Reversal of neurobehavioral social deficits in dystrophic mice using inhibitors of phosphodiesterases PDE5A and PDE9A

Abstract

Duchenne muscular dystrophy is caused by mutations in the DYSTROPHIN gene. Although primarily associated with muscle wasting, a significant portion of patients (approximately 25%) are also diagnosed with autism spectrum disorder. We describe social behavioral deficits in dystrophin-deficient mice and present evidence of cerebellar deficits in cGMP production. We demonstrate therapeutic potential for selective inhibitors of the cGMP-specific PDE5A and PDE9A enzymes to restore social behaviors in dystrophin-deficient mice.

Figure 1

Dystrophic mice have significant neurobehavioral social deficits from juvenile to adult stages. (a and b) Schematic showing the layout of the social approach experiment in which the mouse is placed in the center chamber (2) and will move towards the novel mouse or novel object. (c–f) Social approach data at 5-week-old (c and d) and 8-week-old (e and f) wild-type (WT; open bars) and mdx^5cv (red bars) male mice show persistent neurobehavioral deficits in the dystrophin mice when compared with age-matched wild-type controls. The social approach F-value of time spent in each chamber for WT mice at 5 weeks of age was F_1,8=12.834 and at 8 weeks of age was F_1,8=23.491. The social approach F-value of time spent in each chamber for mdx^5cv mice at 5 weeks of age was F_1,8=1.398 and at 8 weeks of age was F_1,8=1.09. (c and e) The left bar in the figure represents chamber 1 (novel mouse), the middle bar chamber 2 (center point) and right bar chamber 3 (novel object). (d and f) The left bar in the figure represents chamber 1 (familiar mouse) and the right bar chamber 3 (novel object). The time investigating F-value for WT mice at 5 weeks of age was F_1,8=20.134 and 8 weeks of age was F_1,8=39.175. The time investigating F-value for mdx^5cv mice at 5 weeks of age was F_1,8=4.44 and 8 weeks of age was F_1,8=3.54. For all the panels, *P-value <0.05 and NS, no significance. Eight mice per cohort were used for each social approach experiment. We used a 95% confidence interval for significance (P<0.05) with eight degrees of freedom.

Figure 2

Treatment of dystrophic mice with PDE inhibitors rescues neurobehavioral social deficits. (a and b) Social approach data for wild-type (WT; open bars) and dystrophic (mdx^5cv; red bars) mice given either vehicle, PDE5A inhibitor (sildenafil citrate; 400 mg ml⁻¹) or the PDE9A inhibitor (200 mg ml⁻¹). (a) The left bar in the figure represents chamber 1 (familiar mouse), the middle bar chamber 2 (center point) and right bar chamber 3 (novel object). (b) The left bar in the figure represents chamber 1 (familiar mouse) and the right bar chamber 3 (novel object). The data show that the mdx^5cv mice show no preference for the novel mouse or object in the vehicle-treated mice; *P-value <0.05; NS, no significance. Eight mice per cohort were used for each social approach experiment. The time spent in each chamber F-value for WT vehicle mice was F_1,8=6.04 and the time in close interaction F-value was F_1,8=4.82. The time spent in each chamber F-value for mdx^5cv vehicle-treated mice was F_1,8=0.63 and the time in close interaction F-value was F_1,8=0.89. The time spent in each chamber F-value for mdx^5cv PDE5A inhibitor-treated mice was F_1,8=20.10 and the time in close interaction F-value was F_1,8=9.69. The time in close interaction F-value for mdx^5cv PDE9A inhibitor-treated mice was F_1,8=23.93 and the time in close interaction F-value was F_1,8=50.10. A 95% confidence interval for significance (P<0.05) with eight degrees of freedom was used.