Sanguinarine is an allosteric activator of AMP-activated protein kinase

Vasorelaxant and tracheorelaxant effects of Bocconia arborea and their isolated benzophenanthridine alkaloids

Bocconia arborea S. Watson (Papaveraceae) is an abundant medicinal plant in the North of Morelos State, Mexico, which is used for the treatment of several diseases. The aim of current investigation was to isolate the compounds responsible of the relaxant effect shown by the active extracts. Thus, phytochemical bio-guided fractionation allowed the isolation of angoline (1), dihydrosanguinarine (2), bocconarborine A (3), oxisanguinarine (4), and oxychelerithrine (5) from dichloromethanic and methanolic extracts from the bark of Bocconia arborea (Papaveraceae). The relaxant study on aortic and tracheal rat rings of all benzophenanthridines indicates that 1 was the most active compound of the entire series investigated. Angoline (1) induces its relaxant effect by a concentration-dependent manner through the calcium channel blockade in both tissues.

Dietary sanguinarine supplementation recovers the decrease in muscle quality and nutrient composition induced by high-fat diets of grass carp (Ctenopharyngodon idella)

The intake of high-fat diets (HFD) has been shown to diminish the muscle quality of aquatic animals. Sanguinarine, as an excellent additive, exhibits the capability to reduce fat deposition and alleviate inflammation. However, its role in the muscle quality reduction caused by HFD remains unclear. An eight-week trial was conducted to investigate the impacts of dietary supplementation of sanguinarine at 1200 μg/kg (HFDS; crude fat = 10%) on the muscle quality of grass carp (Ctenopharyngodon idellus) in comparison to a basic diet (CON, crude fat = 5%). Each group had 3 replicates, with 40 fish per replicate. This experiment employed one-way ANOVA and Duncan's multiple comparisons of the means. The results showed that the HFD exhibited lower growth performance, reduced protein deposition, myofiber diameter, and muscle hardness, coupled with higher levels of fat deposition and inflammation when compared with the CON. However, HFDS improved growth performance (P < 0.05), fat metabolism (ppar-α ( P = 0.001), lpl (P < 0.001), atgl (P < 0.001), and cpt1 (P = 0.001) expression exhibited a significant elevation), protein deposition (the protein and mRNA levels of AKT (P = 0.004), PI3K (P = 0.027), TOR (P = 0.005), and P70S6K (P = 0.007) demonstrated a marked increase), myofiber diameter, muscle hardness, and the total content of eicosapentaenoic acid and docosahexaenoic acid. Furthermore, the HFDS reduced oxidative damage caused by fat deposition by significantly downregulating nf-κb (P < 0.001), il-1β (P < 0.001), il-6 (P < 0.001), il-8 (P = 0.003), and tnf-α (P < 0.001) expression and markedly upregulated nrf2 (P < 0.001), gpx4 (P < 0.001), cat (P < 0.001), sod (P < 0.001), and gr (P = 0.003) expression. The findings from this study suggest that sanguinarine has the potential to alleviate the adverse effects of HFD on growth and muscle quality, providing a theoretical foundation for its practical implementation.

Phosphoproteomic investigation of targets of protein phosphatases in EGFR signaling

Receptor tyrosine kinases (RTKs) initiate cellular signaling pathways, which are regulated through a delicate balance of phosphorylation and dephosphorylation events. While many studies of RTKs have focused on downstream-activated kinases catalyzing the site-specific phosphorylation, few studies have focused on the phosphatases carrying out the dephosphorylation. In this study, we analyzed six protein phosphatase networks using chemical inhibitors in context of epidermal growth factor receptor (EGFR) signaling by mass spectrometry-based phosphoproteomics. Specifically, we focused on protein phosphatase 2C (PP2C), involved in attenuating p38-dependent signaling pathways in various cellular responses, and confirmed its effect in regulating p38 activity in EGFR signaling. Furthermore, utilizing a p38 inhibitor, we classified phosphosites whose phosphorylation status depends on PP2C inhibition into p38-dependent and p38-independent sites. This study provides a large-scale dataset of phosphatase-regulation of EGF-responsive phosphorylation sites, which serves as a useful resource to deepen our understanding of EGFR signaling.

Plants Secondary Metabolites as Blood Glucose-Lowering Molecules

Recently, significant advances in modern medicine and therapeutic agents have been achieved. However, the search for effective antidiabetic drugs is continuous and challenging. Over the past decades, there has been an increasing body of literature related to the effects of secondary metabolites from botanical sources on diabetes. Plants-derived metabolites including alkaloids, phenols, anthocyanins, flavonoids, stilbenoids, saponins, tannins, polysaccharides, coumarins, and terpenes can target cellular and molecular mechanisms involved in carbohydrate metabolism. In addition, they can grant protection to pancreatic beta cells from damage, repairing abnormal insulin signaling, minimizing oxidative stress and inflammation, activating AMP-activated protein kinase (AMPK), and inhibiting carbohydrate digestion and absorption. Studies have highlighted many bioactive naturally occurring plants' secondary metabolites as candidates against diabetes. This review summarizes the current knowledge compiled from the latest studies published during the past decade on the mechanism-based action of plants-derived secondary metabolites that can target various metabolic pathways in humans against diabetes. It is worth mentioning that the compiled data in this review will provide a guide for researchers in the field, to develop candidates into environment-friendly effective, yet safe antidiabetics.

Hypolipidemic effects of herbal extracts by reduction of adipocyte differentiation, intracellular neutral lipid content, lipolysis, fatty acid exchange and lipid droplet motility

An increase in adipose tissue is caused by the increased size and number of adipocytes. Lipids accumulate in intracellular stores, known as lipid droplets (LDs). Recent studies suggest that parameters such as LD size, shape and dynamics are closely related to the development of obesity. Berberine (BBR), a natural plant alkaloid, has been demonstrated to possess anti-obesity effects. However, it remains unknown which cellular processes are affected by this compound or how effective herbal extracts containing BBR and other alkaloids actually are. For this study, we used extracts of Coptis chinensis, Mahonia aquifolium, Berberis vulgaris and Chelidonium majus containing BBR and other alkaloids and studied various processes related to adipocyte functionality. The presence of extracts resulted in reduced adipocyte differentiation, as well as neutral lipid content and rate of lipolysis. We observed that the intracellular fatty acid exchange was reduced in different LD size fractions upon treatment with BBR and Coptis chinensis. In addition, LD motility was decreased upon incubation with BBR, Coptis chinensis and Chelidonium majus extracts. Furthermore, Chelidonium majus was identified as a potent fatty acid uptake inhibitor. This is the first study that demonstrates the selected regulatory effects of herbal extracts on adipocyte function.

Exploring African Medicinal Plants for Potential Anti-Diabetic Compounds with the DIA-DB Inverse Virtual Screening Web Server

Medicinal plants containing complex mixtures of several compounds with various potential beneficial biological effects are attractive treatment interventions for a complex multi-faceted disease like diabetes. In this study, compounds identified from African medicinal plants were evaluated for their potential anti-diabetic activity. A total of 867 compounds identified from over 300 medicinal plants were screened in silico with the DIA-DB web server (http://bio-hpc.eu/software/dia-db/) against 17 known anti-diabetic drug targets. Four hundred and thirty compounds were identified as potential inhibitors, with 184 plants being identified as the sources of these compounds. The plants Argemone ochroleuca, Clivia miniata, Crinum bulbispermum, Danais fragans, Dioscorea dregeana, Dodonaea angustifolia, Eucomis autumnalis, Gnidia kraussiana, Melianthus comosus, Mondia whitei, Pelargonium sidoides, Typha capensis, Vinca minor, Voacanga africana, and Xysmalobium undulatum were identified as new sources rich in compounds with a potential anti-diabetic activity. The major targets identified for the natural compounds were aldose reductase, hydroxysteroid 11-beta dehydrogenase 1, dipeptidyl peptidase 4, and peroxisome proliferator-activated receptor delta. More than 30% of the compounds had five or more potential targets. A hierarchical clustering analysis coupled with a maximum common substructure analysis revealed the importance of the flavonoid backbone for predicting potential activity against aldose reductase and hydroxysteroid 11-beta dehydrogenase 1. Filtering with physiochemical and the absorption, distribution, metabolism, excretion and toxicity (ADMET) descriptors identified 28 compounds with favorable ADMET properties. The six compounds—crotofoline A, erythraline, henningsiine, nauclefidine, vinburnine, and voaphylline—were identified as novel potential multi-targeted anti-diabetic compounds, with favorable ADMET properties for further drug development.

Extra-virgin olive oil contains a metabolo-epigenetic inhibitor of cancer stem cells

Targeting tumor-initiating, drug-resistant populations of cancer stem cells (CSC) with phytochemicals is a novel paradigm for cancer prevention and treatment. We herein employed a phenotypic drug discovery approach coupled to mechanism-of-action profiling and target deconvolution to identify phenolic components of extra virgin olive oil (EVOO) capable of suppressing the functional traits of CSC in breast cancer (BC). In vitro screening revealed that the secoiridoid decarboxymethyl oleuropein aglycone (DOA) could selectively target subpopulations of epithelial-like, aldehyde dehydrogenase (ALDH)-positive and mesenchymal-like, CD44⁺CD24^−/low CSC. DOA could potently block the formation of multicellular tumorspheres generated from single-founder stem-like cells in a panel of genetically diverse BC models. Pretreatment of BC populations with noncytotoxic doses of DOA dramatically reduced subsequent tumor-forming capacity in vivo. Mice orthotopically injected with CSC-enriched BC-cell populations pretreated with DOA remained tumor-free for several months. Phenotype microarray-based screening pointed to a synergistic interaction of DOA with the mTOR inhibitor rapamycin and the DNA methyltransferase (DNMT) inhibitor 5-azacytidine. In silico computational studies indicated that DOA binds and inhibits the ATP-binding kinase domain site of mTOR and the S-adenosyl-l-methionine (SAM) cofactor-binding pocket of DNMTs. FRET-based Z-LYTE™ and AlphaScreen-based in vitro assays confirmed the ability of DOA to function as an ATP-competitive mTOR inhibitor and to block the SAM-dependent methylation activity of DNMTs. Our systematic in vitro, in vivo and in silico approaches establish the phenol-conjugated oleoside DOA as a dual mTOR/DNMT inhibitor naturally occurring in EVOO that functionally suppresses CSC-like states responsible for maintaining tumor-initiating cell properties within BC populations.

Zerumbone Ameliorates High Glucose-Induced Reduction in AMP-Activated Protein Kinase Phosphorylation in Tubular Kidney Cells

AMP-activated protein kinase (AMPK) plays an important role in pathophysiology of diabetes and its complications. In recent years, its role in kidney as a therapeutic target in ameliorating diabetic kidney damage is receiving renewed attention. Efforts on identifying AMPK modulators from dietary sources have gained prominence because of the tremendous potential it harbors. We therefore, examined the effect of a few bioactives on AMPK phosphorylation in kidney tubular cells. AMPK phosphorylation at Thr¹⁷² was reduced (0.42 ± 0.05-fold change compared to the control; p < 0.01 vs control) after treatment with high glucose (30 mM) for 48 h and restored by zerumbone (1.59 ± 0.20; p < 0.01 vs high glucose) but not by other tested modulators. Zerumbone also increased the phosphorylation of downstream target of AMPK, the acetyl-CoA carboxylase (ACC) without affecting the mitochondrial membrane potential and ADP/ATP ratio. Thus, zerumbone could potentially be explored as a therapeutic agent in bringing about energy homeostasis in diabetes where high glucose suppresses the AMPK pathway.

Sanguinarine and Its Role in Chronic Diseases

The use of natural products derived from plants as medicines precedes even the recorded human history. In the past few years there were renewed interests in developing natural compounds and understanding their target specificity for drug development for many devastating human diseases. This has been possible due to remarkable advancements in the development of sensitive chemistry and biology tools. Sanguinarine is a benzophenanthridine alkaloid derived from rhizomes of the plant species Sanguinaria canadensis. The alkaloid can exist in the cationic iminium and neutral alkanolamine forms. Sanguinarine is an excellent DNA and RNA intercalator where only the iminium ion binds. Both forms of the alkaloid, however, shows binding to functional proteins like serum albumins, lysozyme and hemoglobin. The molecule is endowed with remarkable biological activities and large number of studies on its various activities has been published potentiating its development as a therapeutic agent particularly for chronic human diseases like cancer, asthma, etc. In this article, we review the properties of this natural alkaloid, and its diverse medicinal applications in relation to how it modulates cell death signaling pathways and induce apoptosis through different ways, its utility as a therapeutic agent for chronic diseases and its biological effects in animal and human models. These data may be useful to understand the therapeutic potential of this important and highly abundant alkaloid that may aid in the development of sanguinarine-based therapeutic agents with high efficacy and specificity.

Targeting of AMP-activated protein kinase: prospects for computer-aided drug design

INTRODUCTION

Dysregulation of energy homeostasis has been implicated in a number of human chronic diseases including diabetes, obesity, cancer, and inflammation. Given the functional attributes as a central regulator of energy homeostasis, AMP-activated protein kinase (AMPK) is emerging as a therapeutic target for these diseases, and lines of evidence have highlighted the need for rational and robust screening systems for identifying specific AMPK modulators with a therapeutic potential for preventing and/or curing these diseases. Areas covered: Here, the authors review the recent advances in the understanding of three-dimensional structures of AMPK in relationship with the regulatory mechanisms, potentials of AMPK as a therapeutic target in human chronic diseases, and prospects of computer-based drug design for AMPK. Expert opinion: Accumulating information of AMPK structure has provided us with deep insight into the molecular basis underlying the regulatory mechanisms, and further discloses several structural domains, which can be served for a target site for computer-based drug design. Molecular docking and simulations provides useful information about the binding sites between potent drugs and AMPK as well as a rational screening format to discover isoform-specific AMPK modulators. For these reasons, the authors suggest that computer-aided virtual screening methods hold promise as a rational approach for discovering more specific AMPK modulators.

AMP-activated protein kinase: structure, function, and role in pathological processes

Recently, AMP-activated protein kinase (AMPK) has emerged as a key regulator of energy balance at cellular and whole-body levels. Due to the involvement in multiple signaling pathways, AMPK efficiently controls ATP-consuming/ATP-generating processes to maintain energy homeostasis under stress conditions. Loss of the kinase activity or attenuation of its expression leads to a variety of metabolic disorders and increases cancer risk. In this review, we discuss recent findings on the structure of AMPK, its activation mechanisms, as well as the consequences of its targets in regulation of metabolism. Particular attention is given to low-molecular-weight compounds that activate or inhibit AMPK; the perspective of therapeutic use of such modulators in treatment of several common diseases is discussed.

Pharmacological Targeting of AMP-Activated Protein Kinase and Opportunities for Computer-Aided Drug Design

As a central regulator of metabolism, the AMP-activated protein kinase (AMPK) is an established therapeutic target for metabolic diseases. Beyond the metabolic area, the number of medical fields that involve AMPK grows continuously, expanding the potential applications for AMPK modulators. Even though indirect AMPK activators are used in the clinics for their beneficial metabolic outcome, the few described direct agonists all failed to reach the market to date, which leaves options open for novel targeting methods. As AMPK is not actually a single molecule and has different roles depending on its isoform composition, the opportunity for isoform-specific targeting has notably come forward, but the currently available modulators fall short of expectations. In this review, we argue that with the amount of available structural and ligand data, computer-based drug design offers a number of opportunities to undertake novel and isoform-specific targeting of AMPK.

Small molecule adenosine 5'-monophosphate activated protein kinase (AMPK) modulators and human diseases

Adenosine 5'-monophosphate activated protein kinase (AMPK) is a master sensor of cellular energy status that plays a key role in the regulation of whole-body energy homeostasis. AMPK is a serine/threonine kinase that is activated by upstream kinases LKB1, CaMKKβ, and Tak1, among others. AMPK exists as αβγ trimeric complexes that are allosterically regulated by AMP, ADP, and ATP. Dysregulation of AMPK has been implicated in a number of metabolic diseases including type 2 diabetes mellitus and obesity. Recent studies have associated roles of AMPK with the development of cancer and neurological disorders, making it a potential therapeutic target to treat human diseases. This review focuses on the structure and function of AMPK, its role in human diseases, and its direct substrates and provides a brief synopsis of key AMPK modulators and their relevance in human diseases.

Integrated analysis of transcriptomes of cancer cell lines and patient samples reveals STK11/LKB1-driven regulation of cAMP phosphodiesterase-4D

The recent proliferation of data on large collections of well-characterized cancer cell lines linked to therapeutic drug responses has made it possible to identify lineage- and mutation-specific transcriptional markers that can help optimize implementation of anticancer agents. Here, we leverage these resources to systematically investigate the presence of mutation-specific transcription markers in a wide variety of cancer lineages and genotypes. Sensitivity and specificity of potential transcriptional biomarkers were simultaneously analyzed in 19 cell lineages grouped into 228 categories based on the mutational genotypes of 12 cancer-related genes. Among a total of 1,455 category-specific expression patterns, the expression of cAMP phosphodiesterase-4D (PDE4D) with 11 isoforms, one of the PDE4(A-D) subfamilies, was predicted to be regulated by a mutant form of serine/threonine kinase 11 (STK11)/liver kinase B1 (LKB1) present in lung cancer. STK11/LKB1 is the primary upstream kinase of adenine monophosphate-activated protein kinase (AMPK). Subsequently, we found that the knockdown of PDE4D gene expression inhibited proliferation of STK11-mutated lung cancer lines. Furthermore, challenge with a panel of PDE4-specific inhibitors was shown to selectively reduce the growth of STK11-mutated lung cancer lines. Thus, we show that multidimensional analysis of a well-characterized large-scale panel of cancer cell lines provides unprecedented opportunities for the identification of unexpected oncogenic mechanisms and mutation-specific drug targets.

Sanguinarine non- versus re-circulation during isolated heart perfusion--a Jekyll and Hyde effect?

AIMS

In isolated rat heart perfusion experiments, drug administration occurs via retrograde perfusion. This can be done in the non-recirculating mode (coronary effluent is discarded), or recirculating mode (coronary effluent is collected and reused). It was recently observed in our lab while using sanguinarine, an MKP-1 inhibitor, that there were differences in outcomes depending on the mode of recirculation used.

METHODS AND RESULTS

Hearts from control (C); diet-induced obese (DIO) Wistar rats and their age matched controls (AMC) were perfused on the rig. Hearts received buffer (control) , insulin, sanguinarine, insulin + sanguinarine combination or methanol (vehicle) for 15 mins pre- and 10 mins post-ischemia in either a non- or re-circulating manner. Hearts were subjected to 15 mins global ischemia and 30 mins reperfusion. Mechanical function was documented pre- and post-ischemia . When not-recirculated , sanguinarine alone and in combination with insulin in C, DIO and AMC groups, caused a significant decrease in functional recovery during reperfusion. However, when the coronary effluent was recirculated, hearts perfused with sanguinarine or sanguinarine + insulin exhibited a significant recovery in function when compared with their non-recirculation counterparts (p < 0.01). No differences were seen with either control, insulin nor vehicle hearts.

CONCLUSION

Sanguinarine elicited a vast improvement in perfusion outcomes when recirculated compared to non-recirculation . Since this was seen during perfusion only when sanguinarine was present, it is possible that recirculating reperfusion of the drug caused profound changes in its composition. More investigation is needed into the mechanisms involved. Thus caution should be exercised by researchers when designing a perfusion protocol for drug research.

Activators of AMPK: not just for Type II diabetes

Recent discoveries of AMPK activators point to the large number of therapeutic candidates that can be transformed to successful designs of novel drugs. AMPK is a universal energy sensor and influences almost all physiological processes in the cells. Thus, regulation of the cellular energy metabolism can be achieved in selective tissues via the artificial activation of AMPK by small molecules. Recently, special attention has been given to direct activators of AMPK that are regulated by several nonspecific upstream factors. The direct activation of AMPK, by definition, should lead to more specific biological activities and as a result minimize possible side effects.

ATP sensitive bi-quinoline activator of the AMP-activated protein kinase

The AMP-activated protein kinase (AMPK) regulates cellular and whole-body energy balance in response to changes in adenylate charge and hormonal signals. Activation of AMPK in tissues such as skeletal muscle and liver reverses many of the metabolic defects associated with obesity and Type 2 diabetes. Here we report a bi-quinoline (JJO-1) that allosterically activates all AMPK αβγ isoforms in vitro except complexes containing the γ3 subunit. JJO-1 does not directly activate the autoinhibited α subunit kinase domain and differs among other known direct activators of AMPK in that allosteric activation occurs only at low ATP concentrations, and is not influenced by either mutation of the γ subunit adenylate-nucleotide binding sites or deletion of the β subunit carbohydrate-binding module. Our findings indicate that AMPK has multiple modes of allosteric activation that may be exploited to design isoform-specific activators as potential therapeutics for metabolic diseases.

Strategies for the selective regulation of kinases with allosteric modulators: exploiting exclusive structural features

The modulation of kinase function has become an important goal in modern drug discovery and chemical biology research. In cancer-targeted therapies, kinase inhibitors have been experiencing an upsurge, which can be measured by the increasing number of kinase inhibitors approved by the FDA in recent years. However, lack of efficacy, limited selectivity, and the emergence of acquired drug resistance still represent major bottlenecks in the clinic and challenge inhibitor development. Most known kinase inhibitors target the active kinase and are ATP competitive. A second class of small organic molecules, which address remote sites of the kinase and stabilize enzymatically inactive conformations, is rapidly moving to the forefront of kinase inhibitor research. Such allosteric modulators bind to sites that are less conserved across the kinome and only accessible upon conformational changes. These molecules are therefore thought to provide various advantages such as higher selectivity and extended drug target residence times. This review highlights various strategies that have been developed to utilizing exclusive structural features of kinases and thereby modulating their activity allosterically.