ABSTRACT
Exposure to polycyclic aromatic hydrocarbon (PAH) environmental contaminants has been associated with the development of mutations and cancer. 7,12-Dimethylbenz(a)anthracene ( DMBA), a genotoxic agent, reacts with DNA directly, inducing p53-dependent cytotoxicity resulting in cell death by apoptosis or giving rise to cancer. DMBA metabolism largely depends on activation of the aryl hydrocarbon receptor (AhR). Mice phenotypically selected for high (AIRmax) or low (AIRmin) acute inflammatory response present a complete segregation of Ahr alleles endowed with low (Ahr(d)) or high (Ahr(b1)) affinity to PAHs, respectively. To evaluate the role of AhR genetic polymorphism on the bone marrow susceptibility to DMBA, AIRmax and AIRmin mice were treated with a single intraperitoneal injection of DMBA (50 mg/kg b.w.) in olive oil. Bone marrow cells (BMCs) were phenotyped by both flow cytometry and cytoslide preparations. Despite a significant decrease in total cell count in BM from AIRmin mice, there was an increase of blast cells and immature neutrophils at 1 and 50 days after DMBA treatment, probably due to a cell-cycle blockade at the G1/S transition leading to immature stage cell production. A panel of proteins related to cell cycle regulation was evaluated in immature BM cells (Lin(-)) by Western Blot, and DNA damage and repair were measured using an alkaline version of the Comet assay. In Lin(-) cells isolated from AIRmin mice, high levels were found in both p53 and p21 protein contents in contrast with the low levels of CDK4 and Ciclin D1. Evaluation of DNA repair in DMBA-treated BMCs, indicated long-lasting genotoxicity and cytotoxicity in BMC from AIRmin mice and a blockade of cell cycle progression. On the other hand, AIRmax mice have a high capacity of DNA damage repair and protection. These mechanisms can be associated with the differential susceptibility to the toxic and carcinogenic effects of DMBA observed in these mice. (C) 2015 Elsevier B.V. All rights reserved.
Subject(s)
Genetics , Toxicology , HeredityABSTRACT
AIRmax and AIRmin mice differ in their local acute inflammatory reactions to polyacrylamide beads (Biogel). These lines were developed to identify genes that affect the intensity of the acute inflammatory response (AIR) and to investigate the cellular and molecular mechanisms of acute inflammation. Although these lines are well established, differences in their responses to chronic inflammatory Biogel exposure have not yet been described. We investigated whether the selective process that modified the acute inflammatory responses in these animals also affected the development of their chronic inflammatory responses. Inflammatory exudate cell infiltration was more intense in AIRmax than AIRmin mice at both 48 h and 30 days. Genes involved in signal transduction and immune/inflammatory responses were differentially expressed in the treated skin of AIRmax and AIRmin mice, and divergent expression of some acute inflammatory response genes was detected up to 30 days post-Biogel. However, distinct expression of several pro and anti-inflammatory response genes in both periods was observed. These results indicate that the selective process for acute inflammation affected the development of chronic inflammatory responses to Biogel, suggesting common genetic control
Subject(s)
Cell Biology , Molecular Biology , Allergy and ImmunologyABSTRACT
The brown-rot basidiomycete Gloeophyllum trabeum uses a quinone redox cycle to generate extracellular Fenton reagent, a key component of the biodegradative system expressed by this highly destructive wood decay fungus. The hitherto uncharacterized quinone reductase that drives this cycle is a potential target for inhibitors of wood decay. We have identified the major quinone reductase expressed by G. trabeum under conditions that elicit high levels of quinone redox cycling. The enzyme comprises two identical 22-kDa subunits, each with one molecule of flavin mononucleotide. It is specific for NADH as the reductant and uses the quinones produced by G. trabeum (2,5-dimethoxy-1,4-benzoquinone and 4,5-dimethoxy-1,2-benzoquinone) as electron acceptors. The affinity of the reductase for these quinones is so high that precise kinetic parameters were not obtainable, but it is clear that k(cat)/K(m) for the quinones is greater than 10(8) M(-1) s(-1). The reductase is encoded by a gene with substantial similarity to NAD(P)H:quinone reductase genes from other fungi. The G. trabeum quinone reductase may function in quinone detoxification, a role often proposed for these enzymes, but we hypothesize that the fungus has recruited it to drive extracellular oxyradical production.