Efficacy of chlorthalidone and hydrochlorothiazide in combination with amiloride in multiple doses on blood pressure in patients with primary hypertension: a protocol for a factorial randomized controlled trial

BACKGROUND

Thiazide diuretics have demonstrated favorable blood pressure lowering efficacy, but the equivalent doses of their more common agents, chlorthalidone and hydrochlorothiazide, are still unclear. Further, concerns exist regarding adverse metabolic effects, which may be attenuated with the concomitant administration of a potassium-sparing diuretic, such as amiloride. This trial aims to investigate the efficacy of chlorthalidone and hydrochlorothiazide, in combination with amiloride at different doses, for initial management of patients with primary hypertension.

METHODS/DESIGN

This is a factorial (2 × 2) randomized double-blinded clinical trial comparing the association of a thiazide diuretic (chlorthalidone 25 mg/day or hydrochlorothiazide 50 mg/day) with a potassium-sparing diuretic (amiloride 10 mg/day or amiloride 20 mg/day) in patients with primary hypertension. The primary outcome will be the mean change from baseline in 24-h systolic and diastolic blood pressure measured by ambulatory blood pressure monitoring. The secondary outcomes will be the mean change from baseline in daytime and nighttime systolic and diastolic blood pressure measured by ambulatory blood pressure monitoring, mean change from baseline in systolic and diastolic blood pressure measured by office blood pressure, incidence of adverse events, variation of laboratory parameters, and proportion of patients who achieved blood pressure control. The follow-up will last 12 weeks. For a P alpha of 0.05, power of 80%, standard deviation of 9 mmHg, and absolute difference of 6 mmHg on systolic blood pressure on 24-h ambulatory blood pressure monitoring, it will be necessary to study a total of 76 patients. The sample size will be increased by 10% to compensate for losses, resulting in 84 patients being randomized.

DISCUSSION

Diuretics are pivotal drugs for the treatment of hypertension. Chlorthalidone and hydrochlorothiazide, in combination with amiloride in multiple doses, will be tested in terms of blood pressure lowering efficacy and safety. Since the intensity of blood pressure reduction is the major determinant of reduction in cardiovascular risk in hypertensive patients, this study will help to determine which combination of diuretics represents the most appropriate treatment for this population.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03928145. Registered on 25 April 2019. Last update on 29 April 2019.

Urokinase-type plasminogen activator (uPA) is not essential for epithelial sodium channel (ENaC)-mediated sodium retention in experimental nephrotic syndrome

AIM

In nephrotic syndrome, aberrantly filtered plasminogen (plg) is converted to active plasmin by tubular urokinase-type plasminogen activator (uPA) and thought to lead to sodium retention by proteolytic activation of the epithelial sodium channel (ENaC). This concept predicts that uPA is an important factor for sodium retention and that inhibition of uPA might be protective in nephrotic syndrome.

METHODS

Activation of amiloride-sensitive currents by uPA and plg were studied in Xenopus laevis oocytes expressing murine ENaC. In doxorubicin-induced nephrotic mice, uPA was inhibited pharmacologically by amiloride and genetically by the use of uPA-deficient mice (uPA^-/- ).

RESULTS

Experiments in Xenopus laevis oocytes expressing murine ENaC confirmed proteolytic ENaC activation by a combination of plg and uPA which stimulated amiloride-sensitive currents with concomitant cleavage of the ENaC γ-subunit at the cell surface. Treatment of nephrotic wild-type mice with amiloride inhibited urinary uPA activity, prevented urinary plasmin formation and sodium retention. In nephrotic mice lacking uPA (uPA^-/- ), urinary plasmin formation from plg was suppressed and urinary uPA activity absent. However, in nephrotic uPA^-/- mice, sodium retention was not reduced compared to nephrotic uPA^+/+ mice. Amiloride prevented sodium retention in nephrotic uPA^-/- mice which confirmed the critical role of ENaC in sodium retention.

CONCLUSION

uPA is responsible for the conversion of aberrantly filtered plasminogen to plasmin in the tubular lumen in vivo. However, uPA-dependent plasmin generation is not essential for ENaC-mediated sodium retention in experimental nephrotic syndrome.

Resistant Hypertension: A Clinical Perspective

Resistant hypertension is a common clinical entity, defined as suboptimal blood pressure response to multiple therapies after excluding medication nonadherence and secondary forms of hypertension. Patients with resistant hypertension generally share several comorbidities. Resistant hypertension is more common in individuals of African descent. Blood pressure should be optimized using multiple strategies, including lifestyle changes and single-pill combination therapies, with the aim of reducing cardiovascular events while reducing side effects from using antihypertensive therapy. A renin/aldosterone-based diagnostic and treatment approach will help tailor therapy. The use of mineralocorticoid receptor antagonists or amiloride as appropriate is favored.

6-Substituted amiloride derivatives as inhibitors of the urokinase-type plasminogen activator for use in metastatic disease

The oral K+-sparing diuretic amiloride shows anti-cancer side-activities in multiple rodent models. These effects appear to arise, at least in part, through moderate inhibition of the urokinase-type plasminogen activator (uPA, K_i = 2.4 µM), a pro-metastatic trypsin-like serine protease that is upregulated in many aggressive solid malignancies. In applying the selective optimization of side-activity (SOSA) approach, a focused library of twenty two 6-substituted amiloride derivatives were prepared, with multiple examples displaying uPA inhibitory potencies in the nM range. X-ray co-crystal structures revealed that the potency increases relative to amiloride arise from increased occupancy of uPA's S1β subsite by the appended 6-substituents. Leading compounds were shown to have high selectivity over related trypsin-like serine proteases and no diuretic or anti-kaliuretic effects in rats. Compound 15 showed anti-metastatic effects in a xenografted mouse model of late-stage lung metastasis.

Antiviral effect of amiloride on replication of foot and mouth disease virus in cell culture

Recently, amiloride was shown to potently suppress Coxsackievirus B3 (CVB3) replication. In the current study, we investigated whether amiloride could also exhibit antiviral activity against foot-and-mouth disease virus (FMDV), which belongs to the same family (Picornaviridae) as CVB3. We found that amiloride exerted antiviral activity in a dose-dependent manner against two strains of FMDV in IBRS-2 cells, with slight cytotoxicity at 1000 μM. Besides, amiloride did not inhibit the attachment and entry of FMDV in IBRS-2 cells, but prevented early viral replication. These data implied that amiloride could be a promising candidate for further research as a potential antiviral drug against FMDV infection.

Long-term BP control and vascular health in patients with hyperaldosteronism treated with low-dose, amiloride-based therapy

Whether aldosterone itself contributes directly to macro- or microcirculatory disease in man or to adverse cardiovascular outcomes is not fully known. We report our long-term single-practice experience in 5 patients with chronic hyperaldosteronism (HA, including 3 with glucocorticoid remediable aldosteronism, GRA) treated with low-dose amiloride (a specific epithelial sodium channel [ENaC] blocker) 5-10 (mean 7) mg daily for 14-28 (mean 20) years. Except for 1 GRA diagnosed in infancy, all had severe resistant hypertension. In each case, BP was normal or near-normal within 1-4 weeks after starting amiloride and office BP's were well controlled for 20 years thereafter. Vascular studies and 24-hour ambulatory BP monitoring with pulse wave analysis (cardiac output, vascular resistance, augmentation index, and reflection magnitude) were assessed after a mean of 18 years as were regional pulse wave velocities, pulse stiffening ratio, ankle-brachial index, serum creatinine, estimated glomerular filtration rate, and spot urinary albumin:creatinine ratio. All indicators were completely normal in all patients after 18 years of amiloride, and none had a cardiovascular event during the 20-year mean follow-up. We conclude that long-term ENaC blockade can normalize BP and protect macro- and microvascular function in patients with HA. This suggests that (a) any vasculopathic effects of aldosterone are mediated via ENaC, not MR activation itself, and are fully preventable or reversible with ENaC blockade or (b) aldosterone may not play a major BP-independent role in human macro- and microcirculatory diseases. These and other widely divergent results in the literature underscore the need for additional studies regarding aldosterone, ENaC, and vascular disease.

Effects of amiloride on physiological activity of stem cells of human lung cancer and possible mechanism

Lung cancer is a common malignant tumor, the cancer stem cells (CSCs) were regarded responsible for the development of cancer tissue. The effects of amiloride on lung cancer stem cells and the possible mechanism were not much investigated. In this study, human NCI-H1975 lung CSCs were selected by flow cytometry, and the effects of amiloride at different concentrations (0, 12.5, 25, 50, and 100 μmol/L) were evaluated on proliferation, migration, invasion and apoptosis of CSCs using cell counting kit-8 and Transwell migration assays as well as flow cytometry. Wstern blot analysis was performed to investigate the effect of amiloride on the level of proteins in uPA system, NF-kB pathway, and PI3K-AKT-mTOR pathway in CSCs. As a result, we found that amiloride inhibited proliferation, migration and invasion of lung CSCs, and promoted apoptosis. Further, we found that amiloride decreased levels of target proteins in the uPA system, as well as the NF-kB and PI3K-AKT-mTOR pathways. These results indicated that amiloride could inhibit proliferation, migration and invasion of lung CSCs, and promotes apoptosis, these effects may be related to decreased levels of proteins in the uPA system, the NF-kB pathway, and the PI3K-AKT-mTOR pathway.

The Heptahelical Domain of the Sweet Taste Receptor T1R2 Is a New Allosteric Binding Site for the Sweet Taste Modulator Amiloride That Modulates Sweet Taste in a Species-Dependent Manner

The activity of sweet taste receptor (heterodimeric T1R2 and T1R3) can be modulated by sweet regulators. The compound amiloride can inhibit the sweet sensitivity of the human sweet taste receptor. This study describes the species-dependent regulation of the response of sweet taste receptors by this sweet inhibitor. Amiloride inhibited the sweet taste response of humans and mice but not that of squirrel monkeys. Using human/squirrel monkey/mouse chimeric T1R2 and T1R3 receptors as well as the agonist perillartine (which can activate the single heptahelical domain of T1R2), we found that the heptahelical domain of T1R2 is the molecular determinant that mediates the species-dependent sensitivity to this sweet regulator. Compared to the sweet inhibitor lactisole (which acts on T1R3), amiloride has a different allosteric binding site on the sweet receptor, which is important new information for the design of novel sweet taste modulators that act on T1R2.

Impact of ultrasonication techniques on the preparation of novel Amiloride-nanoemulsion used for intranasal delivery in the treatment of epilepsy

AIM

To develop a nanoemulsion-nanoformulation in order to enhance brain bioavailability for Amiloride (Amilo) via intranasal (i.n.) drug delivery in the brain.

MATERIAL AND METHODS

Oleic Acid, Tween-20 and Carbitol were selected as oil, surfactant and co-surfactant, respectively. For nanoemulsion preparation, an aqueous micro titration method followed by a high energy ultra-sonication method was used whereas three-factor three-level central composite design was employed to get the best formulation. The independent variables selected for the optimization were %oil, % Surfactant and co-surfactant (S_mix) and sonication time (seconds).

RESULTS

Based on the constraints applied for independent and dependent variables, the optimized formulation was selected with 2.5% oil, 10% S_mix and a sonication time of 45 s. The experimental values observed for dependent variables such as hydrodynamic diameter (nm), % transmittance and % cumulative drug release were found to be 89.36 ± 11.18 nm, 99.23 ± 0.84% and 80.36 ± 5.48%, respectively. Results showed; a spherical shape (transmission electron microscopy and scanning electron microscopy - assisted morphological characterization), polydispersity index (0.231 ± 0.018), zeta potential (-9.83 ± 0.12 mV), refractive index (1.38 ± 0.042), viscosity (41 ± 5 cp), pH (6.4 ± 0.18) and drug content of 98.28 ± 0.29%, for optimized Amiloride-loaded-Nanoemulsion (Amilo-NE). For bioavailability evaluation, ultra-performance liquid chromatography-mass spectroscopy based bioanalytical method was developed and validated for pharmacokinetics, biodistribution, brain-targeting efficiency (1992.67 ± 45.63%) and nose-to-brain transport (586.18 ± 11.63%) whereby an enhanced Amilo-brain bioavailability was observed as compared to intravenous administration (i.v.). Furthermore, Amilo-NE enhanced the treatment in seizure threshold i.e. both rodent models of epilepsy (increasing current electroshock and pentylenetetrazole) induced seizures in mice.

CONCLUSION

A significant role of Amilo-NE as observed after high targeting potential and efficiency of the formulation supports the easy brain targeting for Amilo-NE.

Ocean acidification: effects of pH on 45Ca uptake by lobster branchiostegites

Gill chambers of the Atlantic lobster, Homarus americanus, possess three structures that are involved with respiration and ion regulation: gill filaments, epipodites, and branchiostegites. This paper describes ion transport mechanisms present in the plasma membranes of branchiostegite epithelial cells and the effects of pH on the uptake of ⁴⁵Ca by these processes. Partially purified membrane vesicles (PPMV) of branchiostegite cells were produced by a homogenization/centrifugation method that has previously been used to define ion transport processes in both crab and lobster gill tissues. In the present study, lobster branchiostegite PPMV ⁴⁵Ca uptake was highest at pH 8.5 and lowest at pH values between 6.0 and 7.0 (p < 0.02). At pH 8.0, ⁴⁵Ca uptake was a biphasic process consisting of a saturable process at low [Ca] and a linear process at higher [Ca]. At pH 6.0, ⁴⁵Ca uptake was only a linear process and paralleled linear uptake at pH 8.0. A valinomycin/K⁺-induced membrane potential (PD, inside negative) doubled ⁴⁵Ca uptake at pH 7.0 above that in the absence of a PD (p < 0.05). An induced PD at pH 8.0 did not significantly (p > 0.05) affect ⁴⁵Ca uptake observed in the absence of a PD, but was threefold greater than uptake at pH 7.0 in the absence of a PD (p < 0.05). Amiloride (2 mM) did not affect ⁴⁵Ca uptake at pH 8.0, but 2 mM amiloride + 100 µM verapamil reduced uptake by approximately 50%. In the presence of both 2 mM amiloride + 100 µM verapamil, 15 s ⁴⁵Ca influx at pH 8.5 was a hyperbolic function of [Ca] (0.1-5 mM) (K_m = 4.2 ± 0.3 mM; J_max = 9792 ± 439 pmol/mg protein × 15 s). ⁴⁵Ca influxes at pH 7.5 under the same conditions were also hyperbolic with K_m = 8.3 ± 1.4 mM; J_max = 10732 ± 1250 pmol/mg protein × 15 s. K_m values were significantly different (p < 0.05), but J_max values were not (p > 0.05). These results suggest that ⁴⁵Ca uptake by lobster branchiostegites may have occurred by the combination of diffusion through a verapamil-inhibited calcium channel and carrier-mediated transport by amiloride-insensitive, electroneutral, 1Ca²⁺/2H⁺ antiporters. Decreased pH, as might occur during ocean acidification, did not appear to modify calcium diffusion through the channels, but protons acted as competitive inhibitors of calcium transport by carrier-mediated antiport. Decreased calcium uptake with continued ocean acidification may significantly affect calcification processes during periodic molting, potentially influencing mortality.

The Effects of Diuretics on Mineral and Bone Metabolism

The effects of diuretics on water and electrolyte metabolism are well-established, but less known to the clinician are their effects on bone and mineral metabolism, and in particular on that of calcium homeostasis. In general, and clinically most relevant, diuretics acting at the thick ascending limb of the loop of Henle cause loss of calcium into the urine, thus making them a useful tool in treating hypercalcemia. However the hypercalciuria caused by loop diuretics may lead to the development of urolithiasis and nephrocalcinosis, as well as secondary hyperparathyroidism and bone disease. On the other hand, thiazide diuretics that act more distally, increase tubular calcium reabsorption, thus providing protection against hypercalciuria, and with that may raise serum calcium, suppress PTH secretion and improve bone metabolism. Additional hypocalciuric effect may be observed with the use of potassium-sparing diuretics. This review will address the effects of diuretics on mineral metabolism in the kidney and consequently on systemic mineral and bone metabolism.

Capsaicin Used on Skin Influences Ion Transport Pathways: An in vitro Study

Acute, adverse skin effects to capsaicin can be activated by inhibition of sodium transport not only in nociceptive neurons, but also in keratinocytes. The aim of the current study was to describe and compare immediate (15 s) and prolonged (30 min) effects of capsaicin on epidermal (not neural) sodium transport using a rabbit skin model. Skin fragments (n = 169) were incubated in 4 conditions: undisturbed ion transport (U; n = 48); inhibited sodium transport (INa; n = 34) with amiloride used as sodium transport blocker; long-term irritation by capsaicin with undisturbed ion transport (CAPSA-U; n = 43) and with inhibited sodium transport (CAPSA-INa; n = 35). After 30 min of incubation, a solution of capsaicin was applied directly to the skin fragments. The study demonstrated that sodium transport inhibition eliminated the effects of both immediate and prolonged capsaicin application. The results could be the basis for future research considering selective sodium transport inhibitors for human skin to reduce the side effects of capsaicin, related to activation of sodium channels in keratinocytes.

[Immunomodulation and neuroprotection in optic neuritis]

BACKGROUND

To date, high-dose corticosteroids constitute the only established treatment of acute optic neuritis (ON); however, steroids cannot prevent the loss of retinal nerve fibers. New acute therapeutic drugs are therefore being sought for a reduction of ganglion cell death.

METHODS

Literature search comprising clinical studies on treatment of ON with immunomodulatory and neuroprotective drugs.

RESULTS

For the immunomodulatory drug simvastatin some evidence for long-term benefits was shown, particularly regarding visual evoked potentials. For the neuroprotective substance memantine a potential positive effect on retinal nerve fiber layer (RNFL) thickness was revealed. Likewise in one publication a reduction in loss of RNFL thickness could be demonstrated for erythropoietin and this drug is currently being extensively investigated in a phase III randomized controlled trial (RCT). The results of studies with phenytoin, amiloride and anti-leucine-rich repeat and immunoglobulin domain containing 1 protein (anti-LINGO-1) antibodies are awaiting publication.

CONCLUSION

According to the data from recent treatment trials, there is hope that neuronal loss in ON can be reduced with the help of immunomodulatory substances, such as simvastatin or neuroprotective agents, such as memantine and erythropoietin.

Amiloride interferes with platelet- activating factor-induced respiratory burst and MMP-9 release in bovine neutrophils independent of Na+/H+ exchanger 1

Cytoplasmic pH homeostasis is required for an appropriate response in polymorphonuclear neutrophils (PMNs). In these cells, chemotaxis and reactive oxygen species (ROS) production are reduced by the use of Na⁺/H⁺ exchanger (NHE-1) inhibitors, but these results are mainly obtained using amiloride, a non-selective NHE-1 inhibitor. In bovine PMNs, the role of NHE-1 in functional responses has not been confirmed yet. The aim of this study was to determine the role of NHE-1 using amiloride and zoniporide in pH regulation, ROS production, matrix metalloproteinase 9 (MMP-9) release and calcium flux in bovine PMNs induced by the platelet activation factor (PAF), additionally we evaluated the presence of NHE-1 and NHE-2 mRNA Our data show the presence only of NHE-1 but not NHE-2 in bovine PMNs. Amiloride or zoniporide inhibited the intracellular alkalization induced by PAF without affecting calcium flux. Amiloride diminished ROS production and MMP-9 release, while zoniporide enhanced ROS production without change the MMP-9 release induced by PAF. Our work led us to conclude that changes in intracellular pH induced by PAF are regulated by NHE-1 in bovine neutrophils, but the effects of amiloride on ROS production and MMP-9 release induced by PAF are not NHE-1 dependent.

Salt controls feeding decisions in a blood-sucking insect

Salts are necessary for maintaining homeostatic conditions within the body of all living organisms. Like with all essential nutrients, deficient or excessive ingestion of salts can result in adverse health effects. The taste system is a primary sensory modality that helps animals to make adequate feeding decisions in terms of salt consumption. In this work we show that sodium and potassium chloride salts modulate the feeding behavior of Rhodnius prolixus in a concentration-dependent manner. Feeding is only triggered by an optimal concentration of any of these salts (0.1-0.15M) and in presence of the phagostimulant ATP. Conversely, feeding solutions that do not contain salts or have a high-salt concentration (>0.3M) are not ingested by insects. Notably, we show that feeding decisions of insects cannot be explained as an osmotic effect, because they still feed over hyperosmotic solutions bearing the optimal salt concentration. Insects perceive optimal-salt, no-salt and high-salt solutions as different gustatory information, as revealed the electromyogram recordings of the cibarial pump. Moreover, because insects do a continuous gustatory monitoring of the incoming food during feeding, sudden changes beyond the optimal sodium concentration decrease and even inhibit feeding. The administration of amiloride, a sodium channel blocker, noticeably reduces the ingestion of the optimal sodium solution but not of the optimal potassium solution. Salt detection seems to occur at least through two salt receptors, one amiloride-sensitive and another amiloride-insensitive. Our results confirm the importance of the gustatory system in R. prolixus, showing the relevant role that salts play on their feeding decisions.

Simultaneous quantification of amiloride and hydrochlorothiazide in human plasma by liquid chromatography-tandem mass spectrometry

A selective, sensitive and precise assay based on solid phase extraction and liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed for the simultaneous determination of amiloride (AMI) and hydrochlorothiazide (HCTZ) in human plasma. Sample clean-up with 250 µL of plasma was done on Phenomenex Strata™-X extraction cartridges using their labeled internal standards (AMI-15N3 and HCTZ-13C,d2). Chromatography was performed on Hypersil Gold C₁₈ (50 mm×3.0 mm, 5 µm) column using acetonitrile with 4.0 mM ammonium formate (pH 4.0, adjusted with 0.1% formic acid) (80:20, v/v) as the mobile phase. Detection was carried out on a triple quadrupole API 5500 mass spectrometer utilizing an electrospray ionization interface and operating in the positive ionization mode for AMI and negative ionization mode for HCTZ. Multiple reaction monitoring was used following the transitions at m/z 230.6/116.0, m/z 233.6/116.0, m/z 296.0/204.9 and m/z 299.0/205.9 for AMI, AMI-15N3, HCTZ and HCTZ-13C,d2, respectively. Calibration curves were linear (r²≥0.9997) over the concentration range of 0.050–50.0 and 0.50–500 ng/mL for AMI and HCTZ, respectively, with acceptable accuracy and precision. The signal-to-noise ratio at the limit of quantitation was ≥14 for both the analytes. The mean recovery of AMI and HCTZ from plasma was 89.0% and 98.7%, respectively. The IS-normalized matrix factors determined for matrix effect ranged from 0.971 to 1.024 for both the analytes. The validated LC–MS/MS method was successfully applied to a bioequivalence study using 5 mg AMI and 50 mg HCTZ fixed dose tablet formulation in 18 healthy Indian volunteers with good reproducibility.

Chlorthalidone Plus Amiloride Reduces the Central Systolic Blood Pressure in Stage 1 Hypertension Patients

BACKGROUND

Hypertension reduction strategies use blood pressure in the brachial artery as the primary endpoint. Individuals who achieve the target blood pressure reduction with antihypertensive treatment have residual cardiovascular risk attributed to the difference in pressure between the aorta and brachial artery. Antihypertensive treatment affects the intrinsic properties of the vascular wall and arterial stiffness markers and consequently the central pressure. Recent publications stress the importance of adequate control of the central compared to peripheral blood pressure. Related clinical implications suggest that individuals with normal peripheral but high central blood pressure should not receive antihypertensive drugs that act on the central pressure. Therefore, they are at greater cardiovascular risk. The aim of the study was to evaluate the effect of treatment with a thiazide diuretic versus losartan on the central blood pressure in stage 1 hypertensive patients.

METHODS

Twenty-five patients were randomized to the chlorthalidone 25 mg/amiloride 5 mg group (q.d.) and 25 patients received losartan 50 mg (b.i.d). The central systolic blood pressure (CSBP) and augmentation index (AIx 75) were assessed using applanation tonometry. The paired t-test was used to compare the systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure (PP), CSBP and AIx 75 between the thiazide and losartan groups at baseline and after 6 months of treatment.

RESULTS

Significant reductions in CSBP (123.3 ± 14.2 vs. 113.4 ± 111.4, P = 0.0103) and AIx 75 (87.7 ± 9.6 vs. 83.8 ± 8.9, P = 0.0289) were observed after 6 months of drug treatment with chlorthalidone 25 mg/amiloride 5 mg (q.d.). The administration of losartan 50 mg (b.i.d) did not reduce the CSBP and there were insignificant changes in the AIx 75.

CONCLUSIONS

Six-month treatment of chlorthalidone/amiloride but not losartan reduces the CSBP and AIx 75 in adults with stage 1 hypertension.

A modulatory role of ASICs on GABAergic synapses in rat hippocampal cell cultures

Rapid acidification occurring during synaptic vesicle release can activate acid-sensing ion channels (ASICs) both on pre- and postsynaptic neurons. In the latter case, a fraction of postsynaptic current would be mediated by cation-selective acid-sensing ion channels. Additionally, in both cases, activation of acid-sensing ion channels could modulate synaptic strength by affecting transmitter release and/or sensitivity of postsynaptic receptors. To address potential involvement of acid-sensing ion channels in mediation/modulation of synaptic transmission at hippocampal GABAergic synapses, we studied effects of three structurally different blockers of acid-sensing ion channels on evoked postsynaptic currents using the patch-clamp technique. We found that GABAergic postsynaptic currents, recorded below their reversal potential as inward currents, are suppressed by all the employed blockers of acid-sensing ion channels. These currents were suppressed by ~ 20 % in the presence of a novel blocker 5b (1 μM) and by ~30 % in the presence of either amiloride (25 μM) or diminazene (20 μM). In the same cells the suppression of postsynaptic currents, recorded above their reversal potential as outward currents was statistically insignificant. These results imply that the effects of blockers in our experiments are at least partially postsynaptic. On the other hand, in the case of mediation of a fraction of postsynaptic current by acid-sensing ion channels, an increase of outward currents would be expected under our experimental conditions. Our analysis of a bicuculline-resistant fraction of postsynaptic currents also suggests that effects of the blockers are predominantly modulatory. In this work we present evidence for the first time that acid-sensing ion channels play a functional role at hippocampal GABAergic synapses. The suppressing effect of the blockers of acid-sensing ion channels on GABAergic transmission is due, at least partially, to a postsynaptic but (predominantly) modulatory mechanism. We hypothesize that the modulatory effect is due to functional crosstalk between ASICs and GABA_A-receptors recently reported in isolated neurons, however, verification of this hypothesis is necessary.

Changes in selected metabolic parameters in patients over 65 receiving hydrochlorothiazide plus amiloride, atenolol or placebo in the MRC elderly trial

Background

Treatment of hypertension reduces incidence of stroke, myocardial infarction and heart failure perhaps partly by controlling different metabolic parameters. There is limited information regarding the changes in potassium, sodium, weight, cholesterol and glucose levels in patients using anti-hypertensives. This study aimed to determine changes in potassium, sodium, glucose, cholesterol, weight, urea and urate levels in patients using anti-hypertensives. Furthermore, to describe these changes and differences between the atenolol, hydrochlorothiazide plus amiloride and placebo arms of the Medical Research Council (MRC) elderly randomised controlled trial.

Methods

Patients were randomly allocated to one of the three treatment arms. Measurements were taken at baseline, end of year one and end of year two in 4396 subjects. Linear Mixed Models (LMM) were used to determine the longitudinal profiles of sodium, potassium, weight, cholesterol, glucose, urea and urate. Estimates of changes within groups and difference between groups were obtained.

Results

Patients randomised to receive hydrochlorothiazide + amiloride experienced a significantly greater mean reduction in potassium, sodium and weight compared to placebo at end of year one - mean differences in change −0.18 mmol/L, (95 % CI: −0.21, −0.15); −1.45 mmol/L, (95 % CI: −1.62, −1.29) and −0.46 kgs (95 % CI: −0.73, −0.20) respectively, and greater increases in cholesterol, urea and urate - mean differences in change 0.16 mmol/L, (95 % CI: 0.10,0.22); 0.77 mmol/L, (95 % CI: 0.68, 0.87) and 53.10 μmol/L, (95 % CI: 49.35, 56.85) respectively. Changes were in the same direction but smaller in the atenololarm except for potassium and weight (increases). No group differences in glucose were found.

Conclusion

Results were in line with expectation except for lack of change in glucose in the hydrochlorothiazide + amiloride arms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0368-2) contains supplementary material, which is available to authorized users.

Properties of acid-induced currents in mouse dorsal root ganglia neurons

Acid‐sensing ion channels (ASICs) are cation channels that are activated by protons (H⁺). They are expressed in neurons throughout the nervous system and may play important roles in several neurologic disorders including inflammation, cerebral ischemia, seizures, neurodegeneration, anxiety, depression, and migraine. ASICs generally produce transient currents that desensitize in response to a decrease in extracellular pH. Under certain conditions, the inactivation of ASICs can be incomplete and allow them to produce sustained currents. Here, we characterize the properties of both transient and sustained acid‐induced currents in cultured mouse dorsal root ganglia (DRG) neurons. At pH levels between 7.3 and 7.1 they include “window currents” through ASICs. With stronger acid signals sustained currents are maintained in the absence of extracellular Na⁺ or the presence of the ASIC blockers amiloride and Psalmotoxin‐1(PcTx1). These sustained responses may have several different origins in these cells, including acid‐induced stimulation of inward Cl⁻ currents, block of outward K⁺ currents, and augmentation of inward H⁺ currents, properties that distinguish these novel sustained currents from the well‐characterized transient currents.

Cardioprotective role of peroxisome proliferator-activated receptor-γ agonist, rosiglitazone in a unique murine model of diabetic cardiopathy

AIMS

Rosiglitazone (RSZ), a PPARγ agonist was potent efficacious insulin sensitizing blockbuster drug for treatment of Type 2 diabetes mellitus (T2DM) but the benefit of PPARγ activation in congestive heart failure (CHF) was controversial. The present work was planned to study the role of RSZ in diabetic cardiopathy.

MAIN METHODS

Zucker fa/fa rats, the genetic model of T2DM were subjected to constriction of suprarenal abdominal aorta so that they represent a combined model of diabetes and cardiopathy. The development cardiopathy was assessed biochemically (plasma BNP and aldosterone levels), using echocardiography and expression angiotensin II receptor type 1a gene in heart and Endothelin-1 gene in aorta. Rats were treated with RSZ and in combination with amiloride for four weeks and were assessed to evaluate the effect of RSZ or amiloride or its combination on antidiabetic activity, adverse or toxic effects and congestive heart failure status.

KEY FINDINGS

RSZ shows its anti-diabetic effect from 0.3mg/kg dose onwards and at 3mg/kg dose levels it caused beneficial effects (reduction of blood pressure) on cardiovascular system and at highest (30mg/kg) dose it starts showing adverse effects like body weight gain, edema, left ventricular hypertrophy. However, when highest dose of RSZ animals were treated with amiloride (ENaC inhibitor) at 2mg/kg the reversal of the adverse effects was evident, indicating the combination of RSZ and amiloride is beneficial in diabetic cardiopathy model.

SIGNIFICANCE

RSZ and amiloride combination appeared promising treatment in diabetic patients with cardiopathy without any side effect.

Effects of Cr(3+) ions on electrophysiological parameters of isolated skin of toad Pleurodema thaul

In view of the toxicity of chromium (Cr³⁺) ions, it was explored the damaging effects that this ion could induce in cell membranes. The measurement of the effects induced by Cr³⁺ ions on electrophysiological parameters of short-circuit current and on the potential difference were investigated using the outer side (mucosal) and the inner side (serosal) of toad Pleurodema thaul skin. The results showed a decreased on electrophysiological parameters when it were administered concentrations of 33, 100 and 200 μM of Cr³⁺, the results also suggest that the administration of Cr³⁺ inhibits the ion transport in toad skin by the interaction of Cr³⁺ with lipid bilayers or protein constituents of membrane, and not by an inhibition of the active transport of ions across Na⁺ channels.

SFE/SFHTA/AFCE consensus on primary aldosteronism, part 7: Medical treatment of primary aldosteronism

Spironolactone, which is a potent mineralocorticoid receptor antagonist, represents the first line medical treatment of primary aldosteronism (PA). As spironolactone is also an antagonist of the androgen and progesterone receptor, it may present side effects, especially in male patients. In case of intolerance to spironolactone, amiloride may be used to control hypokaliemia and we suggest that eplerenone, which is a more selective but less powerful antagonist of the mineralocorticoid receptor, be used in case of intolerance to spironolactone and insufficient control of hypertension by amiloride. Specific calcic inhibitors and thiazide diuretics may be used as second or third line therapy. Medical treatment of bilateral forms of PA seem to be as efficient as surgical treatment of lateralized PA for the control of hypertension and the prevention of cardiovascular and renal morbidities. This allows to propose medical treatment of PA to patients with lateralized forms of PA who refuse surgery or to patients with PA who do not want to be explored by adrenal venous sampling to determine whether they have a bilateral or lateralized form.

Clinical Utility of Potassium-Sparing Diuretics to Maintain Normal Serum Potassium in Peritoneal Dialysis Patients

♦ BACKGROUND: Hypokalemia is a vexing problem in end-stage renal disease patients on peritoneal dialysis (PD), and oral potassium supplements (OPS) have limited palatability. Potassium-sparing diuretics (KSD) (spironolactone, amiloride) may be effective in these patients. ♦ METHODS: We performed a cross-sectional review of 75 current or past (vintage > 6 months) PD patients with regard to serum potassium (K+), OPS, and KSD utilization. We reviewed charts for multiple clinical and laboratory variables, including dialysis adequacy, residual renal function, nutritional status and co-existing medical therapy. ♦ RESULTS: The cohort was middle-aged with a mean age of 49.2 years (standard deviation [SD] = 14.7) and overweight with a body mass index of 29.5 (6.7) kg/m². Of all the participants, 57.3% were female, 73.3% African-American, and 48% diabetic with an overall PD vintage of 28.2 (24.3) months at the time of enrollment. Weekly Kt/V was 2.12 (0.43), creatinine clearance was 73.5 (33.6) L/week/1.73 m² with total daily exchange volume of 10.8 (2.7) L. Residual urine output (RUO) measured at 440 (494) mL (anuric 30.6%). Three-month averaged serum K⁺ measured at 4 (0.5) mmol/L with 36% of the participants receiving K⁺ supplements (median: 20 [0;20] mmol/day) and 41.3% KSD (spironolactone dose: 25 - 200 mg/day; amiloride dose: 5 - 10 mg/day). Serum K⁺ correlated positively with weekly Kt/V (r = 0.239; p = 0.039), PD vintage (r = 0.272; p = 0.018) but not with PD modality, daily exchange volume, RUO, or KSD use. However, KSD use was associated with decreased use of OPS (r = -0.646; p < 0.0001). ♦ CONCLUSIONS: Potassium-sparing diuretics were effective in this cohort of PD patients and decreased the need for OPS utilization.

Contribution of concentration-sensitive sodium channels to the absorption of alveolar fluid in mice

The concentration-sensitive sodium channel (Nac) is activated by an increase in the extracellular sodium concentration. Although the expression of Nac in alveolar type II epithelial cells (AEC II) has been reported previously, the physiological role of Nac in the lung has not been established. We characterized Nac expression and examined amiloride-insensitive sodium transport mediated by Nac in mouse lung. Immunofluorescence studies revealed that Nac did not colocalize with either aquaporin 5 or cystic fibrosis transmembrane conductance regulator, but partially colocalized with the epithelial sodium channel γ-subunit. Immunoelectron microscopy studies showed that Nac localized at the basolateral membrane of pulmonary microvascular endothelial cells (PMVECs). Nac mRNA and protein were expressed in PMVECs isolated from the lungs of mice. Image analysis indicated that sodium influx into the alveolar wall was dependent on increases in extracellular sodium concentration. We conclude that Nac expressed in PMVECs and AEC II contributes to the reabsorption of sodium via an amiloride-insensitive pathway during alveolar fluid clearance.