Abstract 600: Anti-Angiogenic Effects of Circulating Exosomes From Patients With Acute Coronary Syndrome: Potential Role of miR-199a and miR-125a

Circulating exosomes have a great impact in human health as a biomarker or as messengers in intercellular signaling. In this study we aimed to determine how miRNA profile in circulating exosomes interfere with angiogenic phenotype of endothelial cell (EC) during acute event of coronary syndrome. Exosomes were purified from serum of patients with non-ST segment elevation myocardial infarction in the acute phase (NSTEMI, n=34) during percutaneous coronary intervention. Healthy donors (n=23) were included as control. Purified exosomes were quantified and characterized by nanoparticle tracking analysis (Nanosight). Healthy EC (HUVEC) were treated for 48h with labeled exosomes (5x10 5 particles/1x10 6 cells) and tested for their angiogenic potential (migration and tube formation) and mRNA expression. Exosome miRNA profile was determined by miRNA array. Exosomes levels were markedly increased in NSTEMI (1.3x10 9 particle/ml) vs control (7.5x10 8 particle/ml; p=0.02). HUVEC treatment with healthy exosomes improve migration and tube formation compared to untreated HUVEC. Nevertheless, exosomes from NSTEMI patients, in the acute phase lack their pro-angiogenic potential (Fig A). Network analysis of exosome miRNA and HUVEC mRNA expression revealed a correlation of increased miR-199a and miR-125a expression with decrease of components involved in EC sprout and stabilization (Fig B). Circulating exosomes have an important role in the control of angiogenesis. However, in the acute phase of NSTEMI intercellular communication via exosome is modified and exert an inhibitory effect on angiogenesis. These results could contribute to the progression and outcomes of the disease.

Abstract 888: Exosomes Derived From Endothelial Progenitor Cells Modulate Flow-Induced Remodeling and Increase Angiogenesis/Arteriogenesis in Mesenteric Arteries of Mice

Exosomes are key regulators of cell-to-cell communication, becoming valuable tool as disease biomarker and in the development of new therapeutic strategies. We aimed to determine the role of endothelial progenitor cell (EPC)-derived exosomes (EXO) in vascular remodeling induced by flow. C57BL/6 mice underwent chronic changes in flow by mesenteric resistance arteries ligation. Arteries were thus submitted to high flow (HF), low flow (LF), or normal flow (NF). The day before surgery mice received I.P. injection with saline or exosomes (3x10 9 particle/kg), following the treatment every 3 days until sacrifice. After 14 days, arteries were studied in vitro in a pressure arteriograph. Increase in diameter and compliance by pressure found in HF arteries were not seen in EXO treated mice (Fig A). Decrease in diameter observed in saline treated LF arteries, was also abolished by EXO treatment. Network analysis of miRNA content in exosomes and arterial mRNA expression revealed an increased expression of components involved in angiogenesis/arteriogenesis (Fig B), which could contribute to flow maintenance in the tissue. Mesenteric arteries submitted to LF, HF and NF were isolated and placed in Matrigel matrix for angiogenesis analysis. We observed that change in flow is a trigger for vasculogenesis, which is enhanced by EXO treatment (Fig C). This study establishes the potential role of EPC-derived exosomes to regulate vascular remodeling during changes in flow. The mechanisms for these effects involve exosome-derived miRNA regulation of a network of mRNAs implicated in collateral angiogenesis/arteriogenesis, which in turn, may contribute to maintenance of tissue homeostasis.

The phosphorylation state of eNOS modulates vascular reactivity and outcome of cerebral ischemia in vivo

NO plays critical roles in vascular function. We show that modulation of the eNOS serine 1179 (S1179) phosphorylation site affects vascular reactivity and determines stroke size in vivo. Transgenic mice expressing only a phosphomimetic (S1179D) form of eNOS show greater vascular reactivity, develop less severe strokes, and have improved cerebral blood flow in a middle cerebral artery occlusion model than mice expressing an unphosphorylatable (S1179A) form. These results provide a molecular mechanism by which multiple diverse cardiovascular risks, such as diabetes and obesity, may be centrally integrated by eNOS phosphorylation in vivo to influence blood flow and cardiovascular disease. They also demonstrate the in vivo relevance of posttranslational modification of eNOS in vascular function.

Estrogen enhances vasoconstrictive remodeling after injury in male rabbits

The complete spectrum of estrogen vascular effects remains unclear. In particular, estrogen effects in the vascular response to profound injury in males have not been explored in detail. Therefore, we submitted 44 male New Zealand rabbits weighing 3.4 +/- 0.6 kg to overdistention balloon injury of the right iliac artery. Rabbits were given 17beta-estradiol (5.45 micromol/day, sc) or vehicle for 7 days before and 14 days after injury, when the arteries were examined by post-mortem histomorphometry. Arteriographic caliber was assessed in vivo at baseline and before sacrifice. On day 14 after injury, in vivo arteriographic caliber (baseline = 2.44 +/- 0.43 mm) was decreased by 23.1 +/- 0.1% in controls and by 44.5 +/- 0.1% in estrogen-treated rabbits (P < 0.001). Neither the neointimal area nor the neointima/media area ratio changed after estrogen treatment. Collagen fraction was increased in the media and neointima of estrogen-treated rabbits vs control (1.38 +/- 1.30 vs 0.35 +/- 0.67, respectively, P = 0.01). Taken together, these findings suggest that estrogen increased negative vascular remodeling. Transcription of endothelial and inducible nitric oxide synthases (eNOS and iNOS) was analyzed by RT-PCR. eNOS mRNA expression was marginally increased after estrogen (P = 0.07) and injury. iNOS mRNA was increased 2- to 3-fold on day 14 after injury. With estrogen treatment, iNOS mRNA increased in uninjured arteries and exhibited a further 5.5-fold increase after injury. We concluded that estrogen increased lumen loss after balloon injury in male rabbits, likely by increased negative remodeling, which may be related to increased iNOS transcriptional rates.

Relative contribution of estrogen withdrawal and gonadotropins increase secondary to ovariectomy on prostaglandin generation in mesenteric microvessels

Recent studies have established that ovariectomy impairs endothelial function, partially by increasing vasoconstrictor prostaglandins generation. Because ovariectomy causes concomitant lack of estrogen and increase of gonadotropins (ie, LH and FSH), in this study we explored the relative role of estrogen and LH/FSH in modulating vasoconstrictor prostaglandins generation in mesenteric arteriolar bed of SHR. Endothelium-dependent relaxation to acetylcholine (ACh) and bradykinin (Bk) was markedly reduced in ovariectomized (OVX) compared with SHR in physiological estrus (OE). Estrogen replacement (OVX + E), but not the decrease in LH/FSH levels with leuprolide (OVX + Leu), corrected the altered vasorelaxation response in OVX. Treatment of mesenteries with diclofenac, prostaglandin-H synthase (PGHS) inhibitor, significantly enhanced the relaxing response in arteries from OVX and OVX + Leu, but not those from OE, indicating that a PGHS-derived vasoconstrictor has modified the endothelium-dependent response during estrogen but not LH/FSH deprivation. Confirming these data, in response to exogenous arachidonic acid, whereas arteries from OVX and OVX + Leu exhibited a marked and similar vasoconstrictor response, the arteries from OE and OVX + E rats exhibited a slight vasodilation. We also demonstrated by RT-PCR that ovariectomy significantly increased PGHS-2 but not PGHS-1 mRNA expression in comparison to OE. The PGHS-2 overexpression in OVX was corrected by estrogen replacement, but not by the reduction of LH/FSH levels. Altogether these data strongly support a role for hypoestrogenism rather than LH/FSH enhancement, associated with the removal of ovaries, in the increase of vasoconstrictor prostaglandins, possibly by a mechanism involving PGHS-2 overexpression.

Gender differences in superoxide generation in microvessels of hypertensive rats: role of NAD(P)H-oxidase

OBJECTIVE

This study is aimed to explore whether gender plays a role in the generation of nitric oxide (NO) and superoxide anion (O(2)(-)) in microvessels of hypertensive rats (SHR), as well as the potential mechanisms involved in these effects.

METHODS AND RESULTS

NO generation in mesenteric arterioles was evaluated by measuring NO synthase (NOS) activity and protein expression. Oxidative stress was studied in vivo in mesenteric arterioles from male and female SHR by hydroethidine microfluorography. Although we did not observe any sex-related differences in NO generation, we found that hydroethitine oxidation is markedly increased (30.9+/-2.4%) in male compared to female (12.3+/-2.5%; p<0.05), demonstrating a gender difference in O(2)(-) production. The treatment of mesenteries with DPI (NAD(P)H-oxidase inhibitor) and treatment of SHR with losartan [Angiotensin-II type 1 (AT-1) receptor antagonist] markedly reduced O(2)(-) production in male, while produced a minor effect in female, suggesting that overexpression/activity of AT-1 receptor and NAD(P)H-oxidase contribute for the sexual dimorphism in superoxide generation. Immunoblot analyses provide evidences of overexpression of the NAD(P)H-oxidase components p22(phox), gp91(phox), p47(phox) and p67(phox) in arterioles from male in comparison to female. Losartan treatment inhibited the overexpression of these subunits in male, without affecting the responses in female.

CONCLUSION

Taken together, our findings demonstrate that male SHR presents higher superoxide anion concentration under basal condition than does female. An AT-1-dependent overexpression of the NAD(P)H-oxidase components may account for the sexual dimorphism in oxidative stress, and may play an important role in the noted gender differences on incidence of cardiovascular disease.

Sustained decrease in superoxide dismutase activity underlies constrictive remodeling after balloon injury in rabbits

OBJECTIVE

The redox pathophysiology of vascular repair is incompletely understood. We assessed the role of vascular superoxide dismutase (SOD) activity in oxidative/nitrative stress and caliber loss postinjury (PI).

METHODS AND RESULTS

Rabbits submitted to iliac artery balloon overdistension were followed for 14 days PI. Significant decrease in vascular SOD activity occurred at 7 and 14 days PI (by 45% and 34%, respectively, versus control, 96+/-1 U/mg, P<0.05). Separation in concanavalin-A column showed that both extracellular SOD (ecSOD) and CuZn SOD activities were reduced, whereas Western analysis showed normal or augmented protein expression. Immunoreactivity to nitrotyrosine, neuronal NO synthase (NOS), and inducible NOS (iNOS) increased in media and neointima PI; iNOS mRNA also augmented. Administration of ecSOD from days 7 to 14 PI corrected the SOD activity decrease and minimized caliber loss by 59% (P=0.007) despite unaltered neointima. Nitrate levels markedly increased with ecSOD in injured artery homogenates (26+/-5 versus 4+/-0.3 micromol/L per mg, P=0.001). Such increase was 70% inhibited by specific iNOS antagonist 1400w. Nitrotyrosine and neuronal NOS expression decreased after ecSOD.

CONCLUSIONS

Sustained low vascular SOD activity has a key role in constrictive remodeling after injury, promoting oxidative/nitrative stress and impairment of iNOS-derived NO bioavailability. SOD function may critically determine whether iNOS induction is beneficial or deleterious in vivo.

VEGF induces S1P1 receptors in endothelial cells: Implications for cross-talk between sphingolipid and growth factor receptors

Sphingosine 1-phosphate (S1P) is a platelet-derived sphingolipid that binds to S1P1 (EDG-1) receptors and activates the endothelial isoform of NO synthase (eNOS). S1P and the polypeptide growth factor vascular endothelial growth factor (VEGF) act independently to modulate angiogenesis and activate eNOS. In these studies, we explored the cross-talk between S1P and VEGF signaling pathways. When cultured bovine aortic endothelial cells were treated with VEGF (10 ng/ml), the expression of S1P1 protein and mRNA increased by approximately 4-fold. S1P1 up-regulation by VEGF was seen within 30 min of VEGF addition and reached a maximum after 1.5 h. By contrast, expression of neither bradykinin B2 receptors nor the scaffolding protein caveolin-1 was altered by VEGF treatment. The EC50 for VEGF-promoted induction of S1P1 expression was approximately 2 ng/ml, within its physiological concentration range. S1P1 induction by VEGF was attenuated by the tyrosine kinase inhibitor genistein and by the PKC inhibitor calphostin C. Preincubation of bovine aortic endothelial cells with VEGF (10 ng/ml for 90 min) markedly enhanced subsequent S1P-dependent eNOS activation. VEGF pretreatment of cultured endothelial cells also markedly potentiated S1P-promoted eNOS phosphorylation at Ser-1179, as well as S1P-mediated activation of kinase Akt. In isolated rat arteries, VEGF pretreatment markedly potentiated S1P-mediated vasorelaxation and eNOS Ser-1179 phosphorylation. Taken together, these data indicate that VEGF specifically induces expression of S1P1 receptors, associated with enhanced intracellular signaling responses to S1P and the potentiation of S1P-mediated vasorelaxation. We suggest that VEGF acts to sensitize the vascular endothelium to the effects of lipid mediators by promoting the induction of S1P1 receptors, representing a potentially important point of cross-talk between receptor-regulated eNOS signaling pathways in the vasculature.

Sphingosine 1-phosphate and control of vascular tone

Sphingosine-1-phosphate (S1P) is a platelet-derived lipid mediator that activates the endothelial isoform of nitric oxide synthase (eNOS) in endothelial cells. However, the role of S1P in endothelium-dependent vasodilation and the signaling pathways elicited by S1P in intact vessels are largely unknown. We found that S1P induces dose-dependent transient relaxation of isolated pressurized mesenteric arterioles (EC(50) 10 +/- 3 nM); maximal vasodilation (55 +/- 8%) is seen approximately 2 min after S1P addition and returns to baseline by 5 min. S1P promotes comparable responses in arterioles from wild-type but not eNOS(null) mice. S1P-induced vasodilation is abrogated by removal of endothelium or by the addition of the NOS inhibitor N(omega)-monomethyl-l-arginine but is not affected by the cyclooxygenase inhibitor indomethacin, nor by the blockade of K(+) channels by using 4-aminopyridine. S1P-induced vasodilation is attenuated by pertussis toxin, by the phosphoinositide 3-kinase (PI3-kinase) inhibitor wortmannin, and by the calcium chelator BAPTA. With the use of high-sensitivity protein immunoblots in extracts from single pressurized vessels, we found that S1P, but not bradykinin, promotes the phosphorylation of eNOS at Ser(1179). Maximum S1P-induced eNOS Ser(1179) phosphorylation was reached at the time of maximum vasorelaxation, but enzyme phosphorylation persisted for several minutes after vasodilation had resolved. Thus regulatory pathways distinct from eNOS Ser(1179) dephosphorylation serve to terminate agonist-promoted vasorelaxation. Taken together, our findings demonstrate that S1P, an important intercellular mediator of platelet-vessel wall interactions, is a effective arteriolar vasodilator that acts via G protein-dependent, calcium-sensitive, and PI3-kinase-modulated signaling pathways.

Enhanced oxidative stress as a potential mechanism underlying the programming of hypertension in utero

Maternal undernutrition during critical periods of organ development is known to impair fetal growth and predispose to the development of adulthood diseases, such as hypertension, coronary heart disease and type II diabetes that are linked to low birth weight and are characterized by endothelial dysfunction. Increased oxidative stress, in rats submitted to intrauterine undernutrition, provides a potential explanation for the endothelial dysfunction development. The aim of this study was to determine the oxidative stress and its consequence on mesenteric arteriolar responses to vasoactive agents in offspring from diet-restricted dams. For this, female pregnant Wistar rats were fed either normal or 50% of normal intake diets, during the whole gestational period. In male offspring, arterial blood pressure was determined by the tail cuff method in anesthetized rats, mesenteric arteriolar reactivity and superoxide anion generation were studied using intravital microscopy and superoxide dismutase activity was determined in mesentery by spectrophotometric assay. Intrauterine undernutrition induced hypertension, decreased vasodilation to acetylcholine and bradykinin but did not alter the responses to sodium nitroprusside. Topical application of superoxide dismutase and superoxide dismutase mimetic manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin significantly improved the altered arteriolar responses to acetylcholine and bradykinin. A decreased superoxide dismutase activity and an increased superoxide anion concentration were observed in the offspring of diet-restricted dams. This study shows for the first time that intrauterine undernutrition enhances oxidative stress in vivo and relates this to the impaired endothelium-dependent vasodilation.

In vivo evidence for antioxidant potential of estrogen in microvessels of female spontaneously hypertensive rats

In studies conducted in vitro, it has been demonstrated that estrogen has an antioxidant potential that may contribute to its protective effects on the cardiovascular system. However, the antioxidant effect of estrogen in vivo has not been demonstrated. To address this issue, in this study the effects of estrogen on oxidative stress were evaluated in microvessels studied in vivo. Oxidative stress was evaluated by using intravital microscopy in mesenteric arterioles from female spontaneously hypertensive rats (SHR) in physiological estrous (OE), ovariectomized (OVX), OVX treated with estradiol (E(2)), or estradiol + progesterone (E/P). The mesenteries were superfused with hydroethidine, a reduced and nonfluorescent precursor of ethidium bromide (EB). In the presence of reactive oxygen species, hydroethidine is transformed intracellularly in EB, which binds to DNA and can be detected by its red fluorescence. The percentage of EB-positive nuclei along the arteriolar wall in OVX (28.4 +/- 4.3) was significantly increased compared with OE (14.2 +/- 3.9; P<0.05). The OVX overproduction of oxyradicals was attenuated by E(2) (15.7 +/- 2.2) and E/P (14.8 +/- 0.8). Treatment with the superoxide dismutase mimetic MnTMPyP attenuated by 75% the oxidation of hydroethidine in both OE and OVX. Conversely, mannitol, that decomposes hydroxyl radical, and L-NAME, a nitric oxide synthase inhibitor, had no significant effects on hydroethidine oxidation. No differences on hydrogen peroxide plasma concentration were observed among the groups, suggesting that superoxide anion is the most likely oxyradical involved in the increased oxidative stress observed in OVX. The treatment of mesenteries with diphenyleneiodonium (DPI), an nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase inhibitor, but not with oxypurinol, a xanthine-oxidase inhibitor, produced a significant reduction of oxyradical generation in OVX microvessels and a slight decrease in those from OE. Chronic treatment of female SHR with losartan caused similar decreases in oxyradicals in both OE and OVX, whereas diclofenac and verapamil had no effects. Together these data suggest that estrogen reduces superoxide anion bioavailability in vivo. The antioxidant effect of estrogen, which can contribute to a less pronounced endothelial dysfunction in female SHR, may be dependent on a direct modulatory action of estrogen on NADPH activity.