Paraquat toxicity induced by voltage-dependent anion channel 1 acts as an NADH-dependent oxidoreductase.
Paraquat (PQ), a herbicide used worldwide, causes fatal injury to organs upon high dose ingestion. Treatments for PQ poisoning are unreliable, and numerous deaths have been attributed inappropriate usage of the agent. It is generally speculated that a microsomal drug-metabolizing enzyme system is responsible for PQ toxicity. However, recent studies have demonstrated cytotoxicity via mitochondria, and therefore, the cytotoxic mechanism remains controversial. Here, we demonstrated that mitochondrial NADH-dependent PQ reductase containing a voltage-dependent anion channel 1 (VDAC1) is responsible for PQ cytotoxicity. When mitochondria were incubated with NADH and PQ, superoxide anion (O(2)(*)) was produced, and the mitochondria ruptured. Outer membrane extract oxidized NADH in a PQ dose-dependent manner, and oxidation was suppressed by VDAC inhibitors. Zymographic analysis revealed the presence of VDAC1 protein in the oxidoreductase, and the direct binding of PQ to VDAC1 was demonstrated using biotinylated PQ. VDAC1-overexpressing cells showed increased O(2)(*) production and cytotoxicity, both of which were suppressed in VDAC1 knockdown cells. These results indicated that a VDAC1-containing mitochondrial system is involved in PQ poisoning. These insights into the mechanism of PQ poisoning not only demonstrated novel physiological functions of VDAC protein, but they may facilitate the development of new therapeutic approaches.
Shimada
Hiroki
H
Molecular and Cell Structural Science, Kanazawa Medical University, Uchinada, Ishikawa 920-0293, Japan. simada-h@kanazawa-med.ac.jp
Hirai
Kei-Ichi
K
Simamura
Eriko
E
Hatta
Toshihisa
T
Iwakiri
Hiroki
H
Mizuki
Keiji
K
Hatta
Taizo
T
Sawasaki
Tatsuya
T
Matsunaga
Satoko
S
Endo
Yaeta
Y
Shimizu
Shigeomi
S
D000818:Animals; D002474:Cell-Free System; D006367:HeLa Cells; D006540:Herbicides / Q000633:toxicity*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D008854:Microscopy, Electron / Q000379:methods; D008928:Mitochondria / Q000378:metabolism; D009243:NAD / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism / Q000502:physiology*; D010269:Paraquat / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species; D050995:Voltage-Dependent Anion Channel 1 / Q000378:metabolism / Q000502:physiology*
D006540:Herbicides; D017382:Reactive Oxygen Species; C494762:VDAC1 protein, human; C494764:Vdac1 protein, rat; D009243:NAD; D006861:Hydrogen Peroxide; D009247:NADH, NADPH Oxidoreductases; D050995:Voltage-Dependent Anion Channel 1; D010269:Paraquat