Neuromuscular junction instability with inactivity: morphological and functional changes after 10 days of bed rest in older adults Evgeniia Motanova, Fabio Sarto, Samuele Negro, Marco Pirazzini, Ornella Rossetto, Michela Rigoni, Daniel W. Stashuk, Mladen Gasparini, Boštjan Šimunic, Rado Pišot, Marco V. Narici Journal of Physiology, 2026 The neuromuscular junction (NMJ) plays a key role in modulating muscle contraction, but the impact of short‐term disuse on NMJ structure and function, particularly in older humans, remains unclear. This study aimed to investigate NMJ alterations following 10 days of horizontal bed rest in 10 older males (68.5 ± 2.6 years). Before and after bed rest, vastus lateralis muscle biopsies were obtained to evaluate NMJ morphology, intramuscular EMG (iEMG) was recorded to assess NMJ function and blood samples were collected to determine circulating C‐terminal agrin fragment (CAF) concentration, a biomarker of NMJ remodelling. In a sub‐cohort of six participants who had NMJs in both pre‐ and post‐bed rest biopsies, we observed altered NMJ morphology, including reduced overlap between NMJ terminals, as well as increased endplate area and perimeter. CAF concentration was elevated after bed rest, suggesting ongoing NMJ remodelling. iEMG analysis showed increased motor unit potential complexity and reduced firing rate. In addition, we observed impaired NMJ transmission, inferred from increased near‐fibre jiggle and segment jitter. These findings suggest that older male individuals are susceptible to NMJ remodelling and impaired transmission with short‐term disuse, providing valuable insights into the morphological and functional consequences of inactivity in an ageing population. Our study highlights the importance of developing interventions for mitigating the detrimental consequences of inactivity on neuromuscular health in older adults, which they frequently experience following injury, trauma, illness or surgery. imageKey points The neuromuscular junction (NMJ) is crucial for signal transmission between the motoneuron and skeletal muscle, and NMJ alterations are linked to several neuromuscular disorders, as well as ageing. However, the impact of disuse on the structural and functional integrity of the NMJ, particularly in older humans, is largely unknown. We used the bed rest model to study the impact of inactivity on NMJ morphology and function in older men. We hypothesised that a 10 day bed rest period would lead to alterations in NMJ morphology and transmission. We show that 10 days of bed rest were sufficient to induce marked alterations in NMJ morphology, associated with an impaired NMJ transmission and with changes in motor unit potential properties. These findings suggest that older male individuals are vulnerable to NMJ dysfunction in response to inactivity and emphasise the importance of maintaining an active lifestyle for preserving neuromuscular health with ageing.
Enteric botulinum neurotoxins facilitate infection by Salmonella and Shigella Science Advances, 2026
Kv3 channel agonist ameliorates the phenotype of a mouse model of amyotrophic lateral sclerosis Manuela Marabita, Caterina Marchioretti, Aishwarya Aravamudhan, Simona Zito, Antonella Falconieri, Emanuela Zuccaro, Roberta Andreotti, Lisa Gambarotto, Samuele Metti, Marika Tonellato, Valentina Adami, Kyung Ho Park, Martin J. Gunthorpe, Charles H. Large, Agostino Marasco, Sara Vianello, Jessica Rosati, Elisa Belluzzi, Assunta Pozzuoli, Carlo Biz, Pietro Ruggieri, Manuela Basso, Angelo Poletti, Giuseppe Alvaro, Gianni Sorarù, Paolo Bonaldo, Ornella Rossetto, Nadia Pilati, Maria Pennuto Acta Neuropathologica Communications, 2025 Voltage-gated potassium channels, Kv3.1, Kv3.2, Kv3.3, and Kv3.4, facilitate rapid repolarization and shape action potentials, which are crucial to maintaining high-frequency firing. Little is known about the expression and function of Kv3 channels in skeletal muscle. We show that these channels are expressed in type IIa/IIx fibers, and their transcript levels progressively increase from postnatal age to adulthood in physiological context. In mature myofibers, the Kv3.1 and Kv3.4 channels are enriched in the muscle triads. The expression of the Kv3 channel is lost upon acute motor unit damage, in mouse models of amyotrophic lateral sclerosis (ALS) and spinal and bulbar muscular atrophy (SBMA), and the skeletal muscle of patients with sporadic ALS. Early treatment of ALS and SBMA mice with AUT00201, a positive allosteric modulator of Kv3 channels, improved the phenotype of ALS mice specifically, suggesting that positive modulation of Kv3 channels is a novel therapeutic option for patients with ALS.
Experimental Parkinsonism induced by tetanus toxin injected into basal ganglia Patrik Meglić, Petra Šoštarić, Davor Virag, Ana Knezović, Nikola Habek, Ornella Rossetto, Ivica Matak British Journal of Pharmacology, 2025 Background and PurposeLocal inhibitory circuits and long‐range inhibitory projections within the interconnected basal ganglia nuclei are critical for control of voluntary movement and pathophysiology of different extrapyramidal movement disorders. Herein, we examined the major motor effects of tetanus neurotoxin (TeNT), a presynaptic neurotoxin selectively targeting GABA‐ergic synaptic transmission, injected into individual basal ganglia nuclei.Experimental ApproachRats were injected with low‐dose TeNT unilaterally into globus pallidus internus (GPi, 0.4‐ng TeNT), substantia nigra (SN, 0.4‐ng TeNT) or caudate putamen (CPu, 0.1‐, 0.4‐ and 0.8‐ng TeNT). Effects of TeNT‐induced disinhibition were characterized by repeated assessments of motor coordination, gait and rotational behaviour, followed by measurement of regional protein content of major neuronal monoaminergic, GABA‐ergic and glutamatergic population markers.Key ResultsEffects of TeNT injections into the GPi and CPu were more prominent and associated with decreased stride length and slower step cycle. CPu injections induced contralateral plantar misplacement during beamwalk transition. Rotational behaviour was evident as spontaneous ipsiversive circling during open field observation (augmented by D‐amphetamine) and swimming. Along with gradual recovery of motor impairments over 2 weeks, the effects of TeNT were not associated with epileptogenesis or changed regional content of neuronal markers.Conclusion and ImplicationsTetanus toxin injected into the basal ganglia evokes transient hypokinetic motor dysfunctions, consistent with experimental Parkinsonism, with differential occurrence of individual motor symptoms depending on the region targeted. These results suggest that TeNT might be a useful non‐neurodegenerative pharmacological agent for investigating motor control abnormalities involving GABA‐ergic basal ganglia circuits.
Excitation–contraction coupling inhibitors potentiate the actions of botulinum neurotoxin type A at the neuromuscular junction Mickaël Machicoane, Marika Tonellato, Marica Zainotto, Paul Onillon, Marco Stazi, Mattia Dal Corso, Aram Megighian, Ornella Rossetto, Jean‐Marc Le Doussal, Marco Pirazzini British Journal of Pharmacology, 2025 Background and PurposeBotulinum neurotoxin type A1 (BoNT/A) is one of the most potent neurotoxins known. At the same time, it is also one of the safest therapeutic agents used for the treatment of several human disorders and in aesthetic medicine. Notwithstanding great effectiveness, strategies to accelerate the onset and prolong BoNT/A action would significantly ameliorate its pharmacological effects with beneficial outcomes for clinical use.Experimental ApproachHere, we combined BoNT/A with two fast‐acting inhibitors of excitation–contraction coupling inhibitors (ECCI), either the μ‐conotoxin CnIIIC or dantrolene, and tested the effect of their co‐injection on a model of hind‐limb paralysis in rodents using behavioural, biochemical, imaging and electrophysiological assays.Key ResultsThe BoNT/A‐ECCI combinations accelerated the onset of muscle relaxation. Surprisingly, they also potentiated the peak effect and extended the duration of the three BoNT/A commercial preparations OnabotulinumtoxinA, AbobotulinumtoxinA and IncobotulinumtoxinA. ECCI co‐injection increased the number of BoNT/A molecules entering motoneuron terminals, which induced a faster and greater cleavage of SNAP‐25 during the onset and peak phases, and prolonged the attenuation of nerve‐muscle neurotransmission during the recovery phase. We estimate that ECCI co‐injection yields a threefold potentiation in BoNT/A pharmacological activity.Conclusions and ImplicationsOverall, our results show that the pharmacological activity of BoNT/A can be combined and synergized with other bioactive molecules and uncover a novel strategy to enhance the neuromuscular effects of BoNT/A without altering the neurotoxin moiety or intrinsic activity, thus maintaining its exceptional safety profile.
Impact of ageing and disuse on neuromuscular junction and mitochondrial function and morphology: Current evidence and controversies Evgeniia Motanova, Marco Pirazzini, Samuele Negro, Ornella Rossetto, Marco Narici Ageing Research Reviews, 2024 Inactivity and ageing can have a detrimental impact on skeletal muscle and the neuromuscular junction (NMJ). Decreased physical activity results in muscle atrophy, impaired mitochondrial function, and NMJ instability. Ageing is associated with a progressive decrease in muscle mass, deterioration of mitochondrial function in the motor axon terminals and in myofibres, NMJ instability and loss of motor units. Focusing on the impact of inactivity and ageing, this review examines the consequences on NMJ stability and the role of mitochondrial dysfunction, delving into their complex relationship with ageing and disuse. Evidence suggests that mitochondrial dysfunction can be a pathogenic driver for NMJ alterations, with studies revealing the role of mitochondrial defects in motor neuron degeneration and NMJ instability. Two perspectives behind NMJ instability are discussed: one is that mitochondrial dysfunction in skeletal muscle triggers NMJ deterioration, the other envisages dysfunction of motor terminal mitochondria as a primary contributor to NMJ instability. While evidence from these studies supports both perspectives on the relationship between NMJ dysfunction and mitochondrial impairment, gaps persist in the understanding of how mitochondrial dysfunction can cause NMJ deterioration. Further research, both in humans and in animal models, is essential for unravelling the mechanisms and potential interventions for age- and inactivity-related neuromuscular and mitochondrial alterations.
Genome sequence of the fish brain bacterium Clostridium tarantellae Luca Bano, Matthias Kiel, Gabriele Sales, Andrew C. Doxey, Michael J. Mansfield, Haleluya T. Wami, Marco Schiavone, Ornella Rossetto, Marco Pirazzini, Ulrich Dobrindt, Cesare Montecucco Microbiology Resource Announcements, 2020
