Differences in heating methods may account for variation in reported effects on gammaH2AX focus formation

Area of Science:

• Cellular Biology
• Molecular Biology
• Genotoxicology

Background:

• Conflicting reports exist on whether heat shock induces DNA damage, as measured by gammaH2AX foci.
• Previous studies indicated heat shock does not cause DNA damage in mammalian cell lines.
• Discrepancies may arise from variations in experimental methodologies.

Purpose of the Study:

• To investigate the influence of five distinct heating methods on gammaH2AX foci formation.
• To clarify the reasons for divergent findings regarding heat shock-induced DNA damage.
• To compare the responses of human amnion FL cells and Chinese hamster CHL cells to different heat shock conditions.

Main Methods:

• Exposure of FL and CHL cells to five heating methods (heat block, water bath, half-submerged water bath, pre-heated medium, heating oven) at 42°C and 45°C for 30 minutes.
• Assessment of gammaH2AX foci formation as a marker for DNA damage.
• Evaluation of cytotoxicity at different temperatures.

Main Results:

• Heating at 45°C induced varying degrees of cytotoxicity, while 42°C for 30 minutes showed no significant cytotoxicity.
• Only the heat block method consistently induced gammaH2AX foci in both cell types at both tested temperatures.
• CHL cells demonstrated higher sensitivity to heat shock compared to FL cells across different methods.

Conclusions:

• Specific heating methods can induce gammaH2AX foci formation, with significant differences observed between methods.
• Cellular responses to heat shock vary between thermo-tolerant and non-tolerant cells.
• Discrepancies in reported gammaH2AX foci formation are likely due to the diverse heating methodologies employed in different studies; gammaH2AX expression may not be a reliable surrogate for cell killing.