Expression and localization of heat shock proteins in rat basophilic leukemia cells: Differential modulation by degranulation, thermal or oxidative stress

Abstract

Background: Rat basophilic leukemia (RBL-2H3) cells are well characterized in terms of morphological and biochemical changes upon activation, and have been extensively used as a model system for studying the mechanisms of the immediate hypersensitivity reaction. To investigate whether overexpression of heat shock/stress proteins (HSP) is involved in the mast cell-dependent reactivity, we examined the adaptive responses of RBL-2H3 cells to classical stress conditions such as heat shock or oxidative injury produced by an aqueous extract of tobacco smoke. Methods: HSP were determined by flow cytometry and immunocytochemistry. Degranulation was confirmed as the release of β-hexosaminidase, determined spectrophotometrically, and by electron microscopy experiments. Results: We found that RBL-2H3 cells respond to heat shock or oxidative injury by the synthesis of both the inducible 72 kDa HSP (Hsp70), and the oxidation-specific 32 kDa heine oxygenase (HO)-1. Heat shock induced mainly Hsp70 in a cell growth-dependent manner, whereas oxidative stress induced mainly HO-1 in a cell growth-independent manner. However, heat shock or oxidative stress had no significant effects on degranulation. Conclusion: Stress-mediated synthesis of HSP was not associated with RBL-2H3 degranulation and likewise, degranulation did not induce HSP.