Mitochondrial DNA variants as genetic risk factors for Parkinson disease

BACKGROUND AND PURPOSE

Investigation of the relationship between mitochondrial DNA (mtDNA) variants and Parkinson disease (PD) remains an issue awaiting more supportive evidence. Moreover, an affirming cellular model study is also lacking.

METHODS

The index mtDNA variants and their defining mitochondrial haplogroup were determined in 725 PD patients and 744 non-PD controls. Full-length mtDNA sequences were also conducted in 110 cases harboring various haplogroups. Cybrid cellular models, composed by fusion of mitochondria-depleted rho-zero cells and donor mitochondria, were used for a rotenone-induced PD simulation study.

RESULTS

Multivariate logistic regression analysis revealed that subjects harboring the mitochondrial haplogroup B5 have resistance against PD (odds ratio 0.50, 95% confidence interval 0.32-0.78; P = 0.002). Furthermore, a composite mtDNA variant group consisting of A10398G and G8584A at the coding region was found to have resistance against PD (odds ratio 0.50, 95% confidence interval 0.33-0.78; P = 0.001). In cellular studies, B4 and B5 cybrids were selected according to their higher resistance to rotenone, in comparison with cybrids harboring other haplogroups. The B5 cybrid, containing G8584A/A10398G variants, showed more resistance to rotenone than the B4 cybrid not harboring these variants. This is supported by findings of low reactive oxygen species generation and a low apoptosis rate in the B5 cybrid, whereas a higher expression of autophagy was observed in the B4 cybrid particularly under medium dosage and longer treatment time with rotenone.

CONCLUSIONS

Our studies, offering positive results from clinical investigations and cybrid experiments, provide data supporting the role of variant mtDNA in the risk of PD.

Expression of high-mobility group box protein 1 in diabetic foot atherogenesis

The role of high mobility group box 1 (HMGB1) has been demonstrated in stroke and coronary artery disease but not in peripheral arterial occlusive disease (PAOD). The pathogenesis of HMGB1 in acute and chronic vascular injury is also not well understood. We hypothesized that HMGB1 induces inflammatory markers in diabetic PAOD patients. We studied 36 diabetic patients, including 29 patients with PAOD, who had undergone amputation for diabetic foot and 7 nondiabetic patients who had undergone amputation after traumatic injury. Expression of HMGB1 and inflammatory markers were quantified using immunohistochemical staining. Mitochondrial DNA copy number was quantified using real-time polymerase chain reaction. Compared with that in the traumatic amputation group, HMGB1 expression in vessels was significantly higher in the diabetes and diabetic PAOD groups. In all subjects, arterial stenosis grade was positively correlated with the expression levels of HMGB1, 8-hydroxyguanosine, malondialdehyde, vascular cell adhesion molecule 1, and inflammatory markers CD3, and CD68 in both the intima and the media of vessels. Furthermore, HMGB1 expression level was positively correlated with 8-hydroxyguanosine, vascular cell adhesion molecule 1, nuclear factor-kB, CD3, and CD68 expression. Within the PAOD subgroup, subjects with HMGB1 expression had higher expression of the autophagy marker LC3A/B and higher mitochondrial DNA copy number. HMGB1 may be an inflammatory mediator with roles in oxidative damage and proinflammatory and inflammatory processes in diabetic atherogenesis. Moreover, it may have dual effects by compensating for increased mitochondrial DNA copy number and increased autophagy marker expression.