Down syndrome (DS) is associated with significant perturbances in mitochondrial function. Here we tested the hypothesis that the suppression of mitochondrial electron transport in DS cells is due to high expression of cystathionine-β-synthase (CBS) and subsequent overproduction of the gaseous transmitter hydrogen sulfide (H2S). Fibroblasts from DS individuals showed higher CBS expression than control cells; CBS localization was both cytosolic and mitochondrial. DS cells produced significantly more H2S and polysulfide and exhibited a profound suppression of mitochondrial electron transport, oxygen consumption, and ATP generation. DS cells also exhibited slower proliferation rates. In DS cells, pharmacological inhibition of CBS activity with aminooxyacetate or siRNA-mediated silencing of CBS normalized cellular H2S levels, restored Complex IV activity, improved mitochondrial electron transport and ATP synthesis, and restored cell proliferation. Thus, CBS-derived H2S is responsible for the suppression of mitochondrial function in DS cells. When H2S overproduction is corrected, the tonic suppression of Complex IV is lifted, and mitochondrial electron transport is restored. CBS inhibition offers a potential approach for the pharmacological correction of DS-associated mitochondrial dysfunction.

3-mercaptopyruvate sulfurtransferase (3-MST) has emerged as one of the significant sources of biologically active sulfur species in various mammalian cells. The current study was designed to investigate the functional role of 3-MST's catalytic activity in the murine colon cancer cell line CT26. The novel pharmacological 3-MST inhibitor HMPSNE was used to assess cancer cell proliferation, migration and bioenergetics in vitro. Methods included measurements of cell viability (MTT and LDH assays), cell proliferation and in vitro wound healing (IncuCyte) and cellular bioenergetics (Seahorse extracellular flux analysis). 3-MST expression was detected by Western blotting; H 2 S production was measured by the fluorescent dye AzMC. The results show that CT26 cells express 3-MST protein and mRNA, as well as several enzymes involved in H 2 S degradation (TST, ETHE1). Pharmacological inhibition of 3-MST concentration-dependently suppressed H 2 S production and, at 100 and 300 µM, attenuated CT26 proliferation and migration. HMPSNE exerted a bell-shaped effect on several cellular bioenergetic parameters related to oxidative phosphorylation, while other bioenergetic parameters were either unaffected or inhibited at the highest concentration of the inhibitor tested (300 µM). In contrast to 3-MST, the expression of CBS (another H 2 S producing enzyme which has been previously implicated in the regulation of various biological parameters in other tumor cells) was not detectable in CT26 cells and pharmacological inhibition of CBS exerted no significant effects on CT26 proliferation or bioenergetics. In summary, 3-MST catalytic activity significantly contributes to the regulation of cellular proliferation, migration and bioenergetics in CT26 murine colon cancer cells. The current studies identify 3-MST as the principal source of biologically active H 2 S in this cell line.

26Inflammatory breast cancer (IBC) is the most aggressive form of breast cancer.

Poly(ADP-ribose) polymerase (PARP) is involved in the pathogenesis of cell dysfunction, inflammation and organ failure during septic shock. The goal of the current study was to investigate the efficacy and safety of the clinically approved PARP inhibitor olaparib in experimental models of oxidative stress in vitro and in sepsis in vivo. ln mice subjected to cecal ligation a nd puncture (CLP) organ injury markers, circula ting and splenic immune cell distributions, circulating mediators, DNA integrity and survival was measured. ln U937 cells subjected to oxidative stress, cellular bioenergetics, viability and DNA integrity were measured. Olaparib was used to inhibit PARP. The results show that in adult male mice subjected to CLP, olaparib (1-10 mg/kg i.p.) improved multiorgan dysfonction. Olaparib treatrnent reduced the degree of bacterial CFUs. Olaparib attenuated the increases in the levels of several circulating mediators in the plasma. ln the spleen, the number of CD4 + and CDS + lymphocytes were reduced in response to CLP; this reduction was inhibited by olaparib treatrnent. Treg but not Thl 7 lymphocytes increased in response to CLP; these cell populations were reduced in sepsis when the animais received olaparib. The Thl 7 /Treg ratio was lower in CLP-olaparib group than in the CLP control group. Analysis of miRNA expression identifi ed a multitude of changes in spleen and circulating white blood cell miRNA levels after CLP; olaparib treatrnent selectively modulated these responses. Olaparib extended the survival rate of mice subjected to CLP. ln contrast to males, in female mice olaparib did not have significant protective effects in CLP. ln aged mice olaparib exerted beneficial effects that were Jess pronounced than the effects obtained in young adult males. ln in vitro experiments in U937 cells subjected to oxidative stress, olaparib (1-100 µM) inhibited PARP activity, protected against the Joss of cell viability, preserved NAD + levels and improved cellular bioenergetics. ln none of the in vivo or in vitro experiments did we observe any adverse effects of olaparib on