Toxicogenomic biomarkers for liver toxicity

Toxicogenomics (TGx) is a widely used technique in the preclinical stage of drug development to investigate the molecular mechanisms of toxicity. A number of candidate TGx biomarkers have now been identified and are utilized for both assessing and predicting toxicities. Further accumulation of novel TGx biomarkers will lead to more efficient, appropriate and cost effective drug risk assessment, reinforcing the paradigm of the conventional toxicology system with a more profound understanding of the molecular mechanisms of drug-induced toxicity. In this paper, we overview some practical strategies as well as obstacles for identifying and utilizing TGx biomarkers based on microarray analysis. Since clinical hepatotoxicity is one of the major causes of drug development attrition, the liver has been the best documented target organ for TGx studies to date, and we therefore focused on information from liver TGx studies. In this review, we summarize the current resources in the literature in regard to TGx studies of the liver, from which toxicologists could extract potential TGx biomarker gene sets for better hepatotoxicity risk assessment.     

A cytotoxic ribonuclease targeting specific transfer RNA anticodons

The carboxyl-terminal domain of colicin E5 was shown to inhibit protein synthesis of Escherichia coli. Its target, as revealed through in vivo and in vitro experiments, was not ribosomes as in the case of E3, but the transfer RNAs (tRNAs) for Tyr, His, Asn, and Asp, which contain a modified base, queuine, at the wobble position of each anticodon. The E5 carboxyl-terminal domain hydrolyzed these tRNAs just on the 3' side of this nucleotide. Tight correlation was observed between the toxicity of E5 and the cleavage of intracellular tRNAs of this group, implying that these tRNAs are the primary targets of colicin E5.     

A simple method for long-term cryopreservation of <Emphasis Type="Italic">Calonectria ilicicola</Emphasis> on barley grains

We developed a simple method for long-term preservation of the soybean red crown rot fungus, Calonectria ilicicola, using barley grains. Autoclaved barley grains were inoculated with the fungus, then incubated at 25°C for 1 month. After incubation, grains were dried to approximately 3% moisture content, and stored at 4, −20, or −80°C for 3 years. C. ilicicola preserved on barley grains at −80°C remained viable without any change in mycelial growth and virulence. These results showed that C. ilicicola can be successfully cryopreserved for extended periods on barley grains at −80°C. We also confirmed that cultures preserved on barley grains are suitable for direct use without further manipulation as inocula in pathogenicity tests.     

Calcium uptake and resistance to bacterial wilt of mutually grafted tomato seedlings

Bacterial wilt of tomato (Lycopersicon esculentum Mill.) caused by Ralstonia solanacearum Smith is a serious disease in Japan. We previously reported that calcium (Ca) nutrition in tomato significantly affected the resistance to the disease, and that highly resistant cultivars were characterized by a high Ca uptake. We examined the relationship between the Ca uptake and resistance using mutually grafted seedlings of tomato cultivars differing in their resistance. A susceptible (‘Ponderosa’) or moderately resistant (‘Zuiei’) cultivar (scion) was grafted on the rootstock of a susceptible, moderately resistant, or highly resistant cultivar (‘Hawaii 7998’). Roots or petioles of the grafted seedlings were inoculated with the pathogen, and the development of bacterial wilt was observed. Although Ca uptake by shoot increased by grafting on the rootstock of a highly resistant cultivar, the development of the disease was not influenced by the difference in Ca uptake, and depended on the resistance of the cultivar to which the inoculated part of the graft belonged. It was concluded that the differences in Ca uptake of the shoot of the grafted tomato seedlings might not be related to the expression of the resistance to bacterial wilt.     

Beta3-adrenoceptor agonist AJ-9677 reduces body fat in obese beagles

A selective beta3-adrenoceptor agonist, AJ-9677, was reported to ameliorate obesity and insulin resistance in KK-Ay mice. We examined the acute and chronic effects of AJ-9677 on obese dogs. Oral administration of AJ-9677 (0.01 or 0.1 mg/kg) to overnight fasted obese beagles produced a dose-dependent rise in the plasma levels of non-esterified fatty acids and insulin in 1h, followed by a gradual drop of the plasma glucose level. It produced no apparent abnormal behaviors, but easily detectable cutaneous flushing. Daily treatment of AJ-9677 at a lower dose (0.01 mg/kg) for three weeks produced no notable change in body weight, but at a higher dose (0.1 mg/kg) it reduced the body weight compared to a placebo treatment after seven weeks. Computed tomographic examinations revealed a remarkable reduction of body fat after the AJ treatment, being consistent with the histological observations that the adipose tissue of AJ-9677-treated dogs consisted of smaller and some multilocular adipocytes. The plasma levels of leptin and adiponectin were decreased and increased, respectively, after the AJ treatment, reflecting the reduction of adiposity. It was concluded that AJ-9677 is useful for the treatment of obesity in the dog.     

Pyrolysis reactions of various lignin model dimers

Primary pyrolysis reactions and relative reactivities for depolymerization and condensation/carbonization were evaluated for various lignin model dimers with α-O-4, β-O-4, β-1, and biphenyl substructures by characterizing the tetrahydrofuran (THF)-soluble and THF-insoluble fractions obtained after pyrolysis at 400°C. Reactivity was quite different depending on the model structure: depolymerization: α-O-4 [phenolic (ph), nonphenolic (nonph)], β-O-4 (ph) > β-O-4 (nonph), β-1 (ph, nonph) > biphenyl (ph, nonph); condensation/carbonization: β-1 (ph) > β-O-4 (ph) > α-O-4 (ph) > β-O-4 (nonph), biphenyl (ph, nonph), α-O-4 (nonph), β-1 (nonph). Major degradation pathways were also identified for β-O-4 and β-1 model dimers: β-O-4 types: C_β-O cleavage to form cinnamyl alcohols and phenols and C_γ-elimination yielding vinyl ethers; β-1 types: C_α-C_β cleavage yielding benzaldehydes and styrenes and C_γ-elimination yielding stilbenes. Relative reactivities of these pathways were also quite different between phenolic and nonphenolic forms even in the same types; C_β-O cleavage (β-O-4) and C_γ-elimination (β-1) were substantially enhanced in phenolic forms.     

Adaptive strategy of six native herbaceous species growing over the whole region of Mt. Daisen: characteristics of N,P, K,Ca, and Mg accumulation in leaves

The number of native species growing at all altitudes on Mt. Daisen, which is the highest mountain in the Chugoku District of Japan, is seven. Since soil physical and chemical properties and climate vary due to differences of elevation and habitat, it is logical to assume that they have an adaptive strategy to cope with such changes in the environment. To understand the growth strategy in these species, in the period from July 26 to October 17, 2007, leaves of six herbaceous species (Athyrium vidalii (Fr. et Sav.) Nakai, Carex foliosissima Fr. Schm., Aruncus dioicus (Walt.) Fern., Polygonum cuspidatum Sieb. et Zucc., Artemisia princeps Pamp., and Plantago asiatica L.) were sampled at the different altitudes [Site A; 850?m, Site B; 1200?m, Site C; 1500?m above sea level (a.s.l.)] and nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentrations were determined. Soil chemical properties at sampling day and air and soil temperature during sampling periods at each site were also measured. As a result, we could classify adaptive strategies to the environment for those six species into three types. Type I: mineral accumulation in leaves depends on the habitat and is affected by growing environment with the exception of soil mineral concentration (Pteridophyta, A. vidalii). Type II: mineral accumulation in leaves hardly depends on the habitat and the autonomy of mineral absorption is high, although Ca and Mg concentrations in leaves are affected by soil mineral concentrations and cumulative air temperature (Magnoliophyta, monocotyledon, C. foliosissima). Type III: mineral accumulation in leaves strongly depends on the habitat and soil N concentration, but is also affected by the growing environment, and the autonomy of mineral absorption is weak (Magnoliophyta, dicotyledon, A. dioicus, P. cuspidatum, A. princeps, and P. asiatica).     

Evaluation of feeding value of forage soybean silage as a substitute for wheat bran in sheep

Twelve sheep were used in a 3 × 3 Latin square design to evaluate the effect of substituting wheat bran with forage soybean silage in the diet on apparent digestibility and nitrogen balance. Forage soybean (Glycine max (L.) Merrill) was cultivated in a no‐till, no‐herbicide cropping system with Italian ryegrass (Lolium multiflorum Lam.) as a living mulch. Forage soybean and Italian ryegrass were wilted and ensiled in round bales without additives, respectively. The experimental diets were based on corn silage supplemented with protein sources (tow silages or wheat bran). The crude protein and the acid detergent insoluble protein contents of forage soybean silage were the highest among the protein sources. The apparent digestibility of crude protein and the nitrogen balance did not significantly differ among the diets. In addition, the phytoestrogen content of forage soybean silage was below the level at which animal reproductive performance would be negatively affected. These results suggest that forage soybean silage has comparable feeding value to wheat bran, and can be given at an inclusion level of 17% (dry matter basis) as an alternative protein source to wheat bran without adverse effects on digestion or nitrogen balance in sheep fed a corn silage‐based diet.     

Living Mulch with White Clover Improves Phosphorus Nutrition of Maize of Early Growth Stage

We examined the effect of a living mulch with white clover on the growth of maize in an Andisol. Maize was grown using a living mulch without fertilizer application, or by conventional cultivation with or without fertilizer application. Although the living mulch did not affect the amount of available phosphate in soil, the phosphorus concentration of maize shoots increased due to the living mulch compared with conventional cultivation without fertilizer application. Arbuscular mycorrhizal (AM) colonization of maize roots was higher with the living mulch than with conventional cultivation. These results suggested that a living mulch with white clover enhanced the phosphorus uptake by maize through AM colonization.