Thermal stress in Danio rerio: a link between temperature, light, thermo-TRP channels, and clock genes.

It is believed that the biological systems perceiving temperature and light daily cycles were subjected to the simultaneous selective pressures, which resulted in their co-evolutionary association. We investigated the influence of 1h 33°C heat shock on the expression of clock and heat shock protein genes, as well as the role of the thermo-TRP channel, TRPV1, in ZEM-2S cells of the teleost Danio rerio, in constant dark (DD) or light-dark cycles (LD). After heat shock, we observed an acute increase of hsp90 aa1 levels in both DD and LD conditions. Interestingly, the expression of hsp90 aa1 was two-fold lower in LD than in DD, what suggests an antagonistic effect of white light on heat shock action. Regarding clock genes, no effect was found in cells subjected to the heat shock in DD. When cells were kept in LD, the expression of per1, per2, cry1a, and cry1b increased in response to heat shock, indicating that heat shock only affects clock core of LD-synchronized ZEM-2S cells. We then evaluated whether TRPV1 played a role in heat-mediated hsp90 aa1 and per2 responses: hsp90 aa1 increase was unaffected whereas per2 increase was partially blocked by TRPV1 inhibitor, demonstrating the channel participation in clock gene regulation by heat shock. Taken together, our results open a novel investigative perspective regarding the relationship between temperature and clock genes, placing a new player in the regulation of this phenomenon: the TRPV1 channel.