Arginine Vasopressin V1 Receptor Antagonist Research Articles

#1636 Treatment of Tolvaptan related polyuria with bendroflumethiazide for ADPKD: Does it really work?

Abstract Background and Aims Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease worldwide and accounts for 10% of patients on renal replacement therapy. Currently, the arginine vasopressin (AVP) V2 receptor antagonist Tolvaptan is the only available treatment for ADPKD which slows cyst formation and thus the progression of kidney disease by inducing AVP resistance. However, its aquaretic side effects can be debilitating and is the most common reason for medication discontinuation. Thiazides such as bendroflumethiazide are natriuresis-promoting diuretics through their action on the sodium-chloride channel in the distal convoluted tubule that are widely used to treat polyuria in inherited AVP deficiency or resistance. However, there is limited information about their effect in patients treated with Tolvaptan. The aim of this observational study is to review the impact on patients’ quality of life by using a low dose bendroflumethiazide with Tolvaptan in patients with ADPKD who are suffering from Tolvaptan induced aquaretic side effects. Method Details of all patients with ADPKD who are on Tolvaptan with or without bendroflumethiazide who are currently attending the polycystic kidney disease (PKD) clinic at Royal Free London NHS Foundation Trust were obtained, and their medications reviewed. Patients who have previously been or were currently on bendroflumethiazide to enable them to continue Tolvaptan therapy were identified. Information about the impact of bendroflumethiazide on their quality of life and their aquaretic side effects were obtained via phone call. If they discontinued bendroflumethiazide, the reason for this was explored. In addition, eGFR, sodium, potassium, and calcium at the time of bendroflumethiazide initiation as well as at three, six, nine and twelve months post bendroflumethiazide initiation were obtained. Results Out of 136 patients receiving Tolvaptan for treatment of ADPKD at our centre, eight (5.8%) were prescribed bendroflumethiazide for treatment of their aquaretic side effects from Tolvaptan. Two of these eight patients (25%) stopped bendroflumethiazide due to adverse reactions. The remaining six patients (75%) remained on the medication, and all reported significant subjective improvement in their symptoms of polyuria, nocturia and in their overall quality of life. Two of the six patients (33.3%) that remained on bendroflumethiazide had also subsequently increased their Tolvaptan dose. No electrolyte disturbances were noted after initiation of bendroflumethiazide. Conclusion Using bendroflumethiazide appears to improve the quality of life through reduction of polyuria and nocturia in patients suffering from Tolvaptan-induced aquaretic side effects with some patients subsequently able to increase their Tolvaptan dose by taking bendroflumethiazide which might result in augmented therapeutic benefit of Tolvaptan. Further placebo-controlled randomised studies with longitudinal will be needed to determine the true benefit-disbenefit balance of thiazide therapy in patients taking tolvaptan, especially to determine whether there is a negative effect on efficacy of tolvaptan on the underlying ADPKD. However, based on our small observational study, the number of patients needed to determine whether bendroflumethiazide improves the tolerability and medication adherence in patients who are debilitated by the aquaretic side effects of Tolvaptan would be small.

Research progress of arginine vasopressin V2 receptor antagonist tolvaptan in the treatment of cirrhotic ascites

Research progress of arginine vasopressin V2 receptor antagonist tolvaptan in the treatment of cirrhotic ascites

Management of Decongestion in Acute Heart Failure: Time for a New Approach?

As the primary cause of hospitalization in acute heart failure (AHF) patients, congestion was responsible for a higher risk of mortality, rehospitalization, and renal dysfunction in AHF patients. Although loop diuretic was routinely used as the mainstay of AHF therapy, it is still ineffective to obtain the euvolemic state in most hospitalized AHF patients. Therefore, a higher loop diuretic dose was often required to increase the decongestion effect. However, consequently, it can cause several detrimental complications, including renal dysfunction, neurohormonal activation, hyponatremia, hypokalaemia, and reduced blood pressure, which eventually result in poor prognosis. Hence, the new approach may be proposed to optimize decongestion in acute phase, including the use of arginine vasopressin V2 receptor antagonist – Tolvaptan. As an additive therapy to loop diuretic in AHF patients, it can be considered due to its several beneficial effects, including greater decongestion effect, lowered worsening renal function incidence, counteract neurohormonal activation, neutralized hyponatraemic state, no alteration of potassium metabolism, stabilize the blood pressure, and reduced requirement of a higher dose of loop diuretic to achieve an equal or even greater decongestion effect compared to a high dose of loop diuretic alone. Tolvaptan provided favourable outcomes in several specific populations and was considered safe with several mild adverse effects. Several guidelines across countries have approved the use of Tolvaptan in AHF patients with or without hyponatremia. The initial dose of Tolvaptan was 7.5 to 15 mg and can be titrated up to 30 mg. However, further studies were still required to determine the timing dose and optimal dose of Tolvaptan in general and elderly populations with AHF, respectively.

Clinical Implication of Tolvaptan in Patients with Autosomal Dominant Polycystic Kidney Disease

Tolvaptan, a non-peptide arginine vasopressin V2 receptor antagonist, is a newly developed drug to reduce kidney volume and preserve kidney function in autosomal dominant polycystic kidney disease (ADPKD) patients. We aimed to evaluate the descriptive characteristics of patients according to the use of tolvaptan. Also, we tried to find the efficacy of tolvaptan on kidney volume and kidney function. We included patients with ADPKD who visited a tertiary hospital in South Korea during Sep. 2018 and Apr. 2022. The data was acquired from the Electric Medical Records system. A total of 64 patients were included in the study, and there were 33 (51.6%) patients taking tolvaptan during follow-up periods. During 17.8 ± 13.1 months of follow-up periods, estimated glomerular filtration rate (eGFR) changes were 89.4% compared to the baseline eGFR. Although the latest eGFR was lower in patients with tolvaptan (55.9 ± 24.7 mL/min/1.73 m2) than without tolvaptan (68.4 ± 35.1 mL/min/1.73 m2), there was no statistical significance (p = 0.108). We found that the mean change of height-adjusted total kidney volume (HtTKV) was -2.7% based on the baseline HtTKV in patients taking tolvaptan for more than 1-year. Although there was no statistical significance, the mean change of HtTKV was the highest in patients with 1E of Mayo classification (-4.3%). To anticipate the solid data on the efficacy of tolvaptan in the Asian population, more aggressive efforts are needed to search for suitable patients accompanied by appropriate monitoring over a more extended period. Keywords: Chronic kidney disease, Polycystic kidney, autosomal dominant, Tolvaptan

A selective oral vasopressin V2-receptor antagonist for patients with end-stage liver disease awaiting liver transplantation: a preliminary study

Administration of the selective arginine vasopressin V2 receptor antagonist tolvaptan to cirrhotic patients is controversial. There are no reports of tolvaptan use for patients with far-advanced end-stage liver disease (ESLD) and refractory ascites awaiting liver transplantation. Between 2013 and 2016, 64 patients awaiting adult-to-adult living donor liver transplantation (LDLT) were screened for enrollment. Patients with refractory ascites and on dual conventional diuretics (≥ 50 mg/day of spironolactone and ≥ 20 mg/day of a loop diuretic) were enrolled and assigned to the tolvaptan (TOL) group (n = 10), and low-dose tolvaptan, 3.75 mg/day, was started. The remaining patients who had no or little ascites on conventional diuretic therapy (CDT) were assigned to the CDT group (n = 23). The median model for end-stage liver disease and Child-Pugh scores were 16 (range 7-41) and 10 (7-15), respectively. The median dose of spironolactone in the TOL group was 88 mg (range 50-200) vs. 50 (0-100) in the CDT group (p < 0.01). The median dose of loop diuretics in the TOL group was 70 mg (20-120) vs. 20 (0-80) in the CDT group (p = 0.03). No significant liver damage was detected during tolvaptan therapy. Tolvaptan demonstrated favorable effects in 60% (6/10) of the patients, decreasing the body weight by at least 1.5 kg during the 7 day treatment. These findings suggest that low-dose of tolvaptan may be safe for patients having far-advanced ESLD patients with apparent and refractory ascites taking dual conventional diuretics for a short period before LDLT.

Positive Response to Tolvaptan Treatment Would Be a Good Prognostic Factor for Cirrhotic Patients with Ascites

Aims: Ascites is one of the major complications in advanced cirrhotic patients. Tolvaptan is a non-peptide orally available arginine vasopressin V2 receptor antagonist. We investigated and found that tolvaptan therapy improved the prognosis and predictive factor of cirrhotic patients with ascites. Methods: Overall, 99 patients with newly diagnosed ascites with cirrhosis were enrolled. No patients had intrahepatic malignancy. The patients were divided into 2 groups based on tolvaptan therapy: 86 patients treated with tolvaptan (tolvaptan-group) and 13 patients treated without tolvaptan (non-tolvaptan-group). Tolvaptan-responder was defined as body weight loss of ≥1.5 kg/week after administering tolvaptan. Results: Tolvaptan therapy was effective in 61.6% of cirrhotic patients. There was a significant difference in the overall survival (OS) between the tolvaptan-responder-group and the other groups (p < 0.001). Male (HR 5.05; p = 0.01), tolvaptan responder (HR 0.21; p = 0.02), and dosage of furosemide < 40 mg/day (HR 0.17; p = 0.01) were factors that were independently associated with the OS. The multivariate analysis revealed that C-reactive protein < 0.9 mg/dL (HR 0.07; p = 0.001), and furosemide dosage < 40 mg/day (HR 0.09; p = 0.003) were independently associated with the tolvaptan response. Conclusion: Therapeutic response to tolvaptan was associated with longer survival in cirrhosis patients complicated with ascites. These preliminary findings warrant validation and further exploration.

Is Exaggerated Release of Arginine Vasopressin an Endocrine Disorder? Pathophysiology and Treatment.

Exaggerated release of arginine vasopressin (AVP) is profoundly involved in impaired water excretion and related hyponatremia. Such disorders underlie syndromes of inappropriate secretion of antidiuretic hormone (SIADH) and edematous diseases, such as congestive heart failure and decompensated liver cirrhosis. All the causes are fundamentally from non-endocrine diseases. AVP-induced water retention could produce hyponatremia, and further accelerate poor long-term outcome of edematous diseases. Administration of AVP V2 receptor antagonists verifies how much AVP is involved in the pathogenesis of the impaired water excretion. The present paper demonstrated that exaggerated release of AVP plays a crucial role as an accessory endocrine disorder in pathological states of water retention and dilutional hyponatremia in non-endocrine disorders.

Tolvaptan use during hyperhydration in paediatric intracranial lymphoma with SIADH.

SummaryAn 11-year-old boy developed severe syndrome of inappropriate antidiuretic hormone secretion (SIADH) after diagnosis of an intracranial B-cell lymphoma. His sodium levels dropped to 118–120 mmol/L despite 70% fluid restriction. For chemotherapy, he required hyperhydration, which posed a challenge because of severe hyponatraemia. Tolvaptan is an oral, highly selective arginine vasopressin V2-receptor antagonist, which has been licensed in adults for the management of SIADH and has been used in treating paediatric heart failure. Tolvaptan gradually increased sodium levels and allowed liberalisation of fluid intake and hyperhydration. Tolvaptan had profound effects on urinary output in our patient with increases up to 8 mL/kg/h and required close monitoring of fluid balance, frequent sodium measurements and adjustments to intake. After hyperhydration, tolvaptan was stopped, and the lymphoma went into remission with reversal of SIADH. We report one of the first uses of tolvaptan in a child with SIADH, and it was an effective and safe treatment to manage severe SIADH when fluid restriction was not possible or effective. However, meticulous monitoring of fluid balance and sodium levels and adjustments of fluid intake are required to prevent rapid sodium changes.Learning points:Tolvaptan can be used in paediatric patients with SIADH to allow hyperhydration during chemotherapy.Tolvaptan has profound effects on urinary output and meticulous monitoring of fluid balance and sodium levels is therefore warranted.Tolvaptan was well tolerated without significant side effects.

Progress of tolvaptan in treating heart failure

Tolvaptan is a novel oral selective arginine vasopressin V2-receptor antagonist. Tolvaptan improves heart failure signs and symptoms without serious adverse events. Tolvaptan has no effect on all-cause mortality and cardiovascular death or admission rate for heart failure. But in heart failure patients with hyponatremia, tolvaptan can decrease cardiovascular death and admission rate for heart failure. Key words: Tolvaptan; Heart failure, congestive; Hyponatremia

Relaxin in paraventricular nucleus contributes to sympathetic overdrive and hypertension via PI3K-Akt pathway

Relaxin is recognized as an ovarian polypeptide hormone. Abundant relaxin binding sites are observed in hypothalamic paraventricular nucleus (PVN). This study was conducted to determine the roles and underlying mechanisms of relaxin in the PVN in sympathetic activation and hypertension in spontaneously hypertensive rats (SHR). Experiments were performed in normotensive Wistar-Kyoto rats (WKY) and SHR. Relaxin and its RXFP1 receptors in PVN were up-regulated in SHR. Relaxin-positive neurons existed in both parvocellular and magnocellular parts of the PVN. Presympathetic neurons and AVP neurons in the PVN expressed RXFP1, but not relaxin. Bilateral PVN microinjection of human relaxin-2 increased but anti-relaxin IgG reduced renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP), plasma norepinephrine (NE) and arginine vasopressin (AVP) levels in SHR. The effects of relaxin-2 on RSNA and MAP were abolished by intravenous infusion of ganglionic blocker hexamethonium, and attenuated by AVP V1 receptor antagonist AAVP. Akt phosphorylation was enhanced in SHR, and relaxin-2 stimulated Akt phosphorylation and p85α subunit of PI3K expression. PI3K inhibitor LY294002 or Akt inhibitor MK-2206 abolished the effects of relaxin-2 on the RSNA, MAP and plasma NE, and attenuated the relaxin-2-induced AVP secretion. STAT5a and polymerase II (Pol II) binding to relaxin-promoter were significantly increased in SHR. Chronic PVN infusion of relaxin-2 with osmotic pumps in normal rats induced sympathetic activation, AVP secretion and hypertension accompanied with cardiovascular remodeling. Relaxin in the PVN contributes to sympathetic overdrive and hypertension via PI3K-Akt pathway.

Synthesis and biological evaluation of novel phenothiazine derivatives as non-peptide arginine vasopressin V2 receptor antagonists

Abstract A series of novel phenothiazine derivatives was synthesized and tested for arginine vasopressin receptor antagonist activity. They were synthesized as novel arginine vasopressin receptor antagonists from phenothiazine as a scaffold via successive acylation, reduction and acylation reactions. Their structures were characterized by 1 H NMR, 13 C NMR and HRMS, and biological activity was evaluated by in vitro and in vivo studies. The in vitro binding assay indicated that several compounds are potent selective V2 receptor antagonists. Compounds with promising binding affinity to V2 receptors were selected to conduct the in vivo diuretic studies on Sprague-Dawley rats. Among them, 1n , 1r , 1t and 1v exhibited excellent diuretic activity, especially 1r and 1v . Therefore, 1r and 1v are potent novel AVP V2 receptor antagonist candidates.

Therapeutic effects of short- and intermediate-term tolvaptan administration for refractory ascites in patients with advanced liver cirrhosis.

Tolvaptan, an oral arginine vasopressin V2 receptor antagonist, became available for hepatic ascites. We evaluated the therapeutic efficacy and safety of tolvaptan administration to treat refractory ascites. Data were collected from 15 hospitalized patients with cirrhosis (hepatitis C, 10; alcoholism, five) after adding tolvaptan (3.75-11.25 mg/day) to conventional diuretics. Bodyweights and serum sodium and creatinine concentrations were measured. Tolvaptan was continued for 4 weeks or longer for a median follow-up period of 42 days (range, 28-56). In the first week (introduction phase), tolvaptan significantly reduced median weight (66.6, 65.9 and 63.1 kg on days 0, 1 and 7, respectively; P < 0.004). The numbers of good responders (≥3 kg reduction in 4 days), responders (<3 kg weight reduction) and non-responders (no weight reduction) were seven (46.7%), six (40.0%) and two of the 15 (13.3%), respectively. The two non-responders had concomitant chylous pleural effusion or spontaneous bacterial peritonitis. All patients continued tolvaptan for 2 weeks or longer and six (40%, three good responders and three responders) were treated for a median of 42 days without additional intervention. During this intermediate-term administration of tolvaptan, the median weight reduction was statistically significant (65.4, 61.9 and 56.9 kg on days 0, 7 and 42, respectively; P < 0.030) and there was no serum sodium imbalance or renal dysfunction; but two of these six developed hepatic coma. Tolvaptan safely alleviated fluid retention caused by hepatic cirrhosis. Intermediate-term administration of tolvaptan apparently helped maintain weight reduction achieved during the introduction phase.

Review of Tolvaptan for Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by bilateral renal cysts, kidney pain, hypertension, and progressive loss of renal function. It is a leading cause of end-stage renal disease and the most common inherited kidney disease in the United States. Despite its prevalence, disease-modifying treatment options do not currently exist. Tolvaptan is an orally active, selective arginine vasopressin V2 receptor antagonist already in use for hyponatremia. Tolvaptan exhibits dose-proportional pharmacokinetics with a half-life of ~12 hours. Metabolism occurs through the cytochrome P450 3A4 isoenzyme, and tolvaptan is a substrate for P-glycoprotein, resulting in numerous drug interactions. Recent research has highlighted the beneficial effect of tolvaptan on delaying the progression of ADPKD, which is the focus of this review. Pharmacologic, preclinical, and phase II and III clinical trial studies have demonstrated that tolvaptan is an effective treatment option that targets underlying pathogenic mechanisms of ADPKD. Tolvaptan delays the increase in total kidney volume (surrogate marker for disease progression), slows the decline in renal function, and reduces kidney pain. However, tolvaptan has significant adverse effects including aquaretic effects (polyuria, nocturia, polydipsia) and elevation of aminotransferase enzyme concentrations with the potential for acute liver failure. Appropriate patient selection is critical to optimize long-term benefits while minimizing adverse effects and hepatotoxic risk factors. Overall, tolvaptan is the first pharmacotherapeutic intervention to demonstrate significant benefit in the treatment of ADPKD, but practitioners and regulatory agencies must carefully weigh the risks versus benefits. Additional research should focus on incidence and risk factors of liver injury, cost-effectiveness, clinical management of drug-drug interactions, and long-term disease outcomes.

Riding the waves: evidence for a beneficial effect of increased water intake in autosomal dominant polycystic kidney disease patients?

Autosomal dominant polycystic kidney disease (ADPKD) can lead to end-stage kidney disease and accounts for ∼10% of people receiving renal replacement therapy. Until recently, no treatment had been proven to effectively postpone kidney failure. Interestingly, experimental studies that have been published over the past decades have suggested a detrimental role for the antidiuretic hormone arginine vasopressin (AVP) in ADPKD. V2 receptor activation by AVP was discovered to result in an increase of 30,50-cyclic adenosine monophosphate (cAMP) [1]. In turn, cAMP stimulates cell proliferation and fluid secretion, leading to cyst formation and cyst growth [2–4]. ADPKD patients appeared to have high serum levels of AVP, and AVP levels were, in cross-sectional studies, associated with disease severity [5] and, in longitudinal studies, with disease progression [6, 7]. These observations formed the rationale to study interventions that block this cAMP-mediated pathway using V2 receptor antagonists. In various animal models for cystic kidney disease, these interventions were successful to reduce cyst growth [8–10]. Subsequently, the selective AVP V2 receptor antagonist tolvaptan was tested for its efficacy in ADPKD patients in the TEMPO 3:4 trial. For the first time, a medical treatment proved to be beneficial with respect to kidney outcomes. In 1445 ADPKD patients, relatively early in the disease, treatment with tolvaptan slowed the rate of growth in total kidney volume by ∼50% and the rate of estimated glomerular filtration rate (eGFR) loss by ∼30% compared with placebo. In 2013, however, the US Food and Drug Administration (FDA) decided against approval of tolvaptan for the indication of slowing disease progression in ADPKD (http:// www.fda.gov/downloads/advisorycommittees/committeesmeeting materials/drugs/cardiovascularandrenaldrugsadvisorycommittee/ ucm373520.pdf). This decision was based, amongst others, upon questions relating to the effectiveness of the drug and to tolvaptan’s risk of drug-induced liver injury. This decision felt surprising for some, because the effect on eGFR loss with tolvaptan is comparable with that of, for instance, angiotensin-II receptor blockers that are registered for diabetic nephropathy [11], a disease for which other treatments are available, whereas for ADPKD there is no renoprotective alternative. In addition, all liver function abnormalities that occurred in the TEMPO 3:4 trial were reversible after drug withdrawal. The FDA, however, extrapolated from these data that 1 per 3.000 treated ADPKD patients may develop hepatic failure for which a liver transplant would be needed (http://www.fda.gov/downloads/Advisory Committees/CommitteesMeetingMaterials/Drugs/Cardiovascular andRenalDrugsAdvisoryCommittee/UCM364582.pdf ). This should be weighed against the need for liver transplantation due to the cystic disease which occurs in a number of ADPKD patients anyway [12, 13]. Notwithstanding these considerations, the FDA decided not to register tolvaptan for the indication ADPKD, but to ask for additional evidence. The decision of the European Medicines Agency is expected late in 2014. With tolvaptan at present not being available for clinical care, other options that lower AVP activity should be considered. An alternative might be to lower AVP concentration by increasing water intake [14]. In a rat model for polycystic kidney disease, a 3.5-fold increased water intake reduced urinary osmolality, renal expression of the AVP V2 receptor and reduced kidney weight compared with normal water intake [15] (Figure 1). Given the theoretical background and the promising animal data, Higashihara et al. investigated the effects of increased water intake on disease progression in ADPKD, a clinically important and very timely topic. In their study, published in this issue of NDT, 34 ADPKD patients with a relatively preserved kidney function were divided based upon their preference into a high and a free water intake group.

Synthesis and Biological Evaluation of Substituted Desloratadines as Potent Arginine Vasopressin V2 Receptor Antagonists

Twenty-one non-peptide substituted desloratadine class compounds were synthesized as novel arginine vasopressin receptor antagonists from desloratadine via successive acylation, reduction and acylation reactions. Their structures were characterized by 1H-NMR and HRMS, their biological activity was evaluated by in vitro and in vivo studies. The in vitro binding assay and cAMP accumulation assay indicated that these compounds are potent selective V2 receptor antagonists. Among them compounds 1n, 1t and 1v exhibited both high affinity and promising selectivity for V2 receptors. The in vivo diuretic assay demonstrated that 1t presented remarkable diuretic activity. In conclusion, 1t is a potent novel AVP V2 receptor antagonist candidate.

Glutamate microinjection into the hypothalamic paraventricular nucleus attenuates ulcerative colitis in rats

To investigate the effects of glutamate microinjection into hypothalamic paraventricular nucleus (PVN) on ulcerative colitis (UC) in rats and to explore the relevant mechanisms. 2,4,6-Trinitrobenzenesulfonic acid (100 mg/kg in 50% ethanol) was instilled into the colon of adult male SD rats to induce UC. A colonic damage score (CDS) was used to indicate the severity of the colonic mucosal damage. The pathological changes in the colonic mucosa were evaluated using immunohistochemistry, Western blotting, biochemical analyses or ELISA. Ten minutes before UC induction, drugs were microinjected into the relevant nuclei in rat brain to produce chemical stimulation or chemical lesion. Microinjection of glutamate (3, 6 and 12 μg) into the PVN dose-dependently decreased the CDS in UC rats. This protective effect was eliminated after kainic acid (0.3 μg) was microinjected into PVN or into the nucleus tractus solitarius (NTS) that caused chemical lesion of these nuclei. This protective effect was also prevented when the AVP-V1 receptor antagonist DPVDAV (200 ng) was microinjected into the NTS. The discharge frequency of the vagus was markedly decreased following microinjection of glutamate into the PVN. Microinjection of glutamate into the PVN in UC rats significantly increased the cell proliferation and anti-oxidant levels, and decreased the apoptosis and Bax and caspase 3 expression levels and reduced the pro-inflammatory factors in the colonic mucosa. The activation of hypothalamic PVN exerts protective effects against UC, which is mediated by the NTS and vagus. The effects may be achieved via anti-oxidative, anti-apoptotic, and anti-inflammatory factors.

Role of central arginine vasopressin receptors in the analgesic effect of CDP-choline on acute and neuropathic pain

Recent studies have demonstrated that arginine vasopressin (AVP) plays a crucial role in pain modulation. In addition, our previous studies have proven that centrally administered cytidine-5'-diphosphate-choline (CDP-choline; citicoline) elicits an analgesic effect in different pain models in rats. Given that CDP-choline enhances central and peripheral vasopressin levels, the present study was designed to investigate the role of central AVP receptors in the analgesic effect of CDP-choline in acute and chronic constriction injury-induced neuropathic pain models. For this purpose, rats were pretreated intracerebroventricularly with the AVP V1 or AVP V2 receptor antagonist 15 min before intracerebroventricular injection of CDP-choline or saline, and pain threshold was determined using the Randall-Selitto test. AVP V1 and AVP V2 receptor antagonist blocked the CDP-choline-induced analgesic effect either in acute or neuropathic models of pain in rats. These results suggest, for the first time, that central AVP receptors are involved in the CDP-choline-elicited analgesic effect.

Tolvaptan, an orally active non-peptide arginine vasopressin V2 receptor antagonist, reduces ascites in rats with chronic liver injury

This is a non-clinical, proof of concept study, showing that tolvaptan has efficacy in reducing ascites in chronic liver injury, using a rat model induced by repeated dimethylnitrosamine (DMNA) injection. A rat model of chronic liver injury was induced by 10 mg/kg of repeated i.p. injection with DMNA for 6-9 weeks. Tolvaptan was administrated to rats that showed obvious and stable ascites, and abdominal circumference was evaluated as a surrogate marker of ascites volume. Rats were placed in metabolic cages with free access to food and water to collect urine over a 24-h period. Oral tolvaptan (1 and 3 mg/kg) promoted a remarkable diuretic effect, decreasing bodyweight and abdominal circumference in a dose-dependent manner. Plasma sodium concentration was increased by tolvaptan due to the large amount of free-water excretion following tolvaptan administration. Tolvaptan had therapeutic efficacy in the reduction of ascites in rats with chronic liver injury. These results are consistent with the clinical data showing tolvaptan has therapeutic implications in the reduction of ascites in patients with decompensated cirrhosis.

Salusin-β in paraventricular nucleus increases blood pressure and sympathetic outflow via vasopressin in hypertensive rats

Salusin-β is a bioactive peptide with peripheral hypotensive, mitogenic and pro-atherosclerotic effects. The present study was designed to determine the roles of salusin-β in the paraventricular nucleus (PVN) and its relationship with arginine vasopressin (AVP) in hypertension and sympathetic activation. Renovascular hypertension was induced by two-kidney, one-clip (2K1C) in male Sprague-Dawley rats. Acute experiments were carried out 4 weeks after 2K1C or sham-operation under urethane and alpha-chloralose anaesthesia. Renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP), and heart rate (HR) were recorded. Microinjection of salusin-β into the PVN increased the RSNA, MAP, and HR in a dose-related manner, whereas anti-salusin-β IgG in the PVN decreased the RSNA and MAP, and abolished the effects of salusin-β in 2K1C rats. However, either salusin-β or anti-salusin-β IgG in the PVN failed to cause any significant effects in sham-operated rats. The number of salusin-β-like immunopositive neurons in the PVN was significantly increased in 2K1C rats. Salusin-β in the PVN increased the plasma AVP and norepinephrine levels in 2K1C rats, but not in sham-operated rats. Iv injection of dTyr(CH2)5(Me)AVP (an AVP V1-receptor antagonist, AAVP) decreased RSNA and MAP, and abolished the effects of salusin-β in the PVN in 2K1C rats. Microinjection of AAVP into the rostral ventrolateral medulla (RVLM), but not into the PVN, abolished the effects of salusin-β on RSNA and HR. Salusin-β in the PVN increases blood pressure, heart rate, and sympathetic outflow via both circulating AVP and AVP in the RVLM in hypertensive rats.

Renoprotective Effect of Vasopressin V2 Receptor Antagonist Tolvaptan in Dahl Rats With End-Stage Heart Failure

Tolvaptan is a highly selective and orally effective arginine vasopressin V2 receptor antagonist, and is potentially useful for the treatment of heart failure (HF) patients. However, the renoprotective effect of long-term tolvaptan therapy and its underlying mechanisms remain unknown. We evaluated the effects of chronic treatment with tolvaptan on renal dysfunction, podocyte injury, inflammation, oxidative stress, Rho-kinase, epithelial-mesenchymal transition (EMT), and the extracellular signal-regulated protein kinase (ERK1/2) pathway in the renal cortex of Dahl salt-sensitive hypertensive (DS) rats with end-stage severe HF. DS and Dahl salt-resistant rats were fed a high-salt diet at 6 weeks of age. DS rats were treated with vehicle and tolvaptan (0.05% concentration in diet) from the age of 11 to 18 weeks. Vehicle-treated DS rats developed proteinuria, renal dysfunction, glomerulosclerosis, and interstitial fibrosis, which were ameliorated by tolvaptan without changing blood pressure. Decreased expression of nephrin and podocin and increased desmin-positive area in failing rats were restored by tolvaptan. Upregulation of NAD(P)H oxidase p22(phox), p47(phox), and gp91(phox), EMT markers such as transforming growth factor-β1, vimentin, and fibronectin expression, and Rho-kinase and ERK1/2 phosphorylation in DS rats were significantly suppressed by tolvaptan. Tolvaptan administration resulted in significant inhibition of tumor necrosis factor-α and monocyte chemoattractant protein-1 expression, and nuclear factor-κB phosphorylation. We concluded that long-term tolvaptan therapy may improve renal dysfunction, glomerulosclerosis, podocyte injury, and inflammation associated with oxidative stress, as well as EMT, ERK, and the Rho-kinase pathway in the failing heart of DS rats. Thus, tolvaptan may be a therapeutic strategy for end-stage severe HF.