Browsing by Subject "small molecule"

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  • Tepsell, Juhani (Helsingfors universitet, 2018)
    During and after myocardial infarction, millions to a billion cells die off. Scar tissue formed by fibroblasts replaces the injured myocardium during recovery. While the newly formed tissue is durable and prevents rupture of the heart, it doesn´t contribute to pump function. Depending on the extent of cardiomyocyte loss, the remaining functional myocardium get strained. Adult mammalian heart has inadequate capacity to regenerate after such injury. In case of sustained substantial increase in workload, the compensatory mechanisms turn into pathological processes including excessive fibrosis and myocyte apoptosis. The progressive decline of hearts contractile function results in heart failure (HF). Current drug treatments for managing HF aim to prevent progression of the disease and relieve symptoms. ACE inhibitors, beta blockers and diuretics are effective along with healthy lifestyle. No practical treatments are available to restore cardiac function yet. Human myocardium normally regenerates, but only 1% or less of myocytes get replaced yearly. Heart’s resident stem/progenitor cells (CPCs) likely play a role in the turnover. The aim of this study was to develop a screening method to identify small molecules that possibly promote differentiation of cardiac progenitor cells to cardiomyocytes. Cell population differentiated from mouse embryonic stem cells (mESCs) was used as a model for CPCs. Directed differentiation protocol of mESCs used here promotes commitment to cells of cardiac mesoderm, part of which will further differentiate to cardiac progenitors. The resulting population at day 6 is heterogenous but many of these cells are progenitors that turn into cardiomyocytes (CMs) by day 8. 10 000 cells per well are plated on 384 well plates at day 5. Test compounds are added at day 6 and removed day 8 for effect in progenitors and day 7-9 for effect in early cardiomyocytes. 0,1% DMSO is used as vehicle and Wnt pathway inhibitor XAV939 as positive control. The effects are quantified with plate reader on day 9. E14 derived mESC reporter line was used. Myl2v-eGFP + SMyHC3-RFP double reporter line allows the specific identification of ventricular CMs with green fluorescence and atrial CMs with red fluorescence. Plate reader measures the total fluorescence of the wells at 485/520nm on day 9, which is used as a readout for ventricular CMs. The fluorescence intensity depends on the amount of GFP+ cells but also on the level of Myl2v expression. Atrial CMs could be quantified similarly but the population doesn´t contain enough RFP+ cells. The assay was shown to reliably point out ‘hits’ that have a strong effect. Any compounds that only produce a moderate effect could be a false negative, however. The effect on cardiac progenitors could likely be increased by simply adding the compounds earlier on day 5. Variability of key reagents causes the main technical troubles through unpredictably affecting cytokine concentrations which decreases the amount of cardiac progenitors. Partially similar screening assays are being used by the big pharma where they cryopreserve progenitors in bulk for later use, thus simplifying and speeding up their method. Same approach could be adopted.
  • Sidorova, Yulia A.; Saarma, Mart (2020)
    Glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) are able to promote the survival of multiple neuronal populations in the body and, therefore, hold considerable promise for disease-modifying treatments of diseases and conditions caused by neurodegeneration. Available data reveal the potential of GFLs for the therapy of Parkinson's disease, neuropathic pain and diseases caused by retinal degeneration but, also, amyotrophic lateral sclerosis and, possibly, Alzheimer's disease. Despite promising data collected in preclinical models, clinical translation of GFLs is yet to be conducted. The main reasons for the limited success of GFLs clinical development are the poor pharmacological characteristics of GFL proteins, such as the inability of GFLs to cross tissue barriers, poor diffusion in tissues, biphasic dose-response and activation of several receptors in the organism in different cell types, along with ethical limitations on patients' selection in clinical trials. The development of small molecules selectively targeting particular GFL receptors with improved pharmacokinetic properties can overcome many of the difficulties and limitations associated with the clinical use of GFL proteins. The current review lists several strategies to target the GFL receptor complex with drug-like molecules, discusses their advantages, provides an overview of available chemical scaffolds and peptides able to activate GFL receptors and describes the effects of these molecules in cultured cells and animal models.
  • Jmaeff, Sean; Sidorova, Yulia; Nedev, Hinyu; Saarma, Mart; Saragovi, H. Uri (2020)
    Glial cell line?derived neurotrophic factor (GDNF) is a growth factor that regulates the health and function of neurons and other cells. GDNF binds to GDNF family receptor ?1 (GFRa1), and the resulting complex activates the RET receptor tyrosine kinase and subsequent downstream signals. This feature restricts GDNF activity to systems in which GFRa1 and RET are both present, a scenario that may constrain GDNF breadth of action. Furthermore, this co-dependence precludes the use of GDNF as a tool to study a putative functional cross-talk between GFRa1 and RET. Here, using biochemical techniques, terminal deoxynucleotidyl transferase dUTP nick end labeling staining, and immunohistochemistry in murine cells, tissues, or retinal organotypic cultures, we report that a naphthoquinone/quinolinedione family of small molecules (Q compounds) acts as RET agonists. We found that, like GDNF, signaling through the parental compound Q121 is GFRa1-dependent. Structural modifications of Q121 generated analogs that activated RET irrespective of GFRa1 expression. We used these analogs to examine RET?GFRa1 interactions and show that GFRa1 can influence RET-mediated signaling and enhance or diminish AKT Ser/Thr kinase or extracellular signal-regulated kinase signaling in a biased manner. In a genetic mutant model of retinitis pigmentosa, a lead compound, Q525, afforded sustained RET activation and prevented photoreceptor neuron loss in the retina. This work uncovers key components of the dynamic relationships between RET and its GFRa co-receptor and provides RET agonist scaffolds for drug development.