The tumor suppressor p53 is a transcription factor which binds DNA through a structurally complex domain stabilized by a zinc atom. Zinc chelation disrupts the architecture of this domain, inducing the protein to adopt an immunological phenotype identical to that of many mutant forms of p53. In this report, we used 65 Zn to show that incorporation of zinc within the protein was required for folding in the`wild-type' conformation capable of speci®c DNA-binding. Using a cellular assay, we show that addition of extracellular zinc at concentrations within the physiological range (5 mM) was required for renaturation and reactivation of wild-type p53.

Multipotential stem cells can be selected from the bone marrow by plastic adhesion, expanded, and cultured. They are able to differentiate not only into multiple cell types, including cartilage, bone, adipose and fibrous tissues, and myelosupportive stroma, but also into mesodermal (endothelium), neuroectodermal, or endodermal (hepatocytes) lineages. Our goal was to characterize the multipotential capacities of human mesenchymal stem cells (hMSCs) and to evaluate their ability to differentiate into insulin-secreting cells in vitro. hMSCs were obtained from healthy donors, selected by plastic adhesion, and phenotyped by fluorescence-activated cell sorter and reverse transcription-polymerase chain reaction analysis before and after infection with adenoviruses coding for mouse IPF1, HLXB9, and FOXA2 transcription factors involved early in the endocrine developmental pathway. We found that native hMSCs have a pluripotent phenotype (OCT4 expression and high telomere length) and constitutively express NKX6-1 at a low level but lack all other transcription factors implicated in beta-cell differentiation. In all hMSCs, we detected mRNA of cytokeratin 18 and 19, epithelial markers present in pancreatic ductal cells, whereas proconvertase 1/3 mRNA expression was detected only in some hMSCs. Ectopic expression of IPF1, HLXB9, and FOXA2 with or without islet coculture or islet-conditioned medium results in insulin gene expression. In conclusion, our results demonstrated that in vitro human bone marrow stem cells are able to differentiate into insulin-expressing cells by a mechanism involving several transcription factors of the beta-cell developmental pathway when cultured in an appropriate microenvironment. Stem Cells 2005;23:594-604

We hypothesized that overloaded training (OT) in triathlon would induce oxidative stress and damage on muscle and DNA. Nine male triathletes and 6 male sedentary subjects participated in this study. Before and after a 4-week OT, triathletes exercised for a duathlon. Blood ratio of reduced vs. oxidized glutathione (GSH/GSSG), plasma thiobarbituric acid reactive substances (TBARS), leukocyte DNA damage, creatine kinase (CK), and CK-MB mass in plasma, erythrocyte superoxide dismutase (SOD) activity, erythrocyte and plasma glutathione peroxidase (GSH-Px) activities, and plasma total antioxidant status (TAS) were measured before and after OT in pre- and postexercise situations. Triathletes were overloaded in response to OT. In rest conditions, OT induced plasma GSH-Px activity increase and plasma TAS decrease (both p < 0.05). In exercise conditions, OT resulted in higher exercise-induced variations of blood GSH/GSSG ratio, TBARS level (both p < 0.05), and CK-MB mass (p < 0.01) in plasma; and decreased TAS response (p < 0.05). OT could compromise the antioxidant defense mechanism with respect to exercise-induced response. The resulting increased exercise-induced oxidative stress and further cellular susceptibility to damage needs more study.

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Plasma selenium (Se), zinc (Zn) and copper (Cu) levels and antioxidant metalloenzymes, glutathione peroxidase (GPX) and superoxide dismutase (SOD), were studied in 17 patients on maintenance hemodialysis (HD) (group I), 14 uremic patients (group II) and 14 healthy subjects (group III). Plasma Se levels and erythrocyte GPX were significantly lower in the HD group (for Se: 0.69 ± 0.12 vs. 1.05 ± 0.13 μmol/l in controls; for erythrocyte GPX: 34.4 ± 6.4 vs. 49.2 ± 9 lU/g hemoglobin in controls) and a significant correlation was found between the two parameters (r = 0.66, p < 0.005). There was also a correlation between decreased plasma Zn and erythrocyte SOD activity (r = 0.58, p < 0.02) and between decreased plasma Cu and erythrocyte SOD (r = 0.60, p < 0.02). Plasma malondialdehyde levels were augmented in HD patients (5.08 ± 0.26 vs. 2.55 ± 0.15 μmol/l in controls and 2.79 ± 0.40 μmol/l in the uremic group). The catalase activity was increased in HD patients (202 ± 24 vs. 140 ± 40 IU/mg hemoglobin in group III). A defective antioxidant activity may thus contribute to increased peroxidative damage to cells in the course of dialysis.

Human mesenchymal stem cells (hMSC) are a promising source for cell therapy after stroke. To deliver these cells, an IV injection appears safer than a local graft. We aimed to assess the whole-body biodistribution of IV-injected (99m)Tc-HMPAO-labeled hMSC in normal rats (n = 9) and following a right middle cerebral artery occlusion (MCAo, n = 9). Whole-body nuclear imaging, isolated organ counting (at 2 and 20 h after injection) and histology were performed. A higher activity was observed in the right damaged hemisphere of the MCAo group [6.5 +/- 0.9 x 10(-3) % of injected dose (ID)/g] than in the control group (3.6 +/- 1.2 x 10(-3) %ID/g), 20 h after injection. In MCAo rats, right hemisphere activity was higher than that observed in the contralateral hemisphere at 2 h after injection (11.6 +/- 2.8 vs. 9.8 +/- 1.7 x 10(-3) %ID/g). Following an initial hMSC lung accumulation, there was a decrease in pulmonary activity from 2 to 20 h after injection in both groups. The spleen was the only organ in which activity increased between 2 and 20 h. The presence of hMSC was documented in the spleen, liver, lung, and brain following histology. IV-injected hMSC are transiently trapped in the lungs, can be sequestered in the spleen, and are predominantly eliminated by kidneys. After 20 h, more hMSC are found in the ischemic lesion than into the undamaged cerebral tissue. IV delivery of hMSC could be the initial route for a clinical trial of tolerance.

Photodynamic-induced cytotoxicity by hypericin (HYP) was studied on three human melanoma cell lines: one pigmented cell line (G361) and two amelanotic cell lines (M18 and M6). No significant variation in the rate of uptake and in the maximum level of HYP incorporation for the different cells was observed. In the dark, no cytotoxicity was observed in the range 0-10-6 M HYP for the three cell lines. Amelanotic cells were found to be more sensitive than pigmented cells to irradiation of HYP with visible light (lambda > 590 nm). In addition, for the three cell lines HYP-induced photocytotoxicity was found to be drug-dose and light-dose dependent. Under the conditions used, thiobarbituric acid-reacting substances (TBARs) were significantly increased in amelanotic cells after irradiation (P < 0.0001). By contrast, the amount of TBARS remained unchanged in pigmented cells. Antioxidant defenses including enzymes and glutathione (GSH) were assayed before and after HYP photosensitization. Significantly increased total SOD activity was observed after photosensitizaton for amelanotic cells (P < 0.05), while glutathione peroxidase (GSHPx) and catalase (Cat) activities but also GSH levels were significantly decreased (P < 0.01). In pigmented cells a significantly increased Cat activity was found (P < 0.05), whereas GSHPx was unaffected after irradiation. It can be inferred that (a) HYP may be an effective PDT agent for melanoma and (b) there is a relationship between melanin content and sensitivity to HYP phototoxicity in human melanoma cells.

Abstract. Inflammation results from the recruitement to a given tissue or organ and the activation of leucocytes, among which the monocytes-macrophages play a major role. These phagocytic cells produce high levels of reactive oxygen species (ROS) as well as cytokines. Whereas both ROS and cytokines have the potential to regulate the expression of heat shock (HS)/stress proteins (HSP), it appears that these proteins in turn have the ability to protect cells and tissues from the deleterious effects of inflammation. The mechanisms by which such protection occurs include prevention of ROS,induced DNA strand breaks and lipid peroxidation as well as protection from mitochondrial structure and function. In vivo, HS protects organs against a number of lesions associated with the increased production of ROS and t or cytokines. In an animal model for adult respiratory distress syndrome, an acute pulmonary inflammatory condition, HS completely prevented mortality. HSP (hsp70 in particular) may also exert protective effects in the immune system by contributing to the processing and presentation of bacterial and tumoral anugens. The analysis of the expression of hsp70 may prove of diagnostic and prognostic value in inflammatory conditions and therapeutical applications are being considered.