Astragalus Polysaccharides Reduce High-glucose-induced Rat Aortic Endothelial Cell Senescence and Inflammasome Activation by Modulating the Mitochondrial Na+/Ca2+ Exchanger

Vascular endothelial cells play a vital role in atherosclerotic changes and the progression of cardiovascular disease in older adults. Previous studies have indicated that Astragalus polysaccharides (APS), a main active component of the traditional Chinese medicine Astragalus, protect mitochondria and exert an antiaging effect in the mouse liver and brain. However, the effect of APS on rat aortic endothelial cell (RAEC) senescence and its underlying mechanism have not been investigated. In this study, we extracted RAECs from 2-month-old male Wistar rats by the tissue explant method and found that APS ameliorated the high-glucose-induced increase in the frequency of SA-β-Gal positivity and the levels of the senescence-related proteins p16, p21, and p53. APS increased the tube formation capacity of RAECs under high-glucose conditions. Moreover, APS enhanced the expression of the mitochondrial Na⁺/Ca²⁺ exchanger NCLX, and knockdown of NCLX by small interfering RNA (siRNA) transfection suppressed the antiaging effect of APS under high-glucose conditions. Additionally, APS ameliorated RAEC mitochondrial dysfunction, including increasing ATP production, cytochrome C oxidase activity and the oxygen consumption rate (OCR), and inhibited high-glucose-induced NLRP3 inflammasome activation and IL-1β release, which were reversed by siNCLX. These results indicate that APS reduces high-glucose-induced inflammasome activation and ameliorates mitochondrial dysfunction and senescence in RAECs by modulating NCLX. Additionally, APS enhanced the levels of autophagy-related proteins (LC3B-II/I, Atg7) and increased the quantity of autophagic vacuoles under high-glucose conditions. Therefore, these data demonstrate that APS may reduce vascular endothelial cell inflammation and senescence through NCLX.

Variation of nanoparticle fraction and compositions in two-stage double peaks aging precipitation of Al-Zn-Mg alloy

Atom probe tomography (APT) coupling high-resolution transmission electron microscopy (HRTEM) was used to analyze the fraction and compositions of different nanoparticles in two-stage double peaks aging process of Al-Zn-Mg alloy. Al content is found to be closely related to the size of nanoparticles and it can be greater than ~ 50.0 at. % in the nanoparticle with the equivalent radius under ~ 3.0 nm. Correspondingly, Al content of the nanoparticle, with the equivalent radius over ~ 5.0 nm, is measured under ~ 40.0 at. %. Evolution from Guinier-Preston (G.P.) zone to η phase is a growing process where Mg and Zn atoms enter the nanoparticle, therefore rejecting Al atoms. G.P. zones can take up a number fraction of ~ 85.0 and ~ 22.7% of nanoparticles in the first and second peak-aged samples, respectively, and even in the over-aged (T73) sample, they can still be found. As aging time increases, fraction of η' phases monotonically rises to the peak value (~ 54.5%) in the second peak-aged state and then drops, which is significant for the second hardness peak and directly proves their function as the transitional medium. In T73 state, ~ 63.3% nanoparticles compose of η phases, which were measured to still contain ~ 10.2 to ~ 36.4 at. % Al atoms.

Genetic and molecular analyses of picA, a plant-inducible locus on the Agrobacterium tumefaciens chromosome

picA is an Agrobacterium tumefaciens chromosomal locus, identified by Mu d11681 mutagenesis, that is inducible by certain acidic polysaccharides found in carrot root extract. Cloning and genetic analysis of a picA::lacZ fusion defined a region of the picA promoter that is responsible for the induction of this locus. Furthermore, we identified a possible negative regulator of picA expression upstream of the picA locus. This sequence, denoted pgl, has extensive homology to polygalacturonase genes from several organisms and inhibited the induction of the picA promoter when present in multiple copies in A. tumefaciens. DNA sequence analysis indicated at least two long open reading frames (ORFs) in the picA region. S1 nuclease mapping was used to identify the transcription initiation site of picA. Mutation of ORF1, but not ORF2, of the picA locus was responsible for an increased aggregation of A. tumefaciens, forming "ropes" in the presence of pea root cap cells. In addition, a potato tuber disk virulence assay indicated that a preinduced picA mutant was more virulent than was the wild-type control, a further indication that the picA locus regulates the surface properties of the bacterium in the presence of plant cells or plant cell extracts.