Publications by authors named "Alexanne Cuillerier"

12 Publications

  • Page 1 of 1

A recurrent de novo ATP5F1A substitution associated with neonatal complex V deficiency.

Eur J Hum Genet 2021 Sep 6. Epub 2021 Sep 6.

Metabolics and Newborn Screening, Children's Hospital of Eastern Ontario, Ottawa, ON, Canada.

Mitochondrial disorders are a heterogeneous group of rare, degenerative multisystem disorders affecting the cell's core bioenergetic and signalling functions. Spontaneous improvement is rare. We describe a novel neonatal-onset mitochondriopathy in three infants with failure to thrive, hyperlactatemia, hyperammonemia, and apparent clinical resolution before 18 months. Exome sequencing showed all three probands to be identically heterozygous for a recurrent de novo substitution, c.620G>A [p.(Arg207His)] in ATP5F1A, encoding the α-subunit of complex V. Patient-derived fibroblasts exhibited multiple deficits in complex V function and expression in vitro. Structural modelling predicts the observed substitution to create an abnormal region of negative charge on ATP5F1A's β-subunit-interacting surface, adjacent to the nearby β subunit's active site. This disorder, which presents with life-threatening neonatal manifestations, appears to follow a remitting course; the long-term prognosis remains unknown.
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http://dx.doi.org/10.1038/s41431-021-00956-0DOI Listing
September 2021

Adaptive optimization of the OXPHOS assembly line partially compensates lrpprc-dependent mitochondrial translation defects in mice.

Commun Biol 2021 08 19;4(1):989. Epub 2021 Aug 19.

Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.

Mouse models of genetic mitochondrial disorders are generally used to understand specific molecular defects and their biochemical consequences, but rarely to map compensatory changes allowing survival. Here we took advantage of the extraordinary mitochondrial resilience of hepatic Lrpprc knockout mice to explore this question using native proteomics profiling and lipidomics. In these mice, low levels of the mtRNA binding protein LRPPRC induce a global mitochondrial translation defect and a severe reduction (>80%) in the assembly and activity of the electron transport chain (ETC) complex IV (CIV). Yet, animals show no signs of overt liver failure and capacity of the ETC is preserved. Beyond stimulation of mitochondrial biogenesis, results show that the abundance of mitoribosomes per unit of mitochondria is increased and proteostatic mechanisms are induced in presence of low LRPPRC levels to preserve a balance in the availability of mitochondrial- vs nuclear-encoded ETC subunits. At the level of individual organelles, a stabilization of residual CIV in supercomplexes (SCs) is observed, pointing to a role of these supramolecular arrangements in preserving ETC function. While the SC assembly factor COX7A2L could not contribute to the stabilization of CIV, important changes in membrane glycerophospholipid (GPL), most notably an increase in SC-stabilizing cardiolipins species (CLs), were observed along with an increased abundance of other supramolecular assemblies known to be stabilized by, and/or participate in CL metabolism. Together these data reveal a complex in vivo network of molecular adjustments involved in preserving mitochondrial integrity in energy consuming organs facing OXPHOS defects, which could be therapeutically exploited.
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http://dx.doi.org/10.1038/s42003-021-02492-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8376967PMC
August 2021

Oxidative stress-induced senescence mediates inflammatory and fibrotic phenotypes in fibroblasts from systemic sclerosis patients.

Rheumatology (Oxford) 2021 Jun 11. Epub 2021 Jun 11.

Faculty of Pharmacy, Université de Montréal, Québec, Canada.

Objective: Systemic sclerosis (SSc) is an autoimmune connective tissue disorder characterized by inflammation and fibrosis. Although constitutive activation of fibroblasts is proposed to be responsible for the fibrotic and inflammatory features of the disease, the underlying mechanism remains elusive and, effective therapeutic targets are still lacking. The aim of this study was to evaluate the role of oxidative stress-induced senescence and its contribution to the pro-fibrotic and pro-inflammatory phenotypes of fibroblasts from SSc patients.

Methods: Dermal fibroblasts were isolated from SSc (n = 13) and healthy (n = 10) donors. Fibroblast's intracellular and mitochondrial reactive oxygen species were determined by flow cytometry. Mitochondrial function measured by Seahorse XF24 analyzer. Fibrotic and inflammatory gene expressions were assessed by qPCR and key pro-inflammatory components of the fibroblasts' secretome (interleukin (IL) 6 and IL8) were quantified by ELISA.

Results: Compared to healthy fibroblasts, SSc fibroblasts displayed higher levels of both intracellular and mitochondrial ROS. Oxidative stress in SSc fibroblasts induced the expression of fibrotic genes and activated the transforming growth factor-β-activated kinase 1 (TAK1) -IκB kinase β (IKKβ)- interferon regulatory factor 5 (IRF5) inflammatory signaling cascade. These cellular responses paralleled the presence of a DNA damage response, a senescence-associated secretory phenotype and a fibrotic response. Treatment of SSc fibroblasts with ROS scavengers reduced their pro-inflammatory secretome production and fibrotic gene expression.

Conclusions: Oxidative stress-induced cellular senescence in SSc fibroblasts underlies their pro-inflammatory and pro-fibrotic phenotypes. Targeting redox imbalance of SSc fibroblasts enhances their in vitro functions and could be of relevance for SSc therapy.
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http://dx.doi.org/10.1093/rheumatology/keab477DOI Listing
June 2021

Regulates Skeletal Muscle Mitochondrial Structure and Autophagy.

Front Physiol 2021 5;12:604210. Epub 2021 Mar 5.

Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.

Glutathione is an important antioxidant that regulates cellular redox status and is disordered in many disease states. Glutaredoxin 2 () is a glutathione-dependent oxidoreductase that plays a pivotal role in redox control by catalyzing reversible protein deglutathionylation. As oxidized glutathione (GSSG) can stimulate mitochondrial fusion, we hypothesized that may contribute to the maintenance of mitochondrial dynamics and ultrastructure. Here, we demonstrate that deletion results in decreased GSH:GSSG, with a marked increase of GSSG in primary muscle cells isolated from C57BL/6 mice. The altered glutathione redox was accompanied by increased mitochondrial length, consistent with a more fused mitochondrial reticulum. Electron microscopy of skeletal muscle fibers revealed decreased mitochondrial surface area, profoundly disordered ultrastructure, and the appearance of multi-lamellar structures. Immunoblot analysis revealed that autophagic flux was augmented in muscle as demonstrated by an increase in the ratio of LC3II/I expression. These molecular changes resulted in impaired complex I respiration and complex IV activity, a smaller diameter of muscle, and decreased body weight in deficient mice. Together, these are the first results to show that regulates skeletal muscle mitochondrial structure, and autophagy.
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http://dx.doi.org/10.3389/fphys.2021.604210DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7982873PMC
March 2021

MCL-1 maintains neuronal survival by enhancing mitochondrial integrity and bioenergetic capacity under stress conditions.

Cell Death Dis 2020 05 5;11(5):321. Epub 2020 May 5.

University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular medicine, University of Ottawa, Ottawa, ON, Canada.

Mitochondria play a crucial role in neuronal survival through efficient energy metabolism. In pathological conditions, mitochondrial stress leads to neuronal death, which is regulated by the anti-apoptotic BCL-2 family of proteins. MCL-1 is an anti-apoptotic BCL-2 protein localized to mitochondria either in the outer membrane (OM) or inner membrane (Matrix), which have distinct roles in inhibiting apoptosis and promoting bioenergetics, respectively. While the anti-apoptotic role for Mcl1 is well characterized, the protective function of MCL-1 remains poorly understood. Here, we show MCL-1 and MCL-1 prevent neuronal death through distinct mechanisms. We report that MCL-1 functions to preserve mitochondrial energy transduction and improves respiratory chain capacity by modulating mitochondrial oxygen consumption in response to mitochondrial stress. We show that MCL-1 protects neurons from stress by enhancing respiratory function, and by inhibiting mitochondrial permeability transition pore opening. Taken together, our results provide novel insight into how MCL-1 may confer neuroprotection under stress conditions involving loss of mitochondrial function.
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http://dx.doi.org/10.1038/s41419-020-2498-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7200794PMC
May 2020

Fiber-specific and whole-muscle LRP130 expression in rested, exercised, and fasted human skeletal muscle.

Pflugers Arch 2020 03 17;472(3):375-384. Epub 2020 Feb 17.

School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada.

Leucine-rich pentatricopeptide repeat motif-containing protein (LRP130) is implicated in the control of mitochondrial gene expression and oxidative phosphorylation in the liver, partly due to its interaction with peroxisome proliferator-activated receptor gamma co-activator 1-alpha (PGC-1α). To investigate LRP130's role in healthy human skeletal muscle, we examined LRP130's fiber-type distribution and subcellular localization (n = 6), as well as LRP130's relationship with PGC-1α protein and citrate synthase (CS) maximal activity (n = 33) in vastus lateralis samples obtained from young males. The impact of an acute bout of exercise (endurance [END] and sprint interval training [SIT]) and fasting (8 h) on LRP130 and PGC-1α expression was also determined (n = 10). LRP130 protein content paralleled fiber-specific succinate dehydrogenase activity (I > IIA) and strongly correlated with the mitochondrially localized protein apoptosis-inducing factor in type I (r = 0.75) and type IIA (r = 0.85) fibers. Whole-muscle LRP130 protein content was positively related to PGC-1α protein (r = 0.49, p < 0.01) and CS maximal activity (r = 0.42, p < 0.01). LRP130 mRNA expression was unaltered (p > 0.05) following exercise, despite ~ 6.6- and ~ 3.8-fold increases (p < 0.01) in PGC-1α mRNA expression after END and SIT, respectively. Although unchanged at the group level (p > 0.05), moderate-to-strong positive correlations were apparent between individual changes in LRP130 and PGC-1α expression at the mRNA (r = 0.63, p < 0.05) and protein (r = 0.59, p = 0.07) level in response to fasting. Our findings support a potential role for LRP130 in the maintenance of basal mitochondrial phenotype in human skeletal muscle. LRP130's importance for mitochondrial remodeling in exercised and fasted human skeletal muscle requires further investigation.
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http://dx.doi.org/10.1007/s00424-020-02359-4DOI Listing
March 2020

Lipidomics unveils lipid dyshomeostasis and low circulating plasmalogens as biomarkers in a monogenic mitochondrial disorder.

JCI Insight 2019 07 25;4(14). Epub 2019 Jul 25.

Department of Nutrition and.

Mitochondrial dysfunction characterizes many rare and common age-associated diseases. The biochemical consequences, underlying clinical manifestations, and potential therapeutic targets, remain to be better understood. We tested the hypothesis that lipid dyshomeostasis in mitochondrial disorders goes beyond mitochondrial fatty acid β-oxidation, particularly in liver. This was achieved using comprehensive untargeted and targeted lipidomics in a case-control cohort of patients with Leigh syndrome French-Canadian variant (LSFC), a mitochondrial disease caused by mutations in LRPPRC, and in mice harboring liver-specific inactivation of Lrpprc (H-Lrpprc-/-). We discovered a plasma lipid signature discriminating LSFC patients from controls encompassing lower levels of plasmalogens and conjugated bile acids, which suggest perturbations in peroxisomal lipid metabolism. This premise was reinforced in H-Lrpprc-/- mice, which compared with littermates recapitulated a similar, albeit stronger peroxisomal metabolic signature in plasma and liver including elevated levels of very-long-chain acylcarnitines. These mice also presented higher transcript levels for hepatic markers of peroxisome proliferation in addition to lipid remodeling reminiscent of nonalcoholic fatty liver diseases. Our study underscores the value of lipidomics to unveil unexpected mechanisms underlying lipid dyshomeostasis ensuing from mitochondrial dysfunction herein implying peroxisomes and liver, which likely contribute to the pathophysiology of LSFC, but also other rare and common mitochondrial diseases.
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http://dx.doi.org/10.1172/jci.insight.123231DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6675547PMC
July 2019

Hybrid Clear/Blue Native Electrophoresis for the Separation and Analysis of Mitochondrial Respiratory Chain Supercomplexes.

J Vis Exp 2019 05 19(147). Epub 2019 May 19.

Interdisciplinary School of Health Science, Faculty of Health Sciences and Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa;

Complexes of the oxidative phosphorylation machinery form supramolecular protein arrangements named supercomplexes (SCs), which are believed to confer structural and functional advantages to mitochondria. SCs have been identified in many species, from yeast to mammal, and an increasing number of studies report disruption of their organization in genetic and acquired human diseases. As a result, an increasing number of laboratories are interested in analyzing SCs, which can be methodologically challenging. This article presents an optimized protocol that combines the advantages of Blue- and Clear-Native PAGE methods to resolve and analyze SCs in a time-effective manner. With this hybrid CN/BN-PAGE method, mitochondrial SCs extracted with optimal amounts of the mild detergent digitonin are exposed briefly to the anionic dye Coomassie Blue (CB) at the beginning of the electrophoresis, without exposure to other detergents. This short exposure to CB allows to separate and resolve SCs as effectively as with traditional BN-PAGE methods, while avoiding the negative impact of high CB levels on in-gel activity assays, and labile protein-protein interactions within SCs. With this protocol it is thus possible to combine precise and rapid in gel activity measurements with analytical techniques involving 2D electrophoresis, immuno-detection, and/or proteomics for advanced analysis of SCs.
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http://dx.doi.org/10.3791/59294DOI Listing
May 2019

A Mitochondrial Health Index Sensitive to Mood and Caregiving Stress.

Biol Psychiatry 2018 07 3;84(1):9-17. Epub 2018 Feb 3.

Department of Psychiatry, University of California-San Francisco, San Francisco, California.

Background: Chronic life stress, such as the stress of caregiving, can promote pathophysiology, but the underlying cellular mechanisms are not well understood. Chronic stress may induce recalibrations in mitochondria leading to changes either in mitochondrial content per cell, or in mitochondrial functional capacity (i.e., quality).

Methods: Here we present a functional index of mitochondrial health (MHI) for human leukocytes that can distinguish between these two possibilities. The MHI integrates nuclear and mitochondrial DNA-encoded respiratory chain enzymatic activities and mitochondrial DNA copy number. We then use the MHI to test the hypothesis that daily emotional states and caregiving stress influence mitochondrial function by comparing healthy mothers of a child with an autism spectrum disorder (high-stress caregivers, n = 46) with mothers of a neurotypical child (control group, n = 45).

Results: The MHI outperformed individual mitochondrial function measures. Elevated positive mood at night was associated with higher MHI, and nightly positive mood was also a mediator of the association between caregiving and MHI. Moreover, MHI was correlated to positive mood on the days preceding, but not following the blood draw, suggesting for the first time in humans that mitochondria may respond to proximate emotional states within days. Correspondingly, the caregiver group, which had higher perceived stress and lower positive and greater negative daily affect, exhibited lower MHI. This effect was not explained by a mismatch between nuclear and mitochondrial genomes.

Conclusions: Daily mood and chronic caregiving stress are associated with mitochondrial functional capacity. Mitochondrial health may represent a nexus between psychological stress and health.
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http://dx.doi.org/10.1016/j.biopsych.2018.01.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6014908PMC
July 2018

Mitochondrial Oxidative Stress Reduces the Immunopotency of Mesenchymal Stromal Cells in Adults With Coronary Artery Disease.

Circ Res 2018 01 7;122(2):255-266. Epub 2017 Nov 7.

From the Department of Anatomy and Cell Biology (O.K.M.), Department of Physiology (U.S.), Divisions of Cardiac Surgery and Surgical Research, Department of Surgery (D.S.T.), Division of Rheumatology, Department of Medicine (I.C., M.L.) McGill University, Montreal, Quebec, Canada; Shriners Hospital for Children (R.H.); Department of Cellular and Molecular Medicine, Faculty of Medicine (A.C., Y.B.), University of Ottawa, Ontario, Canada; and Faculty of Pharmacy (M.J.S.), University of Montreal, Quebec, Canada.

Rationale: Mesenchymal stromal cells (MSCs) are promising therapeutic strategies for coronary artery disease; however, donor-related variability in cell quality is a main cause of discrepancies in preclinical studies. In vitro, MSCs from individuals with coronary artery disease have reduced ability to suppress activated T-cells. The mechanisms underlying the altered immunomodulatory capacity of MSCs in the context of atherosclerosis remain elusive.

Objective: The aim of this study was to assess the role of mitochondrial dysfunction in the impaired immunomodulatory properties of MSCs from patients with atherosclerosis.

Methods And Results: Adipose tissue-derived MSCs were isolated from atherosclerotic (n=38) and nonatherosclerotic (n=42) donors. MSCs:CD4T-cell suppression was assessed in allogeneic coculture systems. Compared with nonatherosclerotic-MSCs, atherosclerotic-MSCs displayed higher levels of both intracellular (=0.006) and mitochondrial (=0.03) reactive oxygen species reflecting altered mitochondrial function. The increased mitochondrial reactive oxygen species levels of atherosclerotic-MSCs promoted a phenotypic switch characterized by enhanced glycolysis and an altered cytokine secretion (interleukin-6 <0.0001, interleukin-8/C-X-C motif chemokine ligand 8 =0.04, and monocyte chemoattractant protein-1/chemokine ligand 2 =0.01). Furthermore, treatment of atherosclerotic-MSCs with the reactive oxygen species scavenger N-acetyl-l-cysteine reduced the levels of interleukin-6, interleukin-8/C-X-C motif chemokine ligand 8, and monocyte chemoattractant protein-1/chemokine ligand 2 in the MSC secretome and improved MSCs immunosuppressive capacity (=0.03).

Conclusions: An impaired mitochondrial function of atherosclerotic-MSCs underlies their altered secretome and reduced immunopotency. Interventions aimed at restoring the mitochondrial function of atherosclerotic-MSCs improve their in vitro immunosuppressive ability and may translate into enhanced therapeutic efficiency.
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http://dx.doi.org/10.1161/CIRCRESAHA.117.311400DOI Listing
January 2018

Loss of hepatic LRPPRC alters mitochondrial bioenergetics, regulation of permeability transition and trans-membrane ROS diffusion.

Hum Mol Genet 2017 08;26(16):3186-3201

Faculty of Pharmacy, University of Montreal, Montreal, QC H3C 3J7, Canada.

The French-Canadian variant of Leigh Syndrome (LSFC) is an autosomal recessive oxidative phosphorylation (OXPHOS) disorder caused by a mutation in LRPPRC, coding for a protein involved in the stability of mitochondrially-encoded mRNAs. Low levels of LRPPRC are present in all patient tissues, but result in a disproportionately severe OXPHOS defect in the brain and liver, leading to unpredictable subacute metabolic crises. To investigate the impact of the OXPHOS defect in the liver, we analyzed the mitochondrial phenotype in mice harboring an hepatocyte-specific inactivation of Lrpprc. Loss of LRPPRC in the liver caused a generalized growth delay, and typical histological features of mitochondrial hepatopathy. At the molecular level, LRPPRC deficiency caused destabilization of polyadenylated mitochondrial mRNAs, altered mitochondrial ultrastructure, and a severe complex IV (CIV) and ATP synthase (CV) assembly defect. The impact of LRPPRC deficiency was not limited to OXPHOS, but also included impairment of long-chain fatty acid oxidation, a striking dysregulation of the mitochondrial permeability transition pore, and an unsuspected alteration of trans-membrane H2O2 diffusion, which was traced to the ATP synthase assembly defect, and to changes in the lipid composition of mitochondrial membranes. This study underscores the value of mitochondria phenotyping to uncover complex and unexpected mechanisms contributing to the pathophysiology of mitochondrial disorders.
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http://dx.doi.org/10.1093/hmg/ddx202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5886084PMC
August 2017

Formation of mitochondrial-derived vesicles is an active and physiologically relevant mitochondrial quality control process in the cardiac system.

J Physiol 2016 09 24;594(18):5343-62. Epub 2016 Jul 24.

Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada.

Key Points: Mitochondrial-derived vesicle (MDV) formation occurs under baseline conditions and is rapidly upregulated in response to stress-inducing conditions in H9c2 cardiac myoblasts. In mice formation of MDVs occurs readily in the heart under normal healthy conditions while mitophagy is comparatively less prevalent. In response to acute stress induced by doxorubicin, mitochondrial dysfunction develops in the heart, triggering MDV formation and mitophagy. MDV formation is thus active in the cardiac system, where it probably constitutes a baseline housekeeping mechanism and a first line of defence against stress.

Abstract: The formation of mitochondrial-derived vesicles (MDVs), a process inherited from bacteria, has emerged as a potentially important mitochondrial quality control (QC) mechanism to selectively deliver damaged material to lysosomes for degradation. However, the existence of this mechanism in various cell types, and its physiological relevance, remains unknown. Our aim was to investigate the dynamics of MDV formation in the cardiac system in vitro and in vivo. Immunofluorescence in cell culture, quantitative transmission electron microscopy and electron tomography in vivo were used to study MDV production in the cardiac system. We show that in cardiac cells MDV production occurs at baseline, is commensurate with the dependence of cells on oxidative metabolism, is more frequent than mitophagy and is up-regulated on the time scale of minutes to hours in response to prototypical mitochondrial stressors (antimycin-A, xanthine/xanthine oxidase). We further show that MDV production is up-regulated together with mitophagy in response to doxorubicin-induced mitochondrial and cardiac dysfunction. Here we provide the first quantitative data demonstrating that MDV formation is a mitochondrial QC operating in the heart.
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http://dx.doi.org/10.1113/JP272703DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5023710PMC
September 2016
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