title: Modulation of bradykinin-induced calcium changes in SH-SY5Y cells by neurosteroids and sigma receptor ligands via a shared mechanism.
abstract: In this study we investigated the effects of sigma receptor ligands and neurosteroids on bradykinin-induced intracellular calcium concentration ([Ca2+]i) changes in SH-SY5Y neuroblastoma cells. [Ca2+]i levels in cells loaded with fura-2 were monitored with dual-wavelength ratiometric fluorescence measurement. Submicromolar concentrations of bradykinin elicited [Ca2+]i responses with a fast rise followed by a slow decline in these cells. Preincubation of low micromolar concentrations of the neurosteroids pregnenolone, dehydroepiandrosterone (DHEA), or the prototypic sigma (sigma) receptor agonist (+)pentazocine potentiated bradykinin-induced [Ca2+]i changes in SH-SY5Y cells. The sigma receptor antagonist haloperidol blocked the enhancing effects on [Ca2+]i by (+)pentazocine or pregnenolone. Progesterone did not significantly affect the basal [Ca2+]i level or bradykinin-induced [Ca2+]i changes in these cells. However, coincubation of progesterone with (+)pentazocine, pregnenolone, or DHEA reversed their potentiating effects. The antagonistic effects of haloperidol and progesterone on the potentiating effects of (+)pentazocine and pregnenolone suggested that these ligands might act through a common mechanism. We further showed that progesterone, pregnenolone, and DHEA competed for [3H]+pentazocine binding in SH-SY5Y cells with Ki values of 0.13 +/- 0.03 microM, 0.98 +/- 0.34 microM, and 5.2 +/- 1.4 microM, respectively. Thus, the modulation of bradykinin-induced [Ca2+]i changes by neurosteroids in these cells is likely due to their actions on sigma receptors.
authors.affiliation: Department of Pharmacology and Physiology, The George Washington University Medical Center, Washington, DC 20037, USA.
authors.forename: Weimin
authors.initials: W
authors.lastname: Hong
authors.forename: Samer J
authors.initials: SJ
authors.lastname: Nuwayhid
authors.forename: Linda L
authors.initials: LL
authors.lastname: Werling
mesh_terms: D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D045744:Cell Line, Tumor; D003687:Dehydroepiandrosterone / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D016257:Fura-2; D006220:Haloperidol / Q000494:pharmacology; D006801:Humans; D009294:Narcotics / Q000494:pharmacology*; D009447:Neuroblastoma; D010423:Pentazocine / Q000494:pharmacology*; D011284:Pregnenolone / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D018492:Dopamine Antagonists; D009294:Narcotics; D003687:Dehydroepiandrosterone; D011284:Pregnenolone; D006220:Haloperidol; D010423:Pentazocine; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2