Hyperthermia in the febrile range induces HSP72 expression proportional to exposure temperature but not to HSF-1 DNA-binding activity in human lung epithelial A549 cells

Abstract

Expression of heat shock proteins (HSPs) is classically activated at temperatures above the physiologic range (≥42°C) via activation of the stress-activated transcription factor, heat shock factor-1 (HSF-1). Several studies suggest that less extreme hyperthermia, especially within the febrile range, as occurs during fever and exertional/environmental hyperthemia, can also activate HSF-1 and enhance HSP expression. We compared HSP72 protein and mRNA expression in human A549 lung epithelial cells continuously exposed to 38.5°C, 39.5°C, or 41°C or exposed to a classic heat shock (42°C for 2 h). We found that expression of HSP72 protein and mRNA increased linearly as incubation temperature was increased from 37°C to 41°C, but increased abruptly when the incubation temperature was raised to 42°C. A similar response in luciferase activity was observed using A549 cells stably transfected with an HSF-1-responsive luciferase reporter plasmid. However, activation of intranuclear HSF-1 DNA-binding activity was comparable at 38.5°C, 39.5°C, and 41°C and only modestly greater at 42°C but the mobility of HSF1 protein on a denaturing gel was altered with increasing exposure temperature and was distinctly different at 42°C. These findings indicate that the proportional changes in HSF-1-dependent HSP72 expression at febrile-range temperatures are dependent upon exposure time and temperature but not on the degree of HSF-1 DNA-binding activity. Instead, HSF-1-mediated HSP expression following hyperthermia and heat shock appears to be mediated, in addition to HSF-1 activation, by posttranslational modifications of HSF-1 protein.

Toll-like Receptor Agonists and Febrile Range Hyperthermia Synergize to Induce Heat Shock Protein 70 Expression and Extracellular Release

“…In an earlier study, we found that exposing RAW cells to 40°C failed to activated Hsp70 mRNA expression (45), but the cells were only heated for 30 min in the previous study. The results of the two studies are consistent with our observation that Hsp70 induction at less extreme hyperthermia requires longer exposure time (27). In the present study, we showed that co-treating RAW cells with TLR4 (LPS) or TLR2/1 (Pam3cys) agonists greatly augmented Hsp70 expression in FRT-exposed RAW cells.…”

“…We have previously shown that exposure to FRT (38.5-39.5°C) is sufficient to activate HSF1 and induce expression of Hsp70 but at much lower levels than what occurs in response to temperatures above 42°C (27,40). In the current study, we have extended these findings by showing that stimulating TLR-dependent signaling pathways while exposing cells to FRT or HS greatly augments Hsp70 expression and its release into the extracellular microenvironment in both in vitro cell culture and in vivo in an intratracheal LPS-induced acute lung injury model.…”

“…Transcription of Hsps is also influenced by other transcription factors, including STAT-1, STAT-3, and NF-IL-6 (22)(23)(24), tonicity enhancer-binding protein and hypoxia-inducible factor 1 (25) and NFB (26). We previously showed that HSF1 trimerization and Hsp70 transcription were activated in A549 cells by exposure to mild hyperthermia (38.5°C), that Hsp70 transcription increased as the exposure temperature increased from 38.5°C to 42°C, and that increased transcription was associated with additional HSF1 phosphorylation but not additional HSF1 trimerization (27). Hsp70 is expressed from two genes, HSPA1A and HSPA1B, that code for identical 461-amino acid sequences in humans (28).…”

Shifts in temperature within the physiologic range modify strand-specific expression of select human microRNAs

“…Our previous studies have demonstrated that modest deviations from normothermia can alter stressinduced and proinflammatory signaling pathways, including heat shock factor-1 (HSF-1), p38 MAP kinase, and NFκB (Fairchild et al 2004(Fairchild et al , 2005Tulapurkar et al 2009Tulapurkar et al , 2012) and modify expression of important genes. We have previously identified several mechanisms by which shifts in temperature within the physiologic range modify gene transcription (Singh et al 2002Cooper et al 2010a, b).…”

Hyperthermia Promotes Apoptosis and Suppresses Invasion in C6 Rat Glioma Cells

“…In another study, hyperthermia increases the efficacy of chemotherapeutic agents such as oxaliplatin or melphalan when used in combination with TRAIL, killing the CX-1 colorectal cancer cells more effectively (Yoo and Lee, 2008). Furthermore, it promoted an antitumor immune response by activation of HSP70 (Tulapurkar et al, 2009). …”