Intracellular signals involved in zinc deficit-mediated T lymphocyte apoptosis

BARREIRO ARCOS ML; PAULAZO MA; STERLE HA; KLECHA AJ; GENARO AM; CREMASCHI GA

Creta, Grecia

Workshop; 5 th International Leukocyte Signal Transduction Workshop; 2009

Zinc (Zn) is a required cofactor for key enzymes involved in signaling cascades that regulate T lymphocyte physiology. Its deficiency leads to lymphocyte apoptosis, but the exact biochemical mechanisms involved in this effect have not been clearly elucidated. We here analyze the intracellular events related to Zn deficiency in two T cell types regulated by different signaling molecules, namely T lymphocytes purified from murine lymph nodes (LTN) and T cells from BW5147 T lymphomacell line (BW). Both extra- and intracellular Zn chelators were able to inhibit LTN and BW division leading to apoptosis. This was accompanied by an increase in reactive oxygen species. Both effects were reverted by the addition of Zn and of a precursor of glutathione, the N-acetyl-cysteine. Furthermore, both chelators were able to induce mitochondrial damage as they diminished the activity of mitochondrial dehydrogenase on the two cell types. As protein kinase C (PKC) is a crucial enzyme in T lymphocyte activity that utilized Zn as a cofactor, its participation in these mechanisms was evaluated. DTPA and TPEN equally inhibit the activation of PKC both on LTN and BW cells. Additionally, Zn chelators down-regulate the protein expression of PKC isoforms, with a decrease in PKCα on both cell types, but of PKCθ only on LTN and PKCβ1 and PKCζ on BW cells. Also chelators induce the activation of caspase 3 on LTN and BW. Results indicate that Zn deficiency-induced apoptosis in T lymphocytes through the decrease of protein levels of specific PKC isoenzymes. This is probably related to the activation of caspase 3 leading to mitochondrial damage and cell death.