Cadmium decreases crown root number by decreasing endogenous nitric oxide,which is indispensable for crown root primordia initiation in rice seedlings

Cadmium (Cd) is toxic to crown roots (CR), which are essential for maintaining normal growth and development in rice seedlings. Nitric oxide (NO) is an important signaling molecule that plays a pivotal role in plant root organogenesis. Here, the effects of Cd on endogenous NO content and root growth conditions were studied in rice seedlings. Results showed that similar to the NO scavenger, cPTIO, Cd significantly decreased endogenous NO content and CR number in rice seedlings, and these decreases were recoverable with the application of sodium nitroprusside (SNP, a NO donor). Microscopic analysis of root collars revealed that treatment with Cd and cPTIO inhibited CR primordia initiation. In contrast, although SNP partially recovered Cd-caused inhibition of CR elongation, treatment with cPTIO had no effect on CR elongation. l-NMMA, a widely used nitric oxide synthase (NOS) inhibitor, decreased endogenous NO content and CR number significantly, while tungstate, a nitrate reductase (NR) inhibitor, had no effect on endogenous NO content and CR number. Moreover, enzyme activity assays indicated that treatment with SNP inhibited NOS activity significantly, but had no effect on NR activity. All these results support the conclusions that a critical endogenous NO concentration is indispensable for rice CR primordia initiation rather than elongation, NOS is the main source for endogenous NO generation, and Cd decreases CR number by inhibiting NOS activity and thus decreasing endogenous NO content in rice seedlings.     

Acetyl-Ile-Gly-Leu protects neurons from Aβ1–42 induced toxicity in vitro and in V337M human tau-expressing mice

AimsWe previously reported that the neurotoxicity of amyloid β protein (Aβ_1–42, 10 nM) was blocked by an Aβ-derived tripeptide, Aβ_32–34 (Ile-Gly-Leu, IGL), suggesting that IGL may be a lead compound in the design of Aβ antagonists. In the present study, three stable forms of IGL peptide with acetylation of its N-terminal and/or amidation of its C-terminal (acetyl-IGL, IGL-NH₂ and acetyl-IGL-NH₂) were synthesized and examined for their effects on Aβ-induced neurotoxicity.Main methodsPhosphatidylinositol 4-kinase type II (PI4KII) activity was measured using recombinant human PI4KIIα kinase and cell viability was assessed in primary cultured hippocampal neurons. To test effects in vivo, 1.5 μl of 100 nM Aβ and/or 100 nM acetyl-IGL was injected into the hippocampal CA1 region of right hemisphere in transgenic mice expressing V337M human tau protein. Four weeks later, behavior performance in the Morris water maze was tested and after another 2 weeks, sections of brain were prepared for immunohistochemistry.Key findingsAmong the three modified tripeptides, acetyl-IGL attenuated the Aβ-induced inhibition of PI4KII activity as well as enhancement of glutamate neurotoxicity in primary cultured rat hippocampal neurons. Injection of Aβ into the hippocampus of mice impaired spatial memory and increased the number of degenerating neurons in bilateral hippocampal regions. Co-injection of acetyl-IGL prevented the learning impairment as well as the neuronal degeneration induced by Aβ.SignificanceThese results suggest that a modified tripeptide, acetyl-IGL, may be effective in the treatment of Alzheimer's disease.     

Design,synthesis and biological evaluation of novel dual inhibitors of acetylcholinesterase and β-secretase

To explore novel effective drugs for the treatment of Alzheimer’s disease (AD), a series of dual inhibitors of acetylcholineterase (AChE) and β-secretase (BACE-1) were designed based on the multi-target-directed ligands strategy. Among them, inhibitor 28 exhibited good dual potency in enzyme inhibitory potency assay (BACE-1: IC₅₀ = 0.567 μM; AChE: IC₅₀ = 1.83 μM), and also showed excellent inhibitory effects on Aβ production of APP transfected HEK293 cells (IC₅₀ = 98.7 nM) and mild protective effect against hydrogen peroxide (H₂O₂)-induced PC12 cell injury. Encouragingly, intracerebroventricular injection of 28 into amyloid precursor protein (APP) transgenic mice caused a 29% reduction of Aβ_1–40 production. Therefore, 28 was demonstrated as a good lead compound for the further study and more importantly, the strategy of AChE and BACE-1 dual inhibitors might be a promising direction for developing novel drugs for AD patients.     

Bacterial decolorization and degradation of the reactive dye Reactive Red 180 by Citrobacter sp. CK3

A bacterial strain, CK3, with remarkable ability to decolorize the reactive textile dye Reactive Red 180, was isolated from the activated sludge collected from a textile mill. Phenotypic characterization and phylogenetic analysis of the 16S rDNA sequence indicated that the bacterial strain belonged to the genus Citrobacter. Bacterial isolate CK3 showed a strong ability to decolorize various reactive textile dyes, including both azo and anthraquinone dyes. Anaerobic conditions with 4 g l^?1 glucose, pH = 7.0 and 32 °C were considered to be the optimum decolorizing conditions. Citrobacter sp. CK3 grew well in a high concentration of dye (200 mg l^?1), resulting in approximately 95% decolorization extent in 36 h, and could tolerate up to 1000 mg l^?1 of dye. UV–vis analyses and colorless bacterial cells suggested that Citrobacter sp. CK3 exhibited decolorizing activity through biodegradation, rather than inactive surface adsorption. It is the first time that a bacterial strain of Citrobacter sp. has been reported with decolorizing ability against both azo and anthraquinone dyes. High decolorization extent and facile conditions show the potential for this bacterial strain to be used in the biological treatment of dyeing mill effluents.     

Inhibition of retinal neovascularization by gene transfer of small interfering RNA targeting HIF-1alpha and VEGF

Retinal neovascularization (NV) occurs in various ocular disorders including proliferative diabetic retinopathy, retinopathy of prematurity and secondary neovascular glaucoma, which often result in blindness. Vascular endothelial growth factor (VEGF) is an essential growth factor for angiogenesis, and is particularly regulated by hypoxia inducible factor-1alpha (HIF-1alpha) under hypoxic conditions. Therefore, HIF-1alpha and VEGF could provide targets for therapeutic intervention on retinal NV. In this study, we investigated the inhibitory effects of small interfering RNA (siRNA) targeting HIF-1alpha and VEGF on the expression of HIF-1alpha and VEGF in human umbilical vein endothelial cells (HUVEC) in vitro and on retinal NV in vivo. siRNA-expressing plasmids targeting human HIF-1alpha (HIF-1alpha siRNA) and human VEGF(165) (VEGF siRNA) were constructed. They were transfected and co-transfected to HUVEC and C57BL/6J mice of ischemic retinopathy model. HIF-1alpha siRNA and VEGF siRNA specifically downregulated HIF-1alpha and VEGF at both mRNA and protein levels in vitro and in vivo. Neovascular tufts and neovascular nuclei were decreased in gene therapy group compared to control hypoxia group. Co-transfection of HIF-1alpha siRNA and VEGF siRNA resulted in maximal effects on VEGF suppression in vitro and in vivo. It also manifested the maximal inhibitory effect on retinal NV. These results indicate that the application of HIF-1alpha siRNA and VEGF siRNA technology holds great potential as a novel therapeutic for retinal NV.     

Zn2+ mediates ischemia-induced impairment of the ubiquitin-proteasome system in the rat hippocampus

Deposition of ubiquitinated protein aggregates is a hallmark of neurodegeneration in both acute neural injuries, such as stroke, and chronic conditions, such as Parkinson's disease, but the underlying mechanisms are poorly understood. In the present study, we examined the role of Zn²⁺ in ischemia-induced impairment of the ubiquitin-proteasome system in the CA1 region of rat hippocampus after transient global ischemia. We found that scavenging endogenous Zn²⁺ reduced ischemia-induced ubiquitin conjugation and free ubiquitin depletion. Furthermore, exposure to zinc chloride increased ubiquitination and inhibited proteasomal enzyme activity in cultured hippocampal neurons in a concentration- and time-dependent manner. Further studies of the underlying mechanisms showed that Zn²⁺-induced ubiquitination required p38 activation. These findings indicate that alterations in Zn²⁺ homeostasis impair the protein degradation pathway.