Antibody-mediated inhibition of Nogo-A signaling promotes neurite growth in PC-12 cells

PGC-1a mediated mitochondrial biogenesis promotes recovery and survival of neuronal cells from cellular degeneration

Neurodegenerative disorders are characterized by the progressive loss of structure and function of neurons, often including the death of the neuron. Previously, we reported that, by removing the cell death stimulus, dying/injured neurons could survive and recover from the process of regulated cell death, even if the cells already displayed various signs of cellular damage. Now we investigated the role of mitochondrial dynamics (fission/fusion, biogenesis, mitophagy) in both degeneration and in recovery of neuronal cells. In neuronal PC12 cells, exposure to ethanol (EtOH) induced massive neurite loss along with widespread mitochondrial fragmentation, mitochondrial membrane potential loss, reduced ATP production, and decreased total mitochondrial volume. By removing EtOH timely all these mitochondrial parameters recovered to normal levels. Meanwhile, cells regrew neurites and survived. Study of the mitochondrial dynamics showed that autophagy was activated only during the cellular degeneration phase (EtOH treatment) but not in the recovery phase (EtOH removed), and it was not dependent on the Parkin/PINK1 mediated mitophagy pathway. Protein expression of key regulators of mitochondrial fission, phospho-Drp1Ser616 and S-OPA1, increased during EtOH treatment and recovered to normal levels after removing EtOH. In addition, the critical role of PGC-1α mediated mitochondrial biogenesis in cellular recovery was revealed: inhibition of PGC-1α using SR-18292 after EtOH removal significantly impeded recovery of mitochondrial damage, regeneration of neurites, and cell survival in a concentration-dependent manner. Taken together, our study showed reversibility of mitochondrial morphological and functional damage in stressed neuronal cells and revealed that PGC-1α mediated mitochondrial biogenesis played a critical role in the cellular recovery. This molecular mechanism could be a target for neuroprotection and neurorescue in neurodegenerative diseases.

MicroRNA-194-5p/Heparin-binding EGF-like growth factor signaling mediates dexamethasone-induced activation of pseudorabies virus in rat pheochromocytoma cells

Pseudorabies virus (PRV) is a neurotropic virus, which infects a wide range of mammals. The activity of PRV is gradually suppressed in hosts that have tolerated the primary infection. Increased glucocorticoid levels resulting from stressful stimuli overcome repression of PRV activity. However, the host cell mechanism involved in the activation processes under stressful conditions remains unclear. In this study, infection of rat PC-12 pheochromocytoma cells with neuronal properties using PRV at a multiplicity of infection (MOI) = 1 for 24 h made the activity of PRV be the relatively repressed state, and then incubation with 0.5 μM of the corticosteroid dexamethasone (DEX) for 4 h overcomes the relative repression of PRV activity. RNA-seq deep sequencing and bioinformatics analyses revealed different microRNA and mRNA profiles of PC-12 cells with/without PRV and/or DEX treatment. qRT-PCR and western blot analyses confirmed the negative regulatory relationship of miRNA-194-5p and its target heparin-binding EGF-like growth factor (Hbegf); a dual-luciferase reporter assay revealed that Hbegf is directly targeted by miRNA-194-5p. Further, miRNA-194-5p mock transfection contributed to PRV activation, Hbegf was downregulated in DEX-treated PRV infection cells, and Hbegf overexpression contributed to returning activated PRV to the repression state. Moreover, miRNA-194-5p overexpression resulted in reduced levels of HBEGF, c-JUN, and p-EGFR, whereas Hbegf overexpression suppressed the reduction caused by miRNA-194-5p overexpression. Overall, this study is the first to report that changes in the miR-194-5p-HBEGF/EGFR pathway in neurons are involved in DEX-induced activation of PRV, laying a foundation for the clinical prevention of stress-induced PRV activation.

Single Cell Analysis of Reversibility of the Cell Death Program in Ethanol-Treated Neuronal PC12 Cells

Neurodegenerative diseases are generally characterized clinically by the selective loss of a distinct subset of neurons and a slow progressive course. Mounting evidence in vivo indicates that large numbers of neurons pass through a long period of injury and dysfunction before the actual death of the cells. Whether these dying neurons can be rescued and return to a normal, functional state is uncertain. In the present study, we explored the reversibility of the neuronal cell death pathway at various stages by monitoring the dynamics of single cells with high-resolution live-cell spinning disk confocal microscopy in an in vitro neuronal cell death model. We exposed differentiated neuronal PC12 cells to ethanol as our cell death model. Results showed that exposure to 5% ethanol for 24 h induced cell death in >70% of the cells. Ethanol treatment for 3 h already induced cellular changes and damage such as reactive oxygen species generation, elevation of intracellular Ca2+ level, phosphatidylserine exposure, nuclear shrinkage, DNA damage, mitochondrial fragmentation and membrane potential loss, and retraction of neurites. These phenomena are often associated with programmed cell death. Importantly, after removing ethanol and further culturing these damaged cells in fresh culture medium, cells recovered from all these cell injuries and generated new neurites. Moreover, results indicated that this recovery was not dependent on exogenous NGF and other growth factors in the cell culture medium. Overall, our results suggest that targeting dying neurons can be an effective therapeutic strategy in neurodegenerative diseases.

Affinity improvement of the fully human anti‑TSLP recombinant antibody

Thymic stromal lymphopoietin (TSLP) is a potentially important target for the treatment of asthma and malignancies. However, a fully human antibody reactive with TSLP is currently unavailable for clinical use. In a previous study, a human anti-TSLP-single-chain antibody variable fragment (anti-TSLP-scFv) 84 was selected by phage display from a constructed human scFv library. In the present study, a computer simulation method was developed using Discovery Studio 4.5 software, to increase the affinity of anti-TSLP-scFv-84. Specific primers were designed and mutated DNA sequences of anti-TSLP-scFvs were obtained by overlap extension PCR. The mutant scFvs were expressed in pLZ16 and affinity-enhanced anti-TSLP-scFv-M4 was screened using ELISA. However, in general the scFvs have low stability and short half-lives in vivo. Therefore, scFv-84 and scFv-M4 were inserted into eukaryotic expression vectors (pcDNA3.1-sp-Fc and PMH3^EN-sp-Fc) and then transfected into 293F cells to express anti-TSLP-scFv-Fc. ELISA and western blotting results indicated the size of the anti-TSLP-scFv-Fc to be ~50 kDa. Binding of anti-TSLP-scFv-Fc-M4 to TSLP was enhanced compared with the pre-mutated scFv-Fc-84. The affinity of the mutated recombinant antibody was determined using the BIAcore technique and found to be ~10-fold greater than the pre-mutated antibody.

NogoA Neutralization Promotes Axonal Restoration After White Matter Injury In Subcortical Stroke

Blocking axonal growth inhibitor NogoA has been of great interest for promoting axonal recovery from neurological diseases. The present study investigates the therapeutic effects of blocking NogoA, inducing functional recovery and promoting white matter repair in an experimental animal model of stroke. Adult male rats were subjected to white matter injury by subcortical ischemic stroke. Twenty-four hours after surgery, 250 ug of anti-NogoA or anti-IgG-1 were administered through the tail vein. The quantity of NogoA protein was determined by immunohistochemistry in the brain and peripheral organs. In addition, functional status, lesion size, fiber tract integrity, axonal sprouting and white matter repair markers were analyzed. Moreover, an in vitro study was performed in order to strengthen the results obtained in vivo. A lower quantity of NogoA protein was found in the brain and peripheral organs of the animals that received anti-NogoA treatment. The animals receiving anti-NogoA treatment showed significantly better results in terms of functional recovery, fiber tract integrity, axonal sprouting and white matter repair markers compared with the control group at 28 days. White matter integrity was in part restored by antibody-mediated inhibition of NogoA administration in those animals that were subjected to an axonal injury by subcortical stroke. This white matter restoration triggered functional recovery.