Inhibition of autophagy sensitises cells to hydrogen peroxide-induced apoptosis: Protective effect of mild thermotolerance acquired at 40°C.
Various toxic compounds produce reactive oxygen species, resulting in oxidative stress that threatens cellular homeostasis. Yet, lower doses of stress can stimulate defence systems allowing cell survival, whereas intense stress activates cell death pathways such as apoptosis. Mild thermal stress (40°C, 3h) induces thermotolerance, an adaptive survival response that renders cells less sensitive to subsequent toxic stress, by activating defence systems like heat shock proteins, antioxidants, anti-apoptotic and ER-stress factors. This study aims to understand how autophagy and apoptosis are regulated in response to different doses of H2O2, and whether mild thermotolerance can protect cervical carcinoma cells against apoptosis by stimulating autophagy. Autophagy was monitored through Beclin-1 and LC3 expression and acid compartment activity, whereas apoptosis was tracked by caspase activity and chromatin condensation. Exposure of HeLa and C33 A cells to H2O2for shorter times (15-30min) transiently induced autophagy; apoptosis was activated after longer times (1-3h). Mild thermotolerance at 40°C enhanced activation of autophagy by H2O2. Disruption of autophagy using bafilomycin A1 and 3-methyladenine sensitised cells to apoptosis induced by H2O2, in non-thermotolerant cells and, to a lesser extent, in thermotolerant cells. Inhibition of autophagy enhanced apoptosis through the mitochondrial, death receptor and endoplasmic reticulum pathways. Autophagy was activated by lower doses of stress and protects cells against apoptosis induced by higher doses of H2O2. This work improves understanding of mechanisms that might be involved in toxicity of various compounds and could eventually lead to protective strategies against deleterious effects of toxic compounds.
Département des sciences biologiques (TOXEN, BIOMED), Université du Québec à Montréal, Montréal, Québec, Canada.
Maureen
M
Redza-Dutordoir
Département des sciences biologiques (TOXEN, BIOMED), Université du Québec à Montréal, Montréal, Québec, Canada.
Sarah
S
Kassis
Département des sciences biologiques (TOXEN, BIOMED), Université du Québec à Montréal, Montréal, Québec, Canada.
Hou
H
Ve
Département des sciences biologiques (TOXEN, BIOMED), Université du Québec à Montréal, Montréal, Québec, Canada.
Mélanie
M
Grondin
Département des sciences biologiques (TOXEN, BIOMED), Université du Québec à Montréal, Montréal, Québec, Canada. Electronic address: averill.diana@uqam.ca.
Diana A
DA
Averill-Bates
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D000071186:Beclin-1 / Q000235:genetics / Q000378:metabolism; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D042002:Chromatin Assembly and Disassembly; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D018942:Macrolides / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D053218:Receptors, Death Domain / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013696:Temperature; D000071436:Thermotolerance / Q000187:drug effects* / Q000235:genetics; D013997:Time Factors
C491997:BECN1 protein, human; D000071186:Beclin-1; C477012:MAP1LC3A protein, human; D018942:Macrolides; D008869:Microtubule-Associated Proteins; D017382:Reactive Oxygen Species; D053218:Receptors, Death Domain; C025946:3-methyladenine; C040929:bafilomycin A1; D006861:Hydrogen Peroxide; D020169:Caspases; D000225:Adenine
Autophagy; Caspase; Hormesis; Oxidative stress; Thermotolerance