Thermotolerance induced at a mild temperature of 40°C alleviates heat shock-induced ER stress and apoptosis in HeLa cells.

Abstract

Hyperthermia (39-45°C) has emerged as an alternate prospect for cancer therapy in combination with radiation and chemotherapy. Despite promising progress in the clinic, molecular mechanisms involved in hyperthermia-induced cell death are not clear. Hyperthermia causes protein denaturation/aggregation, which results in cell death by apoptosis and/or necrosis. Hyperthermia also induces thermotolerance, which renders cells resistant to subsequent exposure to lethal heat shock. This study investigates the role of both lethal (42-43°C) and mild (40°C) hyperthermia in regulating ER stress and ER stress-induced apoptosis in HeLa cells. The ability of mild thermotolerance induced at 40°C to alleviate either or both of these processes is also determined. Hyperthermia (42-43°C) induced ER stress, revealed by phosphorylation of PERK, eIF2α and IRE1α, cleavage of ATF6 and increased expression of BiP and sXBP1. Real-time PCR revealed that mRNA levels of ATF6, ATF4, BiP, sXBP1 and CHOP increased in cells exposed to hyperthermia. Moreover, hyperthermia caused disruption of calcium homeostasis and activated the calpain-calpastatin proteolytic system and ER resident caspase 4. Pre-exposure to mild hyperthermia (40°C) alleviated the induction of cytotoxicity and ER stress by hyperthermia (42-43°C) and protected cells against ER stress-induced apoptosis. ShRNA-mediated depletion of Hsp72 abrogated protective effects of mild thermotolerance (40°C) against heat-shock induced ER stress and sensitized cells to ER stress-mediated apoptosis. Our findings show that Hsp72 contributes to the protective effects of mild hyperthermia (40°C) against hyperthermia-induced ER stress and apoptosis.

• Authors: Ahmed Bettaieb, Diana A Averill-Bates
• Journal: Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1853 Issue 1 Pg. 52-62 (Jan 2015) ISSN: 0006-3002 [Print] Netherlands
• PMID: 25260982 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier B.V. All rights reserved.

Chemical References

• HSP72 Heat-Shock Proteins
• Calpain
• Caspases

Topics

• Apoptosis
• Calpain (metabolism)
• Caspases (metabolism)
• Endoplasmic Reticulum Stress
• HSP72 Heat-Shock Proteins (physiology)
• HeLa Cells
• Heat-Shock Response
• Hot Temperature
• Humans