Inhibiting 5‐lipoxygenase prevents skeletal muscle atrophy by targeting organogenesis signalling and insulin‐like growth factor‐1

Abstract

Background Skeletal muscle atrophy can occur in response to numerous factors, such as ageing and certain medications, and produces a major socio-economic burden. At present, there are no approved drugs for treating skeletal muscle atrophy. Arachidonate 5-lipoxygenase (Alox5) is a drug target for a number of diseases. However, pharmacological targeting of Alox5, and its role in skeletal muscle atrophy, is unclear. Methods The potential effects of gene knockdown and pharmacological targeting of Alox5 on skeletal muscle atrophy were investigated using cell-based models, animal models and human skeletal muscle primary cells. Malotilate, a clinically safe drug developed for enhancing liver regeneration and Alox5 inhibitor, was investigated as a repurposing candidate. Mechanism(s) of action in skeletal muscle atrophy was assessed by measuring the expression level or activation status of key regulatory pathways and validated using gene knockdown and RNA sequencing. Results Myotubes treated with the atrophy-inducing glucocorticoid, dexamethasone, were protected from catabolic responses by treatment with malotilate (+41.29%, P < 0.01). Similar anti-atrophy effects were achieved by gene knockdown of Alox5 (+30.4%, P < 0.05). Malotilate produced anti-atrophy effects without affecting the myogenic differentiation programme. In an in vivo model of skeletal muscle atrophy, malotilate treatment preserved muscle force/strength (grip strength: +35.72%, latency to fall: +553.1%, P < 0.05), increased mass and fibre crosssectional area (quadriceps: +23.72%, soleus: +33.3%, P < 0.01) and down-regulated atrogene expression (Atrogin-1: À61.58%, Murf-1: -66.06%, P < 0.01). Similar, beneficial effects of malotilate treatment were observed in an ageing muscle model, which also showed the preservation of fast-twitch fibres (Type 2a: +56.48%, Type 2b: +37.32%, P < 0.01). Leukotriene B4, a product of Alox5 activity with inflammatory and catabolic functions, was found to be elevated in skeletal muscle undergoing atrophy (quadriceps: +224.4%, P < 0.001). Cellular transcriptome analysis showed that targeting Alox5 up-regulated biological processes regulating organogenesis and increased the expression of insulin-like growth factor-1, a key anti-atrophy hormone (+226.5%, P < 0.05). Interestingly, these effects were restricted to the atrophy condition and not observed in normal skeletal muscle cultures with Alox5 inhibition. Human myotubes were also protected from atrophy by pharmacological targeting of Alox5 (+23.68%, P < 0.05). Conclusions These results shed new light on novel drug targets and mechanisms underpinning skeletal muscle atrophy. Alox5 is a regulator and drug target for muscle atrophy, and malotilate is an attractive compound for repurposing studies to treat this disease.

Targeting phosphatase DUSP22 ameliorates skeletal muscle wasting via Akt independent JNK-FOXO3a repression

“…The Dex model of muscle atrophy was based on the previously published protocol [68]. In brief, 12 week old male C57BL/6J mice were treated as follows: 1) Vehicle (DMSO in PBS pH 7.4 with 5% Tween 80) alone, 2) 15 mg/kg Dex dissolved in vehicle, 3) 15 mg/kg Dex and 5 mg/kg BML-260 (n=5 per group).…”

“…The Dex model of muscle atrophy was based on the previously published protocol [68]. In brief, 12 week old male C57BL/6J mice were treated as follows…”

Age Is Just a Number: Progress and Obstacles in the Discovery of New Candidate Drugs for Sarcopenia

“…Grip strength was improved, and immunohistochemical analysis showed an increase in the CSA of type II myofibers. RNA sequencing revealed an upregulation of IGF-1 in murine C2C12 myotubes treated with malotilate [175].…”

“…The biological target is arachidonate 5-lipoxygenase (Alox5), which has been implicated in numerous diseases [174]. Kim et al treated 21-month-old male C57BL/6J mice with malotilate via oral administration for 4 weeks [175]. Malotilate produced increases in the gastrocnemius and soleus mass, along with a reduction in gonadal adipose tissue mass.…”