BACE1 Inhibition Increases Susceptibility to Oxidative Stress by Promoting Mitochondrial Damage

BACE1 is a key enzyme facilitating the generation of neurotoxic β-amyloid (Aβ) peptide. However, given that BACE1 has multiple substrates we explored the importance of BACE1 in the maintenance of retinal pigment epithelial (RPE) cell homeostasis under oxidative stress. Inhibition of BACE1 reduced mitochondrial membrane potential, increased mitochondrial fragmentation, and increased cleaved caspase-3 expression in cells under oxidative stress. BACE1 inhibition also resulted in significantly lower levels of mitochondrial fusion proteins OPA1 and MFN1 suggesting a higher rate of mitochondrial fission while increasing the levels of mitophagic proteins Parkin and PINK1 and autophagosome numbers. In contrast, BACE2 had minimal effect on cellular response to oxidative stress. In summary, our results emphasize the importance of BACE1 in augmenting cellular defense against oxidative stress by protecting mitochondrial dynamics.

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Syntaxin-17-Dependent Mitochondrial Dynamics is Essential for Protection Against Oxidative-Stress-Induced Apoptosis

Antioxidants ◽

10.3390/antiox8110522 ◽

2019 ◽

Vol 8 (11) ◽

pp. 522 ◽

Cited By ~ 4

Author(s):

Wang ◽

Xiao ◽

Huang ◽

Liu

Keyword(s):

Oxidative Stress ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Autophagic Flux ◽

Wild Type ◽

Dual Roles ◽

Defective Mutant ◽

U2os Cells ◽

Induced Apoptosis

In this study, cell death induced by the oxidant tert-butylhydroperoxide (tBH) was observed in U2OS cells; this phenotype was rescued by Syntaxin 17 (STX17) knockout (KO) but the mechanism is unknown. STX17 plays dual roles in autophagosome–lysosome fusion and mitochondrial fission. However, the contribution of the two functions of STX17 to apoptosis has not been extensively studied. Here, we sought to dissect the dual roles of STX17 in oxidative-stress-induced apoptosis by taking advantage of STX17 knockout cells and an autophagosome–lysosome fusion defective mutant of STX17. We generated STX17 knockout U2OS cells using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system and the STX17 knockout cells were reconstituted with wild-type STX17 and its autophagosome–lysosome fusion defective mutant. Autophagy was assessed by autophagic flux assay, Monomer red fluorescent protein (mRFP)–GFP–LC3 assay and protease protection assay. Golgi, endoplasmic reticulum (ER)/ER–Golgi intermediate compartment (ERGIC) and mitochondrial dynamics were examined by staining the different indicator proteins. Apoptosis was evaluated by caspase cleavage assay. The general reactive oxygen species (ROS) were detected by flow cytometry. In STX17 complete knockout cells, sealed autophagosomes were efficiently formed but their fusion with lysosomes was less defective. The fusion defect was rescued by wild-type STX17 but not the autophagosome–lysosome fusion defective mutant. No obvious defects in Golgi, ERGIC or ER dynamics were observed. Mitochondria were significantly elongated, supporting a role of STX17 in mitochondria fission and the elongation caused by STX17 KO was reversed by the autophagosome–lysosome fusion defective mutant. The clearance of protein aggregation was compromised, correlating with the autophagy defect but not with mitochondrial dynamics. This study revealed a mixed role of STX17 in autophagy, mitochondrial dynamics and oxidative stress response. STX17 knockout cells were highly resistant to oxidative stress, largely due to the function of STX17 in mitochondrial fission rather than autophagy.

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MITOL deletion in the brain impairs mitochondrial structure and ER tethering leading to oxidative stress

Life Science Alliance ◽

10.26508/lsa.201900308 ◽

2019 ◽

Vol 2 (4) ◽

pp. e201900308 ◽

Cited By ~ 7

Author(s):

Shun Nagashima ◽

Keisuke Takeda ◽

Nobuhiko Ohno ◽

Satoshi Ishido ◽

Motohide Aoki ◽

...

Keyword(s):

Oxidative Stress ◽

Microglial Activation ◽

Developmental Disorders ◽

Inflammatory Diseases ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Three Dimensional ◽

Abnormal Behavior ◽

Mitochondrial Abnormalities

Mitochondrial abnormalities are associated with developmental disorders, although a causal relationship remains largely unknown. Here, we report that increased oxidative stress in neurons by deletion of mitochondrial ubiquitin ligase MITOL causes a potential neuroinflammation including aberrant astrogliosis and microglial activation, indicating that mitochondrial abnormalities might confer a risk for inflammatory diseases in brain such as psychiatric disorders. A role of MITOL in both mitochondrial dynamics and ER-mitochondria tethering prompted us to characterize three-dimensional structures of mitochondria in vivo. In MITOL-deficient neurons, we observed a significant reduction in the ER-mitochondria contact sites, which might lead to perturbation of phospholipids transfer, consequently reduce cardiolipin biogenesis. We also found that branched large mitochondria disappeared by deletion of MITOL. These morphological abnormalities of mitochondria resulted in enhanced oxidative stress in brain, which led to astrogliosis and microglial activation partly causing abnormal behavior. In conclusion, the reduced ER-mitochondria tethering and excessive mitochondrial fission may trigger neuroinflammation through oxidative stress.

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T-2 Toxin-Induced Oxidative Stress Leads to Imbalance of Mitochondrial Fission and Fusion to Activate Cellular Apoptosis in the Human Liver 7702 Cell Line

Toxins ◽

10.3390/toxins12010043 ◽

2020 ◽

Vol 12 (1) ◽

pp. 43 ◽

Cited By ~ 5

Author(s):

Junhua Yang ◽

Wenbo Guo ◽

Jianhua Wang ◽

Xianli Yang ◽

Zhiqi Zhang ◽

...

Keyword(s):

Oxidative Stress ◽

Cell Apoptosis ◽

Human Liver ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Mitochondrial Fusion ◽

Mitochondrial Dynamic ◽

Normal Human Liver ◽

Induced Apoptosis

T-2 toxin, as a highly toxic mycotoxin to humans and animals, induces oxidative stress and apoptosis in various cells and tissues. Apoptosis and mitochondrial fusion/fission are two tightly interconnected processes that are crucial for maintaining physiological homeostasis. However, the role of mitochondrial fusion/fission in apoptosis of T-2 toxin remains unknown. Hence, we aimed to explore the putative role of mitochondrial fusion/fission on T-2 toxin induced apoptosis in normal human liver (HL-7702) cells. T-2 toxin treatment (0, 0.1, 1.0, or 10 μg/L) for 24 h caused decreased cell viability and ATP concentration and increased production of (ROS), as seen by a loss of mitochondrial membrane potential (∆Ψm) and increase in mitochondrial fragmentation. Subsequently, the mitochondrial dynamic imbalance was activated, evidenced by a dose-dependent decrease and increase in the protein expression of mitochondrial fusion (OPA1, Mfn1, and Mfn2) and fission (Drp1 and Fis1), respectively. Furthermore, the T-2 toxin promoted the release of cytochrome c from mitochondria to cytoplasm and induced cell apoptosis triggered by upregulation of Bax and Bax/Bcl-2 ratios, and further activated the caspase pathways. Taken together, these results indicate that altered mitochondrial dynamics induced by oxidative stress with T-2 toxin exposure likely contribute to mitochondrial injury and HL-7702 cell apoptosis.

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Antioxidants: Pharmacothearapeutic Boon for Diabetes

10.5772/intechopen.98587 ◽

2021 ◽

Author(s):

Varuna Suresh ◽

Amala Reddy ◽

Pavithra Muthukumar ◽

Thendarl Selvam

Keyword(s):

Oxidative Stress ◽

Defense Mechanisms ◽

Cellular Response ◽

Cell Function ◽

Glucose Variability ◽

Diabetic Rats ◽

Long Term Effects ◽

Free Radical Damage ◽

Cellular Defense ◽

Elevated Glucose

Glucose-induced oxidative stress can be found related to “glucose variability” and “glucose memory”. The irregular low and elevated glucose conditions cause damage to endothelial cell function than a steady, constant rise in level of glucose. Activation of PKC, NADPH oxidases, and mitochondrial oxidants are some of the pathways exhibited as a result of this aggravated cellular response. Regarding glucose memory, long after the normalization elevated level of glucose in the endothelial cells of diabetic rats and culture, a existance or ‘memory’ of induced basement membrane mRNA is expressed. This demonstrates that glucose causes dangerous long-term effects beyond the hyperglycemia period. Oxidative stress give rise to glucotoxicity and lipotoxicity which are phenomena’s related to diabetes. Following the pathogenesis of diabetes, hyperglycemia and hyperlipidemia exerts a supplementary toxic effect on the beta-cells. So, hyperglycemia can be considered as a requirement for the destructive effects of lipotoxicity. Thus glucolipotoxicity can be considered as a substitute for lipotoxicity which relates the detrimental correlation between lipids and beta-cell function. Generally, the antioxidant pharmacotherapy can be coupled with drugs to boost the natural cellular defense mechanisms as the naturally existing antioxidant components, which neutralizes free radical damage. This considers antioxidant a boon tool for pharmacotherapeutic agent.

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Mitochondrial protein 18 is a positive apoptotic regulator in cardiomyocytes under oxidative stress

Clinical Science ◽

10.1042/cs20190125 ◽

2019 ◽

Vol 133 (9) ◽

pp. 1067-1084 ◽

Cited By ~ 1

Author(s):

Lynn H.H. Aung ◽

Yu-Zhen Li ◽

Hua Yu ◽

Xiatian Chen ◽

Zhongjie Yu ◽

...

Keyword(s):

Oxidative Stress ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Mitochondrial Protein ◽

Terminal Deoxynucleotidyl Transferase ◽

Cardiac Apoptosis ◽

Inner Membrane Protein ◽

Artery Disease ◽

Subsequent Activation

AbstractAccumulation of reactive oxygen species is a common phenomenon in cardiac stress conditions, for instance, coronary artery disease, aging-related cardiovascular abnormalities, and exposure to cardiac stressors such as hydrogen peroxide (H2O2). Mitochondrial protein 18 (Mtp18) is a novel mitochondrial inner membrane protein, shown to involve in the regulation of mitochondrial dynamics. Although Mtp18 is abundant in cardiac muscles, its role in cardiac apoptosis remains elusive. The present study aimed to detect the role of Mtp18 in H2O2-induced mitochondrial fission and apoptosis in cardiomyocytes. We studied the effect of Mtp18 in cardiomyocytes by modulating its expression with lentiviral construct of Mtp18-shRNA and Mtp18 c-DNA, respectively. We then analyzed mitochondrial morphological dynamics with MitoTracker Red staining; apoptosis with terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling (TUNEL) and cell death detection assays; and protein expression with immunoblotting. Here, we observed that Mtp18 could regulate oxidative stress- mediated mitochondrial fission and apoptosis in cardiac myocytes. Mechanistically, we found that Mtp8 induced mitochondrial fission and apoptosis by enhancing dynamin-related protein 1 (Drp1) accumulation. Conversely, knockdown of Mtp18 interfered with Drp1-associated mitochondrial fission and subsequent activation of apoptosis in both HL-1 cells and primary cardiomyocytes. However, overexpression of Mtp18 alone was not sufficient to execute apoptosis when Drp1 was minimally expressed, suggesting that Mtp18 and Drp1 are interdependent in apoptotic cascade. Together, these data highlight the role of Mtp18 in cardiac apoptosis and provide a novel therapeutic insight to minimize cardiomyocyte loss via targetting mitochondrial dynamics.

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Abstract 392: Angiotensin II TypeI Receptor-mediated Mitochondrial Fission and Suppression of Mitophagy Play Crucial Role in Vascular Senescence and Arteriosclerosis

Circulation Research ◽

10.1161/res.127.suppl_1.392 ◽

2020 ◽

Vol 127 (Suppl_1) ◽

Author(s):

Yoshihiro Uchikado ◽

Yoshiyuki Ikeda ◽

Yuichi Sasaki ◽

Yuichi Akasaki ◽

Mitsuru Ohishi

Keyword(s):

Oxidative Stress ◽

Angiotensin Ii ◽

Mitochondrial Dysfunction ◽

Cellular Senescence ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Double Knockout ◽

Apoe Ko ◽

Vascular Senescence

Introduction: Metabolic stress including oxidized low density lipoprotein (ox-LDL) cause mitochondrial dysfunction and evoke vascular senescence and atherosclerosis. Mitochondria are highly dynamic organelles that undergo quality control by mitochondrial dynamics and mitophagy. This study aims to clarify whether and how mitochondrial dynamics and mitophagy are involved in the etiology of vascular senescence and arteriosclerosis. Methods: VSMC were stimulated by ox-LDL. We also conducted in vivo experiment using C57BL6 (WT), apolipoprotein E (ApoE) deficient and the double knockout of ApoE mice and Angiotensin II Type1 Receptor (AT1R). Results: Treatment of ox-LDL forced mitochondria to fission through activation of Drp1, induced mitochondrial dysfunction and oxidative stress, and developed cellular senescence. Inhibition of either Drp1, AT1R, MAPK retarded them, suggesting that mitochondrial fission plays key roles to develop premature cellular senescence and is modulated by AT1R/MAPK signal.Administration of ox-LDL decreased the number of mitophagy assessed by electron microscopy and immunohistochemistry of LAMP2 and TOMM20. AT1R signal inhibition increased mitophagy which was not affected by Atg7 knockdown, whereas it was decreased by either Rab9 or Ulk1 knockdown. Immunohistochemistry showed Rab9 dots were co-localized to TOMM20 and LAMP2, whereas LC3 dots were not, suggesting that AT1R signal induces mitophagy through Rab9-dependent alternative autophagy. The degree of vascular senescence was higher, the number of fused mitochondria and mitochondrial function were lower and mitochondrial oxidative stress was higher in ApoE KO than those in WT. DKO attenuated these adverse effect of ApoE KO. Conclusion: AT1R regulates vascular senescence and arteriosclerosis via induction of mitochondrial fission and inhibition of mitophagy.

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New Insights into the Role of Mitochondrial Dynamics and Autophagy during Oxidative Stress and Aging in the Heart

Oxidative Medicine and Cellular Longevity ◽

10.1155/2014/210934 ◽

2014 ◽

Vol 2014 ◽

pp. 1-13 ◽

Cited By ~ 55

Author(s):

Yoshiyuki Ikeda ◽

Sebastiano Sciarretta ◽

Narayani Nagarajan ◽

Speranza Rubattu ◽

Massimo Volpe ◽

...

Keyword(s):

Oxidative Stress ◽

Aging Process ◽

Protein Quality ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

The Elderly ◽

Cardiac Response ◽

Highly Sensitive ◽

Close Relationship ◽

Response To Stress

The heart is highly sensitive to the aging process. In the elderly, the heart tends to become hypertrophic and fibrotic. Stiffness increases with ensuing systolic and diastolic dysfunction. Aging also affects the cardiac response to stress. At the molecular level, the aging process is associated with accumulation of damaged proteins and organelles, partially due to defects in protein quality control systems. The accumulation of dysfunctional and abnormal mitochondria is an important pathophysiological feature of the aging process, which is associated with excessive production of reactive oxygen species. Mitochondrial fusion and fission and mitochondrial autophagy are crucial mechanisms for maintaining mitochondrial function and preserving energy production. In particular, mitochondrial fission allows for selective segregation of damaged mitochondria, which are afterward eliminated by autophagy. Unfortunately, recent evidence indicates that mitochondrial dynamics and autophagy are progressively impaired over time, contributing to the aging process. This suggests that restoration of these mechanisms could delay organ senescence and prevent age-associated cardiac diseases. Here, we discuss the current understanding of the close relationship between mitochondrial dynamics, mitophagy, oxidative stress, and aging, with a particular focus on the heart.

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Pathological Roles of Mitochondrial Oxidative Stress and Mitochondrial Dynamics in Cardiac Microvascular Ischemia/Reperfusion Injury

Biomolecules ◽

10.3390/biom10010085 ◽

2020 ◽

Vol 10 (1) ◽

pp. 85 ◽

Cited By ~ 21

Author(s):

Hao Zhou ◽

Sam Toan

Keyword(s):

Oxidative Stress ◽

Endothelial Cells ◽

Endothelial Cell ◽

Cell Function ◽

Mitochondrial Dynamics ◽

Ischemia Reperfusion ◽

Mitochondrial Fission ◽

Mitochondrial Oxidative Stress ◽

Endothelial Cell Function

Mitochondria are key regulators of cell fate through controlling ATP generation and releasing pro-apoptotic factors. Cardiac ischemia/reperfusion (I/R) injury to the coronary microcirculation has manifestations ranging in severity from reversible edema to interstitial hemorrhage. A number of mechanisms have been proposed to explain the cardiac microvascular I/R injury including edema, impaired vasomotion, coronary microembolization, and capillary destruction. In contrast to their role in cell types with higher energy demands, mitochondria in endothelial cells primarily function in signaling cellular responses to environmental cues. It is clear that abnormal mitochondrial signatures, including mitochondrial oxidative stress, mitochondrial fission, mitochondrial fusion, and mitophagy, play a substantial role in endothelial cell function. While the pathogenic role of each of these mitochondrial alterations in the endothelial cells I/R injury remains complex, profiling of mitochondrial oxidative stress and mitochondrial dynamics in endothelial cell dysfunction may offer promising potential targets in the search for novel diagnostics and therapeutics in cardiac microvascular I/R injury. The objective of this review is to discuss the role of mitochondrial oxidative stress on cardiac microvascular endothelial cells dysfunction. Mitochondrial dynamics, including mitochondrial fission and fusion, are critically discussed to understand their roles in endothelial cell survival. Finally, mitophagy, as a degradative mechanism for damaged mitochondria, is summarized to figure out its contribution to the progression of microvascular I/R injury.

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Aberrant mitochondrial fission in neurons induced by protein kinase Cδ under oxidative stress conditions in vivo

Molecular Biology of the Cell ◽

10.1091/mbc.e10-06-0551 ◽

2011 ◽

Vol 22 (2) ◽

pp. 256-265 ◽

Cited By ~ 162

Author(s):

Xin Qi ◽

Marie-Helene Disatnik ◽

Ning Shen ◽

Raymond A. Sobel ◽

Daria Mochly-Rosen

Keyword(s):

Oxidative Stress ◽

Protein Kinase ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Neuronal Cell Death ◽

Neuronal Cell ◽

Mitochondrial Fragmentation ◽

Neurological Pathology ◽

Protein Kinase Cδ

Neuronal cell death in a number of neurological disorders is associated with aberrant mitochondrial dynamics and mitochondrial degeneration. However, the triggers for this mitochondrial dysregulation are not known. Here we show excessive mitochondrial fission and mitochondrial structural disarray in brains of hypertensive rats with hypertension-induced brain injury (encephalopathy). We found that activation of protein kinase Cδ (PKCδ) induced aberrant mitochondrial fragmentation and impaired mitochondrial function in cultured SH-SY5Y neuronal cells and in this rat model of hypertension-induced encephalopathy. Immunoprecipitation studies indicate that PKCδ binds Drp1, a major mitochondrial fission protein, and phosphorylates Drp1 at Ser 579, thus increasing mitochondrial fragmentation. Further, we found that Drp1 Ser 579 phosphorylation by PKCδ is associated with Drp1 translocation to the mitochondria under oxidative stress. Importantly, inhibition of PKCδ, using a selective PKCδ peptide inhibitor (δV1-1), reduced mitochondrial fission and fragmentation and conferred neuronal protection in vivo and in culture. Our study suggests that PKCδ activation dysregulates the mitochondrial fission machinery and induces aberrant mitochondrial fission, thus contributing to neurological pathology.

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HO-1/PINK1 Regulated Mitochondrial Fusion/Fission to Inhibit Pyroptosis and Attenuate Septic Acute Kidney Injury

BioMed Research International ◽

10.1155/2020/2148706 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Hai-Bo Li ◽

Xi-Zhe Zhang ◽

Yi Sun ◽

Qi Zhou ◽

Jian-Nan Song ◽

...

Keyword(s):

Oxidative Stress ◽

Acute Kidney Injury ◽

Renal Function ◽

Inflammatory Response ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Endotoxic Shock ◽

Kidney Injury ◽

Treated Group ◽

Mitochondrial Fusion

Background. Endotoxin-associated acute kidney injury (AKI), a disease characterized by marked oxidative stress and inflammation disease, is a major cause of mortality in critically ill patients. Mitochondrial fission and pyroptosis often occur in AKI. However, the underlying biological pathways involved in endotoxin AKI remain poorly understood, especially those related to mitochondrial dynamics equilibrium disregulation and pyroptosis. Previous studies suggest that heme oxygenase- (HO-) 1 confers cytoprotection against AKI during endotoxic shock, and PTEN-induced putative kinase 1 (PINK1) takes part in mitochondrial dysfunction. Thus, in this study, we examine the roles of HO-1/PINK1 in maintaining the dynamic process of mitochondrial fusion/fission to inhibit pyroptosis and mitigate acute kidney injury in rats exposed to endotoxin. Methods. An endotoxin-associated AKI model induced by lipopolysaccharide (LPS) was used in our study. Wild-type (WT) rats and PINK1 knockout (PINK1KO) rats, respectively, were divided into four groups: the control, LPS, Znpp+LPS, and Hemin+LPS groups. Rats were sacrificed 6 h after intraperitoneal injecting LPS to assess renal function, oxidative stress, and inflammation by plasma. Mitochondrial dynamics, morphology, and pyroptosis were evaluated by histological examinations. Results. In the rats with LPS-induced endotoxemia, the expression of HO-1 and PINK1 were upregulated at both mRNA and protein levels. These rats also exhibited inflammatory response, oxidative stress, mitochondrial fission, pyroptosis, and decreased renal function. After upregulating HO-1 in normal rats, pyroptosis was inhibited; mitochondrial fission and inflammatory response to oxidative stress were decreased; and the renal function was improved. The effects were reversed by adding Znpp (a type of HO-1 inhibitor). Finally, after PINK1 knockout, there is no statistical difference in the LPS-treated group and Hemin or Znpp pretreated group. Conclusions. HO-1 inhibits inflammation response and oxidative stress and regulates mitochondria fusion/fission to inhibit pyroptosis, which can alleviate endotoxin-induced AKI by PINK1.

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