Mito-tempo protects against acute liver injury but induces limited secondary apoptosis during the late phase of acetaminophen hepatotoxicity

Abstract

We previously reported that delayed treatment with Mito-tempo (MT), a mitochondrial targeted superoxide dismutase mimetic, protects against the early phase of acetaminophen (APAP) hepatotoxicity by inhibiting peroxynitrite formation. However, whether this protection is sustained to the late phase of toxicity is unknown. To investigate the late protection, C57Bl/6J mice were treated with 300mg/kg APAP followed by 20mg/kg MT 1.5h or 3h later. We found that both MT treatments protected against the late phase of APAP hepatotoxicity at 12 and 24h. Surprisingly, MT-treated mice demonstrated a significant increase in apoptotic hepatocytes, while the necrotic phenotype was observed almost exclusively in mice treated with APAP alone. In addition, there was a significant increase in caspase-3 activity and cleavage in the livers of MT-treated mice. Immunostaining for active caspase-3 revealed that the positively stained hepatocytes were exclusively in centrilobular areas. Treatment with the pan-caspase inhibitor ZVD-fmk (10mg/kg) 2h post-APAP neutralized this caspase activation and provided additional protection against APAP hepatotoxicity. Treatment with N-acetylcysteine (NAC), the current standard of care for APAP poisoning, protected but did not induce this apoptotic phenotype. Mechanistically, MT treatment inhibited APAP-induced RIP3 kinase expression, and RIP3-deficient mice showed caspase activation and apoptotic morphology in hepatocytes analogous to MT treatment. These data suggest that while necrosis is the primary cause of cell death after APAP hepatotoxicity, treatment with the antioxidant MT may switch the mode of cell death to secondary apoptosis in some cells. Modulation of mitochondrial oxidative stress and RIP3 kinase expression play critical roles in this switch.

Acetaminophen Intoxication Rapidly Induces Apoptosis of Intestinal Crypt Stem Cells and Enhances Intestinal Permeability

“…(2,28) Even to this day, publications report conflicting evidence either in favor of or against a role of hepatic apoptosis in APAP hepatotoxicity. (15,29,30) Although this topic was not the focus of the current study, our data provide the strongest support to the argument that direct hepatic injury due to APAP toxicity is primarily driven by necrotic cell death. Instead, we surprisingly found that widespread apoptosis occurred throughout the crypts of the small intestine rapidly after APAP overdose.…”

“…For instance, a somewhat controversial topic is the relative contributions of the various forms of cell death (e.g., apoptosis, necrosis, pyroptosis) . Even to this day, publications report conflicting evidence either in favor of or against a role of hepatic apoptosis in APAP hepatotoxicity . Although this topic was not the focus of the current study, our data provide the strongest support to the argument that direct hepatic injury due to APAP toxicity is primarily driven by necrotic cell death.…”

Mitochondria‐targeted antioxidant mito‐TEMPO alleviate oxidative stress induced by antimycin A in human mesenchymal stem cells

“…It has been reported that mito‐T is a potent mitochondria‐targeted antioxidant, which could act in ischemic tissues linked with hypoxia‐induced oxidative stress (Ding, Liu, Bi, & Zhang, 2017; Du et al, 2019; Du, Farhood, & Jaeschke, 2017; Li et al, 2018; Liu, Wang, Ding, & Wang, 2018; Nautiyal, Shaltout, Chappell, & Diz, 2019; Shetty, Kumar, & Bharati, 2019; Yang et al, 2018; Zhan et al, 2018). In the present study, mito‐T, a mitochondria‐targeted superoxide dismutase mimetic, dramatically reduced AMA‐induced mitochondrial oxidative stress, and thus effectively protected MSCs.…”

“…It has been reported that mito-T is a potent mitochondriatargeted antioxidant, which could act in ischemic tissues linked with hypoxia-induced oxidative stress (Ding, Liu, Bi, & Zhang, 2017;Du et al, 2019;Du, Farhood, & Jaeschke, 2017;Li et al, 2018;Liu, Wang, Ding, & Wang, 2018;Nautiyal, Shaltout, Chappell, & Diz, 2019;Shetty, Kumar, & Bharati, 2019;Yang et al, 2018;Zhan et al, 2018).…”

Toxicological Property of Acetaminophen: The Dark Side of a Safe Antipyretic/Analgesic Drug?

“…For example, significant hepatoprotection afforded by Mito-TEMPO, a mitochondrial targeted antioxidant, was reported by Jaeschke's group. 116,117) In addition, pleiotropic action of ethical drugs to mitochondria, such as metformin 118) and methylene blue, 119) were identified. Furthermore, a curious recent approach, such as mitochondria replacement or transplantation, has been proposed as possible treatment against APAPinduced liver injury.…”