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Differential expression of heat shock protein 70 (hsp70) in human monocytes rendered apoptotic by IL‐4 or serum deprivation
Author(s) -
Lang Detlef,
Hubrich Andreas,
Dohle Frank,
Terstesse Martin,
Saleh Hilmi,
Schmidt Michael,
Pauels HansGerd,
Heidenreich Stefan
Publication year - 2000
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1189/jlb.68.5.729
Subject(s) - apoptosis , hsp70 , propidium iodide , monocyte , biology , downregulation and upregulation , flow cytometry , annexin , heat shock protein , annexin a5 , microbiology and biotechnology , programmed cell death , immunology , biochemistry , gene
Apoptosis of monocytes is regulated by the balance between pro‐ and antiapoptotic triggers and pathways and may strongly influence inflammatory disorders. The major heat shock protein, hsp70, is an effective inhibitor of apoptosis in lymphocytic and monocytic tumor cell lines, but the implications in the regulation of apoptosis of freshly isolated human monocytes have not been elucidated. In this study, we examined whether two different triggers of monocyte apoptosis, serum deprivation and IL‐4, respectively, altered hsp70 expression and whether expression levels correlated with monocyte survival. Monocyte apoptosis was determined quantitatively by flow cytometry detecting annexin V binding or nuclear stainability with propidium iodide (PI). Hsp70 expression was analyzed by semiquantitative RT‐PCR and immunoblotting. Exposing monocytes to heat shock (47°C, 20 min) induced a rapid and marked upregulation of hsp70 without evoking injury or apoptosis, suggesting that hsp70 conferred protection and survival. In accordance, when monocytes were rendered apoptotic by serum deprivation, a drastic downregulation of hsp70 occurred, which was accompanied by a reduced synthesis of the constitutive family member hsc70. However, induction of monocyte apoptosis by IL‐4 increased hsp70 expression in a concentration and time‐dependent fashion. A neutralizing antibody against IL‐4 abolished hsp70 expression and apoptosis induction after IL‐4 treatment and so excluded indirect effects. LPS rescued monocytes from apoptosis but did not alter hsp70 formation significantly. These findings suggest that, in monocytes, distinct apoptotic triggers induce different responses of hsp70 so that this molecule does not exert protection against cell death directly or in general.