Deposition, Clearance, and Effects of Aerosolized Amiloride in Sheep Airways<sup>1–</sup><sup>3</sup>

Wm, Mentz; Jb, Brown; Friedman, Mitchell; Mj, Stutts; Jt, Gatzy; Rc, Boucher

doi:10.1164/arrd.1986.134.5.938

Cited by 37 publications

(17 citation statements)

References 11 publications

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“…A dose of 30 mg of camostat was required to maximally enhance MCC between 5 to 7 h after compound dosing. Amiloride is rapidly cleared from sheep (Mentz et al, 1986) and human airways (Noone et al, 1997), with estimated half-lives in airway surface fluid of 10 to 23 min, respectively, and with a short pharmacodynamic action. As such, inhaled camostat represents an opportunity to achieve a prolonged mucokinetic activity in the lung relative to amiloride.…”

Section: Discussionmentioning

confidence: 99%

Camostat Attenuates Airway Epithelial Sodium Channel Function in Vivo through the Inhibition of a Channel-Activating Protease

Coote¹,

Atherton-Watson²,

Sugar³

et al. 2009

J Pharmacol Exp Ther

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Inhibition of airway epithelial sodium channel (ENaC) function enhances mucociliary clearance (MCC). ENaC is positively regulated by channel-activating proteases (CAPs), and CAP inhibitors are therefore predicted to be beneficial in diseases associated with impaired MCC. The aims of the present study were to 1) identify low-molecular-weight inhibitors of airway CAPs and 2) to establish whether such CAP inhibitors would translate into a negative regulation of ENaC function in vivo, with a consequent enhancement of MCC. To this end, camostat, a trypsin-like protease inhibitor, provided a potent (IC 50 ϳ50 nM) and prolonged attenuation of ENaC function in human airway epithelial cell models that was reversible upon the addition of excess trypsin. In primary human bronchial epithelial cells, a potency order of placental bikunin Ͼ camostat Ͼ 4-guanidinobenzoic acid 4-carboxymethyl-phenyl ester Ͼ aprotinin Ͼ Ͼ soybean trypsin inhibitor ϭ ␣1-antitrypsin, was largely consistent with that observed for inhibition of prostasin, a molecular candidate for the airway CAP. In vivo, topical airway administration of camostat induced a potent and prolonged attenuation of ENaC activity in the guinea pig trachea (ED 50 ϭ 3 g/kg). When administered by aerosol inhalation in conscious sheep, camostat enhanced MCC out to at least 5 h after inhaled dosing. In summary, camostat attenuates ENaC function and enhances MCC, providing an opportunity for this approach toward the negative regulation of ENaC function to be tested therapeutically.

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Section: Discussionmentioning

confidence: 99%

Camostat Attenuates Airway Epithelial Sodium Channel Function in Vivo through the Inhibition of a Channel-Activating Protease

Coote¹,

Atherton-Watson²,

Sugar³

et al. 2009

J Pharmacol Exp Ther

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“…An increase in MC in this assay reflects an increase in ASL volume (Mentz et al, 1986), and it was used to test the assumption that ENaC blockers increase ASL volume under physiologic, phasic respiratory motion conditions. Compound 552-02 significantly outperformed amiloride when assayed for acute effects (Fig.…”

Section: A Novel Enac Blocker For Cf Lung Disease 85mentioning

confidence: 99%

Pharmacological Properties ofN-(3,5-Diamino-6-chloropyrazine-2-carbonyl)-N′-4-[4-(2,3-dihydroxypropoxy)phenyl]butyl-guanidine Methanesulfonate (552-02), a Novel Epithelial Sodium Channel Blocker with Potential Clinical Efficacy for Cystic Fibrosis Lung Disease

Hirsh¹,

Zhang²,

Zamurs³

et al. 2008

J Pharmacol Exp Ther

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Amiloride improves mucociliary clearance (MC) by blocking airway epithelial sodium channels (ENaC) and expanding airway surface liquid (ASL). However, the low potency and rapid absorption of amiloride by airway epithelia translated into a short duration of efficacy as an aerosolized therapy for cystic fibrosis (CF) patients. To improve ENaC blocker CF pharmacotherapy, a more potent and durable ENaC blocker tailored for aerosol delivery was synthesized. Parion compound N-(3,5-diamino-6-chloropyrazine-2-carbonyl)-NЈ-4-[4-(2,3-dihydroxypropoxy)phenyl]butyl-guanidine methanesulfonate (552-02) was tested for potency and reversibility of ENaC block, epithelial absorption and biotransformation, selectivity, durability of ASL expansion under isotonic and hypertonic conditions in canine and human CF bronchial epithelial cells, and drug dissociation on ENaC in Xenopus oocytes. Short-circuit current assessed compound potency and reversibility, patch-clamp recordings of ENaC current assessed drug off-rate (k off ), a gravimetric method and confocal microscopy measured mucosal water retention and ASL height, and drug absorption and biotransformation were assessed using liquid chromatography-mass spectrometry. Amiloride and 552-02 were tested in vivo for MC activity in sheep immediately and 4 to 6 h after aerosol dosing. Compared with amiloride, compound 552-02 was 60 to 100-fold more potent, it was 2 to 5-fold less reversible, it was slower at crossing the epithelium, and it exhibited a 170-fold slower k off value. 552-02 exhibited greater ASL expansion over 8 h in vitro, and it was more effective than amiloride at increasing MC immediately and 4 to 6 h after dosing. When combining hypertonic saline and 552-02, a synergistic effect on ASL expansion was measured in canine or CF bronchial epithelia. In summary, the preclinical data support the clinical use of 552-02 ϩ/Ϫ hypertonic saline for CF lung disease.The pulmonary disease in patients with cystic fibrosis (CF) reflects genetic mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that produce defective epithelial ion transport. The CF airway epithelial ion transport abnormalities lead to a well described pathophysiological cascade that adversely affects the innate defense Article, publication date, and citation information can be found at

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“…Airway surface fluid has been collected from dogs (9), although their use ofthe airway for evaporative cooling (panting) suggests the possibility that differences between canine and human airway surface fluid may exist. Sheep and human airway surface fluid have been collected in vivo and the electrolyte concentrations in the airway fluid measured ( 10,11 ). However, this technique does not allow net ion transport rates and their regulation to be determined.…”

Section: Introductionmentioning

confidence: 99%

Fluid and electrolyte transport by cultured human airway epithelia.

Smith

Welsh²

1993

J. Clin. Invest.

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An understanding of the fluid and electrolyte transport properties of any epithelium requires knowledge of the direction, rate, and regulation of fluid transport and the composition of the fluid. Although human airway epithelia likely play a key role in controlling the quantity and composition of the respiratory tract fluid, evidence for such a role is not available. To obtain such knowledge, we measured fluid and electrolyte transport by cultured human nasal epithelia. Under basal conditions we found that epithelia absorbed Na+ and fluid; both processes were inhibited by addition of amiloride to the mucosal surface. These data suggest that active Na+ absorption is responsible for fluid absorption. Interestingly, Na+ absorption was not accompanied by the net absorption of Cl ; some other anion accompanied Na+. The combination of cAMP agonists and mucosal amiloride stimulated the secretion of NaCl-rich fluid. But surprisingly, the response to cAMP agonists in the absence of amiloride showed substantial intersubject variability: cAMP stimulated fluid secretion across some epithelia, for others, cAMP stimulated fluid absorption. The explanation for the differences in response is uncertain, but we speculate that the magnitude of apical membrane Na+ conductance may modulate the direction of fluid transport in response to cAMP. We also found that airway epithelia secrete H+ and absorb K+ under basal conditions; both processes were inhibited by cAMP agonists. Because the H+/K+-ATPase inhibitor, SCH 28080, inhibited K+ absorption, an apical membrane H+/K+-ATPase may be at least partly responsible for K+ and H+ transport. However, H+/K+ exchange could not entirely account for the luminal acidification. The finding that cAMP agonists inhibited luminal acidification may be explained by the recent finding that cAMP increases apical HCO3 conductance. These results provide new insights into how the intact airway epithelium may modify the composition of the respiratory tract fluid. (J.

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Deposition, Clearance, and Effects of Aerosolized Amiloride in Sheep Airways^1–³

Cited by 37 publications

References 11 publications

Camostat Attenuates Airway Epithelial Sodium Channel Function in Vivo through the Inhibition of a Channel-Activating Protease

Camostat Attenuates Airway Epithelial Sodium Channel Function in Vivo through the Inhibition of a Channel-Activating Protease

Pharmacological Properties ofN-(3,5-Diamino-6-chloropyrazine-2-carbonyl)-N′-4-[4-(2,3-dihydroxypropoxy)phenyl]butyl-guanidine Methanesulfonate (552-02), a Novel Epithelial Sodium Channel Blocker with Potential Clinical Efficacy for Cystic Fibrosis Lung Disease

Fluid and electrolyte transport by cultured human airway epithelia.

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Deposition, Clearance, and Effects of Aerosolized Amiloride in Sheep Airways1–3

Cited by 37 publications

References 11 publications

Camostat Attenuates Airway Epithelial Sodium Channel Function in Vivo through the Inhibition of a Channel-Activating Protease

Camostat Attenuates Airway Epithelial Sodium Channel Function in Vivo through the Inhibition of a Channel-Activating Protease

Pharmacological Properties ofN-(3,5-Diamino-6-chloropyrazine-2-carbonyl)-N′-4-[4-(2,3-dihydroxypropoxy)phenyl]butyl-guanidine Methanesulfonate (552-02), a Novel Epithelial Sodium Channel Blocker with Potential Clinical Efficacy for Cystic Fibrosis Lung Disease

Fluid and electrolyte transport by cultured human airway epithelia.

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Deposition, Clearance, and Effects of Aerosolized Amiloride in Sheep Airways^1–³