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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.

mpkCCDc14 cells, a polarized epithelial cell line derived from mouse kidney cortical collecting ducts, are known to express the vasopressin V2 receptor (V2R) and aquaporin-2 (AQP2) that are responsive to vasopressin. However, a low abundance of the endogenous AQP2 protein in the absence of vasopressin and heterogeneity of AQP2 protein abundance among the cultured cells may limit the further application of the cell line in AQP2 studies. To overcome the limitation, we aimed to establish mpkCCDc14 cells constitutively expressing V2R and AQP2 via CRISPR/Cas9-mediated genome engineering technology (i.e., V2R-AQP2 cells). 3′- and 5′-Junction PCR revealed that the V2R-AQP2 expression cassette with a long insert size (~2.2 kb) was correctly integrated. Immunoblotting revealed the expression of products of integrated Aqp2 genes. Cell proliferation rate and dDAVP-induced cAMP production were not affected by the knock-in of Avpr2 and Aqp2 genes. The AQP2 protein abundance was significantly higher in V2R-AQP2 cells compared with control mpkCCDc14 cells in the absence of dDAVP and the integrated AQP2 was detected. Immunocytochemistry demonstrated that V2R-AQP2 cells exhibited more homogenous and prominent AQP2 labeling intensity in the absence of dDAVP stimulation. Moreover, prominent AQP2 immunolabeling (both AQP2 and pS256-AQP2) in the apical domain of the genome-edited cells was observed in response to dDAVP stimulation, similar to that in the unedited control mpkCCDc14 cells. Taken together, mpkCCDc14 cells constitutively expressing V2R and AQP2 via genome engineering could be exploited for AQP2 studies.

Diabetes insipidus (DI) after endoscopic transsphenoidal surgery (ETSS) can lead to increased morbidity, longer hospital stays, and increased medication requirements. Predicting which patients are at high risk for developing DI can help direct services to ensure adequate care and follow-up. The objective of this study was to review our institution’s experience with ETSS and determine which clinical/laboratory variables are associated with DI in this patient population. The authors wanted to see if there was an easily determined single value that would help predict which patients develop DI. This represents the largest North American series of this type. We retrospectively reviewed the charts of patients who had undergone ETSS for resection of sellar and parasellar pathology between 2006 and 2011. We examined patient and tumor characteristics and their relationship to postoperative DI. Out of 172 endoscopic transsphenoidal surgeries, there were 15 cases of transient DI (8.7 %) and 14 cases of permanent DI (8.1 %). Statistically significant predictors of postoperative DI ( p  < 0.05) included tumor volume and histopathology (Rathke’s cleft cyst and craniopharyngioma). Significant indicators of development of DI were postoperative serum sodium, preoperative to postoperative change in sodium level, and urine output prior to administration of 1-deamino-8- d -arginine vasopressin. An increase in serum sodium of ≥2.5 mmol/L is a positive marker of development of DI with 80 % specificity, and a postoperative serum sodium of ≥145 mmol/L is a positive indicator with 98 % specificity. Identifying perioperative risk factors and objective indicators of DI after ETSS will help physicians care for patients postoperatively. In this large series, we demonstrated that there were multiple perioperative risk factors for the development of DI. These findings, which are consistent with other reports from microscopic surgical series, will help identify patients at risk for diabetes insipidus, aid in planning treatment algorithms, and increase vigilance in high risk patients.

Trafficking of the water channel aquaporin-2 to the apical plasma membrane of the collecting duct is mediated by arginine vasopressin, rendering the cell permeable to water. We recently identified a novel form of aquaporin-2 that is phosphorylated at serine-269 (pS269-AQP2). Using antibodies specific for this form of the water channel, we detected rat and mouse pS269-AQP2 in the connecting tubule and throughout the collecting duct system. Using confocal immunofluorescence microscopy with organelle-specific markers and immunogold electron microscopy, we found that pS269-AQP2 was found only on the apical plasma membrane of principal cells. In vasopressin-deficient Brattleboro rats, pS269-AQP2 was undetectable but dramatically increased in abundance after these rats were treated with [deamino-Cys-1, d-Arg-8]vasopressin (dDAVP). This increase occurred only at the apical plasma membrane, even after long-term dDAVP treatment. Following dDAVP there was a time-dependent redistribution of total aquaporin-2 from predominantly intracellular vesicles to the apical plasma membrane, clathrin-coated vesicles, early endosomal compartments, and lysosomes. However, pS269-AQP2 was found only on the apical plasma membrane at any time. Our results show that S269 phosphorylated aquaporin-2 is exclusively associated with the apical plasma membrane, where it escapes endocytosis to remain at the cell surface.

Desmopressin (dDAVP) is the best characterized analogue of vasopressin, the endocrine regulator of water balance endowed with potent vasoconstrictive effects. Despite the use of dDAVP in clinical practice, ranging from the treatment of nephrogenic diabetes insipidus to bleeding disorders, much remains to be understood about the impact of the drug on endothelial phenotype. The aim of this study was, thus, to evaluate the effects of desmopressin on the viability and function of human pulmonary microvascular endothelial cells (HLMVECs). The results obtained demonstrate that the vasopressor had no cytotoxic effect on the endothelium; similarly, no sign of endothelial activation was induced by dDAVP, indicated by the lack of effect on the expression of inflammatory cytokines and adhesion molecules. Conversely, the drug significantly stimulated the production of nitric oxide (NO) and the expression of the inducible isoform of nitric oxide synthase, NOS2/iNOS. Since the intracellular level of cAMP also increased, we can hypothesize that NO release is consequent to the activation of the vasopressin receptor 2 (V2R)/guanylate cyclase (Gs)/cAMP axis. Given the multifaceted role of NOS2-deriving NO for many physio-pathological conditions, the meanings of these findings in HLMVECs appears intriguing and deserves to be further addressed.

By phosphoproteome analysis, we identified a phosphorylation site, serine 264 (pS264), in the COOH terminus of the vasopressin-regulated water channel, aquaporin-2 (AQP2). In this study, we examined the regulation of AQP2 phosphorylated at serine 264 (pS264-AQP2) by vasopressin, using a phospho-specific antibody (anti-pS264). Immunohistochemical analysis showed pS264-AQP2 labeling of inner medullary collecting duct (IMCD) from control mice, whereas AQP2 knockout mice showed a complete absence of labeling. In rat and mouse, pS264-AQP2 was present throughout the collecting duct system, from the connecting tubule to the terminal IMCD. Immunogold electron microscopy, combined with double-labeling confocal immunofluorescence microscopy with organelle-specific markers, determined that the majority of pS264 resides in compartments associated with the plasma membrane and early endocytic pathways. In Brattleboro rats treated with [deamino-Cys-1, D-Arg-8]vasopressin (dDAVP), the abundance of pS264-AQP2 increased 4-fold over controls. Additionally, dDAVP treatment resulted in a time-dependent change in the distribution of pS264 from predominantly intracellular vesicles, to both the basolateral and apical plasma membranes. Sixty minutes after dDAVP exposure, a proportion of pS264-AQP2 was observed in clathrin-coated vesicles, early endosomal compartments, and recycling compartments, but not lysosomes. Overall, our results are consistent with a dynamic effect of AVP on the phosphorylation and subcellular distribution of AQP2.

ABSTRACT 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.

It has been proposed that a reduction in intracellular calcium causes an increase in intracellular cAMP and PKA activity through stimulation of calcium inhibitable adenylyl cyclase 6 and inhibition of phosphodiesterase 1 (PDE1), the main enzymes generating and degrading cAMP in the distal nephron and collecting duct, thus contributing to the development and progression of autosomal dominant polycystic kidney disease (ADPKD). In zebrafish pde1a depletion aggravates and overexpression ameliorates the cystic phenotype. To study the role of PDE1A in a mammalian system, we used a TALEN pair to Pde1a exon 7, targeting the histidine-aspartic acid dipeptide involved in ligating the active site Zn++ ion to generate two Pde1a null mouse lines. Pde1a mutants had a mild renal cystic disease and a urine concentrating defect (associated with upregulation of PDE4 activity and decreased protein kinase A dependent phosphorylation of aquaporin-2) on a wild-type genetic background and aggravated renal cystic disease on a Pkd2WS25/- background. Pde1a mutants additionally had lower aortic blood pressure and increased left ventricular (LV) ejection fraction, without a change in LV mass index, consistent with the high aortic and low cardiac expression of Pde1a in wild-type mice. These results support an important role of PDE1A in the renal pathogenesis of ADPKD and in the regulation of blood pressure.

To synthesize a series of reversible fatty acid-desmopressin (DDAVP) conjugates and to study their structure-activity relationship as anti-diuretic drugs. Seven fatty acid conjugates of DDAVP were prepared using various reversible lipidization reagents as described in our previous reports. All products were purified by acid precipitation and/or size-exclusion chromatography. Reversed-phase HPLC was used to evaluate their purity and lipophilicity. The anti-diuretic efficacy of these fatty acid conjugates was assessed in vasopressin-deficient Brattleboro rats. Four selected conjugates, i.e., DPA, DPH, DPD and DPP (acetic, hexanoic. decanoic, and palmitic acid conjugate, respectively), along with DDAVP itself were used in Caco-2 cell uptake studies and their degradation and the regeneration of active DDAVP were investigated using an in vitro liver slice metabolic system coupled with a HPLC assay. All fatty acid-DDAVP conjugates were more lipophilic than DDAVP as examined by HPLC analyses. When cysteine was used as the linker, the capacity index (k', a measure of lipophilicity) of the conjugates was linearly correlated with the number of carbons in the fatty acid chain. The anti-diuretic activity of the conjugates was correlated with the length of the fatty acid chain, with C10 as the minimal requirement for possessing the enhanced anti-diuretic activity. Among the seven fatty acid conjugates, palmitic acid conjugate was the most potent DDAVP derivative. Removal of carboxyl group from the cysteine linker completely abolished the enhancement of the activity. The extent of cellular uptake also positively correlated with the lipophilicity of the conjugates. The metabolism of DDAVP, DPH, DPD, and DPP by liver slices all followed first order kinetics with half-life of 0.30, 0.01, 0.06 and 3.44 hr, respectively. The degradation rates of DPH and DPD in the liver slice incubation were much faster than that of DDAVP and therefore an accumulation of regenerated DDAVP in the media was observed. In contrast, DPP was metabolized much slower than DDAVP and, consequently, no significant accumulation of regenerated DDAVP could be detected. Conjugation of DDAVP with fatty acids increased the lipophilicity and the anti-diuretic activity of this peptide drug. The anti-diuretic activity of lipidized DDAVP was dependent on the chain length of the fatty acid, as well as the structure of the linker in the conjugate. The preservation and enhancement of the in vivo antidiuretic activity of the conjugates is most likely due to a combination of an improved pharmacokinetic behavior and a concurrent regeneration of active DDAVP in tissues.

The article represents a review of recent data about the therapy of von Willebrand disease in children and adolescents (hereditary as well as acquired forms of the disease). The treatment of bleeding events in these patients, the indications in different subtypes, and the future lines of research are mentioned.