Changes in mRNA levels for heat-shock/stress proteins (Hsp) and a secretory vesicle associated cysteine-string protein (Csp1) after amphetamine (AMPH) exposure

Damage to nerve terminals, reactive gliosis and somatic degeneration can result when pronounced hyperthermia occurs during amphetamine (AMPH) exposure. The effects of AMPH-induced hyperthermia and damage on the relative mRNA levels for several heat shock/stress proteins (Hsp27, Hsp60, Hsp70 and Hsc70), as well as secretory vesicle associated cysteine-string protein (Csp1) were determined In both the striatum and substantia nigra using reverse transcriptase polymerase chain reaction (RT-PCR). These changes were compared to changes in Hsp mRNA levels seen in primary rat cerebral astrocyte cultures after heat shock/stress. Striatal Hsp70 mRNA increased about 2-fold over control levels at 16 hr after AMPH-induced hyperthermia, and was the only Hsp species to significantly increase in response to AMPH. Hsp70 mRNA levels returned to control within 14 days after AMPH. Two-fold increases in Hsp79 mRNA were also seen in primary cultures of rat cerebrum 24 hr after heat shock. In primary cultures and brain tissue, the increased Hsp70 mRNA levels were still more than 500-fold less than constitutive Hsc70 mRNA and 50-fold less than Hsp60 levels. Hsp27 mRNA was not present in the striatum, nigra and primary cell cultures. Thus, the expression of Hsp species mRNA measured was very similar in brain tissue and primary cell cultures. Because only a modest induction of Hsp 70 mRNA occurred, the Hsp species evaluated may only play a minor role in AMPH neurotoxicity, However, further studies are necessary to determine whether large increases in Hsp 70 are occurring In selected neurons or glia in the striatum, RT-PCR products for Csp1 were produced in total RNA obtained from brain but not from cultured astrocytes, suggesting that the Csp1 mRNA measured by RT-PCR is of neuronal origin. Csp1 mRNA levels were acutely downregulated in neurons in the substantia nigra, possibly in response to damage, but not the striatum after AMPH exposure. A slight long-term upregulation at 4 months of Csp1 mRNA may occur in the striatum but not in nigra.