Differential participation of CaMKII/ROCK and NOS pathways in the cholinergic inhibitory drive operated by nicotinic α7 receptors in perisynaptic Schwann cells.

Nicotinic α7 receptors (α7 nAChRs) present in perisynaptic Schwann cells (PSCs) control acetylcholine (ACh) spillover from the neuromuscular synapse by transiently increasing intracellular Ca, which fosters adenosine release via type 1 equilibrative nucleoside transporters (ENT1) and retrograde activation of presynaptic A inhibitory receptors. The putative Ca-dependent pathways downstream α7 nAChRs involved in the sensing inhibitory drive operated by PSCs is unknown. Herein, we used phrenic nerve-hemidiaphragm preparations from Wistar rats.

Mechanical stimulation-induced purinome priming fosters osteogenic differentiation and osteointegration of mesenchymal stem cells from the bone marrow of post-menopausal women.

Background: Mechanical stimulation (MS) significantly increases the release of adenine and uracil nucleotides from bone marrow-derived mesenchymal stem cells (BM-MSCs) undergoing osteogenic differentiation. Released nucleotides acting via ionotropic P2X7 and metabotropic P2Y purinoceptors sensitive to ATP and UDP, respectively, control the osteogenic commitment of BM-MSCs and, thus, bone growth and remodelling. Yet, this mechanism is impaired in post-menopausal (Pm)-derived BM-MSCs, mostly because NTPDase3 overexpression decreases the extracellular accumulation of nucleotides below the levels required to activate plasma membrane-bound P2 purinoceptors.

Silencing NTPDase3 activity rehabilitates the osteogenic commitment of post-menopausal stem cell bone progenitors.

Background: Endogenously released adenine and uracil nucleotides favour the osteogenic commitment of bone marrow-derived mesenchymal stromal cells (BM-MSCs) through the activation of ATP-sensitive P2X7 and UDP-sensitive P2Y receptors. Yet, these nucleotides have their osteogenic potential compromised in post-menopausal (Pm) women due to overexpression of nucleotide metabolizing enzymes, namely NTPDase3. This prompted us to investigate whether NTPDase3 gene silencing or inhibition of its enzymatic activity could rehabilitate the osteogenic potential of Pm BM-MSCs.

Purinergic Tuning of the Tripartite Neuromuscular Synapse.

The vertebrate neuromuscular junction (NMJ) is a specialised chemical synapse involved in the transmission of bioelectric signals between a motor neuron and a skeletal muscle fiber, leading to muscle contraction. Typically, the NMJ is a tripartite synapse comprising (a) a presynaptic region represented by the motor nerve ending, (b) a postsynaptic skeletal motor endplate area, and (c) perisynaptic Schwann cells (PSCs) that shield the motor nerve terminal. Increasing evidence points towards the role of PSCs in the maintenance and control of neuromuscular integrity, transmission, and plasticity.

Pitfalls and challenges of the purinergic signaling cascade in obesity.

Obesity is a worldwide health problem which have reached pandemic proportions, now also including low and middle-income countries. Excessive or abnormal fat deposition in the abdomen especially in the visceral compartment is tightly associated with a high metabolic risk for arterial hypertension, type II diabetes, cardiovascular diseases, musculoskeletal disorders (especially articular degeneration) and some cancers. Contrariwise, accumulation of fat in the subcutaneous compartment has been associated with a neutral metabolic impact, favoring a lower risk of insulin resistance.

Nicotinic α7 receptor-induced adenosine release from perisynaptic Schwann cells controls acetylcholine spillover from motor endplates.

Acetylcholine (ACh) spillover from motor endplates occurs after neuronal firing bursts being potentiated by cholinesterase inhibitors (e.g., neostigmine).

Tetanic Facilitation of Neuromuscular Transmission by Adenosine A2A and Muscarinic M1 Receptors is Dependent on the Uptake of Choline via High-Affinity Transporters.

Background/aims: In this study, we evaluated the functional impact of facilitatory presynaptic adenosine A2A and muscarinic M1 receptors in the recovery of neuromuscular tetanic depression caused by the blockage of high-affinity choline transporter (HChT) by hemicholinium-3 (HC-3), a condition that mimics a myasthenia-like condition.

Methods: Rat diaphragm preparations were indirectly stimulated via the phrenic nerve trunk with 50-Hz frequency trains, each consisting of 500-750 supramaximal intensity pulses. The tension at the beginning (A) and at the end (B) of the tetanus was recorded and the ratio (R) B/A calculated.

Neuromuscular paralysis by the basic phospholipase A subunit of crotoxin from Crotalus durissus terrificus snake venom needs its acid chaperone to concurrently inhibit acetylcholine release and produce muscle blockage.

Background And Purpose: Crotoxin (CTX), a heterodimeric phospholipase A (PLA) neurotoxin from Crotalus durissus terrificus snake venom, promotes irreversible blockade of neuromuscular transmission. Indirect electrophysiological evidence suggests that CTX exerts a primary inhibitory action on transmitter exocytosis, yet contribution of a postsynaptic action of the toxin resulting from nicotinic receptor desensitization cannot be excluded. Here, we examined the blocking effect of CTX on nerve-evoked transmitter release measured directly using radioisotope neurochemistry and video microscopy with the FM4-64 fluorescent dye.

P2X7-induced zeiosis promotes osteogenic differentiation and mineralization of postmenopausal bone marrow-derived mesenchymal stem cells.

Polymorphisms of the P2X7 receptor have been associated with increased risk of fractures in postmenopausal women. Although both osteoblasts and osteoclasts express P2X7 receptors, their function in osteogenesis remains controversial. Here, we investigated the role of the P2X7 receptor on osteogenic differentiation and mineralization of bone marrow mesenchymal stem cell (BMSC) cultures from postmenopausal women (age 71±3 yr, n=18).

ATP released via pannexin-1 hemichannels mediates bladder overactivity triggered by urothelial P2Y6 receptors.

In contrast to the well-known signaling role of urothelial ATP to control bladder function, the hypothesis that uracil nucleotides (UTP and/or UDP) also exert autocrine/paracrine actions only recently gained experimental support. Urothelial cells express UDP-sensitive P2Y6 receptors, yet their role in the control of bladder activity has been mostly neglected. This study was designed to investigate the ability of PSB0474, a stable UDP analogue which exhibits selectivity for P2Y6 receptors, to modulate urodynamic responses in the anaesthetized rat in vivo.

Bothropstoxin-I reduces evoked acetylcholine release from rat motor nerve terminals: radiochemical and real-time video-microscopy studies.

Understanding the biological activity profile of the snake venom components is fundamental for improving the treatment of snakebite envenomings and may also contribute for the development of new potential therapeutic agents. In this work, we tested the effects of BthTX-I, a Lys49 PLA(2) homologue from the Bothrops jararacussu snake venom. While this toxin induces conspicuous myonecrosis by a catalytically independent mechanism, a series of in vitro studies support the hypothesis that BthTX-I might also exert a neuromuscular blocking activity due to its ability to alter the integrity of muscle cell membranes.

Synthesis of new chiral xanthone derivatives acting as nerve conduction blockers in the rat sciatic nerve.

The synthesis and structure elucidation of three new chiral xanthone (9H-xanthon-9-one) derivatives (2-4) are fully reported. The coupling reactions of the synthesized building block 6-methoxy-9-oxo-9H-xanthene-2-carboxylic acid (1) with two enantiomerically pure amino alcohols ((S)-(+)-valinol and (S)-(+)-leucinol) and one amine ((S)-(-)-α-4-dimethylbenzylamine), were carried out using the coupling reagent O-(benzotriazol-1-yl-)-N,N,N',N'-tetramethylluronium tetrafluoroborate (TBTU). The coupling reactions were performed with yields higher than 97% and enantiomeric excess higher than 99%.