Complex Mitochondrial Dysfunction Induced by TPP+-Gentisic Acid and Mitochondrial Translation Inhibition by Doxycycline Evokes Synergistic Lethality in Breast Cancer Cells

Abstract

The mitochondrion has emerged as a promising therapeutic target for novel cancer treatments because of its essential role in tumorigenesis and resistance to chemotherapy. Previously, we described a natural compound, 10-((2,5-dihydroxybenzoyl)oxy)decyl) triphenylphosphonium bromide (GA-TPP+C10), with a hydroquinone scaffold that selectively targets the mitochondria of breast cancer (BC) cells by binding to the triphenylphosphonium group as a chemical chaperone; however, the mechanism of action remains unclear. In this work, we showed that GA-TPP+C10 causes time-dependent complex inhibition of the mitochondrial bioenergetics of BC cells, characterized by (1) an initial phase of mitochondrial uptake with an uncoupling effect of oxidative phosphorylation, as previously reported, (2) inhibition of Complex I-dependent respiration, and (3) a late phase of mitochondrial accumulation with inhibition of α-ketoglutarate dehydrogenase complex (αKGDHC) activity. These events led to cell cycle arrest in the G1 phase and cell death at 24 and 48 h of exposure, and the cells were rescued by the addition of the cell-penetrating metabolic intermediates l-aspartic acid β-methyl ester (mAsp) and dimethyl α-ketoglutarate (dm-KG). In addition, this unexpected blocking of mitochondrial function triggered metabolic remodeling toward glycolysis, AMPK activation, increased expression of proliferator-activated receptor gamma coactivator 1-alpha (pgc1α) and electron transport chain (ETC) component-related genes encoded by mitochondrial DNA and downregulation of the uncoupling proteins ucp3 and ucp4, suggesting an AMPK-dependent prosurvival adaptive response in cancer cells. Consistent with this finding, we showed that inhibition of mitochondrial translation with doxycycline, a broad-spectrum antibiotic that inhibits the 28 S subunit of the mitochondrial ribosome, in the presence of GA-TPP+C10 significantly reduces the mt-CO1 and VDAC protein levels and the FCCP-stimulated maximal electron flux and promotes selective and synergistic cytotoxic effects on BC cells at 24 h of treatment. Based on our results, we propose that this combined strategy based on blockage of the adaptive response induced by mitochondrial bioenergetic inhibition may have therapeutic relevance in BC.

Miro, a Rho GTPase genetically interacts with Alzheimer's disease-associated genes (Tau, Aβ42andAppl) inDrosophila melanogaster

“…#M36008, Invitrogen, USA) as prescribed in Liu et al (2013). MitoSOX is a DHE derivative that possesses a cationic triphenylphosphonium group (TPP+), which helps in the transport to the mitochondrial matrix (Fuentes-Retamal et al, 2020;Roelofs et al, 2015). In the presence of ROS, MitoSOX gets oxidized and emits red fluorescence which was used to measure the ROS production (Forkink et al, 2010;Sarmiento-Salinas et al, 2019).…”

Early-adolescent antibiotic exposure results in mitochondrial and behavioral deficits in adult male mice

“…Chloramphenicol, and other antibiotics that target ribosome function, inhibits translation of protein encoded by the mitochondrial, but not the nuclear, genome 32 . A relative imbalance between the expression of nuclear and mitochondrially encoded proteins of the subunits of the mitochondrial complexes, termed mitonuclear protein imbalance, could drive mitochondrial complex instability 50 , 51 , possible resulting in decreased complex IV activity. However, the exact mechanisms through which chloramphenicol impacts complex IV activity in vivo remains to be explored in future studies.…”

Medicinal Chemistry Targeting Mitochondria: From New Vehicles and Pharmacophore Groups to Old Drugs with Mitochondrial Activity

“…Moreover, this drug decreased mitochondrial mass and increased peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) levels as a compensatory effect in vivo in a human mammary carcinoma model. However, the effects of doxycycline on CSCs have not yet been explored by these authors [ 109 , 124 ]. Based on these preclinical findings, Scatena et al conducted the first clinical trial of doxycycline, administering the drug to a small group of patients with early-stage breast cancer.…”