Potential neuroprotective effects of 2-hydroxypropyl-ß cyclodextrin against amyloid ß (1-42)-induced neurotoxicity on the rat hippocampus.

The neurodegenerative mechanisms of Alzheimer's disease (AD) are not fully understood, but it is believed that amyloid beta (Aß) peptide causes oxidative stress, neuroinflammation, and disrupts metabotropic glutamate receptor 5 (mGluR5) signaling by interacting with cholesterol and caveolin-1 (Cav-1) in pathogenic lipid rafts. This study examined the effect of 2-hydroxypropyl-ß-cyclodextrin (HP-CD) on cholesterol, oxidative stress (total oxidant status), neuroinflammation (TNF-α), and mGluR5 signaling molecules such as PKCß1, PKCß2, ERK1/2, CREB, BDNF, and NGF in Aß (1-42)-induced neurotoxicity. The Sprague-Dawley rats were divided into four groups: control (saline), Aß (1-42), HP-CD (100 mg/kg), and Aß (1-42) + HP-CD (100 mg/kg). All groups received bilateral stereotaxic injections of Aß (1-42) or saline into the hippocampus. After surgery, HP-CD was administered intraperitoneally (ip) for 7 days. Cholesterol, TNF-α, and TOS levels were measured in synaptosomes isolated from hippocampus tissue using spectrophotometry, fluorometry, and enzyme immunoassay, respectively. The gene expressions of Cav-1, mGluR5, PKCß1, PKCß2, ERK1/2, CREB, BDNF, and NGF in hippocampus tissue were evaluated using reverse transcription PCR after real-time PCR analysis. Treatment with Aß (1-42) significantly elevated cholesterol, TOS, TNF-α, Cav-1, PKCß2, and ERK1/2 levels. Additionally, mGluR5, CREB, and BDNF levels were shown to be lowered. HP-CD reduced cholesterol, TOS, and TNF-α levels while increasing mGluR5, CREB, and BDNF in response to Aß (1-42) treatment. These findings indicate that HP-CD may have neuroprotective activity due to the decreased levels of cholesterol, oxidative stress, and neuroinflammation, as well as upregulated levels of mGluR5, CREB, and BDNF.

Counteractive and cooperative actions of muscle ß-catenin and CaV1.1 during early neuromuscular synapse formation.

Activity-dependent calcium signals in developing muscle play a crucial role in neuromuscular junction (NMJ) formation. However, its downstream effectors and interactions with other regulators of pre- and postsynaptic differentiation are poorly understood. Here, we demonstrate that the skeletal muscle calcium channel CaV1.1 and ß-catenin interact in various ways to control NMJ development. They differentially regulate nerve branching and presynaptic innervation patterns during the initial phase of NMJ formation. Conversely, they cooperate in regulating postsynaptic AChR clustering, synapse formation, and the proper organization of muscle fibers in mouse diaphragm. CaV1.1 does not directly regulate ß-catenin expression but differentially controls the activity of its transcriptional co-regulators TCF/Lef and YAP. These findings suggest a crosstalk between CaV1.1 and ß-catenin in the activity-dependent transcriptional regulation of genes involved in specific pre- and postsynaptic aspects of NMJ formation.

Postsynaptic CaV1.1-driven calcium signaling coordinates presynaptic differentiation at the developing neuromuscular junction.

Proper formation of neuromuscular synapses requires the reciprocal communication between motor neurons and muscle cells. Several anterograde and retrograde signals involved in neuromuscular junction formation are known. However the postsynaptic mechanisms regulating presynaptic differentiation are still incompletely understood. Here we report that the skeletal muscle calcium channel (CaV1.1) is required for motor nerve differentiation and that the mechanism by which CaV1.1 controls presynaptic differentiation utilizes activity-dependent calcium signaling in muscle. In mice lacking CaV1.1 or CaV1.1-driven calcium signaling motor nerves are ectopically located and aberrantly defasciculated. Axons fail to recognize their postsynaptic target structures and synaptic vesicles and active zones fail to correctly accumulate at the nerve terminals opposite AChR clusters. These presynaptic defects are independent of aberrant AChR patterning and more sensitive to deficient calcium signals. Thus, our results identify CaV1.1-driven calcium signaling in muscle as a major regulator coordinating multiple aspects of presynaptic differentiation at the neuromuscular synapse.

Calcium Influx and Release Cooperatively Regulate AChR Patterning and Motor Axon Outgrowth during Neuromuscular Junction Formation.

Formation of synapses between motor neurons and muscles is initiated by clustering of acetylcholine receptors (AChRs) in the center of muscle fibers prior to nerve arrival. This AChR patterning is considered to be critically dependent on calcium influx through L-type channels (CaV1.1). Using a genetic approach in mice, we demonstrate here that either the L-type calcium currents (LTCCs) or sarcoplasmic reticulum (SR) calcium release is necessary and sufficient to regulate AChR clustering at the onset of neuromuscular junction (NMJ) development. The combined lack of both calcium signals results in loss of AChR patterning and excessive nerve branching. In the absence of SR calcium release, the severity of synapse formation defects inversely correlates with the magnitude of LTCCs. These findings highlight the importance of activity-dependent calcium signaling in early neuromuscular junction formation and indicate that both LTCC and SR calcium release individually support proper innervation of muscle by regulating AChR patterning and motor axon outgrowth.