Increase in cytosolic Ca2+ levels through the activation of non-selective cation channels induced by oxidative stress causes mitochondrial depolarization leading to apoptosis-like death in Leishmania donovani promastigotes.
Reactive oxygen species are important regulators of protozoal infection. Promastigotes of Leishmania donovani, the causative agent of Kala-azar, undergo an apoptosis-like death upon exposure to H2O2. The present study shows that upon activation of death response by H2O2, a dose- and time-dependent loss of mitochondrial membrane potential occurs. This loss is accompanied by a depletion of cellular glutathione, but cardiolipin content or thiol oxidation status remains unchanged. ATP levels are reduced within the first 60 min of exposure as a result of mitochondrial membrane potential loss. A tight link exists between changes in cytosolic Ca2+ homeostasis and collapse of the mitochondrial membrane potential, but the dissipation of the potential is independent of elevation of cytosolic Na+ and mitochondrial Ca2+. Partial inhibition of cytosolic Ca2+ increase achieved by chelating extracellular or intracellular Ca2+ by the use of appropriate agents resulted in significant rescue of the fall of the mitochondrial membrane potential and apoptosis-like death. It is further demonstrated that the increase in cytosolic Ca2+ is an additive result of release of Ca2+ from intracellular stores as well as by influx of extracellular Ca2+ through flufenamic acid-sensitive non-selective cation channels; contribution of the latter was larger. Mitochondrial changes do not involve opening of the mitochondrial transition pore as cyclosporin A is unable to prevent mitochondrial membrane potential loss. An antioxidant like N-acetylcysteine is able to inhibit the fall of the mitochondrial membrane potential and prevent apoptosis-like death. Together, these findings show the importance of non-selective cation channels in regulating the response of L. donovani promastigotes to oxidative stress that triggers downstream signaling cascades leading to apoptosis-like death.
Mukherjee
Sikha Bettina
SB
National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
Das
Manika
M
Sudhandiran
Ganapasam
G
Shaha
Chandrima
C
D000111:Acetylcysteine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002412:Cations; D016923:Cell Death; D003600:Cytosol / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007893:Leishmania donovani / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008928:Mitochondria / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology*; D011188:Potassium / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012430:Ruthenium Red / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
D002412:Cations; D007473:Ion Channels; D017382:Reactive Oxygen Species; D012430:Ruthenium Red; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D012964:Sodium; D006861:Hydrogen Peroxide; D014700:Verapamil; D005978:Glutathione; D011188:Potassium; D000111:Acetylcysteine