A decade of developments in diuretic drug therapy

Pharmacological blockade of aquaporin-1 water channel by AqB013 restricts migration and invasiveness of colon cancer cells and prevents endothelial tube formation in vitro

Background

Aquaporins (AQP) are water channel proteins that enable fluid fluxes across cell membranes, important for homeostasis of the tissue environment and for cell migration. AQP1 knockout mouse models of human cancers showed marked inhibition of tumor-induced angiogenesis, and in pre-clinical studies of colon adenocarcinomas, forced over-expression of AQP1 was shown to increase angiogenesis, invasion and metastasis. We have synthesized small molecule antagonists of AQP1. Our hypothesis is that inhibition of AQP1 will reduce migration and invasiveness of colon cancer cells, and the migration and tube-forming capacity of endothelial cells in vitro.

Methods

Expression of AQP1 in cell lines was assessed by quantitative (q) PCR, western blot and immunofluorescence, while expression of AQP1 in human colon tumour tissue was assessed by immunohistochemistry. The effect of varying concentrations of the AQP1 inhibitor AqB013 was tested on human colon cancer cell lines expressing high versus low levels of AQP1, using wound closure (migration) assays, matrigel invasion assays, and proliferation assays. The effect of AqB013 on angiogenesis was tested using an endothelial cell tube-formation assay.

Results

HT29 colon cancer cells with high AQP1 levels showed significant inhibition of migration compared to vehicle control of 27.9 % ± 2.6 % (p < 0.0001) and 41.2 % ± 2.7 (p <0.0001) treated with 160 or 320 μM AqB013 respectively, whereas there was no effect on migration of HCT-116 cells with low AQP1 expression. In an invasion assay, HT29 cells treated with 160 μM of AqB013, showed a 60.3 % ± 8.5 % decrease in invasion at 144 hours (p < 0.0001) and significantly decreased rate of invasion compared with the vehicle control (F-test, p = 0.001). Almost complete inhibition of endothelial tube formation (angiogenesis assay) was achieved at 80 μM AqB013 compared to vehicle control (p < 0.0001).

Conclusion

These data provide good evidence for further testing of the inhibitor as a therapeutic agent in colon cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0310-6) contains supplementary material, which is available to authorized users.

High-throughput screening for human lysosomal beta-N-Acetyl hexosaminidase inhibitors acting as pharmacological chaperones

The adult forms of Tay-Sachs and Sandhoff diseases result when the activity of beta-hexosaminidase A (Hex) falls below approximately 10% of normal due to decreased transport of the destabilized mutant enzyme to the lysosome. Carbohydrate-based competitive inhibitors of Hex act as pharmacological chaperones (PC) in patient cells, facilitating exit of the enzyme from the endoplasmic reticulum, thereby increasing the mutant Hex protein and activity levels in the lysosome 3- to 6-fold. To identify drug-like PC candidates, we developed a fluorescence-based real-time enzyme assay and screened the Maybridge library of 50,000 compounds for inhibitors of purified Hex. Three structurally distinct micromolar competitive inhibitors, a bisnaphthalimide, nitro-indan-1-one, and pyrrolo[3,4-d]pyridazin-1-one were identified that specifically increased lysosomal Hex protein and activity levels in patient fibroblasts. These results validate screening for inhibitory compounds as an approach to identifying PCs.

Pharmacokinetics and pharmacodynamics of bumetanide after intravenous and oral administration to spontaneously hypertensive rats and DOCA-salt induced hypertensive rats

The pharmacokinetics and pharmacodynamics of bumetanide were investigated after intravenous (i.v.) administration, 10 mg kg-1, and oral administration, 20 mg kg-1, to spontaneously hypertensive rats (SHRs) and deoxycorticosterone acetate-salt induced hypertensive rats (DOCA-salt rats). After i.v. administration, the pharmacokinetic and pharmacodynamic parameters of bumetanide did not vary significantly between SHRs and the control Wistar rats. Similar results were also shown between DOCA-salt rats and the control Sprague-Dawley (SD) rats. After oral administration, the AUC0-12 h decreased significantly (186 versus 335 micrograms min ml-1) in SHRs and this resulted in decreased F(15.4 versus 23.6 and 2.78 versus 5.76% using two equations) in SHRs when compared with the control Wistar rats, although none of the other pharmacokinetic parameters varied significantly between SHRs and Wistar rats. This effect seemed to be due to the decreased enterohepatic recirculation of bumetanide in SHRs: the amounts of both bumetanide and its glucuronide product, which are capable of enterohepatic recirculation, excreted in 8 h bile juice decreased significantly in SHRs (11.3 versus 37.4 micrograms as expressed in terms of bumetanide) when compared with Wistar rats. The pharmacodynamic parameters did not vary significantly between SHRs and Wistar rats after oral administration of bumetanide. The pharmacokinetic and pharmacodynamic parameters of bumetanide did not vary significantly between DOCA-salt rats and SD rats after oral administration of the drug. The liver weights compared to body weight increased significantly in SHRs when compared with Wistar rats and the corresponding values for the kidney increased significantly in DOCA-salt rats when compared with SD rats.

Influence of protein and calorie malnutrition on the pharmacokinetics and pharmacodynamics of bumetanide in rats

Bumetanide is a loop diuretic that is used for the treatment of edema and hypertension. The rapidly developing syndrome of extracellular fluid overload in some malnourished children has been successfully treated with furosemide, another loop diuretic, and digoxin; however, similar studies with bumetanide have not been conducted to date. Therefore, in the present study, the influence of dietary protein deficiency on the pharmacokinetics and pharmacodynamics of bumetanide was investigated after intravenous (i.v.) bolus and oral administration of bumetanide to male Sprague-Dawley rats fed on 23% (control rats) or 5% [protein and calorie malnutrition (PCM) rats] protein diet ad libitum for 4 weeks. After an i.v. dose of bumetanide, 1 mg/100 g body weight, the mean values of renal clearance and percentages of dose excreted as unchanged bumetanide in an 8-h urine sample were 166 and 154% higher, respectively, in PCM than control rats; however, nonrenal clearance (CLNR) was 28% lower. The decrease in nonrenal clearance in PCM rats might be because of the decrease in nonrenal metabolism of bumetanide in PCM rats. The urine output per 100 g of body weight was not significantly different between the two groups of rats after i.v. administration, although the amount of bumetanide excreted in the 8-h urine sample per 100 g body weight increased significantly in PCM rats. These results could be explained by the fact that the dose of bumetanide used results in urinary excretion rate of bumetanide at the plateau of the concentration-effect relationship.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of intravenous infusion time on the pharmacokinetics and pharmacodynamics of the same total dose of bumetanide

The pharmacokinetics and pharmacodynamics of bumetanide were evaluated after intravenous (i.v.) administration of the same total dose of bumetanide in different lengths of infusion times, 10 s (treatment I), 1 h (treatment II), and 4 h (treatment III) to rabbits. The fluid loss in urine was immediately replaced volume for volume with i.v. infusion of lactated Ringer's solution. Some pharmacokinetic parameters of bumetanide were infusion time-dependent and it might be due to the saturable metabolism of bumetanide. For example, the mean values of CL (13.6, 25.3 vs 18.2 ml min-1 kg-1), MRT (9.70, 10.6 vs 21.8 min), Vss (128, 217 vs 378 ml kg-1), and CLNR (2.71, 9.24 vs 6.44 ml min-1 kg-1) increased when the same dose of bumetanide was infused in 1 h or 4 h. However, the mean values of t1/2, and CLR were not significantly different among three treatments. The diuretic effects (urine outputs and urinary excretions of sodium and chloride) increased significantly in 1 and 4 h of infusion although the total amounts of urinary excretion of unchanged bumetanide were 21.8 and 20.5 per cent lower in treatments II and III, respectively, when compared with the value in treatment I; the mean values of 8-h urine outputs were 373, 922, and 1030 ml for 10s, 1 h, and 4 h of infusion, respectively, and the corresponding values for 24-h sodium excretions were 49.0, 82.8, and 121 mmol, and for chloride were 47.5, 71.1, and 114 mmol. It could be due to the higher diuretic efficiencies in treatments II and III. Plasma concentrations of bumetanide, and hourly urine outputs and hourly urinary excretion rates of bumetanide, sodium, potassium, and chloride during the apparent steady state (between 1 and 4 h) in the 4 h infusion study were fairly constant.

Acute and chronic effects of a diuretic monotherapy with piretanide in congestive heart failure--a placebo-controlled trial

To evaluate the acute and chronic effects of diuretic monotherapy with 3 mg piretanide bid, 46 patients (pts) with congestive heart failure (NYHA II-III) secondary to coronary artery disease were studied. Within 3 weeks of therapy, the patients lost 1.6 kg body weight. Forty-four patients reported a subjective feeling of improvement. Echocardiographically, a highly significant (p less than 0.001) reduction of diastolic and systolic diameters was found, as well as an increase of fraction shortening. Chest x-ray indicated a reduction of heart volume from 1012 +/- 263 ml to 936 +/- 233 ml (p less than 0.001). The serum potassium level remained unchanged. A subgroup of 26 pts underwent invasive hemodynamic examinations. IV injection of 6 mg piretanide resulted in an acute reduction of pulmonary wedge pressure (pc) from 20.2 +/- 5.3 mmHg to 11.9 +/- 5.0 mmHg (p less than 0.001); simultaneously a slight decrease of cardiac index from 3.2 +/- 0.6 l/min/m2 to 3.0 +/- 0.4 l/min/m2 was observed. Invasive control after 3 weeks of oral therapy showed no decline of the piretanide effect. The exercise tolerance increased clearly from 135 +/- 161 Wmin to 249 +/- 268 Wmin (p less than 0.05). A control group of further 14 pts was treated with placebo only and did not show any significant changes of pc (20.0 +/- 6.4 mmHg vs. 22.8 +/- 19.2 mmHg), exercise tolerance, or other clinical parameters. Thus, the diuretic monotherapy of congestive heart failure with piretanide is highly effective and shows a significant improvement in all clinical and hemodynamic parameters in the absence of any remarkable side effects.

Biochemical, endocrine, and mineral effects of indapamide in black women

Black women with established essential hypertension, without renal insufficiency or diabetes mellitus, were withdrawn from their usual antihypertensive therapy for 2-3 weeks prior to entry into a study to evaluate pertinent biochemical and mineral effects of indapamide treatment. Twenty patients with a sitting diastolic blood pressure greater than 90 mm Hg had baseline measurements of plasma total cholesterol, HDL cholesterol, triglycerides, glucose, uric acid, potassium, magnesium, calcium, selenium, renin, norepinephrine, whole blood ionized calcium, and glycosylated hemoglobin. Low-density lipoprotein (LDL) cholesterol was calculated by the Friedewald equation. The patients were placed on a fixed daily dose of 2.5 mg indapamide. Blood pressure and blood tests were repeated at 4, 8, and 12 weeks of treatment. The systolic and diastolic blood pressure were both lowered significantly at week 12. Plasma renin activity was significantly increased. There was no significant change in norepinephrine, glucose, glycosylated hemoglobin, uric acid, ionized calcium, calcium, triglycerides, potassium, magnesium, or selenium. Total cholesterol increased with an increase in both high-density lipoprotein (HDL) and LDL cholesterol; however, these increases did not alter significantly either the total/HDL cholesterol or LDL/HDL cholesterol ratios. It is concluded that 2.5 mg of indapamide per day effectively lowers blood pressure with no significant adverse metabolic effects.