AMPK agonists ameliorate sodium and fluid transport and inflammation in cystic fibrosis airway epithelial cells

Spatiotemporal Clusters of Extracellular Signal-Regulated Kinase Activity Coordinate Cytokine-induced Inflammatory Responses in Human Airway Epithelial Cells

Spatially coordinated extracellular signal-regulated kinase (ERK) signaling events (SPREADs) transmit radially from a central point to adjacent cells via secreted ligands for EGFR (epidermal growth factor receptor) and other receptors. SPREADs maintain homeostasis in nonpulmonary epithelia, but it is unknown whether they play a role in the airway epithelium or are dysregulated in inflammatory disease. To address these questions, we measured SPREAD activity with live-cell ERK biosensors in human bronchial epithelial cell lines (HBE1 and 16HBE) and primary human bronchial epithelial cells, in both submerged and biphasic air-liquid interface culture conditions (i.e., differentiated cells). Airway epithelial cells were exposed to proinflammatory cytokines relevant to asthma and chronic obstructive pulmonary disease. Type 1 proinflammatory cytokines significantly increased the frequency of SPREADs, which coincided with epithelial barrier breakdown in differentiated primary human bronchial epithelial cells. Furthermore, SPREADs correlated with IL-6 peptide secretion and the appearance of localized clusters of phospho-STAT3 immunofluorescence. To probe the mechanism of SPREADs, cells were cotreated with pharmacological treatments (gefitinib, tocilizumab, hydrocortisone) or metabolic modulators (insulin, 2-deoxyglucose). Hydrocortisone, inhibitors of receptor signaling, and suppression of metabolic function decreased SPREAD occurrence, implying that proinflammatory cytokines and glucose metabolism modulate SPREADs in human airway epithelial cells via secreted EGFR and IL6R ligands. We conclude that spatiotemporal ERK signaling plays a role in barrier homeostasis and dysfunction during inflammation of the airway epithelium. This novel signaling mechanism could be exploited clinically to supplement corticosteroid treatment for asthma and chronic obstructive pulmonary disease.

Obesity-induced fibrosis in osteoarthritis: Pathogenesis, consequences and novel therapeutic opportunities

Osteoarthritis (OA) is a significant global burden, affecting more than half a billion people across the world. It is characterized by degeneration and loss of articular cartilage, synovial inflammation, and subchondral bone sclerosis, leading to pain and functional impairment. After age, obesity is a major modifiable risk factor for OA, and it has recently been identified as a chronic disease by the World Health Organization (WHO). Obesity is associated with high morbidity and mortality, imposing a significant cost on individuals and society. Obesity increases the risk of knee OA through increased joint loading, altered body composition, and elevated pro-inflammatory adipokines in the systemic circulation. Moreover, obesity triggers fibrotic processes in different organs and tissues, including those involved in OA. Fibrosis in OA refers to the abnormal accumulation of fibrous tissue within and around the joints. It can be driven by increased adiposity, low-grade inflammation, oxidative stress, and metabolic alterations. However, the clinical outcomes of fibrosis in OA are unclear. This review focuses on the link between obesity and OA, explores the mechanism of obesity-driven fibrosis, and examines potential therapeutic opportunities for targeting fibrotic processes in OA.

Fatty acid abnormalities in cystic fibrosis-the missing link for a cure?

The care for cystic fibrosis (CF) has dramatically changed with the development of modulators, correctors, and potentiators of the CFTR molecule, which lead to improved clinical status of most people with CF (pwCF). The modulators influence phospholipids and ceramides, but not linoleic acid (LA) deficiency, associated with more severe phenotypes of CF. The LA deficiency is associated with upregulation of its transfer to arachidonic acid (AA). The AA release from membranes is increased and associated with increase of pro-inflammatory prostanoids and the characteristic inflammation is present before birth and bacterial infections. Docosahexaenoic acid is often decreased, especially in associated liver disease Some endogenously synthesized fatty acids are increased. Cholesterol and ceramide metabolisms are disturbed. The lipid abnormalities are present at birth, and before feeding in transgenic pigs and ferrets. This review focus on the lipid abnormalities and their associations to clinical symptoms in CF, based on clinical studies and experimental research.

Interpretable machine learning uncovers epithelial transcriptional rewiring and a role for Gelsolin in COPD

Transcriptomic analyses have advanced the understanding of complex disease pathophysiology including chronic obstructive pulmonary disease (COPD). However, identifying relevant biologic causative factors has been limited by the integration of high dimensionality data. COPD is characterized by lung destruction and inflammation, with smoke exposure being a major risk factor. To define previously unknown biological mechanisms in COPD, we utilized unsupervised and supervised interpretable machine learning analyses of single-cell RNA-Seq data from the mouse smoke-exposure model to identify significant latent factors (context-specific coexpression modules) impacting pathophysiology. The machine learning transcriptomic signatures coupled to protein networks uncovered a reduction in network complexity and new biological alterations in actin-associated gelsolin (GSN), which was transcriptionally linked to disease state. GSN was altered in airway epithelial cells in the mouse model and in human COPD. GSN was increased in plasma from patients with COPD, and smoke exposure resulted in enhanced GSN release from airway cells from patients with COPD. This method provides insights into rewiring of transcriptional networks that are associated with COPD pathogenesis and provides a translational analytical platform for other diseases.

Jianghu decoction and its active component polydatin inhibit inflammation and fibrotic lesions in the lungs of ILD mice via the AMPK signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Recently, interstitial lung disease (ILD) morbidity and mortality have been increasing with insidious epidemiological characteristics. Jianghu decoction (JH) is an effective Chinese medicine for ILD.

AIM OF THE STUDY

We aimed to reveal the material basis and mechanism of action of JH in the treatment of ILD.

MATERIALS AND METHODS

In this study, an ILD mouse model was constructed with bleomycin. HE staining, transcriptome analysis, parallel reaction monitoring-mass spectrometry (PRM-MS), UPLC‒MS, and western blotting assays were conducted.

RESULTS

HE staining results showed that JH effectively reduced inflammation and fibrosis foci in the lungs of the ILD model. Furthermore, transcriptome analysis revealed that JH regulates a set of biological signaling pathways related to immune inflammation and fibrosis. PRM-MS combined with western blotting was applied to detect inflammation and fibrosis involving proteins in lung tissue. JH effectively reversed the aberrant expression of HMGB1, RAGE, SEPTIN4, ACTA2, and ITGAV proteins in the model group. AMPK was identified as the core upstream regulatory protein for JH-mediated ILD regulation. In addition, UHPLC‒MS technology was applied to determine the active ingredients of JH. A total of 80 components were identified from JH, and polydatin (PD) was identified as the active ingredient that effectively alleviated lung fibrosis and inflammatory injury in ILD mice. To illustrate the molecular regulatory network of JH and PD in alleviating lung fibrosis and inflammatory injury, we also examined inflammation and fibrosis-related molecules downstream of the AMPK pathway with RT‒qPCR and western blotting.

CONCLUSIONS

The results showed that both JH and its active component PD exert synergistic inhibition on pulmonary fibrosis and inflammation. Specifically, the AMPK/PGC1α/PPARγ signaling pathway was activated, and the AMPK/HMGB1/RAGE signaling pathway was inhibited in ILD lungs responding to JH or PD administration.

A review of structural modification and biological activities of oleanolic acid

Oleanolic acid (OA), a pentacyclic triterpenoid, exhibits a broad spectrum of biological activities, including antitumor, antiviral, antibacterial, anti-inflammatory, hepatoprotective, hypoglycemic, and hypolipidemic effects. Since its initial isolation and identification, numerous studies have reported on the structural modifications and pharmacological activities of OA and its derivatives. Despite this, there has been a dearth of comprehensive reviews in the past two decades, leading to challenges in subsequent research on OA. Based on the main biological activities of OA, this paper comprehensively summarized the modification strategies and structure-activity relationships (SARs) of OA and its derivatives to provide valuable reference for future investigations into OA.

Extracellular vesicles-derived miRNAs as mediators of pulmonary exacerbation in pediatric cystic fibrosis

Children with cystic fibrosis (CF) suffer from chronic inflammation and recurrent pulmonary exacerbations (PEs). We aimed to test whether a specific miRNA could be associated with the occurrence of PE. We sequenced extracellular vesicle (EV)-derived miRNA in sputum (n= 20), exhaled breath condensate (EBC) (n= 11), and serum (n= 8) samples from pediatric patients during PE and the stable stage of CF. Four miRNAs: let-7c, miR-16, miR-25-3p and miR-146a, have been selected for validation in a larger group with reverse transcription quantitative real-time PCR (RT-qPCR) in sputum and serum, or droplet digital PCR (ddPCR) in EBC. Next-generation sequencing (NGS) differential expression analysis was done in Base Space, and the correlation between miRNAs expression and clinical data was calculated with Statistica. Functional annotation of selected miRNAs and their potential target genes was performed with miRDip and DAVID software. There were no differences in miRNA expression between stable and exacerbation in sputum and in serum. Validation of four selected miRNAs showed significant downregulation of miR-146a in serum. A panel of all four miRNAs (peripherally) was the best predictive model of exacerbation (p< 0.001, AUC = 0.96). Expression of airway miR-25-3p improved the diagnostic value of FEV1% pred and FVC% pred, while peripheral miR-146a improved the predictive model of C-reactive protein and neutrophilia.In silicoanalysis revealed a potential role for selected miRNAs in regulating processes associated with inflammation and tissue remodeling. We demonstrated that EVs contained in peripheral blood as well as local biomaterials can act as carriers for miRNAs with the diagnostic potential of predicting exacerbation in pediatric CF.

Toll-Like Receptor 4 (TLR4) and AMPK Relevance in Cardiovascular Disease

Toll-like receptors (TLRs) are essential receptors of the innate immune system, playing a significant role in cardiovascular diseases. TLR4, with the highest expression among TLRs in the heart, has been investigated extensively for its critical role in different myocardial inflammatory conditions. Studies suggest that inhibition of TLR4 signaling pathways reduces inflammatory responses and even prevents additional injuries to the already damaged myocardium. Recent research results have led to a hypothesis that there may be a relation between TLR4 expression and 5' adenosine monophosphate-activated protein kinase (AMPK) signaling in various inflammatory conditions, including cardiovascular diseases. AMPK, as a cellular energy sensor, has been reported to show anti-inflammatory effects in various models of inflammatory diseases. AMPK, in addition to its physiological acts in the heart, plays an essential role in myocardial ischemia and hypoxia by activating various energy production pathways. Herein we will discuss the role of TLR4 and AMPK in cardiovascular diseases and a possible relation between TLRs and AMPK as a novel therapeutic target. In our opinion, AMPK-related TLR modulators will find application in treating different immune-mediated inflammatory disorders, especially inflammatory cardiac diseases, and present an option that will be widely used in clinical practice in the future.

Overview of the Mechanisms of Oxidative Stress: Impact in Inflammation of the Airway Diseases

Inflammation of the human lung is mediated in response to different stimuli (e.g., physical, radioactive, infective, pro-allergenic or toxic) such as cigarette smoke and environmental pollutants. They often promote an increase in inflammatory activities in the airways that manifest themselves as chronic diseases (e.g., allergic airway diseases, asthma, chronic bronchitis/chronic obstructive pulmonary disease (COPD) or even lung cancer). Increased levels of oxidative stress (OS) reduce the antioxidant defenses, affect the autophagy/mitophagy processes, and the regulatory mechanisms of cell survival, promoting inflammation in the lung. In fact, OS potentiate the inflammatory activities in the lung, favoring the progression of chronic airway diseases. OS increases the production of reactive oxygen species (ROS), including superoxide anions (O₂^-), hydroxyl radicals (OH) and hydrogen peroxide (H₂O₂), by the transformation of oxygen through enzymatic and non-enzymatic reactions. In this manner, OS reduces endogenous antioxidant defenses in both nucleated and non-nucleated cells. The production of ROS in the lung can derive from both exogenous insults (cigarette smoke or environmental pollution) and endogenous sources such as cell injury and/or activated inflammatory and structural cells. In this review, we describe the most relevant knowledge concerning the functional interrelation between the mechanisms of OS and inflammation in airway diseases.

CTRP9 overexpression attenuates palmitic acid‑induced inflammation, apoptosis and impaired migration in HTR8/SVneo cells through AMPK/SREBP1c signaling

Obesity in pregnant mothers often leads to a range of obstetric complications, including miscarriage, pre-eclampsia, gestational hypertension and diabetes. C1q/TNF-related protein 9 (CTRP9) is an adipokine with an anti-inflammatory effect. The aim of the present study was to identify the role of CTRP9 in the pathogenesis of maternal obesity during pregnancy. Following treatment with palmitic acid (PA), HTR8/SVneo cell viability and CTRP9 expression were analyzed using Cell Counting Kit-8 (CCK-8), reverse transcription-quantitative PCR (RT-qPCR) and western blot analyses. The effects of CTRP9 overexpression on cell viability, apoptosis, pro-inflammatory cytokine levels and migration were assessed using CCK-8, TUNEL, RT-qPCR and Transwell assays, respectively. Subsequently, sterol-regulatory element binding protein 1c (SREBP1c) overexpression efficiency was verified using RT-qPCR, and its effects on cell viability, apoptosis, pro-inflammatory cytokines and migration damage were then examined in HTR8/SVneo cells. The results showed that CTRP9 overexpression attenuated the inhibition of cell viability and apoptosis caused by PA in HTR8/SVneo cells, reduced pro-inflammatory cytokine release, improved cell migration and regulated the protein expression level of AMP-activated protein kinase (AMPK)/SREBP1c signaling. In addition, CTRP9 inhibited SREBP1c expression through AMPK signaling, thereby attenuating the inflammation, apoptosis and inhibited migration caused by PA in HTR8/SVneo cells. In brief, CTRP9 protected against inflammation, apoptosis and migration defects in HTR8/SVneo cells exposed to PA treatment through AMPK/SREBP1c signaling, which suggested the potential role of CTRP9 in alleviating the toxicity of PA.

Metformin Inhibits Na+/H+ Exchanger NHE3 Resulting in Intestinal Water Loss

Glycemic control is the key to the management of type 2 diabetes. Metformin is an effective, widely used drug for controlling plasma glucose levels in diabetes, but it is often the culprit of gastrointestinal adverse effects such as abdominal pain, nausea, indigestion, vomiting, and diarrhea. Diarrhea is a complex disease and altered intestinal transport of electrolytes and fluid is a common cause of diarrhea. Na+/H+ exchanger 3 (NHE3, SLC9A3) is the major Na+ absorptive mechanism in the intestine and our previous study has demonstrated that decreased NHE3 contributes to diarrhea associated with type 1 diabetes. The goal of this study is to investigate whether metformin regulates NHE3 and inhibition of NHE3 contributes to metformin-induced diarrhea. We first determined whether metformin alters intestinal water loss, the hallmark of diarrhea, in type 2 diabetic db/db mice. We found that metformin decreased intestinal water absorption mediated by NHE3. Metformin increased fecal water content although mice did not develop watery diarrhea. To determine the mechanism of metformin-mediated regulation of NHE3, we used intestinal epithelial cells. Metformin inhibited NHE3 activity and the effect of metformin on NHE3 was mimicked by a 5'-AMP-activated protein kinase (AMPK) activator and blocked by pharmacological inhibition of AMPK. Metformin increased phosphorylation and ubiquitination of NHE3, resulting in retrieval of NHE3 from the plasma membrane. Previous studies have demonstrated the role of neural precursor cell expressed, developmentally down-regulated 4-2 (Nedd4-2) in regulation of human NHE3. Silencing of Nedd4-2 mitigated NHE3 inhibition and ubiquitination by metformin. Our findings suggest that metformin-induced diarrhea in type 2 diabetes is in part caused by reduced Na+ and water absorption that is associated with NHE3 inhibition, probably by AMPK.

The protective effects of Omarigliptin against Lipopolysaccharide (LPS)- induced inflammatory response and expression of mucin 5AC (MUC5AC) in human bronchial epithelial cells

The epidemic of chronic inflammatory lung diseases such as asthma, bronchitis, and chronic obstructive pulmonary disease (COPD) has become a global public health problem. Oxidative stress, inflammation, and overproduction of airway mucus play critical roles in the progression of these diseases. Omarigliptin, an oral dipeptidyl peptidase 4 (DPP-4) inhibitor, has been demonstrated to have anti-inflammatory effects in patients with type II diabetes. However, its role in chronic inflammatory lung diseases remains enigmatic. This study is to investigate whether Omarigliptin possesses a beneficial effect against Lipopolysaccharide (LPS)-induced injuries in human BEAS-2B bronchial epithelial cells. Our results show that Omarigliptin suppressed LPS-induced oxidative stress by attenuating the generation of mitochondrial reactive oxygen species (ROS) and decrease in reduced glutathione (GSH) in BEAS-2B cells. Additionally, Omarigliptin mitigated inflammatory response by inhibiting the expression of pro-inflammatory mediators, including interleukin-1β (IL-1β), interleukin-12 (IL-12), and macrophage chemoattractant protein-1 (MCP-1) in LPS-challenged BEAS-2B cells. Moreover, Omarigliptin mitigated the LPS-induced overproduction of MUC5AC by rescuing the expression of the suppressor of cytokine signaling 1(SOCS1). Importantly, we found that this process is mediated by the Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway. Based on these findings, we conclude that Omarigliptin might be a promising agent for the treatment of chronic inflammatory lung diseases.

P53 mediates the protective effects of metformin in inflamed lung endothelial cells

The endothelial barrier regulates interstitial fluid homeostasis by transcellular and paracellular means. Dysregulation of this semipermeable barrier may lead to vascular leakage, edema, and accumulation of pro-inflammatory cytokines, inducing microvascular hyperpermeability. Investigating the molecular pathways involved in those events will most probably provide novel therapeutic possibilities in pathologies related to endothelial barrier dysfunction. Metformin (MET) is an anti-diabetic drug, opposes malignancies, inhibits cellular transformation, and promotes cardiovascular protection. In the current study, we assess the protective effects of MET in LPS-induced lung endothelial barrier dysfunction and evaluate the role of P53 in mediating the beneficial effects of MET in the vasculature. We revealed that this biguanide (MET) opposes the LPS-induced dysregulation of the lung microvasculature, since it suppressed the formation of filamentous actin stress fibers, and deactivated cofilin. To investigate whether P53 is involved in those phenomena, we employed the fluorescein isothiocyanate (FITC) - dextran permeability assay, to measure paracellular permeability. Our observations suggest that P53 inhibition increases paracellular permeability, and MET prevents those effects. Our results contribute towards the understanding of the lung endothelium and reveal the significant role of P53 in the MET-induced barrier enhancement.

A Machine-Generated View of the Role of Blood Glucose Levels in the Severity of COVID-19

SARS-CoV-2 started spreading toward the end of 2019 causing COVID-19, a disease that reached pandemic proportions among the human population within months. The reasons for the spectrum of differences in the severity of the disease across the population, and in particular why the disease affects more severely the aging population and those with specific preconditions are unclear. We developed machine learning models to mine 240,000 scientific articles openly accessible in the CORD-19 database, and constructed knowledge graphs to synthesize the extracted information and navigate the collective knowledge in an attempt to search for a potential common underlying reason for disease severity. The machine-driven framework we developed repeatedly pointed to elevated blood glucose as a key facilitator in the progression of COVID-19. Indeed, when we systematically retraced the steps of the SARS-CoV-2 infection, we found evidence linking elevated glucose to each major step of the life-cycle of the virus, progression of the disease, and presentation of symptoms. Specifically, elevations of glucose provide ideal conditions for the virus to evade and weaken the first level of the immune defense system in the lungs, gain access to deep alveolar cells, bind to the ACE2 receptor and enter the pulmonary cells, accelerate replication of the virus within cells increasing cell death and inducing an pulmonary inflammatory response, which overwhelms an already weakened innate immune system to trigger an avalanche of systemic infections, inflammation and cell damage, a cytokine storm and thrombotic events. We tested the feasibility of the hypothesis by manually reviewing the literature referenced by the machine-generated synthesis, reconstructing atomistically the virus at the surface of the pulmonary airways, and performing quantitative computational modeling of the effects of glucose levels on the infection process. We conclude that elevation in glucose levels can facilitate the progression of the disease through multiple mechanisms and can explain much of the differences in disease severity seen across the population. The study provides diagnostic considerations, new areas of research and potential treatments, and cautions on treatment strategies and critical care conditions that induce elevations in blood glucose levels.

Cystic fibrosis-related diabetes and lung disease: an update

The development of cystic fibrosis-related diabetes (CFRD) often leads to poorer outcomes in patients with cystic fibrosis including increases in pulmonary exacerbations, poorer lung function and early mortality. This review highlights the many factors contributing to the clinical decline seen in patients diagnosed with CFRD, highlighting the important role of nutrition, the direct effect of hyperglycaemia on the lungs, the immunomodulatory effects of high glucose levels and the potential role of genetic modifiers in CFRD.

Oxidative Imbalance as a Crucial Factor in Inflammatory Lung Diseases: Could Antioxidant Treatment Constitute a New Therapeutic Strategy?

Inflammatory lung disease results in a high global burden of death and disability. There are no effective treatments for the most severe forms of many inflammatory lung diseases, such as chronic obstructive pulmonary disease, emphysema, corticosteroid-resistant asthma, and coronavirus disease 2019; hence, new treatment options are required. Here, we review the role of oxidative imbalance in the development of difficult-to-treat inflammatory lung diseases. The inflammation-induced overproduction of reactive oxygen species (ROS) means that endogenous antioxidants may not be sufficient to prevent oxidative damage, resulting in an oxidative imbalance in the lung. In turn, intracellular signaling events trigger the production of proinflammatory mediators that perpetuate and aggravate the inflammatory response and may lead to tissue damage. The production of high levels of ROS in inflammatory lung diseases can induce the phosphorylation of mitogen-activated protein kinases, the inactivation of phosphoinositide 3-kinase (PI3K) signaling and histone deacetylase 2, a decrease in glucocorticoid binding to its receptor, and thus resistance to glucocorticoid treatment. Hence, antioxidant treatment might be a therapeutic option for inflammatory lung diseases. Preclinical studies have shown that antioxidants (alone or combined with anti-inflammatory drugs) are effective in the treatment of inflammatory lung diseases, although the clinical evidence of efficacy is weaker. Despite the high level of evidence for the efficacy of antioxidants in the treatment of inflammatory lung diseases, the discovery and clinical investigation of safer, more efficacious compounds are now a priority.

AMPK Activation by 5-Amino-4-Imidazole Carboxamide Riboside-1-β-D-Ribofuranoside Attenuates Alkali Injury-Induced Corneal Fibrosis

Purpose

Increased TGF-β1 synthesis after corneal alkali injury is implicated in corneal fibrosis, as it promotes transdifferentiation of keratocytes into myofibroblasts. The activation of 5'-adenosine monophosphate-activated protein kinase (AMPK) by 5-amino-4-imidazole carboxamide riboside-1-β-d-ribofuranoside (AICAR) inhibits TGF-β1-induced fibrosis in other cell types. We investigated the antifibrotic effect of AICAR in corneal fibroblasts after alkali injury.

Methods

Mouse models of corneal alkali burn, produced by placing 2-mm-diameter filter paper soaked in 0.1-N NaOH on the right cornea for 30 seconds, were treated with the test drugs 4× daily for 21 days. The central cornea was scanned by optical coherence tomography (OCT). Corneal tissues were obtained and processed for western blotting and immunohistochemistry. For in vitro analysis, primary human corneal fibroblasts were treated directly with TGF-β1 to induce fibrosis, with or without AICAR pretreatment. Myofibroblast activation and extracellular matrix (ECM) protein synthesis were detected by western blotting, real-time PCR, and collagen gel contraction assay. Signaling proteins were analyzed by western blotting.

Results

Alkali injury induced the upregulation of TGF-β1 expression, which led to increased α-smooth muscle actin (α-SMA) and fibronectin synthesis and myofibroblast differentiation. AMPK activation by AICAR significantly suppressed TGF-β1 and ECM protein expression. The antifibrotic effect of AICAR was AMPK dependent, as treatment with the AMPK inhibitor Compound C attenuated the antifibrotic response.

Conclusions

AMPK activation by AICAR suppresses the myofibroblast differentiation and ECM synthesis that occur after alkali injury in corneal fibroblasts.

Synthesis and anti-inflammatory activity of saponin derivatives of δ-oleanolic acid

Pentacyclic triterpenes (PTs) are the active ingredients of many medicinal herbs and pharmaceutical formulations, and are well-known for their anti-inflammatory activity. On the other hand, anti-inflammatory effects of AMP-activated protein kinase (AMPK) have recently drawn much attention. In this study, we found that a variety of naturally occurring PTs sapogenins and saponins could stimulate the phosphorylation of AMPK, and identified δ-oleanolic acid (10) as a potent AMPK activator. Based on these findings, 23 saponin derivatives of δ-oleanolic acid were synthesized in order to find more potent anti-inflammatory agents with improved pharmacokinetic properties. The results of cellular assays showed that saponin 29 significantly inhibited LPS-induced secretion of pro-inflammatory factors TNF-α and IL-6 in THP1-derived macrophages. Preliminary mechanistic studies showed that 29 stimulated the phosphorylation of AMPK and acetyl-CoA carboxylase (ACC). The bioavailability of 29 was significantly improved in comparison with its aglycon. More importantly, 29 showed significant anti-inflammatory and liver-protective effects in LPS/D-GalN-induced fulminant hepatic failure mice. Taken together, PTs saponins hold promise as therapeutic agents for inflammatory diseases.

Capsaicin-Loaded Chitosan Nanocapsules for wtCFTR-mRNA Delivery to a Cystic Fibrosis Cell Line

Cystic fibrosis (CF), a lethal hereditary disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene coding for an epithelial chloride channel, is characterized by an imbalanced homeostasis of ion and water transports in secretory epithelia. As the disease is single-gene based, transcript therapy using therapeutic mRNA is a promising concept of treatment in order to correct many aspects of the fatal pathology on a cellular level. Hence, we developed chitosan nanocapsules surface-loaded with wtCFTR-mRNA to restore CFTR function. Furthermore, we loaded the nanocapsules with capsaicin, aiming to enhance the overall efficiency of transcript therapy by reducing sodium hyperabsorption by the epithelial sodium channel (ENaC). Dynamic light scattering with non-invasive back scattering (DLS-NIBS) revealed nanocapsules with an average hydrodynamic diameter of ~200 nm and a Zeta potential of ~+60 mV. The results of DLS-NIBS measurements were confirmed by asymmetric flow field-flow fractionation (AF4) with multidetection, while transmission electron microscopy (TEM) images confirmed the spherical morphology and size range. After stability measurements showed that the nanocapsules were highly stable in cell culture transfection medium, and cytotoxicity was ruled out, transfection experiments were performed with the CF cell line CFBE41o-. Finally, transepithelial measurements with a new state-of-the-art Ussing chamber confirmed successfully restored CFTR function in transfected cells. This study demonstrates that CS nanocapsules as a natural and non-toxic delivery system for mRNA to target cells could effectively replace risky vectors for gene delivery. The nanocapsules are not only suitable as a transcript therapy for treatment of CF, but open aspiring possibilities for safe gene delivery in general.

Chitosan Nanocomplexes for the Delivery of ENaC Antisense Oligonucleotides to Airway Epithelial Cells

Nanoscale drug delivery systems exhibit a broad range of applications and promising treatment possibilities for various medical conditions. Nanomedicine is of great interest, particularly for rare diseases still lacking a curative treatment such as cystic fibrosis (CF). CF is defined by a lack of Cl⁻ secretion through the cystic fibrosis transmembrane conductance regulator (CFTR) and an increased Na⁺ absorption mediated by the epithelial sodium channel (ENaC). The imbalanced ion and water transport leads to pathological changes in many organs, particularly in the lung. We developed a non-viral delivery system based on the natural aminopolysaccharide chitosan (CS) for the transport of antisense oligonucleotides (ASO) against ENaC to specifically address Na⁺ hyperabsorption. CS–ASO electrostatic self-assembled nanocomplexes were formed at varying positive/negative (P/N) charge ratios and characterized for their physicochemical properties. Most promising nanocomplexes (P/N 90) displayed an average size of ~150 nm and a zeta potential of ~+30 mV. Successful uptake of the nanocomplexes by the human airway epithelial cell line NCI-H441 was confirmed by fluorescence microscopy. Functional Ussing chamber measurements of transfected NCI-H441 cells showed significantly decreased Na⁺ currents, indicating successful downregulation of ENaC. The results obtained confirm the promising characteristics of CS as a non-viral and non-toxic delivery system and demonstrate the encouraging possibility to target ENaC with ASOs to treat abnormal ion transport in CF.

Broussonetia papyrifera Root Bark Extract Exhibits Anti-inflammatory Effects on Adipose Tissue and Improves Insulin Sensitivity Potentially Via AMPK Activation

The chronic low-grade inflammation in adipose tissue plays a causal role in obesity-induced insulin resistance and its associated pathophysiological consequences. In this study, we investigated the effects of extracts of Broussonetia papyrifera root bark (PRE) and its bioactive components on inflammation and insulin sensitivity. PRE inhibited TNF-α-induced NF-κB transcriptional activity in the NF-κB luciferase assay and pro-inflammatory genes’ expression by blocking phosphorylation of IκB and NF-κB in 3T3-L1 adipocytes, which were mediated by activating AMPK. Ten-week-high fat diet (HFD)-fed C57BL6 male mice treated with PRE had improved glucose intolerance and decreased inflammation in adipose tissue, as indicated by reductions in NF-κB phosphorylation and pro-inflammatory genes’ expression. Furthermore, PRE activated AMP-activated protein kinase (AMPK) and reduced lipogenic genes’ expression in both adipose tissue and liver. Finally, we identified broussoflavonol B (BF) and kazinol J (KJ) as bioactive constituents to suppress pro-inflammatory responses via activating AMPK in 3T3-L1 adipocytes. Taken together, these results indicate the therapeutic potential of PRE, especially BF or KJ, in metabolic diseases such as obesity and type 2 diabetes.

Alpha-Mangostin Ameliorates Bleomycin-Induced Pulmonary Fibrosis in Mice Partly Through Activating Adenosine 5'-Monophosphate-Activated Protein Kinase

Background: Pulmonary fibrosis (PF) is a devastating interstitial lung disease and characterized by an abnormal accumulation of extracellular matrix (ECM). Nintedanib (NDN) and pirfenidone are two approved therapies for PF, but their potential side-effects have been reported. Recently, the use of natural supplements for PF is attracting attention. Alpha-mangostin (α-MG) is an active xanthone-type compound isolated from the nutritious fruit mangosteen.

Purpose: In the present study, the potential effect and underlying mechanism of α-MG were evaluated in bleomycin (BLM)-induced PF and activated primary lung fibroblasts (PLFs).

Methods: Histopathological changes and collagen deposition were analyzed via hematoxylin-eosin staining and Masson staining, the expression of nicotinamide adenine dinucleotide phosphate oxidase-4 (NOX4) involved in oxidative stress in lung tissues was analyzed by immunochemistry staining. The expressions of α-smooth muscle actin (α-SMA), collagen I (Col I), p-adenosine 5′-monophosphate-activated protein kinase (AMPK)/AMPK, and NOX4 were detected by Western blot, immunofluorescence or RT-PCR, and effects of α-MG on cell viability were detected using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide.

Results:In vivo results demonstrated that α-MG treatment (10 mg/kg/day) significantly ameliorated BLM-induced deposition of ECM in lung tissues. Moreover, α-MG could inhibit protein expressions of α-SMA and Col I as well as its mRNA levels. In addition, α-MG also significantly inhibited transforming growth factor-β1/Smad2/3 pathway and regulated the protein expression of matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 in lung tissues. In vitro results demonstrated that α-MG significantly increased p-AMPK/AMPK but reduced the protein expression level of α-SMA and Col I as well as NOX4 in activated PLFs. Further study demonstrated that these improvement effects were significantly blocked by compound C.

Conclusion: α-MG treatment significantly decreased oxidative stress in lungs partly by activating AMPK mediated signaling pathway in BLM-induced PF and activated PLFs and decreased the deposition of ECM. The present study provides pharmacological evidence to support therapeutic application of α-MG in the treatment of PF.

The anti-inflammatory function of adenine occurs through AMPK activation and its downstream transcriptional regulation in THP-1 cells

Pathogenic bacteria induced sepsis is a risk factor for hospital mortality. Monocyte-derived inflammatory cytokines participate in the sepsis progression. The anti-inflammatory effect of adenine has been previously reported by our laboratory and others. However, the mechanism of action has different opinions and remains unclear in monocyte. Here, adenine was found to significantly inhibit the secretion of lipopolysaccharide-induced inflammatory cytokines such as TNF-α, IL-1β and IL-6 in THP-1 cells. The bioinformatic analysis results showed that the anti-inflammatory function is possibly due to the inhibition of NF-κB signaling. And this result is confirmed by using immunocytochemistry. Moreover, this effect can be suppressed by the AMPK inhibitor. Results also showed that adenine can activate AMPK and its multiple downstream targets. Data from mass spectrometry showed that adenine promotes significant elevation of intracellular AMP. Our data indicate that the anti-inflammatory mechanism of adenine may involve adenine phosphoribosyltransferase-catalyzed intracellular AMP elevation, which stimulates AMPK activation.

Metformin Regulates the Expression of SK2 and SK3 in the Atria of Rats With Type 2 Diabetes Mellitus Through the NOX4/p38MAPK Signaling Pathway

We previously found that metformin regulates the ion current conducted by the small conductance calcium-activated potassium channels (SK channels) in the atria of rats with type 2 diabetes mellitus (T2DM) as well as the mRNA and protein expression of the SK2 and SK3 subtypes of SK channels. In this study, we hypothesized that the nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4)/p38 mitogen-activated protein kinase (p38MAPK) signaling pathway was involved in the metformin-mediated regulation of SK2 and SK3 expression in the atria of rats with T2DM. We randomly divided Wistar rats into the control group, the untreated T2DM group, the metformin-treated group, the group receiving subcutaneous injections of the nicotinamide adenine dinucleotide phosphate oxidase (NOX) inhibitor diphenyleneiodonium (DPI), and the group receiving tail vein injections of the p38MAPK agonist anisomycin. Real-time polymerase chain reaction, Western blot, and immunohistochemistry were applied to examine the expression levels of SK2, SK3, NOX4, and phospho-p38MAPK (p-p38MAPK) mRNAs and proteins in the atrial tissue of relevant groups. We observed that the expression levels of NOX4 mRNA and protein and p-p38MAPK protein were significantly elevated in the atria of rats with T2DM compared with the control group. In addition, SK2 protein expression was reduced, whereas SK3 protein expression was increased. The 8-week treatment with metformin markedly reduced the expression levels of NOX4 mRNA and protein and p-p38MAPK protein, upregulated the SK2 expression, and downregulated the SK3 expression. Tail vein injection with anisomycin significantly increased the p-p38MAPK expression while further inhibiting the expression of SK2 and enhancing the expression of SK3. Subcutaneous injection with DPI considerably inhibited the expression of NOX4, further enhanced the expression of SK2 and suppressed the expression of SK3. In addition, subcutaneous injection with DPI significantly suppressed the phosphorylation of p38MAPK. In conclusion, the NOX4/p38MAPK signaling pathway mediates the downregulation of SK2 and the upregulation of SK3 in the atria of rats with T2DM. Long-term metformin treatment upregulates SK2 protein expression and downregulates SK3 protein expression by inhibiting the NOX4/p38MAPK signaling pathway.

Acetyl-CoA carboxylase inhibition regulates microtubule dynamics and intracellular transport in cystic fibrosis epithelial cells

The use of high-dose ibuprofen as an anti-inflammatory therapy in cystic fibrosis (CF) has been shown to be an effective intervention although use is limited due to potential adverse events. Identifying the mechanism of ibuprofen efficacy would aid in the development of new therapies that avoid these adverse events. Previous findings demonstrated that ibuprofen treatment restores the regulation of microtubule dynamics in CF epithelial cells through a 5'-adenosine monophosphate-activated protein kinase (AMPK)-dependent mechanism. The goal of this study is to define the AMPK pathway that leads to microtubule regulation. Here, it is identified that inhibition of acetyl-CoA carboxylase (ACC) is the key step in mediating the AMPK effect. ACC inhibition with 5-(tetradecyloxy)-2-furoic acid (TOFA) increases microtubule reformation rates in cultured and primary CF epithelial cells to wild-type (WT) rates. TOFA treatment also restores microtubule-dependent distribution of cholesterol and Rab7-positive organelles, as well as reduces expression of the proinflammatory signaling molecule RhoA to WT levels. ACC activation with citrate replicates these CF phenotypes in WT cells further supporting the role of AMPK signaling through ACC as a key mediator in CF cell signaling. It is concluded that ACC inhibition is the key step in the efficacy of AMPK activation at the cellular level and could represent a novel site of therapeutic intervention to address inflammation in CF.

Small-molecule ion channels increase host defences in cystic fibrosis airway epithelia

Loss-of-function mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) compromise epithelial HCO₃⁻ and Cl⁻ secretion, reduce airway surface liquid (ASL) pH, and impair respiratory host defenses in people with cystic fibrosis (CF) ^1–3. Here we report that apical addition of an unselective ion channel-forming small molecule, amphotericin B (AmB), restored HCO₃⁻ secretion and increased ASL pH in cultured human CF airway epithelia. These effects required the basolateral Na⁺/K⁺ ATPase, indicating that apical AmB channels functionally interfaced with this driver of anion secretion. AmB also restored ASL pH, viscosity, and antibacterial activity in primary cultures of airway epithelia from people with CF caused by different mutations, including ones that yield no CFTR, and increased ASL pH in CFTR-null pigs in vivo. Thus, unselective small molecule ion channels can restore CF airway host defenses via a mechanism that is CFTR-independent and therefore genotype-independent.

Metformin attenuates the effect of Staphylococcus aureus on airway tight junctions by increasing PKCζ-mediated phosphorylation of occludin

Airway epithelial tight junction (TJ) proteins form a resistive barrier to the external environment, however, during respiratory bacterial infection TJs become disrupted compromising barrier function. This promotes glucose flux/accumulation into the lumen which acts as a nutrient source for bacterial growth. Metformin used for the treatment of diabetes increases transepithelial resistance (TEER) and partially prevents the effect of bacteria but the mechanisms of action are unclear. We investigated the effect of metformin and Staphylococcus aureus on TJ proteins, zonula occludins (ZO)-1 and occludin in human airway epithelial cells (H441). We also explored the role of AMP-activated protein kinase (AMPK) and PKCζ in metformin-induced effects. Pretreatment with metformin prevented the S. aureus-induced changes in ZO-1 and occludin. Metformin also promoted increased abundance of full length over smaller cleaved occludin proteins. The nonspecific PKC inhibitor staurosporine reduced TEER but did not prevent the effect of metformin indicating that the pathway may involve atypical PKC isoforms. Investigation of TJ reassembly after calcium depletion showed that metformin increased TEER more rapidly and promoted the abundance and localization of occludin at the TJ. These effects were inhibited by the AMPK inhibitor, compound C and the PKCζ pseudosubstrate inhibitor (PSI). Metformin increased phosphorylation of occludin and acetyl-coA-carboxylase but only the former was prevented by PSI. This study demonstrates that metformin improves TJ barrier function by promoting the abundance and assembly of full length occludin at the TJ and that this process involves phosphorylation of the protein via an AMPK-PKCζ pathway.

AMP-Activated Protein Kinase (AMPK)-Dependent Regulation of Renal Transport

AMP-activated kinase (AMPK) is a serine/threonine kinase that is expressed in most cells and activated by a high cellular AMP/ATP ratio (indicating energy deficiency) or by Ca²⁺. In general, AMPK turns on energy-generating pathways (e.g., glucose uptake, glycolysis, fatty acid oxidation) and stops energy-consuming processes (e.g., lipogenesis, glycogenesis), thereby helping cells survive low energy states. The functional element of the kidney, the nephron, consists of the glomerulus, where the primary urine is filtered, and the proximal tubule, Henle's loop, the distal tubule, and the collecting duct. In the tubular system of the kidney, the composition of primary urine is modified by the reabsorption and secretion of ions and molecules to yield final excreted urine. The underlying membrane transport processes are mainly energy-consuming (active transport) and in some cases passive. Since active transport accounts for a large part of the cell's ATP demands, it is an important target for AMPK. Here, we review the AMPK-dependent regulation of membrane transport along nephron segments and discuss physiological and pathophysiological implications.

Recombinant CTRP9 administration attenuates neuroinflammation via activating adiponectin receptor 1 after intracerebral hemorrhage in mice

Background

Neuroinflammation is a crucial factor contributing to neurological injuries after intracerebral hemorrhage (ICH). C1q/TNF-related protein 9 (CTRP9), an agonist of adiponectin receptor 1 (AdipoR1), has recently been shown to reduce inflammatory responses in systemic diseases. The objective of this study was to investigate the protective role of CTRP9 against neuroinflammation after ICH in a mouse model and to explore the contribution of adenosine monophosphate-activated protein kinase (AMPK)/nuclear factor kappa B (NFκB) pathway in AdipoR1-mediated protection.

Methods

Adult male CD1 mice (n = 218) were randomly assigned to different groups for the study. ICH was induced via intrastriatal injection of bacterial collagenase. Recombinant CTRP9 (rCTRP9) was administered intranasally at 1 h after ICH. To elucidate the underlying mechanism, AdipoR1 small interfering ribonucleic acid (siRNA) and selective phosphorylated AMPK inhibitor Dorsomorphin were administered prior to rCTRP9 treatment. Brain edema, short- and long-term neurobehavior evaluation, blood glucose level, western blot, and immunofluorescence staining were performed.

Results

Endogenous CTRP9 and AdipoR1 expression was increased and peaked at 24 h after ICH. AdipoR1 was expressed by microglia, neurons, and astrocytes. Administration of rCTRP9 reduced brain edema, improved short- and long-term neurological function, enhanced the expression of AdipoR1 and p-AMPK, and decreased the expression of phosphorylated NFκB and inflammatory cytokines after ICH. The protective effects of rCTRP9 were abolished by administration of AdipoR1 siRNA and Dorsomorphin.

Conclusions

Our findings demonstrated that administration of rCTRP9 attenuated neuroinflammation through AdipoR1/AMPK/NFκB signaling pathway after ICH in mice, thereby reducing brain edema and improving neurological function after experimental ICH in mice. Therefore, CTRP9 may provide a potential therapeutic strategy to alleviate neuroinflammation in ICH patients.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1256-8) contains supplementary material, which is available to authorized users.

AMPK orchestrates an elaborate cascade protecting tissue from fibrosis and aging

Fibrosis is a common process characterized by excessive extracellular matrix (ECM) accumulation after inflammatory injury, which is also a crucial cause of aging. The process of fibrosis is involved in the pathogenesis of most diseases of the heart, liver, kidney, lung, and other organs/tissues. However, there are no effective therapies for this pathological alteration. Annually, fibrosis represents a huge financial burden for the USA and the world. 5'-AMP-activated protein kinase (AMPK) is a pivotal energy sensor that alleviates or delays the process of fibrogenesis. In this review, we first present basic background information on AMPK and fibrogenesis and describe the protective roles of AMPK in three fibrogenic phases. Second, we analyze the protective action of AMPK during fibrosis in myocardial, hepatic, renal, pulmonary, and other organs/tissues. Third, we present a comprehensive discussion of AMPK during fibrosis and draw a conclusion. This review highlights recent advances, vital for basic research and clinical drug design, in the regulation of AMPK during fibrosis.

Antofine suppresses endotoxin-induced inflammation and metabolic disorder via AMP-activated protein kinase

The inhibition of activated macrophages has been used to develop anti-inflammatory agents for therapeutic intervention to human diseases that cause excessive inflammatory responses. Antofine, a phenanthroindolizidine alkaloid, has a potent anti-inflammatory effect. However, the molecular mechanisms of its anti-inflammatory activity have not yet been fully detailed. In this study, we comprehensively explored the anti-inflammatory effects of antofine on endotoxin-induced inflammation in macrophages using cDNA microarray analysis, thereby elucidating the potential mechanism by which antofine suppresses inflammation. Antofine significantly suppressed the secretion of proinflammatory cytokines such as TNFα and IL-1β and the production of iNOS in LPS-activated Raw264.7 macrophage cells. In addition, antofine can suppress the expressions of several inflammation-related genes (such as ARG-1, IL1F9, IL-10, and IL-33) and extracellular matrix genes (such as TNC and HYAL1), as well as a vasopressor gene (EDN1) in activated macrophage cells, that are induced by LPS stimulation. The gene expression profiles analyzed by GeneMANIA software showed that antofine not only contributed anti-inflammatory activity but also modulated the cellular metabolism via AMPK. Furthermore, antofine also modulated the activation of AMPK and caspase-1, the key regulator in inflammasome-mediated IL-1β maturation, in activated macrophage cells. In conclusion, these data indicated that antofine potentially can not only contribute an anti-inflammatory effect but can also attenuate the metabolic disorders induced by inflammation via AMPK.

Age-Dependent Changes in AMPK Metabolic Pathways in the Lung in a Mouse Model of Hemorrhagic Shock

The development of multiple organ failure in patients with hemorrhagic shock is significantly influenced by patient age. Adenosine monophosphate-activated protein kinase (AMPK) is a crucial regulator of energy homeostasis, which coordinates metabolic repair during cellular stress. We investigated whether AMPK-regulated signaling pathways are age-dependent in hemorrhage-induced lung injury and whether AMPK activation by 5-amino-4-imidazole carboxamide riboside (AICAR) affords lung protective effects. Male C57/BL6 young mice (3-5 mo), mature adult mice (9-12 mo), and young AMPKα1 knockout mice (3-5 mo) were subjected to hemorrhagic shock by blood withdrawing, followed by resuscitation with shed blood and lactated Ringer's solution. Plasma proinflammatory cytokines were similarly elevated in C57/BL6 young and mature adult mice after hemorrhagic shock. However, mature adult mice exhibited more severe lung edema and neutrophil infiltration, and higher mitochondrial damage in alveolar epithelial type II cells, than did young mice. No change in autophagy was observed. At molecular analysis, the phosphorylation of the catalytic subunit AMPKα1 was associated with nuclear translocation of peroxisome proliferator-activated receptor γ co-activator-α in young, but not mature, adult mice. Treatment with AICAR ameliorated the disruption of lung architecture in mice of both ages; however, effects in mature adult mice were different than young mice and also involved inhibition of nuclear factor-κB. In young AMPKα1 knockout mice, AICAR failed to improve hypotension and lung neutrophil infiltration. Our data demonstrate that during hemorrhagic shock, AMPK-dependent metabolic repair mechanisms are important for mitigating lung injury. However, these mechanisms are less competent with age.

MeSHDD: Literature-based drug-drug similarity for drug repositioning

OBJECTIVE

Drug repositioning is a promising methodology for reducing the cost and duration of the drug discovery pipeline. We sought to develop a computational repositioning method leveraging annotations in the literature, such as Medical Subject Heading (MeSH) terms.

METHODS

We developed software to determine significantly co-occurring drug-MeSH term pairs and a method to estimate pair-wise literature-derived distances between drugs.

RESULTS

We found that literature-based drug-drug similarities predicted the number of shared indications across drug-drug pairs. Clustering drugs based on their similarity revealed both known and novel drug indications. We demonstrate the utility of our approach by generating repositioning hypotheses for the commonly used diabetes drug metformin.

CONCLUSION

Our study demonstrates that literature-derived similarity is useful for identifying potential repositioning opportunities. We provided open-source code and deployed a free-to-use, interactive application to explore our database of similarity-based drug clusters (available at http://apps.chiragjpgroup.org/MeSHDD/ ).

Lack of Effects of Metformin and AICAR Chronic Infusion on the Development of Hypertension in Dahl Salt-Sensitive Rats

In the kidney, reabsorption via the epithelial sodium channel (ENaC) is involved in long-term blood pressure control. Previously we demonstrated that ENaC hyperactivity is associated with development of salt-sensitive (SS) hypertension in Dahl SS rats. AMP-activated kinase (AMPK), playing a role in cellular energy homeostasis, has been shown to decrease ENaC activity. Here, we tested whether metformin and AICAR, two drugs that activate AMPK, affect the development of salt-induced hypertension. High salt diet significantly increased mean arterial pressure (MAP) in Dahl SS rats. Blood pressure elevation was accompanied by a short-term decline of heart rate and increased circadian arterial pressure dipping. Metformin and AICAR were delivered intravenously at doses of 200 and 20 mg/kg/day, respectively. However, both control and drug-treated groups had similar development of high blood pressure within 3 weeks of 8% NaCl dietary salt intake. In the metformin-treated animals MAP reached 164.9 ± 9.1 mmHg, which was not significantly different from the control group (171.8 ± 5.6 mmHg). Patch clamp analysis revealed that the metformin-treated rats had no difference in the activity of ENaC. AICAR treatment also did not affect the development of hypertension and kidney injury. MAP reached 182.8 ± 4.8 and 178.0 ± 2.8 mmHg in AICAR and vehicle treated groups, respectively. Of note, we found that high-salt diet activated AMPK in the Dahl SS rats, and treatment with these AMPK activators had no significant further effect on AMPK activity. We conclude that AMPK activators, at least under these conditions, do not affect development of hypertension during high-salt diet in the Dahl SS rat model.

Adenosine monophosphate-activated protein kinase activation and suppression of inflammatory response by cell stretching in rabbit synovial fibroblasts

Joint mobilization is known to be beneficial in osteoarthritis (OA) patients. This study aimed to investigate the effect of stretching on adenosine monophosphate-activated protein kinase (AMPK) activity and its role in modulating inflammation in rabbit synovial fibroblasts. Uniaxial stretching of isolated rabbit synovial fibroblasts for ten min was performed. Stretching-induced AMPK activation, its underlying mechanism, and its anti-inflammatory effect were investigated using Western blot. Static stretching at 20 % of initial length resulted in AMPK activation characterized by expression of phosphorylated AMPK and phosphorylated acetyl-Co A carboxylase. AMP-activated protein kinase phosphorylation peaked 1 h after stretching and declined toward resting activity. Using cell viability assays, static stretching did not appear to cause cellular damage. Activation of AMPK involves Ca²⁺ influx via a mechanosensitive L-type Ca²⁺ channel, which subsequently raises intracellular Ca²⁺ and activates AMPK via Ca²⁺/calmodulin-dependent protein kinase kinase β (CaMKKβ). Interestingly, stretching suppressed TNFα-induced expression of COX-2, iNOS, and phosphorylated NF-κB. These effects were prevented by pretreatment with compound C, an AMPK inhibitor. These results suggest that mechanical stretching suppressed inflammatory responses in synovial fibroblasts via a L-type Ca²⁺-channel-CaMKKβ-AMPK-dependent pathway which may underlie joint mobilization's ability to alleviate OA symptoms.

5-Aminoimidazole-4-carboxamide ribonucleoside-mediated adenosine monophosphate-activated protein kinase activation induces protective innate responses in bacterial endophthalmitis

The retina is considered to be the most metabolically active tissue in the body. However, the link between energy metabolism and retinal inflammation, as incited by microbial infection such as endophthalmitis, remains unexplored. In this study, using a mouse model of Staphylococcus aureus (SA) endophthalmitis, we demonstrate that the activity (phosphorylation) of 5' adenosine monophosphate-activated protein kinase alpha (AMPKα), a cellular energy sensor and its endogenous substrate; acetyl-CoA carboxylase is down-regulated in the SA-infected retina. Intravitreal administration of an AMPK activator, 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), restored AMPKα and acetyl-CoA carboxylase phosphorylation. AICAR treatment reduced both the bacterial burden and intraocular inflammation in SA-infected eyes by inhibiting NF-kB and MAP kinases (p38 and JNK) signalling. The anti-inflammatory effects of AICAR were diminished in eyes pretreated with AMPK inhibitor, Compound C. The bioenergetics (Seahorse) analysis of SA-infected microglia and bone marrow-derived macrophages revealed an increase in glycolysis, which was reinstated by AICAR treatment. AICAR also reduced the expression of SA-induced glycolytic genes, including hexokinase 2 and glucose transporter 1 in microglia, bone marrow-derived macrophages and the mouse retina. Interestingly, AICAR treatment enhanced the bacterial phagocytic and intracellular killing activities of cultured microglia, macrophages and neutrophils. Furthermore, AMPKα1 global knockout mice exhibited increased susceptibility towards SA endophthalmitis, as evidenced by increased inflammatory mediators and bacterial burden and reduced retinal function. Together, these findings provide the first evidence that AMPK activation promotes retinal innate defence in endophthalmitis by modulating energy metabolism and that it can be targeted therapeutically to treat ocular infections.

Ibuprofen regulation of microtubule dynamics in cystic fibrosis epithelial cells

High-dose ibuprofen, an effective anti-inflammatory therapy for the treatment of cystic fibrosis (CF), has been shown to preserve lung function in a pediatric population. Despite its efficacy, few patients receive ibuprofen treatment due to potential renal and gastrointestinal toxicity. The mechanism of ibuprofen efficacy is also unclear. We have previously demonstrated that CF microtubules are slower to reform after depolymerization compared with respective wild-type controls. Slower microtubule dynamics in CF cells are responsible for impaired intracellular transport and are related to inflammatory signaling. Here, it is identified that high-dose ibuprofen treatment in both CF cell models and primary CF nasal epithelial cells restores microtubule reformation rates to wild-type levels, as well as induce extension of microtubules to the cell periphery. Ibuprofen treatment also restores microtubule-dependent intracellular transport monitored by measuring intracellular cholesterol transport. These effects are specific to ibuprofen as other cyclooxygenase inhibitors have no effect on these measures. Effects of ibuprofen are mimicked by stimulation of AMPK and blocked by the AMPK inhibitor compound C. We conclude that high-dose ibuprofen treatment enhances microtubule formation in CF cells likely through an AMPK-related pathway. These findings define a potential mechanism to explain the efficacy of ibuprofen therapy in CF.

Influenza leaves a TRAIL to pulmonary edema

Influenza infection can cause acute respiratory distress syndrome (ARDS), leading to poor disease outcome with high mortality. One of the driving features in the pathogenesis of ARDS is the accumulation of fluid in the alveoli, which causes severe pulmonary edema and impaired oxygen uptake. In this issue of the JCI, Peteranderl and colleagues define a paracrine communication between macrophages and type II alveolar epithelial cells during influenza infection where IFNα induces macrophage secretion of TRAIL that causes endocytosis of Na,K-ATPase by the alveolar epithelium. This reduction of Na,K-ATPase expression decreases alveolar fluid clearance, which in turn leads to pulmonary edema. Inhibition of the TRAIL signaling pathway has been shown to improve lung injury after influenza infection, and future studies will be needed to determine if blocking this pathway is a viable option in the treatment of ARDS.

HL156A, a novel AMP-activated protein kinase activator, is protective against peritoneal fibrosis in an in vivo and in vitro model of peritoneal fibrosis

HL156A is a novel AMP-activated protein kinase (AMPK) activator. We aimed to investigate the protective mechanism of HL156A against peritoneal fibrosis (PF) in in vivo and in vitro models. The rat PF model was induced by daily intraperitoneally injection of chlorhexidine (CHX) solution containing 0.1% CHX gluconate and 15% ethanol for 4 wk. The rats in the treatment group were treated with HL156A (1 mg·kg−1·day−1). Control rats were injected with vehicle alone. In vitro, cultured rat peritoneal mesothelial cells (RPMCs) were treated with either high glucose (HG; 50 mM), normal glucose (NG; 5 mM), NG+HL156A, or HG+HL156A. HL156A in supplemented rats ameliorated peritoneal calcification, cocoon formation, bowel obstruction, and PF. Immunohistochemistry showed reduced fibronectin accumulation in the peritoneum of HL156A-treated rats compared with those injected with CHX alone. HL156A treatment of RPMCs inhibited HG-induced myofibroblast transdifferentiation and markers of epithelial-mesenchymal transition (EMT). Moreover, HL156A ameliorated HG-induced transforming growth factor-β1, Smad3, Snail, and fibronectin expression in the RPMCs via AMPK upregulation. These results suggest that HL156A exhibits a protective effect in PF progression. Further research is warranted to seek the therapeutic potential of HL156A as an antifibrotic agent in peritoneal dialysis patients.

Metformin prevents the effects of Pseudomonas aeruginosa on airway epithelial tight junctions and restricts hyperglycaemia-induced bacterial growth

Lung disease and elevation of blood glucose are associated with increased glucose concentration in the airway surface liquid (ASL). Raised ASL glucose is associated with increased susceptibility to infection by respiratory pathogens including Staphylococcus aureus and Pseudomonas aeruginosa. We have previously shown that the anti‐diabetes drug, metformin, reduces glucose‐induced S. aureus growth across in vitro airway epithelial cultures. The aim of this study was to investigate whether metformin has the potential to reduce glucose‐induced P. aeruginosa infections across airway epithelial (Calu‐3) cultures by limiting glucose permeability. We also explored the effect of P. aeruginosa and metformin on airway epithelial barrier function by investigating changes in tight junction protein abundance. Apical P. aeruginosa growth increased with basolateral glucose concentration, reduced transepithelial electrical resistance (TEER) and increased paracellular glucose flux. Metformin pre‐treatment of the epithelium inhibited the glucose‐induced growth of P. aeruginosa, increased TEER and decreased glucose flux. Similar effects on bacterial growth and TEER were observed with the AMP activated protein kinase agonist, 5‐aminoimidazole‐4‐carboxamide ribonucleotide. Interestingly, metformin was able to prevent the P. aeruginosa‐induced reduction in the abundance of tight junction proteins, claudin‐1 and occludin. Our study highlights the potential of metformin to reduce hyperglycaemia‐induced P. aeruginosa growth through airway epithelial tight junction modulation, and that claudin‐1 and occludin could be important targets to regulate glucose permeability across airway epithelia and supress bacterial growth. Further investigation into the mechanisms regulating metformin and P. aeruginosa action on airway epithelial tight junctions could yield new therapeutic targets to prevent/suppress hyperglycaemia‐induced respiratory infections, avoiding the use of antibiotics.

Safety of metformin in patients with chronic obstructive pulmonary disease and type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is commonly associated with chronic obstructive pulmonary disease (COPD). Metformin is a valuable treatment for T2DM, and may offer additional benefits in COPD. However, due to its rare association with lactic acidosis, its safety in COPD is uncertain. We retrospectively identified patients with T2DM who had been admitted to hospital for COPD exacerbations. We compared those who were taking metformin with those who were not, with respect to their lactate concentration (primary endpoint) and survival (secondary endpoint). The study cohort (n = 130) had a mean (±standard deviation) age of 73.0 ± 9.8 years and 47 (36%) were female. Arterial blood gases were recorded in 120 cases: 88 (73%) were hypoxemic, 45 (38%) were in respiratory failure and 33 (28%) had respiratory acidosis. The 51 patients (39%) in the metformin group had a median (interquartile range) lactate concentration of 1.45 mmol/L (1.10-2.05) versus 1.10 mmol/L (0.80-1.50) in the non-metformin group (p = 0.012). Median survival was 5.2 years (95% CI 4.5-5.8) versus 1.9 years (1.1-2.6), respectively (hazard ratio 0.57; 95% CI 0.35-0.94). This remained significant in a multivariate model adjusted for measurable confounders. In conclusion, among patients with COPD at high risk for lactate accumulation, metformin therapy was associated with a minor elevation of lactate concentration of doubtful clinical significance. Metformin was associated with a survival benefit, but this must be interpreted cautiously due to possible effects from unmeasured confounders. Viewed collectively, the results suggest that COPD should not present a barrier to the investigational or clinical use of metformin.

Regulation of Cigarette Smoke Induction of IL-8 in Macrophages by AMP-activated Protein Kinase Signaling

Inhaled cigarette smoke (CS) causes persistent lung inflammation in smokers. Interleukin 8 (IL-8) released from macrophages is a key chemokine during initiation and progression of CS-induced lung inflammation, yet its regulation is largely unknown. AMP-activated protein kinase (AMPK), a crucial energy homeostasis regulator, may modulate inflammation. Here we report that CS extract (CSE) increased the level of intracellular reactive oxygen species (ROS), activating AMPK, mitogen-activated protein kinases (MAPKs), and NF-κB, as well as inducing IL-8, in human macrophages. N-acetyl-cysteine (ROS scavenger) or hexamethonium [nicotinic acetylcholine receptor (nAChR) antagonist] attenuated the CSE-induced increase in intracellular ROS, activation of AMPK and NF-κB, as well as IL-8 induction, which suggests that nAChRs and ROS are important. Prevention of AMPK activation by compound C or AMPK siRNA reduced CSE-induced IL-8 production, confirming the role of AMPK. Compound C or AMPK siRNA also inhibited the activation of MAPKs and NF-κB by CSE, which suggests that these molecules are downstream of AMPK. Additionally, exposure of human macrophages to nicotine activated AMPK and induced IL-8 and that these effects were lessened by hexamethonium or compound C, implying that nicotine in CS may be causative. Furthermore, chronic CS exposure in mice promoted AMPK phosphorylation and expression of MIP-2 (an IL-8 homolog) in infiltrated macrophages and in lung tissues, as well as induced lung inflammation, all of which were reduced by compound C treatment. Thus, we identified a novel nAChRs-dependent, ROS-sensitive, AMPK/MAPKs/NF-κB signaling pathway, which seems to be important to CS-induced macrophage IL-8 production and possibly to lung inflammation.