TAT-Ngn2 Enhances Cognitive Function Recovery and Regulates Caspase-Dependent and Mitochondrial Apoptotic Pathways After Experimental Stroke

TAT-PEP Alleviated Cognitive Impairment by Alleviating Neuronal Mitochondria Damage and Apoptosis After Cerebral Ischemic Reperfusion Injury

Paired immunoglobulin-like receptor B (PirB) was identified as a myelin-associated inhibitory protein (MAIP) receptor that plays a critical role in axonal regeneration, synaptic plasticity and neuronal survival after stroke. In our previous study, a transactivator of transcription-PirB extracellular peptide (TAT-PEP) was generated that can block the interactions between MAIs and PirB. We found that TAT-PEP treatment improved axonal regeneration, CST projection and long-term neurobehavioural recovery after stroke through its effects on PirB-mediated downstream signalling. However, the effect of TAT-PEP on the recovery of cognitive function and the survival of neurons also needs to be investigated. In this study, we investigated whether pirb RNAi could alleviate neuronal injury by inhibiting the expression of PirB following exposure to oxygen-glucose deprivation (OGD) in vitro. In addition, TAT-PEP treatment attenuated the volume of the brain infarct and promoted the recovery of neurobehavioural function and cognitive function. This study also found that TAT-PEP exerts neuroprotection by reducing neuronal degeneration and apoptosis after ischemia-reperfusion injury. In addition, TAT-PEP improved neuron survival and reduced lactate dehydrogenase (LDH) release in vitro. Results also showed that TAT-PEP reduced malondialdehyde (MDA) levels, increased superoxide dismutase (SOD) activity and reduced reactive oxygen species (ROS) accumulation in OGD-injured neurons. The possible mechanism was that TAT-PEP could contribute to the damage of neuronal mitochondria and affect the expression of cleaved caspase 3, Bax and Bcl-2. Our results suggest that PirB overexpression in neurons after ischaemic-reperfusion injury induces neuronal mitochondrial damage, oxidative stress and apoptosis. This study also suggests that TAT-PEP may be a potent neuroprotectant with therapeutic potential for stroke by reducing neuronal oxidative stress, mitochondrial damage, degeneration and apoptosis in ischemic stroke.

Autophagy and Apoptosis in Acute Brain Injuries: From Mechanism to Treatment

Significance: Autophagy and apoptosis are two important cellular mechanisms behind brain injuries, which are severe clinical situations with increasing incidences worldwide. To search for more and better treatments for brain injuries, it is essential to deepen the understanding of autophagy, apoptosis, and their interactions in brain injuries. This article first analyzes how autophagy and apoptosis participate in the pathogenetic processes of brain injuries respectively and mutually, then summarizes some promising treatments targeting autophagy and apoptosis to show the potential clinical applications in personalized medicine and precision medicine in the future. Recent Advances: Most current studies suggest that apoptosis is detrimental to brain recovery. Several studies indicate that autophagy can cause unnecessary death of neurons after brain injuries, while others show that autophagy is beneficial for acute brain injuries (ABIs) by facilitating the removal of damaged proteins and organelles. Whether autophagy is beneficial or detrimental in ABIs depends on many factors, and the results from different research groups are diverse or even controversial, making this topic more appealing to be explored further. Critical Issues: Neuronal autophagy and apoptosis are two primary pathological processes in ABIs. How they interact with each other and how their regulations affect the outcome and prognosis of brain injuries remain uncertain, making these answers more critical. Future Directions: Insights into the interplay between autophagy and apoptosis and the accurate regulations of their balance in ABIs may promote personalized and precise treatments in the field of brain injuries. Antioxid. Redox Signal. 38, 234-257.

TAT-LBD-Ngn2-improved cognitive functions after global cerebral ischemia by enhancing neurogenesis

BACKGROUND

Stroke is the major cause of adult neurocognitive disorders (NCDs), and presents a significant burden on both of the families and society. To improve the cerebral injury, we generated a blood-brain barrier penetrating peptide TAT-LBD-Ngn2, in which Ngn2 (Neurogenin2) is a classical preneural gene that enhances neurogenesis, and neural precursor cells survival and differentiation. We previously demonstrated that it has a short-term protective effect against cerebral ischemia-reperfusion injury. However, it is uncertain if TAT-LBD-Ngn2 could promote neurogenesis to exhibit long-term therapeutic impact.

METHODS AND RESULTS

In present study, TAT-LBD-Ngn2 was administered for 14 or 28 days following bilateral common carotid arteries occlusion (BCCAO). After confirming that TAT-LBD-Ngn2 could cross the brain blood barrier and aggregate in the hippocampus, we conducted open field test, Morris water maze and contextual fear conditioning to examine the long-term effect of TAT-LBD-Ngn2 on cognition. We discovered that TAT-LBD-Ngn2 significantly improved the spatial and contextual learning and memory on both days 14 and 28 after BCCAO, while TAT-LBD-Ngn2 exhibited anxiolytic effect only on day 14, but had no effect on locomotion. Using western blot and immunofluorescence, TAT-LBD-Ngn2 was also shown to promote neurogenesis, as evidenced by increased BrdU⁺ and DCX⁺ neurons in dentate gyrus. Meanwhile, TAT-LBD-Ngn2 elevated the expression of brain derived neurotrophic factor rather than nerve growth factor compared to the control group.

CONCLUSIONS

Our findings revealed that TAT-LBD-Ngn2 could dramatically promote learning and memory in long term by facilitating neurogenesis in the hippocampus after global cerebral ischemia, indicating that TAT-LBD-Ngn2 may be an appealing candidate for treating poststroke NCD.

TPPU Downregulates Oxidative Stress Damage and Induces BDNF Expression in PC-12 Cells

Objective

Ischemia-reperfusion is an ongoing clinical challenge that can lead to a series of pathological changes including oxidative stress. The inhibition of soluble epoxide hydrolase inhibitor (sEH) by 1-(1-propanoylpiperidin-4-yl)-3-[4-(trifluoromethoxy)phenyl]urea (TPPU) results in an anti-inflammatory, cardioprotective, and blood vessel growth-promoting effects. Therefore, this study focused on the protective effect of TPPU on a rat pheochromocytoma (PC-12) cell oxidative stress model induced by H2O2.

Methods

CCK-8 and Hoechst 33342 were used to evaluate cell apoptosis and western blot to detect the apoptotic proteins and brain-derived neurotrophic factor (BDNF) expression.

Result

The incubation with 100 μM, 50 μM, and 25 μM TPPU significantly increased PC-12 cell viability. Epoxyeicosatrienoic acid (EET) pretreatment also protected PC-12 cells from oxidative stress. In addition, TPPU reduced caspase-3 and Bax expression and induced Bcl-2 expression, and EETs exerted the same effect on caspase-3 expression as TPPU. A positive relationship was found between TPPU or EET incubation and BDNF expression.

Conclusion

These results revealed that TPPU reduced PC-12 cell oxidative stress injury induced by H2O2 and promoted BDNF expression.

Constitutive deficiency of the neurogenic hippocampal modulator AP2γ promotes anxiety-like behavior and cumulative memory deficits in mice from juvenile to adult periods

The transcription factor activating protein two gamma (AP2γ) is an important regulator of neurogenesis both during embryonic development as well as in the postnatal brain, but its role for neurophysiology and behavior at distinct postnatal periods is still unclear. In this work, we explored the neurogenic, behavioral, and functional impact of a constitutive and heterozygous AP2γ deletion in mice from early postnatal development until adulthood. AP2γ deficiency promotes downregulation of hippocampal glutamatergic neurogenesis, altering the ontogeny of emotional and memory behaviors associated with hippocampus formation. The impairments induced by AP2γ constitutive deletion since early development leads to an anxious-like phenotype and memory impairments as early as the juvenile phase. These behavioral impairments either persist from the juvenile phase to adulthood or emerge in adult mice with deficits in behavioral flexibility and object location recognition. Collectively, we observed a progressive and cumulative impact of constitutive AP2γ deficiency on the hippocampal glutamatergic neurogenic process, as well as alterations on limbic-cortical connectivity, together with functional behavioral impairments. The results herein presented demonstrate the modulatory role exerted by the AP2γ transcription factor and the relevance of hippocampal neurogenesis in the development of emotional states and memory processes.

Huang-Pu-Tong-Qiao Formula Ameliorates the Hippocampus Apoptosis in Diabetic Cognitive Dysfunction Mice by Activating CREB/BDNF/TrkB Signaling Pathway

Background

Huang-Pu-Tong-Qiao formula (HPTQ), a traditional Chinese medicine (TCM) formula used to improve cognitive impairment. However, the underlying neuroprotective mechanism of HPTQ treated for diabetic cognitive dysfunction (DCD) remains unclear. The purpose of this study was to investigate the neuroprotective mechanism of HPTQ in DCD mice based on molecular docking.

Methods

To investigate the neuroprotective effect of HPTQ in DCD, the Morris water maze (MWM), novel object recognition (NOR) test was used to detect the learning and memory changes of mice; hematoxylin-eosin (HE) staining was used to investigate the damage of hippocampal neurons; the western blot (WB) was used to examine the level of brain-derived neurotrophic factor (BDNF) of hippocampus. To investigate the neuroprotective mechanism of HPTQ in DCD, molecular docking was used to predict the possible target proteins of different active components in HPTQ and then the WB was used to verify the expression of key target proteins in the hippocampus of mice.

Results

HPTQ improved the learning and memory ability, hippocampal neuron damage, and the level of BDNF in the hippocampus of the DCD model treated with HFD/STZ for 12 weeks. Besides, the results of molecular docking showed that the main chemical components of HPTQ could be well combined with the targets of Bcl-2-associated X (Bax) and B-cell lymphoma2 (Bcl-2) and caspase-3. The levels of Bax/Bcl-2 protein ratio and caspase-3 increased in the DCD model while the HPTQ inhibited it. In addition, HPTQ restored DCD-induced decline of p-CREB, BDNF, TrkB, and p-Akt in the hippocampus.

Conclusions

These data indicated that HPTQ ameliorates the hippocampus apoptosis in diabetic cognitive dysfunction mice by activating CREB/BDNF/TrkB signaling pathway.

Inhibition of microRNA-10b-5p up-regulates HOXD10 to attenuate Alzheimer's disease in rats via the Rho/ROCK signalling pathway

OBJECTIVE

It is believed that microRNAs (miRNAs) participate in the pathogenesis of Alzheimer's disease (AD), but the specified function of miR-10b-5p in the disease has not been thoroughly understood. Thereafter, this research aimed to assess the function of miR-10b-5p in AD.

METHODS

Rat AD models were established by injected with amyloid-β_1-42 (Aβ_1-42), which were mainly treated with lentivirus-miR-10b-5p inhibitor, or lentivirus-overexpressed homeobox D10 (HOXD10). MiR-10b-5p, HOXD10, RhoA, ROCK1 and ROCK2 expression in rat hippocampal tissues were determined. Afterwards, the behaviour of rats was tested, and neuronal apoptosis, pathological injury, and inflammatory factors and oxidative stress-related factors were all assessed. Finally, the target relation between miR-10b-5p and HOXD10 was detected.

RESULTS

MiR-10b-5p was upregulated while HOXD10 was downregulated, and the Rho/ROCK signalling pathway was activated in hippocampal tissues of rats with AD. Inhibition of miR-10b-5p could attenuate the neuronal apoptosis, pathological injury, inflammation reaction, and oxidative stress by elevating HOXD10 and inhibiting the Rho/ROCK signalling pathway in AD rats. Moreover, HOXD10 was targeted by miR-10b-5p.

CONCLUSION

Inhibited miR-10b-5p decelerated the development of AD by promoting HOXD10 and inactivating the Rho/ROCK signalling pathway, and our findings may contribute to the exploration of AD treatment.

Effect of high-BDNF microenvironment stem cells therapy on neurogenic bladder model in rats

Background

The purpose of this study is to explore the effects of high-BDNF microenvironment produced by engineered immortalized mesenchymal stem cells (imMSCs) on the neurogenic bladder (NB) and investigate underlying mechanism.

Methods

Male Sprague-Dawley rat (12-week-old, weighing about 370-400 g) were purchased from a Korean company (Orient Bio Co. Seongnam, Korea) and divided into the following groups (n=32): sham control group (n=8), NB group (n=8), NB + ImMSCs group (n=8), NB + ImMSCs (BDNF) group (n=8). The major pelvic ganglion (MPG) was observed under anesthesia. Three NB groups of rats were then subjected to bilateral MPG injury. The sham control group of rats was treated with sham surgery. Cystometry were performed before the rats were sacrificed, and then MPG and bladder were collected for histochemical and Western blot analysis.

Results

MSCs treatment improves lower urinary tract function, and the NB + ImMSCs (BDNF) group is better than the NB + ImMSCs group (P<0.01). MSCs treatment accelerates recovery of injured nerve tissue, and the NB + ImMSCs (BDNF) group is better than the NB + ImMSCs group (P<0.01). In high BDNF environment, apoptosis was reduced more significantly and muscle tissue recovered more rapidly (P<0.01). High-BDNF microenvironment activates more BDNF/TrkB/CREB signaling pathways (P<0.01).

Conclusions

In a rat NB model caused by nerve injury, imMSCs have certain effects on nerve tissue repair. At the same time, it was proved that increasing the expression of BDNF which had specific effect on nerve injury repair could more effectively repair injured MPG in local microenvironment. The mechanism may be related to the activation of the BDNF/TrkB/CREB signaling pathway and the reduction of apoptosis by highly expressed BDNF.

Icariside II, a PDE5 Inhibitor, Suppresses Oxygen-Glucose Deprivation/Reperfusion-Induced Primary Hippocampal Neuronal Death Through Activating the PKG/CREB/BDNF/TrkB Signaling Pathway

Background

Ischemic stroke remains the leading cause of death and adult disability. Cerebral ischemic/reperfusion (I/R) injury is caused by ischemic stroke thereafter aggravates overwhelming neuronal apoptosis and even the death of neurons. Of note, hippocampus is more susceptive to cerebral I/R injury than the other brain region. This study was designed to explore the effects and mechanism of icariside II (ICS II), a pharmacologically active compound exists in herbal Epimedii with previous study-proved as a phosphodiesterase 5 (PDE5) inhibitor, on the oxygen glucose deprivation/reoxygenation (OGD/R)-induced primary hippocampal neurons injury.

Methods

Effects of ICS II on primary hippocampal neuronal impairment and apoptosis induced by OGD/R were examined by MTT, lactate dehydrogenase (LDH) release, TUNEL staining, and flow cytometry, respectively. Activation of memory-related signaling pathways was measured using Western blot analysis. The direct interaction between ICS II and PDE5 was further evaluated by molecular docking.

Results

ICS II (12.5, 25, 50 μM) markedly abrogated OGD/R-induced hippocampal neuronal death as suggested by the increase in neurons viability and the decrease in cellular LDH release. Furthermore, ICS II not only effectively decreased the protein expression and activity of PDE5, restored the 3′5′-cyclic guanosine monophosphate (cGMP) level and its downstream target protein kinase G (PKG) activity but also increased the phosphorylation of cAMP response element binding protein (CREB) level, expressions of brain derived neurotrophic factor (BDNF), and tyrosine protein kinase B (TrkB). Mechanistically, the inhibitory effects of ICS II were abrogated by Rp-8-Br-cGMP (a PKG inhibitor) or ANA-12 (a TrkB inhibitor), which further confirmed that the favorable effects of ICS II were attributed to its activation of the PKG/CREB/BDNF signaling pathways. Intriguingly, ICS II might effectively bind and inhibited PDE5 activity as demonstrated by relatively high binding scores (−6.52 kcal/mol).

Conclusions

ICS II significantly rescues OGD/R-induced hippocampal neuronal injury. The mechanism is, at least partly, due to inhibition of PDE5 and activation of PKG/CREB/BDNF/TrkB signaling pathway. Hence it is thought that ICS II might be a potential naturally PDE5 inhibitor to combat cerebral I/R injury.

ALDH 2 conferred neuroprotection on cerebral ischemic injury by alleviating mitochondria-related apoptosis through JNK/caspase-3 signing pathway

Past studies have indicated that the dysregulation of Aldehyde dehydrogenase 2 (ALDH2) is related to the pathogenesis of acute stroke. However, the underlying mechanisms of ALDH2-mediated acute stroke are still not well understood. Thus, our study was designed to explore the influence of ALDH2 in acute stroke and determine whether its related mechanisms are involved in regulating mitochondria-associated apoptosis modulating JNK/caspase-3 pathway. In vitro analysis on the gain and loss of ALDH2 and JNK function were performed to explore its influence on OGD/R injury and relevant signaling pathways. Our findings suggested that ALDH2 expression was significantly down-regulated in rats suffering from acute stroke and also in primary cortical cultured neurons and PC12 cells upon OGD/R stimulation. ALDH2 overexpression markedly decreased infarct size and improved neurological outcomes. Furthermore, ALDH2 overexpression significantly suppressed stroke-induced mitochondria-associated apoptosis and inhibited p-JNK activation and p-JNK/caspase-3 complex formation. Similarly, in in vitro OGD/R models, ALDH2 reintroduction not only promoted cellular viability and moderated LDH release, but also inhibited mitochondria-related apoptosis. Moreover, JNK inhibition relieved OGD/R-induced cellular injury and apoptosis while JNK activation aggravated them. Furthermore, ALDH2 overexpression and JNK inhibition significantly reduced caspase-3 activation and transcription which was triggered by OGD/R damage. Caspase-3 activation and transcription also re-elevated during activation of JNK in ALDH2-reintroduced cells. Finally, ChIP assay revealed that p-JNK was bound to caspase-3 promoter. Collectively, ALDH2 overexpression led to a significant reduction in mitochondria-related apoptosis via JNK-mediated caspase-3 activation and transcription in both in vitro and in vivo cerebral ischemia models.

Up-regulation of miR-106a targets LIMK1 and contributes to cognitive impairment induced by isoflurane anesthesia in mice

BACKGROUND

Postoperative cognitive dysfunction (POCD) had a great relationship with anesthesia during surgery, and miRNAs have been found involved in anesthesia-induced cognitive impairment.

OBJECTIVE

To explore the role and potential mechanism of miR-106a in isoflurane anesthesia-induced cognitive impairment.

METHODS

Adult male mice were treated with isoflurane anesthesia; Morris water maze tests and fear conditioning tests were performed; and expression levels of miR-106a and LIMK1 were determined by quantitative real-time PCR (qRT-PCR) and western blot. Dual luciferase reporter assay was used to determine the binding of miR-106a and 3'UTR of LIMK1. To verify the role of miR-106a, antagomir of miR-106a were intrahippocampally injected. Finally, expression of BCL2 apoptosis regulator (Bcl-2), LIM domain kinase 1 (LIMK1), BCL2-associated X, apoptosis regulator (Bax) and cleaved caspase3 was determined by western blot.

RESULTS

In isoflurane anesthesia-treated group (IS), the percentage of target quadrant dwell time was significantly lower and the escape latency was significantly higher than in the control group (sham), and the freezing behavior of IS was significantly less in contextual fear conditioning tests. Expression levels of miR-106a were increased and those of LIMK1 were decreased in response to IS. Dual luciferase reporter assay showed that miR-106a could bind with the 3'UTR of LIMK1. Decreased expression levels of miR-106a improved the cognitive impairment of the mice treated with isoflurane. Intrahippocampally injected antagomir of miR-106a also increased LIMK1 and Bcl-2 levels, decreased the BAX and cleaved caspase3 expression levels in the mice treated with isoflurane.

CONCLUSION

Decrease of LIMK1 expression by miR-106a played an important role in isoflurane anesthesia-induced cognitive impairment.

Involvement of apoptosis in the protective effects of Dracocephalum moldavaica in cerebral ischemia reperfusion rat model

An extract of Dracocephalum moldevica (DML) was found to exert protective effects on cerebral ischemia-reperfusion injury (CIRI); however, the mechanisms underlying the observed actions of this plant-derived mixture remain to be determined. Thus, the aim of this study was to examine the influence of DML on CIRI rat model induced by middle cerebral artery occlusion (MCAO). The following parameters were measured: (1) viable neurons in the infarcted area using Nissl staining; and (2) immunohistochemistry and Western blot were employed to determine protein expression levels of p53, bcl-2 associated X protein (bax) and B-cell lymphoma-2 (bcl-2), three biomarkers of apoptosis. MCAO significantly decreased the number of viable cortical pyramidal neurons in the infarcted area, while treatment with DML extract significantly elevated the number of viable neurons. MCAO was found to significantly elevate in gene expression levels of p53 and protein expression levels bax accompanied by diminished protein expression levels of bcl-2. Prior administration of DML extract produced marked reduction in gene expression levels of p53 and protein expression levels bax but increased in protein expression levels of bcl-2. Data suggested apoptosis was initiated in MCAO and that DML was effective in treating CIRI via an anti-apoptotic action as evidenced by inhibition of gene expression levels of p53 and protein expression levels of bax with concomitant elevation in protein expression levels of bcl-2. Our findings suggest that extract of DML may prove beneficial in treatment of cerebrovascular disorders.