Targeted overexpression of mitochondrial catalase protects against cancer chemotherapy-induced skeletal muscle dysfunction

Abstract

The loss of strength in combination with constant fatigue is a burden on cancer patients undergoing chemotherapy. Doxorubicin, a standard chemotherapy drug used in the clinic, causes skeletal muscle dysfunction and increases mitochondrial H2O2 We hypothesized that the combined effect of cancer and chemotherapy in an immunocompetent breast cancer mouse model (E0771) would compromise skeletal muscle mitochondrial respiratory function, leading to an increase in H2O2-emitting potential and impaired muscle function. Here, we demonstrate that cancer chemotherapy decreases mitochondrial respiratory capacity supported with complex I (pyruvate/glutamate/malate) and complex II (succinate) substrates. Mitochondrial H2O2-emitting potential was altered in skeletal muscle, and global protein oxidation was elevated with cancer chemotherapy. Muscle contractile function was impaired following exposure to cancer chemotherapy. Genetically engineering the overexpression of catalase in mitochondria of muscle attenuated mitochondrial H2O2 emission and protein oxidation, preserving mitochondrial and whole muscle function despite cancer chemotherapy. These findings suggest mitochondrial oxidants as a mediator of cancer chemotherapy-induced skeletal muscle dysfunction.

Keywords: cancer; chemotherapy; mitochondria; reactive oxygen species; skeletal muscle.

Fig. 1.

Mammary tumor growth in wild-type (WT) and mitochondrial catalase-expressing mice. A: schematic diagram illustrating the experimental protocol. Mice assigned to the tumor-bearing (TB) groups were injected subcutaneously in the mammary fat pad with E0771 cells and euthanized once tumor size reached 100–150 mm². Mice assigned to the doxorubicin (DOX) + TB groups received a single intraperitoneal injection of DOX (20 mg/kg) once tumor size reached 100–150 mm² and were euthanized 72 h postinjection. B: growth of tumor size in female C57BL/6N WT and heterozygous mice expressing catalase in the mitochondrial matrix (MCAT). Data are means ± SE. WT TB, n = 10; WT TB + DOX, n = 9; MCAT TB, n = 10; MCAT TB + DOX, n = 10.

Fig. 2.

Cancer chemotherapy impairs mitochondrial respiratory capacity in skeletal muscle. Permeabilized myofibers were prepared following exposure to tumor cell (TB) and doxorubicin (DOX) administration in both wild-type mice [control (CTRL), n = 9; TB, n = 9; DOX, n = 10, TB + DOX, n = 9; A] and mice expressing catalase in the mitochondrial matrix (MCAT; CTRL, n = 11; MCAT TB, n = 10; MCAT DOX, n = 11; MCAT TB + DOX, n = 10; B). Mitochondrial respiration was measured sequentially in the presence of maximal palmitoyl-CoA + carnitine (P/Car), malate (Mal), ADP (D), pyruvate (Pyr), glutamate (Glut), and succinate (Succ). Data are means ± SE. *P < 0.05 vs. CTRL

Fig. 3.

Mitochondrial H₂O₂ emission in wild-type and mitochondrial catalase-expressing mice following exposure to cancer chemotherapy. Mitochondrial H₂O₂-emitting potential of permeabilized myofibers from wild-type (A) and mitochondrial catalase-expressing mice (MCAT; B) exposed to tumor cells (TB) and chemotherapy (DOX). Substrate conditions were in the presence of maximal succinate (Succ) and inhibitors of both Thioredoxin reductase and glutathione reductase [auranofin/bis-chloroethylnitrosourea (+AF/BCNU)]. Scavening index (SI) indicates calculated index of maximal scavenging. Data are means ± SE. Wild-type CTRL, n = 9; TB, n = 9; DOX, n = 10; TB + DOX, n = 8; MCAT CTRL, n = 8; MCAT TB, n = 8; MCAT DOX, n = 10; MCAT TB + DOX, n = 10. *P < 0.05 vs. CTRL.

Fig. 4.

Detection of global protein oxidation in wild-type and mitochondrial catalase-expressing mice (MCAT) following exposure to cancer chemotherapy. Protein carbonyls in tibialis anterior muscles from wild-type (A) and MCAT (B) exposed to tumor cells (TB) and chemotherapy (DOX). Representative Western blots are shown to the right of quantified data. Data are means ± SE. *P < 0.05 vs. CTRL; n = 6/group.

Fig. 5.

Cancer chemotherapy alters contractile function of hindlimb muscle from wild-type mice. Soleus contractile properties in wild-type mice exposed to tumor cells (TB) and chemotherapy (DOX). Absolute force-frequency relationship (A), maximal tetanic force (B), specific force-frequency relationship (C), and maximum specific force (D). Data are means ± SE. *P < 0.05 vs. CTRL.

Fig. 6.

Overexpression of skeletal muscle mitochondrial catalase protects against cancer chemotherapy contractile dysfunction. Soleus contractile properties in mice expressing catalase in the mitochondrial matrix (MCAT) exposed to tumor cells (TB) and chemotherapy (DOX). Absolute force-frequency relationship (A), maximal tetanic force (B), specific force-frequency relationship (C), and maximum specific force (D). Data are means ± SE.