Assurance of mitochondrial integrity and mammalian longevity by the p62-Keap1-Nrf2-Nqo1 cascade.

Sqstm1/p62 functions in the non-canonical activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2). However, its physiological relevance is not certain. Here, we show that p62(-/-) mice exhibited an accelerated presentation of ageing phenotypes, and tissues from these mice created a pro-oxidative environment owing to compromised mitochondrial electron transport. Accordingly, mitochondrial function rapidly declined with age in p62(-/-) mice. In addition, p62 enhanced basal Nrf2 activity, conferring a higher steady-state expression of NAD(P)H dehydrogenase, quinone 1 (Nqo1) to maintain mitochondrial membrane potential and, thereby, restrict excess oxidant generation. Together, the p62-Nrf2-Nqo1 cascade functions to assure mammalian longevity by stabilizing mitochondrial integrity.

Relationship between zeolite structure and capture capability for radioactive cesium and strontium.

Zeolites are widely used for capturing radioactive Cs+ and Sr2+, but the important structural factors determining their performance have not been clearly understood. To investigate the structure-property relationship, we prepared thirteen zeolites with various structures and Si/Al ratios. Ion-exchange experiments revealed that Cs+ exhibited an enhanced affinity to zeolites with high Si/Al ratios, which could be explained by the dielectric theory. Notably, zeolites containing 8-membered ring (8MR) showed extra-high Cs+ selectivity. Structural analysis using X-ray diffraction proved that Cs+ with an ionic diameter of 3.6 Å was selectively coordinated within 8MR having a cavity diameter of 3.6-4.1 Å. Such unique size-selective Cs+ coordination is analogous to ion complexation by macrocyclic organic ligands (e.g., crown ethers). Divalent Sr2+ showed decreasing affinity to zeolites as the Si/Al ratio increased, because of the increasing average Al-Al distance distribution. Sr2+ exchange exhibited an insignificant dependence on zeolite structures due to its strong hydration, which inhibited close interaction with zeolite frameworks. In terms of kinetics, Sr2+ exchange was significantly slower than Cs+ exchange because of the bulkiness of hydrated Sr2+ ions. Therefore, the micropore channels with large apertures (e.g., 12-membered ring) were beneficial for achieving fast ion-exchange kinetics, especially in the case of Sr2+.