The impact of acute heat exposure on the heat shock response (HSR) between males and females

While acute heat stress induces genomic changes in immune cells of young adults, the influence of ovarian hormones on the molecular response remains unclear, despite their documented role in thermoregulation. This study investigated the molecular response to acute heat stress in males (n=11), eumenorrheic (EUM) females in the mid-luteal phase (n=10), and combined monophasic oral contraceptive (OCP) user females (n=9) who underwent a 20-min far-infrared (IR) sauna session (57.2 ± 2.0ºC, 24.7 ± 5.6% relative humidity). Core temperature, skin temperature, heart rate, and thermal perception were recorded every 5 minutes. Plasma extracellular heat shock protein 70 (eHSP70) and peripheral blood mononuclear cell (PBMC) mRNA were analyzed from venous blood collected at baseline, 1-hr, 4-hrs, and 24-hrs post sauna using ELISA and RNA sequencing, respectively. Timepoint effects were all significant for all physiological and perceptual measures (P<0.001). Mean core temperature was elevated in both female groups (EUM: 37.5±0.2ºC; OCP: 37.4±0.2ºC) compared to males (37.1±0.2ºC) (P<0.001). Skin temperature (39.6±0.5 °C; P=0.496) and heart rate (121±11 beats·min-1; P=0.529), shown here at the 20-minute timepoint, were nonsignificant between all groups. OCP females reported higher thermal comfort scores (greater discomfort) at the end of the sauna and sensed a hotter thermal environment throughout the intervention compared to the males. Timepoint (P=0.773) and group (P=0.066) effects of eHSP70 (0.8±0.8 ng·ml-1) were nonsignificant. OCP females had the greatest number of differentially expressed genes (DEGs) and differentially expressed HSP genes, especially at the 24-hr timepoint. In conclusion, high exogenous ovarian hormones impacted the intracellular heat shock response (HSR) through the increased production of differentially expressed HSP genes, indicating that OCP users have a greater intracellular HSR to acute heat exposure despite thermoregulatory similarities to EUM females.

Name thesis:degree_name

M.Sc. Applied Health Sciences

Level thesis:degree_level

Master

Discipline thesis:degree_discipline

Faculty of Applied Health Sciences

Department dc:contributor.department

Applied Health Sciences Program

Grantor dc:publisher

Brock University

Year dc:date.issued

2026

Author dc:creator

• Andrade, Mariska Jonette

Advisor dc:contributor.advisor

• Mündel, Toby

• ODONTOLOGY::Physiology
• NATURAL SCIENCES::Biology::Cell and molecular biology::Immunology
• NATURAL SCIENCES::Biology::Other biology::Functional genomics

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/10464/20332

OAI identifier oai:identifier

oai:brocku.scholaris.ca:10464/20332