Unambiguous Characterization of Commercial Natural (Dihydro)phenanthrene Compounds Is Vital in the Discovery of AMPK Activators.

These days, easy access to commercially available (poly)phenolic compounds has expanded the scope of potential research beyond the field of chemistry, particularly in the area of their bioactivity. However, the quality of these compounds is often overlooked or not even considered. This issue is illustrated in this study through the example of (dihydro)phenanthrenes, a group of natural products present in yams, as AMP-activated protein kinase (AMPK) activators. A study conducted in our group on a series of compounds, fully characterized using a combination of chemical synthesis, NMR and MS techniques, provided evidence that the conclusions of a previous study were erroneous, likely due to the use of a misidentified commercial compound by its supplier. Furthermore, we demonstrated that additional representatives of the (dihydro)phenanthrene phytochemical classes were able to directly activate AMPK, avoiding the risk of misinterpretation of results based on analysis of a single compound alone.

Natural (dihydro)phenanthrene plant compounds are direct activators of AMPK through its allosteric drug and metabolite-binding site.

AMP-activated protein kinase (AMPK) is a central energy sensor that coordinates the response to energy challenges to maintain cellular ATP levels. AMPK is a potential therapeutic target for treating metabolic disorders, and several direct synthetic activators of AMPK have been developed that show promise in preclinical models of type 2 diabetes. These compounds have been shown to regulate AMPK through binding to a novel allosteric drug and metabolite (ADaM)-binding site on AMPK, and it is possible that other molecules might similarly bind this site. Here, we performed a high-throughput screen with natural plant compounds to identify such direct allosteric activators of AMPK. We identified a natural plant dihydrophenathrene, Lusianthridin, which allosterically activates and protects AMPK from dephosphorylation by binding to the ADaM site. Similar to other ADaM site activators, Lusianthridin showed preferential activation of AMPKß1-containing complexes in intact cells and was unable to activate an AMPKß1 S108A mutant. Lusianthridin dose-dependently increased phosphorylation of acetyl-CoA carboxylase in mouse primary hepatocytes, which led to a corresponding decrease in de novo lipogenesis. This ability of Lusianthridin to inhibit lipogenesis was impaired in hepatocytes from ß1 S108A knock-in mice and mice bearing a mutation at the AMPK phosphorylation site of acetyl-CoA carboxylase 1/2. Finally, we show that activation of AMPK by natural compounds extends to several analogs of Lusianthridin and the related chemical series, phenanthrenes. The emergence of natural plant compounds that regulate AMPK through the ADaM site raises the distinct possibility that other natural compounds share a common mechanism of regulation.

Pluripotent Stem Cell-Based Drug Screening Reveals Cardiac Glycosides as Modulators of Myotonic Dystrophy Type 1.

There is currently no treatment for myotonic dystrophy type 1 (DM1), the most frequent myopathy of genetic origin. This progressive neuromuscular disease is caused by nuclear-retained RNAs containing expanded CUG repeats. These toxic RNAs alter the activities of RNA splicing factors, resulting in alternative splicing misregulation. By combining human mutated pluripotent stem cells and phenotypic drug screening, we revealed that cardiac glycosides act as modulators for both upstream nuclear aggregations of DMPK mRNAs and several downstream alternative mRNA splicing defects. However, these occurred at different drug concentration ranges. Similar biological effects were recorded in a DM1 mouse model. At the mechanistic level, we demonstrated that this effect was calcium dependent and was synergic with inhibition of the ERK pathway. These results further underscore the value of stem-cell-based assays for drug discovery in monogenic diseases.

A High Throughput Phenotypic Screening reveals compounds that counteract premature osteogenic differentiation of HGPS iPS-derived mesenchymal stem cells.

Hutchinson-Gilford progeria syndrome (HGPS) is a rare fatal genetic disorder that causes systemic accelerated aging in children. Thanks to the pluripotency and self-renewal properties of induced pluripotent stem cells (iPSC), HGPS iPSC-based modeling opens up the possibility of access to different relevant cell types for pharmacological approaches. In this study, 2800 small molecules were explored using high-throughput screening, looking for compounds that could potentially reduce the alkaline phosphatase activity of HGPS mesenchymal stem cells (MSCs) committed into osteogenic differentiation. Results revealed seven compounds that normalized the osteogenic differentiation process and, among these, all-trans retinoic acid and 13-cis-retinoic acid, that also decreased progerin expression. This study highlights the potential of high-throughput drug screening using HGPS iPS-derived cells, in order to find therapeutic compounds for HGPS and, potentially, for other aging-related disorders.

High throughput screening for inhibitors of REST in neural derivatives of human embryonic stem cells reveals a chemical compound that promotes expression of neuronal genes.

Decreased expression of neuronal genes such as brain-derived neurotrophic factor (BDNF) is associated with several neurological disorders. One molecular mechanism associated with Huntington disease (HD) is a discrete increase in the nuclear activity of the transcriptional repressor REST/NRSF binding to repressor element-1 (RE1) sequences. High-throughput screening of a library of 6,984 compounds with luciferase-assay measuring REST activity in neural derivatives of human embryonic stem cells led to identify two benzoimidazole-5-carboxamide derivatives that inhibited REST silencing in a RE1-dependent manner. The most potent compound, X5050, targeted REST degradation, but neither REST expression, RNA splicing nor binding to RE1 sequence. Differential transcriptomic analysis revealed the upregulation of neuronal genes targeted by REST in wild-type neural cells treated with X5050. This activity was confirmed in neural cells produced from human induced pluripotent stem cells derived from a HD patient. Acute intraventricular delivery of X5050 increased the expressions of BDNF and several other REST-regulated genes in the prefrontal cortex of mice with quinolinate-induced striatal lesions. This study demonstrates that the use of pluripotent stem cell derivatives can represent a crucial step toward the identification of pharmacological compounds with therapeutic potential in neurological affections involving decreased expression of neuronal genes associated to increased REST activity, such as Huntington disease.

Composite cell sheets: a further step toward safe and effective myocardial regeneration by cardiac progenitors derived from embryonic stem cells.

BACKGROUND: The safety and efficacy of myocardial regeneration using embryonic stem cells are limited by the risk of teratoma and the high rate of cell death. METHODS AND RESULTS: To address these issues, we developed a composite construct made of a sheet of adipose tissue-derived stroma cells and embryonic stem cell-derived cardiac progenitors. Ten Rhesus monkeys underwent a transient coronary artery occlusion followed, 2 weeks later, by the open-chest delivery of the composite cell sheet over the infarcted area or a sham operation. The sheet was made of adipose tissue-derived stroma cells grown from a biopsy of autologous adipose tissue and cultured onto temperature-responsive dishes. Allogeneic Rhesus embryonic stem cells were committed to a cardiac lineage and immunomagnetically sorted to yield SSEA-1(+) cardiac progenitors, which were then deposited onto the cell sheet. Cyclosporine was given for 2 months until the animals were euthanized. Preimplantation studies showed that the SSEA-1(+) progenitors expressed cardiac markers and had lost pluripotency. After 2 months, there was no teratoma in any of the 5 cell-treated monkeys. Analysis of >1500 histological sections showed that the SSEA-1(+) cardiac progenitors had differentiated into cardiomyocytes, as evidenced by immunofluorescence and real-time polymerase chain reaction. There were also a robust engraftment of autologous adipose tissue-derived stroma cells and increased angiogenesis compared with the sham animals. CONCLUSIONS: These data collected in a clinically relevant nonhuman primate model show that developmentally restricted SSEA-1(+) cardiac progenitors appear to be safe and highlight the benefit of the epicardial delivery of a construct harboring cells with a cardiomyogenic differentiation potential and cells providing them the necessary trophic support.

A purified population of multipotent cardiovascular progenitors derived from primate pluripotent stem cells engrafts in postmyocardial infarcted nonhuman primates.

Cell therapy holds promise for tissue regeneration, including in individuals with advanced heart failure. However, treatment of heart disease with bone marrow cells and skeletal muscle progenitors has had only marginal positive benefits in clinical trials, perhaps because adult stem cells have limited plasticity. The identification, among human pluripotent stem cells, of early cardiovascular cell progenitors required for the development of the first cardiac lineage would shed light on human cardiogenesis and might pave the way for cell therapy for cardiac degenerative diseases. Here, we report the isolation of an early population of cardiovascular progenitors, characterized by expression of OCT4, stage-specific embryonic antigen 1 (SSEA-1), and mesoderm posterior 1 (MESP1), derived from human pluripotent stem cells treated with the cardiogenic morphogen BMP2. This progenitor population was multipotential and able to generate cardiomyocytes as well as smooth muscle and endothelial cells. When transplanted into the infarcted myocardium of immunosuppressed nonhuman primates, an SSEA-1+ progenitor population derived from Rhesus embryonic stem cells differentiated into ventricular myocytes and reconstituted 20% of the scar tissue. Notably, primates transplanted with an unpurified population of cardiac-committed cells, which included SSEA-1- cells, developed teratomas in the scar tissue, whereas those transplanted with purified SSEA-1+ cells did not. We therefore believe that the SSEA-1+ progenitors that we have described here have the potential to be used in cardiac regenerative medicine.

Cardiac commitment of primate embryonic stem cells.

Primate nonhuman and human embryonic stem (ES) cells provide a powerful model of early cardiogenesis. Furthermore, engineering of cardiac progenitors or cardiomyocytes from ES cells offers a tool for drug screening in toxicology or to search for molecules to improve and scale up the process of cardiac differentiation using high-throughput screening technology, as well as a source of cell therapy of heart failure. Spontaneous differentiation of ES cells into cardiomyocytes is, however, limited. Herein, we describe a simple protocol to commit both rhesus and human ES cells toward a cardiac lineage and to sort out early cardiac progenitors. Primate ES cells are challenged for 4 d with the cardiogenic morphogen bone morphogenetic protein 2 (BMP2) and sorted out using anti-SSEA-1 antibody-conjugated magnetic beads. Cardiac progenitor cells can be generated and isolated in 4 d using this protocol.