Deficiency of Cardiac Natriuretic Peptide Signaling Promotes Peripartum Cardiomyopathy-Like Remodeling in the Mouse Heart.

BACKGROUND: The maternal circulatory system and hormone balance both change dynamically during pregnancy, delivery, and the postpartum period. Although atrial natriuretic peptides and brain natriuretic peptides produced in the heart control circulatory homeostasis through their common receptor, NPR1, the physiologic and pathophysiologic roles of endogenous atrial natriuretic peptide/brain natriuretic peptide in the perinatal period are not fully understood. METHODS: To clarify the physiologic and pathophysiologic roles of the endogenous atrial natriuretic peptide/brain natriuretic peptide-NPR1 system during the perinatal period, the phenotype of female wild-type and conventional or tissue-specific Npr1-knockout mice during the perinatal period was examined, especially focusing on maternal heart weight, blood pressure, and cardiac function. RESULTS: In wild-type mice, lactation but not pregnancy induced reversible cardiac hypertrophy accompanied by increases in fetal cardiac gene mRNAs and ERK1/2 (extracellular signaling-regulated kinase) phosphorylation. Npr1-knockout mice exhibited significantly higher plasma aldosterone level than did wild-type mice, severe cardiac hypertrophy accompanied by fibrosis, and left ventricular dysfunction in the lactation period. Npr1-knockout mice showed a high mortality rate over consecutive pregnancy-lactation cycles. In the hearts of Npr1-knockout mice during or after the lactation period, an increase in interleukin-6 mRNA expression, phosphorylation of signal transducer and activator of transcription 3, and activation of the calcineurin-nuclear factor of the activated T cells pathway were observed. Pharmacologic inhibition of the mineralocorticoid receptor or neuron-specific deletion of the mineralocorticoid receptor gene significantly ameliorated cardiac hypertrophy in lactating Npr1-knockout mice. Anti-interleukin-6 receptor antibody administration tended to reduce cardiac hypertrophy in lactating Npr1-knockout mice. CONCLUSIONS: These results suggest that the characteristics of lactation-induced cardiac hypertrophy in wild-type mice are different from exercise-induced cardiac hypertrophy, and that the endogenous atrial natriuretic peptide/brain natriuretic peptide-NPR1 system plays an important role in protecting the maternal heart from interleukin-6-induced inflammation and remodeling in the lactation period, a condition mimicking peripartum cardiomyopathy.

Developmental origins of pregnancy-induced cardiac changes: establishment of a novel model using the atrial natriuretic peptide gene-disrupted mice.

Pregnancy evokes many challenges on the maternal cardiovascular system that may unmask predispositions for future disease. This is particularly evident for women who develop pregnancy-related disorders, for example, pre-eclampsia and gestational diabetes or hypertension. Such pregnancy-related syndromes increase the risk for cardiovascular disease (CVD) postpartum. As a result, pregnancy has been termed as a cardiovascular stress test and an indicator or marker to predict the development of CVD later in life. In addition, pregnancy-related disorders impact the development of offspring also placing them at a higher risk for disease. Utilizing pregnancy as a physiological stressor, the current investigation sought to determine whether the cardiovascular system of offspring exposed to gestational hypertension in utero would respond adversely to the stress of pregnancy. Heterozygous atrial natriuretic peptide gene-disrupted (ANP+/-) offspring were generated by either crossing male wildtype ANP+/+ with female knockout ANP-/- to produce ANP+/-KO mice or crossing female wildtype ANP+/+ with male knockout ANP-/- to produce ANP+/-WT mice. To study the cardiovascular stress induced by pregnancy, female ANP+/-WT and ANP+/-KO mice were mated with male wildtype ANP+/+ mice to initiate pregnancy. Cardiac size and molecular expression of the renin-angiotensin (RAS) and natriuretic peptide systems (NPS) were compared between offspring groups. Our data demonstrate that gestational hypertension and lack of maternal ANP did not significantly impact the progression and regression of pregnancy-induced cardiac hypertrophy over gestation and postpartum in ANP+/- offspring. Additionally, the molecular cardiac expression of the RAS and NPS did not differ between offspring groups. Future investigation should assess potential differences in cardiac function and the impact of fetal-programming on offspring cardiovascular adaptations during pregnancy in more severe models of pregnancy-related hypertensive syndrome such as angiotensin II or isoproterenol infusion.

Role of corin in trophoblast invasion and uterine spiral artery remodelling in pregnancy.

In pregnancy, trophoblast invasion and uterine spiral artery remodelling are important for lowering maternal vascular resistance and increasing uteroplacental blood flow. Impaired spiral artery remodelling has been implicated in pre-eclampsia, a major complication of pregnancy, for a long time but the underlying mechanisms remain unclear. Corin (also known as atrial natriuretic peptide-converting enzyme) is a cardiac protease that activates atrial natriuretic peptide (ANP), a cardiac hormone that is important in regulating blood pressure. Unexpectedly, corin expression was detected in the pregnant uterus. Here we identify a new function of corin and ANP in promoting trophoblast invasion and spiral artery remodelling. We show that pregnant corin- or ANP-deficient mice developed high blood pressure and proteinuria, characteristics of pre-eclampsia. In these mice, trophoblast invasion and uterine spiral artery remodelling were markedly impaired. Consistent with this, the ANP potently stimulated human trophoblasts in invading Matrigels. In patients with pre-eclampsia, uterine Corin messenger RNA and protein levels were significantly lower than that in normal pregnancies. Moreover, we have identified Corin gene mutations in pre-eclamptic patients, which decreased corin activity in processing pro-ANP. These results indicate that corin and ANP are essential for physiological changes at the maternal-fetal interface, suggesting that defects in corin and ANP function may contribute to pre-eclampsia.

Natriuretic peptides buffer renin-dependent hypertension.

The renin-angiotensin-aldosterone system and cardiac natriuretic peptides [atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP)] are opposing control mechanisms for arterial blood pressure. Accordingly, an inverse relationship between plasma renin concentration (PRC) and ANP exists in most circumstances. However, PRC and ANP levels are both elevated in renovascular hypertension. Because ANP can directly suppress renin release, we used ANP knockout (ANP(-/-)) mice to investigate whether high ANP levels attenuate the increase in PRC in response to renal hypoperfusion, thus buffering renovascular hypertension. ANP(-/-) mice were hypertensive and had reduced PRC compared with that in wild-type ANP(+/+) mice under control conditions. Unilateral renal artery stenosis (2-kidney, 1-clip) for 1 wk induced similar increases in blood pressure and PRC in both genotypes. Unexpectedly, plasma BNP concentrations in ANP(-/-) mice significantly increased in response to two-kidney, one-clip treatment, potentially compensating for the lack of ANP. In fact, in mice lacking guanylyl cyclase A (GC-A(-/-) mice), which is the common receptor for both ANP and BNP, renovascular hypertension was markedly augmented compared with that in wild-type GC-A(+/+) mice. However, the higher blood pressure in GC-A(-/-) mice was not caused by disinhibition of the renin system because PRC and renal renin synthesis were significantly lower in GC-A(-/-) mice than in GC-A(+/+) mice. Thus, natriuretic peptides buffer renal vascular hypertension via renin-independent effects, such as vasorelaxation. The latter possibility is supported by experiments in isolated perfused mouse kidneys, in which physiological concentrations of ANP and BNP elicited renal vasodilatation and attenuated renal vasoconstriction in response to angiotensin II.

Atrial natriuretic peptide inhibits transforming growth factor beta-induced Smad signaling and myofibroblast transformation in mouse cardiac fibroblasts.

This study tested the hypothesis that activation of atrial natriuretic peptide (ANP)/cGMP/protein kinase G signaling inhibits transforming growth factor (TGF)-beta1-induced extracellular matrix expression in cardiac fibroblasts and defined the specific site(s) at which this molecular merging of signaling pathways occurs. Left ventricular hypertrophy and fibrosis, collagen deposition, and myofibroblast transformation of cardiac fibroblasts in response to pressure overload by transverse aortic constriction were exaggerated in ANP-null mice compared with wild-type controls. ANP and cGMP inhibited TGF-beta1-induced myofibroblast transformation, proliferation, collagen synthesis, and plasminogen activator inhibitor-1 expression in cardiac fibroblasts isolated from wild-type mice. Following pretreatment with cGMP, TGF-beta1 induced phosphorylation of Smad3, but the resultant pSmad3 could not be translocated to the nucleus. pSmad3 that had been phosphorylated with recombinant protein kinase G-1alpha was analyzed by use of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and ion trap tandem mass spectrometry. The analysis revealed phosphorylation of Ser309 and Thr388 residues, sites distinct from the C-terminal Ser423/425 residues that are phosphorylated by TGF-beta receptor kinase and are critical for the nuclear translocation and down-stream signaling of pSmad3. These results suggest that phosphorylation of Smad3 by protein kinase G is a potential molecular mechanism by which activation of ANP/cGMP/protein kinase G signaling disrupts TGF-beta1-induced nuclear translocation of pSmad3 and downstream events, including myofibroblast transformation, proliferation, and expression of extracellular matrix molecules in cardiac fibroblasts. We postulate that this process contributes to the antifibrogenic effects of the natriuretic peptide in heart.

Assessment of embryonic myocardial cell differentiation using a dual fluorescent reporter system.

Recent studies have identified the existence of undifferentiated myocardial cells during early embryonic as well as post-natal stages of heart development. While primitive cells present in the precardiac mesoderm can differentiate into multiple cell types of the cardiovascular system, the developmental potential of undifferentiated cells identified in the ventricular myocardium after chamber formation is not well characterized. A deeper understanding of mechanisms regulating myocardial cell differentiation will provide further insights into the normal and pathological aspects of heart development. Here, we showed that Nkx2.5 positive and sarcomeric myosin negative cells were predominantly localized in the right ventricular myocardium of CD1 mice at E11.5 stage. We confirmed that myocardial regions negative for saromeric myosin were also devoid of atrial natriuretic factor (ANF). These observations are consistent with our previous study, which showed that ANF expression is restricted to moderately differentiated and mature myocardial cells in E11.5 myocardium of C3H/FeJ mice. Further, we found that the receptor c-Kit, a marker for early embryonic myocardial progenitor cells, is not expressed in the undifferentiated cells of the E11.5 myocardium. To monitor the differentiation potential of Nkx2.5(+)/ANF(-) cells in vitro, we developed a novel double fluorescent reporter system. Subsequently, we confirmed that the majority of Nkx2.5(+)/ANF(-) cells expressed mature myocyte markers such as sarcomeric myosin, MLC2V and alpha-cardiac actin after 48 hrs in culture, albeit at lower levels compared to Nkx2.5(+)/ANF(+) or Nkx2.5(-)/ANF(+) cell populations. Our results suggest that fluorescent reporters under the control of lineage-specific promoters can be used to study myocardial cell differentiation in response to various exogenous or pharmacological agents.

Genetic decreases in atrial natriuretic peptide and salt-sensitive hypertension.

To determine if defects in the atrial natriuretic peptide (ANP) system can cause hypertension, mice were generated with a disruption of the proANP gene. Homozygous mutants had no circulating or atrial ANP, and their blood pressures were elevated by 8 to 23 millimeters of mercury when they were fed standard (0.5 percent sodium chloride) and intermediate (2 percent sodium chloride) salt diets. On standard salt diets, heterozygotes had normal amounts of circulating ANP and normal blood pressures. However, on high (8 percent sodium chloride) salt diets they were hypertensive, with blood pressures elevated by 27 millimeters of mercury. These results demonstrate that genetically reduced production of ANP can lead to salt-sensitive hypertension.

Differential Regulation of ANP and BNP in Acute Decompensated Heart Failure: Deficiency of ANP.

OBJECTIVES: This study investigated the differential regulation of circulating atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) in patients with acute decompensated heart failure (ADHF) and tested the hypothesis that a relative deficiency of ANP exists in a subgroup of patients with ADHF. BACKGROUND: The endocrine heart releases the cardiac hormones ANP and BNP, which play a key role in cardiovascular (CV), renal, and metabolic homeostasis. In heart failure (HF), both plasma ANP and BNP are increased as a compensatory homeostatic response to myocardial overload. METHODS: ANP and BNP concentrations were measured in a small group of patients with ADHF (n = 112). To support this study's goal, a total of 129 healthy subjects were prospectively recruited to establish contemporary normal values for ANP and BNP. Plasma 3',5'cyclic guanosine monophosphate (cGMP), ejection fraction (EF), and body mass index (BMI) were measured in these subjects. RESULTS: In cases of ADHF, 74% of patients showed elevated ANP and BNP. Importantly, 26% of patients were characterized as having normal ANP (21% of this subgroup had normal ANP and elevated BNP). Cyclic GMP was lowest in the ADHF group with normal levels of ANP (p < 0.001), whereas BMI and EF were inversely related to ANP levels (p = 0.003). CONCLUSIONS: Among a subgroup of patients hospitalized with ADHF, the presence of an ANP deficiency is consistent with a differential regulation of ANP and BNP and suggests the existence of a potentially compromised compensatory cardiac endocrine response. These findings have implications for the pathophysiology, diagnostics, and therapeutics of human HF.

Pathophysiology of water and sodium retention: edematous states with normal kidney function.

Body fluid volume regulation by the kidney relies upon the complex interaction of numerous factors. However, in edematous disorders, extrarenal factors can override the 'innate wisdom' of the kidney. For example, in patients with cardiac failure or liver disease and in pregnant women, the normal kidney continues to retain sodium and water despite expanded blood, plasma and extracellular fluid volumes. Such fluid retention can ultimately lead to pulmonary congestion, ascites or peripheral edema. Understanding the kidney's modulation of total body sodium and water in these patients has been perplexing. Cardiac output cannot provide the sole afferent signal for the kidney to regulate sodium and water balance, as the normal kidney can retain excessive amounts of sodium and water when cardiac output is low (e.g. in low output cardiac failure) or high (e.g. cirrhosis or pregnancy). Therefore the integrity of the arterial circulation, which can be impaired either by a low cardiac output or arterial vasodilation, is an important factor in body fluid composition and volume regulation in health and disease.

Targeting cardiac natriuretic peptides in the therapy of diabetes and obesity.

INTRODUCTION: Atrial and B-type Natriuretic Peptides (NP) are cardiac hormones with potent cardiovascular and metabolic effects. They signal through the NPRA/cGMP system and are inactivated by a clearance receptor NPRC and neutral endopeptidases (NEP). Recombinant ANP and BNP are currently used as drug treatment for acute decompensated congestive heart failure. Recent literature indicate that a defective NP system is linked to obesity and predict the risk of type 2 diabetes (T2D). Areas covered: This article reviews recent epidemiological, clinical and preclinical evidences that NP system deficiency may be causal of obesity and T2D. The molecular mechanisms of the NP pathway in several metabolic target tissues are presented. The therapeutic potential of NP in obesity and T2D is discussed. Expert opinion: Targeting the NP pathway may offer a novel therapeutic avenue for the management of obesity and T2D. The benefit/risk of drugs increasing circulating NP levels by blocking NPRC and NEP, and/or enhancing NPRA signaling should be assessed in obese and type 2 diabetic individuals.

Dysregulation of atrial natriuretic factor in hypertension-prone man.

To evaluate the hypothesis of an atrial natriuretic factor (ANF) deficiency in hypertension-prone humans, we investigated plasma ANF and other variables in 116 white offspring of normotensive parents (ONorm) or essential hypertensive parents (OHyp). Ten ONorm and 10 OHyp, all men matched for age and body habitus, were studied after 4 days of low (70 mmol/day) and high (350 mmol/day) dietary sodium intake. After mild sodium restriction, plasma ANF did not differ between ONorm and OHyp (9.7 +/- 0.7 vs. 9.0 +/- 1.3 fmol/L). On high sodium intake, plasma ANF increased in ONorm, but not in OHyp (to 18.3 +/- 1.7 vs. 11.7 +/- 1.7 fmol/L; P less than 0.001). On the other hand, acute responses of plasma immunoreactive ANF (irANF) to saline loading or a norepinephrine-induced rise in blood pressure did not differ significantly between 8 ONorm and 8 OHyp. Fifty-one additional ONorm and 45 OHyp were evaluated during liberal sodium intake. Groups were further subdivided according to whether 24-h urinary sodium excretion was 91 mmol/m2 or less (modest salt intake) or more than 91 mmol/m2 (high salt intake). Twenty-four-hour urinary sodium was similar in the 26 ONorm and 21 OHyp on a modest salt intake (121 +/- 6 vs. 116 +/- 9 mmol) and in the 25 ONorm and the 24 OHyp on a high salt intake (226 +/- 10 vs. 221 +/- 9 mmol). However, compared with ONorm, plasma irANF in OHyp was slightly lower on modest sodium intake (7.7 +/- 0.7 vs. 5.3 +/- 0.7 fmol/L; P less than 0.05) and markedly reduced on high sodium intake (15.0 +/- 1.3 vs. 8.0 +/- 1.3 fmol/L; P less than 0.001). Moreover, the slope of the relationship between plasma irANF and 24-h urinary sodium was flatter in OHyp than in ONorm (z test = 2.4). We postulate a new endocrine syndrome characterized by a relative plasma ANF deficiency during high sodium intake in some hypertension-prone humans. This functional defect becomes apparent during chronic, rather than acute, stimulation of ANF release. It occurs as a familial disturbance and may potentially predispose to the development of hypertension.

[Atrial natriuretic factor and the structural and functional condition of the "hypertensive" heart]. / Predserdnyi natriiureticheskii faktor i strukturno-funktsional'noe sostoianie "gipertonicheskogo" serdtsa.

A radioimmunoassay was used to study the structural and functional status of the myocardium and blood natriuretic factor levels in 45 patients with hypertensive disease and 17 healthy subjects. Left atrial dysfunction was revealed to affect natriuretic factor levels in the blood of hypertensive patients with moderate left ventricular hypertrophy. As myocardial contractility became lower, natriuretic factor levels were reduced. The changes found in the levels in left ventricular hypertrophic variants may be accounted for by various values of intramyocardial stress. The findings suggest that cardiohemodynamic abnormalities may affect the secretion of natriuretic factor.

Relative atrial natriuretic peptide deficiency and inadequate renin and angiotensin II suppression in obese hypertensive men.

Obesity is a strong risk factor for hypertension, but the mechanisms by which obesity leads to hypertension are incompletely understood. On this background, we assessed dietary sodium intake, serum levels of natriuretic peptides (NPs), and the activity of the renin-angiotensin system in 63 obese hypertensive men (obeseHT: body mass index, ≥30.0 kg/m(2); 24-hour ambulatory blood pressure, ≥130/80 mm Hg), in 40 obese normotensive men (obeseNT: body mass index, ≥30.0 kg/m(2); 24-hour ambulatory blood pressure, <130/80 mm Hg), and in 27 lean normotensive men (leanNT: body mass index, 20.0-24.9 kg/m(2); 24-hour ambulatory blood pressure, <130/80 mm Hg). All study subjects were medication free. As a surrogate estimate for dietary sodium intake, we measured sodium excretion in a 24-hour urine collection and we measured serum levels of midregional proatrial NP and plasma levels of renin and angiotensin II. The obese men had higher mean (±SD) urinary sodium excretion (obeseHT, 213.6±85.2 mmol; obeseNT, 233.0±70.0 mmol) than the lean normotensive men (leanNT, 155.5±51.7 mmol; P=0.003). ObeseHT had lower (median [interquartile range]) serum midregional proatrial NP levels (49.2 [37.3-64.7] pmol/L) than leanNT (69.3 [54.3-82.9] pmol/L; P=0.003), whereas obeseNT had midregional proatrial NP levels in between (54.1 [43.2-64.7] pmol/L); obeseNT had lower (median [interquartile range]) plasma levels of renin (5.0 [3.0-8.0] mIU/L versus 9.0 [4.0-18.0]) and angiotensin II (2.4 [1.5-3.5] pmol/L versus 4.2 [2.2-7.9]) than obeseHT (P≤0.049), whereas obeseHT had similar plasma levels of renin and angiotensin II as leanNT (P≥0.19). Thus, despite a high sodium intake and a high blood pressure, obese hypertensive men have a relative NP deficiency and an inadequate renin-angiotensin system suppression.

Role of corin and atrial natriuretic peptide in preeclampsia.

In pregnancy, uterine spiral artery remodeling is an adaptive morphological change at the maternal and fetal interface, which is critical for dilating the artery and promoting blood flow to the fetus. Incompletely remodeled spiral arteries have been recognized as a common pathological feature in preeclamptic patients. To date, the molecular mechanism that controls spiral artery remodeling is not well defined. Corin is a transmembrane serine protease discovered in the heart, where it converts pro-atrial natriuretic peptide (pro-ANP) to active ANP, a cardiac hormone that regulates salt-water balance and blood pressure. Recent studies show that corin is up-regulated in the decidua of the pregnant uterus, suggesting a potential role of corin in pregnancy. In mice lacking corin or ANP, high blood pressure and proteinuria were found at late gestational stages. Histological analysis indicated delayed trophoblast invasion and impaired spiral artery remodeling in the uterus. In humans, CORIN gene mutations were identified in patients with preeclampsia. In this review, we discuss the function of corin and ANP in regulating blood pressure and their potential role in preeclampsia.

Gestational hypertension in atrial natriuretic peptide knockout mice and the developmental origins of salt-sensitivity and cardiac hypertrophy.

OBJECTIVE: To determine the effect of gestational hypertension on the developmental origins of blood pressure (BP), altered kidney gene expression, salt-sensitivity and cardiac hypertrophy (CH) in adult offspring. METHODS: Female mice lacking atrial natriuretic peptide (ANP-/-) were used as a model of gestational hypertension. Heterozygous ANP+/- offspring was bred from crossing either ANP+/+ females with ANP-/- males yielding ANP+/-(WT) offspring, or from ANP-/- females with ANP+/+ males yielding ANP+/-(KO) offspring. Maternal BP during pregnancy was measured using radiotelemetry. At 14weeks of age, offspring BP, gene and protein expression were measured in the kidney with real-time quantitative PCR, receptor binding assay and ELISA. RESULTS: ANP+/-(KO) offspring exhibited normal BP at 14weeks of age, but displayed significant CH (P<0.001) as compared to ANP+/-(WT) offspring. ANP+/-(KO) offspring exhibited significantly increased gene expression of natriuretic peptide receptor A (NPR-A) (P<0.001) and radioligand binding studies demonstrated significantly reduced NPR-C binding (P=0.01) in the kidney. Treatment with high salt diet increased BP (P<0.01) and caused LV hypertrophy (P<0.001) and interstitial myocardial fibrosis only in ANP+/-(WT) and not ANP+/-(KO) offspring, suggesting gestational hypertension programs the offspring to show resistance to salt-induced hypertension and LV remodeling. Our data demonstrate that altered maternal environments can determine the salt-sensitive phenotype of offspring.

Atrial natriuretic peptide increases inflammation, infarct size, and mortality after experimental coronary occlusion.

Acute coronary artery occlusion triggers the release of atrial natriuretic peptide (ANP) from the heart. ANP affects vasodilation, natriuresis, and inflammation, but the integrated biological effects of ANP on myocardial infarction are unknown. To elucidate these effects, the left anterior coronary artery was ligated in anesthetized, ANP-deficient (ANP(-/-)) and congenic wild-type (ANP(+/+)) mice. The survival of ANP(-/-) mice was markedly better (56%) at 30 days postinfarction than the survival of ANP(+/+) mice (20%, P < 0.01). Surviving mice were comparable initially, but ANP(-/-) mice developed more cardiac hypertrophy (P < 0.001) and had lower contractility indexes 30 days after infarction (P < 0.05). An analysis 24 h after coronary occlusion showed that ANP(-/-) mice had smaller infarcts than ANP(+/+) mice (62.6 +/- 12.1 vs. 100.8 +/- 3.8%, P < 0.001) adjusted for comparable areas at risk for ischemia. The administration of ANP to ANP(-/-) mice via osmotic minipumps significantly enlarged infarct size to levels comparable with those observed in ANP(+/+) mice (P < 0.05). There was no difference in neutrophil migration into the noninfarcted myocardium of ANP(-/-) mice undergoing actual versus sham-operated coronary occlusion. By comparison, after coronary occlusion, the neutrophil infiltration into the myocardium was enhanced in ANP(+/+) (P < 0.0005) and ANP(-/-) mice administered ANP (P < 0.0005). The expression of P-selectin, a molecule that mediates neutrophil adhesion, was significantly greater after coronary occlusion in the vasculature of ANP(+/+) or ANP(-/-) mice treated with ANP than in ANP(-/-) mice (P < 0.002). Taken together, these results indicate that ANP increases P-selectin, neutrophil infiltration, infarct size, and mortality following experimental coronary occlusion.