Glutathione-S-transferase in Nereis succinea (Polychaeta) and its induction by xeno-estrogen.

The need to replace or at least to reduce the use of vertebrates in toxicity tests is a timely major concern in research and industry but to date, efforts made to minimize their use are still far from complete. Increasing demands for toxicity tests put considerable pressures upon the development of future fast and efficient test methods using invertebrates. In fact, to date, few studies provide links between biochemical and cellular effects of xeno-estrogens in aquatic invertebrates. Glutathione-S-transferase (GST) activity, as a biomarker of stress exposure, was measured in the population of clamworms (Nereis succinea) from Cardiff Bay. In addition, we examined the effect of single exposure to nonylphenol (NP) on this enzymatic activity. Field study results showed a relationship between the worm's size, reproductive status, and GST activity from the field population. In addition, we show a significant increase in the GST activity at 100 µg/L NP with sex-specific responses. The xeno-estrogens, which could affect reproduction of nereid by interfering in normal endocrinological pathways, are eliminated through GST by conjugation with glutathione. This work shows for the first time that GST activity depends on sex and stage of the clamworms and also that the xeno-estrogen NP induces its activity. This study supports the use of this species as a bioindicator of aquatic pollution and lays the foundation to causally link toxic exposure with reproductive output.

High glucose enhances store-operated calcium entry by upregulating ORAI/STIM via calcineurin-NFAT signalling.

UNLABELLED: ORAI and stromal interaction molecule (STIM) are store-operated channel molecules that play essential roles in human physiology through a coupling mechanism of internal Ca(2+) store to Ca(2+) influx. However, the roles of ORAI and STIM in vascular endothelial cells under diabetic conditions remain unknown. Here, we investigated expression and signalling pathways of ORAI and STIM regulated by high glucose or hyperglycaemia using in vitro cell models, in vivo diabetic mice and tissues from patients. We found that ORAI1-3 and STIM1-2 were ubiquitously expressed in human vasculatures. Their expression was upregulated by chronic treatment with high glucose (HG, 25 mM D-glucose), which was accompanied by enhanced store-operated Ca(2+) influx in vascular endothelial cells. The increased expression was also observed in the aortae from genetically modified Akita diabetic mice (C57BL/6-Ins2(Akita)/J) and streptozocin-induced diabetic mice, and aortae from diabetic patients. HG-induced upregulation of ORAI and STIM genes was prevented by the calcineurin inhibitor cyclosporin A and NFATc3 siRNA. Additionally, in vivo treatment with the nuclear factor of activated T cells (NFAT) inhibitor A-285222 prevented the gene upregulation in Akita mice. However, HG had no direct effects on ORAI1-3 currents and the channel activation process through cytosolic STIM1 movement in the cells co-expressing STIM1-EYFP/ORAIs. We concluded that upregulation of STIM/ORAI through Ca(2+)-calcineurin-NFAT pathway is a novel mechanism causing abnormal Ca(2+) homeostasis and endothelial dysfunction under hyperglycaemia. KEY MESSAGE: ORAI1-3 and STIM1-2 are ubiquitously expressed in vasculatures and upregulated by high glucose. Increased expression is confirmed in Akita (Ins2(Akita)/J) and STZ diabetic mice and patients. Upregulation mechanism is mediated by Ca(2+)/calcineurin/NFATc3 signalling. High glucose has no direct effects on ORAI1-3 channel activity and channel activation process.