Publications by authors named "Feliciano Protasi"

93 Publications

Altered Ca Handling and Oxidative Stress Underlie Mitochondrial Damage and Skeletal Muscle Dysfunction in Aging and Disease.

Metabolites 2021 Jun 28;11(7). Epub 2021 Jun 28.

Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA.

Skeletal muscle contraction relies on both high-fidelity calcium (Ca) signals and robust capacity for adenosine triphosphate (ATP) generation. Ca release units (CRUs) are highly organized junctions between the terminal cisternae of the sarcoplasmic reticulum (SR) and the transverse tubule (T-tubule). CRUs provide the structural framework for rapid elevations in myoplasmic Ca during excitation-contraction (EC) coupling, the process whereby depolarization of the T-tubule membrane triggers SR Ca release through ryanodine receptor-1 (RyR1) channels. Under conditions of local or global depletion of SR Ca stores, store-operated Ca entry (SOCE) provides an additional source of Ca that originates from the extracellular space. In addition to Ca, skeletal muscle also requires ATP to both produce force and to replenish SR Ca stores. Mitochondria are the principal intracellular organelles responsible for ATP production via aerobic respiration. This review provides a broad overview of the literature supporting a role for impaired Ca handling, dysfunctional Ca-dependent production of reactive oxygen/nitrogen species (ROS/RNS), and structural/functional alterations in CRUs and mitochondria in the loss of muscle mass, reduction in muscle contractility, and increase in muscle damage in sarcopenia and a wide range of muscle disorders including muscular dystrophy, rhabdomyolysis, central core disease, and disuse atrophy. Understanding the impact of these processes on normal muscle function will provide important insights into potential therapeutic targets designed to prevent or reverse muscle dysfunction during aging and disease.
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http://dx.doi.org/10.3390/metabo11070424DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8304741PMC
June 2021

Improper Remodeling of Organelles Deputed to Ca Handling and Aerobic ATP Production Underlies Muscle Dysfunction in Ageing.

Int J Mol Sci 2021 Jun 8;22(12). Epub 2021 Jun 8.

CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, I-66100 Chieti, Italy.

Proper skeletal muscle function is controlled by intracellular Ca concentration and by efficient production of energy (ATP), which, in turn, depend on: (a) the release and re-uptake of Ca from sarcoplasmic-reticulum (SR) during excitation-contraction (EC) coupling, which controls the contraction and relaxation of sarcomeres; (b) the uptake of Ca into the mitochondrial matrix, which stimulates aerobic ATP production; and finally (c) the entry of Ca from the extracellular space via store-operated Ca entry (SOCE), a mechanism that is important to limit/delay muscle fatigue. Abnormalities in Ca handling underlie many physio-pathological conditions, including dysfunction in ageing. The specific focus of this review is to discuss the importance of the proper architecture of organelles and membrane systems involved in the mechanisms introduced above for the correct skeletal muscle function. We reviewed the existing literature about EC coupling, mitochondrial Ca uptake, SOCE and about the structural membranes and organelles deputed to those functions and finally, we summarized the data collected in different, but complementary, projects studying changes caused by denervation and ageing to the structure and positioning of those organelles: a. denervation of muscle fibers-an event that contributes, to some degree, to muscle loss in ageing (known as sarcopenia)-causes misplacement and damage: (i) of membrane structures involved in EC coupling (calcium release units, CRUs) and (ii) of the mitochondrial network; b. sedentary ageing causes partial disarray/damage of CRUs and of calcium entry units (CEUs, structures involved in SOCE) and loss/misplacement of mitochondria; c. functional electrical stimulation (FES) and regular exercise promote the rescue/maintenance of the proper architecture of CRUs, CEUs, and of mitochondria in both denervation and ageing. All these structural changes were accompanied by related functional changes, i.e., loss/decay in function caused by denervation and ageing, and improved function following FES or exercise. These data suggest that the integrity and proper disposition of intracellular organelles deputed to Ca handling and aerobic generation of ATP is challenged by inactivity (or reduced activity); modifications in the architecture of these intracellular membrane systems may contribute to muscle dysfunction in ageing and sarcopenia.
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http://dx.doi.org/10.3390/ijms22126195DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8228829PMC
June 2021

Endothelial cells from umbilical cord of women affected by gestational diabetes: A suitable in vitro model to study mechanisms of early vascular senescence in diabetes.

FASEB J 2021 06;35(6):e21662

Department of Medical and Oral Sciences and Biotechnologies, University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy.

Human umbilical cord endothelial cells (HUVECs) obtained from women affected by gestational diabetes (GD-HUVECs) display durable pro-atherogenic modifications and might be considered a valid in vitro model for studying chronic hyperglycemia effects on early endothelial senescence. Here, we demonstrated that GD- compared to C-HUVECs (controls) exhibited oxidative stress, altered both mitochondrial membrane potential and antioxidant response, significant increase of senescent cells characterized by a reduced NAD-dependent deacetylase sirtuin-1 (SIRT1) activity together with an increase in cyclin-dependent kinase inhibitor-2A (P16), cyclin-dependent kinase inhibitor-1 (P21), and tumor protein p53 (P53) acetylation. This was associated with the p300 activation, and its silencing significantly reduced the GD-HUVECs increased protein levels of P300 and Ac-P53 thus indicating a persistent endothelial senescence via SIRT1/P300/P53/P21 pathway. Overall, our data suggest that GD-HUVECs can represent an "endothelial hyperglycemic memory" model to investigate in vitro the early endothelium senescence in cells chronically exposed to hyperglycemia in vivo.
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http://dx.doi.org/10.1096/fj.202002072RRDOI Listing
June 2021

Parvalbumin affects skeletal muscle trophism through modulation of mitochondrial calcium uptake.

Cell Rep 2021 May;35(5):109087

Department of Biomedical Sciences, University of Padua, Padua 35131, Italy; Myology Center, University of Padua, via G. Colombo 3, 35100 Padova, Italy. Electronic address:

Parvalbumin (PV) is a cytosolic Ca-binding protein highly expressed in fast skeletal muscle, contributing to an increased relaxation rate. Moreover, PV is an "atrogene" downregulated in most muscle atrophy conditions. Here, we exploit mice lacking PV to explore the link between the two PV functions. Surprisingly, PV ablation partially counteracts muscle loss after denervation. Furthermore, acute PV downregulation is accompanied by hypertrophy and upregulation by atrophy. PV ablation has a minor impact on sarcoplasmic reticulum but is associated with increased mitochondrial Ca uptake, mitochondrial size and number, and contacts with Ca release sites. Mitochondrial calcium uniporter (MCU) silencing abolishes the hypertrophic effect of PV ablation, suggesting that mitochondrial Ca uptake is required for hypertrophy. In turn, an increase of mitochondrial Ca is required to enhance expression of the pro-hypertrophy gene PGC-1α4, whose silencing blocks hypertrophy due to PV ablation. These results reveal how PV links cytosolic Ca control to mitochondrial adaptations, leading to muscle mass regulation.
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http://dx.doi.org/10.1016/j.celrep.2021.109087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8113653PMC
May 2021

A perspective analysis: microRNAs, glucose metabolism, and drug resistance in colon cancer stem cells.

Cancer Gene Ther 2021 Feb 1. Epub 2021 Feb 1.

Center for Advanced Studies and Technology (CAST), "G. d'Annunzio" University of Chieti-Pescara, Chieti, Italy.

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http://dx.doi.org/10.1038/s41417-021-00298-5DOI Listing
February 2021

Long-Term Exercise Reduces Formation of Tubular Aggregates and Promotes Maintenance of Ca Entry Units in Aged Muscle.

Front Physiol 2020 5;11:601057. Epub 2021 Jan 5.

Center for Advanced Studies and Technology (CAST), University G. d'Annunzio (Ud'A) of Chieti-Pescara, Chieti, Italy.

Tubular aggregates (TAs) in skeletal muscle fibers are unusual accumulation of sarcoplasmic reticulum (SR) tubes that are found in different disorders including TA myopathy (TAM). TAM is a muscular disease characterized by muscle pain, cramping, and weakness that has been recently linked to mutations in and STIM1 and ORAI1 are the two main proteins mediating store-operated Ca entry (SOCE), a mechanism activated by depletion of intracellular Ca stores (e.g., SR) that allows recovery of Ca from the extracellular space during repetitive muscle activity. We have recently shown that exercise triggers the formation of unique intracellular junctions between SR and transverse tubules named (CEUs). CEUs promote colocalization of STIM1 with ORAI1 and improve muscle function in presence of external Ca. TAs virtually identical to those of TAM patients are also found in fast-twitch fibers of aging male mice. Here, we used a combination of electron and confocal microscopy, Western blotting, and stimulation protocols (in presence or absence of external Ca) to evaluate the presence of TAs, STIM1-ORAI1 localization and expression and fatigue resistance of intact extensor digitorum longus (EDL) muscles in wild-type male adult (4-month-old) and aged (24-month-old) mice and in mice trained in wheel cages for 15 months (from 9 to 24 months of age). The results collected indicate that (i) aging causes STIM1 and ORAI1 to accumulate in TAs and (ii) long-term exercise significantly reduced formation of TAs. In addition, (iii) EDL muscles from aged mice exhibited a faster decay of contractile force than adult muscles, likely caused by their inability to refill intracellular Ca stores, and (iv) exercise in wheel cages restored the capability of aged EDL muscles to use external Ca by promoting maintenance of CEUs. In conclusion, exercise prevented improper accumulation of STIM1 and ORAI1 in TAs during aging, maintaining the capability of aged muscle to refill intracellular Ca stores SOCE.
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http://dx.doi.org/10.3389/fphys.2020.601057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7813885PMC
January 2021

Calcium entry units (CEUs): perspectives in skeletal muscle function and disease.

J Muscle Res Cell Motil 2020 Aug 18. Epub 2020 Aug 18.

CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy.

In the last decades the term Store-operated Ca entry (SOCE) has been used in the scientific literature to describe an ubiquitous cellular mechanism that allows recovery of calcium (Ca) from the extracellular space. SOCE is triggered by a reduction of Ca content (i.e. depletion) in intracellular stores, i.e. endoplasmic or sarcoplasmic reticulum (ER and SR). In skeletal muscle the mechanism is primarily mediated by a physical interaction between stromal interaction molecule-1 (STIM1), a Ca sensor located in the SR membrane, and ORAI1, a Ca-permeable channel of external membranes, located in transverse tubules (TTs), the invaginations of the plasma membrane (PM) deputed to propagation of action potentials. It is generally accepted that in skeletal muscle SOCE is important to limit muscle fatigue during repetitive stimulation. We recently discovered that exercise promotes the assembly of new intracellular junctions that contains colocalized STIM1 and ORAI1, and that the presence of these new junctions increases Ca entry via ORAI1, while improving fatigue resistance during repetitive stimulation. Based on these findings we named these new junctions Ca Entry Units (CEUs). CEUs are dynamic organelles that assemble during muscle activity and disassemble during recovery thanks to the plasticity of the SR (containing STIM1) and the elongation/retraction of TTs (bearing ORAI1). Interestingly, similar structures described as SR stacks were previously reported in different mouse models carrying mutations in proteins involved in Ca handling (calsequestrin-null mice; triadin and junctin null mice, etc.) or associated to microtubules (MAP6 knockout mice). Mutations in Stim1 and Orai1 (and calsequestrin-1) genes have been associated to tubular aggregate myopathy (TAM), a muscular disease characterized by: (a) muscle pain, cramping, or weakness that begins in childhood and worsens over time, and (b) the presence of large accumulations of ordered SR tubes (tubular aggregates, TAs) that do not contain myofibrils, mitochondria, nor TTs. Interestingly, TAs are also present in fast twitch muscle fibers of ageing mice. Several important issues remain un-answered: (a) the molecular mechanisms and signals that trigger the remodeling of membranes and the functional activation of SOCE during exercise are unclear; and (b) how dysfunctional SOCE and/or mutations in Stim1, Orai1 and calsequestrin (Casq1) genes lead to the formation of tubular aggregates (TAs) in aging and disease deserve investigation.
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http://dx.doi.org/10.1007/s10974-020-09586-3DOI Listing
August 2020

Pre-assembled Ca2+ entry units and constitutively active Ca2+ entry in skeletal muscle of calsequestrin-1 knockout mice.

J Gen Physiol 2020 10;152(10)

Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, NY.

Store-operated Ca2+ entry (SOCE) is a ubiquitous Ca2+ influx mechanism triggered by depletion of Ca2+ stores from the endoplasmic/sarcoplasmic reticulum (ER/SR). We recently reported that acute exercise in WT mice drives the formation of Ca2+ entry units (CEUs), intracellular junctions that contain STIM1 and Orai1, the two key proteins mediating SOCE. The presence of CEUs correlates with increased constitutive- and store-operated Ca2+ entry, as well as sustained Ca2+ release and force generation during repetitive stimulation. Skeletal muscle from mice lacking calsequestrin-1 (CASQ1-null), the primary Ca2+-binding protein in the lumen of SR terminal cisternae, exhibits significantly reduced total Ca2+ store content and marked SR Ca2+ depletion during high-frequency stimulation. Here, we report that CEUs are constitutively assembled in extensor digitorum longus (EDL) and flexor digitorum brevis (FDB) muscles of sedentary CASQ1-null mice. The higher density of CEUs in EDL (39.6 ± 2.1/100 µm2 versus 2.0 ± 0.3/100 µm2) and FDB (16.7 ± 1.0/100 µm2 versus 2.7 ± 0.5/100 µm2) muscles of CASQ1-null compared with WT mice correlated with enhanced constitutive- and store-operated Ca2+ entry and increased expression of STIM1, Orai1, and SERCA. The higher ability to recover Ca2+ ions via SOCE in CASQ1-null muscle served to promote enhanced maintenance of peak Ca2+ transient amplitude, increased dependence of luminal SR Ca2+ replenishment on BTP-2-sensitive SOCE, and increased maintenance of contractile force during repetitive, high-frequency stimulation. Together, these data suggest that muscles from CASQ1-null mice compensate for the lack of CASQ1 and reduction in total releasable SR Ca2+ content by assembling CEUs to promote constitutive and store-operated Ca2+ entry.
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http://dx.doi.org/10.1085/jgp.202012617DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7537346PMC
October 2020

Calsequestrin Deletion Facilitates Hippocampal Synaptic Plasticity and Spatial Learning in Post-Natal Development.

Int J Mol Sci 2020 07 31;21(15). Epub 2020 Jul 31.

Department of Biomolecular Sciences, Università di Urbino Carlo Bo, I-61029 Urbino, Italy.

Experimental evidence highlights the involvement of the endoplasmic reticulum (ER)-mediated Ca signals in modulating synaptic plasticity and spatial memory formation in the hippocampus. Ca release from the ER mainly occurs through two classes of Ca channels, inositol 1,4,5-trisphosphate receptors (InsP3Rs) and ryanodine receptors (RyRs). Calsequestrin (CASQ) and calreticulin (CR) are the most abundant Ca-binding proteins allowing ER Ca storage. The hippocampus is one of the brain regions expressing CASQ, but its role in neuronal activity, plasticity, and the learning processes is poorly investigated. Here, we used knockout mice lacking both CASQ type-1 and type-2 isoforms (double (d)CASQ-null mice) to: a) evaluate in adulthood the neuronal electrophysiological properties and synaptic plasticity in the hippocampal Cornu Ammonis 1 (CA1) field and b) study the performance of knockout mice in spatial learning tasks. The ablation of CASQ increased the CA1 neuron excitability and improved the long-term potentiation (LTP) maintenance. Consistently, (d)CASQ-null mice performed significantly better than controls in the Morris Water Maze task, needing a shorter time to develop a spatial preference for the goal. The Ca handling analysis in CA1 pyramidal cells showed a decrement of Ca transient amplitude in (d)CASQ-null mouse neurons, which is consistent with a decrease in afterhyperpolarization improving LTP. Altogether, our findings suggest that CASQ deletion affects activity-dependent ER Ca release, thus facilitating synaptic plasticity and spatial learning in post-natal development.
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http://dx.doi.org/10.3390/ijms21155473DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7432722PMC
July 2020

Transverse tubule remodeling enhances Orai1-dependent Ca entry in skeletal muscle.

Elife 2019 10 28;8. Epub 2019 Oct 28.

Center for Research on Ageing and Translational Medicine (CeSI-MeT), University Gabriele d'Annunzio, Chieti, Italy.

Exercise promotes the formation of intracellular junctions in skeletal muscle between stacks of sarcoplasmic reticulum (SR) cisternae and extensions of transverse-tubules (TT) that increase co-localization of proteins required for store-operated Ca entry (SOCE). Here, we report that SOCE, peak Ca transient amplitude and muscle force production during repetitive stimulation are increased after exercise in parallel with the time course of TT association with SR-stacks. Unexpectedly, exercise also activated constitutive Ca entry coincident with a modest decrease in total releasable Ca store content. Importantly, this decrease in releasable Ca store content observed after exercise was reversed by repetitive high-frequency stimulation, consistent with enhanced SOCE. The functional benefits of exercise on SOCE, constitutive Ca entry and muscle force production were lost in mice with muscle-specific loss of Orai1 function. These results indicate that TT association with SR-stacks enhances Orai1-dependent SOCE to optimize Ca dynamics and muscle contractile function during acute exercise.
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http://dx.doi.org/10.7554/eLife.47576DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6837846PMC
October 2019

Excessive Accumulation of Ca in Mitochondria of Y522S-RYR1 Knock-in Mice: A Link Between Leak From the Sarcoplasmic Reticulum and Altered Redox State.

Front Physiol 2019 13;10:1142. Epub 2019 Sep 13.

Department of Biomedical Sciences, School of Medicine and Surgery, University of Padova, Padua, Italy.

Mice (Y522S or YS), carrying a mutation of the sarcoplasmic reticulum (SR) Ca release channel of skeletal muscle fibers (ryanodine receptor type-1, RyR1) which causes Ca leak, are a widely accepted and intensively studied model for human malignant hyperthermia (MH) susceptibility. Since the involvement of reactive oxygen species (ROS) and of mitochondria in MH crisis has been previously debated, here we sought to determine Ca uptake in mitochondria and its possible link with ROS production in single fibers isolated from flexor digitorum brevis (FDB) of YS mice. We found that Ca concentration in the mitochondrial matrix, as detected with the ratiometric FRET-based 4mtD3cpv probe, was higher in YS than in wild-type (WT) fibers at rest and after Ca release from SR during repetitive electrical stimulation or caffeine administration. Also mitochondrial ROS production associated with contractile activity (detected with Mitosox probe) was much higher in YS fibers than in WT. Importantly, the inhibition of mitochondrial Ca uptake achieved by silencing MCU reduced ROS accumulation in the matrix and Ca release from SR. Finally, inhibition of mitochondrial ROS accumulation using Mitotempo reduced SR Ca release in YS fibers exposed to caffeine. The present results support the view that mitochondria take up larger amounts of Ca in YS than in WT fibers and that mitochondrial ROS production substantially contributes to the increased caffeine-sensitivity and to the enhanced Ca release from SR in YS fibers.
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http://dx.doi.org/10.3389/fphys.2019.01142DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6755340PMC
September 2019

Functional Electrical Stimulation: A Possible Strategy to Improve Muscle Function in Central Core Disease?

Front Neurol 2019 29;10:479. Epub 2019 May 29.

CeSI-Met-Center for Research on Ageing and Translational Medicine, University G. d'Annunzio, Chieti, Italy.

Central Core Disease (CCD) is a congenital myopathy characterized by presence of amorphous central areas (or ) lacking glycolytic/oxidative enzymes and mitochondria in skeletal muscle fibers. Most CCD families are linked to mutations in ryanodine receptor type-1 (RYR1), the gene encoding for the sarcoplasmic reticulum (SR) Ca release channel of skeletal muscle. As no treatments are available for CCD, currently management of patients is essentially based on a physiotherapic approaches. Functional electrical stimulation (FES) is a technique used to deliver low energy electrical impulses to artificially stimulate selected skeletal muscle groups. Here we tested the efficacy of FES in counteracting muscle loss and improve function in the lower extremities of a 55-year-old female patient which was diagnosed with CCD at the age of 44. Genetic screening of the RyR1 gene identified a missense mutation (c.7354C>T) in exon 46 resulting in an amino acid substitution (p.R2452W) and a duplication (c.12853_12864dup12) in exon 91. The patient was treated with FES for 26 months and subjected before, during, and after training to a series of functional and structural assessments: measurement of maximum isometric force of leg extensor muscles, magnetic resonance imaging, a complete set of functional tests to assess mobility in activities of daily living, and analysis of muscle biopsies by histology and electron microscopy. All results point to an improvement in muscle structure and function induced by FES suggesting that this approach could be considered as an additional supportive measure to maintain/improve muscle function (and possibly reduce muscle loss) in CCD patients.
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http://dx.doi.org/10.3389/fneur.2019.00479DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6548841PMC
May 2019

DRP1-mediated mitochondrial shape controls calcium homeostasis and muscle mass.

Nat Commun 2019 06 12;10(1):2576. Epub 2019 Jun 12.

Venetian Institute of Molecular Medicine, via Orus 2, 35129, Padova, Italy.

Mitochondrial quality control is essential in highly structured cells such as neurons and muscles. In skeletal muscle the mitochondrial fission proteins are reduced in different physiopathological conditions including ageing sarcopenia, cancer cachexia and chemotherapy-induced muscle wasting. However, whether mitochondrial fission is essential for muscle homeostasis is still unclear. Here we show that muscle-specific loss of the pro-fission dynamin related protein (DRP) 1 induces muscle wasting and weakness. Constitutive Drp1 ablation in muscles reduces growth and causes animal death while inducible deletion results in atrophy and degeneration. Drp1 deficient mitochondria are morphologically bigger and functionally abnormal. The dysfunctional mitochondria signals to the nucleus to induce the ubiquitin-proteasome system and an Unfolded Protein Response while the change of mitochondrial volume results in an increase of mitochondrial Ca uptake and myofiber death. Our findings reveal that morphology of mitochondrial network is critical for several biological processes that control nuclear programs and Ca handling.
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http://dx.doi.org/10.1038/s41467-019-10226-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6561930PMC
June 2019

Muscle activity prevents the uncoupling of mitochondria from Ca Release Units induced by ageing and disuse.

Arch Biochem Biophys 2019 03 20;663:22-33. Epub 2018 Dec 20.

CeSI-Met - Center for Research on Ageing and Translational Medicine and DNICS - Dept. of Neuroscience, Imaging and Clinical Sciences, University G. d' Annunzio, I-66100, Italy. Electronic address:

In fast-twitch fibers from adult mice Ca release units (CRUs, i.e. intracellular junctions of excitation-contraction coupling), and mitochondria are structurally linked to each other by small strands, named tethers. We recently showed that aging causes separation of a fraction of mitochondria from CRUs and a consequent impairment of the Ca signaling between the two organelles. However, whether the uncoupling of mitochondria from CRUs is the result of aging per-se or the consequence of reduced muscle activity remains still unclear. Here we studied the association between mitochondria and CRUs: in a) extensor digitorum longus (EDL) muscles from 2 years old mice, either sedentary or trained for 1 year in wheel cages; and b) denervated EDL muscles from adult mice and rats. We analyzed muscle samples using a combination of structural (confocal and electron microscopy), biochemical (assessment of oxidative stress via western blot), and functional (ex-vivo contractile properties, and mitochondrial Ca uptake) experimental procedures. The results collected in structural studies indicate that: a) ageing and denervation result in partial uncoupling between mitochondria and CRUs; b) exercise either maintains (in old mice) or restores (in transiently denervated rats) the association between the two organelles. Functional studies supported the hypothesis that CRU-mitochondria coupling is important for mitochondrial Ca uptake, optimal force generation, and muscle performance. Taken together our results indicate that muscle activity maintains/improves proper association between CRUs and mitochondria.
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http://dx.doi.org/10.1016/j.abb.2018.12.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6377823PMC
March 2019

Addendum: Exercise-dependent formation of new junctions that promote STIM1-Orai1 assembly in skeletal muscle.

Sci Rep 2018 11 27;8(1):17463. Epub 2018 Nov 27.

CeSI-Met - Center for Research on Ageing and Translational Medicine, University G. d'Annunzio, Chieti, I-66100, Italy.

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http://dx.doi.org/10.1038/s41598-018-33063-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6258685PMC
November 2018

Lipin1 deficiency causes sarcoplasmic reticulum stress and chaperone-responsive myopathy.

EMBO J 2019 01 12;38(1). Epub 2018 Nov 12.

Institut Necker-Enfants Malades, Paris, France

As a consequence of impaired glucose or fatty acid metabolism, bioenergetic stress in skeletal muscles may trigger myopathy and rhabdomyolysis. Genetic mutations causing loss of function of the LPIN1 gene frequently lead to severe rhabdomyolysis bouts in children, though the metabolic alterations and possible therapeutic interventions remain elusive. Here, we show that lipin1 deficiency in mouse skeletal muscles is sufficient to trigger myopathy. Strikingly, muscle fibers display strong accumulation of both neutral and phospholipids. The metabolic lipid imbalance can be traced to an altered fatty acid synthesis and fatty acid oxidation, accompanied by a defect in acyl chain elongation and desaturation. As an underlying cause, we reveal a severe sarcoplasmic reticulum (SR) stress, leading to the activation of the lipogenic SREBP1c/SREBP2 factors, the accumulation of the Fgf21 cytokine, and alterations of SR-mitochondria morphology. Importantly, pharmacological treatments with the chaperone TUDCA and the fatty acid oxidation activator bezafibrate improve muscle histology and strength of lipin1 mutants. Our data reveal that SR stress and alterations in SR-mitochondria contacts are contributing factors and potential intervention targets of the myopathy associated with lipin1 deficiency.
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http://dx.doi.org/10.15252/embj.201899576DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6315296PMC
January 2019

PERK inhibition attenuates the abnormalities of the secretory pathway and the increased apoptotic rate induced by SIL1 knockdown in HeLa cells.

Biochim Biophys Acta Mol Basis Dis 2018 10 7;1864(10):3164-3180. Epub 2018 Jul 7.

Department of Medical, Oral and Biotechnological Sciences, University G. d'Annunzio, Chieti 66100, Italy; CeSI-MeT, Centre for Research on Ageing and Translational Medicine, University G. d'Annunzio, Chieti 66100, Italy. Electronic address:

Loss-of-function mutations in the SIL1 gene are linked to Marinesco-Sjögren syndrome (MSS), a rare multisystem disease of infancy characterized by cerebellar and skeletal muscle degeneration. SIL1 is a ubiquitous adenine nucleotide exchange factor for the endoplasmic reticulum (ER) chaperone BiP. The complexity of mechanisms by which loss of SIL1 causes MSS is not yet fully understood. We used HeLa cells to test the hypothesis that impaired protein folding in the ER due to loss of SIL1 could affect secretory trafficking, impairing the transport of cargoes essential for the function of MSS vulnerable cells. Immunofluorescence and ultrastructural analysis of SIL1-knocked-down cells detected ER chaperone aggregation, enlargement of the Golgi complex, increased autophagic vacuoles, and mitochondrial swelling. SIL1-interefered cells also had delayed ER-to-plasma membrane transport with retention of Na/K-ATPase and procollagen-I in the ER and Golgi, and increased apoptosis. The PERK pathway of the unfolded protein response was activated in SIL1-interfered cells, and the PERK inhibitor GSK2606414 attenuated the morphological and functional alterations of the secretory pathway, and significantly reduced cell death. These results indicate that loss of SIL1 is associated with alterations of secretory transport, and suggest that inhibiting PERK signalling may alleviate the cellular pathology of SIL1-related MSS.
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http://dx.doi.org/10.1016/j.bbadis.2018.07.003DOI Listing
October 2018

A 3D diffusional-compartmental model of the calcium dynamics in cytosol, sarcoplasmic reticulum and mitochondria of murine skeletal muscle fibers.

PLoS One 2018 26;13(7):e0201050. Epub 2018 Jul 26.

Department of Biomedical Sciences, University of Padova, Padova, Italy.

Variations of free calcium concentration ([Ca2+]) are powerful intracellular signals, controlling contraction as well as metabolism in muscle cells. To fully understand the role of calcium redistribution upon excitation and contraction in skeletal muscle cells, the local [Ca2+] in different compartments needs to be taken into consideration. Fluorescent probes allow the determination of [Ca2+] in the cytosol where myofibrils are embedded, the lumen of the sarcoplasmic reticulum (SR) and the mitochondrial matrix. Previously, models have been developed describing intracellular calcium handling in skeletal and cardiac muscle cells. However, a comprehensive model describing the kinetics of the changes in free calcium concentration in these three compartments is lacking. We designed a new 3D compartmental model of the half sarcomere with radial symmetry, which accounts for diffusion of Ca2+ into the three compartments and simulates its dynamics at rest and at various rates of stimulation in mice skeletal muscle fibers. This model satisfactorily reproduces both the amplitude and time course of the variations of [Ca2+] in the three compartments in mouse fast fibers. As an illustration of the applicability of the model, we investigated the effects of Calsequestrin (CSQ) ablation. CSQ is the main Ca2+ buffer in the SR, localized in close proximity of its calcium release sites and near to the mitochondria. CSQ knock-out mice muscles still preserve a near-normal contractile behavior, but it is unclear whether this is caused by additional SR calcium buffering or a significant contribution of calcium entry from extracellular space, via stored-operated calcium entry (SOCE). The model enabled quantitative assessment of these two scenarios by comparison to measurements of local calcium in the cytosol, the SR and the mitochondria. In conclusion, the model represents a useful tool to investigate the impact of protein ablation and of pharmacological interventions on intracellular calcium dynamics in mice skeletal muscle.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0201050PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6062086PMC
January 2019

Aerobic Training Prevents Heatstrokes in Calsequestrin-1 Knockout Mice by Reducing Oxidative Stress.

Oxid Med Cell Longev 2018 3;2018:4652480. Epub 2018 Apr 3.

Center for Research on Ageing and Translational Medicine (CeSI-MeT), University G. d'Annunzio, 66100 Chieti, Italy.

Calsequestrin-1 knockout (CASQ1-null) mice suffer lethal episodes when exposed to strenuous exercise and environmental heat, crises known as exertional/environmental heatstroke (EHS). We previously demonstrated that administration of exogenous antioxidants (-acetylcysteine and trolox) reduces CASQ1-null mortality during exposure to heat. As aerobic training is known to boost endogenous antioxidant protection, we subjected CASQ1-null mice to treadmill running for 2 months at 60% of their maximal speed for 1 h, 5 times/week. When exposed to heat stress protocol (41°C/1 h), the mortality rate of CASQ1-null mice was significantly reduced compared to untrained animals (86% versus 16%). Protection from heatstrokes was accompanied by a reduced increase in core temperature during the stress protocol and by an increased threshold of response to caffeine of isolated muscles during contracture test. At cellular and molecular levels, aerobic training (i) improved mitochondrial function while reducing their damage and (ii) lowered calpain activity and lipid peroxidation in membranes isolated from sarcoplasmic reticulum and mitochondria. Based on this evidence, we hypothesize that the protective effect of aerobic training is essentially mediated by a reduction in oxidative stress during exposure of CASQ1-null mice to adverse environmental conditions.
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http://dx.doi.org/10.1155/2018/4652480DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5903204PMC
October 2018

Mechanical parameters of the molecular motor myosin II determined in permeabilised fibres from slow and fast skeletal muscles of the rabbit.

J Physiol 2018 04 17;596(7):1243-1257. Epub 2018 Jan 17.

PhysioLab, Department of Biology, University of Florence, Florence, Italy.

Key Points: The different performance of slow and fast muscles is mainly attributed to diversity of the myosin heavy chain (MHC) isoform expressed within them. In this study fast sarcomere-level mechanics has been applied to Ca -activated single permeabilised fibres isolated from soleus (containing the slow myosin isoform) and psoas (containing the fast myosin isoform) muscles of rabbit for a comparative definition of the mechano-kinetics of force generation by slow and fast myosin isoforms in situ. The stiffness and the force of the slow myosin isoform are three times smaller than those of the fast isoform, suggesting that the stiffness of the myosin motor is a determinant of the isoform-dependent functional diversity between skeletal muscles. These results open the question of the mechanism that can reconcile the reduced performance of the slow MHC with the higher efficiency of the slow muscle.

Abstract: The skeletal muscle exhibits large functional differences depending on the myosin heavy chain (MHC) isoform expressed in its molecular motor, myosin II. The differences in the mechanical features of force generation by myosin isoforms were investigated in situ by using fast sarcomere-level mechanical methods in permeabilised fibres (sarcomere length 2.4 μm, temperature 12°C, 4% dextran T-500) from slow (soleus, containing the MHC-1 isoform) and fast (psoas, containing the MHC-2X isoform) skeletal muscle of the rabbit. The stiffness of the half-sarcomere was determined at the plateau of Ca -activated isometric contractions and in rigor and analysed with a model that accounted for the filament compliance to estimate the stiffness of the myosin motor (ε). ε was 0.56 ± 0.04 and 1.70 ± 0.37 pN nm for the slow and fast isoform, respectively, while the average strain per attached motor (s ) was similar (∼3.3 nm) in both isoforms. Consequently the force per motor (F  = εs ) was three times smaller in the slow isoform than in the fast isoform (1.89 ± 0.43 versus 5.35 ± 1.51 pN). The fraction of actin-attached motors responsible for maximum isometric force at saturating Ca (T ) was 0.47 ± 0.09 in soleus fibres, 70% larger than that in psoas fibres (0.29 ± 0.08), so that F in slow fibres was decreased by only 53%. The lower stiffness and force of the slow myosin isoform open the question of the molecular basis of the higher efficiency of slow muscle with respect to fast muscle.
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http://dx.doi.org/10.1113/JP275404DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5878222PMC
April 2018

Exercise-dependent formation of new junctions that promote STIM1-Orai1 assembly in skeletal muscle.

Sci Rep 2017 10 27;7(1):14286. Epub 2017 Oct 27.

CeSI-Met - Center for Research on Ageing and Translational Medicine, University G. d'Annunzio, Chieti, I-66100, Italy.

Store-operated Ca entry (SOCE), a ubiquitous mechanism that allows recovery of Ca ions from the extracellular space, has been proposed to limit fatigue during repetitive skeletal muscle activity. However, the subcellular location for SOCE in muscle fibers has not been unequivocally identified. Here we show that exercise drives a significant remodeling of the sarcotubular system to form previously unidentified junctions between the sarcoplasmic reticulum (SR) and transverse-tubules (TTs). We also demonstrate that these new SR-TT junctions contain the molecular machinery that mediate SOCE: stromal interaction molecule-1 (STIM1), which functions as the SR Ca sensor, and Orai1, the Ca-permeable channel in the TT. In addition, EDL muscles isolated from exercised mice exhibit an increased capability of maintaining contractile force during repetitive stimulation in the presence of 2.5 mM extracellular Ca, compared to muscles from control mice. This functional difference is significantly reduced by either replacement of extracellular Ca with Mg or the addition of SOCE inhibitors (BTP-2 and 2-APB). We propose that the new SR-TT junctions formed during exercise, and that contain STIM1 and Orai1, function as Ca Entry Units (CEUs), structures that provide a pathway to rapidly recover Ca ions from the extracellular space during repetitive muscle activity.
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http://dx.doi.org/10.1038/s41598-017-14134-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5660245PMC
October 2017

Estrogens Protect Calsequestrin-1 Knockout Mice from Lethal Hyperthermic Episodes by Reducing Oxidative Stress in Muscle.

Oxid Med Cell Longev 2017 10;2017:6936897. Epub 2017 Sep 10.

CeSI-MeT, Center for Research on Ageing and Translational Medicine, University G. d'Annunzio of Chieti, 66100 Chieti, Italy.

Oxidative stress has been proposed to play a key role in malignant hyperthermia (MH), a syndrome caused by excessive Ca release in skeletal muscle. Incidence of mortality in male calsequestrin-1 knockout (CASQ1-null) mice during exposure to halothane and heat (a syndrome closely resembling human MH) is far greater than that in females. To investigate the possible role of sex hormones in this still unexplained gender difference, we treated male and female CASQ1-null mice for 1 month, respectively, with Premarin (conjugated estrogens) and leuprolide (GnRH analog) and discovered that during exposure to halothane and heat Premarin reduced the mortality rate in males (79-27% and 86-20%), while leuprolide increased the incidence of mortality in females (18-73% and 24-82%). We then evaluated the (a) responsiveness of isolated muscles to temperature and caffeine, (b) sarcoplasmic reticulum (SR) Ca release in single fibers, and (c) oxidative stress and the expression levels of main enzymes involved in the regulation of the redox balance in muscle. Premarin treatment reduced the temperature and caffeine sensitivity of EDL muscles, normalized SR Ca release, and reduced oxidative stress in males, suggesting that female sex hormones may protect mice from lethal hyperthermic episodes by reducing both the SR Ca leak and oxidative stress.
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http://dx.doi.org/10.1155/2017/6936897DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5610815PMC
July 2018

Antioxidant Treatment Reduces Formation of Structural Cores and Improves Muscle Function in RYR1 Mice.

Oxid Med Cell Longev 2017 10;2017:6792694. Epub 2017 Sep 10.

Center for Research on Aging and Translational Medicine (CeSI-MeT), University G. d'Annunzio of Chieti, 66100 Chieti, Italy.

Central core disease (CCD) is a congenital myopathy linked to mutations in the ryanodine receptor type 1 (RYR1), the sarcoplasmic reticulum Ca release channel of skeletal muscle. CCD is characterized by formation of amorphous within muscle fibers, lacking mitochondrial activity. In skeletal muscle of RYR1 knock-in mice, carrying a human mutation in RYR1 linked to malignant hyperthermia (MH) with , oxidative stress is elevated and fibers present severe mitochondrial damage and . We treated RYR1 mice with N-acetylcysteine (NAC), an antioxidant provided in drinking water for either 2 or 6 months. Our results show that 2 months of NAC treatment starting at 2 months of age, when mitochondrial and fiber damage was still minimal, (i) reduce formation of and , (ii) improve muscle function, and (iii) decrease mitochondrial damage. The beneficial effect of NAC treatment is also evident following 6 months of treatment starting at 4 months of age, when structural damage was at an advanced stage. NAC exerts its protective effect likely by lowering oxidative stress, as supported by the reduction of 3-NT and SOD2 levels. This work suggests that NAC administration is beneficial to prevent mitochondrial damage and formation of and improve muscle function in RYR1 mice.
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http://dx.doi.org/10.1155/2017/6792694DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5610828PMC
July 2018

Muscle Expression of SOD1 Triggers the Dismantlement of Neuromuscular Junction via PKC-Theta.

Antioxid Redox Signal 2018 04 30;28(12):1105-1119. Epub 2017 Oct 30.

1 Center for Life Nano Science at Sapienza , Istituto Italiano di Tecnologia, Rome, Italy .

Aim: Neuromuscular junction (NMJ) represents the morphofunctional interface between muscle and nerve. Several chronic pathologies such as aging and neurodegenerative diseases, including muscular dystrophy and amyotrophic lateral sclerosis, display altered NMJ and functional denervation. However, the triggers and the molecular mechanisms underlying the dismantlement of NMJ remain unclear.

Results: Here we provide evidence that perturbation in redox signaling cascades, induced by muscle-specific accumulation of mutant SOD1 in transgenic MLC/SOD1 mice, is causally linked to morphological alterations of the neuromuscular presynaptic terminals, high turnover rate of acetylcholine receptor, and NMJ dismantlement. The analysis of potential molecular mechanisms that mediate the toxic activity of SOD1 revealed a causal link between protein kinase Cθ (PKCθ) activation and NMJ disintegration.

Innovation: The study discloses the molecular mechanism that triggers functional denervation associated with the toxic activity of muscle SOD1 expression and suggests the possibility of developing a new strategy to counteract age- and pathology-associated denervation based on pharmacological inhibition of PKCθ activity.

Conclusions: Collectively, these data indicate that muscle-specific accumulation of oxidative damage can affect neuromuscular communication and induce NMJ dismantlement through a PKCθ-dependent mechanism. Antioxid. Redox Signal. 28, 1105-1119.
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http://dx.doi.org/10.1089/ars.2017.7054DOI Listing
April 2018

Allele-Specific Silencing of Mutant mRNA Rescues Ultrastructural and Arrhythmic Phenotype in Mice Carriers of the R4496C Mutation in the Ryanodine Receptor Gene ().

Circ Res 2017 Aug 15;121(5):525-536. Epub 2017 Jun 15.

From the Molecular Cardiology, IRCCS Istituti Clinici Scientifici Maugeri, Pavia, Italy (R.B., M.D., A.M., F.L., A.V., S.F., G.R., D.M., S.B., C.N., S.G.P.); Department of Molecular Medicine, University of Pavia, Italy (R.B., A.M., S.F., S.G.P.); CeSI-Met - Center for Research on Ageing and Translational Medicine & DNICS - Department of Neuroscience, Imaging and Clinical Sciences, University G. d'Annunzio, Chieti, Italy (S.B., A.D.F.); CeSI-Met - Center for Research on Ageing and Translational Medicine and DMSI, Department of Medicine and Aging Sciences, University G. d'Annunzio, Chieti, Italy (F.P.); Telethon Institute of Genetics and Medicine, Naples, Italy (A.A.); and Medical Genetics, Department of Translational Medicine, Federico II University, Naples, Italy (A.A.).

Rationale: Mutations in the cardiac Ryanodine Receptor gene () cause dominant catecholaminergic polymorphic ventricular tachycardia (CPVT), a leading cause of sudden death in apparently healthy individuals exposed to emotions or physical exercise.

Objective: We investigated the efficacy of allele-specific silencing by RNA interference to prevent CPVT phenotypic manifestations in our dominant CPVT mice model carriers of the heterozygous mutation R4496C in .

Methods And Results: We developed an in vitro mRNA and protein-based assays to screen multiple siRNAs for their ability to selectively silence mutant -R4496C mRNA over the corresponding wild-type allele. For the most performant of these siRNAs (siRYR2-U10), we evaluated the efficacy of an adeno-associated serotype 9 viral vector (AAV9) expressing miRYR2-U10 in correcting RyR2 (Ryanodine Receptor type 2 protein) function after in vivo delivery by intraperitoneal injection in neonatal and adult RyR2 (mice heterozygous for the R4496C mutation in the RyR2) heterozygous CPVT mice. Transcriptional analysis showed that after treatment with miRYR2-U10, the ratio between wild-type and mutant mRNA was doubled (from 1:1 to 2:1) confirming the ability of miRYR2-U10 to selectively inhibit -R4496C mRNA, whereas protein quantification showed that total RyR2 was reduced by 15% in the heart of treated mice. Furthermore, AAV9-miRYR2-U10 effectively (1) reduced isoproterenol-induced delayed afterdepolarizations and triggered activity in infected cells, (2) reduced adrenergically mediated ventricular tachycardia in treated mice, (3) reverted ultrastructural abnormalities of junctional sarcoplasmic reticulum and transverse tubules, and (4) attenuated mitochondrial abnormalities.

Conclusions: The study demonstrates that allele-specific silencing with miRYR2-U10 prevents life-threatening arrhythmias in CPVT mice, suggesting that the reduction of mutant RyR2 may be a novel therapeutic approach for CPVT.
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http://dx.doi.org/10.1161/CIRCRESAHA.117.310882DOI Listing
August 2017

Strenuous exercise triggers a life-threatening response in mice susceptible to malignant hyperthermia.

FASEB J 2017 08 2;31(8):3649-3662. Epub 2017 May 2.

Center for Research on Ageing and Translational Medicine (CeSI-MeT), Department of Neuroscience, Imaging, and Clinical Sciences (DNICS), Università degli Studi G. d'Annunzio, Chieti, Italy;

In humans, hyperthermic episodes can be triggered by halogenated anesthetics [malignant hyperthermia (MH) susceptibility] and by high temperature [environmental heat stroke (HS)]. Correlation between MH susceptibility and HS is supported by extensive work in mouse models that carry a mutation in ryanodine receptor type-1 (RYR1) and calsequestrin-1 knockout (CASQ1-null), 2 proteins that control Ca release in skeletal muscle. As overheating episodes in humans have also been described during exertion, here we subjected RYR1 and CASQ1-null mice to an exertional-stress protocol (incremental running on a treadmill at 34°C and 40% humidity). The mortality rate was 80 and 78.6% in RYR1 and CASQ1-null mice, respectively, 0% in wild-type mice. Lethal crises were characterized by hyperthermia and rhabdomyolysis, classic features of MH episodes. Of importance, pretreatment with azumolene, an analog of the drug used in humans to treat MH crises, reduced mortality to 0 and 12.5% in RYR1 and CASQ1-null mice, respectively, thanks to a striking reduction of hyperthermia and rhabdomyolysis. At the molecular level, azumolene strongly prevented Ca-dependent activation of calpains and NF-κB by lowering myoplasmic Ca concentration and nitro-oxidative stress, parameters that were elevated in RYR1 and CASQ1-null mice. These results suggest that common molecular mechanisms underlie MH crises and exertional HS in mice.-Michelucci, A., Paolini, C., Boncompagni, S., Canato, M., Reggiani, C., Protasi, F. Strenuous exercise triggers a life-threatening response in mice susceptible to malignant hyperthermia.
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http://dx.doi.org/10.1096/fj.201601292RDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5503704PMC
August 2017

Fatigue modulates dopamine availability and promotes flexible choice reversals during decision making.

Sci Rep 2017 04 3;7(1):535. Epub 2017 Apr 3.

Institute of Cognitive Sciences and Technologies, National Research Council, Via San Martino della Battaglia 44, 00185, Rome, Italy.

During decisions, animals balance goal achievement and effort management. Despite physical exercise and fatigue significantly affecting the levels of effort that an animal exerts to obtain a reward, their role in effort-based choice and the underlying neurochemistry are incompletely known. In particular, it is unclear whether fatigue influences decision (cost-benefit) strategies flexibly or only post-decision action execution and learning. To answer this question, we trained mice on a T-maze task in which they chose between a high-cost, high-reward arm (HR), which included a barrier, and a low-cost, low-reward arm (LR), with no barrier. The animals were parametrically fatigued immediately before the behavioural tasks by running on a treadmill. We report a sharp choice reversal, from the HR to LR arm, at 80% of their peak workload (PW), which was temporary and specific, as the mice returned to choose the HC when the animals were successively tested at 60% PW or in a two-barrier task. These rapid reversals are signatures of flexible choice. We also observed increased subcortical dopamine levels in fatigued mice: a marker of individual bias to use model-based control in humans. Our results indicate that fatigue levels can be incorporated in flexible cost-benefits computations that improve foraging efficiency.
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http://dx.doi.org/10.1038/s41598-017-00561-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5428685PMC
April 2017

Physical exercise in aging human skeletal muscle increases mitochondrial calcium uniporter expression levels and affects mitochondria dynamics.

Physiol Rep 2016 12;4(24)

Venetian Institute of Molecular Medicine, Padova, Italy.

Age-related sarcopenia is characterized by a progressive loss of muscle mass with decline in specific force, having dramatic consequences on mobility and quality of life in seniors. The etiology of sarcopenia is multifactorial and underlying mechanisms are currently not fully elucidated. Physical exercise is known to have beneficial effects on muscle trophism and force production. Alterations of mitochondrial Ca homeostasis regulated by mitochondrial calcium uniporter (MCU) have been recently shown to affect muscle trophism in vivo in mice. To understand the relevance of MCU-dependent mitochondrial Ca uptake in aging and to investigate the effect of physical exercise on MCU expression and mitochondria dynamics, we analyzed skeletal muscle biopsies from 70-year-old subjects 9 weeks trained with either neuromuscular electrical stimulation (ES) or leg press. Here, we demonstrate that improved muscle function and structure induced by both trainings are linked to increased protein levels of MCU Ultrastructural analyses by electron microscopy showed remodeling of mitochondrial apparatus in ES-trained muscles that is consistent with an adaptation to physical exercise, a response likely mediated by an increased expression of mitochondrial fusion protein OPA1. Altogether these results indicate that the ES-dependent physiological effects on skeletal muscle size and force are associated with changes in mitochondrial-related proteins involved in Ca homeostasis and mitochondrial shape. These original findings in aging human skeletal muscle confirm the data obtained in mice and propose MCU and mitochondria-related proteins as potential pharmacological targets to counteract age-related muscle loss.
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http://dx.doi.org/10.14814/phy2.13005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5210373PMC
December 2016
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