Nuclear factor erythroid‐derived 2–related factor 2 activates glutathione S‐transferase expression in the midgut of Spodoptera litura (Lepidoptera: Noctuidae) in response to phytochemicals and insecticides

Detoxication enzymes play an important role in insect resistance to xenobiotics such as insecticides and phytochemicals. We studied the pathway for activating the expression of glutathione S‐transferases (GSTs) in response to selected xenobiotics. An assay of the promoter activity of GST epsilon 1 (Slgste1) of Spodoptera litura led to the discovery of a cis‐regulating element. An antioxidant response element was activated in response to indole‐3‐carbinol (I3C) and chlorpyrifos (CPF) and was able to bind with the xenobiotic sensor protein nuclear factor erythroid‐derived 2–related factor 2 (SlNrf2). SlNrf2 and Slgste1 were responsive to reactive oxygen species induced by I3C and CPF in a S. litura cell line, as well as in S. litura midguts. SlNrf2 RNA interference (RNAi) reduced the message RNA levels of Slgste1 and the peroxidase activity of GSTs in response to I3C, xanthotoxin, CPF and deltamethrin. SlNrf2 RNAi and inhibitor treatment of GST activity decreased the viability of I3C‐treated cells. These results indicate that SlNrf2 activates the expression of GSTs in response to oxidative stresses caused by exposure to xenobiotics.     

静脉高压导致的剪应力改变在载脂蛋白A-1结合蛋白调控血管内皮生长因子表达中的作用

目的：探讨静脉高压对大鼠上矢状窦的血流剪应力作用，以及载脂蛋白A-1结合蛋白（apoA-I binding protein,AIBP）介导的血管新生作用及潜在机制。方法：建立不同静脉压力梯度的大鼠模型（4组）：A组大鼠行右侧颈动脉-颈外静脉吻合术+左侧横窦闭塞术+顶骨磨除术；B组大鼠行右侧颈动脉-颈外静脉吻合术+顶骨磨除术；C组大鼠行右侧颈动脉结扎术+右侧颈外静脉结扎术+顶骨磨除术；D组大鼠行顶骨磨除术。测量并计算3个月后上矢状窦剪应力。用Western印迹法、real-timePCR及免疫组化检测硬膜组织中AIBP、血管内皮生长因子（vascular endothelial growth factor,VEGF）的表达情况。将人脐静脉内皮细胞(human umbilical vein endothelial cell，HUVEC)分别于不同剪应力环境下培养后，检测细胞中AIBP、VEGF的表达及总胆固醇的含量。结果：静脉高压大鼠模型上矢状窦血流剪应力较D组明显增大（P<0.05），且剪应力改变与静脉端压力正相关。real-timePCR和Western印迹显示，与D组相比，A组和B组大鼠硬脑膜中AIBP的表达下调、VEGF表达上调（P<0.01）。免疫组化结果示，AIBP在硬膜血管全层均有表达。体外实验中，HUVEC在高剪应力环境中与低剪应力环境下相比，AIBP表达量下调、VEGF表达上调、总胆固醇含量升高（P<0.05）。结论：静脉端压力升高可导致上矢状窦内血流剪应力增大，抑制AIBP的表达，减少细胞膜上胆固醇的流出，促进VEGF介导的血管新生。     

Three amino acid residues of an odorant‐binding protein are involved in binding odours in Loxostege sticticalis L.

Odorant‐binding proteins (OBPs) play an important role in insect olfactory processes and are thought to be responsible for the transport of pheromones and other semiochemicals across the sensillum lymph to the olfactory receptors within the antennal sensilla. As an important general odorant binding protein in the process of olfactory recognition, LstiGOBP1 of Loxostege sticticalis L. has been shown to have good affinity to various plant volatiles. However, the binding specificity of LstiGOBP1 should be further explored in order to better understand the olfactory recognition mechanism of L. sticticalis. In this study, real‐time PCR experiments indicated that LstiGOBP1 was expressed primarily in adult antennae. Homology modelling and molecular docking were then conducted on the interactions between LstiGOBP1 and 1‐heptanol to understand the interactions between LstiGOBP1 and their ligands. Hydrogen bonds formed by amino acid residues might be crucial for the ligand‐binding specificity on molecular docking, a hypothesis that was tested by site‐directed mutagenesis. As predicted binding sites for LstiGOBP1, Thr15, Trp43 and Val14 were replaced by alanine to determine the changes in binding affinity. Finally, fluorescence assays revealed that the mutants Thr15 and Trp43 had significantly decreased binding affinity to most odours; in mutants that had two‐site mutations, the binding to the six odours that were tested was completely abolished. This result indicates that Thr15 and Trp43 were involved in binding these compounds, possibly by forming multiple hydrogen bonds with the functional groups of the ligands. These results provide new insights into the detailed chemistry of odours’ interactions with proteins.     

Exenatide upregulates gene expression of glucagon‐like peptide‐1 receptor and nerve growth factor in streptozotocin/nicotinamide‐induced diabetic mice

Glucagon‐like peptide‐1 (GLP‐1) is an incretin hormone that has modulating effects on insulin release. GLP‐1 and receptors for GLP‐1 are widely expressed throughout the body including the brain. The expression of GLP‐1 receptors is very specific to large neurons in hippocampus, neocortex, and cerebellum. GLP‐1 receptor stimulation enhances glucose‐dependent insulin secretion and lowers blood glucose in type 2 diabetes mellitus. Studies on adipobiology of neurotrophins have focused on nerve growth factor (NGF) as an example of adipose‐derived neurotrophins. Compromised trophic factor signaling may underlie neurodegenerative diseases ranging from Alzheimer's disease to diabetic neuropathies. Exenatide, a potent and selective agonist for the GLP‐1 receptor, is currently approved for the treatment of type 2 diabetes mellitus. The aim of this study was to assess the effect of chronic exenatide treatment on the hippocampal gene expression levels of GLP‐1 receptor and NGF in diabetic mice. The effects of chronic exenatide treatment (0.1 μg/kg, s.c., twice daily for 2 weeks) on GLP‐1 receptor and NGF gene expression levels in the hippocampus of streptozotocin/nicotinamide (STZ–NA)‐induced diabetic mice were assessed by quantitative real‐time polymerase chain reaction (RT‐PCR). The results of this study revealed that hippocampal gene expression of GLP‐1 receptor and NGF were downregulated in diabetic mice. Importantly, a significant increase in the gene expression level of GLP‐1 receptor and NGF was determined after 2 weeks of exenatide administration. Increased gene expression level of GLP‐1 receptor and NGF may underlie the beneficial action of exenatide in STZ/NA‐induced diabetes.