Valinomycin

Membrane transporters are involved in enormous number of physiological and pathological processes. Under oxidative stress they become targets for reactive oxygen species and its derivatives which cause protein damage and/or influence protein function(s). The molecular mechanisms of this interaction are poorly understood. Here we describe a novel lipid-mediated mechanism by which biologically important reactive aldehydes (RAs; 4-hydroxy-2-nonenal, 4-hydroxy-2-hexenal and 4-oxo-2-nonenal) modify the activity of several membrane transporters. We revealed that investigated RAs covalently modify the membrane lipid phosphatidylethanolamine (PE), that lead to the formation of different membrane active adducts. Molecular dynamic simulations suggested that anchoring of PE-RA adducts in the lipid headgroup region is primarily responsible for changes in the lipid membrane properties, such as membrane order parameter, boundary potential and membrane curvature.

Spermatozoa are stored in a quiescent state in the male reproductive tract and motility is induced in response to various environmental stimuli, such as change of osmolality (general case) and a decrease of extracellular K(+) in fish from Acipenseridae family. This study was aimed to investigate the relationship between osmolality and extracellular K(+) concentration in controlling sperm motility in sturgeon. Pre-incubation of sturgeon sperm for 5s in hypertonic solutions of glycerol, NaCl, or sucrose (each of 335mOsm/kg osmolality) prepares sturgeon spermatozoa to become fully motile in presence of high concentration of K(+) ions (15mM), which has previously been demonstrated to fully repress motility. Furthermore, presence of 0.5mM KCl during the high osmolality pre-incubation exposure completely prevented subsequent spermatozoa activation in a K(+)-rich media. Manipulating the transport of K(+) ions by the presence of K(+) ionophore (valinomycin), it was concluded that once an efflux of K(+) ions, the precursor of sturgeon sperm motility activation, is taking place, spermatozoa then become insensitive to a large extracellular K(+) concentration.

Osteoclasts (OCs) play a pivotal role in a variety of lytic bone diseases including osteoporosis, arthritis, bone tumors, Paget's disease and the aseptic loosening of orthopedic implants. The primary focus for the development of bone-protective therapies in these diseases has centered on the suppression of OC formation and function. In this study we report that thonzonium bromide (TB), a monocationic surface-active agent, inhibited RANKL-induced OC formation, the appearance of OC-specific marker genes and bone-resorbing activity in vitro. Mechanistically, TB blocked the RANKL-induced activation of NF-κB, ERK and c-Fos as well as the induction of NFATc1 which is essential for OC formation. TB disrupted F-actin ring formation resulting in disturbances in cytoskeletal structure in mature OCs during bone resorption. Furthermore, TB exhibited protective effects in an in vivo murine model of LPS-induced calvarial osteolysis. Collectively, these data suggest that TB might be a useful alternative therapy in preventing or treating osteolytic diseases.

SCOPE: Intestinal cells are constantly exposed to luminal toxins. In this study, we investigated the effect of cellular stress caused by valinomycin, which is structurally and functionally similar to the bacterial toxin cereulide, on quercetin metabolism and cellular localization in undifferentiated cells.