Glaucocalyxin B protects against oxygen-glucose-deprivation/reperfusion-induced neuronal injury in PC-12 cells

4'-O-methylbavachalcone alleviates ischemic stroke injury by inhibiting parthanatos and promoting SIRT3

Cerebral ischemia-reperfusion injury (CIRI) can induce massive death of ischemic penumbra neurons via oxygen burst, exacerbating brain damage. Parthanatos is a form of caspase-independent cell death involving excessive activation of PARP-1, closely associated with intense oxidative stress following CIRI. 4'-O-methylbavachalcone (MeBavaC), an isoprenylated chalcone component in Fructus Psoraleae, has potential neuroprotective effects. This study primarily investigates whether MeBavaC can act on SIRT3 to alleviate parthanatos of ischemic penumbra neurons induced by CIRI. MeBavaC was oral gavaged to the middle cerebral artery occlusion-reperfusion (MCAO/R) rats after occlusion. The effects of MeBavaC on cerebral injury were detected by the neurological deficit score and cerebral infarct volume. In vitro, PC-12 cells were subjected to oxygen and glucose deprivation/reoxygenation (OGD/R), and assessed cell viability and cell injury. Also, the levels of ROS, mitochondrial membrane potential (MMP), and intracellular Ca2+ levels were detected to reflect mitochondrial function. We conducted western blotting analyses of proteins involved in parthanatos and related signaling pathways. Finally, the exact mechanism between the neuroprotection of MeBavaC and parthanatos was explored. Our results indicate that MeBavaC reduces the cerebral infarct volume and neurological deficit scores in MCAO/R rats, and inhibits the decreased viability of PC-12 cells induced by OGD/R. MeBavaC also downregulates the expression of parthanatos-related death proteins PARP-1, PAR, and AIF. However, this inhibitory effect is weakened after the use of a SIRT3 inhibitor. In conclusion, the protective effect of MeBavaC against CIRI may be achieved by inhibiting parthanatos of ischemic penumbra neurons through the SIRT3-PARP-1 axis.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Role of Nrf2 in aging, Alzheimer's and other neurodegenerative diseases

Nuclear Factor-Erythroid Factor 2 (Nrf2) is an important transcription factor that regulates the expression of large number of genes in healthy and disease states. Nrf2 is made up of 605 amino acids and contains 7 conserved regions known as Nrf2-ECH homology domains. Nrf2 regulates the expression of several key components of oxidative stress, mitochondrial biogenesis, mitophagy, autophagy and mitochondrial function in all organs of the human body, in the peripheral and central nervous systems. Mounting evidence also suggests that altered expression of Nrf2 is largely involved in aging, neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's diseases, Amyotrophic lateral sclerosis, Stroke, Multiple sclerosis and others. The purpose of this article is to detail the essential role of Nrf2 in oxidative stress, antioxidative defense, detoxification, inflammatory responses, transcription factors, proteasomal and autophagic/mitophagic degradation, and metabolism in aging and neurodegenerative diseases. This article also highlights the Nrf2 structural and functional activities in healthy and disease states, and also discusses the current status of Nrf2 research and therapeutic strategies to treat aging and neurodegenerative diseases.

Delavatine A attenuates OGD/R-caused PC12 cell injury and apoptosis through suppressing the MKK7/JNK signaling pathway

Delavatine A (DA) is an unusual isoquinoline alkaloid with a novel skeleton isolated from Chinese folk medicine Incarvillea delavayi. Studies conducted in our lab have demonstrated that DA has potential anti-inflammatory activity in LPS-treated BV-2 cells. DA, however, has not been studied for its protective effect on neuronal cells yet. Thus, to explore whether DA can protect neurons, oxygen and glucose deprivation/reperfusion (OGD/R)-injured PC12 cell and middle cerebral artery occlusion/reperfusion (MCAO/R) rat model were used to assess the protective efficacy of DA against OGD/R damaged PC12 cells and MCAO/R injured rats. Our results demonstrated that DA pretreatment (0.31-2.5 μM) dose-dependently increased cell survival and mitochondrial membrane potential (MMP), whereas it lowered the leakage of lactate dehydrogenase (LDH), intracellular cumulation of Ca²⁺, and overproduction of reactive oxygen species (ROS), and inhibited the apoptosis rate in OGD/R-injured PC12 cells. Western blot demonstrated that DA pretreatment lowered the expression of apoptotic proteins and repressed the activation of the MKK7/JNK pathway. It was also found that the neuroprotective efficacy of DA was significantly reversed by co-treatment with the JNK agonist anisomycin, suggesting that DA reduced PC12 cell injury and apoptosis by suppressing the MKK7/JNK pathway. Furthermore, DA oral administration greatly alleviated the neurological dysfunction and reduced the infarct volume of MCAO/R rats. Taken together, DA could ameliorate OGD/R-caused PC12 cell injury and improve brain ischemia/reperfusion (I/R) damage in MCAO/R rats, and its neuroprotection might be attributed to suppressing the MKK7/JNK signaling pathway.

1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) Urea Exerts Neuro-Protective Effects Against Ischemic Injury via Suppressing JNK/p38 MAPK-Mediated Mitochondrial Apoptosis Pathway

BACKGROUND

1-trifluoromethoxyphenyl-3-(1- propionylpiperidin-4-yl) urea (TPPU) is a novel soluble epoxide hydrolase inhibitor which can protect against cerebral ischemic injury in middle cerebral artery occlusion rat model. However, the effects and potential mechanisms of TPPU on mitochondrial dysfunction are poorly understood.

MATERIALS AND METHODS

In oxygen-glucose deprivation/reperfusion (OGD/R)-induced cortical neurons, the effect of TPPU on cell viability was measured by MTT assay and apoptosis was evaluated using TUNEL assay. Mitochondria were observed by transmission electron microscopy and Mitotracker green staining assay, mitochondrial membrane potential was determined by JC-1 staining assay, activities of mitochondrial respiratory chain complexes (MRCC) I-IV and ATPase were measured by MRCC Activity Assay Kits and spectrophotometer. Western blot was used to investigate the effects of TPPU on apoptosis-related proteins.

RESULTS

TPPU treatment demonstrated significant protective effect on the OGD/R-induced cortical neurons by reducing cell death and number of apoptotic cells, stabilizing mitochondrial ultrastructure and morphology, increasing mitochondrial membrane potential and activities of MRCC I-IV and ATPase. Furthermore, TPPU treatment might effectively reverse the upregulation of caspase-3, Bax, p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal protein kinase (JNK), alleviate the inhibition of Bcl-2 in OGD/R-induced cortical neurons.

CONCLUSIONS

TPPU exerts a marked neuroprotective effect against mitochondrial dysfunction after cerebral ischemia potentially via suppressing JNK/p38 MAPK-mediated mitochondrial apoptosis signal pathway, it may be a promising neuroprotective agent for cerebral ischemia.

Ablation of TMEM126B protects against oxygen-glucose deprivation/reoxygenation-induced injuries of PC12 cells via maintaining mitochondrial anti-apoptotic functions

Ischemia reperfusion (I/R) injury is a key contributing factor to the pathogenic mechanism involved in cerebral infarction. Transmembrane protein 126b (TMEM126B), a mitochondrial complex I assembly factor, has been reported to have an intimate association with disease progression, but is little known in ischemia stroke. The present study was designed to explore the effects of TEME126B on oxygen-glucose deprivation/reoxygenation (OGD/R)-induced neuronal PC12 cells. The mRNA level of TMEM126B was determined using qRT-PCR. The levels of ROS, MDA, and SOD, as well as inflammatory cytokines, were measured using corresponding commercial kits. Cell apoptosis rate was assayed by flow cytometry analysis, and the apoptosis-related proteins were measured using western blotting. ATP production measured by colorimetric reaction and mitochondrial membrane potential measured by JC-1 staining were conducted to determine mitochondrial dysfunction. The results showed that TMEM126B was upregulated upon I/R injury in vitro and in clinical, and was positively corrected with the degree of oxidative stress. TMEM126B knockdown significantly reduced oxidative stress and inflammation in OGD/R-induced PC12 cells. TMEM126B knockdown also attenuated cell apoptosis rate, accompanied with increased expressions of Bcl-2, XIAP and cleaved PARP-1, and decreased expressions of Bax, cleaved caspase 3 and cleaved caspase 9. Furthermore, TMEM126B knockdown exhibited cytoprotective roles through alleviating mitochondrial dysfunction, as assessed by ATP production and mitochondrial membrane potential. Collectively, this study indicates that TMEM126B knockdown protects against OGD/R-induced neuronal injuries through relieving oxidative stress, inflammation, apoptosis and mitochondria dysfunction, which provides a promising target for ischemic stroke treatment.

1-Trifluoromethoxyphenyl-3-(1-Propionylpiperidin-4-yl) Urea Protects the Blood-Brain Barrier Against Ischemic Injury by Upregulating Tight Junction Protein Expression, Mitigating Apoptosis and Inflammation In Vivo and In Vitro Model

We previously have revealed that 1-trifluoromethoxyphenyl-3-(1- propionylpiperidin-4-yl) urea (TPPU), as a soluble epoxide hydrolase (sEH) inhibitor can reduce infarct volume, protect blood-brain barrier (BBB) and brain against ischemic injury in rats. Here, we investigated the potential mechanisms of TPPU on BBB integrity in both in permanent middle cerebral artery occlusion (pMCAO) rat model and in oxygen-glucose deprivation/reperfusion (OGD/R)-induced human brain microvascular endothelial cells (HBMVECs) model. In pMCAO rat, TPPU administration decreased brain edema and Evans blue content, increased tight junction proteins (TJs) expression of claudin-5, occludin, and zonula occludens-1 (ZO-1). In OGD/R model, OGD/R significantly increased permeability and cell apoptosis, downregulated the expression of claudin-5, ZO-1, occludin, and lymphoma (Bcl)-2. Notably, TPPU pretreatment effectively protected the BBB integrity by reducing the permeability, promoting expression of claudin-5, ZO-1, occluding and Bcl-2, mitigating reactive oxygen species (ROS) injury and release of interleukin-1β (IL-1β), IL-6β, and tumor necrosis factor-α (TNF-α), downregulating expression of matrix metalloproteinase-9 (MMP-9), MMP-2, bcl-2-associated X protein (Bax), IL-1β, IL-6β, and TNF-α. Moreover, OGD/R induced the up-regulation of p-p65, p-IκB, and p-p38, which were effectively decreased after TPPU pretreatment in comparison with that of the OGD/R group. Furthermore, pyrrolidinedithiocarbamate (PDTC, a selective inhibitor of NF-κB p65) not only alleviated the OGD/R-induced HBMVECs injury and permeability, but also reduced the expression of TNF-α, IL-6, IL-1β, p-p65, and p-IκB, and the protective effect of PDTC was equivalent to that of TPPU. These results indicate that TPPU protects BBB integrity against ischemic injury by multiple protective mechanisms, at least in part, by reducing ROS, inflammation, apoptosis, and suppressing the nuclear factor-κB (NF-κB) and p38 signaling pathways.

Protective effect of microRNA‑340‑5p against oxygen‑glucose deprivation/reperfusion in PC12 cells through targeting neuronal differentiation 4

The expression levels of microRNA (miR)‑340‑5p are reportedly decreased in the peripheral blood during acute ischemic stroke; however, the direct effect and mechanism of action of miR‑340‑5p in ischemic stroke remains largely unknown. The present study aimed to investigate the effects of miR‑340‑5p, and its mechanism of action, on PC12 cells following oxygen‑glucose deprivation/reperfusion (OGD/R) induction. OGD/R‑induced PC12 cells served as the cellular model and subsequently, mRNA expression levels of miR‑340‑5p and neuronal differentiation 4 (Neurod4) were analyzed using reverse transcription‑quantitative PCR. Tumor necrosis factor‑α, interleukin (IL)‑1β and IL‑6 expression levels were detected using ELISA kits, and flow cytometry was used to determine the rate of cellular apoptosis. In addition, a nitric oxide (NO) synthase activity assay kit was used to detect NO levels and a NADPH assay kit was used to measure NADPH levels. Western blotting was also performed to analyze protein expression levels of bax, bcl‑2, cleaved caspase 3 and phosphorylated endothelial NOS (eNOS), and the target gene of miR‑340‑5p was predicted using TargetScan software and verified using a dual‑luciferase reporter assay. The expression levels of miR‑340‑5p were decreased in PC12 cells following OGD/R induction and Neurod4 was identified as a target gene of miR‑340‑5p. In addition, miR‑340‑5p overexpression reduced inflammation, apoptotic rate, NO production and NADPH levels, in addition to increasing eNOS expression in PC12 cells following OGD/R induction. Notably, the overexpression of Neurod4 reversed the aforementioned effects of miR‑340‑5p on PC12 cells following OGD/R induction. In conclusion, the findings of the present study suggested that miR‑340‑5p may protect PC12 cells against OGD/R through targeting Neurod4, which could provide important implications for the treatment of ischemia‑reperfusion injury based on miR‑340‑5p expression levels in vivo.

Thymosin β4 prevents oxygen-glucose deprivation/reperfusion-induced injury in rat cortical neurons

PURPOSE

This study investigated whether thymosin (T) β4 protects against oxygen-glucose deprivation/reperfusion (OGD/R) injury in rat cortical neurons, as well as the underlying mechanisms.

METHODS

Primary rat cortical neurons were transfected with Tβ4 overexpression plasmid; the transfection efficiency was confirmed by detecting Tβ4 expression by fluorescence quantitative PCR and Western blotting. The OGD/R model was established and apoptotic cells were quantified by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling. Structural changes in the endoplasmic reticulum were visualized by transmission electron microscopy. The expression levels of 78-kDa glucose-regulated protein (GRP) 78, C/EBP-homologous protein (CHOP), B-cell lymphoma (Bcl)-2, and Bcl-2-associated X protein (Bax) were determined by Western blotting. The effect of Tβ4 on OGD/R injury was evaluated by adding exogenous Tβ4 to neuronal cultures.

RESULTS

Cortical neurons were identified by the expression of neuron-specific enolase. In OGD/R cells, the rate of apoptosis was increased and GRP78, CHOP, and Bax were upregulated whereas Bcl-2 was downregulated relative to the control group. These effects were reversed by Tβ4 overexpression. Endoplasmic reticulum (ER) stress was observed in the OGD/R group, but this was abolished in neurons overexpressing Tβ4. The protective effect of Tβ4 against OGD/R injury was also demonstrated in cells treated with exogenous Tβ4 (10 ng/mL), which blocked OGD/R-induced apoptosis by inhibiting ER stress-related and pro-apoptotic protein expression.

CONCLUSION

Tβ4 prevents OGD/R-induced ER stress-dependent apoptosis in cortical neurons, and is a potential treatment for cerebral ischemia-reperfusion injury.