Assessment of false transmitters as treatments for nerve agent poisoning.

Nerve agents inhibit acetylcholinesterase (AChE), leading to a build-up of acetylcholine (ACh) and overstimulation at cholinergic synapses. Current post-exposure nerve agent treatment includes atropine to treat overstimulation at muscarinic synapses, a benzodiazepine anti-convulsant, and an oxime to restore the function of AChE. Aside from the oxime, the components do not act directly to reduce the overstimulation at nicotinic synapses. The false transmitters acetylmonoethylcholine (AMECh) and acetyldiethylcholine (ADECh) are analogs of ACh, synthesised similarly at synapses. AMECh and ADECh are partial agonists, with reduced activity compared to ACh, so it was hypothesised the false transmitters could reduce overstimulation. Synthetic routes to AMECh and ADECh, and their precursors, monoethylcholine (MECh) and diethylcholine (DECh), were devised, allowing them to be produced easily on a laboratory-scale. The mechanism of action of the false transmitters was investigated in vitro. AMECh acted as a partial agonist at human muscarinic (M1 and M3) and muscle-type nicotinic receptors, and ADECh was a partial agonist only at certain muscarinic subtypes. Their precursors acted as antagonists at muscle-type nicotinic, but not muscarinic receptors. Administration of MECh and DECh improved neuromuscular function in the soman-exposed guinea-pig hemi-diaphragm preparation. False transmitters may therefore help reduce nerve agent induced overstimulation at cholinergic synapses.

The effect of calorie restriction on mouse skeletal muscle is sex, strain and time-dependent.

Loss of skeletal muscle mass and function occurs with increasing age. Calorie restriction (CR) increases the lifespan of C57Bl/6 mice, but not in the shorter-lived DBA/2 strain. There is some evidence that calorie restriction reduces or delays many of the age-related defects that occur in rodent skeletal muscle. We therefore investigated the effect of short (2.5 month) and longer term (8.5 and 18.5 months) CR on skeletal muscle in male and female C57Bl/6 and DBA/2 mice. We found that short-term CR increased the satellite cell number and collagen VI content of muscle, but resulted in a delayed regenerative response to injury.Consistent with this, the in vitro proliferation of satellite cells derived from these muscles was reduced by CR. The percentage of stromal cells, macrophages, hematopoietic stem cells and fibroadipogenic cells in the mononucleated cell population derived from skeletal muscle was reduced by CR at various stages. But overall, these changes are neither consistent over time, nor between strain and sex. The fact that changes induced by CR do not persist with time and the dissimilarities between the two mouse strains, combined with sex differences, urge caution in applying CR to improve skeletal muscle function across the lifespan in humans.

The transgenic expression of LARGE exacerbates the muscle phenotype of dystroglycanopathy mice.

Mutations in fukutin-related protein (FKRP) underlie a group of muscular dystrophies associated with the hypoglycosylation of α-dystroglycan (α-DG), a proportion of which show central nervous system involvement. Our original FKRP knock-down mouse (FKRP(KD)) replicated many of the characteristics seen in patients at the severe end of the dystroglycanopathy spectrum but died perinatally precluding its full phenotyping and use in testing potential therapies. We have now overcome this by crossing FKRP(KD) mice with those expressing Cre recombinase under the Sox1 promoter. Owing to our original targeting strategy, this has resulted in the restoration of Fkrp levels in the central nervous system but not the muscle, thereby generating a new model (FKRP(MD)) which develops a progressive muscular dystrophy resembling what is observed in limb girdle muscular dystrophy. Like-acetylglucosaminyltransferase (LARGE) is a bifunctional glycosyltransferase previously shown to hyperglycosylate α-DG. To investigate the therapeutic potential of LARGE up-regulation, we have now crossed the FKRP(MD) line with one overexpressing LARGE and show that, contrary to expectation, this results in a worsening of the muscle pathology implying that any future strategies based upon LARGE up-regulation require careful management.

Clinically available iron chelators induce neuroprotection in the 6-OHDA model of Parkinson's disease after peripheral administration.

The iron content of the substantia nigra pars compacta increases in the brains of Parkinson's disease patients. Hence, its removal by iron chelators may retard the progression of the disease. However, information on the ability of clinically available iron chelators to cross the blood brain barrier and be neuroprotective is limited. In this present study three iron chelators, which are currently approved for clinical use, namely the hexadendate, deferrioxamine, the bidentate deferiprone and the tridendate chelator deferasirox have been investigated for their efficacy to induce neuroprotection. Previous studies have shown that both deferiprone and deferrioxamine exert neuroprotection in the 6-hydroxy dopamine (6-OHDA) model but no such studies have investigated deferasirox. Focal administration of deferasirox (0.5, 2 and 10 µg) into the substantia nigra pars compacta of rats significantly attenuated the loss of dopaminergic neurons and striatal dopamine content resulting from 6-OHDA toxicity. Systemic administration of deferasirox (20 mg/kg), deferiprone (10 mg/kg) or deferrioxamine (30 mg/kg), to the 6-OHDA rat model of Parkinson's disease, significantly attenuated the loss of dopaminergic neurons and striatal dopamine content. Further studies to comprehend the action of these chelators showed that local application of either 0.4 mM deferrioxamine, or 1 mM deferasirox, via a microdialysis probe into the striatum, prior to that of 200 µM 6-OHDA, prevented the generation of hydroxyl radicals. Our results confirm that the administration of these chelators show therapeutic efficacy and should be considered as therapeutic agents for the treatment of Parkinson's disease.