Induction of heat shock proteins by hyperthermia and noise overstimulation in hsf1 -/- mice.

Diverse cellular and environmental stresses can activate the heat shock response, an evolutionarily conserved mechanism to protect proteins from denaturation. Stressors activate heat shock transcription factor 1 (HSF1), which binds to heat shock elements in the genes for heat shock proteins, leading to rapid induction of these important molecular chaperones. Both heat and noise stress are known to activate the heat shock response in the cochlea and protect it from subsequent noise trauma.

Heat shock factor 1-deficient mice exhibit decreased recovery of hearing following noise overstimulation.

Heat shock proteins (Hsps) can enhance cell survival in response to stress. Heat shock factor 1 (Hsf1) is the major transcription factor that regulates stress-inducible Hsp expression. We previously demonstrated the presence of Hsf1 in the rodent cochlea and also demonstrated that a heat shock known to precondition the cochlea against noise trauma results in Hsf1 activation in the rodent cochlea.

Induction of heat shock protein 32 (Hsp32) in the rat cochlea following hyperthermia.

The genes for heat shock proteins (Hsps) can be upregulated in response to cellular trauma, resulting in enhanced cell survival and protection. Hsp32, also known as heme oxygenase 1, catalyzes the degradation of heme to produce carbon monoxide and bilirubin, which play a variety of cytoprotective functions at physiological concentrations, and iron, which is rapidly sequestered by the iron-binding protein ferritin. In the present study we examined the expression and localization of Hsp32 in the rat cochlea after heat shock using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), Western blot, and immunocytochemistry.

Expression and localization of heat shock factor (Hsf) 1 in the rodent cochlea.

Activation of heat shock factors (Hsfs) is one of the potential mechanisms for regulating the transcription of the heat shock proteins (Hsps) and certain other stress-responsive genes. Reverse transcription polymerase chain reaction (RT-PCR), Western blot and immunocytochemistry were used to examine the expression and localization of Hsf1, the stress-responsive member of the Hsf family, in the rat and mouse cochlea. Cerebellum was used as a positive control.

Constitutive expression of Hsp27 in the rat cochlea.

Heat shock protein-27 (Hsp27) is known to function as both a stress-inducible molecular chaperone and regulator of actin polymerization. For many cells in the cochlea, actin is part of the cytoskeleton and plays an important role in the maintenance of cochlear function. To understand the molecular processes by which the cochlear actin cytoskeleton is maintained and regulated during normal auditory function, we examined the expression and localization of Hsp27 in the normal rat cochlea.