Arginase inhibition restores endothelial function in diet-induced obesity

Arginase may play a major role in the regulation of vascular function in various cardiovascular disorders by impairing nitric oxide (NO) production. In the current study, we investigated whether supplementation of the arginase inhibitor N^ω-hydroxy-nor-l-arginine (nor-NOHA) could restore endothelial function in an animal model of diet-induced obesity. Arginase 1 expression was significantly lower in the aorta of C57BL/6J mice fed a high-fat diet (HFD) supplemented with nor-NOHA (40 mg kg^-1/day) than in mice fed HFD without nor-NOHA. Arginase inhibition led to considerable increases in eNOS expression and NO levels and significant decreases in the levels of circulating ICAM-1. These findings were further confirmed by the results of siRNA-mediated knockdown of Arg in human umbilical vein endothelial cells. In conclusion, arginase inhibition can help restore dysregulated endothelial function by increasing the eNOS-dependent NO production in the endothelium, indicating that arginase could be a therapeutic target for correcting obesity-induced vascular endothelial dysfunction.     

Chemoselective regulation of TREK2 channel: Activation by sulfonate chalcones and inhibition by sulfonamide chalcones

Although it has not been extensively studied, a significant volume of literature suggests that TREK2 will probably turn out to be an important channel in charge of tuning neuronal transmitter and hormone levels. Thus, pharmacological tools which can manipulate this channel, such as selective agonists are essential both in drug design and to further our understanding of this system. Our investigations have shown that sulfonate (‘O’) chalcone and sulfonamide (‘N’) chalcones regulate the TREK2 channel in remarkably different ways: sulfonamide chalcone 5 behaved as an inhibitor with an IC₅₀ of 62 μM, whereas the sulfonate analogue 11 activated TREK2 with EC₅₀ value of 167 μM.     

Effect of Chord Flexure on Aerodynamic Performance of a Flapping Wing

Inspired by the fact that a high flexible wing in nature generates high aerodynamic performance, we investigated the aerodynamic performance of the flapping wing with different chord flexures. The unsteady, incompressible, and viscous flow over airfoil NACA0012 in a plunge motion was analyzed by using Navier-Stokes equation. Grid deformation, in which finite element and interpolation ideas are mixed, was introduced for computing large grid deformation caused by the chord flexures. We explored the optimal phase angle for thrust force and propulsive efficiency by varying the chord flexure from 0.05 to 0.7 when reduced frequency and plunge amplitude were fixed. Throughout parametric study on the phase angle and chord flexure amplitude, the maximum thrust force is achieved near at 0° in all given conditions, meanwhile, it is found that the optimal phase angle has dependency of chord flexure amplitude, which achieves higher aerodynamic performance compared to previous studies. These findings will provide a useful guideline for determining wing flexibility in design of a bio-mimetic air vehicle.     

Hypoxia-inducible factor-1α mediates oral squamous cell carcinoma invasion via upregulation of α5 integrin and fibronectin

With progressive and rapid growth of malignant tumors, cancer cells in an ischemic condition are expected to develop an increased potential for local invasive growth. To address this hypothesis, we first examined the effect of hypoxia on the invasiveness of oral squamous cell carcinoma (OSCC) cells using the Matrigel invasion assay. We then investigated the effect of hypoxia on the protein and mRNA expression of α5 integrin and fibronectin, which are major factors involved in tumor cell invasion. We showed that (i) hypoxia increased the invasiveness of OSCC cells, (ii) α5 integrin and fibronectin protein and mRNA expression levels were increased in OSCC cells under hypoxic conditions, (iii) hypoxia stimulated autocrine secretion of fibronectin in OSCC cells, (iv) administration of siRNA_HIF-1α caused a significant decrease in α5 integrin and fibronectin protein, confirming that HIF-1α plays a role in their induction, and (v) siRNA_HIF-1α abrogated hypoxia-induced cell invasion. Collectively, these data suggest that hypoxia promotes OSCC cell invasion that is elicited by HIF-1α-dependent α5 integrin and fibronectin induction.     

Crystal structures of two archaeal Pelotas reveal inter-domain structural plasticity

Dom34 from Saccharomyces cerevisiae is one of the key players in no-go mRNA decay, a surveillance pathway by which an abnormal mRNA stalled during translation is degraded by an endonucleolytic cleavage. Its homologs called Pelota are found in other species. We showed previously that S. cerevisiae Dom34 (domain 1) has an endoribonuclease activity, which suggests its direct catalytic role in no-go decay. Pelota from Thermoplasma acidophilum and Dom34 from S. cerevisiae have been structurally characterized, revealing a tripartite architecture with a significant difference in their overall conformations. To gain further insights into structural plasticity of the Pelota proteins, we have determined the crystal structures of two archaeal Pelotas from Archaeoglobus fulgidus and Sulfolobus solfataricus. Despite the structural similarity of their individual domains to those of T. acidophilum Pelota and S. cerevisiae Dom34, their overall conformations are distinct from those of T. acidophilum Pelota and S. cerevisiae Dom34. Different overall conformations are due to conformational flexibility of the two linker regions between domains 1 and 2 and between domains 2 and 3. The observed inter-domain structural plasticity of Pelota proteins suggests that large conformational changes are essential for their functions.     

An enzymatic method to distinguish tetrahydrobiopterin from oxidized biopterins using UDP-glucose:tetrahydrobiopterin glucosyltransferase

The quantitative determination of tetrahydrobiopterin (BH4) and its oxidized forms (dihydrobiopterin and biopterin) is important in searching for possible markers of neuropsychiatric and cardiovascular disorders as well as in diagnosing BH4 deficiencies. Currently, two high-performance liquid chromatography (HPLC) methods are available, although both have some limitations. We developed an enzymatic method to distinguish BH4 from the oxidized forms by employing BH4:UDP-glucose α-glucosyltransferase (BGluT), which catalyzes glucosyl transfer from UDP-glucose to BH4. The recombinant BGluT isolated from Escherichia coli converted essentially all of the BH4 in a mixture containing oxidized biopterins to the glucoside while leaving the oxidized forms intact. Therefore, acidic iodine oxidation of the reaction mixture followed by single fluorescence HPLC permitted the determination of biopterin and biopterin-glucoside, which represent oxidized biopterins and BH4, respectively. The validity of the method was evaluated using authentic biopterins and animal samples such as human urine, rat plasma, and rat liver. The BGluT-catalyzed reaction not only would reduce the burden of chromatographic separation but also would promise non-HPLC analysis of BH4.