Significance of recently identified peptides in hypertension: endothelin, natriuretic peptides, adrenomedullin, leptin

A Review of the Actions of Endogenous and Exogenous Vasoactive Substances during the Estrous Cycle and Pregnancy in Rats

Vascular endothelium plays a key role in regulating cardiovascular homeostasis by controlling the vascular tone. Variations in sex hormones during the reproductive cycle of females affect the homeostasis of the cardiovascular system. Also, the evidence shows that estrogens show a cardioprotective effect. On this basis, this study describes some vascular responses induced by vasoactive substances during the estrous cycle in rats. We obtained the information available on this topic from the online databases that included scientific articles published in the Web of Science, PubMed, and Scielo. Many investigations have evaluated the vasoactive response of substances such as acetylcholine and norepinephrine during the estrous cycle. In this review, we specifically described the vascular response to vasoactive substances in rats during the estrous cycle, pregnancy, and in ovariectomized rats. In addition, we discussed the existence of different signaling pathways that modulate vascular function. The knowledge of these effects is relevant for the optimization and development of new treatments for some vascular pathologies.

Endothelins and Sarafotoxins: Peptides of Similar Structure and Different Function

Endothelins are endogenous vasoactive peptides that are considered among the most potent vasoconstrictor substances known. In addition to their vascular effects, endothelins and their receptors have been shown to be present in many organs and share plenty physiological and pathophysiological functions. Sarafotoxins are natural substances from the venom of snakes genus Atractaspis, structurally and pharmacologically near to endothelins. The current minireview focuses on the chemical and molecular aspects of endothelins and sarafotoxins, and their receptors in physiological and pathophysiological processes.

Endothelin Type A Receptor Genotype is a Determinant of Quantitative Traits of Metabolic Syndrome in Asian Hypertensive Families: A SAPPHIRe Study

Co-heritability of hypertension and insulin resistance (IR) within families not only implies genetic susceptibility may be responsible for these complex traits but also suggests a rational that biological candidate genes for hypertension may serve as markers for features of the metabolic syndrome (MetS). Thus we determined whether the T323C polymorphism (rs5333) of endothelin type A (ETA) receptor, a predominant receptor evoking potent vasoconstrictive action of endothelin-1, contributes to susceptibility to IR-associated hypertension in 1694 subjects of Chinese and Japanese origins. Blood pressures (BPs) and biochemistries were measured. Fasting insulin level, insulin-resistance homeostasis model assessment (HOMAIR) score, and area under curve of insulin concentration (AUCINS) were selected for assessing insulin sensitivity. Genotypes were obtained by methods of polymerase chain reaction-restriction fragment length polymorphism. Foremost findings were that minor allele frequency of the T323C polymorphism was noticeable lower in our overall Asian subjects compared to multi-national population reported in gene database; moreover both the genotypic and allelic frequencies of the polymorphism were significantly different between the two ethnic groups we studied. The genotype distributions at TT/TC/CC were 65, 31, 4% in Chinese and 51, 41, 8% in Japanese, respectively (p < 0.0001). Additionally, carriers of the C homozygote revealed characteristics of IR, namely significantly higher levels of fasting insulin, HOMAIR score, and AUCINS at 29.3, 35.3, and 39.3%, respectively, when compared to their counterparts with TT/TC genotypes in Chinese. Meanwhile, the CC genotype was associated with a higher level of high density lipoprotein cholesterol in Japanese. No association of the polymorphism with BP was observed. This study demonstrated for the first time that T323C polymorphism of ETA receptor gene was associated with an adverse insulin response in Chinese and a favorite atherogenic index in Japanese.

[Epicardial adipose tissue: more than a simple fat deposit?]

Obesity increases the risk of development of atherosclerosis. However, this risk significantly depends on adipose tissue distribution in the body and ectopic accumulation of visceral adipose tissue (VAT). Recent evidence suggests that each visceral fat deposit is anatomically and functionally different. Due to proximity to the organ, each visceral fat deposit exerts a local modulation rather than a systemic effect. Because of its unique location and biomolecular properties, a "non-traditional" fat depot - the epicardial adipose tissue - has been considered to play a causative role in atherosclerosis. Epicardial adipose tissue may be measured with imaging techniques and is clinically related to left ventricular mass, coronary artery disease, and metabolic syndrome. Therefore, epicardial fat measurement may play a role in stratification of cardiometabolic risk and may serve as a therapeutic target.

Resveratrol attenuates oxidative stress and prevents steatosis and hypertension in obese rats programmed by early weaning

We hypothesized that resveratrol, a natural phytoalexin found in grapes, can prevent oxidative stress, obesity and its related disturbances in obese rats programmed by early weaning. Lactating Wistar rats were separated into two groups: early weaning (EW) - dams who were wrapped with a bandage to interrupt the lactation in the last 3 days of lactation; control - dams whose pups had free access to milk during all lactation. At the 150th day, EW offspring were randomly subdivided into EW+resveratrol (EW+Res) - resveratrol (30 mg/kg/day); EW+vehicle (EW) - rats that received 0.5% (w/v) aqueous methylcellulose. The control group received vehicle. Rats were treated by gavage daily for 30 days. EW offspring developed hyperphagia, higher body weight, visceral obesity, higher systolic (SBP) and diastolic blood pressure (DBP) (+15% and +20%, respectively; P<.05) and higher serum triglycerides (TG) and low-density lipoprotein but lower high-density lipoprotein (+55%, +33% and -13%, respectively; P<.05). Resveratrol normalized food intake, SBP and DBP and prevented obesity and dyslipidemia in EW+Res. EW rats had higher plasma and liver thiobarbituric-acid-reactive substances (TBARS) and lower plasma superoxide dismutase (SOD) and liver glutathione peroxidase activities (+51%, +18%, -58%, -31%, respectively; P<.05), and resveratrol normalized both plasma and liver TBARS and increased the activity of SOD and catalase in plasma. EW rats presented liver steatosis and higher liver TG, and resveratrol prevented these hepatic alterations. In conclusion, this study demonstrated a potential therapeutic use of resveratrol in preventing obesity and oxidative stress and reducing the risk of hypertension, dyslipidemia and steatosis in adult rats programmed by early weaning.

Natriuretic peptides and cardiovascular damage in the metabolic syndrome: molecular mechanisms and clinical implications

Natriuretic peptides are endogenous antagonists of vasoconstrictor and salt- and water-retaining systems in the body's defence against blood pressure elevation and plasma volume expansion, through direct vasodilator, diuretic and natriuretic properties. In addition, natriuretic peptides may play a role in the modulation of the molecular mechanisms involved in metabolic regulation and cardiovascular remodelling. The metabolic syndrome is characterized by visceral obesity, hyperlipidaemia, vascular inflammation and hypertension, which are linked by peripheral insulin resistance. Increased visceral adiposity may contribute to the reduction in the circulating levels of natriuretic peptides. The dysregulation of neurohormonal systems, including the renin-angiotensin and the natriuretic peptide systems, may in turn contribute to the development of insulin resistance in dysmetabolic patients. In obese subjects with the metabolic syndrome, reduced levels of natriuretic peptides may be involved in the development of hypertension, vascular inflammation and cardio vascular remodelling, and this may predispose to the development of cardiovascular disease. The present review summarizes the regulation and function of the natriuretic peptide system in obese patients with the metabolic syndrome and the involvement of altered bioactive levels of natriuretic peptides in the pathophysiology of cardiovascular disease in patients with metabolic abnormalities.

Neonatal hyperleptinaemia programmes adrenal medullary function in adult rats: effects on cardiovascular parameters

Epidemiological studies have shown a strong correlation between stressful events (nutritional, hormonal or environmental) in early life and development of adult diseases such as obesity, diabetes and cardiovascular failure. It is known that gestation and lactation are crucial periods for healthy growth in mammals and that the sympathoadrenal system is markedly influenced by environmental conditions during these periods. We previously demonstrated that neonatal hyperleptinaemia in rats programmes higher body weight, higher food intake and hypothalamic leptin resistance in adulthood. Using this model of programming, we investigated adrenal medullary function and effects on cardiovascular parameters in male rats in adulthood. Leptin treatment during the first 10 days of lactation (8 microg 100 g(-1) day(-1), s.c.) resulted in lower body weight (6.5%, P < 0.05), hyperleptinaemia (10-fold, P < 0.05) and higher catecholamine content in adrenal glands (18.5%, P < 0.05) on the last day of treatment. In adulthood (150 days), the rats presented higher body weight (5%, P < 0.05), adrenal catecholamine content (3-fold, P < 0.05), tyrosine hydroxylase expression (35%, P < 0.05) and basal and caffeine-stimulated catecholamine release (53% and 100%, respectively, P < 0.05). Systolic blood pressure and heart rate were also higher in adult rats (7% and 6%, respectively, P < 0.05). Our results show that hyperleptinaemia in early life increases adrenal medullary function in adulthood and that this may alter cardiovascular parameters. Thus, we suggest that imprinting factors which increase leptin and catecholamine levels during the neonatal period could be involved in development of adult chronic diseases.

Intracranial aneurysms: links among inflammation, hemodynamics and vascular remodeling

Abnormal vascular remodeling mediated by inflammatory cells has been identified as a key pathologic component of various vascular diseases, including abdominal aortic aneurysms, brain arteriovenous malformations and atherosclerosis. Based on findings from observational studies that analysed human intracranial aneurysms and experimental studies that utilized animal models, an emerging concept suggests that a key component of the pathophysiology of intracranial aneurysms is sustained abnormal vascular remodeling coupled with inflammation. This concept may provide a new treatment strategy to utilize agents to inhibit inflammation or cytokines produced by inflammatory cells such as matrix metalloproteinases. Such an approach would aim to stabilize these vascular lesions and prevent future expansion or rupture.

Bronchodilator effect of infused B-type natriuretic peptide in asthma

STUDY OBJECTIVE

To determine the bronchodilator effect of recombinant human B-type natriuretic peptide (BNP; nesiritide) on patients with asthma.

DESIGN

A prospective, open-label study.

SETTING

Outpatient setting.

PATIENTS

Eight adult patients with asthma confirmed by > 12% and > 200 mL increase in FEV1 after bronchodilator inhalation.

INTERVENTIONS

An IV nesiritide bolus, 2 microg/kg, followed by continuous infusion for a total of 3 h at escalating doses of 0.01, 0.02, and 0.03 microg/kg/min for 1 h each as tolerated.

MEASUREMENTS

Spirometry and forced oscillation technique (FOT) measurements were both obtained at baseline and every 30 min during the infusion. Two doses of albuterol, 90 microg, inhalation via metered-dose inhaler were then administered at the end of nesiritide infusion, followed by repeat spirometry and FOT measurements after 30 min. Primary end points were FEV1 and FVC changes after the nesiritide infusion for 3 h. Wilcoxon signed-ranks tests were used to compare the effects of nesiritide and albuterol.

RESULTS

Baseline measurements (mean +/- SD) were as follows: FEV1, 1.89 +/- 0.87 L; FVC, 3.02 +/- 0.99 L; respiratory resistance at 5 Hz (Rrs5), 10.3 +/- 3.85 cm H2O . s/L; and mean respiratory resistance at 5 to 20 Hz, 7.56 +/- 1.92 cm H2O/L/s. Mean baseline serum BNP level was 27 +/- 27 pg/mL. After 180 min of nesiritide infusion, the following measurements showed significant changes: FEV1 increased to 2.41 +/- 0.78 L (mean increase, 520 mL), p = 0.012; FVC increased to 3.65 +/- 1.05 L (mean increase, 630 mL), p = 0.017; and Rrs5 decreased to 8.24 +/- 4.02 cm H2O/L/s, p = 0.017. After albuterol, there were no further significant changes in these measurements.

CONCLUSION

IV nesiritide is an effective bronchodilator in patients with asthma.

Functional genomics of the dopaminergic system in hypertension

Abnormalities in dopamine production and receptor function have been described in human essential hypertension and rodent models of genetic hypertension. Under normal conditions, D(1)-like receptors (D(1) and D(5)) inhibit sodium transport in the kidney and intestine. However, in the Dahl salt-sensitive and spontaneously hypertensive rats (SHRs) and in humans with essential hypertension, the D(1)-like receptor-mediated inhibition of epithelial sodium transport is impaired because of an uncoupling of the D(1)-like receptor from its G protein/effector complex. The uncoupling is receptor specific, organ selective, nephron-segment specific, precedes the onset of hypertension, and cosegregates with the hypertensive phenotype. The defective transduction of the renal dopaminergic signal is caused by activating variants of G protein-coupled receptor kinase type 4 (GRK4: R65L, A142V, A486V). The GRK4 locus is linked to and GRK4 gene variants are associated with human essential hypertension, especially in salt-sensitive hypertensive subjects. Indeed, the presence of three or more GRK4 variants impairs the natriuretic response to dopaminergic stimulation in humans. In genetically hypertensive rats, renal inhibition of GRK4 expression ameliorates the hypertension. In mice, overexpression of GRK4 variants causes hypertension either with or without salt sensitivity according to the variant. GRK4 gene variants, by preventing the natriuretic function of the dopaminergic system and by allowing the antinatriuretic factors (e.g., angiotensin II type 1 receptor) to predominate, may be responsible for salt sensitivity. Subclasses of hypertension may occur because of additional perturbations caused by variants of other genes, the quantitative interaction of which may vary depending upon the genetic background.

Similar effects on rat renal mesangial cells by expressing different fragments of adrenomedullin gene in vitro

AIM

To construct pEGFP-N3 recombinant vectors carrying adrenomedullin (AM) or fragments of the AM gene, and to express AM or fragments of AM from the pEGFP-N3 recombinant vectors (pEGFP-N3-AM1-2 and pEGFP-N3-AM1-3) and study their biological properties on cultured rat renal mesangial cells (RMC).

METHODS

Total RNA of rat kidney was obtained using TriZol reagent. The cDNA was synthesized by reverse transcriptase using oligo-deoxythymidine as primer. The fragments of AM gene were then amplified by polymerase chain reaction (PCR) with specific upstream and downstream oligonucleotides. The PCR products were digested with EcoRI and BamHI and subcloned into the plasmid pEGFP-N3. Facilitated by cationic liposomes, RMC were transfected with pEGFP-N3-AM1-2 or pEGFP-N3-AM1-3. After 24 h, green fluorescent protein (GFP) fluorescent images were examined with a fluorescence microscope. After 48 h, the proliferation of RMC was detected using the MTT assay, and the mRNA expression of transforming growth factor-beta1 (TGF-beta1) was measured by semiquantitative PCR.

RESULTS

DNA sequence reports verified that pEGFP-N3-AM1-2, which carried the full length AM gene translation fragment (preproadrenomedullin preproAM1-185), and pEGFP-N3-AM1-3, which carried the translation fragment of preproAM [without adrenotensin (ADT, preproAM150-185)], were constructed successfully. After 24 h, green fluorescence was observed in RMC into which either pEGFP-N3-AM1-2 or pEGFP-N3-AM1-3 was transfected, while in the control cells no fluorescence was observed. Either pEGFP-N3-AM1-2 or pEGFP-N3-AM1-3 delivery inhibited the proliferation of RMC (P<0.01) and decreased the mRNA transcription level of TGF-beta1 in RMC (P<0.05). However, no significant difference was observed between the effects of pEGFP-N3-AM1-2 and pEGFP-N3-AM1-3.

CONCLUSION

pEGFP-N3-AM1-2 and pEGFP-N3-AM1-3 were constructed successfully and were functionally expressed in RMC. Expressing the fragment of AM without ADT has similar inhibitory biological effects on RMS proliferation and TGF-beta1 transcription with full length preproAM.