Ablation of Akt2 prevents paraquat-induced myocardial mitochondrial injury and contractile dysfunction: Role of Nrf2. (5th March 2017)

• Record Type: Journal Article
• Authors: Wang, Shuyi; Zhu, Xiaoling; Xiong, Lize; Ren, Jun
• Is Part Of: Toxicology letters. Volume 269(2017)
• Page Start: 1
• Page End: 14
• Publication Date: 2017-03-05
• Subjects: Paraquat -- Akt2 -- Cardiac -- Contraction -- Nrf2 -- Mitochondrial homeostasis; Toxicology -- Periodicals; 363.179
• DOI: 10.1016/j.toxlet.2017.01.009
• Languages: English
• ISSNs: 0378-4274

Abstract

Highlights: We examined the effect of Akt2 ablation on paraquat-induced mitochondrial and cardiac toxicity. Akt2 ablation attenuated paraquat-induced cardiac contractile defect and apoptosis. The beneficial effect of Akt2 ablation was related to preservation of mitochondrial integrity. Abstract: Paraquat is a quaternary nitrogen herbicide triggering oxidative stress, mitochondrial damage and multi-organ injuries including hearts. To date, effective measure to combat paraquat toxicity is still lacking. Recent evidence has revealed a role for Akt in cardiac homeostasis. To this end, this study was designed to examine the role of Akt2 in acute paraquat exposure-induced cardiac contractile and mitochondrial injury using a unique murine model of Akt2 knockout. Cardiac contractile and intracellular Ca 2+ properties were evaluated. Mitochondrial integrity, ROS production, lipid peroxidation, ER stress and apoptosis were evaluated using aconitase assay, citrate synthase activity, DHE staining, mitochondrial permeation pore opening, 4-hydroxy-nonenal (4-HNE) and Western blot. Our results revealed compromised echocardiographic, contractile and intracellular Ca 2+ handling properties along with overt mitochondrial damage (reduced levels of PGC-1α, aconitase, citrate synthase activity and NAD + ) in mice challenged with paraquat (45 mg/kg, single injection, i.p.), the effects of which were attenuated by Akt ablation. Paraquat triggered O2 − production, lipid peroxidation and apoptosis as evidenced by increased DHE staining, 4-HNE, caspase-3 activity, Bax and reduced Bcl-2 levels in association with unchanged ER stress. The redox signaling molecule nuclear factor erythroid related factor 2 (Nrf2) was upregulated in response to paraquat challenge. Findings from in vitro study revealed that stimulation of Nrf2 using sulforaphane (10 μM) negated Akt2 ablation-offered beneficial effect against paraquat whereas inhibition of Nrf2 using luteolin (20 μM) mimicked Akt2 ablation-induced beneficial effect against paraquat challenge. Taken together, our data indicate that Akt2 ablation may protect against paraquat toxicity-induced cardiac contractile defect and apoptosis possibly via regulation of Nrf2 activation and mitochondrial homeostasis.