BackgroundIn Latin America, 18 million people are infected with Trypanosoma cruzi, the agent of Chagas' disease, with the greatest economic burden. Vertebrate calreticulins (CRT) are multifunctional, intra- and extracellular proteins. In the endoplasmic reticulum (ER) they bind calcium and act as chaperones. Since human CRT (HuCRT) is antiangiogenic and suppresses tumor growth, the presence of these functions in the parasite orthologue may have consequences in the host/parasite interaction. Previously, we have cloned and expressed T. cruzi calreticulin (TcCRT) and shown that TcCRT, translocated from the ER to the area of trypomastigote flagellum emergence, promotes infectivity, inactivates the complement system and inhibits angiogenesis in the chorioallantoid chicken egg membrane. Most likely, derived from these properties, TcCRT displays in vivo inhibitory effects against an experimental mammary tumor.Methodology and Principal FindingsTcCRT (or its N-terminal vasostatin-like domain, N-TcCRT) a) Abrogates capillary growth in the ex vivo rat aortic ring assay, b) Inhibits capillary morphogenesis in a human umbilical vein endothelial cell (HUVEC) assay, c) Inhibits migration and proliferation of HUVECs and the human endothelial cell line Eahy926. In these assays TcCRT was more effective, in molar terms, than HuCRT: d) In confocal microscopy, live HUVECs and EAhy926 cells, are recognized by FITC-TcCRT, followed by its internalization and accumulation around the host cell nuclei, a phenomenon that is abrogated by Fucoidin, a specific scavenger receptor ligand and, e) Inhibits in vivo the growth of the murine mammary TA3 MTXR tumor cell line.Conclusions/SignificanceWe describe herein antiangiogenic and antitumor properties of a parasite chaperone molecule, specifically TcCRT. Perhaps, by virtue of its capacity to inhibit angiogenesis (and the complement system), TcCRT is anti-inflammatory, thus impairing the antiparasite immune response. The TcCRT antiangiogenic effect could also explain, at least partially, the in vivo antitumor effects reported herein and the reports proposing antitumor properties for T. cruzi infection.

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We tested the hypothesis that previously demonstrated gender differences in ACh-induced vascular relaxation could involve diverse Na+-K+-ATPase functions. We determined Na+-K+-ATPase by measuring arterial ouabain-sensitive 86Rb uptake in response to ACh. We found a significant increase of Na+ pump activity only in aortic rings from female rats (control 206 ± 11 vs. 367 ± 29 nmol 86Rb/K·min–1·g wt tissue–1; P < 0.01). Ovariectomy eliminated sex differences in Na+-K+-ATPase function, and chronic in vivo hormone replacement with 17β-estradiol restored the ACh effect on Na+-K+-ATPase. Because ACh acts by enhancing production of NO, we examined whether the NO donor sodium nitroprusside (SNP) mimics the action of ACh on Na+-K+-ATPase activity. SNP increased ouabain-sensitive 86Rb uptake in denuded female arteries (control 123 ± 7 vs. 197 ± 12 nmol 86Rb/K·min–1·g wt tissue–1; P < 0.05). Methylene blue (an inhibitor of guanylate cyclase) and KT-5823 (a cGMP-dependent kinase inhibitor) blocked the stimulatory action of SNP. Exposure of female thoracic aorta to the Na+/K+ pump inhibitor ouabain significantly decreased SNP-induced and ACh-mediated relaxation of aortic rings. At the molecular level, Western blot analysis of arterial tissue revealed significant gender differences in the relative abundance of catalytic isoforms of Na+-K+-ATPase. Female-derived aortas exhibited a greater proportion of α2-isoform (44%) compared with male-derived aortas. Furthermore, estradiol upregulated the expression of α2 mRNA in male arterial explants. Our results demonstrate that enhancement of ACh-induced relaxation observed in female rats may be in part explained by 1) NO-dependent increased Na+-K+-ATPase activity in female vascular tissue and 2) greater abundance of Na+-K+-ATPase α2-isoform in females.

Exposure to high-altitude chronic hypoxia during pregnancy may cause pulmonary hypertension in neonates, as a result of vasoconstriction and vascular remodeling. We hypothesized that susceptibility to pulmonary hypertension, due to an augmented expression and activity of the RhoA/Rho-kinase (ROCK) pathway in these neonates, can be reduced by daily administration of fasudil, a ROCK inhibitor. We studied 10 highland newborn lambs with conception, gestation, and birth at 3,600 m in Putre, Chile. Five highland controls (HLC) were compared with 5 highland lambs treated with fasudil (HL-FAS; 3 mg·kg(-1)·day(-1) iv for 10 days). Ten lowland controls were studied in Lluta (50 m; LLC). During the 10 days of fasudil daily administration, the drug decreased pulmonary arterial pressure (PAP) and resistance (PVR), basally and during a superimposed episode of acute hypoxia. HL-FAS small pulmonary arteries showed diminished muscular area and a reduced contractile response to the thromboxane analog U46619 compared with HLC. Hypoxia, but not fasudil, changed the protein expression pattern of the RhoA/ROCKII pathway. Moreover, HL-FAS lungs expressed less pMYPT1(T850) and pMYPT1T(696) than HLC, with a potential increase of the myosin light chain phosphatase activity. Finally, hypoxia induced RhoA, ROCKII, and PKG mRNA expression in PASMCs of HLC, but fasudil reduced them (HL-FAS) similarly to LLC. We conclude that fasudil decreases the function of the RhoA/ROCK pathway, reducing the PAP and PVR in chronically hypoxic highland neonatal lambs. The inhibition of ROCKs by fasudil may offer a possible therapeutic tool for the pulmonary hypertension of the neonates.

Abstract-Recent studies suggested that type 2 angiotensin receptor (AT2R) could contribute to regulation of blood pressure and/or vascular remodeling. A key question relates to the effects of potential modulators of vascular AT2R expression. In the present work, we evaluated if high salt intake (70 mmol/L NaCl in drinking water) could modulate rat mesenteric artery AT2R function and expression. Angiotensin II dose-response curves were studied in rat perfused pressurized small-diameter arteries in the presence of losartan (AT1R antagonist Key Words: mineralocorticoid Ⅲ sodium Ⅲ hypertension Ⅲ vascular remodeling Ⅲ apoptosis T he renin-angiotensin-aldosterone system (RAAS) regulates vascular tone, body fluid volume, electrolyte balance, hormonal secretion, and neuronal activity. The biological effects of angiotensin II (Ang II), the main effector peptide in the vasculature, are mediated by at least 2 receptor isofoms. 1,2 The type 1 receptor (AT1R) mediates vasoconstriction, sympathetic facilitation, and trophic effects. The type 2 receptor (AT2R) is widely expressed during fetal development, whereas in the adult its expression has been detected in many different vessel types, including mesenteric, coronary, and renal arteries. 3-6 AT2R has opposite effects to those of AT1R, ie, it promotes cell apoptosis and inhibits cell proliferation. 6,7 AT2R also attenuates the pressor action of Ang II 8 and mediates vasodilation. 9,10 Recently, it has been shown that Ang II relaxes small mesenteric arteries via AT2R when AT1R are blocked. [11][12][13] Interestingly, the expression of AT2R is increased in several pathologic conditions such as vascular injury, 14 cardiac remodeling, congestive heart failure, and myocardial infarction. 15,16 It has been suggested that in adults the presence of AT2R in vascular tissues may be playing a role in vascular tone and/or tissue remodeling. [17][18][19] Therefore, a key and complex question that arises is how AT1R and AT2R expression are modulated. Several studies indicate interaction between Ang II and aldosterone, affecting the expression of ATRs. The expression of AT1R appears to be induced by Ang II in vascular smooth muscle, 4 and mineralocorticoids potentiate the action of Ang II in cultured rat vascular smooth muscle cells (VSMCs) by increasing the number of AT1R. 20,21 However, there are few data concerning the physiological regulation of AT2R expression. Dietary sodium depletion, which increases RAAS activity, enhances renal AT2 receptor function 10,22 and expression in both young and mature adult rats, mainly in the glomeruli and interstitial cells. 23 Induction of AT2R-mediated modulation of blood pressure was described in rats fed with a synthetic diet, an effect attributed to the stimulation of the RAAS. 8 Bonnet et al 24 have shown that Ang II infusion in the rat induces the expression of AT2R in the mesenteric vasculature. Nevertheless, it is not clear whether Ang II directly mediates the increased AT2R expression or if it is secondary to direct aldosterone action on arte...

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