Inhibition of the cyclooxygenase isoenzymes COX-1 and COX-2 provide neuroprotection in the MPTP-mouse model of Parkinson's disease

Abstract

To study the possible role of the isoenzymes of cyclooxygenase COX-1 and COX-2 in the MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model of Parkinson's disease we used acetylsalicylic acid, a COX-1/COX-2 inhibitor, in comparison with meloxicam, a preferential COX-2 inhibitor. As markers of protection we determined the effects on MPTP-induced striatal dopamine depletion, locomotor activity, cell loss, and tyrosine hydroxylase immunoreactivity (TH-IR) in the substantia nigra pars compacta. Male C57BL/6 mice (n = 82) were treated with a single dose of acetylsalicylic acid (10, 50, 100 mg/kg i.p.) or meloxicam (2, 7.5, 50 mg/kg i.p.) immediately prior to administration of MPTP (30 mg/kg s.c.) or saline. After 7 days the mice were sacrificed to analyze striatal dopamine and metabolite levels. Nigral sections were processed for Nissl-staining and TH-IR. In the saline-treated MPTP control group striatal dopamine levels were reduced to 15.9% of control values. Dopamine depletion was significantly attenuated to values of 37.1 and 38.6% of saline control values by acetylsalicylic acid (50 and 100 mg/kg) and to values of 36 and 40% by meloxicam (7.5 and 50 mg/kg), respectively. MPTP-induced decrease of locomotor activity was significantly attenuated by acetylsalicylic acid and meloxicam. Remarkably, the MPTP-induced decrease of TH-IR as well as the loss of nigral neurons was nearly completely prevented by acetylsalicylic acid (100 mg/kg) and meloxicam (7.5 and 50 mg/kg). In conclusion, the inhibition of either COX-1/COX-2 by acetylsalicylic acid or preferentially COX-2 by meloxicam provided a clear neuroprotection against MPTP-toxicity on the striatal and nigral levels.