Biology subjects

Bertrand, L.

Publications and source records attributed to Bertrand, L..

23 records · Page 2Linked to original sources

bioRxiv2021

Restore mitophagy is essential to prevent cardiac oxidative stress during hypertrophy

Heart failure, mostly associated with cardiac hypertrophy, is still a major cause of illness and death. Oxidative stress causes contractile failure and the accumulation of reactive oxygen species leads to mitochondrial dysfunction, associated with aging and heart failure, suggesting that mitochondria-targeted therapies could be effective in this context. The purpose of this work was to characterize how mitochondrial oxidative stress is involved in cardiac hypertrophy development and to determine if mitochondria-targeted therapies could improve cardiac phenotypes. We used neonatal and adult rat cardiomyocytes (NCMs and ACMs) hypertrophied by isoproterenol (Iso) to induce an increase of mitochondrial superoxide anion. Superoxide dismutase 2 activity and mitochondrial biogenesis were significantly decreased after 24h of Iso treatment. To counteract the mitochondrial oxidative stress induced by hypertrophy, we evaluated the impact of two different anti-oxidants, mitoquinone (MitoQ) and EUK 134. Both significantly decreased mitochondrial superoxide anion and hypertrophy in hypertrophied NCMs and ACMs. Conversely to EUK 134 which preserved cell functions, MitoQ impaired mitochondrial function by decreasing maximal mitochondrial respiration, mitochondrial membrane potential and mitophagy (particularly Parkin expression) and altering mitochondrial structure. The same decrease of Parkin was found in human cardiomyocytes but not in fibroblasts suggesting a cell specificity deleterious effect of MitoQ. Our data showed the importance of mitochondrial oxidative stress in the development of cardiomyocyte hypertrophy. Interestingly, we observed that targeting mitochondria by an anti-oxidant (MitoQ) impaired metabolism specifically in cardiomyocytes. Conversely, the SOD mimic (EUK 134) decreased both oxidative stress and cardiomyocyte hypertrophy and restored impaired cardiomyocyte metabolism and mitochondrial biogenesis.

cell biology↗

bioRxiv2020

Presenilin-deficient neurons and astrocytes display normal mitochondrial phenotypes

Presenilins 1 and 2 (PS1 and PS2) are predominantly known as the catalytic subunits of the {gamma}-secretase complex which generates the amyloid-{beta} (A{beta}) peptide, the major constituent of the senile plaques found in the brain of Alzheimers disease (AD) patients. Apart from their role in {gamma}-secretase activity, a growing number of cellular functions have been recently attributed to PSs. They are involved in synaptic transmission, endo-lysosomal function and calcium homeostasis. PSs were also found to be enriched in mitochondria-associated membranes (MAMs) where mitochondria and endoplasmic reticulum (ER) interact. PS2 was more specifically reported to regulate calcium shuttling between the ER and mitochondria by controlling the formation of functional MAMs through its interaction with the Mitofusin2 protein. We have previously demonstrated that the absence of PS2 (PS2KO) alters mitochondrial morphology and function. Indeed, a PS2KO cell line showed reduced mitochondrial respiration along with disrupted mitochondrial cristae and increased glycolysis. This phenotype is restored by the stable re-expression of human PS2. Still, all these results were obtained in immortalized Mouse Embryonic Fibroblasts (MEF) and one bottom-line question is to know whether these observations hold true for the Central Nervous System (CNS) cells, and in particular neurons and astrocytes. To that end, we carried out primary PS1KO, PS2KO and PS1/PS2KO (PSdKO) neuronal and astrocyte cultures. All the conditions were obtained in the same litter by crossing PS2 heterozygous and PS1 floxed (PS2+/-; PS1flox/flox) animals. Indeed, contrary to PS2KO mice, PS1KO are not viable and therefore require the use of the Cre-LoxP system to achieve gene deletion in vitro. Strikingly, we did not observe any mitochondrial phenotype in PS1KO, PS2KO or PSdKO primary cultures. Mitochondrial respiration and membrane potential were similar in all models, as were the glycolytic flux and NAD+/NADH ratio. We further investigated the discrepancies between these results and the ones previously reported in the MEF PS2KO cell line by analyzing PS2KO primary fibroblasts. No mitochondrial dysfunction was observed in this model, in line with observations in PS2KO primary neurons and astrocytes. These results indicate that the mitochondrial phenotype observed in immortalized PS2-deficient cell lines cannot be extrapolated to primary neurons, astrocytes and even to primary fibroblasts. The PS-dependent mitochondrial phenotype reported so far might be the consequence of a cell immortalization process and, therefore, should be critically reconsidered regarding its relevance to AD.

neuroscience↗

bioRxiv2020

Beta-3 Adrenoreceptors protect from hypertrophic remodelling through AMP-Activated Protein Kinase and Autophagy.

AimsThe abundance of beta3-adrenergic receptors ({beta}3-ARs) is upregulated in diseased human myocardium. We previously showed that cardiac-specific expression of {beta}3-AR inhibits the hypertrophic response to neurohormonal stimulation. Here, we further analyzed signalling pathways involved in the anti-hypertrophic effect of {beta}3-AR. MethodsIn vitro hypertrophic responses to phenylephrine (PE) were analyzed in neonatal rat ventricular myocytes (NRVM) infected with a recombinant adenovirus expressing the human {beta}3-AR (AdVh{beta}3). We confirmed results in mice with cardiomyocyte-specific moderate expression of human {beta}3-AR ({beta}3-TG) and WT littermates submitted to thoracic transverse aortic constriction (TAC) for 9 weeks. ResultsWe observed a colocalization of {beta}3-AR with the AMP-activated protein kinase (AMPK) both in neonatal rat andin adult mouse cardiomyocytes. Treatment of NRVM with PE induced hypertrophy and a decrease in phosphorylation of Thr172-AMPK (/2, p=0.0487) and phosphorylation of Ser79- acetyl-CoA carboxylase (ACC) (/2.6, p=0.0317), inducing an increase in phosphorylated Ser235/236 S6 protein (x2.5, p=0.0367) known to be involved in protein synthesis. These effects were reproduced by TAC in WT mice, but restored to basal levels in {beta}3-AR expressing cells/mice. siRNA targeting of AMPK partly abrogated the anti-hypertrophic effect of {beta}3-AR in response to PE in NRVM (x1.3, p<0.0001). Concomitant with hypertrophy, autophagy measured by microtubule-associated protein 1 light chain 3 (LC3)-II/LC3-I ratio and p62 abundance was decreased by PE in NRVM (/2.6, p=0.0010 and x3, p=0.0016, respectively) or TAC in WT mice (/5.4, p=0.0159); and preserved in human {beta}3-AR expressing cells and mice, together with reduced hypertrophy. ConclusionsCardiac-specific moderate expression of {beta}3-AR inhibits the hypertrophic response in part through AMPK activation followed byinhibition of protein synthesis and preservation of autophagy. Activation of the cardiac {beta}3-AR pathway may provide future therapeutic avenues for the modulation of hypertrophic remodelling.

cell biology↗

bioRxiv2019

Different salicylic and jasmonic acids imbalances are involved in the oxidative stress-mediated cell death, induced by fumonisin B1 in maize seedlings with contrasting resistance to Fusarium verticillioides ear rot in the field.

Background and aimFungal and plant secondary metabolites modulate the plant-pathogen interactions. However, the participation of fumonisins in the Fusarium verticillioides-maize pathosystem is unclear. In this work was studied the cell death, and the reactive oxygen species (ROS) - phytohormone imbalance interplay underlying the phytotoxicity of fumonisin B1 (FB1) in maize germplasms with contrasting resistance to Fusarium ear rot in the field. MethodsResistant (RH) and susceptible hybrid (SH) maize seedlings, grown from uninoculated seeds irrigated with FB1 (1 and 20 ppm), were harvested at 7, 14 and 21 days after planting, and were examined for electrolyte leakage (aerial parts); and for oxidative stress biomarkers (aerial parts and roots). The phytohormone (salicylic and jasmonic acids) imbalance interplay underlying the FB1-induced cell death were further explored in seedlings exposed 24 h to the mycotoxin (1 ppm) in hydroponics. ResultsCell death increased in RH and SH watered with 1 and 20 ppm of mycotoxin, respectively. Both toxin concentrations were pro-oxidant, and the major perturbations were found in roots. An Integrated Biomarker Response index was calculated suggesting that phytotoxicity occurs in a redox context more efficiently controlled by RH. ConclusionThe pre-treatment with the antioxidant ascorbic acid led to the conclusion that cell death in RH was related to a salicylic acid increase mediated by ROS. Nevertheless, FB1 induced two different phytohormonal regulatory mechanisms mediated by oxidative stress in both maize hybrids.

plant biology↗

bioRxiv2019

Proteolysis and neurogenesis modulated by LNR domain proteins explosion support male differentiation and sacrificial behaviour in the iteroparous crustacean Oithona nana.

Copepods are the most numerous animals and play an essential role in the marine trophic web and biogeochemical cycles. The genus Oithona is described as having the highest numerical density, as the most cosmopolite copepod and iteroparous. The Oithona male paradox obliges it to alternate feeding (immobile) and mating (mobile) phases. As the molecular basis of this trade-off is unknown, we investigated this sexual dimorphism at the molecular level by integrating genomic, transcriptomic and protein-protein interaction analyses.\n\nWhile a ZW sex-determination system was predicted in O. nana, a fifteen-year time-series in the Toulon Little Bay showed a biased sex ratio toward females (male / female ratio < 0.15{+/-}0.11) highlighting a higher mortality in male. Here, the transcriptomic analysis of the five different developmental stages showed enrichment of Lin12-Notch Repeat (LNR) domains-containing proteins coding genes (LDPGs) in male transcripts. The male also showed enrichment in transcripts involved in proteolysis, nervous system development, synapse assembly and functioning and also amino acid conversion to glutamate. Moreover, several male down-regulated genes were involved in the increase of food uptake and digestion. The formation of LDP complexes was detected by yeast two-hybrid, with interactions involving proteases, extracellular matrix proteins and neurogenesis related proteins.\n\nTogether, these results suggest that the O. nana male hypermotility is sustained by LDP-modulated proteolysis allowing the releases and conversions of amino acid into the excitatory neurotransmitter glutamate. This process could permit new axons and dendrites formation suggesting a sexual nervous system dimorphism. This could support the hypothesis of a sacrificial behaviour in males at the metabolic level.

molecular biology↗