ICAR: endoscopic skull‐base surgery

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Contribution of local renin angiotensin system to cardiac hypertrophy, phenotypic modulation, and remodeling in TGR(mRen2)27 transgenic rats

BACKGROUND: The transgenic rat TGR(mRen2)27, carrying the mouse Ren-2 gene, is a new model to elucidate the role of the local renin-angiotensin system in vivo. However, the role of the local renin-angiotensin system in the heart remains to be determined in TGR(mRen2)27. METHODS AND RESULTS: TGR(mRen2)27 were treated with various antihypertensive drugs for 6 weeks to examine the effects on cardiac hypertrophy and gene expression. Cardiac mRNAs were examined by Northern blot analysis. In TGR(mRen2)27, left ventricular hypertrophy was associated with a decrease in alpha-myosin heavy chain expression of 31% and an increase in skeletal alpha-actin and atrial natriuretic polypeptide expression by 2.6- and 21-fold, respectively (P < .05), thereby showing the shift of myocardium to a fetal phenotype. Furthermore, cardiac collagen and laminin expressions were increased in TGR(mRen2)27 (P < .05), suggesting the occurrence of cardiac remodeling. Although treatment of TGR(mRen2)27 with a high dose of TCV-116 (angiotensin AT1 receptor antagonist) or manidipine (calcium antagonist) combined with atenolol (beta 1-adrenergic receptor blocker) completely normalized blood pressure, TCV-116 regressed cardiac hypertrophy and suppressed the changes in cardiac mRNA levels of TGR(mRen2)27 much more potently than manidipine with atenolol. Furthermore, the inhibitory effects of a low dose of TCV-116 on cardiac hypertrophy and altered gene expressions of TGR(mRen2)27 were greater than those of doxazosin (alpha 1-adrenergic receptor blocker) combined with atenolol, despite their similar hypotensive effects. CONCLUSIONS: Our present observations provide evidence that the cardiac renin-angiotensin system in TGR(mRen2)27 is responsible for cardiac hypertrophy, phenotypic modulation, and remodeling

Angiotensin II type 1 receptor blockade inhibits the expression of immediate early genes and fibronectin in rat injured artery

BACKGROUND: Vascular injury activates various kinds of genes, including proto-oncogenes, growth factors, and extracellular matrix proteins. However, the significance of activation of these genes in neointimal formation is poorly understood. Angiotensin II type 1 (AT1) receptor antagonist is shown to prevent neointimal formation after vascular injury, although the mechanism is unclear. To understand the molecular mechanism of vascular thickening, we examined the effects of AT1 receptor blockade on the gene expression of proto-oncogenes, transforming growth factor-beta 1 (TGF-beta 1), and extracellular matrix proteins after vascular injury. METHODS AND RESULTS: Endothelial denudation of the left common carotid artery in Sprague-Dawley rats was performed with a Fogarty 2F balloon catheter. TCV-116 (10 mg.kg-1.d-1), a selective nonpeptide AT1 receptor antagonist, or vehicle was administered orally to rats from 1 day before to 14 days after balloon injury. Injured left and uninjured right common carotid arteries were removed from rats at 1, 6, and 24 hours and 3, 7, and 14 days after balloon injury. Tissue mRNA levels were measured with Northern blot analysis using specific cDNA probes and corrected for 18S ribosomal RNA value. Arterial mRNAs for c-fos, c-jun, jun B, jun D, and Egr-1 increased significantly at 1 hour after balloon injury and decreased rapidly. At 6 hours, ornithine decarboxylase (ODC) mRNA expression reached the maximal levels. TGF-beta 1 and fibronectin mRNA levels started to increase at 6 hours after injury and remained enhanced until 7 days after injury. On the other hand, collagen types I, III, and IV and laminin mRNA levels were not significantly increased over 7 days. Treatment with TCV-116 significantly inhibited the induction of mRNAs for c-fos, c-jun, Egr-1, ODC, and fibronectin in injured artery, whereas the increase in TGF-beta 1 gene expression after injury was not prevented by TCV-116. Immunohistological studies indicated that TCV-116 decreased not only the intimal thickening but also the amount of these extracellular matrix proteins in the intima. CONCLUSIONS: The results indicate that AT1 receptor blockade inhibits the induction of immediate-early genes, ODC, and fibronectin in rat injured artery. Thus, inhibition of intimal thickening by AT1 receptor blockade may be mediated at least in part by suppression of multiple genes related to cell growth and migration in the very early phase after vascular injury

Structural basis for the one-pot formation of the diarylheptanoid scaffold by curcuminoid synthase from Oryza sativa

Curcuminoid synthase (CUS) from Oryza sativa is a plant-specific type III polyketide synthase (PKS) that catalyzes the remarkable one-pot formation of the C6-C7-C6 diarylheptanoid scaffold of bisdemethoxycurcumin, by the condensation of two molecules of 4-coumaroyl-CoA and one molecule of malonyl-CoA. The crystal structure of O. sativa CUS was solved at 2.5-Å resolution, which revealed a unique, downward expanding active-site architecture, previously unidentified in the known type III PKSs. The large active-site cavity is long enough to accommodate the two C6-C3 coumaroyl units and one malonyl unit. Furthermore, the crystal structure indicated the presence of a putative nucleophilic water molecule, which forms hydrogen bond networks with Ser351-Asn142-H2O-Tyr207-Glu202, neighboring the catalytic Cys174 at the active-site center. These observations suggest that CUS employs unique catalytic machinery for the one-pot formation of the C6-C7-C6 scaffold. Thus, CUS utilizes the nucleophilic water to terminate the initial polyketide chain elongation at the diketide stage. Thioester bond cleavage of the enzyme-bound intermediate generates 4-coumaroyldiketide acid, which is then kept within the downward expanding pocket for subsequent decarboxylative condensation with the second 4-coumaroyl-CoA starter, to produce bisdemethoxycurcumin. The structure-based site-directed mutants, M265L and G274F, altered the substrate and product specificities to accept 4-hydroxyphenylpropionyl-CoA as the starter to produce tetrahydrobisdemethoxycurcumin. These findings not only provide a structural basis for the catalytic machinery of CUS but also suggest further strategies toward expanding the biosynthetic repertoire of the type III PKS enzymes