Overexpression of neutrophil neuronal nitric oxide synthase in Parkinson's disease

Abstract

Much evidence supports a role of nitric oxide (·NO) and peroxynitrite (ONOO-) in experimental and idiopathic Parkinson's disease (PD); moreover, an overexpression of neuronal nitric oxide synthase (nNOS) was recently reported in the basal ganglia of PD patients. In accord, we previously found a 50% increased ·NO production rate during the respiratory burst of circulating neutrophils (PMN) from PD patients. As PMN express the nNOS isoform, the objective of the present study was to ascertain whether this increased ·NO production is representative of nNOS gene upregulation. PMN were isolated from blood samples obtained from seven PD patients and seven age- and sex-matched healthy donors; nNOS mRNA was amplified by reverse transcriptase-polymerase chain reaction and the products were hybridized with a probe for nNOS. Nitrotyrosine-containing proteins and nNOS were detected by Western blot and NO production rate was measured spectrophotometrically by the conversion of oxymyoglobin to metmyoglobin. The results showed that both ·NO production and protein tyrosine nitration were significantly increased in PMN isolated from PD patients (PD 0.09 ± 0.01 vs 0.06 ± 0.008 nmol min-1 106 cells-1; P < 0.05). In addition, five of the seven PD patients showed about 10-fold nNOS mRNA overexpression; while two of the seven PD patients showed an expression level similar to that of the controls; detection of nNOS protein was more evident in the former group. In summary, it is likely that overexpression of nNOS and formation of ONOO- in PMN cells from PD patients emphasizes a potential causal role of ·NO in the physiopathology of the illness. (C) 2000 Academic Press.