The Angiotensin Converting Enzyme Inhibitor Lisinopril Improves Muscle Histopathology but not Contractile Function in a Mouse Model of Duchenne Muscular Dystrophy

Abstract

Background Angiotensin converting enzyme inhibitors (ACEi) are the current standard of care treatment for cardiac dysfunction in Duchenne muscular dystrophy patients. We previously showed treatment with an ACEi plus mineralocorticoid receptor (MR) antagonist improves limb and respiratory skeletal muscles, in addition to cardiac muscles, in a dystrophic mouse model at 20 weeks-of-age. Objective To determine whether previously observed preclinical benefits of an ACEi plus MR antagonist on dystrophic skeletal muscles can be reproduced by increasing ACEi dosage alone. We also compared functional and histological outcome measures at 10 and 20 weeks-of-age. Methods Dystrophin deficient utrophin haplo-insufficient (utrn+/−; mdx) “het” mice were treated with 10, 20, or 50 mg/kg × day of the ACEi lisinopril from 4 to 10 weeks-of-age via water bottles and compared with C57BL/10 wild-type control mice and untreated hets. Data from 10 week-old het mice were also compared to data collected from an untreated het group at 20 weeks-old. In vivo cardiac and grip strength measurements, in vitro diaphragm and extensor digitorum longus muscle force measurements, and histopathological analyses were performed. One-way ANOVA followed by Dunnett post hoc comparison was used to determine significance. Results ACEi treatment reduced skeletal muscle damage but had no significant effect on muscle force. Body weight, heart rate, grip strength and blood pressure were unaffected by treatment. Limb muscle histopathology was more informative at 10 than 20 weeks-of-age. Conclusions These results suggest increased ACEi dosage alone cannot improve all dystrophic parameters. Further optimization of MR antagonists in 20 week-old mice is warranted.

Similar Efficacy from Specific and Non-Specific Mineralocorticoid Receptor Antagonist Treatment of Muscular Dystrophy Mice

“…Abdominal muscles that help to support respiration, had a 30% lower amount of damage in the LS treated group compared with the untreated het group (t-test P = 0.01). Surprisingly, and in contrast to our previous studies with either LS or lisinopril alone [6, 8], quadriceps showed only a 9% reduction of damage and only in the EL group, but not the LS group. However ongoing damage in this untreated het cohort was less than 10% overall, and fibrosis has not accumulated in quadriceps of het mice at this age (Fig.…”

“…On the day of sacrifice, the body weight of each mouse was recorded and resting, non-anesthetized, non-invasive electrocardiographic recordings were taken using the ECGenie system (Mouse Specifics Inc.) as previously described [8]. Analysis of QT- interval, heart rate, and heart rate variability was done using time intervals when paws were in contact with the electrodes and heart rate (HR) remained consistent.…”

“…Analysis of QT- interval, heart rate, and heart rate variability was done using time intervals when paws were in contact with the electrodes and heart rate (HR) remained consistent. Forelimb grip strength was then assessed as described in Treat-NMD SOP DMD_M.2.2.001 and previously [8]. The highest value (N) of three measurements separated by one minute rest periods was reported.…”

“…Eight μm cryosections were stained with Hematoxylin and Eosin (H&E) to verify section quality or with an antibody against mouse immunoglobulin (Ig)G (Alexa 488 goat anti-mouse IgG, 1:200; Life Technologies) to quantify ongoing muscle damage as previously described [8]. Damage is reported as a percentage of CSA.…”

“…We have also shown that lisinopril plus spironolactone can improve the prednisolone-induced damage to dystrophic mouse muscles [4]. However, lisinopril treatment alone benefits histopathology, but not function of dystrophic skeletal muscles in mice [8]. …”