Mitochondria-targeted antioxidant Mito-Tempo protects against acetaminophen hepatotoxicity

Abstract

Acetaminophen (APAP) hepatotoxicity is characterized by an extensive mitochondrial oxidant stress. However, its importance as a drug target has not been clarified. To investigate this, fasted C57BL/6J mice were treated with 300 mg/kg APAP and the mitochondria-targeted antioxidant Mito-Tempo (MT) was given 1.5h later. APAP caused severe liver injury in mice, as indicated by the increase in plasma ALT activities and centrilobular necrosis. MT dose-dependently reduced the injury. Importantly, MT did not affect APAP protein adducts formation, glutathione depletion or c-jun N-terminal kinase activation and its mitochondrial translocation. In contrast, hepatic glutathione disulfide and peroxynitrite formation were dose-dependently reduced by MT, indicating its effective mitochondrial oxidant stress scavenging capacity. Consequently, mitochondrial translocation of Bax and release of mitochondrial intermembrane proteins such as apoptosis-inducing factor were prevented and nuclear DNA fragmentation was eliminated. To demonstrate the importance of mitochondria-specific antioxidant property of MT, we compared its efficacy with Tempo, which has the same pharmacological mode of action as MT but lacks the mitochondria targeting moiety. In contrast to the dramatic protection by MT, the same molar dose of Tempo did not significantly reduce APAP hepatotoxicity. In contrast, even a 3h post-treatment with MT reduced 70% of the injury, and the combination of MT with N-acetylcysteine (NAC) provided superior protection than NAC alone. We conclude that MT protects against APAP overdose in mice by attenuating the mitochondrial oxidant stress and preventing peroxynitrite formation and the subsequent mitochondrial dysfunction. MT is a promising therapeutic agent for APAP overdose patients.

Induction of mitochondrial biogenesis protects against acetaminophen hepatotoxicity

“…Numerous studies have established the critical role of mitochondria in the initiation and progression of APAP hepatotoxicity in both mice and humans (Placke et al, 1987; Meyers et al, 1988; Jaeschke, 1990; Kon et al, 2004; LoGuidice and Boelsterli, 2011; Ramachandran et al, 2011; McGill et al, 2012a; 2014; Du et al, 2017). There is considerable evidence that the reactive metabolite of APAP binds to mitochondrial proteins (Tirmenstein and Nelson, 1989; McGill et al, 2012b; Xie et al, 2014, 2015) leading to altered mitochondrial morphology (Placke et al, 1987), inhibition of mitochondrial respiration (Meyers et al, 1988), mitochondrial oxidative stress and peroxynitrite formation (Jaeschke, 1990; Cover et al, 2005), loss of mitochondrial membrane potential (Kon et al, 2004; McGill et al, 2011 ; Xie et al, 2014) and release of mitochondrial proteins into the cytosol and plasma (Bajt et al, 2006; McGill et al, 2012a; 2014).…”

“…There is considerable evidence that the reactive metabolite of APAP binds to mitochondrial proteins (Tirmenstein and Nelson, 1989; McGill et al, 2012b; Xie et al, 2014, 2015) leading to altered mitochondrial morphology (Placke et al, 1987), inhibition of mitochondrial respiration (Meyers et al, 1988), mitochondrial oxidative stress and peroxynitrite formation (Jaeschke, 1990; Cover et al, 2005), loss of mitochondrial membrane potential (Kon et al, 2004; McGill et al, 2011 ; Xie et al, 2014) and release of mitochondrial proteins into the cytosol and plasma (Bajt et al, 2006; McGill et al, 2012a; 2014). In addition, several interventions aimed at preventing or reducing mitochondrial dysfunction have been shown to protect against APAP-induced liver injury, including post-treatment with the antidote GSH or N-acetylcysteine (NAC) (James et al, 2003; Knight et al, 2002; Saito et al, 2010) or SOD-mimetic Mito-Tempo (Du et al, 2017) to scavenge ROS, inhibition of the mitochondrial membrane permeability transition (MPT) (Kon et al, 2004; Ramachandran et al, 2011) and activation of autophagy to remove damaged mitochondria (Ni et al, 2012). …”

Mitochondrial dysfunction as a mechanism of drug-induced hepatotoxicity: current understanding and future perspectives

“…[201]. This re-iterates the importance of SOD2, illustrated by data showing exacerbation of APAP-induced injury in mice with partial SOD2 deficiency [22, 23] and protection offered by the SOD-mimetic mito-tempo in vivo [24]. …”

“…Recent evidence from both in vitro as well as in vivo experiments also indicates that APAP interferes with the formation of mitochondrial respiratory super complexes via the mitochondrial negative regulator MCJ, which could be the cause of decreased production of ATP and increased generation of ROS [21]. The role of free radicals such as superoxide in APAP-induced hepatotoxicity is also illustrated by the exacerbation of injury in mice with partial SOD2 deficiency [22, 23] as well as the protection against APAP hepatotoxicity afforded by the mitochondria-targeted SOD-mimetic mito-tempo in vivo [24]. Another factor which could influence superoxide production within mitochondria is oxygen tension.…”

Acetaminophen Toxicity: Novel Insights Into Mechanisms and Future Perspectives

“…The importance of mitochondrial superoxide in mediating APAP hepatotoxicity is further illustrated by the significant exacerbation of liver injury in mice with a partial deficiency of manganese superoxide dismutase (SOD2) 34, 35 , which would usually scavenge superoxide within the mitochondria. Similarly, the mitochondria-targeted SOD-mimetic mito-tempo effectively protected against APAP hepatotoxicity 36 . The source of the mitochondrial superoxide production is likely the respiratory chain, since APAP has been shown to inhibit respiration through complex II by 47% in isolated mouse hepatocytes, while complex I activity was affected to a lesser extent 37, 38 .…”