AMPK inhibits fatty acid-induced increases in NF-κB transactivation in cultured human umbilical vein endothelial cells

Hypothermia Attenuates Neurotoxic Microglial Activation via TRPV4

Therapeutic hypothermia (TH) provides neuroprotection. However, the cellular mechanisms underlying the neuroprotective effects of TH are not fully elucidated. Regulation of microglial activation has the potential to treat a variety of nervous system diseases. Transient receptor potential vanilloid 4 (TRPV4), a nonselective cation channel, is activated by temperature stimulus at 27-35 °C. Although it is speculated that TRPV4 is associated with the neuroprotective mechanisms of TH, the role of TRPV4 in the neuroprotective effects of TH is not well understood. In the present study, we investigated whether hypothermia attenuates microglial activation via TRPV4 channels. Cultured microglia were incubated under normothermic (37 °C) or hypothermic (33.5 °C) conditions following lipopolysaccharide (LPS) stimulation. Hypothermic conditions suppressed the expression of pro-inflammatory cytokines, inducible nitric oxide synthase, and the number of phagocytic microglia. AMP-activated protein kinase (AMPK)-NF-κB signaling was inhibited under hypothermic conditions. Furthermore, hypothermia reduced neuronal damage induced by LPS-treated microglial cells. Treatment with TRPV4 antagonist in normothermic culture replicated the suppressive effects of hypothermia on microglial activation and microglia-induced neuronal damage. In contrast, treatment with a TRPV4 agonist in hypothermic culture reversed the suppressive effect of hypothermia. These findings suggest that TH suppresses microglial activation and microglia-induced neuronal damage via the TRPV4-AMPK-NF-κB pathway. Although more validation is needed to consider differences according to age, sex, and specific central nervous system regions, our findings may offer a novel therapeutic approach to complement TH.

Shear Stress and the AMP-Activated Protein Kinase Independently Protect the Vascular Endothelium from Palmitate Lipotoxicity

Saturated free fatty acids are thought to play a critical role in metabolic disorders associated with obesity, insulin resistance, type 2 diabetes (T2D), and their vascular complications via effects on the vascular endothelium. The most abundant saturated free fatty acid, palmitate, exerts lipotoxic effects on the vascular endothelium, eventually leading to cell death. Shear stress activates the endothelial AMP-activated protein kinase (AMPK), a cellular energy sensor, and protects endothelial cells from lipotoxicity, however their relationship is uncertain. Here, we used isoform-specific shRNA-mediated silencing of AMPK to explore its involvement in the long-term protection of macrovascular human umbilical vein endothelial cells (HUVECs) against palmitate lipotoxicity and to relate it to the effects of shear stress. We demonstrated that it is the α1 catalytic subunit of AMPK that is critical for HUVEC protection under static conditions, whereas AMPK-α2 autocompensated a substantial loss of AMPK-α1, but failed to protect the cells from palmitate. Shear stress equally protected the wild type HUVECs and those lacking either α1, or α2, or both AMPK-α isoforms; however, the protective effect of AMPK reappeared after returning to static conditions. Moreover, in human adipose microvascular endothelial cells isolated from obese diabetic individuals, shear stress was a strong protector from palmitate lipotoxicity, thus highlighting the importance of circulation that is often obstructed in obesity/T2D. Altogether, these results indicate that AMPK is important for vascular endothelial cell protection against lipotoxicity in the static environment, however it may be dispensable for persistent and more effective protection exerted by shear stress.

Macrophage fatty acid oxidation in atherosclerosis

Atherosclerosis significantly contributes to the development of cardiovascular diseases (CVD) and is characterized by lipid retention and inflammation within the artery wall. Multiple immune cell types are implicated in the pathogenesis of atherosclerosis, macrophages play a central role as the primary source of inflammatory effectors in this pathogenic process. The metabolic influences of lipids on macrophage function and fatty acid β-oxidation (FAO) have similarly drawn attention due to its relevance as an immunometabolic hub. This review discusses recent findings regarding the impact of mitochondrial-dependent FAO in the phenotype and function of macrophages, as well as transcriptional regulation of FAO within macrophages. Finally, the therapeutic strategy of macrophage FAO in atherosclerosis is highlighted.

AMPK negatively regulates RANKL-induced osteoclast differentiation by controlling oxidative stress

AMP-activated protein kinase (AMPK) is a crucial energy sensor of cellular metabolism under various metabolic stresses, such as oxidative stress and inflammation. AMPK deficiency increases osteoclast numbers and reduces bone mass; however, the precise mechanisms remain unclear. This study aimed to clarify the mechanistic connection between AMPK and osteoclast differentiation, and the potential role of AMPK in the anti-resorptive effects of several phytochemicals. We found that receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL)-induced osteoclast differentiation, osteoclastic gene expression, and activation of mitogen-activated protein kinase (MAPK) and NF-κB were promoted in cells transfected with AMPK siRNA. AMPK knockdown led to defective synthesis of heme oxygenase-1, an antioxidant enzyme, and the upstream mediator, nuclear factor erythroid-2-related factor 2. Furthermore, treatment with N-acetyl-l-cysteine, an antioxidant, abolished osteoclast differentiation and MAPK/NF-κB activation induced by AMPK knockdown. AMPK activators, hesperetin, gallic acid, resveratrol, and curcumin, suppressed osteoclast differentiation via the activation of AMPK. These results suggest that AMPK inhibits RANKL-induced osteoclast differentiation by enhancing antioxidant defense system and regulating oxidative stress. AMPK activation by dietary-derived phytochemicals may be effective for the treatment of bone diseases.

A palmitate-rich metastatic niche enables metastasis growth via p65 acetylation resulting in pro-metastatic NF-κB signaling

Metabolic rewiring is often considered an adaptive pressure limiting metastasis formation; however, some nutrients available at distant organs may inherently promote metastatic growth. We find that the lung and liver are lipid-rich environments. Moreover, we observe that pre-metastatic niche formation increases palmitate availability only in the lung, whereas a high-fat diet increases it in both organs. In line with this, targeting palmitate processing inhibits breast cancer-derived lung metastasis formation. Mechanistically, breast cancer cells use palmitate to synthesize acetyl-CoA in a carnitine palmitoyltransferase 1a-dependent manner. Concomitantly, lysine acetyltransferase 2a expression is promoted by palmitate, linking the available acetyl-CoA to the acetylation of the nuclear factor-kappaB subunit p65. Deletion of lysine acetyltransferase 2a or carnitine palmitoyltransferase 1a reduces metastasis formation in lean and high-fat diet mice, and lung and liver metastases from patients with breast cancer show coexpression of both proteins. In conclusion, palmitate-rich environments foster metastases growth by increasing p65 acetylation, resulting in a pro-metastatic nuclear factor-kappaB signaling.

In Vitro Modeling of Diabetes Impact on Vascular Endothelium: Are Essentials Engaged to Tune Metabolism?

Angiopathy is a common complication of diabetes mellitus. Vascular endothelium is among the first targets to experience blood-borne metabolic alterations, such as hyperglycemia and hyperlipidemia, the hallmarks of type 2 diabetes. To explore mechanisms of vascular dysfunction and eventual damage brought by these pathologic conditions and to find ways to protect vasculature in diabetic patients, various research approaches are used including in vitro endothelial cell-based models. We present an analysis of the data available from these models that identifies early endothelial cell apoptosis associated with oxidative stress as the major outcome of mimicking hyperglycemia and hyperlipidemia in vitro. However, the fate of endothelial cells observed in these studies does not closely follow it in vivo where massive endothelial damage occurs mainly in the terminal stages of diabetes and in conjunction with comorbidities. We propose that the discrepancy is likely in missing essentials that should be available to cultured endothelial cells to adjust the metabolic state and withstand the immediate apoptosis. We discuss the role of carnitine, creatine, and AMP-activated protein kinase (AMPK) in suiting the endothelial metabolism for long-term function in diabetic type milieu in vitro. Engagement of these essentials is anticipated to expand diabetes research options when using endothelial cell-based models.

Cardiovascular protection by SGLT2 inhibitors - Do anti-inflammatory mechanisms play a role?

BACKGROUND

Metabolic syndrome and related metabolic disturbances represent a state of low-grade inflammation, which accelerates insulin resistance, type 2 diabetes (T2D) and cardiovascular disease (CVD) progression. Among antidiabetic medications, sodium glucose co-transporter (SGLT) 2 inhibitors are the only agents which showed remarkable reductions in heart failure (HF) hospitalizations and major cardiovascular endpoints (MACE) as well as renal endpoints regardless of diabetes status in large randomized clinical outcome trials (RCTs). Although the exact mechanisms underlying these benefits are yet to be established, growing evidence suggests that modulating inflammation by SGLT2 inhibitors may play a key role.

SCOPE OF REVIEW

In this manuscript, we summarize the current knowledge on anti-inflammatory effects of SGLT2 inhibitors as one of the mechanisms potentially mediating their cardiovascular (CV) benefits. We introduce the different metabolic and systemic actions mediated by these agents which could mitigate inflammation, and further present the signalling pathways potentially responsible for their proposed direct anti-inflammatory effects. We also discuss controversies surrounding some of these mechanisms.

MAJOR CONCLUSIONS

SGLT2 inhibitors are promising anti-inflammatory agents by acting either indirectly via improving metabolism and reducing stress conditions or via direct modulation of inflammatory signalling pathways. These effects were achieved, to a great extent, in a glucose-independent manner which established their clinical use in HF patients with and without diabetes.

The role of AMPK-dependent pathways in cellular and molecular mechanisms of metformin: a new perspective for treatment and prevention of diseases

Metformin can suppress gluconeogenesis and reduce blood sugar by activating adenosine monophosphate-activated protein kinase (AMPK) and inducing small heterodimer partner (SHP) expression in the liver cells. The main mechanism of metformin's action is related to its activation of the AMPK enzyme and regulation of the energy balance. AMPK is a heterothermic serine/threonine kinase made of a catalytic alpha subunit and two subunits of beta and a gamma regulator. This enzyme can measure the intracellular ratio of AMP/ATP. If this ratio is high, the amino acid threonine 172 available in its alpha chain would be activated by the phosphorylated liver kinase B1 (LKB1), leading to AMPK activation. Several studies have indicated that apart from its significant role in the reduction of blood glucose level, metformin activates the AMPK enzyme that in turn has various efficient impacts on the regulation of various processes, including controlling inflammatory conditions, altering the differentiation pathway of immune and non-immune cell pathways, and the amelioration of various cancers, liver diseases, inflammatory bowel disease (IBD), kidney diseases, neurological disorders, etc. Metformin's activation of AMPK enables it to control inflammatory conditions, improve oxidative status, regulate the differentiation pathways of various cells, change the pathological process in various diseases, and finally have positive therapeutic effects on them. Due to the activation of AMPK and its role in regulating several subcellular signalling pathways, metformin can be effective in altering the cells' proliferation and differentiation pathways and eventually in the prevention and treatment of certain diseases.

The Effect of Hyperlipidemia on the Course of Diabetic Retinopathy—Literature Review

Diabetes mellitus is a very important social issue, and its retinal complications continue to be one of the major causes of blindness worldwide. The effect of glucose level on the development of retinal retinopathy has been the subject of numerous studies and is well understood. Hypertension and hyperlipidemia have been known to be important risk factors in the development of diabetes complications. However, the mechanisms of this effect have not been fully explained and raise a good deal of controversy. The latest research results suggest that some lipoproteins are closely correlated with the incidence of diabetic retinopathy and that by exerting an impact on their level the disease course can be modulated. Moreover, pharmacotherapy which reduces the level of lipids, particularly by means of statins and fibrate, has been shown to alleviate diabetic retinopathy. Therefore, we have decided to review the latest literature on diabetic retinopathy with respect to the impact of hyperlipidemia and possible preventive measures

Liensinine alleviates high fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) through suppressing oxidative stress and inflammation via regulating TAK1/AMPK signaling

Nonalcoholic fatty liver disease (NAFLD) is one of the most prevalent liver diseases without effective pharmacological intervention. Liensinine (LIEN), a plant-derived isoquinoline alkaloid, exerts key roles in regulating various cellular processes. However, its potential on NAFLD progression has not been reported. In the study, we attempted to explore the regulatory effects of LIEN on fatty liver, and the underlying molecular mechanisms. Our in vitro experiments showed that LIEN treatments significantly reduced the lipid deposition in palmitate acid (PA)-treated cells by improving AMP-activated protein kinase (AMPK) activation. Additionally, excessive reactive oxygen species (ROS) generation was also strongly down-regulated by LIEN in cells upon PA stimulation through enhancing nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation. Moreover, PA-triggered inflammatory response was markedly restrained by LIEN via the blockage of TGF-β-activating kinase 1/nuclear factor-κB (TAK1/NF-κB) signaling. Intriguingly, we further found that LIEN-prohibited ROS production, lipid disorder and inflammation were largely dependent on AMPK activation through repressing TAK1. Consistently, our in vivo experiments confirmed that LIEN treatments efficiently improved the metabolic disorder, insulin resistance, dyslipidemia in high fat diet (HFD)-fed mice. Furthermore, HFD-triggered oxidative stress and inflammation in liver were greatly meliorated by LIEN administration by mediating Nrf2 and TAK1 signaling pathways, respectively. Collectively, all these findings demonstrated that LIEN exerted anti-dyslipidemia, anti-oxidant and anti-inflammatory effects to alleviate NAFLD progression mainly through modulating TAK1/AMPK signaling, and thus could be considered as a promising therapeutic strategy.

The effect of adenosine monophosphate-activated protein kinase on lipolysis in adipose tissue: an historical and comprehensive review

CONTEXT

Lipolysis is one of the most important pathways for energy management, its control in the adipose tissue (AT) is a potential therapeutic target for metabolic diseases. Adenosine Mono Phosphate-activated Protein Kinase (AMPK) is a key regulatory enzyme in lipids metabolism and a potential target for diabetes and obesity treatment.

OBJECTIVE

The aim of this work is to analyse the existing information on the relationship of AMPK and lipolysis in the AT.

METHODS

A thorough search of bibliography was performed in the databases Scopus and Web of Knowledge using the terms lipolysis, adipose tissue, and AMPK, the unrelated publications were excluded, and the documents were analysed.

RESULTS

Sixty-three works were found and classified in 3 categories: inhibitory effects, stimulatory effect, and diverse relationships; remarkably, the newest researches support an upregulating relationship of AMPK over lipolysis.

CONCLUSION

The most probable reality is that the relationship AMPK-lipolysis depends on the experimental conditions.

Longevity Factor FOXO3: A Key Regulator in Aging-Related Vascular Diseases

Forkhead box O3 (FOXO3) has been proposed as a homeostasis regulator, capable of integrating multiple upstream signaling pathways that are sensitive to environmental changes and counteracting their adverse effects due to external changes, such as oxidative stress, metabolic stress and growth factor deprivation. FOXO3 polymorphisms are associated with extreme human longevity. Intriguingly, longevity-associated single nucleotide polymorphisms (SNPs) in human FOXO3 correlate with lower-than-average morbidity from cardiovascular diseases in long-lived people. Emerging evidence indicates that FOXO3 plays a critical role in vascular aging. FOXO3 inactivation is implicated in several aging-related vascular diseases. In experimental studies, FOXO3-engineered human ESC-derived vascular cells improve vascular homeostasis and delay vascular aging. The purpose of this review is to explore how FOXO3 regulates vascular aging and its crucial role in aging-related vascular diseases.

Dapagliflozin improves steatohepatitis in diabetic rats via inhibition of oxidative stress and inflammation

Type-2 diabetes mellitus and NAFLD are considered as one of the greatest worldwide metabolic disorders with growing incidence. It was found that patients with T2DM have two-fold increase to develop NAFLD. Evidence that some antidiabetic agents improve NAFLD/NASH in patients with T2DM is evolving. However, there are no certain pharmacologic therapies. The current study aimed to investigate the underlying mechanisms for the hepatoprotective effect of dapagliflozin against steatohepatitis in diabetic rats. Type-2 diabetes was induced by HFD followed by a single dose of STZ (30 mg/kg I.P). Fifty rats were randomly divided into 5 groups: Group1; normal control, Group 2; diabetic control, Groups (3-5); diabetic rats received daily dapagliflozin (0.75, 1.5, 3 mg/kg, p.o.) respectively for 6 weeks. At the end of the experiment, blood glucose level and serum insulin were measured. Hepatic tissue homogenization was performed for measuring inflammatory and oxidative stress markers. In addition, histopathological investigation of the hepatic tissue was done. Diabetic rats exhibited remarkable increase in liver weight and liver enzymes, along with histopathological changes, significant elevation in MDA, IL-1 β, TGFβ levels and, NF-κB, alpha-SMA expressions. Dapagliflozin treatment decreased liver weight, liver enzymes, together with marked improvement in histopathological changes. Furthermore, dapagliflozin increased antioxidant enzymes, GSH levels. Interestingly, Dapagliflozin reduced IL-1 β, TGFβ levels and, NF-κB, alpha-SMA expressions. Present data show that dapagliflozin represent a viable approach to protect the liver against diabetes-encouraged steatohepatitis through inhibiting oxidative stress, inflammation and fibrosis progression thus conserving liver function.

AICAR Protects Vascular Endothelial Cells from Oxidative Injury Induced by the Long-Term Palmitate Excess

Hyperlipidemia manifested by high blood levels of free fatty acids (FFA) and lipoprotein triglycerides is critical for the progression of type 2 diabetes (T2D) and its cardiovascular complications via vascular endothelial dysfunction. However, attempts to assess high FFA effects in endothelial culture often result in early cell apoptosis that poorly recapitulates a much slower pace of vascular deterioration in vivo and does not provide for the longer-term studies of endothelial lipotoxicity in vitro. Here, we report that palmitate (PA), a typical FFA, does not impair, by itself, endothelial barrier and insulin signaling in human umbilical vein endothelial cells (HUVEC), but increases NO release, reactive oxygen species (ROS) generation, and protein labeling by malondialdehyde (MDA) hallmarking oxidative stress and increased lipid peroxidation. This PA-induced stress eventually resulted in the loss of cell viability coincident with loss of insulin signaling. Supplementation with 5-aminoimidazole-4-carboxamide-riboside (AICAR) increased endothelial AMP-activated protein kinase (AMPK) activity, supported insulin signaling, and prevented the PA-induced increases in NO, ROS, and MDA, thus allowing to maintain HUVEC viability and barrier, and providing the means to study the long-term effects of high FFA levels in endothelial cultures. An upgraded cell-based model reproduces FFA-induced insulin resistance by demonstrating decreased NO production by vascular endothelium.

AICAR decreases acute lung injury by phosphorylating AMPK and upregulating heme oxygenase-1

AIM

We investigated the mechanisms by which N1-(β-d-ribofuranosyl)-5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), an activator of AMP-activated protein kinase (AMPK), decreases lung injury and mortality when administered to mice post exposure to bromine gas (Br2).

METHODS

We exposed male C57BL/6 mice and heme oxygenase-1 (HO-1)-deficient (HO-1-/-) and corresponding wild-type (WT) littermate mice to Br2 (600 ppm for 45 or 30 min, respectively) in environmental chambers and returned them to room air. AICAR was administered 6 h post exposure (10 mg·kg-1, intraperitoneal). We assessed survival, indices of lung injury, high mobility group box 1 (HMGB1) in the plasma, HO-1 levels in lung tissues and phosphorylation of AMPK and its upstream liver kinase B1 (LKB1). Rat alveolar type II epithelial (L2) cells and human club-like epithelial (H441) cells were also exposed to Br2 (100 ppm for 10 min). After 24 h we measured apoptosis and necrosis, AMPK and LKB1 phosphorylation, and HO-1 expression.

RESULTS

There was a marked downregulation of phosphorylated AMPK and LKB1 in lung tissues and in L2 and H441 cells post exposure. AICAR increased survival in C57BL/6 but not in HO-1-/- mice. In WT mice, AICAR decreased lung injury and restored phosphorylated AMPK and phosphorylated LKB1 to control levels and increased HO-1 levels in both lung tissues and cells exposed to Br2. Treatment of L2 and H441 cells with small interfering RNAs against nuclear factor erythroid 2-related factor 2 or HO-1 abrogated the protective effects of AICAR.

CONCLUSIONS

Our data indicate that the primary mechanism for the protective action of AICAR in toxic gas injury is the upregulation of lung HO-1 levels.

Emodin palliates high-fat diet-induced nonalcoholic fatty liver disease in mice via activating the farnesoid X receptor pathway

BACKGROUND

Cassia mimosoides Linn (CMD) is a traditional Chinese herb that clears liver heat and dampness. It has been widely administered in clinical practice to treat jaundice associated with damp-heat pathogen and obesity. Emodin (EMO) is a major bioactive constituent of CMD that has apparent therapeutic efficacy against obesity and fatty liver. Here, we investigated the protective effects and underlying mechanisms of EMO against high-fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD).

OBJECTIVE

We aimed to investigate whether EMO activates farnesoid X receptor (FXR) signaling to alleviate HFD-induced NAFLD.

MATERIALS AND METHODS

In vivo assays included serum biochemical indices tests, histopathology, western blotting, and qRT-PCR to evaluate the effects of EMO on glucose and lipid metabolism disorders in wild type (WT) and FXR knockout mice maintained on an HFD. In vitro experiments included intracellular triglyceride (TG) level measurement and Oil Red O staining to assess the capacity of EMO to remove lipids induced by oleic acid and palmitic acid in WT and FXR knockout mouse primary hepatocytes (MPHs). We also detected mRNA expression of FXR signaling genes in MPHs.

RESULTS

After HFD administration, body weight and serum lipid and inflammation levels were dramatically increased in the WT mice. The animals also presented with impaired glucose tolerance, insulin resistance, and antioxidant capacity, liver tissue attenuation, and pathological injury. EMO remarkably reversed the foregoing changes in HFD-induced mice. EMO improved HFD-induced lipid accumulation, insulin resistance, inflammation, and oxidative stress in a dose-dependent manner in WT mice by inhibiting FXR expression. EMO also significantly repressed TG hyperaccumulation by upregulating FXR expression in MPHs. However, it did not improve lipid accumulation, insulin sensitivity, or glucose tolerance in HFD-fed FXR knockout mice.

CONCLUSIONS

The present study demonstrated that EMO alleviates HFD-induced NAFLD by activating FXR signaling which improves lipid accumulation, insulin resistance, inflammation, and oxidative stress.

Metformin in cardiovascular diabetology: a focused review of its impact on endothelial function

As a first-line treatment for diabetes, the insulin-sensitizing biguanide, metformin, regulates glucose levels and positively affects cardiovascular function in patients with diabetes and cardiovascular complications. Endothelial dysfunction (ED) represents the primary pathological change of multiple vascular diseases, because it causes decreased arterial plasticity, increased vascular resistance, reduced tissue perfusion and atherosclerosis. Caused by “biochemical injury”, ED is also an independent predictor of cardiovascular events. Accumulating evidence shows that metformin improves ED through liver kinase B1 (LKB1)/5'-adenosine monophosphat-activated protein kinase (AMPK) and AMPK-independent targets, including nuclear factor-kappa B (NF-κB), phosphatidylinositol 3 kinase-protein kinase B (PI3K-Akt), endothelial nitric oxide synthase (eNOS), sirtuin 1 (SIRT1), forkhead box O1 (FOXO1), krüppel-like factor 4 (KLF4) and krüppel-like factor 2 (KLF2). Evaluating the effects of metformin on endothelial cell functions would facilitate our understanding of the therapeutic potential of metformin in cardiovascular diabetology (including diabetes and its cardiovascular complications). This article reviews the physiological and pathological functions of endothelial cells and the intact endothelium, reviews the latest research of metformin in the treatment of diabetes and related cardiovascular complications, and focuses on the mechanism of action of metformin in regulating endothelial cell functions.

Nutrient regulation of inflammatory signalling in obesity and vascular disease

Despite obesity and diabetes markedly increasing the risk of developing cardiovascular diseases, the molecular and cellular mechanisms that underlie this association remain poorly characterised. In the last 20 years it has become apparent that chronic, low-grade inflammation in obese adipose tissue may contribute to the risk of developing insulin resistance and type 2 diabetes. Furthermore, increased vascular pro-inflammatory signalling is a key event in the development of cardiovascular diseases. Overnutrition exacerbates pro-inflammatory signalling in vascular and adipose tissues, with several mechanisms proposed to mediate this. In this article, we review the molecular and cellular mechanisms by which nutrients are proposed to regulate pro-inflammatory signalling in adipose and vascular tissues. In addition, we examine the potential therapeutic opportunities that these mechanisms provide for suppression of inappropriate inflammation in obesity and vascular disease.

Artemisinin improves neurocognitive deficits associated with sepsis by activating the AMPK axis in microglia

Sepsis is life-threatening organ dysfunction due to dysregulated systemic inflammatory and immune response to infection, often leading to cognitive impairments. Growing evidence shows that artemisinin, an antimalarial drug, possesses potent anti-inflammatory and immunoregulatory activities. In this study we investigated whether artemisinin exerted protective effect against neurocognitive deficits associated with sepsis and explored the underlying mechanisms. Mice were injected with LPS (750 μg · kg-1 · d-1, ip, for 7 days) to establish an animal model of sepsis. Artemisinin (30 mg · kg-1 · d-1, ip) was administered starting 4 days prior LPS injection and lasting to the end of LPS injection. We showed that artemisinin administration significantly improved LPS-induced cognitive impairments assessed in Morris water maze and Y maze tests, attenuated neuronal damage and microglial activation in the hippocampus. In BV2 microglial cells treated with LPS (100 ng/mL), pre-application of artemisinin (40 μΜ) significantly reduced the production of proinflammatory cytokines (i.e., TNF-α, IL-6) and suppressed microglial migration. Furthermore, we revealed that artemisinin significantly suppressed the nuclear translocation of NF-κB and the expression of proinflammatory cytokines by activating the AMPKα1 pathway; knockdown of AMPKα1 markedly abolished the anti-inflammatory effects of artemisinin in BV2 microglial cells. In conclusion, atemisinin is a potential therapeutic agent for sepsis-associated neuroinflammation and cognitive impairment, and its effect is probably mediated by activation of the AMPKα1 signaling pathway in microglia.

Vanillic Acid and Non-Alcoholic Fatty Liver Disease: A Focus on AMPK in Adipose and Liver Tissues

Non-alcoholic fatty liver disease (NAFLD), a growing health issue around the world, is defined as the presence of steatosis in the liver without any other detectable byproducts such as alcohol consumption which includes a wide spectrum of pathologies, such as steatohepatitis, cirrhosis, and hepatocellular carcinoma. A growing body of evidence indicates that the reduction in the 5' adenosine monophosphate-activated protein kinase (AMPK) activity, which could be activated by the consumption of the drugs, hormones, cytokines, and dietary restriction, is related to some metabolic disorders such as obesity, diabetes, PCOS, and NAFLD. Vanillic acid (VA), as an anti-inflammatory, anti-oxidative, anti-angiogenic and anti-metastatic factor, has protective effects on the liver as in two animal models of liver damage. It reduces serum levels of transaminases, inflammatory cytokines, and the accumulation of collagen in the liver and prevents liver fibrosis. Besides, it decreases body and adipose tissue weight in a mice model of obesity and, similar to the liver tissue, diminishes adipogenesis through the activation of AMPK. It has been reported that VA can target almost all of the metabolic abnormalities of NAFLD, such as hepatic steatosis, inflammation, and hepatic injury, at least partially through the activation of AMPK. Therefore, in this review, we will discuss the possible and hypothetical roles of VA in NAFLD, with a special focus on AMPK.

AMPK, metabolism, and vascular function

Adenosine monophosphate-activated protein kinase (AMPK) is a cellular energy sensor activated during energy stress that plays a key role in maintaining energy homeostasis. This ubiquitous signaling pathway has been implicated in multiple functions including mitochondrial biogenesis, redox regulation, cell growth and proliferation, cell autophagy and inflammation. The protective role of AMPK in cardiovascular function and the involvement of dysfunctional AMPK in the pathogenesis of cardiovascular disease have been highlighted in recent years. In this review, we summarize and discuss the role of AMPK in the regulation of blood flow in response to metabolic demand and the basis of the AMPK physiological anticontractile, antioxidant, anti-inflammatory, and antiatherogenic actions in the vascular system. Investigations by others and us have demonstrated the key role of vascular AMPK in the regulation of endothelial function, redox homeostasis, and inflammation, in addition to its protective role in the hypoxia and ischemia/reperfusion injury. The pathophysiological implications of AMPK involvement in vascular function with regard to the vascular complications of metabolic disease and the therapeutic potential of AMPK activators are also discussed.

Feprazone Prevents Free Fatty Acid (FFA)-Induced Endothelial Inflammation by Mitigating the Activation of the TLR4/MyD88/NF-κB Pathway

Increased levels of free fatty acid (FFA)-induced endothelial dysfunction play an important role in the initiation and development of atherosclerosis. Feprazone is a nonsteroidal anti-inflammatory compound. However, the beneficial effects of feprazone on FFA-induced endothelial dysfunction have not been reported before. In the current study, we found that treatment with feprazone ameliorated FFA-induced cell death of human aortic endothelial cells (HAECs) by restoring cell viability and reducing the release of lactate dehydrogenase (LDH). Importantly, we found that treatment with feprazone ameliorated FFA-induced oxidative stress by reducing the production of mitochondrial reactive oxygen species (ROS). In addition, feprazone prevented FFA-induced expression and secretion of proinflammatory cytokines and chemokines, such as chemokine ligand 5 (CCL5), interleukin-6 (IL-6), and interleukin-8 (IL-8). We also found that feprazone decreased the expression of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9). Interestingly, we found that feprazone reduced the expression of cell adhesion molecules, such as vascular cell adhesion molecule-1 (VCAM-1) and intercellular cell adhesion molecule-1 (ICAM-1). Our results also demonstrate that feprazone prevented FFA-induced activation of the toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear factor kappa-B (NF-κB) signaling pathway. These findings suggest that feprazone might serve as a potential agent for the treatment of atherosclerosis by improving the endothelial function.

The Potential Roles of Artemisinin and Its Derivatives in the Treatment of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a chronic disease that has become a global public health problem. Studies on T2DM prevention and treatment mostly focus on discovering therapeutic drugs. Artemisinin and its derivatives were originally used as antimalarial treatments. In recent years, the roles of artemisinins in T2DM have attracted much attention. Artemisinin treatments not only attenuate insulin resistance and restore islet ß-cell function in T2DM but also have potential therapeutic effects on diabetic complications, including diabetic kidney disease, cognitive impairment, diabetic retinopathy, and diabetic cardiovascular disease. Many in vitro and in vivo experiments have confirmed the therapeutic utility of artemisinin and its derivatives on T2DM, but no article has systematically demonstrated the specific role artemisinin plays in the treatment of T2DM. This review summarizes the potential therapeutic effects and mechanism of artemisinin and its derivatives in T2DM and associated complications, providing a reference for subsequent related research.

Silymarin in combination with chlorogenic acid protects against hepatotoxicity induced by doxorubicin in rats: possible role of adenosine monophosphate-activated protein kinase pathway

Many xenobiotics are known to cause hepatic damage with subsequent significant morbidity and mortality. Doxorubicin (DOX) is a broad-spectrum antineoplastic agent. DOX is reported to cause hepatocellular damage. Previous studies verified the promising role of many natural antioxidant products against various models of hepatic dysfunction. We conducted this study to evaluate the possible hepatoprotective effect of silymarin (SILY) and/or chlorogenic acid (CGA) in a rat model of DOX-induced hepatotoxicity. For this purpose, we randomly divided 30 adult male rats into five equal groups as control, DOX, co-treated DOX with SILY, co-treated DOX with GCA and co-treated DOX with SILY and CGA groups. All treatments were administered every second day for 4 weeks. Our results showed that simultaneous SILY and CGA administration caused a significant decrease in hepatic apoptosis biomarkers (hepatic caspase-3 and nuclear factor-κB levels), a significant improvement in hepatic oxidant/antioxidant status (malondialdehyde and superoxide dismutase) and significant decrease in hepatic pro-inflammatory biomarkers (tumor necrosis factor-alpha and interlukin-1β) compared with DOX treatment. We concluded that adding CGA to SILY acts as a hepatoprotective agent against DOX-induced liver injury through inhibiting apoptosis biomarkers, maintaining antioxidant enzyme levels, decreasing pro-inflammatory cytokines as well as regulating liver adenosine monophosphate-activated protein kinase signaling.

Comparison of the Apoptotic Effects of Topically Applied Papaverine, Diltiazem, and Nitroprusside to Internal Thoracic Artery

Objective

To detect and to compare the apoptotic effects of intraoperatively topically applied diltiazem, papaverine, and nitroprusside.

Methods

Internal thoracic artery segments of ten patients were obtained during coronary bypass grafting surgery. Each internal thoracic artery segment was divided into four pieces and immersed into four different solutions containing separately saline (Group S), diltiazem (Group D), papaverine (Group P), and nitroprusside (Group N). Each segment was examined with both hematoxylin-eosin and the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method in order to determine and quantify apoptosis.

Results

Apoptotic cells were counted in 50 microscopic areas of each segment. No significant difference was observed among the four groups according to hematoxylin-eosin staining. However, the TUNEL method revealed a significant increase in mean apoptotic cells in the diltiazem group when compared with the other three groups (Group S=4.25±1.4; Group D=13.31±2.8; Group N=9.48±2.09; Group P=10.75±2.37). The differences between groups were significant (P=0.0001). No difference was observed between the samples of the diabetic and non-diabetic patients in any of the study groups.

Conclusion

The benefit of topically applied vasodilator drugs must outweigh the potential adverse effects. In terms of apoptosis, diltiazem was found to have the most deleterious effects on internal thoracic artery graft segments. Of the analyzed medical agents, nitroprusside was found to have the least apoptotic activity, followed by papaverine. Diabetes did not have significant effect on the occurrence of apoptosis in left internal thoracic artery grafts.

Mogrol attenuates lipopolysaccharide (LPS)-induced memory impairment and neuroinflammatory responses in mice

This study aimed to evaluate whether mogrol, a main bioactive ingredient of Siraitia grosvenorii, could attenuate LPS-induced memory impairment in mice. The behavioral tests and immunohistochemical analysis and Western blot were performed. The present results showed that oral administration of mogrol (20, 40, 80 mg/kg) significantly improved LPS-induced memory impairment in mice. The results also indicated that mogrol treatment significantly reduced the number of Iba1-positive cells, the nuclear NF-κB p65 and levels of TNF-α, IL-1β and IL-6 both in the hippocampus and frontal cortex of LPS-challenged mice. [Formula: see text].

From overnutrition to liver injury: AMP-activated protein kinase in nonalcoholic fatty liver diseases

Nonalcoholic fatty liver diseases (NAFLDs), especially nonalcoholic steatohepatitis (NASH), have become a major cause of liver transplant and liver-associated death. However, the pathogenesis of NASH is still unclear. Currently, there is no FDA-approved medication to treat this devastating disease. AMP-activated protein kinase (AMPK) senses energy status and regulates metabolic processes to maintain homeostasis. The activity of AMPK is regulated by the availability of nutrients, such as carbohydrates, lipids, and amino acids. AMPK activity is increased by nutrient deprivation and inhibited by overnutrition, inflammation, and hypersecretion of certain anabolic hormones, such as insulin, during obesity. The repression of hepatic AMPK activity permits the transition from simple steatosis to hepatocellular death; thus, activation might ameliorate multiple aspects of NASH. Here we review the pathogenesis of NAFLD and the impact of AMPK activity state on hepatic steatosis, inflammation, liver injury, and fibrosis during the transition of NAFL to NASH and liver failure.

Pharmacological management of vascular endothelial dysfunction in diabetes: TCM and western medicine compared based on biomarkers and biochemical parameters

Diabetes, a worldwide health concern while burdening significant populace of countries with time due to a hefty increase in both incidence and prevalence rates. Hyperglycemia has been buttressed both in clinical and experimental studies to modulate widespread molecular actions that effect macro and microvascular dysfunctions. Endothelial dysfunction, activation, inflammation, and endothelial barrier leakage are key factors contributing to vascular complications in diabetes, plus the development of diabetes-induced cardiovascular diseases. The recent increase in molecular, transcriptional, and clinical studies has brought a new scope to the understanding of molecular mechanisms and the therapeutic targets for endothelial dysfunction in diabetes. In this review, an attempt made to discuss up to date critical and emerging molecular signaling pathways involved in the pathophysiology of endothelial dysfunction and viable pharmacological management targets. Importantly, we exploit some Traditional Chinese Medicines (TCM)/TCM isolated bioactive compounds modulating effects on endothelial dysfunction in diabetes. Finally, clinical studies data on biomarkers and biochemical parameters involved in the assessment of the efficacy of treatment in vascular endothelial dysfunction in diabetes was compared between clinically used western hypoglycemic drugs and TCM formulas.

Vasculoprotective Effects of Vildagliptin. Focus on Atherogenesis

Vildagliptin is a representative of Dipeptidyl Peptidase-4 (DPP-4) inhibitors, antihyperglycemic drugs, approved for use as monotherapy and combination therapy in type 2 diabetes mellitus. By inhibiting enzymatic decomposition, DPP-4 inhibitors increase the half-life of incretins such as GLP-1 (Glucagon-like peptide-1) and GIP (Gastric inhibitors polypeptide) and prolong their action. Some studies present results suggesting the anti-sclerotic and vasculoprotective effects of vildagliptin reaching beyond glycemic control. Vildagliptin is able to limit inflammation by suppression of the NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signaling pathway and proinflammatory agents such as TNF-α (tumor necrosis factor α), IL-1β (Interleukin-1β), and IL-8 (Interleukin 8). Moreover, vildagliptin regulates lipid metabolism; attenuates postprandial hypertriglyceridemia; and lowers serum triglycerides, apolipoprotein B, and blood total cholesterol levels. This DPP-4 inhibitor also reduces macrophage foam cell formation, which plays a key role in atheromatous plaque formation and stability. Vildagliptin reduces vascular stiffness via elevation of nitric oxide synthesis, improves vascular relaxation, and results in reduction in both systolic and diastolic blood pressure. Treatment with vildagliptin lowers the level of PAI-1 presenting possible antithrombotic effect. By affecting the endothelium, inflammation, and lipid metabolism, vildagliptin may affect the development of atherosclerosis at its various stages. The article presents a summary of the studies assessing vasculoprotective effects of vildagliptin with special emphasis on atherogenesis.

UVB-dependent inhibition of lipin-1 protects against proinflammatory responses in human keratinocytes

Lipin-1 is an Mg²⁺-dependent phosphatidate phosphatase (PAP1) that catalyzes a critical step in the synthesis of glycerophospholipids and is also a cotranscriptional regulator. The role of lipin-1 in the regulation of inflammatory responses has been extensively studied in various cell types but not in skin cells. In the present study, the function of lipin-1 in UVB-induced proinflammatory responses was assessed in normal human epidermal keratinocytes (NHEKs). UVB radiation downregulated lipin-1 expression. Lipin-1 inhibition was mediated by UVB-dependent sterol-response element binding protein-1 (SREBP-1) inhibition. The UVB-dependent inhibition of lipin-1 and SREBP-1 was mediated by AMPK activation. UVB-induced activation of JNK was dependent on AMPK activation and mediated lipin-1 inhibition. Prevention of UVB-mediated lipin-1 repression by introducing a lipin-1 expression vector stimulated IL-6 and IL-8 production, suggesting that lipin-1 inhibition attenuates UVB-induced IL-6 and IL-8 production. The downregulation of lipin-1 ameliorated UVB-induced NF-ĸB phosphorylation, which might be attributed to the suppression of UVB-induced accumulation of free fatty acids (FFAs). Pharmacological inhibition of PAP1 with propranolol suppressed UVB-induced production of IL-6 and IL-8 in NHEKs and reconstituted human skin models. Taken together, lipin-1 is downregulated by exposure to UVB radiation, which confers protection against UVB-induced proinflammatory responses; therefore, the inhibition of lipin-1 is a potential strategy for photoaging.

Reduced production and activity of an enzyme in skin cells helps protect them from damage caused by exposure to ultra-violet light. Minjung Chae and colleagues at the Amorepacific Corporation in Yongin, South Korea, identified an anti-inflammatory effect caused by the reduction in expression of the enzyme lipin-1 when skin cells are exposed to UVB radiation. These ultra-violet rays are associated with aging and increased risk of skin cancer. Lipin-1 is involved in making glycerophospholipid molecules, which are key components of the membranes surrounding and inside cells. Identifying the enzyme’s significance for inflammation in skin cells extends previous similar findings with other cell types. The research also uncovered aspects of the molecular mechanisms mediating the skin cell response. Inhibiting lipin-1 activity might reduce the damage sunlight causes to skin.

Dual Roles of the AMP-Activated Protein Kinase Pathway in Angiogenesis

Angiogenesis plays important roles in development, stress response, wound healing, tumorigenesis and cancer progression, diabetic retinopathy, and age-related macular degeneration. It is a complex event engaging many signaling pathways including vascular endothelial growth factor (VEGF), Notch, transforming growth factor-beta/bone morphogenetic proteins (TGF-β/BMPs), and other cytokines and growth factors. Almost all of them eventually funnel to two crucial molecules, VEGF and hypoxia-inducing factor-1 alpha (HIF-1α) whose expressions could change under both physiological and pathological conditions. Hypoxic conditions stabilize HIF-1α, while it is upregulated by many oncogenic factors under normaxia. HIF-1α is a critical transcription activator for VEGF. Recent studies have shown that intracellular metabolic state participates in regulation of sprouting angiogenesis, which may involve AMP-activated protein kinase (AMPK). Indeed, AMPK has been shown to exert both positive and negative effects on angiogenesis. On the one hand, activation of AMPK mediates stress responses to facilitate autophagy which stabilizes HIF-1α, leading to increased expression of VEGF. On the other hand, AMPK could attenuate angiogenesis induced by tumor-promoting and pro-metastatic factors, such as the phosphoinositide 3-kinase /protein kinase B (Akt)/mammalian target of rapamycin (PI3K/Akt/mTOR), hepatic growth factor (HGF), and TGF-β/BMP signaling pathways. Thus, this review will summarize research progresses on these two opposite effects and discuss the mechanisms behind the discrepant findings.

Artemisinin alleviates atherosclerotic lesion by reducing macrophage inflammation via regulation of AMPK/NF-κB/NLRP3 inflammasomes pathway

There is increasing evidence that atherosclerosis is the significant risk factor for cardiovascular diseases, which are the leading causes of morbidity and mortality worldwide. Artemisinin is a natural endoperoxides quiterpene lactone compound in Artemisia annua L with vasculoprotective effects. The primary aim of this study was to investigate whether artemisinin could be conferred an anti-atherosclerotic effect in high-fat diet (HFD)-fed ApoE^-/- mice and explore the possible mechanism. We found that treatment with artemisinin (50 and 100 mg/kg) effectively ameliorated atherosclerotic lesions, such as foam cell formation, hyperplasia and fibrosis in the aortic intima. Atherosclerotic mice treated with artemisinin showed reduced inflammation by up-regulating adenosine 5'-monophosphate (AMP) activated protein kinase (AMPK) activation and by down-regulating nuclear factor-κB (NF-κB) phosphorylation and nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome expression in the aortas. In addition, artemisinin was found to promote AMPK activity in macrophages and its anti-inflammatory effect was neutralised by AMPK silence using specific siRNA. In conclusion, we demonstrate that artemisinin may protect the aortas from atherosclerotic lesions by suppression of inflammatory reaction via AMPK/NF-κB/NLRP3 inflammasomes signalling in macrophages.

A novel AMPK activator improves hepatic lipid metabolism and leukocyte trafficking in experimental hepatic steatosis

A novel AMP-activated protein kinase (AMPK) activator, IMM-H007 (H007), has been reported to reduce serum lipid levels and inhibit lipid accumulation in the liver in hyperlipidemic animal models. However, how H007 ameliorates hepatic steatosis and inflammation remains unknown. In the present study, H007, at 200 mg/kg, reduced hepatic lipid levels and the levels of collagenous fiber in the liver in high-fat diet (HFD)-fed hamsters compared to those in the HFD group. Meanwhile, compared to the controls, H007 significantly inhibited sterol-regulatory element binding protein (SREBP)-1c and acetyl CoA carboxylase (ACC) expression by upregulating the AMPK activity, suppressing the saturated fatty acid accumulation and increasing polyunsaturated fatty acid synthesis in the liver. Compared to the controls, H007 treatment inhibited the expression of monocyte chemotactic protein (MCP-1) in fatty acid-treated HepG2 cells; suppressed leukocyte adherence and rolling on the liver microvasculature; and suppressed hepatic macrophage infiltration. H007 also suppressed the expression of nuclear factor-κB (NF-κB) p65 in fatty acid- and lipopolysaccharide-treated HepG2 cells compared to that in the controls by activating AMPK. These data suggested that H007 had a beneficial effect by improving the lipid composition in the liver and inhibiting inflammatory cell trafficking in the development of nonalcoholic fatty liver disease.

Nicotine Attenuates Osteoarthritis Pain and Matrix Metalloproteinase-9 Expression via the α7 Nicotinic Acetylcholine Receptor

Osteoarthritis (OA) is a degenerative joint disease that causes chronic disability among the elderly. Despite recent advances in symptomatic management of OA by pharmacological and surgical approaches, there remains a lack of optimal approaches to manage inflammation in the joints, which causes cartilage degradation and pain. In this study, we investigated the efficacy and underlying mechanisms of nicotine exposure in attenuating joint inflammation, cartilage degradation, and pain in a mouse model of OA. A mouse model of OA was induced by injection of monosodium iodoacetate into the knee joint. Cell culture models were also used to study the efficacy and underlying mechanisms of nicotine treatment in attenuating symptoms of OA. Nicotine treatment reduced mechanical allodynia, cartilage degradation, and the upregulation of matrix metalloproteinase-9 (MMP-9), a hallmark of joint inflammation in OA, in mice treated with monosodium iodoacetate. The effects of nicotine were abolished by the selective α7 nicotinic acetylcholine receptor (nAChR) blocker, methyllycaconitine . In RAW264.7 cells and murine primary bone marrow-derived macrophages, nicotine significantly inhibited MMP-9 production induced by LPS. In addition, nicotine significantly enhanced PI3K/Akt and inhibited NF-κB translocation from the cytosol to the nucleus in an α7-nAChR-dependent manner, suggesting that nicotine acts on α7-nAChRs to inhibit MMP-9 production by macrophages through modulation of the PI3K/Akt-NF-κB pathway. Our results provide novel evidence that nicotine can attenuate joint inflammation and pain in experimental OA via α7-nAChRs. α7-nAChR could thus serve as a highly promising target to manage joint inflammation and pain in OA.

AMP-activated protein kinase regulates glycocalyx impairment and macrophage recruitment in response to low shear stress

Low shear stress (LSS) increases degradation of the endothelial glycocalyx, leading to production of endothelial inflammation and atherosclerosis. However, the underlying mechanisms of how LSS diminishes the endothelial glycocalyx remain unclear. We showed that LSS inactivated AMPK, enhanced Na⁺-H⁺ exchanger (NHE)1 activity, and induced glycocalyx degradation. Activation of AMPK prevented LSS-induced NHE1 activity and endothelial glycocalyx impairment. We further identified hyaluronidase 2 (HYAL2) as a mediator of endothelial glycocalyx impairment in HUVECs exposed to LSS. Inactivation of AMPK by LSS up-regulates the activity of HYAL2, which acts downstream of NHE1. We characterized a left common carotid artery partial ligation (PL) model of LSS in C57BL/6 mice. The results showed decreased expression of hyaluronan (HA) in the endothelial glycocalyx and decreased thickness of the endothelial glycocalyx in PL mice. Pharmacological activation of AMPK by ampkinone not only attenuated glycocalyx impairment due to HA degradation but also blocked vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 expression increase and macrophage recruitment in the endothelia of PL mice. Our results revealed that AMPK dephosphorylation induced by LSS activates NHE1 and HYAL2 to promote HA degradation and glycocalyx injury, which may contribute to endothelial inflammatory reaction and macrophage recruitment.-Zhang, J., Kong, X., Wang, Z., Gao, X., Ge, Z., Gu, Y., Ye, P., Chao, Y., Zhu, L., Li, X., Chen, S. AMP-activated protein kinase regulates glycocalyx impairment and macrophage recruitment in response to low shear stress.

Novel therapeutic strategies for stroke: The role of autophagy

Autophagy is an important biological mechanism involved in the regulation of numerous fundamental cellular processes that are mainly associated with cellular growth and differentiation. Autophagic pathways are vital for maintaining cellular homeostasis by enhancing the turnover of nonfunctional proteins and organelles. Neuronal cells, like other eukaryotic cells, are dependent on autophagy for neuroprotection in response to stress, but can also induce cell death in cerebral ischemia. Recent studies have demonstrated that autophagy may induce neuroprotection following acute brain injury, including ischemic stroke. However in some special circumstances, activation of autophagy can induce cell death, playing a deleterious role in the etiology and progression of ischemic stroke. Currently, there are no therapeutic options against stroke that demonstrate efficient neuroprotective abilities. In the present work, we will review the significance of autophagy in the context of ischemic stroke by first outlining its role in ischemic neuronal death. We will also highlight the potential therapeutic applications of pharmacological modulators of autophagy, including some naturally occurring polyphenolic compounds that can target this catabolic process. Our findings provide renewed insight on the mechanism of action of autophagy in stroke together with potential neuroprotective compounds, which may partially exert their function through enhancing mitochondrial function and attenuating damaging autophagic processes.

Nutritional Modulation of AMPK-Impact upon Metabolic-Inflammation

Nutritional status provides metabolic substrates to activate AMP-Activated Protein Kinase (AMPK), the energy sensor that regulates metabolism. Recent evidence has demonstrated that AMPK has wider functions with respect to regulating immune cell metabolism and function. One such example is the regulatory role that AMPK has on NLRP3-inlflammasome and IL-1β biology. This in turn can result in subsequent negative downstream effects on glucose, lipid and insulin metabolism. Nutrient stress in the form of obesity can impact AMPK and whole-body metabolism, leading to complications such as type 2 diabetes and cancer risk. There is a lack of data regarding the nature and extent that nutrient status has on AMPK and metabolic-inflammation. However, emerging work elucidates to a direct role of individual nutrients on AMPK and metabolic-inflammation, as a possible means of modulating AMPK activity. The posit being to use such nutritional agents to re-configure metabolic-inflammation towards more oxidative phosphorylation and promote the resolution of inflammation. The complex paradigm will be discussed within the context of if/how dietary components, nutrients including fatty acids and non-nutrient food components, such as resveratrol, berberine, curcumin and the flavonoid genistein, modulate AMPK dependent processes relating to inflammation and metabolism.

Mechanisms of Dysfunction in the Aging Vasculature and Role in Age-Related Disease

Advancing age promotes cardiovascular disease (CVD), the leading cause of death in the United States and many developed nations. Two major age-related arterial phenotypes, large elastic artery stiffening and endothelial dysfunction, are independent predictors of future CVD diagnosis and likely are responsible for the development of CVD in older adults. Not limited to traditional CVD, these age-related changes in the vasculature also contribute to other age-related diseases that influence mammalian health span and potential life span. This review explores mechanisms that influence age-related large elastic artery stiffening and endothelial dysfunction at the tissue level via inflammation and oxidative stress and at the cellular level via Klotho and energy-sensing pathways (AMPK [AMP-activated protein kinase], SIRT [sirtuins], and mTOR [mammalian target of rapamycin]). We also discuss how long-term calorie restriction-a health span- and life span-extending intervention-can prevent many of these age-related vascular phenotypes through the prevention of deleterious alterations in these mechanisms. Lastly, we discuss emerging novel mechanisms of vascular aging, including senescence and genomic instability within cells of the vasculature. As the population of older adults steadily expands, elucidating the cellular and molecular mechanisms of vascular dysfunction with age is critical to better direct appropriate and measured strategies that use pharmacological and lifestyle interventions to reduce risk of CVD within this population.

Endothelial AMP-Activated Kinase α1 Phosphorylates eNOS on Thr495 and Decreases Endothelial NO Formation

AMP-activated protein kinase (AMPK) is frequently reported to phosphorylate Ser1177 of the endothelial nitric-oxide synthase (eNOS), and therefore, is linked with a relaxing effect. However, previous studies failed to consistently demonstrate a major role for AMPK on eNOS-dependent relaxation. As AMPK also phosphorylates eNOS on the inhibitory Thr495 site, this study aimed to determine the role of AMPKα1 and α2 subunits in the regulation of NO-mediated vascular relaxation. Vascular reactivity to phenylephrine and acetylcholine was assessed in aortic and carotid artery segments from mice with global (AMPKα^-/-) or endothelial-specific deletion (AMPKα^ΔEC) of the AMPKα subunits. In control and AMPKα1-depleted human umbilical vein endothelial cells, eNOS phosphorylation on Ser1177 and Thr495 was assessed after AMPK activation with thiopental or ionomycin. Global deletion of the AMPKα1 or α2 subunit in mice did not affect vascular reactivity. The endothelial-specific deletion of the AMPKα1 subunit attenuated phenylephrine-mediated contraction in an eNOS- and endothelium-dependent manner. In in vitro studies, activation of AMPK did not alter the phosphorylation of eNOS on Ser1177, but increased its phosphorylation on Thr495. Depletion of AMPKα1 in cultured human endothelial cells decreased Thr495 phosphorylation without affecting Ser1177 phosphorylation. The results of this study indicate that AMPKα1 targets the inhibitory phosphorylation Thr495 site in the calmodulin-binding domain of eNOS to attenuate basal NO production and phenylephrine-induced vasoconstriction.

Cellular Stresses and Stress Responses in the Pathogenesis of Insulin Resistance

Insulin resistance (IR), a key component of the metabolic syndrome, precedes the development of diabetes, cardiovascular disease, and Alzheimer's disease. Its etiological pathways are not well defined, although many contributory mechanisms have been established. This article summarizes such mechanisms into the hypothesis that factors like nutrient overload, physical inactivity, hypoxia, psychological stress, and environmental pollutants induce a network of cellular stresses, stress responses, and stress response dysregulations that jointly inhibit insulin signaling in insulin target cells including endothelial cells, hepatocytes, myocytes, hypothalamic neurons, and adipocytes. The insulin resistance-inducing cellular stresses include oxidative, nitrosative, carbonyl/electrophilic, genotoxic, and endoplasmic reticulum stresses; the stress responses include the ubiquitin-proteasome pathway, the DNA damage response, the unfolded protein response, apoptosis, inflammasome activation, and pyroptosis, while the dysregulated responses include the heat shock response, autophagy, and nuclear factor erythroid-2-related factor 2 signaling. Insulin target cells also produce metabolites that exacerbate cellular stress generation both locally and systemically, partly through recruitment and activation of myeloid cells which sustain a state of chronic inflammation. Thus, insulin resistance may be prevented or attenuated by multiple approaches targeting the different cellular stresses and stress responses.

Celecoxib exerts protective effects in the vascular endothelium via COX-2-independent activation of AMPK-CREB-Nrf2 signalling

Although concern remains about the athero-thrombotic risk posed by cyclo-oxygenase (COX)-2-selective inhibitors, recent data implicates rofecoxib, while celecoxib appears equivalent to NSAIDs naproxen and ibuprofen. We investigated the hypothesis that celecoxib activates AMP kinase (AMPK) signalling to enhance vascular endothelial protection. In human arterial and venous endothelial cells (EC), and in contrast to ibuprofen and naproxen, celecoxib induced the protective protein heme oxygenase-1 (HO-1). Celecoxib derivative 2,5-dimethyl-celecoxib (DMC) which lacks COX-2 inhibition also upregulated HO-1, implicating a COX-2-independent mechanism. Celecoxib activated AMPKα^(Thr172) and CREB-1^(Ser133) phosphorylation leading to Nrf2 nuclear translocation. Importantly, these responses were not reproduced by ibuprofen or naproxen, while AMPKα silencing abrogated celecoxib-mediated CREB and Nrf2 activation. Moreover, celecoxib induced H-ferritin via the same pathway, and increased HO-1 and H-ferritin in the aortic endothelium of mice fed celecoxib (1000 ppm) or control chow. Functionally, celecoxib inhibited TNF-α-induced NF-κB p65^(Ser536) phosphorylation by activating AMPK. This attenuated VCAM-1 upregulation via induction of HO-1, a response reproduced by DMC but not ibuprofen or naproxen. Similarly, celecoxib prevented IL-1β-mediated induction of IL-6. Celecoxib enhances vascular protection via AMPK-CREB-Nrf2 signalling, a mechanism which may mitigate cardiovascular risk in patients prescribed celecoxib. Understanding NSAID heterogeneity and COX-2-independent signalling will ultimately lead to safer anti-inflammatory drugs.

Canagliflozin inhibits interleukin-1β-stimulated cytokine and chemokine secretion in vascular endothelial cells by AMP-activated protein kinase-dependent and -independent mechanisms

Recent clinical trials of the hypoglycaemic sodium-glucose co-transporter-2 (SGLT2) inhibitors, which inhibit renal glucose reabsorption, have reported beneficial cardiovascular outcomes. Whether SGLT2 inhibitors directly affect cardiovascular tissues, however, remains unclear. We have previously reported that the SGLT2 inhibitor canagliflozin activates AMP-activated protein kinase (AMPK) in immortalised cell lines and murine hepatocytes. As AMPK has anti-inflammatory actions in vascular cells, we examined whether SGLT2 inhibitors attenuated inflammatory signalling in cultured human endothelial cells. Incubation with clinically-relevant concentrations of canagliflozin, but not empagliflozin or dapagliflozin activated AMPK and inhibited IL-1β-stimulated adhesion of pro-monocytic U937 cells and secretion of IL-6 and monocyte chemoattractant protein-1 (MCP-1). Inhibition of MCP-1 secretion was attenuated by expression of dominant-negative AMPK and was mimicked by the direct AMPK activator, A769662. Stimulation of cells with either canagliflozin or A769662 had no effect on IL-1β-stimulated cell surface levels of adhesion molecules or nuclear factor-κB signalling. Despite these identical effects of canagliflozin and A769662, IL-1β-stimulated IL-6/MCP-1 mRNA was inhibited by canagliflozin, but not A769662, whereas IL-1β-stimulated c-jun N-terminal kinase phosphorylation was inhibited by A769662, but not canagliflozin. These data indicate that clinically-relevant canagliflozin concentrations directly inhibit endothelial pro-inflammatory chemokine/cytokine secretion by AMPK-dependent and -independent mechanisms without affecting early IL-1β signalling.

miR-135b-5p inhibits LPS-induced TNFα production via silencing AMPK phosphatase Ppm1e

AMPK activation in monocytes could suppress lipopolysaccharide (LPS)-induced tissue-damaging TNFa production. We are set to provoke AMPK activation via microRNA (“miRNA”) downregulating its phosphatase Ppm1e. In human U937 and THP-1 monocytes, forced expression of microRNA-135b-5p (“miR-135b-5p”) downregulated Ppm1e and activated AMPK signaling. Further, LPS-induced TNFα production in above cells was dramatically attenuated. Ppm1e shRNA knockdown in U937 cells also activated AMPK and inhibited TNFα production by LPS. AMPK activation is required for miR-135b-induced actions in monocytes, AMPKα shRNA knockdown or T172A dominant negative mutation almost abolished miR-135b-5p's suppression on LPS-induced TNFα production. Significantly, miR-135b-5p inhibited LPS-induced reactive oxygen species (ROS) production, NFκB activation and TNFα mRNA expression in human macrophages. AMPKα knockdown or mutation again abolished above actions by miR-135b-5p. We conclude that miR-135b-5p expression downregulates Ppm1e to activate AMPK signaling, which inhibits LPS-induced TNFα production via suppressing ROS production and NFκB activation.

Cinacalcet-mediated activation of the CaMKKβ-LKB1-AMPK pathway attenuates diabetic nephropathy in db/db mice by modulation of apoptosis and autophagy

Apoptosis and autophagy are harmoniously regulated biological processes for maintaining tissue homeostasis. AMP-activated protein kinase (AMPK) functions as a metabolic sensor to coordinate cellular survival and function in various organs, including the kidney. We investigated the renoprotective effects of cinacalcet in high-glucose treated human glomerular endothelial cells (HGECs), murine podocytes and C57BLKS/J-db/db mice. In cultured HGECs and podocytes, cinacalcet decreased oxidative stress and apoptosis and increased autophagy that were attributed to the increment of intracellular Ca²⁺ concentration and the phosphorylation of Ca²⁺/calmodulin-dependent protein kinase kinaseβ (CaMKKβ)-Liver kinase B1 (LKB1)-AMPK and their downstream signals including the phosphorylation of endothelial nitric oxide synthase (eNOS) and increases in superoxide dismutases and B cell leukemia/lymphoma 2/BCL-2-associated X protein expression. Interestingly, intracellular chelator BAPTA-AM reversed cinacalcet-induced CaMKKβ elevation and LKB1 phosphorylation. Cinacalcet reduced albuminuria without influencing either blood glucose or Ca²⁺ concentration and ameliorated diabetes-induced renal damage, which were related to the increased expression of calcium-sensing receptor and the phosphorylation of CaMKKβ-LKB1. Subsequent activation of AMPK was followed by the activation of peroxisome proliferator-activated receptor γ coactivator-1α and phospho-Ser¹¹⁷⁷eNOS-nitric oxide, resulting in a decrease in apoptosis and oxidative stress as well as an increase in autophagy.

Our results suggest that cinacalcet increases intracellular Ca²⁺ followed by an activation of CaMKKβ-LKB1-AMPK signaling in GECs and podocytes in the kidney, which provides a novel therapeutic means for type 2 diabetic nephropathy by modulation of apoptosis and autophagy.

Linkage of Metabolic Defects to Activated PIK3CA Alleles in Endothelial Cells Derived from Lymphatic Malformation

BACKGROUND

Lymphatic endothelial cells (LECs) derived from lymphatic malformations (LMs) bear activated PIK3CA alleles yet display an inflammatory gene expression profile. A basis for the inflammatory phenotype was sought by screening for coexisting somatic mutations.

METHODS AND RESULTS

Fourteen independent LEC populations bearing activated PIK3CA alleles were isolated from LM. These were characterized by the expression of growth and inflammatory genes (VEGFC, IL-6, COX-2, IL-8, HO-1, E-SEL) by qRT-PCR. Most commonly upregulated gene products were VEGFC, COX2, HO-1, and ANGPTL4. The specific inhibition of PI3K reduced VEGFC expression without resolving inflammation. Whole exome sequencing of six LM-LEC populations identified five novel somatically acquired alleles coexisting with activated PIK3CA alleles. Two affected genes regulate lipid droplet metabolism (FITM2 and ATG2A), two are gene regulators (MTA1 and TAF1L), and the fifth is an isoform of ANK3 (an endosomal/lysosomal protein). Inhibition of AMPK implicated its involvement in regulating COX-2 and HO-1 overexpression. ANGPTL4 expression was independent of AMPK and PI3K activity and reflected lipid stress demonstrated in normal LECs. AMPK activation with AICAR had a selective growth-limiting effect in a subset of LM-LEC isolates.

CONCLUSIONS

Inflammatory stress displayed by LM-LECs is consistent with errors in lipid metabolism that may be linked to acquired mutations. The acquisition of PIK3CA alleles may be a permissive event that antagonizes inflammation and metabolic defect.