T cell activation mediates immunity to pathogens. On the flipside, T cells are also involved in pathological immune responses during chronic autoimmune diseases. We recently reported that zinc aspartate, a registered drug with high bioavailability, dose-dependently inhibits T cell activation and Th1/Th2/Th17 cytokine production of stimulated human and mouse T cells. To understand the suppressive effect of zinc on T cell function, we here investigated the influence of zinc aspartate on human T cells focusing on the secretion of immunosuppressive cytokines, induction of apoptosis, and caspase 3/7 activity. To this end, we monitored either freshly stimulated or pre-activated human T cells in the presence of zinc aspartate from 40–140 µM over a period of 72 h. Under both experimental conditions, we observed a dose-dependent suppression of human T cell proliferation. While IL-1ra, latent TGF-β1, and IL-10 were dose-dependently reduced, we, unexpectedly, detected elevated levels of IL-16 upon zinc supplementation. In addition, the number of cells with active caspase 3/7 and, consecutively, the amount of cells undergoing apoptosis, steadily increased at zinc aspartate concentrations exceeding 100 µM. Taken together, our findings suggest that zinc aspartate impairs T cell fitness and might be beneficial for the treatment of T cell-mediated autoimmune diseases.
