Acetazolamide Attenuates Lithium-Induced Nephrogenic Diabetes Insipidus

Congenital nephrogenic diabetes insipidus treated with acetazolamide

Congenital nephrogenic diabetes insipidus (CNDI) is a rare disorder. The condition is characterised by an inability of distal nephron segments to respond to normal or raised concentrations of serum antidiuretic hormone. In this report, we describe the case of a 13-year-old male known with CNDI who experienced a pedestrian vehicle accident leading to coma following a head injury. Intra-operatively, severe hypernatraemia and polyuria were observed. Following an inadequate response to conventional therapy, acetazolamide was prescribed resulting in an immediate response to therapy. To the best of our knowledge, acetazolamide has not been previously documented as a therapeutic option for CNDI. Additional research is necessary before considering the recommendation of acetazolamide for cases of NDI that do not respond adequately to conventional treatments.

The study of intercalated cells using ex vivo techniques: primary cell culture, cell lines, kidney slices, and organoids

This review summarizes methods to study kidney intercalated cell (IC) function ex vivo. While important for acid-base homeostasis, IC dysfunction is often not recognized clinically until it becomes severe. The advantage of using ex vivo techniques is that they allow for the differential evaluation of IC function in controlled environments. Although in vitro kidney tubular perfusion is a classical ex vivo technique to study IC, here we concentrate on primary cell cultures, immortalized cell lines, and ex vivo kidney slices. Ex vivo techniques are useful in evaluating IC signaling pathways that allow rapid responses to extracellular changes in pH, CO2, and bicarbonate (HCO3-). However, these methods for IC work can also be challenging, as cell lines that recapitulate IC do not proliferate easily in culture. Moreover, a "pure" IC population in culture does not necessarily replicate its collecting duct (CD) environment, where ICs are surrounded by the more abundant principal cells (PCs). It is reassuring that many findings obtained in ex vivo IC systems signaling have been largely confirmed in vivo. Some of these newly identified signaling pathways reveal that ICs are important for regulating NaCl reabsorption, thus suggesting new frontiers to target antihypertensive treatments. Moreover, recent single-cell characterization studies of kidney epithelial cells revealed a dual developmental origin of IC, as well as the presence of novel CD cell types with certain IC characteristics. These exciting findings present new opportunities for the study of IC ex vivo and will likely rediscover the importance of available tools in this field.NEW & NOTEWORTHY The study of kidney intercalated cells has been limited by current cell culture and kidney tissue isolation techniques. This review is to be used as a reference to select ex vivo techniques to study intercalated cells. We focused on the use of cell lines and kidney slices as potential useful models to study membrane transport proteins. We also review how novel collecting duct organoids may help better elucidate the role of these intriguing cells.

Thiazides Attenuate Insulin Secretion Through Inhibition of Mitochondrial Carbonic Anhydrase 5b in β -Islet Cells in Mice

SIGNIFICANCE STATEMENT

Thiazide diuretics (thiazides) are among the most widely prescribed drugs worldwide, but their use is associated with glucose intolerance and new-onset diabetes mellitus. The molecular mechanisms remain elusive. Our study reveals that thiazides attenuate insulin secretion through inhibition of the mitochondrial carbonic anhydrase isoform 5b (CA5b) in pancreatic β cells. We furthermore discovered that pancreatic β cells express only one functional carbonic anhydrase isoform, CA5b, which is critical in replenishing oxaloacetate in the mitochondrial tricarboxylic acid (TCA) cycle (anaplerosis). These findings explain the mechanism for thiazide-induced glucose intolerance and reveal a fundamental role of CA5b in TCA cycle anaplerosis and insulin secretion in β cells.

BACKGROUND

Thiazide diuretics are associated with glucose intolerance and new-onset diabetes mellitus. Previous studies demonstrated that thiazides attenuate insulin secretion, but the molecular mechanisms remain elusive. We hypothesized that thiazides attenuate insulin secretion via one of the known molecular thiazide targets in β cells.

METHODS

We performed static insulin secretion experiments with islets of wild-type, Sodium/chloride co-transporter (NCC) (SLC12A3), and sodium-driven chloride/bicarbonate exchanger (NDCBE) (SLC4A8) knock-out (KO) mice and with murine Min6 cells with individual knockdown of carbonic anhydrase (CA) isoforms to identify the molecular target of thiazides in β cells. CA isoform 5b (CA5b) KO mice were then used to assess the role of the putative thiazide target CA5b in β -cell function and in mediating thiazide sensitivity in vitro and in vivo .

RESULTS

Thiazides inhibited glucose- and sulfonylurea-stimulated insulin secretion in islets and Min6 cells at pharmacologically relevant concentrations. Inhibition of insulin secretion by thiazides was CO 2 /HCO 3- -dependent, not additive to unselective CA inhibition with acetazolamide, and independent of extracellular potassium. By contrast, insulin secretion was unaltered in islets of mice lacking the known molecular thiazide targets NCC or NDCBE. CA expression profiling with subsequent knockdown of individual CA isoforms suggested mitochondrial CA5b as a molecular target. In support of these findings, thiazides significantly attenuated Krebs cycle anaplerosis through reduction of mitochondrial oxaloacetate synthesis. CA5b KO mice were resistant to thiazide-induced glucose intolerance, and thiazides did not alter insulin secretion in CA5b KO islets.

CONCLUSIONS

Thiazides attenuate insulin secretion via inhibition of the mitochondrial CA5b isoform in β cells of mice.

Acetazolamide for Bipolar Disorders: A Scoping Review

Acetazolamide, a carbonic anhydrase inhibitor, is used to treat a variety of ailments. It has been highlighted for its potential to benefit people with bipolar disorders, for whom there are clear current unmet treatment needs. This scoping review sought to synthesise all available evidence related to the potential effects of acetazolamide on symptoms related to bipolar disorder, acceptability and tolerability, and intervention characteristics (e.g., dose and duration). Following publication of the review protocol, the Pubmed, Embase, and PsycInfo databases were searched (all dated to 31 August 2022). A systematic approach was undertaken to identify eligible articles and extract relevant data from these. Five studies were included, assessing a total of 50 patients treated with acetazolamide. Most patients were from two open-label trials, while the others were case reports. Approximately one third of patients were experiencing psychosis or mania before treatment initiation, and one third had refractory depression. Forty-four percent of patients were estimated to achieve a response (not seemingly affected by the baseline episode type, acetazolamide dose, or duration), while a further 22% appeared to experience minimal benefits from the intervention. Acetazolamide was generally reported to be tolerated well and acceptable for up to 2 years, although reporting for acceptability and tolerability was suboptimal. The reviewed evidence is extremely limited in size and methodology (e.g., no randomised studies, blinding, or standardised outcome assessment). We posit that the current findings are sufficiently encouraging to recommend substantive clinical trials, but we emphasise that at present, the evidence is exceedingly preliminary, and there remains evident uncertainty as to whether acetazolamide could be a viable treatment for bipolar disorders.

Inhibition of the glycogen synthase kinase 3β-hypoxia-inducible factor 1α pathway alleviates NLRP3-mediated pyroptosis induced by high glucose in renal tubular epithelial cells

NEW FINDINGS

What is the central question of this study? Activation of the glycogen synthase kinase 3 β (GSK-3β)-hypoxia-inducible factor 1 α (HIF-1α) pathway results in stimulation of pyroptosis under high glucose, and exerts actions in a number renal diseases: does this pathway have a role in renal tubular epithelial cells? What is the main finding and its importance? Down-regulation of GSK-3β can inhibit pyroptosis of renal tubular epithelial cells induced by high glucose and this may be related to down-regulation of HIF-1α. This role of the GSK-3β-HIF-1α pathway has not previously been reported and identifies a potential new therapeutic target in diabetic nephropathy.

ABSTRACT

Diabetic nephropathy (DN) is not only one of the main complications of diabetes, but also has a high incidence rate and a high mortality rate. Glycogen synthase kinase 3 β (GSK-3β) and hypoxia-inducible factor 1 α (HIF-1α) have been demonstrated to influence DN by regulating pyroptosis. This study aimed to investigate the effect of the GSK-3β-HIF-1α pathway on pyroptosis of high-glucose (HG)-induced renal tubular cells. Mouse renal proximal tubular epithelial cells (TKPT cells) were induced by HG to simulate DN cell and we transfected TKPT cells with GSK-3β knockdown lentivirus. Western blot analysis confirmed the transfection effects and detected the expression of GSK-3β, HIF-1α, Nod-like receptor protein 3 (NLRP3), cleaved-caspase-1, pro-caspase-1, gasdermin D (GSDMD) and GSDMD-N. The expression of GSDMD-N and HIF-1α were also verified by immunofluorescence. The levels of interleukin (IL)-1β and IL-18 were measured by enzyme linked immunosorbent assay. Flow cytometric analysis determined the apoptosis rate. Results showed that HIF-1α expression was increased in HG-induced TKPT cells, and GSK-3β knockdown could decrease the levels of NLRP3, cleaved-caspase-1, GSDMD-N and HIF-1α, verified by immunofluorescence. Moreover, GSK-3β knockdown suppressed the expression of IL-1β and IL-18, and reduced the apoptosis rate. Lithium chloride (LiCl) interference could cause the same changes as GSK-3β knockdown for HG-induced TKPT cells, and dimethyloxallyl glycine could reverse the effect of GSK-3β-knockdown interference. Our studies definitively demonstrate that the GSK-3β-HIF-1α signalling pathway mediates HG-stimulated pyroptosis in renal tubular epithelial cells and that down-regulation of GSK-3β inhibited HG-induced pyroptosis by inhibiting the expression of HIF-1α. These findings suggest a new potential target for the treatment of DN.

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.

Folic acid-induced animal model of kidney disease

The kidneys are a vital organ that is vulnerable to both acute kidney injury (AKI) and chronic kidney disease (CKD) which can be caused by numerous risk factors such as ischemia, sepsis, drug toxicity and drug overdose, exposure to heavy metals, and diabetes. In spite of the advances in our understanding of the pathogenesis of AKI and CKD as well AKI transition to CKD, there is still no available therapeutics that can be used to combat kidney disease effectively, highlighting an urgent need to further study the pathological mechanisms underlying AKI, CKD, and AKI progression to CKD. In this regard, animal models of kidney disease are indispensable. This article reviews a widely used animal model of kidney disease, which is induced by folic acid (FA). While a low dose of FA is nutritionally beneficial, a high dose of FA is very toxic to the kidneys. Following a brief description of the procedure for disease induction by FA, major mechanisms of FA-induced kidney injury are then reviewed, including oxidative stress, mitochondrial abnormalities such as impaired bioenergetics and mitophagy, ferroptosis, pyroptosis, and increased expression of fibroblast growth factor 23 (FGF23). Finally, application of this FA-induced kidney disease model as a platform for testing the efficacy of a variety of therapeutic approaches is also discussed. Given that this animal model is simple to create and is reproducible, it should remain useful for both studying the pathological mechanisms of kidney disease and identifying therapeutic targets to fight kidney disease.

An AMPK activator as a therapeutic option for congenital nephrogenic diabetes insipidus

Nephrogenic diabetes insipidus (NDI) patients produce large amounts of dilute urine. NDI can be congenital, resulting from mutations in the type-2 vasopressin receptor (V2R), or acquired, resulting from medications such as lithium. There are no effective treatment options for NDI. Activation of PKA is disrupted in both congenital and acquired NDI, resulting in decreased aquaporin-2 phosphorylation and water reabsorption. We show that adenosine monophosphate–activated protein kinase (AMPK) also phosphorylates aquaporin-2. We identified an activator of AMPK, NDI-5033, and we tested its ability to increase urine concentration in animal models of NDI. NDI-5033 increased AMPK phosphorylation by 2.5-fold, confirming activation. It increased urine osmolality in tolvaptan-treated NDI rats by 30%–50% and in V2R-KO mice by 50%. Metformin, another AMPK activator, can cause hypoglycemia, which makes it a risky option for treating NDI patients, especially children. Rats with NDI receiving NDI-5033 showed no hypoglycemia in a calorie-restricted, exercise protocol. Congenital NDI therapy needs to be effective long-term. We administered NDI-5033 for 3 weeks and saw no reduction in efficacy. We conclude that NDI-5033 can improve urine concentration in animals with NDI and holds promise as a potential therapy for patients with congenital NDI due to V2R mutations.

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.

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 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.

Potent Inhibition of Biphasic Tubular Reabsorption of Lithium by Acetazolamide and Foscarnet in Rats

Lithium is mainly excreted into urine, and a large fraction of lithium filtered through glomeruli is reabsorbed in the proximal tubule. However, the mechanisms responsible for lithium reabsorption remain unclear. We previously reported that the reabsorption of lithium was biphasic in rats, and that foscarnet inhibited lithium reabsorption with a high affinity type. We herein evaluated the effects of acetazolamide and foscarnet on the renal excretion of lithium in rats treated with lithium chloride at 2 doses. In rats intravenously injected with a bolus of 25 mg/kg lithium chloride, acetazolamide facilitated the urinary excretion of lithium, and increased the fractional excretion of lithium from 0.446 to 0.953, near the theoretically maximum value. At a dose of 2.5 mg/kg lithium chloride, the fractional excretion of lithium was 0.241 in control rats, 0.420 in rats administered acetazolamide, and 0.976 in rats administered acetazolamide and foscarnet. These results showed the potent inhibition of lithium reabsorption by acetazolamide and foscarnet in rats. And, it was exhibited that the effects of acetazolamide on lithium reabsorption differed with the dosages of lithium administered.

Systematic review and practical guideline for the prevention and management of the renal side effects of lithium therapy

Lithium is the first line therapy of bipolar mood disorder. Lithium-induced nephrogenic diabetes insipidus (Li-NDI) and lithium nephropathy (Li-NP, i.e., renal insufficiency) are prevalent side effects of lithium therapy, with significant morbidity. The objective of this systematic review is to provide an overview of preventive and management strategies for Li-NDI and Li-NP. For this, the PRISMA guideline for systematic reviews was used. Papers on the prevention and/or treatment of Li-NDI or Li-NP, and (influenceable) risk factors for development of Li-NDI or Li-NP were included. We found that the amount of evidence on prevention and treatment of Li-NDI and Li-NP is scarce. To prevent Li-NDI and Li-NP we advise to use a once-daily dosing schedule, target the lowest serum lithium level that is effective and prevent lithium intoxication. We emphasize the importance of monitoring for Li-NDI and Li-NP, as early diagnosis and treatment can prevent further progression and permanent damage. Collaboration between psychiatrist, nephrologist and patients themselves is essential. In patients with Li-NDI and/or Li-NP cessation of lithium therapy and/or switch to another mood stabilizer should be considered. In patients with Li-NDI, off label therapy with amiloride can be useful.

meta-Substituted benzenesulfonamide: a potent scaffold for the development of metallo-β-lactamase ImiS inhibitors

Metallo-β-lactamase (MβL) ImiS contributes to the emergence of carbapenem resistance. A potent scaffold, meta-substituted benzenesulfonamide, was constructed and assayed against MβLs. The twenty-one obtained molecules specifically inhibited ImiS (IC50 = 0.11-9.3 μM); 2g was found to be the best inhibitor (IC50 = 0.11 μM), and 1g and 2g exhibited partially mixed inhibition with K i of 8.0 and 0.55 μM. The analysis of the structure-activity relationship revealed that the meta-substitutes improved the inhibitory activity of the inhibitors. Isothermal titration calorimetry (ITC) assays showed that 2g reversibly inhibited ImiS. The benzenesulfonamides exhibited synergistic antibacterial effects against E. coli BL21 (DE3) cells with ImiS, resulting in a 2-4-fold reduction in the MIC of imipenem and meropenem. Also, mouse experiments showed that 2g had synergistic efficacy with meropenem and significantly reduced the bacterial load in the spleen and liver after a single intraperitoneal dose. Tracing the ImiS in living E. coli cells by RS at a super-resolution level (3D-SIM) showed that the target was initially associated on the surface of the cells, then there was a high density of uniform localization distributed in the cytosol of cells, and it finally accumulated in the formation of inclusion bodies at the cell poles. Docking studies suggested that the sulfonamide group acted as a zinc-binding group to coordinate with Zn(ii) and the residual amino acid within the CphA active center, tightly anchoring the inhibitor at the active site. This study provides a highly promising scaffold for the development of inhibitors of ImiS, even the B2 subclasses of MβLs.

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 Acer2 as a First Susceptibility Gene for Lithium-Induced Nephrogenic Diabetes Insipidus in Mice

BACKGROUND

Lithium, mainstay treatment for bipolar disorder, causes nephrogenic diabetes insipidus and hypercalcemia in about 20% and 10% of patients, respectively, and may lead to acidosis. These adverse effects develop in only a subset of patients treated with lithium, suggesting genetic factors play a role.

METHODS

To identify susceptibility genes for lithium-induced adverse effects, we performed a genome-wide association study in mice, which develop such effects faster than humans. On day 8 and 10 after assigning female mice from 29 different inbred strains to normal chow or lithium diet (40 mmol/kg), we housed the animals for 48 hours in metabolic cages for urine collection. We also collected blood samples.

RESULTS

In 17 strains, lithium treatment significantly elevated urine production, whereas the other 12 strains were not affected. Increased urine production strongly correlated with lower urine osmolality and elevated water intake. Lithium caused acidosis only in one mouse strain, whereas hypercalcemia was found in four strains. Lithium effects on blood pH or ionized calcium did not correlate with effects on urine production. Using genome-wide association analyses, we identified eight gene-containing loci, including a locus containing Acer2, which encodes a ceramidase and is specifically expressed in the collecting duct. Knockout of Acer2 led to increased susceptibility for lithium-induced diabetes insipidus development.

CONCLUSIONS

We demonstrate that genome-wide association studies in mice can be used successfully to identify susceptibility genes for development of lithium-induced adverse effects. We identified Acer2 as a first susceptibility gene for lithium-induced diabetes insipidus in mice.

Diabetes insipidus

Diabetes insipidus (DI) is a disorder characterized by excretion of large amounts of hypotonic urine. Central DI results from a deficiency of the hormone arginine vasopressin (AVP) in the pituitary gland or the hypothalamus, whereas nephrogenic DI results from resistance to AVP in the kidneys. Central and nephrogenic DI are usually acquired, but genetic causes must be evaluated, especially if symptoms occur in early childhood. Central or nephrogenic DI must be differentiated from primary polydipsia, which involves excessive intake of large amounts of water despite normal AVP secretion and action. Primary polydipsia is most common in psychiatric patients and health enthusiasts but the polydipsia in a small subgroup of patients seems to be due to an abnormally low thirst threshold, a condition termed dipsogenic DI. Distinguishing between the different types of DI can be challenging and is done either by a water deprivation test or by hypertonic saline stimulation together with copeptin (or AVP) measurement. Furthermore, a detailed medical history, physical examination and imaging studies are needed to ensure an accurate DI diagnosis. Treatment of DI or primary polydipsia depends on the underlying aetiology and differs in central DI, nephrogenic DI and primary polydipsia.

[Chronic metabolic and renal disorders related to lithium salts treatment]

Lithium salts are the main treatment of bipolar disorder, which is characterized by potentially life-threatening maniac and/or depressive episodes. They have proven efficient in the prevention and treatment of acute episodes as well as in the prevention of suicidal risk. However, this efficacy is counterbalanced by a narrow therapeutic range that can lead to potentially harmful overdose, and by adverse long-term events. Nevertheless, they remain first-line treatment, notwithstanding therapeutic alternatives. In this review, we will describe toxic effects of long-term treatment at therapeutic levels of lithium salts. Regarding renal effects, early-impaired urine concentrating ability might lead to polyuria and polydipsia, and even to hypernatremia if free access to water is compromised. Long-term lithium treatment might also lead to chronic kidney disease, characterized by tubulo-interstitial multicystic nephropathy. End-stage renal disease requiring renal replacement therapy is a rare complication. Major extra-renal toxic effects are hypercalcemia and hypothyroidism. Treatment cessation due to these adverse events should be a multidisciplinary and case-by-case decision based on the benefit/risk ratio. Since these toxic effects are mild and display slow progression, treatment cessation is uncommon. However, regular medical and biological check-up is needed in order to prevent these disorders, and patients might be referred to nephrologists and/or endocrinologists once the disorders are established.

Effect of Dapagliflozin Treatment on the Expression of Renal Sodium Transporters/Channels on High-Fat Diet Diabetic Mice

BACKGROUND

Inhibition of the Na+/glucose co-transporter 2 is a new therapeutic strategy for diabetes. It is unclear how proximal loss of Na+ (and glucose) affects the subsequent Na+ transporters in the proximal tubule (PT), thick ascending limb of loop of Henle (TAL), distal convoluted tubule (DCT) and collecting duct (CD).

METHODS

Mice on a high fat diet were administered 3 doses streptozotocin 6 days prior to oral dapagliflozin administration or vehicle for 18 days. A control group of lean mice were also included. Body weight and glucose were recorded at regular intervals during treatment. Renal Na+ transporters expression in nephron segments were analyzed by RT-qPCR and Western blot.

RESULTS

Dapagliflozin treatment resulted in a significant reduction in body weight and blood glucose compared to vehicle-treated controls. mRNA results showed that Na+-hydrogen antiporter 3 (NHE3), Na+/phosphate cotransporter (NaPi-2a) and epithelial Na+ channel expression was increased, Ncx1, ENaCβ and ENaCγ expression declined (p all < 0.05), respectively, in dapagliflozin-treated mice when compared with saline vehicle mice. Na-K-2Cl cotransporters and Na-Cl cotransporter mRNA expression was not affected by dapagliflozin treatment. Na+/K+-ATPase (Atp1b1) expression was also increased significantly by dapagliflozin treatment, but it did not affect Atp1a1 and glucose transporter 2 expression. Western blot analysis showed that NaPi-2a, NHE3 and ATP1b1 expression was upregulated in dapagliflozin-treated diabetic mice when compared with saline vehicle mice (p < 0.05).

CONCLUSION

Our findings suggest that dapagliflozin treatment augments compensatory changes in the renal PT in diabetic mice.

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.

Chronic lithium treatment induces novel patterns of pendrin localization and expression

Prolonged lithium treatment is associated with various renal side effects and is known to induce inner medullary collecting duct (IMCD) remodeling. In animals treated with lithium, the fraction of intercalated cells (ICs), which are responsible for acid-base homeostasis, increases compared with renal principal cells (PCs). To investigate the intricacies of lithium-induced IMCD remodeling, male Sprague-Dawley rats were fed a lithium-enriched diet for 0,1, 2, 3, 6, 9, or 12 wk. Urine osmolality was decreased at 1 wk, and from 2 to 12 wk, animals were severely polyuric. After 6 wk of lithium treatment, approximately one-quarter of the cells in the initial IMCD expressed vacuolar H+-ATPase, an IC marker. These cells were localized in portions of the inner medulla, where ICs are not normally found. Pendrin, a Cl-/[Formula: see text] exchanger, is normally expressed only in two IC subtypes found in the convoluted tubule, the cortical collecting duct, and the connecting tubule. At 6 wk of lithium treatment, we observed various patterns of pendrin localization and expression in the rat IMCD, including a novel phenotype wherein pendrin was coexpressed with aquaporin-4. These observations collectively suggest that renal IMCD cell plasticity may play an important role in lithium-induced IMCD remodeling.

[Lithium chloride arrests HK-2 cell cycle in G2 phase through AKT/GSK-3β signal pathway]

OBJECTIVE

To investigate the effect of lithium chloride (LiCl) on cell cycle of HK-2 cells and explore the possible pathways involved.

METHODS

HK-2 cells were treated with LiCl at different concentrations (5, 12.5, 20, and 25 mmol/L) for 12, 24, 48, or 72 h, and the changes in cell cycle and viability were detected using flow cytometry and CCK-8 assay, respectively. Western blotting was used to analyze the changes in the expressions of cyclin B1 and CDK1 (the two G2 phase-related proteins) and those of AKT/GSK-3β signaling pathway-related proteins in the treated cells.

RESULTS

LiCl treatment time- and concentration-dependently increased HK-2 cell percentage in G2 phase and decreased the cell vitality. The expressions of cyclin B1, CDK1, p-GSK-3β, and β-catenin increased and the expression of p-AKT decreased significantly in the cells as LiCl treatment time and concentration increased.

CONCLUSION

LiCl may cause HK-2 cell cycle arrest in G2 phase through activation of the AKT/GSK-3β signaling pathway.

[Lithium chloride arrests HK-2 cell cycle in G2 phase through AKT/GSK-3β signal pathway]

OBJECTIVE

To investigate the effect of lithium chloride (LiCl) on cell cycle of HK-2 cells and explore the possible pathways involved.

METHODS

HK-2 cells were treated with LiCl at different concentrations (5, 12.5, 20, and 25 mmol/L) for 12, 24, 48, or 72 h, and the changes in cell cycle and viability were detected using flow cytometry and CCK-8 assay, respectively. Western blotting was used to analyze the changes in the expressions of cyclin B1 and CDK1 (the two G2 phase-related proteins) and those of AKT/GSK-3β signaling pathway-related proteins in the treated cells.

RESULTS

LiCl treatment time- and concentration-dependently increased HK-2 cell percentage in G2 phase and decreased the cell vitality. The expressions of cyclin B1, CDK1, p-GSK-3β, and β-catenin increased and the expression of p-AKT decreased significantly in the cells as LiCl treatment time and concentration increased.

CONCLUSION

LiCl may cause HK-2 cell cycle arrest in G2 phase through activation of the AKT/GSK-3β signaling pathway.

The New News about Lithium: An Underutilized Treatment in the United States

Lithium use for the treatment of mood disorders remains quite low, particularly in the United States compared with some European countries. Mogens Schou pioneered the study of lithium for prophylaxis of the recurrent mood disorder and encouraged its greater use. In an effort to further address the appropriate role of this drug, the multiple assets of lithium beyond its well-known antimanic effect are reviewed, and a brief summary of its side effects is outlined. It appears that lithium has positive effects in depression and suicide prevention, cognition, and reducing the incidence of dementia. It increases the length of telomeres and has positive effects in prevention of some medical illnesses. Lithium side-effect burden, especially its association with end-stage renal disease, may be less than many have surmised. New data indicate the importance of long-term prophylaxis after a first manic episode to lessen episode recurrence, allow cognition to recover to normal, and prevent various aspects of illness progression. After a first manic episode, 1 year of randomized treatment with lithium was superior to that of quetiapine, suggesting the importance of having lithium in the treatment regimen. Given the highly recurrent and progressive course of bipolar disorder sometimes even in the face of conventional treatment, the role and enhanced use of lithium deserves reconsideration.

Use of acetazolamide in lithium-induced nephrogenic diabetes insipidus: a case report

Lithium-induced nephrogenic diabetes insipidus (Li-NDI) is a rare and difficult-to-treat condition. A study in mice and two recent papers describe the use of acetazolamide in Li-NDI in 7 patients (a case report and a 6 patient series). We describe the case of a 63-year-old woman with bipolar disorder treated with lithium and no previous history of diabetes insipidus. She was hospitalized due to a bowel obstruction and developed severe dehydration after surgery when she was water deprived. After desmopressin administration and unsuccessful thiazide and amiloride treatment, acetazolamide was administrated to control polyuria and hydroelectrolytic disorders without significant side effects. To our knowledge, this is the third publication on acetazolamide use in Li-NDI patients.

Lithium reduces blood glucose levels, but aggravates albuminuria in BTBR-ob/ob mice

Glycogen synthase kinase 3 (GSK3) plays an important role in the development of diabetes mellitus and renal injury. GSK3 inhibition increases glucose uptake in insulin-insensitive muscle and adipose tissue, while it reduces albuminuria and glomerulosclerosis in acute kidney injury. The effect of chronic GSK3 inhibition in diabetic nephropathy is not known. We tested the effect of lithium, the only clinical GSK3 inhibitor, on the development of diabetes mellitus and kidney injury in a mouse model of diabetic nephropathy. Twelve-week old female BTBR-ob/ob mice were treated for 12 weeks with 0, 10 and 40 mmol LiCl/kg after which the development of diabetes and diabetic nephropathy were analysed. In comparison to BTBR-WT mice, ob/ob mice demonstrated elevated bodyweight, increased blood glucose/insulin levels, urinary albumin and immunoglobulin G levels, glomerulosclerosis, reduced nephrin abundance and a damaged proximal tubule brush border. The lithium-10 and -40 diets did not affect body weight and resulted in blood lithium levels of respectively <0.25 mM and 0.48 mM. The Li-40 diet fully rescued the elevated non-fasting blood glucose levels. Importantly, glomerular filtration rate was not affected by lithium, while urine albumin and immunoglobulin G content were further elevated. While lithium did not worsen the glomerulosclerosis, proximal tubule function seemed affected by lithium, as urinary NGAL levels were significantly increased. These results demonstrate that lithium attenuates non-fasting blood glucose levels in diabetic mice, but aggravates urinary albumin and immunoglobulin G content, possibly resulting from proximal tubule dysfunction.

Dexamethasone enhances vasopressin-induced aquaporin-2 gene expression in the mpkCCD cells

The mouse cortical collecting duct cell (mpkCCD) has been an instrumental cell model for studying vasopressin-mediated aquaporin-2 regulation. This cell line was first developed by Vandewalle's group from a transgenic mouse carrying the transforming SV40 antigens driven by the pyruvate kinase promoter. To immortalize the cells, four hormone supplements (dexamethasone, epidermal growth factor, insulin, and triiodothyronine) were used to enhance SV40 antigen expression; however, these hormones appear to have various effects on aquaporin-2 gene expression in the cells. Here, we evaluated the effects of each hormone supplement and found that dexamethasone enhanced vasopressin-induced aquaporin-2 gene expression at both mRNA and protein levels in a dose- and time-dependent manner, without affecting mRNA or protein stability. The effects of dexamethasone were attributed largely to enhanced aquaporin-2 mRNA transcription in association with an enhanced aquaporin-2 promoter activity. Dexamethasone did not affect vasopressin-regulated aquaporin-2 phosphorylation and trafficking. In summary, we optimized the conditions to enhance vasopressin-induced endogenous aquaporin-2 gene expression in the mpkCCD cells. By increasing the amount of aquaporin-2 protein in the cells, our method will facilitate the study of aquaporin-2 cell physiology regulated by vasopressin.

Lithium induces aerobic glycolysis and glutaminolysis in collecting duct principal cells

Lithium, given to bipolar disorder patients, causes nephrogenic diabetes insipidus (Li-NDI), a urinary-concentrating defect. Li-NDI occurs due to downregulation of principal cell AQP2 expression, which coincides with principal cell proliferation. The metabolic effect of lithium on principal cells, however, is unknown and investigated here. In earlier studies, we showed that the carbonic anhydrase (CA) inhibitor acetazolamide attenuated Li-induced downregulation in mouse-collecting duct (mpkCCD) cells. Of the eight CAs present in mpkCCD cells, siRNA and drug treatments showed that downregulation of CA9 and to some extent CA12 attenuated Li-induced AQP2 downregulation. Moreover, lithium induced cell proliferation and increased the secretion of lactate. Lithium also increased urinary lactate levels in wild-type mice that developed Li-NDI but not in lithium-treated mice lacking ENaC, the principal cell entry site for lithium. Inhibition of aerobic glycolysis with 2-deoxyglucose (2DG) attenuated lithium-induced AQP2 downregulation in mpkCCD cells but did not attenuate Li-NDI in mice. Interestingly, NMR analysis demonstrated that lithium also increased the urinary succinate, fumarate, citrate, and NH₄⁺ levels, which were, in contrast to lactate, not decreased by 2DG. Together, our data reveal that lithium induces aerobic glycolysis and glutaminolysis in principal cells and that inhibition of aerobic glycolysis, but not the glutaminolysis, does not attenuate Li-NDI.

Lithium-induced NDI: acetazolamide reduces polyuria but does not improve urine concentrating ability

Lithium is the mainstay treatment for patients with bipolar disorder, but it generally causes nephrogenic diabetes insipidus (NDI), a disorder in which the renal urine concentrating ability has become vasopressin insensitive. Li-NDI is caused by lithium uptake by collecting duct principal cells and downregulation of aquaporin-2 (AQP2) water channels, which are essential for water uptake from tubular urine. Recently, we found that the prophylactic administration of acetazolamide to mice effectively attenuated Li-NDI. To evaluate whether acetazolamide might benefit lithium-treated patients, we administered acetazolamide to mice with established Li-NDI and six patients with a lithium-induced urinary concentrating defect. In mice, acetazolamide partially reversed lithium-induced polyuria and increased urine osmolality, which, however, did not coincide with increased AQP2 abundances. In patients, acetazolamide led to the withdrawal of two patients from the study due to side effects. In the four remaining patients acetazolamide did not lead to clinically relevant changes in maximal urine osmolality. Urine output was also not affected, although none of these patients demonstrated overt lithium-induced polyuria. In three out of four patients, acetazolamide treatment increased serum creatinine levels, indicating a decreased glomerular filtration rate (GFR). Strikingly, these three patients also showed a decrease in systemic blood pressure. All together, our data reveal that acetazolamide does not improve the urinary concentrating defect caused by lithium, but it lowers the GFR, likely explaining the reduced urine output in our mice and in a recently reported patient with lithium-induced polyuria. The reduced GFR in patients prone to chronic kidney disease development, however, warrants against application of acetazolamide in Li-NDI patients without long-term (pre)clinical studies.

Molecular mechanisms regulating aquaporin-2 in kidney collecting duct

The kidney collecting duct is an important renal tubular segment for regulation of body water homeostasis and urine concentration. Water reabsorption in the collecting duct principal cells is controlled by vasopressin, a peptide hormone that induces the osmotic water transport across the collecting duct epithelia through regulation of water channel proteins aquaporin-2 (AQP2) and aquaporin-3 (AQP3). In particular, vasopressin induces both intracellular translocation of AQP2-bearing vesicles to the apical plasma membrane and transcription of the Aqp2 gene to increase AQP2 protein abundance. The signaling pathways, including AQP2 phosphorylation, RhoA phosphorylation, intracellular calcium mobilization, and actin depolymerization, play a key role in the translocation of AQP2. This review summarizes recent data demonstrating the regulation of AQP2 as the underlying molecular mechanism for the homeostasis of water balance in the body.

Physiological insights into novel therapies for nephrogenic diabetes insipidus

Fundamental kidney physiology research can provide important insight into how the kidney works and suggest novel therapeutic opportunities to treat human diseases. This is especially true for nephrogenic diabetes insipidus (NDI). Over the past decade, studies elucidating the molecular physiology and signaling pathways regulating water transport have suggested novel therapeutic possibilities. In patients with congenital NDI due to mutations in the type 2 vasopressin receptor (V2R) or acquired NDI due to lithium (or other medications), there are no functional abnormalities in the aquaporin-2 (AQP2) water channel, or in another key inner medullary transport protein, the UT-A1 urea transporter. If it is possible to phosphorylate and/or increase the apical membrane accumulation of these proteins, independent of vasopressin or cAMP, one may be able to treat NDI. Sildenifil (through cGMP), erlotinib, and simvastatin each stimulate AQP2 insertion into the apical plasma membrane. Some recent human data suggest that sildenafil and simvastatin may improve urine concentrating ability. ONO-AE1-329 (ONO) stimulates the EP4 prostanoid receptor (EP4), which stimulates kinases that in turn phosphorylate AQP2 and UT-A1. Clopidogrel is a P2Y12-R antagonist that potentiates the effect of vasopressin and increases AQP2 abundance. Metformin stimulates AMPK to phosphorylate and activate AQP2 and UT-A1, and it increases urine concentrating ability in two rodent models of NDI. Since metformin, sildenafil, and simvastatin are commercially available and have excellent safety records, the potential for rapidly advancing them into clinical trials is high.