Synergistic and Differential Modulation of Immune Responses by Hsp60 and Lipopolysaccharide

Abstract

Activation of professional antigen-presenting cells (APC) is Activation of antigen-presenting cells (APC)2 such as dendritic cells (DC) and macrophages is a critical step in the initiation of innate as well as adaptive immune responses and is known to be induced by pathogen-associated molecular pattern (PAMP) molecules such as bacterial lipopolysaccharide (LPS) and other endotoxins. These molecules are recognized by pattern recognition receptors (PRR) like members of the conserved Toll-like receptor (TLR) family (1, 2). In the last years, several members of the heat shock protein (HSP) family including Hsp60 have been described to modulate APC functions and to stimulate immune responses in vitro and in vivo (3-6). Therefore, HSP have been suspected to function as endogenous danger signals to the immune system (4, 7-9). HSP are highly conserved and ubiquitously expressed proteins that are normally hidden within the cell and function as molecular chaperons of nascent or aberrantly folded proteins in different cellular compartments (10, 11). HSP are up-regulated and released from cells upon various cellular stresses and necrotic cell death (12, 13). Furthermore, stress-induced cell surface expression of HSP like Hsp60, which is normally localized within the mitochondria playing an essential role in the folding of imported mitochondrial proteins has been observed (14 -17). Extracellular Hsp60 has been shown to induce the maturation of human and murine DC and macrophages indicated by an up-regulation of co-stimulatory cell surface molecules and the production of the proinflammatory cytokines IL-1, and TNF␣ (7,18,19). Moreover, Hsp60 has been shown to enhance IFN␥ production in antigen-dependent T cell activation (4, 6), an effect that was mainly ascribed to the release of IL-12 by APC (20, 21). The receptors that have been proposed to be responsible for Hsp60-mediated immune effects are CD14 (18) and members of the TLR family, namely TLR4 (22, 23) and TLR2 (23,24). The receptor complex consisting of the glycosylphosphatidylinositol-anchored CD14 co-receptor and the TLR4 signaling receptor is known to mediate LPS signaling (25), whereas TLR2 is a receptor for bacterial lipoproteins and lipoteichoic acid (26 -28). The Hsp60 preparations, however, that have been used in earlier studies were expressed in Escherichia coli and, therefore, were likely to be contaminated with bacterial endotoxins. For this reason, it could not be excluded that the observed effects were due to contaminating bacterial structures, especially LPS, rather than the Hsp60 protein itself, although controls like heat sensitivity and polymyxine B insensitivity of Hsp60 versus LPS were included (8).Employing eukaryotic cell lines expressing the murine Hsp60 as a membrane-bound cell surface protein we have shown that Hsp60 enhances IFN␥ production in antigen-dependent T cell activation in an endotoxin-free environment, clearly demon-* The costs of publication of this article were defrayed in part by the payment of page charges. This article must ther...

Exogenous heat shock protein 27 uniquely blocks differentiation of monocytes to dendritic cells

“…A new role has emerged for large HSP as endogenous danger signals which augment the induction of innate and adaptive immunity through interaction with TLR [6,7,9]. In contrast, our data suggest a novel role for HSP-27 as an MO anti-danger signal down-modulating innate and adaptive immunity similar to the role suggested for CD200 [49].…”

“…Circulating large and small heat shock proteins (HSP) are implicated as modulating adaptive and innate immunity in a variety of disease and inflammatory pathologies beyond their defined chaperone effects [1][2][3][4][5][6][7][8]. Large HSP are thought to act as endogenous danger signals augmenting inflammatory cytokines by triggering monocyte (MO) Toll-like receptors (TLR) and scavenger receptors independently of LPS contaminants [6,7,[9][10][11].…”

“…Large HSP are thought to act as endogenous danger signals augmenting inflammatory cytokines by triggering monocyte (MO) Toll-like receptors (TLR) and scavenger receptors independently of LPS contaminants [6,7,[9][10][11]. In contrast, exogenous HSP-27 (a small HSP) predominantly stimulates MO IL-10 [12].…”

Proteomics-based safety evaluation of multi-walled carbon nanotubes

“…induces the production of cytokines that were induced by CNT exposure in previous reports (Cohen-Sfady et al, 2005;Witzmann and Monteiro-Riviere, 2006;Osterloh et al, 2007;Shvedova et al, 2007;Shvedova et al, 2008a;Shvedova et al, 2008b). Thus, our proteomics approach can detect intracellular changes with great sensitivity, which may allow us to predict slowly progressing diseases.…”

Integrating the cell stress response: a new view of molecular chaperones as immunological and physiological homeostatic regulators

“…Another study has suggested that unlike LPS, human Hsp60 stimulates both murine macrophages and dendritic cells to secrete IFNα and neutralisation of this cytokine blocked Hsp60-induced IFNγ production by DCs. This suggests that IFNα production contributes to Hsp60-specific immune stimulation [60].…”