A novel antidiuretic hormone governs tumour-induced renal dysfunction.

Maintenance of renal function and fluid transport are essential for vertebrates and invertebrates to adapt to physiological and pathological challenges. Human patients with malignant tumours frequently develop detrimental renal dysfunction and oliguria, and previous studies suggest the involvement of chemotherapeutic toxicity and tumour-associated inflammation1,2. However, how tumours might directly modulate renal functions remains largely unclear. Here, using conserved tumour models in Drosophila melanogaster3, we characterized isoform F of ion transport peptide (ITPF) as a fly antidiuretic hormone that is secreted by a subset of yki3SA gut tumour cells, impairs renal function and causes severe abdomen bloating and fluid accumulation. Mechanistically, tumour-derived ITPF targets the G-protein-coupled receptor TkR99D in stellate cells of Malpighian tubules-an excretory organ that is equivalent to renal tubules4-to activate nitric oxide synthase-cGMP signalling and inhibit fluid excretion. We further uncovered antidiuretic functions of mammalian neurokinin 3 receptor (NK3R), the homologue of fly TkR99D, as pharmaceutical blockade of NK3R efficiently alleviates renal tubular dysfunction in mice bearing different malignant tumours. Together, our results demonstrate a novel antidiuretic pathway mediating tumour-renal crosstalk across species and offer therapeutic opportunities for the treatment of cancer-associated renal dysfunction.

Vasopressin and Its Analogues: From Natural Hormones to Multitasking Peptides.

Human neurohormone vasopressin (AVP) is synthesized in overlapping regions in the hypothalamus. It is mainly known for its vasoconstricting abilities, and it is responsible for the regulation of plasma osmolality by maintaining fluid homeostasis. Over years, many attempts have been made to modify this hormone and find AVP analogues with different pharmacological profiles that could overcome its limitations. Non-peptide AVP analogues with low molecular weight presented good affinity to AVP receptors. Natural peptide counterparts, found in animals, are successfully applied as therapeutics; for instance, lypressin used in treatment of diabetes insipidus. Synthetic peptide analogues compensate for the shortcomings of AVP. Desmopressin is more resistant to proteolysis and presents mainly antidiuretic effects, while terlipressin is a long-acting AVP analogue and a drug recommended in the treatment of varicose bleeding in patients with liver cirrhosis. Recently published results on diverse applications of AVP analogues in medicinal practice, including potential lypressin, terlipressin and ornipressin in the treatment of SARS-CoV-2, are discussed.

Synthesis of bio-mediated silver nanoparticles from Silybum marianum and their biological and clinical activities.

The purpose of current study was green synthesis of silver nanoparticles (AgNPs) from seeds and wild Silybum plants in comparison with their respective extracts followed by characterization and biological potency. The biologically synthesized AgNPs were subjected to characterization using techniques like XRD, FTIR, TEM, HPLC and SPE. Highly crystalline and stable NPs were obtained using Silybum wild plant (NP1) and seeds (NP3) with size range between 18.12 and 13.20 nm respectively. The synthesized NPs and their respective extracts revealed a vast range of biological applications showing antibacterial, antioxidant, anti-inflammatory, cytotoxic and anti-aging potencies. The highest antioxidant activity (478.23 ± 1.9 µM, 176.91 ± 1.3 µM, 83.5 ± 1.6% µgAAE/mg, 156.32 ± 0.6 µgAAE/mg) for ABTS, FRAP, FRSA, TRP respectively was shown by seed extract (NP4) followed by highest value of (117.35 ± 0.9 µgAAE/mg) for TAC by wild extract (NP2). The highest antifungal activity (13 mm ± 0.76) against Candida albicans was shown by NP3 while antibacterial activity of (6 mm against Klebsiella pneumonia) was shown by NP3 and NP4. The highest anti-inflammatory activity (38.56 ± 1.29 against COX1) was shown by NP2. Similarly, the high value of (48.89 ± 1.34 against Pentosidine-Like AGEs) was shown by NP4. Also, the high anti-diabetic activity (38.74 ± 1.09 against α-amylase) was shown by NP4. The extracts and the synthesized NPs have shown activity against hepato-cellular carcinoma (HepG2) human cells. The HPLC analysis revealed that the highest value of silymarin component (silybin B 2289 mg/g DW) was found for NP4. Silydianin is responsible for capping. Among the green synthesized AgNPs and the extracts used, the effect of NP4 was most promising for further use.

CAPA neuropeptides and their receptor form an anti-diuretic hormone signaling system in the human disease vector, Aedes aegypti.

Insect CAPA neuropeptides are homologs of mammalian neuromedin U and are known to influence ion and water balance by regulating the activity of the Malpighian 'renal' tubules (MTs). Several diuretic hormones are known to increase primary fluid and ion secretion by insect MTs and, in adult female mosquitoes, a calcitonin-related peptide (DH31) called mosquito natriuretic peptide, increases sodium secretion to compensate for the excess salt load acquired during blood-feeding. An endogenous mosquito anti-diuretic hormone was recently described, having potent inhibitory activity against select diuretic hormones, including DH31. Herein, we functionally deorphanized, both in vitro and in vivo, a mosquito anti-diuretic hormone receptor (AedaeADHr) with expression analysis indicating highest enrichment in the MTs where it is localized within principal cells. Characterization using a heterologous in vitro system demonstrated the receptor was highly sensitive to mosquito CAPA neuropeptides while in vivo, AedaeADHr knockdown abolished CAPA-induced anti-diuretic control of DH31-stimulated MTs. CAPA neuropeptides are produced within a pair of neurosecretory cells in each of the abdominal ganglia, whose axonal projections innervate the abdominal neurohaemal organs, where these neurohormones are released into circulation. Lastly, pharmacological inhibition of nitric oxide synthase (NOS) and protein kinase G (PKG) signaling eliminated anti-diuretic activity of CAPA, highlighting the role of the second messenger cGMP and NOS/PKG in this anti-diuretic signaling pathway.

Meloxicam-desmopressin drug-drug interaction producing hyponatremia.

BACKGROUND: People with schizophrenia and medical comorbidities are often on multiple medications to manage their symptoms. Herein we present a case of drug-drug interaction (meloxicam and desmopressin), in a patient also on clozapine, that ultimately resulted in hyponatremia and seizure. METHODS: The patient provided consent to have his case published. We searched PubMed and after reviewing 321 articles, 11 were chosen for relevance. RESULTS: Meloxicam enhanced the adverse effect (hyponatremia) of desmopressin and was the likely culprit. CONCLUSIONS: In a patient with higher ADH levels, as in our patient taking desmopressin, the addition of an NSAID could further increase water retention and worsen hyponatremia; indeed, meloxicam was the only new medication added to the patient's regimen, and a drug interaction calculator supports the desmopressin-meloxicam drug-drug interaction as the culprit. We urge clinicians to avoid the use of desmopressin in patients with schizophrenia as this can lead to water intoxication. As meloxicam may worsen desmopressin-induced hyponatremia and could result in seizure, one should avoid using NSAIDs in patients with schizophrenia whom are also prescribed vasopressin/desmopressin. Serum sodium levels should be closely monitored in patients with schizophrenia whose regimen includes desmopressin.

Anti-diuretic activity of a CAPA neuropeptide can compromise Drosophila chill tolerance.

For insects, chilling injuries that occur in the absence of freezing are often related to a systemic loss of ion and water balance that leads to extracellular hyperkalemia, cell depolarization and the triggering of apoptotic signalling cascades. The ability of insect ionoregulatory organs (e.g. the Malpighian tubules) to maintain ion balance in the cold has been linked to improved chill tolerance, and many neuroendocrine factors are known to influence ion transport rates of these organs. Injection of micromolar doses of CAPA (an insect neuropeptide) have been previously demonstrated to improve Drosophila cold tolerance, but the mechanisms through which it impacts chill tolerance are unclear, and low doses of CAPA have been previously demonstrated to cause anti-diuresis in insects, including dipterans. Here, we provide evidence that low (femtomolar) and high (micromolar) doses of CAPA impair and improve chill tolerance, respectively, via two different effects on Malpighian tubule ion and water transport. While low doses of CAPA are anti-diuretic, reduce tubule K+ clearance rates and reduce chill tolerance, high doses facilitate K+ clearance from the haemolymph and increase chill tolerance. By quantifying CAPA peptide levels in the central nervous system, we estimated the maximum achievable hormonal titres of CAPA and found further evidence that CAPA may function as an anti-diuretic hormone in Drosophila melanogaster We provide the first evidence of a neuropeptide that can negatively affect cold tolerance in an insect and further evidence of CAPA functioning as an anti-diuretic peptide in this ubiquitous insect model.

Muscarinic M2 receptor promotes vasopressin synthesis in mice supraoptic nuclei.

Muscarinic acetylcholine receptors have been suggested to be implicated in arginine-vasopressin secretion because intracerebroventricular muscarinic agonist administration induces arginine-vasopressin release into the circulation. Although which subtype is involved in the regulation of arginine-vasopressin secretion is unclear, M2 receptors have been reported to be highly expressed in the hypothalamus. In the present study, M2 receptor-knockout mice were used to elucidate whether M2 receptor regulates arginine-vasopressin synthesis in the paraventricular nuclei and supraoptic nuclei of the hypothalamus. The number of arginine-vasopressin-immunoreactive neurons in M2 receptor-knockout mice was significantly decreased in the supraoptic nuclei, but not in the paraventricular nuclei compared with wild-type mice. Plasma arginine-vasopressin level in M2 receptor-knockout mice was also significantly lower than in the wild-type mice. Urinary volume and frequency as well as water intake in M2 receptor-knockout mice were significantly higher than those in wild-type mice. The V2 vasopressin receptor expression in kidneys of M2 receptor-knockout mice was comparable with that of wild-type mice, and increased urination in M2 receptor-knockout mice was significantly decreased by administration of desmopressin, a specific V2 receptor agonist, suggesting that V2 receptors in the kidneys of M2 receptor-knockout mice are intact. These results suggest that M2 receptors promote arginine-vasopressin synthesis in the supraoptic nuclei and play a role in the regulation and maintenance of body fluid.

Anti-diuretic action of a CAPA neuropeptide against a subset of diuretic hormones in the disease vector Aedes aegypti.

The mosquito Aedes aegypti is a vector responsible for transmitting various pathogens to humans, and their prominence as chief vectors of human disease is largely due to their anthropophilic blood feeding behaviour. Larval stage mosquitoes must deal with the potential dilution of their haemolymph in freshwater, whereas the haematophagus A. aegypti female faces the challenge of excess ion and water intake after a blood meal. The excretory system, composed of the Malpighian tubules (MTs) and hindgut, is strictly controlled by neuroendocrine factors, responsible for the regulation of diuresis across all developmental stages. The highly studied insect MTs are influenced by a variety of diuretic hormones and, in some insects, anti-diuretic factors. In the present study, we investigated the effects of AedaeCAPA-1 neuropeptide on larval and adult female A. aegypti MTs stimulated with various diuretic factors including serotonin (5-HT), a corticotropin-related factor (CRF) diuretic peptide, a calcitonin-related diuretic hormone (DH31) and a kinin-related diuretic peptide. Overall, our findings establish that AedaeCAPA-1 specifically inhibits secretion of larval and adult MTs stimulated by 5-HT and DH31, whilst having no activity on MTs stimulated by other diuretic factors. Furthermore, although AedaeCAPA-1 acts as an anti-diuretic, it does not influence the relative proportions of cations transported by adult MTs, thus maintaining the kaliuretic activity of 5-HT and natriuretic activity of DH31 In addition, we tested the effects of the second messenger cGMP in adult MTs. We established that cGMP has similar effects to AedaeCAPA-1, strongly inhibiting 5-HT- and DH31-stimulated fluid secretion, but with only minor effects on CRF-stimulated diuresis. Interestingly, although AedaeCAPA-1 has no inhibitory activity on kinin-stimulated fluid secretion, cGMP strongly inhibited fluid secretion by this diuretic hormone, which targets stellate cells specifically. Collectively, these results support that AedaeCAPA-1 inhibits select diuretic factors acting on the principal cells and this probably involves cGMP as a second messenger. Kinin-stimulated diuresis, which targets stellate cells, is also inhibited by cGMP, suggesting that another anti-diuretic factor in addition to AedaeCAPA-1 exists and may utilize cGMP as a second messenger.

Desmopressin and nocturnal voiding dysfunction: Clinical evidence and safety profile in the treatment of nocturia.

INTRODUCTION: Nocturia is a common urinary condition experienced by both men and women. While desmopressin has historically been utilized to treat conditions such as central diabetes insipidus and primary nocturnal enuresis, there is an increased interest in the use of desmopressin in the management of adult nocturia. Areas covered: This article provides a review on the pathophysiology of nocturia and the clinical outcomes and safety profile of desmopressin in the management of adult nocturnal voiding dysfunction. Expert opinion: To date, desmopressin is the only anti-diuretic hormone that is approved for nocturia. Published literature on desmopressin demonstrate good clinical efficacy in terms of number of nocturnal voids, voided volume and sleep period. Newer formulations have shown that a minimum dosage of 25 µg orally disintegrating sublingual desmopressin appears to be ideal for women, whereas men usually benefit from a minimum of 50 µg. Of the known adverse drug reactions, hyponatremia remains a major concern especially in patients over 65 years of age. At present, long term data on desmopressin remains scarce. Lastly, it is important to stress that no single treatment deals with nocturia in all contexts, and careful assessment remains essential to identify the appropriate and safest treatment in each patient.

Solid lipid particles for oral delivery of peptide and protein drugs II--the digestion of trilaurin protects desmopressin from proteolytic degradation.

PURPOSE: To investigate the in vitro release and degradation of desmopressin from saturated triglyceride microparticles under both lipolytic and proteolytic conditions. METHODS: The release of desmopressin from different solid lipid microparticles in the absence and presence of a microbial lipase and protease was determined. Trilaurin (TG12), trimyristin (TG14), tripalmitin (TG16), and tristearin (TG18) were used as lipid excipients to produce solid lipid microparticles. RESULTS: In the presence of lipase, the rate of drug release from different lipid particles was in the order of TG14 > TG16 > TG18, which is the same rank order as the lipid degradation rate. A reverse rank order was found for the protection of desmopressin from enzymatic degradation due to spatial separation of desmopressin from the protease. TG12 accelerated the release of desmopressin from all lipid particles when added as either drug-free microparticles to the lipolysis medium or incorporated in TG16 particles. Additionally, TG12 particles protected desmopressin from degradation when present in the lipolysis medium with the other lipid microparticles. CONCLUSIONS: TG12 is a very interesting lipid for oral lipid formulations containing peptides and proteins as it alters release and degradation of the incorporated desmopressin. The present study demonstrates the possibility of bio-relevant in vitro evaluation of lipid-based solid particles.

Dominant factors that govern pressure natriuresis in diuresis and antidiuresis: a mathematical model.

We have developed a whole kidney model of the urine concentrating mechanism and renal autoregulation. The model represents the tubuloglomerular feedback (TGF) and myogenic mechanisms, which together affect the resistance of the afferent arteriole and thus glomerular filtration rate. TGF is activated by fluctuations in macula densa [Cl(-)] and the myogefnic mechanism by changes in hydrostatic pressure. The model was used to investigate the relative contributions of medullary blood flow autoregulation and inhibition of transport in the proximal convoluted tubule to pressure natriuresis in both diuresis and antidiuresis. The model predicts that medullary blood flow autoregulation, which only affects the interstitial solute composition in the model, has negligible influence on the rate of NaCl excretion. However, it exerts a significant effect on urine flow, particularly in the antidiuretic kidney. This suggests that interstitial washout has significant implications for the maintenance of hydration status but little direct bearing on salt excretion, and that medullary blood flow may only play a signaling role for stimulating a pressure-natriuresis response. Inhibited reabsorption in the model proximal convoluted tubule is capable of driving pressure natriuresis when the known actions of vasopressin on the collecting duct epithelium are taken into account.

Adenylyl cyclase VI mediates vasopressin-stimulated ENaC activity.

Vasopressin modulates sodium reabsorption in the collecting duct through adenylyl cyclase-stimulated cyclic AMP, which exists as multiple isoforms; the specific isoform involved in vasopressin-stimulated sodium transport is unknown. To assess this, we studied mice deficient in adenylyl cyclase type VI specifically in the principal cells of the collecting duct. Knockout mice had increased urine volume and reduced urine sodium concentration, but regardless of the level of sodium intake, they did not exhibit significant alterations in urinary sodium excretion, arterial pressure, or pulse rate. Plasma renin concentration was elevated in knockout mice, however, suggesting a compensatory response. Valsartan significantly reduced arterial pressure in knockout mice but not in controls. Knockout mice had decreased renal cortical mRNA content of all three epithelial sodium channel (ENaC) isoforms, and total cell sodium channel isoforms α and γ were reduced in these animals. Patch-clamp analysis of split-open cortical collecting ducts revealed no difference in baseline activity of sodium channels, but knockout mice had abolished vasopressin-stimulated ENaC open probability and apical membrane channel number. In summary, these data suggest that adenylyl cyclase VI mediates vasopressin-stimulated ENaC activity in the kidney.

Design, synthesis and structure-activity relationship of new arginine vasopressin analogues containing proline derivatives in position 2.

In this study, we present the synthesis and pharmacological properties of new analogues of arginine vasopressin modified in the N-terminal part of the molecule with proline derivatives: indoline-2-carboxylic acid (Ica) and (2S,4R)-4-(naphthalene-2-ylmethyl)pyrrolidine-2-carboxylic acid. All the peptides were tested for pressor, antidiuretic and in vitro uterotonic activities. We also determined their binding affinity to the human oxytocin receptor. The Ica(2) substitution resulted in two moderately potent and selective antioxytocic agents: [Mpa(1), Ica(2), D-Arg(8)]VP and [Mpa(1),Ica(2),Val(4),D-Arg(8)]VP (pA(2) = 7.09 and 7.50, respectively). On the other hand, peptides modified with (2S,4R)-4-(naphthalene-2-ylmethyl)pyrrolidine-2-carboxylic acid, apart from their moderate antioxytocic activity, turned out to be weak antagonists of the pressor response to arginine vasopressin. The results of this study provide useful information about the structure-activity relationship of arginine vasopressin analogues and can help to design compounds with desired biological properties.

Investigation of the potential involvement of eicosanoid metabolites in anti-diuretic hormone signaling in Rhodnius prolixus.

The use of naturally occurring plant-derived compounds for controlling insect pests remains an attractive alternative to potentially dangerous synthetic chemical compounds. One prospective plant-based compound, isoforms of the so-called jack bean urease (JBU) from the jack bean, Canavalia ensiformis, as well a derived peptide, Jaburetox-2Ec, have insecticidal effects on an array of insect species. In the Chagas' disease vector, Rhodnius prolixus, some of the physiological effects attributed to these urease isoforms include inhibition of serotonin (5-HT)-stimulated fluid secretion by the Malpighian tubules (MTs). Here, we investigated whether the effects of these exogenous urease isoforms were targeting the neuroendocrine network involved in the anti-diuretic hormone (RhoprCAPA-2) signaling cascade. We show that pharmacological agents known to interfere with eicosanoid metabolite biosynthesis do not affect RhoprCAPA-2 inhibition of 5-HT-stimulated fluid secretion by MTs. In addition, we demonstrate that RhoprCAPA-2 inhibition of MTs is independent of extracellular or intracellular calcium. Using a heterologous system for analysis of receptor activation, we show that neither JBU nor Jaburetox-2Ec are agonists of the anti-diuretic hormone receptor, RhoprCAPAr1. Finally, activation of the receptor using sub-maximal doses of the natural ligand, RhoprCAPA-2, was not influenced by the presence of either JBU or Jaburetox-2Ec indicating that the urease isoforms do not compete with RhoprCAPA-2 for binding and activation of RhoprCAPAr1. Taken together, these results suggest that at least two distinct mechanisms leading to inhibition of fluid secretion by MTs exist in R. prolixus and, unlike the urease-related effects, the eicosanoid metabolite pathway is not involved in RhoprCAPA-2 mediated anti-diuresis.

Pharmacological characterization of FE 202158, a novel, potent, selective, and short-acting peptidic vasopressin V1a receptor full agonist for the treatment of vasodilatory hypotension.

FE 202158, ([Phe(2),Ile(3),Hgn(4),Orn(iPr)(8)]vasopressin, where Hgn is homoglutamine and iPr is isopropyl), a peptidic analog of the vasoconstrictor hormone [Arg(8)]vasopressin (AVP), was designed to be a potent, selective, and short-acting vasopressin type 1a receptor (V(1a)R) agonist. In functional reporter gene assays, FE 202158 was a potent and selective human V(1a)R agonist [EC(50) = 2.4 nM; selectivity ratio of 1:142:1107:440 versus human vasopressin type 1b receptor, vasopressin type 2 receptor (V(2)R), and oxytocin receptor, respectively] contrasting with AVP's lack of selectivity, especially versus the V(2)R (selectivity ratio of 1:18:0.2:92; human V(1a)R EC(50) = 0.24 nM). This activity and selectivity profile was confirmed in radioligand binding assays. FE 202158 was a potent vasoconstrictor in the isolated rat common iliac artery ex vivo (EC(50) = 3.6 nM versus 0.8 nM for AVP) and reduced rat ear skin blood flow after intravenous infusion in vivo (ED(50) = 4.0 versus 3.4 pmol/kg/min for AVP). The duration of its vasopressor effect by intravenous bolus in rats was as short as AVP at submaximally effective doses. FE 202158 had no V(2)R-mediated antidiuretic activity in rats by intravenous infusion at its ED(50) for reduction of ear skin blood flow, in contrast with the pronounced antidiuretic effect of AVP. Thus, FE 202158 seems suitable for treatment of conditions where V(1a)R activity is desirable but V(2)R activity is potentially deleterious, such as vasodilatory hypotension in septic shock. In addition to the desirable selectivity profile, its short-acting nature should allow dose titration with rapid onset and offset of action to optimize vasoconstriction efficacy and safety.

Vasopressin-inducible ubiquitin-specific protease 10 increases ENaC cell surface expression by deubiquitylating and stabilizing sorting nexin 3.

Adjustment of Na+ balance in extracellular fluids is achieved by regulated Na+ transport involving the amiloride-sensitive epithelial Na+ channel (ENaC) in the distal nephron. In this context, ENaC is controlled by a number of hormones, including vasopressin, which promotes rapid translocation of water and Na+ channels to the plasma membrane and long-term effects on transcription of vasopressin-induced and -reduced transcripts. We have identified a mRNA encoding the deubiquitylating enzyme ubiquitin-specific protease 10 (Usp10), whose expression is increased by vasopressin at both the mRNA and the protein level. Coexpression of Usp10 in ENaC-transfected HEK-293 cells causes a more than fivefold increase in amiloride-sensitive Na+ currents, as measured by whole cell patch clamping. This is accompanied by a three- to fourfold increase in surface expression of alpha- and gamma-ENaC, as shown by cell surface biotinylation experiments. Although ENaC is well known to be regulated by its direct ubiquitylation, Usp10 does not affect the ubiquitylation level of ENaC, suggesting an indirect effect. A two-hybrid screen identified sorting nexin 3 (SNX3) as a novel substrate of Usp10. We show that it is a ubiquitylated protein that is degraded by the proteasome; interaction with Usp10 leads to its deubiquitylation and stabilization. When coexpressed with ENaC, SNX3 increases the channel's cell surface expression, similarly to Usp10. In mCCD(cl1) cells, vasopressin increases SNX3 protein but not mRNA, supporting the idea that the vasopressin-induced Usp10 deubiquitylates and stabilizes endogenous SNX3 and consequently promotes cell surface expression of ENaC.

Distribution, activity and evidence for the release of an anti-diuretic peptide in the kissing bug Rhodnius prolixus.

In the haematophagous insect Rhodnius prolixus, diuresis is accomplished through the combined actions of peptidergic diuretic hormones and 5-HT released from neurohaemal sites on the abdominal nerves. Preliminary work on anti-diuresis in this blood-feeder, previously believed to occur through a decrease in the levels of the diuretic factors, indicates that an anti-diuretic hormone, with properties similar to CAP2b (pELYAFPRVamide; recently renamed Mas-CAPA-1), might also be present in R. prolixus. Here, we present evidence from immunohistochemical analysis that suggests a PRXamide-like neuropeptide may be released from the abdominal neurohaemal sites beginning 3-4 h following feeding; a time that coincides with the cessation of diuresis. We also show evidence for an endogenous factor, isolated from the central nervous system using reversed-phase high performance liquid chromatography, which mimics the effects of Mas-CAPA-1. Specifically, this endogenous anti-diuretic factor inhibits rates of 5-HT-stimulated secretion in a dose-dependent manner and elevates intracellular cGMP levels of Malpighian tubules stimulated with 5-HT.