Angiotensin II acting on brain AT1 receptors induces adrenaline secretion and pressor responses in the rat

Therapeutic targets in the brain for overactive bladder: A focus on angiotensin II type 1 receptor

Overactive bladder is a condition that affects both men and women, and significantly affects patients' quality of life. Anticholinergics, β3-adrenoceptor agonists, and botulinum toxin are currently being used for treatment. However, several patients do not respond to these medications or discontinue them because of adverse events. Angiotensin II (Ang II) is a neuropeptide produced in both brain and peripheral tissues, and Ang II type 1 (AT1) receptors, which are important regions for the micturition reflex, are widely expressed in the cerebral cortex, paraventricular nucleus, solitary tract nucleus, and periaqueductal gray. Our data showed that cumulative central Ang II administration, even at low doses, shortened the intercontraction interval without affecting the blood pressure or blood catecholamine levels. Additionally, Ang II can enhance the micturition reflex by suppressing the GABAergic nervous system and stimulating the downstream pathway of the AT1 receptor. The peripherally administered AT1 receptor blocker telmisartan inhibited central Ang II-induced facilitation of the micturition reflex. Targeting the central AT1 receptor may be a potential treatment approach for patients with overactive bladder. This review introduces the brain AT1 receptor as a therapeutic target in overactive bladder.

Effect of Angiotensin receptor blockade on Plasma Osmolality and Neurohumoral Responses to High Environmental Temperature in Rats Fed a High Salt Diet

Plasma osmolality (pOsmol) and neurohumoral signals play important roles in the pathophysiology of cardiovascular diseases. Our study investigated the effect of high environmental temperature (HET) on neurohumoral responses and pOsmol in rats fed a high salt diet (HSD), with and without angiotensin II receptor blockade (ARB), using telmisartan.  Fifty-six male 8-week old Sprague-Dawley rats (95-110g) were randomly assigned into seven groups of 8 rats. These included control rats (I) fed with 0.3% NaCl diet (normal diet, ND); salt-loaded rats (II) fed with 8% NaCl (high salt) diet; ND rats (III) exposed to HET (38.5±0.5oC ) 4 hours daily per week; rats (IV) fed with 8% NaCl diet and exposed to HET daily. Others included rats (V) fed with 8% NaCl diet and treated with telmisartan (30mg/kg); ND rats (VI) exposed to HET and treated with telmisartan; rats (VI) fed with 8% NaCl diet, exposed to HET and treated with telmisartan. Plasma angiotensin II, aldosterone, vasopressin and norepinephrine (NE) concentrations were determined by ELISA technique; pOsmol from plasma K+, Na+ and Urea. HSD combined with HET in rats synergistically increased pOsmol (P<0.001) with an associated non-synergistic rise in fluid intake (P<0.001), fluid balance (P<0.001), plasma angiotensin II (P<0.01) and aldosterone (P<0.05), NE (P<0.001) and vasopressin (P<0.05) concentrations compared to control. Telmisartan did not alter pOsmol in all the treated-rats, but normalized fluid intake levels and plasma vasopressin in the rats exposed to either HSD or HEt alone. Prolonged exposure of rats to hot environment exacerbated the effect of excess dietary salt on pOsmol, with no effect on angiotensin II-mediated neurohumoral responses.

On the footsteps of Hippocrates, Sanctorius and Harvey to better understand the influence of cold on the occurrence of COVID-19 in European countries in 2020

COVID-19 pandemic has been characterized by a pattern of consecutive declines and regrowth in European countries in 2020. After being partially regressed during the summer, the reappearance of the infection during fall 2020 in many temperate countries strongly suggests that temperature and cold may play a role in influencing the infectivity and virulence of SARS-CoV-2. While promoting medicine as an art, Hippocrates interpreted with logical reasoning the occurrence of diseases such as epidemics, as a consequence of environmental factors, in particular climatic variations. During the Renaissance, Sanctorius was one of the first to perform quantitative measurements, and Harvey discovered the circulation of blood by performing experimental procedures in animals. We think that a reasoning mixing various observations, measurements and experiments is fundamental to understand how cold increases infectivity and virulence of SARS-CoV-2. By this review, we provide evidence linking cold, angiotensin-II, vasoconstriction, hypoxia and aerobic glycolysis (the Warburg effect) to explain how cold affects the epidemiology of COVID-19. Also, a low humidity increases virus transmissibility, while a warm atmosphere, a moderate airway humidity, and the production of vasodilator angiotensin 1-7 by ACE2 are less favorable to the virus entry and/or its development. The meteorological and environmental parameters impacting COVID-19 pandemic should be reintegrated into a whole perspective by taking into account the different factors influencing transmissibility, infectivity and virulence of SARS-CoV-2. To understand the modern enigma represented by COVID-19, an interdisciplinary approach is surely essential.

Potential Effects of Delphinidin-3-O-Sambubioside and Cyanidin-3-O-Sambubioside of Hibiscus sabdariffa L. on Ruminant Meat and Milk Quality

Simple Summary

Hibiscus sabdariffa (HS) calyxes are widely used as nutraceutical supplements in humans; however, stalks, leaves, and seeds are considered as agriculture by-products. Including HS by-products in animal feeding could reduce economic costs and environmental problems, and due to their bioactive compounds, could even improve the quality of meat and milk. However, although HS antioxidants have not been tested enough in ruminants, comparison with other by-products rich in polyphenols allows for hypothesizing on the potential effects of including HS by-products and calyxes in nutrition, animal performance, and meat and milk quality. Antioxidants of HS might affect ruminal fiber degradability, fermentation patterns, fatty acids biohydrogenation (BH), and reduce the methane emissions. After antioxidants cross into the bloodstream and deposit into ruminants’ milk and meat, they increase the quality of fatty acids, the antioxidant activity, and the shelf-life stability of dairy products and meat, which leads to positive effects in consumers’ health. In other animals, the specific anthocyanins of HS have improved blood pressure, which leads to positive clinical and chemicals effects, and those could affect some productive variables in ruminants. The HS by-products rich in polyphenols and anthocyanins can improve fatty acid quality and reduce the oxidative effects on the color, odor, and flavor of milk products and meat.

Abstract

The objective was to review the potential effects of adding anthocyanin delphinidin-3-O-sambubioside (DOS) and cyanidin-3-O-sambubioside (COS) of HS in animal diets. One hundred and four scientific articles published before 2021 in clinics, pharmacology, nutrition, and animal production were included. The grains/concentrate, metabolic exigency, and caloric stress contribute to increasing the reactive oxygen species (ROS). COS and DOS have antioxidant, antibacterial, antiviral, and anthelmintic activities. In the rumen, anthocyanin might obtain interactions and/or synergisms with substrates, microorganisms, and enzymes which could affect the fiber degradability and decrease potential methane (CH₄) emissions; since anthocyanin interferes with ruminal fatty acids biohydrogenation (BH), they can increase the n-3 and n-6 polyunsaturated fatty acids (PUFA), linoleic acid (LA), and conjugated linoleic acid (CLA) in milk and meat, as well as improving their quality. Anthocyanins reduce plasma oxidation and can be deposited in milk and meat, increasing antioxidant activities. Therefore, the reduction of the oxidation of fats and proteins improves shelf-life. Although studies in ruminants are required, COS and DOS act as inhibitors of the angiotensin-converting enzyme (ACEi) and rennin expression, regulating the homeostatic control and possibly the milk yield and body weight. By-products of HS contain polyphenols as calyces with positive effects on the average daily gain and fat meat quality.

Psychological/mental stress-induced effects on urinary function: Possible brain molecules related to psychological/mental stress-induced effects on urinary function

Exposure to psychological/mental stress can affect urinary function, and lead to and exacerbate lower urinary tract dysfunctions. There is increasing evidence showing stress-induced changes not only at phenomenological levels in micturition, but also at multiple levels, lower urinary tract tissues, and peripheral and central nervous systems. The brain plays crucial roles in the regulation of the body's responses to stress; however, it is still unclear how the brain integrates stress-related information to induce changes at these multiple levels, thereby affecting urinary function and lower urinary tract dysfunctions. In this review, we introduce recent urological studies investigating the effects of stress exposure on urinary function and lower urinary tract dysfunctions, and our recent studies exploring "pro-micturition" and "anti-micturition" brain molecules related to stress responses. Based on evidence from these studies, we discuss the future directions of central neurourological research investigating how stress exposure-induced changes at peripheral and central levels affect urinary function and lower urinary tract dysfunctions. Brain molecules that we explored might be entry points into dissecting the stress-mediated process for modulating micturition.

Stimulation of brain α7-nicotinic acetylcholine receptors suppresses the rat micturition through brain GABAergic receptors

Brain nicotinic acetylcholine receptors (nAChRs) reportedly suppress the micturition, but the mechanisms responsible for this suppression remain unclear. We previously reported that intracerebroventricularly administered (±)-epibatidine (non-selective nAChR agonist) activated the sympatho-adrenomedullary system, which can affect the micturition. Therefore, we investigated (1) whether intracerebroventricularly administered (±)-epibatidine-induced effects on the micturition were dependent on the sympatho-adrenomedullary system, and (2) brain nAChR subtypes involved in the (±)-epibatidine-induced effects in urethane-anesthetized male Wistar rats. Plasma noradrenaline and adrenaline (catecholamines) were measured just before and 5 min after (±)-epibatidine administration. Evaluation of urodynamic parameters, intercontraction intervals (ICI) and maximal voiding pressure (MVP) by cystometry was started 1 h before (±)-epibatidine administration or intracerebroventricular pretreatment with other drugs and continued 1 h after (±)-epibatidine administration. Intracerebroventricularly administered (±)-epibatidine elevated plasma catecholamines and prolonged ICI without affecting MVP, and these changes were suppressed by intracerebroventricularly pretreated mecamylamine (non-selective nAChR antagonist). Acute bilateral adrenalectomy abolished the (±)-epibatidine-induced elevation of plasma catecholamines, but had no effect on the (±)-epibatidine-induced ICI prolongation. The latter was suppressed by intracerebroventricularly pretreated methyllycaconitine (selective α7-nAChR antagonist), SR95531 (GABAA antagonist), and SCH50911 (GABAB antagonist), but not by dihydro-β-erythroidine (selective α4β2-nAChR antagonist). Intracerebroventricularly administered PHA568487 (selective α7-nAChR agonist) prolonged ICI without affecting MVP, similar to (±)-epibatidine. These results suggest that stimulation of brain α7-nAChRs suppresses the rat micturition through brain GABAA/GABAB receptors, independently of the sympatho-adrenomedullary outflow modulation.

Adrenal angiotensin II type 1 receptor biased signaling: The case for "biased" inverse agonism for effective aldosterone suppression

Angiotensin II (AngII) uses two distinct G protein-coupled receptor (GPCR) types, AT₁R and AT₂R, to exert a plethora of physiologic effects in the body and to significantly affect cardiovascular homeostasis. Although not much is known about the signaling of the AT₂R, AT₁R signaling is known to be quite pleiotropic, mobilizing a variety of signal transducers inside cells to produce a biological outcome. When the outcome in question is aldosterone production from the adrenal cortex, the main transducers activated specifically by the adrenocortical AT₁R to signal toward that cellular effect are the G_q/11 protein alpha subunits and the β-arrestins (also known as Arrestin-2 and -3). The existence of various downstream pathways the AT₁R signal can travel down on has led to the ever-expanding filed of GPCR pharmacology termed "biased" signaling, which refers to a ligand preferentially activating one signaling pathway over others downstream of the same receptor in the same cell. However, "biased" signaling or "biased" agonism is therapeutically desirable only when the downstream pathways lead to different or opposite cellular outcomes, so the pathway promoting the beneficial effect can be selectively activated over the pathway that leads to detrimental consequences. In the case of the adrenal AT₁R, both G_q/11 proteins and β-arrestins mediate signaling to the same end-result: aldosterone synthesis and secretion. Therefore, both pathways need to remain inactive in the adrenal cortex to fully suppress the production of aldosterone, which is one of the culprit hormones elevated in chronic heart failure, hypertension, and various other cardiovascular diseases. Variations in the effectiveness of the AT₁R antagonists, which constitute the angiotensin receptor blocker (ARB) class of drugs (also known as sartans), at the relative blockade of these two pathways downstream of the adrenal AT₁R opens the door to the flip term "biased" inverse agonism at the AT₁R. ARBs that are unbiased and equipotent inverse agonists for both G proteins and β-arrestins at this receptor, like candesartan and valsartan, are the most preferred agents with the best efficacy at reducing circulating aldosterone, thereby ameliorating heart failure. In the present review, the biased signaling of the adrenal AT₁R, particularly in relation to aldosterone production, is examined and the term "biased" inverse agonism at the AT₁R is introduced and explained, as a means of pharmacological categorization of the various agents within the ARB drug class.

Non-Invasive Strategies for Nose-to-Brain Drug Delivery

Intranasal drug administration is a promising method for delivering drugs directly to the brain. Animal studies have described pathways and potential brain targets, but nose-to-brain delivery and treatment efficacy in humans remains debated. We describe the proposed pathways and barriers for nose-to-brain drug delivery in humans, drug properties that influence central nervous system delivery, clinically tested methods to enhance absorption, and the devices used in clinical trials. This review compiles the available evidence for nose-to-brain drug delivery in humans and summarizes the factors involved in nose-to-brain drug delivery.

Gut microbiota and neuroinflammation in pathogenesis of hypertension: A potential role for hydrogen sulfide

Inflammation and gut dysbiosis are hallmarks of hypertension (HTN). Hydrogen sulfide (H2S) is an important freely diffusing molecule that modulates the function of neural, cardiovascular and immune systems, and circulating levels of H2S are reduced in animals and humans with HTN. While most research to date has focused on H₂S produced endogenously by the host, H2S is also produced by the gut bacteria and may affect the host homeostasis. Here, we review an association between neuroinflammation and gut dysbiosis in HTN, with special emphasis on a potential role of H2S in this interplay.

Angiotensin II, a stress-related neuropeptide in the CNS, facilitates micturition reflex in rats

BACKGROUND AND PURPOSE

We investigated the effects of centrally administered stress-related neuropeptide, angiotensin II, on the micturition reflex and the downstream signalling pathways in rats.

EXPERIMENTAL APPROACH

Male Wistar rats were anaesthetized with urethane for cystometry before and after i.c.v. administration of vehicle or angiotensin II (30 pmol). Muscimol (a GABA_A receptor agonist) or baclofen (a GABA_B receptor agonist) was i.c.v. administered 30 min before or 15 min after central angiotensin II administration. Telmisartan [an angiotensin II type 1 (AT₁ ) receptor antagonist], valsartan (an AT₁ receptor antagonist), PD123319 (an AT₂ receptor antagonist), U-73122 (a PLC inhibitor), chelerythrine chloride (a PKC inhibitor), apocynin (a NADPH oxidase inhibitor) or tempol (an antioxidant) was centrally administered 30 min before central angiotensin II administration.

KEY RESULTS

Centrally administered angiotensin II significantly shortened the intercontraction interval and decreased the voided volume and bladder capacity without altering the maximum voiding pressure, post-voiding residual urine volume or voiding efficacy. Muscimol, baclofen, telmisartan, valsartan, U-73122, chelerythrine chloride, apocynin or tempol pretreatment significantly suppressed the reduction in intercontraction interval induced by central angiotensin II. Post-treatment with muscimol or baclofen also ameliorated the decrease in intercontraction interval induced by central angiotensin II.

CONCLUSIONS AND IMPLICATIONS

Angiotensin II in the CNS facilitates micturition reflex by inhibiting central GABAergic activity and activating the AT₁ receptor/PLC/PKC/NADPH oxidase/superoxide anion pathway.

The role of brain angiotensin II (type 2) receptors and nitric oxide in the renal sympathoinhibitory response to acute volume expansion in conscious rats

OBJECTIVE

The study was performed to investigate the role of angiotensin II type 2 (AT2) receptors and nitric oxide in the renal sympathoinhibitory response to volume expansion (VEP).

METHOD

Conscious rats were subjected to volume expansion (VEP) [0.25% body weight/min saline for 10 min intravenously (i.v.)] following intracerebroventricular (i.c.v.) infusion of either saline or angiotensin II (Ang II), or a combination of Ang II with either losartan, PD123319, or N-nitro-L-arginine methyl ester (L-NAME).

RESULTS

Intracerebroventricular losartan, PD123319, or L-NAME did not change baseline mean arterial pressure, heart rate, or renal sympathetic nerve activity (RSNA). However, i.c.v. Ang II increased mean arterial pressure and decreased heart rate and RSNA baselines (113 ± 2 vs. 107 ± 2 mmHg, 365 ± 7 vs. 379 ± 5 beats/min, 1.03 ± 0.13 vs. 1.29 ± 0.15 μV.s, respectively, all P < 0.05). During i.c.v. saline infusion, VEP decreased RSNA by 27 ± 2% (P < 0.05) after 10 min and the magnitude of this response was unchanged during i.c.v. infusion of Ang II, losartan, or PD123319 but was decreased by L-NAME compared with that obtained with i.c.v. saline (14 ± 3 vs. 30 ± 5%, P < 0.05). i.c.v. Ang II in combination with losartan enhanced (41 ± 3 vs. 29 ± 5%) but with PD123319 decreased (15 ± 2 vs. 28 ± 4%, P < 0.05) the renal sympathoinhibition compared with Ang II alone. The renal sympathoinhibitory response was enhanced (43 ± 5 vs. 29 ± 1%, P < 0.05) by i.c.v. infusion of an AT2 agonist, CGP42112 the magnitude of which was unchanged when combined with L-NAME. The sympathoinhibitory response to VEP following Ang II plus L-NAME was similar to Ang II alone.

CONCLUSION

These findings suggest that activation of central AT2 receptors enhances the renal sympathoinhibitory response to VEP but this effect is not dependent on nitric oxide.

Angiotensin II centrally induces frequent detrusor contractility of the bladder by acting on brain angiotensin II type 1 receptors in rats

Angiotensin (Ang) II plays an important role in the brain as a neurotransmitter and is involved in psychological stress reactions, for example through activation of the sympatho-adrenomedullary system. We investigated the effects of centrally administered Ang II on the micturition reflex, which is potentially affected by the sympatho-adrenomedullary system, and brain Ang II receptors in urethane-anesthetized (1.0 g/kg, intraperitoneally) male rats. Central administration of Ang II (0.01, 0.02, and 0.07 nmol per rat, intracerebroventricularly, icv) but not vehicle rapidly and dose-dependently decreased the urinary bladder intercontraction interval, without altering the bladder detrusor pressure. Central administration of antagonists of Ang II type 1 but not type 2 receptors inhibited the Ang II-induced shortening of intercontraction intervals. Administration of the highest dose of Ang II (0.07 nmol per rat, icv) but not lower doses (0.01 and 0.02 nmol per rat, icv) elevated the plasma concentration of adrenaline. Bilateral adrenalectomy reduced Ang II-induced elevation in adrenaline, but had no effect on the Ang II-induced shortening of the intercontraction interval. These data suggest that central administration of Ang II increases urinary frequency by acting on brain Ang II type 1 receptors, independent of activation of the sympatho-adrenomedullary system.

A Stress-Related Peptide Bombesin Centrally Induces Frequent Urination through Brain Bombesin Receptor Types 1 and 2 in the Rat

Stress exacerbates symptoms of bladder dysfunction including overactive bladder and bladder pain syndrome, but the underlying mechanisms are unknown. Bombesin-like peptides and bombesin receptor types 1 and 2 (BB1 and BB2, respectively) in the brain have been implicated in the mediation/integration of stress responses. In this study, we examined effects of centrally administered bombesin on micturition, focusing on their dependence on 1) the sympathoadrenomedullary system (a representative mechanism activated by stress exposure) and 2) brain BB receptors in urethane-anesthetized (1.0-1.2 g/kg, i.p.) male rats. Intracerebroventricularly administered bombesin significantly shortened intercontraction intervals (ICI) at both doses (0.1 and 1 nmol/animal) without affecting maximal voiding pressure. Bombesin at 1 nmol induced significant increments of plasma noradrenaline and adrenaline levels, which were both abolished by acute bilateral adrenalectomy. On the other hand, adrenalectomy showed no effects on the bombesin-induced shortening of ICI. Much lower doses of bombesin (0.01 and 0.03 nmol/animal, i.c.v.) dose-dependently shortened ICI. Pretreatment with either a BB1 receptor antagonist (BIM-23127; d-Nal-cyclo[Cys-Tyr-d-Trp-Orn-Val-Cys]-Nal-NH2; 3 nmol/animal, i.c.v.) or a BB2 receptor antagonist (BEA; H-d-Phe-Gln-Trp-Ala-Val-Gly-His-Leu-NHEt; 3 nmol/animal, i.c.v.), respectively, suppressed the BB (0.03 nmol/animal, i.c.v.)-induced shortening of ICI, whereas each antagonist by itself (1 and 3 nmol/animal, i.c.v.) had no significant effects on ICI. Bombesin (0.03 nmol/animal, i.c.v.) significantly reduced voided volume per micturition and bladder capacity without affecting postvoid residual volume or voiding efficiency. These results suggest that brain bombesin and BB receptors are involved in facilitation of the rat micturition reflex to induce bladder overactivity, which is independent of the sympathoadrenomedullary outflow modulation.