Therapeutic potentials of nonpeptidic V2R agonists for partial cNDI-causing V2R mutants.

Loss-of-function mutations in the type 2 vasopressin receptor (V2R) are a major cause of congenital nephrogenic diabetes insipidus (cNDI). In the context of partial cNDI, the response to desmopressin (dDAVP) is partially, but not entirely, diminished. For those with the partial cNDI, restoration of V2R function would offer a prospective therapeutic approach. In this study, we revealed that OPC-51803 (OPC5) and its structurally related V2R agonists could functionally restore V2R mutants causing partial cNDI by inducing prolonged signal activation. The OPC5-related agonists exhibited functional selectivity by inducing signaling through the Gs-cAMP pathway while not recruiting ß-arrestin1/2. We found that six cNDI-related V2R partial mutants (V882.53M, Y1283.41S, L1614.47P, T2736.37M, S3298.47R and S3338.51del) displayed varying degrees of plasma membrane expression levels and exhibited moderately impaired signaling function. Several OPC5-related agonists induced higher cAMP responses than AVP at V2R mutants after prolonged agonist stimulation, suggesting their potential effectiveness in compensating impaired V2R-mediated function. Furthermore, docking analysis revealed that the differential interaction of agonists with L3127.40 caused altered coordination of TM7, potentially contributing to the functional selectivity of signaling. These findings suggest that nonpeptide V2R agonists could hold promise as potential drug candidates for addressing partial cNDI.

Successful Treatment of Lithium-Induced Nephrogenic Diabetes Insipidus with Celecoxib: A Promising Therapeutic Option.

BACKGROUND Nephrogenic diabetic insipidus (NDI) poses a challenge in clinical management, particularly when associated with lithium ingestion. Non-selective non-steroidal anti-inflammatory drugs (NSAIDs) have been widely used for the treatment of numerous diseases worldwide, including NDI. However, many studies have reported the diverse adverse effects of long-term use of non-selective NSAIDs. Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, is a better drug to relieve pain and inflammation in terms of long-term safety and efficacy than non-selective NSAIDs. Nevertheless, there are few reports describing the effectiveness of celecoxib in treating NDI. CASE REPORT We report a case of a 46-year-old woman with schizophrenia who presented with severe hypernatremia and refractory polyuria due to lithium-induced NDI. Cessation of lithium ingestion and traditional treatments, including trichlormethiazide and desmopressin, yielded minimal improvement in her hypernatremia and polyuria. Her sodium level needed to be strictly controlled with the infusion of dextrose 5% in water. Given the safety of celecoxib, we decided to initiate celecoxib as the treatment of lithium-induced NDI instead of indomethacin. Notably, the introduction of celecoxib led to a substantial and sustained amelioration of polyuria and hypernatremia without any celecoxib-associated adverse effects. Even after transfer to another hospital, stability in serum sodium levels persisted with celecoxib. CONCLUSIONS We presented a case of lithium-induced NDI successfully treated with celecoxib, a selective COX-2 inhibitor. To the best of our knowledge, this is the first reported case of successful treatment of lithium-induced NDI with celecoxib, and suggests celecoxib is a viable therapeutic option warranting further exploration. Physicians should consider its use when faced with the challenging management of lithium-induced NDI.

ß3 Adrenergic Receptor Agonist Mirabegron Increases AQP2 and NKCC2 Urinary Excretion in OAB Patients: A Pleiotropic Effect of Interest for Patients with X-Linked Nephrogenic Diabetes Insipidus.

We previously reported the novel finding that ß3-AR is functionally expressed in the renal tubule and shares its cellular localization with the vasopressin receptor AVPR2, whose physiological stimulation triggers antidiuresis by increasing the plasma membrane expression of the water channel AQP2 and the NKCC2 symporter in renal cells. We also showed that pharmacologic stimulation of ß3-AR is capable of triggering antidiuresis and correcting polyuria, in the knockout mice for the AVPR2 receptor, the animal model of human X-linked nephrogenic diabetes insipidus (XNDI), a rare genetic disease still missing a cure. Here, to demonstrate that the same response can be evoked in humans, we evaluated the effect of treatment with the ß3-AR agonist mirabegron on AQP2 and NKCC2 trafficking, by evaluating their urinary excretion in a cohort of patients with overactive bladder syndrome, for the treatment of which the drug is already approved. Compared to baseline, treatment with mirabegron significantly increased AQP2 and NKCC2 excretion for the 12 weeks of treatment. This data is a step forward in corroborating the hypothesis that in patients with XNDI, treatment with mirabegron could bypass the inactivation of AVPR2, trigger antidiuresis and correct the dramatic polyuria which is the main hallmark of this disease.

Psychotropic Drugs and Adverse Kidney Effects: A Systematic Review of the Past Decade of Research.

BACKGROUND AND OBJECTIVE: Psychotropic drugs are a heterogenous group of treatments prescribed for many psychiatric disorders, often for long periods. Their effects on the kidney and its functioning are complex and a source of significant research and debate. This article aims to review recent evidence of the acute and chronic kidney adverse events of diverse psychotropes. METHODS: A systematic search of randomized controlled trials and large observational studies (n ≥ 100) reporting the effects of psychotropic drugs on the kidney was conducted. The MEDLINE, PsycInfo, and EMBASE databases from 2011 to 2021, inclusive, were broadly searched with few restrictions and no prespecified outcomes. Two or more independent reviewers assessed and summarized all eligible studies, including risks of bias and levels of evidence. RESULTS: In all, 1999 abstracts were screened for eligibility and 47 articles were included, which examined lithium (33), antiepileptics (10), antipsychotics (13), and antidepressants (9). No studies examining kidney adverse effects of other psychotropes, such as benzodiazepines, met inclusion criteria. Study populations were adult (8), geriatric (9), and mixed (30). Lithium was almost unanimously associated with (1) chronic kidney disease and (2) nephrogenic diabetes insipidus in methodologically diverse studies. The most supported risk factors for declining kidney functioning with lithium were advanced age, duration of lithium treatment, acute lithium toxicity, female sex, medications with known renal interactions, diabetes mellitus/hyperglycemia, and overall medical comorbidity. Supratherapeutic lithium concentrations are both the causes and consequences of acute kidney injury. Once significant chronic kidney disease has developed, four studies found that replacing lithium with other mood stabilizers does not slow progression, and the evolution to end-stage kidney disease is rare overall with modern practices. Compared to lithium, fewer studies examined antipsychotics and antiepileptics but found relatively less direct kidney harms. Antidepressants were not associated with acute or chronic kidney harms. CONCLUSIONS: Despite the heterogeneity of findings, owing to varying methodologies and research challenges, recent studies strongly suggest that lithium is associated with an increased risk of chronic kidney disease and nephrogenic diabetes insipidus, especially in older adults and long-term lithium users. Clinicians should balance the harms of lithium against its established benefits, and ensure adequate monitoring and management of comorbidities in all patients. Weaker evidence suggests that antiepileptics such as valproate and antipsychotics result in comparatively less harm to the kidney than lithium, but warrant monitoring because of multiple direct and indirect mechanisms for potential kidney adverse events. Antidepressants do not have clear kidney adverse effects and appear safe (though potentially less effective) in the setting of kidney disease. Other classes of psychotropic drugs have received little research interest. Further research is warranted, particularly into specific antiepileptics and antipsychotics, and careful attention should be paid to mitigating important sources of bias such as confounding by indication.

[Diagnostic trap: Lithium neurotoxicity with normal lithemia]. / Piège diagnostique : neurotoxicité au lithium avec lithémie normale.

We describe here the case of a 54-year-old bipolar woman, followed in psychiatry and treated with lithium and a selective serotonin reuptake inhibitor (escitalopram) and lamotrigine, presenting a lithium poisoning with an altered state of consciousness caused by a supposed mismanagement of her treatment. Lithium poisoning was suggested based on neurological clinical features, but the blood test brought out a lithium concentration within the therapeutic values at 1,2 mmol/L (N: 0,6-1,2 mmol/L). The classic biological complications related to lithium poisoning (hypercalcemia, diabetes insipidus) confirmed the diagnosis. The patient has been transferred to our nephrology department where she got two hemodialysis sessions conducting to clinical and biological improvement, confirming the diagnosis of lithium poisoning despite the normal blood levels. Later, she was transferred to the psychiatry department for follow-up and for treatment adjustment.

What an endocrinologist should know for patients receiving lithium therapy.

Lithium is an efficient treatment of bipolar disorder. Besides renal insufficiency, many endocrine side effects are described such as the occurrence of thyroid disorders, hypercalcaemia and nephrogenic diabetes insipidus. Lithium inhibits the secretion of thyroid hormones. The prevalence of goiter is 4 times more common in Lithium-treated patients compared as to the general population. Hypothyroidism (8-20%) is more frequent in women and in case of pre-existing thyroid autoimmunity. Grave's disease and other hyperthyroidisms are sometimes reported. Lithium stimulates the proliferation of parathyroid cells by activating the Wnt pathway. An increase in serum calcium and PTH is described in patients treated with Lithium with a 4 to 6-fold higher risk of primary hyperparathyroidism than in the general population. Nevertheless, 24-hour urine calcium is not often increased, and the phenotype can mimic a hypercalcemia-hypocalciuria syndrome that may regress with Lithium discontinuation. Surgery should be cautious since parathyroid hyperplasia is more common than parathyroid adenoma. Nephrogenic diabetes insipidus is frequently reported and may be debilitating, sometimes intricated with severe dehydration, hypernatremia, and acute renal insufficiency. Nephrogenic diabetes insipidus is not generally reversible after Lithium discontinuation, especially in patients who have chronic kidney disease due to interstitial tubule nephritis. In conclusion, clinical assessment (goiter, diuresis) and biological monitoring of serum calcium, sodium creatinine, TSH and lithium are recommended in patients receiving Lithium therapy. The risk of Lithium discontinuation in case of side effects should be weighed against the psychological risk, and must be discussed with the psychiatrist.

Updates and Perspectives on Aquaporin-2 and Water Balance Disorders.

Ensuring the proper amount of water inside the body is essential for survival. One of the key factors in the maintenance of body water balance is water reabsorption in the collecting ducts of the kidney, a process that is regulated by aquaporin-2 (AQP2). AQP2 is a channel that is exclusively selective for water molecules and impermeable to ions or other small molecules. Impairments of AQP2 result in various water balance disorders, including nephrogenic diabetes insipidus (NDI), which is a disease characterized by a massive loss of water through the kidney and consequent severe dehydration. Dysregulation of AQP2 is also a cause of water retention with hyponatremia in heart failure, hepatic cirrhosis, and syndrome of inappropriate antidiuretic hormone secretion (SIADH). Antidiuretic hormone vasopressin is an upstream regulator of AQP2. Its binding to the vasopressin V2 receptor promotes AQP2 targeting to the apical membrane and thus enables water reabsorption. Tolvaptan, a vasopressin V2 receptor antagonist, is effective and widely used for water retention with hyponatremia. However, there are no studies showing improvement in hard outcomes or long-term prognosis. A possible reason is that vasopressin receptors have many downstream effects other than AQP2 function. It is expected that the development of drugs that directly target AQP2 may result in increased treatment specificity and effectiveness for water balance disorders. This review summarizes recent progress in studies of AQP2 and drug development challenges for water balance disorders.

Activation of AQP2 water channels by protein kinase A: therapeutic strategies for congenital nephrogenic diabetes insipidus.

BACKGROUND: Congenital nephrogenic diabetes insipidus (NDI) is primarily caused by loss-of-function mutations in the vasopressin type 2 receptor (V2R). Renal unresponsiveness to the antidiuretic hormone vasopressin impairs aquaporin-2 (AQP2) water channel activity and water reabsorption from urine, resulting in polyuria. Currently available symptomatic treatments inadequately reduce patients' excessive amounts of urine excretion, threatening their quality of life. In the past 25 years, vasopressin/cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) has been believed to be the most important signaling pathway for AQP2 activation. Although cAMP production without vasopressin is the reasonable therapeutic strategy for congenital NDI caused by V2R mutations, the efficacy of candidate drugs on AQP2 activation is far less than that of vasopressin. RESULTS: Intracellular distribution and activity of PKA are largely controlled by its scaffold proteins, A-kinase anchoring proteins (AKAPs). Dissociating the binding of AKAPs and PKA significantly increased PKA activity in the renal collecting ducts and activated AQP2 phosphorylation and trafficking. Remarkably, the AKAPs-PKA disruptor FMP-API-1 increased transcellular water permeability in isolated renal collecting ducts to the same extent as vasopressin. Moreover, derivatives of FMP-API-1 possessed much more high potency. FMP-API-1/27 is the first low-molecular-weight compound to be discovered that can phosphorylate AQP2 more effectively than preexisting drug candidates. CONCLUSION: AKAP-PKA disruptors are a promising therapeutic target for congenital NDI. In this article, we shall discuss the pathophysiological roles of PKA and novel strategies to activate PKA in renal collecting ducts.

Rapid development of vasopressin resistance in dietary K+ deficiency.

The association between diabetes insipidus (DI) and chronic dietary K+ deprivation is well known, but it remains uncertain how the disorder develops and whether it is influenced by the sexual dimorphism in K+ handling. Here, we determined the plasma K+ (PK) threshold for DI in male and female mice and ascertained if DI is initiated by polydipsia or by a central or nephrogenic defect. C57BL6J mice were randomized to a control diet or to graded reductions in dietary K+ for 8 days, and kidney function and transporters involved in water balance were characterized. We found that male and female mice develop polyuria and secondary polydipsia. Altered water balance coincided with a decrease in aquaporin-2 (AQP2) phosphorylation and apical localization despite increased levels of the vasopressin surrogate marker copeptin. No change in the protein abundance of urea transporter-A1 was observed. The Na+-K+-2Cl- cotransporter decreased only in males. Desmopressin treatment failed to reverse water diuresis in K+-restricted mice. These findings indicate that even a small fall in PK is associated with nephrogenic DI (NDI), coincident with the development of altered AQP2 regulation, implicating low PK as a causal trigger of NDI. We found that PK decreased more in females, and, consequently, females were more prone to develop NDI. Together, these data indicate that AQP2 regulation is disrupted by a small decrease in PK and that the response is influenced by sexual dimorphism in K+ handling. These findings provide new insights into the mechanisms linking water and K+ balances and support defining the disorder as "potassium-dependent NDI."NEW & NOTEWORTHY This study shows that aquaporin-2 regulation is disrupted by a small fall in plasma potassium levels and the response is influenced by sexual dimorphism in renal potassium handling. The findings provided new insights into the mechanisms by which water balance is altered in dietary potassium deficiency and support defining the disorder as "potassium-dependent nephrogenic diabetes insipidus."

Triamterene in lithium-induced nephrogenic diabetes insipidus: a case report.

Lithium-induced nephrogenic diabetes insipidus (NDI) is a rare and difficult-to-treat condition. We describe the case of an 81-year-old woman with bipolar treated with lithium and no previous history of diabetes insipidus. She was hospitalized due to disturbance of consciousness and was diagnosed with, hypercalcemia, hyperparathyroidism, and NDI. Parathyroidectomy was contraindicated and parathyroid hormone level was improved insufficiently after cinacalcet initiation, percutaneous ethanol injection therapy was performed for the enlarged parathyroid gland. After improvement in hypercalcemia and unsuccessful indapamide treatment, triamterene was administrated to control polyuria. Lithium is one of the indispensable maintenance treatment options for bipolar disorder, but it has the side effect of NDI. Lithium enters the collecting duct's principal cells mainly via the epithelial sodium channel (ENaC) located on their apical membranes, ENaC shows high selectivity for both sodium and lithium, is upregulated by aldosterone, and inhibited by triamterene. To our knowledge, this is the first publication on triamterene use in lithium-induced NDI patients.

A double-blind, randomized, placebo-controlled pilot trial of atorvastatin for nephrogenic diabetes insipidus in lithium users.

OBJECTIVE: Lithium remains an important treatment for mood disorders but is associated with kidney disease. Nephrogenic diabetes insipidus (NDI) is associated with up to 3-fold risk of incident chronic kidney disease among lithium users. There are limited randomized controlled trials (RCT) for treatments of lithium-induced NDI, and existing therapies can be poorly tolerated. Therefore, novel treatments are needed for lithium-induced NDI. METHOD: We conducted a 12-week double-blind pilot RCT to assess the feasibility and efficacy of 20 mg/d atorvastatin vs placebo in the treatment of NDI in chronic lithium users. Patients, recruited between September 2017 and October 2018, were aged 18 to 85, currently on a stable dose of lithium, and determined to have NDI. RESULTS: Urinary osmolality (UOsm) at 12 weeks adjusted for baseline was not statistically different between groups (+39.6 mOsm/kg [95% CI, -35.3, 114.5] in atorvastatin compared to placebo groups). Secondary outcomes of fluid intake and aquaporin-2 excretions at 12 weeks adjusted for baseline were -0.13 L [95% CI, -0.54, 0.28] and 98.68 [95% CI, -190.34, 387.70], respectively. A moderate effect size was observed for improvements in baseline UOsm by ≥100 mOsm/kg at 12 weeks in patients who received atorvastatin compared to placebo (38.45% (10/26) vs 22.58% (7/31); Cohen's d = 0.66). CONCLUSION: Among lithium users with NDI, atorvastatin 20 mg/d did not significantly improve urinary osmolality compared to placebo over a 12-week period. Larger confirmatory trials with longer follow-up periods may help to further assess the effects of statins on NDI, especially within patients with more severe NDI.

Acute interstitial nephritis and nephrogenic diabetes insipidus following treatment with sulfamethoxazole-trimethoprim and temozolomide.

We report a case of acute interstitial nephritis with associated nephrogenic diabetes insipidus in a patient treated with temozolomide and sulfamethoxazole-trimethoprim for glioblastoma multiforme. Kidney biopsy demonstrated focal tubulointerstitial change with tubular dilatation, epithelial change and interstitial inflammation. The patient's kidney function improved with cessation of sulfamethoxazole-trimethoprim and treatment with hydrochlorothiazide for nephrogenic diabetes insipidus. Recommencement of temozolomide did not result in further deterioration in kidney function. In this case report, we discuss the novel association between sulfamethoxazole-trimethoprim-induced acute interstitial nephritis and nephrogenic diabetes insipidus, and suggest possible mechanisms involved.

[Analysis of AVPR2 variant in a neonate with congenital nephrogenic diabetes insipidus].

OBJECTIVE: To detect potential variant in a male neonate affected with congenital nephrogenic diabetes insipidus (CNDI). METHODS: Clinical data of the patient was collected. Genomic DNA was extracted from peripheral blood samples from the child and his parents. The whole coding regions of the arginine vasopressin V2 receptor (AVPR2) gene were amplified by PCR and subjected to Sanger sequencing. RESULTS: The patient presented recurrent fever and polyuria after birth. Multiple blood gas analyses indicated hypernatremia. Ultrasound showed bilateral hydronephrosis and hydroureter. The patient was partially responsive to hydrochlorothiazide. DNA analysis identified a hemizygous frameshift variant c.890-899delACCCGGAGGC in exon 2 of the AVPR2 gene in the proband. His mother was heterozygous for the same variant. CONCLUSION: The c.890-899delACCCGGAGGC variant of the AVPR2 gene probably underlies the CNDI in the child. Above discovery has enriched to spectrum of CNDI associated variants.

A snake toxin as a theranostic agent for the type 2 vasopressin receptor.

Rationale: MQ1, a snake toxin which targets with high nanomolar affinity and absolute selectivity for the type 2 vasopressin receptor (V2R), is a drug candidate for renal diseases and a molecular probe for imaging cells or organs expressing V2R. Methods: MQ1's pharmacological properties were characterized and applied to a rat model of hyponatremia. Its PK/PD parameters were determined as well as its therapeutic index. Fluorescently and radioactively labeled MQ1 were chemically synthesized and associated with moderate loss of affinity. MQ1's dynamic biodistribution was monitored by positron emission tomography. Confocal imaging was used to observe the labeling of three cancer cell lines. Results: The inverse agonist property of MQ1 very efficiently prevented dDAVP-induced hyponatremia in rats with low nanomolar/kg doses and with a very large therapeutic index. PK (plasma MQ1 concentrations) and PD (diuresis) exhibited a parallel biphasic decrease. The dynamic biodistribution showed that MQ1 targets the kidneys and then exhibits a blood and kidney biphasic decrease. Whatever the approach used, we found a T1/2α between 0.9 and 3.8 h and a T1/2ß between 25 and 46 h and demonstrated that the kidneys were able to retain MQ1. Finally, the presence of functional V2R expressed at the membrane of cancer cells was, for the first time, demonstrated with a specific fluorescent ligand. Conclusion: As the most selective V2 binder, MQ1 is a new promising drug for aquaresis-related diseases and a molecular probe to visualize in vitro and in vivo V2R expressed physiologically or under pathological conditions.

Nrf2 activation protects against lithium-induced nephrogenic diabetes insipidus.

Lithium (Li) is the mainstay pharmacotherapeutic mood stabilizer in bipolar disorder. Its efficacious use is complicated by acute and chronic renal side effects, including nephrogenic diabetes insipidus (NDI) and progression to chronic kidney disease (CKD). The nuclear factor erythroid-derived 2-related factor 2 (Nrf2) pathway senses and coordinates cellular responses to oxidative and electrophilic stress. Here, we identify that graded genetic activation of Nrf2 protects against Li-induced NDI (Li-NDI) and volume wasting via an aquaporin 2-independent mechanism. Renal Nrf2 activity is differentially expressed on functional segments of the nephron, and its activation along the distal tubule and collecting duct directly modulates ion transporter expression, mimicking paradoxical effects of diuretics in mitigating Li-NDI. In addition, Nrf2 reduces cyclooxygenase expression and vasoactive prostaglandin biosynthesis. Pharmacologic activation of Nrf2 confers protective effects, confirming this pathway as a potentially novel druggable target for the prevention of acute and chronic renal sequelae of Li therapy.

Identification of a novel X-linked arginine-vasopressin receptor 2 mutation in nephrogenic diabetes insipidus: Case report and pedigree analysis.

INTRODUCTION: The clinical and genetic characteristics of nephrogenic diabetes insipidus (NDI) were described via assessing 2 cases of NDI patients from a Chinese family. PATIENT CONCERNS: Two patients who manifest polyuria and polydipsia were admitted to hospital for definite diagnosis. DIAGNOSIS: Water deprivation-vasopressin tests showed that the patients may possess renal-origin diabetes insipidus. All the levels of thyroid-stimulating hormone, luteinizing hormone, follicle stimulation hormone, adrenocorticotropic hormone, prolactin, and growth hormone in both patients were normal. These results were certified that both patients possess a nephropathy-type diabetes insipidus. B-mode ultrasonography and urinalysis test demonstrated that the patient's diabetes insipidus is unlikely to originate from renal organic disease. Remarkably, by nucleotide sequencing, we found a novel mutation c.414_418del in arginine-vasopressin receptor 2 (AVPR2) was related to the disease of NDI. INTERVENTIONS: Two patients were treated with oral hydrochlorothiazide and indomethacin. In addition, low salt diet and potassium supplementation throughout the patients' treatment. OUTCOMES: The clinical symptoms of 2 patients were significantly reduced after targeted therapy. CONCLUSION: A mutation in AVPR2 was discovered to be associated with NID. It provides a new target for molecular diagnosis of NDI, enabling families to undergo genetic counseling and obtain prenatal diagnoses.

Partial nephrogenic diabetes insipidus associated with lithium therapy.

A 40-year-old Caucasian man developed excessive thirst and polyuria particularly at night over the preceding 6 months. He had been taking lithium for 16 years for the treatment of bipolar affective disorder. Investigations revealed subnormal maximum urinary concentrating ability after 8 hours of water deprivation and only a borderline response of urine osmolality to exogenous desmopressin given by intramuscular injection. A plasma copeptin concentration was elevated at 23 pmol/L. These results were consistent with partial nephrogenic diabetes insipidus. He was encouraged to increase his water intake as dictated by his thirst. In addition, he received amiloride with some improvement in his symptoms. Clinicians should be aware of the risk of nephrogenic diabetes insipidus with long-term lithium use and seek confirmation by a supervised water deprivation test augmented with a baseline plasma copeptin. If increased water intake is insufficient to control symptoms, amiloride may be considered.

Hypertensive urgency in nephrogenic diabetes insipidus with concomitant Hinman syndrome.

Diabetes insipidus is a syndrome characterised by the inability to conserve water or concentrate urine, leading to excessive excretion of urine. In congenital nephrogenic diabetes insipidus (CNDI), common presentations include failure to thrive, polydipsia, polyuria and dehydration. The long trajectory of the disease, coupled with psycho-behavioural changes as a child grows, can precipitate a period of non-adherence despite initial optimal control, especially in the adolescent age group. Social inconvenience of repeated voiding and nocturnal disturbances can lead to adapted urine holding behaviour, also known as non-neurogenic neurogenic bladder (Hinman syndrome). Anatomical changes in the urinary system, such as bladder trabeculation and hydroureteronephrosis, can subsequently give rise to functional renal impairment. We present a case of CNDI with concomitant Hinman syndrome, resulting in acute renal impairment and hypertensive emergency. We aim to raise awareness of the association between these two entities.

Fluconazole Increases Osmotic Water Transport in Renal Collecting Duct through Effects on Aquaporin-2 Trafficking.

BACKGROUND: Arginine-vasopressin (AVP) binding to vasopressin V2 receptors promotes redistribution of the water channel aquaporin-2 (AQP2) from intracellular vesicles into the plasma membrane of renal collecting duct principal cells. This pathway fine-tunes renal water reabsorption and urinary concentration, and its perturbation is associated with diabetes insipidus. Previously, we identified the antimycotic drug fluconazole as a potential modulator of AQP2 localization. METHODS: We assessed the influence of fluconazole on AQP2 localization in vitro and in vivo as well as the drug's effects on AQP2 phosphorylation and RhoA (a small GTPase, which under resting conditions, maintains F-actin to block AQP2-bearing vesicles from reaching the plasma membrane). We also tested fluconazole's effects on water flow across epithelia of isolated mouse collecting ducts and on urine output in mice treated with tolvaptan, a VR2 blocker that causes a nephrogenic diabetes insipidus-like excessive loss of hypotonic urine. RESULTS: Fluconazole increased plasma membrane localization of AQP2 in principal cells independent of AVP. It also led to an increased AQP2 abundance associated with alterations in phosphorylation status and ubiquitination as well as inhibition of RhoA. In isolated mouse collecting ducts, fluconazole increased transepithelial water reabsorption. In mice, fluconazole increased collecting duct AQP2 plasma membrane localization and reduced urinary output. Fluconazole also reduced urinary output in tolvaptan-treated mice. CONCLUSIONS: Fluconazole promotes collecting duct AQP2 plasma membrane localization in the absence of AVP. Therefore, it might have utility in treating forms of diabetes insipidus (e.g., X-linked nephrogenic diabetes insipidus) in which the kidney responds inappropriately to AVP.

Misfolding of vasopressin receptors: biased agonist pharmacochaperones as potential therapeutics.

Biased agonists and pharmacological chaperones have demonstrated their potential to harness G protein-coupled receptor signaling and trafficking, and have collectively opened new possibilities in G protein-coupled receptor drug discovery. Combining pharmacological chaperoning and biased agonism properties into a unique given molecule would be of high therapeutic interest in many human diseases resulting from G protein-coupled receptor mutation and misfolding. This strategy perfectly fits to congenital Nephrogenic Diabetes Insipidus which is a typical conformational disease. In most of the cases, it is associated to inactivating mutations of the renal arginine-vasopressin V2 receptor leading to misfolding and intracellular retention of the receptor, causing the inability of patients to concentrate their urine in response to the antidiuretic hormone. Cell-permeable pharmacological chaperones have been successfully challenged to restore plasma membrane localization of the receptor mutants and to rescue their function. Interestingly, different classes of pharmacological chaperones of the V2 receptor have proven their usefulness and efficacy, such as antagonists, agonists as well as biased agonists. These compounds, particularly small-molecule biased agonists which elicit the V2-induced Gs protein-dependent signaling pathway, but not V2-related arrestin-dependent cell responses, represent a potential therapeutic treatment of this X-linked genetic pathology.