Activation of poly(ADP-ribose) polymerases-1 and -2 (PARP-1 and PARP-2) deteriorates mitochondrial activity. NAD + and ATP degradation are not coupled to each other upon PARP activation. PARPs interact with transcription factors modulating mitochondrial activity. PARPs can be positive regulators of mitochondrial output under sublethal stress. PARP inhibition is an attractive target for treating mitochondrial dysfunction.

Cancer cells are characterized by metabolic alterations, namely, depressed mitochondrial oxidation, enhanced glycolysis and pentose phosphate shunt flux to support rapid cell growth, which is called the Warburg effect. In our study we assessed the metabolic consequences of a joint treatment of MCF-7 breast cancer cells with AICAR, an inducer of AMP-activated kinase (AMPK) jointly with methotrexate (MTX), a folate-analog antimetabolite that blunts de novo nucleotide synthesis. MCF7 cells, a model of breast cancer cells, were resistant to the individual application of AICAR or MTX, however combined treatment of AICAR and MTX reduced cell proliferation. Prolonged joint application of AICAR and MTX induced AMPK and consequently enhanced mitochondrial oxidation and reduced the rate of glycolysis. These metabolic changes suggest an anti-Warburg rearrangement of metabolism that led to the block of the G1/S and the G2/M transition slowing down cell cycle. The slowdown of cell proliferation was abolished when mitotropic transcription factors, PGC-1α, PGC-1β or FOXO1 were silenced. In human breast cancers higher expression of AMPKα and FOXO1 extended survival. AICAR and MTX exerts similar additive antiproliferative effect on other breast cancer cell lines, such as SKBR and 4T1 cells, too. Our data not only underline the importance of Warburg metabolism in breast cancer cells but nominate the AICAR+MTX combination as a potential cytostatic regime blunting Warburg metabolism. Furthermore, we suggest the targeting of AMPK and FOXO1 to combat breast cancer.

We report the synthesis of the ligand Hnompa (6-((1,4,7-triazacyclononan-1-yl)methyl)picolinic acid) and a detailed characterization of the Mn(2+) complexes formed by this ligand and the related ligands Hdompa (6-((1,4,7,10-tetraazacyclododecan-1-yl)methyl)picolinic acid) and Htempa (6-((1,4,8,11-tetraazacyclotetradecan-1-yl)methyl)picolinic acid). These ligands form thermodynamically stable complexes in aqueous solution with stability constants of logKMnL = 10.28(1) (nompa), 14.48(1) (dompa), and 12.53(1) (tempa). A detailed study of the dissociation kinetics of these Mn(2+) complexes indicates that the decomplexation reaction at about neutral pH occurs mainly following a spontaneous dissociation mechanism. The X-ray structure of [Mn2(nompa)2(H2O)2](ClO4)2 shows that the Mn(2+) ion is seven-coordinate in the solid state, being directly bound to five donor atoms of the ligand, the oxygen atom of a coordinated water molecule and an oxygen atom of a neighboring nompa(-) ligand acting as a bridging bidentate carboxylate group (μ-η(1)-carboxylate). Nuclear magnetic relaxation dispersion ((1)H NMRD) profiles and (17)O NMR chemical shifts and transverse relaxation rates of aqueous solutions of [Mn(nompa)](+) indicate that the Mn(2+) ion is six-coordinate in solution by the pentadentate ligand and one inner-sphere water molecule. The analysis of the (1)H NMRD and (17)O NMR data provides a very high water exchange rate of the inner-sphere water molecule (kex(298) = 2.8 × 10(9) s(-1)) and an unusually high value of the (17)O hyperfine coupling constant of the coordinated water molecule (AO/ℏ = 73.3 ± 0.6 rad s(-1)). DFT calculations performed on the [Mn(nompa)(H2O)](+)·2H2O system (TPSSh model) provide a AO/ℏ value in excellent agreement with the one obtained experimentally.

Poly(ADP-ribose) polymerase-2 (PARP-2) is acknowledged as a DNA repair enzyme. However, recent investigations have attributed unique roles to PARP-2 in metabolic regulation in the liver. We assessed changes in hepatic lipid homeostasis upon the deletion of PARP-2 and found that cholesterol levels were higher in PARP-2(-/-) mice as compared to wild-type littermates. To uncover the molecular background, we analyzed changes in steady-state mRNA levels upon the knockdown of PARP-2 in HepG2 cells and in murine liver that revealed higher expression of sterol-regulatory element binding protein (SREBP)-1 dependent genes. We demonstrated that PARP-2 is a suppressor of the SREBP1 promoter, and the suppression of the SREBP1 gene depends on the enzymatic activation of PARP-2. Consequently, the knockdown of PARP-2 enhances SREBP1 expression that in turn induces the genes driven by SREBP1 culminating in higher hepatic cholesterol content. We did not detect hypercholesterolemia, higher fecal cholesterol content or increase in serum LDL, although serum HDL levels decreased in the PARP-2(-/-) mice. In cells and mice where PARP-2 was deleted we observed decreased ABCA1 mRNA and protein expression that is probably linked to lower HDL levels. In our current study we show that PARP-2 impacts on hepatic and systemic cholesterol homeostasis. Furthermore, the depletion of PARP-2 leads to lower HDL levels which represent a risk factor to cardiovascular diseases.

Poly(ADP-ribose) polymerase (PARP)10 is a PARP family member that performs mono-ADP-ribosylation of target proteins. Recent studies have linked PARP10 to metabolic processes and metabolic regulators that prompted us to assess whether PARP10 influences mitochondrial oxidative metabolism. The depletion of PARP10 by specific shRNAs increased mitochondrial oxidative capacity in cellular models of breast, cervical, colorectal and exocrine pancreas cancer. Upon silencing of PARP10, mitochondrial superoxide production decreased in line with increased expression of antioxidant genes pointing out lower oxidative stress upon PARP10 silencing. Improved mitochondrial oxidative capacity coincided with increased AMPK activation. The silencing of PARP10 in MCF7 and CaCo2 cells decreased the proliferation rate that correlated with increased expression of anti-Warburg enzymes (Foxo1, PGC-1α, IDH2 and fumarase). By analyzing an online database we showed that lower PARP10 expression increases survival in gastric cancer. Furthermore, PARP10 expression decreased upon fasting, a condition that is characterized by increases in mitochondrial biogenesis. Finally, lower PARP10 expression is associated with increased fatty acid oxidation.

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TASK-3 (KCNK9 or K2P9.1) channels are thought to promote proliferation and/or survival of malignantly transformed cells, most likely by increasing their hypoxia tolerance. Based on our previous results that suggested mitochondrial expression of TASK-3 channels, we hypothesized that TASK-3 channels have roles in maintaining mitochondrial activity. In the present work we studied the effect of reduced TASK-3 expression on the mitochondrial function and survival of WM35 and A2058 melanoma cells. TASK-3 knockdown cells had depolarized mitochondrial membrane potential and contained a reduced amount of mitochondrial DNA. Compared to their scrambled shRNA-transfected counterparts, they demonstrated diminished responsiveness to the application of the mitochondrial uncoupler [(3-chlorophenyl)hydrazono]malononitrile (CCCP). These observations indicate impaired mitochondrial function. Further, TASK-3 knockdown cells presented reduced viability, decreased total DNA content, altered cell morphology, and reduced surface area. In contrast to non- and scrambled shRNA-transfected melanoma cell lines, which did not present noteworthy apoptotic activity, almost 50 % of the TASK-3 knockdown cells exhibited strong Annexin-V-specific immunofluorescence signal. Sequestration of cytochrome c from the mitochondria to the cytosol, increased caspase 3 activity, and translocation of the apoptosis-inducing factor from mitochondria to cell nuclei were also demonstrated in TASK-3 knockdown cells. Interference with TASK-3 channel expression, therefore, induces caspase-dependent and -independent apoptosis of melanoma cells, most likely via causing mitochondrial depolarization. Consequently, TASK-3 channels may be legitimate targets of future melanoma therapies.

cis-1S)-4-(3,4-Dichlorophenyl)-1,2,3,4-tetrahydro-N-methyl-1naphthalenamine hydrochloride, or sertraline hydrochloride, is a very effective antidepressant. This report presents a novel industrial synthesis of sertraline hydrochloride that is in many respects more advantageous than processes reported thus far. N-[4-(3,4-Dichlorophenyl)-3,4-dihydro-1(2H)-naphthalenylidene]-methanamine N-oxide is used as intermediate in our process, which is a stable compound in normal conditions. It can be obtained in a simple reaction from the corresponding tetralone in good yield, using acceptable reagents with regard to environmental and safety respects. Its reduction to the desired cisracemic amine is stereoselective, and thus it provides sertraline hydrochloride with a purity required for pharmaceutical ingredients.