The Heart as a Target of Vasopressin and Other Cardiovascular Peptides in Health and Cardiovascular Diseases

The automatism of cardiac pacemaker cells, which is tuned, is regulated by the autonomic nervous system (ANS) and multiple endocrine and paracrine factors, including cardiovascular peptides. The cardiovascular peptides (CPs) form a group of essential paracrine factors affecting the function of the heart and vessels. They may also be produced in other organs and penetrate to the heart via systemic circulation. The present review draws attention to the role of vasopressin (AVP) and some other cardiovascular peptides (angiotensins, oxytocin, cytokines) in the regulation of the cardiovascular system in health and cardiovascular diseases, especially in post-infarct heart failure, hypertension and cerebrovascular strokes. Vasopressin is synthesized mostly by the neuroendocrine cells of the hypothalamus. There is also evidence that it may be produced in the heart and lungs. The secretion of AVP and other CPs is markedly influenced by changes in blood volume and pressure, as well as by other disturbances, frequently occurring in cardiovascular diseases (hypoxia, pain, stress, inflammation). Myocardial infarction, hypertension and cardiovascular shock are associated with an increased secretion of AVP and altered responsiveness of the cardiovascular system to its action. The majority of experimental studies show that the administration of vasopressin during ventricular fibrillation and cardiac arrest improves resuscitation, however, the clinical studies do not present consisting results. Vasopressin cooperates with the autonomic nervous system (ANS), angiotensins, oxytocin and cytokines in the regulation of the cardiovascular system and its interaction with these regulators is altered during heart failure and hypertension. It is likely that the differences in interactions of AVP with ANS and other CPs have a significant impact on the responsiveness of the cardiovascular system to vasopressin in specific cardiovascular disorders.

Use of vasopressors for treatment of vasodilatory hypotension in dogs and cats by Diplomates of the American College of Veterinary Emergency and Critical Care

OBJECTIVE

To identify the most common practices of Diplomates of the American College of Veterinary Emergency and Critical Care (DACVECCs) as they relate to the recognition and treatment of hypotension in dogs and cats, particularly concerning the use of vasopressors in vasodilatory shock states.

DESIGN

A survey regarding vasopressor use was sent to all active DACVECCs using the Veterinary Information Network. Questions focused on respondent characteristics, method of recognition of hypotension, triggers for initiation of vasopressor therapy, first- and second-line vasopressor choice, and methods of determining response to therapy.

SUBJECTS

A total of 734 DACVECCs were invited to participate, and 203 Diplomates (27.7%) completed the survey.

RESULTS

For both dogs and cats, the most common first-line vasopressor was norepinephrine (87.9% in dogs and 83.1% in cats). The most common second-choice vasopressor was vasopressin (44.2% in dogs and 39.0% in cats). Cutoff values for initiating vasopressor therapy varied between species and modality used for blood pressure measurement. In general, most DACVECCs chose to initiate vasopressor therapy at a Doppler blood pressure <90 mm Hg or a mean arterial pressure of <60 or <65 mm Hg when using oscillometric or direct arterial blood pressure measurements in dogs and cats.

CONCLUSIONS

Most DACVECCs adhere to published human guidelines when choosing a first-line vasopressor. However, there is significant variability in blood pressure measurement technique, cutoffs for initiation of vasopressor use, and choice of second-line vasopressors.

Norepinephrine innervation of the supraoptic nucleus contributes to increased copeptin and dilutional hyponatremia in male rats

Dilutional hyponatremia associated with liver cirrhosis is due to inappropriate release of arginine vasopressin (AVP). Elevated plasma AVP causes water retention resulting in a decrease in plasma osmolality. Cirrhosis, in this study caused by ligation of the common bile duct (BDL), leads to a decrease in central vascular blood volume and hypotension, stimuli for nonosmotic AVP release. The A1/A2 neurons stimulate the release of AVP from the supraoptic nucleus (SON) in response to nonosmotic stimuli. We hypothesize that the A1/A2 noradrenergic neurons support chronic release of AVP in cirrhosis leading to dilutional hyponatremia. Adult, male rats were anesthetized with 2-3% isoflurane (mixed with 95% O2/5% CO2) and injected in the SON with anti-dopamine β-hydroxylase (DBH) saporin (DSAP) or vehicle followed by either BDL or sham surgery. Plasma copeptin, osmolality, and hematocrit were measured. Brains were processed for ΔFosB, dopamine β-hydroxylase (DBH), and AVP immunohistochemistry. DSAP injection: 1) significantly reduced the number of DBH immunoreactive A1/A2 neurons (A1, P < 0.0001; A2, P = 0.0014), 2) significantly reduced the number of A1/A2 neurons immunoreactive to both DBH and ΔFosB positive neurons (A1, P = 0.0015; A2, P < 0.0001), 3) reduced the number of SON neurons immunoreactive to both AVP and ΔFosB (P < 0.0001), 4) prevented the increase in plasma copeptin observed in vehicle-injected BDL rats (P = 0.0011), and 5) normalized plasma osmolality and hematocrit (plasma osmolality, P = 0.0475; hematocrit, P = 0.0051) as compared with vehicle injection. Our data suggest that A1/A2 neurons contribute to increased plasma copeptin and hypoosmolality in male BDL rats.

Vasoplegic Syndrome after Cardiopulmonary Bypass in Cardiovascular Surgery: Pathophysiology and Management in Critical Care

Vasoplegic syndrome (VS) is a common complication following cardiovascular surgery with cardiopulmonary bypass (CPB), and its incidence varies from 5 to 44%. It is defined as a distributive form of shock due to a significant drop in vascular resistance after CPB. Risk factors of VS include heart failure with low ejection fraction, renal failure, pre-operative use of angiotensin-converting enzyme inhibitors, prolonged aortic cross-clamp and left ventricular assist device surgery. The pathophysiology of VS after CPB is multi-factorial. Surgical trauma, exposure to the elements of the CPB circuit and ischemia-reperfusion promote a systemic inflammatory response with the release of cytokines (IL-1β, IL-6, IL-8, and TNF-α) with vasodilating properties, both direct and indirect through the expression of inducible nitric oxide (NO) synthase. The resulting increase in NO production fosters a decrease in vascular resistance and a reduced responsiveness to vasopressor agents. Further mechanisms of vasodilation include the lowering of plasma vasopressin, the desensitization of adrenergic receptors, and the activation of ATP-dependent potassium (KATP) channels. Patients developing VS experience more complications and have increased mortality. Management includes primarily fluid resuscitation and conventional vasopressors (catecholamines and vasopressin), while alternative vasopressors (angiotensin 2, methylene blue, hydroxocobalamin) and anti-inflammatory strategies (corticosteroids) may be used as a rescue therapy in deteriorating patients, albeit with insufficient evidence to provide any strong recommendation. In this review, we present an update of the pathophysiological mechanisms of vasoplegic syndrome complicating CPB and discuss available therapeutic options.

Combined Treatment with KV Channel Inhibitor 4-Aminopyridine and either γ-Cystathionine Lyase Inhibitor β-Cyanoalanine or Epinephrine Restores Blood Pressure, and Improves Survival in the Wistar Rat Model of Anaphylactic Shock

Simple Summary

Allergic diseases are presenting a constant increase all over the world and caused by such different substances as food, drugs, and pollens. Anaphylactic shock is the more severe complication of allergy which can induce death if the treatment is not administered immediately. Some patients do not respond to the recommended treatment, intra venous or intramuscular epinephrine. The pathophysiology of anaphylactic shock is still under investigation. The mediators released after the activation of mast cells and basophiles act on endothelial cells and smooth muscle cells, inducing the vasodilation responsible for hypotension and shock. Nitric oxide and hydrogen sulphide are both intracellular mediators that induce vasodilation. The role of potassium voltage dependent channels is suspected. We aimed to demonstrate the ability of a blocker of potassium voltage dependent channels, 4-aminopyridine, alone or in combination with inhibitors of cystathionine γ-lyase to restore blood pressure and improve survival in an ovalbumin rat anaphylactic shock model. The blockade of potassium voltage dependent channels alone or combined with inhibitors of cystathionine γ-lyase, dl-propargylglycine, or β-cyanoalanine restored blood pressure and improved survival. These findings suggest possible investigative treatment pathways for research concerning epinephrine-refractory anaphylactic shock in patients.

Abstract

The mechanism of anaphylactic shock (AS) remains incompletely understood. The potassium channel blocker 4-aminopyridine (4-AP), the inhibitors of cystathionine γ-lyase (ICSE), dl-propargylglycine (DPG) or β-cyanoalanine (BCA), and the nitric oxide (NO) synthase produce vasoconstriction and could be an alternative for the treatment of AS. The aim of this study was to demonstrate the ability of L-NAME, ICSE alone or in combination with 4-AP to restore blood pressure (BP) and improve survival in ovalbumin (OVA) rats AS. Experimental groups included non-sensitized Wistar rats (n = 6); AS (n = 6); AS (n = 10 per group) treated i.v. with 4-AP (AS+4-AP), epinephrine (AS+EPI), AS+DPG, AS+BCA, or with L-NAME (AS+L-NAME); or AS treated with drug combinations 4-AP+DPG, 4-AP+BCA, 4-AP+L-NAME, or 4-AP+EPI. AS was induced by i.v. OVA (1 mg). Treatments were administered i.v. one minute after AS induction. Mean arterial BP (MAP), heart rate (HR), and survival were monitored for 60 min. Plasma levels of histamine, prostaglandin E2 (PGE2) and F2 (PGF2α), leukotriene B4 and C4, angiotensin II, vasopressin, oxidative stress markers, pH, HCO3, PaO2, PaCO2, and K+ were measured. OVA induced severe hypotension and all AS rats died. Moreover, 4-AP, 4-AP+EPI, or 4-AP+BCA normalized both MAP and HR and increased survival. All sensitized rats treated with 4-AP alone or with 4-AP+BCA survived. The time-integrated MAP “area under the curve” was significantly higher after combined 4-AP treatment with ICSE. Metabolic acidosis was not rescued and NO, ICSE, and Kv inhibitors differentially alter oxidative stress and plasma levels of anaphylactic mediators. The AS-induced reduction of serum angiotensin II levels was prevented by 4-AP treatment alone or in combination with other drugs. Further, 4-AP treatment combined with EPI or with BCA also increased serum PGF2α, whereas only the 4-AP+EPI combination increased serum LTB4. Serum vasopressin and angiotensin II levels were increased by 4-AP treatment alone or in combination with other drugs. Moreover, 4-AP alone and in combination with inhibition of cystathionine γ-lyase or EPI normalizes BP, increases serum vasoconstrictor levels, and improves survival in the Wistar rat model of AS. These findings suggest possible investigative treatment pathways for research into epinephrine-refractory anaphylactic shock in patients.

Early Life Trauma and Social Processing in HIV: The Role of Neuroendocrine Factors and Inflammation

OBJECTIVE

Early life trauma (ELT) and HIV are associated with social processing deficits. In people with HIV (PWH), we examined whether facial emotion identification accuracy differs by ELT and whether neuroendocrine factors including cortisol, oxytocin (OT), and arginine vasopressin, and/or immune system measures play a role in the ELT-performance association.

METHODS

We used secondary data from the placebo condition of a pharmacologic challenge study in PWH. Presence of ELT was measured with the Childhood Trauma Questionnaire (at least moderate experiences of sexual, physical, and/or emotional abuse). Social processing was measured with the Facial Emotion Perception Test (FEPT). Salivary immune system measures and cortisol were sampled across a 5-hour study session. Blood was collected at study session start (12 pm ) to measure OT and arginine vasopressin. We examined the association of ELT with FEPT and five biological moderators (from principal components analysis of 12 biomarkers) of ELT-FEPT associations.

RESULTS

Of 58 PWH (42 men; mean [standard deviation] age = 33.7 [8.9] years), 50% endorsed ELT. ELT-exposed PWH demonstrated lower identification accuracy across all emotional expressions (unstandardized β [ B ] = 0.13; standard error [SE] = 0.05; p = .021, d = 0.63) and had higher OT levels compared with ELT-unexposed PWH ( t(1,56) = 2.12, p = .039; d = 0.57). For total accuracy, an OT/C-reactive protein factor moderated the ELT-FEPT association ( B = 0.14; SE = 0.05; p = .014); accuracy was lower in ELT-exposed PWH versus ELT-unexposed PWH when the factor was low but not when high. Similar results were obtained for fearful, neutral, and happy faces ( p values < .05). Regardless of ELT, a myeloid migration (MCP-1/MMP-9) factor was associated with reduced accuracy ( p values < .05).

CONCLUSIONS

Our pilot findings suggest that ELT may alter social processing in PWH, and OT and C-reactive protein may be a target for improving social processing in ELT-exposed PWH, and myeloid migration markers may be a target in PWH more generally.

Chronic activation of vasopressin-2 receptors induces hypertension in Liddle mice by promoting Na+ and water retention

The renin-angiotensin-aldosterone and arginine vasopressin-V2 receptor-aquaporin-2 (AQP2) systems converge on the epithelial Na+ channel (ENaC) to regulate blood pressure and plasma tonicity. Although it is established that V2 receptors initiate renal water reabsorption through AQP2, whether V2 receptors can also induce renal Na+ retention through ENaC and raise blood pressure remains an open question. We hypothesized that a specific increase in V2 receptor-mediated ENaC activity can lead to high blood pressure. Our approach was to test effects of chronic activation of V2 receptors in Liddle mice, a genetic mouse model of high ENaC activity, and compare differences in ENaC activity, urine Na+ excretion, and blood pressure with control mice. We found that ENaC activity was elevated in Liddle mice and could not be stimulated further by administration of desmopressin (dDAVP), a V2 receptor-specific agonist. In contrast, Liddle mice showed higher levels of expression of AQP2 and aquaporin-3, but they could still respond to dDAVP infusion by increasing phospho-AQP2 expression. With dDAVP infusion, Liddle mice excreted smaller urine volume and less urine Na+ and developed higher blood pressure compared with control mice; this hypertension was attenuated with administration of the ENaC inhibitor benzamil. We conclude that V2 receptors contribute to hypertension in the Liddle mouse model by promoting primary Na+ and concomitant water retention.NEW & NOTEWORTHY Liddle syndrome is a classic model for hypertension from high epithelial Na+ channel (ENaC) activity. In the Liddle mouse model, vasopressin-2 receptors stimulate both ENaC and aquaporin-2, which increases Na+ and water retention to such an extent that hypertension ensues. Liddle mice will preserve plasma tonicity at the expense of a higher blood pressure; these data highlight the inherent limitation in which the kidney must use ENaC as a pathway to regulate both plasma tonicity and blood pressure.

Oxytocin, Vasopressin, and Social Behavior: From Neural Circuits to Clinical Opportunities

Oxytocin and vasopressin are peptide hormones secreted from the pituitary that are well known for their peripheral endocrine effects on childbirth/nursing and blood pressure/urine concentration, respectively. However, both peptides are also released in the brain, where they modulate several aspects of social behaviors. Oxytocin promotes maternal nurturing and bonding, enhances social reward, and increases the salience of social stimuli. Vasopressin modulates social communication, social investigation, territorial behavior, and aggression, predominantly in males. Both peptides facilitate social memory and pair bonding behaviors in monogamous species. Here we review the latest research delineating the neural circuitry of the brain oxytocin and vasopressin systems and summarize recent investigations into the circuit-based mechanisms modulating social behaviors. We highlight research using modern molecular genetic technologies to map, monitor activity of, or manipulate neuropeptide circuits. Species diversity in oxytocin and vasopressin effects on social behaviors are also discussed. We conclude with a discussion of the translational implications of oxytocin and vasopressin for improving social functioning in disorders with social impairments, such as autism spectrum disorder.

SGLT2 inhibitor and loop diuretic induce different vasopressin and fluid homeostatic responses in nondiabetic rats

Loop diuretics are commonly used diuretics in the treatment of fluid retention but induce hypovolemia-related renal dysfunction. Na+-glucose cotransporter 2 (SGLT2) inhibitors induce osmotic diuresis, but body fluid volume is maintained by stimulating vasopressin-induced fluid intake and collecting duct water reabsorption as previously reported in diabetic rats. We aimed to test the hypothesis that unlike SGLT2 inhibitors, loop diuretics lack activation of similar fluid homeostatic mechanisms. Nondiabetic male Sprague-Dawley rats were treated daily by oral gavage with vehicle, the SGLT2 inhibitor ipragliflozin (5 mg/kg), or the loop diuretic furosemide (50 mg/kg) and monitored in metabolic cages for 2 or 7 days. Ipragliflozin and furosemide similarly increased urine volume on day 2. This was associated with increased serum Na+ concentration, urine vasopressin excretion, fluid intake, and solute-free water reabsorption in response to ipragliflozin but not to furosemide. Ipragliflozin maintained fluid balance (fluid intake - urine volume) on day 2 and total body water measured by bioimpedance spectroscopy and serum creatinine on day 7. In comparison, furosemide decreased fluid balance on day 2 and decreased total body water and increased serum creatinine on day 7. Furosemide, but not ipragliflozin, increased plasma renin activity, and systolic blood pressure was similar among the groups. In conclusion, the osmotic diuresis of the SGLT2 inhibitor increased serum Na+ concentration and the vasopressin-related stimulation of fluid intake and renal water retention maintained fluid balance, whereas the loop diuretic did not engage the compensatory vasopressin system. The data suggest differences in vasopressin and fluid homeostatic responses between SGLT2 inhibitors and loop diuretics.NEW & NOTEWORTHY In nondiabetic rats, the Na+-glucose cotransporter 2 (SGLT2) inhibitor ipragliflozin increased vasopressin-related stimulation of fluid intake and free water reabsorption and maintained fluid balance and serum creatinine, whereas the loop diuretic furosemide reduced vasopressin and induced a negative fluid balance followed by a subsequent increase in serum creatinine. This study suggests that differences in vasopressin secretion in response to a SGLT2 inhibitor or loop diuretic may contribute to differences in body fluid status and subsequent renal function.

Efficacy and Safety of Vasopressin Alone or in Combination With Catecholamines in the Treatment of Septic Shock: A Systematic Review

Septic shock is one of the life-threatening emergencies in hospital settings. Patients with septic shock have been treated with various vasopressors alone as a first-line or in combination with other agents to improve blood pressure and increase the chance of survival. Our study focuses particularly on the efficacy and safety of vasopressin (VP) alone and in combination with other vasopressors. Our study used Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, 2020 to do our systematic review. We searched thoroughly for articles in PubMed, PubMed Central (PMC), Medline, and ScienceDirect. To locate all pertinent papers, we employed the medical subject headings (MeSH) systematic search technique. Twelve papers that were related to the study's issue and passed the quality check were extracted after we applied inclusion/exclusion criteria and reviewed the titles and abstracts. We used a variety of assessment methods for diverse study designs as a quality check. We compared all included studies after reviewing them thoroughly. VP and its synthetic variants (Terlipressin and Selepressin) have always been given as adjuvants to catecholamine, especially with Noradrenaline, in low to moderate doses with continuous infusion in patients with septic shock. Furthermore, VP is a better adjuvant agent than Dopamine and Dobutamine. Though VP has been proven superior to other vasopressors as an adjuvant agent in patients with septic shock, it can cause digital ischemia in high doses.

Knockdown of sexually differentiated vasopressin expression in the bed nucleus of the stria terminalis reduces social and sexual behaviour in male, but not female, mice

The neuropeptide arginine-vasopressin (AVP) has long been implicated in the regulation of social behaviour and communication, but the sources of AVP release relevant for behaviour have not been precisely determined. Ablations of the sexually dimorphic AVP cells within the bed nucleus of the stria terminalis (BNST), which are more numerous in males, affect social behaviour differently in males and females. However, it is unknown whether these behavioural effects are caused by a reduction of AVP or of other factors associated with these cells. To test the role of AVP specifically, we used an shRNA viral construct to knock down AVP gene expression within the BNST of wild-type male and female mice, using scrambled sequence virus as a control, and evaluated subsequent changes in social behaviours (social investigation, ultrasonic vocalization (USV), scent marking, copulation, and aggression), or anxiety-like behaviours (elevated plus maze). We observed that, in males, knockdown of AVP expression in the BNST strongly reduced investigation of novel males, aggressive signalling towards other males (tail rattling, USV), and copulatory behaviour, but did not alter attack initiation, other measures of social communication, or anxiety-like behaviours. In females, however, BNST AVP knockdown did not alter any of these behaviours. These results point to differential involvement of AVP derived from the BNST in social behaviour.

Demystifying hyponatremia: A clinical guide to evaluation and management

Hyponatremia (serum sodium <135 mEq/L) is a frequent electrolyte abnormality complicating the clinical care of hospitalized patients. Hyponatremia has been associated with an increased risk of mortality. Hyponatremia can be seen in patients with euvolemia, hypovolemia, or hypervolemia. Evaluation of hyponatremia relies on clinical assessment and estimation of serum sodium, urine electrolytes, and serum and urine osmolality in addition to other case-specific laboratory parameters. In addition, point-of-care ultrasonography is an important adjunct to physical assessment in estimation of volume status. Understanding the pathophysiology of the underlying process can lead to a timely diagnosis and appropriate management of hyponatremia.

Evaluating the neuropeptide-social cognition link in ageing: the mediating role of basic cognitive skills

The roles of oxytocin (OT) and arginine-vasopressin (AVP) as crucial modulators of social cognition and related behaviours have been extensively addressed in the literature. The involvement of these neuropeptides in social cognition in ageing, however, and a potential mediating effect of basic cognitive capacities on this link, are not well understood. To fill these research gaps, this study assessed associations of plasma OT and AVP levels with dynamic emotion identification accuracy in generally healthy older men (aged 55-95 years) and probed the underlying roles of crystallized and fluid cognition in these associations. Higher plasma OT levels were associated with lower accuracy in dynamic emotion identification, with this negative relationship fully mediated by cognition. For plasma AVP levels, in contrast, there was no association with dynamic emotion identification accuracy. Integrated within existing theoretical accounts, results from this study advance understanding of the neuropeptide-social cognition link in ageing and support basic cognitive capacities as mediators in this association. This article is part of the theme issue 'Interplays between oxytocin and other neuromodulators in shaping complex social behaviours'.

Serum Osmolarity and Vasopressin Concentration in Acute Heart Failure-Influence on Clinical Course and Outcome

Neurohormone activation plays an important role in Acute Heart Failure (AHF) pathophysiology. Serum osmolarity can affect this activation causing vasopressin excretion. The role of serum osmolarity and vasopressin concentration and its interaction remain still unexplored in AHF. The objective of our study was to evaluate the relationship of serum osmolarity with clinical parameters, vasopressin concentration, in-hospital course, and outcomes in AHF patients. The study group consisted of 338 AHF patients (male (76.3%), mean age of 68 ± 13 years) with serum osmolarity calculated by the equation: 1.86 × sodium [mmol/L] + (glucose [mg/dL]/18) + (urea [mg/dL]/2.8) + 9 and divided into osmolarity quartiles marked as: low: <287 mOsm/L, intermediate low: 287−294 mOsm/L, intermediate high: 295−304 mOsm/L, and high: >304 mOsm/L. There was an increasing age gradient in the groups and patients differed in the occurrence of comorbidities and baseline clinical and laboratory parameters. Importantly, analysis revealed that vasopressin presented a linear correlation with osmolarity (r = −0.221, p = 0.003) and its concentration decreased with quartiles (61.6 [44.0−81.0] vs. 57.8 [50.0−77.3] vs. 52.7 [43.1−69.2] vs. 45.0 [30.7−60.7] pg/mL, respectively, p = 0.034). This association across quartiles was observed among de novo AHF (63.6 [55.3−94.5] vs. 58.0 [50.7−78.6] vs. 52.0 [46.0−58.0] vs. 38.0 [27.0−57.0] pg/mL, respectively, p = 0.022) and was not statistically significant in patients with acute decompensated heart failure (ADHF) (59.5 [37.4−80.0] vs. 52.0 [38.0−74.5] vs. 57.0 [38.0−79.0] vs. 50.0 [33.0−84.0] pg/mL, respectively, p = 0.849). The worsening of renal function episodes were more frequent in quartiles with higher osmolarity (4 vs. 2 vs. 13 vs. 11%, respectively, p = 0.018) and patients that belonged to the quartiles with low and high osmolarity were characterized more often by incidence of worsening heart failure (20 vs. 9 vs. 10 vs. 22%, respectively, p = 0.032). There was also a U-shape distribution in relation to one-year mortality (31 vs. 19 vs. 23 vs. 37%, respectively, p = 0.022). In conclusion, there was an association of serum osmolarity with clinical status and both in-hospital and out-of-hospital outcomes. Moreover, the linear dependence between vasopressin concentration and serum osmolarity in the AHF population was identified and was driven mainly by patients with de novo AHF which suggests different pathophysiological paths in ADHF and AHF de novo.

Uromodulin Regulates Murine Aquaporin-2 Activity via Thick Ascending Limb-Collecting Duct Cross-Talk during Water Deprivation

Uromodulin, a urinary protein synthesized and secreted from the thick ascending limb (TAL) of the loop of Henle, is associated with hypertension through the activation of sodium reabsorption in the TAL. Uromodulin is a potential target for hypertension treatment via natriuresis. However, its biological function in epithelial cells of the distal nephron segment, particularly the collecting duct, remains unknown. Herein, we examined the regulation of uromodulin production during water deprivation in vivo as well as the effect of uromodulin on the activity of the water channel aquaporin−2 (AQP2) in vitro and in vivo using transgenic mice. Water deprivation upregulated uromodulin production; immunofluorescence experiments revealed uromodulin adhesion on the apical surface of the collecting duct. Furthermore, the activation of AQP2 was attenuated in mice lacking uromodulin. Uromodulin enhanced the phosphorylation and apical trafficking of AQP2 in mouse collecting duct cells treated with the vasopressin analog dDAVP. The uromodulin-induced apical trafficking of AQP2 was attenuated via endocytosis inhibitor treatment, suggesting that uromodulin activates AQP2 through the suppression of endocytosis. This study provides novel insights into the cross−talk between TAL and the collecting duct, and indicates that the modulation of uromodulin is a promising approach for diuresis and hypertension treatment.

Transient diabetes insipidus after vasopressin discontinuation in cystic fibrosis with septic shock

Central diabetes insipidus (DI) is an uncommon condition caused by reduced or lack of vasopressin secretion from the posterior pituitary gland, typically caused by gland destruction. Several other causes for central DI have also been proposed. Here we present a case of transient central DI after discontinuation of vasopressin used for septic shock without evidence of overt pituitary damage in a cystic fibrosis patient. The serum sodium concentration peaked at 137 mmol/L in the setting of polyuria within 3 days of vasopressin discontinuation without other identified alternative etiologies. Sodium levels and urine output trended down dramatically with desmopressin administration.

The pharmacotherapeutic options in patients with catecholamine-resistant vasodilatory shock

INTRODUCTION

Septic and vasoplegic shock are common types of vasodilatory shock (VS) with high mortality. After fluid resuscitation and the use of catecholamine-mediated vasopressors (CMV), vasopressin, angiotensin II, methylene blue (MB) and hydroxocobalamin can be added to maintain blood pressure.

AREAS COVERED

VS treatment utilizes a phased approach with secondary vasopressors added to vasopressor agents to maintain an acceptable mean arterial pressure (MAP). This review covers additional vasopressors and adjunctive therapies used when fluid and catecholamine-mediated vasopressors fail to maintain target MAP.

EXPERT OPINION

Evidence supporting additional vasopressor agents in catecholamine resistant VS is limited to case reports, series, and a few randomized control trials (RCTs) to guide recommendations. Vasopressin is the most common agent added next when MAPs are not adequately supported with CMV. VS patients failing fluids and vasopressors with cardiomyopathy may have cardiotonic agents such as dobutamine or milrinone added before or after vasopressin. Angiotensin II, another class of vasopressor is used in VS to maintain adequate MAP. MB and/or hydoxocobalamin, vitamin C, thiamine and corticosteroids are adjunctive therapies used in refractory VS. More RCTs are needed to confirm the utility of these drugs, at what doses, which combinations and in what order they should be given.

Hormone-Dependent Regulation of Renin and Effects on Prorenin Receptor Signaling in the Collecting Duct

The production of renin by the principal cells of the collecting duct has widened our understanding of the regulation of intrarenal angiotensin II (Ang II) generation and blood pressure. In the collecting duct, Ang II increases the synthesis and secretion of renin by mechanisms involving the activation of Ang II type 1 receptor (AT1R) via stimulation of the PKCα, Ca²⁺, and cAMP/PKA/CREB pathways. Additionally, paracrine mediators, including vasopressin (AVP), prostaglandins, bradykinin (BK), and atrial natriuretic peptide (ANP), regulate renin in principal cells. During Ang II-dependent hypertension, despite plasma renin activity suppression, renin and prorenin receptor (RPR) are upregulated in the collecting duct and promote de novo formation of intratubular Ang II. Furthermore, activation of PRR by its natural agonists, prorenin and renin, may contribute to the stimulation of profibrotic factors independent of Ang II. Thus, the interactions of RAS components with paracrine hormones within the collecting duct enable tubular compartmentalization of the RAS to orchestrate complex mechanisms that increase intrarenal Ang II, Na+ reabsorption, and blood pressure.

Vasopressin neurons in the paraventricular hypothalamus promote wakefulness via lateral hypothalamic orexin neurons

The sleep-wakefulness cycle is regulated by complicated neural networks that include many different populations of neurons throughout the brain. Arginine vasopressin neurons in the paraventricular nucleus of the hypothalamus (PVH^AVP) regulate various physiological events and behaviors, such as body-fluid homeostasis, blood pressure, stress response, social interaction, and feeding. Changes in arousal level often accompany these PVH^AVP-mediated adaptive responses. However, the contribution of PVH^AVP neurons to sleep-wakefulness regulation has remained unknown. Here, we report the involvement of PVH^AVP neurons in arousal promotion. Optogenetic stimulation of PVH^AVP neurons rapidly induced transitions to wakefulness from both NREM and REM sleep. This arousal effect was dependent on AVP expression in these neurons. Similarly, chemogenetic activation of PVH^AVP neurons increased wakefulness and reduced NREM and REM sleep, whereas chemogenetic inhibition of these neurons significantly reduced wakefulness and increased NREM sleep. We observed dense projections of PVH^AVP neurons in the lateral hypothalamus with potential connections to orexin/hypocretin (LH^Orx) neurons. Optogenetic stimulation of PVH^AVP neuronal fibers in the LH immediately induced wakefulness, whereas blocking orexin receptors attenuated the arousal effect of PVH^AVP neuronal activation drastically. Monosynaptic rabies-virus tracing revealed that PVH^AVP neurons receive inputs from multiple brain regions involved in sleep-wakefulness regulation, as well as those involved in stress response and energy metabolism. Moreover, PVH^AVP neurons mediated the arousal induced by novelty stress and a melanocortin receptor agonist melanotan-II. Thus, our data suggested that PVH^AVP neurons promote wakefulness via LH^Orx neurons in the basal sleep-wakefulness and some stressful conditions.

Vasopressin for Post-kidney Transplant Hypotension

Introduction

Hypotension after deceased donor kidney transplant (DDKT) is a risk factor for delayed graft function (DGF) and poor graft survival (GS). We hypothesize that vasopressin use in hypotensive DDKT recipients (DDKTRs) to increase blood pressure (BP) reduces DGF rates and is safe without increasing mortality.

Methods

Group with vasopressin "study group" (n = 45) was defined as DDKTRs between 2012 and 2017 who required vasopressin for hypotension systolic BP (SBP) <120 mm Hg or diastolic BP (DBP) <60 mm Hg. DDKTRs with no-vasopressin "comparison group" (n = 90) were propensity score-matched DDKTRs between 2012 and 2017 without vasopressin use. Primary outcomes were GS, creatinine and allograft biopsy rate at 1 year, DGF rate, and death during transplant hospitalization.

Results

Vasopressin group had lower mean maximum and minimum SBP and DBP in the operating room (OR). Median vasopressin start time post-DDKT was 2 hours (interquartile range [IQR] 1-6), and duration of use was 42 hours (IQR 24-63). DGF, creatinine at 1 year, and allograft biopsy rates were comparable. No deaths occurred during transplant hospitalization. Multivariable analysis did not find an effect of vasopressin use on GS.

Conclusion

Treatment of hypotensive DDKTRs with vasopressin is safe and facilitated similar graft function and survival with that of nonhypotensive patients. In the absence of a randomized control trial, our study supports the safety of vasopressin therapy to prevent the adverse effects of hypotension.

Impact of adolescent intermittent ethanol exposure in male and female rats on social drinking and neuropeptide gene expression

BACKGROUND

Alcohol use during adolescence can alter maturational changes that occur in brain regions associated with social and emotional responding. Our previous studies have shown that adult male, but not female rats demonstrate social anxiety-like alterations and enhanced sensitivity to ethanol-induced social facilitation following adolescent intermittent ethanol exposure (AIE). These consequences of AIE may influence adult social drinking in a sex-specific manner.

METHODS

To test the effects of AIE on social drinking, male and female Sprague-Dawley rats exposed to water or ethanol (0 or 4 g/kg, intragastrically, every other day, between postnatal day [P] 25 and 45) were tested as adults (P72-83) in a social drinking paradigm (30-minute access to a 10% ethanol solution in supersac or supersac alone in groups of three same-sex littermates across two 4-day cycles separated by 4 days off). Social behavior was assessed during the last drinking session, along with assessment of oxytocin (OXT), oxytocin receptor (OXTR), vasopressin (AVP), and vasopressin receptors 1a and 1b (AVPR1a, AVPR1b) in the hypothalamus and lateral septum.

RESULTS

Males exposed to AIE consumed more ethanol than water-exposed controls during the second drinking cycle, whereas AIE did not affect supersac intake in males. AIE-exposed females consumed less ethanol and more supersac than water-exposed controls. Water-exposed females drinking ethanol showed more social investigation and significantly higher hypothalamic OXTR, AVP, and AVPR1b gene expression than their counterparts ingesting supersac and AIE females drinking ethanol. In males, hypothalamic AVPR1b gene expression was affected by drinking solution, with significantly higher expression evident in males drinking ethanol than those consuming supersac.

CONCLUSIONS

Collectively, these findings provide new evidence regarding sex-specific effects of AIE on social drinking and suggest that the hypothalamic OXT and AVP systems are implicated in the effects of ingested ethanol on social behavior in a sex- and adolescent-exposure-dependent manner.

Copeptin Release in Arterial Hypotension and Its Association with Severity of Disease in Critically Ill Children

Low copeptin levels may indicate inadequate arginine-vasopressin release promoting arterial hypotension, whereas high copeptin concentrations may reflect disease severity. This single-center prospective non-randomized clinical trial analyzed the course of blood copeptin in critically ill normo- and hypotensive children and its association with disease severity. In 164 patients (median age 0.5 years (interquartile range 0.1, 2.9)), the mean copeptin concentration at baseline was 43.5 pmol/L. Though not significantly different after 61 h (primary outcome, mean individual change: −12%, p = 0.36, paired t-test), we detected 1.47-fold higher copeptin concentrations during arterial hypotension when compared to normotension (mixed-effect ANOVA, p = 0.01). In total, 8 out of 34 patients (23.5%) with low copeptin concentrations <10 pmol/L were hypotensive. Copeptin was highest in the adjusted mixed-effect regression analysis within the first day (+20% at 14 h) and decreased significantly at 108 h (−27%) compared to baseline (p = 0.002). Moreover, we found a significant association with vasopressor-inotrope treatment intensity, infancy (1−12 months) and cardiopulmonary bypass (all p ≤ 0.001). In conclusion, high copeptin values were associated with arterial hypotension and severity of disease in critically ill children. This study does not support the hypothesis that low copeptin values might be indicative of arginine-vasopressin deficiency.

Vasopressin versus norepinephrine as the first-line vasopressor in septic shock: A systematic review and meta-analysis

Background and Aim

Norepinephrine is currently the first-line vasopressor for septic shock. We conducted this meta-analysis to examine the outcomes of adult patients with septic shock who received vasopressin instead of norepinephrine.

Methods

We selected studies in adults with septic shock that compared the outcomes of patients treated with vasopressin versus norepinephrine. Cochrane ROB 2.0 and the Joanna Briggs Institute quality assessment tools were used to assess the risk of bias in RCTs and observational studies. Meta-analysis was conducted using RevMan 5.4.

Results

Eight studies were included in this meta-analysis. There were no significant differences in 28-day mortality rates (OR, 1.07; CI, 0.80-1.44) and intensive care unit (ICU) mortality (OR, 0.74; CI, 0.21-2.67) between the two groups. Similarly, length of ICU stay, length of hospital stay, mean arterial pressure at 24 h, urine output at 24 h, and serious adverse events also did not differ significantly. However, the odds of renal replacement therapy (RRT) requirement in the vasopressin group were substantially lower than in the norepinephrine group (OR, 0.68; CI, 0.47-0.98).

Conclusion

There were no differences in mortality, duration of hospitalization, and adverse effects in adults with septic shock across the two groups. However, the patients treated with vasopressin had lower chances of requiring RRT.

Relevance for Patients

Vasopressin use as the first-line vasopressor in septic shock showed a significant reduction in RRT, though there were no significant differences in terms of mortality and other adverse events. Therefore, vasopressin can be considered as a first-line vasopressor in septic shock patients with other risk factors which may contribute to renal failure requiring RRT.

Glucocorticoid Receptor Maintains Vasopressin Responses in Kidney Collecting Duct Cells

Water permeability of the kidney collecting ducts is regulated in part by the amount of the molecular water channel protein aquaporin-2 (AQP2), whose expression, in turn, is regulated by the pituitary peptide hormone vasopressin. We previously showed that stable glucocorticoid receptor knockdown diminished the vasopressin-induced Aqp2 gene expression in the collecting duct cell model mpkCCD. Here, we investigated the pathways regulated by the glucocorticoid receptor by comparing transcriptomes of the mpkCCD cells with or without stable glucocorticoid receptor knockdown. Glucocorticoid receptor knockdown downregulated 5,394 transcripts associated with 55 KEGG pathways including "vasopressin-regulated water reabsorption," indicative of positive regulatory roles of these pathways in the vasopressin-induced Aqp2 gene expression. Quantitative RT-PCR confirmed the downregulation of the vasopressin V2 receptor transcript upon glucocorticoid receptor knockdown. Glucocorticoid receptor knockdown upregulated 3,785 transcripts associated with 42 KEGG pathways including the "TNF signaling pathway" and "TGFβ signaling pathway," suggesting the negative regulatory roles of these pathways in the vasopressin-induced Aqp2 gene expression. Quantitative RT-PCR confirmed the upregulation of TNF and TGFβ receptor transcripts upon glucocorticoid receptor knockdown. TNF or TGFβ inhibitor alone, in the absence of vasopressin, did not induce Aqp2 gene transcription. However, TNF or TGFβ blunted the vasopressin-induced Aqp2 gene expression. In particular, TGFβ reduced vasopressin-induced increases in Akt phosphorylation without inducing epithelial-to-mesenchymal transition or interfering with vasopressin-induced apical AQP2 trafficking. In summary, our RNA-seq transcriptomic comparison revealed positive and negative regulatory pathways maintained by the glucocorticoid receptor for the vasopressin-induced Aqp2 gene expression.

An Octopus-Derived Peptide with Antidiuretic Activity in Rats

Discovering new drug candidates with high efficacy and few side effects is a major challenge in new drug development. The two evolutionarily related peptides oxytocin (OXT) and arginine vasopressin (AVP) are known to be associated with a variety of physiological and psychological processes via the association of OXT with three types of AVP receptors. Over decades, many synthetic analogs of these peptides have been designed and tested for therapeutic applications; however, only a few studies of their natural analogs have been performed. In this study, we investigated the bioactivity and usefulness of two natural OXT/AVP analogs that originate from the marine invertebrate Octopus vulgaris, named octopressin (OTP) and cephalotocin (CPT). By measuring the intracellular Ca2+ or cyclic AMP increase in each OXT/AVP receptor subtype-overexpressing cell, we found that CPT, but not OTP, acts as a selective agonist of human AVP type 1b and 2 receptors. This behavior is reminiscent of desmopressin, the most widely prescribed antidiuretic drug in the world. Similar to the case for desmopressin, a single intravenous tail injection of CPT into Sprague-Dawley rats reduced urine output and increased urinary osmolality. In conclusion, we suggest that CPT has a significant antidiuretic effect and that CPT might be beneficial for treating urological conditions such as nocturia, enuresis, and diabetes insipidus.