The beneficial effects of nitric oxide (NO)-mediated vasodilation are quickly abolished in the presence of ROS, and this effect may be augmented with aging. We previously demonstrated an age-induced impairment of flow-induced dilation in rat coronary arterioles. Therefore, the purpose of this study was to determine the effects of O 2 Ϫ scavenging, as well as removal of H2O2, the byproduct of O 2 Ϫ scavenging, on flow-mediated dilation in coronary resistance arterioles of young (4 mo) and old (24 mo) male Fischer 344 rats. Flow increased NO and H 2O2 production as evidenced by enhanced diaminofluorescein and dichlorodihydrofluorescein fluorescence, respectively, whereas aging reduced flow-induced NO and H 2O2 production. Endothelium-dependent vasodilation was evaluated by increasing intraluminal flow (5-60 nl/s) before and after treatment with the superoxide dismutase mimetic Tempol (100 M), the H 2O2 scavenger catalase (100 U/ml), or Tempol plus catalase. Catalase reduced flowinduced dilation in both groups, whereas Tempol and Tempol plus catalase diminished vasodilation in young but not old rats. Tempol plus deferoxamine (100 M), an inhibitor of hydroxyl radical formation, reversed Tempol-mediated impairment of flow-induced vasodilation in young rats and improved flow-induced vasodilation in old rats compared with control. Immunoblot analysis revealed increases in endogenous superoxide dismutase, catalase, and nitrotyrosine protein levels with aging. Collectively, these data indicate that NO-and H 2O2-mediated flow-induced signaling decline with age in coronary arterioles and that elevated hydroxyl radical formation contributes to the age-related impairment of flow-induced vasodilation.reactive oxygen species; superoxide dismutase; hydroxyl radical; deferoxamine; nitric oxide; hydrogen peroxide INCREASING EVIDENCE INDICATES that aging contributes significantly to the development of ischemic heart disease. Vascular resistance increases, leading to impairments in coronary blood flow and flow reserve (15). Endothelial dysfunction similarly progresses with aging (4) and may be mediated by impaired nitric oxide (NO) activity (7, 21) or elevated oxidant stress (6, 10). Previous studies have demonstrated age-associated declines in flow-mediated dilation in coronary arterioles due to impaired phosphatidylinositol 3-kinase signaling (21) or elevated superoxide (O 2 Ϫ ) production (7). Because flow-induced vasodilation is inextricably linked to NO-mediated signaling, it is possible that other factors directly involved in the NO pathway may be altered with advancing age.In (6,7,12). Thus ROS production and scavenging are likely carefully modulated to produce appropriate flow-induced dilation. Therefore, the purpose of our study was 1) to investigate age-related changes in NO and H 2 O 2 signaling during flow-induced vasodilation and 2) to examine the effects of ROS scavenging on flow-mediated dilation in coronary arterioles. METHODSAnimals. All procedures in this study were approved by the Institutional Animal Care and U...

October 7, 2009; doi:10.1152/ajpregu.00178.2009.-The risk for cardiovascular disease (CVD) increases with advancing age; however, the age at which CVD risk increases significantly is delayed by more than a decade in women compared with men. This cardioprotection, which women experience until menopause, is presumably due to the presence of ovarian hormones, in particular, estrogen. The purpose of this study was to determine how age and ovarian hormones affect flowinduced vasodilation in the coronary resistance vasculature. Coronary arterioles were isolated from young (6 mo), middle-aged (14 mo), and old (24 mo) intact, ovariectomized (OVX), and ovariectomized ϩ estrogen replaced (OVE) female Fischer-344 rats to assess flowinduced vasodilation. Advancing age impaired flow-induced dilation of coronary arterioles (young: 50 Ϯ 4 vs. old: 34 Ϯ 6; % relaxation). Ovariectomy reduced flow-induced dilation in arterioles from young females, and estrogen replacement restored vasodilation to flow. In aged females, flow-induced vasodilation of arterioles was unaltered by OVX; however, estrogen replacement improved flow-induced dilation by ϳ160%. The contribution of nitric oxide (NO) to flow-induced dilation, assessed by nitric oxide synthase (NOS) inhibition with N G -nitro-L-arginine methyl ester (L-NAME), declined with age. L-NAME did not alter flow-induced vasodilation in arterioles from OVX rats, regardless of age. In contrast, L-NAME reduced flowinduced vasodilation of arterioles from estrogen-replaced rats at all ages. These findings indicate that the age-induced decline of flowinduced, NO-mediated dilation in coronary arterioles of female rats is related, in part, to a loss of ovarian estrogen, and estrogen supplementation can improve flow-induced dilation, even at an advanced age.endothelial nitric oxide synthase; Akt; nitric oxide; ovariectomy THE RISK FOR CARDIOVASCULAR disease (CVD) and heart failure increase with advancing age; however, sexual dimorphism exists in the chronological development of these risks (22,47). Although the chronological rate of aging is independent of sex, mechanisms that regulate the cardiovascular system across the lifespan may differ dramatically between men and women. The risk for CVD in men begins to increase at approximately the same age that flow-mediated vasodilation begins to decline (5). Women also exhibit this age-related impairment of flow-mediated vasodilation; however, significant reduction of flow-mediated dilation becomes apparent at the age of menopause, more than a decade later than in men (5). The cardioprotection that women experience until menopause is presumably due to the presence of ovarian estrogen and results in a sex-related delay of the expression of CVD (49). Chronic estrogen treatment has been shown to enhance endothelial function in a number of vascular beds (27, 31, 39), in part, through a pathway involving activation of Akt/PKB and subsequent phosphorylation of endothelial nitric oxide synthase (eNOS) (3,10,15,43,44). Endothelium-dependent vasodilation to a...

Sindler AL, Reyes R, Chen B, Ghosh P, Gurovich AN, Kang LS, Cardounel AJ, Delp MD, Muller-Delp JM. Age and exercise training alter signaling through reactive oxygen species in the endothelium of skeletal muscle arterioles. J Appl Physiol 114: [681][682][683][684][685][686][687][688][689][690][691][692][693] 2013. First published January 3, 2013; doi:10.1152/japplphysiol.00341.2012.-Exercise training ameliorates age-related impairments in endotheliumdependent vasodilation in skeletal muscle arterioles. Additionally, exercise training is associated with increased superoxide production. The purpose of this study was to determine the role of superoxide and superoxide-derived reactive oxygen species (ROS) signaling in mediating endothelium-dependent vasodilation of soleus muscle resistance arterioles from young and old, sedentary and exercise-trained rats. Young (3 mo) and old (22 mo) male rats were either exercise trained or remained sedentary for 10 wk. To determine the impact of ROS signaling on endothelium-dependent vasodilation, responses to acetylcholine were studied under control conditions and during the scavenging of superoxide and/or hydrogen peroxide. To determine the impact of NADPH oxidase-derived ROS, endothelium-dependent vasodilation was determined following NADPH oxidase inhibition. Reactivity to superoxide and hydrogen peroxide was also determined. Tempol, a scavenger of superoxide, and inhibitors of NADPH oxidase reduced endothelium-dependent vasodilation in all groups. Similarly, treatment with catalase and simultaneous treatment with tempol and catalase reduced endothelium-dependent vasodilation in all groups. Decomposition of peroxynitrite also reduced endothelium-dependent vasodilation. Aging had no effect on arteriolar protein content of SOD-1, catalase, or glutathione peroxidase-1; however, exercise training increased protein content of SOD-1 in young and old rats, catalase in young rats, and glutathione peroxidase-1 in old rats. These data indicate that ROS signaling is necessary for endothelium-dependent vasodilation in soleus muscle arterioles, and that exercise traininginduced enhancement of endothelial function occurs, in part, through an increase in ROS signaling. hydrogen peroxide; superoxide; peroxynitrite; nitric oxide; acetylcholine ENDOTHELIAL FUNCTION IN THE skeletal muscle resistance vasculature declines with age primarily due to decreased nitric oxide (NO) bioavailability (10,38,51,55). In feed arteries from soleus muscle, reductions in NO-dependent vasodilation are accompanied by reduced expression of endothelial NO synthase (eNOS) (65). In contrast, our laboratory has previously reported that NO-mediated vasodilation of soleus muscle arterioles declines with advancing age, despite an increase in eNOS protein levels (51). Thus the age-related decline in bioavailability of NO may be dependent on numerous other factors that regulate both NO production and degradation. eNOS activity, and subsequent NO production, is regulated by availability of substrate and cofactors, by protein-...

Kang LS, Kim SJ, Dominguez JM 2nd, Sindler AL, Dick GM, Muller-Delp JM. Aging and muscle fiber type alter K ϩ channel contributions to the myogenic response in skeletal muscle arterioles. J Appl Physiol 107: 389 -398, 2009. First published April 30, 2009 doi:10.1152/japplphysiol.91245.2008.-Aging diminishes myogenic tone in arterioles from skeletal muscle. Recent evidence indicates that both large-conductance Ca 2ϩ -activated (BKCa) and voltage-dependent (K V) K ϩ channels mediate negative feedback control of the myogenic response. Thus we tested the hypothesis that aging increases the contributions of K V and BKCa channels to myogenic regulation of vascular tone. Because myogenic responsiveness differs between oxidative and glycolytic muscles, we predicted that K V and BK Ca channel contributions to myogenic responsiveness vary with fiber type. Myogenic responses of first-order arterioles from the gastrocnemius and soleus muscles of 4-and 24-mo-old Fischer 344 rats were evaluated in the presence and absence of 4-aminopyridine (5 mM) or iberiotoxin (30 nM), inhibitors of K V and BKCa, respectively. 4-Aminopyridine enhanced myogenic tone with aging and normalized age-related differences in both muscle types. By contrast, iberiotoxin eliminated age-related differences in soleus arterioles and had no effect in gastrocnemius vessels. KV1.5 is an integral component of KV channels in vascular smooth muscle; therefore, we determined the relative protein expression of KV1.5, as well as BKCa, in soleus and gastrocnemius arterioles. Immunoblot analysis revealed no differences in KV1.5 protein with aging or between variant fiber types, whereas BKCa protein levels declined with age in arterioles from both muscle groups. Collectively, these results suggest that the contribution of BKCa to myogenic regulation of vascular tone changes with age in soleus muscle arterioles, whereas increased KV channel expression and negative feedback regulation of myogenic tone increases with advancing age in arterioles from both oxidative and glycolytic muscles. delayed rectifier potassium channel; calcium-activated potassium channel; iberiotoxin; 4-aminopyridine; KV1.5 THE MYOGENIC RESPONSE IS ESSENTIAL in regulating peripheral vascular resistance as well as tissue-specific blood flow. This autoregulatory mechanism, in which vessels contract or dilate in response to changes in transmural pressure, may be impaired with advancing age. The magnitude of myogenic tone development declines with aging in both mesenteric (19) and skeletal muscle arterioles (32), and age-induced modifications of vascular smooth muscle contractile mechanisms may contribute to this reduced myogenic reactivity (32). Myogenic tone development depends on an increase in intracellular Ca2ϩ and subsequent initiation of contractile activity, which is mediated by voltage-gated Ca 2ϩ channels (VGCC). In the presence of steady Ca 2ϩ influx from VGCC, an opposing, hyperpolarizing force is likely required to prevent regenerative Ca 2ϩ entry and tonic contraction (13,21,35). Severa...

Impairment of flow-induced vasodilation in coronary resistance arterioles may contribute to the decline in coronary vasodilatory reserve that occurs with advancing age. This study investigated the effects of age on flow-induced signaling and activation of nitric oxide (NO)-mediated vasodilation in coronary resistance arterioles. Coronary arterioles were isolated from young (approximately 6 mo) and old (approximately 24 mo) male Fischer-344 rats to assess vasodilation to flow, vascular endothelial growth factor (VEGF), and ACh. Flow- and VEGF-induced vasodilation of coronary arterioles was impaired with age (P