Prednisolone Attenuates Improvement of Cardiac and Skeletal Contractile Function and Histopathology by Lisinopril and Spironolactone in the mdx Mouse Model of Duchenne Muscular Dystrophy

Abstract

Duchenne muscular dystrophy (DMD) is an inherited disease that causes striated muscle weakness. Recently, we showed therapeutic effects of the combination of lisinopril (L), an angiotensin converting enzyme (ACE) inhibitor, and spironolactone (S), an aldosterone antagonist, in mice lacking dystrophin and haploinsufficient for utrophin (utrn+/−;mdx, het mice); both cardiac and skeletal muscle function and histology were improved when these mice were treated early with LS. It was unknown to what extent LS treatment is effective in the most commonly used DMD murine model, the mdx mouse. In addition, current standard-of-care treatment for DMD is limited to corticosteroids. Therefore, potentially useful alternative or additive drugs need to be both compared directly to corticosteroids and tested in presence of corticosteroids. We evaluated the effectiveness of this LS combination in the mdx mouse model both compared with corticosteroid treatment (prednisolone, P) or in combination (LSP). We tested the additional combinatorial treatment containing the angiotensin II receptor blocker losartan (T), which is widely used to halt and treat the developing cardiac dysfunction in DMD patients as an alternative to an ACE inhibitor. Peak myocardial strain rate, assessed by magnetic resonance imaging, showed a negative impact of P, whereas in both diaphragm and extensor digitorum longus (EDL) muscle contractile function was not significantly impaired by P. Histologically, P generally increased cardiac damage, estimated by percentage area infiltrated by IgG as well as by collagen staining. In general, groups that only differed in the presence or absence of P (i.e. mdx vs. P, LS vs. LSP, and TS vs. TSP) demonstrated a significant detrimental impact of P on many assessed parameters, with the most profound impact on cardiac pathology.

Intermittent glucocorticoid steroid dosing enhances muscle repair without eliciting muscle atrophy

“…Both weekly and daily steroid regimens induced a comparable reduction in fibrosis and ventricle strain in the heart of treated mice. Additional studies are needed, as GC steroid effects in DMD cardiomyopathy are debated, with contrasting reports of beneficial effects in DMD patients and detrimental effects in DMD models (47,48). In skeletal muscle, molecular pathways of atrophy were triggered by daily dosing and this was accompanied by reduced performance of voluntary hind limb and respiratory skeletal muscles.…”

Glucocorticoids and Skeletal Muscle

“…A study performed on mdx mice showed that daily administration of prednisolone resulted in early (initial 50 days) improvements in muscle strength and motor coordination, but these benefi ts were lost after 100 days of continuous treatment [ 33 ]. Further, there was a deterioration of cardiac function and increased fi brosis of the heart with prolonged glucocorticoid treatment [ 34 ].…”

Caspase-12 ablation preserves muscle function in the mdx mouse

“…Sections were washed in PBS, blocked in 5% bovine serum albumin in PBS, and immunostained using antibodies to laminin (Thermo Scientific), to label the sarcolemma, and MyHC IIb (Developmental Studies Hybridoma Bank). For degeneration, anti-mouse IgG was added without any mouse primary antibody to label degenerating fibres (71), which were co-stained with laminin. Nuclei were labelled with DAPI incorporated into the mounting media (Vectashield).…”