Association of polymorphisms in the MCP-1 and CCR2 genes with the risk of Parkinson's disease.

Studies investigating the impact of polymorphisms on monocyte chemotactic protein-1 (MCP-1) and CC chemokine receptor (CCR2) on the susceptibility of Parkinson's disease (PD) have reported inconsistent results. Owing to mixed and inconclusive results, we conducted a meta-analysis to systematically summarize and clarify the association between the two gene polymorphisms and PD risk. We performed a meta-analysis of five eligible studies to summarize the data describing the association between PD risk and polymorphisms in MCP-1 A2518G and CCR2 V64I. The association was evaluated by calculating the odds ratios (ORs) with the corresponding 95% confidence intervals (CIs). A significant increased risk of PD was observed in the MCP-1 A2518G polymorphism in allele model (G vs. A: OR 1.12, 95% CI 1.01-1.25, p = 0.03). The dominant model of MCP-1 A2518G genotype showed no significant association with PD risk, while the risk tendency was increased (AG + GG vs. AA: OR 1.20, 95% CI 1.00-1.42, p = 0.05). In addition, CCR2 V64I polymorphism showed no significant association with PD risk (I vs. V: OR 0.33, 95% CI 0.06-1.92, p = 0.22; VI + II vs. VV: OR 1.00, 95% CI 0.83-1.21, p = 0.99). In subgroup analysis by ethnicity, no significant difference was found in both Caucasians and Asians between CCR2 V64I polymorphism and PD risk, while a significant statistical association was identified in Asians between MCP-1 A2518G polymorphism and PD risk. When the data were stratified by study area, the increased risk of PD was observed only in studies conducted in China. In summary, the present meta-analysis suggests that genetic polymorphisms of MCP-1 A2518G may influence the susceptibility of PD in Asian countries, especially in China. However, CCR2 V64I polymorphism is not correlated with PD risk. The results should be interpreted with caution due to limited sample and heterogeneity. Large scale and well-designed studies are needed to validate our findings.