Calcium-Mediated Mitochondrial Permeability Transition Involved in Hydrogen Peroxide-Induced Apoptosis in Tobacco Protoplasts

In the present study, we focused on whether Intracellular free Ca^2＋ （[Ca^2＋],） regulates the formation of mltochondrlal permeability transition pore （MPTP） In H2O2-induced apoptosis In tobacco protoplasts. It was shown that the decrease In mltochondrlal membrane potential （△ψm） preceded the appearance of H2O2-Induced apoptosls; pretreatment with the specific MPTP Inhibitor cyclosporine A, which also Inhibits Ca^2＋ cycling by the mitochondria, effectively retarded apoptosls and the decrease In △ψm. Apoptosls and decreased △ψm were exacerbated by CaCl2, whereas the plasma membrane voltage-dependent Ca^2＋ channel blocker lanthanum chloride （LaCl3） attentuated these responses. Chelation of extracellular Ca^2＋ with EGTA almost totally Inhibited apoptosls and the decrease In △ψmInduced by H2O2. The time-course of changes In [Ca^2＋]l In apoptosls was detected using the Ca^2＋ probe Fiuo-3 AM. These studies showed that [Ca^2＋]1 was Increased at the very early stage of H2O2-Induced apoptosls. The EGTA evidently Inhibited the Increase In [Ca^2＋]1 Induced by H=O=, whereas It was only partially Inhibited by LaCl3. The results suggest that H2O2 may elevate cytoplasmic free Ca^2＋ concentrations In tobacco protoplasts, which mainly results from the entry of extracellular Ca^2＋, to regulate mltochondrlal permeability transition. The signaling pathway of [Ca^2＋]1-medlated mltochondrlal permeability transition was associated with H2O2-Induced apoptosis In tobacco protoplaete.

Calcium-Mediated Mitochondrial Permeability Transition Involved in Hydrogen Peroxide-Induced Apoptosis in Tobacco Protoplasts

In the present study, we focused on whether intracellular free Ca2+ ([Ca2+]i) regulates the formation of mitochondrial permeability transition pore (MPTP) in H2O2-induced apoptosis in tobacco protoplasts. It was shown that the decrease in mitochondrial membrane potential (△Ψm) preceded the appearance of H2O2-induced apoptosis;pretreatment with the specific MPTP inhibitor cyclosporine A, which also inhibits Ca2+ cycling by the mitochondria,effectively retarded apoptosis and the decrease in △Ψm. Apoptosis and decreased △Ψm were exacerbated by CaCl2, whereas the plasma membrane voltage-dependent Ca2+ channel blocker lanthanum chloride (LaCl3)attentuated these responses. Chelation of extracellular Ca2+ with EGTA almost totally inhibited apoptosis and the decrease in △Ψm induced by H2O2. The time-course of changes in [Ca2+]i in apoptosis was detected using the Ca2+ probe Fluo-3 AM. These studies showed that [Ca2+]i was increased at the very early stage of H2O2-induced apoptosis. The EGTA evidently inhibited the increase in [Ca2+]i induced by H2O2, whereas it was only partially inhibited by LaCl3. The results suggest that H2O2 may elevate cytoplasmic free Ca2+ concentrations in tobacco protoplasts, which mainly results from the entry of extracellular Ca2+, to regulate mitochondrial permeability transition. The signaling pathway of [Ca2+]i-mediated mitochondrial permeability transition was associated with H2O2-induced apoptosis in tobacco protoplasts.