Heat Shock Protein 70B′ (HSP70B′) Expression and Release in Response to Human Oxidized Low Density Lipoprotein Immune Complexes in Macrophages

Abstract

Heat shock proteins (HSPs) have been implicated in the activation and survival of macrophages. This study examined the role of HSP70B, a poorly characterized member of the HSP70 family, in response to oxidatively modified LDL (oxLDL) and immune complexes prepared with human oxLDL and purified human antibodies to oxLDL (oxLDL-IC) in monocytic and macrophage cell lines. Immunoblot analysis of cell lysates and conditioned medium from U937 cells treated with oxLDL alone revealed an increase in intracellular HSP70B protein levels accompanied by a concomitant increase in HSP70B extracellular levels. Fluorescence immunohistochemistry and confocal microscopy, however, demonstrated that oxLDL-IC stimulated the release of HSP70B, which co-localized with cell-associated oxLDL-IC. In HSP70B-green fluorescent protein-transfected mouse RAW 264.7 cells, oxLDL-IC-induced HSP70B co-localized with membrane-associated oxLDL-IC as well as the lipid moiety of internalized oxLDL-IC. Furthermore, the data demonstrated that HSP70B is involved in cell survival, and this effect could be mediated by sphingosine kinase 1 (SK1) activation. An examination of regularly implicated cytokines revealed a significant relationship between HSP70B and the release of the anti-inflammatory cytokine interleukin-10 (IL-10). Small interfering RNA knockdown of HSP70B resulted in a corresponding decrease in SK1 mRNA levels and SK1 phosphorylation as well as increased release of IL-10. In conclusion, these findings suggest that oxLDL-IC induce the synthesis and release of HSP70B, and once stimulated, HSP70B binds to the cellassociated and internalized lipid moiety of oxLDL-IC. The data also implicate HSP70B in key cellular functions, such as regulation of SK1 activity and release of IL-10, which influence macrophage activation and survival.

Endothelial nitric oxide synthase induces heat shock protein HSPA6 (HSP70B′) in human arterial smooth muscle cells

“…Real-time PCR robustly detected high fold change HSPA6 mRNA levels. HSPA6 protein was widely detected by immunofluorescence in within smooth muscle cells, as has been reported for HSPA6 in colon cells, [17] neurons [18], and macrophages [19] .…”

Expression of Endoplasmic Reticulum Stress Related Genes in Blood Cells of Obese Boys with and without Insulin Resistance

“…The decreased level of ALDH1A2 and HSPA6 gene expressions correlates to data that ALDH1A2 may control the synthesis of retinoic acid, a hormonal signaling molecule that has a relation to suppression of tumor growth, and that the expression of heat shock protein A6, as a stress-responsible protein, responds to oxidized low density lipoprotein immune complexes [17,28,35].…”

Rescuing of deficient killing and phagocytic activities of macrophages derived from non-obese diabetic mice by treatment with geldanamycin or heat shock: potential clinical implications

“…3b). HSP1B expression has been implicated in the increased survival of FcγR-activated Mfs (Smith et al 2010) and its expression regulates the induction of pro-(IL-1β) and anti-(IL-10) inflammatory cytokines. Our data show that treatment with GA ( Fig.…”