Abstract and Introduction
We have conducted a phenotypic screening in endothelial cells exposed to elevated extracellular glucose (an in vitro model of hyperglycemia) to identify compounds that prevent hyperglycemia-induced reactive oxygen species (ROS) formation without adversely affecting cell viability. From a focused library of >6,000 clinically used drug-like and pharmacologically active compounds, several classes of active compounds emerged, with a confirmed hit rate of <0.5%. Follow-up studies focused on paroxetine, a clinically used antidepressant compound that has not been previously implicated in the context of hyperglycemia or diabetes. Paroxetine reduced hyperglycemia-induced mitochondrial ROS formation, mitochondrial protein oxidation, and mitochondrial and nuclear DNA damage, without interfering with mitochondrial electron transport or cellular bioenergetics. The ability of paroxetine to improve hyperglycemic endothelial cell injury was unique among serotonin reuptake blockers and can be attributed to its antioxidant effect, which primarily resides within its sesamol moiety. Paroxetine maintained the ability of vascular rings to respond to the endothelium-dependent relaxant acetylcholine, both during in vitro hyperglycemia and ex vivo, in a rat model of streptozotocin-induced diabetes. Thus, the current work identifies a novel pharmacological action of paroxetine as a protector of endothelial cells against hyperglycemic injury and raises the potential of repurposing of this drug for the experimental therapy of diabetic cardiovascular complications.
Phenotypic screening, cell-based screening, or high-content screening approaches can be used to identify compounds that affect complex cell functions without a priori invoking of a specific molecular pathway. This approach can be used effectively for the repurposing of clinically used therapeutics. Using a cell-based screening in endothelial cells subjected to elevated extracellular glucose concentration (an in vitro model of hyperglycemia), we have tested a focused library of clinical drugs and drug-like molecules to identify compounds with an ability to protect endothelial cells from elevated glucose-induced reactive oxygen species (ROS) production. The rationale of focusing on these classes of compounds is that this approach can facilitate the accelerated translation (repurposing) of existing compounds for potential future clinical therapy. We have followed-up one selected compound, paroxetine, for in vitro and in vivo models of hyperglycemic endothelial cell dysfunction and diabetic vascular dysfunction.