Phenyl Saligenin Phosphate Disrupts Cell Morphology and the Actin Cytoskeleton in Differentiating H9c2 Cardiomyoblasts and Human-Induced Pluripotent Stem-Cell-Derived Cardiomyocyte Progenitor Cells

We have previously shown that phenyl saligenin phosphate (PSP), an organophosphorus compound which is classed as a weak inhibitor of acetylcholinesterase, triggered cytotoxicity in mitotic and differentiated H9c2 cardiomyoblasts. The aim of this study was to assess whether sublethal concentrations of PSP could disrupt the morphology of differentiating rat H9c2 cardiomyoblasts and human-induced pluripotent stem-cell-derived cardiomyocyte progenitor cells (hiPSC-CMs) and to assess the underlying cytoskeletal changes. PSP-induced changes in protein expression were monitored via Western blotting, immunocytochemistry, and proteomic analysis. PSP-mediated cytotoxicity was determined by measuring MTT reduction, LDH release, and caspase-3 activity. Sublethal exposure to PSP (3 μM) induced morphological changes in differentiating H9c2 cells (7, 9, and 13 days), reflected by reduced numbers of spindle-shaped cells. Moreover, this treatment (7 days) attenuated the expression of the cytoskeletal proteins cardiac troponin I, tropomyosin-1, and α-actin. Further proteomic analysis identified nine proteins (e.g., heat shock protein 90-β and calumenin) which were down-regulated by PSP exposure in H9c2 cells. To assess the cytotoxic effects of organophosphorus compounds in a human cell model, we determined their effects on human-induced pluripotent stem-cell-derived cardiomyocyte progenitor cells. Chlorpyrifos and diazinon-induced cytotoxicity (48 h) was evident only at concentrations >100 μM. By contrast, PSP exhibited cytotoxicity in hiPSC-CMs at a concentration of 25 μM following 48 h exposure. Finally, sublethal exposure to PSP (3 μM; 7 days) induced morphological changes and decreased the expression of cardiac troponin I, tropomyosin-1, and α-actin in hiPSC-CMs. In summary, our data suggest cardiomyocyte morphology is disrupted in both cell models by sublethal concentrations of PSP via modulation of cytoskeletal protein expression.