Pyridoxine stimulates filaggrin production in human epidermal keratinocytes

Molecular Biology Reports - Pyridoxine (PN), one of the vitamers of vitamin B6, plays an important role in the maintenance of epidermal function and is used to treat acne and rough skin. Clinical...     

P450 in wild animals as a biomarker of environmental impact

The impact of environmental pollution on selected animals was tested by monitoring the hepatic content of cytochromes P450 and their enzyme activities or by calculating TEQ values from the concentration of pollutants in the body. Fish-eating Stellars Sea Eagles, Haliaeetus pelagicus, found dead in the northern part of Hokkaido island accumulated high levels of PCBs and DDT and metabolites. The TEQ values calculated from the PCB concentration in the eagles were high enough to cause a significant toxic effect in other birds living in the same environment. Some of these birds were also contaminated with high concentrations of lead. Spotted seals, Phoca largha, captured along the coast-line of Hokkaido accumulated PCBs in their fat at about 100 million times the concentrations in the surface sea water. The levels of expressions of hepatic microsomal CYP 1A1and related enzyme activities in these seals showed good correlation to the levels of PCBs accumulated in the fat. The fresh water crabs, Eriocheir japonicus, were captured from three different rivers with various degrees of pollution. The P450 content and the related enzyme activities showed good correlation to TEQ values obtained from the concentrations of PCBs and PCDDs in the crabs from the rivers. The wild rodents, Clethrionomys rufocanus, were captured from urban, agricultural, and forest areas in Hokkaido. Those from the forest area had the lowest CYP content and related enzyme activities, comparable to those in laboratory-raised animals. Those from the urban areas, presumably contaminated with PAHs from fuel combustion, showed increased CYP 1A1 content and related enzyme activities. Those from the agricultural areas showed increased levels of CYP 1A1, 2B, 2E1. Rats treated with some of the agrochemicals used in the area resulted in a similar pattern of induction. It is concluded that P450 can be a useful biomarker for assessing the environmental impact of chemical pollutants on wild animals.     

HLA-DQB1*03 Confers Susceptibility to Chronic Hepatitis C in Japanese: A Genome-Wide Association Study

Hepatitis C virus (HCV) establishes a chronic infection in 70-80% of infected individuals. Many researchers have examined the effect of human leukocyte antigen (HLA) on viral persistence because of its critical role in the immune response against exposure to HCV, but almost all studies have proven to be inconclusive. To identify genetic risk factors for chronic HCV infection, we analyzed 458,207 single nucleotide polymorphisms (SNPs) in 481 chronic HCV patients and 2,963 controls in a Japanese cohort. Next, we performed a replication study with an independent panel of 4,358 cases and 1,114 controls. We further confirmed the association in 1,379 cases and 25,817 controls. In the GWAS phase, we found 17 SNPs that showed suggestive association (P < 1 × 10^-5). After the first replication study, we found one intronic SNP in the HLA-DQ locus associated with chronic HCV infection, and when we combined the two studies, the association reached the level of genome-wide significance. In the second replication study, we again confirmed the association (P _combined = 3.59 × 10⁻¹⁶, odds ratio [OR] = 0.79). Subsequent analysis revealed another SNP, rs1130380, with a stronger association (OR=0.72). This nucleotide substitution causes an amino acid substitution (R55P) in the HLA-DQB1 protein specific to the DQB1*03 allele, which is common worldwide. In addition, we confirmed an association with the previously reported IFNL3-IFNL4 locus and propose that the effect of DQB1*03 on HCV persistence might be affected by the IFNL4 polymorphism. Our findings suggest that a common amino acid substitution in HLA-DQB1 affects susceptibility to chronic infection with HCV in the Japanese population and may not be independent of the IFNL4 genotype.     

Electrochemical Gating of Tricarboxylic Acid Cycle in Electricity-Producing Bacterial Cells of Shewanella

Energy-conversion systems mediated by bacterial metabolism have recently attracted much attention, and therefore, demands for tuning of bacterial metabolism are increasing. It is widely recognized that intracellular redox atmosphere which is generally tuned by dissolved oxygen concentration or by appropriate selection of an electron acceptor for respiration is one of the important factors determining the bacterial metabolism. In general, electrochemical approaches are valuable for regulation of redox-active objects. However, the intracellular redox conditions are extremely difficult to control electrochemically because of the presence of insulative phospholipid bilayer membranes. In the present work, the limitation can be overcome by use of the bacterial genus Shewanella , which consists of species that are able to respire via cytochromes abundantly expressed in their outer-membrane with solid-state electron acceptors, including anodes. The electrochemical characterization and the gene expression analysis revealed that the activity of tricarboxylic acid (TCA) cycle in Shewanella cells can be reversibly gated simply by changing the anode potential. Importantly, our present results for Shewanella cells cultured in an electrochemical system under poised potential conditions showed the opposite relationship between the current and electron acceptor energy level, and indicate that this unique behavior originates from deactivation of the TCA cycle in the (over-)oxidative region. Our result obtained in this study is the first demonstration of the electrochemical gating of TCA cycle of living cells. And we believe that our findings will contribute to a deeper understanding of redox-dependent regulation systems in living cells, in which the intracellular redox atmosphere is a critical factor determining the regulation of various metabolic and genetic processes.     

Metabolism of Glutamate in Purple Nonsulfur Bacteria Participation of Vitamin B12

Purple nonsulfur bacteria, Rhodospirillum rubrum and Rhodopseudomonas spheroides were found to possess coenzyme B₁₂-dependent glutamate mutase activity. Cell-free extracts of these bacteria grown on Co²⁺-containing media catalyzed the conversion of glutamate to β-methylaspartate and further to mesaconate. The activity of the cell-free extracts of these organisms cultivated on Co²⁺-deficient media was markedly lower than that of the normal cells. Addition of coenzyme B₁₂ to the former reaction mixture enhanced the mesaconate formation via β-methylaspartate. These results indicate the involvement of coenzyme Independent glutamate mutase of these bacteria in the dissimilation of glutamate to acetyl-CoA and pyruvate through the following pathway.

glutamate→β→methylaspartate→mesaconate→citramalate→→acetyl-CoA, pyruvate On the other hand, a greater part of glutamate was converted to α-hydroxyglutarate and succinate with the cell-free extracts of these photosynthetic bacteria. This fact, taking account of the presence of propionyl-CoA carboxylase in these bacteria, implies the participation of coenzyme B₁₂-dependent (R)-methylmalonyl-CoA mutase in the formation of succinate via the following route.

glutamate→α-ketoglutarate→α-hydroxyglutarate→propionate→propionyl-CoA→(S)-methylmalonyl-CoA→(R)-methylmalonyl-CoA→succinyl-CoA     

Riboflavin Biosynthesis by Candida robusta

Metal ions had little influence on riboflavin production by Candida robusta, except that Ag, Cu and Hg were strongly inhibitory. The inhibiting action of iron on its production was comparatively small, so that any previous treatment for the removal of iron from the medium was not necessary. Addition of GaCO₃ was found to be essential in media containing sucrose or acetate as a carbon source, as pointed out in the previous paper. This effect of CaCO₃ was attributed to its neutralizing action. When the reaction of the medium was kept at the optimum pH, about 7.0, high yields of riboflavin could be obtained without the presence of CaCO₃.     

l-Malic Acid Fermentation by Mixed Culture of Rhizopus arrhizus and Proteus vulgaris

When Rhizopus arrhizus NRRL 1526 was mix-cultured with Proteus vulgaris AHU 1144, a strain having a high fumarase activity, in a medium containing glucose as a substrate, fumaric acid fermentation was successively converted to l-malic acid fermentation and large amounts of l-malic acid were accumulated as an end product.

As an inoculum of P. vulgaris for this fermentation, cells in the stationary growth phase (48 to 72 hr culture) were much more favorable than those in the exponential growth phase (18 hr culture) and malic acid yields in the former case were as high as about 70 to 75 % based on initial glucose after 3 to 4 days of the mixed culture.     

Evaluation of the Duty Ratio of the Bacterial Flagellar Motor by Dynamic Load Control

The bacterial flagellar motor is one of the most complex and sophisticated nanomachineries in nature. A duty ratio D is a fraction of time that the stator and the rotor interact and is a fundamental property to characterize the motor but remains to be determined. It is known that the stator units of the motor bind to and dissociate from the motor dynamically to control the motor torque depending on the load on the motor. At low load, at which the kinetics such as proton translocation speed limits the rotation rate, the dependency of the rotation rate on the number of stator units N implies D: the dependency becomes larger for smaller D. Contradicting observations supporting both the small and large D have been reported. A dilemma is that it is difficult to explore a broad range of N at low load because the stator units easily dissociate, and N is limited to one or two at vanishing load. Here, we develop an electrorotation method to dynamically control the load on the flagellar motor of Salmonella with a calibrated magnitude of the torque. By instantly reducing the load for keeping N high, we observed that the speed at low load depends on N, implying a small duty ratio. We recovered the torque-speed curves of individual motors and evaluated the duty ratio to be 0.14 ± 0.04 from the correlation between the torque at high load and the rotation rate at low load.     

Map-based cloning of a fertility restorer gene, Rf-1, in rice (Oryza sativa L.)

A rice nuclear gene, Rf-1, restores the pollen fertility disturbed by the BT-type male sterile cytoplasm, and is widely used for commercial seed production of japonica hybrid varieties. Genomic fragments carrying Rf-1 were identified by conducting chromosome walking and a series of complementation tests. Isolation and analysis of cDNA clones corresponding to the fragments demonstrated that Rf-1 encodes a mitochondrially targeted protein containing 16 repeats of the 35-aa pentatricopeptide repeat (PPR) motif. Sequence analysis revealed that the recessive allele, rf-1, lacks one nucleotide in the putative coding region, presumably resulting in encoding a truncated protein because of a frame shift. Rice Rf-1 is the first restorer gene isolated from cereal crops that has the property of reducing the expression of the cytoplasmic male sterility (CMS)-associated mitochondrial gene like many other restorer genes. The present findings may facilitate not only elucidating the mechanisms of male sterility by the BT cytoplasm and its restoration by Rf-1 but also isolating other restorer genes from cereal crops, especially rice.