Apoptosis-related proteins are potential markers of neonatal hypoxic-ischemic encephalopathy (HIE) injury

PKN1 Exerts Neurodegenerative Effects in an In Vitro Model of Cerebellar Hypoxic-Ischemic Encephalopathy via Inhibition of AKT/GSK3β Signaling

We recently identified protein kinase N1 (PKN1) as a negative gatekeeper of neuronal AKT protein kinase activity during postnatal cerebellar development. The developing cerebellum is specifically vulnerable to hypoxia-ischemia (HI), as it occurs during hypoxic-ischemic encephalopathy, a condition typically caused by oxygen deprivation during or shortly after birth. In that context, activation of the AKT cell survival pathway has emerged as a promising new target for neuroprotective interventions. Here, we investigated the role of PKN1 in an in vitro model of HI, using postnatal cerebellar granule cells (Cgc) derived from Pkn1 wildtype and Pkn1-/- mice. Pkn1-/- Cgc showed significantly higher AKT phosphorylation, resulting in reduced caspase-3 activation and improved survival after HI. Pkn1-/- Cgc also showed enhanced axonal outgrowth on growth-inhibitory glial scar substrates, further pointing towards a protective phenotype of Pkn1 knockout after HI. The specific PKN1 phosphorylation site S374 was functionally relevant for the enhanced axonal outgrowth and AKT interaction. Additionally, PKN1pS374 shows a steep decrease during cerebellar development. In summary, we demonstrate the pathological relevance of the PKN1-AKT interaction in an in vitro HI model and establish the relevant PKN1 phosphorylation sites, contributing important information towards the development of specific PKN1 inhibitors.

Abnormal expression and role of MicroRNA-214-3p/SLC8A1 in neonatal Hypoxic-Ischaemic encephalopathy

Neonatal hypoxic-ischaemic encephalopathy (HIE) refers to brain damage caused by intra-uterine distress and asphyxia/hypoxia during the perinatal and neonatal periods. MicroRNA (MiR)-214-3p plays a critical role in cell growth and apoptosis. The aim of this study was to investigate the expression and role of miR-214-3p in neonatal HIE development, and to explore the underlying mechanisms. The expression of miR-214-3p was significantly down-regulated, while that of Slc8a1, a direct target of miR-214-3p, was significantly up-regulated, in the brain tissue of neonatal HIE rats. The over-expression of miR-214-3p promoted the proliferation and inhibited the apoptosis of neurones, while its down-regulation had the opposite effect. Our results indicate that miR-214-3p expression was down-regulated in neonatal HIE rats, and the up-regulation of miR-214-3p expression protected against HIE development by inhibiting neuronal apoptosis.

Apoptotic Markers in the Midbrain of the Human Neonate After Perinatal Hypoxic/Ischemic Injury

Our previous postmortem studies on neonates with neuropathological injury of perinatal hypoxia/ischemia (PHI) showed a dramatic reduction of tyrosine hydroxylase expression (dopamine synthesis enzyme) in substantia nigra (SN) neurons, with reduction of their cellular size. In order to investigate if the above observations represent an early stage of SN degeneration, we immunohistochemically studied the expression of cleaved caspase-3 (CCP3), apoptosis inducing factor (AIF), and DNA fragmentation by using terminal deoxynucleotidyltransferase-mediated dUTP-biotin 3'-end-labeling (TUNEL) technique in the SN of 22 autopsied neonates (corrected age ranging from 34 to 46.5 gestational weeks), in relation to the severity/duration of PHI injury, as estimated by neuropathological criteria. No CCP3-immunoreactive neurons and a limited number of apoptotic TUNEL-positive neurons with pyknotic characteristics were found in the SN. Nuclear AIF staining was revealed only in few SN neurons, indicating the presence of early signs of AIF-mediated degeneration. By contrast, motor neurons of the oculomotor nucleus showed higher cytoplasmic AIF expression and nuclear translocation, possibly attributed to the combined effect of developmental processes and increased oxidative stress induced by antemortem and postmortem factors. Our study indicates the activation of AIF, but not CCP3, in the SN and oculomotor nucleus of the human neonate in the developmentally critical perinatal period.

Retracted: Protection of miR-19b in hypoxia/reoxygenation-induced injury by targeting PTEN

OBJECTIVE

To study the role and mechanism of microRNA 19b (miR-19b) in hypoxia/reoxygenation (H/R)-induced injury by targeting PTEN.

METHODS

PC12 and BV2 cells induced by H/R were treated with miR-19b mimics/inhibitors or small interfering PTEN (si-PTEN), respectively. Lactate dehydrogenase (LDH) level, malondialdehyde (MDA), and superoxide dismutase (SOD) content was detected. Besides, cell viability and apoptosis were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Hoechst33342 staining, and flow cytometry, whereas mitochondrial membrane potential (MMP) tested by JC-1 assay, and reactive oxygen species (ROS) evaluated by the dichloro-dihydro-fluorescein diacetate assay. The ischemia/reperfusion (I/R) rats model was used to investigate the effects of miR-19b in vivo test. The infarct area and apoptosis rates in brain tissues were detected by 2,3,5-triphenyltetrazolium chloride and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining, respectively. miR-19b and PTEN/PI3K/Akt pathway-related proteins were detected by quantitative reverse-transcription polymerase chain reaction and western blot analysis.

RESULTS

miR-19b mimics could reduce LDH, MDA, and ROS levels and decline cell apoptosis, but enhance the viability, MMP, and SOD activity with decreased PTEN and cleaved caspase, as well as increased p-Akt/Akt and Bcl-2/Bax ratios in H/R-induced PC12 and BV2 cells. However, miR-19b inhibitors led to completely opposite results to aggravate H/R-induced cell injury. Meanwhile, si-PTEN could reverse the effect of miR-19b inhibitors on H/R-induced injury. Moreover, treatment with miR-19b agomir after I/R in vivo sufficiently decreased infarct area and reduced apoptosis rates by targeting PTEN through the regulation of the PI3K/Akt pathway.

CONCLUSION

miR-19b could inhibit oxidative stress, enhance cell MMP, promote cell survival, and inhibit cell apoptosis by targeting PTEN via the regulation of the PI3K/Akt pathway, thus playing the neuronal protective effects.

Decreased expression of ubiquilin‑1 following neonatal hypoxia‑ischemic brain injury in mice

Ubiquilin‑1 (Ubqln), a ubiquitin‑like protein, regulates degradation of misfolded proteins and has been reported to have a crucial role in multiple pathologic and physiologic conditions. The current study was undertaken to investigate the expression of Ubqln in the brain of a neonatal hypoxia‑ischemic (HI) brain injury model induced using the Rice method with some modifications. Mouse pups at postnatal day 7 day were used in this study. Pups underwent permanent ligation of the left common carotid artery and a consecutive hypoxic challenge (8% O2 and 92% N2 for 120 min). The expression of Ubqln in the brain of pups following HI was analyzed by immunofluorescence staining and western blot analysis. Immunofluorescence staining demonstrated that Ubqln was extensively distributed in the cerebral cortex and hippocampus, and Ubqln was expressed in neurons, astrocytes and microglia in the brains of the HI brain injury model mice. Western blot analyses revealed decreased expression of Ubqln in the HI penumbra of the mouse model compared with Ubqln in the sham control group. The results of this study revealed that HI alters the expression of Ubqln, thus may provide a novel understanding of role of Ubqln in neonatal hypoxic ischemic encephalopathy.

UHPLC-QTOFMS-Based Metabolomic Analysis of the Hippocampus in Hypoxia Preconditioned Mouse

Background: Hypoxia appears in a number of extreme environments, including high altitudes, the deep sea, and during aviation, and occurs in cancer, cardiovascular disease, respiratory failures and neurological disorders. Though it is well recognized that hypoxic preconditioning (HPC) exerts endogenous neuroprotective effect against severe hypoxia, the mediators and underlying molecular mechanism for the protective effect are still not fully understood. This study established a hippocampus metabolomics approach to explore the alterations associated with HPC.

Methods: In this study, an animal model of HPC was established by exposing the adult BALB/c mice to acute repetitive hypoxia four times. Ultra-high liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOFMS) in combination with univariate and multivariate statistical analyses was employed to deciphering metabolic changes associated with HPC in hippocampus tissue. MetaboAnalyst 3.0 was used to construct HPC related metabolic pathways.

Results: The significant metabolic differences in hippocampus between the HPC groups and control were observed, indicating that HPC mouse model was successfully established and HPC could caused significant metabolic changes. Several key metabolic pathways were found to be acutely perturbed, including phenylalanine, tyrosine and tryptophan biosynthesis, taurine and hypotaurine metabolism, phenylalanine metabolism, glutathione metabolism, alanine, aspartate and glutamate metabolism, tyrosine metabolism, tryptophan metabolism, purine metabolism, citrate cycle, and glycerophospholipid metabolism.

Conclusion: The results of the present study provided novel insights into the mechanisms involved in the acclimatization of organisms to hypoxia, and demonstrated the neuroprotective mechanism of HPC.

Evaluation of 3K3A-Activated Protein C to Treat Neonatal Hypoxic Ischemic Brain Injury in the Spiny Mouse

Neonatal hypoxic ischemic encephalopathy (HIE) resulting from intrapartum asphyxia is a global problem that causes severe disabilities and up to 1 million deaths annually. A variant form of activated protein C, 3K3A-APC, has cytoprotective properties that attenuate brain injury in models of adult stroke. In this study, we compared the ability of 3K3A-APC and APC (wild-type (wt)) to attenuate neonatal brain injury, using the spiny mouse (Acomys cahirinus) model of intrapartum asphyxia. Pups were delivered at 38 days of gestation (term = 39 days), with an intrapartum hypoxic insult of 7.5 min (intrapartum asphyxia cohort), or immediate removal from the uterus (control cohort). After 1 h, pups received a subcutaneous injection of 3K3A-APC or wild-type APC (wtAPC) at 7 mg/kg, or vehicle (saline). At 24 h of age, pups were killed and brain tissue was collected for measurement of inflammation and cell death using RT-qPCR and histopathology. Intrapartum asphyxia increased weight loss, inflammation, and apoptosis/necrosis in the newborn brain. 3K3A-APC administration maintained body weight and ameliorated an asphyxia-induced increase of TGFβ1 messenger RNA expression in the cerebral cortex, immune cell aggregation in the corpus callosum, and cell death in the deep gray matter and hippocampus. In the cortex, 3K3A-APC appeared to exacerbate the immune response to the hypoxic ischemic insult. While wtAPC reduced cell death in the corpus callosum and hippocampus following intrapartum asphyxia, it increased markers of neuro-inflammation and cell death in control pups. These findings suggest 3K3A-APC administration may be a useful therapy to reduce cell death and neonatal brain injury associated with HIE.

Tanshinone IIA improves hypoxic ischemic encephalopathy through TLR‑4‑mediated NF‑κB signal pathway

Hypoxic ischemic encephalopathy (HIE) is the most common brain injury following hypoxia and/or ischemia caused by various factors during the perinatal period, resulting in detrimental neurological deficits in the nervous system. Tanshinone IIA (Tan‑IIA) is a potential agent for the treatment of cardiovascular and cerebrovascular diseases. In this study, the efficacy of Tan‑IIA was investigated in a newborn mouse model of HIE. The dynamic mechanism of Tan‑IIA was also investigated in the central nervous system of neonate mice. Intravenous injection of Tan‑IIA (5 mg/kg) was administered and changes in oxidative stress, inflammation and apoptosis‑associated proteins in neurons. Histology and immunohistochemistry was used to determine infarct volume and the number of damaged neurons by Fluoro‑Jade C staining. The effects of Tan‑IIA on mice with HIE were evaluated by body weight, brain water content, neurobehavioral tests and blood‑brain barrier permeability. The results demonstrated that the apoptosis rate was decreased following Tan‑IIA administration. Expression levels of pro‑apoptotic proteins, caspase‑3 and caspase‑9 and P53 were downregulated. Expression of Bcl‑2 anti‑apoptotic proteins was upregulated by Tan‑IIA treatment in neuro. Results also found that Tan‑IIA treatment decreased production of inflammatory cytokines such as interleukin‑1, tumor necrosis factor‑α, C‑X‑C motif chemokine 10, and chemokine (C‑C motif) ligand 12. Oxidative stress was also reduced by Tan‑IIA in neurons, as determined by the expression levels of superoxide dismutase, glutathione and catalase, and the production of reactive oxygen species. The results demonstrated that Tan‑IIA treatment reduced the infarct volume and the number of damaged neurons. Furthermore, body weight, brain water content and blood‑brain barrier permeability were markedly improved by Tan‑IIA treatment of newborn mice following HIE. Furthermore, the results indicated that Tan‑IIA decreased Toll‑like receptor‑4 (TLR‑4) and nuclear factor‑κB (NF‑κB) expression in neurons. TLR‑4 treatment of neuronal cell in vitro addition stimulated NF‑κB activity, and further enhanced the production of inflammatory cytokines and oxidative stress levels in neurons. In conclusion, these results suggest that Tan‑IIA treatment is beneficial for improvement of HIE through TLR‑4‑mediated NF‑κB signaling.

UPLC‑QTOFMS‑based metabolomic analysis of the serum of hypoxic preconditioning mice

Hypoxic preconditioning (HPC) is well‑known to exert a protective effect against hypoxic injury; however, the underlying molecular mechanism remains unclear. The present study utilized a serum metabolomics approach to detect the alterations associated with HPC. In the present study, an animal model of HPC was established by exposing adult BALB/c mice to acute repetitive hypoxia four times. The serum samples were collected by orbital blood sampling. Metabolite profiling was performed using ultra‑performance liquid chromatography‑quadrupole time‑of‑flight mass spectrometry (UPLC‑QTOFMS), in conjunction with univariate and multivariate statistical analyses. The results of the present study confirmed that the HPC mouse model was established and refined, suggesting significant differences between the control and HPC groups at the molecular levels. HPC caused significant metabolic alterations, as represented by the significant upregulation of valine, methionine, tyrosine, isoleucine, phenylalanine, lysophosphatidylcholine (LysoPC; 16:1), LysoPC (22:6), linoelaidylcarnitine, palmitoylcarnitine, octadecenoylcarnitine, taurine, arachidonic acid, linoleic acid, oleic acid and palmitic acid, and the downregulation of acetylcarnitine, malate, citrate and succinate. Using MetaboAnalyst 3.0, a number of key metabolic pathways were observed to be acutely perturbed, including valine, leucine and isoleucine biosynthesis, in addition to taurine, hypotaurine, phenylalanine, linoleic acid and arachidonic acid metabolism. The results of the present study provided novel insights into the mechanisms involved in the acclimatization of organisms to hypoxia, and demonstrated the protective mechanism of HPC.

Inhibition of endoplasmic reticulum stress is involved in the neuroprotective effect of aFGF in neonatal hypoxic-ischaemic brain injury

Acidic fibroblast growth factor (aFGF) has been shown to exert neuroprotective effects in experimental models and human patients. In this study, we investigated whether aFGF intranasal-treatment protected against neonatal hypoxic-ischaemic brain injury and evaluated the role of endoplasmic reticulum stress. The Rice-Vannucci model of neonatal hypoxic-ischaemic brain injury was used in 7-day-old rats, which were subjected to unilateral carotid artery ligation followed by 2.5 h of hypoxia. Intranasal aFGF or vehicle was administered immediately after hypoxic-ischaemic injury (100 ng/g) and then twice a day for 1 week to evaluate the long-term effects. Here we reported that intranasal-treatment with aFGF significantly reduced hypoxic-ischaemic brain infarct volumes and the protective effects were at least partially via inhibiting endoplasmic reticulum stress. In addition, aFGF exerted long-term neuroprotective effects against brain atrophy and neuron loss at 7-day after injury. Our data indicate that therapeutic strategies targeting endoplasmic reticulum stress may be promising to the treatment of neonatal hypoxic-ischaemic brain injury.