Inhibition of E-selectin gene expression by transforming growth factor beta in endothelial cells involves coactivator integration of Smad and nuclear factor kappaB-mediated signals.

Transforming growth factor (TGF)-beta(1) is a pleiotropic cytokine/growth factor that is thought to play a critical role in the modulation of inflammatory events. We demonstrate that exogenous TGF-beta(1) can inhibit the expression of the proinflammatory adhesion molecule, E-selectin, in vascular endothelium exposed to inflammatory stimuli both in vitro and in vivo. This inhibitory effect occurs at the level of transcription of the E-selectin gene and is dependent on the action of Smad proteins, a class of intracellular signaling proteins involved in mediating the cellular effects of TGF-beta(1). Furthermore, we demonstrate that these Smad-mediated effects in endothelial cells result from a novel competitive interaction between Smad proteins activated by TGF-beta(1) and nuclear factor kappaB (NFkappaB) proteins activated by inflammatory stimuli (such as cytokines or bacterial lipopolysaccharide) that is mediated by the transcriptional coactivator cyclic AMP response element-binding protein (CREB)-binding protein (CBP). Augmentation of the limited amount of CBP present in endothelial cells (via overexpression) or selective disruption of Smad-CBP interactions (via a dominant negative strategy) effectively antagonizes the ability of TGF-beta(1) to block proinflammatory E-selectin expression. These data thus demonstrate a novel mechanism of interaction between TGF-beta(1)-regulated Smad proteins and NFkappaB proteins regulated by inflammatory stimuli in vascular endothelial cells. This type of signaling mechanism may play an important role in the immunomodulatory actions of this cytokine/growth factor in the cardiovascular system.

Angiotensin inhibition potentiates the renal responses to neutral endopeptidase inhibition in dogs with congestive heart failure.

The renal natriuretic actions of endogenous atrial natriuretic factor are enhanced by neutral endopeptidase inhibition (NEP-I). Recognizing that activation of the renin-angiotensin-aldosterone system in congestive heart failure (CHF) antagonizes the renal actions of atrial natriuretic factor, we hypothesized that angiotensin II antagonism with converting enzyme inhibition would potentiate the renal actions of NEP-I in CHF. To test this hypothesis, the renal responses to a specific NEP-I (SQ 28,603) were assessed in dogs with eight days of experimental CHF produced by rapid ventricular pacing. The renal natriuretic responses to NEP-I in experimental CHF were significant. In the same model of CHF, chronic angiotensin antagonism with converting enzyme inhibition potentiated both renal hemodynamic and excretory responses to NEP-I. The potentiated renal hemodynamic response included significant increases in glomerular filtration rate and filtration fraction. In the CHF group with angiotensin antagonism, an intrarenal infusion of low-dose angiotensin abolished the potentiated renal responses to NEP-I, supporting the concept that intrarenal angiotensin antagonism, rather than improved systemic hemodynamics or potentiation of other peptide systems, mediated the enhanced renal responses to NEP-I in the presence of converting enzyme inhibition.

Increased production of nitric oxide in coronary arteries during congestive heart failure.

Experiments were designed to determine whether a heterogeneity of endothelium-dependent relaxations in arteries from different vascular beds exists in experimental congestive heart failure (CHF) and to determine the mediators of those responses. CHF was produced in dogs by rapid ventricular pacing for 15 d. Rings of coronary, femoral, and renal arteries with and without endothelium from control and CHF dogs were suspended in organ chambers for measurement of isometric force. In arteries contracted with prostaglandin F2 alpha, endothelium-dependent relaxations to BHT 920 (an alpha 2-adrenergic agonist) were increased in coronary arteries from dogs with CHF (maximal relaxation: control -15 +/- 9% vs CHF -92 +/- 5%; n = 5-6; P < 0.05), with a modest enhancement in renal arteries. Relaxations to adenosine diphosphate and the calcium ionophore were unchanged. Relaxations to BHT 920 in CHF were reduced by NG monomethyl-L-arginine (L-NMMA) and pertussis toxin but not by indomethacin. These data suggest that endothelium-dependent relaxations are affected heterogeneously in CHF. The enhanced response to alpha 2-adrenergic agonists in the coronary artery is mediated by nitric oxide through a mechanism sensitive to inhibition by pertussis toxin. This selective increase in endothelium-dependent relaxations in the coronary artery may contribute to preserving coronary blood flow during CHF.

Pulmonary and urinary clearance of atrial natriuretic factor in acute congestive heart failure in dogs.

Atrial natriuretic factor (ANF) is a peptide hormone of cardiac origin elevated in acute congestive heart failure (CHF), which is degraded by the enzyme neutral endopeptidase 24.11 (NEP). This study was designed to investigate the pulmonary and urinary clearance of ANF before and after the initiation of acute experimental CHF in dogs, and to assess the contribution of enzymatic degradation to these clearances in CHF. This study demonstrated a significant clearance of plasma ANF across the pulmonary circulation at baseline, and a tendency for pulmonary clearance to decrease in CHF (1115 +/- 268 to 498 +/- 173 ml/min, NS). The pulmonary extraction of ANF present at baseline was not altered with acute CHF (36.0 +/- 7.8 to 34.9 +/- 12.1%, NS). NEP inhibition (NEPI) abolished both the clearance and extraction of plasma ANF across the lung in CHF. Similarly, significant urinary clearance of ANF was present at baseline, and in acute CHF the urinary clearance of ANF decreased (0.14 +/- 0.02 to 0.02 +/- 0.01 ml/min, P less than 0.05). NEPI prevented the decrease in the urinary clearance of ANF, and enhanced the renal response to endogenous ANF, independent of further increases in plasma ANF during CHF. This study supports an important role for NEP in the pulmonary and urinary metabolism of endogenous ANF during acute CHF.

Downregulation of vascular endothelial growth factor receptors by tumor necrosis factor-alpha in cultured human vascular endothelial cells.

Vascular endothelial growth factor (VEGF) potently stimulates angiogenesis, whereas TNF-alpha has both pro- and anti-angiogenic activity. By measuring thymidine uptake, we found that TNF-alpha blocked a 2.3-fold increase in DNA synthesis induced by VEGF in human endothelial cells. To explore the possibility that the two interact to regulate endothelial cell proliferation, we examined the effect of TNF-alpha on VEGF receptor expression. In venous and arterial endothelial cells, TNF-alpha potently reduced mRNA transcripts of the two VEGF receptors (KDR/flk-1 and flt-1) in a dose- and time-dependent fashion. TNF-alpha at 1 ng/ml induced maximal inhibition of mRNA expression, which fell by approximately 70% after 24 h. TNF-alpha treatment did not significantly affect the KDR/flk-1 half-life but did decrease its rate of transcription to 40% of control. The decrease in KDR/flk-1 mRNA depended partially on new protein synthesis and was abolished by phorbol ester pretreatment. TNF-alpha decreased the amount of 35S-labeled KDR/flk-1 immunoprecipitated by an antibody specific for KDR/flk-1 to 18% of control. We conclude that TNF-alpha downregulates expression of both VEGF receptors in human endothelial cells and that this effect is transcriptional (at least for KDR/flk-1). These data support the hypothesis that TNF-alpha exerts its antiangiogenic effect in part by modulating the VEGF-specific angiogenic pathway.

Induction of cyclin A gene expression by homocysteine in vascular smooth muscle cells.

Homocysteine is an important and independent risk factor for arteriosclerosis. We showed previously that homocysteine stimulates vascular smooth muscle cell proliferation, a hallmark of arteriosclerosis. We show here that homocysteine and serum increased DNA synthesis synergistically in both human and rat aortic smooth muscle cells (RASMCs). Treatment of quiescent RASMCs with 1 mM homocysteine or 2% calf serum for 36 h increased cyclin A mRNA levels by 8- and 14-fold, respectively, whereas homocysteine plus serum increased cyclin A mRNA levels by 40-fold, indicating a synergistic induction of cyclin A mRNA. Homocysteine did not increase the half-life of cyclin A mRNA (2.9 h), but it did increase the transcriptional rate of the cyclin A gene in nuclear run-on experiments. The positive effect of homocysteine on cyclin A gene transcription was confirmed by our finding that homocysteine increased cyclin A promoter activity and ATF-binding protein levels in RASMCs. Finally, 1 mM homocysteine increased cyclin A protein levels and cyclin A-associated kinase activity by threefold. This homocysteine-induced expression lesions by promoting proliferation of vascular smooth muscle cells.

Disappearance of cyclin A correlates with permanent withdrawal of cardiomyocytes from the cell cycle in human and rat hearts.

The regulated expression of cyclins controls the cell cycle. Because cardiomyocytes in adult mammals withdraw permanently from the cell cycle and thus cannot regenerate after injury, we examined cyclin expression during development by comparing cyclin A-E mRNA levels in fetal and adult human hearts. Cyclin B mRNA was detectable in adult hearts, although at a level markedly lower than that in fetal hearts. Levels of cyclin C, D1, D2, D3, and E mRNA were essentially identical in the two groups. In contrast, cyclin A mRNA was undetectable in adult hearts whereas cyclin A mRNA and protein were readily detectable in fetal hearts and cardiomyocytes, respectively. We then measured cyclin A mRNA and protein levels in rat hearts at four stages of development (fetal and 2, 14, and 28 d). Cyclin A mRNA and protein levels decreased quickly after birth (to 37% at day 2) and became undetectable within 14 d, an observation consistent with reports that cardiomyocytes stop replicating in rats by the second to third postnatal week. This disappearance of cyclin A gene expression in human and rat hearts at the time cardiomyocytes become terminally differentiated suggests that cyclin A downregulation is important in the permanent withdrawal of cardiomyocytes from the cell cycle.

Hypoxia induces severe right ventricular dilatation and infarction in heme oxygenase-1 null mice.

Heme oxygenase (HO) catalyzes the oxidation of heme to generate carbon monoxide (CO) and bilirubin. CO increases cellular levels of cGMP, which regulates vascular tone and smooth muscle development. Bilirubin is a potent antioxidant. Hypoxia increases expression of the inducible HO isoform (HO-1) but not the constitutive isoform (HO-2). To determine whether HO-1 affects cellular adaptation to chronic hypoxia in vivo, we generated HO-1 null (HO-1(-/-)) mice and subjected them to hypoxia (10% oxygen) for five to seven weeks. Hypoxia caused similar increases in right ventricular systolic pressure in wild-type and HO-1(-/-) mice. Although ventricular weight increased in wild-type mice, the increase was greater in HO-1(-/-) mice. Similarly, the right ventricles were more dilated in HO-1(-/-) mice. After seven weeks of hypoxia, only HO-1(-/-) mice developed right ventricular infarcts with organized mural thrombi. No left ventricular infarcts were observed. Lipid peroxidation and oxidative damage occurred in right ventricular cardiomyocytes in HO-1(-/-), but not wild-type, mice. We also detected apoptotic cardiomyocytes surrounding areas of infarcted myocardium by terminal deoxynucleotide transferase-mediated dUTP nick end-labeling (TUNEL) assays. Our data suggest that in the absence of HO-1, cardiomyocytes have a maladaptive response to hypoxia and subsequent pulmonary hypertension. J.Clin. Invest. 103:R23-R29 (1999).

The ATF site mediates downregulation of the cyclin A gene during contact inhibition in vascular endothelial cells.

Contact inhibition mediates monolayer formation and withdrawal from the cell cycle in vascular endothelial cells. In studying the cyclins--key regulators of the cell cycle--in bovine aortic endothelial cells (BAEC), we found that levels of cyclin A mRNA decreased in confluent BAEC despite the presence of 10% fetal calf serum. We then transfected into BAEC a series of plasmids containing various lengths of the human cyclin A 5' flanking sequence and the luciferase gene. Plasmids containing 3,200, 516, 406, 266, or 133 bp of the human cyclin A promoter directed high luciferase activity in growing but not confluent BAEC. In contrast, a plasmid containing 23 bp of the cyclin A promoter was associated with a 65-fold reduction in activity in growing BAEC, and the promoter activities of this plasmid were identical in both growing and confluent BAEC. Mutation of the activating transcription factor (ATF) consensus sequence at bp -80 to -73 of the cyclin A promoter decreased its activity, indicating the critical role of the ATF site. We identified by gel mobility shift analysis protein complexes that bound to the ATF site in nuclear extracts from growing but not confluent BAEC and identified (with antibodies) ATF-1 as a binding protein in nuclear extracts from growing cells. Also, ATF-1 mRNA levels decreased in confluent BAEC. Taken together, these data suggest that the ATF site and its cognate binding proteins play an important role in the downregulation of cyclin A gene expression during contact inhibition.

Impaired abdominal wall development and deficient wound healing in mice lacking aortic carboxypeptidase-like protein.

Aortic carboxypeptidase-like protein (ACLP) is a member of a diverse group of proteins that contain a domain with similarity to that of the Dictyostelium discoideum protein discoidin I. The discoidin domain has been identified in mammalian milk fat globule membrane proteins, blood coagulation factors, and receptor tyrosine kinases, where it may facilitate cell aggregation, adhesion, or cell-cell recognition. Here we show that ACLP is a secreted protein that associates with the extracellular matrix (ECM). During mouse embryogenesis, ACLP is abundantly expressed in the ECM of collagen-rich tissues, including the vasculature, dermis, and the developing skeleton. We deleted the ACLP gene in mice by homologous recombination. The majority of ACLP(-/-) mice die perinatally due to gastroschisis, a severe disruption of the anterior abdominal wall and herniation of the abdominal organs. ACLP(-/-) mice that survived to adulthood developed nonhealing skin wounds. Following injury by a dermal punch biopsy, ACLP(-/-) mice exhibited deficient wound healing compared with controls. In addition, dermal fibroblasts isolated from ACLP(-/-) 18.5-day-postconception embryos exhibited a reduced proliferative capacity compared with wild-type cells. These results indicate that ACLP is an ECM protein that is essential for embryonic development and dermal wound healing processes.

Prevention of hypoxia-induced pulmonary hypertension by enhancement of endogenous heme oxygenase-1 in the rat.

We investigated the role of heme oxygenase (HO)-1 in the development of hypoxia-induced pulmonary hypertension. HO catalyzes the breakdown of heme to the antioxidant bilirubin and the vasodilator carbon monoxide. Hypoxia is a potent but transient inducer of HO-1 in vascular smooth muscle cells in vitro and in the lung in vivo. By using agonists of HO-1, we sustained a high expression of HO-1 in the lungs of rats for 1 week. We report that this in vivo enhancement of HO-1 in the lung prevented the development of hypoxic pulmonary hypertension and inhibited the structural remodeling of the pulmonary vessels. The mechanism(s) underlying this effect may involve a direct vasodilating and antiproliferative action of endogenous carbon monoxide, as well as an indirect effect of carbon monoxide on the production of vasoconstrictors. These results provide evidence that enhancement of endogenous adaptive responses may be used to prevent hypoxia-induced pulmonary hypertension.

Cardiac-specific expression of heme oxygenase-1 protects against ischemia and reperfusion injury in transgenic mice.

Heme oxygenase (HO)-1 degrades the pro-oxidant heme and generates carbon monoxide and antioxidant bilirubin. We have previously shown that in response to hypoxia, HO-1-null mice develop infarcts in the right ventricle of their hearts and that their cardiomyocytes are damaged by oxidative stress. To test whether HO-1 protects against oxidative injury in the heart, we generated cardiac-specific transgenic mice overexpressing different levels of HO-1. By use of a Langendorff preparation, hearts from transgenic mice showed improved recovery of contractile performance during reperfusion after ischemia in an HO-1 dose-dependent manner. In vivo, myocardial ischemia and reperfusion experiments showed that infarct size was only 14.7% of the area at risk in transgenic mice compared with 56.5% in wild-type mice. Hearts from these transgenic animals had reduced inflammatory cell infiltration and oxidative damage. Our data demonstrate that overexpression of HO-1 in the cardiomyocyte protects against ischemia and reperfusion injury, thus improving the recovery of cardiac function.

Exacerbation of chronic renovascular hypertension and acute renal failure in heme oxygenase-1-deficient mice.

Heme oxygenase (HO) is a cytoprotective enzyme that degrades heme (a potent oxidant) to generate carbon monoxide (a vasodilatory gas that has anti-inflammatory properties), bilirubin (an antioxidant derived from biliverdin), and iron (sequestered by ferritin). Because of properties of HO and its products, we hypothesized that HO would be important for the regulation of blood pressure and ischemic injury. We studied chronic renovascular hypertension in mice deficient in the inducible isoform of HO (HO-1) using a one kidney-one clip (1K1C) model of disease. Systolic blood pressure was not different between wild-type (HO-1(+/+)), heterozygous (HO-1(+/-)), and homozygous null (HO-1(-/-)) mice at baseline. After 1K1C surgery, HO-1(+/+) mice developed hypertension (140+/-2 mm Hg) and cardiac hypertrophy (cardiac weight index of 5.0+/-0.2 mg/g) compared with sham-operated HO-1(+/+) mice (108+/-5 mm Hg and 4.1+/-0.1 mg/g, respectively). However, 1K1C produced more severe hypertension (164+/-2 mm Hg) and cardiac hypertrophy (6.9+/-0.6 mg/g) in HO-1(-/-) mice. HO-1(-/-) mice also experienced a high rate of death (56%) within 72 hours after 1K1C surgery compared with HO-1(+/+) (25%) and HO-1(+/-) (28%) mice. Assessment of renal function showed a significantly higher plasma creatinine in HO-1(-/-) mice compared with HO-1(+/-) mice. Histological analysis of kidneys from 1K1C HO-1(-/-) mice revealed extensive ischemic injury at the corticomedullary junction, whereas kidneys from sham HO-1(-/-) and 1K1C HO-1(+/-) mice appeared normal. Taken together, these data suggest that chronic deficiency of HO-1 does not alter basal blood pressure; however, in the 1K1C model an absence of HO-1 leads to more severe renovascular hypertension and cardiac hypertrophy. Moreover, renal artery clipping leads to an acute increase in ischemic damage and death in the absence of HO-1.

Endotoxin-induced mortality is related to increased oxidative stress and end-organ dysfunction, not refractory hypotension, in heme oxygenase-1-deficient mice.

BACKGROUND: Heme oxygenase (HO)-1 is an enzyme that degrades heme to generate CO (a vasodilatory gas), iron, and the potent antioxidant bilirubin. A disease process characterized by decreases in vascular tone and increases in oxidative stress is endotoxic shock. Moreover, HO-1 is markedly induced in multiple organs after the administration of endotoxin (lipopolysaccharide [LPS]) to mice. METHODS AND RESULTS: To determine the role of HO-1 in endotoxemia, we administered LPS to mice that were wild-type (+/+), heterozygous (+/-), or homozygous null (-/-) for targeted disruption of HO-1. LPS produced a similar induction of HO-1 mRNA and protein in HO-1(+/+) and HO-1(+/-) mice, whereas HO-1(-/-) mice showed no HO-1 expression. Four hours after LPS, systolic blood pressure (SBP) decreased in all the groups. However, SBP was significantly higher in HO-1(-/-) mice (121+/-5 mm Hg) after 24 hours, compared with HO-1(+/+) (96+/-7 mm Hg) and HO-1(+/-) (89+/-13 mm Hg) mice. A sustained increase in endothelin-1 contributed to this SBP response. Even though SBP was higher, mortality was increased in HO-1(-/-) mice, and they exhibited hepatic and renal dysfunction that was not present in HO-1(+/+) and HO-1(+/-) mice. The end-organ damage and death in HO-1(-/-) mice was related to increased oxidative stress. CONCLUSIONS: These data suggest that the increased mortality during endotoxemia in HO-1(-/-) mice is related to increased oxidative stress and end-organ (renal and hepatic) damage, not to refractory hypotension.

Role of macrophage-expressed adipocyte fatty acid binding protein in the development of accelerated atherosclerosis in hypercholesterolemic mice.

Atherosclerosis is an inflammatory disease process associated with elevated levels of plasma cholesterol, especially low-density lipoproteins. The latter become trapped within the arterial wall and are oxidized and taken up by macrophages to form foam cells. This process is an initiating event for atherosclerosis. Fatty acid binding proteins (FABP) are involved in fatty acid metabolism and cellular lipid transport, and adipocyte FABP (aP2) is also expressed in macrophages. We recently generated mice lacking both apolipoprotein (Apo)E and aP2 (ApoE-/-aP2-/-) and found that these mice, compared with ApoE-/- mice, developed markedly smaller atherosclerotic lesions that contained fewer macrophages. Here we investigated the mechanism(s) responsible for this prevention of atherosclerotic lesion formation. Bone marrow transplantations were performed in ApoE-/- mice, receiving cells from either ApoE-/- or ApoE-/-aP2-/- mice. The lack of aP2 in donor marrow cells led to the development of smaller (5.5-fold) atherosclerotic lesions in the recipient mice. No differences were found in plasma cholesterol, glucose, or insulin levels between recipients of bone marrow cells from ApoE-/- or ApoE-/-aP2-/- mice. However, the expression of chemoattractant and inflammatory cytokines was decreased in macrophages from ApoE-/-aP2-/- mice compared with ApoE-/- mice, which may contribute to the decrease in atherosclerotic lesion formation. Taken together, we demonstrate the importance of macrophage aP2 in the development of atherosclerotic lesions.

Absence of heme oxygenase-1 expression in the lung parenchyma exacerbates endotoxin-induced acute lung injury and decreases surfactant protein-B levels.

Acute respiratory distress syndrome (ARDS) is a devastating disease process characterized by severe acute lung injury, inflammatory cell recruitment to the lung, upregulation of pro-inflammatory cytokines and increased oxidative stress. Epithelial cell injury, diffuse alveolar damage and surfactant dysfunction ensue leading to refractory hypoxemic respiratory failure. There are no specific effective therapies for ARDS and novel therapeutic approaches are desperately needed. In this study we assessed the role of the cytoprotective and anti-inflammatory enzyme heme oxygenase (HO)-1 in a model of nebulized endotoxin-induced acute lung injury. HO-1 null (HO-1(-/-)) mice exhibited severe physiologic lung dysfunction following lipopolysaccharide (LPS) nebulization, but had similar inflammatory responses as wild-type (WT) mice. However, a dramatic reduction in surfactant protein-B (SP-B) expression was observed in the lungs of LPS-treated HO-1(-/-) mice compared with similarly treated WT mice. Using reciprocal bone marrow transplantation (BMT) to generate HO-1-chimeric mice, we found that absence of HO-1 in the lung parenchyma, not in bone marrow-derived inflammatory cells, was responsible for enhanced SP-B downregulation and severe physiologic lung dysfunction. These findings have implications for our understanding of the pathophysiology of ARDS and may guide future therapeutic strategies.

Endothelin: a new cardiovascular regulatory peptide.

Endothelin, a recently discovered peptide produced by endothelial cells, contracts vascular strips in vitro with greater potency than any previously known vasoconstrictor. Infusions of pharmacologic doses of endothelin in vivo result in a prolonged pressor response and a preferential impairment of renal hemodynamic and excretory functions. Endothelin also directly stimulates the release of aldosterone from the adrenal gland and inhibits renin release in vitro. A highly sensitive and specific radioimmunoassay has confirmed that endothelin circulates in human plasma, and increased plasma endothelin levels have been associated with various cardiovascular disease states. This review summarizes the current knowledge about the molecular biologic features and physiologic actions of endothelin and also explores the role of endothelin, through its local and systemic function, as a regulator of vascular tone in normal and pathophysiologic states.

Pseudoaneurysm of the aortic root diagnosed by noninvasive imaging: report of a case.

Pseudoaneurysm of the aortic root is a rare condition typically diagnosed by the use of cardiac catheterization and aortography or by surgical exploration. This case describes a patient who was shown to have a pseudoaneurysm of the aortic root without evidence of any acquired etiologic factors other than atherosclerotic vascular disease. Two new advanced techniques of noninvasive imaging were used in confirming the diagnosis: transesophageal echocardiography and gated magnetic resonance imaging. This case highlights the value of techniques such as these to reliably assess the heart and great vessels without the need for more invasive procedures.

Pathophysiology of congestive heart failure: role of atrial natriuretic factor and therapeutic implications.

Endogenous atrial natriuretic factor (ANF) serves a functional role to maintain sodium homeostasis and inhibit activation of the renin-angiotensin-aldosterone system in acute congestive heart failure despite arterial hypotension. However, as heart failure progresses, maximal synthesis and release of ANF from both the atrial and ventricular myocardium may occur resulting in relative ANF deficiency. This relative deficiency of ANF results in a progressive inability to excrete sodium and antagonize the renin-angiotensin-aldosterone system. Consequently, agents that increase circulating ANF and (or) enhance its local action have potential therapeutic efficacy. Recent studies suggest that inhibitors of neutral endopeptidase 24.11, which block ANF degradation, potentiate the natriuretic action of endogenous ANF independent of systemic or renal hemodynamics. This action does not parallel increases in plasma ANF and is associated with marked increases in urinary ANF and cyclic guanosine monophosphate consistent with enhanced local action of the peptide. In addition, agents that selectively bind to biologically inactive ANF clearance receptors increase endogenous plasma ANF and promote increases in renal sodium excretion. These studies suggest a therapeutic role for neutral endopeptidase inhibition and clearance receptor blockade, while advancing our understanding of the pathophysiology of ANF in congestive heart failure.

Role of TGF-beta in vascular development and vascular reactivity.

Transforming growth factor-beta (TGF-beta) is the prototypic member of a large family of structurally related proteins. Three vertebrate TGF-beta isoforms have been identified and termed TGF-beta1, TGF-beta2, and TGF-beta3, respectively. In addition, two receptors of the serine/threonine kinase family termed type I and II have also been identified. In this review, we focused our attention on the effects of TGF-beta on vascular development and vascular reactivity. The critical role of the TGF-beta1 and the TGF-beta type II receptor in blood vessel formation in the yolk sac has been demonstrated by gene deletion experiments. Recent investigations have also shown that isoforms of TGF-beta play a critical role in smooth muscle cell differentiation. And, finally, a role for TGF-beta1 in the regulation of vascular tone and reactivity has been suggested by studies demonstrating that TGF-beta1 can inhibit the production of potent vasodilators (such as nitric oxide) and stimulate the production of potent vasoconstrictors (such as endothelin). Taken together, these studies suggest that TGF-beta plays a critical role in blood vessel development and vascular function.