Journal of Neural Transmission

, Volume 108, Issue 12, pp 1363–1374

Oxidative metabolites of 5-S-cysteinyldopamine inhibit the pyruvate dehydrogenase complex

  • H. Li
  • G. Dryhurst

DOI: 10.1007/s007020100013

Cite this article as:
Li, H. & Dryhurst, G. J Neural Transm (2001) 108: 1363. doi:10.1007/s007020100013

Summary.

The principal neuropathological feature of Parkinson's disease is the degeneration of melanized dopamine neurons in the substantia nigra pars compacta (SNc). Characteristic pathobiochemical changes in the parkinsonian SNc include a fall of both dopamine (DA) and glutathione levels (GSH), increased activity of γ-glutamyl transpeptidase, a key enzyme involved in the degradation of GSH to L-cysteine (CySH), together with evidence for elevated intraneuronal superoxide (O2−•), nitric oxide (NO·) and thence peroxynitrite (ONOO) generation, and accelerated DA oxidation as indicated by a large rise of the 5-S-cysteinyldopamine (5-S-CyS-DA)/DA concentration ratio. The latter effect is consistent with an increased rate of DA oxidation by O2−• and ONOO forming DA-o-quinone which reacts with CySH forming 5-S-CyS-DA. However, 5-S-CyS-DA is readily further oxidized to 7-(2-aminoethyl)-3,4-dihydro-5-hydroxy-2H-1,4-benzothiazine-3-carboxylic acid (DHBT-1). Previous studies have demonstrated that DHBT-1 is rapidly accumulated by isolated intact rat brain mitochondria and selectively inhibits complex I respiration and the α-ketoglutarate dehydrogenase (α-KGDH) complex. In this study it is demonstrated that DHBT-1 also inhibits the pyruvate dehydrogenase complex (PDHC). The mechanism underlying the inhibition of all of these enzyme complexes involves bioactivation of intramitochondrial DHBT-1 by oxidation to highly electrophilic metabolites that covalently bind to active site cysteine residues. Thus, oxidative metabolites of intraneuronal 5-S-CyS-DA may contribute to impaired mitochondrial complex I and α-KGDH activities known to occur in the parkinsonian SNc and suggest that impaired PDHC evoked by the same metabolites may also occur in PD.

Keywords: Parkinson's disease, 5-S-cysteinyldopamine, DHBT-1, pyruvate dehydrogenase complex. 

Copyright information

© Springer-Verlag Wien 2001

Authors and Affiliations

  • H. Li
    • 1
  • G. Dryhurst
    • 1
  1. 1.Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, USAUS