ABSTRACT
Primary open-angle glaucoma (POAG) constitutes the most common type of glaucoma. Emerging evidence suggests that Endoplasmic Reticulum (ER) stress and the protein kinase RNA-like endoplasmic reticulum kinase (PERK)-mediated Unfolded Protein Response (UPR) signaling pathway play a key role in POAG pathogenesis. Thus, the main aim of the study was to evaluate the effectiveness of the PERK inhibitor LDN-0060609 in cellular model of glaucoma using primary human trabecular meshwork (HTM) cells. To evaluate the level of the ER stress marker proteins, Western blotting and TaqMan gene expression assay were used. The cytotoxicity was measured by XTT, LDH assays and Giemsa staining, whereas genotoxicity via comet assay. Changes in cell morphology were assessed by phase-contrast microscopy. Analysis of apoptosis was performed by caspase-3 assay and flow cytometry (FC), whereas cell cycle progression by FC. The results obtained have demonstrated that LDN-0060609 triggered a significant decrease of ER stress marker proteins within HTM cells with induced ER stress conditions. Moreover, LDN-0060609 effectively increased viability, reduced DNA damage, increased proliferation, restored normal morphology, reduced apoptosis and restored normal cell cycle distribution of HTM cells with induced ER stress conditions. Thereby, PERK inhibitors, such as LDN-0060609, may provide an innovative, ground-breaking treatment strategy against POAG.
Subject(s)
Glaucoma, Open-Angle , Protein Kinase Inhibitors/pharmacology , eIF-2 Kinase/antagonists & inhibitors , Apoptosis/drug effects , Cell Line , Cell Proliferation/drug effects , DNA Damage/drug effects , Endoplasmic Reticulum Stress/drug effects , Eukaryotic Initiation Factor-2/metabolism , Glaucoma, Open-Angle/drug therapy , Glaucoma, Open-Angle/metabolism , Humans , Protein Kinase Inhibitors/adverse effects , Unfolded Protein Response/drug effects , eIF-2 Kinase/metabolismABSTRACT
OBJECTIVES: There is a body of evidence that neurodegenerative disease entities are directly correlated with the perturbations on the molecular level. Hence, the ER stress-mediated Unfolded Protein Response (UPR) is activated resulting in PERK-dependent phosphorylation of the Eukaryotic initiation factor 2 (eIF2α). Thus, the levels of ATF4 and CHOP proteins are significantly increased, which subsequently switches the pro-adaptive branch of the UPR into the pro-apoptotic directly leading to neuronal loss and initiation of the neurodegenerative process. The aim of the presented study was the evaluation of the biological activity of highly specific, small-molecule inhibitors of the PERKdependent UPR signaling pathway. METHODS: The study was conducted on rat astrocytic DI TNC1 cell line. The level of p-eIF2α was measured by Western blot technique, the cytotoxicity of the investigated compound was assessed by the MTT assay and using the FITC-conjugated Annexin V (Annexin V-FITC) to indicate apoptosis and propidium iodide (PI) to indicate necrosis. The effect of tested compound on cell cycle progression was measured by flow cytometry, where the PI-labelled nuclei were analysed for DNA content. RESULTS: As a result one of the investigated compound LDN-0060609 triggers a significant inhibition of the eIF2α phosphorylation in DI TNC1 cell line. Moreover, we showed that compound LDN-0060609 is non-cytotoxic and has no effect on cell cycle progression. CONCLUSION: In conclusion, LDN-0060609 may constitute a novel, targeted treatment approach against neurodegenerative diseases, including Alzheimer's disease (AD), where pathogenesis and progression are closely associated with the overactivation of the PERK-dependent UPR signaling pathway.
Subject(s)
Alzheimer Disease/drug therapy , Alzheimer Disease/metabolism , Neuroprotective Agents/pharmacology , Unfolded Protein Response/drug effects , eIF-2 Kinase/antagonists & inhibitors , eIF-2 Kinase/metabolism , Animals , Apoptosis/drug effects , Apoptosis/physiology , Astrocytes/drug effects , Astrocytes/metabolism , Cell Cycle/drug effects , Cell Line , Eukaryotic Initiation Factor-2/metabolism , Mice , Neuroprotective Agents/toxicity , Phosphorylation/drug effects , Rats , Signal Transduction/drug effectsABSTRACT
Clinical evidence suggests that cyclin D1b, a variant of cyclin D1, is associated with tumor progression and poor outcome. However, the underlying molecular basis was unknown. Here, novel models were created to generate a genetic switch from cyclin D1 to cyclin D1b. Extensive analyses uncovered overlapping but non-redundant functions of cyclin D1b compared to cyclin D1 on developmental phenotypes, and illustrated the importance of the transcriptional regulatory functions of cyclin D1b in vivo. Data obtained identify cyclin D1b as an oncogene, wherein cyclin D1b expression under the endogenous promoter induced cellular transformation and further cooperated with known oncogenes to promote tumor growth in vivo. Further molecular interrogation uncovered unexpected links between cyclin D1b and the DNA damage/PARP1 regulatory networks, which could be exploited to suppress cyclin D1b-driven tumors. Collectively, these data are the first to define the consequence of cyclin D1b expression on normal cellular function, present evidence for cyclin D1b as an oncogene, and provide pre-clinical evidence of effective methods to thwart growth of cells dependent upon this oncogenic variant.
