Induction of metallothionein and stomatin by interleukin-6 and glucocorticoids in a human amniotic cell line

Novel ratio-expressions of genes enables estimation of wound age in contused skeletal muscle

Given that combination with multiple biomarkers may well raise the predictive value of wound age, it appears critically essential to identify new features under the limited cost. For this purpose, the present study explored whether the gene expression ratios provide unique time information as an additional indicator for wound age estimation not requiring the detection of new biomarkers and allowing full use of the available data. The expression levels of four wound-healing genes (Arid5a, Ier3, Stom, and Lcp1) were detected by real-time polymerase chain reaction, and a total of six expression ratios were calculated among these four genes. The results showed that the expression levels of four genes and six ratios of expression changed time-dependent during wound repair. The six expression ratios provided additional temporal information, distinct from the four genes analyzed separately by principal component analysis. The overall performance metrics for cross-validation and external validation of four typical prediction models were improved when six ratios of expression were added as additional input variables. Overall, expression ratios among genes provide temporal information and have excellent potential as predictive markers for wound age estimation. Combining the expression levels of genes with ratio-expression of genes may allow for more accurate estimates of the time of injury.

Cell-to-cell contact-mediated regulation of tumor behavior in the tumor microenvironment

Tumor growth and progression are complex processes mediated by mutual interactions between cancer cells and their surrounding stroma that include diverse cell types and acellular components, which form the tumor microenvironment. In this environment, direct intercellular communications play important roles in the regulation of the biological behaviors of tumors. However, the underlying molecular mechanisms are insufficiently defined. We used an in vitro coculture system to identify genes that were specifically expressed at higher levels in cancer cells associated with stromal cells. Major examples included epithelial membrane protein 1 (EMP1) and stomatin, which positively and negatively regulate tumor progression, respectively. EMP1 promotes tumor cell migration and metastasis via activation of the small GTPase Rac1, while stomatin strongly suppresses cell proliferation and induces apoptosis of cancer cells via inhibition of Akt signaling. Here we highlight important aspects of EMP1, stomatin, and their family members in cancer biology. Furthermore, we consider the molecules that participate in intercellular communications and signaling transduction between cancer cells and stromal cells, which may affect the phenotypes of cancer cells in the tumor microenvironment.

Dexamethasone induces primary amnion epithelial cell senescence through telomere-P21 associated pathway†

Dexamethasone (Dex), a corticosteroid hormone, is used during the perinatal period to help fetal lung and other organ development. Conversely, Dex-induced cell proliferation has been associated with accelerated aging. Using primary amnion epithelial cells (AECs) from term, not in labor, fetal membranes, we tested the effects of Dex on cell proliferation, senescence, and inflammation. Primary AECs treated with Dex (100 and 200 nM) for 48 h were tested for cell viability (crystal violet dye exclusion), cell cycle progression and/or type of cell death (flow cytometry), expression patterns of steroid receptors (glucocorticoid receptor, progesterone receptor membrane component 1&2), inflammatory mediators (IL-6 and IL-8), and telomere length (quantitative RT-PCR). Mechanistic mediators of senescence (p38MAPK and p21) were determined by western blot analysis. Dex treatment did not induce AEC proliferation, cell cycle, influence viability, or morphology. However, Dex caused dependent telomere length reduction and p38MAPK-independent but p21-dependent (confirmed by treatment with p21 inhibitor UC2288). Senescence was not associated with an increase in inflammatory mediators, which is often associated with senescence. Co-treatment with RU486 produced DNA damage, cell cycle arrest, and cellular necrosis with an increase in inflammatory mediators. The effect of Dex was devoid of changes to steroid receptors, whereas RU486 increased GR expression. Dex treatment of AECs produced nonreplicative and noninflammatory senescence. Extensive use of Dex during the perinatal period may lead to cellular senescence, contributing to cellular aging associated pathologies during the perinatal and neonatal periods.

Interleukin (IL)-6: A Friend or Foe of Pregnancy and Parturition? Evidence From Functional Studies in Fetal Membrane Cells

Objective

Protection of the fetus within the amniotic sac is primarily attained by remodeling fetal membrane (amniochorion) cells through cyclic epithelial to mesenchymal and mesenchymal to epithelial (EMT and MET) transitions. Endocrine and paracrine factors regulate EMT and MET during pregnancy. At term, increased oxidative stress forces a terminal state of EMT and inflammation, predisposing to membrane weakening and rupture. IL-6 is a constitutively expressed cytokine during gestation, but it is elevated in term and preterm births. Therefore, we tested the hypothesis that IL-6 can determine the fate of amnion membrane cells and that pathologic levels of IL-6 can cause a terminal state of EMT and inflammation, leading to adverse pregnancy outcomes.

Methods

Primary amnion epithelial cells (AECs) were treated with recombinant IL-6 (330, 1,650, 3,330, and 16,000 pg/ml) for 48 h (N = 5). IL-6-induced cell senescence (aging), cell death (apoptosis and necrosis), and cell cycle changes were studied using flow cytometry. Cellular transitions were determined by immunocytochemistry and western blot analysis, while IL-6 signaling (activation of signaling kinases) was measured by immunoassay. Inflammatory marker matrix metalloproteinase (MMP9) and granulocyte-macrophage colony-stimulating factor (GM-CSF) concentrations were measured using a Fluorokine E assay and ELISA, respectively. Amniotic membranes collected on gestational day (D) 12 and D18 from IL-6 knockout (KO) and control C57BL/6 mice (N = 3 each) were used to determine the impact of IL-6 on cell transitions. Fold changes were measured based on the mean of each group.

Results

IL-6 treatment of AECs at physiologic or pathologic doses increased JNK and p38MAPK activation; however, the activation of signals did not cause changes in AEC cell cycle, cellular senescence, apoptosis, necrosis, cellular transitions, or inflammation (MMP9 and GM-CSF) compared to control. EMT markers were higher on D18 compared to D12 regardless of IL-6 status in the mouse amniotic sac.

Conclusion

Physiologic and pathologic concentrations of IL-6 did not cause amnion cell aging, cell death, cellular transitions, or inflammation. IL-6 may function to maintain cellular homeostasis throughout gestation in fetal membrane cells. Although IL-6 is a good biomarker for adverse pregnancies, it is not an indicator of an underlying pathological mechanism in membrane cells.

Increased metallothionein expression reflects steroid resistance in renal allograft recipients

Steroid-refractory acute rejection is a risk factor for inferior renal allograft outcome. We aimed to gain insight into the mechanisms underlying steroid resistance by identifying novel molecular markers of steroid-refractory acute rejection. Eighty-three kidney transplant recipients (1995-2005), who were treated with methylprednisolone during a first acute rejection episode, were included in this study. Gene expression patterns were investigated in a discovery cohort of 36 acute rejection biopsies, and verified in a validation cohort of 47 acute rejection biopsies. In the discovery set, expression of metallothioneins (MT) was significantly (p < 0.000001) associated with decreased response to steroid treatment. Multivariate analysis resulted in a predictive model containing MT-1 as an independent covariate (AUC = 0.88, p < 0.0000001). In the validation set, MT-1 expression was also significantly associated with steroid resistance (p = 0.029). Metallothionein expression was detected in macrophages and tubular epithelial cells. Parallel to the findings in patients, in vitro experiments of peripheral blood mononuclear cells from 11 donors showed that nonresponse to methylprednisolone treatment is related to highly elevated MT levels. High expression of metallothioneins in renal allografts is associated with resistance to steroid treatment. Metallothioneins regulate intracellular concentrations of zinc, through which they may diminish the zinc-requiring anti-inflammatory effect of the glucocorticoid receptor.

Up-regulation of stomatin expression by hypoxia and glucocorticoid stabilizes membrane-associated actin in alveolar epithelial cells

Stomatin is an important lipid raft-associated protein which interacts with membrane proteins and plays a role in the membrane organization. However, it is unknown whether it is involved in the response to hypoxia and glucocorticoid (GC) in alveolar epithelial cells (AEC). In this study we found that hypoxia and dexamethasone (dex), a synthetic GC not only up-regulated the expression of stomatin alone, but also imposed additive effect on the expression of stomatin in A549 cells, primary AEC and lung of rats. Then we investigated whether hypoxia and dex transcriptionally up-regulated the expression of stomatin by reporter gene assay, and found that dex, but not hypoxia could increase the activity of a stomatin promoter-driven reporter gene. Further deletion and mutational studies demonstrated that a GC response element (GRE) within the promoter region mainly contributed to the induction of stomatin by dex. Moreover, we found that hypoxia exposure did not affect membrane-associated actin, but decreased actin in cytoplasm in A549 cells. Inhibiting stomatin expression by stomatin siRNA significantly decreased dense of peripheral actin ring in hypoxia or dex treated A549 cells. Taken all together, these data indicated that dex and/or hypoxia significantly up-regulated the expression of stomatin in vivo and in vitro, which could stabilize membrane-associated actin in AEC. We suppose that the up-regulation of stomatin by hypoxia and dex may enhance the barrier function of alveolar epithelia and mediate the adaptive role of GC to hypoxia.

Distribution of stomatin expressing in the central nervous system and its up-regulation in cerebral cortex of rat by hypoxia

Stomatin is an important membrane raft protein which can combine skeleton protein, some ion channel, and transporter to regulate their functions. However, until now no data on its expression and function in CNS are available. In this study, we examined distribution of stomatin in CNS of rat, and investigated the effects of hypoxia exposure and glucocorticoid on stomatin expression in cerebral cortex of rat. Immunofluorescence staining revealed a broad expression of stomatin protein in many areas of adult rat brain and spinal cord, including the ventral horn of spinal cord, causal magnocellular nucleus of hypothalamus, the V layer of the cerebral cortex, solitary nucleus, 10 and 12 nuclei, and so on. Hypoxia or ischemic hypoxia significantly up-regulated stomatin expression in cerebral cortex, and the up-regulation was independent on adrenocortical steroids since it also occurred in adrenalectomized (ADX) rats. Moreover, treatment of ADX or sham-operated rats with dexamethasone, a synthetic glucocorticoid alone could significantly stimulate expression of stomatin in lung and heart, but not in cerebral cortex. However, dexamethasone could enhance the hypoxia-stimulated expression of stomatin in cerebral cortex of ADX rats. These findings suggested that stomatin might be involved in various physiological functions and cellular events of neurons in CNS under physiological conditions and play a potential protective role under hypoxic conditions.

Inflammatory response: an unrecognised source of variability in the pharmacokinetics and pharmacodynamics of cancer chemotherapy

An important limitation in the use of chemotherapy in cancer treatment is that cytotoxic agents have small margins of safety compared with other drugs. The largely unpredictable pharmacokinetics of cytotoxic agents contribute significantly to differences in toxicity and efficacy between individuals. Over the past few decades, evidence has accumulated that the inflammatory response to conditions such as infection, degenerative disease, and cancer can greatly affect the disposition of drugs. A more recent finding is that the presence of an inflammatory response identifies patients with more aggressive disease and may also compromise the pharmacodynamics of anticancer drugs. In this review, we discuss the changes in the pharmacokinetics of drugs caused by the presence of inflammation. Also, we discuss the modulating role of inflammatory mediators on the pharmacokinetics and pharmacodynamics of cytotoxic agents. We argue that, overall, these factors identify inflammatory response as a potentially important factor in the interindividual variability of response and toxic effects to cancer chemotherapy.

Association of stomatin with lipid-protein complexes in the plasma membrane and the endocytic compartment

Membrane protein - microvilli - lipid raft - GPI-anchored protein - epithelial cell The 31 kDa integral membrane protein stomatin (protein 7.2b) has a monotopic structure and a cytofacial orientation. We have shown previously that stomatin is located in plasma membrane protruding structures and forms high-order homo-oligomers in the human epithelial cell line UAC, suggesting that this protein has a structural function in the cortical morphogenesis of the cells. It is also present in a pool of juxtanuclear vesicles. In this study, we show that stomatin colocalizes with the GPI-anchored proteins placental alkaline phosphatase (PLAP) and membrane folate receptor alpha (MFRalpha) endogenously expressed in UAC cells. This observation enabled us to demonstrate two different aspects of stomatin. First, using anti-PLAP antibody internalization, we show that the peri-centrosomal vesicles containing stomatin correspond to a subset of endosomes, which can also be labeled with the late endosomal/lysosomal marker LAMP-2. Secondly, we found that stomatin is partially present in detergent-insoluble membrane domains and co-patches with PLAP on the plasma membrane, after cross-linking of PLAP by antibodies. These data indicate that stomatin and GPI-anchored proteins are linked through lipid rafts and undergo the same sorting events. We propose that stomatin, through its affinity for lipid rafts, functions in concentrating GPI-anchored proteins in membrane microvillar structures. Consistent with this hypothesis, we found that stomatin is expressed exclusively in microvilli of the apical membrane in polarized Madin-Darby canine kidney (MDCK) cells.

Cysteine 29 is the major palmitoylation site on stomatin

The 31 kDa membrane protein stomatin was metabolically labeled with tritiated palmitic acid in the human amniotic cell line UAC and immunoprecipitated. We show that the incorporated palmitate is sensitive to hydroxylamine, indicating the binding to cysteine residues. Stomatin contains three cysteines. By expressing a myc-tagged stomatin and substituting the three cysteines by serine, individually or in combination, we demonstrate that Cys-29 is the predominant site of palmitoylation and that Cys-86 accounts for the remaining palmitate labeling. Disruption of Cys-52 alone does not show any detectable reduction of palmitic acid incorporation. Given the organization of stomatin into homo-oligomers, the presence of multiple palmitate chains is likely to increase greatly the affinity of these oligomers for the membrane and perhaps particular lipid domains within it.

Molecular cloning of hSLP-1, a novel human brain-specific member of the band 7/MEC-2 family similar to Caenorhabditis elegans UNC-24

We have isolated and characterized cDNA clones encoding a stomatin-like protein (hSLP-1) from a human cerebral cortex cDNA library. The deduced amino acid sequence (394 residues) revealed that hSLP-1 is a bipartite protein, containing a major stomatin-like part, starting at the N-terminus, and a non-specific lipid transfer protein (nsLTP)-domain at the C-terminal end, similar to the Caenorhabditis elegans protein UNC-24. Therefore, we conclude that hSLP-1 is the human homologue of UNC-24. In addition, the identification of an alternatively spliced variant demonstrated that two exon/intron boundaries are conserved in the hSLP-1 and unc-24 genes. Northern blot and RNA dot blot analyses showed that the 2. 2-kb transcript is mainly expressed in the brain, with the highest levels in the frontal lobe, cerebral cortex, caudate nucleus, amygdala, temporal lobe, putamen, substantia nigra, and hippocampus. This high-level expression of hSLP-1 in the basal ganglia may also reflect the evolutionary link to UNC-24.

Oligomeric nature of the integral membrane protein stomatin

The 31-kDa integral membrane protein stomatin (protein 7.2b) is not only an important component of the red cell membrane but can also be found in abundance in different tissues and cell lines. The protein is thought to be anchored to the membrane by a hydrophobic domain while both N and C termini are exposed to the cytoplasm. We have previously shown in the human cell line UAC that stomatin concentrates preferentially in plasma membrane folds and protrusions. There is also evidence that stomatin is linked to the cortical actin cytoskeleton, suggesting a role in cortical morphogenesis of the cell. In this study, we demonstrate that the fundamental structure of stomatin is oligomeric. Whereas interaction of stomatin with itself was suggested by cross-linking experiments, we show by density gradient centrifugation analysis that soluble homo-oligomeric complexes of this protein are present in Triton X-100 extracts of UAC cells. We also show the existence of these oligomers by co-immunoprecipitation of the endogenous stomatin and a recombinantly expressed myc-tagged stomatin, using an anti-myc antibody. The data indicate that these complexes comprise between 9 and 12 monomers of stomatin. Two C-terminally truncated forms of stomatin do not incorporate into these oligomers, suggesting an involvement of the C terminus in the homo-oligomeric interaction.

Synergistic induction of metallothionein synthesis by interleukin-6, dexamethasone and zinc in the rat

We investigated the reciprocal effects of interleukin-6 (IL-6), glucocorticoid and zinc (Zn) on metallothionein (MT) synthesis in rats. MT synthesis in the liver, which is a key responsible organ in acute phase responses, was induced by IL-6 or dexamethasone (Dex), and in an additive manner by a combination of IL-6 and Dex 18 h after injection. MT synthesis in the lung and heart was evaluated by immunoassay using a specific antibody to MT-1, because of its low concentration in these tissues. Heart concentrations of MT-1 were significantly increased by IL-6, and were further increased by the combination of IL-6 and Dex, although Dex by itself had no effect. This suggests a synergistic effect of IL-6 and Dex on MT-I synthesis in the heart. A similar synergism was observed in the lung. To study the effect of Zn on the induction of MT and acute phase proteins, Zn, IL-6 and Dex were administered in various concentrations. The increase in liver MT induced by the combination of IL-6 and Dex with Zn (130 micrograms MT/g of liver) was greater than the sum of the increases induced by (IL-6 + Zn) and by (Dex + Zn) (103 micrograms MT/g), suggesting a synergistic increase. The data indicate that the maximal increase in the induction of MT by a combination of IL-6 and Dex depends on an adequate liver Zn content. Thus, the in vivo synergistic induction of acute phase proteins by IL-6, glucocorticoid and Zn may be required for the maximal and rapid response, not only in liver but also in other tissues including heart and lung. This suggests that the synergistic reaction may be important for an enhancement of the radical scavenging ability of tissues in acute phase responses.