Lung Beractant Increases Free Cytosolic Levels of Ca2+ in Human Lung Fibroblasts

PLoS One. 2015 Jul 31;10(7):e0134564. doi: 10.1371/journal.pone.0134564. eCollection 2015.

Abstract

Beractant, a natural surfactant, induces an antifibrogenic phenotype and apoptosis in normal human lung fibroblasts (NHLF). As intracellular Ca2+ signalling has been related to programmed cell death, we aimed to assess the effect of beractant on intracellular Ca2+ concentration ([Ca2+]i) in NHLF in vitro. Cultured NHLF were loaded with Fura-2 AM (3 μM) and Ca2+ signals were recorded by microfluorimetric techniques. Beractant causes a concentration-dependent increase in [Ca2+]i with a EC50 of 0.82 μg/ml. The application of beractant, at a concentration of 500 μg/ml, which has been shown to exert an apoptotic effect in human fibroblasts, elicited different patterns of Ca2+ signals in NHLF: a) a single Ca2+ spike which could be followed by b) Ca2+ oscillations, c) a sustained Ca2+ plateau or d) a sustained plateau overlapped by Ca2+ oscillations. The amplitude and pattern of Ca2+ transients evoked by beractant were dependent on the resting [Ca2+]i. Pharmacological manipulation revealed that beractant activates a Ca2+ signal through Ca2+ release from intracellular stores mediated by phospholipase Cβ (PLCβ), Ca2+ release from inositol 1,4,5-trisphosphate receptors (IP3Rs) and Ca2+ influx via a store-operated pathway. Moreover, beractant-induced Ca2+ release was abolished by preventing membrane depolarization upon removal of extracellular Na+ and Ca2+. Finally, the inhibition of store-operated channels prevented beractant-induced NHLF apoptosis and downregulation of α1(I) procollagen expression. Therefore, beractant utilizes SOCE to exert its pro-apoptotic and antifibrinogenic effect on NHLF.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Products / pharmacology*
  • Calcium / metabolism*
  • Cytosol / drug effects*
  • Cytosol / metabolism
  • Dose-Response Relationship, Drug
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism
  • Humans
  • Lung / cytology
  • Lung / drug effects*
  • Lung / metabolism
  • Pulmonary Surfactants / pharmacology*

Substances

  • Biological Products
  • Pulmonary Surfactants
  • beractant
  • Calcium

Grants and funding

This work was supported by Vicerrectoría de Investigación y Estudios de Posgrado de la Benemérita Universidad Autónoma de Puebla, Puebla, México, Grant No. BERR-SAL11-I. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.