Search

The present study tested the hypothesis that murine (m)IFN-[beta] or mIFN-[[alpha].sub.2] can eliminate cardiac viral load and protect cardiomyocytes from injury in animals infected with coxsackievirus B3 (CVB3). CVB3-inoculated male Balb/c mice exhibited signs of illness, including lethargy, progressive weight loss, and death (10% on day 3 and 100% on day 8). Cardiac viral load was high [4,277 [+ or -] 1,009 plaque-forming units and 25 [+ or -] 5 copies CVB3/hypoxanthine guanine phosphoribosyl transferase 1 mRNA] on day 4. The cardiac tissue exhibited severe inflammatory infiltration and myocyte damage with an average myocarditis integrated pathology score of 2.1 [+ or -] 0.2 on day 7. Most of the mice infected with CVB3 also developed epicarditis, and 55% had intraventricular thrombi present. Treatment with mIFN-[beta] [2.5 to 10 million international units (MIU)/kg] dose-dependently improved the general health status in CVB3-inoculated mice, as evidenced by reduction in weight loss, prevention of death, elimination of cardiac viral load, protection of myocytes from injury, decrease in inflammatory cell infiltration, and attenuation of intraventricular thrombus formation. Treatment with 10 MIU/kg mIFN-[[alpha].sub.2] resulted in a similar level of efficacy as that induced by 5 MIU/kg mIFN-[beta], with the exception that mIFN-[[alpha].sub.2] did not reduce cardiac CVB3 mRNA. However, mIFN-[[beta].sub.2] , but not any dose group of mIFN-[beta], significantly attenuated CVB3-induced epicarditis. These data demonstrate antiviral effects for both mIFN-[beta] and mIFN-[[alpha].sub.2], which lead to protection of the mice from CVB3-induced myocarditis. However, the potential mechanisms leading to a differential host response for the two isoforms of mIFN remain to be elucidated. viral cardiomyopathy; myocyte infection; antiviral action; immunomodulation doi:10.1152/ajpheart.00154.2007

Role of endogenous nitric oxide in progression of atherosclerosis in apolipoprotein E-deficient mice. Am J Physiol Heart Circ Physiol 278: H1679-H1685, 2000.--This study investigated the role of endogenous nitric oxide (NO) in the progression of atherosclerosis in apolipoprotein E-deficient [apoE-knockout (KO)] mice. Mice were treated with N[Omega]-nitro-L-arginine methyl ester (L-NAME) an inhibitor of nitric oxide synthase (NOS) or with the NOS substrate L-arginine for 8 wk. L-NAME treatment resulted in a significant inhibition of NO-mediated vascular responses and a significant increase in the atherosclerotic plaque/surface area in the aorta of apoE-KO mice. L-arginine treatment had no influence on endothelial function and did not alter lesion size. Mean arterial blood pressure and serum lipid levels were not altered by the treatments. At the beginning of the study impairment in endothelial function was only apparent in the case of [N.sup.G]-nitro-L-arginine-induced, NO-mediated contraction, whereas ACh-induced, NO-mediated relaxation was not different between age-matched apoE-KO and C57B1/6J mice. After the 8-wk treatment with the NOS inhibitor, both NO-mediated responses were significantly inhibited. The acceleration in lesion size concomitant to the severely impaired NO-mediated responses indicates that lack of endogenous NO is an important progression factor of atherosclerosis in the apoE-KO mouse. endothelium; plaque development and progression; L-arginine; N[Omega]-nitro-L-arginine methyl ester

Wang, Yi-Xin, Meredith Halks-Miller, Ron Vergona, Mark E. Sullivan, Richard Fitch, Cornell Mallari, Baby Martin-McNulty, Valdeci Da Cunha, Ana Freay, Gabor M. Rubanyi, and Katalin Kauser. Increased aortic stiffness assessed by pulse wave velocity in apolipoprotein E-deficient mice. Am. J. Physiol. Heart Circ. Physiol. 278: H428-H434, 2000.--Atherosclerosis develops and progresses spontaneously in apolipoprotein E-knockout (apoE-KO) mice. A direct consequence of atherosclerosis is an increase in vascular stiffness. Pulse wave velocity (PWV) has been used to assess the stiffness of large vessels and was found to be increased in patients with atherosclerosis. In the present study, aortic stiffness was assessed by PWV in 4- and 13-mo-old apoE-KO mice and age-matched controls (C57BL/6J). In 13-mo-old apoE-KO mice with extensive atherosclerotic lesions in the aorta (61 [+ or -] 4%), PWV increased significantly (3.8 [+ or -] 0.2 m/s) compared with controls (2.9 [+ or -] 0.2 m/s). Endothelial nitric oxide (EDNO)-mediated vasorelaxation in response to ACh was markedly diminished in the aortic rings isolated from 13-mo-old apoE-KO mice compared with age-matched controls. In contrast, in 4-mo-old apoE-KO mice with only moderate atherosclerotic lesions in the aorta (23 [+ or -] 5%), there were no significant changes in PWV and EDNO-mediated relaxation compared with controls. Blood pressure was not different among the four groups of mice. There were no significant differences in endothelium-independent vascular responses to sodium nitroprusside among different groups investigated. Histological evaluation revealed focal fragmentation of the elastic laminae in the aortic walls of 13-mo-old apoE-KO mice. These results demonstrate for the first time that aortic stiffness determined by PWV increases in 13-mo-old apoE-KO mice. Endothelial dysfunction and elastic destruction in vascular wall caused by atherosclerosis may have contributed compliance; elastin degradation; endothelium-dependent relaxation; nitric oxide

Nitric oxide (NO) plays an important role in vascular protection. It has been reported that endothelial NO synthase (eNOS) deficiency exacerbated carotid artery ligation (CAL)-induced vascular remodeling, which, however, did not elucidate the role of inflammation. Overexpression of eNOS inhibited vascular inflammation and remodeling in a CAL model. However, there is no study that tested the hypothesis that eNOS deficiency can enhance the inflammatory response that plays a critical role in exacerbation of CAL-induced vascular remodeling. Thus, the present study used both eNOS knockout (eNOS-KO) mice and pharmacological blockade of nitric oxide synthase (NOS) to examine the temporal relationship between the inflammatory process and vascular remodeling by CAL and how elimination of NO production affects this. The left common carotid artery was ligated in eNOS-KO, or wild type (WT) mice treated with or without an NOS inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). In WT mice, CAL induced vascular inflammation, characterized by neutrophil and macrophage infiltration into the vessel wall at 1 week. Although the inflammation diminished at 4 weeks, the ligated carotid artery developed prominent vascular remodeling, manifested by smooth muscle cell rich neointimal formation, medial thickening, and adventitial proliferation with reduced luminal diameter. CAL also increased the expression of vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1). VCAM-1 peaked at 1 week, and then slightly declined 4 weeks after CAL, while MCP-1 continued to increase. In eNOS-KO mice, the above changes were exacerbated. Treatment with L-NAME resulted in similar changes as in eNOS-KO mice. Thus, in complement to the previous finding that eNOS overexpression inhibited CAL-induced vascular remodeling, the present study further demonstrated that the absence of eNOS exacerbated vascular remodeling by promoting MCP-1 and VCAM-1 mediated vascular inflammation. These data provided further in vivo evidence supporting the hypothesis that vasculo-protective effects of eNOS are mediated, at least in part, by inhibition of vascular inflammation and smooth muscle cell migration and proliferation induced by vascular injury and blood flow cessation. [ABSTRACT FROM AUTHOR]

The present study was designed to evaluate the role of endothelial NO in the hemodynamics and vascular changes that occur in heart failure following myocardial infarction in rats. Left ventricular systolic pressure (LVSP), mean blood pressure (MBP), aortic morphology (media thickness) and reactivity were evaluated in rats with coronary artery ligation (heart failure, HF) or sham operation (SO) untreated or treated for four weeks with either a low dose of NG-nitro-L-arginine methyl ester (L-NAME, 6 mg-kg-1.day-1) or L-arginine (1.5 g.kg-1.day-1). In rats with HF LVSP (HF = 111 ± 8 mmHg; SO = 143 ± 6 mmHg, p < 0.05), MBP (HF = 98 ± 8 mmHg; SO = 127 ± 6 mmHg, p <0.05) and aortic media thickness (HF = 68 ± 6 μm; SO = 75 ± 2 μm, p < 0.05) were significantly reduced. The contractile response to phenylephrine and the endothelium-independent relaxation to sodium nitroprusside were similar in HF and SO aortas, but the sensitivity (pD2) to acetylcholine (HF = 7.5 ± 0.06; SO = 7.1 ± 0.08, p <0.05) was significantly increased in HF aortas, indicating an enhanced basal NO release. Treatment with L-NAME (LN) reversed the effects of HF on LVSP (HF-LN = 143 ± 9 mmHg, p <0.05 vs. HF), MBP (HF-LN = 128 ± 8 mmHg, p < 0.05 vs. HF), sensitivity to acetylcholine (HF-LN 6.9 ± 0.10, p <0.05 vs. HF) and aortic media thickness (HF-LN = 79 ± 2 μm, p < 0.05 vs. HF), without changing these parameters in SO rats. L-NAME also selectively increased the maximal response to phenylephrine in HF aortas (HF-LN = 2.4 ± 0.20 g; HF = 1.6 ± 0.17 g, p < 0.05). L-arginine (LA) did not change the effects of HF on LSVP, MBP or aortic media thickness, but it reduced the sensitivity to phenylephrine in aortas from SO rats (SO-LA = 6.5 ± 0.12; SO = 7.0 ± 0.09, p < 0.05). Taken together, these results suggest an important role for endothelial NO in mediating the reduced vascular growth, myocardial dysfunction and hypotension in rats with HF. [ABSTRACT FROM AUTHOR]

In this study, we investigated if elevation of endogenous plasminogen activator inhibitor type 1 (PAI-1) by lipopolysaccharide (LPS) can retard thrombolysis in both a rat model of lung vasculature fibrin deposition and a platelet-rich thrombus model induced by endothelial injury. By 3 h following an intravenous bolus injection of 0.5 mg/kg LPS, the plasma PAI-1 level had increased to ∼8 ng/ml. 125I-labeled fibrinogen was injected intravenously followed by an injection of batroxobin. Batroxobin converts fibrinogen into insoluble fibrin, which was then deposited in the lungs within 5 min, followed by spontaneous fibrinolysis that completely cleared fibrin deposition in the lungs by 30 min. In rats pre-treated with LPS, spontaneous fibrinolysis was significantly retarded. In the endothelial injury model, topical application of FeCl2 on the carotid artery induced an occlusive platelet-rich thrombus, which was not sensitive to endogenous thrombolysis. Exogenous tissue-type plasminogen activator (tPA) was required to recanalize the occlusive thrombus in a dose-dependent manner. Pre-treatment with LPS did not alter the dose–response curve of exogenous tPA-induced thrombolysis. These data indicate that batroxobin-induced lung vasculature fibrin deposition in rats, unlike the FeCl2 model, is sensitive to the impact of endogenous PAI-1 on fibrinolysis. [Copyright &y& Elsevier]

Irreversible platelet inhibitors, such as aspirin and clopidogrel, have limited anti-thrombotic efficacy in the clinic due to their bleeding risk. We have developed an orally active reversible P2Y(12) receptor antagonist, BX 667. The aim of this study was to determine if the reversible antagonist BX 667 had a greater therapeutic index than the irreversible P2Y(12) receptor antagonist clopidogrel. Since BX 667 is rapidly converted to its active metabolite BX 048 in rats, we first injected BX 048 intravenously (iv) in a rat arterial venous (A-V) shunt model of thrombosis. BX 048 dose- and concentration-dependently attenuated thrombosis. When administered orally, BX 667 and clopidogrel had similar efficacy, but BX 667 caused less bleeding than clopidogrel. In a rat model of a platelet-rich thrombus induced by vessel injury with FeCl(2), both BX 667 and clopidogrel exhibited higher levels of thrombus inhibition after oral administration compared to their potency in the A-V shunt model. Again, BX 667 caused less bleeding than clopidogrel. In a dog cyclic flow model, iv injection of either BX 667 or clopidogrel dose-dependently reduced thrombus formation with lower bleeding for BX 667 than clopidogrel. Inhibition of thrombosis was highly correlated with inhibition of ADP-induced platelet aggregation in these animal models. In dogs pre-treated with aspirin, BX 667 maintained its wider therapeutic index, measured by inhibition of platelet aggregation over bleeding, compared to the aspirin-clopidogrel combination. These data demonstrate that the reversible P2Y(12) receptor antagonist, BX 667, has a wider therapeutic index than clopidogrel in experimental models of thrombosis.

During thrombosis, P-selectin is expressed on the surface of activated endothelial cells and platelets. We hypothesized that targeting a plasminogen activator (PA) to P-selectin would enhance local thrombolysis and reduce bleeding risk. Previously, a urokinase (uPA)/anti-P-selectin antibody (HuSZ51) fusion protein was shown to increase fibrinolysis in a hamster pulmonary embolism model. To explore the therapeutic potential of this targeting strategy, we fused the fibrin-selective Desmodus rotundus salivary PA alpha1 (dsPA alpha 1) to HuSZ51 and compared the fibrinolytic activity of P-selectin-targeted dsPA alpha 1 (HuSZ51-dsPA alpha 1) to unmodified dsPA alpha 1 in vitro and in vivo. HuSZ51-dsPA alpha 1 and dsPA alpha 1 were expressed in CHO cells and purified to homogeneity by affinity chromatography. HuSZ51-dsPA alpha 1 bound to thrombin-activated human and dog platelets with comparable affinities to that of parental antibody SZ51. The fusion protein retained the catalytic activities of dsPA alpha 1 in chromogenic and clot lysis assays, indicating that dsPA alpha 1 is fully functional when fused to HuSZ51. Compared to dsPA alpha 1, HuSZ51-dsPA alpha 1 had similar thrombolytic efficacy in a rat pulmonary embolism model and anti-thrombotic potency in a dog model of femoral artery thrombosis. However, HuSZ51-dsPA alpha 1 was less effective in lysis of preexisting arterial thrombi in the dog model. The reduced arterial thrombolysis was not due to the pharmacokinetic properties of HuSZ51-dsPA alpha 1 because antigen level and amidolytic activity were higher in plasma from HuSZ51-dsPA alpha 1-treated groups than corresponding dsPA alpha 1-treated groups. These data indicate that the thrombolytic efficacy of HuSZ51-dsPA alpha 1 varied dependent on the physical composition of thrombi. The lack of stimulation by fibrin in arterial thrombi may contribute to the attenuated thrombolytic efficacy of HuSZ51-dsPA alpha 1 in the dog model.

Objective: Angiotensin II (Ang II) promotes vascular inflammation, accelerates atherosclerosis, and induces abdominal aortic aneurysm (AAA). These changes were associated with activation of nuclear factor (NF)-kappaB-mediated induction of proinflammatory genes. The incidence of AAA in this model was higher in male than in female mice, and the vascular effects of estrogen may be associated with anti-inflammatory actions. The present study was undertaken to test the hypothesis that estrogen can attenuate Ang II-induced AAA in apolipoprotein E-deficient mice via its anti-inflammatory mechanism., Methods and Results: Infusion of Ang II (1.44 mg/kg per d for 1 month) induced AAA in 90% of the animals (n=20) with an expansion of the suprarenal aorta (diameter 1.9+/-0.14 mm versus <1 mm in normal mice). In mice treated with 17beta-estradiol (E2, 0.25-mg subcutaneous pellets), Ang II induced AAA only in 42% of the animals (n=19) with a significant reduction of average diameters of the suprarenal aorta (1.5+/-0.14 mm). E2 also decreased the expressions of intracellular adhesion molecule-1, vascular cellular adhesion molecule-1, E-selectin, monocyte chemotactic protein-1, and macrophage-colony stimulating factor in the aorta., Conclusions: These data suggest that attenuation of AAA by E2 is associated with inhibition of proinflammatory gene expression.