Modulation of apoptotic regulatory proteins and early activation of cytochrome C following systemic 3-nitropropionic acid administration.

The present study utilized the administration of the mitochondrial toxin, 3-nitropropionic acid (3-NP), to mimic the pathology associated with Huntington's disease (HD). 3-NP causes striatal cell degeneration via the inhibition of succinate dehydrogenase. There is growing evidence suggesting the role of apoptosis in 3-NP cell death. TUNEL staining, DNA fragmentation, and changes in bcl-2 mRNA levels have been associated with this metabolic impairment. We wish to further elucidate the apoptotic cascade in this model of HD pathogenesis. 3-NP was administered to rats intraperitoneally at 20mg/kg/day for up to 3 days. At 3 days, characteristic behavioral and morphological effects became evident. While cell death did not become apparent within the first 3 days, there were changes in the levels of apoptotic regulatory proteins and translocation of cytochrome c. Within 24 h after 3-NP administration there were elevations in both bcl-xl and bax. However, bcl-xl protein levels quickly returned to control levels while bax levels continued to increase, resulting in a detrimental bax/bcl-xl ratio. Bax has been demonstrated to facilitate cytochrome c release by forming mitochondrial pores. We saw cytochrome c translocate from the mitochondria to the cytosol approximately 24 h after initial 3-NP administration when compared to saline-injected controls. This evidence generated using the 3-NP degeneration model may help elucidate the apoptotic cascade associated with HD neurodegeneration.