Heat shock protein 70 and AMP-activated protein kinase contribute to 17-DMAG-dependent protection against heat stroke.

Yung‐Chieh Tsai,Kwok‐Keung Lam,Yi‐Jen Peng,Yen‐Mei Lee,Pao‐Yun Cheng,Chung‐Yu Yang,Mao‐Hsiung Yen,Yi‐Ju Tsai

doi:10.1111/jcmm.12881

Abstract

Heat shock protein 70 (Hsp70) preconditioning induces thermotolerance, and adenosine monophosphate (AMP)‐activated protein kinase (AMPK) plays a role in the process of autophagy. Here, we investigated whether 17‐dimethylaminoethylamino‐17‐demethoxy‐geldanamycin (17‐DMAG) protected against heat stroke (HS) in rats by up‐regulation of Hsp70 and phosphorylated AMPK (pAMPK). To produce HS, male Sprague–Dawley rats were placed in a chamber with an ambient temperature of 42°C. Physiological function (mean arterial pressure, heart rate and core temperature), hepatic and intestinal injury, inflammatory mediators and levels of Hsp70, pAMPK and light chain 3 (LC3B) in hepatic tissue were measured in HS rats or/and rats pre‐treated with 17‐DMAG. 17‐DMAG pre‐treatment significantly attenuated hypotension and organ dysfunction induced by HS in rats. The survival time during HS was also prolonged by 17‐DMAG treatment. Hsp70 expression was increased, whereas pAMPK levels in the liver were significantly decreased in HS rats. Following pre‐treatment with 17‐DMAG, Hsp70 protein levels increased further, and pAMPK levels were enhanced. Treatment with an AMPK activator significantly increased the LC3BII/LC3BI ratio as a marker of autophagy in HS rats. Treatment with quercetin significantly suppressed Hsp70 and pAMPK levels and reduced the protective effects of 17‐DMAG in HS rats. Both of Hsp70 and AMPK are involved in the 17‐DMAG‐mediated protection against HS. 17‐DMAG may be a promising candidate drug in the clinical setting.

Highlights

Heat stroke (HS) is a life-threatening illness characterized by an elevated core body temperature of above 40°C, resulting in multi-organ failure such as circulatory shock and liver failure [1]
Rats under anaesthesia were randomized into six groups, as follows (Fig. 1): (i) the normothermic control (NT) group, wherein the core temperature was maintained at about 36°C with a heating chamber at a room temperature of 24 Æ 1°C throughout the entire experiment; (ii) the saline-treated HS group, in which HS was induced as described below; (iii) the 17-DMAG pre-treatment with HS (HD) group, in which rats received 17-DMAG (5 mg/kg i.p.; InvivoGen, San Diego, CA, USA) for 20 hrs before heat stress; (iv) the 17-DMAG and quercetin (Hsp70 inhibitor; Cayman Chemical, Ann Arbor, MI, USA) pre-treatment with HS (HDQ) group, in which rats received quercetin (400 mg/kg i.p.) for 6 hrs and 17-DMAG (5 mg/kg i.p.) for 20 hrs before heat stress; (v)
Results are presented as the means Æ S.E.M.s and were evaluated statistically by one-way ANOVA with Newman–Keuls multiple comparisons tests for the post-hoc determination of significant differences

Summary

Introduction

Heat stroke (HS) is a life-threatening illness characterized by an elevated core body temperature of above 40°C, resulting in multi-organ failure such as circulatory shock and liver failure [1]. Heat shock proteins (Hsps) are a group of highly conserved proteins that function as molecular chaperones by facilitating the folding and refolding of proteins, mediating transmembrane transport of secretory proteins and targeting proteins for lysosomal degradation [3]. Heat shock protein 90 is a ubiquitous molecular chaperone that is involved in the folding, activation and assembly of many proteins, including key mediators of signal transduction and transcriptional regulation [7]. Selective Hsp inhibitors, such as 17-dimethylaminoethylamino-17-demethoxy-geldanamycin (17-DMAG), block the ATP-binding site of Hsp and exert pleiotropic functions, including induction of the heat shock response [8]. Previous studies have shown that these drugs can block the activity of certain pro-

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