Adjunctive β2‐agonists reverse neuromuscular involvement in murine Pompe disease

Abstract

Pompe disease has resisted enzyme replacement therapy with acid α-glucosidase (GAA), which has been attributed to inefficient cation-independent mannose-6-phosphate receptor (CI-MPR) mediated uptake. We evaluated β2-agonist drugs, which increased CI-MPR expression in GAA knockout (KO) mice. Clenbuterol along with a low-dose adeno-associated virus vector increased Rotarod latency by 75% at 4 wk, in comparison with vector alone (P<2×10(-5)). Glycogen content was lower in skeletal muscles, including soleus (P<0.01), extensor digitorum longus (EDL; P<0.001), and tibialis anterior (P<0.05) following combination therapy, in comparison with vector alone. Glycogen remained elevated in the muscles following clenbuterol alone, indicating an adjunctive effect with gene therapy. Elderly GAA-KO mice treated with combination therapy demonstrated 2-fold increased wirehang latency, in comparison with vector or clenbuterol alone (P<0.001). The glycogen content of skeletal muscle decreased following combination therapy in elderly mice (P<0.05). Finally, CI-MPR-KO/GAA-KO mice did not respond to combination therapy, indicating that clenbuterol's effect depended on CI-MPR expression. In summary, adjunctive β2-agonist treatment increased CI-MPR expression and enhanced efficacy from gene therapy in Pompe disease, which has implications for other lysosomal storage disorders that involve primarily the brain.

Synergistic Efficacy from Gene Therapy with Coreceptor Blockade and a β2-Agonist in Murine Pompe Disease

“…13 The current study demonstrated increased CI-MPR expression in quadriceps and gastrocnemius by a muscle-specific GAA expression vector, AAV2/8-MHCK7hGAApA (Fig. 3).…”

“…11,13 In this study, clenbuterol significantly increased the expression of CI-MPR in skeletal muscle (Fig. 3), including the quadriceps ( p < 0.01) and gastrocnemius ( p < 0.05).…”

“…Wirehang testing has previously detected changes in muscle strength with more sensitivity than Rotarod testing. 13 Treatment with clenbuterol alone increased wirehang latency, in comparison with untreated mice (Fig. 4D).…”

“…[11][12][13] The underlying mechanism of the therapeutic action of clenbuterol might be related to insulin-like growth factor (IGF)-1-mediated muscle hypertrophy, which has been correlated with increased CI-MPR (also known as IGF-2 receptor) expression. 14 In the present study, we evaluated a combination of anti-CD4 mAb and clenbuterol to induce immune tolerance and to increase CI-MPR-mediated uptake and trafficking of GAA, respectively.…”

“…8 Simultaneous clenbuterol administration could induce CI-MPR expression in striated muscle. 13 The AAV vector containing a muscle-specific promoter, AAV2/8-MHCK7hGAApA, expressed GAA in both cardiac and skeletal muscle. 15 Combined anti-CD4 mAb and clenbuterol with AAV2/8-MHCK7hGAApA, termed triple therapy, revealed a synergistic therapeutic effect on biochemical correction in cardiac and skeletal muscle, as well as improved muscle strength, after AAV vector administration in GAA-KO mice.…”