaches to measuring these responses. These approaches are based on an increased knowledge of both the metabolic and immune effects of stress. Finally, we speculate on how these findings may impact animal agriculture, as well as the potential application of large animal models to understanding human stress.

Fisetin and luteolin protect human retinal pigment epithelial cells from oxidative stress-induced cell death and regulate inflammation

Degeneration of retinal pigment epithelial (RPE) cells is a clinical hallmark of age-related macular degeneration (AMD), the leading cause of blindness among aged people in the Western world. Both inflammation and oxidative stress are known to play vital roles in the development of this disease. Here, we assess the ability of fisetin and luteolin, to protect ARPE-19 cells from oxidative stress-induced cell death and to decrease intracellular inflammation. We also compare the growth and reactivity of human ARPE-19 cells in serum-free and serum-containing conditions. The absence of serum in the culture medium did not prevent ARPE-19 cells from reaching full confluency but caused an increased sensitivity to oxidative stress-induced cell death. Both fisetin and luteolin protected ARPE-19 cells from oxidative stress-induced cell death. They also significantly decreased the release of pro-inflammatory cytokines into the culture medium. The decrease in inflammation was associated with reduced activation of MAPKs and CREB, but was not linked to NF- κB or SIRT1. The ability of fisetin and luteolin to protect and repair stressed RPE cells even after the oxidative insult make them attractive in the search for treatments for AMD.

Inhibition of HMGB1 release via salvianolic acid B-mediated SIRT1 up-regulation protects rats against non-alcoholic fatty liver disease

The inflammatory mediator high-mobility group box 1 (HMGB1) plays a critical role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). However, the regulation of HMGB1 in NAFLD, particularly through sirtuin 1 (SIRT1), remains unclear. In this study, we investigated the role of SIRT1-mediated inhibition of HMGB1 release in NAFLD and the effect of salvianolic acid B (SalB), which is a water-soluble phenolic acid extracted from Radix Salvia miltiorrhiza, on NAFLD through SIRT1/HMGB1 signaling. In vivo, SalB treatment significantly attenuated high-fat diet (HFD)-induced liver damage, hepatic steatosis, and inflammation. Importantly, SalB significantly inhibited HMGB1 nuclear translocation and release, accompanied by SIRT1 elevation. In HepG2 cells, palmitic acid (PA)-induced pro-inflammatory cytokines release were blocked by HMGB1 small interfering RNA (siRNA) transfection. Moreover, pharmacological SIRT1 inhibition by Ex527 induced HMGB1 translocation and release, whereas SIRT1 activation by resveratrol or SalB reversed this trend. SIRT1 siRNA abrogated the SalB-mediated inhibition of HMGB1 acetylation and release, suggesting that SalB-mediated protection occurs by SIRT1 targeting HMGB1 for deacetylation. We are the first to demonstrate that the SIRT1/HMGB1 pathway is a key therapeutic target for controlling NAFLD inflammation and that SalB confers protection against HFD- and PA-induced hepatic steatosis and inflammation through SIRT1-mediated HMGB1 deacetylation.

Drugs acting on homeostasis: challenging cancer cell adaptation

Cancer treatment aims to exploit properties that define malignant cells. In recent years, it has become apparent that malignant cells often survive cancer treatment and ensuing cell stress by switching on auxiliary turnover pathways, changing cellular metabolism and, concomitantly, the gene expression profile. The changed profile impacts the material exchange of cancer cells with affected tissues. Herein, we show that pathways of proteostasis and energy generation regulate common transcription factors. Namely, when one pathway of intracellular turnover is blocked, it triggers alternative turnover mechanisms, which induce transcription factor proteins that control expression of cytokines and regulators of apoptosis, cell division, differentiation, metabolism, and response to hormones. We focus on several alternative turnover mechanisms that can be blocked by drugs already used in clinical practice for the treatment of other non-cancer related diseases. We also discuss paradigms on the challenges posed by cancer cell adaptation mechanisms.

Metformin ameliorates the proinflammatory state in patients with carotid artery atherosclerosis through sirtuin 1 induction

Metformin is a widely used classic antidiabetic drug. However, its clinical pharmacologic mechanism remains poorly understood. In the present study, we investigated the anti-inflammatory effects of metformin on circulating peripheral blood mononuclear cells (MNCs) of patients with carotid artery atherosclerosis (AS). A total of 42 patients with carotid artery AS were randomly assigned to metformin (500 mg twice a day; Met; n = 21) or placebo control (Con; n = 21) groups. After 12 weeks of treatment, plasma concentrations of high-sensitivity C-reactive protein (hs-CRP), interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α) significantly decreased in the Met group compared with the Con group. In addition, treatment with metformin significantly reduced the expression of IL-6 and TNF-α at the messenger RNA level and attenuated nuclear factor kappa B (NF-κB) DNA binding activity in MNCs. Intriguingly, metformin did not alter the expression of NF-κB p65 subunit, but markedly inhibited its acetylation. Furthermore, metformin significantly induced sirtuin 1 (SIRT1) expression in MNCs. Moreover, we found that metformin treatment dramatically induced SIRT1 expression, blocked p65 acetylation, and inhibited NF-κB activity and the expression of inflammatory factors in MNCs in vitro. We conclude that metformin has a novel direct protective role to ameliorate the proinflammatory response through SIRT1 induction, p65 acetylation reduction, NF-κB inactivation, and inflammatory inhibition in peripheral blood MNCs of patients with carotid artery AS.

Inflammation and intracellular metabolism: new targets in OA

Articular cartilage degeneration is hallmark of osteoarthritis (OA). Low-grade chronic inflammation in the joint can promote OA progression. Emerging evidence indicates that bioenergy sensors couple metabolism with inflammation to switch physiological and clinical phenotypes. Changes in cellular bioenergy metabolism can reprogram inflammatory responses, and inflammation can disturb cellular energy balance and increase cell stress. AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1) are two critical bioenergy sensors that regulate energy balance at both cellular and whole-body levels. Dysregulation of AMPK and SIRT1 has been implicated in diverse human diseases and aging. This review reveals recent findings on the role of AMPK and SIRT1 in joint tissue homeostasis and OA, with a focus on how AMPK and SIRT1 in articular chondrocytes modulate intracellular energy metabolism during stress responses (e.g., inflammatory responses) and how these changes dictate specific effector functions, and discusses translational significance of AMPK and SIRT1 as new therapeutic targets for OA.

Increased Oxidative and Nitrative Stress Accelerates Aging of the Retinal Vasculature in the Diabetic Retina

Hyperglycemia-induced retinal oxidative and nitrative stress can accelerate vascular cell aging, which may lead to vascular dysfunction as seen in diabetes. There is no information on whether this may contribute to the progression of diabetic retinopathy (DR). In this study, we have assessed the occurrence of senescence-associated markers in retinas of streptozotocin-induced diabetic rats at 8 and 12 weeks of hyperglycemia as compared to normoglycemic aging (12 and 14 months) and adult (4.5 months) rat retinas. We have found that in the diabetic retinas there was an up-regulation of senescence-associated markers SA-β-Gal, p16^INK4a and miR34a, which correlated with decreased expression of SIRT1, a target of miR34a. Expression of senescence-associated factors primarily found in retinal microvasculature of diabetic rats exceeded levels measured in adult and aging rat retinas. In aging rats, retinal expression of senescence associated-factors was mainly localized at the level of the retinal pigmented epithelium and only minimally in the retinal microvasculature. The expression of oxidative/nitrative stress markers such as 4-hydroxynonenal and nitrotyrosine was more pronounced in the retinal vasculature of diabetic rats as compared to normoglycemic aging and adult rat retinas. Treatments of STZ-rats with the anti-nitrating drug FeTPPS (10mg/Kg/day) significantly reduced the appearance of senescence markers in the retinal microvasculature. Our results demonstrate that hyperglycemia accelerates retinal microvascular cell aging whereas physiological aging affects primarily cells of the retinal pigmented epithelium. In conclusion, hyperglycemia-induced retinal vessel dysfunction and DR progression involve vascular cell senescence due to increased oxidative/nitrative stress.

TRAF1 knockdown alleviates palmitate-induced insulin resistance in HepG2 cells through NF-κB pathway

High-fat diet (HFD) and inflammation are key contributors to insulin resistance (IR) and Type 2 diabetes mellitus (T2DM). With HFD, plasma free fatty acids (FFAs) can activate the nuclear factor-κB (NF-κB) in target tissues, then initiate negative crosstalk between FFAs and insulin signaling. However, the molecular link between IR and inflammation remains to be identified. We here reported that tumor necrosis factor receptor-associated factor 1 (TRAF1), an adapter in signal transduction, was involved in the onset of IR in hepatocytes. TRAF1 was significantly up-regulated in insulin-resistant liver tissues and palmitate (PA)-treated HepG2 cells. In addition, we showed that depletion of TRAF1 led to inhibition of the activity of NF-κB. Given the fact that the activation of NF-κB played a facilitating role in IR, the phosphorylation of Akt and GSK3β was also analyzed. We found that depletion of TRAF1 markedly reversed PA-induced attenuation of the phosphorylation of Akt and GSK3β in the cells. The accumulation of lipid droplets in hepatocyte and expression of two key gluconeogenic enzymes, PEPCK and G6Pase, were also determined and found to display a similar tendency with the phosphorylation of Akt and GSK3β. Glucose uptake assay indicated that knocking down TRAF1 blocked the effect of PA on the suppression of glucose uptake. These data implicated that TRAF1 knockdown might alleviate PA-induced IR in HepG2 cells through NF-κB pathway.

Carnosine and Related Peptides: Therapeutic Potential in Age-Related Disorders

Imidazole dipeptides (ID), such as carnosine (β-alanyl-L-histidine), are compounds widely distributed in excitable tissues of vertebrates. ID are also endowed of several biochemical properties in biological tissues, including antioxidant, bivalent metal ion chelating, proton buffering, and carbonyl scavenger activities. Furthermore, remarkable biological effects have been assigned to such compounds in age-related human disorders and in patients whose activity of serum carnosinase is deficient or undetectable. Nevertheless, the precise biological role of ID is still to be unraveled. In the present review we shall discuss some evidences from clinical and basic studies for the utilization of ID as a drug therapy for age-related human disorders.

Rethinking the paradigm: How comparative studies on fatty acid oxidation inform our understanding of T cell metabolism

The classic paradigm of T cell metabolism posits that activated Teff cells utilize glycolysis to keep pace with increased energetic demands, while resting and Tmem cells rely on the oxidation of fat. In contrast, Teff cells during graft-versus-host disease (GVHD) increase their reliance on oxidative metabolism and, in particular, on fatty acid oxidation (FAO). To explore the potential mechanisms driving adoption of this alternative metabolism, we first review key pathways regulating FAO across a variety of disparate tissue types, including liver, heart, and skeletal muscle. Based upon these comparative studies, we then outline a consensus network of transcriptional and signaling pathways that predict a model for regulating FAO in Teff cells during GVHD. This model raises important implications about the dynamic nature of metabolic reprogramming in T cells and suggests exciting future directions for further study of in vivo T cell metabolism.

Adversity in childhood and depression: linked through SIRT1

Experiencing an adverse childhood and parental neglect is a risk factor for depression in the adult population. Patients with a history of traumatic childhood develop a subtype of depression that is characterized by earlier onset, poor treatment response and more severe symptoms. The long-lasting molecular mechanisms that are engaged during early traumatic events and determine the risk for depression are poorly understood. In this study, we altered adult depression-like behavior in mice by applying juvenile isolation stress. We found that this behavioral phenotype was associated with a reduction in the levels of the deacetylase sirtuin1 (SIRT1) in the brain and in peripheral blood mononuclear cells. Notably, peripheral blood mRNA expression of SIRT1 predicted the extent of behavioral despair only when depression-like behavior was induced by juvenile--but not adult--stress, implicating SIRT1 in the regulation of adult behavior at early ages. Consistent with this hypothesis, pharmacological modulation of SIRT1 during juvenile age altered the depression-like behavior in naive mice. We also performed a pilot study in humans, in which the blood levels of SIRT1 correlated significantly with the severity of symptoms in major depression patients, especially in those who received less parental care during childhood. On the basis of these novel findings, we propose the involvement of SIRT1 in the long-term consequences of adverse childhood experiences.

The antioxidant paradox: what are antioxidants and how should they be used in a therapeutic context for cancer

So-called antioxidants have yet to make a clinical impact on the treatment of human cancer. The reasons for this failure are several. First, many agents that are called antioxidants are truly antioxidants at a given dose, but this dose may not have been given in clinical trials. Second, many agents are not antioxidants at all. Third, not all tumors use reactive oxygen as a signaling mechanism. Finally, reactive oxygen inhibition is often insufficient to kill or regress a tumor cell by itself, but requires sequential introduction of a therapeutic agent for maximal effect. We hope to provide a framework for the logical use of these agents in cancer.

Simiao pill ameliorates renal glomerular injury via increasing Sirt1 expression and suppressing NF-κB/NLRP3 inflammasome activation in high fructose-fed rats

ETHNOPHARMACOLOGICAL RELEVANCE

Simiao pill is one of the most frequently prescriptions in traditional Chinese medicine to treat hyperuricemia and gout. This study was to investigate the protective effects of Simiao pill on renal glomerular injury in a rat model of high fructose intake.

MATERIALS AND METHODS

Sprague-Dawley male rats were given 10% fructose in drinking water and standard laboratory chow for 4 weeks to induce hyperuricemia and metabolic syndrome. Then fructose-fed animals were randomly divided into four groups receiving water, Simiao pill (78.87 and 157.74 mg/kg) and allopurinol (5mg/kg) daily for next 6 weeks, respectively. Serum levels of uric acid, creatinine, triglyceride, total cholesterol, low density lipoprotein, blood urea nitrogen, insulin, as well as urinary albumin were measured. Oral glucose tolerance test (OGTT) was carried out. Kidney pathological changes were detected using periodic-acid schiff-stained (PAS) staining and transmission electron microscopy (TEM) analysis. Glomerular protein levels of nephrin, podocin, CD2-associated protein (CD2AP), interleukin (IL)-1β, sirtuin 1 (Sirt1), nuclear factor kappaB (NF-κB) and pyrin domain containing 3 (NLRP3) inflammasome were measured by Western blot.

RESULTS

Simiao pill effectively restored high fructose-induced hyperuricemia and metabolic syndrome in rats. Simiao pill significantly increased protein levels of nephrin, podocin and CD2AP in renal glomeruli, improved renal inflammatory cell infiltration into interstitium and glomerular injury in high fructose-fed rats with reduction of urine albumin levels. Furthermore, Simiao pill up-regulated Sirt1 protein levels and suppressed NF-κB/NLRP3 inflammasome activation to reduce IL-1β in renal glomeruli of high fructose-fed rats.

CONCLUSIONS

The renal protective effects of Simiao pill may be associated with up-regulation of Sirt1 expression and suppression of NF-κB/NLRP3 inflammasome activation to reduce renal glomerular injury in high fructose-fed rats with metabolic syndrome.

Sirtuin regulation in aging and injury

Sirtuins or Sir2 family of proteins are a class of NAD(+) dependent protein deacetylases which are evolutionarily conserved from bacteria to humans. Some sirtuins also exhibit mono-ADP ribosyl transferase, demalonylation and desuccinylation activities. Originally identified in the yeast, these proteins regulate key cellular processes like cell cycle, apoptosis, metabolic regulation and inflammation. Humans encode seven sirtuin isoforms SIRT1-SIRT7 with varying intracellular distribution. Apart from their classic role as histone deacetylases regulating transcription, a number of cytoplasmic and mitochondrial targets of sirtuins have also been identified. Sirtuins have been implicated in longevity and accumulating evidence indicate their role in a spectrum of diseases like cancer, diabetes, obesity and neurodegenerative diseases. A number of studies have reported profound changes in SIRT1 expression and activity linked to mitochondrial functional alterations following hypoxic-ischemic conditions and following reoxygenation injury. The SIRT1 mediated deacetylation of targets such as PGC-1α, FOXO3, p53 and NF-κb has profound effect on mitochondrial function, apoptosis and inflammation. These biological processes and functions are critical in life-span determination and outcome following injury. Aging is reported to be characterized by declining SIRT1 activity, and its increased expression or activation demonstrated prolonged life-span in lower forms of animals. A pseudohypoxic state due to declining NAD(+) has also been implicated in aging. In this review we provide an overview of studies on the role of sirtuins in aging and injury.

Scutellarein Reduces Inflammatory Responses by Inhibiting Src Kinase Activity

Flavonoids are plant pigments that have been demonstrated to exert various pharmacological effects including anti-cancer, anti-diabetic, anti-atherosclerotic, anti-bacterial, and anti-inflammatory activities. However, the molecular mechanisms in terms of exact target proteins of flavonoids are not fully elucidated yet. In this study, we aimed to evaluate the anti-inflammatory mechanism of scutellarein (SCT), a flavonoid isolated from Erigeron breviscapus, Clerodendrum phlomidis and Oroxylum indicum Vent that have been traditionally used to treat various inflammatory diseases in China and Brazil. For this purpose, a nitric oxide (NO) assay, polymerase chain reaction (PCR), nuclear fractionation, immunoblot analysis, a kinase assay, and an overexpression strategy were employed. Scutellarein significantly inhibited NO production in a dose-dependent manner and reduced the mRNA expression levels of inducible NO synthase (iNOS) and tumor necrosis factor (TNF)-α in lipopolysaccharide (LPS)-activated RAW264.7 cells. In addition, SCT also dampened nuclear factor (NF)-κB-driven expression of a luciferase reporter gene upon transfection of a TIR-domain-containing adapter-inducing interferon-β (TRIF) construct into Human embryonic kidney 293 (HEK 293) cells; similarly, NF-κ B nuclear translocation was inhibited by SCT. Moreover, the phosphorylation levels of various upstream signaling enzymes involved in NF-κB activation were decreased by SCT treatment in LPS-treated RAW264.7 cells. Finally, SCT strongly inhibited Src kinase activity and also inhibited the autophosphorylation of overexpressed Src. Therefore, our data suggest that SCT can block the inflammatory response by directly inhibiting Src kinase activity linked to NF-κB activation.

Sirtuin1 Suppresses Osteoclastogenesis by Deacetylating FoxOs

Activation of Sirtuin1 (Sirt1), an nicotinamide adenine dinucleotide oxidized-dependent deacetylase, by natural or synthetic compounds like resveratrol, SRT2104, or SRT3025 attenuates the loss of bone mass caused by ovariectomy, aging, or unloading in mice. Conversely, Sirt1 deletion in osteoclast progenitors increases osteoclast number and bone resorption. Sirt1 deacetylates forkhead box protein (Fox) O1, FoxO3, and FoxO4, and thereby modulates their activity. FoxOs restrain osteoclastogenesis and bone resorption. Here, we tested the hypothesis that the antiresorptive effects of Sirt1 are mediated by FoxOs. We report that Sirt1 activation by SRT2104 and SRT3025 inhibited murine osteoclast progenitor proliferation and reduced osteoclastogenesis. The effect of Sirt1 stimulators on osteoclastogenesis was abrogated in cells lacking FoxO1, FoxO3, and FoxO4. FoxO1 acetylation was increased by knocking down Sirt1 or addition of receptor activator of nuclear factor kappa-B ligand, the critical cytokine for osteoclast differentiation. Furthermore, acetylation inhibited, whereas deacetylation promoted, FoxO-mediated transcription. SRT3025 increased the expression of the FoxO-target genes catalase and hemeoxygenase-1 (HO-1) in osteoclast progenitors, in a FoxO-dependent manner. HO-1 catabolizes heme and attenuates mitochondrial oxidative phosphorylation and ATP production in macrophages. HO-1 levels were strongly reduced and ATP levels increased by Receptor activator of nuclear factor kappa-B ligand. In contrast, SRT3025 and FoxOs decreased ATP production, and the effect of SRT3025 was mediated by FoxOs. These findings reveal that the antiosteoclastogenic actions of Sirt1 are mediated by FoxOs and result from impaired mitochondria activity. Along with earlier findings that the osteoblastogenic effects of Sirt1 are also mediated by FoxOs, these results establish that the dual antiosteoporotic efficacy of Sirt1 stimulators (ie, decreasing bone resorption and promoting bone formation) is mediated via FoxO deacetylation.

Fumarates modulate microglia activation through a novel HCAR2 signaling pathway and rescue synaptic dysregulation in inflamed CNS

Dimethyl fumarate (DMF), recently approved as an oral immunomodulatory treatment for relapsing-remitting multiple sclerosis (MS), metabolizes to monomethyl fumarate (MMF) which crosses the blood-brain barrier and has demonstrated neuroprotective effects in experimental studies. We postulated that MMF exerts neuroprotective effects through modulation of microglia activation, a critical component of the neuroinflammatory cascade that occurs in neurodegenerative diseases such as MS. To ascertain our hypothesis and define the mechanistic pathways involved in the modulating effect of fumarates, we used real-time PCR and biochemical assays to assess changes in the molecular and functional phenotype of microglia, quantitative Western blotting to monitor activation of postulated pathway components, and ex vivo whole-cell patch clamp recording of excitatory post-synaptic currents in corticostriatal slices from mice with experimental autoimmune encephalomyelitis (EAE), a model for MS, to study synaptic transmission. We show that exposure to MMF switches the molecular and functional phenotype of activated microglia from classically activated, pro-inflammatory type to alternatively activated, neuroprotective one, through activation of the hydroxycarboxylic acid receptor 2 (HCAR2). We validate a downstream pathway mediated through the AMPK-Sirt1 axis resulting in deacetylation, and thereby inhibition, of NF-κB and, consequently, of secretion of pro-inflammatory molecules. We demonstrate through ex vivo monitoring of spontaneous glutamate-mediated excitatory post-synaptic currents of single neurons in corticostriatal slices from EAE mice that the neuroprotective effect of DMF was exerted on neurons at pre-synaptic terminals by modulating glutamate release. By exposing control slices to untreated and MMF-treated activated microglia, we confirm the modulating effect of MMF on microglia function and, thereby, its indirect neuroprotective effect at post-synaptic level. These findings, whereby DMF-induced activation of a new HCAR2-dependent pathway on microglia leads to the modulation of neuroinflammation and restores synaptic alterations occurring in EAE, represent a possible novel mechanism of action for DMF in MS.

Differentiation-Associated Downregulation of Poly(ADP-Ribose) Polymerase-1 Expression in Myoblasts Serves to Increase Their Resistance to Oxidative Stress

Poly(ADP-ribose) polymerase 1 (PARP-1), the major isoform of the poly (ADP-ribose) polymerase family, is a constitutive nuclear and mitochondrial protein with well-recognized roles in various essential cellular functions such as DNA repair, signal transduction, apoptosis, as well as in a variety of pathophysiological conditions including sepsis, diabetes and cancer. Activation of PARP-1 in response to oxidative stress catalyzes the covalent attachment of the poly (ADP-ribose) (PAR) groups on itself and other acceptor proteins, utilizing NAD⁺ as a substrate. Overactivation of PARP-1 depletes intracellular NAD⁺ influencing mitochondrial electron transport, cellular ATP generation and, if persistent, can result in necrotic cell death. Due to their high metabolic activity, skeletal muscle cells are particularly exposed to constant oxidative stress insults. In this study, we investigated the role of PARP-1 in a well-defined model of murine skeletal muscle differentiation (C2C12) and compare the responses to oxidative stress of undifferentiated myoblasts and differentiated myotubes. We observed a marked reduction of PARP-1 expression as myoblasts differentiated into myotubes. This alteration correlated with an increased resistance to oxidative stress of the myotubes, as measured by MTT and LDH assays. Mitochondrial function, assessed by measuring mitochondrial membrane potential, was preserved under oxidative stress in myotubes compared to myoblasts. Moreover, basal respiration, ATP synthesis, and the maximal respiratory capacity of mitochondria were higher in myotubes than in myoblasts. Inhibition of the catalytic activity of PARP-1 by PJ34 (a phenanthridinone PARP inhibitor) exerted greater protective effects in undifferentiated myoblasts than in differentiated myotubes. The above observations in C2C12 cells were also confirmed in a rat-derived skeletal muscle cell line (L6). Forced overexpression of PARP1 in C2C12 myotubes sensitized the cells to oxidant-induced injury. Taken together, our data indicate that the reduction of PARP-1 expression during the process of the skeletal muscle differentiation serves as a protective mechanism to maintain the cellular functions of skeletal muscle during oxidative stress.

Mangiferin Protects Retinal Ganglion Cells in Ischemic Mouse Retina via SIRT1

PURPOSE

To investigate whether mangiferin can increase the viability of retinal ganglion cells (RGCs) in ischemic mouse retina, and to determine the possible mechanism of neuroprotection.

METHODS

C57BL/6J mice underwent constant elevation of intraocular pressure for 60 min and received saline or mangiferin (30 mg/kg) intraperitoneally once daily until sacrifice. HIF-1α, GFAP and SIRT1 expression was assessed at 1, 4, and 7 days after retinal ischemia. Bax and Bcl-2 expression was also analyzed at 1 and 4 days. RGC survival was assessed by labeling flat-mounted retinas with Brn3a at 2 weeks after retinal ischemia. The effect of co-treatment with mangiferin and sirtinol (SIRT1 inhibitor) was also evaluated.

RESULTS

The expression of HIF-1α and GFAP was upregulated in saline-treated retinas within 7 days after ischemia. Mangiferin treatment suppressed this upregulation. The expression of SIRT1 was downregulated in saline-treated ischemic retinas. This downregulation was reversed by mangiferin treatment, resulting in a significant difference from saline-treated ischemic retinas. In mangiferin-treated ischemic retinas, Bax expression was downregulated, whereas Bcl-2 expression was upregulated in comparison with saline-treated ischemic retinas. Mangiferin treatment protected ischemic retinas against RGC loss. Treatment of sirtinol decreased the neuroprotective effect of mangiferin.

CONCLUSIONS

Our findings suggest that mangiferin has a neuroprotective effect on RGC through downregulation of HIF-1a and GFAP, and upregulation of SIRT1 in ischemic mouse retinas. We suggest that mangiferin might be a potential neuroprotective agent against RGC loss under oxidative stress.