Nickel induces intracellular calcium mobilization and pathophysiological responses in human cultured airway epithelial cells.
Environmental exposure to nickel is associated to respiratory disorders and potential toxicity in the lung but molecular mechanisms remain incompletely explored. The extracellular Ca(2+)-sensing receptor (CaSR) is widely distributed and may be activated by divalent cations. In this study, we investigated the presence of CaSR in human cultured airway epithelial cells and its activation by nickel. Nickel transiently increased intracellular calcium (-logEC(50)=4.67+/-0.06) in A549 and human bronchial epithelial cells as measured by epifluorescence microscopy. Nickel (20muM)-induced calcium responses were reduced after thapsigargin or ryanodine exposure but not by Ca(2+)-free medium. Inhibition of phospholipase-C or inositol trisphosphate release reduced intracellular calcium responses to nickel indicating activation of G(q)-signaling. CaSR mRNA and protein expression in epithelial cells was demonstrated by RT-PCR, western blot and immunofluorescence. Transfection of specific siRNA inhibited CaSR expression and suppressed nickel-induced intracellular calcium responses in A549 cells thus confirming nickel-CaSR activation. NPS2390, a CaSR antagonist, abolished the calcium response to nickel. Nickel-induced contraction, proliferation, alpha(1)(I)collagen production and inflammatory cytokines mRNA expression by epithelial cells as measured by traction microscopy, BrdU assay and RT-PCR, respectively. These responses were blocked by NPS2390. In conclusion, micromolar nickel concentrations, relevant to nickel found in the lung tissue of humans exposed to high environmental nickel, trigger intracellular Ca(2+) mobilization in human airway epithelial cells through the activation of CaSR which translates into pathophysiological outputs potentially related to pulmonary disease.
Department of Pharmacology, Faculty of Medicine, University of Valencia, Valencia, Spain.
Julio
J
Cortijo
Javier
J
Milara
Manuel
M
Mata
Eva
E
Donet
Nuria
N
Gavara
Samantha E
SE
Peel
Ian P
IP
Hall
E J
EJ
Morcillo
D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009532:Nickel / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000378:metabolism; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000378:metabolism; D020545:Respiratory Mucosa / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D053583:Interleukin-1beta; D034741:RNA, Small Interfering; D044169:Receptors, Calcium-Sensing; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D012433:Ryanodine; D019284:Thapsigargin; D009532:Nickel; D010738:Type C Phospholipases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D002118:Calcium