Treatment of nephrogenic diabetes insipidus with prostaglandin synthesis inhibitors

V2 vasopressin receptor mutations: future personalized therapy based on individual molecular biology

The diluting and concentrating function of the kidney plays a crucial role in regulating the water homeostasis of the body. This function is regulated by the antidiuretic hormone, arginine vasopressin through the type 2 vasopressin receptor (V2R), allowing the body to adapt to periods of water load or water restriction. Loss-of-function mutations of the V2R cause X-linked nephrogenic diabetes insipidus (XNDI), which is characterized by polyuria, polydipsia, and hyposthenuria. Gain-of-function mutations of the V2R lead to nephrogenic syndrome of inappropriate antidiuresis disease (NSIAD), which results in hyponatremia. Various mechanisms may be responsible for the impaired receptor functions, and this review provides an overview of recent findings about the potential therapeutic interventions in the light of the current experimental data.

Nephrogenic diabetes insipidus: a comprehensive overview

Nephrogenic diabetes insipidus (NDI) is characterized by the inability to concentrate urine that results in polyuria and polydipsia, despite having normal or elevated plasma concentrations of arginine vasopressin (AVP). In this study, we review the clinical aspects and diagnosis of NDI, the various etiologies, current treatment options and potential future developments. NDI has different clinical manifestations and approaches according to the etiology. Hereditary forms of NDI are mainly caused by mutations in the genes that encode key proteins in the AVP signaling pathway, while acquired causes are normally associated with specific drug exposure, especially lithium, and hydroelectrolytic disorders. Clinical manifestations of the disease vary according to the degree of dehydration and hyperosmolality, being worse when renal water losses cannot be properly compensated by fluid intake. Regarding the diagnosis of NDI, it is important to consider the symptoms of the patient and the diagnostic tests, including the water deprivation test and the baseline plasma copeptin measurement, a stable surrogate biomarker of AVP release. Without proper treatment, patients may developcomplications leading to high morbidity and mortality, such as severe dehydration and hypernatremia. In that sense, the treatment of NDI consists in decreasing the urine output, while allowing appropriate fluid balance, normonatremia, and ensuring an acceptable quality of life. Therefore, therapeutic options include nonpharmacological interventions, including sufficient water intake and a low-sodium diet, and pharmacological treatment. The main medications used for NDI are thiazide diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs), and amiloride, used isolated or in combination.

Central Diabetes Insipidus Masked by Uncontrolled Diabetes Mellitus: A Challenging Case Managed With Indapamide

A 44-year-old man with a history of traumatic brain injury (TBI) presented to the emergency room (ER) with diabetic ketoacidosis (DKA). After resolution of DKA, the patient had persistent polyuria (up to 5.5 L/24 h) associated with low specific gravity (1.002-1.005) and severe hypernatremia (up to 186 mmol/L) that led us to consider the possibility of central diabetes insipidus (DI). Due to the lack of desmopressin availability in our country, we managed the patient using indapamide. Polydipsia and polyuria in a patient with controlled diabetes mellitus (DM) should raise suspicion for alternative etiologies, including DI. Appropriate fluid management during hospitalization is critical to avoid life-threatening complications. TBI is an important cause of central DI and should be treated with desmopressin, an arginine-vasopressin (AVP) analog. In the absence of desmopressin, alternative options can help patients with central DI, including thiazides, carbamazepine, chlorpropamide, among others less studied.

Aquaporins and diseases pathogenesis: From trivial to undeniable involvements, a disease-based point of view

Aquaporins (AQPs), as transmembrane proteins, were primarily identified as water channels with the ability of regulating the transmission of water, glycerol, urea, and other small-sized molecules. The classic view of AQPs involvement in therapeutic plan restricted them and their regulators into managing only a narrow spectrum of the diseases such as diabetes insipidus and the syndrome of inappropriate ADH secretion. However, further investigations performed, especially in the third millennium, has found that their cooperation in water transmission control can be manipulated to handle other burden-imposing diseases such as cirrhosis, heart failure, Meniere's disease, cancer, bullous pemphigoid, eczema, and Sjögren's syndrome.

A mini-review of pharmacological strategies used to ameliorate polyuria associated with X-linked nephrogenic diabetes insipidus

Nephrogenic diabetes insipidus (NDI) is characterized by renal resistance to the antidiuretic hormone arginine vasopressin (AVP), which leads to polyuria, plasma hyperosmolarity, polydipsia, and impaired quality of living. Inherited forms are caused by X-linked loss-of-function mutations in the gene encoding the vasopressin 2 receptor (V2R) or autosomal recessive/dominant mutations in the gene encoding aquaporin 2 (AQP2). A common acquired form is lithium-induced NDI. AVP facilitates reabsorption of water through increased abundance and insertion of AQP2 in the apical membrane of principal cells in the collecting ducts. In X-linked NDI, V2R is dysfunctional, which leads to impaired water reabsorption. These patients have functional AQP2, and thus the challenge is to achieve AQP2 membrane insertion independently of V2R. The current treatment is symptomatic and is based on distally acting diuretics (thiazide or amiloride) and cyclooxygenase inhibitors (indomethacin). This mini-review covers published data from trials in preclinical in vivo models and a few human intervention studies to improve NDI by more causal approaches. Promising effects on NDI in preclinical studies have been demonstrated by the use of pharmacological approaches with secretin, Wnt5a, protein kinase A agonist, fluconazole, prostaglandin E₂ EP2 and EP4 agonists, statins, metformin, and soluble prorenin receptor agonists. In patients, only casuistic reports have evaluated the effect of statins, phosphodiesterase inhibitors (rolipram and sildenafil), and the guanylate cyclase stimulator riociguat without amelioration of symptoms. It is concluded that there is currently no established intervention that causally improves symptoms or quality of life in patients with NDI. There is a need to collaborate to improve study quality and conduct formal trials.

Nephrogenic Diabetes Insipidus

Nephrogenic diabetes insipidus (NDI) results from the inability of the late distal tubules and collecting ducts to respond to vasopressin. The lack of ability to concentrate urine results in polyuria and polydipsia. Primary and acquired forms of NDI exist in children. Congenital NDI is a result of mutation in AVPR2 or AQP2 genes. Secondary NDI is associated with electrolyte abnormalities, obstructive uropathy, or certain medications. Management of NDI can be difficult with only symptomatic treatment available, using low-solute diet, diuretics, and prostaglandin inhibitors.

Nephrogenic Diabetes Insipidus

Body fluid homeostasis is essential for normal life. In the maintenance of water balance, the most important factor and regulated process is the excretory function of the kidneys. The kidneys are capable to compensate not only the daily fluctuations of water intake but also the consequences of fluid loss (respiration, perspiration, sweating, hemorrhage). The final volume and osmolality of the excreted urine is set in the collecting duct via hormonal regulation. The hormone of water conservation is the vasopressin (AVP), and a large volume of urine is produced and excreted in the absence of AVP secretion or if AVP is ineffective in the kidneys. The aquaporin-2 water channel (AQP2) is expressed in the principal cells, and it plays an essential role in the reabsorption of water in the collecting ducts via type 2 vasopressin receptor (V2R)-mediated mechanism. If neural or hormonal regulation fails to operate the normal function of AVP-V2R-AQP2 system, it can result in various diseases such as diabetes insipidus (DI) or nephrogenic syndrome of inappropriate diuresis (NSIAD). The DI is characterized by excessive production of hyposmotic urine ("insipidus" means tasteless) due to the inability of the kidneys to concentrate urine. In this chapter, we focus and discuss the pathophysiology of nephrogenic DI (NDI) and the potential therapeutic interventions in the light of the current experimental data.

Hereditary Nephrogenic Diabetes Insipidus: Pathophysiology and Possible Treatment. An Update

Under physiological conditions, excessive loss of water through the urine is prevented by the release of the antidiuretic hormone arginine-vasopressin (AVP) from the posterior pituitary. In the kidney, AVP elicits a number of cellular responses, which converge on increasing the osmotic reabsorption of water in the collecting duct. One of the key events triggered by the binding of AVP to its type-2 receptor (AVPR2) is the exocytosis of the water channel aquaporin 2 (AQP2) at the apical membrane the principal cells of the collecting duct. Mutations of either AVPR2 or AQP2 result in a genetic disease known as nephrogenic diabetes insipidus, which is characterized by the lack of responsiveness of the collecting duct to the antidiuretic action of AVP. The affected subject, being incapable of concentrating the urine, presents marked polyuria and compensatory polydipsia and is constantly at risk of severe dehydration. The molecular bases of the disease are fully uncovered, as well as the genetic or clinical tests for a prompt diagnosis of the disease in newborns. A real cure for nephrogenic diabetes insipidus (NDI) is still missing, and the main symptoms of the disease are handled with s continuous supply of water, a restrictive diet, and nonspecific drugs. Unfortunately, the current therapeutic options are limited and only partially beneficial. Further investigation in vitro or using the available animal models of the disease, combined with clinical trials, will eventually lead to the identification of one or more targeted strategies that will improve or replace the current conventional therapy and grant NDI patients a better quality of life. Here we provide an updated overview of the genetic defects causing NDI, the most recent strategies under investigation for rescuing the activity of mutated AVPR2 or AQP2, or for bypassing defective AVPR2 signaling and restoring AQP2 plasma membrane expression.

Genetics of Diabetes Insipidus

Diabetes insipidus is a disease characterized by polyuria and polydipsia due to inadequate release of arginine vasopressin from the posterior pituitary gland (neurohypophyseal diabetes insipidus) or due to arginine vasopressin insensitivity by the renal distal tubule, leading to a deficiency in tubular water reabsorption (nephrogenic diabetes insipidus). This article reviews the genetics of diabetes insipidus in the context of its diagnosis, clinical presentation, and therapy.

Physiology and pathophysiology of cyclooxygenase-2 and prostaglandin E2 in the kidney

The cyclooxygenase (COX) enzyme system is the major pathway catalyzing the conversion of arachidonic acid into prostaglandins (PGs). PGs are lipid mediators implicated in a variety of physiological and pathophysiological processes in the kidney, including renal hemodynamics, body water and sodium balance, and the inflammatory injury characteristic in multiple renal diseases. Since the beginning of 1990s, it has been confirmed that COX exists in 2 isoforms, referred to as COX-1 and COX-2. Even though the 2 enzymes are similar in size and structure, COX-1 and COX-2 are regulated by different systems and have different functional roles. This review summarizes the current data on renal expression of the 2 COX isoforms and highlights mainly the role of COX-2 and PGE2 in several physiological and pathophysiological processes in the kidney.

Pathophysiology, diagnosis and management of nephrogenic diabetes insipidus

Healthy kidneys maintain fluid and electrolyte homoeostasis by adjusting urine volume and composition according to physiological needs. The final urine composition is determined in the last tubular segment: the collecting duct. Water permeability in the collecting duct is regulated by arginine vasopressin (AVP). Secretion of AVP from the neurohypophysis is regulated by a complex signalling network that involves osmosensors, barosensors and volume sensors. AVP facilitates aquaporin (AQP)-mediated water reabsorption via activation of the vasopressin V2 receptor (AVPR2) in the collecting duct, thus enabling concentration of urine. In nephrogenic diabetes insipidus (NDI), inability of the kidneys to respond to AVP results in functional AQP deficiency. Consequently, affected patients have constant diuresis, resulting in large volumes of dilute urine. Primary forms of NDI result from mutations in the genes that encode the key proteins AVPR2 and AQP2, whereas secondary forms are associated with biochemical abnormalities, obstructive uropathy or the use of certain medications, particularly lithium. Treatment of the disease is informed by identification of the underlying cause. Here we review the clinical aspects and diagnosis of NDI, the various aetiologies, current treatment options and potential future developments.

X-Linked Recessive form of Nephrogenic Diabetes Insipidus in a 7-Year-Old Boy

Nephrogenic diabetes insipidus (NDI) is caused by the inability of renal collecting duct cells to respond to arginine vasopressin (AVP)/antidiuretic hormone (ADH). We present the case of a 7-year-old boy with a history of excretion of large amounts of dilute urine and polydipsia since infancy. The boy had several vomiting episodes with mild dehydration during the first 3 years of life. There was no evidence of headaches, dizziness or visual problems. He drinks between 2 and 3 L/day and has 24-hour diuresis of 2 liters, now. He has prepubertal appearance with appropriate weight [+0.85 standard deviation score (SDS)] and height (+0.15 SDS) for his age. His intelligence was also normal. The water deprivation test showed low urine osmolality after 8 hours of dehydration. After desmopressin administration, urine osmolality remained low. Serum osmolality was in the normal range for sex and age before and after desmopressin administration. This indicated a nephrogenic form of diabetes insipidus. Molecular analyses revealed a P286L [p.Pro(CCC)286Leu(CTC)] mutation in the AVPR2 gene, that was inherited from his mother. This patient is the first case with genetically confirmed X-linked inherited form of NDI in the Republic of Macedonia. Molecular analysis confirmed the clinical diagnosis and enabled genetic advice for this family.

The long-term complications of the inherited tubulopathies: an adult perspective

The inherited tubulopathies are lifelong disorders and their clinical features and complications may present quite different challenges in adulthood from those in childhood. In this review we outline the pathophysiology and documented complications (including the late and unusual) of the monogenic tubulopathies from the perspective of the adult nephrologist.

A novel therapeutic effect of statins on nephrogenic diabetes insipidus

Statins competitively inhibit hepatic 3-hydroxy-3-methylglutaryl-coenzyme A reductase, resulting in reduced plasma total and low-density lipoprotein cholesterol levels. Recently, it has been shown that statins exert additional ‘pleiotropic’ effects by increasing expression levels of the membrane water channels aquaporin 2 (AQP2). AQP2 is localized mainly in the kidney and plays a critical role in determining cellular water content. This additional effect is independent of cholesterol homoeostasis, and depends on depletion of mevalonate-derived intermediates of sterol synthetic pathways, i.e. farnesylpyrophosphate and geranylgeranylpyrophosphate. By up-regulating the expression levels of AQP2, statins increase water reabsorption by the kidney, thus opening up a new avenue in treating patients with nephrogenic diabetes insipidus (NDI), a hereditary disease that yet lacks high-powered and limited side effects therapy. Aspects related to water balance determined by AQP2 in the kidney, as well as standard and novel therapeutic strategies of NDI are discussed.

[Vasopressin V2 receptor-related pathologies: congenital nephrogenic diabetes insipidus and nephrogenic syndrome of inappropiate antidiuresis]

Congenital nephrogenic diabetes insipidus is a rare hereditary disease with mainly an X-linked inheritance (90% of the cases) but there are also autosomal recessive and dominant forms. Congenital nephrogenic diabetes insipidus is characterized by a resistance of the renal collecting duct to the action of the arginine vasopressin hormone responsible for the inability of the kidney to concentrate urine. The X-linked form is due to inactivating mutations of the vasopressin 2 receptor gene leading to a loss of function of the mutated receptors. Affected males are often symptomatic in the neonatal period with a lack of weight gain, dehydration and hypernatremia but mild phenotypes may also occur. Females carrying the mutation may be asymptomatic but, sometimes, severe polyuria is found due to the random X chromosome inactivation. The autosomal recessive and dominant forms, occurring in both genders, are linked to mutations in the aquaporin-2 gene. The treatment remains difficult, especially in infants, and is based on a low osmotic diet with increased water intake and the use of thiazides and indomethacin. The main goal is to avoid hypernatremic episodes and maintain a good hydration state. Potentially, specific treatment, in some cases of X-linked congenital nephrogenic diabetes insipidus, with pharmacological chaperones such as non-peptide vasopressin-2 receptor antagonists will be available in the future. Conversely, the nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is linked to a constitutive activation of the V(2)-receptor due to activating mutations with clinical and biological features of inappropriate antidiuresis but with low or undetectable plasma arginine vasopressin hormone levels.

High-throughput chemical screening identifies AG-490 as a stimulator of aquaporin 2 membrane expression and urine concentration

A reduction or loss of plasma membrane aquaporin 2 (AQP2) in kidney principal cells due to defective vasopressin (VP) signaling through the VP receptor causes excessive urine production, i.e., diabetes insipidus. The amount of AQP2 on the plasma membrane is regulated by a balance of exocytosis and endocytosis and is the rate limiting step for water reabsorption in the collecting duct. We describe here a systematic approach using high-throughput screening (HTS) followed by in vitro and in vivo assays to discover novel compounds that enhance vasopressin-independent AQP2 membrane expression. We performed initial chemical library screening with a high-throughput exocytosis fluorescence assay using LLC-PK1 cells expressing soluble secreted yellow fluorescent protein and AQP2. Thirty-six candidate exocytosis enhancers were identified. These compounds were then rescreened in AQP2-expressing cells to determine their ability to increase AQP2 membrane accumulation. Effective drugs were then applied to kidney slices in vitro. Three compounds, AG-490, β-lapachone, and HA14-1 increased AQP2 membrane accumulation in LLC-PK1 cells, and both AG-490 and β-lapachone were also effective in MDCK cells and principal cells in rat kidney slices. Finally, one compound, AG-490 (an EGF receptor and JAK-2 kinase inhibitor), decreased urine volume and increased urine osmolality significantly in the first 2-4 h after a single injection into VP-deficient Brattleboro rats. In conclusion, we have developed a systematic procedure for identifying new compounds that modulate AQP2 trafficking using initial HTS followed by in vitro assays in cells and kidney slices, and concluding with in vivo testing in an animal model.

Skewed X-chromosome inactivation causing diagnostic misinterpretation in congenital nephrogenic diabetes insipidus

OBJECTIVE

To establish the clinical phenotype and genetic background in a family with diabetes insipidus.

MATERIAL AND METHODS

The subjects were a sister and brother, aged 34 and 27 years, respectively, with a history of polyuria since infancy. Clinical testing confirmed a diagnosis of congenital nephrogenic diabetes insipidus (CNDI) in both. Samples of purified genomic DNA were analysed.

RESULTS

The sequence of the entire coding region of the AQP2 gene as well as the AVPR2 gene was determined. Sequence analysis revealed no variations in the AQP2 gene. A missense variation in exon 2 of the AVPR2 gene (g.685G>A), predicting a p.Asp85Asn substitution, was identified in the X-chromosome of the affected male and one allele in the sister and the asymptomatic mother. The p.Asp85Asn variation in AVPR2 is known to cause CNDI, and has previously been described as inducing a partial phenotype treatable with dDAVP. However, in this family dDAVP had no influence on urine osmolality, whereas combination therapy with indomethacin and hydrochlorothiazide increased urine osmolality to 299 mosm/l in the proband. A skewed X-inactivation pattern (93%) occurring in the normal X allele was recognized in the sister.

CONCLUSIONS

This study demonstrates the effect of skewed X-chromosome inactivation associated with X-linked CNDI. Polydipsia in early childhood could be due to X-linked CNDI despite affecting both genders. The significant heterogeneity in the clinical phenotype in CNDI carries a risk of diagnostic misinterpretation and emphasizes the need for genetic characterization. Treatment combining indomethacin and hydrochlorothiazide results in a marked response on both urine output and urine osmolality.

Novel treatment for lithium-induced nephrogenic diabetes insipidus rat model using the Sendai-virus vector carrying aquaporin 2 gene

Congenital nephrogenic diabetes insipidus (NDI) is a chronic disorder involving polyuria and polydipsia that results from unresponsiveness of the renal collecting ducts to the antidiuretic hormone vasopressin. Either of the genetic defects in vasopressin V2 receptor or the water channel aquaporin 2 (AQP2) cause the disease, which interfere the water reabsorption at the epithelium of the collecting duct. An unconscious state including a perioperative situation can be life threatening because of the difficulty to regulate their water balance. The Sendai virus (SeV) vector system deleting fusion protein (F) gene (SeV/DeltaF) is considered most suitable because of the short replication cycle and nontransmissible character. An animal model for NDI with reduced AQP2 by lithium chloride was used to develop the therapy. When the SeV/DeltaF vector carrying a human AQP2 gene (AQP2-SeV/DeltaF) was administered retrogradely via ureter to renal pelvis, AQP2 was expressed in the renal collecting duct to reduce urine output and water intake by up to 40%. In combination with the retorograde administration to pelvis, this system could be the cornerstone for the applicable therapies on not only NDI patients but also other diseases associate with the medullary collecting duct.

The management of central diabetes insipidus in infancy: desmopressin, low renal solute load formula, thiazide diuretics

Infants consume most of their calories as formula. Because of this large fluid intake, infants normally produce dilute urine, not far off from that seen in individuals with diabetes insipidus (DI). Infants with DI are therefore prone to water intoxication if fixed antidiuresis is achieved using the long-acting vasopressin analog desmopressin (DDAVP), which induces a state of high urine concentration. DI treatment approaches applied to older children and adults, who consume the their calories as solids, are difficult to apply to infants with DI. When used in infants, oral and intranasal DDAVP can be associated with wide swings in serum sodium concentration (SNA). In comparison, precisely administered subcutaneous doses of DDAVP can be successfully used in infants with DI, and appear to be superior to oral or intranasal DDAVP therapy. Alternatively, consistent eunatremia can be simply achieved in infantile DI using low renal solute load (RSL) formula and thiazide diuretics. Low RSL formula reduces obligatory urinary water losses, and thiazide diuretics concentrate the urine to levels seen in normal formula-fed infants. This report addresses treatment options of DI in infancy and the delicate management issues involved.

Lithium: a review of its metabolic adverse effects

Treatment with lithium has long been recognized to be associated with metabolic adverse effects notably hypothyroidism, hyperparathyroidism, weight gain and nephrogenic diabetes insipidus. It is important that clinicians prescribing lithium are aware of these adverse effects and have a strategy for their detection and management. We review aspects of these actions of lithium including their prevalence, risk factors, biochemical changes involved and management, and discuss some advances that have been made in their understanding in recent years.

Efficacy of COX-2 inhibitors in a case of congenital nephrogenic diabetes insipidus

A 17-month-old boy presented with failure to thrive, polyuria, and vomiting. He had been diagnosed clinically with nephrogenic diabetes insipidus and treated by amiloride and hydrochlorothiazide combination without a satisfactory outcome at another center since 1 year of age. The diagnosis was confirmed by genetic analysis (AVPR2mutation), and the treatment was modified to include rofecoxib (a selective cyclooxygenase-2 inhibitor) in addition to hydrochlorothiazide and amiloride. This combination along with a low-salt diet resulted in a dramatic decrease in urinary free-water loss, while no side effect was noted. Because of prohibition of rofecoxib, it had to be substituted first by indomethacin and then by ibuprofen. However, both drugs were ineffective in controlling water diuresis. Thus, we had to replace these drugs by celecoxib (another selective cyclooxygenase-2 inhibitor). We conclude that the combination hydrochlorothiazide/amiloride/cyclooxygenase-2 inhibitor could be successfully used to treat congenital nephrogenic diabetes insipidus.

[Congenital nephrogenic diabetes insipidus]

Nephrogenic diabetes insipidus is a rare hereditary disease, characterized by a resistance of the renal collecting duct to the action of the antidiuretic hormone, arginine vasopressin, responsible for the inability of the kidney to concentrate urine. More than 90% of the patients are males and have the X-linked recessive form of the disease usually presenting with polyuria and polydipsia in infancy. This mode of inheritance is related to mutations in the V(2) receptor gene, located in the Xq28 chromosomal region. Less than 10% of the patients have an autosomal-recessive or an autosomal-dominant mode of inheritance with clinical manifestations occurring in males and females, related to mutations in the aquaporin-2 gene, located in chromosome region 12q13. The aim of the treatment is to avoid chronic and acute dehydration episodes. It remains symptomatic, mainly based on an hypoosmotic diet and the use of hydrochlorothiazide and indomethacin. Recent findings showed that pharmacological chaperones, such as V(2) nonpeptide antagonists, are able to rescue some of the V(2) receptor mutants and could be useful tools for treatment in the future.

Altered expression of COX-1, COX-2, and mPGES in rats with nephrogenic and central diabetes insipidus

Prostaglandins have an important role in renal salt and water reabsorption. PGE2is the main kidney prostaglandin and is thought to be mainly produced in the kidney inner medulla (IM). There are indications that PGE2synthesis in nephrogenic (NDI) and central (CDI) diabetes insipidus is altered. We hypothesize that the expression of the major PGE2synthesis enzymes cyclooxygenases 1 and 2 (COX-1, COX-2) and membrane-associated PGE2synthase (mPGES) is altered in the kidneys of rats with NDI and CDI. Wistar rats treated with lithium for 4 wk were used as the NDI model. One-half of the NDI model rats were additionally dehydrated for 48 h. Brattleboro (BB) rats that lack endogenous antidiuretic hormone were used as the CDI model. Expression and localization of COX-1, COX-2, and mPGES in IM, inner stripe of outer medulla (ISOM), and cortex were determined by immunoblotting and immunohistochemistry. In lithium-induced NDI, expression of COX-1, COX-2, and mPGES was markedly decreased in IM. In ISOM and cortex, COX-1 expression was marginally reduced and mPGES expression was unaltered. COX-2 expression was undetected in ISOM and marginally increased in cortex. Consistent with this, the density of COX-2-expressing cells in macula densa was significantly increased, indicating differential regulation of COX-2 in IM and cortex. Dehydration of NDI rats resulted in a marked increase in COX-2 immunolabeling in IM interstitial cells, and there was no significant change in COX-1 and mPGES expression in any kidney zone. Treatment of DDAVP in BB rats for 6 days resulted in a markedly increased expression of COX-1, COX-2, and mPGES in IM. In the cortex, there were no changes in the expression of COX-1 and mPGES, whereas COX-2 expression was decreased. These results identify markedly reduced expression of COX-1, COX-2, and mPGES in IM in lithium-induced NDI. Furthermore, there were major changes in the expression of COX-1, COX-2, and mPGES in rats with CDI.

Risks and benefits of nonsteroidal anti-inflammatory drugs in children: a comparison with paracetamol

Nonsteroidal anti-inflammatory drugs (NSAIDs) possess antipyretic, analgesic and anti-inflammatory effects. They are frequently used in children and have numerous therapeutic indications, the most common ones being fever, postoperative pain and inflammatory disorders, such as juvenile idiopathic arthritis (JIA) and Kawasaki disease. Their major mechanism of action is through inhibition of prostaglandin biosynthesis by blockade of cyclo-oxygenase (COX). The disposition of most NSAIDs has been mainly studied in infants > or = 2 years of age. Compared with adults, the volume of distribution and clearance of NSAIDs such as diclofenac, ibuprofen (infants aged between 3 months and 2.5 years), ketorolac and nimesulide were increased in children. The elimination half-life was similar in children to that in adults. These pharmacokinetic differences might be clinically significant with the need for higher loading and/or maintenance doses in children. Ibuprofen, acetylsalicylic acid (ASA) and acetaminophen are the most frequently used agents for fever reduction in children. Over the past 20 years, because of the association between ASA use and Reye's syndrome, most of the interest has been directed toward ibuprofen and acetaminophen. In view of its comparable antipyretic efficacy, but superior tolerability profile, acetaminophen, when used appropriately with age-adapted formulations, should remain the first-line therapy in the treatment of childhood fever. At the moment, there is no scientific evidence to recommend simultaneous use of these two antipyretic drugs. Most NSAIDs provide mild to moderate analgesia, with the exception of ketorolac which has a strong analgesic activity. The analgesic efficacy of ketorolac, ketoprofen, diclofenac and ibuprofen in the treatment of postoperative pain has been mainly studied following a single dose, in children of > or = 1 year of age undergoing minor surgeries. In this setting, when used either alone or in adjunct to caudal or epidural anaesthesia, they were associated with an opioid-sparing effect and were well tolerated. With the exception of ketorolac use in children undergoing tonsillectomy, where controversy exists regarding the risk of postoperative haemorrhage, NSAIDs have not been associated with an increased risk of perioperative bleeding. NSAIDs are the first-line therapy in JIA. They appear to be equally effective and tolerated, with the exception of ASA which is associated with more adverse effects. ASA has been used for many years in the treatment of Kawasaki disease and is part of the standard modality of treatment in combination with intravenous gammaglobulins. More recently, lung inflammation associated with cystic fibrosis (CF) has become a new target for NSAIDs. Despite promising preliminary results with ibuprofen, numerous questions need to be answered before this new strategy becomes part of the conventional treatment of patients with CF. In summary, NSAIDs are effective in reducing fever, alleviating pain and reducing inflammation in children, with a good tolerance profile. Pharmacokinetic studies are needed to characterise the disposition of NSAIDs in very young infants in order to use them rationally. To date, no studies have been published on the disposition, tolerability and efficacy of specific COX-2 inhibitors in children. Further clinical experience with these agents in adults is warranted before undergoing trials with specific COX-2 inhibitors in children.

Treatment of nephrogenic diabetes insipidus with hydrochlorothiazide and amiloride

Nephrogenic diabetes insipidus (NDI) is characterised by the inability of the kidney to concentrate urine in response to arginine vasopressin. The consequences are severe polyuria and polydipsia, often associated with hypertonic dehydration. Intracerebral calcification, seizures, psychosomatic retardation, hydronephrosis, and hydroureters are its sequelae. In this study, four children with NDI were treated with 3 mg/kg/day hydrochlorothiazide and 0.3 mg/kg/day amiloride orally three times a day for up to five years. While undergoing treatment, none of the patients had signs of dehydration or electrolyte imbalance, all showed normal body growth, and there was no evidence of cerebral calcification or seizures. All but one had normal psychomotor development and normal sonography of the urinary tract. However, normal fluid balance was not attainable (fluid intake, 3.8-7.7 l/m2/day; urine output, 2.2-7.4 l/m2/day). The treatment was well tolerated and no side effects could be detected. Prolonged treatment with hydrochlorothiazide/amiloride appears to be more effective and better tolerated than just hydrochlorothiazide. Its efficacy appears to be similar to that of hydrochlorothiazide/indomethacin but without their severe side effects.

Amelioration of polyuria in nephrogenic diabetes insipidus due to aquaporin-2 deficiency

OBJECTIVE

We have recently reported a large cluster of patients with nephrogenic diabetes insipidus (NDI) due to an autosomal recessive aquaporin-2 (AQP-2) early-stop codon. This paper describes the clinical manifestations and evaluation of therapeutic approaches to this new entity.

PATIENTS AND DESIGN

Nine patients with an AQP-2 mutation were studied. Urine osmolality was measured in five patients before and at 3 x 30 min intervals after desmopressin given in increasing doses of 5-100 micrograms. Urinary prostaglandins PGE2 and 6-keto PGF1 alpha, were extracted from 24-h urine samples and estimated by radioimmunoassays. Eight NDI patients were given a combination of a low-sodium diet and hydrochlorothiazide. Four to 11 weeks later, ibuprofen was added, and the patients were retested within the following 4-9 weeks.

RESULTS

Urine osmolality remained unchanged after supra-pharmacological doses of desmopressin, at 60-70 mOsm/kg. Urinary PGE2 in control subjects was 0.74 +/- 0.1 microgram/g creatinine (mean +/- SD) compared to 5.0 +/- 2.6 micrograms/g creatinine in AQP-2 deficient patients (P < 0.05). Urinary 6-keto PGF1 alpha, was 0.20 +/- 0.03 microgram/g creatinine in controls and 0.75 +/- 0.31 microgram/g creatinine in AQP-2 deficiency (P < 0.05). Urinary volumes decreased by a mean 31% on a low-salt diet and hydrochlorothiazide, and by a mean of 38% on the combination therapy. Plasma osmolality decreased by a mean 15 mOsm/kg on the low-salt diet and hydrochlorothiazide, and by 22 mOsm/kg on the combination therapy. Urinary osmolality increased from a mean 80 mOsm/kg to 96 mOsm/kg on the low-salt diet and hydrochlorothiazide, and to 146 mOsm/kg on the combination therapy.

CONCLUSION

AQP-2 deficiency in these patients with an early-stop codon is associated with complete unresponsiveness of the collecting duct to vasopressin, implying an indispensable role for AQP-2 in vasopressin antidiuresis. Urinary PGE2 and 6-keto PGF1 alpha are elevated, the former being extremely high, apparently due to the extreme vasopressin unresponsiveness. Combination therapy with a combination of a low-salt diet, thiazide and non-steroidal anti-inflammatory drug is partially effective.

Emergency treatment of lithium-induced diabetes insipidus with nonsteroidal anti-inflammatory drugs

Thiazides and amiloride are the most often suggested treatment for nephrogenic diabetic insipidus. We found this ineffectual in a patient with acute problems and reviewed the literature to see if there were other more efficient approaches. A 47-year-old woman on lithium had polyuria. When inadvertently fasted for 48 h she became confused, had a seizure, and her sodium was 170 mmol/L. Urinary output was 24 L/day. Large volumes of intravenous fluids were given but sodium remained > 170 mmol/L. Treatment with DDAVP, thiazides, and amiloride did not decrease urinary output. Indomethacin 150 mg was started and urine volume immediately fell to one-half. However, because of persistent high urine output the patient was then fluid depleted, with further reduction to normal in urine volume, and Na decreased to 140 mmol/L. Creatinine rose from 135 mumol/L to 173 mumol/L, but decreased to 152 mumol/L when indomethacin was decreased to 75 mg q.d.; urinary output remained stable around 2 L/day. The literature described 22 patients with nephrogenic diabetes insipidus (16 congenital, 6 lithium) treated with nonsteroidal anti-inflammatory drugs. Urine flow was reduced to 1/3, within hours. Rarely, mild renal failure ensued, improving in all but one case when nonsteroidal anti-inflammatory drugs were reduced. Indomethacin (and controlled volume reduction if continued high urine output), while observing renal function, appears the emergency treatment of choice for serious complications of nephrogenic diabetes insipidus.

Pressor effect of ethanol in the isolated perfused human placental lobule

Pharmacologically relevant concentrations of ethanol (0.01-0.3 g/%) were perfused via the fetal circulation in isolated human placental lobules. This resulted in a dose-related rise in fetal arterial pressure, which at 0.3 g/% ethanol, was 10.1 +/- 1.1 mmHg above the pre-drug baseline. The pressor responses to ethanol were (i) rapid in onset, reaching a stable plateau within 5-10 min following administration, (ii) readily reversible by perfusion with drug-free media, (iii) non-tachyphylactic and (iv) largely inhibited by the cyclo-oxygenase inhibitor, inhibitor, indomethacin (5 microM). This pressor action of ethanol in the fetal circulation may contribute to the pathogenesis of the fetal alcohol syndrome as well as represent an underlying mechanism of ethanol-induced hypertension.

X-linked nephrogenic diabetes insipidus mutations in North America and the Hopewell hypothesis

In X-linked nephrogenic diabetes insipidus (NDI) the urine of male patients is not concentrated after the administration of the antidiuretic hormone arginine-vasopressin. This disease is due to mutations in the V2 receptor gene that maps to chromosome region Xq28. In 1969, Bode and Crawford suggested that most NDI patients in North America shared common ancestors of Ulster Scot immigrants who arrived in Halifax in 1761 on the ship Hopewell. A link between this family and a large Utah kindred was also suggested. DNA was obtained from 17 affected male patients from the "Hopewell" kindred and from four additional families from Nova Scotia and New Brunswick who shared the same Xq28 NDI haplotype. The Utah kindred and two families (Q2, Q3) from Quebec were also studied. The "Hopewell" mutation, W71X, is a single base substitution (G-->A) that changes codon 71 from TGG (tryptophan) to TGA (stop). The W71X mutation was found in affected members of the Hopewell and of the four satellite families. The W71X mutation is the cause of X-linked NDI for the largest number of related male patients living in North America. Other families (Utah, Q2 and Q3) that are historically and ethnically unrelated bear other mutations in the V2 receptor gene.

Nephrogenic diabetes insipidus: clinical symptoms, pathogenesis, genetics and treatment

This review summarizes various aspects of the inherited kidney disorder nephrogenic diabetes insipidus (NDI). The clinical manifestations of the disease are presented. The important role of the genetic localization of the NDI gene to the X-chromosome long arm, in region Xq28, for carrier detection and early (prenatal) diagnosis of the disorder is emphasized. Following an overview of the cellular physiology involved in the antidiuretic action of vasopressin, possible mechanisms in the pathogenesis of NDI are discussed. We hypothesize that NDI is most probably due to the absence or abnormality of the renal V2 receptor. This assumption is strengthened by recent findings in receptor studies, which indicate a general V2 receptor defect in NDI, and in experiments with somatic cell hybrid cell lines, which are consistent with a co-localization of the genes for NDI and for the V2 receptor in the Xq28 region. Finally, the efficacy of the combination amiloride-hydrochlorothiazide, compared with the indomethacin-hydrochlorothiazide regimen, in the treatment of NDI is presented and the advantages of the former combination are discussed.

Congenital nephrogenic diabetes insipidus-vasopressin and prostaglandins in response to treatment with hydrochlorothiazide and indomethacin

In four boys with congenital nephrogenic diabetes insipidus, plasma arginine-vasopressin (AVP) and urinary excretion of prostaglandins were studied in response to treatment with hydrochlorothiazide and indomethacin. An abnormal relationship between AVP and urine osmolality was demonstrated in all patients. In the first patient, treatment with indomethacin (3 mg/kg per day) resulted in a drop of the insulin and paraminohippurate clearances. In the other three patients urinary excretion of PGE2 was raised, and fell during treatment with hydrochlorothiazide (2 mg/kg per day) and indomethacin (2 mg/kg per day). Urine flow, free water clearance and osmolar clearance decreased during treatment. A combination of both drugs is more effective than hydrochlorothiazide alone and the effect appears to be additive.