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UV irradiation of lymphocytes triggers an increase in intracellular Ca2+ and prevents lectin-stimulated Ca2+ mobilization: evidence for UV- and nifedipine-sensitive Ca2+ channels.

Authors
  • Spielberg, H
  • June, C H
  • Blair, O C
  • Nystrom-Rosander, C
  • Cereb, N
  • Deeg, H J
Type
Published Article
Journal
Experimental Hematology
Publisher
Elsevier
Publication Date
Sep 01, 1991
Volume
19
Issue
8
Pages
742–748
Identifiers
PMID: 1651252
Source
Medline
License
Unknown

Abstract

UV irradiation induces in vitro and in vivo immunosuppression. Because mobilization of intracellular calcium ([Ca2+]i) represents a central step in cell activation and immune response, we investigated the effect of UV irradiation on Ca2+ homeostasis. Using indo-1 and cytofluorometry, [Ca2+]i kinetics in UVC- or UVB-exposed human peripheral blood leukocytes (PBL) and Jurkat cells were determined in parallel with functional assays. Increases in [Ca2+]i were observed within 2-3 h of irradiation; these increases were UV-dose dependent and reached maxima of 240% and 180% above baseline level (130 nM) for UVB and UVC, respectively. The UV-induced [Ca2+]i rise was predominantly due to influx of extracellular calcium, and it was more pronounced in T than in non-T cells. Concurrent with [Ca2+]i shifts following UV treatment, there was a loss of ability to respond to phytohemagglutinin (PHA) or to proliferate or stimulate in mixed leukocyte culture. This loss of function appeared to be related not only to UV-induced calcium shifts, but also to effects of UV irradiation on the plasma membrane. No [Ca2+]i mobilization was induced by gamma irradiation, and gamma-irradiated cells showed a normal [Ca2+]i increase in response to PHA. UV-induced Ca2+ flux into the cells was blocked by nifedipine. These data indicate that UV and gamma irradiation have different effects on lymphocyte membranes and suggest that a disruption of Ca2+ homeostasis may be involved in UV-induced lymphocyte inhibition. The data suggest, furthermore, the presence of Ca2+ channels in lymphocyte membranes that are sensitive to UV irradiation and Ca2+ channel blockers such as nifedipine.

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