Therapeutic Targeting of the Mitochondria Initiates Excessive Superoxide Production and Mitochondrial Depolarization Causing Decreased mtDNA Integrity

Pokrzywinski, Kaytee L.; Biel, Thomas; Kryndushkin, Dmitry; Rao, V. Ashutosh

doi:10.1371/journal.pone.0168283

Cited by 58 publications

(45 citation statements)

References 56 publications

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“…Considering that ROS is primarily generated in mitochondria [21] , we used Mitosox Red to examine shikonin-induced changes in the generation of mitochondrial superoxide. Fluorescence microscopy proved that the levels of mitochondrial superoxide detected by Mitosox Red were markedly increased in the C6 cells treated with shikonin, and the level of mito- chondrial superoxide in the 6 μmol/L group was higher than that in the 3 μmol/L group ( Figure 1F).…”

Section: Shikonin Induced Necrosis and Ros Overproduction In Glioma Cmentioning

confidence: 99%

Shikonin induces glioma cell necroptosis in vitro by ROS overproduction and promoting RIP1/RIP3 necrosome formation

et al. 2017

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Necroptosis is a type of programmed necrosis regulated by receptor interacting protein kinase 1 (RIP1) and RIP3. Necroptosis is found to be accompanied by an overproduction of reactive oxygen species (ROS), but the role of ROS in regulation of necroptosis remains elusive. In this study, we investigated how shikonin, a necroptosis inducer for cancer cells, regulated the signaling leading to necroptosis in glinoma cells in vitro. Treatment with shikonin (2-10 μmol/L) dose-dependently triggered necrosis and induced overproduction of intracellular ROS in rat C6 and human SHG-44, U87 and U251 glioma cell lines. Moreover, shikonin treatment dose-dependently upregulated the levels of RIP1 and RIP3 and reinforced their interaction in the glioma cells. Pretreatment with the specific RIP1 inhibitor Nec-1 (100 μmol/L) or the specific RIP3 inhibitor GSK-872 (5 μmol/L) not only prevented shikonin-induced glioma cell necrosis but also significantly mitigated the levels of intracellular ROS and mitochondrial superoxide. Mitigation of ROS with MnTBAP (40 μmol/L), which was a cleaner of mitochondrial superoxide, attenuated shikonin-induced glioma cell necrosis, whereas increasing ROS levels with rotenone, which improved the mitochondrial generation of superoxide, significantly augmented shikonin-caused glioma cell necrosis. Furthermore, pretreatment with MnTBAP prevented the shikonin-induced upregulation of RIP1 and RIP3 expression and their interaction while pretreatment with rotenone reinforced these effects. These findings suggest that ROS is not only an executioner of shikonin-induced glioma cell necrosis but also a regulator of RIP1 and RIP3 expression and necrosome assembly.

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Section: Shikonin Induced Necrosis and Ros Overproduction In Glioma Cmentioning

confidence: 99%

Shikonin induces glioma cell necroptosis in vitro by ROS overproduction and promoting RIP1/RIP3 necrosome formation

et al. 2017

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“…For example, a recent study has reported that MitoQ can actually increase ROS production in some cancer cells, and this is associated with a decrease in Δ ψ m and mitochondrial DNA (mtDNA) copy number (Pokrzywinski et al. ). Moreover, MitoQ has also been found to induce autophagy in liver cells (Sun et al.…”

Section: Introductionmentioning

confidence: 99%

“…However, since MitoQ accumulates into mitochondria at very high concentrations, the possibility remains that it could have effects on mitochondrial function other than on ROS levels, not all of which might be beneficial. For example, a recent study has reported that MitoQ can actually increase ROS production in some cancer cells, and this is associated with a decrease in Dw m and mitochondrial DNA (mtDNA) copy number (Pokrzywinski et al 2016). Moreover, MitoQ has also been found to induce autophagy in liver cells (Sun et al 2017).…”

Section: Introductionmentioning

confidence: 99%

The targeted anti-oxidant MitoQ causes mitochondrial swelling and depolarization in kidney tissue

et al. 2018

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Kidney proximal tubules (PTs) contain a high density of mitochondria, which are required to generate ATP to power solute transport. Mitochondrial dysfunction is implicated in the pathogenesis of numerous kidney diseases. Damaged mitochondria are thought to produce excess reactive oxygen species (ROS), which can lead to oxidative stress and activation of cell death pathways. MitoQ is a mitochondrial targeted anti‐oxidant that has shown promise in preclinical models of renal diseases. However, recent studies in nonkidney cells have suggested that MitoQ might also have adverse effects. Here, using a live imaging approach, and both in vitro and ex vivo models, we show that MitoQ induces rapid swelling and depolarization of mitochondria in PT cells, but these effects were not observed with SS‐31, another targeted anti‐oxidant. MitoQ consists of a lipophilic cation (Tetraphenylphosphonium [TPP]) joined to an anti‐oxidant component (quinone) by a 10‐carbon alkyl chain, which is thought to insert into the inner mitochondrial membrane (IMM). We found that mitochondrial swelling and depolarization was also induced by dodecyltriphenylphosphomium (DTPP), which consists of TPP and the alkyl chain, but not by TPP alone. Surprisingly, MitoQ‐induced mitochondrial swelling occurred in the absence of a decrease in oxygen consumption rate. We also found that DTPP directly increased the permeability of artificial liposomes with a cardiolipin content similar to that of the IMM. In summary, MitoQ causes mitochondrial swelling and depolarization in PT cells by a mechanism unrelated to anti‐oxidant activity, most likely because of increased IMM permeability due to insertion of the alkyl chain.

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“…2018). In this regard, a comparison of the effects of mitoQ and a very similar compound (mitoTEMPOL) in human cancer cell lines revealed lower levels of superoxide generation in those cells treated with the second compound (Pokrzywinski et al . 2016).…”

Section: Discussionmentioning

confidence: 99%

A mitochondria-targeted antioxidant and a thyroid hormone affect carotenoid ketolase gene expression and bill redness in zebra finches

Cantarero

Andrade

Carneiro

et al. 2020

Preprint

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Conspicuous ornaments in animals can evolve to reveal individual quality when their production/maintenance costs make them reliable as signals or if their expression level is intrinsically linked to quality by some unfalsifiable mechanism (quality indices). The latter has been mostly associated with traits constrained by body size. However, red ketocarotenoid-based coloured ornaments may also have evolved as quality indices because their production could be closely linked to individual metabolism and, particularly, to the cell respiration at the inner mitochondrial membrane (IMM). This mechanism would supposedly not depend on resource (yellow carotenoids) availability, thus discarding allocation trade-offs. A gene coding for a ketolase enzyme (CYP2J19) responsible for converting dietary yellow carotenoids to red ketocarotenoids has recently been described in birds. It is not known, however, if this ketolase is involved in mitochondrial metabolism and if its expression level and activity is resource independent. Here, we manipulated the metabolism of captive male zebra finches by an antioxidant designed to penetrate the IMM (mitoTEMPO) and a thyroid hormone (triiodothyronine; T3) with known hypermetabolic effects. The expression levels of a ketocarotenoid-based ornament (bill redness) and CYP2J19 were measured. MitoTEMPO downregulated CYP2J19 expression, supporting the mitochondrial involvement in ketolase function. T3 also reduced CYP2J19 expression, but at an intermediate dosage, this effect being buffered by mitoTEMPO. Bill redness seemed to show a similar interacting effect. Nevertheless, this faded when CYP2J19 expression level was controlled for as a covariate. We argue that the well-known mitoTEMPO effect in reducing mitochondrial reactive oxygen species (ROS) production (particularly superoxide) could have interfered on redox signalling mechanisms controlling ketolase transcription. High T3 levels, contrarily, can lead to high ROS production but also trigger compensatory mechanisms, which may explain the U-shaped effect with dosage on CYP2J19 expression levels. Bill CYP2J19 expression values were also positively correlated to redness and circulating substrate carotenoid levels. Nonetheless, treatment effects did not change when controlling for blood carotenoid concentration, suggesting that resource-availability dependence was irrelevant. Finally, our findings reveal a role for thyroid hormones in the expression of carotenoid-based ornaments that has virtually been ignored until now.

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Therapeutic Targeting of the Mitochondria Initiates Excessive Superoxide Production and Mitochondrial Depolarization Causing Decreased mtDNA Integrity

Cited by 58 publications

References 56 publications

Shikonin induces glioma cell necroptosis in vitro by ROS overproduction and promoting RIP1/RIP3 necrosome formation

Shikonin induces glioma cell necroptosis in vitro by ROS overproduction and promoting RIP1/RIP3 necrosome formation

The targeted anti-oxidant MitoQ causes mitochondrial swelling and depolarization in kidney tissue

A mitochondria-targeted antioxidant and a thyroid hormone affect carotenoid ketolase gene expression and bill redness in zebra finches

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