No abstract

Background/Aims: β-Dystroglycan (β-DG) is a transmembrane glycoprotein that links the intracellular cytoskeleton to the extracellular matrix and is crucial for the molecular pathway of lateral force transmission in muscle. We aimed to investigate the effect of decreasing sarcolemmal cholesterol on the distribution of β-DG, its interaction with dystrophin and the impact on the contraction efficiency of muscle. Methods: Isolated rat extensor digitorum longus muscles were incubated with methyl β-cyclodextrin (MβCD) to deplete cholesterol and with MβCD-cholesterol to restore cholesterol. Electric stimulation protocols were used to determine muscle force and fatigue. Detergent-resistant membranes (lipid rafts) were separated from isolated skeletal muscle sarcolemma. The distribution and interactions of β-DG, caveolin-3 and dystrophin were determined by an immunoreactivity analysis. Results: Cholesterol depletion in muscle results in a weakened force of contraction, which recovers after cholesterol restoration. The rate of fatigue is unaffected, but fatigue recovery is dependent upon cholesterol restoration. MβCD modifies the structures of lipid rafts obtained from MβCD-treated muscles by, displacing the membrane proteins β-DG and caveolin-3 f from the lipid raft, thus reducing the interaction of β-DG with dystrophin. Conclusion: Cholesterol depletion weakens the muscle contractile force by disturbing the sarcolemmal distribution of β-dystroglycan and its interaction with dystrophin, two key proteins in the alignment of lateral force transmission pathway.

Incubation of bovine adrenal chromaffin cells in high K ϩ (38 mM) during 24 -48 h enhanced 2.5 to five times the expression of SNAP-25 protein and mRNA, respectively. This increase was reduced 86% by furnidipine (an L-type Ca 2ϩ channel blocker) but was unaffected by either -conotoxin GVIA (an N-type Ca 2ϩ channel blocker) or -agatoxin IVA (a P/Q-type Ca 2ϩ channel blocker). Combined blockade of N and P/Q channels with -conotoxin MVIIC did, however, block by 76% the protein expression. The inhibitory effects of furnidipine were partially reversed when the external Ca 2ϩ concentration was raised from 1.6 to 5 mM. These findings, together with the fact that nicotinic receptor activation or Ca 2ϩ release from internal stores also enhanced SNAP-25 protein expression, suggest that an increment of cytosolic Ca 2ϩ concentration ([Ca 2ϩ ] i ), rather than its source or Ca 2ϩ entry pathway, is the critical signal to induce the protein expression. The greater coupling between L-type Ca 2ϩ channels and protein expression might be due to two facts: (a) L channels contributed 50% to the global [Ca 2ϩ ] i rise induced by 38 mM K ϩ in indo-1-loaded chromaffin cells and (b) L channels undergo less inactivation than N or P/Q channels on sustained stimulation of these cells.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease, presenting the most devastating consequences on human health and life quality. Coumarin‐quinoline hybrids were synthesized following a very efficient and versatile strategy. Small structural variations contributed to dual acetyl/butyrylcholinesterases (AChE/BuChE) activity or selectivity towards one of these enzymes. In addition, some of the studied compounds are interesting iron chelators, presenting a tendency to be neuroprotective. Moreover, the compounds are not cytotoxic for SH‐SY5Y neuroblastoma cells. Compound 9c proved to be the most interesting compound of the studied series. This compound is selective against AChE and proved to be an excellent iron chelating agent (iron chelation at 100 μM=72.87%). Molecular docking studies were performed to establish the nature of the interaction between the studied compounds and the binding pockets, leading to a rationalization of structure–activity relationships. Compound 9c forms a well‐defined π‐stacking interaction with Phe330 and interacts with Tyr121 residue via a hydrogen bond, while the inactive compounds cannot establish these interactions. Important preliminary results against different targets, as well as some structure–activity relationships, were concluded from the experimental results.

We established two immortalized cell lines from cerebral cortex of normal (CNh) and trisomy 16 (CTb) mouse fetuses, an animal model of human trisomy 21. Those cells loaded with the fluorescent Ca2+ dyes, Indo-1 and Fluo-3, exhibited increments of intracellular Ca2+ ([Ca2+]i) in response to external glutamate, NMDA, AMPA and kainate. CTb cells exhibited higher basal Ca2+ concentrations and had higher amplitude and slower time-dependent kinetics in the decay than CNh cells, suggesting an impaired Ca2+ buffering capacity in the trisomy 16-derived cell line. Nicotine also induced increments of [Ca2+]i. The CTb cell line could represent a model for studying cellular alterations related to Down syndrome.