Effects of PTEN inhibition on the regulation of Tau phosphorylation in rat cortical neuronal injury after oxygen and glucose deprivation

Implications of miR-148a-3p/p35/PTEN signaling in tau hyperphosphorylation and autoregulatory feedforward of Akt/CREB in Alzheimer's disease

Existing studies have revealed that microRNAs (miRNAs) have a role in cognitive deficits in Alzheimer's disease (AD). However, the function and pathophysiological mechanism of deregulated miRNAs underlying AD pathology remain to be investigated. The present study aimed to clarify the role and mechanism of miR-148a-3p in AD. RNA sequencing, qRT-PCR, and western blot analysis were used to identify the aberrant expression and signaling of miR-148a-3p within cells, mice, and patients with AD. Molecular biology techniques involving luciferase reporter assays, gene overexpression and silencing, chromatin immunoprecipitation, and adeno-associated virus-based miRNA overexpression were used to explore the biological function and mechanisms of miR-148a-3p. Downregulation of miR-148a-3p was identified in AD. Upregulation of miR-148a-3p was found to protect neuronal cells against Aβ-associated tau hyperphosphorylation by directly targeting p35/CDK5 and PTEN/p38 mitogen-activated protein kinase (MAPK) pathways. A mutual regulatory link between miR-148a-3p and PTEN using a feedforward arrangement was confirmed via promotion of transcription and expression of miR-148a-3p by way of the PTEN/Akt/CREB pathway. Significantly, in vivo targeting of miR-148a-3p signaling ameliorated cognitive deficits by decreasing p35/PTEN-elicited tau hyperphosphorylation, accompanied by feedforward transduction of the PTEN/Akt/CREB pathway. In conclusion, the present study implicated the miR-148a-3p/p35/PTEN pathway as an essential contributor to tau hyperphosphorylation and feedforward regulation in AD.

PTEN nuclear translocation enhances neuronal injury after hypoxia-ischemia via modulation of the nuclear factor-κB signaling pathway

The occurrence of hypoxia-ischemia (HI) in the developing brain is closely associated with neuronal injury and even death. However, the underlying molecular mechanism is not fully understood. This study was designed to investigate phosphatase and tensin homolog (PTEN) nuclear translocation and its possible role in rat cortical neuronal damage following oxygen-glucose deprivation (OGD) in vitro. An in vitro OGD model was established using primary cortical neurons dissected from newborn Sprague-Dawley rats to mimic HI conditions. The PTENK13R mutant plasmid, which contains a lysine-to-arginine mutation at the lysine 13 residue, was constructed. The nuclei and cytoplasm of neurons were separated. Neuronal injury following OGD was evidenced by increased lactate dehydrogenase (LDH) release and apoptotic cell counts. In addition, PTEN expression was increased and the phosphorylation of extracellular signal-regulated kinase 1/2 (p-ERK1/2) and activation of nuclear factor kappa B (NF-κB) were decreased following OGD. PTENK13R transfection prevented PTEN nuclear translocation; attenuated the effect of OGD on nuclear p-ERK1/2 and NF-κB, apoptosis, and LDH release; and increased the expression of several anti-apoptotic proteins. We conclude that PTEN nuclear translocation plays an essential role in neuronal injury following OGD via modulation of the p-ERK1/2 and NF-κB pathways. Prevention of PTEN nuclear translocation might be a candidate strategy for preventing brain injury following HI.

GSK-3β/mTORC1 Couples Synaptogenesis and Axonal Repair to Reduce Hypoxia Ischemia-Mediated Brain Injury in Neonatal Rats

Glycogen synthase kinase 3 beta (GSK-3β) plays an important role in neurological outcomes after brain injury. However, its roles and mechanisms in hypoxia-ischemia (HI) are unclear. Activation of mTOR complex 1 (mTORC1) has been proven to induce the synthesis of proteins associated with regeneration. We hypothesized that GSK-3β inhibition could activate the mTORC1 signaling pathway, which may reduce axonal injury and induce synaptic protein synthesis and functional recovery of synapses after HI. By analyzing a P7 rat model of cerebral HI and an in vitro ischemic (oxygen glucose deprivation) model, we found that GSK-3β inhibitors (GSK-3β siRNA or lithium chloride) activated mTORC1 signaling, leading to increased expression of synaptic proteins, including synapsin 1, PSD95, and GluR1, and the microtubule-associated protein Tau and decreased expression of the axonal injury-associated protein amyloid precursor protein. These changes contributed to attenuated axonal injury (decreased amyloid precursor protein staining and axonal loss by silver staining), improved electrophysiological properties of synapses, and enhanced spatial memory performance in the Morris water maze. However, inhibition of mTORC1 by rapamycin blocked the benefits induced by GSK-3β inhibition, suggesting that GSK-3β inhibition induces synaptogenesis and axonal repair via mTORC1 signaling, which may benefit neonatal rats subjected to HI.

Plasma Biomarkers of Brain Injury in Neonatal Hypoxic-Ischemic Encephalopathy

OBJECTIVES

To evaluate plasma brain specific proteins and cytokines as biomarkers of brain injury in newborns with hypoxic-ischemic encephalopathy (HIE) and, secondarily, to assess the effect of erythropoietin (Epo) treatment on the relationship between biomarkers and outcomes.

STUDY DESIGN

A study of candidate brain injury biomarkers was conducted in the context of a phase II multicenter randomized trial evaluating Epo for neuroprotection in HIE. Plasma was collected at baseline (<24 hours) and on day 5. Brain injury was assessed by magnetic resonance imaging (MRI) and neurodevelopmental assessments at 1 year. The relationships between Epo, brain-specific proteins (S100B, ubiquitin carboxy-terminal hydrolase-L1 [UCH-L1], total Tau, neuron specific enolase), cytokines (interleukin [IL]-1β, IL-6, IL-8, IL-10, IL-12P70, IL-13, interferon-gamma [IFN-γ], tumor necrosis factor alpha [TNF-α], brain-derived neurotrophic factor [BDNF], monocyte chemoattractant protein-1), and brain injury were assessed.

RESULTS

In 50 newborns with encephalopathy, elevated baseline S100B, Tau, UCH-L1, IL-1β, IL-6, IL-8, IL-10, IL-13, TNF-α, and IFN-γ levels were associated with increasing brain injury severity by MRI. Higher baseline Tau and lower day 5 BDNF were associated with worse 1 year outcomes. No statistically significant evidence of Epo treatment modification on biomarkers was detected in this small cohort.

CONCLUSIONS

Elevated plasma brain-specific proteins and cytokine levels in the first 24 hours of life are associated with worse brain injury by MRI in newborns with HIE. Only Tau and BDNF levels were found to be related to neurodevelopmental outcomes. The effect of Epo treatment on the relationships between biomarkers and brain injury in HIE requires further study.

TRIAL REGISTRATION

ClinicalTrials.gov: 01913340.

SBDPs and Tau proteins for diagnosis and hypothermia therapy in neonatal hypoxic ischemic encephalopathy

The use of spectrin breakdown products (SBDPs) and Tau protein levels for diagnosis and a mild hypothermia therapy for treatment of neonatal hypoxic-ischemic encephalopathy (HIE) was evaluated. One hundred and fifty infants, with HIE within 12 h after birth, participated in the study. There were 30 newborns with mild symptoms, 60 with moderate symptoms, 60 with severe symptoms, and 30 in a control group. Regular therapy was used for the control and the mild HIE groups, and also for 30 cases in the group with moderate symptoms and for 30 in the group with severe symptoms. For the remaining infants, with moderate and severe symptoms, mild hypothermia therapy was used instead. A sandwich ELISA measured plasma concentrations of SBDPs and Tau proteins, at different time-points. For clinical follow-up, the neonatal behavioral neurological assessment (NBNA) assay and the Gesell development scale were performed at different time-points. The levels of SBDP and Tau proteins increased with the exacerbation of HIE, and decreased with the prolongation of therapy with statistically significant differences amongst groups. After treatment, the levels of SBDP and Tau proteins in groups with moderate and severe symptoms treated with mild hypothermia therapy were significantly lower than those of the groups treated with regular therapy. NBNA scores and the developmental quotient (DQ) were both worse with the increase in severity of HIE, however, the scores of groups with moderate and severe symptoms treated with mild hypothermia therapy were significantly better than those of groups treated with regular therapy (P<0.05). A gradual improvement of DQ was seen in the process of therapy in each group (P<0.05). According to a receiver operating characteristic (ROC) curve analysis, at a critical plasma concentration of SBDPs of 1.58 ng/ml, the sensitivity and specificity for HIE diagnosis was 84.6 and 87.5%, respectively. The ROC analysis for Tau protein yielded a sensitivity and specificity of 79.5 and 96.9%, respectively, at a critical plasma concentration of 4.76 pg/ml. Given our results, SBDPs and Tau proteins are very useful for the early diagnosis of HIE. Early application of mild hypothermia therapy for the treatment of HIE can greatly improve the function of neural development. These findings should greatly improve the evaluation and treatment approaches for HIE.