Serum heme oxygenase-1 levels are increased in Parkinson's disease but not in Alzheimer's disease

Objective - Oxidative stress is implicated in Parkinson's disease (PD) and Alzheimer's disease (AD), and heme oxygenase-1 (HO-1) is a potent antioxidant overexpressed in PD substantia nigra and AD cerebral cortex and hippocampus, indicating a possible up-regulation of antioxidant defenses in both neurodegenerative diseases. The role of HO-1 in peripheral blood of PD and AD patients remains unresolved. Methods - We measured serum HO-1 levels in 107 patients with PD, 105 patients with AD, 104 controls for PD and 120 controls for AD. Results - The median serum concentration of HO-1 was significantly higher in PD patients (2.04 ng/ml) compared with that of PD controls (1.69 ng/ml, P = 0.016), with PD patients predominating over controls in the upper tertile of serum HO-1 levels, whereas there was more PD controls than PD patients in the lower tertile (P = 0.006). Median serum levels of HO-1 did not differ significantly between AD patients and AD controls. Conclusion - The increase of serum HO-1 levels in PD patients could indicate a systemic antioxidant reaction related to a chronic oxidative stress state in PD brain.