The mitochondrial-targeted antioxidant SkQ1 prevents mitochondrial-linked apoptosis but not necroptosis or skeletal muscle atrophy in ovarian cancer
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The degree to which mitochondrial-linked cell death pathways contribute to skeletal muscle atrophy during cancer remain unknown. Here, we combined a novel and robust mouse model of metastatic ovarian cancer with chronic administration of the mitochondrial-targeted antioxidant SkQ1 to determine the time-dependent and muscle-specific relationships of mitochondrial-linked apoptosis and necroptosis to the development of muscle atrophy in the type II B-rich gastrocnemius. Early-stage ovarian cancer reduced type II B fibre cross-sectional area in the gastrocnemius but did not alter mitochondrial H 2 O 2 emission despite increased activities of mitochondrial-linked caspase-9 and-3 regulators of apoptosis. During late-stage ovarian cancer, sustained atrophy was associated with increased mitochondrial H 2 O 2 emission potential in vitro , a greater probability of calcium-triggered mitochondrial permeability transition and increases in downstream caspase-9 and −3 activity. SkQ1 attenuated mitochondrial H 2 O 2 emission and caspase-9 and −3 activity in late-stage ovarian cancer but did not prevent atrophy. Necroptosis markers were heterogeneous across time with total RIPK1 increasing during early-stage cancer which reverted to normal levels by late-stages while phosphorylated RIPK3 decreased below control levels. These discoveries indicate that preventing increases in mitochondrial-linked apoptotic caspase-9 and −3 activity during late-stage ovarian cancer with SkQ1 does not prevent atrophy of type II B fibres. Furthermore, necroptotic markers are inconclusive during cancer in this muscle type but are not modified by SkQ1. These results do not support a causal relationship between mitochondrial H 2 O 2 -linked apoptosis or necroptosis and atrophy in type II B fibres during ovarian cancer but do not rule out potential relationships in other muscle types.
Key Points
Cancer increases mitochondrial reactive oxygen species (ROS) in skeletal muscle during atrophy, but the role of ROS in regulating cell death remains unknown.
We show that attenuating gastrocnemius mitochondrial ROS with the mitochondrial-targeted antioxidant SkQ1 prevented mitochondrial-linked pro-apoptotic caspase 9- and 3-activities but did not affect markers of necroptosis in a mouse model of ovarian cancer.
Reductions in gastrocnemius muscle fibre cross-sectional areas and the wet weights of several muscles were not prevented by SkQ1.
These findings demonstrate that mitochondrial ROS regulate apoptotic caspases but not necroptosis, and neither pathway is linked to gastrocnemius atrophy in mice with ovarian cancer.
The degree to which mitochondrial ROS-linked cell death pathways regulate muscle mass in other muscle types and cancer models requires further investigation.
