Cody R. Kilar

Structural remodeling of coronary resistance arteries: effects of age and exercise training.

Age is known to induce remodeling and stiffening of large-conduit arteries; however, little is known of the effects of age on remodeling and mechanical properties of coronary resistance arteries. We employed a rat model of aging to investigate whether 1) age increases wall thickness and stiffness of coronary resistance arteries, and 2) exercise training reverses putative age-induced increases in wall thickness and stiffness of coronary resistance arteries. Young (4 mo) and old (21 mo) Fischer 344 rats remained sedentary or underwent 10 wk of treadmill exercise training. Coronary resistance arteries were isolated for determination of wall-to-lumen ratio, effective elastic modulus, and active and passive responses to changes in intraluminal pressure. Elastin and collagen content of the vascular wall were assessed histologically. Wall-to-lumen ratio increased with age, but this increase was reversed by exercise training. In contrast, age reduced stiffness, and exercise training increased stiffness in coronary resistance arteries from old rats. Myogenic responsiveness was reduced with age and restored by exercise training. Collagen-to-elastin ratio (C/E) of the wall did not change with age and was reduced with exercise training in arteries from old rats. Thus age induces hypertrophic remodeling of the vessel wall and reduces the stiffness and myogenic function of coronary resistance arteries. Exercise training reduces wall-to-lumen ratio, increases wall stiffness, and restores myogenic function in aged coronary resistance arteries. The restorative effect of exercise training on myogenic function of coronary resistance arteries may be due to both changes in vascular smooth muscle phenotype and expression of extracellular matrix proteins.

Computational design and experimental characterization of a novel β-common receptor inhibitory peptide

Highlights&bgr;IP Inhibits EPO Stimulation of Nitric Oxide in HUVEC.The inhibition of the &bgr;CR by P7 &bgr;IP is Competitive in Nature.&bgr;CR‐Induced Angiogenesis is Blocked with Novel &bgr;IP.Novel &bgr;CR Inhibitory Peptide does not Inhibit Erythropoiesis. ABSTRACT In short‐term animal models of ischemia, erythropoietin (EPO) signaling through the heterodimeric EPO receptor (EPOR)/&bgr;‐common receptor (&bgr;CR) is believed to elicit tissue protective effects. However, large, randomized, controlled trials demonstrate that targeting a higher hemoglobin level by administering higher doses of EPO, which are more likely to activate the heterodimeric EPOR/&bgr;CR, is associated with an increase in adverse cardiovascular events. Thus, inhibition of long‐term activation of the &bgr;CR may have therapeutic implications. This study aimed to design and evaluate the efficacy of novel computationally designed &bgr;CR inhibitory peptides (&bgr;IP). These novel &bgr;IPs were designed based on a truncated portion of Helix‐A from EPO, specifically residues 11–26 (VLERYLLEAKEAEKIT). Seven novel peptides (P1 to P7) were designed. Peptide 7 (P7), VLERYLHEAKHAEKIT, demonstrated the most robust inhibitory activity. We also report here the ability of P7 to inhibit &bgr;CR‐induced nitric oxide (NO) production and angiogenesis in human umbilical vein endothelial cells (HUVECs). Specifically, we found that P7 &bgr;IP completely abolished EPO‐induced NO production. The inhibitory effect could be overcome with super physiological doses of EPO, suggesting a competitive inhibition. &bgr;CR‐induced angiogenesis in HUVECs was also abolished with treatment of P7 &bgr;IP, but P7 &bgr;IP did not inhibit vascular endothelial growth factor (VEGF)‐induced angiogenesis. In addition, we demonstrate that the novel P7 &bgr;IP does not inhibit EPO‐induced erythropoiesis with use of peripheral blood mononuclear cells (PBMCs). These results, for the first time, describe a novel, potent &bgr;CR peptide inhibitor that inhibit the actions of the &bgr;CR without affecting erythropoiesis.

Activation of the β-common receptor by erythropoietin impairs acetylcholine-mediated vasodilation in mouse mesenteric arterioles

Clinically, erythropoietin (EPO) is known to increase systemic vascular resistance and arterial blood pressure. However, EPO stimulates the production of the potent vasodilator, nitric oxide (NO), in culture endothelial cells. The mechanism by which EPO causes vasoconstriction despite stimulating NO production may be dependent on its ability to activate two receptor complexes, the homodimeric EPO (EPOR2) and the heterodimeric EPOR/β‐common receptor (βCR). The purpose of this study was to investigate the contribution of each receptor to the vasoactive properties of EPO. First‐order, mesenteric arteries were isolated from 16‐week‐old male C57BL/6 mice, and arterial function was studied in pressure arteriographs. To determine the contribution of each receptor complex, EPO‐stimulating peptide (ESP), which binds and activates the heterodimeric EPOR/βCR complex, and EPO, which activates both receptors, were added to the arteriograph chamber 20 min prior to evaluation of endothelium‐dependent (acetylcholine, bradykinin, A23187) and endothelium‐independent (sodium nitroprusside) vasodilator responses. Only ACh‐induced vasodilation was impaired in arteries pretreated with EPO or ESP. EPO and ESP pretreatment abolished ACh‐induced vasodilation by 100% and 60%, respectively. EPO and ESP did not affect endothelium‐independent vasodilation by SNP. Additionally, a novel βCR inhibitory peptide (βIP), which was computationally developed, prevented the impairment of acetylcholine‐induced vasodilation by EPO and ESP, further implicating the EPOR/βCR complex. Last, pretreatment with either EPO or ESP did not affect vasoconstriction by phenylephrine and KCl. Taken together, these findings suggest that acute activation of the heterodimeric EPOR/βCR in endothelial cells leads to a selective impairment of ACh‐mediated vasodilator response in mouse mesenteric resistance arteries.