Imaging techniques applied for detection of secretion, transgene delivery and G proteincoupled receptors in reproductive and endocrine cells in vivo and in vitro

Post-testicular sperm maturation occurs in the epididymis. The ion concentration and proteins secreted into the epididymal lumen, together with testicular factors, are believed to be responsible for the maturation of spermatozoa. Disruption of the maturation of spermatozoa in the epididymis provides a promising strategy for generating a male contraceptive. However, little is known about the proteins involved. For drug development, it is also essential to have tools to study the function of these proteins in vitro. One approach for screening novel targets is to study the secretory products of the epididymis or the G protein-coupled receptors (GPCRs) that are involved in the maturation process of the spermatozoa. The modified Ca2+ imaging technique to monitor release from PC12 pheochromocytoma cells can also be applied to monitor secretory products involved in the maturational processes of spermatozoa. PC12 pheochromocytoma cells were chosen for evaluation of this technique as they release catecholamines from their cell body, thus behaving like endocrine secretory cells. The results of the study demonstrate that depolarisation of nerve growth factor -differentiated PC12 cells releases factors which activate nearby randomly distributed HEL erythroleukemia cells. Thus, during the release process, the ligands reach concentrations high enough to activate receptors even in cells some distance from the release site. This suggests that communication between randomly dispersed cells is possible even if the actual quantities of transmitter released are extremely small. The development of a novel method to analyse GPCR-dependent Ca2+ signalling in living slices of mouse caput epididymis is an additional tool for screening for drug targets. By this technique it was possible to analyse functional GPCRs in the epithelial cells of the ductus epididymis. The results revealed that, both P2X- and P2Y-type purinergic receptors are responsible for the rapid and transient Ca2+ signal detected in the epithelial cells of caput epididymides. Immunohistochemical and reverse transcriptase-polymerase chain reaction (RTPCR) analyses showed the expression of at least P2X1, P2X2, P2X4 and P2X7, and P2Y1 and P2Y2 receptors in the epididymis. Searching for epididymis-specific promoters for transgene delivery into the epididymis is of key importance for the development of specific models for drug development. We used EGFP as the reporter gene to identify proper promoters to deliver transgenes into the epithelial cells of the mouse epididymis in vivo. Our results revealed that the 5.0 kb murine Glutathione peroxidase 5 (GPX5) promoter can be used to target transgene expression into the epididymis while the 3.8 kb Cysteine-rich secretory protein-1 (CRISP-1) promoter can be used to target transgene expression into the testis. Although the visualisation of EGFP in living cells in culture usually poses few problems, the detection of EGFP in tissue sections can be more difficult because soluble EGFP molecules can be lost if the cell membrane is damaged by freezing, sectioning, or permeabilisation. Furthermore, the fluorescence of EGFP is dependent on its conformation. Therefore, fixation protocols that immobilise EGFP may also destroy its usefulness as a fluorescent reporter. We therefore developed a novel tissue preparation and preservation techniques for EGFP. In addition, fluorescence spectrophotometry with epididymal epithelial cells in suspension revealed the expression of functional purinergic, adrenergic, cholinergic and bradykinin receptors in these cell lines (mE-Cap27 and mE-Cap28). In conclusion, we developed new tools for studying the role of the epididymis in sperm maturation. We developed a new technique to analyse GPCR dependent Ca2+ signalling in living slices of mouse caput epididymis. In addition, we improved the method of detecting reporter gene expression. Furthermore, we characterised two epididymis-specific gene promoters, analysed the expression of GPCRs in epididymal epithelial cells and developed a novel technique for measurement of secretion from cells.

Proteomics and chronic inflammatory bowel diseases.

Inflammatory bowel diseases (IBD) are relatively frequent in developed countries. Physiopathological events involved in the etiology of IBDs include activation of immune, mesenchymal and epithelial cells. This review gives an overview of the currently applied proteomics technologies. It describes metabolic changes and goes into the approaches using this methodology to understand the molecular mechanisms implicated in the development of the disease.

Delivery of antigen to nasal-associated lymphoid tissue microfold cells through secretory IgA targeting local dendritic cells confers protective immunity.

BACKGROUND: Transmission of mucosal pathogens relies on their ability to bind to the surfaces of epithelial cells, to cross this thin barrier, and to gain access to target cells and tissues, leading to systemic infection. This implies that pathogen-specific immunity at mucosal sites is critical for the control of infectious agents using these routes to enter the body. Although mucosal delivery would ensure the best onset of protective immunity, most of the candidate vaccines are administered through the parenteral route. OBJECTIVE: The present study evaluates the feasibility of delivering the chemically bound p24gag (referred to as p24 in the text) HIV antigen through secretory IgA (SIgA) in nasal mucosae in mice. RESULTS: We show that SIgA interacts specifically with mucosal microfold cells present in the nasal-associated lymphoid tissue. p24-SIgA complexes are quickly taken up in the nasal cavity and selectively engulfed by mucosal dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin-positive dendritic cells. Nasal immunization with p24-SIgA elicits both a strong humoral and cellular immune response against p24 at the systemic and mucosal levels. This ensures effective protection against intranasal challenge with recombinant vaccinia virus encoding p24. CONCLUSION: This study represents the first example that underscores the remarkable potential of SIgA to serve as a carrier for a protein antigen in a mucosal vaccine approach targeting the nasal environment.

Proliferative enteropathy (Lawsonia intracellularis) outbreak in rabbits in Brazil

An outbreak of Lawsonia intracellularis infection in rabbits, which occurred in 1988 in Rio de Janeiro state, Brazil, is reported. The disease had an acute course (24-48 hours) with clinical signs characterized by brownish or green diarrhea and dehydration. Occasionally, the animals died one day after the onset of diarrhea, without showing any other clinical signs. At necropsy, the ileum was prominent, firm and had a thickened wall; it was dilated in the caudal direction and had a somewhat reticulated appearance, perceptible through the serosa. The thickened mucous membrane had finely corrugated aspect and a shiny surface. The ileocecal valve and surrounding areas were slightly edematous and irregular. The Peyer's patches were sometimes more evident. There was moderate enlargement of the mesenteric lymph nodes. The histological examination revealed different degrees of hyperplasia of the epithelial cells of intestinal crypts consisting of poorly differentiated, hyperchromatic cells with high mitotic index, arranged in a pseudostratified layer which, in some cases, reached the apical portions of the villi. The inflammatory infiltrate between the hyperplastic epithelial cells was composed of lymphocytes, plasma cells, macrophages, some eosinophils and globular leukocytes. Silver impregnation revealed large numbers of bacteria with morphology of the genus Lawsonia in the apical pole of cryptal enterocytes. These bacteria reacted positively to a Lawsonia intracellularis polyclonal antibody by the avidin-biotin immunohistochemistry method.

Nephrotoxicity of Bence-Jones proteins: interference in renal epithelial cell acidification

The aim of the present study was to evaluate the acidification of the endosome-lysosome system of renal epithelial cells after endocytosis of two human immunoglobulin lambda light chains (Bence-Jones proteins, BJP) obtained from patients with multiple myeloma. Renal epithelial cell handling of two BJP (neutral and acidic BJP) was evaluated by rhodamine fluorescence. Renal cells (MDCK) were maintained in culture and, when confluent, were incubated with rhodamine-labeled BJP for different periods of time. Photos were obtained with a fluorescence microscope (Axiolab-Zeiss). Labeling density was determined on slides with a densitometer (Shimadzu Dual-Wavelength Flying-Spot Scanner CS9000). Endocytosis of neutral and acidic BJP was correlated with acidic intracellular compartment distribution using acridine orange labeling. We compared the pattern of distribution after incubation of native neutral and acidic BJP and after complete deglycosylation of BJP by periodate oxidation. The subsequent alteration of pI converted neutral BJP to acidic BJP. There was a significant accumulation of neutral BJP in endocytic structures, reduced lysosomal acidification, and a diffuse pattern of acidification. This pattern was reversed after total deglycosylation and subsequent alteration of the pI to an acidic BJP. We conclude that the physicochemical characteristics of BJP interfere with intracellular acidification, possibly explaining the strong nephrotoxicity of neutral BJP. Lysosomal acidification is fundamental for adequate protein processing and catabolism.

Effect of the Escherichia coli EMO strain on experimental infection by Salmonella enterica serovar Typhimurium in gnotobiotic mice

An experimental infection with Salmonella enterica subsp. enterica serovar Typhimurium was evaluated in gnotobiotic mice previously exposed to a plasmid-free non-pathogenic Escherichia coli (EMO strain). Mice were exposed to EMO (experimental) or not (control) 10 days before challenge with Salmonella Typhimurium (10² colony forming units (CFU)/mouse). Survival after challenge was higher (P < 0.05) in the experimental group (16%) than in the control animals (0%). Histopathological examination of the colon and ileum mucosa of the experimental group showed less extensive lesions such as edema, cell inflammatory infiltration and hyperemia. The epithelial cells of the mucosal surface and the production of the mucous layer were also better preserved in the experimental group. The population levels of Salmonella Typhimurium in the feces were initially 10-fold lower (P < 0.05) in the experimental groups. However, 3 days after challenge both experimental and control groups showed similar population levels ranging from 10(8) to()10(9) CFU/g of feces. The intestinal contents of total and anti-Salmonella Typhimurium sIgA were higher in the experimental groups 10 days after inoculation of E. coli EMO strain. Translocation of Salmonella Typhimurium to the spleen was 10-fold lower (P < 0.05) in the experimental group only on day 3 after infection. This was not related to an increase in the bacterial blood clearance of the animals, as shown by experimental venous challenge with E. coli B41. In conclusion, treatment of mice with E. coli EMO strain promoted a relative protection against experimental infection with Salmonella Typhimurium. This protection was not due to the reduction of the population of pathogens in the intestine but was probably related to stimulation of the immune response.

TMEM16 proteins: the long awaited calcium-activated chloride channels?

Currents mediated by calcium-activated chloride channels (CaCCs), observed for the first time in Xenopus oocytes, have been recorded in many cells and tissues ranging from different types of neurons to epithelial and muscle cells. CaCCs play a role in the regulation of excitability in neurons including sensory receptors. In addition, they are crucial mediators of chloride movements in epithelial cells where their activity regulates electrolyte and fluid transport. The roles of CaCCs, particularly in epithelia, are briefly reviewed with emphasis on their function in secretory epithelia. The recent identification by three independent groups, using different strategies, of TMEM16A as the molecular counterpart of the CaCC is discussed. TMEM16A is part of a family that has 10 other members in mice. The discovery of the potential TMEM16 anion channel activity opens the way for the molecular investigation of the role of these anion channels in specific cells and in organ physiology and pathophysiology. The identification of TMEM16A protein as a CaCC chloride channel molecule represents a great triumph of scientific perseverance and ingenuity. The varied approaches used by the three independent research groups also augur well for the solidity of the discovery.

Effect of blocking Rac1 expression in cholangiocarcinoma QBC939 cells

Cholangiocarcinomas (CCs) are malignant tumors that originate from epithelial cells lining the biliary tree and gallbladder. Ras correlative C3 creotoxin substrate 1 (Rac1), a small guanosine triphosphatase, is a critical mediator of various aspects of endothelial cell functions. The objective of the present investigation was to study the effect of blocking Rac1 expression in CCs. Seventy-four extrahepatic CC (ECC) specimens and matched adjacent normal mucosa were obtained from the Department of Pathology, Inner Mongolia Medicine Hospital, between 2007 and 2009. Our results showed that the expression of Rac1 was significantly higher (53.12%) in tumor tissues than in normal tissues. Western blotting data indicated a significant reduction in Rac1-miRNA cell protein levels. Rac1-miRNA cell growth rate was significantly different at 24, 48, and 72 h after transfection. Flow cytometry analysis showed that Rac1-miRNA cells undergo apoptosis more effectively than control QBC939 cells. Blocking Rac1 expression by RNAi effectively inhibits the growth of CCs. miRNA silencing of the Rac1 gene suppresses proliferation and induces apoptosis of QBC939 cells. These results suggest that Rac1 may be a new gene therapy target for CC. Blocking Rac1 expression in CC cells induces apoptosis of these tumor cells and may thus represent a new therapeutic approach.

In vitro proliferation and differentiation of hepatic oval cells and their potential capacity for intrahepatic transplantation

Hepatic oval cells (HOCs) are recognized as facultative liver progenitor cells that play a role in liver regeneration after acute liver injury. Here, we investigated the in vitro proliferation and differentiation characteristics of HOCs in order to explore their potential capacity for intrahepatic transplantation. Clusters or scattered HOCs were detected in the portal area and interlobular bile duct in the liver of rats subjected to the modified 2-acetylaminofluorene and partial hepatectomy method. Isolated HOCs were positive for c-kit and CD90 staining (99.8% and 88.8%, respectively), and negative for CD34 staining (3.6%) as shown by immunostaining and flow cytometric analysis. In addition, HOCs could be differentiated into hepatocytes and bile duct epithelial cells after leukemia inhibitory factor deprivation. A two-cuff technique was used for orthotopic liver transplantation, and HOCs were subsequently transplanted into recipients. Biochemical indicators of liver function were assessed 4 weeks after transplantation. HOC transplantation significantly prolonged the median survival time and improved the liver function of rats receiving HOCs compared to controls (P=0.003, Studentt-test). Administration of HOCs to rats also receiving liver transplantation significantly reduced acute allograft rejection compared to control liver transplant rats 3 weeks following transplantation (rejection activity index score: control=6.3±0.9; HOC=3.5±1.5; P=0.005). These results indicate that HOCs may be useful in therapeutic liver regeneration after orthotopic liver transplantation.

Stress-related hormone norepinephrine induces interleukin-6 expression in GES-1 cells

In the current literature, there is evidence that psychological factors can affect the incidence and progression of some cancers. Interleukin 6 (IL-6) is known to be elevated in individuals experiencing chronic stress and is also involved in oncogenesis and cancer progression. However, the precise mechanism of IL-6 induction by the stress-related hormone norepinephrine (NE) is not clear, and, furthermore, there are no reports about the effect of NE on IL-6 expression in gastric epithelial cells. In this study, we examined the effect of NE on IL-6 expression in immortalized human gastric epithelial cells (GES-1 cells). Using real-time PCR and enzyme-linked immunoassay, we demonstrated that NE can induce IL-6 mRNA and protein expression in GES-1 cells. The induction is through the β-adrenergic receptor-cAMP-protein kinase A pathway and mainly at the transcriptional level. Progressive 5′-deletions and site-directed mutagenesis of the parental construct show that, although activating-protein-1 (AP-1), cAMP-responsive element binding protein (CREB), CCAAT-enhancer binding protein-β (C/EBP-β), and nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) binding sites are all required in the basal transcription of IL-6, only AP-1 and CREB binding sites in the IL-6 promoter are required in NE-induced IL-6 expression. The results suggest that chronic stress may increase IL-6 secretion of human gastric epithelial cells, at least in part, by the stress-associated hormone norepinephrine, and provides basic data on stress and gastric cancer progression.

Comparative antiproliferation of human prostate cancer cells by ethanolic extracts of two groups of Brazilian propolis

Two groups of propolis, group 12, which was collected in the southeastern Brazil and group 13, which was collected in the northeastern Brazil, were examined for antiproliferation of primary malignant tumor (RC-58T/h/SA#4)-derived human prostate cancer cells and human prostate epithelial cells. The strongest inhibition of RC-58T/h/SA#4 cells was observed in propolis group 13 extracts, whereas moderate growth inhibition was observed in human prostate epithelial cells in comparison with group 12. It can be said that the Brazilian propolis of group 13 contains important chemical ingredients.

The effects of mutated cationic amino acid transporter y+LAT1 at the cellular and systemic level

y+LAT1 is a transmembrane protein that, together with the 4F2hc cell surface antigen, forms a transporter for cationic amino acids in the basolateral plasma membrane of epithelial cells. It is mainly expressed in the kidney and small intestine, and to a lesser extent in other tissues, such as the placenta and immunoactive cells. Mutations in y+LAT1 lead to a defect of the y+LAT1/4F2hc transporter, which impairs intestinal absorbance and renal reabsorbance of lysine, arginine and ornithine, causing lysinuric protein intolerance (LPI), a rare, recessively inherited aminoaciduria with severe multi-organ complications. This thesis examines the consequences of the LPI-causing mutations on two levels, the transporter structure and the Finnish patients’ gene expression profiles. Using fluorescence resonance energy transfer (FRET) confocal microscopy, optimised for this work, the subunit dimerisation was discovered to be a primary phenomenon occurring regardless of mutations in y+LAT1. In flow cytometric and confocal microscopic FRET analyses, the y+LAT1 molecules exhibit a strong tendency for homodimerisation both in the presence and absence of 4F2hc, suggesting a heterotetramer for the transporter’s functional form. Gene expression analysis of the Finnish patients, clinically variable but homogenic for the LPI-causing mutation in SLC7A7, revealed 926 differentially-expressed genes and a disturbance of the amino acid homeostasis affecting several transporters. However, despite the expression changes in individual patients, no overall compensatory effect of y+LAT2, the sister y+L transporter, was detected. The functional annotations of the altered genes included biological processes such as inflammatory response, immune system processes and apoptosis, indicating a strong immunological involvement for LPI.

From epithelial to mesenchymal: regulation of invasive cancer cell motility

Metastasis is the main cause of death among cancer patients. In order to initiate the metastatic cascade cancer cells have to undergo epithelial-to-mesenchymal transition (EMT). In EMT epithelial cells lose their cell-cell and cell-extracellular matrix (ECM) contacts and become more motile. The expression of the transcription factor Slug and of the mesenchymal intermediate filament vimentin is induced during EMT. Vimentin is often overexpressed in malignant epithelial cancers but the functional role of vimentin remains incompletely understood. In addition, kinases such as AKT and ERK are known to be involved in the regulation of EMT and cancer cell motility but the mechanisms underlining their functions are often unclear. Integrins are heterodimeric receptors that attach cells to the surrounding tissue and participate in regulating cell migration and invasion. Changes in integrin activity are linked to increased cell motility and further cancer metastasis. The aim for my PhD studies was to investigate the role of cellular signalling pathways and vimentin in the regulation of cancer cell motility and EMT. Our results revealed that in prostate cancer the downregulation of AKT1 and AKT2, but not AKT3, induces activation of cell surface 1-integrins leading to enhanced cell adhesion, migration and invasion. In addition, our findings demonstrated a reciprocal regulatory interaction between vimentin and ERK2 facilitating ERK-mediated phosphorylation of Slug at serine-87 (S87) in breast cancer. Surprisingly, Slug S87 phosphorylation is dispensable for E-cadherin repression but essential for the induction of vimentin and Axl expression in early onset of EMT. Our findings reveal previously unknown mechanistic information of how prostate and breast cancer cell motility and disease progression is regulated

Caractérisation phénotypique et génotypique d’isolats de Salmonella Typhimurium provenant de porcs sains ou septicémiques

Les infections à Salmonella Typhimurium constituent un problème de taille pour l’industrie porcine et la santé publique car cet animal est un réservoir pour les infections chez l’homme. De plus, on observe, chez des souches appartenant au lysotype (LT) 104, des résistances multiples aux antimicrobiens associées à des septicémies chez les porcs en engraissement, ce qui peut contribuer à la contamination des carcasses. Il faut donc contrôler l’infection au niveau du troupeau. Pour ce faire, il importe donc de mieux caractériser ces souches, comprendre la pathogénie de l’infection et identifier des facteurs de virulence. L’objectif principal de cette étude était de caractériser des isolats de S. Typhimurium provenant de porcs septicémiques et de les comparer avec ceux de porcs sains. Une banque d’isolats provenant de porcs septicémiques (ASC) et de porcs sains à l’abattoir (SSC) était constituée. Le lysotype des isolats a été identifié et ceux-ci ont été caractérisés selon le profil de résistance aux antimicrobiens, le SDS-PAGE et l’immunobuvardage et le PFGE. Chez les isolats ASC, LT 104 représentait 36.4% des isolats et chez les isolats SSC la proportion était de 51.5%. Les isolats pouvaient être résistants jusqu’à douze antimicrobiens, peu importe leur origine. Il n’a toutefois pas été possible d’associer une protéine spécifique au groupe d’isolats ASC. Parmi les souches LT 104, plusieurs groupes génétiques ont été identifiés. Les différentes étapes de la pathogénie de Salmonella ont ensuite été évaluées, dont l’adhésion et l’invasion des isolats des deux banques sur des cellules intestinales humaines. Nos résultats ont démontré que les isolats ASC avaient un pouvoir accru d’invasion comparés aux isolats SSC (P=0.003). Pour un sous-groupe d’isolats sélectionnés selon leur taux d’invasion, des tests de phagocytose, d’apoptose et d’adhésion au mucus intestinal ont été effectués en utilisant la cytométrie en flux. La survie des bactéries après la phagocytose a aussi été évaluée et la méthode MATS a été utilisée pour évaluer l'adhésion aux solvants. Les pourcentages de phagocytose chez les isolats SSC par les monocytes porcins étaient plus élevés que chez les isolats ASC à 15 minutes (P=0.02). Nous n’avons trouvé aucune différence significative pour les autres méthodes utilisées. Nous avons ensuite comparé le génome d’un isolat ASC (#36) à celui d’un isolat SSC (#1) par le SSH pour identifier des facteurs de virulence potentiels. Des clones correspondant à des gènes retrouvés sur le chromosome ainsi que sur des plasmides ont été identifiés. Ces résultats nous ont dirigés vers l’analyse des profils plasmidiques de tous les isolats. Les différents profils étaient retrouvés autant chez les isolats ASC que chez les isolats SSC. Deux profils (PL14 et PL20) étaient observés plus fréquemment chez les isolats LT 104 que chez les isolats d’autres lysotypes (P=0.01 et P=0.01, respectivement). Le séquençage d’un des plasmides de l’isolat ASC, démontrait la présence d’informations génétiques codant pour la réplication et une bêta-galactosidase-α. Il serait intéressant de préciser le rôle exact de ces gènes dans l’infection. Nos travaux suggèrent que les isolats de S. Typhimurium provenant de porcs septicémiques se distinguent par un pouvoir d’invasion accru ainsi que par des taux de phagocytose plus faibles dans les phases initiales de l’infection. Cette étude aura donc permis d’accroître les connaissances sur la pathogénie des infections à S. Typhimurium chez le porc.

Étude des voies d’internalisation de l’entérotoxine STb d’Escherichia coli dans des lignées cellulaires

L’entérotoxine stable à la chaleur STb est produite par les Escherichia coli entérotoxinogènes (ETEC). Son rôle dans la diarrhée post-sevrage porcine est établi. L’internalisation de STb a été observée dans des cellules épithéliales intestinales humaines et de rat. Cependant, le mécanisme d’internalisation n’est pas totalement compris, particulièrement dans le jéjunum porcin, la cible in vivo de STb. Par la cytométrie en flux, nous avons examiné l’internalisation de STb couplée à un marqueur fluorescent dans les cellules épithéliales intestinales porcines IPEC-J2 et les fibroblastes murins NIH3T3. Nos résultats révèlent que l’internalisation de STb est températureindépendante dans les IPEC-J2 tandis qu’elle est température-dépendante dans les NIH3T3, où la réorganisation de l’actine est aussi nécessaire. Toutefois, les niveaux de sulfatide, le récepteur de STb, sont semblables à la surface des deux lignées. Le sulfatide est internalisé à 37°C de façon similaire entre les deux types cellulaires. La rupture des lipid rafts, les microdomaines membranaires contenant le sulfatide, par la méthyl-βcyclodextrine ou la génistéine, n’affecte pas l’internalisation de STb dans les deux lignées. Notre étude indique que le mécanisme d’internalisation de STb est dépendant du type cellulaire. L’activité de la cellule hôte peut être requise ou non. Le récepteur de STb, le sulfatide, n’est pas directement impliqué dans ces mécanismes. L’internalisation activité cellulaire-dépendante suggère une endocytose, nécessitant la réorganisation de l’actine mais pas les lipid rafts. L’internalisation de STb est donc un processus complexe dépendant du type cellulaire, qu’il apparait plus relevant d’étudier dans des modèles cellulaires représentatifs des conditions in vivo.