MitoPQ (MitoParaquat) is a mitochondria-targeted redox cycler that selectively increases superoxide production within the mitochondrial matrix in vivo and in cells[1]. MitoPQ accumulates in the mitochondrial matrix and generates O2- through redox cycling at the flavin site of complex I (Fig. 1)[1,2]. MitoPQ is commonly used to study the role of mitochondrial superoxide production in health and disease in both cells and in vivo[3,4].
Fig. 1. Rationale for the development of MitoParaquat[1,2]. MitoParaquat (MitoPQ) is composed of a redox cycling paraquat moiety, and a hydrophobic carbon chain linking it to a mitochondria-targeting triphenylphosphonium cation. MitoPQ is accumulated by mitochondria driven by the plasma (Δψp) and mitochondrial (Δψm) membrane potentials. Within the matrix, the dicationic viologen component of MitoPQ is reduced to a radical monocation by one-electron reduction at the flavin site of complex I. The radical monocation then reacts very rapidly with O2 to generate superoxide. This localized redox cycling leads to the selective production of superoxide within the mitochondrial matrix.
In vitro, treatment of C2C12 myoblasts with MitoPQ (5μM) for 20min time-dependently and significantly increased MitoSOX fluorescence intensity, whereas paraquat (PQ) at equivalent conditions failed to increase MitoSOX oxidation within this timeframe. Treatment of HCT116 cells with MitoPQ (1-10μM) for 24h induced cell death in a dose-dependent manner, with significantly higher toxicity compared to PQ[1]. Treatment of Raw264.7 cells with MitoPQ (0.5μM) for 16h significantly disrupted the mitochondrial membrane potential, an effect that was attenuated by the addition of 10mM N-acetylcysteine (NAC)[5]. Treatment of 3T3-L1 adipocytes with MitoPQ (10μM) for 2h specifically increased mitochondrial superoxide and hydrogen peroxide levels without affecting global cellular respiration[6].
In vivo, acute intraperitoneal injection of MitoPQ (0.16mg/kg) into wild-type mice fasted for 16h significantly impaired glucose tolerance 2h post-injection. Intraperitoneal injection of MitoPQ (0.16mg/kg) in wild-type mice for 1.5h impaired hepatic insulin signaling in vivo, as evidenced by reduced levels of phosphorylated insulin receptor (IR), AKT, and GSK3α[7]. Daily intraperitoneal injection of MitoPQ (0.1mg/kg/day) for 7 days in cardiomyocyte-specific Nrf3 knockout mice significantly reduced survival rates and attenuated the beneficial effects of Nrf3 gene deletion on cardiac function and remodeling after myocardial infarction[8].
References:
[1] ROBB E L, GAWEL J M, AKSENTIJEVIĆ D, et al. Selective superoxide generation within mitochondria by the targeted redox cycler MitoParaquat[J]. Free Radical Biology and Medicine, 2015, 89: 883-894.
[2] COCHENÉ H M, MURPHY M P. Complex I is the major site of mitochondrial superoxide production by paraquat[J]. Journal of Biological Chemistry, 2008, 283(4): 1786-1798.
[3] ANTONUCCI S, MULVEY J F, BURGER N, et al. Selective mitochondrial superoxide generation in vivo is cardioprotective through hormesis[J]. Free Radical Biology and Medicine, 2019, 134: 678-687.
[4] GOLEVA T N, LYAMZAEV K G, ROGOV A G, et al. Mitochondria-targeted 1, 4-naphthoquinone (SkQN) is a powerful prooxidant and cytotoxic agent[J]. Biochimica et Biophysica Acta (BBA)-Bioenergetics, 2020, 1861(8): 148210.
[5] CHOWDHURY A R, ZIELONKA J, KALYANARAMAN B, et al. Mitochondria-targeted paraquat and metformin mediate ROS production to induce multiple pathways of retrograde signaling: A dose-dependent phenomenon[J]. Redox Biology, 2020, 36: 101606.
[6] FAZAKERLEY D J, MINARD A Y, KRYCER J R, et al. Mitochondrial oxidative stress causes insulin resistance without disrupting oxidative phosphorylation[J]. Journal of Biological Chemistry, 2018, 293(19): 7315-7328.
[7] GONCALVES R L, WANG Z B, RIVEROS J K, et al. CoQ imbalance drives reverse electron transport to disrupt liver metabolism[J]. Nature, 2025.
[8] CHEN Q, ZHENG A, XU X, et al. Nrf3-Mediated mitochondrial superoxide promotes cardiomyocyte apoptosis and impairs cardiac functions by suppressing Pitx2[J]. Circulation, 2025, 151(14): 1024-1046.