The effect of melatonin treatment on doxorubicin-induced skeletal muscle atrophy within a cancer model

[摘要] ENGLISH ABSTRACT: Background and Aim: Skeletal muscle atrophy is a major concern in patients suffering withmalignancy. Chemotherapeutic agents, such as doxorubicin (DOX), can further exacerbate this loss ofskeletal muscle. Although many cancer patients on chemotherapeutic agents suffer from thiscondition, there are no therapies routinely used to moderate muscle atrophy. The aim of the studywas to investigate whether melatonin (MLT) can attenuate doxorubicin‐induced skeletal muscle andmyotube atrophy in an in vivo rodent model of breast cancer as well as in an in vitro model of DOXinducedmyotoxicity respectively. The safe and cost‐effective role of melatonin as a possible therapyto limit the burden of doxorubicin‐induced muscle toxicity in cancer patients serves as rationale forthe in vivo study and the in vitro study allows for the exploration of more invasive mechanistic aspectsusing the cell lines, which would not be possible when viewing excised tissue.Methods: Female Sprague‐Dawley rats were inoculated with LA7 cancer cells and were randomlyassigned to six groups: Control, Tumour control (TCON), Vehicle control (VEH), MLT, DOX and DOX +MLT (DM). Prophylactic treatment of MLT (6 mg/kg) was administered in drinking water daily and ratsreceived three intraperitoneal injections of DOX (4 mg/kg, 3 times at 3‐day intervals). Followingsacrifice blood samples (whole blood counts) and skeletal muscle tissue were collected for histological,immunoblot, antioxidant capacity and immunofluorescence analyses. Furthermore, C2C12 myoblastsgrown to confluency and differentiated into myotubes were pretreated with MLT (50 nM) for 48hfollowed by DOX treatment (0.8 μM) for 24h. The effect of MLT treatment on C2C12 myotubediameter, mitochondrial reactive oxygen species (mtROS) production, sirtuin levels and autophagyactivity was then assessed.Results: DOX treatment significantly reduced animal weight (279.1 ± 21.34 g vs. 222.2 ± 20.40 g,p˂0.0001) compared to DM weight (281.5 ± 7.11 g vs. 284.0 ± 6.53 g) and gastrocnemius muscleweight (1.4 ± 0.13 g vs. 0.99 ± 0.076 g, p˂0.0001) and cross sectional area (CSA), while increasing markers of muscle degradation compared to MLT treated groups. Serum myoglobin levels weresignificantly elevated in the DOX group compared to the DM group (572.6 ± 444.19 ng/mL vs. 218.2 ±83.66 ng/mL, p˂0.0001); while, white & red blood cell counts (WBC & RBC) were significantlydecreased in the DOX group compared to the MLT treated groups respectively (2.06 ± 1.59 x 109L‐1 vs.4.13 ± 1.56 x 109L‐1 & 4.00 ± 1.52 x 1012L‐1 vs. 5.66 ± 1.03 x 1012L1, p˂0.0001). Furthermore, MLTtreatment significantly increased intramuscular antioxidant capacity, mitochondrial biogenesis andsatellite cell number. In vitro DOX treatment resulted in increased myotube atrophy, mitochondrialROS levels and these effects were significantly reduced with MLT pre‐treatment.Discussion: The improvement in animal weight, muscle to body weight ratio, muscle CSA as well asthe reduction in myoglobin levels in the treatment groups compared to the DOX group indicate thatMLT protects against DOX‐induced atrophy. Moreover, MLT pre‐treatment improved circulating levelsof WBC & RBC compared to the DOX only group and attenuated skeletal muscle atrophy by reducingcell apoptosis and increasing satellite cell number suggesting that MLT assists with muscle repair. Thein vitro study indicated that DOX‐induced myotube atrophy was preceded by increases inmitochondrial ROS.Conclusion: Results indicate that pre‐treatment with exogenous MLT protects against skeletal musclewasting induced by DOX in a pre‐cachectic tumour‐bearing rat model.

[发布机构] Stellenbosch University