Dibenzo(def,p)chrysene (DBC), (also known as dibenzo[a,l]pyrene), is a high molecular weight polycyclic aromatic hydrocarbon (PAH) found in the environment, including food, produced by the incomplete combustion of hydrocarbons. DBC, classified by IARC as a 2A probable human carcinogen, has a relative potency factor (RPF) in animal cancer models 30-fold higher than benzo[a]pyrene. No data are available describing disposition of high molecular weight (>4 rings) PAHs in humans to compare to animal studies. Pharmacokinetics of DBC was determined in 3 female and 6 male human volunteers following oral micro-dosing (29 ng, 5 nCi) of [14C]-DBC. This study was made possible with highly sensitive accelerator mass spectrometry (AMS), capable of detecting [14C]-DBC equivalents in plasma and urine following a dose considered of de minimus risk to human health. Plasma and urine were collected over 72 h. The plasma Cmax was 68.8 ± 44.3 fg*mL-1 with a Tmax of 2.25 ± 1.04 h. Elimination occurred in two distinct phases; a rapid (α)-phase, with a T1/2 of 5.8 ± 3.4 h and apparent elimination rate constant (Kel) of 0.17 ± 0.12 fg*h-1 followed by a slower (β)-phase, with a T1/2 of 41.3 ± 29.8 h and apparent Kel of 0.03 ± 0.02 fg*h-1. In spite of the high degree of hydrophobicity (log Kow of 7.4), DBC was eliminated rapidly in humans, as are most PAHs in animals, compared to other hydrophobic persistent organic pollutants such as, DDT, PCBs and TCDD. Preliminary examination utilizing a new UHPLC-AMS interface, suggests the presence of polar metabolites in plasma as early as 45 min following dosing. This is the first in vivo dataset describing pharmacokinetics in humans of a high molecular weight PAH and should be a valuable addition to risk assessment paradigms.

Tenofovir (TFV) disoproxil fumarate and emtricitabine (FTC) are used in combination for HIV treatment and pre-exposure prophylaxis (PrEP). TFV disoproxil fumarate is a prodrug that undergoes diester hydrolysis to TFV. FTC and TFV are nucleoside/nucleotide reverse transcriptase inhibitors that upon phosphorylation to nucleotide triphosphate analogs competitively inhibit HIV reverse transcriptase. We previously demonstrated that adenylate kinase 2, pyruvate kinase, muscle and pyruvate kinase, liver and red blood cell phosphorylate TFV in peripheral blood mononuclear cells (PBMC). To identify the kinases that phosphorylate FTC in PBMC, siRNAs targeted toward kinases that phosphorylate compounds structurally similar to FTC were delivered to PBMC, followed by incubation with FTC and the application of a matrix-assisted laser desorption ionization-mass spectrometry method and ultra high performance liquid chromatography-UV to detect the formation of FTC phosphates. Knockdown of deoxycytidine kinase decreased the formation of FTC-monophosphate, while siRNA targeted toward thymidine kinase 1 decreased the abundance of FTC-diphosphate. Knockdown of either cytidine monophosphate kinase 1 or phosphoglycerate kinase 1 decreased the abundance of FTC-triphosphate. Next-generation sequencing of genomic DNA isolated from 498 HIV-uninfected participants in the HIV Prevention Trials Network 069/AIDS Clinical Trials Group A5305 clinical study, revealed 17 previously unreported genetic variants of TFV or FTC phosphorylating kinases. Of note, four individuals were identified as simultaneous carriers of variants of both TFV and FTC activating kinases. These results identify the specific kinases that activate FTC in PBMC, while also providing further insight into the potential for genetic variation to impact TFV and FTC activation.

Cruciferous vegetable components have been documented to exhibit anticancer properties. Targets of action span multiple mechanisms deregulated during cancer progression, ranging from altered carcinogen metabolism to the restoration of epigenetic machinery. Furthermore, the developing fetus is highly susceptible to changes in nutritional status and to environmental toxicants. Thus, we have exploited a mouse model of transplacental carcinogenesis to assess the impact of maternal dietary supplementation on cancer risk in offspring. In this study, transplacental and lactational exposure to a maternal dose of 15 mg/Kg B.W. of dibenzo[def,p]chrysene (DBC) resulted in significant morbidity of offspring due to an aggressive T-cell lymphoblastic lymphoma. As in previous studies, indole-3-carbinol (I3C, feed to the dam at 100, 500 or 1000 ppm), derived from cruciferous vegetables, dose-dependently reduced lung tumor multiplicity and also increased offspring survival. Brussels sprout and broccoli sprout powders, selected for their relative abundance of I3C and the bioactive component sulforaphane (SFN), respectively, surprisingly enhanced DBC-induced morbidity and tumorigenesis when incorporated into the maternal diet at 10% wt/wt. Purified SFN, incorporated in the maternal diet at 400 ppm, also decreased the latency of DBC-dependent morbidity. Interestingly, I3C abrogated the effect of SFN when the two purified compounds were administered in equimolar combination (500 ppm I3C and 600 ppm SFN). SFN metabolites measured in the plasma of neonates positively correlated with exposure levels via the maternal diet but not with offspring mortality. These findings provide justification for further study of the safety and bioactivity of cruciferous vegetable phytochemicals at supplemental concentrations during the perinatal period.

Benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon (PAH), is a known human carcinogen. In non-smoking adults greater than 95% of BaP exposure is through diet. The carcinogenicity of BaP is utilized by the U.S. EPA to assess relative potency of complex PAH mixtures. PAH relative potency factors (RPFs, BaP = 1) are determined from high dose animal data. We employed accelerator mass spectrometry (AMS) to determine pharmacokinetics of [C]-BaP in humans following dosing with 46 ng (an order of magnitude lower than human dietary daily exposure and million-fold lower than animal cancer models). To assess the impact of co-administration of food with a complex PAH mixture, humans were dosed with 46 ng of [C]-BaP with or without smoked salmon. Subjects were asked to avoid high BaP-containing diets and a 3-day dietary questionnaire given to assess dietary exposure prior to dosing and three days post-dosing with [C]-BaP. Co-administration of smoked salmon, containing a complex mixture of PAHs with an RPF of 460 ng BaP, reduced and delayed absorption. Administration of canned commercial salmon, containing very low amounts of PAHs, showed the impacts on pharmacokinetics were not due to high amounts of PAHs but rather a food matrix effect.