beta-Adrenergic signaling and thyroid hormones affect HSP72 expression during heat acclimation.
Heat acclimation upregulates 72-kDa heat shock protein (HSP72) and predisposes to faster activation of the heat shock response (HSR). This study investigates the role played by beta-adrenergic signaling and/or plasma thyroxine level in eliciting these features by using rats undergoing 1) heat acclimation (AC; 34 degrees C, 2 and 30 days); 2) AC with beta-adrenergic blockade; 3) AC-maintained euthyroid; 4) hypothyroid; 5) hyperthyroid; and 6) controls. The hsp72 mRNA (RT-PCR) and HSP72 levels (Western blot) were measured before and after heat stress (2 h, 41 degrees C, rectal temperature monitored). beta-Adrenergic blockade during AC abolished HSP72 accumulation, without disrupting HSR. Low thyroxine blunted the HSR at posttranscriptional level, whereas thyroxine administration in hyperthyroid and AC-maintained euthyroid rats arrested heat stress-evoked hsp72 transcription. We conclude that beta-adrenergic signaling contributes to the high HSP72 level characterizing the AC state. Thyroxine has two opposing effects: 1) direct repressive on rapid hsp72 transcription after heat stress; and 2) indirect stimulatory via beta-adrenergic signaling. Low thyroxine could account for diminished HSP72 synthesis via lower heat production and thermoregulatory set point.
Maloyan
Alina
A
Division of Physiology, Faculty of Dental Medicine, The Hebrew University, Jerusalem 91120, Israel.
Horowitz
Michal
M
D000064:Acclimatization / Q000502:physiology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics; D006358:Hot Temperature / Q000009:adverse effects*; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020239:Receptor Cross-Talk / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D013963:Thyroid Hormones / Q000494:pharmacology*; D013974:Thyroxine / Q000008:administration & dosage / Q000494:pharmacology; D015854:Up-Regulation / Q000502:physiology
D000319:Adrenergic beta-Antagonists; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D013963:Thyroid Hormones; D013974:Thyroxine