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To investigate the role of PINK1/Parkin-mediated mitophagy in regulating synaptic remodeling of neuronal cells in depression-like behaviors induced by nonylphenol (NP). In vitro experiments: HT-22 neuronal cells were exposed to NP, and mitophagy and Parkin expression were inhibited using specific inhibitors. The cells were categorized into the following groups: (1) control (C) and low-dose NP group (L: 2.5 µM), medium-dose NP group (M: 50 µM), and high-dose NP groups (H: 100 µM); (2) control (C), NP (100 µM), Mdivi-1 (5 µM), and Mdivi-1 + NP (5 µM Mdivi-1 +100 µM NP) groups; (3) control (C), NP (100 µM), AC220 (2 nM), and AC220 + NP (2 nM AC220 +100 µM NP) groups. In vivo experiments: a total of 48 mice, including 24 C57BL/6 wild-type mice and 24 PKRK2 gene-knockout mice, were randomly assigned to the following four groups: control (C), NP (100 mg/kg/day), PKRK2-knockout (KO), and PKRK2-knockout + NP (100 mg/kg/day, KH) groups, with 12 mice in each group. In vitro: With increasing NP concentration, the ATP content reduced and the expressions of synaptic remodeling-related proteins (i.e., PSD-95, BDNF, SYN) decreased. In contrast, the expressions of mitophagy-related proteins and those involved in the PINK1/Parkin-signaling pathway (such as p62, Beclin1, PINK1, Parkin) increased (P < 0.05). Inhibition of mitophagy with Mdivi-1 alleviated the NP-induced changes in synaptic, mitophagy-related, and PINK1/Parkin pathway-related proteins. Similarly, the inhibition of Parkin with AC220 mitigated NP-induced effects on synaptic, mitophagy-related, and PINK1/Parkin-signaling pathway-related proteins and mRNA expression. In vivo: PKRK2 gene-knockout mice exhibited improved NP-induced depression-like behaviors and decreased NP-induced synaptic morphology and mitochondrial ultrastructure changes. Moreover, the gene knockout alleviated the downregulation of synaptic remodeling-related proteins and inhibited the PINK1/Parkin-signaling pathway-mediated mitophagy activated by NP. Mitophagy inhibition or PKRK2 knockout can alleviate NP-induced downregulation of synaptic remodeling-related proteins, protect synaptic morphology and ultrastructure, and improve NP-induced depression-like behaviors. Show less

A vital question in neuroscience is whether and how efficiently cellular models may be differentiated into functional neuronal cells in culture. Despite the frequent use of the human neuroblastoma cell line SH-SY5Y, differentiation protocols vary extensively, with the most common being differentiation via the addition of retinoic acid and brain-derived neurotrophic factor. However, due to the lack of a reliable evaluation method, their adequacy as synaptic models remains unclear. Here, we investigate whether SH-SY5Y cells constitute a functional model for synaptic studies by phenotypically and ultrastructurally analyzing synaptogenesis in SH-SY5Y cells subjected to different differentiation protocols. Electron microscopy (EM) techniques, including conventional EM, cryo-EM, and cryo-electron tomography, were systematically applied to characterize synaptogenesis in SH-SY5Y cells. Further characterization was performed using immunostaining and functional assays, such as live exocytosis assays and whole-cell patch-clamp electrophysiology. Despite exhibiting some presynaptic-like features, differentiated SH-SY5Y cells do not form morphologically or functionally complete synapses under the conditions tested. Immunostaining results were consistent with previous findings, showing synaptic markers. However, functional investigations did not detect synaptic activity. High-throughput EM analyses revealed an absence of synaptic structures in these cells. Additionally, an alternative differentiation approach incorporating additional neurotrophic factors promoted the formation of presynaptic-like compartments containing synaptic vesicle-like vesicles (SVLVs). In contrast to typical synaptic vesicles, these SVLVs exhibited a pleomorphic size distribution and lacked connectors. These findings underscore the need for cautious interpretation of results derived from SH-SY5Y cells when investigating molecular synaptic architecture or function, as well as neurodegenerative diseases. Show less

Neurotrophins are a class of proteins that maintain the health and phenotype of neuronal cells under normal physiological conditions. Nerve growth factor was the first neurotrophin to be discovered, supporting the survival and cholinergic phenotype of basal forebrain cholinergic neurons, which are crucial in maintaining cognitive function in healthy individuals. Nerve growth factor metabolism is altered in Alzheimer's disease and, along with the degeneration of basal forebrain cholinergic neurons and loss of cholinergic pathways in the affected brain, contributes to cognitive problems. These findings initiated the application of nerve growth factor supplementation as a regenerative strategy against Alzheimer's disease in the late 20 th century. Later decades witnessed the development of drugs that support cholinergic activity, namely, cholinesterase inhibitors offering small but persisting cognitive benefits in Alzheimer's disease patients. Further developments in the Alzheimer's disease field have witnessed the rise of anti-amyloid immunotherapies that target the amyloid plaques in Alzheimer's disease brains in an attempt to reduce disease pathology. Over the years, several reports have appeared in support of or undermining the therapeutic claims of each strategy, while many other therapeutic approaches are being presently tested. In this narrative review, we present broader perspectives regarding cholinergic therapeutic strategies against Alzheimer's disease, highlighting aspects in the Alzheimer's disease field that need to be addressed, and propose future perspectives. We provide a special focus on neurotrophic molecules, especially on nerve growth factor, due to its close association with cognitive pathways and its relationship with cholinergic pathways, since cholinesterase inhibitors remain a widely used medication for Alzheimer's disease patients even after 30 years of research. Show less

Repetitive magnetic stimulation (rMS) is used to treat neurological conditions. Understanding its modulatory effects requires investigating cellular processes and molecular pathways Active (75-, 150-, and 300-sec exposure) or sham rMS was administered daily (4 days/300mT-1Hz) to two neuronal [SK-N-BE(2) and SH-SY5Y] and one non-neuronal (HOS) tumor line. Cell viability, cell death, and gene expression of Both neuroblastoma cell lines, SH-SY5Y (150-sec) and SK-N-BE(2) (75-sec), exhibited increased viability compared to the 300-sec group immediately after treatment; however, none of the stimulated groups was different from sham. rMS increased rMS did not affect cell viability or death in these Show less

Pathological neuroinflammation is a critical factor that disrupts neuronal activity and, when sustained, ultimately contributes to neuronal death. Among the primary mediators of neuroinflammation, microglia play a central role in modulating brain immunity. However, their overactivation is closely associated with neuronal damage and structural remodeling of brain tissue, leading to the onset and progression of various neurodegenerative diseases. We investigated the neuroprotective effects of avarol, a marine-derived sesquiterpenoid, focusing on its ability to inhibit lipopolysaccharide (LPS)-induced overactivation of BV2 microglial cells and its subsequent impact on neuronal activity in HT-22 hippocampal neuronal cells. Pretreatment with avarol significantly attenuated the LPS-induced release of pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), as well as oxidative stress markers such as reactive oxygen species (ROS) and nitric oxide (NO). These inhibitory effects were further substantiated by a dose-dependent reduction in nuclear translocation of nuclear factor-kappa B (NF-κB), a key transcription factor involved in the inflammatory signaling cascade. Regarding the interaction between microglia and neurons, both conditioned medium and co-culture systems demonstrated that avarol significantly attenuated alterations in neuronal plasticity-related molecules-such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF)-induced by activated microglia. Overall, these findings suggest that avarol exerts neuroprotective effects through the modulation of microglia-mediated neuroinflammation. Importantly, avarol's capacity to traverse the blood-brain barrier highlights its potential as an effective pharmacological agent in mitigating neuroinflammation-associated neurological disorders. Show less