Skin-derived precursor Schwann cells protect SH-SY5Y cells against 6-OHDA-induced neurotoxicity by PI3K/AKT/Bcl-2 pathway

Promotive effect of skin precursor-derived Schwann cells on brachial plexus neurotomy and motor neuron damage repair through milieu-regulating secretome

Brachial plexus injury (BPI) with motor neurons (MNs) damage still remain poor recovery in preclinical research and clinical therapy, while cell-based therapy approaches emerged as novel strategies. Previous work of rat skin precursor-derived Schwann cells (SKP-SCs) provided substantial foundation for repairing peripheral nerve injury (PNI). Given that, our present work focused on exploring the repair efficacy and possible mechanisms of SKP-SCs implantation on rat BPI combined with neurorrhaphy post-neurotomy. Results indicated the significant locomotive and sensory function recovery, with improved morphological remodeling of regenerated nerves and angiogenesis, as well as amelioration of target muscles atrophy and motor endplate degeneration. Besides, MNs could restore from oxygen-glucose-deprivation (OGD) injury upon SKP-SCs-sourced secretome treatment, implying the underlying paracrine mechanisms. Moreover, rat cytokine array assay detected 67 cytokines from SKP-SC-secretome, and bioinformatic analyses of screened 32 cytokines presented multiple functional clusters covering diverse cell types, including inflammatory cells, Schwann cells, vascular endothelial cells (VECs), neurons, and SKP-SCs themselves, relating distinct biological processes to nerve regeneration. Especially, a panel of hypoxia-responsive cytokines (HRCK), can participate into multicellular biological process regulation for permissive regeneration milieu, which underscored the benefits of SKP-SCs and sourced secretome, facilitating the chorus of nerve regenerative microenvironment. Furthermore, platelet-derived growth factor-AA (PDGF-AA) and vascular endothelial growth factor-A (VEGF-A) were outstanding cytokines involved with nerve regenerative microenvironment regulating, with significantly elevated mRNA expression level in hypoxia-responsive SKP-SCs. Altogether, through recapitulating the implanted SKP-SCs and derived secretome as niche sensor and paracrine transmitters respectively, HRCK would be further excavated as molecular underpinning of the neural recuperative mechanizations for efficient cell therapy; meanwhile, the analysis paradigm in this study validated and anticipated the actions and mechanisms of SKP-SCs on traumatic BPI repair, and was beneficial to identify promising bioactive molecule cocktail and signaling targets for cell-free therapy strategy on neural repair and regeneration.

The PI3K-AKT pathway: A plausible therapeutic target in Parkinson's disease

Parkinson's disease is a common progressive and multifactorial neurodegenerative disease, characterized by the loss of midbrain dopaminergic neurons. Numerous pathological processes including, inflammation, oxidative stress, mitochondrial dysfunction, neurotransmitter imbalance, and apoptosis as well as genetic factors may lead to neuronal degeneration. With the emergence of aging population, the health problem and economic burden caused by PD also increase. Phosphatidylinositol 3-kinases-protein kinase B (PI3K-AKT) signaling pathway regulates signal transduction and biological processes such as cell proliferation, apoptosis and metabolism. According to reports, it regulates neurotoxicity and mediates the survival of neurons. Accumulating evidences indicate that some natural products can play a neuroprotective role by activating PI3K-AKT pathway, providing an effective resource for the discovery of potential therapeutic drugs. The current review provides an overview of the PI3K-AKT signaling pathway and review the relationship between this signaling pathway and PD.

Progesterone exerts a neuroprotective action in a Parkinson's disease human cell model through membrane progesterone receptor α (mPRα/PAQR7)

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, and current treatment options are unsatisfactory on the long term. Several studies suggest a potential neuroprotective action by female hormones, especially estrogens. The potential role of progestogens, however, is less defined, and no studies have investigated the potential involvement of membrane progesterone receptors (mPRs). In the present study, the putative neuroprotective role for mPRs was investigated in SH-SY5Y cells, using two established pharmacological treatments for cellular PD models, 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenylpyridinium (MPP+). Our results show that both the physiologic agonist progesterone and the specific mPR agonist Org OD 02-0 were effective in reducing SH-SY5Y cell death induced by 6-OHDA and MPP⁺, whereas the nuclear PR agonist promegestone (R5020) and the GABA_A receptor agonist muscimol were ineffective. Experiments performed with gene silencing technology and selective pharmacological agonists showed that mPRα is the isoform responsible for the neuroprotective effects we observed. Further experiments showed that the PI3K-AKT and MAP kinase signaling pathways are involved in the mPRα-mediated progestogen neuroprotective action in SH-SY5Y cells. These findings suggest that mPRα could play a neuroprotective role in PD pathology and may be a promising target for the development of therapeutic strategies for PD prevention or management.

Neuroprotective effects of insulin-like growth factor-2 in 6-hydroxydopamine-induced cellular and mouse models of Parkinson's disease

Skin-derived precursor Schwann cells have been reported to play a protective role in the central nervous system. The neuroprotective effects of skin-derived precursor Schwann cells may be attributable to the release of growth factors that nourish host cells. In this study, we first established a cellular model of Parkinson's disease using 6-hydroxydopamine. When SH-SY5Y cells were pretreated with conditioned medium from skin-derived precursor Schwann cells, their activity was greatly increased. The addition of insulin-like growth factor-2 neutralizing antibody markedly attenuated the neuroprotective effects of skin-derived precursor Schwann cells. We also found that insulin-like growth factor-2 levels in the peripheral blood were greatly increased in patients with Parkinson's disease and in a mouse model of Parkinson's disease. Next, we pretreated cell models of Parkinson's disease with insulin-like growth factor-2 and administered insulin-like growth factor-2 intranasally to a mouse model of Parkinson's disease induced by 6-hydroxydopamine and found that the level of tyrosine hydroxylase, a marker of dopamine neurons, was markedly restored, α-synuclein aggregation decreased, and insulin-like growth factor-2 receptor down-regulation was alleviated. Finally, in vitro experiments showed that insulin-like growth factor-2 activated the phosphatidylinositol 3 kinase (PI3K)/AKT pathway. These findings suggest that the neuroprotective effects of skin-derived precursor Schwann cells on the central nervous system were achieved through insulin-like growth factor-2, and that insulin-like growth factor-2 may play a neuroprotective role through the insulin-like growth factor-2 receptor/PI3K/AKT pathway. Therefore, insulin-like growth factor-2 may be an useful target for Parkinson's disease treatment.

Membrane Progesterone Receptor α (mPRα/PAQR7) Promotes Survival and Neurite Outgrowth of Human Neuronal Cells by a Direct Action and Through Schwann Cell-like Stem Cells

We recently showed that membrane progesterone receptor α (mPRα/PAQR7) promotes pro-regenerative effects in Schwann cell-like adipose stem cells (SCL-ASC), an alternative model to Schwann cells for the promotion of peripheral nerve regeneration. In this study, we investigated how mPRα activation with the mPR-specific agonist Org OD 02-0 in SCL-ASC affected regenerative parameters in two neuronal cell lines, IMR-32 and SH-SY-5Y. In a series of conditioned medium experiments, we found that mPR activation of SCL-ASC led to increased neurite outgrowth, protection from cell death and increased expression of peripheral nerve regeneration markers (CREB3, ATF3, GAP43) in neuronal cell lines. These effects were stronger than the ones observed with the conditioned medium from untreated SCL-ASC. The addition of Org OD 02-0 to the untreated cell medium mimicked the effects of mPR activation of SCL-ASC on cell death, but not on neurite outgrowth. Therefore, the effect of Org OD 02-0 on neurite outgrowth is SCL-ASC-dependent, while its effect on cell survivability is likely due to the direct activation of mPRs on neuronal cells. SCL-ASC transfection with mPRα siRNA showed that this isoform is responsible for the beneficial effect on neurite outgrowth. Further experiments showed that SCL-ASC-dependent outcomes likely involved the release of BDNF and IGF-2 from these cells. The beneficial mPRα effect on neurite outgrowth was confirmed in co-culture conditions. These findings strengthen the hypothesis that mPRα could play a pro-regenerative role in SCL-ASC and be a therapeutic target for the promotion of peripheral nerve regeneration.

Protective Effects of Jujubosides on 6-OHDA-Induced Neurotoxicity in SH-SY5Y and SK-N-SH Cells

6-hydroxydopamine (6-OHDA) is used to induce oxidative damage in neuronal cells, which can serve as an experimental model of Parkinson’s disease (PD). Jujuboside A and B confer free radical scavenging effects but have never been examined for their neuroprotective effects, especially in PD; therefore, in this study, we aimed to investigate the feasibility of jujubosides as protectors of neurons against 6-OHDA and the underlying mechanisms. 6-OHDA-induced neurotoxicity in the human neuronal cell lines SH-SY5Y and SK-N-SH, was used to evaluate the protective effects of jujubosides. These findings indicated that jujuboside A and B were both capable of rescuing the 6-OHDA-induced loss of cell viability, activation of apoptosis, elevation of reactive oxygen species, and downregulation of the expression levels of superoxide dismutase, catalase, and glutathione peroxidase. In addition, jujuboside A and B can reverse a 6-OHDA-elevated Bax/Bcl-2 ratio, downregulate phosphorylated PI3K and AKT, and activate caspase-3, -7, and -9. These findings showed that jujubosides were capable of protecting both SH-SY5Y and SK-N-SH neuronal cells from 6-OHDA-induced toxicity via the rebalancing of the redox system, together with the resetting of the PI3K/AKT apoptotic signaling cascade. In conclusion, jujuboside may be a potential drug for PD prevention.

Schwann cells differentiated from skin-derived precursors provide neuroprotection via autophagy inhibition in a cellular model of Parkinson's disease

Autophagy has been shown to play an important role in Parkinson’s disease. We hypothesized that skin-derived precursor cells exhibit neuroprotective effects in Parkinson’s disease through affecting autophagy. In this study, 6-hydroxydopamine-damaged SH-SY5Y cells were pretreated with a culture medium containing skin-derived precursors differentiated into Schwann cells (SKP-SCs). The results showed that the SKP-SC culture medium remarkably enhanced the activity of SH-SY5Y cells damaged by 6-hydroxydopamine, reduced excessive autophagy, increased tyrosine hydroxylase expression, reduced α-synuclein expression, reduced the autophagosome number, and activated the PI3K/AKT/mTOR pathway. Autophagy activator rapamycin inhibited the effects of SKP-SCs, and autophagy inhibitor 3-methyladenine had the opposite effect. These findings confirm that SKP-SCs modulate the PI3K/AKT/mTOR pathway to inhibit autophagy, thereby exhibiting a neuroprotective effect in a cellular model of Parkinson’s disease. This study was approved by the Animal Ethics Committee of Laboratory Animal Center of Nantong University (approval No. S20181009-205) on October 9, 2018.

Protective Effect of Butylphthalide on Neuronal Apoptosis in Parkinson Rats and Its Effect on miR-146a-5p Expression and Phosphatidylinositide 3-Kinases/Protein Kinase B Pathway

80 male Wistar rats were stochastically assigned to Sham + Vehicle group, Sham + BUT group, PD + Vehicle group and PD + BUT group. Rotenone PD model rats were prepared by subcutaneous injection of rotenone sunflower oil emulsion 2 mg/(kg · d) for 5 consecutive weeks. Butylphthalide 80 mg/(kg · d) were given to the rats in Sham + BUT group and PD + BUT group by gavage from the first day of rotenone injection for 5 weeks. Subsequently, the motor retardation ability and the morphological changes of the substantia nigra (SN) of each group were evaluated. Meanwhile, the levels of neuronal injury, apoptosis, inflammation and oxidative stress in each group of rats were assayed. The impact of BUT treatment on miR-146a-5p expression and PI3K/AKT signal pathway in rat brain tissue was assayed. Finally, by constructing a PD cell model of the neurotoxin 6-hydroxydopamine (6-OHDA)-treated human neuroblastoma cell line SH-SY5Y, the in vitro anti-PD pharmacological effect of BUT was further verified.

SKP-SCs transplantation alleviates 6-OHDA-induced dopaminergic neuronal injury by modulating autophagy

Parkinson's disease is a common neurodegenerative disease. Cell transplantation is a promising therapeutic option for improving the survival and function of dopaminergic neurons, but the mechanisms underlying the interaction between the transplanted cells and the recipient neurons remain to be studied. In this study, we investigated the effects of skin precursor cell-derived Schwann cells (SKP-SCs) directly cocultured with 6-OHDA-injured dopaminergic neurons in vitro and of SKP-SCs transplanted into the brains of 6-OHDA-induced PD mice in vivo. In vitro and in vivo studies revealed that SKP-SCs could reduce the damage to dopaminergic neurons by enhancing self-autophagy and modulating neuronal autophagy. Thus, the present study provides the first evidence that cell transplantation mitigates 6-OHDA-induced damage to dopaminergic neurons by enhancing self-autophagy, suggesting that earlier transplantation of Schwann cells might help alleviate the loss of dopaminergic neurons.

Intracarotid Transplantation of Skin-Derived Precursor Schwann Cells Promotes Functional Recovery After Acute Ischemic Stroke in Rats

Purpose: Skin-derived Precursor Schwann cells (SKP-SCs) have been reported to provide neuroprotection for the injured and dysmyelinated nervous system. However, little is known about SKP-SCs on acute ischemic stroke (AIS). We aimed to explore the efficacy and the potential mechanism of action of SKP-SCs on AIS in a rat ischemic stroke model.

Methods: Adult male Sprague–Dawley rats were subjected to a middle cerebral artery occlusion (MCAO) for 1.5 h on Day 0 and subsequently received an intracarotid injection of 2 × 10⁶ green fluorescent protein (GFP) -labeled SKP-SCs or phosphate buffered saline (PBS) during reperfusion. Neurological function was assessed by behavioral tests on Days 1, 4, 7, 14, and 28. In a satellite cohort, rat brains were harvested and infarct volume was measured with 2,3,5-triphenyltetrazolium chloride (TTC) staining on Days 1 and 7, and migration and survival of SKP-SCs in the brain were traced by monitoring green fluorescence at 6 and12 h on Day 0, and on Days 1, 4, 7, 14, and 28. Histopathology and immunofluorescence staining were used to analyze the morphology, survival and apoptosis of neurons. Additionally, in an in vitro SKP-SC co-culture model using fetal rat primary cortical neurons underwent oxygen glucose deprivation/reoxygenation (OGD/R), Western blot was used to detect the expression of apoptosis indicators including activated caspase-3, Bax, and Bcl-2. TUNEL staining was used to count apoptotic cells.

Results: Intracarotid transplantation of SKP-SCs effectively migrated to the periinfarct area and survived for at least 4 weeks. Transplanted SKP-SCs inhibited neuronal apoptosis, reduced infarct volume, and improved neurological recovery in the MCAO rats. Moreover, in vitro data showed that SKP-SCs treatment inhibited OGD/R-induced neuronal apoptosis and promoted survival of the cultured primary cortical neurons.

Conclusions: Intracarotid transplantation of SKP-SCs promoted functional recovery in the rat AIS model and possesses the potential to be further developed as a novel therapy to treat ischemic stroke in humans.

Extracellular vesicles from skin precursor-derived Schwann cells promote axonal outgrowth and regeneration of motoneurons via Akt/mTOR/p70S6K pathway

Background

Skin precursor-derived Schwann cells (SKP-SCs) have been shown to benefit the recovery of spinal cord injury (SCI) and peripheral nerve injury (PNI) with motor dysfunction. However, the effect of extracellular vesicles (EVs) from SKP-SCs responsible for neuroregeneration remains unknown.

Methods

Based on the obtainment and identification of rat SKP-SCs and their derived EVs, the primary rat injury model of motoneurons resulting from axotomy in vitro or nerve crush in vivo, as well as the secondary rat ischemic hypoxic injury model of motoneuron exposure to oxygen-glucose-deprivation (OGD) in vitro, were treated with EVs from skin precursor-derived Schwann cells (SKP-SC-EVs), respectively. Then, the axonal outgrowth and regrowth was observed and compared, and cell viability as well as the protein kinase B/mammalian target of rapamycin/p70 S6 kinase (Akt/mTOR/p70S6K) signaling pathway was detected, moreover, rapamycin (an mTOR inhibitor) was used to further reveal the underlying molecular mechanism.

Results

The internalization of SKP-SC-EVs by neuronal cells was identified in vitro and in vivo. Besides the pro-axonal outgrowth effect of SKP-SC-EVs, prospectively, the treatment of OGD-injured motoneurons with SKP-SC-EVs potentiated the restoration of neuronal viability and axonal regrowth. Furthermore, the axotomizing injury could be improved with SKP-SC-EVs treatment in vitro and in vivo. Finally, it was shown that the application of SKP-SC-EVs could activate the Akt/mTOR/p70S6K signaling pathway that can be abolished by rapamycin.

Conclusions

In summary, the addition of SKP-SC-EVs could regulate the cell growth and death signaling pathway mediated by Akt/mTOR/p70S6K, owing to the transmission of cargos in EVs to damaged motoneurons, which leads to axonal regrowth and neuronal resurrection. Thus, SKP-SC-EVs treatment could be a novel promising strategy for improving the axonal outgrowth and regeneration of motoneurons.

Galangin Reverses Hepatic Fibrosis by Inducing HSCs Apoptosis via the PI3K/Akt, Bax/Bcl-2, and Wnt/β-Catenin Pathway in LX-2 Cells

Hepatic fibrosis (HF) is a common disease, with currently no available treatment. Galangin, a natural flavonoid extracted from Alpinia officinaruim Hance, has multiple effects demonstrated in previous studies. The aim of the present study was to explore the anti-fibrogenic effect of galangin in vitro, and research its potential molecular mechanisms. LX-2 cells were chosen as an in vitro HF model, and were treated with galangin in different concentrations. Cell viability was analyzed using Cell Counting Kit-8 (CCK-8) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cell apoptosis was measured using flow cytometry, and the anti-fibrogenic effect of galangin was determined using RT-quantitative (q)PCR, immunofluorescence, and Western blotting. The results show that the proliferation of LX-2 cells was efficiently inhibited by galangin, and apoptosis was induced in a dose-dependent manner. Both the mRNA and protein expression of alpha-smooth muscle actin (α-SMA) and collagen I were markedly downregulated. Galangin also inhibited the phosphatidylinositol 3-kinase (PI3K)/Akt and Wnt/β-catenin signaling pathways and increased the Bax/Bcl-2 ratio. The results of this study suggest that galangin has an anti-fibrogenic effect and may represent a promising agent in the treatment of hepatic fibrosis.