Fig. 1

Parkin deficiency increases cytosolic hydrogen peroxide in the brain when MnSOD activity is reduced. a Schema of mouse chromosome 17, where prkn and Sod2 loci are separated by 1 centimorgan (cM) and b the breeding strategy used to generate bi-genic prkn^−/−//Sod2^± mice and littermate controls. c Representative Western blot of parkin, MnSOD and actin levels from ~ 3 month-old mouse brains (representative of n = 3 mice/genotype). d Relative MnSOD activity in isolated mitochondria from whole brain lysates of wild-type (WT) and bi-genic littermates, as shown in (c). e–f Ratio of endogenous levels of H₂O₂ (μM) to total protein concentration (μg/μL) in the cortex (e) and midbrain (f) homogenates from 6 month-old mice. g Representative Western blots of constituents from mitochondrial and cytosolic fractions of WT and prkn^−/− mouse brains, with parkin, Dj-1, MnSOD, aconitase-2 and actin as markers (*denotes a non-specific band). h–i Ratio of endogenous levels of H₂O₂ (μM) to total protein concentration (μg/μL) in mitochondria-enriched (h) and cytosolic fractions of the brain (i) from 6 to 8 month-old WT and prkn^−/− animals (left panel), and from 2 to 4 month-old prkn^−/−, Sod2^± as well as bi-genic mice (right panel). Data represent the mean normalized to WT using n = 3/genotype d–f or n = 4–7/genotype (h–i) ± SEM. Significance was determined using unpaired Student T-test d, h and 1-way ANOVA with Tukey’s post-hoc (e, f, i), where *p ≤ 0.05, **p ≤ 0.01, and ***p ≤ 0.001