Microglia-Based Phenotypic Screening Identifies a Novel Inhibitor of Neuroinflammation Effective in Alzheimer's Disease Models.

Currently, anti-AD drug discovery using target-based approaches is extremely challenging due to unclear etiology of AD and absence of validated therapeutic protein targets. Neuronal death, regardless of causes, plays a key role in AD progression, and it is directly linked to neuroinflammation. Meanwhile, phenotypic screening is making a resurgence in drug discovery process as an alternative to target-focused approaches. Herein, we employed microglia-based phenotypic screenings to search for small molecules that modulate the release of detrimental proinflammatory cytokines. The identified novel pharmacological inhibitor of neuroinflammation (named GIBH-130) was validated to alter phenotypes of neuroinflammation in AD brains. Notably, this molecule exhibited comparable in vivo efficacy of cognitive impairment relief to donepezil and memantine respectively in both ß amyloid-induced and APP/PS1 double transgenic Alzheimer's murine models at a substantially lower dose (0.25 mg/kg). Therefore, GIBH-130 constitutes a unique chemical probe for pathogenesis research and drug development of AD, and it also suggests microglia-based phenotypic screenings that target neuroinflammation as an effective and feasible strategy to identify novel anti-AD agents.

Expression changes of hypothalamic Ahi1 in mice brain: implication in sensing insulin signaling.

Growing evidence suggests that the brain, in particular the hypothalamus, directly senses hormones and nutrients to initiate feeding behavior and metabolic responses in the control of energy homeostasis. However, the molecular mechanisms underlying this important process have remained largely unknown. Our study provides the evidence for the role of Abelson helper integration site 1 (Ahi1) protein as a sensor of insulin signaling in the hypothalamus. We found that fasting increased the expression of hypothalamic Ahi1 which was accompanied by lower levels of circulating insulin compared with satiated mice, while re-feeding decreased the expression of hypothalamic Ahi1 which was accompanied by higher levels of circulating insulin. We also found the up-regulated expression of hypothalamic Ahi1 in high-fat induced obese mice, db/db mice, and streptozotocin induced diabetic mice. In addition, we demonstrated that insulin could decrease the expression of Ahi1 in neuroblastoma cell line N18TG2. Taken together, our results indicate that hypothalamic Ahi1 functions as a sensor of insulin signaling.

Identification of aminopyridazine-derived antineuroinflammatory agents effective in an Alzheimer's mouse model.

Targeting neuroinflammation may be a new strategy to combat Alzheimer's disease. An aminopyridazine 1b previously reported as a novel antineuroinflammatory agent was considered to have a potential therapeutic effect for Alzheimer's disease. In this study, we further explored the chemical space to identify more potent antineuroinflammatory agents and validate their in vivo efficacy in an animal model. Compound 14 was finally identified as an effective agent with comparable in vivo efficacy to the marketed drug donepezil in counteracting spatial learning and working memory impairment in an Aß-induced Alzheimer's mouse model.

Retinoic acid promotes neural conversion of mouse embryonic stem cells in adherent monoculture.

Retinoic acid (RA) plays multiple roles in the nervous system, including induction of neural differentiation, axon outgrowth and neural patterning. Previously, RA for neural differentiation of embryonic stem (ES) cells always relies on embryoid bodies (EBs) formation. Here we report an in vitro adherent monoculture system to induce mouse ES cells into neural cells accompanied with RA. RA (1 µM) treatment, during initial 2 days of differentiation, can enhance the expression of neural markers, such as Nestin, Tuj1 and MAP2, and result in an earlier neural differentiation of ES cells. Furthermore, RA promotes a significant increase in neurite elongation of ES-derived neurons. Our study also implies that RA induced to express Wnt antagonist Dickkopf-1 (Dkk-1) for neural differentiation. However, the mechanisms of RA triggering neural induction remain to be determined. Our simple and efficient strategy is proposed to provide a basis for studying RA signaling pathways in neural differentiation in vitro.

Hypothalamic Ahi1 mediates feeding behavior through interaction with 5-HT2C receptor.

It is indicated that there are important molecules interacting with brain nervous systems to regulate feeding and energy balance by influencing the signaling pathways of these systems, but relatively few of the critical players have been identified. In the present study, we provide the evidence for the role of Abelson helper integration site 1 (Ahi1) protein as a mediator of feeding behavior through interaction with serotonin receptor 2C (5-HT(2C)R), known for its critical role in feeding and appetite control. First, we demonstrated the co-localization and interaction between hypothalamic Ahi1 and 5-HT(2C)R. Ahi1 promoted the degradation of 5-HT(2C)R through the lysosomal pathway. Then, we investigated the effects of fasting on the expression of hypothalamic Ahi1 and 5-HT(2C)R. Fasting resulted in an increased Ahi1 expression and a concomitant decreased expression of 5-HT(2C)R. Knockdown of hypothalamic Ahi1 led to a concomitant increased expression of 5-HT(2C)R and a decrease of food intake and body weight. Last, we found that Ahi1 could regulate the expression of neuropeptide Y and proopiomelanocortin. Taken together, our results indicate that Ahi1 mediates feeding behavior by interacting with 5-HT(2C)R to modulate the serotonin signaling pathway.

Brainstem Hap1-Ahi1 is involved in insulin-mediated feeding control.

The function of the brainstem Hap1-Ahi1 complex in the regulation of feeding behavior was investigated. When mice were fasted or treated with 2-deoxy-D-glucose (2-DG), Hap1-Ahi1 was significantly upregulated. By using streptozotocin (STZ) to decrease the circulating insulin in mice, Hap1-Ahi1 was significantly increased. Furthermore, intra-brain injection of insulin decreased the expression of Hap1-Ahi1 in the brainstem. Moreover, when we knocked down the expression of brainstem Hap1 by RNAi, the mice showed decreased food intake and lower body weights. Collectively, our results indicate that the Hap1-Ahi1 complex in the brainstem works as a sensor for insulin signals in feeding control.

Different effects of scopolamine on the retrieval of spatial memory and fear memory.

Retrieval of memory is fundamental for our life as individuals. The participation of cholinergic system in memory consolidation process has been extensively studied, but there are few data concerning the function of this system in memory retrieval process. In the current study, we inject non-selective muscarinic antagonist scopolamine peripherally 20 min before training or testing to see whether cholinergic modulation has effects on the acquisition or retrieval of spatial memory by water maze task and fear memory by inhibitory avoidance task. We find that the cholinergic system is essential for the acquisition of both spatial memory and fear memory. As for the memory retrieval, the cholinergic system has a positive role in the retrieval of spatial memory, because mice injected with scopolamine 20 min before the testing in the water maze show impaired spatial memory retrieval. Whereas injection of scopolamine 20 min before the testing in the inhibitory avoidance task does not cause memory retrieval deficits. That indicates the cholinergic system is not essential for the retrieval of fear memory.

Effects of immune activation on the retrieval of spatial memory.

OBJECTIVE: It has been shown that there are extensive interactions between the central nervous system and the immune system. The present study focused on the effects of lipopolysaccharide (LPS) on memory retrieval, to explore the interaction between immune activation and memory. METHODS: C57BL/6J mice (8 weeks old) were first trained in the Morris water maze to reach asymptotic performance. Then mice were tested 24 h after the last training session and LPS was administered (1.25 mg/kg, i.p.) 4 h prior to the testing. The retrieval of spatial memory was tested by probe trial, and the time spent in the target quadrant and the number of platform location crosses were recorded. ELISA was performed to detect interleukin-1ß (IL-1ß) protein level in the hippocampus of mice tested in the water maze. RESULTS: Although LPS induced overt sickness behavior and a significant increase in the level of IL-1ß in the hippocampus of mice, there was no significant difference in the time spent in the target quadrant or in the number of platform location crosses between LPS-treated and control groups in the probe trial testing. CONCLUSION: Immune activation induced by LPS does not impair the retrieval of spatial memory.