[Show abstract][Hide abstract] ABSTRACT: Exposure to ambient fine particulate matter air pollution (PM(2.5); < 2.5 µm in aerodynamic diameter) induces endothelial dysfunction and increases the risk for cardiovascular disease. Endothelial progenitor cells (EPCs) contribute to postnatal endothelial repair and regeneration. In humans and mice, EPC levels are decreased upon exposure to elevated levels of PM(2.5).
We examined the mechanism by which PM(2.5) exposure suppresses circulating levels of EPCs.
Mice were exposed to HEPA-filtered air or concentrated ambient fine particulate matter (CAP, 30-100 µg/m³) from downtown Louisville (Kentucky) air, and progenitor cells from peripheral blood or bone marrow were analyzed by flow cytometry or by culture ex vivo.
Exposure of the mice to CAP (6 hr/day) for 4-30 days progressively decreased circulating levels of EPCs positive for both Flk-1 and Sca-1 (Flk-1(+)/Sca-1(+)) without affecting stem cells positive for Sca-1 alone (Sca-1(+)). After 9 days of exposure, a 7-day exposure-free period led to complete recovery of the circulating levels of Flk-1(+)/Sca-1(+) cells. CAP exposure decreased circulating levels of EPCs independent of apoptosis while simultaneously increasing Flk-1(+)/Sca-1(+) cells in the bone marrow. We observed no change in tissue deposition of these cells. CAP exposure suppressed vascular endothelial growth factor (VEGF)-induced Akt and endothelial nitric oxide synthase (eNOS) phosphorylation in the aorta, and it prevented VEGF/AMD3100-induced mobilization of Flk-1(+)/Sca-1(+) cells into the peripheral blood. Treatment with stem cell factor/AMD3100 led to a greater increase in circulating Flk-1(+)/Sca-1(+) cells in CAP-exposed mice than in mice breathing filtered air.
Exposure to PM(2.5) increases EPC levels in the bone marrow by preventing their mobilization to the peripheral blood via inhibition of signaling events triggered by VEGF-receptor stimulation that are upstream of c-kit activation. Suppression of EPC mobilization by PM(2.5) could induce deficits in vascular repair or regeneration.
Full-text · Article · Mar 2012 · Environmental Health Perspectives
[Show abstract][Hide abstract] ABSTRACT: Cardiovascular disease (CVD) affects 71 million American adults and remains the leading cause of death in the United States and Europe. Despite studies that suggest that the development of CVD may be linked to intrauterine growth or early events in childhood, little direct experimental evidence supports the notion.
We investigated whether exposure to cigarette smoke in utero alters the risk of developing CVD later in life.
We exposed B(6)C(3)F(1) mice (via whole-body inhalation) to either filtered air or mainstream cigarette smoke (MCS, at a particle concentration of 15 mg/m(3)) from gestational day 4 to parturition. Adult offspring were fed a normal chow diet or switched to a high-fat diet 2 weeks before sacrifice. We measured dam and offspring body weight, plasma lipid parameters, lipoprotein subclass particle numbers and sizes, and total antioxidant capacities.
Adult female mice prenatally exposed to MCS demonstrated significantly higher body weight and levels of plasma high-density lipoprotein (HDL) and low-density lipoprotein than did their air-exposed counterparts. When fed a high-fat diet for 2 weeks, males, but not females, exposed prenatally to MCS gained substantially more weight and exhibited dramatic alterations in total cholesterol and HDL levels compared with their air-exposed counterparts.
These data provide, for the first time, direct experimental evidence supporting the notion that prenatal exposure to cigarette smoke affects offspring weight gain and induces a lipid profile that could alter the offspring's risk of developing CVD later in life.
Full-text · Article · Aug 2009 · Environmental Health Perspectives
[Show abstract][Hide abstract] ABSTRACT: Digoxin-like immunoreactive factors (DLIFs) are endogenous mammalian cardenolides with structural features similar to those of the plant-derived digitalis compounds. DLIFs and their structurally related forms (Dh-DLIFs) may serve as effectors of ion-transport activity mediated by their interaction with Na,K-ATPase and thus play a role as a new hormonal axis. Although some evidence implicates the adrenal gland as a tissue source for the DLIFs, little is known about the biosynthetic pathway producing these compounds. We now demonstrate de novo biosynthesis of DLIF by incorporation of radioactive carbon ((14)C) into the structures of both DLIF and Dh-DLIF.
We used a combination of reversed-phase HPLC techniques to separate the radioactive DLIF components after incorporation of (14)C into their structure by use of either [1,2-(14)C]acetic acid or [4-(14)C]cholesterol as precursors and a Y-1 mouse adrenocortical tumor cell line. We also stimulated and suppressed production of steroidogenesis by use of cAMP analogs and Mevastatin, respectively, to demonstrate the dependence of DLIF production on the cholesterol-dependent biosynthetic pathway. A combination of chromatographic mobility, immunoassays specific for digoxin and dihydrodigoxin, and deglycosylation using 5-sulfosalicylic acid were used to identify the DLIF and Dh-DLIF components.
With cholesterol as precursor, the cells produced DLIF (7.5 mCi/mmol) with a labeling efficiency of 10%, whereas with acetate the cells produced DLIF (72.2 mCi/mmol) with a labeling efficiency of 0.08% of the total DLIF produced. The radiolabeled DLIF and Dh-DLIF molecules had identical chromatographic mobilities and stoichiometric removal of sugars as the previously characterized DLIFs isolated from different mammalian species and tissues. With radioactive cholesterol as precursor, the (14)C was incorporated into the DLIF-genin portion of the compounds and not the sugars. Interestingly, treatment of Y-1 cells with 8-bromoadenosine 3':5'-cAMP to stimulate steroidogenesis did not increase production of DLIF or Dh-DLIF but did increase production of progesterone. Mevastatin (5 micromol), an inhibitor of the enzyme hydroxymethylglutaryl-CoA reductase and thus of cholesterol biosynthesis, gave an 85% decrease in the production of (14)C-DLIF and progesterone, but only a modest 15% decrease in (14)C-Dh-DLIF production.
These data demonstrate that the adrenal cell has the cellular machinery necessary for de novo biosynthesis of DLIF and Dh-DLIF starting from a simple carbon pool and also support the concept that cholesterol is a major precursor of the DLIF compounds. This cell culture model provides a source of radiolabeled DLIF compounds for future experimental work.
[Show abstract][Hide abstract] ABSTRACT: Electrospray mass spectrometry allows direct identification and sensitive detection of multiple phospholipids in non-derivatized cell extracts. However, quantitative analyses are not straightforward, and are confounded by analyte and mass discrimination effects, and non-linear dependence of the ion intensity on concentration. This non-linearity is particularly severe in the negative mode and precludes even comparative measurements of anion concentrations. Herein, we report a general method for relating negative electrospray ion intensity to concentration when analyzing multicomponent phospholipid samples. In this method, the intensity of individual ions is measured at several different concentrations of the total mixture and the slope (n(E)) of the double log plot of sample concentration vs. intensity for each analyte is determined. The n(E) is then used to map intensity data to a quantity proportional to concentration for each analyte. The method allows facile and accurate comparison of negative spectra of complex mixtures containing structurally different anions.
Preview · Article · Oct 2002 · Analytical Biochemistry