Structural insight into hormone recognition by the natriuretic peptide receptor-A.

Atrial natriuretic peptide (ANP) plays a central role in the regulation of blood pressure and volume. ANP activities are mediated by natriuretic peptide receptor-A (NPR-A), a single-pass transmembrane receptor harboring intrinsic guanylate cyclase activity. This study investigated the mechanism underlying NPR-A-dependent hormone recognition through the determination of the crystal structures of the NPR-A extracellular hormone-binding domain complexed with full-length ANP, truncated mutants of ANP, and dendroaspis natriuretic peptide (DNP) isolated from the venom of the green Mamba snake, Dendroaspis angusticeps. The bound peptides possessed pseudo-two-fold symmetry, despite the lack of two-fold symmetry in the primary sequences, which enabled the tight coupling of the peptide to the receptor, and evidently contributes to guanylyl cyclase activity. The binding of DNP to the NPR-A was essentially identical to that of ANP; however, the affinity of DNP for NPR-A was higher than that of ANP owing to the additional interactions between distinctive sequences in the DNP and NPR-A. Consequently, our findings provide valuable insights that can be applied to the development of novel agonists for the treatment of various human diseases.

"Meiosis arrester" C-natriuretic peptide directly stimulates oocyte mtDNA accumulation and is implicated in aging-associated oocyte mtDNA loss.

C-natriuretic peptide (CNP) is the central regulator of oocyte meiosis progression, thus coordinating synchronization of oocyte nuclear-cytoplasmic maturation. However, whether CNP can independently regulate cytoplasmic maturation has been long overlooked. Mitochondrial DNA (mtDNA) accumulation is the hallmark event of cytoplasmic maturation, but the mechanism underlying oocyte mtDNA replication remains largely elusive. Herein, we report that CNP can directly stimulate oocyte mtDNA replication at GV stage, and deficiency of follicular CNP may contribute largely to lower mtDNA copy number in in vitro matured oocytes. The mechanistic study showed that cAMP-PKA-CREB1 signaling cascade underlies the regulatory role of CNP in stimulating mtDNA replication and upregulating related genes. Of interest, we also report that CNP-NPR2 signaling is inhibited in aging follicles, and this inhibition is implicated in lower mtDNA copy number in oocytes from aging females. Together, our study provides the first direct functional link between follicular CNP and oocyte mtDNA replication, and identifies its involvement in aging-associated mtDNA loss in oocytes. These findings, not only update the current knowledge of the functions of CNP in coordinating oocyte maturation but also present a promising strategy for improving in vitro fertilization outcomes of aging females.

Serum Atrial Natriuretic Peptide, NPPA Promoter Methylation, and Cardiovascular Disease: A 10-year Follow-Up Study in Chinese Adults.

Background: Atrial natriuretic peptide (ANP) has been associated with cardiovascular disease (CVD) and related risk factors, but the clinical application is limited and the underlying mechanisms are not very clear. Here, we aimed to examine whether proANP and its coding gene methylation were associated with CVD in the Chinese population. Methods: Serum proANP and peripheral blood DNA methylation of natriuretic peptide A gene (NPPA) promoter was quantified at baseline for 2,498 community members (mean aged 53 years, 38% men) in the Gusu cohort. CVD events were obtained during 10 years of follow-up. A competing-risks survival regression model was applied to examine the prospective associations of proANP and NPPA promoter methylation with incident CVD. Results: During follow-up, 210 participants developed CVD events, 50 participants died from non-cardiovascular causes, and 214 participants were lost. Per 1-nmol/L increment of serum proANP was associated with a 22% (HR = 1.22, 95%CI: 1.03-1.44, P = 0.025) higher risk of CVD during follow-up. Of the 9 CpG sites assayed, per 2-fold increment of DNA methylation at CpG3 (located at Chr1:11908299) was significantly associated with a half lower risk of CVD (HR = 0.50, 95%CI: 0.30-0.82, P = 0.006). The gene-based analysis found that DNA methylation of the 9 CpGs at NPPA promoter as a whole was significantly associated with incident CVD (P < 0.05). Conclusions: Increased proANP and hypomethylation at NPPA promoter at baseline predicted an increased future risk of CVD in Chinese adults. Aberrant DNA methylation of the NPPA gene may participate in the mechanisms of CVD.

New insights into plant natriuretic peptide evolution: From the lysogenic conversion in Xanthomonas to the lateral transfer to the whitefly Bemisia tabaci.

Plant natriuretic peptide-like (PNP) are signaling molecules related to adaptive responses to stress. The Arabidopsis thaliana PNP (AtPNP-A) is capable of modulating catalase 2 (CAT2) and rubisco activase (RCA) activity in some circumstances. Interestingly, many plant-pathogens co-opted PNP-like molecules to their benefit. For instance, the citrus pathogen Xanthomonas citri carries a PNP-like (XacPNP) that can mimic and regulate plant homeostasis, and many phytopathogenic fungi carry effectors (e.g., Ave1 and AvrLm6) that are indeed PNP-like homologs. This work investigates the PNP-like evolution across the tree of life, revealing many parallel gains and duplications in plant and fungi kingdoms. All PNP-like proteins in the final dataset are structurally similar, containing the AtPNP-A active domains modulating CAT2 activity and RCA interaction. Comparative genomics evinced that XacPNP is a lysogenic conversion factor associated with a Myoviridae-like prophage identified in many Xanthomonas species. Surprisingly, a PNP-like homolog was identified in Bemisia tabaci, an important agricultural pest, being to date the second example of lateral gene transfer (LGT) from plant to the whitefly. Moreover, the Bemisia PNP-like homolog can also be considered a potential new effector of this phloem-feeding insect. Noteworthy, the whiteflies infest many plants carrying PNP-like copies and interact with some of their bacterial and fungal pathogens, strongly suggesting complex recipient/donor traits of PNP by LGT and bringing new insights into the evolution of host-pathogen arms race across the tree of life.

Diarrheal pathogens trigger rapid evolution of the guanylate cyclase-C signaling axis in bats.

The pathogenesis of infectious diarrheal diseases is largely attributed to enterotoxins that cause dehydration by disrupting intestinal water absorption. We investigated patterns of genetic variation in mammalian guanylate cyclase-C (GC-C), an intestinal receptor targeted by bacterially encoded heat-stable enterotoxins (STa), to determine how host species adapt in response to diarrheal infections. Our phylogenetic and functional analysis of GC-C supports long-standing evolutionary conflict with diarrheal bacteria in primates and bats, with highly variable susceptibility to STa across species. In bats, we further show that GC-C diversification has sparked compensatory mutations in the endogenous uroguanylin ligand, suggesting an unusual scenario of pathogen-driven evolution of an entire signaling axis. Together, these findings suggest that conflicts with diarrheal pathogens have had far-reaching impacts on the evolution of mammalian gut physiology.

The CR9 element is a novel mechanical load-responsive enhancer that regulates natriuretic peptide genes expression.

Enhancers regulate gene expressions in a tissue- and pathology-specific manner by altering its activities. Plasma levels of atrial and brain natriuretic peptides, encoded by the Nppa and Nppb, respectively, and synthesized predominantly in cardiomyocytes, vary depending on the severity of heart failure. We previously identified the noncoding conserved region 9 (CR9) element as a putative Nppb enhancer at 22-kb upstream from the Nppb gene. However, its regulatory mechanism remains unknown. Here, we therefore investigated the mechanism of CR9 activation in cardiomyocytes using different kinds of drugs that induce either cardiac hypertrophy or cardiac failure accompanied by natriuretic peptides upregulation. Chronic treatment of mice with either catecholamines or doxorubicin increased CR9 activity during the progression of cardiac hypertrophy to failure, which is accompanied by proportional increases in Nppb expression. Conversely, for cultured cardiomyocytes, doxorubicin decreased CR9 activity and Nppb expression, while catecholamines increased both. However, exposing cultured cardiomyocytes to mechanical loads, such as mechanical stretch or hydrostatic pressure, upregulate CR9 activity and Nppb expression even in the presence of doxorubicin. Furthermore, the enhancement of CR9 activity and Nppa and Nppb expressions by either catecholamines or mechanical loads can be blunted by suppressing mechanosensing and mechanotransduction pathways, such as muscle LIM protein (MLP) or myosin tension. Finally, the CR9 element showed a more robust and cell-specific response to mechanical loads than the -520-bp BNP promoter. We concluded that the CR9 element is a novel enhancer that responds to mechanical loads by upregulating natriuretic peptides expression in cardiomyocytes.

Assessment and Management of Cardiotoxicity in Hematologic Malignancies.

With the increasing overall survival of cancer patients due to recent discoveries in oncology, the incidence of side effects is also rising, and along with secondary malignancies, cardiotoxicity is one of the most concerning side effects, affecting the quality of life of cancer survivors. There are two types of cardiotoxicity associated with chemotherapy; the first one is acute, life-threatening but, fortunately, in most of the cases, reversible; and the second one is with late onset and mostly irreversible. The most studied drugs associated with cardiotoxicity are anthracyclines, but many new agents have demonstrated unexpected cardiotoxic effect, including those currently used in multiple myeloma treatment (proteasome inhibitors and immunomodulatory agents), tyrosine kinase inhibitors used in the treatment of chronic myeloid leukemia and some forms of acute leukemia, and immune checkpoint inhibitors recently introduced in treatment of refractory lymphoma patients. To prevent irreversible myocardial damage, early recognition of cardiac toxicity is mandatory. Traditional methods like echocardiography and magnetic resonance imaging are capable of detecting structural and functional changings, but unable to detect early myocardial damage; therefore, more sensible biomarkers like troponins and natriuretic peptides have to be introduced into the current practice. Baseline assessment of patients allows the identification of those with high risk for cardiotoxicity, while monitoring during and after treatment is important for early detection of cardiotoxicity and prompt intervention.

The endogenous ligand for guanylate cyclase-C activation reliefs intestinal inflammation in the DSS colitis model.

Ulcerative colitis (UC) is a major type of inflammatory bowel disease (IBD) and significantly impacts patient quality of life. Previous research revealed that the guanylate cyclase-C (GC-C) signaling pathway is associated with the severity of UC. We aimed to investigate the effect of the GC-C agonist, guanylin (Gn), on inflammatory injury in mice with colitis. An experimental UC model was established in Balb/c mice. Mesalamine served as a positive control. The Gn overexpression vector was administered once per day for 1 week. Intestinal permeability of the mice was measured using fluorescein isothiocyanate-dextran after the treatment. Histopathologic grading was estimated to assess the inflammatory injury of the colon. The expression level of crucial mediators of the GC-C signaling pathway (Gn, Ugn and GC-C) and tight junction proteins (occludin, claudin-1 and ZO-1) was measured in the colon. Additionally, the level of pro-inflammatory cytokines (IL-8 and TNF-α) in serum was measured. After injecting the UC mice with the Gn overexpression vector, the body weight increased, and the frequency of loose stools and bloody stools was decreased. Intestinal permeability and histopathologic score were significantly reduced (P<0.05). The expression level of GC-C, Gn, Ugn, claudin-1 and ZO-1 was significantly increased (P<0.05). The level of IL-8 and TNF-α in the serum was significantly decreased (P<0.01). Therefore, the application of Gn overexpression vector can ameliorate the intestinal inflammatory injury and repair the mucosal barrier in colitis mice, which further suggests the clinical therapeutic potential of GC-C agonists in IBD.

Assessment of causality of natriuretic peptides and atrial fibrillation and heart failure: a Mendelian randomization study in the FINRISK cohort.

AIMS: Natriuretic peptides are extensively studied biomarkers for atrial fibrillation (AF) and heart failure (HF). Their role in the pathogenesis of both diseases is not entirely understood and previous studies several single-nucleotide polymorphisms (SNPs) at the NPPA-NPPB locus associated with natriuretic peptides have been identified. We investigated the causal relationship between natriuretic peptides and AF as well as HF using a Mendelian randomization approach. METHODS AND RESULTS: N-terminal pro B-type natriuretic peptide (NT-proBNP) (N = 6669), B-type natriuretic peptide (BNP) (N = 6674), and mid-regional pro atrial natriuretic peptide (MR-proANP) (N = 6813) were measured in the FINRISK 1997 cohort. N = 30 common SNPs related to NT-proBNP, BNP, and MR-proANP were selected from studies. We performed six Mendelian randomizations for all three natriuretic peptide biomarkers and for both outcomes, AF and HF, separately. Polygenic risk scores (PRSs) based on multiple SNPs were used as genetic instrumental variable in Mendelian randomizations. Polygenic risk scores were significantly associated with the three natriuretic peptides. Polygenic risk scores were not significantly associated with incident AF nor HF. Most cardiovascular risk factors showed significant confounding percentages, but no association with PRS. A causal relation except for small causal betas is unlikely. CONCLUSION: In our Mendelian randomization approach, we confirmed an association between common genetic variation at the NPPA-NPPB locus and natriuretic peptides. A strong causal relationship between natriuretic peptides and incidence of AF as well as HF at the community-level was ruled out. Therapeutic approaches targeting natriuretic peptides will therefore very likely work through indirect mechanisms.

Epigenetic control of natriuretic peptides: implications for health and disease.

The natriuretic peptides (NPs) family, including a class of hormones and their receptors, is largely known for its beneficial effects within the cardiovascular system to preserve regular functions and health. The concentration level of each component of the family is of crucial importance to guarantee a proper control of both systemic and local cardiovascular functions. A fine equilibrium between gene expression, protein secretion and clearance is needed to achieve the final optimal level of NPs. To this aim, the regulation of gene expression and translation plays a key role. In this regard, we know the existence of fine regulatory mechanisms, the so-called epigenetic mechanisms, which target many genes at either the promoter or the 3'UTR region to inhibit or activate their expression. The gene encoding ANP (NPPA) is regulated by histone modifications, DNA methylation, distinct microRNAs and a natural antisense transcript (NPPA-AS1) with consequent implications for both health and disease conditions. Notably, ANP modulates microRNAs on its own. Histone modifications of BNP gene (NPPB) are associated with several cardiomyopathies. The proBNP processing is regulated by miR30-GALNT1/2 axis. Among other components of the NPs family, CORIN, NPRA, NPRC and NEP may undergo epigenetic regulation. A better understanding of the epigenetic control of the NPs family will allow to gain more insights on the pathological basis of common cardiovascular diseases and to identify novel therapeutic targets. The present review article aims to discuss the major achievements obtained so far with studies on the epigenetic modulation of the NPs family.

ScPNP-A, a plant natriuretic peptide from Stellera chamaejasme, confers multiple stress tolerances in Arabidopsis.

As a class of peptide hormone, plant natriuretic peptides (PNPs) play an important role in maintaining water and salt balance in plants, as well as in the physiological processes of biotic stress and pathogen resistance. However, in plants, except for some PNPs, such as the Arabidopsis thaliana PNP-A (AtPNP-A), of which the function has not yet been thoroughly revealed, few PNPs in other plants have been reported. In this study, a PNP-A (ScPNP-A) has been identified and characterized in Stellera chamaejasme for the first time. ScPNP-A is a double-psi beta-barrel (DPBB) fold containing protein and is localized in the extracellular (secreted) space. In S. chamaejasme, the expression of ScPNP-A was significantly up-regulated by salt, drought and cold stress. Changes at the physiological and biochemical levels and the expression of resistance-related genes indicated that overexpression of ScPNP-A can significantly improve salt, drought and freezing tolerance in Arabidopsis. ScPNP-A could stimulate the opening, not the closing of stomata, and its expression was not enhanced by external application of ABA. Furthermore, overexpression of ScPNP-A resulted in the elevated expression of genes in the ABA biosynthesis and reception pathway. These suggested that there may be some cross-talk between ScPNP-A and the ABA-dependent signaling pathways to regulate water related stress, however further experimentation is required to understand this relationship. In addition, overexpression of ScPNP-A can enhance the resistance to pathogens by enhancing SAR in Arabidopsis. These results indicate that ScPNP-A could function as a positive regulator in plant response to biotic stress and abiotic stress.

Tuscany Sangiovese grape juice imparts cardioprotection by regulating gene expression of cardioprotective C-type natriuretic peptide.

PURPOSE: A regular intake of red grape juice has cardioprotective properties, but its role on the modulation of natriuretic peptides (NPs), in particular of C-type NP (CNP), has not yet been proven. The aims were to evaluate: (1) in vivo the effects of long-term intake of Tuscany Sangiovese grape juice (SGJ) on the NPs system in a mouse model of myocardial infarction (MI); (2) in vitro the response to SGJ small RNAs of murine MCEC-1 under physiological and ischemic condition; (3) the activation of CNP/NPR-B/NPR-C in healthy human subjects after 7 days' SGJ regular intake. METHODS: (1) C57BL/6J male and female mice (n = 33) were randomly subdivided into: SHAM (n = 7), MI (n = 15) and MI fed for 4 weeks with a normal chow supplemented with Tuscany SGJ (25% vol/vol, 200 µl/per day) (MI + SGJ, n = 11). Echocardiography and histological analyses were performed. Myocardial NPs transcriptional profile was investigated by Real-Time PCR. (2) MCEC-1 were treated for 24 h with a pool of SGJ small RNAs and cell viability under 24 h exposure to H2O2 was evaluated by MTT assay. (3) Human blood samples were collected from seven subjects before and after the 7 days' intake of Tuscany SGJ. NPs and miRNA transcriptional profile were investigated by Real-Time PCR in MCEC-1 and human blood. RESULTS: Our experimental data, obtained in a multimodal pipeline, suggest that the long-term intake of SGJ promotes an adaptive response of the myocardium to the ischemic microenvironment through the modulation of the cardiac CNP/NPR-B/NPR-C system. CONCLUSIONS: Our results open new avenue in the development of functional foods aimed at enhancing cardioprotection of infarcted hearts through action on the myocardial epigenome.

Skeletal muscle alterations in tachycardia-induced heart failure are linked to deficient natriuretic peptide signalling and are attenuated by RAS-/NEP-inhibition.

BACKGROUND: Heart failure induced cachexia is highly prevalent. Insights into disease progression are lacking. METHODS: Early state of left ventricular dysfunction (ELVD) and symptomatic systolic heart failure (HF) were both induced in rabbits by tachypacing. Tissue of limb muscle (LM) was subjected to histologic assessment. For unbiased characterisation of early and late myopathy, a proteomic approach followed by computational pathway-analyses was performed and combined with pathway-focused gene expression analyses. Specimen of thoracic diaphragm (TD) served as control for inactivity-induced skeletal muscle alterations. In a subsequent study, inhibition of the renin-angiotensin-system and neprilysin (RAS-/NEP) was compared to placebo. RESULTS: HF was accompanied by loss of protein content (8.7±0.4% vs. 7.0±0.5%, mean±SEM, control vs. HF, p<0.01) and a slow-to-fast fibre type switch, establishing hallmarks of cachexia. In ELVD, the enzymatic set-up of LM and TD shifted to a catabolic state. A disturbed malate-aspartate shuttle went well with increased enzymes of glycolysis, forming the enzymatic basis for enforced anoxic energy regeneration. The histological findings and the pathway analysis of metabolic results drew the picture of suppressed PGC-1α signalling, linked to the natriuretic peptide system. In HF, natriuretic peptide signalling was desensitised, as confirmed by an increase in the ratio of serum BNP to tissue cGMP (57.0±18.6pg/ml/nM/ml vs. 165.8±16.76pg/ml/nM/ml, p<0.05) and a reduced expression of natriuretic peptide receptor-A. In HF, combined RAS-/NEP-inhibition prevented from loss in protein content (8.7±0.3% vs. 6.0±0.6% vs. 8.3±0.9%, Baseline vs. HF-Placebo vs. HF-RAS/NEP, p<0.05 Baseline vs. HF-Placebo, p = 0.7 Baseline vs. HF-RAS/NEP). CONCLUSIONS: Tachypacing-induced heart failure entails a generalised myopathy, preceding systolic dysfunction. The characterisation of "pre-cachectic" state and its progression is feasible. Early enzymatic alterations of LM depict a catabolic state, rendering LM prone to futile substrate metabolism. A combined RAS-/NEP-inhibition ameliorates cardiac-induced myopathy independent of systolic function, which could be linked to stabilised natriuretic peptide/cGMP/PGC-1α signalling.

Expression patterns of natriuretic peptides in pre-hibernating and hibernating Anatolian ground squirrel (Spermophilus xanthoprymnus) kidney.

Hibernation is characterized by marked suppression of renal function. Natriuretic peptides (NPs) are involved in the regulation of renal function. However, the role of NPs in the renal function during hibernation remains unclear. We aimed to investigate the distribution patterns of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) in Anatolian ground squirrel (Spermophilus xanthoprymnus) kidneys during pre-hibernation and hibernation periods. Cortical proximal tubules showed weak ANP immunoreactivity, with moderate staining on the brush border during the pre-hibernation period. In the hibernation period, moderate ANP immunoreactivity was seen in cortical proximal tubules, with very weak reaction in hibernating cortical distal tubules, medullary proximal and collecting tubules. Cortical proximal and distal tubules of both periods had strong and weak BNP immunoreactivity, respectively. Medullary proximal, distal and Henle's loop segments showed very weak BNP immunoreactivity during pre-hibernation. Medullary distal, proximal and collecting tubules and Henle's loop segments had moderate staining during hibernation. In both periods, cortical proximal tubules displayed strong immunoreactivity to CNP. Distal tubules had moderate CNP staining during pre-hibernation, albeit weak staining during hibernation. Medullary proximal tubules exhibited moderate to strong immunoreactivity during pre-hibernation. Medullary distal and proximal tubules had weak and moderate CNP staining, respectively, during pre-hibernation. In both periods, Henle's loop segments displayed moderate CNP immunoreactivity. Glomeruli had similar weak ANP, BNP and CNP staining in both periods. These results suggest that heterothermic conditions differently affected the expression of NPs in the squirrel kidney. This different expression of NPs may contribute to the renal adaptation during hibernation.

Natriuretic peptides appeared after their receptors in vertebrates.

BACKGROUND: In mammals, the natriuretic system contains three natriuretic peptides, NPPA, NPPB and NPPC, that bind to three transmembrane receptors, NPR1, NPR2 and NPR3. The natriuretic peptides are known only in vertebrates. In contrast, the receptors have orthologs in all the animal taxa and in plants. However, in non-vertebrates, these receptors do not have natriuretic properties, and most of their ligands are unknown. How was the interaction of the NP receptors and the NP established in vertebrates? Do natriuretic peptides have orthologs in non-vertebrates? If so, what was the function of the interaction? How did that function change? If not, are the NP homologous to ancestral NPR ligands? Or did the receptor's binding pocket completely change during evolution? METHODS: In the present study, we tried to determine if the pairs of natriuretic receptors and their ligands come from an ancestral pair, or if the interaction only appeared in vertebrates. Alignments, modeling, docking, research of positive selection, and motif research were performed in order to answer this question. RESULTS: We discovered that the binding pocket of the natriuretic peptide receptors was completely remodeled in mammals. We found several peptides in non vertebrates that could be related to human natriuretic peptides, but a set of clues, as well as modeling and docking analysis, suggest that the natriuretic peptides undoubtedly appeared later than their receptors during animal evolution. We suggest here that natriuretic peptide receptors in non vertebrates bind to other ligands. CONCLUSIONS: The present study further support that vertebrate natriuretic peptides appeared after their receptors in the tree of life. We suggest the existence of peptides that resemble natriuretic peptides in non-vertebrate species, that might be the result of convergent evolution.

Palmitic acid induces guanylin gene expression through the Toll-like receptor 4/nuclear factor-κB pathway in rat macrophages.

Recently, we showed that double-transgenic rats overexpressing guanylin (Gn), a bioactive peptide, and its receptor, guanylyl cyclase-C (GC-C), specifically in macrophages demonstrate an antiobesity phenotype and low-expression levels of proinflammatory cytokines in the mesenteric fat even when fed a high-fat diet. Here, we examined the levels and mechanism of Gn and GC-C transcription following saturated fatty acid and lipopolysaccharide (LPS), an activator of Toll-like receptor 4 (TLR4), exposure by using the NR8383 macrophage cell line. In addition, the levels of guanylin and cGMP were increased by addition of either palmitic acid or LPS. Next, we investigated the interaction of the gene transcription and nuclear factor-κB (NF-κB) by using an NF-κB inhibitor and chromatin immunoprecipitation assay. We showed that palmitic acid induced Gn gene expression via TLR4 and NF-κB. Moreover, we demonstrated that NF-κB binding to the Gn promoter was responsible for the induction of gene transcription by palmitic acid or LPS. Our results indicate that saturated fatty acids such as palmitic acid activate Gn gene expression via the NF-κB pathway, raising the possibility that the activated Gn-GC-C system may contribute to the inhibition of high-fat diet-induced proinflammatory cytokines in macrophages.

Relationship of Natriuretic Peptides with Left Atrial Structure and Function within 1 Month after Electrical Cardioversion in Patients with Persistent Atrial Fibrillation.

Atrial fibrillation (AF) despite the absence of heart failure is related to increased levels of natriuretic peptides (NPs). NPs have not been widely investigated in relation to left atrium (LA) function after sinus rhythm (SR) restoration and duration of AF. The aim of the study was to determine the changes of NPs levels and to define their relation with LA phasic function after electrical cardioversion (ECV). Methods. The study included 48 persistent AF patients with restored SR after ECV. NT-proANP and NT-proBNP were measured for all patients before the ECV. LA phasic function (reservoir, conduit, and pump phases) was assessed using echocardiographic volumetric analysis within the first 24 hours after ECV. Patients were repeatedly tested after 1 month in case of SR maintenance. Results. After 1 month, SR was maintained in 26 (54%) patients. For those patients, NT-proBNP decreased significantly (p=0.0001), whereas NT-proANP tended to decrease (p=0.13). Following 1 month after SR restoration, LA indexed volume decreased (p=0.0001) and all phases of LA function improved (p=<0.01). Patients with AF duration < 3 months had lower NT-proANP compared to patients with AF duration from 6 to 12 months (p = 0.005). Higher NT-proANP concentration before ECV was associated with lower LA reservoir function during the first day after SR restoration (R=-0.456, p=0.005), whereas higher NT-proBNP concentration after 1 month in SR was significantly related to lower LA reservoir function (R=-0.429, p=0.047). Conclusions. LA indexed volume, all phases of LA function, and NT-proBNP levels improved significantly following 1 month of SR restoration. Preliminary results suggest that higher baseline NT-proANP levels and higher NT-proBNP for patients with maintained SR for 1 month are related to lower LA reservoir function. The longer duration of persistent AF is associated with higher NT-proANP concentration.

Comprehensive Study of the Proteome and Transcriptome of the Venom of the Most Venomous European Viper: Discovery of a New Subclass of Ancestral Snake Venom Metalloproteinase Precursor-Derived Proteins.

The nose-horned viper, its nominotypical subspecies Vipera ammodytes ammodytes ( Vaa), in particular, is, medically, one of the most relevant snakes in Europe. The local and systemic clinical manifestations of poisoning by the venom of this snake are the result of the pathophysiological effects inflicted by enzymatic and nonenzymatic venom components acting, most prominently, on the blood, cardiovascular, and nerve systems. This venom is a very complex mixture of pharmacologically active proteins and peptides. To help improve the current antivenom therapy toward higher specificity and efficiency and to assist drug discovery, we have constructed, by combining transcriptomic and proteomic analyses, the most comprehensive library yet of the Vaa venom proteins and peptides. Sequence analysis of the venom gland cDNA library has revealed the presence of messages encoding 12 types of polypeptide precursors. The most abundant are those for metalloproteinase inhibitors (MPis), bradykinin-potentiating peptides (BPPs), and natriuretic peptides (NPs) (all three on a single precursor), snake C-type lectin-like proteins (snaclecs), serine proteases (SVSPs), P-II and P-III metalloproteinases (SVMPs), secreted phospholipases A2 (sPLA2s), and disintegrins (Dis). These constitute >88% of the venom transcriptome. At the protein level, 57 venom proteins belonging to 16 different protein families have been identified and, with SVSPs, sPLA2s, snaclecs, and SVMPs, comprise ∼80% of all venom proteins. Peptides detected in the venom include NPs, BPPs, and inhibitors of SVSPs and SVMPs. Of particular interest, a transcript coding for a protein similar to P-III SVMPs but lacking the MP domain was also found at the protein level in the venom. The existence of such proteins, also supported by finding similar venom gland transcripts in related snake species, has been demonstrated for the first time, justifying the proposal of a new P-IIIe subclass of ancestral SVMP precursor-derived proteins.

Histone Acetylation Regulates Natriuretic Peptides and Neprilysin Gene Expressions in Diabetic Cardiomyopathy and Nephropathy.

BACKGROUND: Natriuretic peptide system (NPS) alterations are involved in pathogenesis of diabetic cardiomyopathy (DCM) and nephropathy (DN), however its epigenetic regulation is still unclear. Interestingly, histone acetylation epigenetically regulates neprilysin expression in Alzheimer's disease. OBJECTIVES: The present study was aimed at delineating role of histone acetylation in regulation of NPS in DCM and DN. METHODS: Streptozotocin (55 mg/kg, i.p.)-induced diabetic male Wistar rats were used to mimic pathogenesis of DCM and DN. After haemodynamic measurements, all the rat's plasma, heart and kidney were collected for biochemistry, ELISA, protein isolation and western blotting, RT-PCR and chromatin immunoprecipitation (ChIP) assay. RESULTS: Diabetic rats heart and kidney exhibited activation of NF-κB and TGF-ß signalling with increased histone acetyl transferases (PCAF/CBP) expressions and augmented H2AK5Ac, H2BK5Ac, H3K18Ac, and H4K8Ac levels. ChIP assay results showed increased enrichment of H3K18Ac and H2BK5Ac at Nppa, Nppb (Heart) and Mme promoter (Heart/Kidney) in diabetic rats. Enrichment of H2AK5Ac was augmented on Nppa and Mme promoters in diabetic heart, while it remained unchanged on Nppb promoter in heart and Mme promoter in kidney. CONCLUSION: Augmented histone acetylation at promoter regions of NPS gene(s), at least in a part, is responsible for increased expressions of ANP, BNP and NEP in diabetic heart and kidney. Hence, histone acetylation inhibitors can be considered as novel therapeutic targets against DCM and DN.

Characteristic expressions of the natriuretic peptide family in the telencephalon of juvenile chick.

Elucidation of the genes regulating the critical (sensitive) period of imprinting behavior may shed light on the mechanism underlying neural plasticity in early childhood learning. We focused on the family of natriuretic peptides (NPs) as candidates involved in the regulation of the critical period. In avians, several structurally related molecules comprised the NP family, including renal NP (RNP), B-type NP (BNP) and C-type NP (CNP1, CNP3 and CNPP). To understand the functional roles of NPs in neural plastic changes, we aimed to characterize NPs and their receptors in chick brain. We found that CNP3 mRNA was expressed in several regions in the telencephalon, including the visual Wulst (VW, considered as mammalian visual cortex) and amygdala. CNP1 mRNA was expressed throughout the telencephalon. Using real-time PCR, the gene expression levels of NPs and their receptors (NPR1 and NPR2) were studied during and after the critical period of imprinting (post-hatching day [P]1 and P7). CNP3 mRNA was found to show higher expression in the VW of P1 chicks than in VW of P7 chicks. Moreover, the ability of these peptides to stimulate chicken NPR1 or NPR2 was tested in HEK293 cells expressing either of the receptors. The activation of NPR1 was stronger with CNP3 than with other subtypes of CNP. In the VW, CNP3-expressing cells were negative for NPR1, but they resided in the vicinity of NPR1-expressing cells. These results suggest that CNP3 and its receptor NPR1 in the VW may have functional roles in the early learning.