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

Combination of paeoniflorin and calycosin-7-glucoside alleviates ischaemic stroke injury via the PI3K/AKT signalling pathway

CONTEXT

Paeoniflorin (PF) and calycosin-7-glucoside (CG, Paeonia lactiflora Pall. extract) have demonstrated protective effects in ischaemic stroke.

OBJECTIVE

To investigate the synergistic effects of PF + CG on ischaemia/reperfusion injury in vivo and in vitro.

MATERIALS AND METHODS

Male Sprague-Dawley rats were subjected to the middle cerebral artery occlusion/reperfusion (MCAO/R). After MCAO/R for 24 h, rats were randomly subdivided into 5 groups: sham, model (MCAO/R), study treatment (PF + CG, 40 + 20 mg/kg), LY294002 (20 mg/kg), and study treatment + LY294002. Males were given via intragastric administration; the duration of the in vivo experiment was 8 days. Neurologic deficits, cerebral infarction, brain edoema, and protein levels were assessed in vivo. Hippocampal neurons (HT22) were refreshed with glucose-free DMEM and placed in an anaerobic chamber for 8 h. Subsequently, HT22 cells were reoxygenated in a 37 °C incubator with 5% CO₂ for 6 h. SOD, MDA, ROS, LDH and protein levels were measured in vitro.

RESULTS

PF + CG significantly reduced neurobehavioral outcomes (21%), cerebral infarct volume (44%), brain edoema (1.6%) compared with the MCAO/R group. Moreover, PF + CG increased p-PI3K/PI3K (4.69%, 7.4%), p-AKT/AKT (6.25%, 60.6%) and Bcl-2/BAX (33%, 49%) expression in vivo and in vitro, and reduced GSK-3β (10.5%, 9.6%) expression. In vitro, PF + CG suppressed apoptosis in HT22 cells and decreased ROS and MDA levels (20%, 50%, respectively).

CONCLUSIONS

PF + CG showed a synergistic protective effect against ischaemic brain injury, potentially being a future treatment for ischaemic stroke.

Methylglyoxal in the Brain: From Glycolytic Metabolite to Signalling Molecule

Advances in molecular biology technology have piqued tremendous interest in glycometabolism and bioenergetics in homeostasis and neural development linked to ageing and age-related diseases. Methylglyoxal (MGO) is a by-product of glycolysis, and it can covalently modify proteins, nucleic acids, and lipids, leading to cell growth inhibition and, eventually, cell death. MGO can alter intracellular calcium homeostasis, which is a major cell-permeant precursor to advanced glycation end-products (AGEs). As side-products or signalling molecules, MGO is involved in several pathologies, including neurodevelopmental disorders, ageing, and neurodegenerative diseases. In this review, we demonstrate that MGO (the metabolic side-product of glycolysis), the GLO system, and their analogous relationship with behavioural phenotypes, epigenetics, ageing, pain, and CNS degeneration. Furthermore, we summarise several therapeutic approaches that target MGO and the glyoxalase (GLO) system in neurodegenerative diseases.

Effects of treatment with a carbon monoxide donor and an activator of heme oxygenase 1 on the nociceptive, apoptotic and/or oxidative alterations induced by persistent inflammatory pain in the central nervous system of mice

The activation of heme oxygenase 1 (HO-1)/carbon monoxide (CO) inhibits chronic inflammatory pain, but its role in the central nervous system (CNS) is not entirely known. We evaluated whether the treatment with an HO-1 inducer, cobalt protoporphyrin IX (CoPP), or a CO-releasing molecule, tricarbonyldichlororuthenium(II)dimer (CORM-2), modulates the nociceptive, apoptotic and/or oxidative responses provoked by persistent inflammatory pain in the CNS. In C57BL/6 male mice with peripheral inflammation caused by complete Freund's adjuvant (CFA), we assessed the effects of CORM-2 and CoPP on the expression of protein kinase B (Akt), the apoptotic protein BAX, and the antioxidant enzymes HO-1 and NADPH quinone oxidoreductase 1 (NQO1) in the periaqueductal gray matter (PAG), amygdala (AMG), ventral hippocampus (VHPC) and medial septal area (MSA). Our results showed that the increased expression of p-Akt caused by peripheral inflammation in the four analyzed brain areas was reversed by CORM-2 and CoPP therapies. Both treatments also normalized the upregulation of BAX induced by CFA on the VHPC and MSA. Oxidative stress, demonstrated with the decreased expression of HO-1 on the PAG and AMG, was normalized in CORM-2 and CoPP treated animals. CoPP also increased the expression of HO-1 on VHPC, and both treatments up-regulated the NQO1 levels on the PAG of CFA-injected animals. In conclusion, both CORM-2 and CoPP treatments inhibited the nociceptive and apoptotic responses generated by peripheral inflammation and/or potentiated the antioxidant responses in several brain areas revealing the new modulatory effects of these treatments in the CNS of animals with chronic inflammatory pain.

Liraglutide reduces oxidative stress and improves energy metabolism in methylglyoxal-induced SH-SY5Y cells

Diabetes mellitus can result in severe complications, such as neurodegenerative diseases including cognitive impairment and dementia. The glucagon-like peptide-1 (GLP-1) receptor agonist, liraglutide, is a novel antidiabetic drug with neuroprotective effects against neurodegenerative diseases. In this study, we explored the protective effect of liraglutide on SH-SY5Y cells exposed to methylglyoxal (MG), a byproduct of glucose metabolism that plays a key role in the development of diabetic encephalopathy. We found that liraglutide reduced the MG-induced oxidative stress, increased the activity of superoxide dismutase (SOD) and expression levels of P22phox, Gp91phox, and Xdh genes, and reduced reactive oxygen species (ROS) content. Metabolomics analysis based on ¹H nuclear magnetic resonance showed that liraglutide induced alterations in metabolites involved in energy metabolism，including promotion of gluconeogenesis. Moreover, we found that liraglutide promoted oxidative phosphorylation and inhibited glycolysis in SH-SY5Y cells. This study revealed that liraglutide improved diabetes-related neuropathy damage by reducing the level of oxidative stress and maintaining the balance of energy metabolism, thus offering new insights into the potential mechanism of liraglutide in neuronal protection.

High frequency repetitive transcranial magnetic stimulation alleviates cognitive deficits in 3xTg-AD mice by modulating the PI3K/Akt/GLT-1 axis

OBJECTIVE

Glutamate mediated excitotoxicity, such as oxidative stress, neuroinflammation, synaptic loss and neuronal death, is ubiquitous in Alzheimer's disease (AD). Our previous study found that 15 Hz repetitive transcranial magnetic stimulation (rTMS) could reduce cortical excitability. The purpose of this study was to explore the therapeutic effect of higher frequency rTMS on 3xTg-AD model mice and further explore the mechanisms of rTMS.

METHODS

First, WT and 3xTg-AD model mice received 25 Hz rTMS treatment for 21 days. The Morris water maze test was used to evaluate the cognitive function. The levels of Aβ and neuroinflammation were assessed by ELISA and immunofluorescence. Oxidative stress was quantified by biochemical assay kits. Brain glucose metabolism was assessed by 18F-FDG PET. Apoptosis was assessed by western blot and TUNEL staining. Synaptic plasticity and PI3K/Akt/GLT-1 pathway related protein expression were assessed by western blot. Next, to explore the activity of PI3K/Akt in the therapeutic effect of rTMS, 3xTg-AD model mice were given LY294002 intervention and rTMS treatment for 21 days, the experimental method was the same as before.

RESULTS

We found that 25 Hz rTMS could improve cognitive function of 3xTg-AD model mice, reduce hippocampal Aβ1-42 levels, ameliorate oxidative stress and improve glucose metabolism. rTMS alleviated neuroinflammatory response, enhanced synaptic plasticity and reduced neuronal loss and cell apoptosis, accompanied by activation of PI3K/Akt/GLT-1 pathway. After administration of PI3K/Akt inhibitor LY294002, 25 Hz rTMS could not improve the cognitive function and reduce neuron damage of 3xTg-AD model mice, nor could it upregulate the expression of GLT-1, indicating that its therapeutic and protective effects required the involvement of PI3K/Akt/GLT-1 pathway.

CONCLUSION

rTMS exerts protective role for AD through regulating multiple pathological processes. Meanwhile, this study revealed the key role of PI3K/Akt/GLT-1 pathway in the treatment of AD by rTMS, which might be a new target.

Sipeimine ameliorates PM2.5-induced lung injury by inhibiting ferroptosis via the PI3K/Akt/Nrf2 pathway: A network pharmacology approach

Fine particulate matter (PM2.5) exposure can cause lung injury and a large number of respiratory diseases. Sipeimine is a steroidal alkaloid isolated from Fritillaria roylei which has been associated with anti-inflammatory, antitussive and antiasthmatic properties. In this study, we explored the potential effects of sipeimine against PM2.5-induced lung injury in Sprague Dawley rats. Sipeimine alleviated lung injury caused by PM2.5 and decreased pulmonary edema, inflammation and the levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in the bronchoalveolar lavage fluid. In addition, sipeimine upregulated the glutathione (GSH) expression and downregulated the expression of 4-hydroxynonenal (4-HNE), tissue iron and malondialdehyde (MDA). The downregulation of proteins involved in ferroptosis, including nuclear factor E2-related factor 2 (Nrf2), glutathione peroxidase 4 (GPX4), heme oxygenase-1 (HO-1) and solute carrier family 7 member 11 (SLC7A11) was reversed by sipeimine. The administration of RSL3, a potent ferroptosis-triggering agent, blocked the effects of sipeimine. Using network pharmacology, we found that the effects of sipeimine were presumably mediated through the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway. A PI3K inhibitor (LY294002) blocked the PI3K/Akt signaling pathway and reversed the effects of sipeimine. Overall, this study suggested that the protective effect of sipeimine against PM2.5-induced lung injury was mainly mediated through the PI3K/Akt pathway, ultimately leading to a reduction in ferroptosis.

Chloroquine Attenuates Asthma Development by Restoring Airway Smooth Muscle Cell Phenotype Via the ROS-AKT Pathway

Switching of airway smooth muscle (ASM) cell phenotype from differentiated-contractile to dedifferentiated-proliferative/synthetic state often occurs in asthmatic subjects with airway dysfunction. Evidence has been provided that chloroquine (an agonist of bitter taste receptors) presented benefits to ASM cell function implicated in asthma. However, the underlying mechanism is unclear. House dust mite (HDM)-sensitized mice were administered with chloroquine or dexamethasone before challenge. BALF and lung tissue were obtained for cell counting, histological analysis or ELISA. Primary cultured ASM cells were stimulated with transforming growth factor (TGF)-β1 or H₂O₂. Cells and supernatant were collected for the detection of ASM phenotype, ROS level, and proinflammatory cytokine production. In HDM-sensitized mice, chloroquine attenuated airway hyperresponsiveness (AHR), inflammation and remodeling with an inhibition of immunoglobulin E, IL-4/-13, and TGF-β1 in BALF. ASM cell proliferation (PCNA), hypertrophy (α-SMA), and parasecretion (MMP-9 and MMP-13) were strongly suppressed by chloroquine, hinting the rebalance of the heterogeneous ASM populations in asthmatic airway. Our data in vitro indicated that chloroquine markedly restrained maladaptive alteration in ASM phenotype in concert with a remission of ROS. Using H₂O₂ and PI3K inhibitor (LY294002), we found that the inhibition of oxidative stress level and ROS-AKT signal by chloroquine may serve as a potential mechanism that dedicates to the restoration of the phenotypic imbalance in ASM cells. Overall, the present findings suggested that chloroquine improves asthmatic airway function by controlling ASM cell phenotype shift, sketching a novel profile of chloroquine as a new therapeutic candidate for airway remodeling.

Protection of pancreatic β-cell by phosphocreatine through mitochondrial improvement via the regulation of dual AKT/IRS-1/GSK-3β and STAT3/Cyp-D signaling pathways

Diabetes mellitus (DM) is a metabolic syndrome, caused by insufficient insulin secretion or insulin resistance (IR). DM enhances oxidative stress and induces mitochondrial function in different kinds of cell types, including pancreatic β-cells. Our previous study has showed phosphocreatine (PCr) can advance the mitochondrial function through enhancing the oxidative phosphorylation and electron transport ability in mitochondria damaged by methylglyoxal (MG). Our aim was to explore the potential role of PCr as a molecule to protect mitochondria from diabetes-induced pancreatic β-cell injury with insulin secretion deficiency or IR through dual AKT/IRS-1/GSK-3β and STAT3/Cyclophilin D (Cyp-D) signaling pathways. MG-induced INS-1 cell viability, apoptosis, mitochondrial division and fusion, the morphology, and function of mitochondria were suppressed. Flow cytometry was used to detect the production of intracellular reactive oxygen species (ROS) and the changes of intracellular calcium, and the respiratory function was measured by oxygraph-2k. The expressions of AKT, IRS-1, GSK-3β, STAT3, and Cyp-D were detected using Western blot. The result showed that the oxidative stress-related kinases were significantly restored to the normal level after the pretreatment with PCr. Moreover, PCr pretreatment significantly inhibited cell apoptosis, decreased intracellular calcium, and ROS production, and inhibited mitochondrial division and fusion, and increased ATP synthesis damaged by MG in INS-1 cells. In addition, pretreatment with PCr suppressed Cytochrome C, p-STAT3, and Cyp-D expressions, while increased p-AKT, p-IRS-1, p-GSK-3β, caspase-3, and caspase-9 expressions. In conclusion, PCr has protective effect on INS-1 cells in vitro and in vivo, relying on AKT mediated STAT3/ Cyp-D pathway to inhibit oxidative stress and restore mitochondrial function, signifying that PCr might become an emerging candidate for the cure of diabetic pancreatic cancer β-cell damage.

Silibinin Protects against H2O2-Induced Oxidative Damage in SH-SY5Y Cells by Improving Mitochondrial Function

Oxidative stress plays a critical role in the pathogenesis of various neurodegenerative diseases. Increasing evidence suggests the association of mitochondrial abnormalities with oxidative stress-related neural damage. Silibinin, a natural flavonol compound isolated from Silybum marianum, exhibits multiple biological activities. The present study investigated the effects of silibinin on H₂O₂-induced oxidative stress in human neuroblastoma SH-SY5Y cells. Exposure to H₂O₂ (750 µM) reduced the viability of SH-SY5Y cells, which was coupled with increased reactive oxygen species (ROS), abnormal cell morphology, and mitochondrial dysfunction. Remarkably, silibinin (1, 5, and 10 µM) treatment attenuated the H₂O₂-induced cell death. Moreover, silibinin reduced ROS production and the levels of malondialdehyde (MDA), increased the levels of superoxide dismutase (SOD) and glutathione (GSH), and increased mitochondrial membrane potential. Moreover, silibinin normalized the expression of nuclear factor 2-related factor 2 (Nrf2)-related and mitochondria-associated proteins. Taken together, our findings demonstrated that silibinin could attenuate H₂O₂-induced oxidative stress by regulating Nrf2 signaling and improving mitochondrial function in SH-SY5Y cells. The protective effect against oxidative stress suggests silibinin as a potential candidate for preventing neurodegeneration.

Neuroprotective Effect of Dioscin against Parkinson's Disease via Adjusting Dual-Specificity Phosphatase 6 (DUSP6)-Mediated Oxidative Stress

Exploration of lead compounds against Parkinson's disease (PD), a neurodegenerative disease, is of great important. Dioscin, a bioactive natural product, shows various pharmacological effects. However, the activities and mechanisms of dioscin against PD have not been well investigated. In this study, the tests on 6-hydroxydopamine (6-OHDA)-induced PC12 cells and rats were carried out. The results showed that dioscin dramatically improved cell viability, decreased reactive oxygen species (ROS) levels, improved motor behavior and tyrosine hydroxylase(TH) levels and restored the levels of glutathione (GSH) and malondialdehyde (MDA) in rats. Mechanism investigation showed that dioscin not only markedly increased the expression level of dual- specificity phosphatase 6 (DUSP6) by 1.87-fold in cells and 2.56-fold in rats, and decreased phospho-extracellular regulated protein kinases (p-ERK) level by 2.12-fold in cells and 2.34-fold in rats, but also increased the levels of nuclear factor erythroid2-related factor 2 (Nrf2), hemeoxygenase-1 (HO-1), superoxide dismutase (SOD) and decreased the levels of kelch-1ike ECH-associated protein l (Keap1) in vitro and in vivo. Furthermore, DUSP6 siRNA transfection experiment in PC12 cells validated the protective effects of dioscin against PD via regulating DUSP6 to adjust the Keap1/Nrf2 pathway. Our data supported that dioscin has protection against PD in regulating oxidative stress via DUSP6 signal, which should be considered as an efficient candidate for the treatment of PD in the future.

Effect of Donepezil on Vascular Dementia in Rats via PI3K/AKT Pathway

Background: Previous studies have shown that Donepezil has therapeutic effects on vascular dementia (VD). PI3K/AKT involves in oxidative stress injury and cell apoptosis. This study investigated whether Donepezil affects the neurological function and apoptosis of VD mice via PI3K/AKT signaling. Methods: Mice were assigned into Sham group, VD group, VD+Donepezil groupfollowed by analysis of mice learning and memory ability by Water maze test, p-AKT expression by Western blot, Caspase-3 activity, MDA content, SOD activity and GSH-Px in hippocampus. HT22 cells were cultured and separated into control group, I-R group and I-R+Donepezil group followed by measuring p-AKT level, ROS content and apoptosis. Results: Learning and memory abilities of VD group mice were significantly decreased, Caspase-3 activity and MDA in brain tissue were significantly increased, along with decreased SOD activity, GSH-Px and p-AKT level. Donepezil treatment can significantly improve VD mice learning and memory ability, reduce Caspase-3 activity and MDA in brain tissue, increase SOD activity, GSH-Px and p-AKT level. In vitro, I-R treatment significantly induced apoptosis of HT22 cells, increased ROS production and decreased p-AKT level. Donepezil treatment could up-regulate p-AKT in HT22 cells and reduce apoptosis and ROS production in HT22 cells. Conclusion: Donepezil improves the function of brain nerve in VD mice through regulating PI3K/AKT pathway, thus reducing oxidative stress injury and apoptosis of brain nerve cells.

Cardamomin protects from diabetes-induced kidney damage through modulating PI3K/AKT and JAK/STAT signaling pathways in rats

BACKGROUND

Diabetic nephropathy is one of the common complications of diabetes mellitus, which seriously affects the life quality and health of patients. In this study, we aimed to investigate the function of cardamonin (CAD) in diabetes-induced kidney damage in rats.

METHODS

The normal rat kidney tubular epithelial cells (NRK-52E) were pre-treated with different doses of CAD and then stimulated with methylglyoxal (MGO). Streptozotocin (STZ) induced diabetes rat model were received different doses of CAD treatment. MTT, EdU, Transwell, and flow cytometry was used to detect cell viability, proliferation, migration, and apoptosis. Western blot analysis was used to detect the expression of apoptosis related proteins, advanced glycation end-products (AGEs), receptor for AGEs (RAGE), epithelial mesenchymal transition (EMT) related proteins, phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway related proteins, and janus kinas/signal transducer and activator of transcription 3 (JAK/STAT3) related proteins. ELISA assay was used to detect the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β). The levels of malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) were detected using commercial kit. Hematoxylin and eosin staining was used to assess pathological changes in rat kidney.

RESULTS

Compared with control group, MGO reduced cell viability and proliferation, enhanced migration and apoptosis of NRK-52E cells, while CAD inhibited these effects induced by MGO in NRK-52E cells. Moreover, CAD increased Bcl-2 expression and decreased the expression of Bax and cleaved caspase-3 in MGO-treated NRK-52E cells. Compared with control group, MGO increased the AGEs formation, the expression of RAGE and p-p65, the levels of TNF-α, IL-6, IL-1β, MDA in NRK-52E cells and reduced the levels of GSH and SOD, while treatment of CAD dose-dependently prevented these results. In addition, CAD attenuated MGO-induced EMT of MGO-treated NRK-52E cells. Mechanically, we identified that CAD repressed PI3K/AKT and JAK/STAT3 signaling in NRK-52E cells. Importantly, the kidney injury of diabetes rats was attenuated by CAD. Besides, STZ-induced inflammatory response, oxidative stress, and phosphorylation levels of PI3K, AKT, JAK2, and STAT3 were reduced by CAD in the rats.

CONCLUSION

CAD protects from diabetes-induced kidney damage through modulating PI3K/AKT and JAK/STAT signaling pathways in rats.

PI3K/Akt Signaling Pathway Ameliorates Oxidative Stress-Induced Apoptosis upon Manganese Exposure in PC12 Cells

Manganese (Mn)-induced neurotoxicity has aroused public concerns for many years, but its precise mechanism is still poorly understood. Herein, we report the impacts of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway in mediating neurological effects induced by manganese sulfate (MnSO₄) exposure in PC12 cells. In this study, cells were treated with MnSO₄ for 24 h in the absence or presence of LY294002 (a special inhibitor of PI3K). We investigated cell viability and apoptosis signals, as well as levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde (MDA). The mRNA levels of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and Caspase-3 were also quantified through real-time quantitative PCR (RT-qPCR); protein levels of serine/threonine protein kinase (Akt) and forkhead box O3A (Foxo3a) were determined by western blot. Increasing of MnSO₄ doses led to decreased SOD, GSH-Px, and CAT activities, while the level of MDA was upregulated. Moreover, cell apoptosis was significantly increased, as the mRNA of Bcl-2 and Caspase-3 was significantly decreased, while Bax mRNA was increased. Phosphorylated Akt (p-Akt) and Foxo3a (p-Foxo3a) were upregulated in a dose-dependent manner. In addition, LY294002 pretreatment reduced the activity of SOD, GSH-Px, and CAT but elevated MDA levels. Meanwhile, LY294002 pretreatment also increased cell apoptosis given the upregulated Bax and Caspase-3 mRNAs and decreased Bcl-2 mRNA. In summary, the PI3K/Akt signaling pathway can be activated by MnSO₄ exposure and mediate MnSO₄-induced neurotoxicity.

Reduced Hippocampal Volume and Neurochemical Response to Adult Stress Exposure in a Female Mouse Model of Urogenital Hypersensitivity

Early life stress exposure significantly increases the risk of developing chronic pain syndromes and comorbid mood and metabolic disorders later in life. Structural and functional changes within the hippocampus have been shown to contribute to many early life stress-related outcomes. We have previously reported that adult mice that underwent neonatal maternal separation (NMS) exhibit urogenital hypersensitivity, altered anxiety- and depression-like behaviors, increased adiposity, and decreased gene expression and neurogenesis in the hippocampus. Here, we are using magnetic resonance imaging and spectroscopy (MRI and MRS) to further investigate both NMS- and acute stress-induced changes in the hippocampus of female mice. Volumetric analysis of the whole brain revealed that the left hippocampus of NMS mice was 0.038 mm3 smaller compared to naïve mice. MRS was performed only on the right hippocampus and both total choline (tCho) and total N-acetylaspartate (tNAA) levels were significantly decreased due to NMS, particularly after WAS. Phosphoethanolamine (PE) levels were decreased in naïve mice after WAS, but not in NMS mice, and WAS increased ascorbate levels in both groups. The NMS mice showed a trend toward increased body weight and body fat percentage compared to naïve mice. A significant negative correlation was observed between body weight and phosphocreatine levels post-WAS in NMS mice, as well as a positive correlation between body weight and glutamine for NMS mice and a negative correlation for naïve mice. Together, these data suggest that NMS in mice reduces left hippocampal volume and may result in mitochondrial dysfunction and reduced neuronal integrity of the right hippocampus in adulthood. Hippocampal changes also appear to be related to whole body metabolic outcomes.

Metformin prevents methylglyoxal-induced apoptosis by suppressing oxidative stress in vitro and in vivo

Methylglyoxal (MGO) is an active metabolite of glucose and plays a prominent role in the pathogenesis of diabetic vascular complications, including endothelial cell apoptosis induced by oxidative stress. Metformin (MET), a widely prescribed antidiabetic agent, appears to reduce excessive reactive oxygen species (ROS) generation and limit cell apoptosis. However, the molecular mechanisms underlying this process are still not fully elucidated. We reported here that MET prevents MGO-induced apoptosis by suppressing oxidative stress in vitro and in vivo. Protein expression and protein phosphorylation were investigated using western blotting, ELISA, and immunohistochemical staining, respectively. Cell viability and apoptosis were assessed by the MTT assay, TUNEL staining, and Annexin V-FITC and propidium iodide double staining. ROS generation and mitochondrial membrane potential (MMP) were measured with fluorescent probes. Our results revealed that MET prevented MGO-induced HUVEC apoptosis, inhibited apoptosis-associated biochemical changes such as loss of MMP, the elevation of the Bax/Bcl-2 ratio, and activation of cleaved caspase-3, and attenuated MGO-induced mitochondrial morphological alterations in a dose-dependent manner. MET pretreatment also significantly suppressed MGO-stimulated ROS production, increased signaling through the ROS-mediated PI3K/Akt and Nrf2/HO-1 pathways, and markedly elevated the levels of its downstream antioxidants. Finally, similar results were obtained in vivo, and we demonstrated that MET prevented MGO-induced oxidative damage, apoptosis, and inflammation. As expected, MET reversed MGO-induced downregulation of Nrf2 and p-Akt. In addition, a PI3K inhibitor (LY-294002) and a Nrf2 inhibitor (ML385) observably attenuated the protective effects of MET on MGO-induced apoptosis and ROS generation by inhibiting the Nrf2/HO-1 pathways, while a ROS scavenger (NAC) and a permeability transition pores inhibitor (CsA) completely reversed these effects. Collectively, these findings broaden our understanding of the mechanism by which MET regulates apoptosis induced by MGO under oxidative stress conditions, with important implications regarding the potential application of MET for the treatment of diabetic vascular complications.

Sleeve gastrectomy attenuated diabetes-related cognitive decline in diabetic rats

OBJECTIVE

To investigate the effects of sleeve gastrectomy (SG) on diabetes-related cognitive decline (DCD) in rats with diabetic mellitus (DM).

METHODS AND METHODS

Forty Wistar rats were randomly divided into control (CON) group (n=10), diabetes mellitus (DM) group (n=10), sham operation (SHAM) group (n=10) and SG group (n=10). DM model was established by high-fat diet (HFD) combined with intraperitoneal injection of streptozocin (STZ). Behavioral evaluation was given using Morris water maze test and Y-maze. In addition, PET-CT, TUNEL assay, histological analysis, transmission electron microscopy (TEM), immunohistochemistry (IHC) and Western blot analysis were used to evaluate the alleviating effects and potential mechanisms of SG on DCD in DM rats.

RESULTS

Compared with the sham group, SG induced significant improvement in the metabolic indices such as blood glucose and body weight. Besides, it could attenuate the insulin resistance compared with SHAM group. In addition, SG could improve the cognitive function of DM rats, which were featured by significant decrease in the escape latency (P<0.05), and significant increase in the time in target quadrant and platform crossings (P<0.05) compared with the SHAM group. SG induced significant elevation in the spontaneous alternation compared with SHAM group (P<0.05). Moreover, SG could improve the arrangement and biosynthesis of hippocampus neuron. Moreover, SG triggered the inhibition of apoptosis of hippocampus neurons, and Western blot analysis showed SG induced significant increase in the ratios of Bcl-2/Bax and Caspase3/cleaved Caspase 3. TEM demonstrated SG could significantly improve the microstructure of hippocampus neurons compared with the SHAM group. Western blot and IHC confirmed the significant decrease in the phosphorylation of tau at Ser404 and Ser396 sites in the SG group. Furthermore, SG activated the PI3K signaling pathway by elevating the phosphorylation of PI3K and Akt and GSK3β compared with the SHAM group.

CONCLUSION

SG attenuated the DCD in DM rats, which may be related to the activation of PI3K signaling pathway.

Protective effects of Huang-Lian-Jie-Du Decoction on diabetic nephropathy through regulating AGEs/RAGE/Akt/Nrf2 pathway and metabolic profiling in db/db mice

BACKGROUND

Diabetic nephropathy (DN) is a severe diabetic complication that is the principal cause of end-stage kidney disease worldwide. Huang-Lian-Jie-Du Decoction (HLJDD) is widely used to treat diabetes clinically. However, the nephroprotective effects and potential mechanism of action of HLJDD against DN have not yet been fully elucidated.

PURPOSE

This study aimed to investigate the potential roles of HLJDD in DN and elucidate its mechanisms in db/db mice.

METHODS

An integrated strategy of network pharmacology, pharmacodynamics, molecular biology, and metabolomics was used to reveal the mechanisms of HLJDD in the treatment of DN. First, network pharmacology was utilized to predict the possible pathways for DN using the absorbed ingredients of HLJDD in rat plasma in silico. Then, combined with histopathological examination, biochemical evaluation immunohistochemistry/immunofluorescence assay, western blot analysis, and UPLC-Q-Orbitrap HRMS/MS-based metabolomics approach were applied to evaluate the efficacy of HLJDD against DN and its underlying mechanisms in vivo.

RESULTS

In silico, network pharmacology indicated that the AGEs/RAGE pathway was the most prominent pathway for HLJDD against DN. In vivo, HLJDD exerted protective effects against DN by ameliorating glycolipid metabolic disorders and kidney injury. Furthermore, we verified that HLJDD protected against DN by regulating the AGEs/RAGE/Akt/Nrf2 pathway for the first time. In addition, 22 potential biomarkers were identified in urine, including phenylalanine metabolism, tryptophan metabolism, glucose metabolism, and sphingolipid metabolism.

CONCLUSION

These findings suggest that HLJDD ameliorates DN by regulating the AGEs/RAGE/Akt/Nrf2 pathway and metabolic profiling.

Evaluation of the Anti-Aging Effects of a Probiotic Combination Isolated From Centenarians in a SAMP8 Mouse Model

Population aging is a prominent global problem in today’s society. However, there are currently no good methods to treat or prevent aging, so anti-aging research has crucial implications. In this research, we screened bacteria from centenarians, and finally selected four probiotics (Lactobacillus fermentum SX-0718, L. casei SX-1107, Bifidobacterium longum SX-1326, and B. animalis SX-0582) to form a probiotic combination. By using the senescence accelerated mouse prone 8 (SAMP8) model, the anti-aging effects of the probiotic combination were evaluated by using behavioural testing, neuroinflammation, intestinal inflammation, and intestinal microbiota. The results showed that probiotic combination improved the impaired spatial memory, motor dysfunction, and decreased exploratory behavior in aging mice. The probiotic combination inhibited Toll-like receptor 4 (TLR4)/nuclear factor kappa B (NFκB)-induced neuroinflammation and up-regulated the expression of Sirt 1 to protect hippocampal neurons. At the same time, the probiotic combination regulated the intestinal microbiota, reduced the relative abundance of Alistipes and Prevotella in SAMP8 mice, inhibited TLR4/NFκB-induced intestinal inflammation, and increased the expression of intestinal permeability related proteins zonula occludens-1 (ZO-1) and Occuldin. The anti-aging effects of the probiotic combination may be through the regulating intestinal microbiota and inhibiting TLR4/NFκB-induced inflammation. This research provides the basis and technical support for the future production and application of the probiotic combination.

Investigating the Regulation of Neural Differentiation and Injury in PC12 Cells Using Microstructure Topographic Cues

In this study, we designed and manufactured a series of different microstructure topographical cues for inducing neuronal differentiation of cells in vitro, with different topography, sizes, and structural complexities. We cultured PC12 cells in these microstructure cues and then induced neural differentiation using nerve growth factor (NGF). The pheochromocytoma cell line PC12 is a validated neuronal cell model that is widely used to study neuronal differentiation. Relevant markers of neural differentiation and cytoskeletal F-actin were characterized. Cellular immunofluorescence detection and axon length analysis showed that the differentiation of PC12 cells was significantly different under different isotropic and anisotropic topographic cues. The expression differences of the growth cone marker growth-associated protein 43 (GAP-43) and sympathetic nerve marker tyrosine hydroxylase (TH) genes were also studied in different topographic cues. Our results revealed that the physical environment has an important influence on the differentiation of neuronal cells, and 3D constraints could be used to guide axon extension. In addition, the neurotoxin 6-hydroxydopamine (6-OHDA) was used to detect the differentiation and injury of PC12 cells under different topographic cues. Finally, we discussed the feasibility of combining the topographic cues and the microfluidic chip for neural differentiation research.

Enhancement of gemcitabine efficacy by K73-03 via epigenetically regulation of miR-421/SPINK1 in gemcitabine resistant pancreatic cancer cells

BACKGROUND

Gemcitabine (GCB) is a first-line chemotherapeutic drug for pancreatic cancer (PCa). However, the resistance begins developing within weeks of chemotherapy. SPINK1 overexpression enhances resistance to chemotherapy. In a recent study, our laboratory established that the oleanolic acid (OA) derivative, K73-03, had a strong inhibitory effect on a SPINK1 overexpressed PCa cells.

PURPOSE

In our current study, we studied the enhancement of GCB inhibitory effect by K73-03, a new novel OA derivative, alone or in combination with GCB on the GCB-resistant PCa cells by mitochondrial damage through regulation of the miR-421/SPINK1.

METHODS

We detected the binding between miR-421 and SPINK1-3'-UTR in GCB-resistant PCa cells using Luciferase reporter assays. Cells viability, apoptosis, migration, and mitochondrial damage were investigated.

RESULTS

The results demonstrated that the combination of K73-03 and GCB suppressed the growth of AsPC-1 and MIA PaCa-2 cells synergistically, with or without GCB resistance. Mechanistic findings showed that a combination of K73-03 and GCB silences SPINK1 epigenetically by miR-421 up-regulating, which leads to mitochondrial damage and inducing apoptosis in GCB-resistant PCa cells.

CONCLUSION

We found an interesting finding that the 73-03 in combination with GCB can improve GCB efficacy and decrease PCa resistance, which induced apoptosis and mitochondrial damage through epigenetic inhibition of SPINK1 transcription by miR-421 up-regulation. This was the first study that used OA derivatives on GCB-resistant PCa cells, so this combined strategy warrants further investigation.

The Nrf2 Pathway in Ischemic Stroke: A Review

Ischemic stroke, characterized by the sudden loss of blood flow in specific area(s) of the brain, is the leading cause of permanent disability and is among the leading causes of death worldwide. The only approved pharmacological treatment for acute ischemic stroke (intravenous thrombolysis with recombinant tissue plasminogen activator) has significant clinical limitations and does not consider the complex set of events taking place after the onset of ischemic stroke (ischemic cascade), which is characterized by significant pro-oxidative events. The transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates the expression of a great number of antioxidant and/or defense proteins, has been pointed as a potential pharmacological target involved in the mitigation of deleterious oxidative events taking place at the ischemic cascade. This review summarizes studies concerning the protective role of Nrf2 in experimental models of ischemic stroke, emphasizing molecular events resulting from ischemic stroke that are, in parallel, modulated by Nrf2. Considering the acute nature of ischemic stroke, we discuss the challenges in using a putative pharmacological strategy (Nrf2 activator) that relies upon transcription, translation and metabolically active cells in treating ischemic stroke patients.

Biomarkers and Mechanisms of Oxidative Stress-Last 20 Years of Research with an Emphasis on Kidney Damage and Renal Transplantation

Oxidative stress is an imbalance between pro- and antioxidants that adversely influences the organism in various mechanisms and on many levels. Oxidative damage occurring concomitantly in many cellular structures may cause a deterioration of function, including apoptosis and necrosis. The damage leaves a molecular “footprint”, which can be detected by specific methodology, using certain oxidative stress biomarkers. There is an intimate relationship between oxidative stress, inflammation, and functional impairment, resulting in various diseases affecting the entire human body. In the current narrative review, we strengthen the connection between oxidative stress mechanisms and their active compounds, emphasizing kidney damage and renal transplantation. An analysis of reactive oxygen species (ROS), antioxidants, products of peroxidation, and finally signaling pathways gives a lot of promising data that potentially will modify cell responses on many levels, including gene expression. Oxidative damage, stress, and ROS are still intensively exploited research subjects. We discuss compounds mentioned earlier as biomarkers of oxidative stress and present their role documented during the last 20 years of research. The following keywords and MeSH terms were used in the search: oxidative stress, kidney, transplantation, ischemia-reperfusion injury, IRI, biomarkers, peroxidation, and treatment.

Non-energy mechanism of phosphocreatine on the protection of cell survival

If mitochondrial energy availability or oxidative metabolism is altered, patients will suffer from insufficient energy supply Phosphocreatine (PCr) not only acts as an energy carrier, but also acts as an antioxidant and defensive agent to maintain the integrity and stability of the membrane, to maintain ATP homeostasis through regulating mitochondrial respiration. Meanwhile, PCr can enhance calcium balance and reduce morphological pathological changes, ultimately, PCr helps to reduce apoptosis. On the other aspect, the activities of ATP synthase and MitCK play a crucial role in the maintenance of cellular energy metabolic function. It is interesting to note, PCr not only rises the activities of ATP synthase as well as MitCK, but also promotes these two enzymatic reactions. Additionally, PCr can also inhibit mitochondrial permeability transition in a concentration-dependent manner, prevent ROS and CytC from spilling into the cytoplasm, thereby inhibit the release of proapoptotic factors caspase-3 and caspase-9, and eventually, effectively prevent LPS-induced apoptosis of cells. Understandably, PCr prevents the apoptosis caused by abnormal mitochondrial energy metabolism and has a protective role in a non-energy manner. Moreover, recent studies have shown that PCr protects cell survival through PI3K/Akt/eNOS, MAPK pathway, and inhibition of Ang II-induced NF-κB activation. Furthermore, PCr antagonizes oxidative stress through the activation of PI3K/Akt/GSK3b intracellular pathway, PI3K/AKT-PGC1α signaling pathway, while through the promotion of SIRT3 expression to maintain normal cell metabolism. Interestingly, PCr results in delaying the time to enter pathological metabolism through the delayed activation of AMPK pathway, which is different from previous studies, now we propose the hypothesis that the "miRNA-JAK2/STAT3 -CypD pathway" may take part in protecting cells from apoptosis, PCr may be further be involved in the dynamic relationship between CypD and STAT3. Furthermore, we believe that PCr and CypD would be the central link to maintain cell survival and maintain cell stability and mitochondrial repair under the mitochondrial dysfunction caused by oxidative stress. This review provides the modern progress knowledge and views on the molecular mechanism and molecular targets of PCr in a non-energy way.

Cytoprotection against Oxidative Stress by Methylnissolin-3-O-β-d-glucopyranoside from Astragalus membranaceus Mainly via the Activation of the Nrf2/HO-1 Pathway

Astragalus membranaceus is a famous herb found among medicinal and food plants in East and Southeastern Asia. The Nrf2-ARE assay-guided separation of an extract from Jing liqueur led to the identification of a nontoxic Nrf2 activator, methylnissolin-3-O-β-d-glucopyranoside (MNG, a component of A. membranaceus). Nrf2 activation by MNG has not been reported before. Using Western Blot, RT-qPCR and imaging, we investigated the cytoprotective effect of MNG against hydrogen peroxide-induced oxidative stress. MNG induced the expression of Nrf2, HO-1 and NQO1, accelerated the translocation of Nrf2 into nuclei, and enhanced the phosphorylation of AKT. The MNG-induced expression of Nrf2, HO-1, and NQO1 were abolished by Nrf2 siRNA, while the MNG-induced expression of Nrf2 and HO-1 was abated and the AKT phosphorylation was blocked by LY294002 (a PI3K inhibitor). MNG reduced intracellular ROS generation. However, the protection of MNG against the H₂O₂ insult was reversed by Nrf2 siRNA with decreased cell viability. The enhancement of Nrf2 and HO-1 by MNG upon H₂O₂ injury was reduced by LY294002. These data showed that MNG protected EA.hy926 cells against oxidative damage through the Nrf2/HO-1 and at least partially the PI3K/Akt pathways.

Hydrogen sulfide alleviates apoptosis and autophagy induced by beryllium sulfate in 16HBE cells

Beryllium and its compounds are systemic toxicants that are widely applied in many industries. Hydrogen sulfide has been found to protect cells. The present study aimed to determine the protective mechanisms involved in hydrogen sulfide treatment of 16HBE cells following beryllium sulfate-induced injury. 16HBE cells were treated with beryllium sulfate doses ranging between 0 and 300 μM BeSO₄ . Additionally, 16HBE cells were subjected to pretreatment with either a 300 μM dose of sodium hydrosulfide (a hydrogen sulfide donor) or 10 mM DL-propargylglycine (a cystathionine-γ-lyase inhibitor) for 6 hr before then being treated with 150 μM beryllium sulfate for 48 hr. This study illustrates that beryllium sulfate induces a reduction in cell viability, increases lactate dehydrogenase (LDH) release, and increases cellular apoptosis and autophagy in 16HBE cells. Interestingly, pretreating 16HBE cells with sodium hydrosulfide significantly reduced the beryllium sulfate-induced apoptosis and autophagy. Moreover, it increased the mitochondrial membrane potential and alleviated the G2/M-phase cell cycle arrest. However, pretreatment with 10 mM DL-propargylglycine promoted the opposite effects. PI3K/Akt/mTOR and Nrf2/ARE signaling pathways are also activated following pretreatment with sodium hydrosulfide. These results indicate the protection provided by hydrogen sulfide in 16HBE cells against beryllium sulfate-induced injury is associated with the inhibition of apoptosis and autophagy through the activation of the PI3K/Akt/mTOR and Nrf2/ARE signaling pathways. Therefore, hydrogen sulfide has the potential to be a promising candidate in the treatment against beryllium disease.

Thiamine Alleviates High-Concentrate-Diet-Induced Oxidative Stress, Apoptosis, and Protects the Rumen Epithelial Barrier Function in Goats

High-concentrate diets are continually used in ruminants to meet the needs of milk yield, which can lead to the occurrence of subacute rumen acidosis in ruminants. This study investigated the protective effects of dietary thiamine supplementation on the damage of the ruminal epithelium barrier function in goats fed a high-concentrate diet. Twenty-four healthy Boer goats (live weight of 35.62 ± 2.4 kg; age, 1 year) were randomly assigned into three treatments, with eight goats in each treatment, consuming one of three diets: a low-concentrate diet (CON; concentrate/forage, 30:70), a high-concentrate diet (HC; concentrate/forage, 70:30), or a high-concentrate diet with 200 mg of thiamine/kg of dry matter intake (HCT; concentrate/forage, 70:30) for 12 weeks. The additional dose of thiamine was based on our previous study wherein thiamine ameliorates inflammation. Compared with HC treatment, the HCT treatment had markedly higher concentrations of glutathione, superoxide dismutase, and glutathione peroxidase and total antioxidant capacity (P < 0.05) in plasma and rumen epithelium. The results showed that the apoptosis index was lower (P < 0.05) in the HCT treatment than in that of the HC treatment. Compared with the HC treatment, permeability and the electrophysiology parameter short circuit current for ruminal epithelial tissue were significantly decreased (P < 0.05) in the HCT treatment. The immunohistochemical results showed that the expression distribution of tight junctions including claudin-1, claudin-4, occludin, and zonula occludin-1 (ZO-1) was greater (P < 0.05) in the HCT treatments than in the HC treatment. The mRNA expression in the rumen epithelium of ZO-1, occludin, claudin-1, B-cell lymphoma/leukemia 2, nuclear factor erythroid-2 related factor 2 (Nrf2), superoxide dismutase 2 (SOD2), glutathione peroxidase 1, and the phase II metabolizing enzymes quinone oxidoreductase and heme oxygenase in the HCT group was significantly increased in comparison with the HC diet treatment (P < 0.05), whereas the mRNA expression of caspase 3, caspase 8, caspase 9, bcl-2 associated X protein, lipopolysaccharide binding protein, toll-like receptor 4, nuclear factor kappa-B (NFκB), tumor necrosis factor alpha, interleukin-1β, interleukin, and tumor necrosis factor receptor-associated factor 6 decreased significantly in the HCT treatment (P < 0.05). Compared with the HC treatment, the HCT diet significantly increased the protein expression of ZO-1, occludin, claudin-1, NQO1, HO-1, SOD2, serine/threonine kinase, p-Akt, Nrf2, and p-Nrf2; conversely, the expression of NFκB-related proteins p65 and pp65 was significantly decreased (P < 0.05). In addition, thiamine relieved the damage on the ruminal epithelium caused by the HC diet. The results show that dietary thiamine supplementation improves the rumen epithelial barrier function by regulating Nrf2-NFκB signaling pathways during high-concentrate-diet feeding.

Adlay hull extracts attenuate β-amyloid-induced neurotoxicity and oxidative stress in PC12 cells through antioxidative, anti-inflammatory, and antiapoptotic activities

Alzheimer's disease (AD) is characterized by accumulation of β-amyloid (Aβ) in senile plaques, contributing to oxidative stress, mitochondrial diseases, and synaptic atrophy, consequently leading to the deterioration of brain function. Adlay (Coix lacryma-jobi L.) is an annual botanical. Here, a 95% ethanol extract of adlay hull (AHEE) was partitioned by ethyl acetate (AHEAE), n-butanol (AHBUE), and water (AHWE), and the effects of these extracts on lipopolysaccharide (LPS)-induced RAW264.7 cells and Aβ-induced PC12 cells, as experimental models of neurotoxicity, were evaluated. The expression of anti-inflammatory and antiapoptosis-related proteins was investigated and AHEE, AHEAE, and AHWE were found to exert anti-inflammatory effects. AHWE exhibited antiapoptotic effects and inhibited inducible nitric oxide synthase expression and nitric oxide production. We investigated the protective effects of AHWE against Aβ-induced neurotoxicity in dPC12 cells and explored the underlying mechanism. Pretreatment with AHWE significantly attenuated cell death and Aβ-mediated increase in B cell lymphoma (Bcl)-2/Bax ratio. AHWE significantly inhibited Aβ and enhanced protein kinase B (Akt) level in dPC12 cells, suggesting that its protective effect against Aβ-induced apoptosis in dPC12 cells was mediated through upregulation of the phosphoinositide 3-kinases (PI3K)/Akt signaling pathway. These extracts and its bioactive compound K36-21 may be potentially useful to treat neurodegenerative disorders.

Ophiopogonin D alleviates diabetic myocardial injuries by regulating mitochondrial dynamics

ETHNOPHARMACOLOGICAL RELEVANCE

Ophiopogonin D (OP-D) is a steroidal saponin extracted from Ophiopogon japonicus (Thunb.) Ker Gawl. (Liliaceae), that has been traditionally used to treat cough, sputum, and thirst in some Asian countries. Recently, various pharmacological roles of OP-D have been identified, including anti-inflammatory, cardioprotective, and anti-cancer effects. However, whether OP-D can prevent diabetic myocardial injury remains unknown.

AIM OF THE STUDY

In this study, we aimed to observe the effects of OP-D on the diabetic myocardium.

MATERIALS AND METHODS

Leptin receptor-deficient db/db mice were used as an animal model for type 2 diabetes. The effects of OP-D on blood glucose, blood lipids, myocardial ultrastructure, and mitochondrial function in mice were observed after four weeks of intragastric administration. Palmitic acid was used to stimulate cardiomyocytes to establish a myocardial lipotoxicity model. Cell apoptosis, mitochondrial morphology, and function were observed.

RESULTS

Blood glucose and blood lipid levels were significantly increased in db/db mice, accompanied by myocardial mitochondrial injury and dysfunction. OP-D treatment reduced blood lipid levels in db/db mice and relieved mitochondrial injury and dysfunction. OP-D inhibited palmitic acid induced-mitochondrial fission and dysfunction, reduced endogenous apoptosis, and improved cell survival rate in H9C2 cardiomyocytes. Both in vivo and in vitro models showed increased phosphorylation of DRP1 at Ser-616, reduced phosphorylation of DRP1 at Ser-637, and reduced expression of fusion proteins MFN1/2 and OPA1. Meanwhile, immunofluorescence co-localization analysis revealed that palmitic acid stimulated the translocation of DRP1 protein from the cytoplasm to the mitochondria in H9C2 cardiomyocytes. The imbalance of mitochondrial dynamics, protein expression, and translocation of DRP1 were effectively reversed by OP-D treatment. In isolated mice ventricular myocytes, palmitic acid enhanced cytoplasmic Ca²⁺ levels and suppressed contractility in ventricular myocytes, accompanied by activation of calcineurin, a key regulator of DRP1 dephosphorylation at Ser-637. OP-D reversed the changes caused by palmitic acid.

CONCLUSIONS

Our findings indicate that OP-D intervention could alleviate lipid accumulation and mitochondrial injury in diabetic mouse hearts and palmitic acid-stimulated cardiomyocytes. The cardioprotective effect of OP-D may be mediated by the regulation of mitochondrial dynamics.

The Keap1-Nrf2 System: A Mediator between Oxidative Stress and Aging

Oxidative stress, a term that describes the imbalance between oxidants and antioxidants, leads to the disruption of redox signals and causes molecular damage. Increased oxidative stress from diverse sources has been implicated in most senescence-related diseases and in aging itself. The Kelch-like ECH-associated protein 1- (Keap1-) nuclear factor-erythroid 2-related factor 2 (Nrf2) system can be used to monitor oxidative stress; Keap1-Nrf2 is closely associated with aging and controls the transcription of multiple antioxidant enzymes. Simultaneously, Keap1-Nrf2 signaling is also modulated by a more complex regulatory network, including phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt), protein kinase C, and mitogen-activated protein kinase. This review presents more information on aging-related molecular mechanisms involving Keap1-Nrf2. Furthermore, we highlight several major signals involved in Nrf2 unbinding from Keap1, including cysteine modification of Keap1 and phosphorylation of Nrf2, PI3K/Akt/glycogen synthase kinase 3β, sequestosome 1, Bach1, and c-Myc. Additionally, we discuss the direct interaction between Keap1-Nrf2 and the mammalian target of rapamycin pathway. In summary, we focus on recent progress in research on the Keap1-Nrf2 system involving oxidative stress and aging, providing an empirical basis for the development of antiaging drugs.

Xiaoyao Pills Ameliorate Depression-like Behaviors and Oxidative Stress Induced by Olfactory Bulbectomy in Rats via the Activation of the PIK3CA-AKT1-NFE2L2/BDNF Signaling Pathway

Numerous studies have revealed that oxidative stress is closely associated with the occurrence and development of depression. Xiaoyao Pills (XYW) are included in the Chinese Pharmacopoeia and are frequently used for treating anxiety and depression by smoothing the liver, strengthening the spleen, and nourishing the blood. However, the antidepressant effects of XYW have not yet been thoroughly investigated. The objective of our study was to investigate the antidepressant-like effects of XYW and the underlying molecular mechanism in the olfactory bulbectomized (OB) rat model of depression using the open field test (OFT), sucrose preference test (SPT), splash test (ST), and novelty suppressed feeding test (NSFT). Results showed that XYW (0.93 and 1.86 g·kg⁻¹) significantly alleviated depression-like behaviors in rats, which was indicated by increased sucrose preference in the SPT, prolonged grooming time in the ST, decreased horizontal movement in the OFT, and shorter feeding latency in the NSFT. In addition, XYW treatment dramatically reversed the reduced activity of superoxide dismutase and the decreased level of glutathione, while also lowering levels of malondialdehyde, an inflammatory mediator (nitric oxide), and pro-inflammatory cytokines (interleukin-6 and 1β) in the serum and cortex of OB rats. Mechanistically, XYW induced marked upregulation of mRNA and protein expression levels of NFE2L2, KEAP1, GPX3, HMOX1, SOD1, NQO1, OGG1, PIK3CA, p-AKT1/AKT1, NTRK2, and BDNF, and downregulation of ROS in the cortex and hippocampus via the activation of the NFE2L2/KEAP1, PIK3CA/AKT1, and NTRK2/BDNF pathways. These findings suggest that XYW exert antidepressant-like effects in OB rats with depression-like symptoms, and these effects are mediated by the alleviation of oxidative stress and the enhancement of neuroprotective effects through the activation of the PIK3CA-AKT1-NFE2L2/BDNF signaling pathways.

Morroniside protects OLN-93 cells against H2O2-induced injury through the PI3K/Akt pathway-mediated antioxidative stress and antiapoptotic activities

Neurodegenerative disorders, including spinal cord injury (SCI), result in oxidative stress-induced cell damage. Morroniside (MR), a major active ingredient of the Chinese herb Shan Zhu Yu, has been shown to ameliorate oxidative stress and inflammatory response. Our previous study also confirmed that morroniside protects SK-N-SH cell line (human neuroblastoma cells) against oxidative impairment. However, it remains unclear whether MR also plays a protective role for oligodendrocytes that are damaged following SCI. The present study investigated the protective effects of MR against hydrogen peroxide (H₂O₂)-induced cell death in OLN-93 cells. MR protected OLN-93 cells from H₂O₂-induced injury, attenuated H₂O₂-induced increase in reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and blocked the reduction of mitochondrial membrane potential (MMP) induced by H2O2. MR enhanced the activity of the antioxidant enzyme superoxide dismutase (SOD) and suppressed H₂O₂-induced downregulation of the antiapoptotic protein Bcl-2 and activation of the proapoptotic protein caspase-3. Finally, we found that LY294002, a specific inhibitor of the PI3K/Akt pathway, inhibited the protective effect of MR against H₂O₂-induced OLN-93 cell injury in the MTT and TUNEL assays. LY294002 also inhibited the expression of SOD and Bcl-2, and increased the expression of iNOS and c-caspase-3 induced by MR treatment. MR exerts protective effects against H₂O₂-induced OLN-93 cell injury through the PI3K/Akt signaling pathway-mediated antioxidative stress and antiapoptotic activities. MR may provide a potential strategy for SCI treatment or other related neurodegeneration.

Cytotoxicity of adducts formed between quercetin and methylglyoxal in PC-12 cells

Quercetin (Que) or quercetin-containing food stuffs are widely incorporated in bakery foods for improving food texture and health effects, and scavenging reactive aldehydes, such as methylglyoxal (MGO) that exhibits various deleterious effects including contribution to neurodegeneration. This study aimed to investigate the cytotoxicity of the adducts formed between quercetin and MGO resulted from the incorporation of quercetin in foods. Two highly-purified adducts (Que-mono-MGO and Que-di-MGO) were found to display higher cytotoxicity than their precursor MGO and quercetin. They elevated apoptosis via upregulation of expression of apoptotic markers, including p-P38, cleaved caspase-9 and -3, and pro-apoptotic Bax. They induced mitochondrial dysfunction via decreasing mitochondrial membrane potential and increasing lactate dehydrogenase release. Moreover, they attenuated levels of p-Akt, Nrf2, NQO-1, and HO-1, proving that they induced neurodegeneration apoptosis through mitochondria-mediated signaling pathways (PI3K-Akt and Nrf2-HO-1/NQO-1). These findings indicated that the safety consequence of MGO after scavenged by polyphenols needs to be concerned.

Intracellular ethanol-mediated oxidation and apoptosis in HepG2/CYP2E1 cells impaired by two active peptides from seahorse (Hippocampus kuda bleeler) protein hydrolysates via the Nrf2/HO-1 and akt pathways

Seahorse (Hippocampus kuda Bleeler) are representative marine species in aquaculture, with special value of medicine and food. In this study, the protective effects of two peptides from seahorse hydrolysates (SHP-1 and SHP-2) against ethanol-mediated oxidative stress in HepG2/CYP2E1 cells were investigated. Firstly, SHP-1 and SHP-2 presented no cytotoxicity. Compared with the ethanol-treated groups, SHP-1 and SHP-2 increased cell viability in a concentration-dependent manner. Secondly, SHP-1 and SHP-2 markedly reduced intracellular reactive oxygen species (ROS) generation, gamma-glutamyltranspeptidase (GGT) activity, and tumor necrosis factor-α (TNF-α) levels and remarkably enhanced superoxide dismutase (SOD) and glutathione (GSH) activities. SHP-1 and SHP-2 also down-regulated the expressions of GGT, bax, c-caspase-8/-9/-3, p-Akt, p-IκB-α, p-p65, p-ERK, and p-p38 but up-regulated SOD, GSH, NF-E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and bcl-2 levels, as revealed by Western blot analysis. Moreover, SHP-1 and SHP-2 increased the mitochondrial membrane potential (MMP), reduced DNA damage, and suppressed the nuclear translocation of p65. These results suggest that two peptides from seahorse hydrolysates can be considered a potential functional biomaterial and further improve the use value of seahorse in aquaculture.

Mechanism of Action of Xiaoyao San in Treatment of Ischemic Stroke is Related to Anti-Apoptosis and Activation of PI3K/Akt Pathway

OBJECTIVE

The traditional Chinese medicine (TCM) formulation Xiaoyao San (XYS) has a good clinical effect in treating ischemic stroke (IS). We explored the mechanism and material basis of XYS in IS treatment.

METHODS

Network pharmacology was used to construct a network of XYS components and IS targets. R software was used to analyze the biological process and pathway analysis of the targets of XYS in IS treatment. In vitro, a model of apoptosis of PC12 cells induced by oxygen-glucose deprivation/reperfusion (OGD/R) was established to evaluate the neuroprotective effect of XYS and its influence on the expression of apoptotic protein-related genes. The affinity between the potentially active compounds in XYS and apoptotic proteins was evaluated by molecular docking.

RESULTS

XYS was shown to have 136 chemical components that exert potential anti-IS activity by acting on 175 proteins. Bioinformatics analysis showed that apoptosis and the phosphoinositide 3-kinase/protein kinase B (PI3K-Akt) signaling pathway were the main signaling pathways of XYS. In vitro experiments showed that XYS could improve the effect of OGD/R on PC12-cell activity (EC50 = 0.43 mg/mL) and inhibit apoptosis. The main mechanisms were related to the improvement of oxidative stress and regulation of apoptosis-related gene expression. Molecular docking showed that C22, C102 and other components in XYS had a strong affinity with apoptosis-related proteins.

CONCLUSION

Network pharmacology, in vitro experiments, and molecular docking were used, for the first time, to study the material basis and molecular mechanism of XYS in IS treatment from the perspective of multiple targets and multiple pathways. We provided a new approach for the future study of TCM formulations in the treatment of complex diseases.

N-acetylserotonin Derivative Exerts a Neuroprotective Effect by Inhibiting the NLRP3 Inflammasome and Activating the PI3K/Akt/Nrf2 Pathway in the Model of Hypoxic-Ischemic Brain Damage

Neonatal hypoxic-ischemic encephalopathy (HIE) is one of the main causes of neonatal disability and death. As a derivative of N-acetylserotonin, N-[2-(5-hydroxy-1H-indol-3-yl) ethyl]-2-oxopiperidine-3-carboxamide (HIOC) can easily cross the blood-brain barrier and have a long half-life in the brain. In this study, the hypothesis was verified that HIOC plays a neuroprotective role in the HIE model and its potential mechanism was evaluated. Firstly, an HIE rat model was established to deliver HIOC, revealing that it can reduce cerebral infarction volume, cerebral edema, and neuronal apoptosis. The results of immunofluorescence staining, Western blots and RT-PCR further showed that HIOC could inhibit the activation of the NLRP3 inflammasome and the expression of related proteins. Finally, the activation of the phosphatidylinositol-3-kinase (PI3K)/Akt/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway by HIOC was verified in vitro and in vivo. It was discovered that HIOC could increase the nuclear translocation of Nrf2, and that this induction can be reversed by the PI3K/Akt pathway inhibitor LY294002. In general terms, the neuroprotective effect of HIOC was confirmed in the HIE model, which is related to the activation of the Pi3k/Akt/Nrf2 signal pathway and the inhibition of the NLRP3 inflammasome.

Antitumor effects of dioscin in A431 cells via adjusting ATM/p53-mediated cell apoptosis, DNA damage and migration

Skin cancer is the deadliest type of malignant disease and causes primary mortality worldwide. Dioscin, which exists in medicinal plants, has potent anticancer effects. However, its effects on skin cancer remain unknown. In the present study, the activity and mechanism of dioscin on the human skin cancer A431 cell line were investigated, MTT, colony formation, Transwell, wound-healing, TUNEL, Comet, immunofluorescence and western blot assays were used to assess the effects of dioscin on A431 cells. The results of MTT, colony formation, Transwell and wound-healing assays revealed that dioscin suppressed proliferation, colony formation and invasion of the cancer cells. TUNEL and comet assays demonstrated that dioscin exhibited significant effects on cell apoptosis and DNA damage. Investigations into the mechanism revealed that the expression levels of phosphorylated Ataxia telangiectasia-mutated (ATM) were considerably activated by dioscin, which significantly upregulated the expression levels of p53 to activate mitochondrial apoptosis signaling. Furthermore, the expression levels of BAX, cleaved caspase-3/9 and cleaved poly (ADP-ribose) polymerase were upregulated, and the expression levels of BCL-2 were downregulated by dioscin. Additionally, dioscin markedly downregulated the expression levels of matrix metalloproteinase 2 (MMP2), MMP9, RHO and cdc42, which are all associated with tumor invasion. In addition, p53-small interfering RNA transfection experiments indicated that dioscin exhibited excellent activity against skin cancer in vitro by decreasing p53 expression. Overall, the present results suggested that dioscin inhibited skin cancer cell proliferation via adjusting ATM/p53-mediated cell apoptosis, migration and DNA damage, which should be considered as a potential option for future treatments of skin cancer.

Rutin ameliorates copper sulfate-induced brain damage via antioxidative and anti-inflammatory activities in rats

Excessive exposure to Copper (Cu) may result in Cu toxicity and adversely affect health outcomes. We investigated the protective role of rutin on Cu-induced brain damage. Experimental rats were treated as follows: group I: control; group II: Cu-sulfate: 200 mg/kg; group III: Cu-sulfate, and rutin 100 mg/kg; and group IV: rutin 100 mg/kg, for 7 weeks. Cu only treatment significantly decreased body weight gain, while rutin cotreatment reversed this decrease. Cu treatment increased malondialdehyde, nitric oxide level, and myeloperoxidase activity and decreased superoxide dismutase and catalase activities in rat brain. Immunohistochemistry showed that COX-2, iNOS, and Bcl-2 proteins were strongly expressed, while Bax was mildly expressed in the brain of Cu-treated rats. Furthermore, brain histology revealed degenerated neurons, and perforated laminae of cerebral cortex in the Cu-only treated rats. Interestingly, coadministration of Cu and rutin reduced the observed histological alteration, improved inflammatory and antioxidant biomarkers, thereby protecting against Cu-induced brain damage via antioxidative and anti-inflammatory mechanisms.

Hydroxy-α-sanshool Possesses Protective Potentials on H2O2-Stimulated PC12 Cells by Suppression of Oxidative Stress-Induced Apoptosis through Regulation of PI3K/Akt Signal Pathway

Zanthoxylum bungeanum pericarp is a commonly used herbal medicine in China with effects of anti-inflammatory and analgesic, improving learning and memory ability, while hydroxy-α-sanshool (HAS) is the most important active ingredient of Z. bungeanum pericarps. The purpose of this study was to investigate the neuroprotective effect of HAS and its related possible mechanisms using a H₂O₂-stimulated PC12 cell model. CCK-8 assay results showed that HAS had a significant protective effect on H₂O₂-stimulated PC12 cells without obvious cytotoxicity on normal PC12 cells. Flow cytometry and fluorescence microscope (DAPI staining and DCFH-DA staining) indicated that HAS could reduce the H₂O₂-induced apoptosis in PC12 cells via reduction of intracellular ROS and increase of mitochondrial membrane potential (MMP). Subsequently, results of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) determination suggested that HAS could increase the enzyme activities of SOD, CAT, and GSH-Px whereas it could decrease the MDA contents in H₂O₂-stimulated PC12 cells. Furthermore, the western blotting assays showed that HAS could upregulate the expressions of p-PI3k, Akt, p-Akt, and Bcl-2, while it could downregulate the expressions of cleaved caspase-3 and Bax in H₂O₂-stimulated PC12 cells. Collectively, it could be concluded according to our results that HAS possesses protective potentials on H₂O₂-stimulated PC12 cells through suppression of oxidative stress-induced apoptosis via regulation of PI3K/Akt signal pathway.

D-Lactic Acid as a Metabolite: Toxicology, Diagnosis, and Detection

Two enantiomers of lactic acid exist. While L-lactic acid is a common compound of human metabolism, D-lactic acid is produced by some strains of microorganism or by some less relevant metabolic pathways. While L-lactic acid is an endogenous compound, D-lactic acid is a harmful enantiomer. Exposure to D-lactic acid can happen by various ways including contaminated food and beverages and by microbiota during some pathological states like short bowel syndrome. The exposure to D-lactic acid cannot be diagnosed because the common analytical methods are not suitable for distinguishing between the two enantiomers. In this review, pathways for D-lactic acid, pathological processes, and diagnostical and analytical methods are introduced followed by figures and tables. The current literature is summarized and discussed.

Berberine attenuated the cytotoxicity induced by t-BHP via inhibiting oxidative stress and mitochondria dysfunction in PC-12 cells

Neurodegenerative diseases all share several common features such as involvement of oxidative damage and mitochondrial dysfunction in pathogenesis. Oxidative stress induced by overproduction of mitochondrial reactive oxygen species (ROS) or impairment of the antioxidant deficiency results in mitochondrial dysfunction and initiation of the cell death cascade. Berberine (BBR), a traditional Chinese medicine, has been reported to exert anti-oxidative stress and anti-apoptosis effect in CNS diseases. However, the mechanism of BBR on regulating mitophagy and protecting mitochondrial function under oxidative stress remains unclear. In present study, we evaluated the beneficial effects of BBR on the tert-butyl hydroperoxide (t-BHP)-induced cytotoxicity. Furthermore, we explored the protective role of BBR in mitochondrial function and mitophagy under oxidative stress in PC-12 cells. Our results demonstrated that BBR effectively inhibited t-BHP-induced apoptosis which is associated with the decreased leakage of lactate dehydrogenase (LDH) and ROS overproduction. Moreover, BBR significantly suppressed cytochrome c expression, upregulated the ratio of Bcl-2/Bax, and ameliorated mitochondrial dysfunction by optimizing mitochondria membrane potential (ΔΨm) status and ATP production. In addition, BBR reduced the expression of autophagy-specific marker LC3, SQTM1/p62, and maintained lysosome normal function which involved the restoration of upstream signaling pathway AKT and mTOR phosphorylation level. Collectively, these findings suggested that BBR protects PC-12 cells from oxidative injury through inhibiting ROS level, mitochondria dysfunction, and mitophagy via PI3K/AKT/mTOR signaling pathways, which suggest a potential therapeutic strategy for oxidative stress and neurotoxic damages.

The Secretion from Bone Marrow Mesenchymal Stem Cells Pretreated with Berberine Rescues Neurons with Oxidative Damage Through Activation of the Keap1-Nrf2-HO-1 Signaling Pathway

Oxidative stress is a potential pathological mechanism of Alzheimer's disease (AD). Berberine (BBR) can improve antioxidative capacity and inhibit Aβ protein aggregation and tau protein hyperphosphorylation in AD, and stem cell therapy is also increasingly recognized as a therapy for AD. Bone marrow mesenchymal stem cells (BMSCs) have many advantages, as they exhibit antioxidant and anti-inflammatory activity and secrete a variety of neurotrophic factors, and play important roles in neurodegenerative disease treatment. In this study, we investigated the antioxidant effects of secretions from BMSCs pretreated with BBR on tert-butyl hydroperoxide (t-BHP)-damaged neurons. We demonstrated that BBR can enhance BMSC viability and the secretion of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), both of which are vital neurotrophic factors that maintain neuronal growth. Moreover, conditioned medium from BBR-treated BMSCs (BBR-BMSC-CM) reduced reactive oxygen species (ROS) production, attenuated a decrease in the mitochondrial membrane potential, and ameliorated neuronal apoptosis by decreasing levels of the apoptotic proteins Bax/Bcl-2, cytochrome c, and cleaved caspase-3/caspase-3. In addition, increased synaptophysin (SYP) and postsynaptic density protein 95 (PSD95) levels indicated that neuronal synaptic function was restored. Further study revealed that BBR-BMSC-CM activated the antioxidant proteins Keap1, Nrf2, and HO-1. In conclusion, our results showed that BBR-BMSC-CM attenuated apoptosis and oxidative damage in neurons by activating the Keap1-Nrf2-HO-1 signaling pathway. Taken together, these results also suggest BBR as a drug to stimulate the secretion of nutritional cytokines with the potential to treat AD.

Protection of diabetes-induced kidney injury by phosphocreatine via the regulation of ERK/Nrf2/HO-1 signaling pathway

Diabetic nephropathy is the most common long-term complication of diabetes mellitus. The Methylglyoxal (MGO) production is mainly by metabolic pathways, such as lipolysis and glycolysis, its increases in the DM enhances oxidative stress and plays a crucial role in the diabetic nephrotic pathogenesis. Phosphocreatine (PCr) can improve lipopolysaccharide, ox-LDL-induced atherosclerosis, and alleviate vascular endothelial cell injury in diabetes. The aim of our present study is to examine the potential role of phosphocreatine (PCr) as a molecule protects against diabetes-induced Kidney Injury in-vitro and in-vivo through ERK/Nrf2/HO-1 signaling pathway. NRK-52E cells treatment with PCr obviously suppressed MGO-induced change of viability, apoptosis, coupled with decreased Bax/Bcl-2ratio, casapse-9 and caspase-3expressions. We determined the generation of reactive oxygen species (ROS) using membrane permeable fluorescent probe DCFH-DA as well as intracellular calcium by flow cytometry. ERK, Nrf2 and HO-1 expressions were determined by Western blot. PCr pretreatment significantly returned the oxidative stress enzymes to normal condition in-vitro and in-vivo. PCr pretreatment significantly reduced apoptosis, calcium and ROS production, induced by MGO, in NRK-52E cells. Moreover, pretreatment with PCr significantly inhibited cleaved caspase-3, cleaved caspase-9 and p-ERK expressions, while increased Nrf-2 and HO-1 expressions. Furthermore, PCr pretreatment significantly decreased p-ERK expression of MGO-induced injury in NRK-52E cells transfected with p-ERK cDNA. In conclusion, the renal protective effect of PCr in-vitro and in-vivo depends on suppressing apoptosis and ROS generation through ERK mediated Nrf-2/HO-1 pathway, suggesting that PCr may be a novel therapeutic candidate for the diabetic nephropathy treatment.

Mn-TAT PTD-Ngb attenuates oxidative injury by an enhanced ROS scavenging ability and the regulation of redox signaling pathway

Neurological diseases have a close relationship to excessive reactive oxygen species (ROS). Neuroglobin (Ngb), an intrinsic protective factor, protected cells from hypoxic/ischemic injury. In the present, we reported a novel neuroprotective manganese porphyrin reconstituted metal protein, Mn-TAT PTD-Ngb, consisting of a HIV Tat protein transduction domain sequence (TAT PTD) attached to the N-terminal of apo-Ngb. Mn-TAT PTD-Ngb had a stronger ROS scavenging ability than that of TAT PTD-Ngb, and reduced intracellular ROS production and restored the function of the mitochondria and inhibited the mitochondria-dependent apoptosis. Besides, Mn-TAT PTD-Ngb activated the phosphoinositide-3 kinase (PI3K)/Akt signaling pathway, which up-regulated the expression of nuclear factor E2-related factor 2 (Nrf2), Heme oxygenase-1 (HO-1), superoxide dismutase (SOD), catalase (CAT). The results showed that the redox chemistry of Mn-TAT PTD-Ngb and redox regulation of multiple signaling pathways attenuated the oxidative injury.

Pterostilbene Prevents Early Diabetic Retinopathy Alterations in a Rabbit Experimental Model

Oxidative stress generated by diabetes plays a key role in the development of diabetic retinopathy (DR), a common diabetic complication. DR remains asymptomatic until it reaches advanced stages, which complicate its treatment. Although it is known that good metabolic control is essential for preventing DR, knowledge of the disease is incomplete and an effective treatment with no side effects is lacking. Pterostilbene (Pter), a natural stilbene with good antioxidant activity, has proved to beneficially affect different pathologies, including diabetes. Therefore, our study aimed to analyse the protective and/or therapeutic capacity of Pter against oxidant damage by characterising early retinal alterations induced by hyperglycaemia, and its possible mechanism of action in a rabbit model of type 1 diabetes mellitus. Pter reduced lipid and protein oxidative damage, and recovered redox status and the main activities of antioxidant enzymes. Moreover, the redox regulation by Pter was associated with activation of the PI3K/AKT/GSK3β/NRF2 pathway. Our results show that Pter is a powerful protective agent that may delay early DR development.

Effects of quercetin on cadmium-induced toxicity in rat urine using metabonomics techniques

This study aimed to analyse the protective effects of quercetin on the toxicity of cadmium (Cd) using metabonomics techniques. Sixty male Sprague-Dawley rats were randomly divided into six groups (n = 10): control group (C), low-dose quercetin-treated group (Q1; 10 mg/kg bw/day), high-dose quercetin-treated group (Q2; 50 mg/kg bw/day), Cd-treated group (D; 4.89 mg/kg bw/day), low-dose quercetin plus Cd-treated group (DQ1) and high-dose quercetin plus Cd-treated group (DQ2). The rats continuously received quercetin and Cd via gavage and drinking water for 12 weeks, respectively. The rat urine samples were collected for metabonomics analysis. Finally, 10 metabolites were identified via the metabonomics profiles of the rat urine samples. Compared with the control group, the intensities of taurine, phosphocreatine, l-carnitine and uric acid were significantly decreased (p < 0.01) and those of LysoPC (18: 2 (9Z, 12Z)), guanidinosuccinic acid, dopamine, 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman and allantoic acid were significantly increased (p < 0.01) in the Cd-treated group. However, the intensities of the aforementioned metabolites had restorative changes in the high-dose quercetin plus Cd-treated groups unlike those in Cd-treated group (p < 0.01 or p < 0.05). Results indicated that quercetin exerts protective effects on Cd-induced toxicity by regulating energy and lipid metabolism, enhancing the antioxidant defence system and protecting liver and kidney function and so on.

Succinate accumulation induces mitochondrial reactive oxygen species generation and promotes status epilepticus in the kainic acid rat model

Though succinate accumulation is associated with reactive oxygen species (ROS) production and neuronal injury, which play critical roles in epilepsy, it is unclear whether succinate accumulation contributes to the onset of epilepsy or seizures. We sought to investigate changes in succinate, oxidative stress, and mito-SOX levels, as well as mitophagy and neuronal change, in different status epilepticus (SE) rat models. Our results demonstrate that KA-induced SE was accompanied by increased levels of succinate, oxidative stress, and mito-SOX, as well as mitophagy and neuronal degeneration. The similarly increased levels of succinate, oxidative stress, and mito-SOX were also found in pilocarpine-induced SE. Moreover, the reduction of succinate accumulation by the inhibition of succinate dehydrogenase (SDH), malate/aspartate shuttle (MAS), or purine nucleotide cycle (PNC) served to reduce succinate, oxidative stress, and mito-SOX levels, thereby preventing oxidative stress-related neuronal damage and lessening seizure severity. Interestingly, simulating succinate accumulation with succinic acid dimethyl ester may induce succinate accumulation and increased oxidative stress and mito-SOX levels, as well as behavior and seizures in electroencephalograms similar to those observed in rats exposed to KA. Our results indicate that succinate accumulation may contribute to the increased oxidative stress/mitochondrial ROS levels, neuronal degeneration, and SE induced by KA administration. Furthermore, we found that succinate accumulation was mainly due to the inverse catalysis of SDH from fumarate, which was supplemented by the MAS and PNC pathways. These results reveal new insights into the mechanisms underlying SE and that reducing succinate accumulation may be a clinically useful therapeutic target in SE.

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KA- or pilocarpine-induced SE was accompanied by succinate accumulation.

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Succinate accumulation caused elevated ROS/mito-ROS levels and neuronal injury.

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Inverse catalysis of SDH from fumarate mainly caused succinate accumulation.

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Inhibiting succinate accumulation relieved oxidative stress level, neuronal injury, and seizure.

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Simulating succinate accumulation induced elevated oxidative stress level and seizure.