Triclabendazole protects yeast and mammalian cells from oxidative stress: identification of a potential neuroprotective compound

Identification of Compounds Protecting Pancreatic Islets against Oxidative Stress using a 3D Pseudoislet Screening Platform

Oxidative stress leads to a lower success rate of clinical islet transplantation. Here, FDA-approved compounds are screened for their potential to decrease oxidative stress and to protect or enhance pancreatic islet viability and function. Studies are performed on in vitro "pseudoislet" spheroids, which are pre-incubated with 1280 different compounds and subjected to oxidative stress. Cell viability and oxidative stress levels are determined using a high-throughput fluorescence microscopy pipeline. Initial screening on cell viability results in 59 candidates. The top ten candidates are subsequently screened for their potential to decrease induced oxidative stress, and eight compounds efficient reduction of induced oxidative stress in both alpha and beta cells by 25-50%. After further characterization, the compound sulfisoxazole is found to be the most capable of reducing oxidative stress, also at short pre-incubation times, which is validated in primary human islets, where low oxidative stress levels and islet function are maintained. This study shows an effective screening strategy with 3D cell aggregates based on cell viability and oxidative stress, which leads to the discovery of several compounds with antioxidant capacity. The top candidate, sulfisoxazole is effective after a 30 min pre-incubation, maintains baseline islet function, and may help alleviate oxidative stress in pancreatic islets.

Endophytic Fusarium species, a unique bioresource for disaggregator of misfolded alpha-synuclein

Aggregation of α-synuclein into toxic oligomeric structures has been implicated in the pathogenesis of Parkinson's disease via several key stages of fibrillation, oligomerization, and aggregation. Disaggregation or prevention of aggregation has garnered a lot of attention as a therapeutic strategy to prevent or delay the progression of Parkinson's disease. It has been recently established that certain polyphenolic compounds and catechins present in plants and tea extracts exhibit the potential to inhibit the α-synuclein aggregation. However, their copious supply for therapeutic development is still unsolved. Herein, we report for the first time the disaggregation potential of α-synuclein by an endophytic fungus residing in tea leaves (Camellia sinensis). Briefly, a recombinant yeast expressing α-synuclein was used for pre-screening of 53 endophytic fungi isolated from tea using anti-oxidant activity as a marker for the disaggregation of the protein. One isolate #59CSLEAS exhibited 92.4% reduction in production of the superoxide ions, which were similar to the already established α-synuclein disaggregator, Piceatannol exhibiting 92.8% reduction. Thioflavin T assay further established that #59CSLEAS decreased the oligomerization of α-synuclein by 1.63-fold. Subsequently Dichloro-dihydro-fluorescein diacetate-based fluorescence assay exhibited a reduction in total oxidative stress in the recombinant yeast in the presence of fungal extract, thereby indicating the prevention of oligomerization. Oligomer disaggregation potential of the selected fungal extract was found to be 56.5% as assessed by sandwich ELISA assay. Using morphological as well as molecular methods, the endophytic isolate #59CSLEAS was identified as Fusarium sp. The sequence was submitted in the Genbank with accession number ON226971.1.

Exploiting Post-mitotic Yeast Cultures to Model Neurodegeneration

Over the last few decades, the budding yeast Saccharomyces cerevisiae has been extensively used as a valuable organism to explore mechanisms of aging and human age-associated neurodegenerative disorders. Yeast models can be used to study loss of function of disease-related conserved genes and to investigate gain of function activities, frequently proteotoxicity, exerted by non-conserved human mutant proteins responsible for neurodegeneration. Most published models of proteotoxicity have used rapidly dividing cells and suffer from a high level of protein expression resulting in acute growth arrest or cell death. This contrasts with the slow development of neurodegenerative proteotoxicity during aging and the characteristic post-mitotic state of the affected cell type, the neuron. Here, we will review the efforts to create and characterize yeast models of neurodegeneration using the chronological life span model of aging, and the specific information they can provide regarding the chronology of physiological events leading to neurotoxic proteotoxicity-induced cell death and the identification of new pathways involved.

The small molecule triclabendazole decreases the intracellular level of cyclic AMP and increases resistance to stress in Saccharomyces cerevisiae

The Ras-adenylyl cyclase-protein kinase A nutrient-sensing pathway controls metabolism, proliferation and resistance to stress in Saccharomyces cerevisiae. The genetic disruption of this pathway increases resistance to a variety of stresses. We show here that the pharmacological inhibition of this pathway by the drug triclabendazole increases resistance to oxidants, heat stress and extends the chronological life. Evidence is presented that triclabendazole decreases the intracellular level of cyclic AMP by inhibiting adenylyl cyclase and triggers the parallel rapid translocation of the stress-resistance transcription factor Msn2 from the cytosol into the nucleus, as deduced from experiments employing a strain in which MSN2 is replaced with MSN2-GFP (GFP, green fluorescent protein). Msn2 and Msn4 are responsible for activating the transcription of numerous genes that encode proteins that protect cells from stress. The results are consistent with triclabendazole either inhibiting the association of Ras with adenylyl cyclase or directly inhibiting adenylyl cyclase, which in turn triggers Msn2/4 to enter the nucleus and activate stress-responsible element gene expression.