Effect of Diphenyl-1,2,4-triazole-3-thione and Its Derivatives on the Volume Regulation System and Related Cellular Processes in Thymocytes

Triazole-containing drugs are widely used to treat cancer, fungal infections, anxiety, migraines, viral infections, and diabetes. Although different molecular targets have been identified for these compounds, their effects on the system of regulation of cellular volume and the underlying ion channels remain unexplored. In the present study, we address this important question by examining newly synthesized derivatives of 4,5-diphenyl-2H-1,2,4-triazole-3-thione (DPTT). Unmodified DPTT had the weakest effect on regulatory volume decrease (RVD) of osmotically swollen thymocytes. Introducing side chains at the sulfur atom increased RVD-inhibiting activity, which was maximal for the N,N-dibutylacetamide-derivative (compound 5) , which completely abolished thymocyte RVD with a concentration of half-maximal effect ( C 50 ) of 10.8 µM. In patch-clamp experiments, compound 5 blocked the volume-sensitive/volume-regulated anion channel (VSOR/VRAC) in a manner independent of the applied voltage with C 50 of ~14 µM. The substance suppressed the proliferation of thymocytes in primary culture and increased the proportion of PI-positive cells without a corresponding increase in annexin V-positive cells, suggesting predominantly membrane-compromising, non-apoptotic cell death. Similar C 50 values indicate an association consistent with a possible mechanistic relationship between ion channel blockage, RVD inhibition, and suppression of cell proliferation. The obtained data reveal a novel pharmacological activity of triazole derivatives that has not been considered before, mediated by ion channel modulation and targeting the machinery of regulation of cellular volume.