Distinct cellular tools of mild hyperthermia-induced acquired stress tolerance in Chinese Hamster Ovary cells

Mild stress could help cells to survive more severe environmental or pathophysiological conditions. In the current study, we investigated the cellular mechanisms which contribute to the development of stress tolerance upon a prolonged (0-12h) fever-like (40 °C) or a moderate (42.5 °C) hyperthermia in mammalian CHO cells. Our results indicate that mild heat triggers a distinct, dose dependent remodeling of the cellular lipidome followed by the expression of heat shock proteins only at higher heat dosages. A significant elevation in the relative concentration of sat-urated membrane lipid species, specific lysophosphatidylinositol and sphingolipid species sug-gests prompt membrane microdomain reorganization and an overall membrane rigidification in response to the fluidizing heat in a time dependent manner. RNAseq experiments reveal that mild heat initiate endoplasmic reticulum stress-related signaling cascades resulting in lipid re-arrangement and ultimately in an elevated resistance against membrane fluidization by benzyl alcohol. To protect cells against lethal, protein denaturing high temperatures the classical heat shock protein response was required. The different layers of stress response elicited by different heat dosages highlights the capability of cells to utilize multiple tools to gain resistance against or to survive lethal stress conditions. Overall design: CHO cells were seeded on culture plates for 24h prior to heat treatments which included 4 bio-logical repeats of 4 sample groups (37 °C, 40 °C for 1 h, 6 h and 42.5 °C for 1 h)