There is now strong epidemiological evidence that estrogen replacement therapy has a protective effect in postmenopausal women. The cardiovascular protective action of estrogen is reported to be mediated indirectly by an effect on lipoprotein metabolism and by a direct effect on the vessel wall itself. Estrogen is active both in vascular smooth muscle and endothelium. Functionally competent estrogen receptors have been identified in vascular smooth muscle cells, and specific binding sites have been demonstrated in endothelium. Estrogen administration promotes vasodilation both in human and experimental animals, in part by stimulating] prostacyclin and nitric oxide synthesis. Both the prostaglandin synthase and the constitutive nitric oxide synthase were recently reported to be induced by estrogen treatment. In vitro, estrogen exerts a direct inhibitory effect on the smooth muscle by inhibiting calcium influx. In addition, estrogen inhibits vascular smooth muscle cell proliferation. In vivo, estradiol-17 beta prevents neointimal thickening after balloon injury and in rabbit cardiac transplant allografts. These data are consistent with in vitro studies wherein estrogen inhibits [3H]thymidine uptake by arterial segments from porcine coronary artery as well as proliferation of rabbit aortic vascular smooth muscle cells induced by hyperlipedemic serum. Recent studies have also reported an effect of estrogen on directed vascular smooth muscle cell migration. Furthermore, like other steroids, the effect of estrogen on the vessel wall has a rapid nongenomic component involving membrane phenomena, such as alteration of membrane ionic permeability and activation of membrane-bound enzymes, as well as the classical genomic effect involving estrogen receptor activation and gene expression. The nature of these estrogen response genes in the vessel wall and their relation to vasodilation and antiproliferation remain to be determined.

Amyloid-␤, the pathologic protein in Alzheimer's disease, induces chemotaxis and production of reactive oxygen species in phagocytic cells, but mechanisms have not been fully defined. Here we provide three lines of evidence that the phagocyte G protein-coupled receptor (N-formylpeptide receptor 2 (FPR2)) mediates these amyloid-␤-dependent functions in phagocytic cells. First, transfection of FPR2, but not related receptors, including the other known N-formylpeptide receptor FPR, reconstituted amyloid-␤-dependent chemotaxis and calcium flux in HEK 293 cells. Second, amyloid-␤ induced both calcium flux and chemotaxis in mouse neutrophils (which express endogenous FPR2) with similar potency as in FPR2-transfected HEK 293 cells. This activity could be specifically desensitized in both cell types by preincubation with a specific FPR2 agonist, which desensitizes the receptor, or with pertussis toxin, which uncouples it from G i -dependent signaling. Third, specific and reciprocal desensitization of superoxide production was observed when N-formylpeptides and amyloid-␤ were used to sequentially stimulate neutrophils from FPR ؊/؊ mice, which express FPR2 normally. Potential biological relevance of these results to the neuroinflammation associated with Alzheimer's disease was suggested by two additional findings: first, FPR2 mRNA could be detected by PCR in mouse brain; second, induction of FPR2 expression correlated with induction of calcium flux and chemotaxis by amyloid-␤ in the mouse microglial cell line N9. Further, in sequential stimulation experiments with N9 cells, N-formylpeptides and amyloid-␤ were able to reciprocally cross-desensitize each other. Amyloid-␤ was also a specific agonist at the human counterpart of FPR2, the FPR-like 1 receptor. These results suggest a unified signaling mechanism for linking amyloid-␤ to phagocyte chemotaxis and oxidant stress in the brain.

Background-Previous investigations provide evidence that an enzyme related to the phagocyte NADPH oxidase produces superoxide in the blood vessel wall. These data, however, are confounded by observations that both NADPH and NADH serve as substrates for superoxide production in vascular cells. To clarify this issue, we compared the superoxidegenerating capabilities of vascular smooth muscle cells (VSMCs) derived from wild-type (p47phox ϩ/ϩ ; phagocyte oxidase) mice with those from mice that lack p47phox (p47phox Ϫ/Ϫ ; "knockout"), an essential component of the phagocyte NADPH oxidase. Methods and Results-VSMCs were derived from aortic explants harvested from p47phox ϩ/ϩ or p47phox Ϫ/Ϫ mice. VSMCs from p47phox ϩ/ϩ but not those from p47phox Ϫ/Ϫ mice produced superoxide after stimulation by phorbol myristate acetate. Consistent with this, p47phox was detected only in p47phox ϩ/ϩ VSMCs. p47phox-transduced p47phox Ϫ/Ϫ but not enhanced green fluorescent protein-transduced p47phox Ϫ/Ϫ VSMCs generated significant levels of superoxide after stimulation by angiotensin II or platelet-derived growth factor-BB (PDGF-BB). Enhanced expression of recombinant p47phox in p47phox-transduced p47phoxϪ/Ϫ cells correlated with superoxide production in these cells. Conclusions-These