Role of HSP70 in cellular thermotolerance

Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee 37232, USA.
Lasers in Surgery and Medicine (Impact Factor: 2.62). 12/2008; 40(10):704-15. DOI: 10.1002/lsm.20713
Source: PubMed


Thermal pretreatment has been shown to condition tissue to a more severe secondary heat stress. In this research we examined the particular contribution of heat shock protein 70 (HSP70) in thermal preconditioning.
For optimization of preshock exposures, a bioluminescent Hsp70-luciferase reporter system in NIH3T3 cells tracked the activation of the Hsp70 gene. Cells in 96-well plates were pretreated in a 43 degrees C water bath for 30 minutes, followed 4 hours later with a severe heat shock at 45 degrees C for 50 minutes. Bioluminescence was measured at 2, 4, 6, 8, and 10 hours after preshock only (PS) and at 4 hours after preshock with heatshock (PS+HS). Viability was assessed 48 hours later with a fluorescent viability dye. Preshock induced thermotolerance was then evaluated in hsp70-containing Murine Embryo Fibroblast (+/+) cells and Hsp70-deficient MEF cells (-/-) through an Arrhenius damage model across varying temperatures (44.5-46 degrees C).
A time gap of 4 hours between preconditioning and the thermal insult was shown to be the most effective for thermotolerance with statistical confidence of P<0.05. The benefit of preshocking was largely abrogated in Hsp70-deficient cells. The Arrhenius data showed that preshocking leads to increases in the activation energies, E(a), and increases in frequency factors, A. The frequency factor increase was significantly greater in Hsp70-deficient cells.
The data shows that HSP70 contributes significantly to cellular thermotolerance but there are other pathways that provide residual thermotolerance in cells deficient in Hsp70.

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    • "Acquired cellular thermotolerance confers cytoprotection against subsequent thermal exposure, translating to complimentary reductions in endogenous physiological and systemic strain (Yamada et al., 2007; McClung et al., 2008). An established element of acquired cellular thermotolerance involves changes in heat shock proteins (HSP; Moseley, 1997), in particular, increases in the inducible and thermosensitive protein heat shock protein HSPA1A (HSP72; Beckham et al., 2008; McClung et al., 2008; Kampinga et al., 2009) following transcription of its gene (Hsp72 mRNA) as part of the heat shock response (HSR). Increased basal HSP72 is commonly reported following repeated exercise heat stress, as is the inducibility of the protein (Maloyan et al., 1999; McClung et al., 2008; Selkirk et al., 2009; Magalhães et al., 2010a; Amorim et al., 2011). "
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    ABSTRACT: Thermotolerance, to which heat shock protein-72 (Hsp72) contributes, is an acquired state achieved following heat acclimation (HA), eliciting cellular adaption and protection against thermal stress. Optimal HA methods achieving the greatest heat shock response (HSR) are equivocal; therefore, investigation of methods provoking the greatest sustained HSR is required to optimize cellular adaptation. Twenty-four males performed short-term HA (STHA; five sessions) and long-term HA (LTHA; STHA plus further five sessions) utilizing fixed-intensity (FIXED; workload = 50% V ˙ O 2 p e a k ), continuous isothermic HA [ISOCONT ; target rectal temperature (Trec ) = 38.5 °C], or progressive isothermic HA (ISOPROG ; target Trec = 38.5 °C for STHA then target Trec = 39.0 °C for LTHA). Leukocyte Hsp72 mRNA was measured pre- and post day 1, day 5, and day 10 of HA via reverse transcription quantitative polymerase chain reaction to determine the HSR. Hsp72 mRNA increased (P < 0.05) pre- to post day 1, pre- to post day 5, and pre to post day 10 in FIXED, ISOCONT , and ISOPROG , but no differences were observed between methods (P > 0.05). The equal Hsp72 mRNA increases occurring from consistent, reduced, or increased endogenous strain following STHA and LTHA suggest that transcription occurs following attainment of sufficient endogenous criteria. These data give confidence that all reported HA methods increase Hsp72 mRNA and are capable of eliciting adaptations toward thermotolerance. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
    Full-text · Article · May 2015 · Scandinavian Journal of Medicine and Science in Sports
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    • "Our search to find networks describing functional relationships between gene products based on known interactions reported in the literature demonstrated that only Hspa1a and Dnajb1 are differentially expressed by more than 2.5-fold. The major contribution of these two genes to heat tolerance mechanisms have been previously reported, but have not been directly linked to processes involving skeletal muscle [8], [12], [13], [21]. Further studies will be needed to investigate these genes in more detail for their direct influence on mechanisms contributing to heat tolerance/thermoregulation. "
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    ABSTRACT: Individuals who rapidly develop hyperthermia during heat exposure (heat-intolerant) are vulnerable to heat associated illness and injury. We recently reported that heat intolerant mice exhibit complex alterations in stress proteins in response to heat exposure. In the present study, we further explored the role of genes and molecular networks associated with heat tolerance in mice. Heat-induced physiological and biochemical changes were assessed to determine heat tolerance levels in mice. We performed RNA and microRNA expression profiling on mouse gastrocnemius muscle tissue samples to determine novel biological pathways associated with heat tolerance. Mice (n = 18) were assigned to heat-tolerant (TOL) and heat-intolerant (INT) groups based on peak core temperatures during heat exposures. This was followed by biochemical assessments (Hsp40, Hsp72, Hsp90 and Hsf1 protein levels). Microarray analysis identified a total of 3,081 mRNA transcripts that were significantly misregulated in INT compared to TOL mice (p<0.05). Among them, Hspa1a, Dnajb1 and Hspb7 were differentially expressed by more than two-fold under these conditions. Furthermore, we identified 61 distinct microRNA (miRNA) sequences significantly associated with TOL compared to INT mice; eight miRNAs corresponded to target sites in seven genes identified as being associated with heat tolerance pathways (Hspa1a, Dnajb1, Dnajb4, Dnajb6, Hspa2, Hspb3 and Hspb7). The combination of mRNA and miRNA data from the skeletal muscle of adult mice following heat stress provides new insights into the pathophysiology of thermoregulatory disturbances of heat intolerance.
    Full-text · Article · Aug 2013 · PLoS ONE
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    • "The 70 kDa Hsp (Hsp70) is particularly known to be induced by thermal, ischemic, and oxidative stress. Acting as a molecular chaperone, Hsp70 can assist in the refolding of denatured proteins and inhibit improper protein aggregation [10-12]. Moreover, the induction of Hsp70 may be responsible for the protective effect against apoptosis and inflammation [13-17]. "
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    ABSTRACT: To investigate the biologic effect of an 810 nm diode laser on the induction of heat shock protein 70 (Hsp70) in choroid-retinal endothelial cells in vitro. Cultured rhesus macaque choroid-retinal endothelial cells (RF/6A) were irradiated using an 810 nm diode laser (spot size, 10 mm; duration, 60 s; power, 400-1,500 mW). Cell viability was assessed by annexin V- fluorescein isothiocyanate (FITC) and propidium iodide flow cytometric assay. Hsp70 expression was determined by western blot at 6, 12, 18, 24, and 48 h following laser exposure. Intracellular distribution of Hsp70 was examined by immunofluorescence staining. The laser-induced cell injury threshold was found to be at a power of 1,100 mW power (fluence, 84.08 J/cm(2)), above which there was significant cell death. Under this power, Hsp70 expression elevated obviously and was stronger at 600-1,000 mW power settings (fluences, 45.86-76.43 J/cm(2)). The expression of Hsp70 peaked at 12-18 h postirradiation, and returned to baseline by 48 h. Immunofluorescence staining indicated the induced Hsp70 expression in both the cytoplasm and the nucleus. Subthreshold 810 nm diode laser exposure can induce Hsp70 hyperexpression from 12 to 18 h postirradiation in cultured choroid-retinal endothelial cells without obvious cell death. The results could be useful for investigating and designing more effective laser therapies.
    Full-text · Article · Sep 2012 · Molecular vision
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