Background A family of aspartate-specific cysteinyl proteases, named caspases, mediates programmed cell death, apoptosis. In this function, caspases are important for physiological processes such as development and maintenance of organ homeostasis. Caspases are, however, also engaged in aging and disease development. The factors inducing age-related caspase activation are not known. Xanthurenic acid, a product of tryptophan degradation, is present in blood and urine, and accumulates in organs with aging. Results Here, we report triggering of apoptotic key events by xanthurenic acid in vascular smooth muscle and retinal pigment epithelium cells. Upon exposure of these cells to xanthurenic acid a degradation of ICAD/DFF45, poly(ADP-ribose) polymerase, and gelsolin was observed, giving a pattern of protein cleavage characteristic for caspase-3 activity. Active caspase-3, -8 and caspase-9 were detected by Western blot analysis and immunofluorescence. In the presence of xanthurenic acid the amino-terminal fragment of gelsolin bound to the cytoskeleton, but did not lead to the usually observed cytoskeleton breakdown. Xanthurenic acid also caused mitochondrial migration, cytochrome C release, and destruction of mitochondria and nuclei. Conclusions These results indicate that xanthurenic acid is a previously not recognized endogenous cell death factor. Its accumulation in cells may lead to accelerated caspase activation related to aging and disease development.

Background Dictyostelium cells exhibit an unusual response to hyperosmolarity that is distinct from the response in other organisms investigated: instead of accumulating compatible osmolytes as it has been described for a wide range of organisms, Dictyostelium cells rearrange their cytoskeleton and thereby build up a rigid network which is believed to constitute the major osmoprotective mechanism in this organism. To gain more insight into the osmoregulation of this amoeba, we investigated physiological processes affected under hyperosmotic conditions in Dictyostelium. Results We determined pH changes in response to hyperosmotic stress using FACS or 31P-NMR. Hyperosmolarity was found to acidify the cytosol from pH 7.5 to 6.8 within 5 minutes, whereas the pH of the endo-lysosomal compartment remained constant. Fluid-phase endocytosis was identified as a possible target of cytosolic acidification, as the inhibition of endocytosis observed under hypertonic conditions can be fully attributed to cytosolic acidification. In addition, a deceleration of vesicle mobility and a decrease in the NTP pool was observed. Conclusion Together, these results indicate that hyperosmotic stress triggers pleiotropic effects, which are partially mediated by a pH signal and which all contribute to the downregulation of cellular activity. The comparison of our results with the effect of hyperosmolarity and intracellular acidification on receptor-mediated endocytosis in mammalian cells reveals striking similarities, suggesting the hypothesis of the same mechanism of inhibition by low internal pH.

Background During apoptosis, Ca2+-dependent events participate in the regulation of intracellular and morphological changes including phosphatidylserine exposure in the exoplasmic leaflet of the cell plasma membrane. The occurrence of phosphatidylserine at the surface of specialized cells, such as platelets, is also essential for the assembly of the enzyme complexes of the blood coagulation cascade, as demonstrated by hemorrhages in Scott syndrome, an extremely rare genetic deficiency of phosphatidylserine externalization, without other apparent pathophysiologic consequences. We have recently reported a reduced capacitative Ca2+ entry in Scott cells which may be part of the Scott phenotype. Results Taking advantage of these mutant lymphoblastoid B cells, we have studied the relationship between this mode of Ca2+ entry and phosphatidylserine redistribution during apoptosis. Ca2+ ionophore induced apoptosis in Scott but not in control cells. However, inhibition of store-operated Ca2+ channels led to caspase-independent DNA fragmentation and decrease of mitochondrial membrane potential in both control and Scott cells. Inhibition of cytochrome P450 also reduced capacitative Ca2+ entry and induced apoptosis at comparable extents in control and Scott cells. During the apoptotic process, both control and more markedly Scott cells externalized phosphatidylserine, but in the latter, this membrane feature was however dissociated from several other intracellular changes. Conclusions The present results suggest that different mechanisms account for phosphatidylserine transmembrane migration in cells undergoing stimulation and programmed death. These observations testify to the plasticity of the plasma membrane remodeling process, allowing normal apoptosis even when less fundamental functions are defective.

Background It has become increasingly clear that β-cell failure plays a critical role in the pathogenesis of type 2 diabetes. Free-radical mediated β-cell damage has been intensively studied in type 1 diabetes, but not in human type 2 diabetes. Therefore, we studied the protein expression of the DNA repair enzyme Ogg1 in pancreases from type 2 diabetics. Ogg1 was studied because it is the major enzyme involved in repairing 7,8-dihydro-8-oxoguanosine DNA adducts, a lesion previously observed in a rat model of type 2 diabetes. Moreover, in a gene expression screen, Ogg1 was over-expressed in islets from a human type 2 diabetic. Methods Immunofluorescent staining of Ogg1 was performed on pancreatic specimens from healthy controls and patients with diabetes for 2–23 years. The intensity and islet area stained for Ogg1 was evaluated by semi-quantitative scoring. Results Both the intensity and the area of islet Ogg1 staining were significantly increased in islets from the type 2 diabetic subjects compared to the healthy controls. A correlation between increased Ogg1 fluorescent staining intensity and duration of diabetes was also found. Most of the staining observed was cytoplasmic, suggesting that mitochondrial Ogg1 accounts primarily for the increased Ogg1 expression. Conclusion We conclude that oxidative stress related DNA damage may be a novel important factor in the pathogenesis of human type 2 diabetes. An increase of Ogg1 in islet cell mitochondria is consistent with a model in which hyperglycemia and consequent increased β-cell oxidative metabolism lead to DNA damage and the induction of Ogg1 expression.

The kinetics of apoptosis and the apoptosis-regulating gene p53 in adjuvant arthritis (AA) were investigated to assess the value of the AA rat model for testing apoptosis-inducing therapies. Very few terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end-labeling (TUNEL)-positive cells were detected during the early phases of AA, but on day 23 (chronic arthritis) the percentage of TUNEL-positive cells was significantly increased. Expression of p53 in synovial tissue gradually increased from days 5-23, which was markedly higher than p53 levels in rheumatoid arthritis (RA) synovium. Significant apoptosis only occurs late in rat AA and is concordant with marked p53 overexpression, making it useful model for testing proapoptotic therapies, but rat AA is not the best model for p53 gene therapy because dramatic p53 overexpression occurs in the latter stages of the disease.

Background Dictyostelium cells exhibit an unusual stress response as they protect themselves against hyperosmotic stress. Cytoskeletal proteins are recruited from the cytosolic pool to the cell cortex, thereby reinforcing it. In order to gain more insight into the osmoprotective mechanisms of this amoeba, we used 1-D and 2-D gel electrophoresis to identify new proteins that are translocated during osmotic shock. Results We identified hisactophilin as one of the proteins that are enriched in the cytoskeletal fraction during osmotic shock. In mutants lacking hisactophilin, viability is reduced under hyperosmotic stress conditions. In wild type cells, serine phosphorylation of hisactophilin was specifically induced by hypertonicity, but not when other stress conditions were imposed on cells. The phosphorylation kinetics reveals a slow accumulation of phosphorylated hisactophilin from 20–60 min after onset of the hyperosmotic shock condition. Conclusion In the present study, we identified hisactophilin as an essential protein for the osmoprotection of Dictyostelium cells. The observed phosphorylation kinetics suggest that hisactophilin regulation is involved in long-term osmoprotection and that phosphorylation occurs in parallel with inactivation of the dynamic actin cytoskeleton.

Background The human FHIT gene is inactivated early in the development of many human cancers and loss of Fhit in mouse predisposes to cancer while reintroduction of FHIT suppresses tumor formation via induction of apoptosis. Fhit protein, a diadenosine polyphosphate hydrolase, does not require hydrolase activity to function in tumor suppression and may signal for apoptosis as an enzyme-substrate complex. Thus, high affinity nonhydrolyzable substrate analogs may either promote or antagonize Fhit function, depending on their features, in Fhit + cells. Previously synthesized analogs with phosphorothioadenosyl substitutions and "supercharged" branches do not bind better than natural substrates and thus have limited potential as cellular probes. Results Here we link adenosine 5'-O-phosphates and phosphorothioates to short-chain polyols to generate a series of substrate analogs. We obtain structure-activity data in the form of in vitro Fhit inhibition for four types of analog substitutions and describe two compounds, inhibitory constants for which are 65 and 75-fold lower than natural substrates. Conclusions The best Fhit inhibitors obtained to date separate two or more 5'-O-phosphoromonothioadenosyl moieties with as many bond lengths as in AppppA, maintain oxygen at the location of the α-β bridging oxygen, and replace carbon for the β phosphorus.

The dataset includes: TEM micrographs of rGO-Ag0/Fe3O4 NH. XRD patterns, FT-IR spectra, and UV-Vis absorption spectra of rGO, AgNP, and rGO-Ag0/Fe3O4 NH. X-ray photoelectron spectra of rGO and rGO-Ag0/Fe3O4 NH. Concentrations of phenol, acetaminophen, ibuprofen, naproxen, BPA, E2, and EE2 as a function of time in graphs. This dataset is associated with the following publication: Park, C.M., J. Heo, D. Wang, C. Su, and Y. Yoon. Heterogeneous activation of persulfate by reduced graphene oxide–elemental silver/magnetite nanohybrids for the oxidative degradation of pharmaceuticals and endocrine disrupting compounds in water. APPLIED CATALYSIS B: ENVIRONMENTAL. Elsevier Science Ltd, New York, NY, USA, 225: 91-99, (2018).

A landmark investigation into the genetic basis of murine progressive ankylosis has clarified the physiologic role of extracellular inorganic pyrophosphate (ePPi) in suppressing pathologic deposition of basic calcium phosphate (BCP) (an inclusive term for hydroxyapatite, octacalcium phosphate, and tricalcium phosphate) in articular tissue [1]. A cell membrane protein, ANK, affects ePPi concentrations and the balance of mineralization in articular tissues.