Amyotrophic lateral sclerosis (ALS) is manifested as skeletal muscle denervation, loss of motor neurons and finally severe respiratory failure. Mutations of RNA-binding protein FUS are one of the common genetic reasons of ALS accompanied by a ‘dying back’ type of degeneration. Using fluorescent approaches and microelectrode recordings, the early structural and functional alterations in diaphragm neuromuscular junctions (NMJs) were studied in mutant FUS mice at the pre-onset stage. Lipid peroxidation and decreased staining with a lipid raft marker were found in the mutant mice. Despite the preservation of the end-plate structure, immunolabeling revealed an increase in levels of presynaptic proteins, SNAP-25 and synapsin 1. The latter can restrain Ca²⁺-dependent synaptic vesicle mobilization. Indeed, neurotransmitter release upon intense nerve stimulation and its recovery after tetanus and compensatory synaptic vesicle endocytosis were markedly depressed in FUS mice. There was a trend to attenuation of axonal [Ca²⁺]_in increase upon nerve stimulation at 20 Hz. However, no changes in neurotransmitter release and the intraterminal Ca²⁺ transient in response to low frequency stimulation or in quantal content and the synchrony of neurotransmitter release at low levels of external Ca²⁺ were detected. At a later stage, shrinking and fragmentation of end plates together with a decrease in presynaptic protein expression and disturbance of the neurotransmitter release timing occurred. Overall, suppression of synaptic vesicle exo–endocytosis upon intense activity probably due to alterations in membrane properties, synapsin 1 levels and Ca²⁺ kinetics could be an early sign of nascent NMJ pathology, which leads to neuromuscular contact disorganization.

Carbon monoxide (CO) is an endogenous gaseous messenger, which regulates numerous physiological functions in a wide variety of tissues. Using extracellular microelectrode recording from frog neuro-muscular preparation the mechanisms of exogenous and endogenous CO action on evoked quantal acetyl-choline (Ach) release were studied. It was shown that CO application increases Ach-release in dose-dependent manner without changes in pre-synaptic Na+ and K+ currents. The effect of exogenous CO on Ach-release was decreased by prior application of guanylate cyclase inhibitor ODQ and prevented by application of a cyclic guanylate monophospate (cGMP) analog 8Br-cGMP. Pre-treatment of the preparation with adenylate cyclase inhibitor MDL-12330A has completely abolished the effect of CO, whereas elevation of intracellular level of cyclic adenosine monophospate (cAMP) mimicked and eliminated CO action. Application of cGMP-activated phosphodiestherase-2 inhibitor EHNA did not prevent CO action, whereas inhibition of cGMP-inhibited phosphodiestherase-3 by quazinone has partially blocked the effect of CO. Utilizing immuno-histochemical methods COproducing enzyme heme-oxygenase-2 (HO-2) was shown to be expressed in skeletal muscle fibers, mostly in subsarcolemmal region, karyolemma and sarcoplasmic reticulum. Zn-protoporphirin-IX, the selective HO-2 blocker, has depressed Ach-release, suggesting the tonic activating effect of endogenous CO on pre-synaptic function. These results suggest that facilitatory effect of CO on Ach-release is mediated by elevation of intracellular cAMP level due to activation of adenylate cyclase and decrease of cAMP breakdown. As such, endogenous skeletal muscle-derived CO mediates tonic retrograde up-regulation of neuro-transmitter release at the frog neuro-muscular junction.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that has no effective treatment. To date, ALS is considered as a multifactorial heterogeneous disease, in which the death of motor neurons is a final result of the different pathological pathways. Modern diagnostic criteria and classification of ALS do not take into account all heterogeneity of the disease. Despite the development of molecular neurobiology and neurophysiology, genetics, and technology, significant progress in understanding the pathogenesis of ALS, the disease is diagnosed primarily on the basis of clinical manifestations. In recent years, a number of clinical trials of promising drugs have failed to show positive results. Among the reasons for these failures are variability of ALS forms, patients enrollment already at a late stage of the disease, the lack of use of biomarkers for patients selection and drugs' pharmacodynamics assessment. The study of biomarkers and their implementation in clinical practice can help to solve these problems. Here we will discuss the fluid-based biomarkers for ALS.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by the death of upper and lower motor neurons. Numerous studies show that structural and functional impairments of neuromuscular junctions (NMJ) occur as early as the presymptomatic stage of ALS. NMJ involvement is independent and one of the primary events in ALS pathogenesis. Aim: to review the data on characteristics and mechanisms of NMJ dysfunction at pre- and postsynaptic levels in ALS patients and a transgenic animal model of the disease. Furthermore, we report on the dysfunction of perisynaptic Schwann cells and impaired mechanisms of motor neuron and skeletal muscle interaction in ALS, with a focus on reviewed publications on targeting of molecular mechanisms underlying NMJ dysfunction and disruption in ALS. The NMJ may be a potential target for novel therapeutic approaches for ALS.