Angiotensin and renin in rat and dog brain

An enzyme with the characteristics of classical renin was isolated from brain extracts of nephrectomized dogs. This enzyme is thermolabile, nondialyzable, and forms a vasoconstrictive material when incubated with renin plasma substrate at pH 7. A short lasting pressor activity was also found in brain extracts of dogs and rats. This activity was due to a substance identified by chemical and pharmacological tests as angiotensin. Countercurrent distribution of brain extracts of rats showed that 38% of the pressor activity corresponded to angiotensin II and the remainder to angiotensin I. A remarkable correlation was found between angiotensin and norepinphrine concentrations in different portions of the encephalon of the dog.

Serotonin and melatonin synthesis in peripheral blood mononuclear cells: stimulation by interferon-gamma as part of an immunomodulatory pathway

Serotonin and melatonin inhibit phytohemagglutinin- (PHA) induced interferon-gamma (IFN-gamma) production by lymphocytes. In this paper, it is shown that IFN-gamma-increased tryptophan uptake by lymphocytes and macrophages led to an enhanced production of serotonin. When IFN-gamma and serotonin were added together to a lymphocyte culture, N-acetyl serotonin and melatonin production was increased, whereas the path to 5-hydroxy-indoleacetic acid remained unchanged. Therefore, the stimulated IFN-gamma production of serotonin and melatonin by lymphocytes and macrophages and the inhibition of IFN-gamma synthesis by these indoleamines suggest a hypothesis for an immunoregulatory circuit.

Immunomodulation by indoleamines: serotonin and melatonin action on DNA and interferon-gamma synthesis by human peripheral blood mononuclear cells

Different concentrations of indoleamines, serotonin and melatonin, inhibited phytohemagglutinin stimulated DNA synthesis. Thus, 10(-3) to 10(-4) M of either indoleamine acted at the optimal phytohemagglutinin concentration, while 10(-3) to 10(-7) M acted at suboptimal phytohemagglutinin levels. The serotonin effect was reversed by the serotonergic S1-S2 receptor antagonist methysergide but not by the S2 antagonist ketanserin. This indicates that only the S1 receptor is involved in the inhibitory effect. Inhibition of lymphoproliferation by indoleamines was also exerted on pokeweed mitogen and protein A from Staphylococcus aureus stimulations. Serotonin and melatonin also inhibited phytohemagglutinin and protein A from Staphylococcus aureus induction of interferon-gamma synthesis. The initial uptake of Ca2+ was not affected by indoleamines, suggesting that it is not the mechanism of their inhibitory effects. As interferon-gamma induced tryptophan uptake by T lymphocyte- and macrophage-depleted populations, and tryptophan is the metabolic precursor of serotonin and melatonin, a new immunoregulatory circuit is postulated.

Angiotensin regulates release and synthesis of serotonin in brain

Angiotensin II released serotonin from neuron terminals and accelerated synthesis of the serotonin. This increase in synthesis depended on the activation of tryptophan hydroxylase. A biphasic effect was observed: at high doses the stimulatory effect depended on conversion of angiotensin II to angiotensin III. At low doses an inhibitory effect was found, possible dependent on an angiotensin II metabolite. These actions represent a subtle regulation of the open-loop serotonin system.

Serotonin inhibition of tumor necrosis factor-alpha synthesis by human monocytes

Serotonin inhibited in a concentration dependent way (10(-3) M to 10(-10) M) the LPS induced Tumor Necrosis Factor-alpha synthesis both, when added to the monocyte cultures from the beginning and when added together with the activating stimulus 8 hours before the end of the culture. The inhibitory effect was specifically blocked by the 5-HT1 and 5-HT2 serotonin antagonist methysergide and the 5-HT2 receptor antagonist ketanserin. This indicates that only the 5-HT2 receptor family (5-HT2 or 5-HT1C) may be involved in the inhibitory effect. Serotonin seems to play an important immunomodulatory role in macrophage functions.

A pressor substance in the cerebrospinal fluid of normotensive and hypertensive patients

A pressor polypeptide was isolated from the cerebrospinal fluid of normotensive and hypertensive patients. Pharmacologically it behaves like angiotensin I. A very significant correlation (r = 0.83, P < 0.001) was found between the concentration of this polypeptide and the blood pressure of essential hypertensive patients.

Neurogenic hypertension after depletion of norepinephrine in anterior hypothalamus induced by 6-hydroxydopamine administration into the ventral pons: role of serotonin

Destruction of the ventral noradrenergic pathway elicited by administration of 6-hydroxydopamine (6-OHDA, 5 micrograms into each side of the ventral pons) reduced the content of norepinephrine (NE) in the anterior hypothalamus (-80%) and induced an increase in arterial blood pressure (ABP) and in heart rate. These hypertensive rats, showed hypersensitivity to the hypotensive effect of NE (0.5-2 micrograms) and clonidine (0.75-1.5 micrograms) administered into the anterior hypothalamic preoptic (AH/PO) region. Methysergide (1-2 micrograms) and, to a lesser extent, ketanserin (1-2 micrograms) administered into the anterior hypothalamic preoptic region also reduced the arterial blood pressure in these rats treated with 6-OHDA. Bilateral administration of 5,7-dihydroxytryptamine (5,7-DHT, 8 micrograms) into the median forebrain bundle decreased the content of serotonin (5-HT) in the hypothalamus (-85%) without change in arterial blood pressure but largely prevented the development of hypertension after treatment with 6-OHDA in the ventral pons. These results suggest that neurogenic hypertension is produced after the removal of NE tonic depressor activity in the anterior hypothalamus and that serotonergic mechanisms play a major role in the development of the increased arterial blood pressure in this preparation.

Low lymphocyte interferon-gamma production and variable proliferative response in anorexia nervosa patients

Interferon-gamma (IFN-gamma) production by peripheral blood mononuclear cells (PBMC) in 14 patients with anorexia nervosa (AN) was significantly lower than in 14 age-matched healthy controls. Follow-up samples in four patients displayed low levels, except in two when they recovered the IFN-gamma production as the hormonal cycles were restored. A large interindividual variation for the lymphocyte proliferative response was observed in 30 AN patients. DNA synthesis of PBMC was normal in 8 patients (27%), significantly increased in 6 (20%) (P < 0.001), and significantly decreased in 16 (53%) (P < 0.001). IFN-gamma inhibition was reversed by culturing a control lymphocyte population with monocytes from patients with AN. This was not observed in cultures of control monocytes and AN lymphocytes. IL-2 receptor (TAC subunit) was assessed and no difference was found in the number of TAC-positive cells between patients and controls. These results point out impaired production of the immunomodulator cytokine IFN-gamma as a major functional defect of AN peripheral lymphocytes.

Central bradykininergic system in normotensive and hypertensive rats

1. The kinin antagonist des-Arg9-[Leu8]bradykinin, injected into the lateral ventricle, caused a long-lasting, dose-dependent reduction in arterial blood pressure and heart rate in spontaneously hypertensive rats but not in normotensive Wistar-Kyoto rats; the antagonist also blocked the pressor response to ventricularly infused bradykinin in both strains. 2. Bradykinin content was increased in the hypothalamus and septum and decreased in the dorsal medulla of spontaneously hypertensive rats when compared with those of normotensive Wistar-Kyoto rats, whereas similar bradykinin contents were observed in the pineal gland, hypophysis and rostroventrolateral medulla of both rat strains. 3. Increased concentrations of bradykinin and its precursor kininogen were found in the cerebrospinal fluid of spontaneously hypertensive rats. 4. Bradykinin receptor numbers, measured as the binding of [125I-Tyr1]bradykinin to nervous tissue, were found to be increased in the dorsal medulla and hypophysis, and to be decreased in the pineal gland, of spontaneously hypertensive rats. 5. Therefore, the central kinin system may participate, by both pre- and post-synaptic mechanisms, in the maintenance of hypertension in spontaneously hypertensive rats.

Thyrotropin-releasing hormone increases the number of muscarinic receptors in the lateral septal area of the rat brain

Stereotactic injection of acetylcholine (0.5-2 micrograms) into the lateral septal region of the rat brain produces a long-lasting sympathetic-mediated increase of the arterial blood pressure. This effect is mediated by muscarinic receptors since 1 microgram atropine abolishes this response. In this same brain region, TRH (0.5-4 micrograms) did not elicit any significant change in the arterial blood pressure, but potentiated the effect of acetylcholine. This phenomenon is apparently due to an increase of the number of muscarinic receptors in the lateral septal area of the rat brain.

Corticotropin-releasing hormone differentially modulates the interleukin-1 system according to the level of monocyte activation by endotoxin

The interleukin-1 (IL-1) system is constituted by IL-1 alpha and IL-1 beta and IL-1 receptor antagonist (IL-1ra) that bind the same IL-1 receptors. Hypothalamic-pituitary-adrenal axis hormones are major mediators of the neuroendocrine control over immune function. Corticotropin-releasing hormone (CRH) is produced in peripheral inflammatory sites; its direct effects on inflammatory cytokine synthesis, however, remain unclear. We have studied the effects of CRH (0.1-100 nM) on IL-1 beta and IL-1ra expression by human peripheral monocytes in culture activated with different doses of lipopolysaccharide (LPS). In the absence of LPS, CRH up-regulated IL-1ra and IL-1 beta messenger RNA expression as well as protein synthesis. No significant changes were observed with low doses of LPS (1 ng/ml). In contrast, in combination with high doses of LPS (1 microgram/ml), CRH caused inhibition of IL-1ra and IL-1 beta transcription and secretion. The CRH effects were blocked by its antagonist alpha-helical CRH and mediated by intracellular cAMP. These data indicate that CRH modulates the IL-1 system; depending on the state of activation of the monocyte, CRH exerts an inhibitory control on the activated cell and a stimulatory action on the resting monocyte.

Angiotensin II regulates interferon-gamma production

An extensive literature links the immune responses to neuroendocrine regulation. We have examined the effects of the neuropeptide hormone angiotensin II on the production of the immunomodulatory lymphokine interferon-gamma (IFN-gamma). Angiotensin II (10(-6)-10(-8) M) stimulated (three- to fivefold) the IFN-gamma production in human blood lymphocytes obtained from normal individuals. At 10(-9) M angiotensin II stimulation disappeared and was reestablished at physiological concentrations of the neuropeptide (10(-10)-10(-11) M). Stimulation by angiotensin II was compared with the classical effect of the lectin phytohemagglutinin, and it was seen that both actions are mediated by external calcium (as they are blocked by EGTA 2.5 mM) and that the stimuli follow different kinetics, reaching the steady state at 6 h with angiotensin II and later (18 h) when the lectin was used. The effect of angiotensin II over the IFN-gamma production was blocked by its analog sarcosine 1-isoleucine 8-angiotensin II, showing the specificity of angiotensin II action. These findings demonstrate a selective biological regulation of IFN-gamma production by angiotensin II and suggest another regulation pathway of immune responses.

Serotonin mediates cardiovascular responses to acetylcholine, bradykinin, angiotensin II and norepinephrine in the lateral septal area of the rat brain

The infusion of acetylcholine, bradykinin, angiotensin II, norepinephrine and serotonin into the lateral septal area produced a dose-dependent increase of arterial blood pressure and heart rate. A pattern of inhibition of these cardiovascular responses, produced by pretreatment of the lateral septal area with phentolamine, 6-hydroxydopamine, methysergide and 5,7-dihydroxytryptamine was disclosed. These results suggest that the effects of acetylcholine, bradykinin and partially of angiotensin II, depend on the release of norepinephrine and the actions of this neurotransmitter in turn depend on the integrity of the serotonergic system in the lateral septal area.

Proenkephalin system in human polymorphonuclear cells. Production and release of a novel 1.0-kD peptide derived from synenkephalin

In the hematopoietic system a pluripotent stem cell generates precursors for lymphoid and myeloid lineages. Proenkephalin-derived peptides were previously detected in differentiated lymphoid cells. We have studied whether the proenkephalin system is expressed in a typical differentiated cell of the myeloid lineage, the neutrophil. Human peripheral polymorphonuclear cells contain and release proenkephalin-derived peptides. The opioid portion of proenkephalin (met-enkephalin-containing peptides) was incompletely processed, resulting in the absence of low molecular weight products. The nonopioid synenkephalin (proenkephalin 1-70) molecule was completely processed to a 1.0-kD peptide derived from the COOH-terminal. This molecule was characterized in neutrophils by biochemical and immunocytochemical methods. The chemotactic peptide FMLP and the calcium ionophore A23187 induced the release of the proenkephalin-derived peptides, and this effect was potentiated by cytochalasin B. The materials secreted were similar to those present in the cell, although in the supernatant a higher proportion corresponded to more processed products. The 1.0-kD peptide was detected in human, bovine, and rat neutrophils, but the chromatographic pattern of synenkephalin-derived peptides suggests a differential posttranslational processing among species. These findings demonstrate the existence of the proenkephalin system in human neutrophils and the production and release of a novel 1.0-kD peptide derived from the synenkephalin molecule. The presence of opioid peptides in neutrophils suggests their participation in the inflammatory process, including a local analgesic effect.

Antisense inhibition of thyrotropin-releasing hormone reduces arterial blood pressure in spontaneously hypertensive rats

Thyrotropin-releasing hormone (TRH) plays an important role in central cardiovascular regulation. Recently, we described that the TRH precursor gene overexpression induces hypertension in the normal rat. In addition, we published that spontaneously hypertensive rats (SHR) have central extrahypothalamic TRH hyperactivity with increased TRH synthesis and release and an elevated TRH receptor number. In the present study, we report that intracerebroventricular antisense (AS) treatment with a phosphorothioate oligonucleotide against the TRH precursor gene significantly diminished up to 72 hours and in a dose-dependent manner the increased diencephalic TRH content, whereas normalized systolic blood pressure (SABP) was present in the SHR compared with Wistar-Kyoto (WKY) rats. Although basal thyrotropin was higher in SHR compared with WKY rats and this difference disappeared after antisense treatment, no differences were observed in plasma T4 or T3 between strains with or without AS treatment, indicating that the effect of the AS on SABP was independent of the thyroid status. Because the encephalic renin-angiotensin system seems to be crucial in the development and/or maintenance of hypertension in SHR, we investigated the effect of antisense inhibition of TRH on that system and found that TRH antisense treatment significantly diminished the elevated diencephalic angiotensin II (Ang II) content in the SHR without any effect in control animals, suggesting that the Ang II system is involved in the TRH cardiovascular effects. To summarize, the central TRH system seems to be involved in the etiopathogenesis of hypertension in this model of essential hypertension.

Cholinergic hyperactivity in the lateral septal area of spontaneously hypertensive rats: depressor effect of hemicholinium-3 and pirenzepine

In the lateral septal area of spontaneously hypertensive rats, but not in Wistar-Kyoto rats, the selective M1 antagonist, pirenzepine, and the depletion of acetylcholine storage, by hemicholinium-3 (HC-3), decreased blood pressure. The selective M1 agonist McNeil-A-343, produced a pressor response only after treatment of the lateral septal area with HC-3 in spontaneously hypertensive rats. Carbachol, at doses that mainly affect M2 muscarinic receptors, caused no cardiovascular changes in either strain, pointing to the main intervention of the M1 subtype of muscarinic receptor in the hypertensive condition. In addition, increases in the density of binding sites for [3H]QNB and in Vmax of sodium-dependent, HC-3-inhibitable, high affinity uptake of choline were demonstrated, without significant changes of the activity of choline acetyltransferase in the lateral septal area of spontaneously hypertensive rats. These results suggest that a hyperactivity of the cholinergic system of this area could play a role in the development and/or maintenance of hypertension in spontaneously hypertensive rats.

Mitogenic activation of the human lymphocytes induce the release of proenkephalin derived peptides

Several reports indicate that enkephalins participate in lymphocyte proliferation and several events of the immune response. It has been proposed that peptides involved in these processes may originate in the nervous system or endocrine glands. We have found that human peripheral blood lymphocytes (PBL) activated with a mitogenic agent contain and release proenkephalin derived peptides. The kinetics of met-enkephalin and cryptic products of proenkephalin in PBL activated with phytohemaglutinin (PHA) were studied. Peptides were released to the supernatant of stimulated PBL, reaching the highest values after 18 to 24 hours. The material secreted corresponds to high, intermediate and low molecular weight peptides derived from proenkephalin, displaying met-enkephalin and synenkephalin (proenkephalin 1-70) immunoreactivity. Therefore, an intrinsic lymphocytic proenkephalin system is induced by PHA and may play an important role in the regulation of the immune response.

Interaction of angiotensin II with the cholinergic and noradrenergic systems in the rat pineal gland: regulation of indole metabolism

The pineal gland, angiotensin, and noradrenergic and cholinergic systems are involved in the regulation of tissue indole metabolism. Angiotensin II increased noradrenaline release and the production of hydroxy- and methoxyindoles by pineal slices. Electrical field stimulation (EFS) of pineal slices released angiotensin II and reproduced many of the actions of exogenous angiotensin II on serotonin and melatonin biosynthesis and release. Both sarcosine-isoleucine-angiotensin II ([Sar, Ile]-ANG II) and atropine blocked, and nadolol increased, the effect of EFS and exogenous angiotensin II on serotonin production. Nadolol blocked both the EFS-induced and the angiotensin II-induced production of melatonin. Atropine and [Sar, Ile]-ANG II did not modify melatonin biosynthesis in electrically stimulated slices, but the muscarinic receptor antagonist increased the stimulatory effect of angiotensin II. These data showed that EFS released angiotensin II and noradrenaline from pineal slices and that a close functional connection exists between the peptide and acetylcholine. The stimulation of serotonin biosynthesis and release by these two neurotransmitters was negatively regulated by noradrenaline acting through beta-adrenergic receptors.

The muscarinic agonist pilocarpine inhibits DNA and interferon-gamma synthesis in peripheral blood mononuclear cells

Lymphocyte basal DNA synthesis and proliferative responses to phytohemagglutinin (PHA) showed a dose-dependent (5 X 10(-5)-5 X 10(-3) M) inhibition by the muscarinic agonist pilocarpine, in contrast to the basal enhancing effect produced by the M2 muscarinic-nicotinic agonist carbachol. The effect of pilocarpine was reversed by both atropine (1 X 10(-6) M) and pirenzepine (1 X 10(-7)-1 X 10(-8) M), M1-M2 and M1 muscarinic antagonists, respectively. The effect of pilocarpine may thus be specific for the M1 muscarinic receptor. Pilocarpine also inhibited interferon-gamma (IFN-gamma)-PHA induced production, but was unable to reverse the pokeweed mitogen (PWM)-induced DNA synthesis. Distinct immunoregulatory activities are suggested for cholinergic muscarinic receptors M1 and M2.

Thyrotropin-releasing hormone hyperactivity in the preoptic area of spontaneously hypertensive rats

Thyrotropin-releasing hormone (TRH) plays an important role in central cardiovascular regulation through the activation of different neurotransmitter systems at distinct extrahypothalamic sites. To study possible alterations in the TRH system in the hypertensive state, we measured TRH concentration in cerebrospinal fluid and TRH content of the preoptic area in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) by radioimmunoassay. In addition, we also measured the density of the TRH receptor in this area by a rapid filtration technique using [3H]methyl-TRH. We found a significant increase in both the TRH content (634 +/- 61 versus 350 +/- 26 pg/mg protein, SHR versus WKY; P < .01, n = 5) and density of TRH receptors without changes in affinity (Bmax, 5.0 +/- 0.1 versus 3.3 +/- 0.1 fmol/mg protein, P < .01, n = 4). An increase in TRH concentration was also found in the cerebrospinal fluid of SHR (30 +/- 3 versus 21 +/- 2 pg/mL, P < .01, n = 5), suggesting increased TRH release in the central nervous system. Northern blot analysis indicated a threefold augmented abundance of TRH precursor mRNA in the preoptic area of SHR. A polyclonal antibody raised against TRH injected peripherally or intracerebroventricularly lowered arterial blood pressure in SHR but not in WKY. In addition, long-term treatment with enalapril (5 mg/kg twice daily), which was effective in inhibiting serum angiotensin-converting enzyme activity by more than 50%, decreased arterial blood pressure and preoptic area TRH content of SHR, whereas another vasodilator, diltiazem (10 mg/kg every 8 hours), failed to produce a similar change.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscarinic effects on the hydroxy- and methoxyindole pathway in the rat pineal gland

[3H]Quinuclidinyl benzylate ([3H]QNB)-binding sites, showing similar properties to cholinergic muscarinic receptors in other tissues, were disclosed in the rat pineal gland. Functionality of these receptors was demonstrated, as in-vitro muscarinic activation by pilocarpine increased the pineal metabolic production of the hydroxyindole derivatives 5-hydroxytryptophan and serotonin, with a slight effect on melatonin biosynthesis. Electric-field stimulation of pineal slices caused similar metabolic effects. These effects were inhibited by muscarinic blockade with atropine and enhanced by neostigmine inactivation of acetylcholinesterase. These results suggest that acetylcholine is the neurotransmitter involved. Cholinergic activity may, therefore, regulate indole metabolism in the pineal gland.

Muscarinic M1 receptors in the lateral septal area mediate cardiovascular responses to cholinergic agonists and bradykinin: supersensitivity induced by chronic treatment with atropine

The infusion of pilocarpine, acetylcholine, bradykinin and the selective M1 muscarinic agonist McNeil-A-343 into the lateral septal area produced a dose-dependent increase of arterial blood pressure and heart rate. The M1 muscarinic agonist carbamylcholine that causes a rise in arterial blood pressure when injected into the anterior lateral ventricles did not produce any cardiovascular effects when infused into the lateral septal area. Chronic treatment with atropine induced supersensitivity to the muscarinic agonists and a significant increase in the number of muscarinic receptors. In this study bradykinin failed to produce any significant change in cardiovascular activity. Pirenzepine, a M1 muscarinic blocking agent, inhibited completely the effect of both muscarinic agonists and bradykinin on cardiovascular activity. In fact, in vitro studies shows that the displacement of the binding of [3H]QNB by pirenzepine is compatible with the presence of the M1 subtype of muscarinic receptor in the lateral septal area, where it may play a major role on cardiovascular regulation.

Circadian rhythm and neural regulation of rat pineal angiotensin converting enzyme

Angiotensin converting enzyme was detectable in rat pineal gland and exhibited a circadian rhythm in activity with maximum at the end of the light phase of daily photoperiod. Superior cervical ganglionectomy (SCGx) or exposure to light for 6 days increased enzyme activity and obliterated morning-evening differences, whereas injection of the beta-agonist isoproterenol depressed the high values observed in SCGx animals. These results indicate that angiotensin converting enzyme in the pineal gland is under negative control by the norepinephrine released from pineal sympathetic nerves.

Angiotensin blood levels during the evolution of acute renal failure

1. Angiotensin blood levels (ABL) have been measured in thirteen white patients with diagnoses of acute renal failure of different aetiologies during several stages of the disease and with no evidence of other conditions that could stimulate renin release by the kidney.

2. Mean ABL on admission was 770 SEM 62 ng/l. When daily urinary volume was higher than 1500 ml, these values were significantly lower: 114 SEM 49·6 ng/l.

3. A negative correlation between ABL and systolic blood pressure was obtained (r = −0·35, P = 0·01). The partial correlation coefficients between ABL and systolic blood pressure showed the same results.

4. A negative correlation between the logarithm of ABL and daily urinary volume was obtained. The partial linear correlation coefficients between ABL and urine volume confirmed this relationship.

5. There was no correlation between the ABL and the aetiology of the anuria, its final course, the duration of the disease, the arterial blood pressure and the plasma urea, sodium or potassium levels.

6. It is suggested that the decrease in the ABL has some connection with the re-establishment of the diuresis, possibly through an increase of glomerular filtration rate and in sodium excretion affecting the macula densa cells.