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Neuroinflammation is principally linked to glial function and has been demonstrated to participate in the pathogenesis of Alzheimer's disease, a neurodegenerative disorder characterized by beta-amyloid ccumulation and neurotransmission disruption. Previous findings suggest acetylcholine exerts anti-inflammatory and neuroprotective properties in several neurodegenerative disorders. However, the underlying mechanisms remain elusive. Here evaluation of the influence of acetylcholine on neuroinflammation and neurodegeneration in Alzheimer's disease is reported and further neuroprotective mechanisms are investigated. Investigation of microglia in lipopolysaccharide-induced hippocampal neuronal toxicity employed α7nAChR gene silencing and demonstrated that both the anti-inflammatory and neuroprotective effects of acetylcholine rely on α7nAChR pathways. As expected, in neuron-microglia co-cultures lipopolysaccharide induced an increase in expression of pro-inflammatory factors, including inducible nitric oxide synthase, interleukin-1α, and tumor necrosis factor-α, and decreased expression of neurotrophic factors such as insulin-like growth factor-1, and neuronal apoptosis. Acetylcholine protects against lipopolysaccharide-elicited neuronal injury by inhibiting the microglial inflammatory response and promoting microglial neurotrophic factor production via the action of α7nAChR on microglia. These findings establish that ACh activates α7nAChR in microglia, which in turn protects hippocampal neurons.

Background/Aims: Regulatory T (Treg) cells have been associated with neuroprotection by inhibiting microglial activation in animal models of Parkinson's disease (PD), a progressive neurodegenerative disease characterized by dopaminergic neuronal loss in the nigrostriatal system. Herein, we show that Treg cells directly protect dopaminergic neurons against 1-methyl-4-phenylpyridinium (MPP+) neurotoxicity via an interaction between the two transmembrane proteins CD47 and signal regulatory protein α (SIRPA). Methods: Primary ventral mesencephalic (VM) cells or VM neurons were pretreated with Treg cells before MPP+ treatment. Transwell co-culture of Treg cells and VM neurons was used to assess the effects of the Treg cytokines transforming growth factor (TGF)-β1 and interleukin (IL)-10 on dopaminergic neurons. Live cell imaging system detected a dynamic contact of Treg cells with VM neurons that were stained with CD47 and SIRPA, respectively. Dopaminergic neuronal loss, which was assessed by the number of tyrosine hydroxylase (TH)-immunoreactive cells, was examined after silencing CD47 in Treg cells or silencing SIRPA in VM neurons. Results: Treg cells prevented MPP+-induced dopaminergic neuronal loss and glial inflammatory responses. TGF-β1 and IL-10 secreted from Treg cells did not significantly prevent MPP+-induced dopaminergic neuronal loss in transwell co-culture of Treg cells and VM neurons. CD47 and SIRPA were expressed by Treg cells and VM neurons, respectively. CD47-labeled Treg cells dynamically contacted with SIRPA-labeled VM neurons. Silencing CD47 gene in Treg cells impaired the ability of Treg cells to protect dopaminergic neurons against MPP+ toxicity. Similarly, SIRPA knockdown in VM neurons reduced the ability of Treg cell neuroprotection. Rac1/Akt signaling pathway in VM neurons was activated by CD47-SIRPA interaction between Treg cells and the neurons. Inhibiting Rac1/Akt signaling in VM neurons compromised Treg cell neuroprotection. Conclusion: Treg cells protect dopaminergic neurons against MPP+ neurotoxicity by a cell-to-cell contact mechanism underlying CD47-SIRPA interaction and Rac1/Akt activation.

We have previously shown that interleukin-6 (IL-6)-protected neurons against the suppression of neuronal vitality and overload of intracellular Ca(2+) induced by glutamate or N-methyl-D: -aspartate (NMDA). Herein we provide further evidence for IL-6 neuroprotection against NMDA-induced apoptosis and explore the signal-transduction mechanisms underlying the anti-apoptotic action of IL-6. Cerebellar granule neurons (CGNs) from postnatal 8-day infant rats were chronically exposed to IL-6 (40 or 120 ng/ml) for 8 days, and stimulated with NMDA (100 μM) for 30 min. To observe the signaling pathways, we employed AG490 (5 or 10 μM), an inhibitor of Janus kinases (JAKs), or LY294002 (5 or 10 μM), an inhibitor of phosphatidylinositol 3-kinase (PI3K), to pretreat the CGNS together with IL-6. The levels of phosphorylation for the downstream effectors of JAKs and PI3K, i.e., phosphorylated STAT3 and Akt, were quantified by Western blot assay. In the cultured CGNs with various drug exposures, the expressions of Bcl-2, Bax, and caspase-3 were measured by real-time PCR and Western blot, and the percentage of apoptotic nuclei was tested by Hoechst 33342 staining. After the CGNs were chronically exposed to IL-6, NMDA stimulation led to an increase in the expression of Bcl-2 mRNA and a decrease in the expression of Bax and caspase-3 mRNAs and proteins when compared with those neurons lacking IL-6 exposure. IL-6 pretreatment of the neurons without NMDA stimulation concentration-dependently enhanced the expressions of Bcl-2 mRNA and protein while attenuating the expressions of Bax and caspase-3 mRNAs and proteins in comparison with control lacking any treatment. Furthermore, IL-6 prevented the increase in the percentage of apoptotic neurons induced by NMDA. The combined pretreatment of the CGNs with AG490 and IL-6 or with LY294002 and IL-6 reduced these anti-apoptotic effects of IL-6. Neither AG490 nor LY294002 exposure alone altered the expressions of Bcl-2, Bax, and cleaved caspase-3 proteins. IL-6 up-regulated the levels of phosphorylated STAT3 and Akt, and this was blocked by AG490 and LY294002, respectively. These results suggest that IL-6 protects neurons against NMDA-induced apoptosis, and that the IL-6 neuroprotection is jointly mediated by JAK-STAT3 and PI3K-Akt signaling pathways.

This work presents a constructive design approach for the problem of stabilization of switched linear systems. The idea is to first transform a controllable switched linear system into a norm form, and then a constructive design procedure is developed for the norm form. Detailed design steps are presented to achieve non-quadratic stability for a class of third-order systems.