Adaptive cellular response to hyperthermia: 31P-NMR studies.

Area of Science:

• Cell Biology
• Biochemistry
• NMR Spectroscopy

Background:

• Thermotolerance, or acquired heat resistance, is a crucial cellular defense mechanism.
• Heat-shock proteins (HSPs) are involved in cellular protection against stress.
• Intracellular energy status, particularly ATP levels, is vital for cellular function during stress.

Purpose of the Study:

• To investigate dynamic intracellular ATP and inorganic phosphate (Pi) levels in Chinese hamster V79 cells during thermotolerance acquisition.
• To correlate ATP/Pi levels with heat-shock protein synthesis and cell survival under thermal stress.
• To assess the role of glutathione (GSH) in thermotolerance and its impact on ATP levels.

Main Methods:

• Non-invasive measurement of intracellular ATP and Pi using 31P-NMR spectroscopy.
• Induction of thermotolerance and HSP synthesis by controlled heat treatments (43°C followed by 37°C).
• Assessment of cell survival and HSP synthesis (70 kDa and 103 kDa) via parallel cultures and post-treatment analysis.
• Glutathione (GSH) depletion prior to and during heat treatment to study its inhibitory effects.

Main Results:

• Thermotolerance and synthesis of 70 kDa and 103 kDa HSPs were successfully induced after heat shock.
• Depletion of GSH partially inhibited thermotolerance and HSP synthesis.
• Dynamic measurements showed no significant change in intracellular ATP steady-state levels immediately after heating or during the 5-hour post-heating incubation period, even with GSH depletion.

Conclusions:

• Steady-state intracellular ATP levels in mammalian cells are maintained during the acquisition of the thermotolerant state.
• Cellular energy homeostasis is preserved despite the development of thermotolerance and HSP synthesis.
• GSH plays a role in thermotolerance, but ATP levels are not directly dependent on GSH during this process.