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 m RNA expression levels of BDNF and its processing enzymes and receptors(Furin, matrix metallopeptidase 9, tissuetype 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 m RNAs 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.

Offspring of rats with cerebral hypoxia-ischemia manifest cognitive dysfunction in learning and memory abilities

Neonatal hypoxic-ischemic encephalopathy is a serious neurological disease,often resulting in long-term neurodevelopmental disorders among surviving children.However,whether these neurodevelopmental issues can be passed to offspring remains unclear.The right common carotid artery of 7-day-old parental-generation rats was subjected to permanent ligation using a vessel electrocoagulator.Neonatal hypoxic-ischemic rat models were established by subjecting the rats to 8%O2–92%N2 for 2 hours.The results showed that 24 hours after hypoxia and ischemia,pathological damage,cerebral atrophy,liquefaction,and impairment were found,and Zea-Longa scores were significantly increased.The parental-generation rats were propagated at 3 months old,and offspring were obtained.No changes in the overall brain structures of these offspring rats were identified by magnetic resonance imaging.However,the escape latency was longer and the number of platform crossings was reduced among these offspring compared with normal rats.These results indicated that the offspring of hypoxic-ischemic encephalopathy model rats displayed cognitive impairments in learning and memory.This study was approved by the Animal Care&Welfare Committee of Kunming Medical University,China in 2018(approval No.kmmu2019072).

Single-nucleotide polymorphism screening and RNA sequencing of key messenger RNAs associated with neonatal hypoxic-ischemia brain damage

A single-nucleotide polymorphism(SNP)is an alteration in one nucleotide in a certain position within a genome.SNPs are associated with disease susceptibility.However,the influences of SNPs on the pathogenesis of neonatal hypoxic-ischemic brain damage remain elusive.Seven-day-old rats were used to establish a hypoxic ischemic encephalopathy model.SNPs and expression profiles of mRNAs were analyzed in hypoxic ischemic encephalopathy model rats using RNA sequencing.Genes exhibiting SNPs associated with hypoxic ischemic encephalopathy were identified and studied by gene ontology and pathway analysis to identify their possible involvement in the disease mechanism.We identified 89 up-regulated genes containing SNPs that were mainly located on chromosome 1 and 2.Gene ontology analysis indicated that the up-regulated genes containing SNPs are mainly involved in angiogenesis,wound healing and glutamatergic synapse and biological processing of calcium-activated chloride channels.Signaling pathway analysis indicated that the differentially expressed genes play a role in glutamatergic synapses,long-term depression and oxytocin signaling.Moreover,intersection analysis of high throughput screening following PubMed retrieval and RNA sequencing for SNPs showed that CSRNP1,DUSP5 and LRRC25 were most relevant to hypoxic ischemic encephalopathy.Significant up-regulation of genes was confirmed by quantitative real-time polymerase chain reaction analysis of oxygen-glucose-deprived human fetal cortical neurons.Our results indicate that CSRNP1,DUSP5 and LRRC25,containing SNPs,may be involved in the pathogenesis of hypoxic ischemic encephalopathy.These findings indicate a novel direction for further hypoxic ischemic encephalopathy research.This animal study was approved on February 5,2017 by the Animal Care and Use Committee of Kunming Medical University,Yunnan Province,China(approval No.kmmu2019038).Cerebral tissue collection from a human fetus was approved on September 30,2015 by the Ethics Committee of Kunming Medical University,China(approval No.2015-9).

Nerve growth factor promotes in vitro proliferation of neural stem cells from tree shrews

Neural stem cells promote neuronal regeneration and repair of brain tissue after injury,but have limited resources and proliferative ability in vivo.We hypothesized that nerve growth factor would promote in vitro proliferation of neural stem cells derived from the tree shrews,a primate-like mammal that has been proposed as an alternative to primates in biomedical translational research.We cultured neural stem cells from the hippocampus of tree shrews at embryonic day 38,and added nerve growth factor（100 μg/L） to the culture medium.Neural stem cells from the hippocampus of tree shrews cultured without nerve growth factor were used as controls.After 3 days,fluorescence microscopy after DAPI and nestin staining revealed that the number of neurospheres and DAPI/nestin-positive cells was markedly greater in the nerve growth factor-treated cells than in control cells.These findings demonstrate that nerve growth factor promotes the proliferation of neural stem cells derived from tree shrews.

Structural insights into substrate recognition and translocation of human peroxisomal ABC transporter ALDP

Dysfunctions of ATP-binding cassette,subfamily D,member 1(ABCD1)cause X-linked adrenoleukodystrophy,a rare neurodegenerative disease that affects all human tissues.Residing in the peroxisome membrane,ABCD1 plays a role in the translocation of very long-chain fatty acids for theirβ-oxidation.Here,the six cryo-electron microscopy structures of ABCD1 in four distinct conformational states were presented.In the transporter dimer,two transmembrane domains form the substrate translocation pathway,and two nucleotide-binding domains form the ATP-binding site that binds and hydrolyzes ATP.The ABCD1 structures provide a starting point for elucidating the substrate recognition and translocation mechanism of ABCD1.Each of the four inward-facing structures of ABCD1 has a vestibule that opens to the cytosol with variable sizes.Hexacosanoic acid(C26:0)-CoA substrate binds to the transmembrane domains(TMDs)and stimulates the ATPase activity of the nucleotide-binding domains(NBDs).W339 from the transmembrane helix 5(TM5)is essential for binding substrate and stimulating ATP hydrolysis by substrate.ABCD1 has a unique C-terminal coiled-coil domain that negatively modulates the ATPase activity of the NBDs.Furthermore,the structure of ABCD1 in the outward-facing state indicates that ATP molecules pull the two NBDs together and open the TMDs to the peroxisomal lumen for substrate release.The five structures provide a view of the substrate transport cycle and mechanistic implication for disease-causing mutations.