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Mitochondrial fission occurs before dendritic injury and without AIF or cytochrome c release from mitochondria. Neurons were cotransfected with vectors encoding (A) Mito-DsRed2 and (B) MyrPalm-mCFP plus (C) AIF-GFP and the effects of SNOC were recorded using 3D time-lapse imaging. Projection images zoomed in onto the dendritic arbor of one neuron (representative of n ¼ 42). Arrows indicate dendritic spines. The inset shows the soma at appropriate grayscale levels. The apparent brightening of AIF-GFP fluorescence in the nucleus at 5 h was due to nuclear and cell body shrinkage rather than nuclear translocation of AIF. Scale bars, 10 mm. See also Supplementary Video 2. (D-E) Neurons transfected with Mito-DsRed2-plus cytochrome c-GFP were exposed to 300 mM SNOC. 3D time-lapse images were captured by fluorescence deconvolution microscopy and analyzed using Volocity software. (D) 3D time-lapse image reconstructions of mitochondria and cytochrome c in a dendritic arbor at indicated time points following SNOC addition. Scale bar, 10 mm. Five mitochondria were selected and motion tracked throughout the imaging series. (E) Traces show the ratio of mean GFP to DsRed2 emission intensity from each mitochondrion. Each trace color corresponds to the same colored mitochondrion. (representative of n ¼ 9) (F-G). Immunocytochemistry for staining anti-AIF antibodies (red) anti-NeuN antibodies (green) and nuclei labeled with Hoechst 33342 dye (blue) after (F) aged SNOC or (G) SNOC (150 mM; 4 h) treatment. Volume rendered 3D reconstruction of confocal image stacks are shown above, and a single confocal plane in grayscale below. Grid, 3.3 mm for (F) and 1.9 mm for (G), scale bars, 5 mm. (H) Ratio of nuclear to somal AIF signal was measured as mean fluorescence intensity in the center of nuclei divided by the mean fluorescence intensity in the cell body, outlined by the NeuN staining (excluding the nucleus). The bar diagram summarizes the mean7s.e.m. of 282 and 262 neurons measured in n ¼ 19 and 20 image stacks in three independent experiments for aged SNOC and SNOC, respectively (PB0.99 not significant by Student's t-test). (I) DEVDase activity. Purified cortical neurons were exposed to either 200 mM SNOC or 1 mM staurosporine, as positive control. The rate of zDEVD-AMC caspase substrate cleavage per minute was monitored and expressed in arbitrary fluorescence units. Data show mean7s.e.m. for four independent experiments (*significance at Po0.01 by ANOVA).
Source publication
Mitochondria are present as tubular organelles in neuronal projections. Here, we report that mitochondria undergo profound fission in response to nitric oxide (NO) in cortical neurons of primary cultures. Mitochondrial fission by NO occurs long before neurite injury and neuronal cell death. Furthermore, fission is accompanied by ultrastructural dam...
Contexts in source publication
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... verify our results with GFP fusion proteins we evaluated the distribution of the endogenous AIF protein by immuno- cytochemistry ( Figure 2F-H). 3D reconstructions derived of confocal image z-Stacks show, using an independent approach, that AIF remains in mitochondria in control and SNOC exposed neurons ( Figure 2F-G). Statistical analysis of the ratio of nuclear over soma AIF fluorescence intensity showed no significant difference between control and SNOC treated samples ( Figure ...
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... verify our results with GFP fusion proteins we evaluated the distribution of the endogenous AIF protein by immuno- cytochemistry ( Figure 2F-H). 3D reconstructions derived of confocal image z-Stacks show, using an independent approach, that AIF remains in mitochondria in control and SNOC exposed neurons ( Figure 2F-G). Statistical analysis of the ratio of nuclear over soma AIF fluorescence intensity showed no significant difference between control and SNOC treated samples ( Figure ...
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... verify our results with GFP fusion proteins we evaluated the distribution of the endogenous AIF protein by immuno- cytochemistry ( Figure 2F-H). 3D reconstructions derived of confocal image z-Stacks show, using an independent approach, that AIF remains in mitochondria in control and SNOC exposed neurons ( Figure 2F-G). Statistical analysis of the ratio of nuclear over soma AIF fluorescence intensity showed no significant difference between control and SNOC treated samples ( Figure ...
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... establish the temporal relationship between mitochondrial fission and events linked to neurodegeneration, neuronal cultures were co-transfected with Mito-DsRed2 to trace mitochondrial dynamics, plus MyrPalm-mCFP to observe changes in neurite morphology and apoptosis inducing factor (AIF)-GFP to determine potential release of AIF from mitochondria ( Susin et al, 1999). Neurons grown on a two- chambered glass coverslips were exposed to either fresh or aged SNOC (200 mM), and both conditions were imaged simultaneously by revisiting 8-10 selected neurons at 20 min intervals for 12 h (Figure 2). Interestingly, mitochondrial fission occurs before any overt neurite damage. Typically, SNOC exposure leads to mitochon- drial fission within 30 min, followed by focal neurite swellings (varicosities) at 1 h and further swelling at 5 h visualized by MyrPalm-mCFP fluorescence. However, neur- ites remained connected until 5 h following SNOC exposure, based on their joint movements in time-lapse recordings ( Figure 2B). Additionally, nuclear shrinkage was apparent only at 5 h after SNOC exposure ( Figure 2C) (see Supple- mentary Video 2a). Control neurons treated with aged SNOC retained baseline morphology during the course of the time- lapse experiment (see Supplementary Video 2b). During the experiment AIF-GFP remained localized within mitochondria, and its intensity in the nucleus did not increase, suggesting that AIF-GFP was not released from mitochondria ( Figure ...
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... establish the temporal relationship between mitochondrial fission and events linked to neurodegeneration, neuronal cultures were co-transfected with Mito-DsRed2 to trace mitochondrial dynamics, plus MyrPalm-mCFP to observe changes in neurite morphology and apoptosis inducing factor (AIF)-GFP to determine potential release of AIF from mitochondria ( Susin et al, 1999). Neurons grown on a two- chambered glass coverslips were exposed to either fresh or aged SNOC (200 mM), and both conditions were imaged simultaneously by revisiting 8-10 selected neurons at 20 min intervals for 12 h (Figure 2). Interestingly, mitochondrial fission occurs before any overt neurite damage. Typically, SNOC exposure leads to mitochon- drial fission within 30 min, followed by focal neurite swellings (varicosities) at 1 h and further swelling at 5 h visualized by MyrPalm-mCFP fluorescence. However, neur- ites remained connected until 5 h following SNOC exposure, based on their joint movements in time-lapse recordings ( Figure 2B). Additionally, nuclear shrinkage was apparent only at 5 h after SNOC exposure ( Figure 2C) (see Supple- mentary Video 2a). Control neurons treated with aged SNOC retained baseline morphology during the course of the time- lapse experiment (see Supplementary Video 2b). During the experiment AIF-GFP remained localized within mitochondria, and its intensity in the nucleus did not increase, suggesting that AIF-GFP was not released from mitochondria ( Figure ...
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... establish the temporal relationship between mitochondrial fission and events linked to neurodegeneration, neuronal cultures were co-transfected with Mito-DsRed2 to trace mitochondrial dynamics, plus MyrPalm-mCFP to observe changes in neurite morphology and apoptosis inducing factor (AIF)-GFP to determine potential release of AIF from mitochondria ( Susin et al, 1999). Neurons grown on a two- chambered glass coverslips were exposed to either fresh or aged SNOC (200 mM), and both conditions were imaged simultaneously by revisiting 8-10 selected neurons at 20 min intervals for 12 h (Figure 2). Interestingly, mitochondrial fission occurs before any overt neurite damage. Typically, SNOC exposure leads to mitochon- drial fission within 30 min, followed by focal neurite swellings (varicosities) at 1 h and further swelling at 5 h visualized by MyrPalm-mCFP fluorescence. However, neur- ites remained connected until 5 h following SNOC exposure, based on their joint movements in time-lapse recordings ( Figure 2B). Additionally, nuclear shrinkage was apparent only at 5 h after SNOC exposure ( Figure 2C) (see Supple- mentary Video 2a). Control neurons treated with aged SNOC retained baseline morphology during the course of the time- lapse experiment (see Supplementary Video 2b). During the experiment AIF-GFP remained localized within mitochondria, and its intensity in the nucleus did not increase, suggesting that AIF-GFP was not released from mitochondria ( Figure ...
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... establish the temporal relationship between mitochondrial fission and events linked to neurodegeneration, neuronal cultures were co-transfected with Mito-DsRed2 to trace mitochondrial dynamics, plus MyrPalm-mCFP to observe changes in neurite morphology and apoptosis inducing factor (AIF)-GFP to determine potential release of AIF from mitochondria ( Susin et al, 1999). Neurons grown on a two- chambered glass coverslips were exposed to either fresh or aged SNOC (200 mM), and both conditions were imaged simultaneously by revisiting 8-10 selected neurons at 20 min intervals for 12 h (Figure 2). Interestingly, mitochondrial fission occurs before any overt neurite damage. Typically, SNOC exposure leads to mitochon- drial fission within 30 min, followed by focal neurite swellings (varicosities) at 1 h and further swelling at 5 h visualized by MyrPalm-mCFP fluorescence. However, neur- ites remained connected until 5 h following SNOC exposure, based on their joint movements in time-lapse recordings ( Figure 2B). Additionally, nuclear shrinkage was apparent only at 5 h after SNOC exposure ( Figure 2C) (see Supple- mentary Video 2a). Control neurons treated with aged SNOC retained baseline morphology during the course of the time- lapse experiment (see Supplementary Video 2b). During the experiment AIF-GFP remained localized within mitochondria, and its intensity in the nucleus did not increase, suggesting that AIF-GFP was not released from mitochondria ( Figure ...
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... then tested whether cytochrome c would be released from mitochondria in cytochrome c-GFP plus Mito-DsRed2 transfected neurons ( Figure 2D). Following exposure to SNOC, fission of tubular mitochondria began at around 25 min. In most (8 of 9) observed neurons, however, cyto- chrome c-GFP remained in fragmented mitochondria, as evidenced by the overlap of both signals at 210 min. To quantify cytochrome c distribution, individual mitochondria were randomly selected and the mean fluorescence intensity ratio of GFP to DsRed2 signal was plotted over time ( Figure 2E). The fluorescence ratio remained constant during the entire imaging period, indicating that cytochrome c was not released from fragmented mitochondria ( Figure ...
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... then tested whether cytochrome c would be released from mitochondria in cytochrome c-GFP plus Mito-DsRed2 transfected neurons ( Figure 2D). Following exposure to SNOC, fission of tubular mitochondria began at around 25 min. In most (8 of 9) observed neurons, however, cyto- chrome c-GFP remained in fragmented mitochondria, as evidenced by the overlap of both signals at 210 min. To quantify cytochrome c distribution, individual mitochondria were randomly selected and the mean fluorescence intensity ratio of GFP to DsRed2 signal was plotted over time ( Figure 2E). The fluorescence ratio remained constant during the entire imaging period, indicating that cytochrome c was not released from fragmented mitochondria ( Figure ...
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... then tested whether cytochrome c would be released from mitochondria in cytochrome c-GFP plus Mito-DsRed2 transfected neurons ( Figure 2D). Following exposure to SNOC, fission of tubular mitochondria began at around 25 min. In most (8 of 9) observed neurons, however, cyto- chrome c-GFP remained in fragmented mitochondria, as evidenced by the overlap of both signals at 210 min. To quantify cytochrome c distribution, individual mitochondria were randomly selected and the mean fluorescence intensity ratio of GFP to DsRed2 signal was plotted over time ( Figure 2E). The fluorescence ratio remained constant during the entire imaging period, indicating that cytochrome c was not released from fragmented mitochondria ( Figure ...
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... with a lack of cytochrome c release from mitochondria, 200 mM SNOC did not evoke a robust effector caspase enzyme activity in purified cortical neuronal cultures ( Figure 2I), which is in agreement with previous findings that caspases can be inactivated by NO ( Melino et al, 1997Melino et al, , 2000). In contrast, 1 mM staurosporine, a kinase inhibitor that typi- cally evokes apoptotic responses in a large variety of cell types triggered significant effector caspase ...
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... test whether mitochondrial fission plays a causal role in NO-mediated neurotoxicity, the expression levels of Drp1, Fis1 and Mfn1 in primary neurons were manipulated. The expression of Drp1 K38A and Mfn1 were confirmed by immuno- cytochemistry (Supplementary Figure 2). Expression of either dominant-negative Drp1 K38A harboring an inactive GTPase domain, wild-type Mfn1, or both, prevents mitochondrial fission in response to NO ( Figure 7A and B). Most impor- tantly, overexpression of Drp1 K38A , Mfn1, or both, protects neurons from NO-induced cell death ( Figure 7B). Surviving neurons did not develop focal neurite varicosities or Bax foci on mitochondria (H Yuan unpublished results). We have never observed dead neurons without fragmented mitochon- dria. Of note is that, Drp1 K38A and Mfn1 did not block NMDA- induced mitochondrial fission and cell death (Supplementary Figure 3). Forced expression of wild-type Drp1, Fis1 or both, in- creased the rate of mitochondrial fission and sporadic cell death ( Figure 7C). However, in a portion of neurons (20- 40%), mitochondrial fission occurred without signs of cell death. Thus, mitochondrial fission in neurons is mediated by the relative activities of fission and fusion factors, including Drp1, Fis1 and Mfn1. Collectively, these results indicate that mitochondrial fission is required but not sufficient for neuronal cell ...
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Recent studies have demonstrated a potential role for oligomeric forms of amyloid-β (Aβ) in the pathogenesis of Alzheimer's disease (AD), although it remains unclear which aspects of AD may be mediated by oligomeric Aβ. In the present study, we found that primary cultures of rat cortical neurons exhibit a dose-dependent increase in cell death follo...
Citations
... SNO-Cdk5 mediates the Aβ-induced loss of dendritic spines and neuronal damage through the transnitrosylation of Drp1, forming SNO-Drp1, which regulates mitochondrial quality control [17,98]. Aβ [25][26][27][28][29][30][31][32][33][34][35] induces mitochondrial fission in a NOdependent manner, leading to synaptic loss and neuronal damage [106,107]. Additionally, NO donors induced the formation of SNO-Drp1. The treatment of brain cortical neurons with Aβ25-35 reportedly induced pathologic mitochondrial fragmentation via the SNO of Drp1. ...
... In a study focusing on lung cancer [NSCLC], the expression of a spliced isoform of Mfn1 is found to be upregulated at the mRNA level and is associated with suppressed apoptosis in NSCLC cells [174]. On initiation of apoptosis, Drp1 is recruited to the outer mitochondrial membrane from the cytoplasm [175][176][177][178]. Downregulation of Drp1 is shown to lower cytochrome c release, mitochondrial fragmentation, caspase activation, and apoptosis [175,[179][180]. ...
... On initiation of apoptosis, Drp1 is recruited to the outer mitochondrial membrane from the cytoplasm [175][176][177][178]. Downregulation of Drp1 is shown to lower cytochrome c release, mitochondrial fragmentation, caspase activation, and apoptosis [175,[179][180]. On initiation of apoptosis, Drp1 is recruited to the outer mitochondrial membrane from the cytoplasm [175][176][177][178]. Prohibitins are inner mitochondrial membrane proteins that play a role in regulating cell cycle and apoptosis [181]. ...
Mitochondria are double-walled organelles that generate energy in the form of ATP. ATP is an energy-rich compound and a driver of fundamental cell functions. Mitochondria-oriented studies help design advanced therapies to target lung cancer. Lung cancer is the leading cause of cancer incidences and death globally. Various studies have supported that mitochondrial function is disrupting cancerous cells. Mitochondrial dysfunctions lead to dysregulated ATP synthesis, disturbed respiratory chain, unbalanced mitochondrial fission or fusion, disturbed cellular redox homeostasis, dysregulated apoptosis, and interfered non-smooth intracellular calcium signaling. Dysfunction mitochondria are associated with cancer cell proliferation, metastasis, and death. In this review, we have tried to elaborate on how normal cell mitochondria function differently from the mitochondria of lung cancer cells. It includes various targets such as mitochondrial proteins and related pathways, along with new drug molecules like Militarin analog-1, Dihydromyricetin, and papuamine. As mitochondrial metabolism is associated with the proliferation and metastasis of lung cancer cells, finding interlinks between malfunctioning mitochondria and the process of lung cancer can promote the development of new treatments.
... 19 Mitochondrial fission accelerates inner membrane proton leakage and thus increases reactive oxygen species (ROS) levels, which causes increased oxidative stress and inflammation. 20 Nevertheless, whether excessive glycolysis and mitochondrial dysfunction under hypoxia result in gastric mucosal lesion progression in PHT and GC has not yet been fully evaluated. ...
Introduction
Hypoxia is an important characteristic of gastric mucosal diseases, and hypoxia‐inducible factor‐1α (HIF‐1α) contributes to microenvironment disturbance and metabolic spectrum abnormalities. However, the underlying mechanism of HIF‐1α and its association with mitochondrial dysfunction in gastric mucosal lesions under hypoxia have not been fully clarified.
Objectives
To evaluate the effects of hypoxia‐induced HIF‐1α on the development of gastric mucosal lesions.
Methods
Portal hypertensive gastropathy (PHG) and gastric cancer (GC) were selected as representative diseases of benign and malignant gastric lesions, respectively. Gastric tissues from patients diagnosed with the above diseases were collected. Portal hypertension (PHT)‐induced mouse models in METTL3 mutant or NLRP3 ‐deficient littermates were established, and nude mouse gastric graft tumour models with relevant inhibitors were generated. The mechanisms underlying hypoxic condition, mitochondrial dysfunction and metabolic alterations in gastric mucosal lesions were further analysed.
Results
HIF‐1α, which can mediate mitochondrial dysfunction via upregulation of METTL3/IGF2BP3‐dependent dynamin‐related protein 1 (Drp1) N6‐methyladenosine modification to increase mitochondrial reactive oxygen species (mtROS) production, was elevated under hypoxic conditions in human and mouse portal hypertensive gastric mucosa and GC tissues. While blocking HIF‐1α with PX‐478, inhibiting Drp1‐dependent mitochondrial fission via mitochondrial division inhibitor 1 (Mdivi‐1) treatment or METTL3 mutation alleviated this process. Furthermore, HIF‐1α influenced energy metabolism by enhancing glycolysis via lactate dehydrogenase A. In addition, HIF‐1α‐induced Drp1‐dependent mitochondrial fission also enhanced glycolysis. Drp1‐dependent mitochondrial fission and enhanced glycolysis were associated with alterations in antioxidant enzyme activity and dysfunction of the mitochondrial electron transport chain, resulting in massive mtROS production, which was needed for activation of NLRP3 inflammasome to aggravate the development of the PHG and GC.
Conclusions
Under hypoxic conditions, HIF‐1α enhances mitochondrial dysfunction via Drp1‐dependent mitochondrial fission and influences the metabolic profile by altering glycolysis to increase mtROS production, which can trigger NLRP3 inflammasome activation and mucosal microenvironment alterations to contribute to the development of benign and malignant gastric mucosal lesions.
... Moreover, the dynamic morphology of mitochondria is retained through two opposite processes-fission and fusion. While the fission process involves the constriction and cleavage of mitochondria, the elongation of mitochondria via the joining and tethering of the mitochondria in close proximity constitutes the fusion process [143][144][145][146]. Accumulating evidence indicates that the maintenance of the mitochondrial function is crucial for neuron survival and neurological improvement. ...
... Dynamin-related protein 1 (Drp1) is a mitochondrial-binding GTPase that mediates mitochondrial fission [148]. Maintaining mitochondrial dynamics has emerged as a crucial process in the regulation of cell survival and death, particularly as the fission process precedes neuronal death after cerebral ischemia [145,146]. Expectedly, Drp1 inhibitors such as mdivi-1, mdivi-A, and mdivi-B were shown to reduce infarct volume in a focal cerebral Ischemia model [147][148][149] (Figure 3). ...
The majority of approved therapies for many diseases are developed to target their underlying pathophysiology. Understanding disease pathophysiology has thus proven vital to the successful development of clinically useful medications. Stroke is generally accepted as the leading cause of adult disability globally and ischemic stroke accounts for the most common form of the two main stroke types. Despite its health and socioeconomic burden, there is still minimal availability of effective pharmacological therapies for its treatment. In this review, we take an in-depth look at the etiology and pathophysiology of ischemic stroke, including molecular and cellular changes. This is followed by a highlight of drugs, cellular therapies, and complementary medicines that are approved or undergoing clinical trials for the treatment and management of ischemic stroke. We also identify unexplored potential targets in stroke pathogenesis that can be exploited to increase the pool of effective anti-stroke and neuroprotective agents through de novo drug development and drug repurposing.
... To sustain tissue viability, mitochondria showed quality control systems through dynamics such as fusion and fission [29]. Injured mitochondria can be repaired by fusion (with healthy mitochondria) and fission (segregation of injured mitochondria) [20,30]. ...
The design and optimization of nanostructures with unique morphologies and properties are at the forefront of biomedical nanotechnology. Cerium oxides are widely used to investigate the effect of morphology on performance. However, elucidating the morphology–activity relationship of cerium oxide nanocrystals in biomedical applications remains challenging. Herein, the therapeutic effects of cerium oxide nanoparticles with different morphologies: cerium oxide nanorods with two different aspect ratios (CeOx NRs_A and CeOx NRs_B), cerium oxide nanopolyhedra (CeOx NPs), and cerium oxide nanocubes (CeOx NCs) are investigated in in vivo and in vitro mild traumatic brain injury (TBI) models. Cerium oxide nanoparticles inhibit oxidative stress and inflammation after mild TBI, alleviating cognitive impairment; furthermore, the therapeutic effect is significantly affected by their morphology. Owing to the higher Ce³⁺/Ce⁴⁺ ratio, exposure of more active crystal surfaces, and greater number of exposed oxygen vacancies, CeOx NRs show better activity than CeOx NPs and CeOx NCs for mild TBI. Among the two investigated types of cerium oxide nanorods, CeOx NRs_A, with a higher Ce³⁺/Ce⁴⁺ ratio on the surface, appear to spread better than CeOx NRs_B in the injured lesions. The factors causing morphology‐controlled biomedical performance, such as Ce³⁺/Ce⁴⁺ molar ratio, surface area, and aspect ratio, are discussed.
... Altered mitochondrial dynamics was also observed in cerebral ischemia. In a permanent middle cerebral artery occlusion (MCAO) model, MFN2 expression was reduced [142] and mitochondrial fission preceded neuronal loss [143]. Similarly, inhibition of DRP1 improved mitochondrial function, reduced mitochondrial fragmentation, and reduced infarct volume [144,145]. ...
Cardiovascular disease (CVD) frequently complicates chronic kidney disease (CKD). The risk of all-cause mortality increases from 20% to 500% in patients who suffer both conditions; this is referred to as the so-called cardio-renal syndrome (CRS). Preclinical studies have described the key role of mitochondrial dysfunction in cardiovascular and renal diseases, suggesting that maintaining mitochondrial homeostasis is a promising therapeutic strategy for CRS. In this review, we explore the malfunction of mitochondrial homeostasis (mitochondrial biogenesis, dynamics, oxidative stress, and mitophagy) and how it contributes to the development and progression of the main vascular pathologies that could be affected by kidney injury and vice versa, and how this knowledge may guide the development of novel therapeutic strategies in CRS.
... Notably, NO-induced neuronal cell death could be alleviated by Mfn1 and dominant-negative Drp1, whereas overexpression of Drp1 or Fis1 caused cleavage and increased neuronal loss. Thus, sustained mitochondrial fission may play a causal role in NO-mediated neurotoxicity (167). Similarly, when Mdivi-1 was given as an inhibitor of Drp1 prior to cerebral ischemia, it attenuated ischemia-induced brain injury, reduced infarct volume, and improved neurological function. ...
Vascular remodeling is the pathological basis for the development of many cardiovascular diseases. The mechanisms underlying endothelial cell dysfunction, smooth muscle cell phenotypic switching, fibroblast activation, and inflammatory macrophage differentiation during vascular remodeling remain elusive. Mitochondria are highly dynamic organelles. Recent studies showed that mitochondrial fusion and fission play crucial roles in vascular remodeling and that the delicate balance of fusion-fission may be more important than individual processes. In addition, vascular remodeling may also lead to target-organ damage by interfering with the blood supply to major body organs such as the heart, brain, and kidney. The protective effect of mitochondrial dynamics modulators on target-organs has been demonstrated in numerous studies, but whether they can be used for the treatment of related cardiovascular diseases needs to be verified in future clinical studies. Herein, we summarize recent advances regarding mitochondrial dynamics in multiple cells involved in vascular remodeling and associated target-organ damage.
... The S-nitrosylation of the mitochondrial fission initiator, DRP1, has been extensively studied in AD pathogenesis [109,186,187]. More specifically, the incubation of rat cortical cell cultures and cortico-hippocampal splices with Aβ1-42, high glucose, or both led to S-nitrosylated DRP1-formation levels that are comparable to AD brains [146]. The S-nitrosylation of DRP1 results in excessive mitochondrial fragmentation, bioenergetic deficits and consequent synaptic loss [186,188] (Table 1). ...
Redox post-translational modifications are derived from fluctuations in the redox potential and modulate protein function, localization, activity and structure. Amongst the oxidative reversible modifications, the S-glutathionylation of proteins was the first to be characterized as a post-translational modification, which primarily protects proteins from irreversible oxidation. However, a growing body of evidence suggests that S-glutathionylation plays a key role in core cell processes, particularly in mitochondria, which are the main source of reactive oxygen species. S-nitrosylation, another post-translational modification, was identified >150 years ago, but it was re-introduced as a prototype cell-signaling mechanism only recently, one that tightly regulates core processes within the cell’s sub-compartments, especially in mitochondria. S-glutathionylation and S-nitrosylation are modulated by fluctuations in reactive oxygen and nitrogen species and, in turn, orchestrate mitochondrial bioenergetics machinery, morphology, nutrients metabolism and apoptosis. In many neurodegenerative disorders, mitochondria dysfunction and oxidative/nitrosative stresses trigger or exacerbate their pathologies. Despite the substantial amount of research for most of these disorders, there are no successful treatments, while antioxidant supplementation failed in the majority of clinical trials. Herein, we discuss how S-glutathionylation and S-nitrosylation interfere in mitochondrial homeostasis and how the deregulation of these modifications is associated with Alzheimer’s, Parkinson’s, amyotrophic lateral sclerosis and Friedreich’s ataxia.
... The early occurrence of the enhanced fission at 4 °C (Fig. 2) underlines a potential relevance during organ preservation with many organs being stored for hours until transplantation (Jing et al. 2018). The cold-induced mitochondrial fragmentation observed here was very marked (Figs. 1, 2, 3), similar to other models of cold exposure of isolated cells (Hendriks et al. 2017;Kerkweg et al. 2003;Rauen et al. 2006;Zhang et al. 2010), but exceeding the fission described in many normothermic models by far (Barsoum et al. 2006, Toyama et al. 2016. Mitochondrial fission as occurring under physiological and most pathophysiological conditions, i.e. under conditions of normothermia, is regarded to be mediated by the GTPase Drp1 (Kraus et al. 2021) and its receptors fission 1 protein (Fis1), mitochondrial fission factor (Mff ), mitochondrial dynamics proteins of 49 kDa (MiD49) and of 51 kDa (MiD51; Pernas et al. 2016). ...
Background
Previously, we observed that hypothermia, widely used for organ preservation, elicits mitochondrial fission in different cell types. However, temperature dependence, mechanisms and consequences of this cold-induced mitochondrial fission are unknown. Therefore, we here study cold-induced mitochondrial fission in endothelial cells, a cell type generally displaying a high sensitivity to cold-induced injury.
Methods
Porcine aortic endothelial cells were incubated at 4–25 °C in modified Krebs–Henseleit buffer (plus glucose to provide substrate and deferoxamine to prevent iron-dependent hypothermic injury).
Results
Cold-induced mitochondrial fission occurred as early as after 3 h at 4 °C and at temperatures below 21 °C, and was more marked after longer cold incubation periods. It was accompanied by the formation of unusual mitochondrial morphologies such as donuts, blobs, and lassos. Under all conditions, re-fusion was observed after rewarming. Cellular ATP content dropped to 33% after 48 h incubation at 4 °C, recovering after rewarming. Drp1 protein levels showed no significant change during cold incubation, but increased phosphorylation at both phosphorylation sites, activating S616 and inactivating S637. Drp1 receptor protein levels were unchanged. Instead of increased mitochondrial accumulation of Drp1 decreased mitochondrial localization was observed during hypothermia. Moreover, the well-known Drp1 inhibitor Mdivi-1 showed only partial protection against cold-induced mitochondrial fission. The inner membrane fusion-mediating protein Opa1 showed a late shift from the long to the fusion-incompetent short isoform during prolonged cold incubation. Oma1 cleavage was not observed.
Conclusions
Cold-induced mitochondrial fission appears to occur over almost the whole temperature range relevant for organ preservation. Unusual morphologies appear to be related to fission/auto-fusion. Fission appears to be associated with lower mitochondrial function/ATP decline, mechanistically unusual, and after cold incubation in physiological solutions reversible at 37 °C.
... A role of mitochondrial network dynamics in response to ischemiareperfusion injury has already been studied and various relationships have been described [9][10][11][12][13]87]. Enhanced mitochondrial fission is observed as a frequent consequence of ischemic injury preceding apoptotic neuronal death [10,15] while increased mitochondrial fusion emerges as a pro-survival response of post-ischemic neurons, supporting the maintenance of normal mitochondrial morphology and function [12,13]. ...
... Enhanced mitochondrial fission is observed as a frequent consequence of ischemic injury preceding apoptotic neuronal death [10,15] while increased mitochondrial fusion emerges as a pro-survival response of post-ischemic neurons, supporting the maintenance of normal mitochondrial morphology and function [12,13]. An inhibition of mitochondrial fission was observed to produce a protective effect in I/R neuronal injury in both, in vitro and in vivo models [9,[16][17][18]. As observed later on, maintained phosphorylation of Drp1 at Ser637 improved mitochondrial respiratory capacity, Ca 2+ homeostasis, and it attenuated superoxide production in response to ischemia and excitotoxicity in vitro and ex vivo [11], thereby demonstrating that the status of mitochondrial connectivity and Drp1 phosphorylation play a critical role in determining the severity of cerebral ischemic injury. ...
Transient ischemic attacks (TIA) result from a temporary blockage in blood circulation in the brain. As TIAs cause disabilities and often precede full-scale strokes, the effects of TIA are investigated to develop neuroprotective therapies. We analyzed changes in mitochondrial network dynamics, mitophagy and biogenesis in sections of gerbil hippocampus characterized by a different neuronal survival rate after 5-minute ischemia-reperfusion (I/R) insult.
Our research revealed a significantly greater mtDNA/nDNA ratio in CA2–3, DG hippocampal regions (5.8 ± 1.4 vs 3.6 ± 0.8 in CA1) that corresponded to a neuronal resistance to I/R. During reperfusion, an increase of pro-fission (phospho-Ser616-Drp1/Drp1) and pro-fusion proteins (1.6 ± 0.5 and 1.4 ± 0.3 for Mfn2 and Opa1, respectively) was observed in CA2–3, DG. Selective autophagy markers, PINK1 and SQSTM1/p62, were elevated 24-96 h after I/R and accompanied by significant elevation of transcription factors proteins PGC-1α and Nrf1 (1.2 ± 0.4, 1.78 ± 0.6, respectively) and increased respiratory chain proteins (e.g., 1.5 ± 0.3 for complex IV at I/R 96 h).
Contrastingly, decreased enzymatic activity of citrate synthase, reduced Hsp60 protein level and electron transport chain subunits (0.88 ± 0.03, 0.74 ± 0.1 and 0.71 ± 0.1 for complex IV at I/R 96 h, respectively) were observed in I/R-vulnerable CA1. The phospho-Ser616-Drp1/Drp1 was increased while Mfn2 and total Opa1 reduced to 0.88 ± 0.1 and 0.77 ± 0.17, respectively. General autophagy, measured as LC3-II/I ratio, was activated 3 h after reperfusion reaching 2.37 ± 0.9 of control.
This study demonstrated that enhanced mitochondrial fusion, followed by late and selective mitophagy and mitochondrial biogenesis might together contribute to reduced susceptibility to TIA.
