Elsevier

Redox Biology

Volume 36, September 2020, 101606
Redox Biology

Research Paper
Mitochondria-targeted paraquat and metformin mediate ROS production to induce multiple pathways of retrograde signaling: A dose-dependent phenomenon

https://doi.org/10.1016/j.redox.2020.101606Get rights and content
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Highlights

  • Mitochondrial ROS (O2.•–, H2O2) induce a stress signaling pathway implicated in many diseases.

  • Mitochondrial ROS induce the Ca2+/Cn pathway in addition to HIF1α and AMPK pathways.

  • Mitochondria-targeted agents MitoPQ and MitoMet induce the Ca2+/Cn and AMPK pathways.

  • Inhibition of complex III by Antimycin A also activates the Ca2+/Cn and AMPK pathways but not HIF1α.

  • The three pathways appear to require different thresholds of mitochondrial ROS.

Abstract

The mitochondrial electron transport chain is a major source of reactive oxygen species (ROS) and is also a target of ROS, with an implied role in the stabilization of hypoxia-inducible factor (HIF) and induction of the AMPK pathway. Here we used varying doses of two agents, Mito-Paraquat and Mito-Metformin, that have been conjugated to cationic triphenylphosphonium (TPP+) moiety to selectively target them to the mitochondrial matrix compartment, thereby resulting in the site-specific generation of ROS within mitochondria. These agents primarily induce superoxide (O2•–) production by acting on complex I. In Raw264.7 macrophages, C2C12 skeletal myocytes, and HCT116 adenocarcinoma cells, we show that mitochondria-targeted oxidants can induce ROS (O2•– and H2O2). In all three cell lines tested, the mitochondria-targeted agents disrupted membrane potential and activated calcineurin and the Cn-dependent retrograde signaling pathway. Hypoxic culture conditions also induced Cn activation and HIF1α activation in a temporally regulated manner, with the former appearing at shorter exposure times. Together, our results indicate that mitochondrial oxidant-induced retrograde signaling is driven by disruption of membrane potential and activation of Ca2+/Cn pathway and is independent of ROS-induced HIF1α or AMPK pathways.

Keywords

Mitochondrial ROS
Calcineurin activation
HIF1α
Retrograde signaling
Hypoxia mediated stress
Macrophage cell line
Mitochondria targeted agents

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