Determinants of inducible brain natriuretic peptide promoter activity

N-terminal Pro-B-Type Natriuretic Peptide is a Myocardial Biomarker in Pulmonary Sepsis and Septic Shock

The objective: to study changes and prognostic significance of the blood NT-proBNP in the patients with pulmonary sepsis.

Subjects and Methods. The study included 34 patients aged 54.5 ± 2.9 years with pulmonary sepsis or septic shock. Lethality in the intensive care unit (ICU) was 47.1%. NT-proBNP, procalcitonin (PCT) levels, blood lactate and hemodynamic parameters were registered on the 1st day (stage 1) and on the 4th-5th day of the ICU stay (stage 2). Hemodynamics was assessed through transpulmonary thermodilution. The differences were considered statistically significant at p < 0.05.

Results: At stage 1, NT-proBNP level was 5,220 [1,380‒17,850] pg/ml, did not decrease (p = 0.726) at stage 2 and amounted to 1,760 [631‒847] pg/ml. At stage 1, NT-proBNP correlated with extravascular lung water index (rho = 0.445; p = 0.038) and systolic pulmonary artery pressure (rho = 0.414; p = 0.023). At stage 2, NT-proBNP correlated with PCT (rho = 0.569; p = 0.003), blood lactate (rho = 0.525; p = 0.001), and mean arterial pressure to norepinephrine dosage ratio (rho = -0.422; p = 0.035). At stage 1, NT-proBNP was no predictor of lethality in the ICU: OR 1.0000; 95% CI 1.0000-1.0001. At stage 2, NT-proBNP > 4,260 pg/ml (sensitivity 87.5%, specificity 94.4%) was a predictor of lethality: OR 1.0004, 95% CI 1.0000-1.0008, p = 0.046 (AUC 0.893, 95% CI 0.732-0.974). Any increase of NT-proBNP level (> 0 pg/ml) between stages 2 and 1 was a predictor of lethality (sensitivity 87.5%, specificity 94.4%): OR 119.0, 95% CI 9.7432‒1,453.4241, p = 0.0002 (AUC 0.903, 95% CI 0.751-0.977).

Conclusion: Patients with pulmonary sepsis are characterized by a significant increase of blood NT-proBNP. At stage 1, the biomarker correlated with pulmonary hypertension and moderate pulmonary edema and was no predictor of lethality. At stage 2, NT-proBNP correlated with the indices of infection and sepsis severity (procalcitonin, blood lactate, and mean arterial blood pressure/norepinephrine dosage ratio). At this stage, NT-proBNP levels greater than 4,000 pg/mL and/or any degree of increase in blood levels of the biomarker were both sensitive and specific predictors of a lethal outcome. Specific features of etiopathogenesis of BNP hyperproduction in pulmonary sepsis make it difficult to interpret the elevation of NT-proBNP as an indicator of septic cardiomyopathy but does not reduce its value as a sensitive and specific predictor of lethality.

B-Type Natriuretic Peptide (BNP) Revisited—Is BNP Still a Biomarker for Heart Failure in the Angiotensin Receptor/Neprilysin Inhibitor Era?

Simple Summary

Active BNP-32, less active proBNP-108, and inactive N-terminal proBNP-76 all circulate in the blood. The circulating protease neprilysin has lower substrate specificity for BNP than ANP, while proBNP and N-terminal proBNP are not degraded by neprilysin. Currently available BNP immunoassays react with both mature BNP and proBNP; therefore, measured plasma BNP is mature BNP + proBNP. Because ARNI administration increases mature BNP, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI administration reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase of mature BNP due to inhibition of degradation by neprilysin, resulting in lower plasma BNP levels. In the ARNI era, BNP remains a useful biomarker for heart failure, though mild increases early during ARNI administration should be taken into consideration.

Abstract

Myocardial wall stress, cytokines, hormones, and ischemia all stimulate B-type (or brain) natriuretic peptide (BNP) gene expression. Within the myocardium, ProBNP-108, a BNP precursor, undergoes glycosylation, after which a portion is cleaved by furin into mature BNP-32 and N-terminal proBNP-76, depending on the glycosylation status. As a result, active BNP, less active proBNP, and inactive N-terminal proBNP all circulate in the blood. There are three major pathways for BNP clearance: (1) cellular internalization via natriuretic peptide receptor (NPR)-A and NPR-C; (2) degradation by proteases in the blood, including neprilysin, dipeptidyl-peptidase-IV, insulin degrading enzyme, etc.; and (3) excretion in the urine. Because neprilysin has lower substrate specificity for BNP than atrial natriuretic peptide (ANP), the increase in plasma BNP after angiotensin receptor neprilysin inhibitor (ARNI) administration is much smaller than the increase in plasma ANP. Currently available BNP immunoassays react with both mature BNP and proBNP. Therefore, BNP measured with an immunoassay is mature BNP + proBNP. ARNI administration increases mature BNP but not proBNP, as the latter is not degraded by neprilysin. Consequently, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase in mature BNP mediated by inhibiting degradation by neprilysin, which lowers plasma BNP levels. These results suggest that even in the ARNI era, BNP can be used for diagnosis and assessment of the pathophysiology and prognosis of heart failure, though the mild increases early during ARNI administration should be taken into consideration.

Cardiac natriuretic peptides

Investigations into the mixed muscle-secretory phenotype of cardiomyocytes from the atrial appendages of the heart led to the discovery that these cells produce, in a regulated manner, two polypeptide hormones - the natriuretic peptides - referred to as atrial natriuretic factor or atrial natriuretic peptide (ANP) and brain or B-type natriuretic peptide (BNP), thereby demonstrating an endocrine function for the heart. Studies on the gene encoding ANP (NPPA) initiated the field of modern research into gene regulation in the cardiovascular system. Additionally, ANP and BNP were found to be the natural ligands for cell membrane-bound guanylyl cyclase receptors that mediate the effects of natriuretic peptides through the generation of intracellular cGMP, which interacts with specific enzymes and ion channels. Natriuretic peptides have many physiological actions and participate in numerous pathophysiological processes. Important clinical entities associated with natriuretic peptide research include heart failure, obesity and systemic hypertension. Plasma levels of natriuretic peptides have proven to be powerful diagnostic and prognostic biomarkers of heart disease. Development of pharmacological agents that are based on natriuretic peptides is an area of active research, with vast potential benefits for the treatment of cardiovascular disease.

Atrial and brain natriuretic peptides: Hormones secreted from the heart

The natriuretic peptide family consists of three biologically active peptides: atrial natriuretic peptide (ANP), brain (or B-type) natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). Among these, ANP and BNP are secreted by the heart and act as cardiac hormones. Both ANP and BNP preferentially bind to natriuretic peptide receptor-A (NPR-A or guanylyl cyslase-A) and exert similar effects through increases in intracellular cyclic guanosine monophosphate (cGMP) within target tissues. Expression and secretion of ANP and BNP are stimulated by various factors and are regulated via multiple signaling pathways. Human ANP has three molecular forms, α-ANP, β-ANP, and proANP (or γ-ANP), with proANP predominating in healthy atrial tissue. During secretion proANP is proteolytically processed by corin, resulting in secretion of bioactive α-ANP into the peripheral circulation. ProANP and β-ANP are minor forms in the circulation but are increased in patients with heart failure. The human BNP precursor proBNP is proteolytically processed to BNP_1-32 and N-terminal proBNP (NT-proBNP) within ventricular myocytes. Uncleaved proBNP as well as mature BNP_1-32 and NT-proBNP is secreted from the heart, and its secretion is increased in patients with heart failure. Mature BNP, its metabolites including BNP_3-32, BNP_4-32, and BNP_5-32, and proBNP are all detected as immunoreactive-BNP by the current BNP assay system. We recently developed an assay system that specifically detects human proBNP. Using this assay system, we observed that miR30-GALNTs-dependent O-glycosylation in the N-terminal region of proBNP contributes to regulation of the processing and secretion of proBNP from the heart.

N-terminal pro-B-type natriuretic peptide diagnostic algorithm versus American Heart Association algorithm for Kawasaki disease

BACKGROUND

Diagnosis of Kawasaki disease (KD) can be challenging in the absence of a confirmatory test or pathognomonic finding, especially when clinical criteria are incomplete. We recently proposed serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) as an adjunctive diagnostic test.

METHODS

We retrospectively tested a new algorithm to help KD diagnosis based on NT-proBNP, coronary artery dilation (CAD) at onset, and abnormal serum albumin or C-reactive protein (CRP). The goal was to assess the performance of the algorithm and compare its performance with that of the 2004 American Heart Association (AHA)/American Academy of Pediatrics (AAP) algorithm.

RESULTS

The algorithm was tested on 124 KD patients with NT-proBNP measured on admission at the present institutions between 2007 and 2013. Age at diagnosis was 3.4 ± 3.0 years, with a median of five diagnostic criteria; and 55 of the 124 patients (44%) had incomplete KD. CA complications occurred in 64 (52%), with aneurysm in 14 (11%). Using this algorithm, 120/124 (97%) were to be treated, based on high NT-proBNP alone for 79 (64%); on onset CAD for 14 (11%); and on high CRP or low albumin for 27 (22%). Using the AHA/AAP algorithm, 22/47 (47%) of the eligible patients with incomplete KD would not have been referred for treatment, compared with 3/55 (5%) with the NT-proBNP algorithm (P < 0.001).

CONCLUSION

This NT-proBNP-based algorithm is efficient to identify and treat patients with KD, including those with incomplete KD. This study paves the way for a prospective validation trial of the algorithm.

Different Effects of Phase Advance and Delay in Rotating Light-Dark Regimens on Clock and Natriuretic Peptide Gene Expression in the Rat Heart

Under physiological conditions the mammalian circadian system is synchronized to a cyclic environment. The central oscillator in the suprachiasmatic nuclei (SCN) responds predominantly to an external light (L) dark (D) cycle. Peripheral oscillators are more efficiently synchronized by metabolic cues. When the circadian system is exposed to opposing synchronizing cues, peripheral oscillators uncouple from the SCN. To consider influence of phase advances and delays in light regimens mimicking shift work, we analyzed the expression of clock genes (per2, bmal1) and natriuretic peptides (anp, bnp) in the heart of male rats. Experimental groups were exposed to a rotating LD regimen with either 8 h phase advance or delay for 11 weeks. Samples were taken for a 24 h cycle in 4 h intervals. Peripheral oscillators responded to rotating phase advance by decreasing rhythm robustness, while phase delay mostly influenced the phase angle between the acrophase of rhythmic gene expression and the external LD cycle. The expression of anp was arrhythmic in the heart of control rats and was not influenced by rotating LD regimens. The expression of bnp showed a daily rhythm with a nadir during the active phase. The daily rhythm in bnp expression diminished under rotating LD regimen conditions.

Transcriptional regulation of the fetal cardiac gene program

Reactivation of the fetal cardiac gene program in adults is a reliable marker of cardiac hypertrophy and heart failure. Normally, genes within this group are expressed in the fetal ventricles during development, but are silent after birth. However, their expression is re-induced in the ventricular myocardium in response to various cardiovascular diseases, and potentially plays an important role in the pathological process of cardiac remodeling. Thus, analysis of the molecular mechanisms that govern the expression of fetal cardiac genes could lead to the discovery of transcriptional regulators and signaling pathways involved in both cardiac differentiation and cardiac disease. In this review we will summarize what is currently known about the transcriptional regulation of the fetal cardiac gene program.

Atrial natriuretic peptides in Han Wistar, Sprague-Dawley and spontaneously hypertensive rats

The atrial natriuretic peptide (ANP) and its precursor (N-terminal fragment of atrial natriuretic peptide, NT-proANP) are natriuretic peptides released into the circulation as a consequence of an acute atrial stretch. As for the brain natriuretic peptide and its N-terminal fragment, the biological significance of ANP and NT-proANP has been widely studied in humans, but the literature is lacking information about the determination of these biomarkers in veterinary medicine and, in particular, in the toxicological species used in preclinical pharmaceutical drug development. This paper describes the evaluation of ANP and NT-proANP levels in a healthy population of Han Wistar and Sprague-Dawley rats, as well as in a rodent model of hypertension (Spontaneously Hypertensive rats). Both biomarkers were measured by mean of two commercially available enzyme immunoassays and serum levels were correlated with heart weight and histopathological findings in the heart, with the aim of building an integrated assessment of the significance of these biomarkers. Results obtained demonstrated that NT-proANP and ANP can be accurately measured in the different rat strains, with NT-proANP concentrations higher than those of ANP, as expected because of its longer half-life. In addition, both correlated well with cardiac hypertrophy evaluated by means of heart weight and histopathological examination. NT-proANP and ANP represent reliable markers of cardiac hypertrophy in the rat.

Blood N-terminal proBNP as a potential indicator of cardiac preload in patients with high volume load

Stroke volume is mainly determined by preload, afterload and contractility. Accordingly, measuring cardiac preload provides essential information for treatment of hemodynamically unstable patients. Hemodynamic monitoring is widely used to measure cardiac preload, but the monitoring method is time-consuming and invasive. It is therefore important to establish a simple and non-invasive test for monitoring cardiac preload. Brain natriuretic peptide (BNP), which lowers systemic vascular resistance, is synthesized as proBNP in response to myocardial wall stretch, and blood BNP has been used as an indicator of preload. Here, we measured blood level of N-terminal proBNP (NT-proBNP), which is generated during processing of proBNP, because NT-proBNP is stable and easily measured at the bedside. To assess the correlation between blood NT-proBNP and preload, we also measured the global end-diastolic volume index (GEDVI) that reflects the cardiac preload. GEDVI was calculated with the volumes in all chambers of the heart at the time of end-diastole. Eight male patients (57.6 +/- 25.3 years old) with high volume load (1,000 ml within 4 hours) were included in the present study: 3 subjects with burn, 3 subjects with sepsis, a patient with alcoholic ketoacidosis and a resuscitated patient. Blood levels of NT-proBNP were 1,316.3 +/- 1,154.5 pg/ml (47 blood samples from the eight patients; the normal range, < 125 pg/ml). Notably, the increase in the NT-proBNP levels was associated with the increased GEDVI (r = 0.61, p < 0.0001). Therefore, blood NT-proBNP may be a good indicator of cardiac preload in patients with high volume load.

Myocardin-related transcription factor A is a common mediator of mechanical stress- and neurohumoral stimulation-induced cardiac hypertrophic signaling leading to activation of brain natriuretic peptide gene expression

Subjecting cardiomyocytes to mechanical stress or neurohumoral stimulation causes cardiac hypertrophy characterized in part by reactivation of the fetal cardiac gene program. Here we demonstrate a new common mechanism by which these stimuli are transduced to a signal activating the hypertrophic gene program. Mechanically stretching cardiomyocytes induced nuclear accumulation of myocardin-related transcription factor A (MRTF-A), a coactivator of serum response factor (SRF), in a Rho- and actin dynamics-dependent manner. Expression of brain natriuretic peptide (BNP) and other SRF-dependent fetal cardiac genes in response to acute mechanical stress was blunted in mice lacking MRTF-A. Hypertrophic responses to chronic pressure overload were also significantly attenuated in mice lacking MRTF-A. Mutation of a newly identified, conserved and functional SRF-binding site within the BNP promoter, or knockdown of MRTF-A, reduced the responsiveness of the BNP promoter to mechanical stretch. Nuclear translocation of MRTF-A was also involved in endothelin-1- and angiotensin-II-induced activation of the BNP promoter. Moreover, mice lacking MRTF-A showed significantly weaker hypertrophic responses to chronic angiotensin II infusion than wild-type mice. Collectively, these findings point to nuclear translocation of MRTF-A as a novel signaling mechanism mediating both mechanical stretch- and neurohumoral stimulation-induced BNP gene expression and hypertrophic responses in cardiac myocytes.

B-type natriuretic peptide as a marker of heart failure: new insights from biochemistry and clinical implications

The mature, biologically active 32-amino acid long B-type natriuretic peptide (BNP(1-32)), is cleaved by corin from the BNP prohormone. Recent data demonstrated that BNP(1-32) might be an ideal substrate for the endogenous aminopeptidase, dipeptidyl-peptidase (DPP) IV. DPP IV removes the two amino-terminal amino acids (Ser and Pro) from BNP(1-32) to produce BNP(3-32), which has been detected in plasma of patients with heart failure. In a canine model, intravenous BNP(3-32) infusion resulted in less natriuresis, diuresis and vasodilation compared to intravenous infusion of BNP(1-32). The clinical relevance of these observations may be important for patients with high plasma BNP concentrations, which can be measured by commercially available immunoassays. Further studies are needed to explore whether DPP IV inhibitors increase the bioavailability of BNP(1-32), delay the progression of heart failure and increase the efficacy of exogenously administered BNP(1-32) in decompensated heart failure.

Cardiac hormones ANF and BNP modulate proliferation in the unidirectional mixed lymphocyte reaction

BACKGROUND

Previous investigations have shown that the plasma levels of the cardiac hormone brain natriuretic peptide (BNP) increase during acute cardiac allograft rejection as diagnosed by endomyocardial biopsy. Successful immunosuppressant treatment decreased plasma BNP levels, suggesting a role for BNP in transplantation immunity. We tested a possible immunomodulatory effect of the natriuretic peptides (NPs) BNP, atrial natriuretic factor (ANF), and C-type NP (CNP) using the unidirectional mixed lymphocyte reaction (MLR).

METHODS

Lymphocytes were isolated from the lymph nodes of Brown Norway (BN) and Lewis (L) rats. BN lymphocytes were gamma-irradiated to inhibit DNA synthesis. Lymphocytes at 2.5 x 10(6) cell/ml were mixed (at an L:BN ratio of 4:1) and incubated. On Days 2 and 3, ANF (10(-6) to 10(-11) mol/liter), BNP (10(-5) to 10(-11) mol/liter), or CNP (10(-6) to 10(-12) mol/liter) were added. Cell proliferation was measured on Day 4.

RESULTS

Reverse transcript-polymerase chain reaction (RT-PCR) analysis of BN and L lymphocytes detected NP receptor (NPR) mRNA amplicons of the expected size. MLR induced an increase in relative receptor abundance as follows: NPRA > NPRB > NPRC. ANF and BNP significantly inhibited up to approximately 50% lymphocyte proliferation in a dose-dependent manner in the range of 10(-11) to 10(-6) mol/liter, whereas CNP significantly decreased lymphocyte proliferation only modestly (approximately 20%) at 10(-8) mol/liter and at 10(-6) mol/liter.

CONCLUSIONS

Both ANF and BNP have immunomodulatory functions, although the response to cardiac rejection observed clinically involves increases in plasma levels of BNP only. This is likely related to BNP gene promoter sequences previously reported to be responsive to specific cytokines and related substances. The modulation of the MLR by NP suggests a possible clinical use of these peptides in transplantation immunity.

Hypoxia induces B-type natriuretic peptide release in cell lines derived from human cardiomyocytes

B-type natriuretic peptide (BNP) is a peptide hormone of myocardial origin with significant cardioprotective properties. Patients with myocardial ischemia present with high levels of BNP in plasma and elevated expression in the myocardium. However, the molecular mechanisms of BNP induction in the ischemic myocardium are not well understood. The aim of the investigation was to assess whether myocardial hypoxia induces the production of BNP in human ventricular myocytes. To test the hypothesis that reduced oxygen tension can directly stimulate BNP gene expression and release in the absence of hemodynamic or neurohormonal stimuli, we used an in vitro model system of cultured human ventricular myocytes (AC16 cells). Cells were cultured under normoxic (21% O2) or hypoxic (5% O2) conditions for up to 48 h. The accumulation of BNP, atrial natriuretic peptide (ANP), and vascular endothelial growth factor (VEGF) was then measured. Hypoxia stimulated the protein release of BNP and VEGF but not ANP. In concordance, the increased mRNA levels of BNP and VEGF but not ANP were found on culturing AC16 cells under hypoxic conditions. The analysis of the transcriptional activity of the hypoxia-inducible factor 1 (HIF-1) in nuclear extracts showed that HIF-1 activity was induced under hypoxic conditions. Finally, the treatment of AC16 cells with the HIF-1 inhibitor rotenone in hypoxia inhibited BNP and VEGF release. In conclusion, these data indicate that hypoxia induces the synthesis and secretion of BNP in human ventricular myocytes, likely through HIF-1-enhanced transcriptional activity.

Dipeptidyl-peptidase IV and B-type natriuretic peptide. From bench to bedside

B-type natriuretic peptide (BNP) has emerged as a reliable biomarker in patients with congestive heart failure. The mature, biologically active B-type natriuretic peptide, BNP

Clin Chem Lab Med 2009;47:248–52.

Angiotensin II receptor antagonism reverts the selective cardiac BNP upregulation and secretion observed in myocarditis

The cardiac natriuretic peptides atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP) are discoordinately regulated in myocardial inflammation associated with acute allograft rejection in humans and during in vitro exposure of cardiocyte cultures to some proinflammatory cytokines. We used experimental autoimmune myocarditis (EAM) to determine whether the discoordinate regulation of ANF and BNP was specific to the situations above or was generally associated with other types of myocardial inflammation. The dependency of this process to angiotensin signaling was also determined, given that previous work demonstrated beneficial effects of the angiotensin receptor blocker olmesartan in myocarditis. Histopathological changes, plasma and cardiac ANF, BNP, and selected cytokines gene expression as well as plasma cytokine levels using a cytokine array were determined in EAM, angiotensin receptor blocker-treated, and control rats. It was found that EAM specifically increases BNP but not ANF circulating levels, thus mimicking the findings in acute cardiac allograft rejection and the effect of some proinflammatory cytokines on cardiocyte cultures in vitro. Plasma cytokine array and real-time PCR revealed that lipopolysaccharide-induced CXC chemokine, monocyte chemotactic protein-1, and tissue inhibitor of metalloproteinase-1 were increased in plasma and in the myocardium of EAM rats. Olmesartan treatment reversed virtually all neuroendocrine and histopathological cardiac changes induced by EAM, thus providing a mechanistic insight into this phenomenon. It is concluded that the inflammatory process contributes specific cytokines, leading to the disregulation of cardiac ANF and BNP production observed during myocardial inflammation, and that this process is angiotensin receptor 1 dependent.

Phenomic, convergent functional genomic, and biomarker studies in a stress-reactive genetic animal model of bipolar disorder and co-morbid alcoholism

We had previously identified the clock gene D-box binding protein (Dbp) as a potential candidate gene for bipolar disorder and for alcoholism, using a Convergent Functional Genomics (CFG) approach. Here we report that mice with a homozygous deletion of DBP have lower locomotor activity, blunted responses to stimulants, and gain less weight over time. In response to a chronic stress paradigm, these mice exhibit a diametric switch in these phenotypes. DBP knockout mice are also activated by sleep deprivation, similar to bipolar patients, and that activation is prevented by treatment with the mood stabilizer drug valproate. Moreover, these mice show increased alcohol intake following exposure to stress. Microarray studies of brain and blood reveal a pattern of gene expression changes that may explain the observed phenotypes. CFG analysis of the gene expression changes identified a series of novel candidate genes and blood biomarkers for bipolar disorder, alcoholism, and stress reactivity.

Predictive value of N-terminal pro-brain natriuretic peptide in severe sepsis and septic shock

OBJECTIVE

The aim of this study was to evaluate the predictive value of N-terminal pro-brain natriuretic peptide (NT-proBNP) on mortality in a large, unselected patient population with severe sepsis and septic shock.

DESIGN AND SETTING

Prospective observational cohort study about incidence and prognosis of sepsis in 24 intensive care units in Finland (the FINNSEPSIS study).

PATIENTS

A total of 254 patients with severe sepsis or septic shock.

MEASUREMENTS

After informed consent, the blood tests for NT-proBNP analyses were drawn on the day of admission and 72 hrs thereafter. Patients' demographic data were collected, and intensive care unit and hospital mortality and basic hemodynamic and laboratory data were recorded daily.

MAIN RESULTS

NT-proBNP levels at admission were significantly higher in hospital nonsurvivors (median, 7908 pg/mL) compared with survivors (median, 3479 pg/mL; p = .002), and the difference remained after 72 hrs (p = .002). The receiver operating characteristic curves of admission and 72-hr NT-proBNP levels for hospital mortality resulted in area under the curve values of 0.631 (95% confidence interval, 0.549-0.712; p = .002) and 0.648 (95% confidence interval, 0.554-0.741; p = .002), respectively. In logistic regression analyses, NT-proBNP values at 72 hrs after inclusion and Simplified Acute Physiology Score for the first 24 hrs were independent predictors of hospital mortality. Pulmonary artery occlusion pressure (p < .001), plasma creatinine clearance (p = .001), platelet count (p = .03), and positive blood culture (p = .04) had an independent effect on first-day NT-proBNP values, whereas after 72 hrs, only plasma creatinine clearance (p < .001) was significant in linear regression analysis.

CONCLUSION

NT-proBNP values are frequently increased in severe sepsis and septic shock. Values are significantly higher in nonsurvivors than survivors. NT-proBNP on day 3 in the intensive care unit is an independent prognostic marker of mortality in severe sepsis.

Bladder inflammatory transcriptome in response to tachykinins: neurokinin 1 receptor-dependent genes and transcription regulatory elements

BACKGROUND

Tachykinins (TK), such as substance P, and their neurokinin receptors which are ubiquitously expressed in the human urinary tract, represent an endogenous system regulating bladder inflammatory, immune responses, and visceral hypersensitivity. Increasing evidence correlates alterations in the TK system with urinary tract diseases such as neurogenic bladders, outflow obstruction, idiopathic detrusor instability, and interstitial cystitis. However, despite promising effects in animal models, there seems to be no published clinical study showing that NK-receptor antagonists are an effective treatment of pain in general or urinary tract disorders, such as detrusor overactivity. In order to search for therapeutic targets that could block the tachykinin system, we set forth to determine the regulatory network downstream of NK1 receptor activation. First, NK1R-dependent transcripts were determined and used to query known databases for their respective transcription regulatory elements (TREs).

METHODS

An expression analysis was performed using urinary bladders isolated from sensitized wild type (WT) and NK1R-/- mice that were stimulated with saline, LPS, or antigen to provoke inflammation. Based on cDNA array results, NK1R-dependent genes were selected. PAINT software was used to query TRANSFAC database and to retrieve upstream TREs that were confirmed by electrophoretic mobility shift assays.

RESULTS

The regulatory network of TREs driving NK1R-dependent genes presented cRel in a central position driving 22% of all genes, followed by AP-1, NF-kappaB, v-Myb, CRE-BP1/c-Jun, USF, Pax-6, Efr-1, Egr-3, and AREB6. A comparison between NK1R-dependent and NK1R-independent genes revealed Nkx-2.5 as a unique discriminator. In the presence of NK1R, Nkx2-5 _01 was significantly correlated with 36 transcripts which included several candidates for mediating bladder development (FGF) and inflammation (PAR-3, IL-1R, IL-6, alpha-NGF, TSP2). In the absence of NK1R, the matrix Nkx2-5_02 had a predominant participation driving 8 transcripts, which includes those involved in cancer (EYA1, Trail, HSF1, and ELK-1), smooth-to-skeletal muscle trans-differentiation, and Z01, a tight-junction protein, expression. Electrophoretic mobility shift assays confirmed that, in the mouse urinary bladder, activation of NK1R by substance P (SP) induces both NKx-2.5 and NF-kappaB translocations.

CONCLUSION

This is the first report describing a role for Nkx2.5 in the urinary tract. As Nkx2.5 is the unique discriminator of NK1R-modulated inflammation, it can be imagined that in the near future, new based therapies selective for controlling Nkx2.5 activity in the urinary tract may be used in the treatment in a number of bladder disorders.

The repressor element 1-silencing transcription factor regulates heart-specific gene expression using multiple chromatin-modifying complexes

Cardiac hypertrophy is associated with a dramatic change in the gene expression profile of cardiac myocytes. Many genes important during development of the fetal heart but repressed in the adult tissue are reexpressed, resulting in gross physiological changes that lead to arrhythmias, cardiac failure, and sudden death. One transcription factor thought to be important in repressing the expression of fetal genes in the adult heart is the transcriptional repressor REST (repressor element 1-silencing transcription factor). Although REST has been shown to repress several fetal cardiac genes and inhibition of REST function is sufficient to induce cardiac hypertrophy, the molecular mechanisms employed in this repression are not known. Here we show that continued REST expression prevents increases in the levels of the BNP (Nppb) and ANP (Nppa) genes, encoding brain and atrial natriuretic peptides, in adult rat ventricular myocytes in response to endothelin-1 and that inhibition of REST results in increased expression of these genes in H9c2 cells. Increased expression of Nppb and Nppa correlates with increased histone H4 acetylation and histone H3 lysine 4 methylation of promoter-proximal regions of these genes. Furthermore, using deletions of individual REST repression domains, we show that the combined activities of two domains of REST are required to efficiently repress transcription of the Nppb gene; however, a single repression domain is sufficient to repress the Nppa gene. These data provide some of the first insights into the molecular mechanism that may be important for the changes in gene expression profile seen in cardiac hypertrophy.

Evidence for Functional Heterogeneity of Circulating B-Type Natriuretic Peptide

OBJECTIVES

These studies describe molecular forms of circulating B-type natriuretic peptide (BNP) as well as their biological activity.

BACKGROUND

Increased circulating levels of immunoreactive BNP correlate with the severity of heart failure and are considered a sensitive biomarker. However, little is known about the molecular forms of circulating BNP and their biological activity.

METHODS

Western blot analysis was used to characterize immunoreactive BNP species in heart failure plasma. Recombinant proBNP was assessed for reactivity in commercially available BNP assays and cell activity by cyclic guanosine monophosphate production in vascular cells.

RESULTS

Heart failure plasma contained both low- (LMW-BNP) and high-molecular-weight (HMW-BNP) forms. The LMW-BNP migrated similarly to a 32-amino acid BNP standard, whereas HMW-BNP, when deglycosylated, was similar to deglycosylated recombinant proBNP. Recombinant proBNP and BNP were equally recognized by the Triage BNP assay (Biosite, San Diego, California). Furthermore, recombinant proBNP and BNP were both recognized by the Advia Centaur BNP test (Bayer Diagnostics, Tarrytown, New York), but only recombinant proBNP was recognized by the Elecsys NTproBNP assay (Roche Diagnostics, Indianapolis, Indiana). Recombinant proBNP exerted significantly less biological activity than BNP on human endothelial and vascular smooth muscle cells. Comparison of effective concentration (50%) values indicates that proBNP is 6- to 8-fold less potent than BNP in these human cells.

CONCLUSIONS

This study demonstrates that proBNP, constituting a substantial portion of immunoreactive BNP in heart failure plasma, possesses significantly lower biological activity than the processed 32-amino acid hormone. These results implicate a discordance in heart failure between the high circulating levels of immunoreactive BNP and hormone activity, suggesting that some patients may be in a state of natriuretic peptide deficiency.

Natriuretic peptide testing for the evaluation of critically ill patients with shock in the intensive care unit: a prospective cohort study

Introduction

Amino-terminal pro-brain natriuretic peptide (NT-proBNP) is useful in evaluating heart failure, but its role in evaluating patients with shock in the intensive care unit (ICU) is not clear.

Method

Forty-nine consecutive patients in four different ICUs with shock of various types and with an indication for pulmonary artery catheter placement were evaluated. Analyses for NT-proBNP were performed on blood obtained at the time of catheter placement and results were correlated with pulmonary artery catheter findings. Logistic regression identified independent predictors of mortality.

Results

A wide range of NT-proBNP levels were observed (106 to >35,000 pg/ml). There was no difference in median NT-proBNP levels between patients with a cardiac and those with a noncardiac origin to their shock (3,046 pg/ml versus 2,959 pg/ml; P = 0.80), but an NT-proBNP value below 1,200 pg/ml had a negative predictive value of 92% for cardiogenic shock. NT-proBNP levels did not correlate with filling pressures or hemodynamics (findings not significant). NT-proBNP concentrations were higher in patients who died in the ICU (11,859 versus 2,534 pg/ml; P = 0.03), and the mortality rate of patients in the highest log-quartile of NT-proBNP (66.7%) was significantly higher than those in other log-quartiles (P < 0.001); NT-proBNP independently predicted ICU mortality (odds ratio 14.8, 95% confidence interval 1.8–125.2; P = 0.013), and was superior to Acute Physiology and Chronic Health Evaluation II score and brain natriuretic peptide in this regard.

Conclusion

Elevated levels of NT-proBNP do not necessarily correlate with high filling pressures among patients with ICU shock, but marked elevation in NT-proBNP is strongly associated with ICU death. Low NT-proBNP values in patients with ICU shock identifed those at lower risk for death, and may be useful in excluding the need for pulmonary artery catheter placement in such patients.

Intrathecal and Systemic Concentration of NT-proBNP in Patients with Severe Traumatic Brain Injury

Outcome of patients suffering from traumatic brain injury (TBI) depends on the development of secondary brain damage. In this context, recent studies underlined the role of the natriuretic peptides- atrial natriuretic peptide and brain natriuretic peptide (BNP)-in aneurysmatic subarachnoidal hemorrhage (SAH). Especially BNP correlates with intracranial pressure and clinical outcome after SAH. Since its role in TBI remains unclear, the intracranial and systemic concentrations of N-terminal (NT)-proBNP were analyzed in patients suffering from severe TBI. We measured NT-proBNP levels in cerebrospinal fluid (CSF) and serum of 14 patients suffering from severe TBI (GCS<or=8 points) and 10 healthy control patients, using proBNP assay (Roche Diagnostics). Samples were collected after placement of a ventricular catheter, and at 12, 24, 48, and 72 h after TBI. CSF/serum albumin ratio (Q<a) was daily calculated. At 90 days after TBI, outcome was evaluated using the Glasgow Outcome Scale (GOS). In patients exhibiting a mean ICP of >15 mm Hg (n=6), the serum (800+/-150 pg/mL) and CSF levels (55+/-9 pg/mL) of NT-proBNP were significantly increased after 24 h, as compared to patients with ICP<or=15 mm of Hg (n=8) as well as to control group. However, Qa as well as GOS did not significantly differ among both groups. For the first time, we evaluated intrathecal and systemic NT-proBNP concentrations in patients suffering from severe TBI. Interestingly, NT-proBNP in CSF and serum was significantly elevated in patients exhibiting an ICP of >15 mm Hg. Further studies are currently performed to elucidate the physiologic role of NT-proBNP in TBI.