👤 Michele Zoli

Electrical stimulation (ES) is emerging as a non-pharmacological neuromodulation strategy, but its direct impact on human dopaminergic neurons and its relationship to rapid-acting antidepressant mechanisms remain unclear. This study aimed to investigate whether brief biphasic low-frequency low-intensity (LF-LI) ES can induce structural and molecular plasticity in human induced pluripotent stem cell (iPSC)-derived mesencephalic dopaminergic neurons, identify the underlying signaling mechanisms, and evaluate its potential to rescue cortisol-induced impairments as in-vitro endocrine model of depression. iPSC-derived dopaminergic neurons were exposed to LF-LI ES using a custom culture-compatible stimulator, and structural plasticity was quantified three days later by computer-assisted morphometry. Pharmacological blockers, quantitative PCR and Western blot analyses were employed to assess calcium influx, brain-derived neurotrophic factor (BDNF)-TrkB-extracellular signal-regulated kinase (ERK)-mTOR signaling, and dopamine D3 auto-receptor roles in mediating LF-LI ES effects. A single 1h LF-LI ES session at 4 mA induced robust increases in maximal dendrite length, primary dendrite number, and soma area, comparable to 1 μM ketamine. LF-LI ES rapidly enhanced ERK and p70-S6K phosphorylation and required L-type voltage-gated calcium channels, TrkB and mTOR, as their inhibition prevented structural remodeling. LF-LI ES increased dopamine D3 auto-receptors mRNA, and its antagonism attenuated LF-LI ES-induced plasticity. In cortisol-treated neurons, LF-LI ES fully reversed dendritic hypotrophy and soma shrinkage. In conclusion, brief LF-LI ES elicits long-lasting, ketamine-like structural and molecular plasticity in human dopaminergic neurons and rescues stress hormone-induced impairments, supporting LF-LI ES-based neuromodulation approaches targeting dopaminergic circuits in major depressive disorder and treatment-resistant depression. Show less

Increasing evidence highlights the importance of novel players in Alzheimer's disease (AD) pathophysiology, including alterations of lipid metabolism and neuroinflammation. Indeed, a potential involvement of Proprotein convertase subtilisin/kexin type 9 (PCSK9) in AD has been recently postulated. Here, we first investigated the effects of PCSK9 on neuroinflammation in vitro. Then, we examined the impact of a genetic ablation of PCSK9 on cognitive performance in a severe mouse model of AD. Finally, in the same animals we evaluated the effect of PCSK9 loss on Aβ pathology, neuroinflammation, and brain lipids. For in vitro studies, U373 human astrocytoma cells were treated with Aβ fibrils and human recombinant PCSK9. mRNA expression of the proinflammatory cytokines and inflammasome-related genes were evaluated by q-PCR, while MCP-1 secretion was measured by ELISA. For in vivo studies, the cognitive performance of a newly generated mouse line - obtained by crossing 5XFAD In vitro, PCSK9 significantly increased IL6, IL1B and TNFΑ mRNA levels in Aβ fibrils-treated U373 cells, without influencing inflammasome gene expression, except for an increase in NLRC4 mRNA levels. In vivo, PCSK9 ablation in 5XFAD mice significantly improved the performance at the Morris water maze test; these changes were accompanied by a reduced corticohippocampal Aβ burden without affecting plaque spatial/regional distribution and composition or global BACE1 expression. Furthermore, PCSK9 loss in 5XFAD mice induced decreased microgliosis and astrocyte reactivity in several brain regions. Conversely, knocking out PCSK9 had minimal impact on brain cholesterol and hydroxysterol levels. In vitro studies showed a pro-inflammatory effect of PCSK9. Consistently, in vivo data indicated a protective role of PCSK9 ablation against cognitive impairments, associated with improved Aβ pathology and attenuated neuroinflammation in a severe mouse model of AD. PCSK9 may thus be considered a novel pharmacological target for the treatment of AD. Show less