The use of flow cytometric applications to measure the effects of PAHs on growth, membrane integrity, and relative lipid content of the benthic diatom, Nitzschia brevirostris.

This laboratory study measured the direct effects of three polycyclic aromatic hydrocarbon (PAH) compounds (naphthalene, pyrene, and benzo(a)pyrene) upon cell growth, membrane integrity, and BODIPY-stained lipid fluorescence intensity of the benthic diatom Nitzschia brevirostris using flow cytometry as an analysis tool. Previous field and laboratory studies have reported reductions in algal populations following PAH exposure, but specific, functional responses of the microalgae to these pollutants could not be revealed by cell numbers alone. Using flow-cytometric measurements, we confirmed that maximal cell densities in PAH-exposed diatom cultures were significantly lower compared to controls; however, we also discovered increases in lipids and cells with compromised membranes in PAH-exposed cultures. These results highlight new tools for measuring the direct effects of organic pollutants upon the physiology of taxa comprising microphytobenthic communities important in estuarine food webs.

Characterization of 2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine at androgen receptor: mechanistic support for its role in prostate cancer.

2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine (PhIP) is a dietary mutagenic carcinogen that has been shown not only to induce the formation of DNA adducts, but is capable of inducing tumors in the colon, mammary, and prostate glands. The normal development and maturation of the prostate gland, as well as early progression of prostate cancer, is dependent on androgens acting on the androgen receptor (AR). The actual mechanism by which PhIP interacts with our biological system and its potential interaction at the AR has yet to be fully defined. Here, we describe our work in evaluating the molecular events associated with PhIP-mediated disruption of AR function in LNCaP human prostate cancer cells. We demonstrate, by molecular docking simulation, that PhIP and its metabolite can bind to the ligand-binding domain (LBD). The binding competes with dihydrotestosterone (DHT) in the native AR binding cavity of the receptor. In vitro assays show that PhIP increase AR protein expression in LNCaP cells and alters its responsiveness through PSA protein and mRNA expression. We propose that the mechanism for the tissue-specific carcinogenicity seen in the rat prostate tumors and the presumptive human prostate cancer associated with the consumption of well-done meat may be mediated by this receptor activation. Our results indicate that PhIP may play an important role in modifications of AR function.

Immunomodulation in eastern oysters, Crassostrea virginica, exposed to a PAH-contaminated, microphytobenthic diatom.

The trophic transfer of sediment-associated pollutants is a growing concern in shellfish harvesting areas. Previous studies have examined the role of phytoplankton in the transport of organic contaminants to bivalve species, but little information on microphytobenthic communities and their role as contaminant vectors exists. Polycyclic aromatic hydrocarbons (PAHs) are organic compounds formed during natural and industrial processes; they are termed "persistent organic pollutants" because they are only slowly degraded by natural processes. This study examined the transfer of PAH compounds (naphthalene, pyrene, and benzo(a)pyrene) by a microphytobenthic diatom to the eastern oyster, a commercially important shellfish species, to determine if dietary accumulation is a route of contaminant exposure capable of inducing physiological responses. PAH compounds were adsorbed to a diatom culture (Nitzschia brevirostris) in a range of concentrations (5, 125, 625, and 1000 µg L(-1)), and eastern oysters were exposed experimentally to the contaminated diatom cultures to assess possible effects upon oyster hemocytes and selected immune-defense functions. A preliminary experiment was designed to identify individual effects of several PAH compounds (naphthalene, pyrene, and benzo(a)pyrene) on hemocyte viability and phagocytic activity. Results from this experiment revealed that the most-toxic compound, benzo(a)pyrene, at the highest concentration, stimulated an increase in agranular hemocyte counts. A follow-up study examined the effects of benzo(a)pyrene on hemocyte viability, adhesion, phagocytosis, and reactive oxygen species (ROS). These studies showed the ability of this benthic diatom to transport PAHs to the eastern oyster and to cause immunomodulation. Hemocyte responses to dietary PAH exposure included an increase in circulating hemocytes and increased production of reactive oxygen species by these cells.

Social and Environmental Risk Factors for Hypertension in African Americans.

This study tests the hypothesis that disparities of hypertension risk in African Americans is related to lead exposure, perceptions of racism, and stress, among urban (Roxbury, MA) and rural (Gadsden, FL) communities. Analysis of preliminary data from Phase I reveal 60% in Gadsden and 39% in Roxbury respondents self-reported having hypertension. In Gadsden 80% people did not know if their residence contained lead paint, compared to 45% in Roxbury. In Gadsden County, 58% of respondents reported experiencing racial discrimination in different settings compared with 72% in Roxbury. In regression analyses high cholesterol emerged as a significant predictors of hypertension in Gadsden County (OR=8.29, CI=1.4-49.3), whereas monthly household income (OR=0.15, CI=0.04-0.7) and diabetes (OR=6.06, CI=1.4-26.17) were significant predictors of hypertension in Roxbury after adjusting for other covariates. These preliminary findings set the stage for initiating Phase II (Phase I continues recruitment), that entail biological marker measurements to rigorously test main hypothesis.

Induction of cell death, DNA strand breaks, and cell cycle arrest in DU145 human prostate carcinoma cell line by benzo[a]pyrene and benzo[a]pyrene-7,8-diol-9,10-epoxide.

Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon, is a major environmental pollutant. In this study, the effects of this carcinogen/mutagen and one of its metabolites, benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), on human prostate carcinoma cell line DU145, were examined. Cell viability, DNA damage, and cell cycle progression were evaluated as toxic end-points. We have shown that B[a]P and BPDE inhibited cell viability following 48 hr of exposure. Furthermore, comet assay analyses revealed that both B[a]P and BPDE induced DNA strand breaks in a concentration-dependent fashion. Flow cytometric analyses showed that about 70% of DU145 cells were arrested by B[a]P at the G1 phase, while about 76% were arrested at G1 phase by BPDE. These data reveal that B[a]P and BPDE are cytotoxic and genotoxic to DU145 prostate cancer cells.