Essential Role of Endothelial Nitric Oxide Synthase in Vascular Effects of Erythropoietin

Abstract

Abstract-Erythropoietin (EPO) fosters tissue oxygenation by stimulating erythropoiesis. More recently, EPO has been recognized as a tissue-protective cytokine.In this study, we tested the hypothesis that endothelial NO synthase (eNOS) plays a key role in the vascular protective effect of EPO. A murine model of wire-induced injury of carotid artery was used to examine the effect of EPO on endothelial repair and arterial wall architecture. Recombinant human EPO (1000 U/kg, SC, biweekly) was administered for 2 weeks in wild-type and eNOS-deficient mice after which reactivity of isolated carotid arteries was studied in vitro, and the vasculature was histologically assessed. Key Words: nitric oxide synthase Ⅲ endothelium Ⅲ vasculature Ⅲ erythropoietin Ⅲ mice N itric oxide is a potent vasodilator that is generated in endothelial cells from L-arginine by constitutively expressed endothelial NO synthase (eNOS). 1,2 It has been recognized that reduced NO bioavailability is a major mechanism responsible for initiation and progression of endothelial dysfunction in vascular disease. 3 Furthermore, removal of the endothelium by mechanical vascular injury invariably leads to hyperplasia at the site of injury. 4 -7 This suggests that the endothelium also regulates vascular structure and that its presence assures quiescence of vascular smooth muscle cells.Erythropoietin (EPO) is a hypoxia-inducible hormone that is essential for normal erythropoiesis in bone marrow. Administration of recombinant human EPO is an efficient and safe therapeutic approach to anemia associated with chronic renal failure. 8 However, EPO receptors are also widely distributed in the cardiovascular system, including endothelial, smooth muscle, cardiac, and other cell types, and nonhematopoietic effects of EPO are increasingly recognized. 9 -11 For example, it has been reported that EPO has potentially beneficial effects on cardiovascular function. 11 Furthermore, EPO increases the number of functionally active endothelial progenitor cells, thus enhancing angiogenesis. 12,13 However, little is known about the mechanisms underlying vascular effects of EPO in vivo. The present study was, thus, designed to determine whether EPO prevents pathological repair of injured blood vessel. We hypothesized that eNOS plays a critical role in vascular protective effects of EPO. Methods Experimental Animals of Carotid Artery InjuryMale C57BL/6J (wild-type) and eNOS-deficient mice (C57BL/6J-Nos3 tm1Unc ) were obtained from Jackson Laboratory (Bar Harbor, Maine) and were maintained on standard chow with free access to drinking water. All of the experimental protocols were approved by the institutional animal care and use committee of Mayo Clinic. Wire-induced vascular injury was performed in the left common carotid artery. 7 Twelve-week-old mice were anesthetized with 90 mg/kg of ketamine and 10 mg/kg of xylazine (IP). Using a dissecting microscope, a midline incision (1 to 1.5 cm) was made, and the salivary glands were moved laterally to access the left carotid artery. Tw...

The protective effects of IgM-enriched immunoglobulin and erythropoietin on the lung and small intestine tissues of rats with induced sepsis: Biochemical and histopathological evaluation

“…Also EPO has anti-apoptotic, antiinflammatory, and antioxidative activities. EPO receptor was detected in some tissues such as brain, heart, lung, liver, kidney, and vascular endothelium (Brines & Cerami, 2006;d'Uscio et al, 2007;Heeschen et al, 2003;Sharples & Yaqoob, 2006;Wu et al, 2010b). EPO may prevent the hemorrhagic shock-induced organ damage in rats by decreasing the production of pro-inflammatory cytokines (Wu et al, 2010b).…”

“…Nitric oxide plays a major role in the pathogenesis of sepsis (Santos et al, 2012) and EPO inhibits the activity of nitric oxide synthase (d'Uscio et al, 2007) which is responsible for the synthesis of nitric oxide. Wu et al (2010b) reported that pre-treatment with low dose (300 U/kg) EPO suppresses the release of TNF-a and IL-6 production, decreases organ damage, and improves survival rate after hemorrhagic shock in conscious rats.…”

Activation of endothelial nitric oxide synthase is critical for erythropoietin-induced mobilization of progenitor cells

“…Male C57BL/6J (wild-type) and eNOS-deficient mice (C57BL/6J-Nos3 tm1Unc ) (Jackson Laboratory, Bar Harbor, ME) were distributed into two groups: no treatment (n = 6 mice) and EPO treatment (n = 6 mice, recombinant human EPO 1000 U/kg body weight subcutaneous, bi-weekly, Amgen Thousand Oaks, CA) [10,12]. After 14 days, mice were anesthetized and euthanized by an intraperitoneal injection of pentobarbital (Nembutal Sodium, 60 mg/kg body weight).…”

“…The profile of blood cells in wild type and eNOS-deficient mice treated with EPO were performed with ABAXIS VetScan HMII Hematology System (Union City, CA), as reported in our previous study [10].…”

Effect of Erythropoietin on Angiogenesis With the Increased Adhesion of Platelets to the Microvessels in the Hind-Limb Ischemia Model in Mice

“…Human recombinant EPO (100 or 1000 IU/kg) (Chugai, Tokyo) (13,14) or PBS was injected intraperitoneally three times per week, that is, at 0, 3,6,9,12,15,18,21,24, and 27 days after surgery. There were six animals in each group.…”