Cholinesterase activity of motor end plate in human skeletal muscle

Namba, Tatsuji; Grob, David

doi:10.1172/jci106313

Cited by 15 publications

(2 citation statements)

References 17 publications

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“…The signals are amplified and digitized using a voltage-clamp amplifier and the software program pCLAMP (Molecular Devices). Histochemical (tissue) stains for acetylcholinesterase and GBHA were described previously (48,49). Caspase-3 immunostaining and microscopy were performed as previously described (16).…”

Section: Methodsmentioning

confidence: 99%

Calpain activation impairs neuromuscular transmission in a mouse model of the slow-channel myasthenic syndrome

et al. 2007

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The slow-channel myasthenic syndrome (SCS) is a hereditary disorder of the acetylcholine receptor (AChR) of the neuromuscular junction (NMJ) that leads to prolonged AChR channel opening, Ca 2+ overload, and degeneration of the NMJ. We used an SCS transgenic mouse model to investigate the role of the calcium-activated protease calpain in the pathogenesis of synaptic dysfunction in SCS. Cleavage of a fluorogenic calpain substrate was increased at the NMJ of dissociated muscle fibers. Inhibition of calpain using a calpastatin (CS) transgene improved strength and neuromuscular transmission. CS caused a 2-fold increase in the frequency of miniature endplate currents (MEPCs) and an increase in NMJ size, but MEPC amplitudes remained reduced. Persistent degeneration of the NMJ was associated with localized activation of the non-calpain protease caspase-3. This study suggests that calpain may act presynaptically to impair NMJ function in SCS but further reveals a role for other cysteine proteases whose inhibition may be of additional therapeutic benefit in SCS and other excitotoxic disorders. IntroductionThe slow-channel congenital myasthenic syndrome (SCS) is a dominantly inherited neuromuscular disorder characterized by impaired neuromuscular transmission and degeneration of the neuromuscular junction (NMJ) (1-3). Patients with SCS manifest fatigability and progressive weakness of the skeletal muscles, with symptoms ranging from eye muscle and mild limb weakness to severe incapacitation and respiratory failure. Ultrastructural study of muscle in SCS reveals a focal degenerative and remodeling process selectively localized to the NMJ termed endplate myopathy. This progressive, purely synaptic disease process, in which the cleft is widened and nerve terminals are shrunken, is characterized by expansion and degeneration of postsynaptic folds as well as degeneration of subsynaptic nuclei, mitochondria, and myofibrils (1-4).The SCS is caused by missense mutations within the genes encoding nicotinic acetylcholine receptor (AChR) subunits. The mutations alter the AChR channel gating function, causing prolonged activation events, persistent synaptic currents, and localized calcium overload at the NMJ, amplified by calcium release from intracellular stores (1, 3, 5-10). These changes lead to weakness and impaired neuromuscular transmission through an effect on both pre- and postsynaptic determinants of synaptic transmission, including quantal release, synaptic cleft anatomy, and the

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Section: Methodsmentioning

confidence: 99%

Calpain activation impairs neuromuscular transmission in a mouse model of the slow-channel myasthenic syndrome

et al. 2007

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“… Structures or parameters Skeletal muscle Intestinal smooth muscle Discharge frequency Rather high and modulated over wide range, e.g. around 40 Hz for full activation of upper extremity muscles 23 Rather low and discontinuous, maximum around 10 Hz 24 Nerve-muscle-interface Direct: neuromuscular synapse (chemical) between motoaxon and muscle fiber 25 , 26 Indirect: chemical synapse between motoneuron and ICC, electrical synapse between ICC and SMC 20 , 27 , 28 Neurotransmitters Acetylcholine, possibly modulated by glutamate (no human data) 29 – 31 Acetylcholine, purines, and neuropeptides, e.g. substance P, complex local network with even more transmitters and mediators 22 , 32 , 33 Muscle cell acetylcholine receptor Nicotinic receptor (α 1 ) 2 β 1 δε 34 Muscarinic receptors (M 2, M 3 ), nicotinic receptors of α3β2-, α3β4- and/or α7-subtype 35 , 36 neuronal action potential carried by sodium channels, most likely NaV 1.6 37 , 38 carried by sodium channels, most likely NaV 1.5, NaV 1.9 39 …”

Section: Introductionmentioning

confidence: 99%

A novel ex vivo model for critical illness neuromyopathy using freshly resected human colon smooth muscle

Patejdl

Klawitter

Walter

et al. 2021

Sci Rep

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Patients suffering from critical illness are at risk to develop critical illness neuromyopathy (CINM). The underlying pathophysiology is complex and controversial. A central question is whether soluble serum factors are involved in the pathogenesis of CINM. In this study, smooth muscle preparations obtained from the colon of patients undergoing elective surgery were used to investigate the effects of serum from critically ill patients. At the time of blood draw, CINM was assessed by clinical rating and electrophysiology. Muscle strips were incubated with serum of healthy controls or patients in organ baths and isometric force was measured. Fifteen samples from healthy controls and 98 from patients were studied. Ratios of responses to electric field stimulation (EFS) before and after incubation were 118% for serum from controls and 51% and 62% with serum from critically ill patients obtained at day 3 and 10 of critical illness, respectively (p = 0.003, One-Way-ANOVA). Responses to carbachol and high-K+ were equal between these groups. Ratios of post/pre-EFS responses correlated with less severe CINM. These results support the existence of pathogenic, i.e. neurotoxic factors in the serum of critically ill patients. Using human colon smooth muscle as a bioassay may facilitate their future molecular identification.

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Choline Acetyltransferase and Acetylcholinesterase

Gentner¹

1972

Arch Neurol

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Choline acetyltransferase, acetylcholinesterase, and pseudocholinesterase levels were measured in needle biopsy samples of deltoid muscle from subjects with myasthenia gravis and from normal controls. Choline acetyltransferase activities were about 30% lower and acetylcholinesterase activities about 45% lower in myasthenics as compared with controls. These decreased activities, however, are not significant in the cause of the disease; it is postulated that the primary defect at the neuromuscular junction may be the presence of a false transmitter in the synaptic vesicle or defective release of the vesicle contents at the synaptic cleft. (27:521-525, 1972) Jthough myasthenia gravis was first de¬ scribed 300 years ago1 and effective drug therapy has been used since 1934,2 the cause and basic defect are still unknown. It is generally agreed that defective transmission across the neuromuscular junction is direct¬ ly involved.35 The effectiveness of anticholinesterase drugs has focused considerable attention on the enzymes catalyzing synthe¬ sis and hydrolysis of acetylcholine (ACh). Numerous investigators have measured lev¬ els of cholinesterase (ChE) in serum of myasthénies, generally finding no difference from controls.6 There have been few studies of ChE levels in muscle of myasthénies. Jones and Stadie7 reported on one patient and found no difference from controls. Goodman et al8 found that neostigmine bro¬ mide (Prostigmine [France]; Prostigmin Bromide, comparable US product) lowered ChE levels in one myasthénie, but they did not have any normal controls. Wilson et al8reported that ChE levels in myasthénie mus¬ cle averaged 20% lower than controls, but this was not statistically significant due to the large scatter in their data. Rosenberg et al10 in a study of three myasthénies, found no difference from controls in acetylcholin¬ esterase (AChE) activities, but found a significant 26% reduction in choline acetyl¬ transferase (ChAc) specific activities. How¬ ever, that study was not ideal, since the biopsied muscle samples were infused with propoxycaine hydrochloride which inhibited the ChAc activity by 50%. This left open the possibility that myasthénies were merely more sensitive to propoxycaine. Accordingly, we have now extended and refined these studies with larger sample sizes and a new needle biopsy technique which allows us to circumvent the difficulties with propoxycaine. Methods and MaterialsNeedle biopsy samples of human muscle were obtained from the deltoid muscle of volun¬ teers using a Vim disposable biopsy needle. The motor point was located on the skin by stimulation with a constant current stimulator

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Cholinesterase activity of motor end plate in human skeletal muscle

Abstract: A B S T R A C T The activity and properties of cholines

Cited by 15 publications

References 17 publications

Calpain activation impairs neuromuscular transmission in a mouse model of the slow-channel myasthenic syndrome

Calpain activation impairs neuromuscular transmission in a mouse model of the slow-channel myasthenic syndrome

A novel ex vivo model for critical illness neuromyopathy using freshly resected human colon smooth muscle

Choline Acetyltransferase and Acetylcholinesterase

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