Poly(ADP-ribose) polymerase (PARP)-1-independent apoptosis-inducing factor (AIF) release and cell death are induced by eleostearic acid and blocked by alpha-tocopherol and MEK inhibition.
Poly(ADP-ribose)polymerase-1 (PARP-1) is thought to be required for apoptosis-inducing factor (AIF) release from mitochondria in caspase-independent apoptosis. The mechanism by which AIF is released through PARP-1 remains unclear. Here, we provide evidence that PARP-1-independent AIF release and cell death are induced by a trienoic fatty acid, alpha-eleostearic acid (alpha-ESA). Alpha-ESA induced the caspase-independent and AIF-initiated apoptotic death of neuronal cell lines, independently of PARP-1 activation. The cell death was inhibited by the MEK inhibitor U0126 and by knockdown of MEK using small interfering RNA. However, inhibitors for JNK, p38 inhibitors, calpain, phospholipase A(2), and phosphatidylinositol 3-kinase, did not block cell death. AIF was translocated to the nucleus after the induction of apoptosis by alpha-ESA in differentiated PC12 cells without activating caspase-3 and PARP-1. The alpha-ESA-mediated cell death was not inhibited by PARP inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-isoquinoline and by knockdown of PARP-1 using small interfering RNA. Unlike N-methyl-N'-nitro-N-nitrosoguanidine treatment, histone-phosphorylated histone 2AX was not phosphorylated by alpha-ESA, which suggests no DNA damage. Overexpression of Bcl-2 did not inhibit the cell death. alpha-ESA caused a small quantity of superoxide production in the mitochondria, resulting in the reduction of mitochondrial membrane potential, both of which were blocked by a trace amount of alpha-tocopherol localized in the mitochondria. Our results demonstrate that alpha-ESA induces PARP-1-independent AIF release and cell death without activating Bax, cytochrome c, and caspase-3. MEK is also a key molecule, although the link between ERK, AIF release, and cell death remains unknown. Finding molecules that regulate AIF release may be an important therapeutic target for the treatment of neuronal injury.
Kondo
Kazunari
K
Division of Novel Food and Immunochemistry, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan. kondo@nihs.go.jp
Obitsu
Saemi
S
Ohta
Sayaka
S
Matsunami
Katsuyoshi
K
Otsuka
Hideaki
H
Teshima
Reiko
R
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008042:Linolenic Acids / Q000494:pharmacology*; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009474:Neurons / Q000378:metabolism; D016716:PC12 Cells; D010766:Phosphorylation / Q000187:drug effects; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D024502:alpha-Tocopherol / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
C494829:AIFM1 protein, human; C494831:Aifm1 protein, rat; D000975:Antioxidants; D051033:Apoptosis Inducing Factor; C494826:BAX protein, human; C494827:Bax protein, mouse; C494828:Bax protein, rat; D004791:Enzyme Inhibitors; D008042:Linolenic Acids; C494830:AIFM1 protein, mouse; D051028:bcl-2-Associated X Protein; C004934:eleostearic acid; C499320:PARP1 protein, human; C499321:Parp1 protein, mouse; C499322:Parp1 protein, rat; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D020930:MAP Kinase Kinase Kinases; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; D053148:Caspase 3; D024502:alpha-Tocopherol