Blockade of ERK1/2 activation with U0126 or PEP7 reduces sodium appetite and angiotensin II-induced pressor responses in spontaneously hypertensive rats

Inhibition of salty taste and sodium appetite by estrogens in spontaneously hypertensive rats

Estrogen has a well-known effect of reducing salt intake in rats. This mini review focuses on recent findings regarding the interaction of estradiol with brain angiotensin II to control increased sodium palatability that occurs as a result of sodium appetite in spontaneously hypertensive rats.

Molecular neurobiological markers in the onset of sodium appetite

Sodium appetite is a motivational state involving homeostatic behavior, seeking the ingest of salty substances after sodium loss. There is a temporal dissociation between sodium depletion (SD) and the appearance of sodium appetite. However, the responsible mechanisms for this delay remain poorly elucidated. In the present study, we measured the temporal changes at two and 24 h after SD in the gene expression of key elements within excitatory, inhibitory, and sensory areas implicated in the signaling pathways involved in the onset of sodium appetite. In SD rats, we observed that the expression of critical components within the brain control circuit of sodium appetite, including Angiotensin-type-1 receptor (Agtr1a), Oxytocin-(OXT-NP)-neurophysin-I, and serotonergic-(5HT)-type-2c receptor (Htr2c) were modulated by SD, regardless of time. However, we observed reduced phosphorylation of mitogen-activated protein kinases (MAPK) at the paraventricular nucleus (PVN) and increased oxytocin receptor (Oxtr) mRNA expression at the anteroventral of the third ventricle area (AV3V), at two hours after SD, when sodium appetite is inapparent. At twenty-four hours after SD, when sodium appetite is released, we observed a reduction in the mRNA expression of the transient receptor potential channel 1gene (Trpv1) and Oxtr in the AV3V and the dorsal raphe nucleus, respectively. The results indicate that SD exerts a coordinated timing effect, promoting the appearance of sodium appetite through changes in MAPK activity and lower Trpv1 channel and Oxtr expression that trigger sodium consumption to reestablish the hydroelectrolytic homeostasis.

Signal Transduction of Mineralocorticoid and Angiotensin II Receptors in the Central Control of Sodium Appetite: A Narrative Review

Sodium appetite is an innate behavior occurring in response to sodium depletion that induces homeostatic responses such as the secretion of the mineralocorticoid hormone aldosterone from the zona glomerulosa of the adrenal cortex and the stimulation of the peptide hormone angiotensin II (ANG II). The synergistic action of these hormones signals to the brain the sodium appetite that represents the increased palatability for salt intake. This narrative review summarizes the main data dealing with the role of mineralocorticoid and ANG II receptors in the central control of sodium appetite. Appropriate keywords and MeSH terms were identified and searched in PubMed. References to original articles and reviews were examined, selected, and discussed. Several brain areas control sodium appetite, including the nucleus of the solitary tract, which contains aldosterone-sensitive HSD2 neurons, and the organum vasculosum lamina terminalis (OVLT) that contains ANG II-sensitive neurons. Furthermore, sodium appetite is under the control of signaling proteins such as mitogen-activated protein kinase (MAPK) and inositol 1,4,5-thriphosphate (IP3). ANG II stimulates salt intake via MAPK, while combined ANG II and aldosterone action induce sodium intake via the IP3 signaling pathway. Finally, aldosterone and ANG II stimulate OVLT neurons and suppress oxytocin secretion inhibiting the neuronal activity of the paraventricular nucleus, thus disinhibiting the OVLT activity to aldosterone and ANG II stimulation.

Angiotensin-(3-7) alleviates isoprenaline-induced cardiac remodeling via attenuating cAMP-PKA and PI3K/Akt signaling pathways

The renin-angiotensin system is involved in the regulation of various heart diseases. The present study aimed to determine the effects of angiotensin (Ang)-(3-7) on cardiac remodeling and its downstream signaling pathways in neonatal rat cardiomyocytes (NRCMs) and neonatal rat cardiac fibroblasts (NRCFs). The administration of Ang-(3-7) alleviated isoprenaline (ISO)-induced cardiac hypertrophy and fibrosis of mice. ISO treatment increased the levels of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and beta-myosin heavy chain (β-MHC) in NRCMs, and reduced the levels of collagen I, collagen III, fibronectin, and alpha-smooth muscle actin (α-SMA) in NRCFs. These changes were inhibited by Ang-(3-7) administration. The levels of protein kinase A (PKA), phosphorylated phosphatidylinositol-3-kinase (p-PI3K), and phosphorylated protein kinase B (p-Akt) were increased in NRCMs and NRCFs treated with ISO. The increase of PKA, but not p-PI3K or p-Akt was attenuated by Ang-(3-7) treatment in NRCMs. The increases of p-PI3K and p-Akt, but not PKA were reversed by Ang-(3-7) treatment in NRCFs. Treatment with cAMP or PKA overexpression reversed the attenuating effects of Ang-(3-7) on ISO-induced hypertrophy of NRCMs. The administration of PI3K inhibitor or Akt inhibitor alleviated ISO-induced fibrosis of NRCFs. These results indicated that Ang-(3-7) could alleviate cardiac remodeling. The administration of Ang-(3-7) attenuated hypertrophy of NRCMs via inhibiting the cAMP/PKA signaling pathway, and alleviated fibrosis of NRCFs via inhibiting PI3K/Akt signaling pathway.