Prevention of methamphetamine-induced microglial cell death by TNF-α and IL-6 through activation of the JAK-STAT pathway

<p><b>Abstract</b></p> <p><b>Background</b></p> <p>It is well known that methamphetamine (METH) is neurotoxic and recent studies have suggested the involvement of neuroinflammatory processes in brain dysfunction induced by misuse of this drug. Indeed, glial cells seem to be activated in response to METH, but its effects on microglial cells are not fully understood. Moreover, it has been shown that cytokines, which are normally released by activated microglia, may have a dual role in response to brain injury. This led us to study the toxic effect of METH on microglial cells by looking to cell death and alterations of tumor necrosis factor-alpha (TNF-α) and interleukine-6 (IL-6) systems, as well as the role played by these cytokines.</p> <p><b>Methods</b></p> <p>We used the N9 microglial cell line, and cell death and proliferation were evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling assay and incorporation of bromodeoxyuridine, respectively. The TNF-α and IL-6 content was quantified by enzyme-linked immunosorbent assay, and changes in TNF receptor 1, IL-6 receptor-alpha, Bax and Bcl-2 protein levels by western blotting. Immunocytochemistry analysis was also performed to evaluate alterations in microglial morphology and in the protein expression of phospho-signal transducer and activator of transcription 3 (pSTAT3).</p> <p><b>Results</b></p> <p>METH induced microglial cell death in a concentration-dependent manner (EC₅₀ = 1 mM), and also led to significant morphological changes and decreased cell proliferation. Additionally, this drug increased TNF-α extracellular and intracellular levels, as well as its receptor protein levels at 1 h, whereas IL-6 and its receptor levels were increased at 24 h post-exposure. However, the endogenous proinflammatory cytokines did not contribute to METH-induced microglial cell death. On the other hand, exogenous low concentrations of TNF-α or IL-6 had a protective effect. Interestingly, we also verified that the anti-apoptotic role of TNF-α was mediated by activation of IL-6 signaling, specifically the janus kinase (JAK)-STAT3 pathway, which in turn induced down-regulation of the Bax/Bcl-2 ratio.</p> <p><b>Conclusions</b></p> <p>These findings show that TNF-α and IL-6 have a protective role against METH-induced microglial cell death via the IL-6 receptor, specifically through activation of the JAK-STAT3 pathway, with consequent changes in pro- and anti-apoptotic proteins.</p

The effect of structural characteristics of ZnO and NiO thin films on the performance of NiO/ZnO photodetectors

Material properties play an important role in the fabrication of optoelectronic devices such as photodetectors because it is ultimately reflected in their efficiency and performance. To fabricate a NiO/ZnO heterojunction with better structural properties using a low-cost and uncomplicated deposition process, we studied the influence of NiO and ZnO thickness by taking different volumes of spray solution (5, 10, and 15 ml) on the structural and morphological properties that were investigated using the spray pyrolysis technique. When the films' thickness increased, the crystalline structure of both films improved. The deposited ZnO layers have a hexagonal Wurtzite structure with preferable growth orientations along (002). The NiO X-ray diffraction patterns showed that the films were in cubic phase with orientation (111) and the peak density increased with the film thickness. According to our experimental conditions and XRD results, we suggest that thicker NiO and ZnO are the optimal films to fabricate a NiO/ZnO heterostructure. It is found that Raman and XRD results confirm the formation of NiO/ZnO heterostructure. The morphology of NiO/ZnO is smooth and completely covers the substrate without any pinholes. The further investigation related to the effect of NiO and ZnO thin films' structural properties on NiO/ZnO heterostructure photodetector performance is presented using the simulations. It is worth mentioning that based on the suggested transport models, the results confirm that the origin of the dark current has been attributed to the tunneling and thermionic emission at the interface while bulk defects, leading to the increase Shockley-Read-Hall recombination and generation, control the carrier transport. Furthermore, we studied the effect of Gaussian and tail acceptor/donor defects on the current-voltage (J-V) characteristics and responsivity. The obtained results showed that increasing NiO tail states cause an increase in tunneling current. In contrast, the deep defects density in both ZnO and NiO affects the photodetection characteristics, resulting in a decrease in responsivity and photocurrent when these defects increase

Effect of the source solution quantity on optical characteristics of ZnO and NiO thin films grown by spray pyrolysis for the design NiO/ZnO photodetectors

Zinc Oxide (ZnO) and Nickel Oxide (NiO) thin films were prepared using the spray pyrolysis technique using three different quantities of solution 5, 10, and 15 ml, to modify their optical properties. Optical characterization of the obtained thin films showed that the bandgap and the transparency of NiO and ZnO decrease with increasing solution quantity. The films are highly transparent making them suitable for optoelectronic applications. It is worth noting that NiO has a low growth rate compared to ZnO due to its larger bandgap. The different parameters obtained for both films are then used to simulate the electrical characteristics and the responsivity of a NiO/ZnO heterojunction based PN photodiode. Both the electrical characteristics and the responsivity improve with increasing quantities of solution. These findings may help to find an optimal design for photodiode fabrication

Clusterin expression during fetal and postnatal CNS development in mouse

Clusterin (or apolipoprotein J) is a widely distributed multifunctional glycoprotein involved in CNS plasticity and post-traumatic remodeling. Using biochemical and morphological approaches, we investigated the clusterin ontogeny in the CNS of wild-type (WT) mice and explored developmental consequences of clusterin gene knock-out in clusterin null (Clu-/-) mice. A punctiform expression of clusterin mRNA was detected through the hypothalamic region, neocortex and hippocampus at embryonic stages E14/E15. From embryonic stage E16 to the first week of the postnatal life, the vast majority of CNS neurons expressed low levels of clusterin mRNA. In contrast, a very strong hybridizing signal mainly localized in pontobulbar and spinal cord motor nuclei was observed from the end of the first postnatal week to adulthood. Astrocytes expressing clusterin mRNA were often detected through the hippocampus and neocortex in neonatal mice. Real-time polymerase chain amplification and clusterin-immunoreactivity dot-blot analyses indicated that clusterin levels paralleled mRNA expression. Comparative analyses between WT and Clu-/- mice during postnatal development showed no significant differences in brain weight, neuronal, synaptic and astrocyte markers as well myelin basic protein expression. However, quantitative estimation of large motor neuron populations in the facial nucleus revealed a significant deficit in motor cells (-16%) in Clu-/- compared with WT mice. Our data suggest that clusterin expression is already present in fetal life mainly in subcortical structures. Although the lack of this protein does not significantly alter basic aspects of the CNS development, it may have a negative impact on neuronal development in certain motor nuclei

Interleukin-6 and Neural Stem Cells: More Than Gliogenesis

Besides its wide range of action as a proinflammatory cytokine in the immune system, interleukin-6 (IL-6) has also attracted much attention due to its influence on the nervous system. In the present study we show that the designer fusion protein H-IL-6, consisting of IL-6 and its specific receptor IL-6R-α, but not IL-6 alone, mediates both neuro- as well as gliogenesis. Using immunocytochemistry, Western blot, and patch-clamp recording, we demonstrate that H-IL-6 induces the differentiation of neural stem cells (NSCs) specifically into glutamate-responsive neurons and two morphological distinctive astroglia cell types. H-IL-6–activated neurogenesis seems to be induced by the MAPK/CREB (mitogen-activated protein kinase/cAMP response element-binding protein) cascade, whereas gliogenesis is mediated via the STAT-3 (signal transducers and activators of transcription protein-3) signaling pathway. Our finding that IL-6 mediates both processes depending on its specific soluble receptor sIL-6R-α has implications for the potential treatment of neurodegenerative diseases