Neurosignals最新文献

Background/aims: Alzheimer's disease (AD) is characterized by accumulation of β-amyloid (Aβ), However, the mechanism of how Aβ affects neuronal cell death remains elusive. The balance of pro- and anti-apoptotic Bcl-2 family proteins (e.g., Bcl-2 and Bax) has been known to play a pivotal role in neuronal cell death. Of note, expression levels of these proteins are changed in the neurons in AD. To date no study has elusidated the relationship between Aβ and Bax.

Methods: The present study explored the role of Wnt/β-catenin pathway in the neurotoxic effect of Aβ25-35. Flow cytometry was employed to determine the apoptosis, western blotting to assess the protein abundance of Bcl-2 and BAX, MTT assay to decipher the cells viability.

Results: As a result, the addition of Wnt3a significantly prevented oligomeric Aβ-induced neuronal cell death and viability. Furthermore, treatment with Aβ25-35 increased Bax and Bcl-2 protein abundance and mRNA levels, an effect significantly blocked by Wnt3a (100 ng/ml) and GSK3β inhibitor TWS119 (10µM).

Conclusion: These findings are first to demonstrate that Wnt/β-catenin signaling pathway regulates Aβ25-35-induced apoptosis.

Background/aims: Major depressive disorder is a severe, common and often chronic disease with a significant mortality due to suicide. The pathogenesis of major depression is still unknown. It is assumed that a reduction of neurogenesis in the hippocampus plays an important role in the development of major depressive disorder. However, the mechanisms that control proliferation of neuronal stem cells in the hippocampus require definition. Here, we investigated the role of Janus-Kinase 3 (Jak-3) for stress-induced inhibition of neurogenesis and the induction of major depression symptoms in mice.

Methods: Stress was induced by the application of glucocorticosterone. Brain sections were stained with phospho-specific antibodies and analysed by confocal microscopy to measure phosphorylation of Jak-3 specifically in the hippocampus. Jak-3 inhibitors and the antidepressant amitriptyline were applied to counteract stress. The effects of the inhibitors were determined by a set of behavioural tests and analysis of Jak-3 phosphorylation in brain sections. Acid sphingomyelinase-deficient mice were employed to test whether Jak3 is downstream of ceramide.

Results: The data show that stress reduces neurogenesis, which is restored by simultaneous application of Jak-3 inhibitors. Inhibition of neurogenesis correlated with an anxious-depressive behaviour that was also normalized upon application of a Jak-3-inhibitor. Confocal microscopy data revealed that stress triggers a phosphorylation and thereby activation of Jak-3 in the hippocampus. Amitriptyline, a commonly used antidepressant that blocks the acid sphingomyelinase, or acid sphingomyelinase-deficiency reduced stress-induced phosphorylation of Jak-3.

Conclusion: Our data show that Jak-3 is activated by stress at least partially via the acid sphingomyelinase and is involved in the mediation of stress-induced major depression.

Background: Regeneration of injured axons in adult mammalian central nervous system (CNS) is not spontaneous. Nogo is a major inhibitory molecule contributing to axon regeneration failure. The molecular mechanisms of Nogo inhibition of axon regeneration are not completely understood. To further investigate the underlying mechanisms, we studied the effects of Nogo-p4, a 25-amino acid core inhibitory fragment of Nogo, on nerve growth factor (NGF)-induced TrkA signaling.

Methods: NGF-differentiated PC12 cells were used as cell models. The effects of Nogo-p4 on two key components of TrkA signaling, phosphorylated Erk1/2 and Akt, were analyzed by western blot. Co-immunoprecipitation experiments were performed to detect the formation of NgR1/p75 complexes. Neurite growth was quantified by measuring the neurite length.

Results: Nogo-p4 did not significantly affect TrkA signaling induced by 100 ng/ml NGF, but signaling was suppressed when an NGF concentration of 5 ng/ml was used. Further investigation demonstrated that Nogo-p4 affected TrkA signaling in an NGF concentration-dependent manner. Nogo-p4 suppression of TrkA signaling was strong at low (1 and 5 ng/ml), moderate at intermediate (25 ng/ml), but absent at high (50 and 100 ng/ml) NGF concentrations. NEP1-40 attenuated, and NgR1 overexpression enhanced, Nogo-p4 suppression of TrkA signaling induced by low concentrations of NGF. High but not low concentrations of NGF reduced the formation of NgR1/p75 complexes triggered by Nogo-p4. Nogo-p4 strongly inhibited neurite growth induced by low rather than high concentrations of NGF.

Conclusion: Nogo-p4 binding with NgR1 suppresses TrkA signaling induced by low concentrations of NGF in differentiated PC12 cells. Suppression of NGF-induced TrkA signaling may be another mechanism by which Nogo inhibits neurite growth.

Background: Monosodium glutamate (MSG) is a flavor enhancer used in food industries. MSG is well documented to induce neurotoxicity. Curcumin (CUR) reportedly possesses beneficial effects against various neurotoxic insults. Hence, this present study has been designed to evaluate the neuroprotective effect of curcumin on MSG-induced neurotoxicity in rats.

Methods: Thirty-two male Wister rats were divided into four groups (n=8): Control group, MSG group, CUR group and MSG + CUR group. CUR (Curcumin 150 mg/kg, orally) was given day after day for four weeks along with MSG (4 mg/kg, orally). After 4 weeks, rats were sacrificed and brain hippocampus was isolated immediately on ice. Inflammatory marker TNFα and acetylcholinesterase (AChE) activity (marker for cholinergic function) were estimated. Gene expressions of metabotropic glutamate receptor 5 (mGluR5) and N-methyl-D-aspartate receptor 2B (NMDA2B) along with glutamate concentration were assessed.

Results: Treatment with CUR significantly attenuated AChE activity and TNFα in MSG-treated animals. The anti-inflammatory properties of CUR may be responsible for this observed neuroprotective action. A possible role of CUR to attenuate both glutamate level and gene expression of NMDA2B and mGLUR5 in brain hippocampus was established when compared to MSG group.

Conclusion: We concluded that CUR as flavor enhancer protects against MSG-induced neurotoxicity in rats.

Background/aims: Taste perception is one of the most important primary oral reinforcers, driving nutrient and energy intake as well as toxin avoidance. Taste receptors in the gastrointestinal tract might as well impact appetitive or aversive behavior and thus influence learning tasks and a close relation of neural taste processing and working memory networks seems plausible.

Methods: In the present pilot study, we determined the effects of five taste qualities "bitter" (quinine), "sweet" (glucose), "sour" (citric acid), "salty" (NaCl) and "umami" (monosodium glutamate, MSG) on working memory processing using functional MRI and their effect on plasma insulin and glucose levels. On six separate occasions, subjects received one of the following test substances dissolved in 200 mL tap water via a nasogastric tube (to circumvent the oral cavity): 1) 2g citric acid corresponding to 52 mM, 2) 2g NaCl; 171 mM, 3) 0.017g quinine; 0.26 mM, 4) 1g monosodium glutamate; 30 mM, 5) 25g glucose; 694 mM and 6) 200 mL tap water (placebo).

Results: The taste qualities "bitter" and "umami" significantly altered brain activation patterns in the primary gustatory cortex as well as in subcortical structures, previously reported to be involved in emotional learning and memory. In contrast, glucose did not reveal any statistically significant brain activation difference. Working memory performance was not different over the six treatments. Plasma insulin and glucose levels were not affected by the different taste substances (MSG, quinine, NaCl and citric acid).

Conclusions: in this pilot trial, we demonstrate that acute intragastric administration of different taste substances does not affect working memory performance in humans. However, "umami" and "bitter" have effects on brain areas involved in neural working memory, overpowering the effects of "sweet", "salty" and "sour" reception.

Background/aims: Alzheimer's disease (AD) is characterized by two major hallmarks: the deposition and accumulation of β-amyloid (Aβ) peptide and hyperphosphorylated tau in intracellular neurofibrillary tangles. Sets of evidence show that leptin reduces Aβ production and tau phosphorylation. Herein, we investigated the signaling pathways activated by leptin, to extensively understand its mechanism.

Methods: Western blotting was employed to assess the protein abundance of p-tau and BAX, MTT assay to decipher the cells viability.

Results: Leptin decreased tau phosphorylation, an effect was dependent on the activation of JAK2.

Conclusion: The data suggest that JAK2 is involved in AD-related pathways.