Assessment of Endothelin-A Receptor Expression in Subcutaneous and Orthotopic Thyroid Carcinoma Xenografts in Vivo Employing Optical Imaging Methods

Endothelin (ET) receptor dysregulation has been described in a number of pathophysiological processes, including cardiovascular disorders, renal failure, and cancer. The aim of this study was to evaluate the expression of the ET-A receptor (ETAR) in murine models of thyroid carcinoma using optical imaging methods. A recently developed near-infrared fluorescent tracer was first assessed in isolated artery preparations for its functional performance in comparison with known ETAR antagonists BQ123 and PD156707. Before evaluation of the tracer in vivo, different thyroid carcinoma cell lines were characterized with respect to their ET receptor expression by RT-PCR and autoradiography. In vivo, sc and orthotopic papillary thyroid tumor xenografts were clearly visualized by fluorescence reflectance imaging and fluorescence-mediated tomography up to 48 h after injection of the tracer. Binding specificity of the probe was demonstrated by predosing with PD156707 as a competing inhibitor. In conclusion, optical imaging with a fluorescent ETAR tracer allows the noninvasive imaging of tumor-associated ETAR expression in vivo. In the future, this technique may help surgeons to evaluate lesion dimensions in intraoperative settings (e.g. thyroidectomy).

Role of store-operated Ca2+ entry in adenosine-induced vasodilatation of rat small mesenteric artery

Store-operated Ca2+ entry (SOCE) has recently been proposed to contribute to Ca2+ influx in vascular smooth muscle cells (VSMCs). Adenosine is known for its protective role against hypoxia and ischemia by increasing nutrient and oxygen supply through vasodilation. This study was designed to examine the hypothesis that SOCE have a functional role in adenosine-induced vasodilation. Small mesenteric resistance arteries and mesenteric VSMCs were obtained from rats. Isometric tensions of isolated artery rings were measured by a sensitive myograph system. Laser-scanning confocal microscopy was used to determine the intracellular Ca2+ concentration of fluo 3-loaded VSMCs. Adenosine (0.1–100 μM) relaxed artery rings that were precontracted by phenylephrine in a concentration-dependent manner. In cultured mesenteric VSMCs, passive store depletion by thapsigargin and active store depletion by phenylephrine both induced Ca2+ influx due to SOCE. Adenosine inhibited SOCE-mediated increases in cytosolic Ca2+ levels evoked by the emptying of the stores. In isolated artery rings, adenosine inhibited SOCE-induced contractions due to store depletion. A2A receptor antagonism with SCH-58261 and adenylate cyclase inhibition with SQ-22536 largely attenuated adenosine responses. The cAMP analog 8-bromo-cAMP mimicked the effects of adenosine on SOCE. Our results indicate a novel mechanism of vasodilatation by adenosine that involves regulation of SOCE through the cAMP signaling pathway due to activation of adenosine A2A receptors.

ENaC proteins contribute to VSMC migration

Vascular smooth muscle cell (VSMC) migration plays a key role in tissue repair after arterial wall injury. VSMC migration requires integration of chemical and mechanical signaling mechanisms. Recently, we showed that epithelial Na+ channel (ENaC) proteins are expressed in VSMCs and that ENaC inhibition abolishes pressure-induced constriction in isolated artery segments. However, whether ENaC proteins play a role in VSMC migration is unknown. The goal of this study was to determine whether ENaC molecules are required for VSMC migration. Using RT-PCR, immunoblotting, and immunolabeling, we detected expression of α-, β-, and γENaC transcripts and proteins in cultured VSMCs (SV40-LT and A10 cells). Of the three proteins, βENaC was the most readily detected in both cell lines by immunolocalization and Western blotting. Inhibition of ENaC activity with 1 μM benzamil blunted VSMC migration associated with wound healing (40.3% at 8 h and 26.2% at 24 h) and in response to the chemotactic stimulant platelet-derived growth factor-BB (38.1%). Furthermore, silencing ENaC gene expression with small interfering RNA blunted VSMC migration. These data indicate that expression of ENaC proteins is required for normal VSMC migration and suggest a potential new role for ENaC proteins in vascular tissue repair.

Microsurgical anatomy of the arterial compartment of the cavernous sinus: analysis of 24 cavernous sinus

The cavernous sinus is a complex compartment situated in both sides of the sella turcica, being its microsurgical anatomy knowledge of fundamental importance when consider to approach surgically. We studied the arterial microanatomy of 24 cavernous sinus at the microsurgical laboratory, considering that in all the internal carotid artery were filled with colored latex. The meningohypophyseal trunk was present in 18 cases (75%) with its origin in intracavernous portion of the internal carotid artery. In relation to the 18 presented cases with meningohypophyseal trunk, 14 (77.7%) had a trifurcate and 4 (23.3%) had a bifurcate pattern. The tentorial artery was present in all. Its origin was observed, arising from the meningohypophyseal trunk in 17 (70.8%) and as an isolated artery in some extension of the intracavernous portion in 7 (29.1%). An accessory tentorial artery was found in one specimen. The dorsal meningeal artery was present in 22 cases (91.6%). Its origin was in the meningohypophyseal trunk in 17 cases (77.2%), arising from internal carotid artery in 4 cases (18.1%) and from inferior hypophyseal artery in one case (4.1%).The inferior hypophyseal artery was present in all cases, having its origin at the meningohypophyseal trunk in 16 cases (66.6%). In the remaining 8 cases (33.3%) the artery was found arising alone from the intracavernous portion also. The artery of the inferior cavernous sinus or inferolateral trunk was present in all cases and had its origin from internal carotid artery in its intracavernous segment. The McConnell's artery was not found in any cavernous sinus.

Effect of length changes on sensitivity of helical artery strips to adenosine

The relationship between length and the responses of helical strips of rabbit femoral and coronary arteries to vasoactive agents was investigated by conducting concentration–response determinations at the length for maximum active force (Lmax) and a shorter length. The mean effective dose (ED50) values for norepinephrine (NE) were smaller when femoral artery strips were set at Lmax, in comparison to the values at the shorter length. Maximal relaxation of femoral artery strips by adenosine was greater when the strips were set at Lmax. However, adenosine ED50 values were smaller at Lmax only in groups of strips in which responses at Lmax were obtained prior to those at the shorter length. Experiments with coronary artery strips did not demonstrate consistent relationships between strip length and ED50 values for acetylcholine (ACh) or adenosine. The results of experiments with artery strips from normotensive and those from one-kidney, one-clip hypertensive rabbits were similar. Thus, the femoral artery data indicate that helical artery strip preparations may exhibit length-dependent sensitivity to a vasodilator agent as well as vasoconstrictor agents under certain experimental conditions. However, the coronary artery data suggest that length may not affect sensitivity of isolated artery preparations from all vascular beds in the same manner.

The Release Of Prostacyclin (PGI2) By Pentoxyfyl- Line From Human And Animal Vascular Tissue And Its Implications For Vascular And Antiplatelet Activities

The action of pentoxyfylline (POF) on vascular tone and PGI2-release was studied in-vitro and compared to its antiplatelet activities. POF at concentrations of 10-40 μM dose-dependently increased the PGI2-formation of isolated bovine coronary arteries and veins in-vitro. Similar data were obtained with human umbilical arteries and veins. The maximum stimulation in all of the vascular tissues studied was about 2-3-fold above basal levels. Dose-dependent increase of PGI2-production was observed at concentrations of POF comparable to those which dose-dependently relaxed isolated artery strips, whereas the investigated venous tissue was relaxed by both POF and nitroglycerine but not by PGI2. In isolated guinea pig hearts the positive ionotropic action of POF (100 μM) was blocked by propranolol (10 μM), whereas the coronary relaxation remained unchanged. POF did not influence the ADP- and collagen-induced platelet aggregation in-vitro in concentrations up to 100 μM. The data suggest that POF is able to increase significantly the vascular PGI2-form- ation at concentrations above 10 μM, whereas minimum concentrations for obtaining significant inhibition of platelet aggregation in-vitro are above 100 μM. This indicates that the reported clinical efficiency of POF in protecting blood cells and improvement of regional perfusion might in part be due to stimulation of the vascular PGI2-formation.