Melatonin Protects Neural Stem Cells Against Tri-Ortho-Cresyl Phosphate-Induced Autophagy

SIRT1-Dependent Neuroprotection by Resveratrol in TOCP-Induced Spinal Cord Injury: Modulation of ER Stress and Autophagic Flux

This study explores the neuroprotective effects of resveratrol (Resv) against tri-o-cresyl phosphate (TOCP)-induced neurotoxicity in the spinal cord of adult hens. It is well documented that TOCP exposure causes significant neurodegeneration via mechanisms that involve endoplasmic reticulum (ER) stress and impaired autophagy. In this experiment, adult hens were assigned to one of four groups: Control, Resv, TOCP, and TOCP + Resv. The spinal cord tissues were examined through transmission electron microscopy, hematoxylin and eosin (HE) staining, Nissl staining, and Western blotting to evaluate key proteins associated with ER stress and autophagy. Additionally, RT-qPCR and immunofluorescence were employed to measure sirtuin1 (SIRT1) expression. The findings revealed that TOCP induced severe ultrastructural damage, including disrupted myelin sheaths, dilated ER, and extensive neurodegeneration, as confirmed by histological evaluations. The expression levels of GRP78, p-PERK, p-eIF2α, ATF4, CHOP, Beclin-1, P62, and LC3-II were also significantly elevated by TOCP. However, Resv treatment markedly attenuated these pathological changes by reducing ER stress, restoring autophagic flux, and upregulating SIRT1 expression, preserving spinal cord integrity. These results indicate that Resv can effectively counteract TOCP-induced neurotoxicity by modulating ER stress and autophagy, underscoring its potential as a therapeutic agent for neuroprotection.

Effect of Melatonin on Alpha Synuclein and Autophagy in Dopaminergic Neuronal Differentiation of Adipose Mesenchymal Stem Cells

Background

The current work investigated the effect of melatonin on differentiation of adipose mesenchymal stem cells (AD-MSCs) into dopamine producing cells and its effect on autophagy process and alpha-Synuclein (α-Syn) secretion.

Methods

AD-MSCs were characterized by flow cytometry and divided into 4 groups; i) control group (AD-MSCs without any treatment), ii) M+MSCs group (MSCs treated with 1 µM melatonin for 12 days), iii) DN group (MSCs cultured in neurobasal A medium and essential neuronal growth factors for 12 days) and iv) DN+M group (MSCs cultured in neurobasal A medium and 1µM melatonin for 12 days. By the end of experiments, the dopamine and α-Syn levels using ELISA, the expression of MAP-2, m-TOR and α-Syn genes at the level of mRNA and detection of autophagosomes formation using transmission electron microscope were performed.

Results

We found that the isolated cells were MSCs due to their positivity expression for CD105 and CD90 and negativity expression for CD34 and CD45. The concentration of dopamine was significantly higher and α-Syn concentration was significantly lower in DN+M group when compared to other groups (P< 0.005). Also, this group showed the highly expression for MAP-2 gene and less expression for m-TOR and α-Syn genes (P< 0.005). Moreover, there was significantly increase in autophagosomes formation in this group than another group (P< 0.005).

Conclusions

It is concluded that the melatonin promotes the differentiation of rat AD-MSCs into dopaminergic cells via induction of autophagy process and reduction of α-Syn secretion.

Melatonin and the Programming of Stem Cells

Melatonin interacts with various types of stem cells, in multiple ways that comprise stimulation of proliferation, maintenance of stemness and self-renewal, protection of survival, and programming toward functionally different cell lineages. These various properties are frequently intertwined but may not be always jointly present. Melatonin typically stimulates proliferation and transition to the mature cell type. For all sufficiently studied stem or progenitor cells, melatonin’s signaling pathways leading to expression of respective morphogenetic factors are discussed. The focus of this article will be laid on the aspect of programming, particularly in pluripotent cells. This is especially but not exclusively the case in neural stem cells (NSCs) and mesenchymal stem cells (MSCs). Concerning developmental bifurcations, decisions are not exclusively made by melatonin alone. In MSCs, melatonin promotes adipogenesis in a Wnt (Wingless-Integration-1)-independent mode, but chondrogenesis and osteogenesis Wnt-dependently. Melatonin upregulates Wnt, but not in the adipogenic lineage. This decision seems to depend on microenvironment and epigenetic memory. The decision for chondrogenesis instead of osteogenesis, both being Wnt-dependent, seems to involve fibroblast growth factor receptor 3. Stem cell-specific differences in melatonin and Wnt receptors, and contributions of transcription factors and noncoding RNAs are outlined, as well as possibilities and the medical importance of re-programming for transdifferentiation.

Mitochondria-Inspired Nanoparticles with Microenvironment-Adapting Capacities for On-Demand Drug Delivery after Ischemic Injury

Stimuli-responsive nanoparticles (NPs), so-called "smart" NPs, possess great potentials in drug delivery. Presently, the intelligence of smart NPs is mainly based on their chemical or physical changes to stimuli, which are usually "mechanical" and fundamentally different from biological intelligence. Inspired by mitochondria (MT), a biosmart nanoparticle with microenvironment targeting and self-adaptive capacity (MTSNP) was fabricated for ischemic tissue repair. The nanoparticles were designed as shell@circular DNA@shell@core. The double shells were like the two-layered membranes of MT, the melatonin-loaded cores corresponded to the MT matrix, and the circular DNA corresponded to MTDNA. In function, melatonin-loaded cores simulated the cell-protective mechanism of MT, which naturally synthesized melatonin to resist ischemia, while circular DNA was constructed to mimic the biological oxygen-sensing mechanism, synthesizing VEGF for vascularization according to oxygen level, like the ATP supply by MT according to microenvironment demand. At the acute stage of ischemia, melatonin was rapidly released from MTSNP to scavenge reactive oxygen species and activated melatonin receptor I on MT to prevent cytochrome c release, which would activate apoptosis. During the chronic stage, circular DNA could sense hypoxia and actively secrete VEGF for revascularization as a response. Importantly, circular DNA could also receive feedback of revascularization and shut down VEGF secretion as an adverse response. Then, the therapeutic potentials of the MTSNP were verified in myocardial ischemia by the multimodality of the methods. Such nanoparticles may represent a promising intelligent nanodrug system.

Protective Effects of Melatonin on Neurogenesis Impairment in Neurological Disorders and Its Relevant Molecular Mechanisms

Neurogenesis is the process by which functional new neurons are generated from the neural stem cells (NSCs) or neural progenitor cells (NPCs). Increasing lines of evidence show that neurogenesis impairment is involved in different neurological illnesses, including mood disorders, neurogenerative diseases, and central nervous system (CNS) injuries. Since reversing neurogenesis impairment was found to improve neurological outcomes in the pathological conditions, it is speculated that modulating neurogenesis is a potential therapeutic strategy for neurological diseases. Among different modulators of neurogenesis, melatonin is a particularly interesting one. In traditional understanding, melatonin controls the circadian rhythm and sleep-wake cycle, although it is not directly involved in the proliferation and survival of neurons. In the last decade, it was reported that melatonin plays an important role in the regulation of neurogenesis, and thus it may be a potential treatment for neurogenesis-related disorders. The present review aims to summarize and discuss the recent findings regarding the protective effects of melatonin on the neurogenesis impairment in different neurological conditions. We also address the molecular mechanisms involved in the actions of melatonin in neurogenesis modulation.