Communication
Glucocorticoids activate a suicide process in thymocytes through an elevation of cytosolic Ca2+ concentration

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Abstract

Glucocorticoid hormones kill immature thymocytes through the induction of a suicide process commonly referred to as “apoptosis.” A characteristic marker for this process is the stimulation of endogenous endonuclease activity which results in the extensive cleavage of cell chromatin. In an attempt to characterize the biochemical events involved in this process, we studied the role of Ca2+ in glucocorticoid-induced DNA fragmentation and cell killing in thymocytes. Treatment of thymocytes from immature rats with the synthetic glucocorticoid methylprednisolone resulted in extensive DNA fragmentation which was preceded by an early, sustained increase in cytosolic Ca2+ concentration. This increase in Ca2+ level was blocked by cycloheximide and actinomycin D, inhibitors of de novo protein and mRNA synthesis, respectively. Prevention of the Ca2+ increase by buffering cytosolic Ca2+ with quin-2, or through incubation of the thymocytes in a “Ca2+-free” medium, prevented endonuclease activation and cell killing. Inhibitors of calmodulin also prevented DNA fragmentation without inhibiting the glucocorticoid-stimulated elevation of cytosolic Ca2+ concentration. The Ca2+ increase appeared to be due to the action of a heat-labile cytosolic factor, synthesized in response to glucocorticoids, which facilitated the influx of extracellular Ca2+. Our findings suggest that glucocorticoids induce thymocyte suicide through an elevation of cytosolic Ca2+ concentration resulting in endonuclease activation, DNA fragmentation, and cell death.

References (29)

  • J.N. Vanderbilt et al.

    J. Biol. Chem

    (1982)
  • D.J. McConkey et al.

    Toxicol. Lett

    (1988)
  • P. Nicotera et al.

    J. Biol. Chem

    (1986)
  • G. Grynkiewicz et al.

    J. Biol. Chem

    (1985)
  • V. von Tscharner et al.

    J. Biol. Chem

    (1986)
  • O. Bachs et al.

    J. Biol. Chem

    (1987)
  • K. Gietzen et al.

    Biochem. Biophys. Res. Commun

    (1981)
  • J. Ng et al.

    Biochem. Pharmacol

    (1987)
  • T. Pawson

    Trends Genet

    (1987)
  • E.V. Maytin et al.

    J. Biol. Chem

    (1983)
  • A.H. Wyllie

    Nature (London)

    (1980)
  • R.C. Duke et al.
  • D.S. Ucker

    Nature (London)

    (1987)
  • R.C. Duke et al.

    J. Immunol

    (1986)
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    Permanent address: Dipartimento di Medicina Interna e Terapia Medica, Clinica Medica I, University of Pavia, 27100 Pavia, Italy.

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    Permanent address: Department of Pathology, University Medical School, Teviot Place, Edinburgh EH8 9AG, Scotland.

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