17-β-estradiol Decreases Neutrophil Superoxide Production through Rac1

Neutrophil granulocytes form the biggest free radical producing system of the human body. The importance of this system in atherosclerotic plaque formation and other free radical mediated disorders is confirmed by both in vivo and in vitro studies. Estrogen's effect on free radical production involves multiple estrogen receptors and occurs both on transcriptional and on protein phosphorylational level. Estrogen decreases the superoxide production of neutrophil granulocytes in such a short time frame it is unlikely to be mediated by transcription regulation. We investigated the underlying mechanism through which the mentioned estrogen effect takes place using an immunabsorption-based method. Phosphorylation data of 43 different messenger proteins were used for pathway analysis. The newly identified pathway involved largely second messengers from previously described non-genomic estrogen effects and affected superoxide production via Rac1 - an important regulator of free radical production and chemotaxis. Selective inhibition of the participating second messengers altered superoxide production in the predicted direction confirming that this pathway is at least partly responsible for the effect of 17-β-estradiol on chemoattractant induced superoxide production.

Time course of inducible nitric oxide synthase activity following endotoxin administration in dogs

An increased production of nitric oxide (NO) via the inducible isoform of NO synthase (iNOS) has been incriminated in the pathogenesis of septic shock. Since the time course of iNOS activity is not known during endotoxic shock in dogs, we measured iNOS activity, estimated by the rate of conversion of (14)C-arginine to (14)C-citrulline in the absence of calcium, in the heart, lung, liver, kidney, and gut at 1, 2, 3, 4, and 6 h after a bolus of Escherichia coli endotoxin (2 mg/kg, iv), in the dog. This model, including generous fluid administration, is associated with typical features of human septic shock, including low systemic vascular resistance, altered myocardial function and limited oxygen extraction capability. An increase in iNOS activity was observed at 4 h in the liver (0.24 vs 0.04 mU/mg/min) and at 6 h in the heart (0.26 vs 0.09 mU/mg/min). These findings may contribute to a better delineation of the involvement of NO in endotoxic shock, and to the evaluation of the therapeutic effects of NO inhibitors.