Mitochondria-targeted Antioxidant SS31 Research Articles

Real-time imaging of mitochondrial redox reveals increased mitochondrial oxidative stress associated with amyloid β aggregates in vivo in a mouse model of Alzheimer’s disease

BackgroundReactive oxidative stress is a critical player in the amyloid beta (Aβ) toxicity that contributes to neurodegeneration in Alzheimer’s disease (AD). Damaged mitochondria are one of the main sources of reactive oxygen species and accumulate in Aβ plaque-associated dystrophic neurites in the AD brain. Although Aβ causes neuronal mitochondria reactive oxidative stress in vitro, this has never been directly observed in vivo in the living mouse brain. Here, we tested for the first time whether Aβ plaques and soluble Aβ oligomers induce mitochondrial oxidative stress in surrounding neurons in vivo, and whether this neurotoxic effect can be abrogated using mitochondrial-targeted antioxidants.MethodsWe expressed a genetically encoded fluorescent ratiometric mitochondria-targeted reporter of oxidative stress in mouse models of the disease and performed intravital multiphoton microscopy of neuronal mitochondria and Aβ plaques.ResultsFor the first time, we demonstrated by direct observation in the living mouse brain exacerbated mitochondrial oxidative stress in neurons after both Aβ plaque deposition and direct application of soluble oligomeric Aβ onto the brain, and determined the most likely pathological sequence of events leading to oxidative stress in vivo. Oxidative stress could be inhibited by both blocking calcium influx into mitochondria and treating with the mitochondria-targeted antioxidant SS31. Remarkably, the latter ameliorated plaque-associated dystrophic neurites without impacting Aβ plaque burden.ConclusionsConsidering these results, combination of mitochondria-targeted compounds with other anti-amyloid beta or anti-tau therapies hold promise as neuroprotective drugs for the prevention and/or treatment of AD.

Blocking exosomal secretion aggravates 1,4-benzoquinone-induced mitochondrial fission activated by the AMPK/MFF/Drp1 pathway in HL-60 cells.

There is in vivo and in vitro evidence that exposure to benzene or its metabolites could affect the mitochondrial function. However, the underlying molecular mechanism of mitochondrial damage remains to be elucidated. In this study, exposure of human promyelocytic leukemia cells (HL-60) to 1,4-benzoquinone (1,4-BQ; an active metabolite of benzene) increased the intracellular reactive oxygen species levels, decreased the mitochondrial membrane potential, adenosine triphosphate production and mitochondrial DNA (mtDNA) copy number, up-regulated the expression of mitochondrial fission proteins Drp1 and Fis1, and down-regulated the expression of mitochondrial fusion proteins Mfn2 and Opa1. Further study showed that 1,4-BQ mediated mitochondrial fission through activation of the AMP-activated protein kinase/mitochondrial fission factor/dynamin-related protein 1 pathway. Additionally, we also examined the role of exosomal secretion in mitochondrial damage under 1,4-BQ treatment. Results showed that 1,4-BQ increased the total protein level and mtDNA content in exosomes. Upon pre-treatment with the mitochondria-targeted antioxidant SS-31, there was attenuation of the mitochondrial damage induced by 1,4-BQ, accompanied by a change in the exosome release characteristics, while inhibition of exosomal secretion using GW4869 aggravated the 1,4-BQ-mediated mitochondrial fission. We concluded that exosomal secretion may serve as a self-protective mechanism of cells against 1,4-BQ-induced mitochondria damage and mitochondrial dynamics interference.

Influence of mitochondria-targeted antioxidant SS-31 on acute liver injury in a mouse model of sepsis

Influence of mitochondria-targeted antioxidant SS-31 on acute liver injury in a mouse model of sepsis

Mitochondria-Targeted Antioxidant SS-31 Attenuates Mitochondrial Dysfunction, Reduces Pyroptosis and Improves Locomotor Functional Recovery After Spinal Cord Injury

Background: Oxidative stress, neuroinflammation, neuronal loss, and demyelination contribute to mechanisms of s pinal cord injury (SCI). Reactive oxygen species (ROS) have been reported to be associated with SCI , which can trigger the pathways toward cellular pyroptosis. Accumulating evidence has suggested that oxidative stress caused by mitochondrial dysfunction play a vital role in the pathophysiology of SCI. In the present study, we explore the effects and mechanisms of SS-31, a mitochondria-targeted antioxidant , on SCI in vivo and vitro. Methods: Functional recovery was assessed using Basso Mouse Scale (BMS) and BMS subscore. Oxidative stress was evaluated using detection of malonaldehyde (MDA) and 3-nitrotyrosine(3-NT). Neuronal loss was evaluated by immunochemistry staining of NeuN. Pyroptosis was assessed by flow cytometry and western blot. Findings: Administration of SS-31 to mice significantly improved locomotor functional recovery up to 28 days after SCI and suppressed neuronal loss and demyelination in mice. Moreover, SS-31 attenuated oxidative stress, inhibited nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome activation and pyroptosis occurrence, and decreased proinflammatory cytokines levels in mice. Furthermore, SS-31 in oxygen-glucose deprivation neurons promoted the survival , alleviated mitochondrial dysfunction, decreased oxidative stress, and suppressed NLRP3 inflammasome activation and pyroptosis . Interpretations: Together, our findings reveal that mitochondria-targeted antioxidant SS-31 can improves locomotor functional recovery in mice after SCI and that SS-31-mediated neuroprotection presumably depends on the attenuation of pyroptosis, mitochondrial dysfunction, neuroinflammation and oxidative stress. Funding Statement: This study was supported by National Natural Science Foundation of China (grant.81702163), Zhejiang Provincial Public Welfare Research Project (grant.LGF20H060014), Zhejiang Provincial Medical and Health Technology Project (grant.2020KY699), Science and Technology Development Project of Hangzhou (grant.20170533838), Zhejiang Provincial Public Welfare Research Project (grant.LGF21H060004). Declaration of Interests: The authors declare no competing financial interest. Ethics Approval Statement: All animal studies (including the mice euthanasia procedure) were done in compliance with the regulations and guidelines of Hangzhou First People's Hospital's institutional animal care and conducted according to the Association for Assessment and Accreditation of Laboratory Animal Care international (AAALAC) and the Institutional Animal Care and Use Committee (IACUC) guidelines.

Synergistic Protective Effects of Mitochondrial Division Inhibitor 1 and Mitochondria-Targeted Small Peptide SS31 in Alzheimer's Disease.

The purpose of our study was to determine the synergistic protective effects of mitochondria-targeted antioxidant SS31 and mitochondria division inhibitor 1 (Mdivi1) in Alzheimer's disease (AD). Using biochemical methods, we assessed mitochondrial function by measuring the levels of hydrogen peroxide, lipid peroxidation, cytochrome c oxidase activity, mitochondrial ATP, and GTPase Drp1 enzymatic activity in mutant AβPP cells. Using biochemical methods, we also measured cell survival and apoptotic cell death. Amyloid-β (Aβ) levels were measured using sandwich ELISA, and using real-time quantitative RT-PCR, we assessed mtDNA (mtDNA) copy number in relation to nuclear DNA (nDNA) in all groups of cells. We found significantly reduced levels of Aβ40 and Aβ42 in mutant AβPP cells treated with SS31, Mdivi1, and SS31+Mdivi1, and the reduction of Aβ42 levels were much higher in SS31+Mdivi1 treated cells than individual treatments of SS31 and Mdivi1. The levels of mtDNA copy number and cell survival were significantly increased in SS31, Mdivi1, and SS31+Mdivi1 treated mutant AβPP cells; however, the increased levels of mtDNA copy number and cell survival were much higher in SS31+Mdivi1 treated cells than individual treatments of SS31 and Mdivi1. Mitochondrial dysfunction is significantly reduced in SS31, Mdivi1, and SS31+Mdivi1 treated mutant AβPP cells; however, the reduction is much higher in cells treated with both SS31+Mdvi1. Similarly, GTPase Drp1 activity is reduced in all treatments, but reduced much higher in SS31+Mdivi1 treated cells. These observations strongly suggest that combined treatment of SS31+Mdivi1 is effective than individual treatments of SS31 and Mdivi1. Therefore, we propose that combined treatment of SS31+Mdivi1 is a better therapeutic strategy for AD. Ours is the first study to investigate combined treatment of mitochondria-targeted antioxidant SS31 and mitochondrial division inhibitor 1 in AD neurons.

Interferon-gamma induces autophagy-associated apoptosis through induction of cPLA2-dependent mitochondrial ROS generation in colorectal cancer cells

Colorectal cancer (CRC) is the second most commonly diagnosed cancer in females and the third in males. In this work, we aim to investigate the possible anti-cancer effects of interferon-gamma (IFN-γ) in CRC cells. We observed that IFN-γ induced mitochondria-derived reactive oxygen species (ROS) production in a time-dependent manner in SW480 and HCT116 cell lines. The IFN-γ-induced mitochondrial ROS generation was dependent on the activation of cytosolic phospholipase A2 (cPLA2). In addition, a mitochondria-targeted antioxidant SS31 and/or cPLA2 inhibitor AACOCF3 abolished the IFN-γ-induced ROS production and subsequent autophagy and apoptosis. Moreover, suppression of autophagy by CQ was able to reduce IFN-γ-induced cell apoptosis. Beclin-1 gene silencing resulted in caspase-3 inactivation, decreased Bax/Bcl-2 ratio and less population of apoptotic cells. Collectively, our results suggested that IFN-γ induces autophagy-associated apoptosis in CRC cells via inducing cPLA2-dependent mitochondrial ROS production.

Protective effect of mitochondria-targeted antioxidant SS31 on early brain injury following subarachnoid hemorrhage in rats

To evaluate protective effects of SS31 on early brain injury (EBI) induced by subarachnoid hemorrhage (SAH) in rats. Methods: A total of 96 Sprague-Dawley rats were randomly divided into 4 groups: A sham group, an SAH group, an SAH+vehicle group (SAH+V), and an SAH+SS31 group. The SAH-induced prechiasmatic cistern rat model was established in this study. Neurological deficit scores were evaluated at 24 h after SAH. The SS31 (5 mg/kg) as well as equal volume of vehicle were administrated intraperitoneally at 2 h after SAH. The neurological scores, brain edema, blood-brain barrier (BBB) permeability, apoptosis, malondialdehyde (MDA), glutathione peroxidase (GPx) activity, superoride dismutase (SOD) activity, and the expression of cytosolic cytochrome c (Cyt C) and Bax were analyzed at 24 h after SAH. Results: Treatment with SS31 could significantly reduce MDA levels, and restored the activities of GPx and SOD in the cortex following SAH when compared with the SAH+V group. In addition, Bax SS31 trearment increased or decreased the levels of mitochondrial Cyt C or Bax, respectively. Moreover, SS31 treatment ameliorated brain edema and Evans blue dye extravasation, improved neurological deficits, and decreased neuronal apoptosis at 24 h after SAH. Conclusion: SS31 could alleviate EBI after SAH through its antioxidant property and ability in inhibition of neuronal apoptosis.

Impaired mitochondrial biogenesis, defective axonal transport of mitochondria, abnormal mitochondrial dynamics and synaptic degeneration in a mouse model of Alzheimer's disease

Increasing evidence suggests that the accumulation of amyloid beta (Aβ) in synapses and synaptic mitochondria causes synaptic mitochondrial failure and synaptic degeneration in Alzheimer's disease (AD). The purpose of this study was to better understand the effects of Aβ in mitochondrial activity and synaptic alterations in neurons from a mouse model of AD. Using primary neurons from a well-characterized Aβ precursor protein transgenic (AβPP) mouse model (Tg2576 mouse line), for the first time, we studied mitochondrial activity, including axonal transport of mitochondria, mitochondrial dynamics, morphology and function. Further, we also studied the nature of Aβ-induced synaptic alterations, and cell death in primary neurons from Tg2576 mice, and we sought to determine whether the mitochondria-targeted antioxidant SS31 could mitigate the effects of oligomeric Aβ. We found significantly decreased anterograde mitochondrial movement, increased mitochondrial fission and decreased fusion, abnormal mitochondrial and synaptic proteins and defective mitochondrial function in primary neurons from AβPP mice compared with wild-type (WT) neurons. Transmission electron microscopy revealed a large number of small mitochondria and structurally damaged mitochondria, with broken cristae in AβPP primary neurons. We also found an increased accumulation of oligomeric Aβ and increased apoptotic neuronal death in the primary neurons from the AβPP mice relative to the WT neurons. Our results revealed an accumulation of intraneuronal oligomeric Aβ, leading to mitochondrial and synaptic deficiencies, and ultimately causing neurodegeneration in AβPP cultures. However, we found that the mitochondria-targeted antioxidant SS31 restored mitochondrial transport and synaptic viability, and decreased the percentage of defective mitochondria, indicating that SS31 protects mitochondria and synapses from Aβ toxicity.

Mitochondrial production of reactive oxygen species contributes to the β‐adrenergic stimulation of mouse cardiomycytes

The sympathetic adrenergic system plays a central role in stress signalling and stress is often associated with increased production of reactive oxygen species (ROS). Furthermore, the sympathetic adrenergic system is intimately involved in the regulation of cardiomyocyte Ca2+ handling and contractility. In this study we hypothesize that endogenously produced ROS contribute to the inotropic mechanism of β-adrenergic stimulation in mouse cardiomyocytes. Cytoplasmic Ca2+ transients, cell shortening and ROS production were measured in freshly isolated cardiomyocytes using confocal microscopy and fluorescent indicators. As a marker of oxidative stress, malondialdehyde (MDA) modification of proteins was detected with Western blotting. Isoproterenol (ISO), a β-adrenergic agonist, increased mitochondrial ROS production in cardiomyocytes in a concentration- and cAMP–protein kinase A-dependent but Ca2+-independent manner. Hearts perfused with ISO showed a twofold increase in MDA protein adducts relative to control. ISO increased Ca2+ transient amplitude, contraction and L-type Ca2+ current densities (measured with whole-cell patch-clamp) in cardiomyocytes and these increases were diminished by application of the general antioxidant N-acetylcysteine (NAC) or the mitochondria-targeted antioxidant SS31. In conclusion, increased mitochondrial ROS production plays an integral role in the acute inotropic response of cardiomyocytes to β-adrenergic stimulation. On the other hand, chronically sustained adrenergic stress is associated with the development of heart failure and cardiac arrhythmias and prolonged increases in ROS may contribute to these defects.

Toxicity of Neurons Treated with Herbicides and Neuroprotection by Mitochondria-Targeted Antioxidant SS31

The purpose of this study was to determine the neurotoxicity of two commonly used herbicides: picloram and triclopyr and the neuroprotective effects of the mitochondria-targeted antioxidant, SS31. Using mouse neuroblastoma (N2a) cells and primary neurons from C57BL/6 mice, we investigated the toxicity of these herbicides, and protective effects of SS1 peptide against picloram and triclopyr toxicity. We measured total RNA content, cell viability and mRNA expression of peroxiredoxins, neuroprotective genes, mitochondrial-encoded electron transport chain (ETC) genes in N2a cells treated with herbicides and SS31. Using primary neurons from C57BL/6 mice, neuronal survival was studied in neurons treated with herbicides, in neurons pretreated with SS31 plus treated with herbicides, neurons treated with SS31 alone, and untreated neurons. Significantly decreased total RNA content, and cell viability in N2a cells treated with picloram and triclopyr were found compared to untreated N2a cells. Decreased mRNA expression of neuroprotective genes, and ETC genes in cells treated with herbicides was found compared to untreated cells. Decreased mRNA expression of peroxiredoxins 1–6 in N2a cells treated with picloram was found, suggesting that picloram affects the antioxidant enzymes in N2a cells. Immunofluorescence analysis of primary neurons revealed that decreased neuronal branching and degenerating neurons in neurons treated with picloram and triclopyr. However, neurons pretreated with SS31 prevented degenerative process caused by herbicides. Based on these results, we propose that herbicides—picloram and triclopyr appear to damage neurons, and the SS31 peptide appears to protect neurons from herbicide toxicity.