Selective and reversible disruption of mitochondrial inner membrane protein complexes by lipophilic cations

Elevated mitochondrial membrane potential is a therapeutic vulnerability in Dnmt3a-mutant clonal hematopoiesis

The competitive advantage of mutant hematopoietic stem and progenitor cells (HSPCs) underlies clonal hematopoiesis (CH). Drivers of CH include aging and inflammation; however, how CH-mutant cells gain a selective advantage in these contexts is an unresolved question. Using a murine model of CH (Dnmt3aR878H/+), we discover that mutant HSPCs sustain elevated mitochondrial respiration which is associated with their resistance to aging-related changes in the bone marrow microenvironment. Mutant HSPCs have DNA hypomethylation and increased expression of oxidative phosphorylation gene signatures, increased functional oxidative phosphorylation capacity, high mitochondrial membrane potential (Δψm), and greater dependence on mitochondrial respiration compared to wild-type HSPCs. Exploiting the elevated Δψm of mutant HSPCs, long-chain alkyl-TPP molecules (MitoQ, d-TPP) selectively accumulate in the mitochondria and cause reduced mitochondrial respiration, mitochondrial-driven apoptosis and ablate the competitive advantage of HSPCs ex vivo and in vivo in aged recipient mice. Further, MitoQ targets elevated mitochondrial respiration and the selective advantage of human DNMT3A-knockdown HSPCs, supporting species conservation. These data suggest that mitochondrial activity is a targetable mechanism by which CH-mutant HSPCs gain a selective advantage over wild-type HSPCs.

3-methyl-4-nitrophenol disturbs the maternal-to-zygotic transition of early embryos by damaging mitochondrial function and histone modification

3-methyl-4-nitrophenol (PNMC), a chemical prevalent in various industries for drug, dye, and leather production, also serves as a primary byproduct of organophosphate insecticides. Despite its global recognition as an endocrine disruptor with documented reproductive toxicity, its detrimental impact on preimplantation embryonic development has yet to be thoroughly investigated. In this study, through the in vitro culture of mice embryos, it was initially observed that even low concentrations of PNMC exposure led to a significant reduction in blastocyst formation and a sharp decline in the ratio of inner cell mass within the blastocysts. SMART-seq2 transcriptome sequencing further confirmed that PNMC treatment disrupted global gene expression in 2-cell embryos, with differentially expressed genes enriched in multiple signaling pathways, including those related to autophagy, apoptosis, fertilization, embryonic development, transcription, and mRNA processing. Integration of transcriptome data with open databases revealed that both zygotic genome activation genes and maternal factors experienced significant transcript-level disruptions. Moreover, the study demonstrated that these gene expression changes were closely associated with mitochondrial dysfunction, evidenced by diminished mitochondrial membrane potential, reduced ATP production, aberrant expression of mitochondria-related genes, increased ROS accumulation, and heightened DNA damage in PNMC-treated embryos. Additionally, PNMC exposure induced defects in histone modification, as shown by altered levels of H3K9me3 and H3K27me3, H3K9ac and H3K27ac. Lastly, the findings indicated that PNMC triggered apoptosis in embryos, validated by elevated BAX and CASPASE3 expression, alongside positive TUNEL staining. In summary, PNMC exposure impairs the maternal-to-zygotic transition, likely through mitochondrial dysfunction and histone modification, culminating in developmental arrest and apoptosis in mouse preimplantation embryos.

Hormonal orchestra: mastering mitochondria's role in health and disease

Mitochondria is a subcellular organelle involved in the pathogenesis of cellular stress, immune responses, differentiation, metabolic disorders, aging, and death by regulating process of fission, fusion, mitophagy, and transport. However, an increased interest in mitochondria as powerhouse for ATP production, the mechanisms of mitochondria-mediated cellular dysfunction in response to hormonal interaction remains unknown. Mitochondrial matrix contains chaperones and proteases that regulate intrinsic apoptosis pathway through pro-apoptotic Bcl-2 family's proteins Bax/Bak, and Cyt C release, and induces caspase-dependent and independent cells death. Energy and growth regulators such as thyroid hormones have profound effect on mitochondrial inner membrane protein and lipid compositions, ATP production by regulating oxidative phosphorylation system. Mitochondria contain cholesterol side-chain cleavage enzyme, P450scc, ferredoxin, and ferredoxin reductase providing an essential site for steroid hormones biosynthesis. In line with this, neurohormones such as oxytocin, vasopressin, and melatonin are correlated with mitochondrial integrity, displaying therapeutic implications for inflammatory and immune responses. Melatonin's also displayed protective role against oxidative stress and mitochondrial synthesis of ROS, suggesting a defense mechanism against aging-related diseases. An imbalance in mitochondrial bioenergetics can cause neurodegenerative disorders, cardiovascular diseases, and cancers. Hormone-induced PGC-1α stimulates mitochondrial biogenesis via activation of NRF1 and NRF2, which in turn triggers mtTFA in brown adipose and cardiac myocytes. Mitochondria can be transferred through cells merging, exosome-mediated transfer, and tunneling through nanotubes. By delineating the underlying molecular mechanism of hormonal mitochondrial interaction, this study reviews the dynamics mechanisms of mitochondria and its effects on cellular level, health, diseases, and therapeutic strategies targeting mitochondrial diseases.

Chelating mitochondrial iron and copper: Recipes, pitfalls and promise

Iron and copper chelation therapy plays a crucial role in treating conditions associated with metal overload, such as hemochromatosis or Wilson's disease. However, conventional chelators face challenges in reaching the core of iron and copper metabolism - the mitochondria. Mitochondria-targeted chelators can specifically target and remove metal ions from mitochondria, showing promise in treating diseases linked to mitochondrial dysfunction, including neurodegenerative diseases and cancer. Additionally, they serve as specific mitochondrial metal sensors. However, designing these new molecules presents its own set of challenges. Depending on the chelator's intended use to prevent or to promote redox cycling of the metals, the chelating moiety must possess different donor atoms and an optimal value of the electrode potential of the chelator-metal complex. Various targeting moieties can be employed for selective delivery into the mitochondria. This review also provides an overview of the current progress in the design of mitochondria-targeted chelators and their biological activity investigation.

Synthesis of Triphenylphosphonium-Linked Derivative of 3,5-Ditert-butyl-4-hydroxybenzylidene-malononitrile (SF6847) via Knoevenagel Reaction Yields an Effective Mitochondria-Targeted Protonophoric Uncoupler

Mitochondrial uncouplers are actively sought as potential therapeutics. Here, we report the first successful synthesis of mitochondria-targeted derivatives of the highly potent uncoupler 3,5-ditert-butyl-4-hydroxybenzylidene-malononitrile (SF6847), bearing a cationic alkyl(triphenyl)phosphonium (TPP) group. As a key step of the synthesis, we used condensation of a ketophenol with malononitrile via the Knoevenagel reaction. SF-C5-TPP with a pentamethylene linker between SF6847 and TPP, stimulating respiration and collapsing membrane potential of rat liver mitochondria at submicromolar concentrations, proved to be the most effective uncoupler of the series. SF-C5-TPP showed pronounced protonophoric activity on a model planar bilayer lipid membrane. Importantly, SF-C5-TPP exhibited rather low toxicity in fibroblast cell culture, causing mitochondrial depolarization in cells at concentrations that only slightly affected cell viability. SF-C5-TPP was more effective in decreasing the mitochondrial membrane potential in the cell culture than SF6847, in contrast to the case of isolated mitochondria. Like other zwitterionic uncouplers, SF-C5-TPP inhibited the growth of Bacillus subtilis in the micromolar concentration range.

High Concentrations of Cannabidiol Induce Neurotoxicity in Neurosphere Culture System

Recent studies have demonstrated that cannabinoids are potentially effective in the treatment of various neurological conditions, and cannabidiol (CBD), one of the most studied compounds, has been proposed as a non-toxic option. However, the adverse effects of CBD on neurodevelopmental processes have rarely been studied in cell culture systems. To better understand CBD's influence on neurodevelopment, we exposed neural progenitor cells (NPCs) to different concentrations of CBD (1 µM, 5 µM, and 10 µM). We assessed the morphology, migration, differentiation, cell death, and gene expression in 2D and 3D bioprinted models to stimulate physiological conditions more effectively. Our results showed that CBD was more toxic at higher concentrations (5 µM and 10 µM) and affected the viability of NPCs than at lower concentrations (1 µM), in both 2D and 3D models. Moreover, our study revealed that higher concentrations of CBD drastically reduced the size of neurospheres and the number of NPCs within neurospheres, impaired the morphology and mobility of neurons and astrocytes after differentiation, and reduced neurite sprouting. Interestingly, we also found that CBD alters cellular metabolism by influencing the expression of glycolytic and β-oxidative enzymes in the early and late stages of metabolic pathways. Therefore, our study demonstrated that higher concentrations of CBD promote important changes in cellular functions that are crucial during CNS development.

Evaluation of the Antitumor Effects of Platinum-Based [Pt(η1-C2H4-OR)(DMSO)(phen)]+ (R = Me, Et) Cationic Organometallic Complexes on Chemoresistant Pancreatic Cancer Cell Lines

Pancreatic cancer is one of the most lethal malignancies with an increasing incidence and a high mortality rate, due to its rapid progression, invasiveness, and resistance to anticancer therapies. In this work, we evaluated the antiproliferative and antimigratory activities of the two organometallic compounds, [Pt(η1-C2H4-OMe)(DMSO)(phen)]Cl (1) and [Pt(η1-C2H4-OEt)(DMSO)(phen)]Cl (2), on three human pancreatic ductal adenocarcinoma cell lines with different sensitivity to cisplatin (Mia PaCa-2, PANC-1, and YAPC). The two cationic analogues showed superimposable antiproliferative effects on the tested cells, without significant differences depending on alkyl chain length (Me or Et). On the other hand, they demonstrated to be more effective than cisplatin, especially on YAPC cancer cells. For the interesting cytotoxic activity observed on YAPC, further biological assays were performed, on this cancer cell line, to evaluate the apoptotic and antimetastatic properties of the considered platinum compounds (1 and 2). The cytotoxicity of 1 and 2 compounds appeared to be related to their intracellular accumulation, which was much faster than that of cisplatin. Both 1 and 2 compounds significantly induced apoptosis and cell cycle arrest, with a high accumulation of sub-G1 phase cells, compared to cisplatin. Moreover, phenanthroline-containing complexes caused a rapid loss of mitochondria membrane potential, ΔΨM, if compared to cisplatin, probably due to their cationic and lipophilic properties. On 3D tumor spheroids, 1 and 2 significantly reduced migrated area more than cisplatin, confirming an antimetastatic ability.

Redox-crippled MitoQ potently inhibits breast cancer and glioma cell proliferation: A negative control for verifying the antioxidant mechanism of MitoQ in cancer and other oxidative pathologies

Mitochondria-targeted coenzyme Q10 (Mito-ubiquinone, Mito-quinone mesylate, or MitoQ) was shown to be an effective antimetastatic drug in patients with triple-negative breast cancer. MitoQ, sold as a nutritional supplement, prevents breast cancer recurrence. It potently inhibited tumor growth and tumor cell proliferation in preclinical xenograft models and in vitro breast cancer cells. The proposed mechanism of action involves the inhibition of reactive oxygen species by MitoQ via a redox-cycling mechanism between the oxidized form, MitoQ, and the fully reduced form, MitoQH2 (also called Mito-ubiquinol). To fully corroborate this antioxidant mechanism, we substituted the hydroquinone group (-OH) with the methoxy group (-OCH3). Unlike MitoQ, the modified form, dimethoxy MitoQ (DM-MitoQ), lacks redox-cycling between the quinone and hydroquinone forms. DM-MitoQ was not converted to MitoQ in MDA-MB-231 cells. We tested the antiproliferative effects of both MitoQ and DM-MitoQ in human breast cancer (MDA-MB-231), brain-homing cancer (MDA-MB-231BR), and glioma (U87MG) cells. Surprisingly, DM-MitoQ was slightly more potent than MitoQ (IC50 = 0.26 μM versus 0.38 μM) at inhibiting proliferation of these cells. Both MitoQ and DM-MitoQ potently inhibited mitochondrial complex I-dependent oxygen consumption (IC50 = 0.52 μM and 0.17 μM, respectively). This study also suggests that DM-MitoQ, which is a more hydrophobic analog of MitoQ (logP: 10.1 and 8.7) devoid of antioxidant function and reactive oxygen species scavenging ability, can inhibit cancer cell proliferation. We conclude that inhibition of mitochondrial oxidative phosphorylation by MitoQ is responsible for inhibition of breast cancer and glioma proliferation and metastasis. Blunting the antioxidant effect using the redox-crippled DM-MitoQ can serve as a useful negative control in corroborating the involvement of free radical-mediated processes (e.g., ferroptosis, protein oxidation/nitration) using MitoQ in other oxidative pathologies.