DAPT protects brain against cerebral ischemia by down-regulating the expression of Notch 1 and nuclear factor κB in rats

The Jagged-1/Notch1 Signaling Pathway Promotes the Construction of Tissue-Engineered Heart Valves

Background: Tissue-engineered heart valves (TEHVs) are promising new heart valve substitutes for valvular heart disease. The Notch signaling pathway plays a critical role in the development of congenital heart valves. Objective: To investigate the role of the Notch signaling pathway in the construction of TEHVs. Methods: The induced endothelial cells, which act as seed cells, were differentiated from adipose-derived stem cells and were treated with Jagged-1 (JAG-1) protein and γ-secretase inhibitor (DAPT, N-[N-(3,5-difluorophenacetyl)-l-alanyl]-s-phenylglycine t-butyl ester), respectively. Cell phenotypic changes, the expression of proteins relating to the epithelial-mesenchymal transition (EMT), and changes in paxillin expression were detected. Decellularized valve scaffolds were produced from decellularized porcine aortic valves. The seed cells were them inoculated into Matrigel-coated flap scaffolds for complex culture and characterization. Results: JAG-1 significantly reduced apoptosis and promoted the seeded cells' proliferation and migration ability, in contrast to the treatment of DAPT. In addition, the expression of EMT-related proteins, E-cadherin and N-cadherin, was significantly increased after treatment with JAG-1 and was reduced after the application of DAPT. Meanwhile, the adhesive-related expression of paxillin and fibronectin proteins was increased after the activation of Notch1 signaling and vice versa. Of interest, activation of the Notch1 signaling pathway resulted in more closely arranged cells on the valve surface after recellularization. Conclusion: Activation of the JAG-1/Notch1 signaling pathway increased seeded cells' proliferation and migratory ability and promoted the EMT and adhesion of seed cells, which was conducive to binding to the matrix, facilitating accelerated endothelialization of TEHVs.

Notch Signaling Inhibition Alleviates Allergies Caused by Antarctic Krill Tropomyosin through Improving Th1/Th2 Imbalance and Modulating Gut Microbiota

Antarctic krill tropomyosin (AkTM) has been shown in mice to cause IgE-mediated food allergy. The objective of this work was to investigate the role of Notch signaling in AkTM-sensitized mice, as well as to determine the changes in gut microbiota composition and short-chain fatty acids (SCFAs) in the allergic mice. An AkTM-induced food allergy mouse model was built and N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) was used as an γ-secretase inhibitor to inhibit the activation of Notch signaling. Food allergy indices, some key transcription factors, histologic alterations in the small intestine, and changes in gut microbiota composition were examined. The results showed that DAPT inhibited Notch signaling, which reduced AkTM-specific IgE, suppressed mast cell degranulation, decreased IL-4 but increased IFN-γ production, and alleviated allergic symptoms. Quantitative real-time PCR and Western blotting analyses revealed that expressions of Hes-1, Gata3, and IL-4 were down-regulated after DAPT treatment, accompanied by increases in T-bet and IFN-γ, indicating that Notch signaling was active in AkTM-sensitized mice and blocking it could reverse the Th1/Th2 imbalance. Expressions of key transcription factors revealed that Notch signaling could promote Th2 cell differentiation in sensitized mice. Furthermore, 16S rRNA sequencing results revealed that AkTM could alter the diversity and composition of gut microbiota in mice, leading to increases in inflammation-inducing bacteria such as Enterococcus and Escherichia-Shigella. Correlation analysis indicated that reduced SCFA concentrations in AkTM-allergic mice may be related to decreases in certain SCFA-producing bacteria, such as Clostridia_UCG-014. The changes in gut microbiota and SCFAs could be partially restored by DAPT treatment. Our findings showed that inhibiting Notch signaling could alleviate AkTM-induced food allergy by correcting Th1/Th2 imbalance and modulating the gut microbiota.

Notch Signaling in Acute Inflammation and Sepsis

Notch signaling, a highly conserved pathway in mammals, is crucial for differentiation and homeostasis of immune cells. Besides, this pathway is also directly involved in the transmission of immune signals. Notch signaling per se does not have a clear pro- or anti-inflammatory effect, but rather its impact is highly dependent on the immune cell type and the cellular environment, modulating several inflammatory conditions including sepsis, and therefore significantly impacts the course of disease. In this review, we will discuss the contribution of Notch signaling on the clinical picture of systemic inflammatory diseases, especially sepsis. Specifically, we will review its role during immune cell development and its contribution to the modulation of organ-specific immune responses. Finally, we will evaluate to what extent manipulation of the Notch signaling pathway could be a future therapeutic strategy.

Targeting Common Signaling Pathways for the Treatment of Stroke and Alzheimer's: a Comprehensive Review

Neurodegenerative diseases such as stroke and Alzheimer's disease (AD) are two inter-related disorders that affect the neurons in the brain and central nervous system. Alzheimer's is a disease by undefined origin and causes. Stroke and its most common type, ischemic stroke (IS), occurs due to the blockade of cerebral blood vessels. As an important feature, both of disorders are associated with irreversible damages to the brain and nervous system. In this regard, finding common signaling pathways and the same molecular origin between these two diseases may be a promising way for their solution. On the basis of literature appraisal, the most common signaling cascades implicated in the pathogenesis of AD and stroke including notch, autophagy, inflammatory, and insulin signaling pathways were reviewed. Furthermore, current therapeutic strategies including natural and synthetic pharmaceuticals aiming modulation of respective signaling factors were scrutinized to ameliorate neural deficits in AD and stroke. Taken together, digging deeper in the common connections and signal targeting can be greatly helpful in understanding and unified treating of these disorders.

γ-Secretase inhibitors for breast cancer and hepatocellular carcinoma: From mechanism to treatment

The γ-secretase complex is a key hydrolase for many type 1 transmembrane proteins. It is very important for activation of the Notch receptor and regulation of target-gene transcription. Abnormal activation and expression of the Notch pathway are closely related to the occurrence and development of many tumor types, including breast cancer and liver cancer. In this review, we elaborated on the basic situation of γ-secretase complex and the biological function and role of γ-secretase in APP and Notch signal pathway are described in detail. Subsequently, all currently known γ-secretase inhibitors and γ-secretase modulators are listed and their mechanism of action, value of IC₅₀, chemical structure and current research stage are summarized. Next, the selection presented the treatment progress of γ-secretase inhibitors in breast cancer and hepatocellular carcinoma in the past five years. Finally, the mechanism of action of γ-secretase-mediated breast cancer and hepatocellular carcinoma and the advantages and disadvantages of γ-secretase inhibitors are discussed, and the concept of further research is proposed.

MiR-429/200a/200b negatively regulate Notch1 signaling pathway to suppress CoCl2-induced apoptosis in PC12 cells

Neuronal apoptosis is a central hallmark of cerebral ischemia, which is serious threats to human health. Notch1 signaling pathway and three members of miR-200 family, miR-429, miR-200a and miR-200b, are reported to have tight connection with hypoxia-induced injury. However, their mutual regulation relationship and their roles in neuronal apoptosis caused by hypoxia are rarely reported. In the present study, differentiated pheochromocytoma (PC12) cells were treated with chemical hypoxia inducer, cobalt chloride (CoCl₂) to establish in vitro neuronal hypoxia model. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, Western blot assay and Hoechst staining indicated that CoCl₂ caused apoptosis of PC12 cells along with the activation of Notch1 signallilng pathway. The treatment of N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butylester (DAPT) inhibited Notch1 signaling pathway and attenuated the apoptosis induced by CoCl₂. Real-time polymerase chain reaction (RT-PCR) showed that expressions of miR-429/200a/200b were dynamically changed during the treatment of CoCl₂, and significantly decreased after 12-hour treatment of CoCl₂. Overexpression of miR-429/200a/200b inhibited the Notch1 signaling pathway and suppressed CoCl₂-induced apoptosis in PC12 cells. These results may clarify the roles of miR-429/200a/200b and Notch1 signaling pathway in hypoxia-induced nerve injury and provide a new theoretical basis to relieve nerve injury.

Botch protects neurons from ischemic insult by antagonizing Notch-mediated neuroinflammation

Owing to the continued high morbidity and high mortality rate after stroke, it is important to seek treatments other than conventional thrombolysis. Notch1 up-regulation participates in inflammatory responses after cerebral ischemia-reperfusion (I/R) injury, and it has been reported that Botch binds to and blocks Notch1 maturation. In this study, we investigated the role of Botch during cerebral (I/R) injury and explored its potential mechanisms. A middle-cerebral-artery occlusion/reperfusion (MCAO/R) model was established in adult male Sprague-Dawley rats in vivo, and cultured neurons and microglia were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic I/R injury in vitro. The results showed that protein levels of Botch and the Notch1 intracellular domain (NICD) were increased after MCAO/R. Furthermore, after overexpression of Botch, the generation of the activated form of Notch1, NICD, was decreased, while Botch knockdown or mutation led to an increase in NICD generation. As a result, Botch overexpression exhibited neuroprotective effects by significantly decreasing neurobehavioral phenotypes, improving infiltration of activated microglia, ameliorating inflammatory cytokine release, and inhibiting neuronal cell death. Conversely, Botch knockdown and mutation induced opposite effects. In addition, NICD was found to translocate to the mitochondria after OGD/R in neurons and microglia, which stimulated accumulation of reactive oxygen species in mitochondria and resulted in neuronal cell death and microglial activation. Botch overexpression inhibited the generation of NICD and decreased the translocation of NICD to the mitochondria, which inhibited neuronal cell death and ameliorated neuroinflammation. In conclusion, we found that Botch exerts neuroprotective effects via antagonizing the maturation of Notch1-induced neuronal injury and neuroinflammation, which may provide insights into novel therapeutic targets for the treatment of I/R injury.

Folic acid deficiency enhanced microglial immune response via the Notch1/nuclear factor kappa B p65 pathway in hippocampus following rat brain I/R injury and BV2 cells

Recent studies revealed that folic acid deficiency (FD) increased the likelihood of stroke and aggravated brain injury after focal cerebral ischaemia. The microglia-mediated inflammatory response plays a crucial role in the complicated pathologies that lead to ischaemic brain injury. However, whether FD is involved in the activation of microglia and the neuroinflammation after experimental stroke and the underlying mechanism is still unclear. The aim of the present study was to assess whether FD modulates the Notch1/nuclear factor kappa B (NF-κB) pathway and enhances microglial immune response in a rat middle cerebral artery occlusion-reperfusion (MCAO) model and oxygen-glucose deprivation (OGD)-treated BV-2 cells. Our results exhibited that FD worsened neuronal cell death and exaggerated microglia activation in the hippocampal CA1, CA3 and Dentate gyrus (DG) subregions after cerebral ischaemia/reperfusion. The hippocampal CA1 region was more sensitive to ischaemic injury and FD treatment. The protein expressions of proinflammatory cytokines such as tumour necrosis factor-α, interleukin-1β and interleukin-6 were also augmented by FD treatment in microglial cells of the post-ischaemic hippocampus and in vitro OGD-stressed microglia model. Moreover, FD not only dramatically enhanced the protein expression levels of Notch1 and NF-κB p65 but also promoted the phosphorylation of pIkBα and the nuclear translocation of NF-κB p65. Blocking of Notch1 with N-[N-(3, 5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester partly attenuated the nuclear translocation of NF-κB p65 and the protein expression of neuroinflammatory cytokines in FD-treated hypoxic BV-2 microglia. These results suggested that Notch1/NF-κB p65 pathway-mediated microglial immune response may be a molecular mechanism underlying cerebral ischaemia-reperfusion injury worsened by FD treatment.

Interplay between Notch and p53 promotes neuronal cell death in ischemic stroke

Stroke is the world's second leading cause of mortality, with a high incidence of morbidity. Numerous neuronal membrane receptors are activated by endogenous ligands and may contribute to infarct development. Notch is a well-characterized membrane receptor involved in cell differentiation and proliferation, and now shown to play a pivotal role in cell death during ischemic stroke. Blockade of Notch signaling by inhibition of γ-secretase, an enzyme that generates the active form of Notch, is neuroprotective following stroke. We have also identified that Pin1, a peptidyl-prolyl isomerase that regulates p53 transactivation under stress, promotes the pathogenesis of ischemic stroke via Notch signaling. Moreover, Notch can also mediate cell death through a p53-dependent pathway, resulting in apoptosis of neural progenitor cells. The current study has investigated the interplay between Notch and p53 under ischemic stroke conditions. Using pharmacological inhibitors, we have demonstrated that a Notch intracellular domain (NICD)/p53 interaction is involved in transcriptional regulation of genes downstream of p53 and NICD to modify stroke severity. Furthermore, the NICD/p53 interaction confers stability to p53 by rescuing it from ubiquitination. Together, these results indicate that Notch contributes to the pathogenesis of ischemic stroke by promoting p53 stability and signaling.

Inhibition of Notch1 Signaling at the Subacute Stage of Stroke Promotes Endogenous Neurogenesis and Motor Recovery After Stroke

Background and Purpose: It is still not clear whether Notch1 signaling inhibition can promote functional outcomes after stroke, given that it plays time-dependent roles in the sequential process of endogenous neurogenesis. The purpose of this study was to identify the appropriate time frame for Notch1 signaling inhibition according to the temporal evolution of Notch1 signaling activation and the responses of neural stem cells (NSCs), in order to target it for therapeutic intervention and stimulate neurorestorative strategies after stroke.

Methods: Sprague-Dawley (SD) rats were subjected to 90-min of middle cerebral artery occlusion (MCAO). Rats were sacrificed before, and at day 1, day 2, day 3, day 4, and day 7 after ischemia for immunohistochemical analysis of the Notch intracellular domain (NICD), Nestin and doublecortin (Dcx). Next, MCAO rats were treated with the γ-secretase inhibitor N-[N-(3,5-di uorophenacetyl)-1-alanyl]-S-phenylglycine t-butylester (DAPT) or with saline at day 4 after ischemia, and subsequently evaluated with behavioral test analysis and magnetic resonance imaging (MRI). The rat brains were then harvested for immunohistochemical analysis of Dcx, NeuN and myelin basic protein (MBP) at 2, 3, 4, and 8 weeks.

Results: Notch1 signaling was maximally activated at day 3 after ischemia in parallel with the temporal evolution of NSCs. Inhibiting Notch1 signaling at day 4 after reperfusion with DAPT further promoted recovery of MRI parameters of the corticospinal tract (CST) and the functional outcomes, concomitantly with an increase in neuroblasts, their migration to the ischemic boundary, and potential differentiation to mature neurons, as well as the amelioration of axonal bundle integrity.

Conclusion: Inhibition of Notch1 signaling at the subacute stage of stroke could maximally promote endogenous neurogenesis and axonal reorganization.

Dynamic Evaluation of Notch Signaling-Mediated Angiogenesis in Ischemic Rats Using Magnetic Resonance Imaging

Objective

The Notch signaling pathway is involved in angiogenesis induced by brain ischemia and can be efficiently inhibited by the γ-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-1-alanyl]-S-phenylglycine t-butyl ester (DAPT). The aim of the present study was to noninvasively investigate the effect of DAPT treatment on angiogenesis in brain repair after stroke using magnetic resonance imaging (MRI).

Methods

Sprague-Dawley rats (n = 40) were subjected to 90 minutes of transient middle cerebral artery (MCA) occlusion and treated with PBS (n = 20) or DAPT (n = 20) at 72 hours after the onset of ischemia. MRI measurements including T2-weighted imaging (T2WI), susceptibility-weighted imaging (SWI), and cerebral blood flow (CBF) were performed at 24 hours after reperfusion and weekly up to 4 weeks using a 3-Tesla system. Histological measurements were obtained at each time point after MRI scans.

Results

SWI showed that DAPT treatment significantly enhanced angiogenesis in the ischemic boundary zone (IBZ) with respect to the control group, with local CBF in the angiogenic area elevated, along with increases in vascular density confirmed by histology.

Conclusion

Treatment of ischemic stroke with DAPT significantly augments angiogenesis, which promotes poststroke brain remodeling by elevating CBF level, and these processes can be dynamically monitored and evaluated by MRI.

Inhibition of Dll4/Notch1 pathway promotes angiogenesis of Masquelet's induced membrane in rats

The Masquelet’s induced membrane technique for repairing bone defects has been demonstrated to be a promising treatment strategy. Previous studies have shown that the vessel density of induced membrane is decreased in the late stage of membrane formation, which consequently disrupts the bone healing process. However, relatively little is known about certain mechanisms of vessel degeneration in the induced membrane tissue and whether promotion of angiogenesis in induced membranes can improve bone regeneration. Here, we showed that the Delta-like ligand 4/ Notch homolog 1 (Dll4/Notch1) pathway was relatively activated in the late stage of induced membrane, especially at the subcutaneous site. Then, DAPT, a classical γ-secretase inhibitor, was applied to specifically inhibit Notch1 activation, followed by up-regulation of vascular endothelial growth factor receptor 2 (VEGFR2) and CD31 expression. DAPT-modified induced membranes were further confirmed to contribute to bone regeneration after autogenous bone grafting. Finally, in vitro experiments revealed that knocking down Notch1 contributed to the functional improvement of endothelial progenitor cells (EPCs) and that DAPT-treated induced membrane tissue was more favorable for angiogenesis of EPCs compared with the vehicle group. In conclusion, the present findings demonstrate that Dll4/Notch1 signaling is negatively associated with the vessel density of induced membrane. Pharmacological inhibition of Notch1 attenuated the vessel degeneration of induced membrane both in vitro and in vivo, which consequently improved bone formation at the bone defect site and graft resorption at the subcutaneous site.

Repairs to serious bone injuries may be improved by blocking a signaling pathway that causes newly forming membranes to fail. Masquelet’s technique involves placing acrylic spacers in areas of bone damage, inducing the formation of vascularised membranes which encourage the body to accept bone grafts. However, sometimes Masquelet’s membranes do not form correctly, leading to weaknesses in bone repairs and potential graft rejection. In experiments on rats, Qian Tang from Wenzhou Medical University, China, and coworkers found that a particular signaling pathway, D114/Notch1, was upregulated around 6 weeks post-operation, reducing blood vessel density and limiting new vessel growth, weakening the membranes. The team inhibited this pathway using an existing therapy that prevents blood clots. This treatment improved bone repairs by promoting the formation and function of blood vessels in membranes.

Notch signaling and neuronal death in stroke

Ischemic stroke is a leading cause of morbidity and death, with the outcome largely determined by the amount of hypoxia-related neuronal death in the affected brain regions. Cerebral ischemia and hypoxia activate the Notch1 signaling pathway and four prominent interacting pathways (NF-κB, p53, HIF-1α and Pin1) that converge on a conserved DNA-associated nuclear multi-protein complex, which controls the expression of genes that can determine the fate of neurons. When neurons experience a moderate level of ischemic insult, the nuclear multi-protein complex up-regulates adaptive stress response genes encoding proteins that promote neuronal survival, but when ischemia is more severe the nuclear multi-protein complex induces genes encoding proteins that trigger and execute a neuronal death program. We propose that the nuclear multi-protein transcriptional complex is a molecular mediator of neuronal hormesis and a target for therapeutic intervention in stroke.

Effect of the Notch signaling pathway on retinal ganglion cells and its neuroprotection in rats with acute ocular hypertension

AIM

To explore the effect of the Notch signaling pathway on retinal ganglion cells (RGCs) and optic nerve in rats with acute ocular hypertension (OH).

METHODS

Totally 48 Sprague-Dawley (SD) rats were included, among which 36 rats were selected to establish acute OH models. OH rats received a single intravitreal injection of 2 µL phosphate buffered solution (PBS) and another group of OH rats received a single intravitreal injection of 10 µmol/L γ-secretase inhibitor (DAPT). Quantitative real-time polymerase chain reaction (qPCR) and Western blot assay were adopted to determine the mRNA level of Notch and the protein levels of Notch, Bcl-2, Bax, caspase-3, and growth-associated protein 43 (GAP-43). The RGC apoptosis conditions were assessed by TUNEL staining.

RESULTS

The OH rats and PBS-injected rats had increased expression levels of Notch1, Bax, caspase-3, and GAP-43, decreased expression levels of Bcl-2, and increased RGC apoptosis, with severer macular edema and RGCs more loosely aligned, when compared with the normal rats. The DAPT-treated rats displayed increased expression levels of Notch1, Bax, caspase-3, and GAP-43, decreased expression levels of Bcl-2, and increased RGC apoptosis, in comparison with the OH rats and PBS-injected rats. RGCs were hardly observed and macular edema became severe in the DAPT-treated rat.

CONCLUSION

The Notch signaling pathway may suppress the apoptosis of retinal ganglion cells and enhances the regeneration of the damaged optic nerves in rats with acute OH.

Notch signaling inhibitor DAPT provides protection against acute craniocerebral injury

Notch signaling pathway is involved in many physiological and pathological processes. The γ-secretase inhibitor DAPT inhibits Notch signaling pathway and promotes nerve regeneration after cerebral ischemia. However, neuroprotective effects of DAPT against acute craniocerebral injury remain unclear. In this study, we established rat model of acute craniocerebral injury, and found that with the increase of damage grade, the expression of Notch and downstream protein Hes1 and Hes5 expression gradually increased. After the administration of DAPT, the expression of Notch, Hes1 and Hes5 was inhibited, apoptosis and oxidative stress decreased, neurological function and cognitive function improved. These results suggest that Notch signaling can be used as an indicator to assess the severity of post-traumatic brain injury. Notch inhibitor DAPT can reduce oxidative stress and apoptosis after acute craniocerebral injury, and is a potential drug for the treatment of acute craniocerebral injury.

Activation of the Notch-1 signaling pathway may be involved in intracerebral hemorrhage-induced reactive astrogliosis in rats

OBJECTIVE Reactive astrogliosis, a key feature that is characterized by glial proliferation, has been observed in rat brains after intracerebral hemorrhage (ICH). However, the mechanisms that control reactive astrogliosis formation remain unknown. Notch-1 signaling plays a critical role in modulating reactive astrogliosis. The purpose of this paper was to establish whether Notch-1 signaling is involved in reactive astrogliosis after ICH. METHODS ICH was induced in adult male Sprague-Dawley rats via stereotactic injection of autologous blood into the right globus pallidus. N-[ N-(3,5-difluorophenacetyl)-l-alanyl]- S-phenylglycine t-butyl ester (DAPT) was injected into the lateral ventricle to block Notch-1 signaling. The rats' brains were perfused to identify proliferating cell nuclear antigen (PCNA)-positive/GFAP-positive nuclei. The expression of GFAP, Notch-1, and the activated form of Notch-1 (Notch intracellular domain [NICD]) and its ligand Jagged-1 was assessed using immunohistochemical and Western blot analyses, respectively. RESULTS Notch-1 signaling was upregulated and activated after ICH as confirmed by an increase in the expression of Notch-1 and NICD and its ligand Jagged-1. Remarkably, blockade of Notch-1 signaling with the specific inhibitor DAPT suppressed astrocytic proliferation and GFAP levels caused by ICH. In addition, DAPT improved neurological outcome after ICH. CONCLUSIONS Notch-1 signaling is a critical regulator of ICH-induced reactive astrogliosis, and its blockage may be a potential therapeutic strategy for hemorrhagic injury.

MRI detects protective effects of DAPT treatment with modulation of microglia/macrophages at subacute and chronic stages following cerebral ischemia

Notch homolog 1 (Notch 1) signaling is regarded as a potential therapeutic target for modulating the inflammatory response and exhibiting neuroprotective effects in cerebral injury following stroke. N-[N-(3,5-difluorophenacetyl)-1-alanyl]-S-phenylglycine t-butylester (DAPT) efficiently inhibits activation of the Notch 1 signaling pathway in microglia and may protect brain tissue from ischemic damage. However, the temporal proliferation and morphological alterations of microglia/macrophages throughout progression of the disease, as well as the comprehensive alterations of the whole brain following DAPT treatment, remain to be elucidated. The present study evaluated the temporal proliferation and the morphological alterations of microglia/macrophages over the period of the subacute and chronic stages, in addition to dynamic alterations of brain tissue, using the magnetic resonance imaging (MRI) method, following DAPT treatment. Sprague-Dawley rats (n=40) were subjected to 90 min of middle cerebral artery occlusion and were treated with DAPT (n=20) or acted as controls with no treatment (n=20). The two groups of rats underwent MRI scans prior to the induction of stroke symptoms and at 24 h, 7, 14, 21 and 28 days following the stroke. A total of five rats from each group were sacrificed at 7, 14, 21 and 28 days following induction of stroke. Compared with control rats, the MRI data of the ipsilateral striatum in treated rats revealed ameliorated brain edema at the subacute stage and recovered brain tissue at the chronic stage. In addition to this, treatment attenuated the round-shape and promoted a ramified-shape of microglia/macrophages. The present study confirmed the protective effect of DAPT treatment by dynamically monitoring the cerebral alterations and indicated the possibility of DAPT treatment to alter microglial characteristics to induce a protective effect, via inhibition of the Notch signaling pathway.

Basic fibroblast growth factor reduces scar by inhibiting the differentiation of epidermal stem cells to myofibroblasts via the Notch1/Jagged1 pathway

Background

Basic fibroblast growth factor (bFGF) plays an important role in promoting wound healing and reducing scar, but the possible molecular mechanisms are still unclear. Our previous studies have found that activating the Notch1/Jagged1 pathway can inhibit the differentiation of epidermal stem cells (ESCs) to myofibroblasts (MFB). Herein, we document that bFGF reduces scar by inhibiting the differentiation of ESCs to MFB via activating the Notch1/Jagged1 pathway.

Methods

In in-vitro study, ESCs were isolated from 10 neonatal SD rats (1–3 days old), cultured in keratinocyte serum-free medium, and divided into six groups: bFGF group, bFGF + SU5402 group, bFGF + DAPT group, siJagged1 group, bFGF + siJagged1 group, and control group. Jagged1 of the ESCs in the siJagged1 group and bFGF + siJagged1 group was knocked down by small-interfering RNA transfection. Expression of ESC markers (CK15/CK10), MFB markers (α-SMA, Collagen I, Collagen III), and Notch1/Jagged1 components (Jagged1, Notch1, Hes1) was detected by FCM, qRT-PCR, and western blot analysis to study the relationships of bFGF, ESCs, and Notch1/Jagged1 pathway. In in-vivo study, the wound healing time and scar hyperplasia were observed on rabbit ear scar models. The quality of wound healing was estimated by hematoxylin and eosin staining and Masson staining. Expression of ESC markers, MFB markers and Notch1/Jagged1 components was elucidated by immunohistochemistry, immunofluorescence, and western blot analysis.

Results

The in-vitro study showed that bFGF could significantly upregulate the expression of ESC markers and Notch1/Jagged1 components, while downregulating the expression of MFB markers at the same time. However, these effects could be obviously decreased when we knocked down Jagged1 or added DAPT. Similarly, in in-vivo study, bFGF also exhibited its functions in inhibiting the differentiation of rabbit ESCs to MFB by activating the Notch1/Jagged1 pathway, which improved the wound healing quality and alleviated scar significantly.

Conclusion

These results provide evidence that bFGF can reduce scar by inhibiting the differentiation of ESCs to MFB via the Notch1/Jagged1 pathway, and present a new promising potential direction for the treatment of scar.

Hypertonic saline attenuates expression of Notch signaling and proinflammatory mediators in activated microglia in experimentally induced cerebral ischemia and hypoxic BV-2 microglia

Background

Ischemic stroke is a major disease that threatens human health in ageing population. Increasing evidence has shown that neuroinflammatory mediators play crucial roles in the pathophysiology of cerebral ischemia injury. Notch signaling is recognized as the cell fate signaling but recent evidence indicates that it may be involved in the inflammatory response in activated microglia in cerebral ischemia. Previous report in our group demonstrated hypertonic saline (HS) could reduce the release of interleukin-1 beta and tumor necrosis factor-alpha in activated microglia, but the underlying molecular and cellular mechanisms have remained uncertain. This study was aimed to explore whether HS would partake in regulating production of proinflammatory mediators through Notch signaling.

Results

HS markedly attenuated the expression of Notch-1, NICD, RBP-JK and Hes-1 in activated microglia both in vivo and in vitro. Remarkably, HS also reduced the expression of iNOS in vivo, while the in vitro levels of inflammatory mediators Phos-NF-κB, iNOS and ROS were reduced by HS as well.

Conclusion

Our results suggest that HS may suppress of inflammatory mediators following ischemia/hypoxic through the Notch signaling which operates synergistically with NF-κB pathway in activated microglia. Our study has provided the morphological and biochemical evidence that HS can attenuate inflammation reaction and can be neuroprotective in cerebral ischemia, thus supporting the use of hypertonic saline by clinicians in patients with an ischemia stroke.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-017-0351-6) contains supplementary material, which is available to authorized users.

VEGF165 induces differentiation of hair follicle stem cells into endothelial cells and plays a role in in vivo angiogenesis

Within the vascular endothelial growth factor (VEGF) family of five subtypes, VEGF165 secreted by endothelial cells has been identified to be the most active and widely distributed factor that plays a vital role in courses of angiogenesis, vascularization and mesenchymal cell differentiation. Hair follicle stem cells (HFSCs) can be harvested from the bulge region of the outer root sheath of the hair follicle and are adult stem cells that have multi-directional differentiation potential. Although the research on differentiation of stem cells (such as fat stem cells and bone marrow mesenchymal stem cells) to the endothelial cells has been extensive, but the various mechanisms and functional forms are unclear. In particular, study on HFSCs' directional differentiation into vascular endothelial cells using VEGF165 has not been reported. In this study, VEGF165 was used as induction factor to induce the differentiation from HFSCs into vascular endothelial cells, and the results showed that Notch signalling pathway might affect the differentiation efficiency of vascular endothelial cells. In addition, the in vivo transplantation experiment provided that HFSCs could promote angiogenesis, and the main function is to accelerate host-derived neovascularization. Therefore, HFSCs could be considered as an ideal cell source for vascular tissue engineering and cell transplantation in the treatment of ischaemic diseases.

MiR-181b Antagonizes Atherosclerotic Plaque Vulnerability Through Modulating Macrophage Polarization by Directly Targeting Notch1

Atherosclerotic plaque vulnerability is the major cause for acute stroke and could be regulated by macrophage polarization. MicroRNA-181b (miR-181b) was involved in macrophage differential. Here, we explore whether miR-181b could regulate atherosclerotic plaque vulnerability by modulating macrophage polarization and the underline mechanisms. In acute stroke patients with atherosclerotic plaque, we found that the serum level of miR-181b was decreased. Eight-week apolipoprotein E knockout (ApoE^-/-) mice were randomly divided into three groups (N = 10): mice fed with normal saline (Ctrl), mice fed with high-fat diet, and tail vein injection with miRNA agomir negative control (AG-NC)/miR-181b agomir (181b-AG, a synthetic miR-181b agonist). We found that the serum level of miR-181b in AG-NC group was lower than that in Ctrl group. Moreover, 181b-AG could upregulate miR-181b expression, reduce artery burden and attenuate atherosclerotic plaque vulnerability by modulating macrophage polarization. In RAW264.7 cells treated with oxidized low-density lipoprotein (ox-LDL), we found miR-181b could reverse the function of ox-LDL on M1/M2 markers at both mRNA and protein levels. Furthermore, by employing luciferase reporter assay, we found that Notch1 was a direct target of miR-181b and could be regulated by miR-181b in vivo and in vitro. Finally, inhibition of Notch1 could abolish the function of downregulating miR-181b on increasing M2 phenotype macrophages. Our study demonstrates that administration of miR-181b could reduce atherosclerotic plaque vulnerability partially through modulating macrophage phenotype by directly targeting Notch1.

Notch signaling in cerebrovascular diseases (Review)

The Notch signaling pathway is a crucial regulator of numerous fundamental cellular processes. Increasing evidence suggests that Notch signaling is involved in inflammation and oxidative stress, and thus in the progress of cerebrovascular diseases. In addition, Notch signaling in cerebrovascular diseases is associated with apoptosis, angiogenesis and the function of blood-brain barrier. Despite the contradictory results obtained to date as to whether Notch signaling is harmful or beneficial, the regulation of Notch signaling may provide a novel strategy for the treatment of cerebrovascular diseases.

Amantadine alleviates postoperative cognitive dysfunction possibly by increasing glial cell line-derived neurotrophic factor in rats

BACKGROUND

Postoperative cognitive dysfunction is a clinical entity that is associated with poor outcome. We determined the effectiveness of amantadine in reducing surgery-induced cognitive impairment and the role of glial cell line-derived neurotrophic factor (GDNF) in this effect.

METHODS

Four-month old male Fischer 344 rats were subjected to right carotid exposure under intravenous anesthesia. Some rats received intraperitoneal injection of 25 mg/kg/day amantadine for 3 days with the first dose at 15 min before the surgery or intracerebroventricular injection of GDNF or an anti-GDNF antibody at the end of surgery. One week later, rats were started to be tested by Barnes maze and fear conditioning. Hippocampus was harvested at 6 h, 24 h or 10 days after the surgery for biochemical analysis. C8-B4 cells, a microglial cell line, were pretreated with 1 ng/ml GDNF for 30 min before being exposed to 5 ng/ml lipopolysaccharide for 2 h.

RESULTS

Surgery increased the time to identify the target box in the Barnes maze when tested 1 day [22 (median) (11-66) (interquartile range) of control group vs. 158 (29-180) of surgery group, n = 15, P = 0.022) or 8 days after the training sessions and reduced context-related freezing behavior in the fear conditioning test. These effects were attenuated by amantadine (25 (14-90), n = 15, P = 0.029 compared with surgery group at 1 day after the training sessions in Barnes maze) and intracerebroventricular GDNF. Amantadine increased GDNF that was co-localized with glial fibrillary acidic protein, an astrocytic marker, in the hippocampus. Intracerebroventricular injection of an anti-GDNF antibody but not the denatured antibody blocked the effects of amantadine on cognition. Surgery induced neuroinflammation that was inhibited by amantadine. Lipopolysaccharide increased interleukin 1β production from C8-B4 cells. This effect was inhibited by GDNF.

CONCLUSIONS

Our results suggest that amantadine attenuated surgery-induced learning and memory impairment. This effect may be mediated by GDNF via inhibition of neuroinflammation.

Evidence that neuronal Notch-1 promotes JNK/c-Jun activation and cell death following ischemic stress

Notch signaling is a highly conserved pathway that regulates cell fate decisions during embryonic development. We have recently identified that in ischemic stroke, activity of γ-secretase and the resulting Notch activation may endanger neurons by modulating NF-κB and HIF-1α pathways. Notch signaling can also modulate MAPK-related pathways. However, the role of γ-secretase-mediated Notch signaling in activating MAPK following ischemic stroke has not been investigated. We used control and NICD1-overexpressing HEK and SH-SY5Y cell lines, and inhibitors of γ-secretase and JNK, to explore novel roles of Notch in modulating cell death following ischemic stress in vitro. Our findings indicate that expression of NICD1, JNK/cJun, p38-MAPK and the pro-apoptotic marker, cleaved caspase-3, increased during ischemic conditions. γ-Secretase inhibitors reduced ischemia-induced increase in NICD1 and JNK/p-cJun. Furthermore, NICD overexpression augmented JNK/cJun levels and cell death under these conditions. These results suggest that Notch signaling contributes to the pathogenesis of ischemic stroke, in part by promoting JNK/cJun signaling. These results provide further support for the potential use of γ-secretase inhibitors as therapy for ischemic stroke.

Perioperative aspirin improves neurological outcome after focal brain ischemia possibly via inhibition of Notch 1 in rat

BACKGROUND

Perioperative discontinuation of aspirin is often considered due to bleeding concern. We determined whether this discontinuation affected neurological outcome after brain ischemia.

METHODS

Adult male Sprague-Dawley rats were subjected to a 90-minute right middle cerebral arterial occlusion (MCAO). They received 30 mg/kg/day aspirin via gastric gavage: 1) for 2 days at 5 days before MCAO; 2) for 2 days at 5 days before MCAO and for 3 days after MCAO; 3) for 7 days before MCAO; or 4) for 7 days before MCAO and for 3 days after MCAO. Neurological outcome was evaluated 3 days after the MCAO. Ischemic penumbral cortex was harvested 1 or 3 days after MCAO for determining Notch intracellular domain (NICD), IL-6 and IL-1β levels.

RESULTS

Aspirin given by regimen 2 and 3 but not by regimen 1 improved neurological outcome. Neuroprotection was achieved by N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), a Notch activation inhibitor. DAPT and aspirin given only by regimen 2 and 3 reduced NICD, IL-6 and IL-1β in the ischemic penumbral cortex. NICD was found in microglial nuclei. Microglial activation in the ischemic tissues was inhibited by aspirin.

CONCLUSION

Aspirin use during the perioperative period provides neuroprotection. Inhibition of Notch activation and neuroinflammation may contribute to the neuroprotection of aspirin.

Exogenous and endogenous therapeutic effects of combination Sodium Ferulate and bone marrow stromal cells (BMSCs) treatment enhance neurogenesis after rat focal cerebral ischemia

Combining bone marrow stromal cells (BMSCs) with pharmacological therapy is an attractive approach for neurological function recovery of stroke. Our previous reports demonstrated that Sodium Ferulate (SF) combined with BMSCs administration could facilitate BMSCs migration into the ischemic brain by up-regulation of stromal cell-derived factor-1 alpha (SDF-1α)/chemokine (CXC motif) receptor-4 axis after stroke. To further investigate whether combination treatment could enhance neurogenesis through exogenous and endogenous therapeutic effects, we established rat permanent middle cerebral artery occlusion (pMCAo) model and measured ischemic infarct size by magnetic resonance imaging (MRI) scanning in the present study. The results showed that combination treatment could dramatically reduce ischemic infarction size which may be attributed to the effects on decreasing brain edema and enhancing cerebral tissue perfusion at 3 days after stroke. Immunofluorescence staining results indicated that combination treatment could not only promote expression of Glucose transporter 1(Glut1) and Neuron-specific class III beta-tubulin (Tuj1) in the periinfarct area, but also improve BMSCs expression of Glut1, GFAP and Tuj1. Moreover, it showed combination treatment could enhance the endogenous expression of Tuj-1 in ischemic boundary zone. These results perhaps associated with combination treatment up-regulating bone morphogenetic proteins (BMP)2/4 expressions and down-regulating Notch-1, Hes1 and Hes5 expressions as detected by Western Blot analysis. Our study firstly demonstrated in vivo that combination treatment could facilitate exogenous BMSCs differentiation into neural-and astrocytic-like cells, as well as enhance repair capacity of brain parenchymal cells by promoting glucose metabolism and endogenous neurogenesis after stroke. These results illustrate that administration of SF and BMSCs is a potential pathway of cell-based pharmacological treatment towards ischemic stroke.

Neuroinflammation in ischemic brain injury as an adaptive process

Cerebral ischaemia triggers various physiological processes, some of which have been considered deleterious and others beneficial. These processes have been characterized in one influential model as being part of a transition from injury to repair processes. We argue that another important distinction is between dysregulated and regulated processes. Although intervening in the course of dysregulated processes may be neuroprotective, this is unlikely to be true for regulated processes. This is because from an evolutionary perspective, regulated complex processes that are conserved across many species are likely to be adaptive and provide a survival advantage. We argue that the neuroinflammatory cascade is an adaptive process in this sense, and contrast this with a currently popular theory which we term the maladaptive immune response theory. We review the evidence from clinical and preclinical pharmacology with respect to this theory, and deduced that the evidence is inconclusive at best, and probably falsifies the theory. We argue that this is why there are no anti-inflammatory treatments for cerebral ischaemia, despite 30 years of seemingly promising preclinical results. We therefore propose an opposing theory, which we call the adaptive immune response hypothesis.

The γ-secretase blocker DAPT reduces the permeability of the blood-brain barrier by decreasing the ubiquitination and degradation of occludin during permanent brain ischemia

BACKGROUND

Tight junction protein degradation is a principal characteristic of the blood-brain barrier (BBB) damage that occurs during brain ischemia.

AIMS

We investigated the mechanisms of occludin degradation that underlie permanent middle cerebral artery occlusion (pMCAO) in rats.

METHODS AND RESULTS

Western blot and Co-immunoprecipitation data indicated ubiquitination and degradation of occludin in brain after pMCAO, which was consistent with ZO-1 degradation in penumbra regions as observed at 24 h after pMCAO. We further investigated candidate protease(s) responsible for the degradation of occludin during pMCAO. The intraventricular administration of γ-secretase blocker DAPT significantly inhibited the pMCAO-induced neurovascular damage, whereas ALLM and Batimastat, which are inhibitors of calpain and metalloproteinase proteases, respectively, were less effective. Notably, we found that DAPT significantly inhibited BBB disruption in comparison with vehicle treatment, as assessed by Evans blue excretion. Interestingly, the confocal immunostaining revealed that activation of the E3 ubiquitin ligase Itch is associated with degradation of occludin in brain microvessels following ischemia. Furthermore, our data demonstrate that the inhibition of γ-secretase signaling and the itch-mediated ubiquitination of occludin likely underlie the vasoprotective effect of DAPT after pMCAO.

CONCLUSION

The γ-secretase blocker DAPT reduces the permeability of the BBB by decreasing the ubiquitination and degradation of occludin during permanent brain ischemia, suggesting that γ-secretase may represent a novel therapeutic target for preventing neurovascular damage.