Ko Yasumoto

Recent advances in antituberculous drug development and novel drug targets

TB, especially multidrug-resistant TB and extensively drug-resistant TB, is an important global health concern, and the novel development of effective anti-tuberculous drugs is urgently needed. Newly elucidated, critical information on the entire genome of Mycobacterium tuberculosis (MTB) and advances in knowledge regarding various mycobacterial virulence genes are promoting progression in the identification of genes that code for new drug targets. With this background, this review deals with the following areas: first, the future development of new anti-tuberculous drugs is discussed according to the potential pharmacological targets of MTB; and second, a review of the present development status of new anti-tuberculous drugs is conducted, particularly focusing on some promising new anti-tuberculous agents, such as nitroimidazoles, diarylquinolines and oxazolidinones.

Isolation and Absolute Configuration Determination of Aliphatic Sulfates as the Daphnia Kairomones Inducing Morphological Defense of a Phytoplankton—Part 2

4,8-Dimethylnonyl sulfate (1) and 3-methyl-4E-decenyl sulfate (2) were isolated from Daphnia pulex as the Daphnia kairomones that induced morphological defense of a freshwater phytoplankton Scenedesmus gutwinskii var. heterospina (NIES-802). The absolute configuration at C4 of 1 was determined by Ohruis method applied to alcohol 3. The absolute stereochemistry at C3 of 2 was determined by (1)H-NMR analysis of the (R)-1NMA ester of alcohol 11.

New Sulfoalkylresorcinol from Marine-derived Fungus, Zygosporium sp. KNC52

A new sulfoalkylresorcinol (1) was isolated from the marine-derived fungus, Zygosporium sp. KNC52. The structure of 1 was elucidated by spectroscopic methods including MS and NMR, and the absolute stereochemistry was determined by the modified Moshers method. Compound 1 inhibited FtsZ polymerization in vitro and exhibited weak antimicrobial activity against multi-drugresistant bacteria.

Dynamic changes in the accumulation of metabolites in brackish water clam Corbicula japonica associated with alternation of salinity

The brackish water clam Corbicula japonica inhabits rivers and brackish waters throughout Japan where the major fishing grounds in the Ibaraki Prefecture, Japan, are located at the Hinuma Lake and Hinuma River. Water salinity in the Lake Hinuma is low and stable due to the long distance from the Pacific Ocean, whereas that in the downstream of the river varies daily due to a strong effect of tidal waters. In the present study, we dissected the gill and foot muscle of brackish water clam collected from these areas, and subjected them to metabolome analysis by capillary electrophoresis-time-of-flight mass spectrometry. More than 200 metabolites including free amino acids, peptides and organic acids were identified, and their amounts from the foot muscle tend to be higher than those from the gill. The principal component analysis revealed that the amount of each metabolite was different among sampling areas and between the gill and foot muscle, whereas no apparent differences were observed between male and female specimens. When the metabolites in the female clam at high salinity were compared with those at low salinity, concentrations of β-alanine, choline, γ-aminobutyric acid, ornithine and glycine betaine were found to be changed in association with salinity. We also compared various metabolites in relation to metabolic pathways, suggesting that many enzymes were involved in their changes depending on salinity.

Correlation between variable-number tandem-repeat-based genotypes and drug susceptibility in Mycobacterium avium isolates

Little is known about the correlation between genotype and drug susceptibility in Mycobacterium avium (Mav) strains isolated from patients with Mav infections. To examine whether drug susceptibility profile of Mav is associated with genotype, we carried out variable-number tandem-repeat (VNTR) typing and drug susceptibility testing for Mav isolates from Japanese with nodular-bronchiectasis (NB)-type and cavitary disease (CA)-type diseases. We performed M. avium tandem repeat (MATR)-VNTR typing and drug susceptibility testing by the broth dilution method, using macrolides, rifamycins, ethambutol, isoniazid, aminoglycosides, and quinolones, for Mav isolates from patients with NB and CA-type diseases (NB-Mav and CA-Mav). Based on the VNTR genotyping, the Mav strains were grouped into three clusters. There was no difference with respect to the distribution of NB-Mav and CA-Mav among the clusters. We observed a strong association between VNTR genotype and susceptibility to quinolones (levofloxacin, moxifloxacin, gatifloxacin, sitafloxacin, and garenoxacin) and ethambutol. There was essentially no significant difference in drug susceptibility between NB- and CA-Mav strains, although NB-Mav was somewhat more resistant to fluoroquinolones, especially gatifloxacin, than CA-Mav. There was a significant association between VNTR genotype and susceptibility to quinolones and ethambutol in Mav isolates from Japanese patients.

Comparative study for the virulence of Mycobacterium avium isolates from patients with nodular-bronchiectasis- and cavitary-type diseases

Mycobacterium avium (Mav) lung infections, called nodular-bronchiectasis (NB)-type M. avium complex (MAC) disease, are globally increasing. To elucidate whether there are unusual populations of Mav, causing NB-type disease rather than cavitary (CA)-type disease, we compared the virulence of Mav isolates from patients with NB-type (NB-Mav) and those from CA-type (CA-Mav) diseases, based on intracellular growth in various types of human cells. Five strains each of NB-Mav and CA-Mav were compared with each other for their invasiveness and ability to intracellularly replicate in various types of cultured cells of human origin. The two types of Mav isolates showed a similar ability, on average, to replicate in macrophages and lung epithelial cells. Moreover, they showed a similar ability to induce the production of reactive nitrogen intermediates and reactive oxygen intermediates by macrophages and susceptibility to antimicrobial molecules. Therefore, it appears that there is no essential difference in virulence in terms of infectivity to human macrophages and lung cells between Mav strains isolated from NB-MAC disease and those from CA-MAC disease. These findings indicate the importance of further studies to elucidate the mechanism for the establishment of NB-type MAC diseases based on host immunological conditions rather than the pathogenic nature of MAC organisms themselves.

Establishment of a model for chemoattraction of Symbiodinium and characterization of chemotactic compounds in Acropora tenuis

Corals harbor symbiotic dinoflagellates, Symbiodinium spp., acquired from surrounding environments. Because Symbiodinium are present at low densities in the water column, corals may attract these symbionts using chemotactic compounds. To examine whether corals contain chemotactic compounds, we established an assay to measure the chemotactic activity for Symbiodinium using an extract of the coral Acropora tenuis, a major reef-building coral in Japan. Our assay revealed that Symbiodinium strain NBRC102920 (clade A), which is taken up by juvenile A. tenuis polyps, is attracted to crude A. tenuis extracts. We found that the chemotactic compounds are water-soluble, heat-labile macromolecules and that the chemotactic activity was inhibited by N-acetyl-d-glucosamine (GlcNAc). We separated the GlcNAc-binding fraction (Fr-ActL) and identified it as the most plausible candidate for the chemoattractant, since the chemotactic activity of the crude A. tenuis extract appeared to be mainly attributable to the activity of Fr-ActL and was also inhibited by the addition of GlcNAc. These results indicate that chemoattraction is mediated via the binding of Symbiodinium to Fr-ActL.

Changes in free amino acid concentrations and associated gene expression profiles in the abdominal muscle of kuruma shrimp Marsupenaeus japonicus acclimated at different salinities

ABSTRACT Shrimps inhabiting coastal waters can survive in a wide range of salinity. However, the molecular mechanisms involved in their acclimation to different environmental salinities have remained largely unknown. In the present study, we acclimated kuruma shrimp (Marsupenaeus japonicus) at 1.7%, 3.4% and 4.0% salinities. After acclimating for 6, 12, 24 and 72 h, we determined free amino acid concentrations in their abdominal muscle, and performed RNA sequencing analysis on this muscle. The concentrations of free amino acids were clearly altered depending on salinity after 24 h of acclimation. Glutamine and alanine concentrations were markedly increased following the increase of salinity. In association with such changes, many genes related to amino acid metabolism changed their expression levels. In particular, the increase of the expression level of the gene encoding glutamate-ammonia ligase, which functions in glutamine metabolism, appeared to be associated with the increased glutamine concentration at high salinity. Furthermore, the increased alanine concentration at high salinity was likely associated with the decrease in the expression levels of the the gene encoding alanine-glyoxylate transaminase. Thus, there is a possibility that changes in the concentration of free amino acids for osmoregulation in kuruma shrimp are regulated by changes in the expression levels of genes related to amino acid metabolism. Summary: Kuruma shrimp, Marsupenaeus japonicus, change free amino acid concentrations and associated gene expression levels in their muscle to adjust effectively to different salinities.