Shear stress modulates the expression of thrombospondin-1 and CD36 in endothelial cells in vitro and during shear stress-induced angiogenesis in vivo

Binding of thrombospondin-1 (TSP-1) to the CD36 receptor inhibits angiogenesis and induces apoptosis in endothelial cells (EC). Conversely, matrix-bound TSP-1 supports vessel formation. In this study we analyzed the shear stress-dependent expression of TSP-1 and CD36 in endothelial cells in vitro and in vivo to reveal its putative role in the blood flow-induced remodelling of vascular networks. Shear stress was applied to EC using a cone-and-plate apparatus and gene expression was analyzed by RT-PCR, Northern and Western blot. Angiogenesis in skeletal muscles of prazosin-fed (50 mg/l drinking water; 4 d) mice was assessed by measuring capillary-to-fiber (C/F) ratios. Protein expression in whole muscle homogenates (WMH) or BS-1 lectin-enriched EC fractions (ECF) was analyzed by Western blot. Shear stress downregulated TSP-1 and CD36 expression in vitro in a force- and time-dependent manner sustained for at least 72 h and reversible by restoration of no-flow conditions. In vivo, shear stress-driven increase of C/F in prazosin-fed mice was associated with reduced expression of TSP-1 and CD36 in ECF, while TSP-1 expression in WMH was increased. Down-regulation of endothelial TSP-1/CD36 by shear stress suggests a mechanism for inhibition of apoptosis in perfused vessels and pruning in the absence of flow. The increase of extra-endothelial (e.g. matrix-bound) TSP-1 could support a splitting type of vessel growth.

Variation in stress reactivity affects cage-induced stereotypies in female CD-1 (ICR) mice

Stereotypies in captive animals typically occur under conditions that are stressful for the animals, and there is some anecdotal evidence that stress levels during early stereotypy development predict later stereotypy levels. Based on this and on the involvement of stress in the behavioural sensitization to psychostimulant drugs, it has been hypothesized that stereotypy development might be causally related to stress. To address this question further, we used mice of the commercial outbred stock CD-1 (ICR) and mice of two lines derived from the outbred CD-1 (ICR) strain by selective breeding for high (HR) and low (LR) stress reactivity, respectively, and examined whether genetically driven variation in stress reactivity is associated with variation in the expression of cage-induced stereotypies. From 21 days of age, 10 females of each line were housed in pairs under standard laboratory conditions until they were video recorded for stereotypic behaviour and tested for corticosterone responses in a stress reactivity test (SRT) at 12 weeks of age. As expected, HR females showed a significantly stronger corticosterone response in the SRT than LR females, while ICR females were intermediate. Unexpectedly, however, both HR and LR females showed very low levels of stereotypic behaviour, while ICR females developed the high levels of stereotypies typical for this strain of mouse. Consequently, there was no significant relationship between measures of acute corticosterone reactivity and stereotypy performance, but a trend for reduced recovery of the corticosterone response in the ICR line suggests that variation in recovery rather than the acute response might predict stereotypy levels in these mice. (C) 2011 Elsevier B.V. All rights reserved.

Coronary artery disease, nitric oxide and oxidative stress: the "Yin-Yang" effect--a Chinese concept for a worldwide pandemic

Prevention of coronary artery disease (CAD) and reduction of its mortality and morbidity remains a major public health challenge throughout the "Western world". Recent evidence supports the concept that the impairment of endothelial function, a hallmark of insulin resistance states, is an upstream event in the pathophysiology of insulin resistance and its main corollaries: atherosclerosis and myocardial infarction. Atherosclerosis is currently thought to be the consequence of a subtle imbalance between pro- and anti-oxidants that produces favourable conditions for lesion progression towards acute thrombotic complications and clinical events. Over the last decade, a remarkable burst of evidence has accumulated, offering the new perspective that bioavailable nitric oxide (NO) plays a pivotal role throughout the CAD-spectrum, from its genesis to the outcome after acute events. Vascular NO is a critical modulator of coronary blood flow by inhibiting smooth muscle contraction and platelet aggregation. It also acts in angiogenesis and cytoprotection. Defective endothelial nitric oxide synthase (eNOS) driven NO synthesis causes development of major cardiovascular risk factors (insulin resistance, arterial hypertension and dyslipidaemia) in mice, and characterises CAD-prone insulin-resistant humans. On the other hand, stimulation of inducible nitric oxide synthase (iNOS) and NO overproduction causes metabolic insulin resistance and characterises atherosclerosis, heart failure and cardiogenic shock in humans, suggesting a "Yin-Yang" effect of NO in the cardiovascular homeostasis. Here, we will present a concise overview of the evidence for this novel concept, providing the conceptual framework for developing a potential therapeutic strategy to prevent and treat CAD.

Temporary hypoxic stress protects the liver from Fas-mediated apoptosis and ischemia reperfusion injury

Molecular responses to hypoxia restore oxygen homeostasis and promote cell survival, and are mainly regulated through the activation of the hypoxia-inducible transcription factor (HIF)-1 and its target genes. In this study we questioned whether surgically depleting the liver s arterial blood supply, by clamping the hepatic artery (HA), would be sufficient to mount a hypoxia-driven molecular response, the up-regulation of hepatoprotective genes and thereby protect the liver from subsequent damaging insults.;;The HA of normal male Balb/c mice was clamped with a micro vascular clip for 2 hours. The liver s saturated oxygen concentration (SO2) was measured using an O2C surface probe (LEA-Medizintechnik) and interstitial fluid was collected with microdialysis membranes to monitor tissue damage. Mice without clamping served as sham operated controls. Interstitial fluid was assessed for lactate pyruvate (L/P) and glycerol content and the mRNA of hepatoprotective genes was analyzed by real time PCR. Subsequently, mice received either a tail vein injection of anti-Fas antibody (Jo2, 0.2 mg/kg) or the liver was made ischemic (60min) followed by 6 hours reperfusion. Caspase 3-activity and cleaved lamin A were used to assess apoptosis. In separate groups, animal were monitored for survival.;;After 30min of clamping the HA the SO2 of the liver decreased and remained at a reduced level for up to 2 hours, without an increase in L/P ratio or glycerol release. We demonstrate the activation of a hypoxia-inducible signaling pathway by the stabilization of HIF-1 protein (Western blot) and by an increase of its target gene, Epo, mRNA. There was an up-regulation of the hepatoprotective genes IL-6, IGFBP-1, HO-1 and A20 mRNA. When subsequently injected with Jo2, animals preconditioned with HA clamping, had a significantly decreased caspase-3 activity (avg21044 vs. avg3637; p=0.001, T-test) and there were fewer positive cells for cleaved Lamin A. The survival probability (10.5 hours, n=12) of mice with HA clamping was significantly higher (3.2 hours, n=13; p=0.014, Logrank test). Likewise, survival after 60 minutes of partial hepatic ischemia and 6 hours of reperfusion was reduced from 86% in mice with pretreatment by HA clamping to 56% in sham treated controls.;;This study demonstrates that a localized hypoxic stress can be achieved by surgically removing the livers arterial blood supply. Furthermore it can stimulate a hepatoprotective response that protects the liver against Fas-mediated apoptosis and ischemia-reperfusion injury. Our findings offer an innovative approach to induce hepatoprotective genes to defend the liver against subsequent insults.