Erythrophagocytosis induces heat shock protein synthesis by human monocytes-macrophages.

Abstract

Exposure of cells to elevated temperatures and other environmental stresses results in the expression of specific genes encoding the so-called heat shock proteins (HSPs). Since exogenous H202 induces in human monocytes the synthesis of HSPs, and previous induction of HSPs protects these cells from oxidative hnjury, we investigated whether HSP synthesis was also induced during generation ofreactive oxygen species by the phagocyte itself during phagocytosis. As a model system, we analyzed the effects of erythrophagocytosis on protein synthesis by the human premonocytic line U937, in which phagocytosis is induced during differentiation with 1,25-dihydroxyvitamin D3. Exposure to whole erythrocytes, but not to erythrocyte ghosts, induced in the phagocytic cells only the synthesis of the 70-and 83-to 90-kDa HSPs and a 32-kDa oxidation-related stress protein identical by partial peptide mapping to heme oxygenase. The radioprotective aminothiol N-(2'-mercaptoethyl)-1,3-propanediamine (WR-1065), which can substitute for glutathione as hydrogen donor, prevented this induction. These results suggest that oxygen free radicals generated in the presence of hemoglobin-derived iron and consecutive glutathione depletion are involved in induction of stress protein synthesis during erythrophagocytosis. HSPs synthesized during phagocytosis may play a role in the phagocyte's defense mechanisms and in protective immunity.As a model system, we used the human premonocytic line U937 and phagocytosis of erythrocytes. (4), that preexposure to temperatures inducing the synthesis of HSPs partially protects monocytic cells from H202-induced cell death (5), and that in human neutrophils induction of a heat shock response by heat or cadmium is associated with an inhibition of superoxide production (6). These observations suggested potential implications of HSPs in the phagocytes' biology (7). We therefore asked the question whether HSP synthesis was also induced in association with the generation of reactive oxygen species by the phagocyte itself during phagocytosis. The analysis of the stress response in phagocytes is of particular relevance since it has been shown that several immunodominant antigens of intracellular microorganisms such as mycobacteria or plasmodia are indeed, by sequence homology, HSPs, and the potential role ofHSPs in protective immunity and/or immunopathology is an area of intense interest (8-11). Mycoplasma-free U937 cells were grown in RPMI 1640 medium (GIBCO) with 10% fetal calf serum/1% glutamine, with or without 1,25-(OH)2D3 (10 ng/ml) for 72 hr, then counted, centrifuged, and resuspended at 0.8 x 106 cells per ml in RPMI 1640 medium without methionine and incubated with or without SRBCs for 3 hr at 37°C. Peripheral blood monocytes from normal volunteers were isolated by gradient centrifugation and purified by adherence (4), and human alveolar macrophages were obtained as described (22) from bronchoalveolar lavage of lungs excised during surgery for carcinoma, then isolated by adherence, cultured, and stimul...

Peripheral Artery Disease Is Associated With a High CD163/TWEAK Plasma Ratio

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Arachidonate is a potent modulator of human heat shock gene transcription.

“…Separately, heat shock proteins induced during inflammation have a critical role in cytoprotection. Phagocytosis and bacterial infection induce heat shock protein synthesis, and these events have been shown to protect cells against subsequent exposure to cytotoxic forms of stress (52)(53)(54)(55)(56)(57)(58). Thus, induction of the heat shock response during inflammation could provide both regulatory and cytoprotective functions.…”

TNF-a, IL-1a, IL-6 and ICAM-1 Expression in Human Keratinocytes Stimulated in Vitro with Escherichia Coli Heat-Shock Proteins

“…A wide variety of stimuli such as temperature (Lindquist & Craig, 1989), oxygen radicals (H202) (Clerget & Polla, 1990) and cytokines (Gromkowski et af., 1989) al., 1990;Polla, 1988;Kaufmann et af., 1991). Therefore, in this work we evaluated the effect of E. coli HSPs with different molecular masses on the expression and release of some cytokines (TNFa, IL-la and IL-6) and of one adhesion molecule (ICAM-1) in human keratinocytes.…”