Possible Involvement of PI3-K/Akt-Dependent GSK-3β Signaling in Proliferation of Neural Progenitor Cells After Hypoxic Exposure

Role of senkyunolide I in the promotion of neural stem/progenitor cell proliferation via the Akt/β-catenin pathway

Following brain injury, neural stem cells (NSCs) can generate mature neurons and replace damaged cells. However, the capacity of endogenous NSCs to self-repair from injured brain is limited as most NSCs die before becoming mature neurons. Therefore, a boosting endogenous NSCs by pharmacological support offers the potential to repair the damaged brain. Recently, small molecules have hold considerable promise for neuron regeneration and repair as they can penetrate the blood-brain barrier easily. Senkyunolide I (SEI) is a bioactive constituent derived from traditional Chinese medicines Ligusticum chuanxiong Hort. and Angelica sinensis (Oliv.) Diels, and was found to able to prevent ischemic stroke. This study examined the effects of SEI on the proliferation and neuronal lineage differentiation of prepared neural stem/progenitor cells (NS/PCs). The NS/PC proliferation was determined by 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt, and neurosphere formation assays. The NS/PC differentiation was also investigated by immunocytochemistry, and western blotting was employed to measure phosphorylated Akt (pAkt) and GSK-3β (pGSK-3β), and active-β-catenin protein levels. We showed that the NS/PC proliferation was enhanced after SEI exposure. Elevated cell numbers were also observed in neurospheres, which were incubated with SEI for 3 days, whereas the NS/PC differentiation was decreased after SEI exposure for 5 days. Furthermore, SEI upregulated pAkt/Akt and active-β-catenin levels and increased NS/PC proliferation after SEI treatment was reversed by phosphatidylinositol 3-kinase inhibitor LY294002. downregulated differentiated processes. Thus, SEI promoted the NS/PC proliferation and suppressed NS/PC differentiation into neurons and/or astrocytes, therefore SEI could be an interesting and promising candidate for stimulating NSCs.

Extracellular vesicles from neural progenitor cells promote functional recovery after stroke in mice with pharmacological inhibition of neurogenesis

Neural progenitor cells (NPCs) of the subventricular zone proliferate in response to ischemic stroke in the adult mouse brain. Newly generated cells have been considered to influence recovery following a stroke. However, the mechanism underlying such protection is a matter of active study since it has been thought that proliferating NPCs mediate their protective effects by secreting soluble factors that promote recovery rather than neuronal replacement in the ischemic penumbra. We tested the hypothesis that this mechanism is mediated by the secretion of multimolecular complexes in extracellular vesicles (EVs). We found that the molecular influence of oxygen and glucose-deprived (OGD) NPCs-derived EVs is very limited in improving overt neurological alterations caused by stroke compared to our recently reported astrocyte-derived EVs. However, when we inhibited the ischemia-triggered proliferation of NPCs with the chronic administration of the DNA synthesis inhibitor Ara-C, the effect of NPC-derived EVs became evident, suggesting that the endogenous protection exerted by the proliferation of NPC is mainly carried out through a mechanism that involves the intercellular communication mediated by EVs. We analyzed the proteomic content of NPC-derived EVs cargo with label-free relative abundance mass spectrometry and identified several molecular mediators of neuronal recovery within these vesicles. Our findings indicate that NPC-derived EVs are protective against the ischemic cascade activated by stroke and, thus, hold significant therapeutic potential.

Tetramethylpyrazine protects neural stem cells against sevoflurane-induced toxicity through Akt/GSK-3β pathway

Sevoflurane, a commonly used anesthetic, has been found to cause neural stem cell (NSC) injury, thereby contributing to neurocognitive impairment following general anesthesia. Tetramethylpyrazine (TMP), one of the most widely used medicinal compounds isolated from a traditional Chinese herb, possess neuroprotective activity. However, its effect on sevoflurane-induced NSC injury remains unclear. NSCs were pretreated with indicated concentrations of TMP for 2 h and then exposed to sevoflurane for 6 h. Cell injury was measured using lactate dehydrogenase (LDH) release assay. Cell viability and proliferation were detected by cell counting kit-8 (CCK-8) assay and 5-bromo-2'-deoxyuridine (BrdU) labeling, respectively. Apoptotic cells were detected using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The levels of cleaved caspase-3, phosphorylated protein kinase B (Akt) and phosphorylated glycogen synthase kinase-3β (GSK-3β) were detected by western blotting. Our results showed exposure to sevoflurane decreased the viability and proliferation of NSCs, while TMP preserved NSC viability and proliferation after sevoflurane exposure. In addition, the expression of cleaved caspase-3 and TUNEL positive cells were markedly decreased in TMP-treated NSCs compared with the control. Furthermore, pretreatment with TMP significantly increased the levels of phosphorylated Akt and GSK-3β in sevoflurane-injured NSCs. However, an upstream inhibitor of Akt, LY294002 abolished the protective of TMP on the cell viability of NSCs. In conclusion, these findings indicate that TMP protects NSCs from sevoflurane-induced toxicity through Akt/GSK-3β pathway.

Application of extracorporeal shock wave therapy in nervous system diseases: A review

Neurological disorders are one of the leading causes of morbidity and mortality worldwide, and their therapeutic options remain limited. Recent animal and clinical studies have shown the potential of extracorporeal shock wave therapy (ESWT) as an innovative, safe, and cost-effective option to treat neurological disorders. Moreover, the cellular and molecular mechanism of ESWT has been proposed to better understand the regeneration and repairment of neurological disorders by ESWT. In this review, we discuss the principles of ESWT, the animal and clinical studies involving the use of ESWT to treat central and peripheral nervous system diseases, and the proposed cellular and molecular mechanism of ESWT. We also discuss the challenges encountered when applying ESWT to the human brain and spinal cord and the new potential applications of ESWT in treating neurological disorders.

Effect of Progranulin on Proliferation and Differentiation of Neural Stem/Progenitor Cells after Oxygen/Glucose Deprivation

We previously demonstrated that sivelestat, a selective neutrophil elastase inhibitor, attenuates the cleavage of progranulin (PGRN) and ischemia-induced cell injury in the brain. To obtain further insight into the role of PGRN, in the present study we evaluated the direct effects of sivelestat and recombinant PGRN (rPGRN) on the proliferation and differentiation of neural stem cells in cultures of neural stem/progenitor cells (NS/PC) under the ischemic condition in vitro. We demonstrated that oxygen/glucose deprivation (OGD)-induced cell proliferation of NS/PC was increased by rPGRN treatment. In addition, this increase was accompanied by increased phosphorylation of Akt and GSK-3β (Ser9) after OGD. But none of these responses occurred by treatment with sivelestat. Therefore, activation of the Akt/GSK-3β pathway could well be involved in this proliferative effect of rPGRN. Although OGD and reoxygenation-induced changes in the differentiation of NS/PC into neurons or astrocytes was not affected by treatment with rPGRN or sivelestat, it is noteworthy that rPGRN enhanced neurite outgrowth of β3-tubulin-positive neurons that had differentiated from the NS/PC. These findings suggest that enhancement of proliferation of endogenous NS/PC and neurite outgrowth of differentiated neurons from NS/PC by PGRN could be useful for a new therapeutic approach for cerebral ischemia.

Research advances in the role of endogenous neurogenesis on neonatal hypoxic-ischemic brain damage

Hypoxic-ischemic brain damage (HIBD) is the main cause of perinatal mortality and neurologic complications in neonates, but it remains difficult to cure due to scarce treatments and complex molecular mechanisms remaining incompletely explained. Recent, mounting evidence shows that endogenous neurogenesis can improve neonatal neurological dysfunction post-HIBD. However, the capacity for spontaneous endogenous neurogenesis is limited and insufficient for replacing neurons lost to brain damage. Therefore, it is of great clinical value and social significance to seek therapeutic techniques that promote endogenous neurogenesis, to reduce neonatal neurological dysfunction from HIBD. This review summarizes the known neuroprotective effects of, and treatments targeting, endogenous neurogenesis following neonatal HIBD, to provide available targets and directions and a theoretical basis for the treatment of neonatal neurological dysfunction from HIBD.

The role of hypoxia in stem cell regulation of the central nervous system: From embryonic development to adult proliferation

Hypoxia is involved in the regulation of various cell functions in the body, including the regulation of stem cells. The hypoxic microenvironment is indispensable from embryonic development to the regeneration and repair of adult cells. In addition to embryonic stem cells, which need to maintain their self-renewal properties and pluripotency in a hypoxic environment, adult stem cells, including neural stem cells (NSCs), also exist in a hypoxic microenvironment. The subventricular zone (SVZ) and hippocampal dentate gyrus (DG) are the main sites of adult neurogenesis in the brain. Hypoxia can promote the proliferation, migration, and maturation of NSCs in these regions. Also, because most neurons in the brain are non-regenerative, stem cell transplantation is considered as a promising strategy for treating central nervous system (CNS) diseases. Hypoxic treatment also increases the effectiveness of stem cell therapy. In this review, we firstly describe the role of hypoxia in different stem cells, such as embryonic stem cells, NSCs, and induced pluripotent stem cells, and discuss the role of hypoxia-treated stem cells in CNS diseases treatment. Furthermore, we highlight the role and mechanisms of hypoxia in regulating adult neurogenesis in the SVZ and DG and adult proliferation of other cells in the CNS.

Progranulin promotes functional recovery and neurogenesis in the subventricular zone of adult mice after cerebral ischemia

Progranulin (PGRN), a secreted glycosylated protein, has been reported to attenuate ischemia-induced cerebral injury through anti-inflammation, attenuation of blood-brain barrier disruption and neuroprotection. However, the effect of PGRN on neurogenesis in the subventricular zone (SVZ) after cerebral ischemia remains unclear. In this study, adult C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO), and different doses of recombinant mouse PGRN (r-PGRN, 0.3 ng, 1 ng, 5 ng) were intracerebroventricularly administered 30 min after pMCAO. Results showed that 1 ng r-PGRN markedly reduced infarct volume and rescued functional deficits 24 h after pMCAO. Meanwhile, 1 ng r-PGRN increased SVZ cell proliferation, as shown by a high number of bromodeoxyuridine-positive (BrdU+) cells and Ki-67+ cells in the ischemic ipsilateral SVZ 7 d after pMCAO. Additionally, PGRN increased the percentage of BrdU+/Doublecortin (DCX)+ cells in the ipsilateral SVZ 14 d after pMCAO and increased the percentage of new neurons (BrdU+/NeuN+ cells) in the peri-infarct striatum 28 d after pMCAO, suggesting that PGRN promotes neuronal differentiation. PGRN also upregulated phosphorylation of ERK1/2 and Akt in the ipsilateral SVZ 3 d after pMCAO. Our data indicate that PGRN treatment promotes acute functional recovery; most importantly, it also stimulates neurogenesis in the SVZ, which could be beneficial for long-term recovery after cerebral ischemia. The increase in neurogenesis could be associated with activation of the MAPK/ERK and PI3K/Akt pathways. These results suggest a potential new strategy utilizing PGRN in ischemic stroke therapy.

Effects of laminin-111 peptide coatings on rat neural stem/progenitor cell culture

Neurons require adhesive scaffolds for their growth and differentiation. Laminins are a major cell adhesive component of basement membranes and have various biological activities in the peripheral and central nervous systems. Here, we evaluated the biological activities of 5 peptides derived from laminin-111 as a scaffold for mouse neuroblastoma Neuro2a cells and rat neural stem/progenitor cells (NPCs). The 5 peptides showed Neuro2a cell attachment activity similar to that of poly-d-lysine. However, when NPCs were cultured on the peptides, 2 syndecan-binding peptides, AG73 (RKRLQVQLSIRT, mouse laminin α1 chain 2719-2730) and C16 (KAFDITYVRLKF, laminin γ1 chain 139-150), demonstrated significantly higher cell attachment and neurite extension activities than other peptides including integrin-binding ones. Long-term cell culture experiments showed that both AG73 and C16 supported the growth of neurons and astrocytes that had differentiated from NPCs. Furthermore, C16 markedly promoted the expression of neuronal markers such as synaptosomal-associated protein-25 and syntaxin 1A. These results indicate that AG73 and C16 are useful for NPC cultures and that C16 can be applied to specialized research on synapses in differentiated neurons. These peptides have the potential for use as valuable biomaterials for NPC research.

Astragaloside IV-induced Nrf2 nuclear translocation ameliorates lead-related cognitive impairments in mice

Recently, oxidative stress is a common denominator in the pathogenesis of metal-induced neurotoxicity. Thus, antioxidant therapy is considered as a promising strategy for treating lead-related cognitive impairment. Here, we tested the hypothesis that astragaloside IV (AS-IV) ameliorates lead-associated cognitive deficits through Nrf2-dependent antioxidant mechanisms. Male Nrf2-KO and WT mice received drinking water with 2000 ppm lead and/or AS-IV by gavage for 8 weeks starting at 4 weeks of age. Morris water maze test and biochemical assays were employed to study cognition-enhancing and antioxidant effects of AS-IV. The signaling pathways involved were analyzed using RT-PCR and western blot technology. Significantly, AS-IV attenuated Morris water maze-based cognitive impairment in lead-intoxicated mice. Importantly, cognition-enhancing effect of AS-IV was lost in Nrf2-KO mice. In parallel, AS-IV suppressed lead acetate (PbAc)-induced oxidative stress, as measured by MDA. Mechanistically, AS-IV can up-regulate the expressions of the GCLc and HO-1 at the level of transcription and translation, but not SOD, TrxR activity, GCLm, Trx1, and NQO1 expression. Interestingly, AS-IV induced accumulation of Nrf2 in the nucleus, whereas Nrf2 mRNA levels were unchanged. Furthermore, AS-IV treatment resulted in elevated levels of phosphorylated Akt (active form) and phosphorylated GSK-3β (inactive forms) but decreased level of phosphorylated Fyn. Collectively, our findings indicate that AS-IV may target Nrf2 to attenuate lead-triggered oxidative stress and subsequent cognitive impairments, suggesting that AS-IV is a potential candidate for the treatment of lead-associated cognitive diseases.

XQ-1H attenuates ischemic injury in PC12 cells via Wnt/β-catenin signaling though inhibition of apoptosis and promotion of proliferation

10-O-(N,N-dimethylaminoethyl)-ginkgolide B methanesulfonate (XQ-1H) is a new derivative of ginkgolide B and has previously been proven to exert neuroprotective effects on ischemic injury. However, it is not clear whether XQ-1H affects the cell survival and proliferation in oxygen-glucose deprivation/reoxygenation (OGD/R) damaged PC12 cells. Our results showed that OGD/R improved cell viability after 24 hr of posttreatment with XQ-1H (10 or 5 μM), inhibiting cell injury and apoptosis by upregulating the expression of brain-derived neurotrophic factor, nerve growth factor, and antiapoptotic B-cell lymphoma-extra large, while reducing proapoptotic cleaved caspase-3 protein. By introducing the Wnt/β-catenin signaling inhibitor XAV-939 and 5-bromo-2'-deoxyuridine staining, it was proved that XQ-1H promoted the proliferation of PC12 cells in a Wnt-signal-dependent manner via inhibiting the activation of glycogen synthase kinase-3β after phosphatidylinositol 3-kinase/protein kinase B signal activation, thereby activating Wnt1, β-catenin, and the expression of downstream neurogenic differentiation 1 and cyclin D1, which was comparable to Wnt/β-catenin signaling agonist 4,6-disubstituted pyrrolopyrimidine. We conclude that XQ-1H, after OGD/R damage to PC12 cells, may limit cell apoptosis in a Wnt/β-catenin signal-dependent manner, promoting cell proliferation and survival.

Kaempferol Protects Against Cerebral Ischemia Reperfusion Injury Through Intervening Oxidative and Inflammatory Stress Induced Apoptosis

The aim of this research is to investigate the potential neuro-protective effect of kaempferol which with anti-oxidant, anti-inflammatory, and immune modulatory properties, and understand the effect of kaempferol on reducing cerebral ischemia reperfusion (I/R) injury in vivo. Male adult Sprague Dawley (SD) rats were pretreated with kaempferol for one week via gavage before cerebral I/R injury operation. We found that kaempferol treatment can reduce the cerebral infarct volume and neurological score after cerebral I/R. Rats were sacrificed after 24 h reperfusion. We observed that kaempferol improved the arrangement, distribution, and morphological structure of neurons, as well as attenuated cell apoptosis in brain tissue via hematoxylin and eosin (H&E) staining, Nissl staining and TUNEL staining. Superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GSH) kit analysis, enzyme-linked immunosorbent (ELISA) assay, real-time PCR, Western blot, and immunohistochemical examination indicated that kaempferol mitigated oxidative and inflammatory stress via regulating the expression of proteins, p-Akt, p-GSK-3β, nuclear factor erythroid2-related factor 2 (Nrf-2), and p-NF-κB during cerebral I/R, thus increasing the activity of SOD and GSH, meanwhile decreasing the content of MDA in serum and brain tissue, as well as restoring the expression levels of tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and IL-6 in vivo. Taken together, this study suggested that kaempferol protects against cerebral I/R induced brain damage. The possible mechanism is related with inhibiting oxidative and inflammatory stress induced apoptosis.

Repurposing antimycotic ciclopirox olamine as a promising anti-ischemic stroke agent

Ischemic stroke is a severe disorder resulting from acute cerebral thrombosis. Here we demonstrated that post-ischemic treatment with ciclopirox olamine (CPX), a potent antifungal clinical drug, alleviated brain infarction, neurological deficits and brain edema in a classic rat model of ischemic stroke. Single dose post-ischemic administration of CPX provided a long-lasting neuroprotective effect, which can be further enhanced by multiple doses administration of CPX. CPX also effectively reversed ischemia-induced neuronal loss, glial activation as well as blood–brain barrier (BBB) damage. Employing quantitative phosphoproteomic analysis, 130 phosphosites in 122 proteins were identified to be significantly regulated by CPX treatment in oxygen glucose deprivation (OGD)-exposed SH-SY5Y cells, which revealed that phosphokinases and cell cycle-related phosphoproteins were largely influenced. Subsequently, we demonstrated that CPX markedly enhanced the AKT (protein kinase B, PKB/AKT) and GSK3β (glycogen synthase kinase 3β) phosphorylation in OGD-exposed SH-SY5Y cells, and regulated the cell cycle progression and nitric oxide (NO) release in lipopolysaccharide (LPS)-induced BV-2 cells, which may contribute to its ameliorative effects against ischemia-associated neuronal death and microglial inflammation. Our study suggests that CPX could be a promising compound to reduce multiple ischemic injuries; however, further studies will be needed to clarify the molecular mechanisms involved.

Expression and regulation of miR-449a and AREG in cerebral ischemic injury

Rodent focal ischemia models are widely used to mimic and examine human strokes. To the best of our knowledge, no investigation has systematically examined the expression changes of microRNA (miR)-449a and Amphiregulin (AREG) as well as their biological relationship during middle cerebral artery occlusion (MCAO) and oxygen and glucose deprivation/reperfusion (OGD/R). The present study examined the histological and behavioral outcomes of MCAO and the function of miR-449a and AREG in cerebral ischemic injury. Rats were subjected to 2 h MCAO, which was followed by reperfusion. miR-449a and AREG were examined in the injury tissues of MCAO rats and the OGD/R cell line by reverse transcription-quantitative polymerase chain reaction. Protein expressions of AREG in the injury tissues of MCAO rats was measured using an immunohistochemistry and the protein expression levels of AREG, epidermal growth factor receptor (EGFR), phosphatidylinositol 3-kinase (PI3K)/ protein kinase B (Akt) and the phosphorylation level of Akt (p-Akt) were analyzed by western blotting. Cell apoptosis was examined following the knock down and subsequent overexpression of AREG in a human OGD/R neuronal cell line by small interfering RNAs (siRNAs) and plasmid transfection. Luciferase reporter assays were used to validate the target of miR-449a. The expression changes and regulatory mechanisms of miR-449a and AREG in an ischemia/reperfusion (I/R) injury model were examined in vivo and in vitro. The neurological deficit score, brain edema volume, cerebral infarct area, and the number of apoptosis cells in ischemic rats were all markedly elevated, than that in the control rats. The expression of miR-449a was decreased and AREG was increased in the MCAO rats and human OGD/R neuronal cell line. miR-449a inhibition or AREG overexpression in OGD/R cells resulted in a significant decrease in apoptotic cells, and AREG was revealed to be one of the direct targets of miR-449a. Molecular recovery was observed following transfection with miR-449a mimics and AREG knockdown in an OGD/R model in vitro. The present study demonstrated that miR-449a was downregulated while AREG was upregulated in cerebral ischemic injury, and the recovery of neurological function can be obtained following the overexpression of miR-449a and the knockdown of AREG in an I/R injury model. miR-449a functions in ischemic stroke via directly targeting AREG. These findings suggest a novel mechanism involving in cerebral I/R injury model and may aid investigators in gaining a deeper understanding of strokes in a clinical setting.