Enhancement of HSP72 Gene Expression in Spinal Cord After Preconditioning for Transient Ischemia in Rabbits

Abstract

We investigated induction of the heat shock protein 72 (HSP72) gene and protein in rabbit spinal cord with or without preconditioning. Neurological function, morphological changes, and induction of HSP72 mRNA and protein were compared for rabbits exposed to 15 min of ischemia 2 days after sham treatment and those with 15 min of ischemia 2 days after 10 min of preconditioning. HSP72 mRNA was induced at 8 h of reperfusion following a 15-min period of ischemia 2 days after the sham treatment. HSP72 protein was slightly induced selectively in motor neuron cells after 8 h of reperfusion, and about 70% of motor neuron cells showed selective cell death after 7 days of reperfusion (P < 0.01). In contrast, large populations of motor neuron cells survived 7 days following 15 min of ischemia that was applied 2 days after preconditioning (P < 0.01). HSP72 mRNA was induced persistently, in contrast to that in rabbits exposed to 15 min of ischemia 2 days after the sham treatment. The motor neuron cells produced strongly immunoreactive HSP72 from 8 h to 2 days. Preconditioning with 10 min of ischemia enhanced and prolonged HSP72 gene expression at both mRNA and protein levels and saved the motor neuron cells from subsequent lethal ischemia. These changes in HSP72 gene expression may play an important role in the acquisition of ischemic tolerance of motor neuron cells in rabbit spinal cord.