Resatorvid protects against hypoxic-ischemic brain damage in neonatal rats

Synergistic anti-oxidant and anti-inflammatory effects of ceria/resatorvid co-decorated nanoparticles for acute lung injury therapy

BACKGROUND

Acute lung injury (ALI) is a critical inflammatory response syndrome that rapidly develops into acute respiratory distress syndrome (ARDS). Currently, no effective therapeutic modalities are available for patients with ALI/ARDS. According to recent studies, inhibiting both the release of pro-inflammatory cytokines and the formation of reactive oxygen species (ROS) as early as possible may be a promising therapy for ALI.

RESULTS

In this study, a ROS-responsive nano-delivery system based on oxidation-sensitive chitosan (Ox-CS) was fabricated for the simultaneous delivery of Ce NPs and RT. The in vitro experiments have shown that the Ox-CS/Ceria-Resatorvid nanoparticles (Ox-CS/CeRT NPs) were rapidly and efficiently internalised by inflammatory endothelial cells. Biological evaluations validated the significant attenuation of ROS-induced oxidative stress and cell apoptosis by Ox-CS/CeRT NPs, while maintaining mitochondrial function. Additionally, Ox-CS/CeRT NPs effectively inhibited the release of pro-inflammatory factors. After intraperitoneal (i.p.) administration, Ox-CS/CeRT NPs passively targeted the lungs of LPS-induced inflamed mice and released the drug activated by the high ROS levels in inflammatory tissues. Finally, Ox-CS/CeRT NPs significantly alleviated LPS-induced lung injury through inhibiting both oxidative stress and pro-inflammatory cytokine expression.

CONCLUSIONS

The created Ox-CS/CeRT NPs could act as a prospective nano-delivery system for a combination of anti-inflammatory and anti-oxidant therapy of ALI.

N6-methyladenosine demethylase FTO regulates synaptic and cognitive impairment by destabilizing PTEN mRNA in hypoxic-ischemic neonatal rats

Hypoxic-ischemic brain damage (HIBD) can result in significant global rates of neonatal death or permanent neurological disability. N6-methyladenosine (m6A) modification of RNA influences fundamental aspects of RNA metabolism, and m6A dysregulation is implicated in various neurological diseases. However, the biological roles and clinical significance of m6A in HIBD remain unclear. We currently evaluated the effect of HIBD on cerebral m6A methylation in RNAs in neonatal rats. The m6A dot blot assay showed a global augmentation in RNA m6A methylation post-HI. Herein, we also report on demethylase FTO, which is markedly downregulated in the hippocampus and is the main factor involved with aberrant m6A modification following HI. By conducting a comprehensive analysis of RNA-seq data and m6A microarray results, we found that transcripts with m6A modifications were more highly expressed overall than transcripts without m6A modifications. The overexpression of FTO resulted in the promotion of Akt/mTOR pathway hyperactivation, while simultaneously inhibiting autophagic function. This is carried out by the demethylation activity of FTO, which selectively demethylates transcripts of phosphatase and tensin homolog (PTEN), thus promoting its degradation and reduced protein expression after HI. Moreover, the synaptic and neurocognitive disorders induced by HI were effectively reversed through the overexpression of FTO in the hippocampus. Cumulatively, these findings demonstrate the functional importance of FTO-dependent hippocampal m6A methylome in cognitive function and provides novel mechanistic insights into the therapeutic potentials of FTO in neonatal HIBD.

Femoral Structure and Biomechanical Characteristics in Sanfilippo Syndrome Type-B Mice

Sanfilippo syndrome Type-B, also known as mucopolysaccharidosis IIIB (MPS IIIB), accounts for approximately one-third of all Sanfilippo syndrome patients and is characterized by a similar natural history as Type-A. Patients suffer from developmental regression, bone malformation, organomegaly, GI distress, and profound neurological deficits. Despite human trials of enzyme replacement therapy (ERT) (SBC-103, AX250) in MPS IIIB, there is currently no FDA approved treatment and a few palliative options. The major concerns of ERT and gene therapy for the treatment of bone malformation are the inadequate biodistribution of the missing enzyme, N-acetyl-α-glucosaminidase (NAGLU), and that the skeleton is a poorly hit target tissue in ERT and gene therapy. Each of the four known human types of MPS III (A, B, C, and D) is usually regarded as having mild bone manifestations, yet it remains poorly characterized. This study aimed to determine bone mineral content (BMC), volumetric bone mineral density (vBMD), and biomechanical properties in femurs MPS IIIB C57BL/6 mice compared to phenotypic control C57BL/6 mice. Significant differences were observed in MPS IIIB mice within various cortical and cancellous bone parameters for both males and females (p < 0.05). Here, we establish some osteogenic manifestations of MPS IIIB within the mouse model by radiographic and biomechanical tests, which are also differentially affected by age and sex. This suggests that some skeletal features of the MPS IIIB mouse model may be used as biomarkers of peripheral disease correction for preclinical treatment of MPS IIIB.

TAK-242, a toll-like receptor 4 antagonist, against brain injury by alleviates autophagy and inflammation in rats

Inhibition of Toll-like receptor 4 (TLR4)-mediated inflammatory pathways exerts a critical effect on neuronal death; therefore, it is a possible new therapeutic approach for traumatic brain injury (TBI). Resatorvid (TAK-242) is a novel small-molecule compound widely used to inhibit TLR4-mediated pathways, but the protective mechanism of TAK-242 in TBI remains unclear. Herein, we analyzed the neuroprotective effects of TAK-242 in rats after TBI. The rat model of brain injury was established using a modified Free-fall device, and the rats were injected with TAK-242 (0.5 mg/kg) through the caudal vein before TBI. The rats were allocated into four groups: a sham group, a TBI group, a TBI + vehicle group, and a TBI + TAK-242 group. The brain tissue was extracted for histology and determination of the expression of autophagy-related proteins and inflammatory mediators. TAK-242 pretreatment significantly reduced the damage to hippocampal neurons. Neuronal autophagy increased after brain injury, whereas TAK-242 significantly reduced autophagy marker protein LC3-II in the hippocampus. In addition, TAK-242 pretreatment significantly downregulated NF-κB p65, TNF-α, and IL-1β in the hippocampus. In conclusion, TAK-242 significantly reduced hippocampal neuronal damage by inhibiting autophagy and neuroinflammatory activity, possibly via the NF-κB signaling pathway.

Xenon attenuates hypoxic-ischemic brain damage by inhibiting autophagy in neonatal rats

Xenon (Xe) is an inert, colorless and odorless heavy gas and has many biological functions. However, little is known about whether and how Xe can modulate hypoxic-ischemic brain damage (HIBD) in neonatal rats. This study employed a neonatal rat model to explore the potential effect of Xe on neuron autophagy and the severity of HIBD. Neonatal Sprague-Dawley rats were subjected to HIBD, randomized and treated with Xe or mild hypothermia (at 32 °C) for 3 h. The degrees of HIBD, neuron autophagy and the neuronal functions in some neonates from each group were tested by histopathology, immunochemistry, transmission electron microscopy, western blot, open-field and Trapeze tests at 3 and 28 days post-induction of HIBD, respectively. Compared with the Sham group, hypoxic-ischemia caused larger volumes of cerebral infarction and severe brain damage, and increased autophagosome formation and Beclin-1 and microtubule-associated protein 1A/1B-light chain 3 class II (LC3-II) expression in the brain of rats, accompanied by the defect in neuronal functions. In contrast, treatment with Xe and/or hypothermia significantly reduced infarct volumes and ameliorated neurological defects in the HIBD rats, particularly for the combination of Xe and hypothermia. Xe significantly mitigated the relative levels of Beclin-1 and LC3-II expression and autophagosome formation induced by HIBD in rats. Xe acted as a neuroprotective factor against HIBD, possibly by inhibiting the hypoxia-induced neuron autophagy in rats.

Up-regulating microRNA-214-3p relieves hypoxic-ischemic brain damage through inhibiting TXNIP expression

A list of microRNAs (miRs) has been referred to involve in the development of hypoxic-ischemic brain damage (HIBD). Based on that, we probed the concrete role of miR-214-3p regulating thioredoxin-interacting protein (TXNIP) in the illness. A neonatal HIBD mouse model was established using the Rice-Vannucci method, followed by measurements of miR-214-3p and TXNIP levels in brain tissues. After modeling, mice were given brain injection of the compounds that could alter miR-214-3p and TXNIP expression. Afterward, neurological function, neuronal inflammation, neuronal apoptosis, neuron morphology, and the number of Nissl body were assessed in HIBD mice. The binding of miR-214-3p to TXNIP was analyzed. Lower miR-214-3p and higher TXNIP were analyzed in brain tissues of mice with HIBD. Up-regulating miR-214-3p or depleting TXNIP improved neurological function, reduced neuronal inflammation and neuronal apoptosis, attenuated morphological damage of neurons, and increased the number of Nissl bodies in mice with HIBD. TXNIP was targeted by miR-214-3p and overexpressing TXNIP reversed the therapeutic effect of miR-214-3p on HIBD mice. It is noted that promotion of miR-214-3p relieves HIBD in mice through inhibiting TXNIP expression.

Mfsd2a attenuated hypoxic-ischemic brain damage via protection of the blood-brain barrier in mfat-1 transgenic mice

Previous studies have shown that mfat-1 transgenic mice have protective effects against some central nervous system (CNS) disorders, owing to the high docosahexaenoic acid (DHA) content enriched in their brains. However, whether this protective effect is connected to the blood-brain barrier (BBB) remains unclear. This study aims to investigate the mechanisms of the protective effect against hypoxic-ischemic brain damage (HIBD) of mfat-1 transgenic mice. mfat-1 mice not only demonstrated a significant amelioration of neurological dysfunction and neuronal damage but also partly maintained the physiological permeability of the BBB after HIBD. We initially showed this was associated with elevated major facilitator superfamily domain-containing 2a (Mfsd2a) expression on the BBB, resulting from more lysophosphatidylcholine (LPC)-DHA entering the brain. Wild-type (WT) mice showed a similar Mfsd2a expression trend after long-term feeding with an LPC-DHA-rich diet. Knockdown of Mfsd2a by siRNA intra-cerebroventricular (ICV) injection neutralized the protective effect against HIBD-induced BBB disruption in mfat-1 mice, further validating the protective function of Mfsd2a on BBB. HIBD-induced BBB high permeability was attenuated by Mfsd2a, primarily through a transcellular pathway to decrease caveolae-like vesicle-mediated transcytosis. Taken together, these findings not only reveal that mfat-1 transgenic mice have higher expression of Mfsd2a on the BBB, which partly sustains BBB permeability via vesicular transcytosis to alleviate the severity of HIBD, but also suggest that dietary intake of LPC-DHA may upregulate Mfsd2a expression as a novel therapeutic strategy for BBB dysfunction and survival in HIBD patients.

Identification of Lipocalin 2 as a Ferroptosis-Related Key Gene Associated with Hypoxic-Ischemic Brain Damage via STAT3/NF-κB Signaling Pathway

Hypoxic-ischemic brain damage (HIBD) is a common cause of death or mental retardation in newborns. Ferroptosis is a novel form of iron-dependent cell death driven by lipid peroxidation, and recent studies have confirmed that ferroptosis plays an important role in the development of HIBD. However, HIBD ferroptosis-related biomarkers remain to be discovered. An artificial neural network (ANN) was established base on differentially expressed genes (DEGs) related to HIBD and ferroptosis and validated by external dataset. The protein-protein interaction (PPI) network, support vector machine-recursive feature elimination (SVM-RFE) algorithms, and random forest (RF) algorithm were utilized to identify core genes of HIBD. An in vitro model of glutamate-stimulated HT22 cell HIBD was constructed, and glutamate-induced ferroptosis and mitochondrial structure and function in HT22 cells were examined by propidium iodide (PI) staining, flow cytometry, Fe²⁺ assay, Western blot, JC-1 kit, and transmission electron microscopy (TEM). In addition, Western blot and immunofluorescence assays were used to detect the NF-κB/STAT3 pathway. An HIBD classification model was constructed and presented excellent performance. The PPI network and two machine learning algorithms indicated two hub genes in HIBD. Lipocalin 2 (LCN2) was the core gene correlated with the risk of HIBD according to the results of differential expression analysis and logistic regression diagnostics. Subsequently, we verified in an in vitro model that LCN2 is highly expressed in glutamate-induced ferroptosis in HT22 cells. More importantly, LCN2 silencing significantly inhibited glutamate-stimulated ferroptosis in HT22 cells. We also found that glutamate-stimulated HT22 cells produced mitochondrial dysfunction. Furthermore, in vitro experiments confirmed that NF-κB and STAT3 were activated and that silencing LCN2 could have the effect of inhibiting their activation. In short, our findings reveal a molecular mechanism by which LCN2 may promote ferroptosis in HIBD through activation of the NF-κB/STAT3 pathway, providing new and unique insights into LCN2 as a biomarker for HIBD and suggesting new preventive and therapeutic strategies for HIBD.

Effect of Hypoxia-Ischemia on the Expression of Iron-Related Proteins in Neonatal Rat Brains

Hypoxic-ischemic white matter injury (WMI) pathogenesis in preterm infants is not well established, and iron-related proteins in the brain may play an important role in imbalanced iron metabolism. We aimed to investigate the iron-related protein changes in neonatal rats after hypoxia-ischemia (HI), clarify the role of iron-related proteins in hypoxic-ischemic WMI, and potentially provide a new target for the clinical treatment of hypoxic-ischemic WMI in preterm infants. We adopted a WMI animal model of bilateral common carotid artery electrocoagulation combined with hypoxia in neonatal 3-day-old Sprague-Dawley rats. We observed basic myelin protein (MBP) and iron-related protein expression in the brain (ferritin, transferrin receptor [TfR], and membrane iron transporter 1 [FPN1]) via Western blot and double immunofluorescence staining. The expression of MBP in the WMI group was significantly downregulated on postoperative days (PODs) 14, 28, and 56. Ferritin levels were significantly increased on PODs 3, 7, 14, and 28 and were most significant on POD 28, returning to the sham group level on POD 56. FPN1 levels were significantly increased on PODs 7, 28, and 56 and were still higher than those in the sham group on POD 56. TfR expression was significantly upregulated on PODs 1, 7, and 28 and returned to the sham group level on POD 56. Immunofluorescence staining showed that ferritin, TfR, and FPN1 were expressed in neurons, blood vessels, and oligodendrocytes in the cortex and corpus callosum on POD 28. Compared with the sham group, the immune-positive markers of three proteins in the WMI group were significantly increased. The expression of iron-related proteins in the brain (ferritin, FPN1, and TfR) showed spatiotemporal dynamic changes and may play an important role in hypoxic-ischemic WMI.

Systematic analysis of critical genes and pathways identified a signature of neuropathic pain after spinal cord injury

Spinal cord injury (SCI) damages sensory systems, producing chronic neuropathic pain that is resistant to medical treatment. The specific mechanisms underlying SCI-induced neuropathic pain (SCI-NP) remain unclear, and protein biomarkers have not yet been integrated into diagnostic screening. To better understand the host molecular pathways involved in SCI-NP, we used the bioinformatics method, the PubMed database, and bioinformatics methods to identify target genes and their associated pathways. We reviewed 2504 articles on the regulation of SCI-NP and used the text mining of PubMed database abstracts to determine associations among 12 pathways and networks. Based on this method, we identified two central genes in SCI-NP: interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Adult male Sprague-Dawley rats were used to build the SCI-NP models. The threshold for paw withdrawal was significantly reduced in the SCI group and TLR4 was activated in microglia after SCI. ELISA analysis of TNF-α and IL-6 levels was significantly higher in the SCI group than in the sham group. Western blot showed that expressions of the TLR4/MyD88/NF-κB inflammatory pathway protein increased dramatically in the SCI group. Using the TLR4 inhibitor TAK-242, the pain threshold and expressions of inflammatory factors and proteins of the proteins of the inflammatory signal pathway were reversed, TLR4 in microglia was suppressed, suggesting that SCI-NP was related to neuroinflammation mediated by the TLR4 signaling pathway. In conclusion, we found TNF-α and IL-6 were the neuroinflammation-related genes involved in SCI-NP that can be alleviated by inhibiting the inflammatory pathway upstream of the TLR4/MyD88/NF-κB inflammatory pathway.

Stellate ganglion block reduces inflammation and improves neurological function in diabetic rats during ischemic stroke

Diabetes mellitus is an independent risk factor for ischemic stroke. Both diabetes mellitus and stroke are linked to systemic inflammation that aggravates patient outcomes. Stellate ganglion block can effectively regulate the inflammatory response. Therefore, it is hypothesized that stellate ganglion block could be a potential therapy for ischemic stroke in diabetic subjects. In this study, we induced diabetes mellitus in rats by feeding them a high-fat diet for 4 successive weeks. The left middle cerebral artery was occluded to establish models of ischemic stroke in diabetic rats. Subsequently, we performed left stellate ganglion block with 1% lidocaine using the percutaneous posterior approach 15 minutes before reperfusion and again 20 and 44 hours after reperfusion. Our results showed that stellate ganglion block did not decrease the blood glucose level in diabetic rats with diabetes mellitus but did reduce the cerebral infarct volume and the cerebral water content. It also improved the recovery of neurological function, increased 28-day survival rate, inhibited Toll like receptor 4/nuclear factor kappa B signaling pathway and reduced inflammatory response in the plasma of rats. However, injection of Toll like receptor 4 agonist lipopolysaccharide 5 minutes before stellate ganglion block inhibited the effect of stellate ganglion block, whereas injection of Toll like receptor 4 inhibitor TAK242 had no such effect. We also found that stellate ganglion block performed at night had no positive effect on diabetic ischemic stroke. These findings suggest that stellate ganglion block is a potential therapy for diabetic ischemic stroke and that it may be mediated through the Toll like receptor 4/nuclear factor kappa B signaling pathway. We also found that the therapeutic effect of stellate ganglion block is affected by circadian rhythm.

Long Non-coding RNA Peg13 Alleviates Hypoxic-Ischemic Brain Damage in Neonatal Mice via miR-20a-5p/XIAP Axis

Long noncoding RNA (LncRNA) Peg13 has been demonstrated to protect against neurological diseases. However, its underlying mechanism in the progression of hypoxic-ischemic brain damage (HIBD) has not been well investigated. The expression of target genes was determined in neonatal mice with HIBD and in mouse hippocampal neurons during oxygen-glucose deprivation (OGD) using quantitative real-time PCR (qRT-PCR) and immunoblotting. Functional assays, including CCK-8 cell viability and apoptotic cell detection using TdT mediated dUTP nick ending labeling (TUNEL) assay were used to examine the neuroprotective role of Peg13 in mouse hippocampal neurons. Luciferase assays were performed to determine the regulatory mechanism of Peg13 in OGD-induced neuronal apoptosis. Peg13 was reduced in HIBD mice and OGD-treated mouse hippocampal neurons. Altered Peg13 expression relieved OGD-induced neuronal apoptosis. Mechanistically, Peg13 may serve as a sponge for miR-20a-5p to increase the expression of X chromosome-linked inhibitor of apoptosis (XIAP), a downstream target of miR-20a-5p. Our study showed that Peg13 fulfilled its anti-apoptotic function in neurons through suppressing XIAP expression by sponging miR-20a-5p. Together, Peg13 binds to miR-20a-5p to upregulate XIAP and alleviate HIBD in neonatal mice. The Peg13/miR-20a-5p/XIAP competing endogenous RNA (ceRNA) axis could be a potential therapeutic target for HIBD.

Inhibition of TLR4 prevents hippocampal hypoxic-ischemic injury by regulating ferroptosis in neonatal rats

Inflammation and cell death play important roles in the pathogenesis of hypoxic-ischemic brain damage (HIBD). Toll-like receptor 4 (TLR4) triggers the activation of the inflammatory pathway. Ferroptosis, a newly identified type of regulated cell death, is implicated in various diseases involving neuronal injury. However, the role of ferroptosis in HIBD has not been elucidated. The objectives of this study were to explore the function and mechanism of TLR4 in neuronal ferroptosis in the context of HIBD. A neonatal rat model of hypoxia-ischemia (HI) and a cell model of oxygen-glucose deprivation (OGD) were employed. TAK-242, a TLR4-specific antagonist, was used to evaluate the effect of TLR4 on neuronal ferroptosis in vivo. A TAK-242 inhibitor and a p38 inhibitor (SB203580) were administered to HT22 hippocampal neurons to explore the association between TLR4 in inflammation and ferroptosis in vitro. The effects of TLR4 on ferroptosis were assessed by the Western blot, real-time PCR, immunofluorescence staining, cell viability and transmission electron microscopy (TEM) assays. HI insult significantly upregulated the TLR4, increased the p53 level, reduced the SLC7A11 and GPX4 levels, and caused mitochondrial damage, thereby inducing neuronal ferroptosis in the hippocampus. Inhibition of TLR4 inhibited the expression of ferroptosis-related proteins, decreased the expression of ferroptosis-related genes and the proinflammatory milieu, attenuated oxidative stress and mitochondrial injury and, finally, ameliorated the activation of hippocampal neuronal ferroptosis following HIBD. Consistent with the results of these in vivo experiments, TLR4 inhibition also attenuated OGD-induced ferroptosis by suppressing oxidative stress and p38MAPK signaling, ultimately increasing neuronal cell viability. Finally, the in vitro and in vivo results demonstrated that TAK-242 exerted neuroprotective and antiferroptotic effects by suppressing TLR4-p38 MAPK signaling. TLR4 activation induced neuronal ferroptosis following both HIBD and OGD. Inhibition of TLR4 attenuated oxidative stress-induced damage, decreased the activation of ferroptosis, and attenuated neuroinflammation following HIBD. In this study, we demonstrated that the inhibition of TLR4-p38 MAPK signaling modulates HIBD- or OGD-induced ferroptosis in neuronal cells and may play a novel role in brain homeostasis.

The role of pineal microRNA-325 in regulating circadian rhythms after neonatal hypoxic-ischemic brain damage

Circadian rhythm disorder is a common, but often neglected, consequence of neonatal hypoxic-ischemic brain damage (HIBD). However, the underlying molecular mechanisms remain largely unknown. We previously showed that, in a rat model of HIBD, up-regulation of microRNA-325 (miR-325) in the pineal gland is responsible for the suppression of Aanat, a key enzyme involved in melatonin synthesis and circadian rhythm regulation. To better understand the mechanism by which miR-325 affects circadian rhythms in neonates with HIBD, we compared clinical samples from neonates with HIBD and samples from healthy neonates recruited from the First Affiliated Hospital of Soochow University (Dushuhu Branch) in 2019. We found that circulating miR-325 levels correlated positively with the severity of sleep and circadian rhythm disorders in neonates with HIBD. Furthermore, a luciferase reporter gene assay revealed that LIM homeobox 3 (LHX3) is a novel downstream target of miR-325. In addition, in miR-325 knock-down mice, the transcription factor LHX3 exhibited an miR-325-dependent circadian pattern of expression in the pineal gland. We established a neonatal mouse model of HIBD by performing double-layer ligation of the left common carotid artery and exposing the pups to a low-oxygen environment for 2 hours. Lhx3 mRNA expression was significantly down-regulated in these mice and partially rescued in miR-325 knockout mice subjected to the same conditions. Finally, we showed that improvement in circadian rhythm-related behaviors in animals with HIBD was dependent on both miR-325 and LHX3. Taken together, our findings suggest that the miR-325-LHX3 axis is responsible for regulating circadian rhythms and provide novel insights into the identification of potential therapeutic targets for circadian rhythm disorders in patients with neonatal HIBD. The clinical trial was approved by Institutional Review Board of Children's Hospital of Soochow University (approval No. 2015028) on July 20, 2015. Animal experiments were approved by Animal Care and Use Committee, School of Medicine, Soochow University, China (approval No. XD-2016-1) on January 15, 2016.

TP53-induced glycolysis and apoptosis regulator alleviates hypoxia/ischemia-induced microglial pyroptosis and ischemic brain damage

Our previous studies have demonstrated that TP53-induced glycolysis and apoptosis regulator (TIGAR) can protect neurons after cerebral ischemia/reperfusion. However, the role of TIGAR in neonatal hypoxic-ischemic brain damage (HIBD) remains unknown. In the present study, 7-day-old Sprague-Dawley rat models of HIBD were established by permanent occlusion of the left common carotid artery followed by 2-hour hypoxia. At 6 days before induction of HIBD, a lentiviral vector containing short hairpin RNA of either TIGAR or gasdermin D (LV-sh_TIGAR or LV-sh_GSDMD) was injected into the left lateral ventricle and striatum. Highly aggressively proliferating immortalized (HAPI) microglial cell models of in vitro HIBD were established by 2-hour oxygen/glucose deprivation followed by 24-hour reoxygenation. Three days before in vitro HIBD induction, HAPI microglial cells were transfected with LV-sh_TIGAR or LV-sh_GSDMD. Our results showed that TIGAR expression was increased in the neonatal rat cortex after HIBD and in HAPI microglial cells after oxygen/glucose deprivation/reoxygenation. Lentivirus-mediated TIGAR knockdown in rats markedly worsened pyroptosis and brain damage after hypoxia/ischemia in vivo and in vitro. Application of exogenous nicotinamide adenine dinucleotide phosphate (NADPH) increased the NADPH level and the glutathione/oxidized glutathione ratio and decreased reactive oxygen species levels in HAPI microglial cells after oxygen/glucose deprivation/reoxygenation. Additionally, exogenous NADPH blocked the effects of TIGAR knockdown in neonatal HIBD in vivo and in vitro. These findings show that TIGAR can inhibit microglial pyroptosis and play a protective role in neonatal HIBD. The study was approved by the Animal Ethics Committee of Soochow University of China (approval No. 2017LW003) in 2017.

Magnet-targeted delivery of bone marrow-derived mesenchymal stem cells improves therapeutic efficacy following hypoxic-ischemic brain injury

Stem cell transplantation may represent a feasible therapeutic option for the recovery of neurological function in children with hypoxic-ischemic brain injury; however, the therapeutic efficacy of bone marrow-derived mesenchymal stem cells largely depends on the number of cells that are successfully transferred to the target. Magnet-targeted drug delivery systems can use a specific magnetic field to attract the drug to the target site, increasing the drug concentration. In this study, we found that the double-labeling using superparamagnetic iron oxide nanoparticle and poly-L-lysine (SPIO-PLL) of bone marrow-derived mesenchymal stem cells had no effect on cell survival but decreased cell proliferation 48 hours after labeling. Rat models of hypoxic-ischemic brain injury were established by ligating the left common carotid artery. One day after modeling, intraventricular and caudal vein injections of 1 × 10⁵ SPIO-PLL-labeled bone marrow-derived mesenchymal stem cells were performed. Twenty-four hours after the intraventricular injection, magnets were fixed to the left side of the rats’ heads for 2 hours. Intravoxel incoherent motion magnetic resonance imaging revealed that the perfusion fraction and the diffusion coefficient of rat brain tissue were significantly increased in rats treated with SPIO-PLL-labeled cells through intraventricular injection combined with magnetic guidance, compared with those treated with SPIO-PLL-labeled cells through intraventricular or tail vein injections without magnetic guidance. Hematoxylin-eosin and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining revealed that in rats treated with SPIO-PLL-labeled cells through intraventricular injection under magnetic guidance, cerebral edema was alleviated, and apoptosis was decreased. These findings suggest that targeted magnetic guidance can be used to improve the therapeutic efficacy of bone marrow-derived mesenchymal stem cell transplantation for hypoxic-ischemic brain injury. This study was approved by the Animal Care and Use Committee of The Second Hospital of Dalian Medical University, China (approval No. 2016-060) on March 2, 2016.

Brain-derived neurotrophic factor and its related enzymes and receptors play important roles after hypoxic-ischemic brain damage

Brain-derived neurotrophic factor (BDNF) regulates many neurological functions and plays a vital role during the recovery from central nervous system injuries. However, the changes in BDNF expression and associated factors following hypoxia-ischemia induced neonatal brain damage, and the significance of these changes are not fully understood. In the present study, a rat model of hypoxic-ischemic brain damage was established through the occlusion of the right common carotid artery, followed by 2 hours in a hypoxic-ischemic environment. Rats with hypoxic-ischemic brain damage presented deficits in both sensory and motor functions, and obvious pathological changes could be detected in brain tissues. The mRNA expression levels of BDNF and its processing enzymes and receptors (Furin, matrix metallopeptidase 9, tissue-type plasminogen activator, tyrosine Kinase receptor B, plasminogen activator inhibitor-1, and Sortilin) were upregulated in the ipsilateral hippocampus and cerebral cortex 6 hours after injury; however, the expression levels of these mRNAs were found to be downregulated in the contralateral hippocampus and cerebral cortex. These findings suggest that BDNF and its processing enzymes and receptors may play important roles in the pathogenesis and recovery from neonatal hypoxic-ischemic brain damage. This study was approved by the Animal Ethics Committee of the University of South Australia (approval No. U12-18) on July 30, 2018.

Transplantation of umbilical cord blood mononuclear cells attenuates the expression of IL-1β via the TLR4/NF-κB pathway in hypoxic-ischemic neonatal rats

Objective:

This study aims to observe the effects of transplantation of umbilical cord blood mononuclear cells (UCBMCs) on the expression of interleukin (IL)-1β and explore the mechanism via the toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) pathway in hypoxic-ischemic neonatal rats.

Methods:

Seven-day-old Sprague-Dawley neonatal rats were randomly divided into Sham, hypoxic-ischemic brain damage (HIBD), and UCBMC groups. The HIBD model was prepared by Rice-Vannucci method, and UCBMC were transplanted 24 h after HIBD in the UCBMC group. At 7 days after transplantation, changes in neurons and the TLR4 protein were examined by neuronal nuclei (NeuN)/TLR4 immunofluorescence staining. The expression of pNF-κB and IL-1β proteins was detected by immunohistochemical staining and enzyme linked immunosorbent assay (ELISA).

Results:

The percentage of NeuN⁺DAPI⁺ cells in the injured cortex in the UCBMC group was significantly higher than that in the HIBD group and lower than that in the Sham group (P < 0.05). The number of NeuN⁺TLR4⁺DAPI⁺cells in the UCBMC group was significantly lower than that in the HIBD group (P < 0.05) but higher than that in the Sham group (P < 0.05). More pNF-κB⁺ cells were observed in the HIBD group than in Sham and UCBMC groups (P < 0.05), and more pNF-κB⁺ cells were observed in the UCBMC group than in the Sham group (P < 0.05). ELISA results showed that the IL-1β expression in the injured cerebral cortex in the UCMBC group was significantly lower than that in the HIBD group but remained higher than that in the Sham group (P < 0.05).

Conclusions:

UCBMC transplantation could inhibit the IL-1β protein expression in the injured cortex, thereby alleviating HIBD in neonatal rats. The underlying mechanism might be associated with the down- regulation of TLR4 and pNF-κB proteins.