Atrial natriuretic peptide signal pathway upregulated in stomach of streptozotocin-induced diabetic mice

AIM:To investigate atrial natriuretic peptide(ANP) secretion from gastric mucosa and the relationship between the ANP/natriuretic peptide receptor type A (NPR-A)pathway and diabetic gastroparesis. METHODS:Male imprinting control region(ICR)mice (4 wk old)were divided into two groups:control mice, and streptozotocin-induced diabetic mice.Eight weeks after injection,spontaneous gastric contraction was recorded by using physiography in control and streptozotocin-induced diabetic mice.The ANP-positive cells in gastric mucosa and among dispersed gastric epithelial cells were detected by using immunohistochemistry and flow cytometry,respectively.ANP and natriureticpeptide receptor type A(NPR-A)gene expression in gastric tissue was observed by using the reverse transcriptase polymerase chain reaction. RESULTS:The frequency of spontaneous gastric contraction was reduced from 12.9±0.8 cycles/min in the control group to 8.4±0.6 cycles/min in the diabetic mice(n=8,P<0.05).However,the amplitude of contraction was not significantly affected in the diabetic group.The depletion of interstitial cells of Cajal in the gastric muscle layer was observed in the diabetic mice.ANP-positive cells were distributed in the gastric mucosal layer and the density index of ANP-positive cells was increased from 20.9±2.2 cells/field in control mice to 51.8±2.9 cells/field in diabetic mice(n=8, P<0.05).The percentage of ANP-positive cells among the dispersed gastric epithelial cells was increased from 10.0%±0.9%in the control mice to 41.2%± 1.0%in the diabetic mice(n=3,P<0.05).ANP and NPR-A genes were both expressed in mouse stomach, and the expression was significantly increased in the diabetic mice. CONCLUSION:These results suggest that the ANP/ NPR-A signaling pathway is upregulated in streptozotocin-induced diabetic mice,and contributes to the development of diabetic gastroparesis.

Endogenous Endothelin-1 Regulates Hypoxia-Induced Atrial Natriuretic Peptide Secretion by Activating the MAPK/ERK and PI3K/Akt Signaling Pathways in Isolated Beating Rabbit Atria

The present study investigated a possible mechanism for endogenous endothelin-1 (ET-1) regulation of atrial natriuretic peptide (ANP) secretion in isolated perfused acute hypoxic rabbit atria. Acute hypoxia significantly enhanced the release of ET-1 and the expression of the ET receptor (ETR) type A and B (ETRA and ETRB) in atrial tissues, with a concomitant increase in ANP secretion. The ETRA or ETRB antagonist, BQ123 (0.3 μmol/L) or BQ788 (0.3 μmol/L), respectively attenuated hypoxia-induced ANP secretion. Both antagonists significantly attenuated the levels of hypoxiainduced atrial phosphorylated (p)-extracellular signal-regulated kinase (ERK) and p-protein kinase B (Akt). The ERK and Akt inhibitors, PD098059 (30 μmol/L) and LY294002 (30 μmol/L), respectively mimicked the effect of the ETR antagonists. These results demonstrated that acute hypoxia- mediated atrial ET-1 regulated ANP secretion through ETR and the subsequent mitogenactivated protein kinase (MAPK)/ERK and ETR-phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathways. These pathways may mediate atrial endocrine functions under hypoxic conditions.

The Role of Atrial Natriuretic Peptide (ANP) in Cardiopulmonary Diseases

Atrial natriuretic peptide (ANP) is a peptide hormone that has potent natriuretic, diuretic, vasodilator, sympatholytic, and renin - and aldos-terone - suppressing activities and is involved in the regulation of volume and electrolyte balance and blood pressure. Further, ANP has also been shown to inhibit cellular growth, proliferation and induce apoptosis in a variety of cell lines, including vascular smooth muscle cells and cardiac myocytes. Recent studies have demonstrated that ANP is not only involved in blood pressure and volume homeostasis but also in the direct regulation of cardiac growth. We and other investigators have demonstrated the existence of natriuretic peptide receptors in the heart and cardiac cells, suggesting that ANP has direct actions on cardiac tissue. Several recent in vivo studies have suggested that statement of ANP is inversely related to cardiac growth/hypertrophy. Transgenic mice overexpressing ANP have lower heart weight and blood pressure than wild type mice. Conversely, we demonstrated that transgenic mice with homozygous disruption of the pro - ANP gene (Nppa) (ANP -/- mice) have no circulating or tissue ANP and exhibit significant cardiac hypertrophy and increased blood pressure. Further, transgenic mice lacking a functional natriuretic peptide receptor A (NPR-A) gene display elevated blood pressure and marked cardiac hypertrophy. The role of ANP in the development of cardiac hypertrophy in response to hemodynamic stress has not previously been studied. Our previous studies demonstrated that ANP - / -mice with hypoxia - induced pulmonary hypertension and high salt diet - induced systemic hypertension develop greater cardiac enlargement than their wild type controls under same experimental conditions, suggest-ing that cardiac enlargement in ANP -/- mice might, at least in part, be related to increased afterload. In a recent study, we used ANP -/- mice to further test the hypothesis that ANP plays an important role in protecting against the development of cardiac enlargement induced by volume overload stress. Adult (8-10 wk old) male ANP -/- and wild type ANP+/+ mice underwent an aorto - caval fistula (ACF) or sham surgery and were subjected to echocardiographic examination at 2 wks. Mean arterial pressure (MAP) and atrial, left ventricular (LV) and right ventricular (RV) mass were greater in sham - operated ANP-/-mice than in ANP+/+mice. MAP decreased following ACF to a similar extent in both genotypes. ACF induced significant concentric cardiac enlargement in both genotypes. Cardiac enlargement and lung weight increased to a greater extent in ANP - / - mice than in ANP+/ + mice, indicating that disrupted ANP statement worsens ACF- induced cardiac enlargement and pulmonary congestion. LV function (velocity of circumferential shortening [VCFr], circumferential stress, fraction shortening, fraction shortening, and e-jection time and fraction) assessed by echocardiography did not differ between sham - operated ANP + / + and ANP - / - mice and remained unchanged after ACF. These findings indicate that ANP deletion results in biventricular enlargement and an exaggerated response to the stress of volume overload. This support the hypothesis that ANP has direct antihypertrophic and car-dioprotective actions in heart. Further study is needed to dissect the contributions of increased afterload from those of removing the antihypertrophic effects of ANP to basal and stress induced cardiac enlargement in this animal model.

Effects and safety of natriuretic peptides as treatment of cirrhotic ascites:A systematic review and meta-analysis

BACKGROUND Natriuretic peptides are involved in the cascade of pathophysiological events occurring in liver cirrhosis,counterbalancing vasoconstriction and anti-natriuretic factors.The effects of natriuretic peptides as treatment of cirrhotic ascites have been investigated only in small studies,and definitive results are lacking.AIM To examine the effects and safety of natriuretic peptides in cirrhosis patients with ascites.METHODS We searched MEDLINE,Web of Science,Scopus,Cochrane Library and Embase for all available studies applying intravenous administration of any natriuretic peptide to patients suffering from cirrhotic ascites.Inclusion was not limited by treatment duration or dose,or by follow-up duration.Both randomised controlled trials and non-randomised studies were eligible for inclusion.The primary outcome was change in renal sodium excretion.Secondary outcomes included safety measures and changes in renal water excretion,plasma aldosterone concentration,and plasma renin activity.RESULTS Twenty-two studies were included.Atrial natriuretic peptide(ANP)was the only intensively studied treatment.Sodium excretion increased in response to continuous ANP infusion and was more pronounced when infusion rates of>30 ng/kg/min were administered compared with≤30 ng/kg/min(P<0.01).Moreover,natriuresis was significantly higher in study subgroups with mild/moderate ascites compared with moderate/severe and refractory ascites(P<0.01).ANP infusions increased renal water excretion,although without reaching a statistically significant dose-response gradient.Plasma aldosterone concentration and plasma renin activity were significantly lower at baseline in study subgroups achieving a negative sodium balance in response to an ANP administration compared with treatment non-responders(P<0.01).Blood pressure decreases occurred less frequently when ANP doses≤30 ng/kg/min were applied.The quality of evidence for a natriuretic response to ANP was low,mainly due to small sample sizes and considerable between-study heterogeneity.Data were sparse for the other natriuretic peptides;B-type natriuretic peptide and urodilatin.CONCLUSION Intravenous ANP infusions increase sodium excretion in patients with cirrhotic ascites.Continuous infusion rates>30 ng/kg/min are the most effective.However,safety increases with infusion rates≤30 ng/kg/min.

Plasma natriuretic peptides during supraventricular tachycardia: A study in patients with atrioventricular nodal reentry tachycardia

Aims: To characterize the plasma levels of the atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in patients with atrioventricular nodal reentry tachycardia (AVNRT), we measured the plasma levels of these peptides before and during tachycardia. Methods: We included 10 consecutive patients scheduled for ablation of typical AVNRT without structural heart disease. Catheters were inserted in the femoral artery, femoral vein, and coronary sinus (CS) prior to the ablation procedure. Blood samples were drawn before and after 3 min of tachycardia to measure plasma levels of ANP and BNP. Right atrial pressure (RAP) was measured at baseline. Results: Of the 10 patients, in three patients it was not possible to induce tachycardia leaving a total of 7 patients available for analysis. Mean age of the seven included patients was 40 ± 12 years (mean ± SD), five were female. ANP levels increased significantly during tachycardia in the artery (p = 0.0009) and vein (p = 0.003), but only borderline in CS (p = 0.09). BNP levels did not change during tachycardia in any location. Conclusion: ANP levels measured in the peripheral circulation increased acutely during tachycardia due to AVNRT. BNP levels did not increase.

Software-aided detection and structural characterization of cyclic peptide metabolites in biological matrix by high-resolution mass spectrometry

Compared to their linear counterparts,cyclic peptides show better biological activities,such as antibacterial,immunosuppressive,and anti-tumor activities,and pharmaceutical properties due to their conformational rigidity.However,cyclic peptides could form numerous putative metabolites from potential hydrolytic cleavages and their fragments are very difficult to interpret.These characteristics pose a great challenge when analyzing metabolites of cyclic peptides by mass spectrometry.This study was to assess and apply a software-aided analytical workflow for the detection and structural characterization of cyclic peptide metabolites.Insulin and atrial natriuretic peptide(ANP)as model cyclic peptides were incubated with trypsin/chymotrypsin and/or rat liver S9,followed by data acquisition using TripleTOF?5600.Resultant full-scan MS and MS/MS datasets were automatically processed through a combination of targeted and untargeted peak finding strategies.MS/MS spectra of predicted metabolites were interrogated against putative metabolite sequences,in light of a,b,y and internal fragment series.The resulting fragment assignments led to the confirmation and ranking of the metabolite sequences and identification of metabolic modification.As a result,29 metabolites with linear or cyclic structures were detected in the insulin incubation with the hydrolytic enzymes.Sequences of twenty insulin metabolites were further determined,which were consistent with the hydrolytic sites of these enzymes.In the same manner,multiple metabolites of insulin and ANP formed in rat liver S9 incubation were detected and structurally characterized,some of which have not been previously reported.The results demonstrated the utility of software-aided data processing tool in detection and identification of cyclic peptide metabolites.

Atrial natriuretic peptide attenuates inflammatory responses on oleic acid-induced acute lung injury model in rats

Background An inflammatory response leading to organ dysfunction and failure continues to be a major problem after injury in many clinical conditions such as sepsis, severe burns, and trauma. It is increasingly recognized that atrial natriuretic peptide （ANP） possesses a broad range of biological activities, including effects on endothelial function and inflammation. A recent study has revealed that ANP exerts anti-inflammatory effects. In this study we tested the effects of human ANP （hANP） on lung injury in a model of oleic acid （OA）-induced acute lung injury （ALl） in rats. Methods Rats were randomly assigned to three groups （n=6 in each group）. Rats in the control group received a 0.9% solution of NaCI （1 ml-kg-l.h1） by continuous intravenous infusion, after 30 minutes a 0.9% solution of NaCI （1 ml/kg） was injected intravenously, and then the 0.9% NaCI infusion was restarted. Rats in the ALl group received a 0.9% NaCI solution （1 ml-kgl-h-~） intravenous infusion, after 30 minutes OA was injected intravenously （0.1 ml/kg）, and then the 0.9% NaCI infusion was restarted. Rats in the hANP-treated ALl group received a hANP （0.1 IJg.kg-Lmin~） infusion, after 30 minutes OA was injected intravenously （0.1 ml/kg）, and then the hANP infusion was restarted. The anti-inflammation effects of hANP were evaluated by histological examination and determination of serum cytokine levels. Results Serum interleukin （IL）-113, IL-6, IL-10 and tumor necrosis factor （TNF） a were increased in the ALl group at six hours. The levels of all factors were significantly lower in the hANP treated rats （P 〈0.005）. Similarly, levels of IL-113, IL-6, IL-10 and TNF-a were higher in the lung tissue in the ALl group at six hours, hANP treatment significantly reduced the levels of these factors in the lungs （P 〈0.005）. Histological examination revealed marked reduction in interstitial congestion, edema, and inflammation. Conclusion hANP can attenuate inflammation in OA-induced lung injury in rat model.

Changes of atrial natriuretic peptide and antidiuretic hormone in children with postural tachycardia syndrome and orthostatic hypertension： a case control study

Background The abnormal blood volume regulation is one of the most important pathogenesis in postural tachycardia syndrome in children.This study was designed to investigate the plasma atrial natriuretic peptide and antidiuretic hormone levels in postural tachycardia syndrome children,and their associations with the changes in heart rate and blood pressure in head-up test.Methods Twenty-one postural tachycardia syndrome patients （（12±2） years） and 26 healthy children （（12±1） years） were included.According to blood pressure changes in head-up test,the postural tachycardia syndrome patients were divided into two subgroups：postural tachycardia syndrome with orthostatic hypertension and postural tachycardia syndrome without orthostatic hypertension.The plasma atrial natriuretic peptide and antidiuretic hormone levels were measured using enzyme-linked immunosorbent assay.Results The plasma atrial natriuretic peptide level in postural tachycardia syndrome patients was higher than the control （P=0.004）,whereas the difference in plasma antidiuretic hormone level between postural tachycardia syndrome and controls was not significant （P=0.222）.The plasma antidiuretic hormone level of patients suffering from postural tachycardia syndrome with orthostatic hypertension was much higher than that of children having postural tachycardia syndrome without orthostatic hypertension （P ＜0.05）.In postural tachycardia syndrome patients,the updght max heart rate was positively correlated with the plasma atrial natriuretic peptide level （r=0.490,P＜0.05） and the upright systolic blood pressure was positively correlated with the plasma antidiuretic hormone levels （r=0.472,P ＜0.05）.Conclusions There was a disturbance of plasma atrial natriuretic peptide and antidiuretic hormone in postural tachycardia syndrome children.

EffectofDihydroxyacetophenoneonPulmonaryHemodynamicsandAtrialNatriureticPeptideaswellasAdenosineCyclophosphatesLevelinPatient

In order to study the effect of dihydroxyacetophenone ( DHAP) on pulmonary hemodynamicsand its relationship to plasma atrial natriuretic peptide (ANP) as well as adenosine cyclophosphates in chron-ic obstractive pulmonary disease (COPD) , right heart catheterization was used to examine some parametersof hemodynamics in 11 COPD patients before and after the application of DHAP, and at the same time ra-dioimmunoassay was used to measure the plasma ANP and cyclo-adenosine monophosphate/cyclic guanosinemonophosphate (cAMP/cGMP) . The results showed that DHAP 640 mg given intravenously could decreasemean pulmonary arterial pressure, pulmonary vascular resistance and systemic vascular resistance ( P <0 . 05) , but increase cardiac output from 4. 10 ±1 . 08 L/min to 5.13 ± 1 . 19 L/min ( P>0. 05) and without af-fecting systemic arterial blood pressure ( P >0. 05) as well as blood gas analysis; it could also reduce theplasma ANP and cGMP Ievel from 0. 73 ± 0. 42 pg/ml to 0. 41 ± 0. 33 pg/ml ( P<0. 01 ) and trom 9 . 82 ± 5. 75pm/ml to 8. 01 ± 4. 80 pm/ml( P< 0. 05) respectively, but did not affect the plasma cAMP level ( P>0. 05) .It is suggested that DHAP may relax pulmonary vessels by adjusting the ratio of cAMP to cGMP, and the low-ering of plasma ANP level might be a secondary reaction. So DHAP was considered a quick-acting, safe andpotential drug in treating pulmonary arterial hypertension by COPD.

DISTRIBUTION AND LOCATION OF IMMUNOREACTIVE ATRIAL NATRIURETIC PEPTIDES IN COCHLEAR STRIA VASCULARIS OF GUINEA PIG

The distribution and location of atrial natriuretic peptides(ANP) in the cochlear stria vaseularis of normal guinea pigswere studied to find out regional regulating factors of cochlearblood flow (CBF) and productive foundation of cochlearendolymph by ABC immunocytochemistry and immunoele-ctronmicroscopy. The ANP-IR products were seen in the striavascularis of the 1-4 turns of the lateral wall of the cochlea,more markedly along its margin; and were negative in the spi-ral ligaments. Immunoelectronmicroscopically, a plenty ofsphericals of 250-350nm in diameter were noted in thecytoplasm of marginal and intermediate cells, but few in thebasal cells. The results suggest that the cochlear striavascularis had the function of secreting ANP in the guinea pig.

Influence of Cardiac Structure, Blood Blow, Velocity and Heart Function on Circulating Atrial Natriuretic Peptide and Reninangiotension System

Heart function and plasma atrial natriuretic peptide (ANP).plasma renin actiity(PRA) andangiotensionⅡ(Ang Ⅱ) were examined with echocardiography and radioimmunoassay in patients with dilated cardiomyopathy(DCM),

Atrial natriuretic peptide gene polymorphism is not associated with hypertrophic cardiomyopathy

Background Hypertrophic cardiomyopathy （HCM） is a primary autosomal dominant inheritant myocardial disease with heterogeneity in clinical manifestations, natural history and prognosis. Even carrying an identical gene mutation among family members, a va[iety of clinical phenotypes have been found in patients with HCM. Modifier genes may contribute to the diversity. The plasma levels of atrial natriuretic peptides （ANP） were found previously to be elevated in HCM. Our studies suggested that ANP gene promoter polymorphism is associated with left ventricular hypertrophy in hypertension. The present study aimed to determine whether the two SNPs in the ANP gene are associated with HCM Methods We determined the relationships between the ANP gene polymorphism and HCM in 262 HCM patients and 614 age- and sex-matched healthy individuals. All of the subjects were genotyped for -A2843G and A188G polymorphisms. Results The genotype frequency in the -A2843G and A188G polymorphisms of the ANP gene was not significantly different between the HCM patients and controls. The -A2843G and A188G polymorphisms were also not associated with clinical phenotype in cardiomyopathy patients. Conclusions The polymorphisms of the ANP gene are not associated with increasing risk of HCM or clinical phenotypes. The variations of the ANP gene may not serve as a genetic modifier for the development of HCM.

Decorin Induces Cardiac Hypertrophy by Regulating the CaMKⅡ/MEF-2 Signaling Pathway In Vivo

Objective:Cardiac hypertrophy is an adaptive reaction of the heart against cardiac overloading,but continuous cardiac hypertrophy can lead to cardiac remodeling and heart failure.Cardiac hypertrophy is mostly considered reversible,and recent studies have indicated that decorin not only prevents cardiac fibrosis associated with hypertension,but also achieves therapeutic effects by blocking fibrosis-related signaling pathways.However,the mechanism of action of decorin remains unknown and unconfirmed.Methods:We determined the degree of myocardial hypertrophy by measuring the ratios of the heart weight/body weight and left ventricular weight/body weight,histological analysis and immunohistochemistry.Western blotting was performed to detect the expression levels of CaMKⅡ,p-CaMKⅡ and MEF-2 in the heart.Results:Our results confirmed that decorin can regulate the CaMKⅡ/MEF-2 signaling pathway,with inhibition thereof being similar to that of decorin in reducing cardiac hypertrophy.Conclusion:Taken together,the results of the present study showed that decorin induced cardiac hypertrophy by regulating the CaMKⅡ/MEF-2 signaling pathway in vivo,revealing a new therapeutic approach for the prevention of cardiac hypertrophy.

Progesterone Receptor Antagonists-A Novel Treatment for Severe Hyponatremia from the Endocrine Paraneoplastic Syndrome

Hyponatremia related to ectopic secretion of cancer cells of arginine vasopressin(AVP)or atrial natriuretic peptide(ANP)is most commonly caused by small cell lung cancer.The ideal treatment would be one that not only corrects the hyponatremia,especially if it is life threatening,but at the same time causes regression of the cancer,and thus improves both quality and length of life.As one is waiting for chemotherapy,surgery,or radiotherapy to decrease the cancer burden,tolvaptan has been used to correct the hyponatremia to improve symptoms or prevent death.Mifepristone,a progesterone receptor modulator/antagonist has been used to treat various cancers.The oral 200mg tablet was given to an 80-year-old woman who developed sudden extensive lung cancer with a serum sodium of 118 mmol/L.She refused chemotherapy but agreed to take mifepristone.The hyponatremia was completely corrected(145 mmol/L)within one month of treatment.She was in complete remission for 5 years and died not from lung cancer,but an acute myocardial infarction.Mifepristone may serve the purpose to not only quickly correct hyponatremia when it is related to an endocrine paraneoplastic syndrome,but also to provide improved quality and length of life.

SUPPRESSION OF ANGⅡ AFTER ACUTE SALINE LOAD ASSOCIATED WITH THE CHANGES OF PLASMA ANP AND SODIUM METABOLISM IN SALT-SENSITIVE HYPERTENSION PATIENTS

Objective To observe the changes of plasma AngⅡ,ANP and their relationship with urine sodium excretion in salt sensitive hypertension. Methods The salt sensitivity was determined by acute saline loading test in 173 primary hypertensives of Stage Ⅰ or Stage Ⅱ. Plasma AngⅡand ANP was determined by radioimmunoassay. Results After acute salt load, AngⅡ was suppressed inadequately. The plasma ANP secretion was not increased. The urine sodiun excretion was delayed, Na + in RBC was increased in salt sensitive subjects. The plasma ANP was decreased in the salt sensitive subjects without AngⅡ suppressed. The 24 hours urine sodium excretion was lower than those AngⅡ suppressed.Conclusion The changes of plasma RAS are not homogeneous after salt load. Those without the plasma AngⅡ suppressed have more severe sodium metabolism abnormalities and the endogenous ANP secretion is impaired in salt sensitive patients.

ANPT2238C,C-664G Gene Polymorphism and Coronary Heart Diseasein Chinese Population

The association between atrial natriuretic peptide （ANP） polymorphism and coronary heart disease （CHD） was studied in Chinese population. The genotypes of ANP T2238C and ANP C-664G were detected by polymerase chain reaction and restriction fragment length polymorphism （PCR-RFLP） methods in 158 consecutive CHD patients and 165 controls. It was found that the distribution of A2A2 genotype in CHD group was significantly higher than that in control group （P〈0.05）. Stepwise Logistic regression analysis revealed that male, smoking, history of hypertension, history of diabetes, family history of hypertension, high level of serum cholesterol, and ANP T2238C polymorphism were the possible risk factors in patients with CHD （P〈0.05）. However, there was no significant difference between the patients with CHD and the control group in the distribution of ANP C-664G polymorphism （P〉0.05）. The results suggest that A2A2 T2238C genotype could be one of the risk factors for CHD （P〈0.05, OR： 1.80, 95 % CI： 1.03-3.15）.