beta-Adrenergic signaling and thyroid hormones affect HSP72 expression during heat acclimation

J Appl Physiol (1985). 2002 Jul;93(1):107-15. doi: 10.1152/japplphysiol.01122.2001.

Abstract

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.

MeSH terms

  • Acclimatization / physiology*
  • Adrenergic beta-Antagonists / pharmacology
  • Animals
  • Blotting, Western
  • Body Temperature / drug effects
  • Body Temperature / physiology
  • Body Weight / physiology
  • HSP72 Heat-Shock Proteins
  • Heat-Shock Proteins / biosynthesis*
  • Heat-Shock Proteins / genetics
  • Hot Temperature / adverse effects*
  • Male
  • RNA, Messenger / biosynthesis
  • Rats
  • Receptor Cross-Talk / physiology
  • Receptors, Adrenergic, beta / physiology*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / physiology*
  • Thyroid Hormones / pharmacology*
  • Thyroxine / administration & dosage
  • Thyroxine / pharmacology
  • Up-Regulation / physiology

Substances

  • Adrenergic beta-Antagonists
  • HSP72 Heat-Shock Proteins
  • Heat-Shock Proteins
  • RNA, Messenger
  • Receptors, Adrenergic, beta
  • Thyroid Hormones
  • Thyroxine