Combination therapies of AON and antioxidants for Duchenne

In Vivo validation of a combination therapy of antisense oligonucleotides and antioxidants for Duchenne muscular dystrophy

Summary of research

Duchenne muscular dystrophy (DMD) is one of the most severe muscle disorders to affect young children, lacking effective treatment options beyond symptom management. The disease is caused by lack of dystrophin protein, which leads to chronic, progressive muscle damage and wasting. One of the most potent, albeit currently underachieving, pharmaceutical interventions with potential to slow disease progression in patients are antisense oligonucleotides (AONs) to restore dystrophin expression. 

Due to lack of dystrophin, patients have chronic inflammation, which results in elevated levels of reactive oxygen species (ROS) in patient muscles. ROS cause damage to cellular components, leading to further detrimental damaging effects on the already affected muscle tissue. Antioxidants such as N-Acetyl cysteine (NAC) have been tested in models of DMD, such as the mdx mouse, and significant improvement of muscle quality was observed. However, a direct relationship with dystrophin was never investigated.

We hypothesized that on top of the direct damaging effects of ROS, the synthesis and maintenance of the large 427 kDa dystrophin protein could be hampered by the disturbed cellular homeostasis caused by ROS, eventually diminishing observed AON efficiency. We observed that dystrophin is rapidly degraded by exposure of myotubes to various sources of ROS. This effect is inhibited by blocking cellular protein degradation, halting and even increasing dystrophin levels compared to untreated samples. This suggests that ROS-induced loss of dystrophin is likely directly related to protein degradation, an observation of which we are further investigating the molecular mechanisms and signaling pathways.

Furthermore, we found that a combination of AON-mediated exon skipping and antioxidant treatment in DMD-patient myocytes vastly improves dystrophin protein levels independent of DMD mRNA levels.

We are currently investigating a combination treatment of AONs and NAC in vivo, in the mdx mouse model, assessing dystrophin protein restoration and histological improvements in various muscle tissues.

Awarded grant, amount: €25.000,-

Funding agency: Duchenne Parent Project NL/Duchenne Parent Project Belgium vzw