Focus: The Science of Stress: Mesenchymal Stem/Stromal Cells and Their Role in Oxidative Stress Associated with Preeclampsia

Preeclampsia (PE) is a serious medically important disorder of human pregnancy, which features de novo pregnancy-induced hypertension and proteinuria. The severe form of PE can progress to eclampsia, a convulsive, life-threatening condition. When placental growth and perfusion are abnormal, the placenta experiences oxidative stress and subsequently secretes abnormal amounts of certain pro-angiogenic factors (eg, PlGF) as well as anti-angiogenic factors (eg, sFlt-1) that enter the maternal circulation. The net effect is damage to the maternal vascular endothelium, which subsequently manifests as the clinical features of PE. Other than delivery of the fetus and placenta, curative treatments for PE have not yet been forthcoming, which reflects the complexity of the clinical syndrome. A major source of reactive oxygen species that contributes to the widespread maternal vascular endothelium damage is the PE-affected decidua. The role of decidua-derived mesenchymal stem/stromal cells (MSC) in normotensive and pathological placenta development is poorly understood. The ability to respond to an environment of oxidative damage is a “universal property” of MSC but the biological mechanisms that MSC employ in response to oxidative stress are compromised in PE. In this review, we discuss how MSC respond to oxidative stress in normotensive and pathological conditions. We also consider the possibility of manipulating the oxidative stress response of abnormal MSC as a therapeutic strategy to treat preeclampsia.     

In vivo and in vitro function of the Escherichia coli periplasmic cysteine oxidoreductase DsbG

We have characterized in vivo and in vitro the recently identified DsbG from Escherichia coli. In addition to sharing sequence homology with the thiol disulfide exchange protein DsbC, DsbG likewise was shown to form a stable periplasmic dimer, and it displays an equilibrium constant with glutathione comparable with DsbA and DsbC. DsbG was found to be expressed at approximately 25% the level of DsbC. In contrast to earlier results (Andersen, C. L., Matthey-Dupraz, A., Missiakas, D., and Raina, S. (1997) Mol. Microbiol. 26, 121-132), we showed that dsbG is not essential for growth and that dsbG null mutants display no defect in folding of multiple disulfide-containing heterologous proteins. Overexpression of DsbG, however, was able to restore the ability of dsbC mutants to express heterologous multidisulfide proteins, namely bovine pancreatic trypsin inhibitor, a protein with three disulfides, and to a lesser extent, mouse urokinase (12 disulfides). As in DsbC, the putative active site thiols in DsbG are completely reduced in vivo in a dsbD-dependent fashion, as would be expected if DsbG is acting as a disulfide isomerase or reductase. However, the latter is not likely because DsbG could not catalyze insulin reduction in vitro. Overall, our results indicate that DsbG functions primarily as a periplasmic disulfide isomerase with a narrower substrate specificity than DsbC.     

Cell-Surface display of heterologous proteins: From high-throughput screening to environmental applications

A variety of expression systems for the display of either short peptides or fully folded proteins on E.coli and, to a lesser extent, on Gram-positive bacteria have been developed. The expression of proteins on the surface of microbial cells has proved extremely important for numerous applications ranging from combinatorial library screening and protein engineering, to whole cell biocatalysts and adsorbants for bioremediation purposes.     

The role of ascorbic acid role in the differentiation of sclerotia in Sclerotinia minor

Sclerotinia minor in culture produces ascorbic acid in levels dependent on oxidative growth conditions and stage of development. During differentiation reduced/oxidized ascorbate ratio decreased by 12 and 6 fold at high and low oxidative stress, respectively. Exogenous ascorbate caused a concentration-dependent decrease of oxidative stress (lipid peroxidation), inhibition of sclerotial differentiation (up to 100%) and delay of differentiatlon (up to 10 days). Ascorbic acid may be produced to help the fungus reduce oxidative stress during growth. The data of this study support our theory proposing that oxidative stress is the inducing factor of sclerotial differentiation in fungi.This revised version was published online in October 2005 with corrections to the Cover Date.     

Lipofuscins and sclerotial differentiation in phytopathogenic fungi

Lipofuscins of lipidic and proteinaceous origin were identified by their excitation and emission spectra in phytopathogenic fungal representatives of different sclerotial differentiation types. Lipofuscin pigments in Sclerotium rolfsii, Rhizoctonia solani, Sclerotinia minor and Sclerotinia sclerotiorum showed similar excitation and emission maxima (ex-em 330–450, 330–450, 330–470 and 3307–470 nm, respectively). Sclerotial differentiation of these fungi was proceeded by a 4.2, 2.5, 2.7, 2.5 and 6, 2.9, 3.8, 3.1 fold increase of lipofuscin accumulation (per lipid and protein content), per respective fungus, as compared to their undifferentiated stage. Lipofuscin levels were higher in older than in younger mycelia and this phenomenon was more profound in S. rolfsii. Since lipofuscins are considered as indicators of oxidative stress, these data are in accordance with the hypothesis that suggests oxidative stress to be a common underlying factor in sclerotial differentiation of sclerotia-forming filamentous phytopathogenic fungi. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cationic double-hydrophilic model networks: synthesis,characterization, modeling and protein adsorption studies

Group transfer polymerization (GTP) was used for the preparation of eight networks based on two hydrophilic monomers, 2-(dimethylamino)ethyl methacrylate (DMAEMA) and poly(ethylene glycol) methacrylate (PEGMA). Ethylene glycol dimethacrylate (EGDMA) served as the cross-linker, whereas 1,4-bis(methoxytrimethylsiloxymethylene)cyclohexane (MTSMC) was used as a bifunctional initiator. Seven of the networks had linear segments of accurate molecular weight between the cross-links, i.e., they were model networks, whereas the eighth was an equimolar randomly cross-linked network. Five of the seven model networks were based on ABA triblock copolymers with PEGMA midblocks and DMAEMA endblocks, in which the DMAEMA/PEGMA ratio was varied. The remaining two model networks were equimolar isomers, the one based on BAB triblocks (with a DMAEMA midblock) and the other based on the statistical copolymer. The degrees of swelling of all of the networks were measured as a function of pH and were found to increase below pH 7. The degrees of swelling at low pH values increased with the percentage of the DMAEMA monomer, which is ionized under these conditions. These swelling results were confirmed qualitatively by theoretical calculations. Finally, the pH-dependence of the adsorption of the proteins pepsin, bovine serum albumin, and lysozyme onto one of the model networks was studied.     

Disruption of the endocytic protein HIP1 results in neurological deficits and decreased AMPA receptor trafficking

Huntingtin interacting protein 1 (HIP1) is a recently identified component of clathrin-coated vesicles that plays a role in clathrin-mediated endocytosis. To explore the normal function of HIP1 in vivo, we created mice with targeted mutation in the HIP1 gene (HIP1(-/-)). HIP1(-/-) mice develop a neurological phenotype by 3 months of age manifest with a failure to thrive, tremor and a gait ataxia secondary to a rigid thoracolumbar kyphosis accompanied by decreased assembly of endocytic protein complexes on liposomal membranes. In primary hippocampal neurons, HIP1 colocalizes with GluR1-containing AMPA receptors and becomes concentrated in cell bodies following AMPA stimulation. Moreover, a profound dose-dependent defect in clathrin-mediated internalization of GluR1-containing AMPA receptors was observed in neurons from HIP1(-/-) mice. Together, these data provide strong evidence that HIP1 regulates AMPA receptor trafficking in the central nervous system through its function in clathrin-mediated endocytosis.     

Bombesin and neurotensin exert antiproliferative effects on oval cells and augment the regenerative response of the cholestatic rat liver

The regenerative capacity of the cholestatic liver is significantly attenuated. Oval cells are hepatic stem cells involved in liver's regeneration following diverse types of injury. The present study investigated the effect of the neuropeptides bombesin (BBS) and neurotensin (NT) on oval cell proliferation as well as on hepatocyte and cholangiocyte proliferation and apoptosis in the cholestatic rat liver. Seventy male Wistar rats were randomly divided into five groups: controls, sham operated, bile duct ligated (BDL), BDL + BBS (30 μg/kg/d), BDL + NT (300 μg/kg/d). Ten days later, alpha-fetoprotein (AFP) mRNA (in situ hybridization), cytokeratin-19 and Ki67 antigen expression (immunohistochemistry) and apoptosis (TUNEL) were evaluated on liver tissue samples. Cells with morphologic features of oval cells that were cytokeratin-19(+) and AFP mRNA(+) were scored in morphometric analysis and their proliferation was recorded. In addition, the proliferation and apoptotic rates of hepatocytes and cholangiocytes were determined. Alanine aminotransferase (ALT) levels and hepatic oxidative stress (lipid peroxidation and glutathione redox state) were also estimated. The neuropeptides BBS and NT significantly reduced ALT levels and hepatic oxidative stress. Both agents exerted similar and cell type-specific effects on oval cells, hepatocytes and cholangiocytes: (a) oval cell proliferation and accumulation in the cholestatic liver was attenuated, (b) hepatocyte proliferation was increased along with a decreased rate of their apoptosis and (c) cholangiocyte proliferation was attenuated and their apoptosis was increased. These observations might be of potential value in patients with extrahepatic cholestasis.