Cell death in pure-neuronal and neuron-astrocyte mixed primary culture subjected to oxygen-glucose deprivation: The contribution of poly(ADP-ribose) polymerases and caspases

Strategies for the development of in vitro models of spinal cord ischemia-reperfusion injury: Oxygen-glucose deprivation and reoxygenation

BACKGROUND

In vitro models tailored for spinal cord ischemia-reperfusion injury are pivotal for investigation of the mechanisms underlying spinal cord injuries. We conducted a two-phased study to identify the optimal conditions for establishing an in vitro model of spinal cord ischemia-reperfusion injury using primary rat spinal motor neurons.

NEW METHOD

In the first phase, cell cultures were subjected to oxygen deprivation (OD) only, glucose deprivation (GD) only, or simultaneous deprivation of oxygen and glucose [oxygen-glucose deprivation (OGD)] for different durations (1, 2, and 6 h). In the second phase, different durations of re-oxygenation (1, 12, and 24 h) were applied after 1 h of OGD to determine the optimal duration simulating reperfusion injury.

RESULTS AND COMPARISON WITH EXISTING METHOD(S)

GD for 6 h significantly reduced cell viability (91 % of control, P<0.001) and increase cytotoxicity (111 % of control, P<0.001). OGD for 1 h and 2 h, resulted in a significant decrease in cell viability (80 % of control P<0.001, respectively), and increase in cytotoxicity (130 % of control, P<0.001, respectively). Re-oxygenation for 1, 12, and 24 h worsened ischemic injury following 1 h of OGD (all P<0.05).

CONCLUSIONS

Our results may provide a valuable guide to devise in vitro models of spinal cord ischemia-reperfusion injury using primary spinal motor neurons.

Photobiomodulation at Defined Wavelengths Regulates Mitochondrial Membrane Potential and Redox Balance in Skin Fibroblasts

Starting from the discovery of phototherapy in the beginning of the last century, photobiomodulation (PBM) has been defined in late 1960s and, since then, widely described in different in vitro models. Robust evidence indicates that the effect of light exposure on the oxidative state of the cells and on mitochondrial dynamics, suggesting a great therapeutic potential. The translational scale-up of PBM, however, has often given contrasting and confusing results, mainly due to light exposure protocols which fail to adequately control or define factors such as emitting device features, emitted light characteristics, exposure time, cell target, and readouts. In this in vitro study, we describe the effects of a strictly controlled light-emitting diode (LED)-based PBM protocol on human fibroblasts, one of the main cells involved in skin care, regeneration, and repair. We used six emitter probes at different wavelengths (440, 525, 645, 660, 780, and 900 nm) with the same irradiance value of 0.1 mW/cm2, evenly distributed over the entire surface of the cell culture well. The PBM was analyzed by three main readouts: (i) mitochondrial potential (MitoTracker Orange staining), (ii) reactive oxygen species (ROS) production (CellROX staining); and (iii) cell death (nuclear morphology). The assay was also implemented by cell-based high-content screening technology, further increasing the reliability of the data. Different exposure protocols were also tested (one, two, or three subsequent 20 s pulsed exposures at 24 hr intervals), and the 645 nm wavelength and single exposure chosen as the most efficient protocol based on the mitochondrial potential readout, further confirmed by mitochondrial fusion quantification. This protocol was then tested for its potential to prevent H2O2-induced oxidative stress, including modulation of the light wave frequency. Finally, we demonstrated that the controlled PBM induced by the LED light exposure generates a preconditioning stimulation of the mitochondrial potential, which protects the cell from oxidative stress damage.

Intra-individual variability in the neuroprotective and promyelinating properties of conditioned culture medium obtained from human adipose mesenchymal stromal cells

BACKGROUND

Greater knowledge of mesenchymal stromal cell (MSC)-based therapies is driving the research into their secretome, identified as the main element responsible for their therapeutic effects. The aim of this study is to characterize the individual variability of the secretome of adipose tissue-derived MSCs (adMSCs) with regard to potential therapeutical applications in neurology.

METHODS

adMSCs were isolated from the intact adipose tissue of ten subjects undergoing abdominal plastic surgery or reduction mammoplasty. Two commercial lines were also included. We analyzed the expansion rate, production, and secretion of growth factors of interest for neurological applications (VEGF-A, BDNF, PDGF-AA and AA/BB, HGF, NGF, FGF-21, GDNF, IGF-I, IGF-II, EGF and FGF-2). To correlate these characteristics with the biological effects on the cellular targets, we used individual media conditioned with adMSCs from the various donors on primary cultures of neurons/astrocytes and oligodendrocyte precursor cells (OPCs) exposed to noxious stimuli (oxygen-glucose deprivation, OGD) to evaluate their protective and promyelinating properties, using MSC medium as a control group.

RESULTS

The MSC secretome showed significant individual variability within the considered population with regard to PDGF-AA, PDGF-AB/BB, VEGF-A and BDNF. None of the MSC-derived supernatants affected neuron viability in normoxia, while substantial protection by high BDNF-containing conditioned MSC medium was observed in neuronal cultures exposed to OGD conditions. In OPC cultures, the MSC-derived supernatants protected cells from OGD-induced cell death, also increasing the differentiation in mature oligodendrocytes. Neuroprotection showed a positive correlation with VEGF-A, BDNF and PDGF-AA concentrations in the culture supernatants, and an inverse correlation with HGF, while OPC differentiation following OGD was positively correlated to PDGF-AA concentration.

CONCLUSIONS

Despite the limited number of adMSC donors, this study showed significant individual variability in the biological properties of interest for neurological applications for adMSC secretome, an under-researched aspect which may represent an important step in the translation of MSC-derived acellular products to clinical practice. We also showed the potential protection capability of MSC conditioned medium on neuronal and oligodendroglial lineages exposed to oxygen-glucose deprivation. These effects are directly correlated to the concentration of specific growth factors, and indicate that the remyelination should be included as a primary target in MSC-based therapies.

Nerve growth factor promotes differentiation and protects the oligodendrocyte precursor cells from in vitro hypoxia/ischemia

Introduction

Nerve growth factor (NGF) is a pleiotropic molecule acting on different cell types in physiological and pathological conditions. However, the effect of NGF on the survival, differentiation and maturation of oligodendrocyte precursor cells (OPCs) and oligodendrocytes (OLs), the cells responsible for myelin formation, turnover, and repair in the central nervous system (CNS), is still poorly understood and heavily debated.

Methods

Here we used mixed neural stem cell (NSC)-derived OPC/astrocyte cultures to clarify the role of NGF throughout the entire process of OL differentiation and investigate its putative role in OPC protection under pathological conditions.

Results

We first showed that the gene expression of all the neurotrophin receptors (TrkA, TrkB, TrkC, and p75^NTR ) dynamically changes during the differentiation. However, only TrkA and p75^NTR expression depends on T3-differentiation induction, as Ngf gene expression induction and protein secretion in the culture medium. Moreover, in the mixed culture, astrocytes are the main producer of NGF protein, and OPCs express both TrkA and p75^NTR . NGF treatment increases the percentage of mature OLs, while NGF blocking by neutralizing antibody and TRKA antagonist impairs OPC differentiation. Moreover, both NGF exposure and astrocyte-conditioned medium protect OPCs exposed to oxygenglucose deprivation (OGD) from cell death and NGF induces an increase of AKT/pAKT levels in OPCs nuclei by TRKA activation.

Discussion

This study demonstrated that NGF is implicated in OPC differentiation, maturation, and protection in the presence of metabolic challenges, also suggesting implications for the treatment of demyelinating lesions and diseases.

White Matter and Neuroprotection in Alzheimer's Dementia

Myelin is the main component of the white matter of the central nervous system (CNS), allowing the proper electrical function of the neurons by ensheathing and insulating the axons. The extensive use of magnetic resonance imaging has highlighted the white matter alterations in Alzheimer’s dementia (AD) and other neurodegenerative diseases, alterations which are early, extended, and regionally selective. Given that the white matter turnover is considerable in the adulthood, and that myelin repair is currently recognized as being the only true reparative capability of the mature CNS, oligodendrocyte precursor cells (OPCs), the cells that differentiate in oligodendrocyte, responsible for myelin formation and repair, are regarded as a potential target for neuroprotection. In this review, several aspects of the OPC biology are reviewed. The histology and functional role of OPCs in the neurovascular-neuroglial unit as described in preclinical and clinical studies on AD is discussed, such as the OPC vulnerability to hypoxia-ischemia, neuroinflammation, and amyloid deposition. Finally, the position of OPCs in drug discovery strategies for dementia is discussed.

Differential effects of glucose deprivation on the survival of fetal versus adult neural stem cells-derived oligodendrocyte precursor cells

Impaired myelination is a key feature in neonatal hypoxia/ischemia (HI), the most common perinatal/neonatal cause of death and permanent disabilities, which is triggered by the establishment of an inflammatory and hypoxic environment during the most critical period of myelin development. This process is dependent on oligodendrocyte precursor cells (OPCs) and their capability to differentiate into mature oligodendrocytes. In this study, we investigated the vulnerability of fetal and adult OPCs derived from neural stem cells (NSCs) to inflammatory and HI insults. The resulting OPCs/astrocytes cultures were exposed to cytokines to mimic inflammation, or to oxygen-glucose deprivation (OGD) to mimic an HI condition. The differentiation of both fetal and adult OPCs is completely abolished following exposure to inflammatory cytokines, while only fetal-derived OPCs degenerate when exposed to OGD. We then investigated possible mechanisms involved in OGD-mediated toxicity: (a) T3-mediated maturation induction; (b) glutamate excitotoxicity; (c) glucose metabolism. We found that while no substantial differences were observed in T3 intracellular content regulation and glutamate-mediated toxicity, glucose deprivation lead to selective OPC cell death and impaired differentiation in fetal cultures only. These results indicate that the biological response of OPCs to inflammation and demyelination is different in fetal and adult cells, and that the glucose metabolism perturbation in fetal central nervous system (CNS) may significantly contribute to neonatal pathologies. An understanding of the underlying molecular mechanism will contribute greatly to differentiating myelination enhancing and neuroprotective therapies for neonatal and adult CNS white matter lesions.

Neuroprotective effect of licochalcone A against oxygen-glucose deprivation/reperfusion in rat primary cortical neurons by attenuating oxidative stress injury and inflammatory response via the SIRT1/Nrf2 pathway

Perinatal hypoxic-ischemic encephalopathy (HIE) is a leading cause of neonatal death and neurological disability. Oxidative stress and neuroinflammation are typical pathogenic factors of HIE. Licochalcone A (LCA) exerts various biological properties, including anti-inflammatory and antioxidant activities. However, no data have been reported to elucidate the role of LCA in the development of HIE. In the present study, primary cultured rat cortical neurons were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro to simulate the in vivo situation of neonatal HIE. Interestingly, LCA significantly antagonized cell injury under OGD/R by increasing cell survival, inhibiting lactate dehydrogenase (LDH) release and cell apoptosis. Furthermore, treatment with LCA suppressed oxidative stress by decreasing reactive oxygen species (ROS) production and malondialdehyde (MDA) content, and increasing superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in primary rat cortical neurons after OGD/R. LCA stimulation also restrained OGD/R-triggered increase in pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production. Importantly, LCA treatment effectively counteracts OGD/R-mediated downregulation of silent information regulator 1 (SIRT1), nuclear factor erythroid2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1), and upregulation of nuclear factor kappa B p65 (NF-κB p65). Moreover, administration with SIRT1 inhibitor EX527 partly abolished LCA-induced neuroprotective effects on rat cortical neurons exposed to OGD/R. In conclusion, our study indicates that LCA exerts a neuroprotective effect against OGD/R-induced neuronal injury in rat primary cortical neurons, suggesting that LCA might act as a candidate therapeutic target drug used for HIE and related diseases.

Vulnerability of primary neurons derived from Tg2576 Alzheimer mice to oxygen and glucose deprivation: role of intraneuronal amyloid-β accumulation and astrocytes

Microvascular dysfunction is considered an integral part of Alzheimer disease (AD) pathogenesis, but the possible relationship between amyloid pathology, microvascular dysfunction and cell death is still unclear. In order to investigate the influence of intraneuronal amyloid-β (Aβ) accumulation on vulnerability to hypoxia, we isolated primary cortical neurons from Tg2576 (carrying the amyloid precursor protein APPSwe mutation) and wild-type fetal mice. We first demonstrated that neurons isolated from Tg2576 newborn mice show an increase in VEGFa mRNA expression and a decrease in the expression of the two VEGF receptors, Flt1 and Kdr, compared with wild-type cells. Moreover, APPSwe primary neurons displayed higher spontaneous and glutamate-induced cell death. We then deprived the cultures of oxygen and glucose (OGD) as an in vitro model of hypoxia. After OGD, APPSwe neurons display higher levels of cell death in terms of percentage of pyknotic/fragmented nuclei and mitochondrial depolarization, accompanied by an increase in the intraneuronal Aβ content. To explore the influence of intraneuronal Aβ peptide accumulation, we used the γ-secretase inhibitor LY450139, which showed that the reduction of the intracellular amyloid fully protects APPSwe neurons from OGD-induced degeneration. Conditioned medium from OGD-exposed APPSwe or wild-type astrocytes protected APPswe neurons but not wild-type neurons, during OGD. In conclusion, the presence of the mutated human APP gene, leading to the intracellular accumulation of APP and Aβ fragments, worsens OGD toxicity. Protection of APPSwe neurons can be obtained either using a γ-secretase inhibitor or astrocyte conditioned medium.

Summary:In vitro systems derived from AD mice can be used to investigate the vulnerability of AD neurons to different neurotoxic challenges, including oxygen glucose deprivation.