Anionic liposomes for small interfering ribonucleic acid （siRNA） delivery to primary neuronal cells： Evaluation of alpha-synuclein knockdown efficacy

Alpha-synuclein （a-syn） deposition in Lewy bodies （LB） is one of the main neuropathological hallmarks of Parkinson＇s disease （PD）. LB accumulation is considered a causative factor of PD, which suggests that strategies aimed at reducing a-syn levels could be relevant for its treatment. In the present study, we developed novel nanocarriers suitable for systemic delivery of small interfering ribonucleic acid （siRNA） that were specifically designed to reduce neuronal α-syn by RNA interference. Anionic liposomes loaded with an siRNA-protamine complex for α-syn gene silencing and decorated with a rabies virus glycoprotein （RVG）-derived peptide as a targeting agent were prepared. The nanoparticles were characterized for their ability to load, protect, and deliver the functional siRNA to mouse primary hippocampal and cortical neurons as well as their efficiency to induce gene silencing in these cells. Moreover, the nanocarriers were evaluated for their stability in serum. The RVG-decorated liposomes displayed suitable characteristics for future in vivo applications and successfully induced α-syn gene silencing in primary neurons without altering cell viability. Collectively, our results indicate that RVG-decorated liposomes may be an ideal tool for further studies aimed at achieving efficient in vivo α-syn gene silencing in mouse models of PD.

Bis(7)-Tacrine, a Promising Anti-Alzheimer's Agent,Attenuates Glutamate-Induced Cell Injury in Primary Cultured Cerebrocortical Neurons of Rats

The effects of bis(7) tacrine, a novel dimeric acetylcholinesterase (AChE) inhibitor, on glutamate induced cell injury were investigated in primary cerebral cortical neurons of rats. Exposure of cultured neurons (12 days after plating) to 0.5 mmol/L glutamate for 30 min resulted in significant cell damage. Pretreatment with bis(7) tacrine (0.03 1.0 μmol/L) reduced the glutamate induced neurotoxicity in a concentration dependent manner and the maximal response was seen at 1 μmol/L with approximately 30% protection. A receptor binding assay showed that bis(7) tacrine can completely displace MK 801 binding to rat cortical membrane with an IC 50 of 0.57 μmol/L. These findings suggest that bis(7) tacrine can directly interact with N methyl D aspartate receptor channel complex, which may contribute to the inhibitor's protective effects against glutamate induced excitotoxicity. Thus, it is possible that anti glutamate/anti AChE synergism is responsible for potentially better Alzheimer's therapy of bis(7) tacrine relative to tacrine.

Effects of Single and Repeated Exposure to a 50-Hz 2-mT Electromagnetic Field on Primary Cultured Hippocampal Neurons

The prevalence of domestic and industrial electrical appliances has raised concerns about the health risk of extremely low-frequency magnetic fields（ELF-MFs）. At present, the effects of ELF-MFs on the central nervous system are still highly controversial, and few studies have investigated its effects on cultured neurons. Here, we evaluated the biological effects of different patterns of ELF-MF exposure on primary cultured hippocampal neurons in terms of viability, apoptosis, genomic instability,and oxidative stress. The results showed that repeated exposure to 50-Hz 2-mT ELF-MF for 8 h per day after different times in culture decreased the viability and increased the production of intracellular reactive oxidative species in hippocampal neurons. The mechanism was potentially related to the up-regulation of Nox2 expression.Moreover, none of the repeated exposure patterns had significant effects on DNA damage, apoptosis, or autophagy, which suggested that ELF-MF exposure has no severe biological consequences in cultured hippocampal neurons.

Activation of Parvalbumin-Positive Neurons in Both Retina and Primary Visual Cortex Improves the Feature-Selectivity of Primary Visual Cortex Neurons

Several recent studies using either viral or transgenic mouse models have shown different results on whether the activation of parvalbumin-positive（PV~＋）neurons expressing channelrhodopsin-2（ChR2） in the primary visual cortex（V1） improves the orientation-and direction-selectivity of V1 neurons. Although this discrepancy was thoroughly discussed in a follow-up communication, the issue of using different models to express ChR2 in V1 was not mentioned. We found that ChR2 was expressed in retinal ganglion cells（RGCs） and V1 neurons in ChR2fl/~＋; PV-Cre mice. Our results showed that the activation of PV~＋RGCs using white drifting gratings alone significantly decreased the firing rates of V1 neurons and improved their direction-and orientation-selectivity. Longduration activation of PV~＋interneurons in V1 further enhanced the feature-selectivity of V1 neurons in anesthetized mice, confirming the conclusions from previous findings. These results suggest that the activation of both PV~＋RGCs and V1 neurons improves feature-selectivity in mice.