Structure of an archaeal non-discriminating glutamyl-tRNA synthetase: a missing link in the evolution of Gln-tRNAGln formation

The molecular basis of the genetic code relies on the specific ligation of amino acids to their cognate tRNA molecules. However, two pathways exist for the formation of Gln-tRNAGln. The evolutionarily older indirect route utilizes a non-discriminating glutamyl-tRNA synthetase (ND-GluRS) that can form both Glu-tRNAGlu and Glu-tRNAGln. The Glu-tRNAGln is then converted to Gln-tRNAGln by an amidotransferase. Since the well-characterized bacterial ND-GluRS enzymes recognize tRNAGlu and tRNAGln with an unrelated α-helical cage domain in contrast to the β-barrel anticodon-binding domain in archaeal and eukaryotic GluRSs, the mode of tRNAGlu/tRNAGln discrimination in archaea and eukaryotes was unknown. Here, we present the crystal structure of the Methanothermobacter thermautotrophicus ND-GluRS, which is the evolutionary predecessor of both the glutaminyl-tRNA synthetase (GlnRS) and the eukaryotic discriminating GluRS. Comparison with the previously solved structure of the Escherichia coli GlnRS-tRNAGln complex reveals the structural determinants responsible for specific tRNAGln recognition by GlnRS compared to promiscuous recognition of both tRNAs by the ND-GluRS. The structure also shows the amino acid recognition pocket of GluRS is more variable than that found in GlnRS. Phylogenetic analysis is used to reconstruct the key events in the evolution from indirect to direct genetic encoding of glutamine

Effect of a thromboxane A2 receptor antagonist ramatroban (BAY u 3405), on inflammatory cells, chemical mediators and non-specific nasal hyperreactivity after allergen challenge in patients with perennial allergic rhinitis

In some clinical studies performed in patients with perennial allergic rhinitis, ramatroban, a new thromboxane A2 receptor antagonist, significantly improved nasal symptoms. As yet the mechanism of action of this drug has not been fully elucidated. In the present study we investigated the effects of ramatroban on changes in nasal reactivity and levels of inflammatory cells and mediators in nasal lavage fluid after allergen challenge. Ramatroban was administered orally at a daily dose of 150 mg (b.i.d.) for 4 weeks to 11 patients with perennial allergic rhinitis exhibiting positive responses to nasal allergen challenge with house dust mite. Analysis of variance revealed that there was a significant decrease in eosinophil counts and eosinophil cationic protein levels in nasal lavage fluid when compared with values immediately before allergen challenge before and after ramatroban treatment. Histamine, tryptase and albumin levels were significantly decreased in analysis of variance before and after ramatroban treatment. The degree of nasal reactivity to histamine was also significantly decreased after the ramatroban treatment. These findings indicate that ramatroban decreases important pathogenic factors in allergic rhinitis, resulting in an improvement in nasal symptoms

Involvement of vascular endothelial growth factor in nasal obstruction in patients with nasal allergy

It has recently been shown that vascular endothelial growth factor (VEGF) enhances vascular permeability and that mast cells produce VEGF, suggesting the involvement of VEGF in allergic diseases. In the present study we quantitatively analyzed VEGF in the nasal lavage fluid of patients with nasal allergy. We performed nasal antigen challenge with Japanese cedar pollen antigen in 10 healthy adult volunteers and in 10 cedar pollen IgE-positive patients with nasal allergy. In all patients with nasal allergy, VEGF and histamine levels in the nasal lavage fluid reached a peak 30 min after antigen challenge, then returned to prechallenge values 2 h after antigen challenge. In these patients, the histamine level increased three-fold, while the VEGF level increased 10-fold. However, in all healthy adult volunteers, VEGF and histamine levels did not increase. A stronger correlation was noted between the ratio of decreased nasal cavity volume and the ratio of increased VEGF levels (R = 0.823; P < 0.001) than between the ratio of nasal cavity volume and the ratio of increased histamine levels (R = 0.660; P < 0.01). These results suggest that VEGF may contribute to the pathogenesis of nasal obstruction in the early phase of nasal allergy as a new factor involved in increasing vascular permeability

The Effect of Suplatast Tosilate on TARC Production in Peripheral Blood Mononuclear Cells and TARC Plasma Levels

Background: Thymus and activation-regulated chemokine (TARC/CCL17) is a highly specific ligand for CCR 4. TARC may contribute to the recruitment, activation, and development of Th2 polarized cells that express CCR4. These characteristics have led investigators to hypothesize that TARC is involved in the development of Th2 responses. Suplatast tosilate ((±)-[2-[4-(3-ethoxy-2-hydroxy-propoxy) phenylcarbamoyl] ethyl] dimethylsulfonium p-toluenesulfonate) is an anti-allergic agent that selectively suppresses the synthesis of Th2 cytokines. We examined the effect of suplatast tosilate on TARC production and CCR-4 expression in vitro. Furthermore, we attempted to clarify whether TARC production was suppressed after clinical administration of suplatast tosilate. Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from patients with allergic rhinitis who tested positive to house dust. PBMCs were stimulated with mite antigen. TARC mRNA was detected by real time PCR. The amount of TARC was estimated using an ELISA kit. PBMCs expressing CCR-4 were sorted by flow cytometry. The plasma level of TARC was examined in patients with chronic allergic rhinitis before and after treatment with suplatast tosilate for 4 weeks. Results: Suplatast tosilate significantly reduced TARC production by PBMCs. TARC mRNA was also suppressed in a concentration dependent manner. However, suplatast tosilate did not inhibit the expression of CCR-4 on PBMCs. The plasma level of TARC was significantly decreased in patients administered suplatast tosilate. Conclusions: Suplatast tosilate suppressed TARC production by PBMCs and decreased the plasma level of TARC in patients with chronic allergic rhinitis

The Influence of Environmental Exposure to Formaldehyde in Nasal Mucosa of Medical Students during Cadaver Dissection

ABSTRACTBackgroundEnvironmental exposure to formaldehyde is commonly associated with clinical symptoms such as mucosal irritation and olfactory disorders. However, the impact of such exposure on the development of mucosal inflammation and its outcome has not been carefully evaluated.MethodsThe observational non-comparative study was planned. The study population consisted of group of 41 medical students who had signed up for a cadaver dissection course as part of their gross anatomy teaching at the school of medicine Chiba University in Japan. During such dissection course, the students are exposed to variable levels of environmental formaldehyde routinely employed for the preservation the cadavers. The subjects were evaluated by a detailed medical examination. We measured their serum IgE levels. In addition, an olfaction test and nasal mucosal sensitivity to histamine was serially determined, immediately before and after the course and 6 months after the completion of the course.ResultsOlfactory abnormalities were observed in 13/41 (32%) subjects and increased nasal mucosal hypersensitivity to histamine was observed in 17/41 (41%) during and immediately after completion of the course. These subjects had evidence of preexisting allergic rhinitis. 6/41 (15%) other students with no prior evidence of allergic rhinitis also exhibited formaldehyde associated clinical symptoms during the dissecting course. However, the symptoms disappeared upon completion of the course in all subjects studied.ConclusionsTemporary abnormalities in the olfaction test and increased nasal mucosal hypersensitivity to histamine were observed in a few students with preexisting allergic rhinitis after environmental exposure of high concentrations of formaldehyde. These effects appeared to be transient