Group II Metabotropic Glutamate Receptors Reduce Apoptosis and Regulate BDNF and GDNF Levels in Hypoxic-Ischemic Injury in Neonatal Rats

Effects of the PAM of mGluR2, JNJ-46356479, on brain apoptotic protein levels in a mouse model of schizophrenia

Current treatment for schizophrenia (SZ) ameliorates the positive symptoms, but is inefficient in treating the negative and cognitive symptoms. The SZ glutamatergic dysfunction hypothesis has opened new avenues in the development of novel drugs targeting the glutamate storm, an inducer of progressive neuropathological changes. Positive allosteric modulators of metabotropic glutamate receptor 2 (mGluR2), such as JNJ-46356479 (JNJ), reduce the presynaptic release of glutamate, which has previously been demonstrated to attenuate glutamate- and dopamine-induced apoptosis in human neuroblastoma cell cultures. We hypothesised that JNJ treatment would modify the brain levels of apoptotic proteins in a mouse model of ketamine (KET)-induced schizophrenia. We analysed the levels of proapoptotic (caspase-3 and Bax) and antiapoptotic (Bcl-2) proteins by western blot in the prefrontal cortex and hippocampus of JNJ-treated mice. JNJ attenuated apoptosis in the brain by partially restoring the levels of the antiapoptotic Bcl-2 protein, which is significantly reduced in animals exposed to KET. Additionally, a significant inverse correlation was observed between proapoptotic protein levels and behavioural deficits in the mice. Our findings suggest that JNJ may attenuate brain apoptosis in vivo, as previously described in cell cultures, providing a link between neuropathological deficits and SZ symptomatology.

Transcriptional and Translational Regulation of Differentially Expressed Genes in Yucatan Miniswine Brain Tissues following Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of morbidity, disability, and mortality worldwide. Motor and cognitive deficits and emotional disturbances are long-term consequences of TBI. A lack of effective treatment for TBI-induced neural damage, functional impairments, and cognitive deficits makes it challenging in the recovery following TBI. One of the reasons may be the lack of knowledge underlying the complex pathophysiology of TBI and the regulatory factors involved in the cellular and molecular mechanisms of inflammation, neural regeneration, and injury repair. These mechanisms involve a change in the expression of various proteins encoded by genes whose expression is regulated by transcription factors (TFs) at the transcriptional level and microRNA (miRs) at the mRNA level. In this pilot study, we performed the RNA sequencing of injured tissues and non-injured tissues from the brain of Yucatan miniswine and analyzed the sequencing data for differentially expressed genes (DEGs) and the TFs and miRs regulating the expression of DEGs using in-silico analysis. We also compared the effect of the electromagnetic field (EMF) applied to the injured miniswine on the expression profile of various DEGs. The results of this pilot study revealed a few DEGs that were significantly upregulated in the injured brain tissue and the EMF stimulation showed effect on their expression profile.

Cognitive impairment is associated with BDNF-TrkB signaling mediating synaptic damage and reduction of amino acid neurotransmitters in heart failure

Heart failure (HF) is often accompanied by cognitive impairment (CI). Brain-derived neurotrophic factor (BDNF) deficiency is closely associated with CI. However, the role and mechanism of BDNF in HF with CI is still not fully understood. Here, the case-control study was designed including 25 HF without CI patients (HF-NCI) and 50 HF with CI patients (HF-CI) to investigate the predictive value of BDNF in HF-CI while animal and cell experiments were used for mechanism research. Results found that BDNF levels in serum neuronal-derived exosomes were downregulated in HF-CI patients. There was no significant difference in serum BDNF levels among the two groups. HF rats showed obvious impairment in learning and memory; also, they had reduced thickness and length of postsynaptic density (PSD) and increased synaptic cleft width. Expression of BDNF, TrkB, PSD95, and VGLUT1 was significantly decreased in HF rats brain. In addition, compared with sham rats, amino acids were significantly reduced with no changes in the acetylcholine and monoamine neurotransmitters. Further examination showed that the number of synaptic bifurcations and the expression of BDNF, TrkB, PSD95, and VGLUT1 were all decreased in the neurons that interfered with BDNF-siRNA compared with those in the negative control neurons. Together, our results demonstrated that neuronal-derived exosomal BDNF act as effective biomarkers for prediction of HF-CI. The decrease of BDNF in the brain triggers synaptic structural damage and a decline in amino acid neurotransmitters via the BDNF-TrkB-PSD95/VGLUT1 pathway. This discovery unveils a novel pathological mechanism underlying cognitive impairment following heart failure.

Dexmedetomidine alleviates cognitive impairment by promoting hippocampal neurogenesis via BDNF/TrkB/CREB signaling pathway in hypoxic-ischemic neonatal rats

AIMS

Dexmedetomidine (DEX) has been reported to alleviate hypoxic-ischemic brain damage (HIBD) in neonates. This study aimed to investigate whether DEX improves cognitive impairment by promoting hippocampal neurogenesis via the BDNF/TrkB/CREB signaling pathway in neonatal rats with HIBD.

METHODS

HIBD was induced in postnatal day 7 rats using the Rice-Vannucci method, and DEX (25 μg/kg) was administered intraperitoneally immediately after the HIBD induction. The BDNF/TrkB/CREB pathway was regulated by administering the TrkB receptor antagonist ANA-12 through intraperitoneal injection or by delivering adeno-associated virus (AAV)-shRNA-BDNF via intrahippocampal injection. Western blot was performed to measure the levels of BDNF, TrkB, and CREB. Immunofluorescence staining was utilized to identify the polarization of astrocytes and evaluate the levels of neurogenesis in the dentate gyrus of the hippocampus. Nissl and TTC staining were performed to evaluate the extent of neuronal damage. The MWM test was conducted to evaluate spatial learning and memory ability.

RESULTS

The levels of BDNF and neurogenesis exhibited a notable decrease in the hippocampus of neonatal rats after HIBD, as determined by RNA-sequencing technology. Our results demonstrated that treatment with DEX effectively increased the protein expression of BDNF and the phosphorylation of TrkB and CREB, promoting neurogenesis in the dentate gyrus of the hippocampus in neonatal rats with HIBD. Specifically, DEX treatment significantly augmented the expression of BDNF in hippocampal astrocytes, while decreasing the proportion of detrimental A1 astrocytes and increasing the proportion of beneficial A2 astrocytes in neonatal rats with HIBD. Furthermore, inhibiting the BDNF/TrkB/CREB pathway using either ANA-12 or AAV-shRNA-BDNF significantly counteracted the advantageous outcomes of DEX on hippocampal neurogenesis, neuronal survival, and cognitive improvement.

CONCLUSIONS

DEX promoted neurogenesis in the hippocampus by activating the BDNF/TrkB/CREB pathway through the induction of polarization of A1 astrocytes toward A2 astrocytes, subsequently mitigating neuronal damage and cognitive impairment in neonates with HIBD.

Exploring the Neuroprotective Effects of Lithium in Ischemic Stroke: A literature review

Ischemic stroke ranks among the foremost clinical causes of mortality and disability, instigating neuronal degeneration, fatalities, and various sequelae. While standard treatments, such as intravenous thrombolysis and endovascular thrombectomy, prove effective, they come with limitations. Hence, there is a compelling need to develop neuroprotective agents capable of improving the functional outcomes of the nervous system. Numerous preclinical studies have demonstrated that lithium can act in multiple molecular pathways, including glycogen synthase kinase 3(GSK-3), the Wnt signaling pathway, the mitogen-activated protein kinase (MAPK)/ extracellular signal-regulated kinase (ERK) signaling pathway, brain-derived neurotrophic factor (BDNF), mammalian target of rapamycin (mTOR), and glutamate receptors. Through these pathways, lithium has been shown to affect inflammation, autophagy, apoptosis, ferroptosis, excitotoxicity, and other pathological processes, thereby improving central nervous system (CNS) damage caused by ischemic stroke. Despite these promising preclinical findings, the number of clinical trials exploring lithium's efficacy remains limited. Additional trials are imperative to thoroughly ascertain the effectiveness and safety of lithium in clinical settings. This review delineates the mechanisms underpinning lithium's neuroprotective capabilities in the context of ischemic stroke. It elucidates the intricate interplay between these mechanisms and sheds light on the involvement of mitochondrial dysfunction and inflammatory markers in the pathophysiology of ischemic stroke. Furthermore, the review offers directions for future research, thereby advancing the understanding of the potential therapeutic utility of lithium and establishing a theoretical foundation for its clinical application.

Maternal diabetes decreases the expression of GABAAα1, GABAB1, and mGlu2 receptors in the visual cortex of male rat neonates

AIMS

This study examines the impact of maternal diabetes on the expression of GABAB1, GABAAα1, and mGlu2 receptors in the primary visual cortex layers of male rat newborns.

MAIN METHODS

In diabetic group (Dia), diabetes was induced in adult female rats using an intraperitoneal dose of Streptozotocin (STZ) 65 (mg/kg). Diabetes was managed by daily subcutaneous injection of NPH insulin in insulin-treated diabetic group (Ins). Control group (Con) received normal saline intraperitoneally rather than STZ. Male offspring born to each group of female rats were euthanized via CO2 inhalation at P0, P7, and P14 days after delivery and the expression of GABAB1, GABAAα1, and mGlu2 receptors in their primary visual cortex was determined using immunohistochemistry (IHC).

KEY FINDINGS

The expression of GABAB1, GABAAα1, and mGlu2 receptors increased gradually with age in the male offspring born to Con group while the highest expression was detected in layer IV of the primary visual cortex. In Dia group newborns, the expression of these receptors was significantly reduced in all layers of the primary visual cortex at every three days. Insulin treatment in diabetic mothers restored the expression of these receptors to normal levels in their newborns.

SIGNIFICANCE

The study indicates that diabetes reduces the expression of GABAB1, GABAAα1, and mGlu2 receptors in the primary visual cortex of male offspring born to diabetic rats at P0, P7, and P14. However, insulin treatment can counteract these effects.

Salidroside intensifies mitochondrial function of CoCl2-damaged HT22 cells by stimulating PI3K-AKT-MAPK signaling pathway

BACKGROUND

Salidroside (Sal), an active component from Rhodiola crenulata, has been confirmed to exert neuroprotective effects against hypoxia. However, its molecular mechanisms of intensifying mitochondrial function still largely unknown. In the present study, we aimed to explore the mechanisms by which Sal heightened mitochondrial function in CoCl₂-induced HT22 hypoxic injury.

METHODS

The hypoxic condition of HT22 cells was performed by CoCl₂ stimulus. We then investigated the effects of Sal on the viability of hypoxic HT22 cells by cell counting kit-8. The contents of lactate dehydrogenase (LDH) release in cultured supernatant were detected by using commercial biochemical kit. Superoxide free radical scavenging activity, total antioxidant capacity assay kit with ferric reducing ability of plasma and 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) methods were employed to detect the free radical scavenging ability and antioxidant capacity of Sal. Meanwhile, intracellular reactive oxygen species (ROS), Ca2+ and mitochondrial membrane potential (MMP) were determined by corresponding specific labeled probes. Mitochondrial morphology was tested by Mito-tracker green with confocal microscopy. Hoechst 33342 and Annexin V-FITC/propidium iodide staining were also employed to evaluate the effect of Sal on cell apoptosis. Oxygen consumption rate (OCR), real-time ATP production and proton efflux rate were measured using a Seahorse analyzer. Additionally, the potential interactions of Sal with PI3K-AKT signaling pathway-related proteins were predicted and tested by molecular docking, molecular dynamics simulation (MDS) and localized surface plasmon resonance (LSPR) techniques, respectively. Furthermore, the protein levels of p-PI3K, PI3K, p-AKT, AKT, p-JNK, JNK, p-p38 and p38 were estimated by western blot analysis.

RESULTS

Sal alleviated CoCl2-induced hypoxic injury in HT22 cells as evidenced by increased cell viability and decreased LDH release. In vitro antioxidant test confirmed that Sal had marvelous antioxidant abilities. The protected mitochondrial function by Sal treatment was illustrated by the decrease of ROS, Ca2+, mitochondrial fragment and the increase of MMP. In addition, Sal ameliorated the apoptosis of HT22 cells by decreasing Hoechst 33342 positive cells and the rate of apoptotic cells. Enhancement of energy metabolism in HT22 by Sal was demonstrated by increased OCR, real-time ATP generation and proton efflux rate. The molecular docking confirmed the potential binding of Sal to PI3K, AKT and CaMK II proteins with calculated binding energy of -1.32, -4.21 and -4.38 kcal/mol, respectively. The MDS test revealed the average hydrogen bond of complex Sal-PI3K and Sal-AKT were 0.79 and 4.46, respectively. The results of LSPR verified the potential binding of Sal to proteins PI3K, AKT and HIF-1α with affinity values of 5.20 × 10 - 3, 2.83 × 10 - 3 and 3.97 × 10 - 3 KD, respectively. Western blot analysis further argued that Sal consolidated the levels of p-PI3K and p-AKT. Meanwhile, Sal could downregulate the proteins expression of p-JNK and p-p38.

CONCLUSION

Collectively, our findings suggested that Sal can intensify mitochondrial function of CoCl2-simulated hypoxia injury in HT22 cells by stimulating PI3K-AKT-MAPK signaling pathway. Sal is a potential agent for mitochondrial protection against hypoxia with the underlying molecular mechanisms of energy metabolism being further elucidated.

Overexpression of Brain- and Glial Cell Line-Derived Neurotrophic Factors Is Neuroprotective in an Animal Model of Acute Hypobaric Hypoxia

Currently, the role of the neurotrophic factors BDNF and GDNF in maintaining the brain’s resistance to the damaging effects of hypoxia and functional recovery of neural networks after exposure to damaging factors are actively studied. The assessment of the effect of an increase in the level of these neurotrophic factors in brain tissues using genetic engineering methods on the resistance of laboratory animals to hypoxia may pave the way for the future clinical use of neurotrophic factors BDNF and GDNF in the treatment of hypoxic damage. This study aimed to evaluate the antihypoxic and neuroprotective properties of BDNF and GDNF expression level increase using adeno-associated viral vectors in modeling hypoxia in vivo. To achieve overexpression of neurotrophic factors in the central nervous system’s cells, viral constructs were injected into the brain ventricles of newborn male C57Bl6 (P0) mice. Acute hypobaric hypoxia was modeled on the 30th day after the injection of viral vectors. Survival, cognitive, and mnestic functions in the late post-hypoxic period were tested. Evaluation of growth and weight characteristics and the neurological status of animals showed that the overexpression of neurotrophic factors does not affect the development of mice. It was found that the use of adeno-associated viral vectors increased the survival rate of male mice under hypoxic conditions. The present study indicates that the neurotrophic factors’ overexpression, induced by the specially developed viral constructs carrying the BDNF and GDNF genes, is a prospective neuroprotection method, increasing the survival rate of animals after hypoxic injury.