Prostaglandin D2 synthase: Apoptotic factor in alzheimer plasma, inducer of reactive oxygen species, inflammatory cytokines and dialysis dementia.

BACKGROUND: Apoptosis, reactive oxygen species (ROS) and inflammatory cytokines have all been implicated in the development of Alzheimer's disease (AD). OBJECTIVES: The present study identifies the apoptotic factor that was responsible for the fourfold increase in apoptotic rates that we previously noted when pig proximal tubule, LLC-PK1, cells were exposed to AD plasma as compared to plasma from normal controls and multi-infarct dementia. PATIENTS AND METHODS: The apoptotic factor was isolated from AD urine and identified as lipocalin-type prostaglandin D2 synthase (L-PGDS). L-PGDS was found to be the major apoptotic factor in AD plasma as determined by inhibition of apoptosis approximating control levels by the cyclo-oxygenase (COX) 2 inhibitor, NS398, and the antibody to L-PGDS. Blood levels of L-PGDS, however, were not elevated in AD. We now demonstrate a receptor-mediated uptake of L-PGDS in PC12 neuronal cells that was time, dose and temperature-dependent and was saturable by competition with cold L-PGDS and albumin. Further proof of this endocytosis was provided by an electron microscopic study of gold labeled L-PGDS and immunofluorescence with Alexa-labeled L-PGDS. RESULTS: The recombinant L-PGDS and wild type (WT) L-PGDS increased ROS but only the WTL-PGDS increased IL6 and TNFα, suggesting that differences in glycosylation of L-PGDS in AD was responsible for this discrepancy. CONCLUSIONS: These data collectively suggest that L-PGDS might play an important role in the development of dementia in patients on dialysis and of AD.

Estradiol enhances recovery after myocardial infarction by augmenting incorporation of bone marrow-derived endothelial progenitor cells into sites of ischemia-induced neovascularization via endothelial nitric oxide synthase-mediated activation of matrix metalloproteinase-9.

BACKGROUND: Recent data have indicated that estradiol can modulate the kinetics of endothelial progenitor cells (EPCs) via endothelial nitric oxide synthase (eNOS)-dependent mechanisms. We hypothesized that estradiol could augment the incorporation of bone marrow (BM)-derived EPCs into sites of ischemia-induced neovascularization, resulting in protection from ischemic injury. METHODS AND RESULTS: Myocardial infarction (MI) was induced by ligation of the left coronary artery in ovariectomized mice receiving either 17beta-estradiol or placebo. Estradiol induced significant increases in circulating EPCs 2 and 3 weeks after MI in estradiol-treated animals, and capillary density was significantly greater in estradiol-treated animals. Greater numbers of BM-derived EPCs were observed at ischemic sites in estradiol-treated animals than in placebo-treated animals 1 and 4 weeks after MI. In eNOS-null mice, the effect of estradiol on mobilization of EPCs was lost, as was the functional improvement in recovery from acute myocardial ischemia. A decrease was found in matrix metalloproteinase-9 (MMP-9) expression in eNOS-null mice under basal and estradiol-stimulated conditions after MI, the mobilization of EPCs by estradiol was lost in MMP-9-null mice, and the functional benefit conferred by estradiol treatment after MI in wild-type mice was significantly attenuated. CONCLUSIONS: Estradiol preserves the integrity of ischemic tissue by augmenting the mobilization and incorporation of BM-derived EPCs into sites of neovascularization by eNOS-mediated augmentation of MMP-9 expression in the BM. Moreover, these data have broader implications with regard to our understanding of the role of EPCs in post-MI recovery and on the sex discrepancy in cardiac events.

Estrogen-mediated, endothelial nitric oxide synthase-dependent mobilization of bone marrow-derived endothelial progenitor cells contributes to reendothelialization after arterial injury.

BACKGROUND: We hypothesized that estrogen-induced acceleration of reendothelialization might be mediated in part by effects involving mobilization and incorporation of bone marrow-derived endothelial progenitor cells (EPCs). METHODS AND RESULTS: Carotid injury was induced in ovariectomized wild-type mice receiving either 17beta-estradiol or placebo. Estradiol treatment significantly accelerated reendothelialization of injured arterial segments within 7 days and resulted in a significant reduction of medial thickness 14 and 21 days after the injury. Significant increases in circulating EPCs 3 days after the injury were observed in the estradiol group compared with placebo-treated mice. These data were further supported by fluorescence-activated cell sorting analysis, which disclosed a significant increase in Sca-1/Flk-1-positive cells in estradiol versus control mice. To evaluate the effects of estradiol on bone marrow-derived EPC incorporation at sites of reendothelialization, carotid injury was established in ovariectomized wild-type mice transplanted with bone marrow from transgenic donors expressing beta-galactosidase transcriptionally regulated by the Tie-2 promoter. Significantly greater numbers of X-gal-positive cells were observed at reendothelialized areas in the estradiol group 3 days after injury as compared with placebo. Fluorescent immunohistochemistry 14 days after the injury documented a marked increase in cells expressing both beta-gal, indicating bone marrow origin and Tie-2 expression, and isolectin B4, also indicating endothelial lineage, in the estradiol group compared with control. In contrast, estradiol did not accelerate reendothelialization or augment EPC mobilization into the peripheral circulation after injury in endothelial nitric oxide synthase-deficient mice (eNOS-/-). Furthermore, estradiol exhibited direct stimulatory effects on EPC mitogenic and migration activity and inhibited EPC apoptosis. CONCLUSIONS: Estradiol accelerates reendothelialization and attenuates medial thickening after carotid injury in part by augmenting mobilization and proliferation of bone marrow-derived EPCs and their incorporation into the recovering endothelium at the site of injury.

Geldanamycin attenuates NO-mediated dilation in human skin.

The binding of heat shock protein 90 (HSP90) to endothelial nitric oxide (NO) synthase (eNOS) can enhance eNOS activation. Studies have shown that the HSP90-specific inhibitor geldanamycin (GA) can cause attenuation of NO-mediated processes. Twenty subjects participated in one of two protocols. In each protocol, one forearm of each subject was instrumented with two intradermal microdialysis probes for drug delivery. Laser Doppler flowmeters were used to measure cutaneous blood flow. Skin sites were either treated with the endothelial agonist acetylcholine or locally heated to 42 degrees C, a maneuver that evokes NO-mediated dilation. Interventions were performed with and without GA. In the presence of GA, maximal cutaneous vascular conductance (CVC) to ACh was 20 +/- 3% lower than with ACh alone (P < 0.001). During local heating, maximal CVC in the presence of GA was 22 +/- 6% lower than during heating alone (P < 0.01). The results show that GA can attenuate NO-mediated dilation in human skin, suggesting a potential role for HSP90 in activation of eNOS in the microcirculation.