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Scientific article
English

Amiloride derivatives induce apoptosis by depleting ER Ca(2+) stores in vascular endothelial cells

Published inBritish journal of pharmacology, vol. 156, no. 8, p. 1296-1304
Publication date2009
Abstract

BACKGROUND AND PURPOSE: Amiloride derivatives are blockers of the Na(+)/H(+) exchanger (NHE) and at micromolar concentrations have protective effects on cardiac and brain ischaemia/reperfusion injury but at higher concentrations also induce apoptosis. Here, we aimed to elucidate the mechanism related to this cytotoxic action. EXPERIMENTAL APPROACH: We quantified the expression of genes associated with endoplasmic reticulum (ER) stress and measured changes in luminal ER Ca(2+) concentration ([Ca(2+)](ER)) with a 'cameleon' indicator, D1ER. KEY RESULTS: Amiloride derivatives induced apoptosis in vascular endothelial cells, an effect that increased at alkaline extracellular pH. The potency order for cytotoxicity was 5-(N,N-hexamethylene)-amiloride (HMA) > 5-(N-methyl-N-isobutyl) amiloride > 5-(N-ethyl-N-isopropyl) amiloride (EIPA) >> amiloride. HMA dose-dependently increased the transcription of the ER stress genes GADD153 and GADD34 and rapidly depleted [Ca(2+)](ER), mimicking the effects of the sarco/endoplasmic reticulum ATPase (SERCA) inhibitor thapsigargin. The NHE1-specific inhibitor HOE 694 inhibited NHE activity by 87% but did not alter [Ca(2+)](ER). The decrease in [Ca(2+)](ER) evoked by amiloride derivatives was also observed in HeLa cells and was mirrored by an increase in cytosolic Ca(2+) concentration. CONCLUSIONS AND IMPLICATIONS: Amiloride derivatives disrupt ER and cytosolic Ca(2+) homeostasis by a mechanism unrelated to NHE inhibition, most likely by interfering with the activity of SERCA. We propose that ER Ca(2+) depletion and subsequent ER stress provide a rationale framework for the apoptotic effects of amiloride derivatives.

Keywords
  • Amiloride/analogs & derivatives/*toxicity
  • Antigens, Differentiation/genetics
  • Apoptosis/*drug effects
  • Calcium/*metabolism
  • Cell Cycle Proteins/genetics
  • Diuretics/*toxicity
  • Dose-Response Relationship, Drug
  • Endoplasmic Reticulum/*drug effects/metabolism
  • Endothelial Cells/*drug effects/metabolism/pathology
  • Enzyme Inhibitors/pharmacology
  • Guanidines/pharmacology
  • HeLa Cells
  • Humans
  • Hydrogen-Ion Concentration
  • Kinetics
  • Protein Phosphatase 1
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism
  • Sodium-Hydrogen Antiporter/antagonists & inhibitors/metabolism
  • Sulfones/pharmacology
  • Thapsigargin/pharmacology
  • Transcription Factor CHOP/genetics
  • Transcription, Genetic/drug effects
Citation (ISO format)
PARK, Kyu-Sang et al. Amiloride derivatives induce apoptosis by depleting ER Ca(2+) stores in vascular endothelial cells. In: British journal of pharmacology, 2009, vol. 156, n° 8, p. 1296–1304. doi: 10.1111/j.1476-5381.2009.00133.x
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ISSN of the journal0007-1188
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