All-trans retinoic acid inhibits fluctuations in intracellular Ca2+ resulting from changes in extracellular Ca2+.
Previous studies have shown that all-trans retinoic acid (RA) preserves fibroblast viability and stimulates their proliferation, in part, by reducing the extracellular Ca2+ requirement (Am J Pathol 1990, 130:1275). Based on this observation, we have in the present study examined the effects of RA on Ca2+ mobilization in human dermal fibroblasts. For these studies we used the Ca(2+)-binding dyes, Fluo-3 and Indo-1. Using fluorescence of Fluo-3-loaded cells or Indo-1-loaded cells as indicators of intracellular free Ca2+, we observed that treatment of the cells with RA did no, by itself, alter the concentration of intracellular Ca2+. Nor did it interfere with the rapid, transient rise in intracellular Ca2+ induced by treatment with ionomycin. However, treatment of the cells with RA prevented re-equilibration of intracellular Ca2+ when the cells were initially equilibrated in low Ca2+ (0.15 mmol/L) culture medium and then switched to high Ca2+ (1.4 mmol/L) medium or when cells were first equilibrated in high Ca2+ medium and then switched to low Ca2+ medium. This effect of RA could be seen within seconds after treatment and the effect was observed 1 day after treatment (longest time point examined). The effect was concentration dependent and concentrations of RA that modulated Ca2+ re-equilibration (0.3 to 3.0 mumol/L) were the same as those that have previously been shown to promote fibroblast survival and growth. A biologically inactive retinoid did not have this effect. Specificity of the response was suggested by the finding that concentrations of RA that modulated Ca2+ movement had no effect on Ba2+ transport. These data suggest that RA prevents re-equilibration of intracellular Ca2+ in human dermal fibroblasts by interfering with Ca2+ movement across the plasma membrane.
Varani
J
J
Department of Pathology, University of Michigan, Ann Arbor 48109, USA.
Burmeister
B
B
Perone
P
P
Bleavins
M
M
Johnson
K J
KJ
D000814:Aniline Compounds; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D003470:Culture Media / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005456:Fluorescent Dyes; D006801:Humans; D007211:Indoles; D007425:Intracellular Membranes / Q000378:metabolism*; D015603:Keratinocytes / Q000378:metabolism; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D014212:Tretinoin / Q000494:pharmacology*; D014966:Xanthenes
D000814:Aniline Compounds; D003470:Culture Media; D005456:Fluorescent Dyes; D007211:Indoles; D014966:Xanthenes; C059715:Fluo-3; D001464:Barium; D014212:Tretinoin; C048960:indo-1; D002118:Calcium