Doxorubicin Induces Bone Loss by Increasing Autophagy through a Mitochondrial ROS/TRPML1/TFEB Axis in Osteoclasts

Doxorubicin (DOX), a widely used chemotherapeutic agent, has been linked to an increased risk of bone damage in human patients and induces bone loss in mice. DOX induces autophagy, which contributes to bone homeostasis and excess autophagy in osteoclasts (OCs), resulting in bone loss. We hypothesized that DOX-induced bone loss is caused by the induction of autophagy in OCs. In vitro, DOX significantly increased the area of OCs and bone resorption activity, whereas it decreased OC number through apoptosis. DOX enhanced the level of LC3II and acidic vesicular organelles-containing cells in OCs, whereas an autophagy inhibitor, 3-methyladenine (3-MA), reversed these, indicating that enhanced autophagy was responsible for the effects of DOX. Increased mitochondrial reactive oxygen species (mROS) by DOX oxidized transient receptor potential mucolipin 1 (TRPML1) on the lysosomal membrane, which led to nuclear localization of transcription factor EB (TFEB), an autophagy-inducing transcription factor. In vivo, micro-computerized tomography analysis revealed that the injection of 3-MA reversed DOX-induced bone loss, and tartrate-resistant acid phosphatase staining showed that 3-MA reduced the area of OCs on the bone surface, which was enhanced upon DOX administration. Collectively, DOX-induced bone loss is at least partly attributable to autophagy upregulation in OCs via an mROS/TRPML1/TFEB axis.

Automated summary

This study found that doxorubicin-induced bone loss is partly caused by the upregulation of autophagy in osteoclasts (OCs). Doxorubicin induces autophagy in OCs through the mitochondrial reactive oxygen species (mROS)/transient receptor potential mucolipin 1 (TRPML1)/transcription factor EB (TFEB) axis pathway. The results show that doxorubicin-induced autophagy increases the area of OCs and bone resorption activity, while decreasing the number of OCs through apoptosis, resulting in bone loss. The autophagy inhibitor 3-methyladenine (3-MA) reverses the effects of doxorubicin by reducing the area of OCs, thus reversing doxorubicin-induced bone loss.