Complement expression in retinal pigment epithelial cells is modulated by activated macrophages

Complement activation is involved in a variety of retinal diseases. We have shown previously that a number of complement components and regulators can be produced locally in the eye, and that retinal pigment epithelial (RPE) cells are the major source of complement expression at the retina-choroidal interface. The expression of complement components by RPE cells is regulated by inflammatory cytokines. Under aging or inflammatory conditions, microglia and macrophages accumulate in the subretinal space, where they are in close contact with RPE cells. In this study, we investigated the effect of activated macrophages on complement expression by RPE cells. Mouse RPE cells were treated with the supernatants from un-activated bone marrow-derived macrophages (BM-DMs), the classically activated BM-DMs (M1) and different types of the alternatively activated BM-DMs (M2a by IL-4, M2b by immune complex and lipopolysaccharide (LPS), M2c by IL-10). The expression of inflammatory cytokines and complement genes by RPE cells were determined by real-time RT-PCR. The protein expression of CFB, C3, C1INH, and C1r was examined by Western blot. Our results show that un-stimulated RPE cells express a variety of complement-related genes, and that the expression levels of complement regulators, including C1r, factor H (CFH), DAF1, CD59, C1INH, Crry, and C4BP genes are significantly higher than those of complement component genes (C2, C4, CFB, C3, and C5). Macrophage supernatants increased inflammatory cytokine (IL-1ß, IL-6, iNOS), chemokine (CCL2) and complement expression in RPE cells. The supernatants from M0, M2a and M2c macrophages mildly up-regulated (2~3.5-fold) CFB, CFH and C3 gene expression in RPE cells, whereas the supernatants from M1 and M2b macrophages massively increased (10~30-fold) CFB and C3 gene expression in RPE cells. The expression of other genes, including C1r, C2, C4, CFH, Masp1, C1INH, and C4BP in RPE cells was also increased by the supernatants of M1 and M2b macrophages; however, the increment levels were significantly lower than CFB and C3 genes. M1 and M2b macrophage supernatants enhanced CFB (Bb fragment) protein expression and C3 secretion by RPE cells. M1 macrophages may affect complement expression in RPE cells through the STAT1 pathway. Our results suggest that under inflammatory conditions, activated macrophages could promote the alternative pathway of complement activation in the retina via induction of RPE cell CFB and C3 expression.

Addiction to Runx1 is partially attenuated by loss of p53 in the Eµ-Myc lymphoma model

The Runx genes function as dominant oncogenes that collaborate potently with Myc or loss of p53 to induce lymphoma when over-expressed. Here we examined the requirement for basal Runx1 activity for tumor maintenance in the Eµ-Myc model of Burkitt's lymphoma. While normal Runx1fl/fl lymphoid cells permit mono-allelic deletion, primary Eµ-Myc lymphomas showed selection for retention of both alleles and attempts to enforce deletion in vivo led to compensatory expansion of p53null blasts retaining Runx1. Surprisingly, Runx1 could be excised completely from established Eµ-Myc lymphoma cell lines in vitro without obvious effects on cell phenotype. Established lines lacked functional p53, and were sensitive to death induced by introduction of a temperature-sensitive p53 (Val135) allele. Transcriptome analysis of Runx1-deleted cells revealed a gene signature associated with lymphoid proliferation, survival and differentiation, and included strong de-repression of recombination-activating (Rag) genes, an observation that was mirrored in a panel of human acute leukemias where RUNX1 and RAG1,2 mRNA expression were negatively correlated. Notably, despite their continued growth and tumorigenic potential, Runx1null lymphoma cells displayed impaired proliferation and markedly increased sensitivity to DNA damage and dexamethasone-induced apoptosis, validating Runx1 function as a potential therapeutic target in Myc-driven lymphomas regardless of their p53 status.

From embryonic stem cells to sensory hair cells : a programming approach

Tese de doutoramento, Ciências Biomédicas (Biologia do Desenvolvimento), Universidade de Lisboa, Faculdade de Medicina, 2014

Localization of Cathepsins D and B at the Maternal-Fetal Interface and the Invasiveness of the Trophoblast during the Postimplantation Period in the Mouse

A survey of existing data suggests that trophoblast cells produce factors involved in extracellular matrix degradation. In this study, we correlated the expression of cathepsins D and B in the murine ectoplacental cone with the ultrastructural progress of decidual invasion by trophoblast cells. Both proteases were immunolocalized at implantation sites in lysosome-endosome-like compartments of trophoblast giant cells. Cathepsin D, but not cathepsin B, was also detected ultrastructurally in extracellular compartments surrounded by processes of the invading trophoblast containing extracellular matrix components and endometrial cell debris. The expression of cathepsins D and B by trophoblast cells was confirmed by RT-PCR in ectoplacental cones isolated from implantation chambers at gestation day 7.5. Our data addressed a positive relationship between the expression and presence of cathepsin D at the extracellular compartment of the maternal-fetal interface and the invasiveness of the trophoblast during the postimplantation period, suggesting a participation of invading trophoblast cells in the cathepsin D release. Such findings indicate that mouse trophoblast cells might exhibit a proteolytic ability to partake in the decidual invasion process at the maternal-fetal interface. Copyright (C) 2010 S. Karger AG, Basel

IMMUNOCYTOCHEMICAL DIFFERENTIATION OF REACTIVE HYPERPLASIA FROM FOLLICULAR LYMPHOMA USING MONOCLONAL-ANTIBODIES TO CELL-SURFACE AND PROLIFERATION-RELATED MARKERS

We tested the hypothesis that a panel of antibodies to cell surface, cytoplasmic, and nuclear antigens could reliably distinguish the cells composing reactive germinal centers from those composing follicular lymphoma. Immunocytochemistry was performed on deparaffinized sections of methacarn-fixed lymph node and tonsil (15 cases of reactive hyperplasia and 14 cases of follicular lymphoma) using antibodies to the nerve growth factor receptor (NGFR5), bcl-2 protein (124), proliferating cell nuclear antigen (PCNA; 19A2), and CD45RA (MT2). In 100% of cases of reactive hyperplasia, both MT2 and 124 showed positive immunostaining of mantle zone and scattered interfollicular lymphocytes, but in all cases there was a sharply demarcated absence of immunostaining of germinal center cells. However, diffuse immunostaining of follicular centers with MT2 (64%) and 124 (93%) and scattered intervening cells were seen in follicular lymphoma. The combination of antibodies to CD45RA and bcl-2 yielded positive immunostaining of follicular center cells in 93% of follicular lymphomas. The germinal center cells of reactive hyperplasia showed >75% nuclear positivity with antibodies to PCNA, in contrast to the follicular lymphoma cells, which showed variable PCNA indices ranging from 25 to >75%. A minority of follicular lymphoma cases (29%) showed PCNA indices comparable with those seen in cases of reactive hyperplasia. Antibodies to NGFR were positive in all cases of reactive hyperplasia and in 79% of cases of follicular hyperplasia, although the immunostaining intensity was generally decreased in follicular hyperplasia. In summary, antibodies to bcl-2 appear to be superior to those to CD45RA in distinguishing reactive hyperplasia from follicular lymphoma. Reactive hyperplasia cannot be discriminated from follicular hyperplasia using antibodies to PCNA or to nerve growth factor receptor.

Antitumor activity of irradiated riboflavin on human renal carcinoma cell line 786-O

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Interferon-gamma alters the phagocytic activity of the mouse trophoblast

Interferon-gamma (IFN-gamma) mediates diverse functions in bone marrow-derived phagocytes, including phagocytosis and microbe destruction. This cytokine has also been detected at implantation sites under both physiological and pathological conditions in many different species. At these particular sites, the outermost embryonic cell layer in close contact with the maternal tissues, the trophoblast exhibits intense phagocytic activity. To determine whether IFN-gamma affects phagocytosis of mouse-trophoblast cells, ectoplacental cone-derived trophoblast was cultured and evaluated for erythrophagocytosis. Phagocytic activity was monitored ultrastructurally and expressed as percentage of phagocytic trophoblast in total trophoblast cells. Conditioned medium from concanavalin-A-stimulated spleen cells significantly enhanced trophoblast phagocytosis. This effect was blocked by pre-incubation with an anti-IFN-gamma neutralizing antibody. Introduction of mouse recombinant IFN-gamma (mrIFN-gamma) to cultures did not increase cell death, but augmented the percentage of phagocytic cells in a dose-dependent manner. Ectoplacental cones from mice deficient for IFN-gamma receptor alpha-chain showed a significant decrease of the phagocytosis, even under mrIFN-gamma stimulation, suggesting that IFN-gamma-induced phagocytosis are receptor-mediated. Reverse transcriptase-PCR analyses confirmed the presence of mRNA for IFN-gamma receptor alpha and beta-chains in trophoblast cells and detected a significant increase in the mRNA levels of IFN-gamma receptor beta-chain, mainly, when cultured cells were exposed to IFN-gamma. Immunohistochemistry and Western blot analyses also revealed protein expression of the IFN-gamma receptor alpha-chain. These results suggest that IFN-gamma may participate in the phagocytic activation of the mouse trophoblast, albeit the exact mechanism was not hereby elucidated. Protective and/or nutritional fetal benefit may result from this physiological response. In addition, our data also shed some light on the understanding of trophoblast tolerance to inflammatory/immune cytokines during normal gestation.

Mechanistic study of the effects of 8-oxo-7,8-dihydroguanine (8-oxoG) on reporter gene expression in mammalian cells

DNA damage causes replication errors, leading to genetic instability or cell death. Besides that, many types of DNA base modifications have been shown to interfere with transcriptional elongation if they are located in the transcribed DNA strand of active genes, acting as roadblocks for RNA polymerases. It is widely assumed that transcription blockage by endogenous DNA damage is responsible for the early cell senescence in organs and accelerated ageing observed in individuals with compromised nucleotide excision repair.rnThe aims of this work were to design new experimental systems for testing transcription blocking potentials of DNA base modifications in an individual gene and to apply these test systems to the investigation of the effects of a frequent endogenously generated base modification, namely 8-oxo-7,8-hydroxyguanine (8-oxoG), on the gene transcription in cells. Several experimental strategies were employed for this purpose. First, I constructed an episomal vector encoding for a short-lived EGFP-ODC fusion protein and measured expression of the reporter gene in permanently transfected clonal cell lines exposed to DNA damaging agents. Second, the expression of plasmid-borne EGFP gene damaged with photosensitisers to obtain one or several oxidative purine modifications per plasmid molecule was determined in transiently transfected human and mouse host cells in an approach known as “host cell reactivation”. As a prerequisite for these experiments, a robust method of precise quantitative measurement of the EGFP gene expression in transiently transfected cells by flow cytometry was developed and validated. Third, I elaborated a very efficient procedure for insertion of synthetic oligonucleotides carrying 8-oxoG into plasmid DNA, avoiding any unwanted base damage and strand breaks. The consequences of 8-oxoG placed in defined positions in opposing DNA strands of the EGFP gene for transcription were measured by host cell reactivation in cells with functional 8-oxoguanine DNA glycosylase (OGG1) gene and in OGG1 null cells.rnThe results obtained in Ogg1-/- cells demonstrated that unrepaired 8-oxoG, even if situated in the transcribed DNA strand, does not have any negative effect on the reporter gene transcription. On the other hand, as few as one 8-oxoG was sufficient to cause a significant decrease of the gene expression in OGG1-proficient cell lines, i.e. in the presence of base excision repair. For two analysed positions of 8-oxoG in the plasmid DNA, the inhibition of gene transcription by the base modification correlated with the efficiency of its excision by purified OGG1 protein under cell-free conditions. Based on these findings, it has to be concluded that the observed decrease of transcription is mediated by excision of the base modification by OGG1 and probably caused by the repair-induced single-strand breaks. The mechanism of transcription inhibition by 8-oxoG is therefore clearly distinct from stalling of elongating RNA polymerase II complexes at the modified base.

Synthesis and cytotoxic activity of non-naturally substituted 4-oxycoumarin derivatives

Coumarins are a large family of natural and synthetic compounds exerting different pharmacological effects, including cytotoxic, anti-inflammatory or antimicrobial. In the present communication we report the synthesis of a series of 12 diversely substituted 4-oxycoumarin derivatives including methoxy substituted 4-hydroxycoumarins, methyl, methoxy or unsubstituted 3-aryl-4-hydroxycoumarins and 4-benzyloxycoumarins and their anti-proliferative effects on breast adenocarcinoma cells (MCF-7), human promyelocytic leukemia cells (HL-60), human histiocytic lymphoma cells (U937) and mouse neuroblastoma cells (Neuro2a). The most potent bioactive molecule was the 4-hydroxy-5,7-dimethoxycoumarin (compound 1) which showed similar potency (IC(50) 0.2-2 μM) in all cancer cell lines tested. This non-natural product reveals a simple bioactive scaffold which may be exploited in further studies.

T cell interaction with ICAM-1-deficient endothelium in vitro: essential role for ICAM-1 and ICAM-2 in transendothelial migration of T cells

Transendothelial migration is a crucial step in the complex process of lymphocyte extravasation during lymphocyte homing, immunosurveillance and inflammation. However, little is known about the precise role of cell adhesion molecules (CAM) involved in this particular event. To define the CAM involved in T cell adhesion versus transendothelial migration, we have previously established an in vitro transendothelial migration system using mouse T cells and mouse endothelioma cells. We demonstrate here that, using ICAM-1-deficient endothelioma cells derived from ICAM-1 mutant mice, transendothelial migration of T cells was inhibited to a much greater extent when compared to migration across wild-type cells treated with a blocking anti-ICAM-1 monoclonal antibody. This unexpected result was confirmed by a rescue experiment using retroviral transfer of wild-type ICAM-1 into ICAM-1-deficient endothelial cells. Additional experiments showed that, in the absence of functional ICAM-1, only ICAM-2 was involved in transendothelial migration, but not PECAM-1, VCAM-1, or E-selectin. Taking this novel approach, we show that ICAM-1 and ICAM-2 are essential for transendothelial migration of T cells.

K1 protein of human herpesvirus 8 suppresses lymphoma cell Fas-mediated apoptosis.

Expression of the K1 gene of human herpesvirus 8 activates nuclear factor-kappaB and induces lymph node hyperplasia and lymphomas in transgenic mice. To further delineate its role in cell survival, we determined whether K1 altered apoptosis of lymphoma cells. K1 protein is expressed in Kaposi sarcoma and primary effusion lymphoma. We retrovirally transfected BJAB lymphoma, THP-1, U937, and Kaposi sarcoma SLK cells to express K1 and a K1 mutant with the deleted immunoreceptor tyrosine-based activation motif (K1m). We challenged cells with an agonistic anti-Fas antibody, Fas ligand, irradiation, and tumor necrosis factor-related apoptosis-inducing ligand. K1 transfectants but not K1m transfectants exhibited reduced levels of apoptosis induced by the anti-Fas antibody but not apoptosis induced by the tumor necrosis factor-related apoptosis-inducing ligand or irradiation. K1 expression resulted in reduced apoptosis rates as shown in several assays. K1 induced a modest reduction in levels of Fas-associated death domain protein, and procaspase 8 recruited to the death-inducing signaling complex. Finally, K1 transfectants cleaved procaspase 8 at significantly lower rates than did K1m transfectants. K1-transfected mice, compared with vector-transfected mice, showed lower death rates after challenge with anti-Fas antibody. K1 may contribute to lymphoma development by stimulating cell survival by selectively blocking Fas-mediated apoptosis.

REST maintains self-renewal and pluripotency of embryonic stem cells.

The neuronal repressor REST (RE1-silencing transcription factor; also called NRSF) is expressed at high levels in mouse embryonic stem (ES) cells, but its role in these cells is unclear. Here we show that REST maintains self-renewal and pluripotency in mouse ES cells through suppression of the microRNA miR-21. We found that, as with known self-renewal markers, the level of REST expression is much higher in self-renewing mouse ES cells than in differentiating mouse ES (embryoid body, EB) cells. Heterozygous deletion of Rest (Rest+/-) and its short-interfering-RNA-mediated knockdown in mouse ES cells cause a loss of self-renewal-even when these cells are grown under self-renewal conditions-and lead to the expression of markers specific for multiple lineages. Conversely, exogenously added REST maintains self-renewal in mouse EB cells. Furthermore, Rest+/- mouse ES cells cultured under self-renewal conditions express substantially reduced levels of several self-renewal regulators, including Oct4 (also called Pou5f1), Nanog, Sox2 and c-Myc, and exogenously added REST in mouse EB cells maintains the self-renewal phenotypes and expression of these self-renewal regulators. We also show that in mouse ES cells, REST is bound to the gene chromatin of a set of miRNAs that potentially target self-renewal genes. Whereas mouse ES cells and mouse EB cells containing exogenously added REST express lower levels of these miRNAs, EB cells, Rest+/- ES cells and ES cells treated with short interfering RNA targeting Rest express higher levels of these miRNAs. At least one of these REST-regulated miRNAs, miR-21, specifically suppresses the self-renewal of mouse ES cells, corresponding to the decreased expression of Oct4, Nanog, Sox2 and c-Myc. Thus, REST is a newly discovered element of the interconnected regulatory network that maintains the self-renewal and pluripotency of mouse ES cells.

CREB trans-activation of disruptor of telomeric silencing-1 mediates forskolin inhibition of CTGF transcription in mesangial cells.

Connective tissue growth factor (CTGF) participates in diverse fibrotic processes including glomerulosclerosis. The adenylyl cyclase agonist forskolin inhibits CTGF expression in mesangial cells by unclear mechanisms. We recently reported that the histone H3K79 methyltransferase disruptor of telomeric silencing-1 (Dot1) suppresses CTGF gene expression in collecting duct cells (J Clin Invest 117: 773-783, 2007) and HEK 293 cells (J Biol Chem In press). In the present study, we characterized the involvement of Dot1 in mediating the inhibitory effect of forskolin on CTGF transcription in mouse mesangial cells. Overexpression of Dot1 or treatment with forskolin dramatically suppressed basal CTGF mRNA levels and CTGF promoter-luciferase activity, while hypermethylating H3K79 in chromatin associated with the CTGF promoter. siRNA knockdown of Dot1 abrogated the inhibitory effect of forskolin on CTGF mRNA expression. Analysis of the Dot1 promoter sequence identified a CREB response element (CRE) at -384/-380. Overexpression of CREB enhanced forskolin-stimulated Dot1 promoter activity. A constitutively active CREB mutant (CREB-VP16) strongly induced Dot1 promoter-luciferase activity, whereas overexpression of CREBdLZ-VP16, which lacks the CREB DNA-binding domain, abolished this activation. Mutation of the -384/-380 CRE resulted in 70% lower levels of Dot1 promoter activity. ChIP assays confirmed CREB binding to the Dot1 promoter in chromatin. We conclude that forskolin stimulates CREB-mediated trans-activation of the Dot1 gene, which leads to hypermethylation of histone H3K79 at the CTGF promoter, and inhibition of CTGF transcription. These data are the first to describe regulation of the Dot1 gene, and disclose a complex network of genetic and epigenetic controls on CTGF transcription.

Versatile applications of transcriptional pulsing to study mRNA turnover in mammalian cells.

Development of transcriptional pulsing approaches using the c-fos and Tet-off promoter systems greatly facilitated studies of mRNA turnover in mammalian cells. However, optimal protocols for these approaches vary for different cell types and/or physiological conditions, limiting their widespread application. In this study, we have further optimized transcriptional pulsing systems for different cell lines and developed new protocols to facilitate investigation of various aspects of mRNA turnover. We apply the Tet-off transcriptional pulsing strategy to investigate ARE-mediated mRNA decay in human erythroleukemic K562 cells arrested at various phases of the cell cycle by pharmacological inhibitors. This application facilitates studies of the role of mRNA stability in control of cell-cycle dependent gene expression. To advance the investigation of factors involved in mRNA turnover and its regulation, we have also incorporated recently developed transfection and siRNA reagents into the transcriptional pulsing approach. Using these protocols, siRNA and DNA plasmids can be effectively cotransfected into mouse NIH3T3 cells to obtain high knockdown efficiency. Moreover, we have established a tTA-harboring stable line using human bronchial epithelial BEAS-2B cells and applied the transcriptional pulsing approach to monitor mRNA deadenylation and decay kinetics in this cell system. This broadens the application of the transcriptional pulsing system to investigate the regulation of mRNA turnover related to allergic inflammation. Critical factors that need to be considered when employing these approaches are characterized and discussed.

The effect of v-{\it mos\/} expression on the regulation of the {\it fos\/} promoter in 490N3T cells

The v-mos oncogene acquired by Moloney murine sarcoma viruses by recombination with the c-mos proto-oncogene encodes a 37kD cytoplasmic serine/threonine protein kinase which can phosphorylate tubulin and vimentin, as well as the cyclin B component of the maturation promotion factor complex (MPF). Our earliest experiments asked whether the v-mos protein could activate the transcription of transin. Since the transcription of transin was known to be mediated by both fos-dependent and fos-independent pathways, it seemed possible that the induction of transin transcription by v-mos might be mediated by p55$\sp{\rm c-}\sp{fos}$. Surprisingly, when we examined the effect of v-mos on the fos promoter, we observed a significant inhibition of transcription in 49ON3T cells, a subclone of N1H3T3 mouse fibroblasts.^ In this thesis we show that in mouse 49ON3T cells, transcription from the fos promoter is up to 10-fold repressed in the presence of v-mos. Moreover, in this cell line several other transforming constructs (v-ras, v-src, neu) also cause repression of the fos promoter. Interestingly, nontransforming oncogenes (e.g. myc) do not repress fos transcription. The repressive effect was lost in v-mos mutants lacking in ATP-binding or kinase domain, arguing that the effect on fos transcription was mediated by v-mos transforming kinase activity. As mos is a cytoplasmic protein, it was assumed that transcriptional repression was mediated by conversion of a transcriptional regulator to a repressor by mos-induced phosphorylation. As a first approximation of the identity of this factor, we mapped the position of the mos effect on the fos promoter using reporter (CAT) constructs. We found that repression was mediated by regions $-$221 to $-$106 and $-$122 to $-$65 relative to the fos transcriptional start site, both of which regions regulate baseline fos transcription. There are direct repeats containing E2F transcriptional activator/repressor recognition motifs in these regions which bind similar nuclear proteins independently of v-mos presence or absence. Our data show that the contribution of the direct repeat to baseline fos transcription is mediated by these E2F sites with perhaps some contribution from the overlapping retinoblastoma control element (RCE). We have shown that there is a separate DNA protein interaction in the direct repeat which is more pronounced in the presence of v-mos. The recognition site for this protein, which we speculate mediates the mos-induced downregulation of fos transcription, overlaps but is distinct from the E2F and RCE binding sites. (Abstract shortened by UMI.) ^