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Pharmacological Research Dec 2020Cystic fibrosis (CF) is a lethal autosomal recessive genetic disease, caused by a mutation in the cystic fibrosis transmembrane conductance regulator gene (CFTR), which... (Review)
Review
Cystic fibrosis (CF) is a lethal autosomal recessive genetic disease, caused by a mutation in the cystic fibrosis transmembrane conductance regulator gene (CFTR), which primarily affects the lungs and digestive system. This gene encodes the CFTR protein, a distinctive membrane transporter of the ATP-binding cassette (ABC) superfamily. It functions as a chloride channel, allowing the balance and transport of chloride through the apical membrane of epithelial cells. Due to its ubiquitous location, mutations in the CFTR gene trigger multiple changes in ion transport and metabolic pathways, affecting various organs, as it will be herein explained. Pulmonary impairment is the most characteristic comorbidity of CF and respiratory failure is the main cause of death. This review presents the importance of an early diagnosis of CF to establish, as soon as possible, a primary therapy for symptomatic prevention and relief. It also mentions new therapeutic approaches that include CFTR modulators. They are correctors and/or potentiators of the deficient CFTR channel. In an attempt to overcome the disadvantages of CFTR modulators, the application of biotechnology techniques is addressed, such as gene therapy, gene editing, RNA therapy and therapeutic microRNAs. The potential of the intranasal administration route is another presented aspect.
Topics: Animals; Biotechnology; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Humans
PubMed: 33127556
DOI: 10.1016/j.phrs.2020.105267 -
Virus Research Sep 2021Ibaraki virus (IBAV) is the pathogen associated with Ibaraki disease. In a previous study, we suggested that IBAV enters hamster lung (HmLu-1) cells via endocytosis and...
Ibaraki virus (IBAV) is the pathogen associated with Ibaraki disease. In a previous study, we suggested that IBAV enters hamster lung (HmLu-1) cells via endocytosis and subsequently escapes into the cytoplasm upon endosomal acidification. However, it is unclear which of the endocytic pathways IBAV utilizes. In this study, we aimed to further elucidate the pathway of IBAV entry into host cells. We found that IBAV replication was not suppressed by inhibitors of clathrin-mediated or caveolin-mediated endocytosis but was markedly suppressed by 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and cytochalasin D, both of which inhibit macropinocytosis. Monensin, which inhibits endosomal acidification, also suppressed IBAV replication. To assess the inhibitory effects of these reagents on endocytosis, dextran and transferrin were used as indicators of macropinocytosis and clathrin-mediated endocytic activity, respectively. Our data confirmed that EIPA and monensin inhibited dextran uptake, and cytochalasin D inhibited the uptake of both. Additionally, we confirmed that endosomal/lysosomal acidification was inhibited by monensin. These results suggest that the macropinocytosis pathway is the major route of IBAV entry and confirm that IBAV infection of HmLu-1 cells is dependent on endosomal acidification.
Topics: Animals; Cell Line; Clathrin; Cricetinae; Cytochalasin D; Dextrans; Endocytosis; Monensin; Orbivirus; Pinocytosis; Virus Internalization
PubMed: 34174342
DOI: 10.1016/j.virusres.2021.198492 -
Acta Neurologica Scandinavica Jul 2020Comorbidity between epilepsy and heart diseases is frequent. (Review)
Review
OBJECTIVE
Comorbidity between epilepsy and heart diseases is frequent.
METHODS
All drugs classified within the group of drugs for cardiovascular system according to the Anatomical Therapeutic Chemical (ATC) classification system were reviewed for their effects on seizures or epilepsy.
RESULTS
Several agents showed antiseizure properties in animal models of seizures and/or in patients with epilepsy and only few were proconvulsant. Drugs with anticonvulsant effects include mecamylamine and guanfacine (antihypertensive drugs), indapamide, amiloride, furosemide and bumetanide (diuretics), fasudil (peripheral vasodilator), bioflavonoids (vasoprotective drug), propranolol (beta blocking agent), isradipine, nimodipine, verapamil and diltiazem (calcium channel blockers: CCBs), fosinopril and zofenopril (agents acting on the renin-angiotensin system), several statins, and fenofibrate (lipid-modifying agents). Drugs with proconvulsant properties in experimental models or in patients include reserpine, buflomedil, naftidrofuryl, and clonidine and propranolol at high doses. Drug-drug interactions (DDI) between antiseizure medications (ASMs) and drugs for cardiovascular system were also searched in two leading publicly accessible drug compendia. The most important DDIs occur between enzyme-inducing (EI) ASMs and ivabradine, ranolazine, macitenan and between EI-ASMs and the CCBs felodipine, nicardipine, nisoldipine, and verapamil. Simvastatin and atorvastatin are the lipid-modifying agents with more DDIs with EI-ASMs. Several pharmacodynamic interactions have been also documented.
DISCUSSION AND CONCLUSIONS
Available data show that the treatment of patients with epilepsy and vascular comorbidities is challenging and requires the appropriate knowledge of pharmacological properties of drugs and drug interactions.
Topics: Animals; Anticonvulsants; Cardiovascular Agents; Drug Interactions; Epilepsy; Heart Diseases; Humans
PubMed: 32259277
DOI: 10.1111/ane.13249 -
Membranes Aug 2020Macropinocytosis is a unique pathway of endocytosis characterised by the nonspecific internalisation of large amounts of extracellular fluid, solutes and membrane in... (Review)
Review
Macropinocytosis is a unique pathway of endocytosis characterised by the nonspecific internalisation of large amounts of extracellular fluid, solutes and membrane in large endocytic vesicles known as macropinosomes. Macropinocytosis is important in a range of physiological processes, including antigen presentation, nutrient sensing, recycling of plasma proteins, migration and signalling. It has become apparent in recent years from the study of specialised cells that there are multiple pathways of macropinocytosis utilised by different cell types, and some of these pathways are triggered by different stimuli. Understanding the physiological function of macropinocytosis requires knowledge of the regulation and fate of the macropinocytosis pathways in a range of cell types. Here, we compare the mechanisms of macropinocytosis in different primary and immortalised cells, identify the gaps in knowledge in the field and discuss the potential approaches to analyse the function of macropinocytosis in vivo.
PubMed: 32756454
DOI: 10.3390/membranes10080177 -
Journal of the American Society of... Apr 2024Proteinuria predicts accelerated decline in kidney function in CKD. The pathologic mechanisms are not well known, but aberrantly filtered proteins with enzymatic...
SIGNIFICANCE STATEMENT
Proteinuria predicts accelerated decline in kidney function in CKD. The pathologic mechanisms are not well known, but aberrantly filtered proteins with enzymatic activity might be involved. The urokinase-type plasminogen activator (uPA)-plasminogen cascade activates complement and generates C3a and C5a in vitro / ex vivo in urine from healthy persons when exogenous, inactive, plasminogen, and complement factors are added. Amiloride inhibits uPA and attenuates complement activation in vitro and in vivo . In conditional podocin knockout (KO) mice with severe proteinuria, blocking of uPA with monoclonal antibodies significantly reduces the urine excretion of C3a and C5a and lowers tissue NLRP3-inflammasome protein without major changes in early fibrosis markers. This mechanism provides a link to proinflammatory signaling in proteinuria with possible long-term consequences for kidney function.
BACKGROUND
Persistent proteinuria is associated with tubular interstitial inflammation and predicts progressive kidney injury. In proteinuria, plasminogen is aberrantly filtered and activated by urokinase-type plasminogen activator (uPA), which promotes kidney fibrosis. We hypothesized that plasmin activates filtered complement factors C3 and C5 directly in tubular fluid, generating anaphylatoxins, and that this is attenuated by amiloride, an off-target uPA inhibitor.
METHODS
Purified C3, C5, plasminogen, urokinase, and urine from healthy humans were used for in vitro / ex vivo studies. Complement activation was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, and ELISA. Urine and plasma from patients with diabetic nephropathy treated with high-dose amiloride and from mice with proteinuria (podocin knockout [KO]) treated with amiloride or inhibitory anti-uPA antibodies were analyzed.
RESULTS
The combination of uPA and plasminogen generated anaphylatoxins C3a and C5a from intact C3 and C5 and was inhibited by amiloride. Addition of exogenous plasminogen was sufficient for urine from healthy humans to activate complement. Conditional podocin KO in mice led to severe proteinuria and C3a and C5a urine excretion, which was attenuated reversibly by amiloride treatment for 4 days and reduced by >50% by inhibitory anti-uPA antibodies without altering proteinuria. NOD-, LRR- and pyrin domain-containing protein 3-inflammasome protein was reduced with no concomitant effect on fibrosis. In patients with diabetic nephropathy, amiloride reduced urinary excretion of C3dg and sC5b-9 significantly.
CONCLUSIONS
In conditions with proteinuria, uPA-plasmin generates anaphylatoxins in tubular fluid and promotes downstream complement activation sensitive to amiloride. This mechanism links proteinuria to intratubular proinflammatory signaling. In perspective, amiloride could exert reno-protective effects beyond natriuresis and BP reduction.
CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER
Increased Activity of a Renal Salt Transporter (ENaC) in Diabetic Kidney Disease, NCT01918488 and Increased Activity of ENaC in Proteinuric Kidney Transplant Recipients, NCT03036748 .
Topics: Humans; Mice; Animals; Urokinase-Type Plasminogen Activator; Plasminogen; Amiloride; Fibrinolysin; Diabetic Nephropathies; Inflammasomes; Mice, Inbred NOD; Proteinuria; Complement Activation; Anaphylatoxins; Fibrosis
PubMed: 38254266
DOI: 10.1681/ASN.0000000000000312 -
American Journal of Physiology. Renal... Jun 2024Ubiquitination influences the expression of the epithelial Na channel (ENaC). We assessed the mechanisms of selective ubiquitination of the mature, cleaved form of...
Ubiquitination influences the expression of the epithelial Na channel (ENaC). We assessed the mechanisms of selective ubiquitination of the mature, cleaved form of γENaC in both native rodent kidneys and in Fisher Rat Thyroid (FRT) cells expressing the channel heterologously. In both models, singly cleaved and fully cleaved γENaC were both strongly ubiquitinated, implying that the second cleavage releasing an inhibitory peptide was not essential for the process. To see if location of the protein in or near the apical membrane rather than cleavage influences ubiquitination we studied mutants of γENaC in which cleavage sites are abolished. These subunits were ubiquitinated only when co-expressed with α and βENaC, facilitating trafficking through the Golgi apparatus. To test whether reaching the apical surface is necessary we performed surface biotinylation and measured ENaC ubiquitination in the apical membrane of rat kidney. Ubiquitination of cleaved γENaC was similar in whole-kidney and surface fractions, implying that both apical and subapical channels could be modified. In FRT cells, inhibiting clathrin-mediated endocytosis with Dyngo-4a increased both total the ubiquitinated γENaC at the cell surface. Finally, we tested the idea that increased intracellular Na could stimulate ubiquitination. Administration of amiloride to block Na entry through the channels did not affect ubiquitination of γENaC in either FRT cells or rat kidney. However, presumed large increases in cellular Na produced by monensin in FRT cells or acute Na repletion in rats increased ubiquitination and decreased overall ENaC expression.
PubMed: 38867672
DOI: 10.1152/ajprenal.00037.2024 -
PloS One 2020Anxiety disorders (AD) are the most common mental conditions affecting an estimated 40 million adults in the United States. Amiloride, a diuretic agent, has shown...
Anxiety disorders (AD) are the most common mental conditions affecting an estimated 40 million adults in the United States. Amiloride, a diuretic agent, has shown efficacy in reducing anxious responses in preclinical models by inhibiting the acid-sensing ion channels (ASIC). By delivering amiloride via nasal route, rapid onset of action can be achieved due to direct "nose-to-brain" access. Therefore, this study reports the formulation, physical, chemical, and microbiological stability of an extemporaneously prepared amiloride 2 mg/mL nasal spray. The amiloride nasal spray was prepared by adding 100 mg of amiloride hydrochloride to 50 mL of sterile water for injection in a sterile reagent bottle. A stability-indicating high-performance liquid chromatography (HPLC) method was developed and validated. Forced-degradation studies were performed to confirm the ability of the HPLC method to identify the degradation products from amiloride distinctively. The physical stability of the amiloride nasal spray was assessed by pH, clarity, and viscosity assessments. For chemical stability studies, samples of nasal sprays stored at room temperature were collected at time-points 0, 3 hr., 24 hr., and 7 days and were assayed in triplicate using the stability-indicating HPLC method. Microbiological stability of the nasal spray solution was evaluated for up to 7 days based on the sterility test outlined in United States Pharmacopoeia (USP) chapter 71. The stability-indicating HPLC method identified the degradation products of amiloride without interference from amiloride. All tested solutions retained over 90% of the initial amiloride concentration for the 7-day study period. There were no changes in color, pH, and viscosity in any sample. The nasal spray solutions were sterile for up to 7 days in all samples tested. An extemporaneously prepared nasal spray solution of amiloride hydrochloride (2 mg/mL) was physically, chemically, and microbiologically stable for 7 days when stored at room temperature.
Topics: Amiloride; Drug Compounding; Drug Stability; Drug Storage; Nasal Sprays
PubMed: 32649677
DOI: 10.1371/journal.pone.0232435 -
Chemical Senses May 2020Among the 5 taste qualities, salt is the least understood. The receptors, their expression pattern in taste cells, and the transduction mechanisms for salt taste are... (Review)
Review
Among the 5 taste qualities, salt is the least understood. The receptors, their expression pattern in taste cells, and the transduction mechanisms for salt taste are still unclear. Previous studies have suggested that low concentrations of NaCl are detected by the amiloride-sensitive epithelial Na+ channel (ENaC), which in other systems requires assembly of 3 homologous subunits (α, β, and γ) to form a functional channel. However, a new study from Lossow and colleagues, published in this issue of Chemical Senses, challenges that hypothesis by examining expression levels of the 3 ENaC subunits in individual taste cells using gene-targeted mice in combination with immunohistochemistry and in situ hybridization. Results show a lack of colocalization of ENaC subunits in taste cells as well as expression of subunits in taste cells that show no amiloride sensitivity. These new results question the molecular identity of the amiloride-sensitive Na+ conductance in taste cells.
Topics: Amiloride; Animals; Epithelial Sodium Channels; Gene Expression; Humans; Immunohistochemistry; In Situ Hybridization; Protein Conformation; Taste; Taste Buds
PubMed: 32099995
DOI: 10.1093/chemse/bjaa011 -
Clinical Endocrinology Apr 2023Human physiology and epidemiology studies have demonstrated complex interactions between the renin-angiotensin-aldosterone system, parathyroid hormone and calcium... (Randomized Controlled Trial)
Randomized Controlled Trial
Evaluating the clinical and mechanistic effects of eplerenone and amiloride monotherapy, and combination therapy with cinacalcet, in primary hyperparathyroidism: A placebo-controlled randomized trial.
OBJECTIVES
Human physiology and epidemiology studies have demonstrated complex interactions between the renin-angiotensin-aldosterone system, parathyroid hormone and calcium homeostasis. Several of these studies have suggested that aldosterone inhibition may lower parathyroid hormone (PTH) levels. The objective of this study was to assess the effect of 4 weeks of maximally tolerated mineralocorticoid receptor antagonist therapy with eplerenone on PTH levels in patients with primary hyperparathyroidism (P-HPT) when compared to amiloride and placebo. We also investigated the synergistic effect of these interventions when combined with cinacalcet for an additional 2 weeks.
DESIGN
Randomized, double-blinded, three parallel-group, placebo-controlled trial.
PATIENTS
Patients with P-HPT.
RESULTS
Most patients were women (83%) and White (76%). Maximally tolerated doses of eplerenone and amiloride induced significant reductions in blood pressure and increases in renin and aldosterone production; however, despite these physiologic changes, neither intervention induced significant changes in PTH or calcium levels when compared to the placebo. Both eplerenone and amiloride therapy induced significant reductions in procollagen type 1 N-terminal propeptide levels when compared to placebo. When cinacalcet therapy was added, PTH and calcium levels were markedly reduced in all groups; however, there was no significant difference in PTH or serum calcium reductions between groups.
CONCLUSIONS
Although maximally tolerated therapy with eplerenone and amiloride induced expected changes in renin, aldosterone and blood pressure, there were no meaningful changes in PTH or serum calcium levels in P-HPT patients. These results suggest that inhibition of aldosterone action does not have a clinically meaningful role in medical therapy for P-HPT.
Topics: Humans; Female; Male; Eplerenone; Cinacalcet; Amiloride; Aldosterone; Calcium; Renin; Hyperparathyroidism, Primary; Parathyroid Hormone
PubMed: 36316798
DOI: 10.1111/cen.14840 -
Biomolecules Sep 2022P2X7 is an extracellular adenosine 5'-triphopshate (ATP)-gated cation channel present on leukocytes, where its activation induces pro-inflammatory cytokine release and...
P2X7 is an extracellular adenosine 5'-triphopshate (ATP)-gated cation channel present on leukocytes, where its activation induces pro-inflammatory cytokine release and ectodomain shedding of cell surface molecules. Human P2X7 can be partially inhibited by amiloride and its derivatives at micromolar concentrations. This study aimed to screen a library of compounds derived from amiloride or its derivative 5-(,-hexamethylene) amiloride (HMA) to identify a potential P2X7 antagonist. 6-Furopyridine HMA (6-FPHMA) was identified as a novel P2X7 antagonist and was characterized further. 6-FPHMA impaired ATP-induced dye uptake into human RPMI8226 multiple myeloma cells and human P2X7-HEK293 cells, in a concentration-dependent, non-competitive manner. Likewise, 6-FPHMA blocked ATP-induced Ca fluxes in human P2X7-HEK293 cells in a concentration-dependent, non-competitive manner. 6-FPHMA inhibited ATP-induced dye uptake into human T cells, and interleukin-1β release within human blood and CD23 shedding from RPMI8226 cells. 6-FPHMA also impaired ATP-induced dye uptake into murine P2X7- and canine P2X7-HEK293 cells. However, 6-FPHMA impaired ATP-induced Ca fluxes in human P2X4-HEK293 cells and non-transfected HEK293 cells, which express native P2Y, P2Y and P2Y. In conclusion, 6-FPHMA inhibits P2X7 from multiple species. Its poor selectivity excludes its use as a specific P2X7 antagonist, but further study of amiloride derivatives as P2 receptor antagonists is warranted.
Topics: Adenosine; Adenosine Triphosphate; Amiloride; Animals; Dogs; HEK293 Cells; Humans; Interleukin-1beta; Mice; Purinergic P2X Receptor Antagonists; Receptors, Purinergic P2X7
PubMed: 36139148
DOI: 10.3390/biom12091309