Satratoxin G-induced apoptosis in PC-12 neuronal cells is mediated by PKR and caspase independent.
Satratoxin G (SG) is a macrocyclic trichothecene mycotoxin produced by Stachybotrys chartarum, a mold suggested to play an etiologic role in damp building-related illnesses. Acute intranasal exposure of mice to SG specifically induces apoptosis in olfactory sensory neurons of the nose. The PC-12 rat pheochromocytoma cell model was used to elucidate potential mechanisms of SG-induced neuronal cell death. Agarose gel electrophoresis revealed that exposure to SG at 10 ng/ml or higher for 48-h induced DNA fragmentation characteristic of apoptosis in PC-12 cells. SG-induced apoptosis was confirmed by microscopic morphology, hypodiploid fluorescence and annexin V-fluorescein isothiocyanate (FITC) uptake. Messenger RNA expression of the proapoptotic genes p53, double-stranded RNA-activated protein kinase (PKR), BAX, and caspase-activated DNAse was significantly elevated from 6 to 48 h after SG treatment. SG also induced apoptosis and proapoptotic gene expression in neural growth factor-differentiated PC-12 cells. Although SG-induced caspase-3 activation, caspase inhibition did not impair apoptosis. Moreover, SG induced nuclear translocation of apoptosis-inducing factor (AIF), a known contributor to caspase-independent neuronal cell death. SG-induced apoptosis was not affected by inhibitors of oxidative stress or mitogen-activated protein kinases but was suppressed by the PKR inhibitor C16 and by PKR siRNA transfection. PKR inhibition also blocked SG-induced apoptotic gene expression and AIF translocation but not caspase-3 activation. Taken together, SG-induced apoptosis in PC-12 neuronal cells is mediated by PKR via a caspase-independent pathway possibly involving AIF translocation.
Islam
Zahidul
Z
Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824-1224, USA.
Hegg
Colleen C
CC
Bae
Hee Kyong
HK
Pestka
James J
JJ
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D053148:Caspase 3 / Q000235:genetics / Q000502:physiology*; D016158:Genes, p53; D009474:Neurons / Q000187:drug effects*; D016716:PC12 Cells; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D014255:Trichothecenes / Q000633:toxicity*; D051028:bcl-2-Associated X Protein / Q000235:genetics; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors / Q000502:physiology*
D051033:Apoptosis Inducing Factor; D012333:RNA, Messenger; D014255:Trichothecenes; D051028:bcl-2-Associated X Protein; C028268:satratoxin G; D019892:eIF-2 Kinase; D053148:Caspase 3