A potential therapeutic effect of catalpol in Duchenne muscular dystrophy revealed by binding with TAK1

Abstract

Background Duchenne muscular dystrophy (DMD) is a progressive muscle disease caused by the loss of dystrophin, which results in inflammation, fibrosis, and the inhibition of myoblast differentiation in skeletal muscle. Catalpol, an iridoid glycoside, improves skeletal muscle function by enhancing myogenesis; it has potential to treat DMD. We demonstrate the positive effects of catalpol in dystrophic skeletal muscle. Methods mdx (loss of dystrophin) mice (n = 18 per group) were treated with catalpol (200 mg/kg) for six consecutive weeks. Serum analysis, skeletal muscle performance and histology, muscle contractile function, and gene and protein expression were performed. Molecular docking and ligand-target interactions, RNA interference, immunofluorescence, and plasmids transfection were utilized to explore the protective mechanism in DMD by which catalpol binding with transforming growth factor-βactivated kinase 1 (TAK1) in skeletal muscle. Results Six weeks of catalpol treatment improved whole-body muscle health in mdx mice, which was characterized by reduced plasma creatine kinase (n = 18, À35.1%, P < 0.05) and lactic dehydrogenase (n = 18, À10.3%, P < 0.05) activity. These effects were accompanied by enhanced grip strength (n = 18, +25.4%, P < 0.05) and reduced fibrosis (n = 18, À29.0% for hydroxyproline content, P < 0.05). Moreover, catalpol treatment protected against muscle fatigue and promoted muscle recovery in the tibialis anterior (TA) and diaphragm (DIA) muscles (n = 6, +69.8%, P < 0.05 and + 74.8%, P < 0.001, respectively), which was accompanied by enhanced differentiation in primary myoblasts from DMD patients (n = 6, male, mean age: 4.7 ± 1.9 years) and mdx mice. In addition, catalpol eliminated p-TAK1 overexpression in mdx mice (n = 12, À21.3%, P < 0.05) and primary myoblasts. The catalpol-induced reduction in fibrosis and increased myoblast differentiation resulted from the inhibition of TAK1 phosphorylation, leading to reduced myoblast trans-differentiation into myofibroblasts. Catalpol inhibited the phosphorylation of TAK1 by binding to TAK1, possibly at Asp-206, Thr-208, Asn-211, Glu-297, Lys-294, and Tyr-293. Conclusions Our findings show that catalpol and TAK1 inhibitors substantially improve whole-body muscle health and the function of dystrophic skeletal muscles and may provide a novel therapy for DMD.

TAK1 inhibition improves myoblast differentiation and alleviates fibrosis in a mouse model of Duchenne muscular dystrophy

“…A recent study reported that TGF‐β1 induced the transdifferentiation of myoblasts into fibroblasts 49 . Similarly, in our previous study, TAK1 activation induced transdifferentiation of myoblasts into fibroblasts 50 . In addition, TAK1 was activated by TGF‐β1, IL‐1β, and TNF‐α in this study.…”

“…To specifically knock down TAK1 in skeletal muscles, the AAV‐shRNA‐control and AAV‐shRNA‐TAK1 were intramuscularly injected into the right and left TA muscles, respectively, of mdx and control mice. We found that TAK1 inhibition improved myoblast differentiation and alleviated fibrosis in mdx mice 50 . In addition, we found that p38‐MAPK and MAP 4K2 were activated in the skeletal muscle of mdx mice, while AAV‐shTAK1 and NG25 did not affect MAP 4K2 expression in mdx mice ( Figure S7B and S7C).…”

Rebuttal to: Simvastatin Treatment Does Not Ameliorate Muscle Pathophysiology in a Mouse Model for Duchenne Muscular Dystrophy, Verhaart et al. 2020

“…More recently, we have shown that cardiac function in the mdx mouse is also improved by simvastatin, due in part to the prevention of fibrosis [3]. In strong support of our findings, two recent studies have independently validated our results by showing positive effects of simvastatin treatment in mdx mice [4,5]. In one of these studies, significant improvements in muscle function (force and fatigue resistance), as well as reduced inflammation, fibrosis and plasma CK were comparable to those in our original paper [5].…”

Targeting fibrosis in the Duchenne Muscular Dystrophy mice model: an uphill battle

“…Growing evidence supports the role of TAK1 as a significant regulator of TGFb signaling through the regulation of the profibrotic response in several systems [43][44][45][83][84][85][86][87]. Very recently, it has been shown that the action of Catalpol (an anti-inflammatory and antioxidant drug from Chinese medicinal herb Rehmannia) on DMD histopathology was due to its binding to TAK1 [88,89]. Besides its role in fibrosis, TAK1 also has been described as an important mediator of carcinogenesis and cell survival [90].…”