Systems toxicology identifies mechanistic impacts of 2-amino-4,6-dinitrotoluene (2A-DNT) exposure in Northern Bobwhite.

BACKGROUND: A systems toxicology investigation comparing and integrating transcriptomic and proteomic results was conducted to develop holistic effects characterizations for the wildlife bird model, Northern bobwhite (Colinus virginianus) dosed with the explosives degradation product 2-amino-4,6-dinitrotoluene (2A-DNT). A subchronic 60 d toxicology bioassay was leveraged where both sexes were dosed via daily gavage with 0, 3, 14, or 30 mg/kg-d 2A-DNT. Effects on global transcript expression were investigated in liver and kidney tissue using custom microarrays for C. virginianus in both sexes at all doses, while effects on proteome expression were investigated in liver for both sexes and kidney in males, at 30 mg/kg-d. RESULTS: As expected, transcript expression was not directly indicative of protein expression in response to 2A-DNT. However, a high degree of correspondence was observed among gene and protein expression when investigating higher-order functional responses including statistically enriched gene networks and canonical pathways, especially when connected to toxicological outcomes of 2A-DNT exposure. Analysis of networks statistically enriched for both transcripts and proteins demonstrated common responses including inhibition of programmed cell death and arrest of cell cycle in liver tissues at 2A-DNT doses that caused liver necrosis and death in females. Additionally, both transcript and protein expression in liver tissue was indicative of induced phase I and II xenobiotic metabolism potentially as a mechanism to detoxify and excrete 2A-DNT. Nuclear signaling assays, transcript expression and protein expression each implicated peroxisome proliferator-activated receptor (PPAR) nuclear signaling as a primary molecular target in the 2A-DNT exposure with significant downstream enrichment of PPAR-regulated pathways including lipid metabolic pathways and gluconeogenesis suggesting impaired bioenergetic potential. CONCLUSION: Although the differential expression of transcripts and proteins was largely unique, the consensus of functional pathways and gene networks enriched among transcriptomic and proteomic datasets provided the identification of many critical metabolic functions underlying 2A-DNT toxicity as well as impaired PPAR signaling, a key molecular initiating event known to be affected in di- and trinitrotoluene exposures.

A comparison between intubation and food addition as routes of oral exposure for northern bobwhites to DDT insecticide.

Our objective was to compare two methods of oral dosing of p,p'-DDT (1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane) on uptake of DDT metabolites and isomers (i.e., p,p'-DDT, o,p'-DDT, p,p'-DDE, o,p'-DDE, p,p'-DDD, o,p'-DDD) in livers and brains. p,p'-DDT was administered to northern bobwhite (Colinus virginianus) by intubation with corn oil or as a feed additive for 56 days. When adjusted for amount of DDT consumed, total DDT (sigma DDT, the summation of all DDT metabolites and isomers) and p,p'-DDE concentrations differed significantly (P less than 0.10) in both brains and livers, whereas p,p'-DDD differed only in brains and p,p'-DDT differed only in livers. Paired comparisons between brains and livers differed significantly for sigma DDT, (P less than 0.05), p,p'-DDE (P less than 0.05) and p,p'-DDT (P less than 0.1) for both intubated and food-dosed treatment groups, whereas p,p'-DDD (P less than 0.05) differed only in the intubated group. We concluded that method of oral exposure affected the uptake of DDT in livers and brains for northern bobwhites.

Influence of dietary protein and excess methionine on choline needs for young bobwhite quail.

Experiments were conducted with young Bobwhite quail (Colinus virginianus) to investigate the effect of differing dietary protein levels and nondetrimental amounts of excess methionine on choline needs. Growth and feed consumption of quail fed an adequate (27.3%) protein purified diet supplemented with 2000 mg/kg of choline were unaffected by increasing the level of excess methionine to 1.75%; however, greater amounts (2.0%, 2.25%) of excess methionine depressed growth (P less than .01), reduced feed consumption (P less than .01), and decreased feed utilization (P less than .05). Quail fed a purified diet containing 13.85% protein and 515 mg/kg of choline grew poorly. Growth was unaffected by additional choline in this diet. Growth was suboptimal among quail fed purified diets containing adequate or high (41.55%) levels of protein in which choline was limiting; however, a high level of protein did not in itself affect performance. Growth was improved by supplemental choline in these diets. Growth of quail fed purified diets with up to 1.35% excess methionine which were limiting (531 mg/kg) in choline was less than that of groups fed 2000 mg/kg of added dietary choline (P less than .01); however, excess methionine did not significantly influence growth of quail fed choline-deficient diets. These experiments indicate that neither high dietary protein nor excess methionine, fed at non-growth-depressing levels, increases dietary choline needs for young Bobwhite quail.