Intranasal administration of recombinant Netrin-1 attenuates neuronal apoptosis by activating DCC/APPL-1/AKT signaling pathway after subarachnoid hemorrhage in rats

MFGE8 promotes adult hippocampal neurogenesis in rats following experimental subarachnoid hemorrhage via modifying the integrin β3/Akt signaling pathway

Subarachnoid hemorrhage (SAH) is one of the most severe type of cerebral strokes, which can cause multiple cellular changes in the brain leading to neuronal injury and neurological deficits. Specifically, SAH can impair adult neurogenesis in the hippocampal dentate gyrus, thus may affecting poststroke neurological and cognitive recovery. Here, we identified a non-canonical role of milk fat globule epidermal growth factor 8 (MFGE8) in rat brain after experimental SAH, involving a stimulation on adult hippocampal neurogenesis(AHN). Experimental SAH was induced in Sprague-Dawley rats via endovascular perforation, with the in vivo effect of MFGE8 evaluated via the application of recombinant human MFGE8 (rhMFGE8) along with pharmacological interventions, as determined by hemorrhagic grading, neurobehavioral test, and histological and biochemical analyses of neurogenesis related markers. Results: Levels of the endogenous hippocampal MFGE8 protein, integrin-β3 and protein kinase B (p-Akt) were elevated in the SAH relative to control groups, while that of hippocalcin (HPCA) and cyclin D1 showed the opposite change. Intraventricular rhMGFE8 infusion reversed the decrease in doublecortin (DCX) immature neurons in the DG after SAH, along with improved the short/long term neurobehavioral scores. rhMGFE8 treatment elevated the levels of phosphatidylinositol 3-kinase (PI3K), p-Akt, mammalian target of rapamycin (mTOR), CyclinD1, HPCA and DCX in hippocampal lysates, but not that of integrin β3 and Akt, at 24 hr after SAH. Treatment of integrin β3 siRNA, the PI3K selective inhibitor ly294002 or Akt selective inhibitor MK2206 abolished the effects of rhMGFE8 after SAH. In conclusion, MFGE8 is upregulated in the hippocampus in adult rats with reduced granule cell genesis. rhMFGE8 administration can rescue this impaired adult neurogenesis and improve neurobehavioral recovery. Mechanistically, the effect of MFGE8 on hippocampal adult neurogenesis is mediated by the activation of integrin β3/Akt pathway. These findings suggest that exogenous MFGE8 may be of potential therapeutic value in SAH management. Graphical abstract and proposed pathway of rhMFGE8 administration attenuate hippocampal injury by improving neurogenesis in SAH models. SAH caused hippocampal injury and neurogenesis interruption. Administered exogenous MFGE8, recombinant human MFGE8(rhMFGE8), could ameliorate hippocampal injury and improve neurological functions after SAH. Mechanistically, MFGE8 bind to the receptor integrin β3, which activated the PI3K/Akt pathway to increase the mTOR expression, and further promote the expression of cyclin D1, HPCA and DCX. rhMFGE8 could attenuated hippocampal injury by improving neurogenesis after SAH, however, know down integrin β3 or pharmacological inhibited PI3K/Akt by ly294002 or MK2206 reversed the neuro-protective effect of rhMFGE8.

Netrin-1-engineered endothelial cell exosomes induce the formation of pre-regenerative niche to accelerate peripheral nerve repair

The formation of vascular niche is pivotal during the early stage of peripheral nerve regeneration. Nevertheless, the mechanisms of vascular niche in the regulation of peripheral nerve repair remain unclear. Netrin-1 (NTN1) was found up-regulated in nerve stump after peripheral nerve injury (PNI). Herein, we demonstrated that NTN1-high endothelial cells (NTN1+ECs) were the critical component of vascular niche, fostering angiogenesis, axon regeneration, and repair-related phenotypes. We also found that NTN1+EC-derived exosomes (NTN1 EC-EXO) were involved in the formation of vascular niche as a critical role. Multi-omics analysis further verified that NTN1 EC-EXO carried a low-level expression of let7a-5p and activated key pathways associated with niche formation including focal adhesion, axon guidance, phosphatidylinositol 3-kinase-AKT, and mammalian target of rapamycin signaling pathway. Together, our study suggested that the construction of a pre-regenerative niche induced by NTN1 EC-EXO could establish a beneficial microenvironment for nerve repair and facilitate functional recovery after PNI.

Netrin-1 Alleviates Early Brain Injury by Regulating Ferroptosis via the PPARγ/Nrf2/GPX4 Signaling Pathway Following Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a type of stroke with high morbidity and mortality. Netrin-1 (NTN-1) can alleviate early brain injury (EBI) following SAH by enhancing peroxisome proliferator-activated receptor gamma (PPARγ), which is an important transcriptional factor modulating lipid metabolism. Ferroptosis is a newly discovered type of cell death related to lipid metabolism. However, the specific function of ferroptosis in NTN-1-mediated neuroprotection following SAH is still unclear. This study aimed to evaluate the neuroprotective effects and the possible molecular basis of NTN-1 in SAH-induced EBI by modulating neuronal ferroptosis using the filament perforations model of SAH in mice and the hemin-stimulated neuron injury model in HT22 cells. NTN-1 or a vehicle was administered 2 h following SAH. We examined neuronal death, brain water content, neurological score, and mortality. NTN-1 treatment led to elevated survival probability, greater survival of neurons, and increased neurological score, indicating that NTN-1-inhibited ferroptosis ameliorated neuron death in vivo/in vitro in response to SAH. Furthermore, NTN-1 treatment enhanced the expression of PPARγ, nuclear factor erythroid 2-related factor 2 (Nrf2), and glutathione peroxidase 4 (GPX4), which are essential regulators of ferroptosis in EBI after SAH. The findings show that NTN-1 improves neurological outcomes in mice and protects neurons from death caused by neuronal ferroptosis. Furthermore, the mechanism underlying NTN-1 neuroprotection is correlated with the inhibition of ferroptosis, attenuating cell death via the PPARγ/Nrf2/GPX4 pathway and coenzyme Q10-ferroptosis suppressor protein 1 (CoQ10-FSP1) pathway.

Radioprotective effect of Ginkgolide B on brain: the mediating role of DCC/MST1 signaling

PURPOSE

The risk of brain exposure to ionizing radiation increases gradually due to the extensive application of nuclear technology in medical, industrial, and aerospace fields. Radiation-induced brain injury (RBI) is highly likely to cause a wide range of neurological complications, including schizophrenia, Alzheimer's disease (AD), depression. Ginkgolide B (GB) is one of the effective active components extracted from ginkgo biloba leaves, exerts protective effects on CNS, which is involved in the regulation of the Hippo signaling pathway. MST1, as one of the core kinases of the Hippo pathway, participated in regulating cell proliferation, differentiation, and apoptosis. However, it remains unclear whether GB attenuates radiation brain injury (RBI) and whether the radioprotective effect of GB refers to MST1 signaling. Hence, our study aimed to explore the radiation protection effect and the potential mechanism of GB.

MATERIALS AND METHODS

C57BL/6 mice were stimulated with an X-ray (20 Gy) to establish an RBI model. Then, morris water maze test (MWM) and step-down passive avoidance test (SDPAT) were used to assess the learning and memory function of mice. The open field test (OFT), tail suspension test (TST), and forced swimming test (FST) were used to assess changes in locomotor activity and hopelessness. Besides, X-ray-stimulated SH-SY5Y cells were used to verify the radioprotective effect of GB. Immunofluorescence double staining, Dihydroethidium (DHE), western blot, and flow cytometry were used to explore the role of DCC/MST1 signaling in RBI.

RESULTS

In this study, X-ray-treated mice exhibited cognitive impairment and depression-like behavior, which was ameliorated by GB treatment. GB also reduced the ROS production and the number of TUNEL-positive cells in the hippocampus. Moreover, GB increased the protein levels of p-AKT and Bcl2, while decreased the protein levels of MST1, p-p38, p-JNK, cleaved-caspase-3 and Bax both in vivo and in vitro. Additionally, exogenous Netrin-1 alleviated X-ray-induced ROS production and apoptosis, whereas knockout of Netrin-1 receptor DCC abolished the protective effect of GB.

CONCLUSION

Oxidative stress and MST1-mediated neuronal apoptosis participated in radiation-induced cognitive impairment and depression-like behaviors, and modulation of DCC by GB was an effective intervention against RBI.

CDGSH iron sulfur domain 2 over-expression alleviates neuronal ferroptosis and brain injury by inhibiting lipid peroxidation via AKT/mTOR pathway following intracerebral hemorrhage in mice

Ferroptosis has been implicated in the pathogenesis of secondary brain injury following intracerebral hemorrhage (ICH), and regulating this process is considered a potential therapy for alleviating further brain injury. A previous study showed that CDGSH iron sulfur domain 2 (CISD2) can inhibit ferroptosis in cancer. Thus, we investigated the effects of CISD2 on ferroptosis and the mechanisms underlying its neuroprotective role in mice after ICH. CISD2 expression markedly increased after ICH. CISD2 over-expression significantly decreased the number of Fluoro-Jade C-positive neurons and alleviated brain edema and neurobehavioral deficits at 24 h after ICH. In addition, CISD2 over-expression up-regulated the expression of p-AKT, p-mTOR, ferritin heavy chain 1, glutathione peroxidase 4, ferroportin, glutathione, and glutathione peroxidase activity, which are markers of ferroptosis. Additionally, CISD2 over-expression down-regulated the levels of malonaldehyde, iron content, acyl-CoA synthetase long-chain family member 4, transferrin receptor 1, and cyclooxygenase-2 at 24 h after ICH. It also alleviated mitochondrial shrinkage and decreased the density of the mitochondrial membrane. Furthermore, CISD2 over-expression increased the number of GPX4-positive neurons following ICH induction. Conversely, knockdown of CISD2 aggravated neurobehavioral deficits, brain edema, and neuronal ferroptosis. Mechanistically, MK2206, an AKT inhibitor, suppressed p-AKT and p-mTOR and reversed the effects of CISD2 over-expression on markers of neuronal ferroptosis and acute neurological outcome. Taken together, CISD2 over-expression alleviated neuronal ferroptosis and improved neurological performance, which may be mediated through the AKT/mTOR pathway after ICH. Thus, CISD2 may be a potential target to mitigate brain injury via the anti-ferroptosis effect after ICH.

Engineered exosomes enriched in netrin-1 modRNA promote axonal growth in spinal cord injury by attenuating inflammation and pyroptosis

BACKGROUND

Spinal cord injury (SCI) brings a heavy burden to individuals and society, and there is no effective treatment at present. Exosomes (EX) are cell secreted vesicles containing molecules such as nucleic acids and proteins, which hold promise for the treatment of SCI. Netrin-1 is an axon guidance factor that regulates neuronal growth. We investigated the effects of engineered EX enriched in netrin-1 chemically synthetic modified message RNA (modRNA) in treating SCI in an attempt to find a novel therapeutic approach for SCI.

METHODS

Netrin-1 modRNA was transfected into bone marrow mesenchymal stem cells to obtain EX enriched with netrin-1 (EX-netrin1). We built an inflammatory model in vitro with lipopolysaccharide (LPS) in vitro to study the therapeutic effect of EX-netrin1 on SCI. For experiments in vitro, ELISA, CCK-8 assay, immunofluorescence staining, lactate dehydrogenase release experiments test, real-time quantitative polymerase chain reaction, and western blot were conducted. At the same time, we constructed a rat model of SCI. MRI, hematoxylin-eosin and Nissl staining were used to assess the extent of SCI in rats.

RESULTS

In vitro experiments showed that EX had no effect on the viability of oligodendrocytes and PC12 cells. EX-netrin1 could attenuate LPS-induced inflammation and pyroptosis and accelerate axonal/dentritic growth in PC12 cells/oligodendrocytes. In addition, netrin-1 could activate the PI3K/AKT/mTOR signalling pathway upon binding to its receptor unc5b. When Unc5b and PI3K were inhibited, the effect of EX-netrin1 was weakened, which could be reversed by PI3K or mTOR activator. Our in vivo experiments indicated that EX-netrin1 could promote recovery in rats with SCI.

CONCLUSION

We found that EX-netrin1 regulated inflammation, pyroptosis and axon growth in SCI via the Unc5b/PI3K/AKT/mTOR pathway, which provides a new strategy for the treatment of SCI.

The mechanism and relevant mediators associated with neuronal apoptosis and potential therapeutic targets in subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a dominant cause of death and disability worldwide. A sharp increase in intracranial pressure after SAH leads to a reduction in cerebral perfusion and insufficient blood supply for neurons, which subsequently promotes a series of pathophysiological responses leading to neuronal death. Many previous experimental studies have reported that excitotoxicity, mitochondrial death pathways, the release of free radicals, protein misfolding, apoptosis, necrosis, autophagy, and inflammation are involved solely or in combination in this disorder. Among them, irreversible neuronal apoptosis plays a key role in both short- and long-term prognoses after SAH. Neuronal apoptosis occurs through multiple pathways including extrinsic, mitochondrial, endoplasmic reticulum, p53 and oxidative stress. Meanwhile, a large number of blood contents enter the subarachnoid space after SAH, and the secondary metabolites, including oxygenated hemoglobin and heme, further aggravate the destruction of the blood-brain barrier and vasogenic and cytotoxic brain edema, causing early brain injury and delayed cerebral ischemia, and ultimately increasing neuronal apoptosis. Even there is no clear and effective therapeutic strategy for SAH thus far, but by understanding apoptosis, we might excavate new ideas and approaches, as targeting the upstream and downstream molecules of apoptosis-related pathways shows promise in the treatment of SAH. In this review, we summarize the existing evidence on molecules and related drugs or molecules involved in the apoptotic pathway after SAH, which provides a possible target or new strategy for the treatment of SAH.

The Prognostic Value of Deleted in Colorectal Cancer (DCC) Receptor and Serum Netrin-1 in Severe Traumatic Brain Injury

Traumatic brain injury (TBI) is a common neurological disease. Netrin-1 and deleted in colorectal cancer (DCC) receptor are potential biomarkers associated with nerve regeneration and immune regulation. We aimed to investigate the ability of the DCC receptor and Netrin-1 to predict a high ICP level after operation in severe traumatic brain injury and their prognostic significance. This study is a prospective observational study. We selected 23 patients with traumatic brain injury who had undergone surgical operations as subjects. Immunohistochemical staining was performed on the contusion tissue that was removed by the operation to determine the expression of DCC receptor. At the same time, enzyme-linked immunosorbent assay (ELISA) kits were used to detect the serum Netrin-1 content. Determination of intracranial pressure (ICP) value was measured by intraventricular catheter. The Glasgow Outcome Scale (GOS) score at six months after trauma was defined as the main study endpoint. The results showed that serum Netrin-1 concentrations of patients in the critical TBI group (GCS 3–5 points) was significantly lower than that in the severe TBI group (GCS 6–8 points). The ICP peak and average mannitol consumption in the high Netrin-1 group were significantly lower than those in the low Netrin-1 group. DCC receptor-positive patients had a significantly lower ICP peak. There was no significant difference in six month-GOS scores between patients in the high and low Netrin-1 groups, while DCC receptor concentrations below 3.82 ng/mL predicted poor prognosis (GOS 1–3 points). In conclusion, the expression level of the DCC receptor can better evaluate the postoperative high ICP level and prognosis than the level of serum Netrin-1 in severe traumatic brain injury.

The blood-brain barrier and the neurovascular unit in subarachnoid hemorrhage: molecular events and potential treatments

The response of the blood-brain barrier (BBB) following a stroke, including subarachnoid hemorrhage (SAH), has been studied extensively. The main components of this reaction are endothelial cells, pericytes, and astrocytes that affect microglia, neurons, and vascular smooth muscle cells. SAH induces alterations in individual BBB cells, leading to brain homeostasis disruption. Recent experiments have uncovered many pathophysiological cascades affecting the BBB following SAH. Targeting some of these pathways is important for restoring brain function following SAH. BBB injury occurs immediately after SAH and has long-lasting consequences, but most changes in the pathophysiological cascades occur in the first few days following SAH. These changes determine the development of early brain injury as well as delayed cerebral ischemia. SAH-induced neuroprotection also plays an important role and weakens the negative impact of SAH. Supporting some of these beneficial cascades while attenuating the major pathophysiological pathways might be decisive in inhibiting the negative impact of bleeding in the subarachnoid space. In this review, we attempt a comprehensive overview of the current knowledge on the molecular and cellular changes in the BBB following SAH and their possible modulation by various drugs and substances.

ER Stress is Involved in Mast Cells Degranulation via IRE1α/miR-125/Lyn Pathway in an Experimental Intracerebral Hemorrhage Mouse Model

The degranulation of mast cells accounts for the development of neuroinflammation following intracerebral hemorrhage (ICH). Inhibition of IRE1α, a sensor signaling protein related to endoplasmic reticulum stress, has been shown to exert anti-inflammatory effects in several neurological diseases. The objective of this study was to investigate the effects of IRE1α inhibition on mast cells degranulation in an ICH mouse model and to explore the contribution of miR-125/Lyn pathway in IRE1α-mediated mast cells degranulation. Male mice were subjected to ICH by intraparenchymal injection of autologous blood. STF083010, an inhibitor of IRE1α, was administered intranasally at 1 h after ICH induction. AntimiR-125 was delivered by intracerebroventricular (i.c.v.) injection prior to ICH induction to elucidate the possible mechanisms. Western blot analysis, immunofluorescence staining, neurological test, hematoma volume, brain water content, toluidine blue staining and reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) were performed. Endogenous phosphorylated IRE1α (p-IRE1α), tryptase, interleukin-17A (IL-17A), tumor necrosis factor α (TNF-α) and tryptase mRNA were increased in time dependent manner while miR-125b-2-3p was decreased after ICH. Inhibition of IRE1α, with STF083010, remarkably reduced brain water content, improved neurological function, decreased hematoma volume, upregulated the expression of miR-125b-2-3p, decreased the number of mast cells, and downregulated the protein expression of Lyn kinase, XBP1s (spliced X-box binding protein-1), tryptase, IL-17A and TNF-α. The downregulation of Lyn kinase, tryptase, IL-17A, TNF-α, and decreased mast cells number were reversed by antimiR-125. The present findings demonstrate that IRE1α inhibition attenuates mast cells degranulation and neuroinflammation, at least partially, through IRE1α/miR-125/Lyn signaling pathway after ICH.

Dihydrolipoic acid enhances autophagy and alleviates neurological deficits after subarachnoid hemorrhage in rats

Autophagy is a crucial pathological process in early brain injury (EBI) after subarachnoid hemorrhage (SAH). In this study, we investigated the role of dihydrolipoic acid (DHLA) on enhancing autophagy and alleviating neurological deficits after SAH. SAH was induced by endovascular perforation in male Sprague-Dawley rats. DHLA (30 mg/kg) was administered intraperitoneally 1 h (h) after SAH. Small interfering ribonucleic acid (siRNA) for lysosome-associated membrane protein-1 (LAMP1) was administered through intracerebroventricular (i.c.v) route 48 h before SAH induction. SAH grading score, neurological score, immunofluorescence staining, Fluoro-Jade C (FJC) staining, and Western blot were examined. DHLA treatment increased autophagy-related protein expression and downregulated the apoptosis-related protein expression 24 h after SAH. In addition, the DHLA treatment reduced neuronal cell death and alleviated neurological deficits after SAH. Furthermore, knockdown of LAMP1 abolished the neuroprotective effects of DHLA. These results indicate that LAMP1 may participate in autophagy after SAH. DHLA treatment can enhance autophagy, attenuate apoptosis, and alleviate neurofunctional deficits in EBI after SAH. It may provide an effective alternative method for the treatment of EBI after SAH.

A Novel Netrin-1-Derived Peptide Enhances Protection against Neuronal Death and Mitigates of Intracerebral Hemorrhage in Mice

It has been reported that Netrin-1 is involved in neuroprotection following injury to the central nervous system. However, the minimal functional domain of Netrin-1 which can preserve the neuroprotection but avoid the major side effects of Netrin remains elusive. Here, we investigated the neuroprotective effect of a peptide E1 derived from Netrin-1′s EGF3 domain (residues 407–422). We found that it interacts with deleted colorectal carcinoma (DCC) to activate focal adhesion kinase phosphorylation exhibiting neuroprotection. The administration of the peptide E1 was able to improve functional recovery through reduced apoptosis in an experimental murine model of intracerebral hemorrhage (ICH). In summary, we reveal a functional sequence of Netrin-1 that is involved in the recovery process after ICH and identify a candidate peptide for the treatment of ICH.

Serum netrin-1 as a potential biomarker for functional outcome of traumatic brain injury

BACKGROUND

Decreased serum netrin-1 concentrations have been found after acute brain injury. We investigated the role of serum netrin in prognosis of traumatic brain injury (TBI).

METHODS

In this prospective and observational study, enzyme-linked immunosorbent assay was used to detect serum netrin-1 concentrations in 50 mild TBI patients (Glasgow coma scale (GCS) score, 13-15), 83 moderate TBI patients (GCS score, 9-12), 69 severe TBI patients (GCS score, 3-8) and 50 healthy controls. Glasgow outcome scale score of 1-3 at 6 months after trauma was defined as poor outcome.

RESULTS

Serum netrin-1 concentrations were significantly lower in moderate or severe TBI patients than in controls and in severe TBI patients than in moderate TBI patients, while not in mild TBI patients than in controls. GCS score and Rotterdam computed tomography classification were closely correlated with serum netrin-1 concentrations among TBI patients. Forty-two (20.8%) patients had poor outcome. Receiver operating characteristic curve analysis revealed that serum netrin-1 concentrations could distinguish patients with poor outcome from the other remainders significantly. In addition, serum netrin-1 concentrations were independently associated with poor outcome.

CONCLUSIONS

Serum netrin-1 might serve as a potential biomarker for prognosis of TBI.

Decreased serum netrin-1 is associated with ischemic stroke: A case-control study

BACKGROUND AND AIMS

Netrin-1 was a laminin-related protein involved in neurovascular protection, and we previously discovered that decreased serum netrin-1 was associated with poor prognosis of ischemic stroke. However, the relationship between serum netrin-1 level and the risk of ischemic stroke remains unclear. The aim of this study was to investigate the association between netrin-1 level and risk of ischemic stroke.

METHODS AND RESULTS

A case-control study including 591 ischemic stroke patients and 591 age- and sex-matched healthy individuals was conducted, and serum netrin-1 concentrations were quantitatively determined via enzyme-linked immunosorbent assay for all participants. The serum netrin-1 levels were significantly lower in the ischemic stroke patients than those in matched controls (median, 496.4 vs 652.1 pg/mL; P < 0.001). After adjustment for potential confounders, the odds ratio of ischemic stroke associated with the highest quartile of netrin-1 was 0.07 (95% CI: 0.01-0.65; P_trend = 0.018) compared with the lowest quartile of netrin-1. Each 1-standard deviation increase of log-transformed netrin-1 was associated with a lower odds of ischemic stroke (odds ratio: 0.45, 95% CI: 0.22-0.94; P = 0.032), and a dose-response relationship between serum netrin-1 and ischemic stroke was observed (P_linearity = 0.003). Incorporating netrin-1 to conventional risk factors improved the discriminatory power for ischemic stroke (net reclassification index = 98.0%, P < 0.001; integrated discrimination improvement = 0.28%, P = 0.027).

CONCLUSIONS

Serum netrin-1 was decreased in patients with ischemic stroke compared with healthy controls, suggesting that there was a potential role of netrin-1 in the pathogenesis of ischemic stroke.

TREM2 ameliorates neuroinflammatory response and cognitive impairment via PI3K/AKT/FoxO3a signaling pathway in Alzheimer's disease mice

Triggering receptor expressed on myeloid cells 2 (TREM2) has been shown with a neuroprotective function against inflammation and neuronal injury in Alzheimer's disease (AD). However, the TREM2 induced anti-inflammatory mechanism is still not well known. In this study it has been demonstrated that the expression of TREM2 was upregulated in hippocampus of 5xFAD mice, whereas TREM2 knock-out mediated by AAV significantly increased the levels of pro-inflammatory cytokines and aggravated cognitive defect. Additionally, FoxO3a, a downstream member of the PI3K/AKT pathway, could be activated by TREM2 defect via the PI3K/AKT signaling in 5xFAD mice. That suggests TREM2-induced protection is associated with the PI3K-FoxO3a axis. On the contrary, overexpression of TREM2 alleviated the LPS-induced inflammatory response and induced M2 phenotype microglia in vitro. This phenomenon can be abolished by applying the PI3K inhibitor LY294002, suggesting FoxO3a not only participates in TREM2-induced anti-inflammation response, but is also involved in regulating the phenotype of microglia. Taken together, our results show that the protective functions of TREM2, both in inflammatory response and cognitive impairment as well as in the decrease of M1 phenotype microglia, are related to PI3K/AKT/FoxO3a signaling pathway in AD mice.

HSPB8 overexpression prevents disruption of blood-brain barrier after intracerebral hemorrhage in rats through Akt/GSK3β/β-catenin signaling pathway

Blood brain barrier (BBB) disruption is a crucial factor contributing to secondary brain injury after intracerebral hemorrhage (ICH). Heat shock protein B8 (HSPB8) has been recently reported to confer neuroprotection against against ischaemic stroke through maintaining BBB integrity. However, the role of HSPB8 in ICH is still elusive. In this study, we found that HSPB8 was upregulated by ICH and extensively expressed in neurovascular structure including endothelial cells and astrocytes. lentivirus intracerebroventricular (i.c.v) injection achieved a widespread and persistent HSPB8 overexpression in brain tissues. HSPB8 overexpression significantly ameliorated neurobehavioral deficits and brain edema at 24 and 72h following ICH. Moreover, HSPB8 overexpression remarkedly inhibited BBB disruption and significantly increase the level of p-Akt, p-GSKβ and intranuclear β-catenin 24h post-ICH. This effect was obviously reversed by Akt specific inhibitor, MK2206. Based on these findings, HSPB8 exerted its protective effect on BBB, at least partly, via Akt/ p-GSKβ/β-catenin pathways.

ENT1 inhibition attenuates apoptosis by activation of cAMP/pCREB/Bcl2 pathway after MCAO in rats

BACKGROUND AND PURPOSE

The present study was designed to investigate the potential role and the mechanism of equilibrative nucleoside transporter 1 (ENT1) on neuronal apoptosis and neurological deficits after middle cerebral artery occlusion (MCAO) in rats.

METHODS

One hundred and thirty-four male Sprague-Dawley rats were subjected to two hours of MCAO followed by reperfusion. The time course of the expression level of ENT1 and phosphorylation of CREB were detected by western blot and immunofluorescence staining. Another set of animals were administrated with NBTI, the ENT1 inhibitor, by daily intraperitoneal injection starting at 0.5 h post-MCAO, infarction volume and neurological deficits were measured both at 24 h and 72 h post MCAO. We further explored the neuroprotection machenism by using H89, cAMP dependent protein kinase inhibitor, the expression of Bcl-2, Bax, phosphorylated CREB and Cleaved caspase-3 were quantified by Western blot, neuronal apoptosis were analyed by TUNEL staining.

RESULTS

The endogenous expression of ENT1 were significantly increased and peaked at 12 h after MCAO. High-dose of NBTI (15 mg/kg) reduced brain infarction volume and improved neurologic deficits both at 24 h and 72 h post MCAO. Moreover, NBTI significantly increased the level of CREB phosphorylation and extracellular adenosine concentration, and decreased the neuronal apoptosis 24 h after MCAO. NBTI treatment reduced the expression of Bax and cleaved caspase-3, while up-regulated Bcl-2 compared with vehicle group. These effects were abolished by H89 pretreatment.

CONCLUSIONS

ENT1 inhibition prevented neuronal apoptosis and improves neurological deficits through cAMP/PKA/CREB/Bcl-2 signaling pathway after MCAO in rats. ENT1 might be an effective target in the treatment strategy for ischemic stroke.

The Activation of Phosphatidylserine/CD36/TGF-β1 Pathway prior to Surgical Brain Injury Attenuates Neuroinflammation in Rats

Neuroinflammation plays an important pathological role in experimental surgical brain injury (SBI). Apoptotic associated with phosphatidylserine (PS) externalization promotes anti-inflammatory mediator TGF-β1 release. In the present study, we investigated the anti-neuroinflammation effect of PS liposome or isoflurane pretreatment via PS/CD36/TGF-β1 signaling in a rat model of SBI. A total of 120 male Sprague-Dawley rats (weighing 280-330 gms) were used. SBI was induced by partial right frontal lobe corticotomy. Intranasal PS liposome or isoflurane inhalation was administered prior to SBI induction. CD36 small interfering RNA (siRNA) was administered intracerebroventricularly. Recombinant Annexin V protein (rAnnexin V) was delivered intranasally. Post-SBI assessments included neurological tests, brain water content, Western blot, and immunohistochemistry. Endogenous CD36 protein levels but not TGF-β1 was significantly increased within peri-resection brain tissues over 72 h after SBI. SBI rats were associated with increased brain water content surrounding corticotomy and neurological deficits. PS liposome pretreatment significantly reduced brain water content and improved some neurological deficits at 24 hours and 72 hours after SBI. PS liposome increased CD36 and TGF-β1 protein levels, but decreased IL-1β and TNFα protein levels in peri-resection brain tissues at 24 hours after SBI. CD36 siRNA or rAnnexin V partially countered the protective effect of PS liposome. Isoflurane pretreatment produced similar antineuroinflammation and neurological benefits in SBI rats partially by upregulating CD36/Lyn/TGF-β1 signaling. Collectively, our findings suggest that the activation of PS/CD36/TGF-β1 pathway by PS liposome or isoflurane prior to SBI could attenuate neuroinflammation and improve neurological outcomes in rats. PS liposome or isoflurane pretreatment may serve as an effective preventive strategy to minimize the brain injury caused by neurosurgical procedures in patients.

HLY78 Attenuates Neuronal Apoptosis via the LRP6/GSK3β/β-Catenin Signaling Pathway After Subarachnoid Hemorrhage in Rats

Neuronal apoptosis is one of the essential mechanisms of early brain injury after subarachnoid hemorrhage (SAH). Recently, HLY78 has been shown to inhibit apoptosis in tumor cells and embryonic cells caused by carbon ion radiation through activation of the Wnt/β-catenin pathway. This study was designed to explore the anti-apoptotic role of HLY78 in experimental SAH. The results demonstrated that HLY78 attenuated neuronal apoptosis and the neurological deficits after SAH through the activation of low-density lipoprotein receptor-related protein 6 (LRP6), which subsequently increased the level of phosphorylated glycogen synthesis kinase 3 beta (p-GSK3β) (Ser9), β-catenin, and Bcl-2, accompanied by a decrease of p-β-catenin, Bax, and cleaved caspase 3. An LRP6 small-interfering ribonucleic acid reversed the effects of HLY78. In conclusion, HLY78 attenuates neuronal apoptosis and improves neurological deficits through the LRP6/GSK3β/β-catenin signaling pathway after SAH in rats. HLY78 is a promising therapeutic agent to attenuate early brain injury after SAH.

Inhalation of high-concentration hydrogen gas attenuates cognitive deficits in a rat model of asphyxia induced-cardiac arrest

Cognitive deficits are a devastating neurological outcome seen in survivors of cardiac arrest. We previously reported water electrolysis derived 67% hydrogen gas inhalation has some beneficial effects on short-term outcomes in a rat model of global brain hypoxia-ischemia induced by asphyxia cardiac arrest. In the present study, we further investigated its protective effects in long-term spatial learning memory function using the same animal model. Water electrolysis derived 67% hydrogen gas was either administered 1 hour prior to cardiac arrest for 1 hour and at 1-hour post-resuscitation for 1 hour (pre- & post-treatment) or at 1-hour post-resuscitation for 2 hours (post-treatment). T-maze and Morris water maze were used for hippocampal memory function evaluation at 7 and 14 days post-resuscitation, respectively. Neuronal degeneration within hippocampal Cornu Ammonis 1 (CA1) regions was examined by Fluoro-Jade staining ex vivo. Hippocampal deficits were detected at 7 and 18 days post-resuscitation, with increased neuronal degeneration within hippocampal CA1 regions. Both hydrogen gas treatment regimens significantly improved spatial learning function and attenuated neuronal degeneration within hippocampal CA1 regions at 18 days post-resuscitation. Our findings suggest that water electrolysis derived 67% hydrogen gas may be an effective therapeutic approach for improving cognitive outcomes associated with global brain hypoxia-ischemia following cardiac arrest. The study was approved by the Animal Health and Safety Committees of Loma Linda University, USA (approval number: IACUC #8170006) on March 2, 2017.

PTEN Inhibition Protects Against Experimental Intracerebral Hemorrhage-Induced Brain Injury Through PTEN/E2F1/β-Catenin Pathway

Intracerebral hemorrhage (ICH) is a subtype of stroke with highest mortality and morbidity. We have previously demonstrated that dipotassium bisperoxo (picolinato) oxovanadate (V), (bpV[pic]) inhibits phosphatase and tensin homolog (PTEN) and activates extracellular signal-regulated kinase (ERK)1/2. In this study, we examined the effect of bpV[pic] in the rat ICH model in vivo and the hemin-induced injury model in rat cortical cultures. The rat model of ICH was created by injecting autologous blood into the striatum, and bpV[pic] was intraperitoneally injected. The effects of bpV[pic] were evaluated by neurological tests, Fluoro-Jade C (FJC) staining, and Nissl staining. We demonstrate that bpV[pic] attenuates ICH-induced brain injury in vivo and hemin-induced neuron injury in vitro. The expression of E2F1 was increased, but β-catenin expression was decreased after ICH, and the altered expressions of E2F1 and β-catenin after ICH were blocked by bpV[pic] treatment. Our results further show that bpV[pic] increases β-catenin expression through downregulating E2F1 in cortical neurons and prevents hemin-induced neuronal damage through E2F1 downregulation and subsequent upregulation of β-catenin. By testing the effect of PTEN-siRNA, PTEN cDNA, or combined use of ERK1/2 inhibitor and bpV[pic] in cultured cortical neurons after hemin-induced injury, we provide evidence suggesting that PTEN inhibition by bpV[pic] confers neuroprotection through E2F1 and β-catenin pathway, but the neuroprotective role of ERK1/2 activation by bpV[pic] cannot be excluded.

Adenoviral TMBIM6 vector attenuates ER-stress-induced apoptosis in a neonatal hypoxic-ischemic rat model

Endoplasmic reticulum (ER) stress is a major pathology encountered after hypoxic-ischemic (HI) injury. Accumulation of unfolded proteins triggers the unfolded protein response (UPR), resulting in the activation of pro-apoptotic cascades that lead to cell death. Here, we identified Bax inhibitor 1 (BI-1), an evolutionarily conserved protein encoded by the transmembrane BAX inhibitor motif-containing 6 (TMBIM6) gene, as a novel modulator of ER-stress-induced apoptosis after HI brain injury in a neonatal rat pup. The main objective of our study was to overexpress BI-1, via viral-mediated gene delivery of human adenoviral-TMBIM6 (Ad-TMBIM6) vector, to investigate its anti-apoptotic effects as well as to elucidate its signaling pathways in an in vivo neonatal HI rat model and in vitro oxygen-glucose deprivation (OGD) model. Ten-day-old unsexed Sprague Dawley rat pups underwent right common carotid artery ligation followed by 1.5 h of hypoxia. Rat pups injected with Ad-TMBIM6 vector, 48 h pre-HI, showed a reduction in relative infarcted area size, attenuated neuronal degeneration and improved long-term neurological outcomes. Furthermore, silencing of BI-1 or further activating the IRE1α branch of the UPR, using a CRISPR activation plasmid, was shown to reverse the protective effects of BI-1. Based on our in vivo and in vitro data, the protective effects of BI-1 are mediated via inhibition of IRE1α signaling and in part via inhibition of the second stress sensor receptor, PERK. Overall, this study showed a novel role for BI-1 and ER stress in the pathophysiology of HI and could provide a basis for BI-1 as a potential therapeutic target.

The Neuroprotective Effects of Necrostatin-1 on Subarachnoid Hemorrhage in Rats Are Possibly Mediated by Preventing Blood-Brain Barrier Disruption and RIP3-Mediated Necroptosis

Despite the substantial efforts to elucidate the role of early brain injury in subarachnoid hemorrhage (SAH), an effective pharmaceutical therapy for patients with SAH continues to be unavailable. This study aims to reveal the role of necroptosis after SAH, and explore whether the disruption of the blood-brain barrier (BBB) and RIP3-mediated necroptosis following SAH in a rat SAH model are altered by necrostatin-1 via its selective inhibition of receptor-interacting protein kinase 1 (RIP1). Sixty-five rats were used in the experiments. The SAH model was established using endovascular perforation. Necrostatin-1 was intracerebroventricularly injected 1 h before SAH induction. The neuroprotective effects of necrostatin-1 were evaluated with multiple methods such as magnetic resonance imaging (MRI) scanning, immunohistochemistry, propidium iodide (PI) labeling, and western blotting. Pretreatment with necrostatin-1 attenuated brain swelling and reduced the lesion volume on T2 sequence and ventricular volume on MRI 72 h after SAH induction. Albumin leakage and the degradation of tight junction proteins were also ameliorated by necrostatin-1 administration. In addition, necrostatin-1 decreased the number of PI-positive cells in the basal cortex, reduced the levels of the RIP3 and MLKL proteins, and inhibited the production of the pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. Based on the findings from the present study, the selective RIP1 inhibitor necrostatin-1 functioned as a neuroprotective agent after SAH by attenuating brain swelling and BBB disruption. Moreover, the necrostatin-1 pretreatment prevented SAH-induced necroptosis by suppressing the activity of the RIP3/MLKL signaling pathway. These results will provide insights into new drugs and pharmacological targets to manage SAH, which are worth further study.

Recombinant Slit2 attenuates neuronal apoptosis via the Robo1-srGAP1 pathway in a rat model of neonatal HIE

Apoptosis following hypoxic-ischemic injury to the brain plays a major role in neuronal cell death. The neonatal brain is more susceptible to injury as the cortical neurons are immature and there are lower levels of antioxidants. Slit2, an extracellular matrix protein, has been shown to be neuroprotective in various models of neurological diseases. However, there is no information about the role of Slit2 in neonatal hypoxia-ischemia. In this study, we evaluated the effect of Slit2 and its receptor Robo1 in a rat model with neonatal HIE. 10-day old rat pups were used to create the neonatal HIE model. The right common carotid artery was ligated followed by 2.5 h of hypoxia. Recombinant Slit2 was administered intranasally 1 h post HI, recombinant Robo1 was used as a decoy receptor and administered intranasally 1h before HI and srGAP1-siRNA was administered intracerebroventricularly 24 h before HI. Brain infarct area measurement, short-term and long-term neurological function tests, Western blot, immunofluorescence staining, Fluoro-Jade C staining, Nissl staining and TUNEL staining were the assessments done following drug administration. Recombinant Slit2 administration reduced neuronal apoptosis and neurological deficits after neonatal HIE which were reversed by co-administration of recombinant Robo1 and srGAP1-siRNA administration. Recombinant Slit2 showed improved outcomes possibly via the robo1-srGAP1 pathway which mediated the inhibition of RhoA. In this study, the results suggest that Slit2 may help in attenuation of apoptosis and could be a therapeutic agent for treatment of neonatal hypoxic ischemic encephalopathy.

Immune response mediates the cardiac damage after subarachnoid hemorrhage

Cardiac dysfunction is a common adverse effect of subarachnoid hemorrhage (SAH). Autopsy of SAH patients shows immunocyte infiltration into the heart. In this study, a SAH model of endovascular perforation was performed in adult male mice in order to test whether SAH causes cardiac dysfunction in non-primary cardiac disease young adult male mice and whether immune response mediates SAH induced cardiac and neurological deficit. Splenectomy was performed on a subpopulation of mice one week prior to induction of the SAH. Neurological functional tests, transthoracic Doppler echocardiography, immunofluorescent staining, and flow cytometry were performed to investigate neurological and cardiac function and immune/inflammatory effects of SAH in mice with or without splenectomy. We found that SAH significantly induces ventricular fibrillation and cardiac dysfunction identified by significantly reduced left ventricular ejection fraction, left ventricular fractional shortening, decreased heart rate, as well as increased macrophage and neutrophil infiltration into heart and inflammatory factor expression in the heart compared to sham control mice. SAH also induces neurological deficit, increases astrocyte and microglial activity, and inflammatory cell infiltration into brain as well as up-regulates inflammatory factor expression in the brain tissue. Splenectomy not only significantly improves neurological function, but also reduces cardiac dysfunction compared to SAH alone mice. Splenectomy in SAH mice significantly reduces inflammatory cell infiltration, and decreases NADPH oxidase-2 and macrophage chemokine protein-1 expression in heart and brain when compared to non-splenectomy SAH mice. Our data suggest that, SAH induces acute cardiac dysfunction in non-primary cardiac disease mice. Secondary immune response may play an important role in mediating brain-heart damage after SAH.

NDP-MSH binding melanocortin-1 receptor ameliorates neuroinflammation and BBB disruption through CREB/Nr4a1/NF-κB pathway after intracerebral hemorrhage in mice

Background

Neuroinflammation and blood-brain barrier (BBB) disruption are two vital mechanisms of secondary brain injury following intracerebral hemorrhage (ICH). Recently, melanocortin-1 receptor (Mc1r) activation by Nle4-D-Phe7-α-MSH (NDP-MSH) was shown to play a neuroprotective role in an experimental autoimmune encephalomyelitis (EAE) mouse model. This study aimed to investigate whether NDP-MSH could alleviate neuroinflammation and BBB disruption after experimental ICH, as well as the potential mechanisms of its neuroprotective roles.

Methods

Two hundred and eighteen male C57BL/6 mice were subjected to autologous blood-injection ICH model. NDP-MSH, an agonist of Mc1r, was administered intraperitoneally injected at 1 h after ICH insult. To further explore the related protective mechanisms, Mc1r small interfering RNA (Mc1r siRNA) and nuclear receptor subfamily 4 group A member 1 (Nr4a1) siRNA were administered via intracerebroventricular (i.c.v) injection before ICH induction. Neurological test, BBB permeability, brain water content, immunofluorescence staining, and Western blot analysis were implemented.

Results

The Expression of Mc1r was significantly increased after ICH. Mc1r was mainly expressed in microglia, astrocytes, and endothelial cells following ICH. Treatment with NDP-MSH remarkably improved neurological function and reduced BBB disruption, brain water content, and the number of microglia in the peri-hematoma tissue after ICH. Meanwhile, the administration of NDP-MSH significantly reduced the expression of p-NF-κB p65, IL-1β, TNF-α, and MMP-9 and increased the expression of p-CREB, Nr4a1, ZO-1, occludin, and Lama5. Inversely, the knockdown of Mc1r or Nr4a1 abolished the neuroprotective effects of NDP-MSH.

Conclusions

Taken together, NDP-MSH binding Mc1r attenuated neuroinflammation and BBB disruption and improved neurological deficits, at least in part through CREB/Nr4a1/NF-κB pathway after ICH.

Viral-mediated gene delivery of TMBIM6 protects the neonatal brain via disruption of NPR-CYP complex coupled with upregulation of Nrf-2 post-HI

BACKGROUND

Oxidative stress, inflammation, and endoplasmic reticulum (ER) stress play a major role in the pathogenesis of neonatal hypoxic-ischemic (HI) injury. ER stress results in the accumulation of unfolded proteins that trigger the NADPH-P450 reductase (NPR) and the microsomal monooxygenase system which is composed of cytochrome P450 members (CYP) generating reactive oxygen species (ROS) as well as the release of inflammatory cytokines. We explored the role of Bax Inhibitor-1 (BI-1) protein, encoded by the Transmembrane Bax inhibitor Motif Containing 6 (TMBIM6) gene, in protection from ER stress after HI brain injury. BI-1 may attenuate ER stress-induced ROS production and release of inflammatory mediators via (1) disruption of the NPR-CYP complex and (2) upregulation of Nrf-2, a redox-sensitive transcription factor, thus promoting an increase in anti-oxidant enzymes to inhibit ROS production. The main objective of our study is to evaluate BI-1's inhibitory effects on ROS production and inflammation by overexpressing BI-1 in 10-day-old rat pups.

METHODS

Ten-day-old (P10) unsexed Sprague-Dawley rat pups underwent right common carotid artery ligation, followed by 1.5 h of hypoxia. To overexpress BI-1, rat pups were intracerebroventricularly (icv) injected at 48 h pre-HI with the human adenoviral vector-TMBIM6 (Ad-TMBIM6). BI-1 and Nrf-2 silencing were achieved by icv injection at 48 h pre-HI using siRNA to elucidate the potential mechanism. Percent infarcted area, immunofluorescent staining, DHE staining, western blot, and long-term neurobehavior assessments were performed.

RESULTS

Overexpression of BI-1 significantly reduced the percent infarcted area and improved long-term neurobehavioral outcomes. BI-1's mediated protection was observed to be via inhibition of P4502E1, a major contributor to ROS generation and upregulation of pNrf-2 and HO-1, which correlated with a decrease in ROS and inflammatory markers. This effect was reversed when BI-1 or Nrf-2 were inhibited.

CONCLUSIONS

Overexpression of BI-1 increased the production of antioxidant enzymes and attenuated inflammation by destabilizing the complex responsible for ROS production. BI-1's multimodal role in inhibiting P4502E1, together with upregulating Nrf-2, makes it a promising therapeutic target.

Delayed recanalization at 3 days after permanent MCAO attenuates neuronal apoptosis through FGF21/FGFR1/PI3K/Caspase-3 pathway in rats

Reperfusion exceeded time window may induce ischemia/reperfusion injury, increase hemorrhagic transformation, and deteriorate neurological outcomes in ischemic stroke models. However, the increasing clinical evidences supported that reperfusion even within 6-24 h may salvage ischemic tissue and improve neurological outcomes in selected large vessel occlusion patients, without inducing serious ischemia/reperfusion injury and hemorrhagic transformation. The underlying molecular mechanisms are less clear. In present study, we demonstrated that delayed recanalization at 3 days after permanent middle cerebral artery occlusion (MCAO) decreased infarct volumes and improved neurobehavioral deficits in rats, with no increasing animal mortality and intracerebral hemorrhage. Meanwhile, we observed that endogenous neuroprotective agent fibroblast growth factor 21 (FGF21) significantly increased in serum after MCAO, but which did not synchronously increase in penumbra due to permanent MCAO. Recanalization dramatically increased the endogenous FGF21 expression on neurons in penumbra after MCAO. We confirmed that FGF21 activated the FGFR1/PI3K/Caspase-3 signaling pathway, which attenuated neuronal apoptosis in penumbra. Conversely, knockdown of FGFR1 via FGFR1 siRNA abolished the anti-apoptotic effects of FGF21, and in part abrogated beneficial effects of recanalization on neurological outcomes. These findings suggested that delayed recanalization at 3 days after MCAO improved neurological outcomes in rats via increasing endogenous FGF21 expression and activating FGFR1/PI3K/Caspase-3 pathway to attenuate neuronal apoptosis in penumbra. Delayed recanalization at 3 days after ischemic stroke onset may be a promising treatment strategy in selected patients.

Decreased Netrin-1 and Correlated Th17/Tregs Balance Disorder in Aβ1-42 Induced Alzheimer's Disease Model Rats

There is increasing evidence indicating that inflammation represents a key pathological component of Alzheimer’s disease (AD). A possible factor that may contribute to this process is netrin-1, a neuronal guidance molecule. This molecule has been shown to exert an unexpected immunomodulatory function. However, the potential changes and correlations of netrin-1 with T helper 17/regulatory T cells (Th17/Tregs) as related to inflammation in AD has yet to be examined. In this study, netrin-1 and Th17/Tregs balance were investigated, and the relationship among netrin-1, Th17/Tregs and cognitive function were analyzed in a rat model of AD. In this model, a bilateral intracerebroventricular administration of Amyloid β_1-42 (Aβ_1–42) was used to produce spatial learning and memory deficits, as well as increased neuronal apoptosis, which were detected 7 days after injection for AD7d group and 14 days for AD14d group. Netrin-1 concentrations were significantly down regulated in both serum and cerebrospinal fluid (CSF) of these AD rats, effects which were strongly correlated with cognitive deficits. Increased levels of interleukin (IL)-17 and deceased IL-10 were observed in both the circulation and CSF and were also correlated with the percent of time spent in the target quadrant of AD in these rats. These changes resulted in netrin-1 concentrations being negatively correlated with IL-17 but positively correlated with IL-10 concentrations in the serum and CSF. We also found that the Th17/Tregs balance was disrupted in these AD rats. Collectively, these findings reveal that the reduction in netrin-1 and the correlated disruption of Th17/Tregs balance in AD rats may diminish the immunosuppressive effect of netrin-1 on Th17/Tregs in AD pathogenesis.

Tristetraprolin attenuates brain edema in a rat model of cerebral hemorrhage

OBJECTIVES

We evaluated the protective effects of protein phosphatase 2A (PP2A)/tristetraprolin (TTP) against brain edema in a rat model of cerebral hemorrhage, bleeding in the brain that occurs in tissues and ventricles. TTP is a well-known mRNA-binding protein and essential regulatory molecule for gene expression.

METHODS

Cerebral hemorrhage was induced in male albino rats divided into four homogeneous groups: normal control (I), control (II), PP2A siRNA (III), and scrambled siRNA (IV). Neurological scores, caspase-3 mRNA and protein expression, PP2A and TTP protein expression, apoptosis, and water content in the brain were determined.

RESULTS

The neurological score decreased substantially to 8.2 in rats in which cerebral hemorrhage was induced and was further reduced to 7.4 and 7.7 in groups III and IV, respectively. Caspase-3 expression increased significantly by 90% in group II and by 26.9% in group III. Apoptosis increased by 26.1% in rats in which cerebral hemorrhage was induced and increased considerably by 35.3% and 33.4% in groups III and IV, respectively. PP2A and TTP protein expression increased significantly by 87% and 59%, as compared to their respective sham controls. However, PP2A and TTP siRNA treatment reduced the protein expression of PP2A and TTP in groups III and IV. The water content in the brain increased significantly by 77.4% in rats in which cerebral hemorrhage was induced (group II), as compared to the sham group. The water content in the brain increased by 84.1% and 78.7% in groups III and IV, respectively.

CONCLUSION

Taken together, these data indicate that TTP has a protective role against brain edema by reducing inflammation, apoptosis, and water content in the brain at 48 hr after cerebral hemorrhage. Our findings may be useful for developing important approaches to treating brain injury.

A global analysis of CNVs in diverse yak populations using whole-genome resequencing

Background

Genomic structural variation represents a source for genetic and phenotypic variation, which may be subject to selection during the environmental adaptation and population differentiation. Here, we described a genome-wide analysis of copy number variations (CNVs) in 16 populations of yak based on genome resequencing data and CNV-based cluster analyses of these populations.

Results

In total, we identified 51,461 CNV events and defined 3174 copy number variation regions (CNVRs) that covered 163.8 Mb (6.2%) of yak genome with more “loss” events than both “gain” and “both” events, and we confirmed 31 CNVRs in 36 selected yaks using quantitative PCR. Of the total 163.8 Mb CNVR coverage, a 10.8 Mb region of high-confidence CNVRs directly overlapped with the 52.9 Mb of segmental duplications, and we confirmed their uneven distributions across chromosomes. Furthermore, functional annotation indicated that the CNVR-harbored genes have a considerable variety of molecular functions, including immune response, glucose metabolism, and sensory perception. Notably, some of the identified CNVR-harbored genes associated with adaptation to hypoxia (e.g., DCC, MRPS28, GSTCD, MOGAT2, DEXI, CIITA, and SMYD1). Additionally, cluster analysis, based on either individuals or populations, showed that the CNV clustering was divided into two origins, indicating that some yak CNVs are likely to arisen independently in different populations and contribute to population difference.

Conclusions

Collectively, the results of the present study advanced our understanding of CNV as an important type of genomic structural variation in yak, and provide a useful genomic resource to facilitate further research on yak evolution and breeding.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5451-5) contains supplementary material, which is available to authorized users.

Administration of rCTRP9 Attenuates Neuronal Apoptosis Through AdipoR1/PI3K/Akt Signaling Pathway after ICH in Mice

Targeting neuronal apoptosis after intracerebral hemorrhage (ICH) may be an important therapeutic strategy for ICH patients. Emerging evidence indicates that C1q/TNF-Related Protein 9 (CTRP9), a newly discovered adiponectin receptor agonist, exerts neuroprotection in cerebrovascular disease. The aim of this study was to investigate the anti-apoptotic role of CTRP9 after experimental ICH and to explore the underlying molecular mechanisms. ICH was induced in mice via intrastriatal injection of bacterial collagenase. Recombinant CTRP9 (rCTRP9) was administrated intranasally at 1 h after ICH. To elucidate the underlying mechanisms, adiponectin receptor1 small interfering ribonucleic acid (AdipoR1 siRNA) and selective PI3 K inhibitor LY294002 were administered prior to rCTRP9 treatment. Western blots, neurofunctional assessments, immunofluorescence staining, and Fluoro-Jade C (FJC) staining experiments were performed. Administration of rCTRP9 significantly improved both short- and long-term neurofunctional behavior after ICH. RCTRP9 treatment significantly increased the expression of AdipoR1, PI3 K, p-Akt, and Bcl-2, while at the same time was found to decrease the expression of Bax in the brain, which was reversed by inhibition of AdipoR1 and PI3 K. The neuroprotective effect of rCTRP9 after ICH was mediated by attenuation of neuronal apoptosis via the AdipoR1/PI3K/Akt signaling pathway; therefore, rCTRP9 should be further evaluated as a potential therapeutic agent for ICH patients.

Netrin-1 attenuates brain injury after middle cerebral artery occlusion via downregulation of astrocyte activation in mice

Background

Netrin-1 functions largely via combined receptors and downstream effectors. Evidence has shown that astrocytes express netrin-1 receptors, including DCC and UNC5H2. However, whether netrin-1 influences the function of astrocytes was previously unknown.

Methods

Lipopolysaccharide was used to stimulate the primary cultured astrocytes; interleukin release was used to track astrocyte activation. In vivo, shRNA and netrin-1 protein were injected in the mouse brain. Infarct volume, astrocyte activation, and interleukin release were used to observe the function of netrin-1 in neuroinflammation and brain injury after middle cerebral artery occlusion.

Results

Our results demonstrated that netrin-1 reduced lipopolysaccharide-induced interleukin-1β and interleukin-12β release in cultured astrocytes, and blockade of the UNC5H2 receptor with an antibody reversed this effect. Additionally, netrin-1 increased p-AKT and PPAR-γ expression in primary cultured astrocytes. In vivo studies showed that knockdown of netrin-1 increased astrocyte activation in the mouse brain after middle cerebral artery occlusion (p < 0.05). Moreover, injection of netrin-1 attenuated GFAP expression (netrin-1 0.27 ± 0.06 vs. BSA 0.62 ± 0.04, p < 0.001) and the release of interleukins and reduced infarct volume after brain ischemia (netrin-1 0.27 ± 0.06 vs. BSA 0.62 ± 0.04 mm³, p < 0.05).

Conclusion

Our results indicate that netrin-1 is an important molecule in regulating astrocyte activation and neuroinflammation in cerebral ischemia and provides a potential target for ischemic stroke therapy.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1291-5) contains supplementary material, which is available to authorized users.

Ezetimibe, a NPC1L1 inhibitor, attenuates neuronal apoptosis through AMPK dependent autophagy activation after MCAO in rats

Autophagy activation exerts neuroprotective effects in the ischemic stroke model. Ezetimibe (Eze), a Niemann-Pick disease type C1-Like 1 (NPC1L1) pharmacological inhibitor, has been reported to protect hepatocytes from apoptosis via autophagy activation. In this study, we explored whether Eze could attenuate neuronal apoptosis in the rat model of middle cerebral artery occlusion (MCAO), specifically via activation of the AMPK/ULK1/autophagy pathway. Two hundred and one male Sprague-Dawley rats were subjected to transient MCAO followed by reperfusion. Eze was administered 1 h after MCAO. To elucidate the underlying molecular mechanism, Dorsomorphin, a selective AMPK inhibitor, and 3-methyladenine (3-MA), an autophagy inhibitor, were injected intracerebroventricularly before MCAO. Infarct volume, neurological score, brain cholesterol levels, immunofluorescence staining, Western blot, and Fluoro-Jade C (FJC) staining were used to evaluate the effects of Eze. The endogenous NPC1L1 expression increased and mainly expressed in neurons after MCAO. Intranasal administration of Eze reduced brain infarct volume at 24 and 72 h after MCAO, with improved short and long-term neurological functions after MCAO. Eze reduced brain cholesterol levels (total cholesterol, free cholesterol and cholesteryl esters) and the number of FJC-positive neurons. The expression of phosphorylated AMPK (p-AMPK) and downstream ULK1, Beclin1, LC3BII, Bcl-2, and Bcl-xl increased, while P62 and proapoptotic Bax decreased after treatment with Eze. Pretreatment with Dorsomorphin and 3-MA reversed the beneficial effects of Eze. These findings suggest that intranasal administration of Eze plays neuroprotective role through autophagy activation after MCAO in rats. Lowered cholesterol levels and AMPK activation may act in conjunction to induce autophagy after treatment with Eze. Eze merits further investigation as a potential therapeutic agent in ischemic stroke patients.

Aggf1 attenuates neuroinflammation and BBB disruption via PI3K/Akt/NF-κB pathway after subarachnoid hemorrhage in rats

Background

Neuroinflammation and blood-brain barrier (BBB) disruption are two critical mechanisms of subarachnoid hemorrhage (SAH)-induced brain injury, which are closely related to patient prognosis. Recently, angiogenic factor with G-patch and FHA domain 1 (Aggf1) was shown to inhibit inflammatory effect and preserve vascular integrity in non-nervous system diseases. This study aimed to determine whether Aggf1 could attenuate neuroinflammation and preserve BBB integrity after experimental SAH, as well as the underlying mechanisms of its protective roles.

Methods

Two hundred forty-nine male Sprague-Dawley rats were subjected to the endovascular perforation model of SAH. Recombinant human Aggf1 (rh-Aggf1) was administered intravenously via tail vein injection at 1 h after SAH induction. To investigate the underlying neuroprotection mechanism, Aggf1 small interfering RNA (Aggf1 siRNA) and PI3K-specific inhibitor LY294002 were administered through intracerebroventricular (i.c.v.) before SAH induction. SAH grade, neurological score, brain water content, BBB permeability, Western blot, and immunohistochemistry were performed.

Results

Expression of endogenous Aggf1 was markedly increased after SAH. Aggf1 was primarily expressed in endothelial cells and astrocytes, as well as microglia after SAH. Administration of rh-Aggf1 significantly reduced brain water content and BBB permeability, decreased the numbers of infiltrating neutrophils, and activated microglia in the ipsilateral cerebral cortex following SAH. Furthermore, rh-Aggf1 treatment improved both short- and long-term neurological functions after SAH. Meanwhile, exogenous rh-Aggf1 significantly increased the expression of PI3K, p-Akt, VE-cadherin, Occludin, and Claudin-5, as well as decreased the expression of p-NF-κB p65, albumin, myeloperoxidase (MPO), TNF-α, and IL-1β. Conversely, knockdown of endogenous Aggf1 aggravated BBB breakdown, inflammatory response and neurological impairments at 24 h after SAH. Additionally, the protective roles of rh-Aggf1 were abolished by LY294002.

Conclusions

Taken together, exogenous Aggf1 treatment attenuated neuroinflammation and BBB disruption, improved neurological deficits after SAH in rats, at least in part through the PI3K/Akt/NF-κB pathway.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1211-8) contains supplementary material, which is available to authorized users.

Osteopontin attenuates inflammation via JAK2/STAT1 pathway in hyperglycemic rats after intracerebral hemorrhage

Acute intracerebral hemorrhage (ICH) complicated by hyperglycemia is associated with aggravation of post-stroke inflammation, leading to exacerbation of brain edema and predicting poor neurological outcomes and higher mortality of patients. Osteopontin (OPN) is a neuroprotective glycoprotein, which is able to attenuate brain injury induced by hemorrhagic stroke. In the current study we investigated whether OPN will decrease the inflammatory post-ICH response as well as attenuate brain edema and neurological deficits in hyperglycemic rats. We employed a collagenase model of ICH on male Sprague-Dawley rats (n = 148) rats and 50% of Dextrose was injected intraperitoneally (i.p) 3 h after ICH (ICH + HG). Intranasal administration of recombinant OPN (rOPN) was performed 1 h after ICH. The development of brain injury was evaluated by brain water content (BWC) and neurological deficits, western blot and immunohistochemistry study. Small interfering ribonucleic acid (siRNA) for integrin-β1 receptor and a JAK2 agonist, Coumermycin A1 (C-A1), were used for detailed investigation of the molecular pathway. The administration of OPN (3 μg) significantly improved neurobehavior and increased expression of OPN and integrin-β1 receptor in the brain followed with decrease of neutrophil infiltration, JAK2, STAT1, TNF-a, IL-1b, MMP-9 and brain edema in the ICH + HG + OPN rats compared with ICH + HG rats. The effects of OPN were reversed by the intervention of intergrin-β1 siRNA and C-A1. In conclusion, rOPN attenuated ICH-induced brain inflammation in hyperglycemic rats, leading to attenuation of brain edema and improving neurological functions. Effects of rOPN were mediated at least partly by integrin-β1 induced inhibition of JAK2/STAT1 pathway.

Adiponectin attenuates neuronal apoptosis induced by hypoxia-ischemia via the activation of AdipoR1/APPL1/LKB1/AMPK pathway in neonatal rats

Adiponectin is an important adipocyte-derived plasma protein that has beneficial effects on cardio- and cerebrovascular diseases. A low level of plasma Adiponectin is associated with increased mortality post ischemic stroke; however, little is known about the causal role of Adiponectin as well as its molecular mechanisms in neonatal hypoxia ischemia (HI). In the present study, ten-day-old rat pups were subjected to right common carotid artery ligation followed by 2.5 h hypoxia. Recombinant human Adiponectin (rh-Adiponectin) was administered intranasally 1 h post HI. Adiponectin Receptor 1 (AdipoR1) siRNA, APPL1 siRNA, LKB1 siRNA were administered through intracerebroventricular injection 48 h before HI. Brain infarct area measurement, neurological function test, western blot, Fluoro Jade C (FJC), TUNEL, and immunofluorescence staining were conducted. Results revealed that endogenous Adiponectin, AdipoR1 and APPL1 were increased in a time dependent manner after HI. Administration of rh-Adiponectin reduced brain infarct area, neuronal apoptosis, brain atrophy and improved neurological function at 24 h and 4 weeks post HI. Furthermore, rh-Adiponectin treatment increased Adiponectin, AdipoR1, APPL1, cytosolic LKB1, p-AMPK expression levels and thereby attenuated apoptosis as shown by the decreased expression of the pro-apoptotic marker, Cleaved Caspase 3 (C-Cas3), as well as the number of FJC and TUNEL positively stained neurons. AdipoR1, APPL1 and LKB1 siRNAs abolished the anti-apoptotic effects of rh-Adiponectin at 24 h after HI. Collectively, the data provided evidence that intranasal administration of rh-Adiponectin attenuated neuronal apoptosis at least in part via activating AdipoR1/APPL1/LKB1/AMPK signaling pathway. Adiponectin could represent a therapeutic target for treatment of neonatal hypoxic ischemic encephalopathy.

Recombinant Netrin-1 binding UNC5B receptor attenuates neuroinflammation and brain injury via PPARγ/NFκB signaling pathway after subarachnoid hemorrhage in rats

Neuroinflammation is an essential mechanism involved in the pathogenesis of subarachnoid hemorrhage (SAH)-induced brain injury. Recently, Netrin-1 (NTN-1) is well established to exert anti-inflammatory property in non-nervous system diseases through inhibiting infiltration of neutrophil. The present study was designed to investigate the effects of NTN-1 on neuroinflammation, and the potential mechanism in a rat model of SAH. Two hundred and ninety-four male Sprague Dawley rats (weight 280-330 g) were subjected to the endovascular perforation model of SAH. Recombinant human NTN-1 (rh-NTN-1) was administered intravenously. Small interfering RNA (siRNA) of NTN-1 and UNC5B, and a selective PPARγ antagonist bisphenol A diglycidyl ether (BADGE) were applied. Post-SAH evaluations included neurobehavioral function, brain water content, Western blot analysis, and immunohistochemistry. Our results showed that endogenous NTN-1 and its receptor UNC5B level were increased after SAH. Administration of rh-NTN-1 reduced brain edema, ameliorated neurological impairments, and suppressed microglia activation after SAH, which were concomitant with PPARγ activation, inhibition of NFκB, and decrease in TNF-α, IL-6, and ICAM-1, as well as myeloperoxidase (MPO). Knockdown of endogenous NTN-1 increased expression of pro-inflammatory mediators and MPO, and aggravated neuroinflammation and brain edema. Moreover, knockdown of UNC5B using specific siRNA and inhibition of PPARγ with BADGE blocked the protective effects of rh-NTN-1. In conclusion, our findings indicated that exogenous rh-NTN-1 treatment attenuated neuroinflammation and neurological impairments through inhibiting microglia activation after SAH in rats, which is possibly mediated by UNC5B/PPARγ/NFκB signaling pathway. Exogenous NTN-1 may be a novel therapeutic agent to ameliorating early brain injury via its anti-inflammation effect.

Neuroprotective Effect of Protein Phosphatase 2A/Tristetraprolin Following Subarachnoid Hemorrhage in Rats

Early brain injury (EBI) following subarachnoid hemorrhage (SAH) can lead to inflammation and neuronal dysfunction. There is a need for effective strategies to mitigate these effects and improve the outcome of patients who experience SAH. The mRNA-destabilizing protein tristetraprolin (TTP) is an anti-inflammatory factor that induces the decay of cytokine transcripts and has been implicated in diseases such as glioma. However, the mechanism of action of TTP in EBI after SAH is unclear. The present study investigated the effects of TTP regulation via phosphorylation in a rat model of SAH by protein phosphatase (PP)2A, which is a pleiotropic enzyme complex with multiple substrate phospho-proteins. We hypothesized that inhibitory phosphorylation of TTP by PP2A would reduce neuroinflammation and apoptosis. To evaluate the function of each factor, the PP2A agonist FTY720, short interfering (si)RNAs targeting TTP and PP2A were administered to rats by intracerebroventricular injection 24 h before SAH. Rats were evaluated with SAH grade, neurological score, brain water content and by western blotting, and terminal deoxynucleotidyltransferase dUTP nick-end labeling. We found that endogenous PP2A and TTP levels were increased after SAH. FTY720 induced PP2A activation would lead to dephosphorylation and activation of TTP and decreased production of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-8. SiRNA-mediated TTP knockdown abolished anti-inflammatory effects of FTY720 treatment, indicating that PP2A was associated with TTP activation in vivo. Decreased TNF-α, IL-6, and IL-8 levels were associated with improvement of neurological function, reduction of brain edema, suppression of caspase-3, and up-regulation of B cell lymphoma-2. These results demonstrated that PP2A activation could enhance the anti-inflammatory and anti-apoptotic effects of TTP, by which it might shed light on the development of an effective therapeutic strategy against EBI following SAH.

Early maternal separation promotes apoptosis in dentate gyrus and alters neurological behaviors in adolescent rats

Adverse early-life experience such as maternal separation (MS) affects the behavior of adult, and may also aggravate the outcome of neurological insults. In this study, we aimed to investigate the effects of early MS on hippocampus-related behaviors, and to assess the mechanisms. Newborn rats were randomly divided into normal control and MS groups. Our data showed that MS (P3-P21) impaired learning ability as well as memory retrieval, and caused depression-like activity, but decreased anxiety-like activity. Glutamate receptor 1 (GluR1) expression in the dentate gyrus (DG) region was significantly reduced in the adults (P60). Mechanically, MS promoted apoptosis, and reduced protein kinase B (AKT) phosphorylation in the DG region in the early phase (P21). By contrast, MS did not affect ERK phosphorylation. Our data implicate that the inactivation of AKT pathway and apoptosis of DG cells might contribute to MS-induced behavioral changes. This study would provide useful evidence implicating the pathological changes for MS.

Exendin-4 attenuates neuronal death via GLP-1R/PI3K/Akt pathway in early brain injury after subarachnoid hemorrhage in rats

Neuronal apoptosis is considered to be a crucial therapeutic target against early brain injury (EBI) after subarachnoid hemorrhage (SAH). Emerging evidence indicates that Exendin-4 (Ex-4), a glucagon-like peptide 1 receptor (GLP-1R) agonist, plays a neuroprotective role in cerebrovascular disease. This study was conducted in order to verify the neuroprotective role of EX-4 in EBI after SAH in rats. The endovascular perforation model of SAH was performed in Sprague-Dawley rats (n = 153). Ex-4 was intraperitoneally injected 1 h after SAH induction in the rats (SAH + Ex-4). To elucidate the underlying molecular mechanism, small interfering ribonucleic acid (siRNA) for GLP-1R and a specific inhibitor of PI3K, LY294002, were injected intracerebroventricularly into SAH + Ex-4 rats before induction of SAH (n = 6 per group). SAH grading evaluation, immunohistochemistry, Western blots, neurobehavioral assessment, and Fluoro-Jade C (FJC) staining experiments were performed. Expression of GLP-1R was significantly increased and mainly expressed in neurons at 24 h after SAH induction. Administration of Ex-4 significantly improved both short- and long-term neurobehavior in SAH + Ex-4 group compared to SAH + Vehicle group after SAH. Ex-4 treatment significantly increased the expression of GLP-1R, PI3K, p-Akt, Bcl-xl, and Bcl-2, while at the same time was found to decrease expression of Bax in the brain. Effects of Ex-4 were reversed by the intervention of GLP-1R siRNA and LY294002 in SAH + Ex-4+GLP-1R siRNA and SAH + Ex-4+LY294002 groups, respectively. In conclusion, the neuroprotective effect of Ex-4 in EBI after SAH was mediated by attenuation of neuronal apoptosis via GLP-1R/PI3K/Akt signaling pathway, therefore EX-4 should be further investigated as a potential therapeutic agent in stroke patients.