Neuroprotective effect of phosphocreatine on oxidative stress and mitochondrial dysfunction induced apoptosis in vitro and in vivo: Involvement of dual PI3K/Akt and Nrf2/HO-1 pathways

FGF10 Enhances Peripheral Nerve Regeneration via the Preactivation of the PI3K/Akt Signaling-Mediated Antioxidant Response

The process of axonal regeneration after peripheral nerve injury (PNI) is slow and mostly incomplete. Previous studies have investigated the neuroprotective effects of fibroblast growth factor 10 (FGF10) against spinal cord injury and cerebral ischemia brain injury. However, the role of FGF10 in peripheral nerve regeneration remains unknown. In this study, we aimed to investigate the underlying therapeutic effects of FGF10 on nerve regeneration and functional recovery after PNI and to explore the associated mechanism. Our results showed that FGF10 administration promoted axonal regeneration and functional recovery after nerve damage. Moreover, exogenous FGF10 treatment also prevented SCs from excessive oxidative stress-induced apoptosis, which was probably related to the activation of phosphatidylinositol-3 kinase/protein kinase B (PI3K/Akt) signaling. The inhibition of the PI3K/Akt pathway by the specific inhibitor LY294002 partially reversed the therapeutic effects of FGF10 both in vivo and in vitro. Thus, from our perspective, FGF10 may be a promising therapeutic drug for repairing sciatic nerve damage through countering excessive oxidative stress-induced SC apoptosis.

Nrf2 Overexpression for the Protective Effect of Skin-Derived Precursors against UV-Induced Damage: Evidence from a Three-Dimensional Skin Model

Background

Skin photodamage is associated with ultraviolet- (UV-) induced reactive oxygen species (ROS) overproduction and nuclear factor erythroid 2-related factor 2 (Nrf2) inactivation. In our previous study, skin-derived precursors (SKPs) were shown to ameliorate a UV-induced damage in mice, probably through Nrf2 activation and ROS scavenging.

Objective

To clarify the mechanism underlying the photoprotective effect of SKPs against UV-induced damage in a three-dimensional (3D) skin model.

Methods

The Nrf2 gene in SKPs was modified using lentiviral infection, and 3D skin models were reconstructed with keratinocytes and fibroblasts on the basis of type I collagen. Subsequently, these models were divided into the following six groups: normal, model, overexpressed, control, silenced, and negative control groups. Prior to irradiation, respective SKPs were injected into the last four groups. Next, all groups except the normal group were exposed to UVA+UVB. Lastly, the pathological and molecular-biological techniques were employed to determine the parameters. Additionally, LY294002, a PI3K inhibitor, was used to investigate the roles of PI3K/Akt and Nrf2/hemeoxygenase-1 (HO-1) in SKP photoprotection.

Results

Normal 3D skin models appeared as milky-white analogs with a clear, well-arranged histological structure. After the skin was exposed to irradiation, it exhibited cell swelling and a disorganized structure and developed nuclear condensation with numerous apoptotic cells. The expressions of cellular protective genes and Nrf2/HO-1/PI3K/Akt proteins remarkably decreased, which were accompanied by increased oxidative stress and decreased antioxidants (P < 0.05). However, these phenomena were reversed by nrf2-overexpressing SKPs. The 3D skin in the overexpressed group showed mild swelling, neatly arranged cells, and few apoptotic cells. Cellular protective genes and Nrf2/HO-1/PI3K/Akt proteins were highly expressed, and the oxidative biomarkers were remarkably ameliorated (P < 0.05). Nevertheless, the expression of these proteins decreased after LY294002 pretreatment regardless of SKP treatment or not. Meanwhile, there were increases in both UV-induced apoptotic cells and ROS level accompanied with SOD and GPX decrease in the presence of LY294002.

Conclusions

Evidence from the 3D skin model demonstrates that the protection of SKPs against UV-mediated damage is primarily via the PI3K/Akt-mediated activation of the Nrf2/HO-1 pathway, indicating that SKPs may be a promising candidate for the treatment of photodermatoses.

Antiepileptic Effects of Protein-Rich Extract from Bombyx batryticatus on Mice and Its Protective Effects against H2O2-Induced Oxidative Damage in PC12 Cells via Regulating PI3K/Akt Signaling Pathways

Bombyx batryticatus is a known traditional Chinese medicine (TCM) utilized to treat convulsions, epilepsy, cough, asthma, headaches, and purpura in China for thousands of years. This study is aimed at investigating the antiepileptic effects of protein-rich extracts from Bombyx batryticatus (BBPs) on seizure in mice and exploring the protective effects of BBPs against H₂O₂-induced oxidative stress in PC12 cells and their underlying mechanisms. Maximal electroshock-induced seizure (MES) and pentylenetetrazole- (PTZ-) induced seizure in mice and the histological analysis were carried out to evaluate the antiepileptic effects of BBPs. The cell viability of PC12 cells stimulated by H₂O₂ was determined by MTT assay. The apoptosis and ROS levels of H₂O₂-stimulated PC12 cells were determined by flow cytometry analysis. Furthermore, the levels of malondialdehyde (MDA), superoxide dismutase (SOD), lactate dehydrogenase (LDH), and glutathione (GSH) in PC12 cells were assayed by ELISA and expressions of caspase-3, caspase-9, Bax, Bcl-2, PI3K, Akt, and p-Akt were evaluated by Western blotting and quantitative real-time polymerase chain reaction (RT-qPCR) assays. The results revealed that BBPs exerted significant antiepileptic effects on mice. In addition, BBPs increased the cell viability of H₂O₂-stimulated PC12 cells and reduced apoptotic cells and ROS levels in H₂O₂-stimulated PC12 cells. By BBPs treatments, the levels of MDA and LDH were reduced and the levels of SOD and GSH-Px were increased in H₂O₂-stimulated PC12 cells. Moreover, BBPs upregulated the expressions of PI3K, Akt, p-Akt, and Bcl-2, whereas they downregulated the expressions of caspase-9, caspase-3, and Bax in H₂O₂-stimulated PC12 cells. These findings suggested that BBPs possessed potential antiepileptic effects on MES and PTZ-induced seizure in mice and protective effects on H₂O₂-induced oxidative stress in PC12 cells by exerting antioxidative and antiapoptotic effects via PI3K/Akt signaling pathways.

Rhein from Rheum rhabarbarum Inhibits Hydrogen-Peroxide-Induced Oxidative Stress in Intestinal Epithelial Cells Partly through PI3K/Akt-Mediated Nrf2/HO-1 Pathways

Rheum rhabarbarum has been widely used as a herbal medicine and food in China. The objective of this study was to investigate the cytoprotective action and underlying mechanisms of rhein, one active ingredient isolated from R. rhabarbarum, on H₂O₂-challenged rat small intestine epithelial cells (IEC-6 cells). H₂O₂-challenged IEC-6 cells were incubated in the pretreatment with or without rhein or LY294002, a PI3K/Akt inhibitor. The cell viability, apoptosis, intracellular reactive oxygen species (ROS), and antioxidants were measured. The expressions of heme oxygenase 1 (HO-1), nuclear factor erythroid 2-related factor (Nrf2), Akt, and p-Akt were evaluated by western blotting. Meanwhile, LY294002 was also used to investigate the role of PI3K/Akt in the rhein-induced cytoprotective role. The results showed that pretreatment of rhein could reverse the inhibition of cell viability and suppress the apoptosis, caspase-3 activity, and intracellular ROS induced by H₂O₂. Rhein also supported SOD activity catalase activity, glutathione S-transferase activity, and glutathione content. Furthermore, rhein induced the protein expression of HO-1 together with its upstream mediator Nrf2 and activated the phosphorylation of Akt in IEC-6 cells. LY294002 inhibited increased cell viability, upregulated the lowered apoptotic rate, and enhanced the weakened ROS levels. Although the inhibition of PI3K/Akt did not inhibit the Nrf2 nuclear level under 4 μM rhein, LY294002 inhibited the Nrf2 nuclear level under 2 μM rhein and blocked HO-1 expression. These data demonstrated that rhein protected IEC-6 cells against oxidative damage partly via PI3K/Akt and Nrf2/HO-1 pathways.

2,5-Hexanedione mediates neuronal apoptosis through suppression of NGF via PI3K/Akt signaling in the rat sciatic nerve

Because precise mechanism for 2,5-hexanedione (HD)-induced neuronal apoptosis largely remains unknown, we explored the potential mechanisms both in vivo and in vitro Rats were intraperitoneally exposed to HD at different doses for 5 weeks, following which the expression levels of nerve growth factor (NGF), phosphorylation of Akt and Bad, dimerization of Bad and Bcl-xL, as well as the release of cytochrome c and the caspase-3 activity were measured. Moreover, these variables were also examined in vitro in HD-exposed VSC4.1 cells with or without a PI3K-specific agonist (IGF-1), and in HD-exposed VSC4.1 cells with or without a PI3K-specific inhibitor (LY294002) in the presence or absence of NGF. The data indicate that, as the concentration of HD increased, rats exhibited progressive gait abnormalities, and enhanced neuronal apoptosis in the rat sciatic nerve, compared with the results observed in the control group. Furthermore, HD significantly down-regulated NGF expression in the rat sciatic nerve. Moreover, suppression of NGF expression inhibited the phosphorylation of Akt and Bad. Meanwhile, an increase in the dimerization of Bad and Bcl-xL in mitochondria resulted in cytochrome c release and caspase-3 activation. In contrast, HD-induced apoptosis was eliminated by IGF-1. Additionally, NGF supplementation reversed the decrease in phosphorylation of Akt and Bad, as well as reversing the neuronal apoptosis in HD-exposed VSC4.1 cells. However, LY294002 blocked these effects of NGF. Collectively, our results demonstrate that mitochondrial-dependent apoptosis is induced by HD through NGF suppression via the PI3K/Akt pathway both in vivo and in vitro.

Preventive Effect of YGDEY from Tilapia Fish Skin Gelatin Hydrolysates against Alcohol-Induced Damage in HepG2 Cells through ROS-Mediated Signaling Pathways

According to a previous study, YGDEY from tilapia fish skin gelatin hydrolysates has strong free radical scavenging activity. In the present study, the protective effect of YGDEY against oxidative stress induced by ethanol in HepG2 cells was investigated. First, cells were incubated with YGDEY (10, 20, 50, and 100 μM) to assess cytotoxicity, and there was no significant change in cell viability. Next, it was established that YGDEY decreased the production of reactive oxygen species (ROS). Western blot results indicated that YGDEY increased the levels of superoxide dismutase (SOD) and glutathione (GSH) and decreased the expression of gamma-glutamyltransferase (GGT) in HepG2 cells. It was then revealed that YGDEY markedly reduced the expressions of bax and cleaved-caspase-3 (c-caspase-3); inhibited phosphorylation of Akt, IκB-α, p65, and p38; and increased the level of bcl-2. Moreover, the comet assay showed that YGDEY effectively decreased the amount of ethanol-induced DNA damage. Thus, YGDEY protected HepG2 cells from alcohol-induced injury by inhibiting oxidative stress, and this may be associated with the Akt/nuclear factor-κB (NF-κB)/mitogen-activated protein kinase (MAPK) signal transduction pathways. These results demonstrate that YGDEY from tilapia fish skin gelatin hydrolysates protects HepG2 cells from oxidative stress, making it a potential functional food ingredient.

Metabo-lipidomics of Fibroblasts and Mitochondrial-Endoplasmic Reticulum Extracts from ALS Patients Shows Alterations in Purine, Pyrimidine, Energetic, and Phospholipid Metabolisms

Amyotrophic lateral sclerosis (ALS) is characterized by a wide metabolic remodeling, as shown by recent metabolomics and lipidomics studies performed in samples from patient cohorts and experimental animal models. Here, we explored the metabolome and lipidome of fibroblasts from sporadic ALS patients (n = 13) comparatively to age- and sex-matched controls (n = 11), and the subcellular fraction containing the mitochondria and endoplasmic reticulum (mito-ER), given that mitochondrial dysfunctions and ER stress are important features of ALS patho-mechanisms. We also assessed the mitochondrial oxidative respiration and the mitochondrial genomic (mtDNA) sequence, although without yielding significant differences. Compared to controls, ALS fibroblasts did not exhibit a mitochondrial respiration defect nor an increased proportion of mitochondrial DNA mutations. In addition, non-targeted metabolomics and lipidomics analyses identified 124 and 127 metabolites, and 328 and 220 lipids in whole cells and the mito-ER fractions, respectively, along with partial least-squares-discriminant analysis (PLS-DA) models being systematically highly predictive of the disease. The most discriminant metabolomic features were the alteration of purine, pyrimidine, and energetic metabolisms, suggestive of oxidative stress and of pro-inflammatory status. The most important lipidomic feature in the mito-ER fraction was the disturbance of phosphatidylcholine PC (36:4p) levels, which we had previously reported in the cerebrospinal fluid of ALS patients and in the brain from an ALS mouse model. Thus, our results reveal that fibroblasts from sporadic ALS patients share common metabolic remodeling, consistent with other metabolic studies performed in ALS, opening perspectives for further exploration in this cellular model in ALS.

The memory improving effects of round scad (Decapterus maruadsi) hydrolysates on sleep deprivation-induced memory deficits in rats via antioxidant and neurotrophic pathways

Sleep deprivation negatively influences memory formation and consolidation, which leads to memory impairment associated with oxidative stress and neurotrophic pathways.

Panax notoginseng Saponins Protect Cerebral Microvascular Endothelial Cells against Oxygen-Glucose Deprivation/Reperfusion-Induced Barrier Dysfunction via Activation of PI3K/Akt/Nrf2 Antioxidant Signaling Pathway

Oxidative stress plays a critical role in cerebral ischemia/reperfusion (I/R)-induced blood-brain barrier (BBB) disruption. Panax notoginseng saponins (PNS) possess efficient antioxidant activity and have been used in the treatment of cerebral ischemic stroke in China. In this study, we determined the protective effects of PNS on BBB integrity and investigated the underlying mechanism in cerebral microvascular endothelial cells (bEnd.3) exposed to oxygen-glucose deprivation/reperfusion (OGD/R). MTT and LDH release assays revealed that PNS mitigated the OGD/R-induced cell injury in a dose-dependent manner. TEER and paracellular permeability assays demonstrated that PNS alleviated the OGD/R-caused disruption of BBB integrity. Fluorescence probe DCFH-DA showed that PNS suppressed ROS generation in OGD/R-treated cells. Immunofluorescence and western blot analysis indicated that PNS inhibited the degradation of tight junction proteins triggered by OGD/R. Moreover, mechanism investigations suggested that PNS increased the phosphorylation of Akt, the activity of nuclear Nrf2, and the expression of downstream antioxidant enzyme HO-1. All the effects of PNS could be reversed by co-treatment with PI3K inhibitor LY294002. Taken together, these observations suggest that PNS may act as an extrinsic regulator that activates Nrf2 antioxidant signaling depending on PI3K/Akt pathway and protects against OGD/R-induced BBB disruption in vitro.

Connection between Systemic Inflammation and Neuroinflammation Underlies Neuroprotective Mechanism of Several Phytochemicals in Neurodegenerative Diseases

Oxidative damage, mitochondrial dysfunction, and neuroinflammation are strongly implicated in the pathogenesis of neurodegenerative diseases including Alzheimer's disease (AD) and Parkinson's disease (PD), and a substantial portion of elderly population at risk of these diseases requires nutritional intervention to benefit health due to lack of clinically relevant drugs. To this end, anti-inflammatory mechanisms of several phytochemicals such as curcumin, resveratrol, propolis, polyunsaturated fatty acids (PUFAs), and ginsenosides have been extensively studied. However, correlation of the phytochemicals with neuroinflammation or brain nutrition is not fully considered, especially in their therapeutic mechanism for neuronal damage or dysfunction. In this article, we review the advance in antioxidative and anti-inflammatory effects of phytochemicals and discuss the potential communication with brain microenvironment by improved gastrointestinal function, enhanced systemic immunity, and neuroprotective outcomes. These data show that phytochemicals may modulate and suppress neuroinflammation of the brain by several approaches: (1) reducing systemic inflammation and infiltration via the blood-brain barrier (BBB), (2) direct permeation into the brain parenchyma leading to neuroprotection, (3) enhancing integrity of disrupted BBB, and (4) vagal reflex-mediated nutrition and protection by gastrointestinal function signaling to the brain. Therefore, many phytochemicals have multiple potential neuroprotective approaches contributing to therapeutic benefit for pathogenesis of neurodegenerative diseases, and development of strategies for preventing these diseases represents a considerable public health concern and socioeconomic burden.

Protective Effects of Oleuropein Against Cerebral Ischemia/Reperfusion by Inhibiting Neuronal Apoptosis

BACKGROUND In this study, we investigated the potential neuroprotective effect of oleuropein (OLE) on apoptotic changes via modulating Akt/glycogen synthase kinase 3 beta (Akt/GSK-3b) signaling in a rat model of cerebral ischemia/reperfusion injury (IRI). MATERIAL AND METHODS Sprague-Dawley male rats (12 weeks, n=200) were randomly assigned to 5 groups: sham group, vehicle (IRI+ vehicle) group, OLE (IRI+OLE) group, OLE+LY294002 (IRI+OLE+LY294002) group, and LY294002(IRI+LY294002) group. The rats were subjected to cerebral ischemia/reperfusion injury (IRI) model and treated once daily for 5 days with vehicle and OLE (100 mg/kg via intraperitoneal injection) after IRI injury. LY294002 (0.3 mg/kg) was intraperitoneally injected once at 30 min after IRI injury. Brain edema, neurological deficit, rotarod latencies, and Morris water maze (MWM) performance were evaluated after IRI. The number of dead cells were assayed by TUNEL staining. Western blot was used to detect the expression of Bcl-2, Bax, cleaved caspase-3 (CC3), neurotrophic factors, and the phosphorylation levels of Akt and GSK-3β. RESULTS Compared with the vehicle group, brain water content, neurological deficits, rotarod latencies, and escape latency following IRI were reduced in the OLE group. Cell apoptosis and reduced neurotrophic factor caused by IRI was also attenuated by OLE. Furthermore, increased p-Akt and decreased p-GSK-3β were caused by OLE, which were associated with decrease of Bax/Bcl-2 ratio and the suppression of Caspase-3 activity after IRI. Importantly, all the beneficial effects of OLE in the vehicle group were abrogated by PI3K inhibitor LY294002. CONCLUSIONS Cerebral ischemia was protected by OLE via suppressing apoptosis through the Akt/GSK-3β pathway and upregulating neurotrophic factor after IRI.