[Use of local estrogenotherapy in urology and pelviperineology: A systematic review]. / Œstrogénothérapie locale en urologie et pelvi-périnéologie. Revue de littérature.

OBJECTIVE: To conduct a literature review of the efficiency of vaginal local estrogenotherapy (LE) on genitourinary disorders related to menopause and those side effects. MATERIALS: A literature review was conducted using Pubmed database using the keywords vaginal estrogen, urinary incontinence, urgency, urinary tract infection, vulvar and vaginal atrophy, dyspareunia, breast cancer, endometrial cancer, thrombosis. The most relevant articles were selected and analyzed. RESULTS: The LE demonstrates its efficiency on preventing urinary tract infections, treatment of overactive bladder and vaginal disorders of postmenopausal women in controlled studies or meta-analysis level of evidence 1. Local side effects (discharge, erythema, vaginal bleeding, etc.) are rare. The systemic diffusion of low dose LE is limited and allowed to prescribe it to postmenopausal women without special supervision. However, using LE might be avoided in women with a history of oncological breast due to the lack of controlled studies evaluating the risk of developing breast cancer under LE. Except for high-risk women, LE does not increase the risk of thrombosis. CONCLUSION: Vaginal administration of low dose of estrogen is an effective and safe treatment in the management of postmenopausal genitourinary disorders. However, using LE for women with history of breast cancer or high risk of thrombisis should be avoided.

Role of estrogens and age in flow-mediated outward remodeling of rat mesenteric resistance arteries.

In resistance arteries, a chronic increase in blood flow induces hypertrophic outward remodeling. This flow-mediated remodeling (FMR) is absent in male rats aged 10 mo and more. As FMR depends on estrogens in 3-mo-old female rats, we hypothesized that it might be preserved in 12-mo-old female rats. Blood flow was increased in vivo in mesenteric resistance arteries after ligation of the side arteries in 3- and 12-mo-old male and female rats. After 2 wk, high-flow (HF) and normal-flow (NF) arteries were isolated for in vitro analysis. Arterial diameter and cross-sectional area increased in HF arteries compared with NF arteries in 3-mo-old male and female rats. In 12-mo-old rats, diameter increased only in female rats. Endothelial nitric oxide synthase expression and endothelium-mediated relaxation were higher in HF arteries than in NF arteries in all groups. ERK1/2 phosphorylation, NADPH oxidase subunit expression levels, and arterial contractility to KCl and to phenylephrine were greater in HF vessels than in NF vessels in 12-mo-old male rats only. Ovariectomy in 12-mo-old female rats induced a similar pattern with an increased contractility without diameter increase in HF arteries. Treatment of 12-mo-old male rats and ovariectomized female rats with hydralazine, the antioxidant tempol, or the angiotensin II type 1 receptor blocker candesartan restored HF remodeling and normalized arterial contractility in HF vessels. Thus, we found that FMR of resistance arteries remains efficient in 12-mo-old female rats compared with age-matched male rats. A balance between estrogens and vascular contractility might preserve FMR in mature female rats.

Key role of estrogens and endothelial estrogen receptor α in blood flow-mediated remodeling of resistance arteries.

OBJECTIVE: Flow- (shear stress-)mediated outward remodeling of resistance arteries is involved in collateral growth during postischemic revascularization. As this remodeling is especially important during pregnancy, we hypothesized that estrogens may be involved. A surgical model eliciting a local increase in blood flow in 1 mesenteric resistance artery was used in 3-month-old ovariectomized female rats either treated with 17-ß-estradiol (E2) or left untreated. METHODS AND RESULTS: After 14 days, arterial diameter was greater in high-flow arteries than in normal-flow vessels. An ovariectomy suppressed high-flow remodeling, while E2 restored it. High-flow remodeling was absent in mice lacking the estrogen receptor α but not estrogen receptor ß. The kinetics of inflammatory marker expression, macrophage infiltration, oxidative stress, and metaloproteinases expression were not altered by the absence of E2 after 2 and 4 days, that is, during remodeling. Nevertheless, E2 was required for the increase in endothelial nitric oxide synthase expression and activation at day 4 when diameter expansion occurs. Finally, the impact of E2 on the endothelium appeared crucial for high-flow remodeling, as this E2 action was abrogated in mice lacking endothelial NOS, as well as in Tie2-Cre(+) ERα(f/f) mice. CONCLUSIONS: We demonstrate the essential role of E2 and endothelial estrogen receptor α in flow-mediated remodeling of resistance arteries in vivo.

[Nitric oxide pathway and female lower urinary tract. Physiological and pathophysiological role]. / Voie du monoxyde d'azote et bas appareil urinaire féminin. Rôles physiologique et physiopathologique.

GOAL: The aim was to review the literature on nitric oxide and female lower urinary tract. MATERIAL: A literature review through the PubMed library until December, 31 2012 was carried out using the following keywords: lower urinary tract, bladder, urethra, nervous central system, innervation, female, women, nitric oxide, phosphodiesterase, bladder outlet obstruction, urinary incontinence, overactive bladder, urinary tract infection. RESULTS: Two nitric oxide synthase isoforms, the neuronal (nNOS) and the endothelial (eNOS), are constitutively expressed in the lower urinary tract. Nevertheless, nNOS is mainly expressed in the bladder neck and the urethra. In the bladder, NO modulates the afferent neurons activity. In pathological condition, inducible NOS expression induces an increase in detrusor contractility and bladder wall thickness and eNOS facilitates Escherichia coli bladder wall invasion inducing recurrent urinary tract infections. In the urethra, NO play a major role in smooth muscle cells relaxation. CONCLUSION: The NO pathway plays a major role in the female lower urinary tract physiology and physiopathology. While it acts mainly on bladder outlet, in pathological condition, it is involved in bladder dysfunction occurrence.

[Role of estrogens in lower urinary tract physiology and physiopathology]. / Rôle des estrogènes sur la physiologie et la physiopathologie du bas appareil urinaire.

GOAL: The aim was to review the literature on estrogens and lower urinary tract. MATERIAL: A review of literature through the PubMed library until December 31, 2012 was carried out using the following keywords: lower urinary tract, bladder, urethra, nervous central system, innervation, female, women, estrogen, estradiol, urogenital atrophy, urinary incontinence, overactive bladder, urinary tract infection. RESULTS: On the bladder, estrogens are involved in the trophicity, vascularisation, alpha-adrenergic, cholinergic and muscarinic receptor density, detrusor contractility and inflammation. On the urethra, they impact vascularisation, contractility, urethral pulse and tone, anatomical and functional length. On the neurological control, they act on capsaicin-sensitive afferent fibres, neurological regeneration, nerve growth factor expression and viscerovisceral sensitisation. CONCLUSION: Estrogens play a major role on the lower urinary tract physiology and physiopathology both on the urethra and the bladder.

Estrogen receptor actions on vascular biology and inflammation: implications in vascular pathophysiology.

Whereas hormonal therapy (HT) may increase the risk of coronary heart disease (CHD) and stroke in menopausal women, epidemiological studies (protection in premenopausal women) suggest and experimental studies (prevention of fatty streak development in animals) demonstrate a major atheroprotective action of estradiol (E2). The understanding of the deleterious and beneficial effects of estrogens is thus required at both a cellular and molecular level. Both the endothelium and the immuno-inflammatory system play a key role in the development of fatty streak deposit as well as in the rupture of the atherosclerotic plaque. Whereas E2 favors an anti-inflammatory effect in vitro (cultured cells), it rather elicits a pro-inflammatory response in vivo at the level of several subpopulations of the immuno-inflammatory system, which could contribute to plaque destabilization. E2 promotes beneficial actions on the endothelium such as nitric oxide and prostacyclin production. E2 actions are essentially mediated by two molecular targets: estrogen receptor alpha (ER-alpha) and beta (ER-beta), but the former appears to mediate most of the actions of E2 on the endothelium and on the immune system. ER-alpha modulates target gene transcription through two activation functions (AF), AF-1 and AF-2, even though signalling via ER-alpha located at the plasma membrane (responsible for membrane-initiated steroid signalling (MISS)/(extra-genomic)) can also lead to an indirect effect on gene transcription. Recently, we demonstrated that ER-alpha AF-1 is not required for the vasculoprotective actions of E2, whereas it is necessary for the effects of E2 on its reproductive targets. These results suggest that selective estrogen receptor modulators stimulating ER-alpha with minimal activation of ER-alpha AF-1 could retain beneficial vascular actions, while minimizing the sexual effects.

Role of inflammatory cytokines in the effect of estradiol on atheroma.

1. Although hormonal therapy (HT) may increase the risk of coronary heart disease (CHD) and stroke in postmenopausal women, epidemiological studies (protection in premenopausal women) suggest and experimental studies (prevention of fatty streak development in animals) demonstrate a major atheroprotective action of estradiol (E2). The understanding of the deleterious and beneficial effects of oestrogens is thus required. 2. The immuno-inflammatory system plays a key role in the development of fatty streak deposit as well as in the rupture of the atherosclerotic plaque. Although E2 favours an anti-inflammatory effect in vitro (cultured cells), it rather elicits a pro-inflammatory response in vivo involving several subpopulations of the immuno-inflammatory system, which could contribute to plaque destabilization. The functional role of several cytokines was explored in hypercholesterolemic mice. The atheroprotective effect of E2 was fully maintained in mice deficient in interferon-g or interleukin-12, as well as IL-10. In contrast, the protective effect of estradiol was abolished and even reversed in hypercholesterolemic mice given a neutralizing anti-transforming growth factor-b (TGF-b) antibody. Endothelium is another important target for E2, since it not only potentiates endothelial nitric oxide and prostacyclin production, but also controls trafficking of the populations of the immuno-inflammatory system. 3. To conclude, the respective actions of oestrogens on the cell populations involved in the pathophysiology of atherothrombosis may be influenced, among others, by the timing of HT initiation, the status of the vessel wall and, as recently demonstrated the status of the TGF-b pathway.

Determinants of aortic cyclic guanosine monophosphate in hypertension induced by chronic inhibition of nitric oxide synthase.

Nitric oxide (NO) and atrial natriuretic factor (ANF) cause vascular relaxation by generating cyclic guanosine monophosphate (cGMP) via activation of the soluble and particulate guanylate cyclases, respectively. The chronic effects of NG-nitro-L-arginine methyl ester (L-NAME), an L-arginine antagonist and NO synthase inhibitor, on the blood pressure and plasma and aortic cGMP levels of rats were tested. Wistar rats (n = 10 per group) were given doses of L-NAME (0, 1, 5, 10, 20, 50, and 100 mg/kg.d) by gavage twice a day for 4 wk. Chronic L-NAME induced a time- and dose-dependent increase in blood pressure. The total heart weight/body weight ratio did not change in any group, despite the hypertension. The plasma levels of cGMP did not change significantly in any group, and were correlated with the plasma ANF levels (r = 0.51, P less than 0.0001). Aortic cGMP decreased in negative correlation with increasing L-NAME from 0 to 10 mg/kg.d, culminating in a 10-fold drop arterial wall cGMP. The aortic cGMP content of rats in the four highest dose groups (from 10 to 100 mg/d) tended to increase slightly and was positively correlated with endogenous ANF (r = 0.48, P less than 0.002, n = 40). Intravenous L-arginine decreased arterial blood pressure and reversed the decline in aortic cGMP. Exogenous ANF and sodium nitroprusside both significantly increased aortic cGMP. Neither the arterial wall concentrations of cGMP-dependent kinase nor cAMP was changed by L-NAME. Thus, chronic blockade of NO synthase with L-NAME induces a dose-dependent increase in blood pressure and decrease in aortic cGMP. The in vivo basal aortic cGMP seems to be mainly dependent on NO synthase: soluble guanylate cyclase activity and to a minor extent on particulate guanylate cyclase activity.

Interactions between L-arginine and L-glutamine change endothelial NO production. An effect independent of NO synthase substrate availability.

The effect of extracellular L-arginine and L-glutamine on nitric oxide (NO) release was studied in cultured bovine aortic endothelial cells and in rabbit aortic rings. Increasing L-arginine (0.01 to 10 mM) did not alter NO release from cultured endothelial cells or modify endothelium-dependent relaxation to acetylcholine in isolated vessels. L-Glutamine (0.6 and 2 mM) inhibited NO release from cultured cells (in response to bradykinin) and from aortic rings (in response to acetylcholine or ADP). L-Arginine (0.1-10 mM) dose-dependently reversed the L-glutamine inhibition of receptor-stimulated NO release in both models. In contrast to its inhibitory response to receptor-mediated stimuli, glutamine alone slightly potentiated NO release in both models when the calcium ionophore, A23187, was added. Furthermore, cultured cells incubated with L-arginine (0.01-10 mM), in the presence or absence of glutamine, released similar amounts of NO in response to A23187. L-Glutamine did not affect intracellular L-arginine levels. Neither D-glutamine nor D-arginine affected NO release or endothelium-dependent vascular relaxation. L-Glutamine had no effect on the activity of endothelial NOS assessed by L-arginine to L-citrulline conversion. These findings show that in the absence of L-glutamine, manipulating intracellular L-arginine levels over a wide range does not affect NO release. L-Glutamine in concentrations circulating in vivo may tonically inhibit receptor-mediated NO release by interfering with signal transduction. One mechanism by which L-arginine may enhance NO release is via reversal of the inhibitory effect of L-glutamine, but apparently independently of enhancing NO synthase substrate.

Understanding the controversy about hormonal replacement therapy: insights from estrogen effects on experimental and clinical atherosclerosis.

Whereas hormonal replacement/menopause therapy (HRT) in post-menopausal women increases the coronary artery risk, epidemiological studies (protection in pre-menopaused women) suggest and experimental studies (prevention of the development of fatty streaks in animals) demonstrate a major atheroprotective action of estradiol (E2). The understanding of the deleterious and beneficial effects of estrogens is thus required. The immuno-inflammatory system plays a key role in the development of fatty streak deposit as well as in the atherosclerotic plaque rupture. Whereas E2 favors an anti-inflammatory effect in vitro (cultured cells), it rather elicits pro-inflammation in vivo, at the level of several subpopulations of the immuno-inflammatory system, which could contribute to plaque destabilization. Endothelium is another important target for E2, since it stimulates endothelial NO and prostacyclin production, thus promoting beneficial effects of vasorelaxation and platelet aggregation inhibition. Prostacyclin, but not NO, appears to be involved in the atheroprotective effect of E2. Estradiol accelerates also endothelial regrowth, thus favoring vascular healing. Finally, most of these effects of E2 are mediated by estrogen receptor alpha, and are independent of estrogen receptor beta. In summary, a better understanding of the mechanisms of estrogen action is required not only on the normal and atheromatous arteries, but also on innate and adaptive immune responses. This should help cardiovascular disease prevention optimization after menopause. These mouse models should help to screen existing and future Selective Estrogen Receptor Modulators (SERMs).

Role of fibroblast growth factor-2 isoforms in the effect of estradiol on endothelial cell migration and proliferation.

Both 17beta-estradiol (E2) and fibroblast growth factor-2 (FGF2) stimulate angiogenesis and endothelial cell migration and proliferation. The first goal of this study was to explore the potential link between this hormone and this growth factor. E2-stimulated angiogenesis in SC Matrigel plugs in Fgf2+/+ mice, but not in Fgf2-/- mice. Cell cultures from subcutaneous Matrigel plugs demonstrated that E2 increased both migration and proliferation in endothelial cells from Fgf2+/+ mice, but not from in Fgf2-/- mice. Several isoforms of fibroblast growth factor-2 (FGF2) are expressed: the low molecular weight 18-kDa protein (FGF2lmw) is secreted and activates tyrosine kinase receptors (FGFRs), whereas the high molecular weight (21 and 22 kDa) isoforms (FGF2hmw) remains intranuclear, but their role is mainly unknown. The second goal of this study was to explore the respective roles of FGF2 isoforms in the effects of E2. We thus generated mice deficient only in the FGF2lmw (Fgf2lmw-/-). E2 stimulated in vivo angiogenesis and in vitro migration in endothelial cells from Fgf2lmw-/- as it did in Fgf2+/+ mice. E2 increased FGF2hmw protein abundance in endothelial cell cultures from Fgf2+/+ and Fgf2lmw-/- mice. As shown using siRNA transfection, these effects were FGFR independent but involved FGF2-Interacting Factor, an intracellular FGF2hmw partner. This is the first report for a physiological role for the intracellular FGF2hmw found to mediate the effect of E2 on endothelial cell migration via an intracrine action.

Estradiol alters nitric oxide production in the mouse aorta through the alpha-, but not beta-, estrogen receptor.

Although estradiol (E(2)) has been recognized to exert several vasculoprotective effects in several species, its effects in mouse vasomotion are unknown, and consequently, so is the estrogen receptor subtype mediating these effects. We investigated the effect of E(2) (80 microg/kg/day for 15 days) on NO production in the thoracic aorta of ovariectomized C57Bl/6 mice compared with those given placebo. E(2) increased basal NO production. In contrast, the relaxation in response to ATP, to the calcium ionophore A23187, and to sodium nitroprusside was unaltered by E(2), whereas acetylcholine-elicited relaxation was decreased. The abundance of NO synthase I, II, and III immunoreactive proteins (using Western blot) in thoracic aorta homogenates was unchanged by E(2). To determine the estrogen receptor (ER) subtype involved in these effects, transgenic mice in which either the ERalpha or ERbeta has been disrupted were ovariectomized and treated, or not, with E(2). Basal NO production was increased and the sensitivity to acetylcholine decreased in ERbeta knockout mice in response to E(2), whereas this effect was abolished in ERalpha knockout mice. Finally, these effects of E(2) on vasomotion required long-term and/or in vivo exposure, as short-term incubation of aortic rings with 10 nmol/L E(2) in the isolated organ chamber did not elicit any vasoactive effects. In conclusion, this study demonstrates that ERalpha, but not ERbeta, mediates the beneficial effect of E(2) on basal NO production.

Understanding the oestrogen action in experimental and clinical atherosclerosis.

Whereas hormone replacement/menopause therapy (HRT) in postmenopausal women increases the coronary artery risk, epidemiological studies (protection in premenopaused women) suggest and experimental studies (prevention of the development of fatty streaks in animals) demonstrate a major atheroprotective action of oestradiol (E2). The understanding of the deleterious and beneficial effects of oestrogens is thus required. The immuno-inflammatory system plays a key role in the development of fatty streak deposit as well as in the rupture of the atherosclerotic plaque. Whereas E2 favours an anti-inflammatory effect in vitro (cultured cells), it rather elicits in vivo a proinflammation at the level of several subpopulations of the immuno-inflammatory system, which could contribute to plaque destabilization. Endothelium is another important target for E2, as it potentiates endothelial NO and prostacyclin production, thus promoting the beneficial effects as vasorelaxation and inhibition of platelet aggregation. Prostacyclin, but not NO, appears to be involved in the atheroprotective effect of E2. E2 also accelerates endothelial regrowth, thus favouring vascular healing. Finally, most of these effects of E2 are mediated by oestrogen receptor alpha, and are independent of oestrogen receptor beta. In summary, a better understanding of the mechanisms of oestrogen action not only on the normal and atheromatous arteries, but also on innate and adaptive immune responses is required and should help to optimize the prevention of cardiovascular disease after menopause. These mouse models should help to screen existing and future selective oestrogen receptor modulators.

Estrogens are needed for the improvement in endothelium-mediated dilation induced by a chronic increase in blood flow in rat mesenteric arteries.

Resistance arteries play a key role in the control of local blood flow. They undergo outward remodeling in response to a chronic increase in blood flow as seen in collateral artery growth in ischemic disorders. We have previously shown that mesenteric artery outward remodeling depends on the endothelial estrogen receptor alpha. As outward arterial remodeling is associated with improved endothelium-dependent dilation, we hypothesized that estrogens might also play a role in flow-mediated improvement of endothelium-dependent dilation. Local increase in blood flow in first order mesenteric arteries was obtained after ligation of adjacent arteries in three-month old ovariectomized female rats treated with 17-beta-estradiol (OVX+E2) or vehicle (OVX). After 2 weeks, diameter was equivalent in high flow (HF) than in normal flow (NF) arteries with a greater wall to lumen ratio in HF vessels in OVX rats. Acetylcholine-mediated relaxation was lower in HF than in NF vessels. eNOS and caveolin-1 expression level was equivalent in HF and NF arteries. By contrast, arterial diameter was 30% greater in HF than in NF arteries and the wall to lumen ratio was not changed in OVX+E2 rats. Acetylcholine-mediated relaxation was higher in HF than in NF arteries. The expression level of eNOS was higher and that of caveolin-1 was lower in HF than in NF arteries. Acetylcholine (NO-dependent)-mediated relaxation was partly inhibited by the NO-synthesis blocker L-NAME in OVX rats whereas L-NAME blocked totally the relaxation in OVX+E2 rats. Endothelium-independent relaxation (sodium nitroprusside) was equivalent in OXV and OVX+E2 rats. Similarly, serotonin- and phenylephrine-mediated contractions were higher in HF than in NF arteries in both OVX and OVX+E2 rats in association with high ratio of phosphorylated ERK1/2 to ERK1/2. Thus, we demonstrated the essential role of endogenous E2 in flow-mediated improvement of endothelium (NO)-mediated dilatation in rat mesenteric arteries.

Estradiol accelerates reendothelialization in mouse carotid artery through estrogen receptor-alpha but not estrogen receptor-beta.

BACKGROUND: The atheroprotective effect of 17beta-estradiol (E(2)) has been suggested in women and clearly demonstrated in animals through both an effect on lipid metabolism and a direct effect on the cells of the arterial wall. It has been shown, for example, that E(2) promotes endothelium-dependent relaxation and accelerates reendothelialization in rats. Similar studies have been undertaken in mice to appreciate the molecular mechanism of this process. METHODS AND RESULTS: We report here a model of electric carotid injury adapted from that described by Carmeliet et al (1997) that allows us to precisely evaluate the reendothelialization process. We demonstrate that E(2) accelerates endothelial regeneration in castrated female wild-type mice. In ovariectomized transgenic mice in which either the estrogen receptor (ER)-alpha or ERbeta gene has been disrupted, E(2) accelerated reendothelialization in female ERbeta knockout mice, whereas this effect was abolished in female ERalpha knockout mice. CONCLUSIONS: This study demonstrates that ERalpha but not ERbeta mediates the beneficial effect of E(2) on reendothelialization and potentially the prevention of atherosclerosis.

Mildly oxidized LDL induces activation of platelet-derived growth factor beta-receptor pathway.

BACKGROUND: Mildly oxidized LDL (moxLDL) is thought to play a role in atherogenesis. MoxLDL induces derivatization of cell proteins and triggers a variety of intracellular signaling. We aimed to investigate whether moxLDL-induced protein derivatization may influence the activity of platelet-derived growth factor receptor beta (PDGFRbeta), a tyrosine kinase receptor of major importance in vascular biology and atherogenesis. METHODS AND RESULTS: In cultured rabbit arterial smooth muscle cells, moxLDL induces activation of the PDGFRbeta signaling pathway, as shown by PDGFRbeta tyrosine phosphorylation on Western blot and coimmunoprecipitation of SH2-containing proteins. The cellular events involved in the moxLDL-induced PDGFRbeta activation can be summarized as follows. Oxidized lipids from moxLDL trigger two phases of PDGFRbeta activation involving two separate mechanisms, as shown by experiments on cultured cells (in situ) and on immunopurified PDGFRbeta (in vitro): (1) the first phase may be mediated by 4-hydroxynonenal, which induces PDGFRbeta adduct formation and subsequent PDGFRbeta activation (antioxidant-insensitive step); (2) the second phase involves ceramide-mediated generation of H(2)O(2) (these steps being inhibited by tosylphenylalanylchloromethylketone, an inhibitor of ceramide formation, and by antioxidant BHT, exogenous catalase, or overexpressed human catalase). Because 4-hydroxynonenal-PDGFRbeta adducts are also detected in atherosclerotic aortas, it is suggested that this novel mechanism of moxLDL-induced PDGFRbeta activation may occur during atherogenesis. CONCLUSIONS: MoxLDL acts as a local autoparacrine mediator in the vascular wall, and PDGFRbeta acts as a sensor for both oxidized lipids and oxidative stress. This constitutes a novel mechanism of PDGFRbeta activation in atherosclerotic areas.

Discrepancy between plasma and aortic wall cyclic guanosine monophosphate in an experimental model of congestive heart failure.

OBJECTIVES: The state of the vasodilator systems in congestive heart failure is poorly defined. Plasma atrial natriuretic peptide is increased, whereas endothelium derived relaxing factor activity can be decreased. Atrial natriuretic peptide and endothelium derived relaxing factor both cause vascular relaxation by generating cyclic guanosine monophosphate (cGMP), by activating the particulate and the soluble guanylate cyclase, respectively. This study examines the biological effects of atrial natriuretic peptide and endothelium derived relaxing factor in experimental heart failure by assessing the plasma, urinary, and tissue concentrations of their common second messenger cGMP. METHODS: Myocardial infarctions (n = 31) were induced and sham operations (n = 25) were performed on Wistar rats, and the rats were monitored for three months. Aortic and pulmonary cGMP contents were measured, as the aorta is mainly matrix and smooth muscle cells, and the lung is particularly rich in capillaries, hence in endothelial cells. The concentrations of the other second messenger cyclic adenosine monophosphate (cAMP) was also determined, as were those of cGMP dependent protein kinase in the arteries. RESULTS: 17 of the 31 rats with myocardial infarction had oedema. The total heart weight to body weight ratio and the ratio of the myocardium haemodynamically upstream from the infarcted left ventricle to body weight were increased in proportion to the infarct size. Plasma atrial natriuretic peptide and plasma and urinary cGMP concentrations were increased in proportion to the degree of heart failure (p < 0.0001). The pulmonary cGMP concentration was significantly higher in the rats with myocardial infarction than in the control group (p < 0.0001). Pulmonary cGMP concentrations were correlated with the plasma concentrations of atrial natriuretic peptide and cGMP (r2 = 0.59 and 0.66 respectively, p < 0.0001). The cGMP, cAMP, and cGMP, and cGMP dependent kinase concentrations in the aortic wall of rats with myocardial infarctions were the same as in control rats. CONCLUSIONS: The increase in plasma, urinary, and pulmonary cGMP in rats with myocardial infarctions were highly correlated with the increase in circulating atrial natriuretic peptide. By contrast, the aortic cGMP concentration was unchanged in these rats, despite high plasma atrial natriuretic peptide. In congestive heart failure, a discrepancy seems to exist between pulmonary (mainly endothelium) and aortic wall (mainly smooth muscle cells) cGMP.

Vascular relaxation and cyclic guanosine monophosphate in a rat model of high output heart failure.

OBJECTIVE: Low output heart failure induces abnormalities of endothelium dependent vasodilation, but the mechanisms responsible for this remain unclear. As blood flow can alter endothelial cell function, in particular nitric oxide (NO) release, the activity of endothelium derived relaxing factor (EDRF) was investigated in a rat model of high output heart failure. METHODS: The thoracic aorta upstream of an aorto-caval fistula in rats was submitted to hormonal changes (similar to those in heart failure) and to high blood flow (opposite to that found in low output heart failure). Functional and biochemical arterial properties were studied in aorto-caval fistula rats and in sham operated rats three months after operation. The vascular responses were studied by exposing aortic segments from fistula and sham operated rats to increasing concentrations of agonists. Aortic cyclic guanosine monophosphate (cGMP) concentration was assessed as an index of NO synthase activity. The effect of NO synthase blockade on functional and biochemical arterial properties was also studied. RESULTS: Plasma atrial natriuretic factor (ANF) was increased in fistula rats compared to sham operated rats. The concentrations of acetylcholine or the calcium ionophore A23187 required to produce 10% and 50% maximum relaxation (EC10 and EC50) were similar in the two groups. Relaxation in response to low concentrations of Sin-1 (an NO donor) was shifted rightwards in fistula rats and EC10 was greater than in the controls. The aortic cGMP concentration was higher in aorto-caval fistula rats than in sham operated rats (p = 0.008). The differences between aorto-caval fistula rats and sham operated rats were probably the result of increased basal EDRF-NO release in the former, since NO synthase blockade abolished the differences in both aortic cGMP and the dose-response curve to Sin-1. CONCLUSIONS: The arterial wall upstream of a chronic aorto-caval fistula has increased cGMP content and hyposensitivity to Sin-1, which may be due to enhanced basal EDRF-NO release. These changes, strikingly different from those found in the low output heart failure, suggest that haemodynamic rather than neuroendocrine factors play a determinant role in the altered vasodilator response in heart failure.

Alteration of plasmalemmal caveolae mimics endothelial dysfunction observed in atheromatous rabbit aorta.

OBJECTIVE: In endothelial cells, nitric oxide (NO) is produced by the endothelial isoform of nitric oxide synthase (eNOS), which is localized in the cholesterol-rich plasmalemmal microdomains involved in signal transduction, known as caveolae. The present study was undertaken to evaluate the effect of hypercholesterolemia and fatty streak formation on the endothelial caveolae and on endothelial function, and attempted to determine to what extent the caveolae were involved in endothelium-derived NO production. METHODS AND RESULTS: We first studied the effect of atheroma on endothelial NO production. Fatty streak infiltrated aorta of cholesterol-fed New Zealand White rabbits demonstrated an impairment of acetylcholine-induced relaxation and nearly normal calcium ionophore A23187-induced maximal relaxation. The abundance of caveolae in the endothelium covering the fatty streak, as well as their 'grape-like' clustering, appeared to be decreased. We therefore investigated the effect, on endothelial NO production, of the cholesterol-binding agents 2-hydroxypropyl-beta-cyclodextrin (hp-beta-CD) and filipin, known to alter caveolae structure and/or function. Treatment with either hp-beta-CD (2%) or filipin (4 microg/ml) did not affect contraction to phenylephrine or relaxant responses to A23187 or to the NO donor sodium nitroprusside. In contrast, both treatments impaired acetylcholine-induced relaxation. Cultured bovine aortic endothelial cells (BAEC) similarly treated with hp-beta-CD demonstrated a 50% decrease of total cellular cholesterol and a decreased abundance of caveolae as well as their 'grape-like' clustering. Cholesterol depletion decreased the bradykinin-induced transient peak of free intracellular calcium and subsequent receptor-stimulated NO production (assessed using reporter cells rich in soluble guanylyl cyclase), whereas that elicited by A23187 remained unaltered. CONCLUSION: Fatty streak deposit is associated with a decrease in caveolae 'transductosomes' abundance which appears to represent a novel mechanism of endothelial dysfunction.