Antimicrobial peptide-induced apoptotic death of leishmania results from calcium-de pend ent, caspase-independent mitochondrial toxicity.
alpha- and -defensin-, magainin-, and cathelicidin-type antimicrobial peptides (AMPs) can kill the pathogenic protozoan Leishmania. Comparative studies of a panel of AMPs have defined two distinct groups: those that induce nonapoptotic (Class I) and apoptotic (Class II) parasite killing based on their differential ability to induce phosphatidyl serine exposure, loss of mitochondrial membrane potential and decreased ATP production, induction of caspase-3/7 and -12 activity, and DNA degradation. Class II AMPs cause rapid influx of the vital stain SYTOX and an increase in intracellular Ca2+, whereas Class I AMPs cause a slow accumulation of SYTOX and do not affect intracellular Ca2+ levels. Inhibitors of cysteine or caspase proteases diminished fast influx of SYTOX through the surface membrane and DNA degradation but do not ablate the annexin V staining or the induction of apoptosis by Class II AMPs. This suggests that the changes in surface permeability in AMP-mediated apoptosis are related to the downstream events of intracellular cysteine/caspase activation or the loss of ATP. The activation of caspase-12-like activity was Ca(2+)-dependent, and inhibitors of voltage-gated and nonspecific Ca2+ channels diminished this activity. Flufenamic acid, a nonspecific Ca2+ inhibitor, completely ablated AMP-induced mitochondrial dysfunction and cell death, indicating the importance of dysregulation of Ca2+ in antimicrobial peptide-induced apoptosis.
Division of Infectious Diseases and Center for Microbial Interface Biology, The Ohio State University Medical Center, Columbus, Ohio 43210, USA.
Manjusha M
MM
Kulkarni
W Robert
WR
McMaster
Wojciech
W
Kamysz
Bradford S
BS
McGwire
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects; D005434:Flow Cytometry; D018320:Leishmania major / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D054806:Magainins / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects / Q000473:pathology*; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000502:physiology; D023084:alpha-Defensins / Q000494:pharmacology*; D054804:Cathelicidins
D023181:Antimicrobial Cationic Peptides; D000981:Antiprotozoal Agents; D015220:Calcium Channels; D054806:Magainins; D023084:alpha-Defensins; D000249:Adenosine Monophosphate; D020169:Caspases; D002118:Calcium; D054804:Cathelicidins