Background: Adipose-derived stem cells have attracted significant interest, especially in stem cell therapy and regenerative medicine. However, these cells undergo gradual premature senescence in long-term cultures, which are essential for clinical applications that require cell-assisted lipotransfer or tissue repair. Methods: Since the extracellular matrix forms the microenvironment around stem cells in vitro and regulates self-renewal and multipotency in part by slowing down stem cell aging, we evaluated its potential to protect against senescence, using H 2 O 2 -induced adipose-derived stem cells as a model. Results: We found that supplementing cultures with decellularized extracellular matrix harvested from the same cells significantly promotes proliferation and reverses signs of senescence, including decreased multipotency, increased expression of senescence-associated β-galactosidase, and accumulation of reactive oxygen species. Conclusion: These findings suggest a novel approach in which an autologous decellularized extracellular matrix is used to prevent cellular senescence to enable the use of adipose-derived stem cells in regenerative medicine.

Catalpol, an iridoid glucoside, has been reported to inhibit apoptosis of neuron and endothelial cells. In the present study, we investigated the mechanism of catalpol-mediated cardioprotection. The rat embryonic ventricular myocardial cell line (H9c2) cells were first incubated with catalpol, and then exposed to hydrogen peroxide (H 2 O 2 ). The concentration of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) were all determined by using commercially available kits. Apoptotic cells were assessed by Hoechst 33258 and Annexin V-fluorescein isothiocyanate binding assay. Synthesis of Bcl-2, Bax, cytochrome c and caspase-3 were analysed by real-time semiquantitative reverse transcription-PCR and Western blotting. We observed that apoptosis in H9c2 was associated with increased Bax, cytochrome c , caspase-3, decreased Bcl-2 activity after 24 h of H 2 O 2 exposure. Catalpol pretreatment afforded a marked protection against the above H 2 O 2 -mediated cytotoxicity and apoptosis in H9c2 cells. Moreover, the catalpol pretreatment led to a great reduction in H 2 O 2 -induced MDA release and increased SOD. These findings indicated for the first time that pretreatment of H9c2 cells with catalpol can be against H 2 O 2 -induced apoptosis, and the protective effect of catalpol involves the mitochondrial-dependent caspase pathway and is associated with increased Bcl-2 and decreased Bax expression.

In the present study, we cloned and sequenced the mRNAs of the Sod3 [extracellular Cu Zn SOD (superoxide dismutase)] gene in Drosophila and identified two mRNA products formed by alternative splicing. These products code for a long and short protein derived from the four transcripts found in global expression studies (Flybase numbers Dmel\CG9027 , FBgn0033631). Both mRNA process variants contain an extracellular signalling sequence, a region of high homology to the Sod1 (cytoplasmic Cu Zn SOD) including a conserved AUG start, with the longer form also containing a hydrophobic tail. The two fully processed transcripts are homologous to Caenorhabditis elegans Sod3 mRNA showing the same processing pattern. Using an established KG p-element+ insertion line (KG06029), we demonstrate that the Sod3 codes for an active Cu Zn SOD. We found differing expression patterns across sex with higher levels of expression of Sod3 in females. There is a correlation of Sod1 and Sod3 gene expression and activity that can explain why Sod3 was not seen in earlier studies of Sod1 . Finally, we found no effect on lifespan with the Sod3 hypomorph mutation ( Sod3 KG06029 ) but did observe a significant increase in resistance to paraquat and H 2 O 2 (hydrogen peroxide).

MST3 (mammalian sterile 20-like kinase 3) is a sterile 20 kinase reported to have a role in Fas-ligation- and staurosporine-induced cell death by unknown mechanism(s). We found that MST3-deficient cells are resistant to H 2 O 2 , which was reversed by reconstituting recombinant MST3. H 2 O 2 -induced JNK (c-Jun N-terminal kinase) activation was greatly enhanced in shMST3 cells (a cell line treated with short hairpin RNA against MST3). Suppression of JNK activity by the inhibitor SP600125 or by dominant-negative JNK2 re-sensitized cells to H 2 O 2 . Furthermore, c-Jun Ser-63 phosphorylation was augmented in shMST3 cells, whereas JunAA (dominant-negative c-Jun) reduced H 2 O 2 resistance, implicating an AP-1 (activator protein 1) pathway in H 2 O 2 -induced survival signalling. Total cytoprotective HO-1 (haem oxygenase 1) expression, which was attenuated by JunAA, was induced up to 5-fold higher in shMST3 cells compared with controls. Zinc protoporphyrin IX, a potent inhibitor of HO reversed the H 2 O 2 -resistance of shMST3 cells. Our results reveal that H 2 O 2 -induced MST3-mediated cell death involves suppressing both a JNK survival pathway and up-regulation of HO-1.

The combination of hydroxocobalamin (vitamin B 12b ) and ascorbicacid (vitamin C) can cause the death of tumor cells at the concentrationsof the components at which they are nontoxic when administeredseparately. This cytotoxic action on epidermoid human larynx carcinomacells HEp-2 in vitro is shown to be due to the hydrogen peroxidegenerated by the combination of vitamins B 12b and C. The drop inthe glutathione level preceding cell death was found to be the result ofcombined action of the vitamins. It is supposed that the induction of celldeath by combined action of vitamins B 12b and C is connected to the damageof the cell redox system.

Data on alterations of the properties of glyceraldehyde-3-phosphate dehydrogenase upon oxidation of its functional groups are reviewed; a mechanism of uncoupling of oxidation and phosphorylation in glycolysis is considered. Possible ways of regulating uncoupling, and the physiological importance of this process, are discussed.

Recently, we proposed a hypothetical model of coexistence of “Reactive oxygen cycle” with Q cycle and H + cycle in mitochondrial respiratory chain to combine both processes of univalent electron leak for production of superoxide and of proton leak across inner mitochondrial membrane. This review presents a more detailed description of this model and summarizes the supporting experimental evidence obtained.

The molecular properties of a novel membrane quinol oxidase from the marine bacterium Pseudomonas nautica 617 are presented. The protein contains 2b hemes/mole which may be distinguished by EPR spectroscopy but not by optical spectroscopy and electrochemistry. Respiration, though being cyanide insensitive, is not inhibited by carbon monoxide and oxygen reduction is carried out only half-way with production of hydrogen peroxide. The terminal oxidase represents, therefore, a unique example in the large family of terminal oxidases known up to date.

In contrast to plant agglutinins, biological activities of animal/human lectins are not well defined yet. Testing a panel of seven mammalian carbohydrate-binding proteins we have found that the dimeric lectin from chicken liver (CL-16) was a stimulator of H 2 O 2 release from human neutrophils as well as effector for induction of cytosolic Ca 2+ and pH increase in rat thymocytes. Activity of this lectin was comparable to potent galactoside-specific plant lectins such as Viscum album L. agglutinin. The activities of the tested plant lectins depended significantly on their nominal carbohydrate specificity as well as on the source. The results indicate that endogenous lectins may be involved in the regulation of neutrophil and lymphocyte functions by elicitation of selective biosignaling reactions.

This mini-review describes the role of different mitochondrial components in the formation of reactive oxygen species under normal and pathological conditions and the effect of inhibitors and uncouplers on superoxide formation.