Synthesis and biological evaluation of pyrethroid insecticide-derivatives as a chemical inducer for Bdnf mRNA expression in neurons

Synthesis and Catalytic Application of Knölker-Type Iron Complexes with a Novel Asymmetric Cyclopentadienone Ligand Design

Asymmetric catalysis is an essential tool in modern chemistry, but increasing environmental concerns demand the development of new catalysts based on cheap, abundant, and less toxic iron. As a result, Knölker-type catalysts have emerged as a promising class of iron catalysts for various chemical transformations, notably the hydrogenation of carbonyls and imines, while asymmetric versions are still under exploration to achieve optimal enantio-selectivities. In this work, we report a novel asymmetric design of a Knölker-type catalyst, in which the C2-rotational symmetric cyclopentadienone ligand possesses chiral substituents on the 2- and 5-positions near the active site. Four examples of the highly modular catalyst design were synthesized via standard organic procedures, and their structures were confirmed with NMR, IR, MS, and polarimetry analysis. Density functional theory (DFT) calculations were conducted to elucidate the spatial conformation of the catalysts, and therewith to rationalize the influence of structural alterations. Transfer- and H2-mediated hydrogenations were successfully established, leading to appreciable enantiomeric excesses (ee) values up to 70%. Amongst all reported Knölker-type catalysts, our catalyst design achieves one of the highest ee values for hydrogenation of acetophenone and related compounds.

[Gene regulation involved in the formation of long-term memory]

My former research focused on silk fibroin gene transcription. The in vivo transcription initiation site of the fibroin gene, which is similar to the site corresponding to the 5'-terminal of mature fibroin mRNA, was determined. By developing a cell-free transcription system prepared from silk glands, it was found that the upstream region of the fibroin gene is responsible for efficient transcription initiation, which has enhancer-like features. More recent research has switched my focus to cellular neurobiology to understand the molecular mechanisms of long-term memory at the level of gene expression in terms of cell differentiation. I first developed an experimental system to analyze promoter activity in primary cultured neuronal cells. Particularly focusing on the transcription regulation of the brain-derived neurotrophic factor (BDNF) gene (Bdnf), I found that the interaction of the cAMP response element-binding protein (CREB) with the CRE sequence is important for the activity-dependent activation of the Bdnf promoter. In addition, this activity-dependent transcriptional regulation occurs in cultured neurons stimulated with excitatory GABAergic inputs, which plays a critical role in promoting the step of neuronal differentiation. Finally, I found that stimulation of the G-protein coupled receptor (GPCR) effectively activates Bdnf promoter IV through selective activation of the calcineurin pathway, irrespective of the type of GPCR if the protein kinase A or C pathway is activated. This induction mechanism appears important to understand intracellular mechanisms evoked via simultaneous neurotransmission of excitatory and modulatory inputs into neurons of the brain.

Lambda-cyhalothrin disrupts the up-regulation effect of 17β-estradiol on post-synaptic density 95 protein expression via estrogen receptor α-dependent Akt pathway

Lambda-cyhalothrin (LCT), one of the type II pyrethroids, has been widely used throughout the world. The estrogenic effect of LCT to increase cell proliferation has been well established. However, whether the estrogenic effect of LCT will influence neurodevelopment has not been investigated. In addition, 17β-Estradiol (E2) plays a crucial role in neurodevelopment and induces an increase in synaptic proteins. The post-synaptic density 95 (PSD95) protein, which is involved in the development of the structure and function of new spines and localized with estrogen receptor α (ERα) at the post-synaptic density (PSD), was detected in our study by using hippocampal neuron cell line HT22. We found that LCT up-regulated PSD95 and ERα expression, estrogen receptor (ER) antagonist ICI182,780 and phosphatidylinositol-4; 5-bisphosphate 3-kinase (PI3K) inhibitor LY294,002 blocked this effect. In addition, LCT disrupted the promotion effect of E2 on PSD95. To investigate whether the observed changes are caused by ERα-dependent signaling activation, we next detected the effects of LCT on the ERα-mediated PI3K-Protein kinase B (PKB/Akt)-eukaryotic initiation factor (eIF) 4E-binding protein 1 (4E-BP1) pathway. There existed an activation of Akt and the downstream factor 4E-BP1 after LCT treatment. In addition, LCT could disrupt the activation effect of E2 on the Akt pathway. However, no changes in cAMP response element-binding protein (CREB) activation and PSD95 messenger ribonucleic acid (mRNA) were observed. Our findings demonstrated that LCT could increase the PSD95 protein level via the ERα-dependent Akt pathway, and LCT might disrupt the up-regulation effect of E2 on PSD95 protein expression via this signaling pathway.

Cu-Mediated 2,2,2-trifluoroethylation of terminal alkynes using 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123)

Cu-Promoted coupling reactions of HCFC-123 with terminal alkynes give trifluoroethylated internal alkynes.

Type II pyrethroid deltamethrin produces antidepressant-like effects in mice

Pyrethroids, which are widely used insecticides with low acute toxicity in mammals, affect sodium channels in neurons. In primary culture of rat cortical neurons, the type II pyrethroid deltamethrin (DM) markedly enhances the expression of the mRNA of brain-derived neurotrophic factor (BDNF) and exerts neurotrophic effects. In this study, we investigated the antidepressant-like effect of DM in mice. The effects of DM were assessed using the forced swimming test (FST) and were compared with those of type I pyrethroid permethrin (PM). Intraperitoneal administration of DM (5 and 10mg/kg), but not of PM (10mg/kg), increased the expression of BDNF mRNA in the hippocampus. DM, but not PM, significantly decreased the immobility time in the FST, and did not affect locomotor activity and motor coordination, suggesting that DM has an antidepressant-like effect. This effect of DM was inhibited by intracerebroventricular injection of K252a, which is an inhibitor of the BDNF receptor TrkB, indicating that the antidepressant-like effects of DM are mediated by BDNF/TrkB signaling pathways. Repeated administration of DM, but not of PM, also exerted antidepressant-like effects, which were long lasting. The results of the present study suggest that DM possesses antidepressant-like properties, and may be a possible source for the development of drugs to treat neurodegenerative and psychiatric disorders including depression.

Using mouse models of autism spectrum disorders to study the neurotoxicology of gene-environment interactions

To better study the role of genetics in autism, mouse models have been developed which mimic the genetics of specific autism spectrum and related disorders. These models have facilitated research on the role genetic susceptibility factors in the pathogenesis of autism in the absence of environmental factors. Inbred mouse strains have been similarly studied to assess the role of environmental agents on neurodevelopment, typically without the complications of genetic heterogeneity of the human population. What has not been as actively pursued, however, is the methodical study of the interaction between these factors (e.g., gene and environmental interactions in neurodevelopment). This review suggests that a genetic predisposition paired with exposure to environmental toxicants plays an important role in the etiology of neurodevelopmental disorders including autism, and may contribute to the largely unexplained rise in the number of children diagnosed with autism worldwide. Specifically, descriptions of the major mouse models of autism and toxic mechanisms of prevalent environmental chemicals are provided followed by a discussion of current and future research strategies to evaluate the role of gene and environment interactions in neurodevelopmental disorders.