{'fraction_non_alphanumeric': 0.03237410071942446, 'fraction_numerical': 0.023741007194244605, 'mean_word_length': 5.6875, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Thermotolerance induced at a mild temperature of 40°C protects cells against heat shock‐induced apoptosis

Apoptosis constitutes a response of organisms to various physiological or pathological stimuli, and to different stresses. The ability of thermotolerance induced at a mild temperature of 40°C to protect against activation of the apoptotic cascade by heat shock was investigated. When Chinese hamster ovary and human adenocarcinoma cervical cells were pretreated at 40°C for 3 h, they were resistant to subsequent lethal heat shock at 43°C. Induction of thermotolerance at 40°C led to increased expresssion of heat shock proteins 27, 32, 72, and 90. Heat shock induced apoptotic events at the mitochondrial level, involving a decrease in membrane potential, translocation of Bax to mitochondria, and liberation of cytochrome c into the cytosol. These events were diminished in thermotolerant cells. Heat shock (42–45°C) caused activation of initiator caspase‐9 and effector caspases‐3, ‐6, and ‐7, relative to controls at 37°C. Activation of caspases was decreased in thermotolerant cells. Heat shock caused fragmentation of the caspase substrate, inhibitor of caspase‐activated DNase. Fragmentation was diminished in thermotolerant cells. Thermotolerance afforded protection against heat shock‐induced nuclear chromatin condensation, but not against necrosis. © 2005 Wiley‐Liss, Inc.