Comprehensive behavioral testing in the R6/2 mouse model of Huntington's disease shows no benefit from CoQ10 or minocycline

Previous studies of the effects of coenzyme Q10 and minocycline on mouse models of Huntington’s disease have produced conflicting results regarding their efficacy in behavioral tests. Using our recently published best practices for husbandry and testing for mouse models of Huntington’s disease, we report that neither coenzyme Q10 nor minocycline had significant beneficial effects on measures of motor function, general health (open field, rotarod, grip strength, rearing-climbing, body weight and survival) in the R6/2 mouse model. The higher doses of minocycline, on the contrary, reduced survival. We were thus unable to confirm the previously reported benefits for these two drugs, and we discuss potential reasons for these discrepancies, such as the effects of husbandry and nutrition

The Michael J. Fox Foundation for Parkinson’s Research Strategy to Advance Therapeutic Development of PINK1 and Parkin

The role of mitochondria in Parkinson’s disease (PD) has been investigated since the 1980s and is gaining attention with recent advances in PD genetics research. Mutations in PRKN and PTEN-Induced Putative Kinase 1 (PINK1) are well-established causes of autosomal recessive early-onset PD. Genetic and biochemical studies have revealed that PINK1 and Parkin proteins function together in the same biological pathway to govern mitochondrial quality control. These proteins have also been implicated in the regulation of innate and adaptive immunity and other mitochondrial functions. Additionally, structural studies on Parkin have delineated an activation mechanism and have identified druggable regions that are currently being explored by academic and industry groups. To de-risk therapeutic development for these genetic targets, The Michael J. Fox Foundation for Parkinson’s Research (MJFF) has deployed a strategic funding and enabling framework that brings together the research community to discuss important breakthroughs and challenges in research on PINK1-Parkin biology, supports collaborative initiatives to further our understanding within this field and develops high-quality research tools and assays that are widely available to all researchers. The Foundation’s efforts are leading to significant advances in understanding of the underlying biology of these genes, proteins and pathways and in the development of Parkinson’s therapies

Comprehensive behavioral and molecular characterization of a new knock-in mouse model of Huntington's disease: zQ175.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder characterized by motor, cognitive and psychiatric manifestations. Since the mutation responsible for the disease was identified as an unstable expansion of CAG repeats in the gene encoding the huntingtin protein in 1993, numerous mouse models of HD have been generated to study disease pathogenesis and evaluate potential therapeutic approaches. Of these, knock-in models best mimic the human condition from a genetic perspective since they express the mutation in the appropriate genetic and protein context. Behaviorally, however, while some abnormal phenotypes have been detected in knock-in mouse models, a model with an earlier and more robust phenotype than the existing models is required. We describe here for the first time a new mouse line, the zQ175 knock-in mouse, derived from a spontaneous expansion of the CAG copy number in our CAG 140 knock-in colony [1]. Given the inverse relationship typically observed between age of HD onset and length of CAG repeat, since this new mouse line carries a significantly higher CAG repeat length it was expected to be more significantly impaired than the parent line. Using a battery of behavioral tests we evaluated both heterozygous and homozygous zQ175 mice. Homozygous mice showed motor and grip strength abnormalities with an early onset (8 and 4 weeks of age, respectively), which were followed by deficits in rotarod and climbing activity at 30 weeks of age and by cognitive deficits at around 1 year of age. Of particular interest for translational work, we also found clear behavioral deficits in heterozygous mice from around 4.5 months of age, especially in the dark phase of the diurnal cycle. Decreased body weight was observed in both heterozygotes and homozygotes, along with significantly reduced survival in the homozygotes. In addition, we detected an early and significant decrease of striatal gene markers from 12 weeks of age. These data suggest that the zQ175 knock-in line could be a suitable model for the evaluation of therapeutic approaches and early events in the pathogenesis of HD

Mean plasma and brain levels of minocycline.

<p><b>Experiment 3.</b> Both plasma and brain minocycline levels were higher in WT mice compared to R6/2 mice (Plasma: F(1,19) = 1.4, p<0.01; brain: genotype main effect: F(1,10) = 19.6, p<0.002). <b>Experiment 4.</b> Brain and plasma concentrations of minocycline in R6/2 mice were significantly higher than in WT treated mice (Brain: treatment×genotype main effect: F(1,16) = 7.67, p<0.02, simple main effects: p<0.0001; plasma: genotype main effect: F(1,17) = 27.89, p<0.03) in the two 0.375% dosing groups.</p

Effect of the administration of 0.6% of CoQ10 in food in R6/2 mice.

<p>WT mice and R6/2 mice were fed with a diet with HydroQsorb (HQD) alone or with 0.6% CoQ10 in HQD. There was no treatment effect on survival (A). CoQ10 significantly decreased the body weight (B) of R6/2 males between 6 and 10 weeks of age (treatment×age×gender interaction: F(22,330) = 4.1, p<0.0001; simple main effects: ps<0.05). There were no effects of treatment on the latency to fall from the rotarod (C). In mutant females, CoQ10 diminished locomotor activity in the open field (D). Treated R6/2 females were significantly hypoactive at 4 weeks (0–5 min), 6 weeks (last 10 min), at 12 weeks of age (20 to 25 min; treatment×gender interaction: F(1,35) = 6.7, p<0.02; simple main effects: p<0.007; treatment×age×time interaction: F(30,460) = 3.4, p<0.0001; simple main effects: ps<0.05). R6/2 treated mice reared significantly less in the open field (E) at 6 weeks of age compared with untreated mutant mice (treatment×age interaction: F(3,92) = 3.2, p<0.03; simple main effects: p<0.035). There were no treatment effects on either grip strength (F) or in the rearing climbing test (G). CoQ10 had no effects in WT mice (A–F).</p

Effect of the administration of 0.2% of CoQ10 in food in R6/2 mice.

<p>WT mice received unsupplemented diet (UD) and R6/2 mice received either UD or 0.2% CoQ10. There were no significant treatment effects on survival (A), body weight (B) or rotarod (C: latency to fall). Deleterious effects of 0.2% CoQ10 were observed in the total distance traveled in the open field (D) at 4 and 12 weeks of age, mainly in the first 5 min of the session (treatment×age interaction: F(3,213) = 7.5, p<0.0001; treatment×session time interaction: F(5,375) = 2.5, p<0.04; simple main effects: p<0.05). There were no effects on the rearing frequency in the open field (E); CoQ10 impaired grip strength (F) of female mice at 12 weeks of age (treatment×gender interaction (F(1,76) = 11.3, p<0.002, simple main effects: p<0.001) and decreased the number of mice that climbed in the rearing climbing test (G, p<0.04).</p

Effect of daily i.p. administration of 5mg/kg of minocycline in R6/2 mice.

<p>WT and R6/2 mice received either 5mg/kg of minocycline or its vehicle by intraperitoneal injection. Minocycline had no effects on survival (A) on either R6/2 or WT mice, but transiently increased the body weight (B) of mutant male mice at 8, 10, 11 and 12 weeks of age (treatment×gender×age interaction: F(22,312) = 4.2, p<0.0001; simple main effects: ps<0.05). In the WT group, minocycline did not produce significant effects in body weight. In the rotarod test (C), although there was a triple interaction of treatment, age and day for R6/2 mice, simple main effects did not reveal a consistent pattern (overall effects: treatment×age×day interaction: F(10,143) = 3.2, p<0.001). There were no effects for the WT mice. Minocycline transiently increased locomotion (D) in R6/2 male mice (treatment×gender×age: F(6,87) = 4.5; p<0.0005; simple main effects: ps<0.05 at 4 weeks of age) but decreased locomotion in the male WT mice (treatment×gender×week interaction, F(6,102) = 2.6, p<0.03, simple main effects and post hocs, ps<0.05 at 4 weeks of age). Rearing frequency (E) was transiently decreased by minocycline in female R6/2 mice at 6 weeks, but increased in male R6/2 mice at 6 and 8 weeks of age (treatment×gender interaction: F(1,33) = 11.2, p<0.002; treatment×age interaction: F(3,87) = 6.4, p<0.001; treatment×gender×age interaction: F(6,87) = 5.4, p<0.0001; simple main effects: ps<0.05). Minocycline decreased rearing in WT mice at 8 and 12 weeks of age especially in the male group (treatment×gender interaction, F(1,37) = 9.9, p<0.0005; treatment×age interaction: F(3,102) = 8.9, p<0.0001, simple main effects, ps<0.05). Minocycline did not affect grip strength (F) or rearing (G) in either R6/2 or WT mice although the latter showed a tendency to rear less (p<.07).</p