Effect of phytochemical intervention on dibenzo[a,l]pyrene-induced DNA adduct formation.

Dibenzo[a,l]pyrene (DBP) has been found to be the most potent carcinogen of the polycyclic aromatic hydrocarbons (PAHs). Primary sources for DBP in the environment are combustion of wood and coal burning, gasoline and diesel exhaust, and tires. Given the likelihood of environmental exposure to DBP and strong experimental evidence of its potency, it is likely to contribute to lung cancer development. Intervention with compounds of natural origin ("phytochemicals") is considered an effective means to prevent cancer development and favorably modulate the underlying mechanisms, including DNA adduct formation. In this study, several agents have been identified that inhibit environmental carcinogen-induced DNA adduct formation using a cell-free microsomal system. Of the ten agents tested, resveratrol (648 ± 26 adducts/10(9) nucleotides), oltipraz (1007 ± 348 adducts/10(9) nucleotides), delphinidin (1252 ± 142 adducts/10(9) nucleotides), tanshinone I (1981 ± 213 adducts/10(9) nucleotides), tanshinone IIA (2606 ± 478 adducts/10(9) nucleotides) and diindoylmethane (3643 ± 469 adducts/10(9) nucleotides) were the most effective compared to vehicle treatment (14,062 ± 1097 adducts/10(9) nucleotides). DBP is metabolized by phase I metabolizing enzymes CYP1A1, CYP1A2, and CYP1B1. DBP-induced DNA adducts can be inhibited by several mechanisms. We found that all the test agents inhibited DNA adducts by inhibiting one or more of these enzymes. Oltipraz inhibited DNA adducts entirely by inhibiting the CYP450s, while resveratrol and delphinidin inhibited DNA adducts by also interacting directly with the carcinogenic metabolite, anti-dibenzo(a,l)pyrene-11,12-dihydrodiol-13,14-epoxide.

Controlled-release systemic delivery - a new concept in cancer chemoprevention.

Many chemopreventive agents have encountered bioavailability issues in pre-clinical/clinical studies despite high oral doses. We report here a new concept utilizing polycaprolactone implants embedded with test compounds to obtain controlled systemic delivery, circumventing oral bioavailability issues and reducing the total administered dose. Compounds were released from the implants in vitro dose dependently and for long durations (months), which correlated with in vivo release. Polymeric implants of curcumin significantly inhibited tissue DNA adducts following the treatment of rats with benzo[a]pyrene, with the total administered dose being substantially lower than typical oral doses. A comparison of bioavailability of curcumin given by implants showed significantly higher levels of curcumin in the plasma, liver and brain 30 days after treatment compared with the dietary route. Withaferin A implants resulted in a nearly 60% inhibition of lung cancer A549 cell xenografts, but no inhibition occurred when the same total dose was administered intraperitoneally. More than 15 phytochemicals have been tested successfully by this formulation. Together, our data indicate that this novel implant-delivery system circumvents oral bioavailability issues, provides continuous delivery for long durations and lowers the total administered dose, eliciting both chemopreventive/chemotherapeutic activities. This would also allow the assessment of activity of minor constituents and synthetic metabolites, which otherwise remain uninvestigated in vivo.

DNA damage associated with PCBs in the whole blood cells of Inuit.

Lower chlorinated PCBs can damage DNA directly or via free radical mechanisms. In order to assess the DNA-damaging potential of PCBs in humans, blood samples were collected from Inuit population from Salluit, Northern Canada. Their diet comprises blubber from sea mammals and fatty fish, which accumulate non-biodegradable PCBs at varying levels. The 103 samples thus collected were categorized into low-, medium- and high-PCB exposure groups. A comprehensive (32)P-postlabeling adductomics technology, which allows measure differences in DNA adduct profiles of polar and lipophilic adducts between control and exposure groups, was applied to these samples to assess the effect of PCB on DNA damage. The adduct patterns obtained were qualitatively similar to other human tissues studied previously. A range of highly polar to lipophilic subgroups of adducts were detected. The known oxidative lesion, 8-oxodG was predominant. While some individual adducts appear to accumulate with increasing PCB levels, a definitive association could not be made. A possible confounder effect of selenium is discussed.

Metformin prevents endotoxin-induced liver injury after partial hepatectomy.

Metformin [2-(N,N-dimethylcarbamimidoyl)guanidine] is a drug used in the treatment of type 2 diabetes. Recent studies have suggested that metformin may have effects in addition to lowering serum glucose concentrations (e.g., anti-inflammatory). The aim of the present study was to determine whether metformin prevents the inflammatory reaction and liver damage in a model of postsurgical sepsis. Accordingly, rats underwent 2/3 partial hepatectomy (PH; or sham surgery); 48 h after surgery, animals were administered endotoxin (LPS; 1.5 mg/kg i.v.). Both PH and LPS alone caused some minor liver damage. However, their combined effect (PH/LPS) was synergistic, leading to robust hepatic damage, as indicated by plasma enzymes and histological assessment. Although metformin treatment did not alter changes caused by PH alone, it almost completely blunted the effects of LPS in the PH/LPS group. Increases in biomarkers of inflammation (e.g., interleukin 6, interferon gamma, and neutrophil number) were also blunted by metformin treatment. Furthermore, PH/LPS caused a >200x increase in hepatic plasminogen activator inhibitor 1 (PAI-1) mRNA expression and plasma PAI-1 protein. These increases were associated with inhibition of hepatic urokinase plasminogen activator activity and an increase in fibrin deposition, indicative of local thrombosis. These effects were markedly reduced by metformin treatment. In conclusion, these data demonstrate that metformin prevents liver damage in a model of postsurgical sepsis in rats by decreasing proinflammatory and hemostatic responses.