Increasing evidence points to the respiratory Complex II (CII) as a source and modulator of reactive oxygen species (ROS). Both functional loss of CII as well as its pharmacological inhibition can lead to ROS generation in cells, with a relevant impact on the development of pathophysiological conditions, i.e. cancer and neurodegenerative diseases. While the basic framework of CII involvement in ROS production has been defined, the fine details still await clarification. It is important to resolve these aspects to fully understand the role of CII in pathology and to explore its therapeutic potential in cancer and other diseases.

• Klíčová slova
• OXPHOS, Respiratory complex II, cancer, mitochondria, reactive oxygen species, succinate, succinate dehydrogenase, tricarboxylic acid cycle,
• MeSH
• cílená molekulární terapie * MeSH
• lidé MeSH
• mitochondriální nemoci farmakoterapie   metabolismus   patologie   MeSH
• mitochondrie metabolismus   patologie   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• respirační komplex II metabolismus   MeSH
• transport elektronů MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• reaktivní formy kyslíku MeSH
• respirační komplex II MeSH

PURPOSE: Pheochromocytomas and paragangliomas (PCPG) are usually benign neuroendocrine tumors. However, PCPGs with mutations in the succinate dehydrogenase B subunit (SDHB) have a poor prognosis and frequently develop metastatic lesions. SDHB-mutated PCPGs exhibit dysregulation in oxygen metabolic pathways, including pseudohypoxia and formation of reactive oxygen species, suggesting that targeting the redox balance pathway could be a potential therapeutic approach. EXPERIMENTAL DESIGN: We studied the genetic alterations of cluster I PCPGs compared with cluster II PCPGs, which usually present as benign tumors. By targeting the signature molecular pathway, we investigated the therapeutic effect of ascorbic acid on PCPGs using in vitro and in vivo models. RESULTS: By investigating PCPG cells with low SDHB levels, we show that pseudohypoxia resulted in elevated expression of iron transport proteins, including transferrin (TF), transferrin receptor 2 (TFR2), and the divalent metal transporter 1 (SLC11A2; DMT1), leading to iron accumulation. This iron overload contributed to elevated oxidative stress. Ascorbic acid at pharmacologic concentrations disrupted redox homeostasis, inducing DNA oxidative damage and cell apoptosis in PCPG cells with low SDHB levels. Moreover, through a preclinical animal model with PCPG allografts, we demonstrated that pharmacologic ascorbic acid suppressed SDHB-low metastatic lesions and prolonged overall survival. CONCLUSIONS: The data here demonstrate that targeting redox homeostasis as a cancer vulnerability with pharmacologic ascorbic acid is a promising therapeutic strategy for SDHB-mutated PCPGs.

• MeSH
• antioxidancia farmakologie   terapeutické užití   MeSH
• apoptóza účinky léků   MeSH
• feochromocytom farmakoterapie   genetika   patologie   MeSH
• genový knockdown MeSH
• kyselina askorbová farmakologie   terapeutické užití   MeSH
• léky antitumorózní - screeningové testy MeSH
• lidé MeSH
• modely nemocí na zvířatech MeSH
• mutace MeSH
• myši MeSH
• nádorové buněčné linie transplantace   MeSH
• oxidační stres účinky léků   MeSH
• paragangliom MeSH
• poškození DNA účinky léků   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• sukcinátdehydrogenasa nedostatek   genetika   MeSH
• železo metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antioxidancia MeSH
• kyselina askorbová MeSH
• reaktivní formy kyslíku MeSH
• SDHB protein, human MeSH Prohlížeč
• sukcinátdehydrogenasa MeSH
• železo MeSH

Respiratory complex II (CII, succinate dehydrogenase, SDH) inhibition can induce cell death, but the mechanistic details need clarification. To elucidate the role of reactive oxygen species (ROS) formation upon the ubiquinone-binding (Qp) site blockade, we substituted CII subunit C (SDHC) residues lining the Qp site by site-directed mutagenesis. Cell lines carrying these mutations were characterized on the bases of CII activity and exposed to Qp site inhibitors MitoVES, thenoyltrifluoroacetone (TTFA) and Atpenin A5. We found that I56F and S68A SDHC variants, which support succinate-mediated respiration and maintain low intracellular succinate, were less efficiently inhibited by MitoVES than the wild-type (WT) variant. Importantly, associated ROS generation and cell death induction was also impaired, and cell death in the WT cells was malonate and catalase sensitive. In contrast, the S68A variant was much more susceptible to TTFA inhibition than the I56F variant or the WT CII, which was again reflected by enhanced ROS formation and increased malonate- and catalase-sensitive cell death induction. The R72C variant that accumulates intracellular succinate due to compromised CII activity was resistant to MitoVES and TTFA treatment and did not increase ROS, even though TTFA efficiently generated ROS at low succinate in mitochondria isolated from R72C cells. Similarly, the high-affinity Qp site inhibitor Atpenin A5 rapidly increased intracellular succinate in WT cells but did not induce ROS or cell death, unlike MitoVES and TTFA that upregulated succinate only moderately. These results demonstrate that cell death initiation upon CII inhibition depends on ROS and that the extent of cell death correlates with the potency of inhibition at the Qp site unless intracellular succinate is high. In addition, this validates the Qp site of CII as a target for cell death induction with relevance to cancer therapy.

• MeSH
• buněčná smrt fyziologie   MeSH
• konformace proteinů MeSH
• lidé MeSH
• mitochondrie metabolismus   fyziologie   MeSH
• molekulární sekvence - údaje MeSH
• mutageneze cílená MeSH
• respirační komplex II chemie   genetika   metabolismus   fyziologie   MeSH
• sekvence aminokyselin MeSH
• ubichinon chemie   genetika   metabolismus   MeSH
• vazebná místa MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• respirační komplex II MeSH
• respiratory complex II MeSH Prohlížeč
• ubichinon MeSH