Cognitive Deficits and Alzheimer's Disease-Like Pathologies in the Aged Chinese Tree Shrew.

Alzheimer's disease (AD) is the most common chronic progressive neurodegenerative disease in the elderly. It has an increasing prevalence and a growing health burden. One of the limitations in studying AD is the lack of animal models that show features of Alzheimer's pathogenesis. The tree shrew has a much closer genetic affinity to primates than to rodents and has great potential to be used for research into aging and AD. In this study, we aimed to investigate whether tree shrews naturally develop cognitive impairment and major AD-like pathologies with increasing age. Pole-board and novel object recognition tests were used to assess the cognitive performance of adult (about 1 year old) and aged (6 years old or older) tree shrews. The main AD-like pathologies were assessed by Western blotting, immunohistochemical staining, immunofluorescence staining, and Nissl staining. Our results showed that the aged tree shrews developed an impaired cognitive performance compared to the adult tree shrews. Moreover, the aged tree shrews exhibited several age-related phenotypes that are associated with AD, including increased levels of amyloid-ß (Aß) accumulation and phosphorylated tau protein, synaptic and neuronal loss, and reactive gliosis in the cortex and the hippocampal tissues. Our study provides further evidence that the tree shrew is a promising model for the study of aging and AD.

Naringin exerts antiarrhythmic effects by inhibiting channel currents in mouse cardiomyocytes.

INTRODUCTION: Naringin, a flavonoid extracted from citrus plants, has a variety of biological effects. Studies have shown that increasing the consumption of flavonoid-rich foods can reduce the incidence of cardiac arrhythmia. Naringin has been reported to have beneficial cardiovascular effects and thus can be used to prevent cardiovascular diseases, but the electrophysiological mechanism through which it prevents arrhythmias has not been elucidated. This study was conducted to investigate the effect of naringin on the transmembrane ion channel currents in mouse ventricular myocytes and the antiarrhythmic effect of this compound on Langendorff-perfused mouse hearts. METHODS: Action potentials (APs) and ionic currents were recorded in isolated ventricular myocytes using the whole-cell patch-clamp technique. Anemone toxin II (ATX II) and CaCl2 were used to induce early afterdepolarizations (EADs) and delayed afterdepolarizations (DADs), respectively. Electrocardiogram (ECG) recordings were conducted in Langendorff-perfused mouse hearts with a BL-420F biological signal acquisition and analysis system. RESULTS: At the cellular level, naringin shortened the action potential duration (APD) of ventricular myocytes and decreased the maximum depolarization velocity (Vmax) of APs.Naringin inhibited the L-type calcium current (ICa.L) and ATX II enhanced the late sodium current (INa.L) in a concentration-dependent manner with IC50 values of 508.5 µmol/L (n = 9) and 311.6 µmol/L (n = 10), respectively. In addition, naringin also inhibited the peak sodium current (INa·P) and delayed the rectifier potassium current (IK) and the transient outward potassium current (Ito). Moreover, naringin reduced ATX II-induced APD prolongation and EADs and had a significant inhibitory effect on CaCl2-induced DADs as well. At the organ level, naringin reduced the incidence of ventricular tachycardia (VT) and ventricular fibrillation (VF) induced by ATX II and shortened the duration of both in isolated hearts. CONCLUSION: Naringin can inhibit the occurrence of EADs and DADs at the cellular level; furthermore, it can inhibit INa.L, ICa.L, INa·P, IK, and Ito in ventricular myocytes. Naringin also inhibits arrhythmias induced by ATX II in hearts. By investigating naringin with this electrophysiological method for the first time, we determined that this flavonoid may be a multichannel blocker with antiarrhythmic effects.

Novel polypyridyl ruthenium complexes acting as high affinity DNA intercalators, potent transcription inhibitors and antitumor reagents.

Six novel polypyridyl ruthenium complexes with (E)-2-styryl-1H- imidazo[4,5-f][1,10]phenanthroline ligand and its analogues have been designed to enhance the DNA intercalation ability of their model compound [Ru(bpy)2(pip)]2+ (bpy = 2,2'-bipyridine, pip = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline). As shown in the optimized geometry of the complexes, the introduction of styryl group not only extended the conjugated area of the intercalative ligand, but also retained the excellent planarity. These two merits have been proven to be beneficial for their DNA intercalation, thus greatly improved their inhibition activity towards DNA transcription by RNA polymerase and DNA topoisomerase, two enzymes closely related to both DNA and tumor cell growth. The relationships between the substituent group structures and the biological activities have also been investigated from energetic and electronic aspects by quantum chemistry calculations. Results from cell cytotoxicity and apoptosis assay testified that the styryl substituted ruthenium complexes possessed higher antitumor activity than [Ru(bpy)2(pip)]2+, as expected. As quantified in the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the tumor cell death is caused mostly through apoptosis for Ru2 and Ru3, while non-apoptotic processes for Ru1, Ru4 and Ru5. In vitro fluorescence evaluation revealed that all complexes located mainly in cytoplasm, but the three complexes with high antiproliferative activity could enter nucleus. All complexes have shown apparent lower cytotoxicity towards normal human colon epithelial cell CCD-841-CON than the examined tumor cell lines.