Name: improved renal denervation mitigated hypertension induced by angiotensin ii infusion
Uploaded: 2022-05-26T13:00:00.000+00:00
Duration: 8 min 35 s
Description: Watch this Scientific Journal Video about Improved Renal Denervation Mitigated Hypertension Induced by Angiotensin II Infusion at JoVE.com

This work was supported by the National Natural Science Foundation of China (81770420), Science and Technology Commission of Shanghai Municipality (20140900600), Shanghai Key Laboratory of Clinical Geriatric Medicine (13dz2260700), Shanghai Municipal Key Clinical Specialty (shslczdzk02801) and Center of geriatric coronary artery disease, Huadong Hospital Affiliated to Fudan University.

All animal experimental procedures complied with the relevant ethical Guide for the Care and Use of Laboratory Animals (NIH Publication no. 85-23, revised 2011) and were approved by the committees on animal research of Huadong Hospital affiliated to Fudan University. Fourteen-week-old male C57BL/6 mice (28-30g) were randomly divided into four groups: Sham group, Sham+Ang II group, RDN group, RDN+Ang II group, n = 6 in each group. All animals were maintained under specific closed pathogen-free conditions in a temperature-controlled room at 24 &#177; 1 &#176;C with a 12h light/dark cycle and free access to standard rodent chow and water ad libitum.
1. Preparation of the operation field
<ol>
	<li>Disinfect the operation table with 70% ethanol. Adjust the heating pad temperature to 37 &#176;C.</li>
	<li>Ensure that all surgical instruments are sterilized before surgery at 121 &#176;C for 30 min or by other methods. This procedure requires micro surgical scissors, two fine straight forceps, two fine curved forceps, hemostatic forceps, sterile gauzes, and weighing papers.</li>
</ol>
2. Angiotensin II induced hypertension
<ol>
	<li>Provide meloxicam (0.5 mg/kg, SC) to the C57BL/6 mice shortly before anesthesia induction. Then, anesthetize the mice using sodium pentobarbital injection as previously described20,21. Isoflurane can also be used, if preferred. Confirm anesthesia depth with a negative toe pinch reflex.</li>
	<li>Remove the hair on the back with a shaver. Apply vet ointment to the eyes to prevent dryness while under anesthesia.</li>
	<li>Place the animal on an operating table in the dorsal position. Swab and wipe the shaved area with povidone-iodine followed by three wipes with 70% ethanol.</li>
	<li>Make a 1 cm incision using a sterile scalpel blade, perpendicular to the tail, behind the ear over the shoulder blade of the front leg.</li>
	<li>Use a sterile hemostat to make a subcutaneous tunnel under the skin and create a pocket for the pump22. Insert an osmotic pump filled with Angiotensin II (1,000 ng/kg/min) into the pocket gently. Ensure that there is enough free space to suture the wound without stretching the skin.</li>
	<li>Suture the muscle with interrupted 6-0 Vicryl sutures and close the skin with interrupted 4-0 nylon sutures. Swab and wipe the wound site with povidone-iodine. Perform the same surgery with equal volume of saline for the control group.</li>
	<li>Place all the surgical instruments into a sterilizer for 10 s and replace the sterile gloves between surgeries. Monitor all mice until fully recovered.</li>
	<li>Closely monitor and observe wound healing in mice at least twice a day during the first week and once every day subsequently, including redness, swelling, and infection. Perform dissection immediately if the mice die during Ang II infusion.</li>
	<li>Measure blood pressure at baseline and every week after Ang II infusion with the tail-cuff plethysmography method23 in conscious mice. Ensure that the blood pressure measurement experiments are conducted in a quiet area, at 22 &#177; 2 &#176;C, where mice are acclimatized for 1 h before the experiment begins. Habituate mice for at least 5 consecutive days before baseline blood pressure measurements23,24.</li>
</ol>
3. Bilateral renal denervation
<ol>
	<li>Select the mice with elevated blood pressure (BP) &#8805;140/90mmHg or 25% increase in systolic BP/diastolic BP, 1 week after the Ang II infusion.</li>
	<li>Record animal weight before surgery and choose animals with a minimum weight of 24 g for renal denervation surgery.</li>
	<li>Anesthetize the mice using sodium pentobarbital. Confirm anesthesia depth with a negative toe pinch reflex.</li>
	<li>Remove the hair on the abdomen with a shaver. Perform this procedure carefully and thoroughly to avoid any surgical contamination.</li>
	<li>Place the mice on the operating table, keeping the abdomen up and fix its limbs with tape. Disinfect abdominal skin with povidone-iodine followed by three wipes with 70% ethanol.</li>
	<li>Make a 2 cm ventral midline abdominal incision using a scalpel blade. Pull back the intestine with gauze soaked in 37 &#176;C saline to expose the left renal artery. Carefully yet bluntly dissect the fat away from the renal artery using curved tweezers. (Figure 1A-C).</li>
	<li>Cut the weighing paper into a rectangle of the same size as the renal artery with sterile sharp scissors. For reference, cut the weighing paper in the same size as shown by the dotted line in Figure 1C. 
	NOTE: It is a critical part of the surgery, try to cut several pieces of the weighing paper at a time to keep the same shape.</li>
	<li>Dip the weighing paper in 10% phenol/ethanol solution for at least 30 s. Cover the surface of the left renal artery and wrap the vessel with the weighing paper, keep for 2 min (Figure 1D). Use gauze to protect the surrounding tissues to avoid the weighing paper from touching the surrounding kidney and intestine. 
	&#8203;NOTE: The phenol solution is stable in plastic tubes but not in glass vials. Therefore, the solution must be freshly prepared for every experiment18.</li>
	<li>Perform the same procedure for the right renal artery. Perform the sham surgery with weighing paper immersed in saline.</li>
	<li>Reposition muscles into their initial position and close the peritoneum with 6-0 Vicryl sutures in an interrupted suture. Then, close the skin with interrupted 4-0 nylon sutures. Monitor all mice until fully recovered.</li>
</ol>
4. Post-operative care
<ol>
	<li>Apply povidone-iodine to the incision and place the animal in a warmed electric blanket for recovery and post-operative monitoring.</li>
	<li>Monitor the mice twice a day to assess for redness, swelling, and pain or abdominal infection. Provide meloxicam (0.5 mg/kg, SC) to all mice about 1 h before and 24 h after the RDN procedure.</li>
</ol>

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There are no conflicts of interest, financial or otherwise, as declared by the authors.

Whether RDN could lower blood pressure has become controversial since the publication of the negative result of the symplicity HTN-3 trial7,25. However, the several clinical trials and animal experiments have demonstrated positive and effective results of RDN on hypertensive humans and animals9,10,11,12,13</...

Hypertension is a major chronic cardiovascular disease around the world. Uncontrolled hypertension could damage target organs and contribute to heart failure, stroke, and chronic kidney diseases1,2,3. The prevalence of hypertension has increased from 20% to 31% between 1991 and 2007 in China. The number of adults with hypertension in China could double following a recent revision of the diagnostic criteria for hypertension (130/80 mmHg)4. Hypertension can be controlled by medicine, however, approximately 20% of patients are unable to control their hypertension, even when receiving at least three antihypertensive drugs (including one diuretic) at maximally tolerated dose, which may lead to the development of drug-resistant hypertension5.
Renal sympathetic denervation (RDN) has been proven to be a potential treatment for hypertension. In 2009, Krum and colleagues reported resistant hypertension treatment using RDN for the first time. It was found that percutaneous renal artery ablation can effectively cause persistent blood pressure reduction in patients6. However, the failure of the Symplicity Hypertension 3 (HTN-3) trial impeded the application of RDN7, turning RDN into a controversial therapy. Nevertheless, the prospect of RDN have not yet been ruled out. Recent clinical trials, including RADIANCE-HTN SOLO, SPYRAL HTN-OFF MED/ON MED, and SPYRAL HTN-OFF MED Pivotal have confirmed the efficacy of RDN on hypertension8,9,10,11,12. Thus, more detailed mechanistic research needs to be performed to explore the effects of RDN.
The overall purpose of this study is to demonstrate how RDN in mice can be modified to produce a simpler and more stable surgery. A large number of experiments have studied various approaches of RDN, such as intravascular cryoablation, extracorporeal ultrasound and local application of a chemical or neurotoxin in different animal models13,14,15,16,17. The RDN model generated using chemical ablation with phenol is a well-established experimental model to study the pathogenesis of sympathetic activation on hypertension. This model is generated by chemical corrosion of the renal sympathetic nerves with 10% phenol/ethanol solution using a cotton swab18. On one hand, the conventional RDN potentially inhibit renal sympathetic activity, which then decreases renin secretion and sodium reabsorption, and increases renal blood flow. On the other hand, it suppresses renin-angiotensin-aldosterone system19. Thereby, RDN has a beneficial effect on hypertension. However, the chemical ablation generated RDN model lacks ablation criteria and ablation time and the details of the experimental procedure are yet unclear. Also, there are no technical reports available. In this report, we describe a surgical protocol for the generation of RDN model with phenol using weigh paper in Angiotensin II (Ang II) induced hypertension in C57BL/6 mice. We wrap the renal artery with weighing paper containing phenol and unify the ablation time, which helps to establish a more reproducible, reliable RDN model. This experimental model is aimed to evaluate the effect of RDN on hypertension.

<table><tbody><tr><td>Angiotensin II</td><td>Sangon Biotech</td><td>CAS:4474-91-3</td><td>To make a hypertensive animol model</td></tr><tr><td>Anti-Tyrosine Hydroxylase antibody</td><td>Abcam</td><td>ab137869</td><td>To evaluate the expression of TH of renal nerves</td></tr><tr><td>Blood Pressure Analysis</td><td>Visitech Systems</td><td>BP-2000</td><td>Measure the blood pressure of mice</td></tr><tr><td>Mini-osmotic pump</td><td>DURECT Corporation</td><td>CA 95014</td><td>To fill with Angiotensin II</td></tr><tr><td>Norepinephrine ELISA Kit</td><td>Abcam</td><td>ab287789</td><td>to measure renal norepinephrine levels</td></tr><tr><td>Phenol</td><td>Sangon Biotech</td><td>CAS:108-95-2</td><td>Damage the renal sympathetic nerve</td></tr><tr><td>Weighing paper</td><td>Sangon Biotech</td><td>F512112</td><td>To destroy renal nerve with weighing paper immersed with phenol; https://www.sangon.com/productDetail?productInfo.code=F512112.&amp;nbsp;</td></tr></tbody></table>

improved renal denervation mitigated hypertension induced by angiotensin ii infusion

The benefits of renal sympathetic denervation (RDN) on blood pressure have been proved in a large number of clinical trials in recent years. However, the regulatory mechanism of RDN on hypertension remains elusive. Thus, it&#39;s essential to establish a simpler RDN model in mice. In this study, osmotic mini pumps filled with Angiotensin II were implanted in 14-week-old C57BL/6 mice. One week after the implantation of the mini-osmotic pump, a modified RDN procedure was performed on bilateral renal arteries of the mice using phenol. Age-sex-matched mice were given saline and served as sham group. Blood pressure was measured at baseline and every week subsequently for 21 days. Then, renal artery, abdominal aorta and heart were collected for histological examination using H&#38;E and Masson staining. In this study, we present a simple, practical, repeatable, and standardized RDN model, which can control hypertension and alleviate cardiac hypertrophy. The technique can denervate peripheral renal sympathetic nerves without renal artery damage. Compared to previous models, the modified RDN facilitates the study of the pathobiology and pathophysiology of hypertension.

Statistics 
All data are expressed as mean &#177; standard deviation. One-way ANOVA was used for experiments with three or more conditions followed by Bonferroni posthoc tests for comparisons between individual groups. Consider a p-value equal or less than 0.05 as significant. A commercial software was used to perform all statistical analysis.
Increase in blood pressure induced by Ang II was attenuated after RDN 
Significant increase in systolic BP (...

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Improved Renal Denervation Mitigated Hypertension Induced by Angiotensin II Infusion

Here, we present a protocol for renal sympathetic denervation (RDN) in mice with hypertension induced by Angiotensin II infusion. The procedure is repeatable, convenient and allows to study the regulatory mechanisms of RDN on hypertension and cardiac hypertrophy.

The benefits of renal sympathetic denervation (RDN) on blood pressure have been proved in a large number of clinical trials in recent years. However, the ...

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3.0K Views.  Huadong Hospital Affiliated to Fudan University. Here, we present a protocol for renal sympathetic denervation (RDN) in mice with hypertension induced by Angiotensin II infusion. The procedure is repeatable, convenient and allows to study the regulatory mechanisms of RDN on hypertension and cardiac hypertrophy.

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5/6th Nephrectomy in Combination with High Salt Diet and Nitric Oxide Synthase Inhibition to Induce Chronic Kidney Disease in the Lewis Rat

Chronic kidney disease (CKD) is a global problem. Slowing CKD progression is a major health priority. Since CKD is characterized by complex derangements of homeostasis, integrative animal models are necessary to study development and progression of CKD. To study development of CKD and novel therapeutic interventions in CKD, we use the 5/6th nephrectomy ablation model, a well known experimental model of progressive renal disease, resembling several aspects of human CKD. The gross reduction in renal mass causes progressive glomerular and tubulo-interstitial injury, loss of remnant nephrons and development of systemic and glomerular hypertension. It is also associated with progressive intrarenal capillary loss, inflammation and glomerulosclerosis. Risk factors for CKD invariably impact on endothelial function. To mimic this, we combine removal of 5/6th of renal mass with nitric oxide (NO) depletion and a high salt diet. After arrival and acclimatization, animals receive a NO synthase inhibitor (NG-nitro-L-Arginine) (L-NNA) supplemented to drinking water (20 mg/L) for a period of 4 weeks, followed by right sided uninephrectomy. One week later, a subtotal nephrectomy (SNX) is performed on the left side. After SNX, animals are allowed to recover for two days followed by LNNA in drinking water (20 mg/L) for a further period of 4 weeks. A high salt diet (6%), supplemented in ground chow (see time line Figure 1), is continued throughout the experiment. Progression of renal failure is followed over time by measuring plasma urea, systolic blood pressure and proteinuria. By six weeks after SNX, renal failure has developed. Renal function is measured using 'gold standard' inulin and para-amino hippuric acid (PAH) clearance technology. This model of CKD is characterized by a reduction in glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), hypertension (systolic blood pressure&gt;150 mmHg), proteinuria (&gt; 50 mg/24 hr) and mild uremia (&gt;10 mM). Histological features include tubulo-interstitial damage reflected by inflammation, tubular atrophy and fibrosis and focal glomerulosclerosis leading to massive reduction of healthy glomeruli within the remnant population (&lt;10%). Follow-up until 12 weeks after SNX shows further progression of CKD.

A two-stage method to establish chronic kidney disease (CKD) in the Lewis rat by surgically removing 5/6th of renal mass is described. Combination of the surgical procedure, NOS-inhibition and a high-salt diet leads to a model resembling human CKD, allowing study of causal mechanisms and development of novel therapeutic interventions.

Chronic kidney disease (CKD) is a global problem. Slowing CKD progression is a major health priority. Since CKD is characterized by complex derangements ...

Novel Approach for Simultaneous Recording of Renal Sympathetic Nerve Activity and Blood Pressure with Intravenous Infusion in Conscious, Unrestrained Mice.

Renal sympathetic nerves contribute significantly to both physiological and pathophysiological phenomena. Evaluating renal sympathetic nerve activity (RSNA) is of great interest in many areas of research such as chronic kidney disease, hypertension, heart failure, diabetes and obesity. Unequivocal assessment of the role of the sympathetic nervous system is thus imperative for proper interpretation of experimental results and understanding of disease processes. RSNA has been traditionally measured in anesthetized rodents, including mice. However, mice usually exhibit very low systemic blood pressure and hemodynamic instability for several hours during anesthesia and surgery. Meaningful interpretation of RSNA is confounded by this non-physiological state, given the intimate relationship between sympathetic nervous tone and cardiovascular status. To address this limitation of traditional approaches, we developed a new method for measuring RSNA in conscious, freely-moving mice. Mice were chronically instrumented with radio-telemeters for continuous monitoring of blood pressure as well as a jugular venous infusion catheter and custom-designed bipolar electrode for direct recording of RSNA. Following a 48-72 hour recovery period, survival rate was 100% and all mice behaved normally. At this time-point, RSNA was successfully recorded in 80% of mice, with viable signals acquired up to 4 and 5 days post-surgery in 70% and 50% of mice, respectively. Physiological blood pressures were recorded in all mice (116&plusmn;2 mmHg; n=10). Recorded RSNA increased with eating and grooming, as well-established in the literature. Furthermore, RSNA was validated by ganglionic blockade and modulation of blood pressure with pharmacological agents. Herein, an effective and manageable method for clear recording of RSNA in conscious, freely-moving mice is described.

Anesthetized mice exhibit non-physiological systemic blood pressure, which precludes meaningful assessment of autonomic tone given the intimate relationship between blood pressure and the autonomic nervous system. Thus, a novel method to simultaneously record renal sympathetic nerve activity and blood pressure with intravenous infusion in conscious mice is outlined.

Renal sympathetic nerves contribute significantly to both physiological and pathophysiological phenomena. Evaluating renal sympathetic nerve activity ...

A Modified Two Kidney One Clip Mouse Model of Renin Regulation in Renal Artery Stenosis

Renal artery stenosis is a common condition in patients with coronary or peripheral vascular disease where the renin angiotensin aldosterone system (RAAS) is overactivated. In this context, there is a narrowing of the renal arteries that stimulate an increase in the expression and release of renin, the rate-limiting protease in RAAS. The resulting rise in renin expression is a known driver of renovascular hypertension, frequently associated with kidney injury and end organ damage. Thus, there is a great interest in developing novel treatments for this condition. The molecular and cellular mechanism of renin control in renal artery stenosis is not fully understood and warrants further investigation. To induce renal artery stenosis in mice, a modified 2 kidney 1 clip (2K1C) Goldblatt mouse model was developed. The right kidney was stenosed in wild type mice and sham operated mice were used as control. After renal artery stenosis, we determined renin expression and kidney injury. Kidneys were harvested, and fresh cortices were used to determine protein and mRNA expression of renin. This animal model is reproducible and can be used to study pathophysiological responses, molecular and cellular pathways involved in renovascular hypertension and kidney injury.

A modified 2 kidney 1 clip (2K1C) Goldblatt mouse model was developed using polyurethane tubing to initiate renal artery stenosis, inducing an increase in renin expression and kidney injury. Here, we describe a detailed procedure of preparing and placing the cuff onto the renal artery to generate a reproducible and consistent 2K1C mouse model.

Renal artery stenosis is a common condition in patients with coronary or peripheral vascular disease where the renin angiotensin aldosterone system (RAAS) ...

Jiawei Shengjiang San to Address Diabetic Nephropathy Using Network Pharmacology

Antagonistic Effect of Jiawei Shengjiang San on a Rat Model of Diabetic Nephropathy: Related to EGFR/MAPK3/1 Signaling Pathway

We aimed to delve into the mechanisms underpinning Jiawei Shengjiang San's (JWSJS) action in treating diabetic nephropathy and deploying network pharmacology. Employing network pharmacology and molecular docking techniques, we predicted the active components and targets of JWSJS and constructed a meticulous "drug-component-target" network. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses were utilized to discern the therapeutic pathways and targets of JWSJS. Autodock Vina 1.2.0 was deployed for molecular docking verification, and a 100-ns molecular dynamics simulation was conducted to affirm the docking results, followed by in vivo animal verification. The findings revealed that JWSJS shared 227 intersecting targets with diabetic nephropathy, constructing a protein-protein interaction network topology. KEGG enrichment analysis denoted that JWSJS mitigates diabetic nephropathy by modulating lipids and atherosclerosis, the PI3K-Akt signaling pathway, apoptosis, and the HIF-1 signaling pathway, with mitogen-activated protein kinase 1 (MAPK1), MAPK3, epidermal growth factor receptor (EGFR), and serine/threonine-protein kinase 1 (AKT1) identified as collective targets of multiple pathways. Molecular docking asserted that the core components of JWSJS (quercetin, palmitoleic acid, and luteolin) could stabilize conformation with three pivotal targets (MAPK1, MAPK3, and EGFR) through hydrogen bonding. In vivo examinations indicated notable augmentation in body weight and reductions in glycated serum protein (GSP), low-density lipoprotein cholesterol (LDL-C), uridine triphosphate (UTP), and fasting blood glucose (FBG) levels due to JWSJS. Electron microscopy coupled with hematoxylin and eosin (HE) and Periodic acid-Schiff (PAS) staining highlighted the potential of each treatment group in alleviating kidney damage to diverse extents, exhibiting varied declines in p-EGFR, p-MAPK3/1, and BAX, and increments in BCL-2 expression in the kidney tissues of the treated rats. Conclusively, these insights suggest that the protective efficacy of JWSJS on diabetic nephropathy might be associated with suppressing the activation of the EGFR/MAPK3/1 signaling pathway and alleviating renal cell apoptosis.

Author Spotlight: Network Pharmacology and Molecular Docking to Decipher the Action of Jiawei Shengjiang San Against Diabetic Kidney Disease

Here, we present a protocol describing network pharmacology and molecular docking techniques to explore the mechanism of action of Jiawei Shengjiang San (JWSJS) in treating diabetic nephropathy.

We aimed to delve into the mechanisms underpinning Jiawei Shengjiang San's (JWSJS) action in treating diabetic nephropathy and deploying network ...

Sympathetic Denervation of Renal Arteries in an Angiotensin II-Induced Hypertension Mouse Model

Source: Wang, M., et al., <a href="https://app.jove.com/v/63719">Improved Renal Denervation Mitigated Hypertension Induced by Angiotensin II Infusion.</a> J. Vis. Exp. (2022)
This video demonstrates a procedure for renal artery sympathetic denervation in an angiotensin II-induced hypertensive mouse model, using phenol to disrupt sympathetic nerve function and reduce blood pressure.

Source: Wang, M., et al., Improved Renal Denervation Mitigated Hypertension Induced by Angiotensin II Infusion. J. Vis. Exp. (2022)
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JoVE Encyclopedia of Experiments

Neuroscience

Neuropathology

Cerebrovascular Diseases

Recording Changes in Renal Sympathetic Nerve Activity in Response to Arterial Pressure in Rats

Source: Fink, A. M., et al. <a href="https://app.jove.com/v/58205">Quantifying Acute Changes in Renal Sympathetic Nerve Activity in Response to Central Nervous System Manipulations in Anesthetized Rats.</a> J. Vis. Exp. (2018).
This video demonstrates a technique of studying the activity of renal sympathetic nerves (RSNs) in response to changes in arterial pressure in rats. Upon attaching a pressure-sensing catheter to the femoral artery, the renal sympathetic nerves are exposed. The nerves are then lifted onto a recording electrode, and their electrical activity is recorded. Next, a vasoconstricting drug is injected to elevate blood pressure, and corresponding changes in RSN activity are monitored.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
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Neurophysiology

Electrophysiology Techniques

Antihypertensive Drugs: Angiotensin-Converting Enzyme Inhibitors

Angiotensin-converting enzyme (ACE), a vital component of the renin-angiotensin-aldosterone system, is abundant in lung endothelial cells. ACE converts the inactive decapeptide, angiotensin I, into the active octapeptide, angiotensin II. This potent vasoconstrictor narrows blood vessels, increasing resistance to blood flow and elevating blood pressure. Angiotensin II also stimulates aldosterone production, encouraging kidney cells to reabsorb more sodium and water from urine, thereby increasing blood volume and pressure. In addition, ACE interacts with the endogenous vasodilator peptide bradykinin and degrades it,&#160; promoting nitric oxide generation and relaxing smooth muscle cells in blood vessels. However, ACE degrades bradykinin into inactive peptides, reducing its vasodilatory effect. ACE inhibitors halt ACE&#39;s action, preventing the conversion of angiotensin I to angiotensin II, allowing blood vessels to dilate, and reducing blood pressure. Lower levels of angiotensin II yield less aldosterone, prompting the kidneys to excrete more sodium and water, further decreasing blood volume and pressure. ACE inhibitors also slow the degradation of bradykinin, contributing to decreased blood pressure and vasodilation. Structurally, ACE inhibitors are categorized into sulfhydryl-containing, dicarboxylate-containing, and phosphorus-containing groups. Sulfhydryl-containing ACE inhibitors, such as captopril, have a sulfhydryl group. Dicarboxylate-containing ones, like enalapril and lisinopril, contain two carboxylate groups, while phosphorus-containing ACE inhibitors, like fosinopril, feature a phosphonate group.

Angiotensin-converting enzyme (ACE), a vital component of the renin-angiotensin-aldosterone system, is abundant in lung endothelial cells. ACE converts ...

KEY TERMS AND CONCEPTS

Antihypertensive Drugs: Angiotensin II Receptor Blockers

In the renin-angiotensin-aldosterone system, a hormone called angiotensin II plays a crucial role. It binds to the AT1 receptors in vascular smooth muscles coupled with Gq proteins. The activation of these receptors activates an enzyme called phospholipase C, which releases two molecules: inositol trisphosphate and diacylglycerol. These molecules cause a chain reaction that leads to the phosphorylation of myosin light chains and promotes interaction between actin and myosin, leading to smooth muscle contraction and blood vessel constriction. This vasoconstriction effect increases the resistance to blood flow in the peripheral parts of the body, leading to an increase in blood pressure.
The activation of the AT1 receptor also stimulates the secretion of aldosterone, a hormone that promotes sodium and water retention in the kidneys, increasing blood volume and pressure. Angiotensin receptor blockers (ARBs) such as losartan and valsartan are used to treat high blood pressure. These medications compete with angiotensin II to bind to the AT1 receptor and deactivate it, reducing vasoconstriction. As a result, blood vessels dilate, peripheral resistance decreases, and blood pressure is reduced. AT1 receptor blockage also suppresses aldosterone secretion, which decreases sodium and water reabsorption by the kidneys and lowers blood volume and pressure. Unlike ACE inhibitors, which increase bradykinin levels, leading to a dry cough, ARBs do not have this effect, resulting in no dry cough.

In the renin-angiotensin-aldosterone system, a hormone called angiotensin II plays a crucial role. It binds to the AT1 receptors in vascular smooth ...

Antihypertensive Drugs: Direct Renin Inhibitors

The renin-angiotensin-aldosterone system (RAAS) is an intricate physiological pathway involving numerous enzymes and hormones, including renin, angiotensin-converting enzyme (ACE), angiotensin I and II, and aldosterone. Imbalances within this system increase the production of angiotensin II and aldosterone. Increased angiotensin II levels promote vasoconstriction and blood pressure elevation. Concurrently, higher aldosterone levels stimulate sodium and water reabsorption in the kidneys, resulting in augmented blood volume and pressure. Hypertension, or high blood pressure, is often managed with inhibitors targeting different stages of RAAS. Angiotensin II receptor blockers (ARBs) obstruct angiotensin II from binding to receptors, instigating vasodilation and blood pressure reduction. ACE inhibitors hinder the transformation of angiotensin I to angiotensin II, lessening vasoconstriction and fluid volume, thereby lowering blood pressure. However, these inhibitors cannot inhibit ACE-independent pathways mediated by enzymes such as chymase or cathepsin G, which can enable angiotensin II production and its effects. To completely inhibit angiotensin II production, the initial step must be blocked. Direct renin inhibitors, like aliskiren, achieve this by directly binding to renin and preventing the conversion of angiotensinogen to angiotensin I. As a result, angiotensin II production decreases, leading to decreased vasoconstriction and lower blood pressure. Reduced angiotensin II production also diminishes aldosterone secretion, decreasing renal sodium and water reabsorption and reducing blood volume and pressure. However, aliskiren has side effects such as headache, gastroesophageal reflux, dizziness, fatigue, allergic reactions, and angioedema.

The renin-angiotensin-aldosterone system (RAAS) is an intricate physiological pathway involving numerous enzymes and hormones, including renin, ...

Heart Failure Drugs: Inhibitors of Renin-Angiotensin System

The activation of the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS) contributes to cardiac remodeling, and inhibiting the RAAS is a pharmacological target in heart failure management. As a result, neurohumoral modulation is a crucial treatment principle for managing heart failure. This approach involves using medications like ACE inhibitors (ACEIs), angiotensin receptor blockers (ARBs), &#946;-blockers, mineralocorticoid receptor antagonists (MRAs), and neutral endopeptidase inhibitors to counter the harmful effects of neurohumoral activation on the heart, blood vessels, and kidneys.
ACEIs work by reducing angiotensin II levels. They have several physiological effects, including vasodilation, reduced aldosterone release, anti-remodeling effects on the heart, and sympatholytic effects. ACEIs can cause dry cough or rare angioedema due to increased bradykinin and substance P levels. ARBs are highly selective AT1 receptor antagonists used as alternatives to ACEIs in patients who cannot tolerate them. They can increase hypotension, hyperkalemia, and renal dysfunction. &#946;-blockers reduce the actions of catecholamines on &#946;-adrenoceptors, leading to decreased heart rate, force, and AV conduction. They also suppress arrhythmias and lower renin levels and may have varying effects on bronchoconstriction and vasoconstriction. MRAs, such as spironolactone and eplerenone, block aldosterone receptors and reduce fibrosis. These drugs have a documented life-prolonging effect in heart failure patients but can precipitate dysmenorrhea, gynecomastia, and hyperkalemia. Sacubitril/valsartan, a combination drug, activates the beneficial axis of neurohumoral activation and provides multiple benefits such as natriuresis, vasodilation, inhibition of thrombosis, and cardiac remodeling. ACEIs and ARBs reduce peripheral resistance, afterload, salt/water retention, and sympathetic activity. ACEIs are the preferred initial treatment for left ventricular dysfunction without edema. ARBs are alternatives for patients intolerant to ACEIs.

The activation of the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS) contributes to cardiac remodeling, and inhibiting the ...