Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 99-131).

published_or_final_version / Obstetrics and Gynaecology / Master / Master of Philosophy

In normal adult physiology, intestinal smooth muscle cells (ISMC) are characterized as contractile and non-proliferative. Inflammation induces permanent changes to the intestine including hypertrophy of the smooth muscle layer largely due to smooth muscle cell (SMC) proliferation. While the consequences of this hyperplasia are largely unknown, increased muscularis mass may present permanent challenges to organ motility. Similar SMC hyperplasia is observed in other inflammatory pathologies including atherosclerosis and pulmonary arterial hypertension (PAH) where SMC de-differentiate into a ‘synthetic’ phenotype and the mitogens responsible for hyperplasia have been well studied. However, there are limited investigations of SMC mitogens in intestinal inflammation. The identification of these factors may be of critical importance in the case of intestinal strictures, whereby recurring inflammation can lead to bowel obstruction requiring surgical intervention. A novel, primary rat ISMC model was developed to identify the factors responsible for ISMC proliferation in vitro. Primary ISMC cultures are likely more representative of SMC in vivo than the commonly used late-passage cultures. As such, this primary ISMC model is valuable in the evaluation of mitogens involved in the onset of proliferation. This primary ISMC model was used to conduct a comprehensive evaluation of potential mitogens including basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), insulin-like growth factor-1 (IGF-1) and platelet-derived growth factor-BB (PDGF-BB. This work identified IGF-1 and PDGF-BB as ISMC mitogens. However, multiple lines of evidence indicated that PDGF-BB was a more potent mitogen and the involvement of PDGF-BB was subsequently examined in vivo using the trinitrobenzenesulfonic acid (TNBS) model of rat intestinal inflammation. While control ISMC lacked expression of the PDGF-BB receptor (PDGF-Rβ), robust expression was observed within only 6 hr following the induction of TNBS inflammation. By Day 2, when ISMC proliferation in vivo is maximal, freshly isolated ISMC showed on-going PDGF-Rβ activation that was further increased by exogenous PDGF-BB. Taken together, the conclusions from this work in vitro identify PDGF-BB as a potent ISMC mitogen in vivo. Further, this work establishes PDGF-BB and its receptor as potential targets in the medical treatment of intestinal stricture formation. / Thesis (Ph.D, Biology) -- Queen's University, 2012-09-24 19:26:57.201

G protein-coupled receptors (GPCRs) comprise the largest family of transmembrane receptors. The beta-arrestins, adaptor proteins involved in GPCR desensitization, may also act as scaffolds for signaling pathways such as the mitogen-activated protein kinase (MAPK) cascade. The MAPK family, which includes the extracellular-signal regulated kinases (ERK) 1 and 2, promotes cellular differentiation and proliferation. Herein, the activation of ERK1/2 upon stimulation of the GPCR bradykinin type 2 receptor (B2R) with bradykinin was examined. Various B2R mutants with modified C-termini were employed to examine the temporal kinetics of ERK1/2. One of these receptor mutants displayed a loss of beta-arrestin binding as well as greatly enhanced ERK1/2 activation, compared to the wild-type receptor, when a cluster of serine/threonine residues important for B2R internalization was mutated. The other receptor mutants exhibited a correlation between their affinity for beta-arrestin and the intensity of ERK1/2 activation. Data from a mouse embryonic fibroblast cell line null for beta-arrestin suggested that beta-arrestin is involved in late-phase ERK1/2 activation by the B2R. These data point to the involvement of beta-arrestin in the activation of the ERK1/2 MAPKs through the B2R.

During the growth phase of oogenesis, mammalian oocytes increase several hundred-fold in volume. Although it is known that ovarian granulosa cells send growth promoting signals, neither these external signals nor the transduction pathways that become activated in the oocyte are known. Therefore, the presence and the activity of candidate signaling pathways in growing murine oocytes were investigated. By immunoblotting, the MAP kinases, ERK1 and ERK2, as well as their activating kinase MEK, were detected in oocytes at all stages of growth. However, using a phospho-specific anti-ERK antibody, no immunoreactive species were detectable in isolated granulosa cells or oocytes at any stage of growth, except metaphase II. Phosphorylated ERK was also present, although in smaller quantities, in oocyte-granulosa cell complexes at the later stages of growth. Furthermore, when ovarian sections were stained with an anti-ERK antibody, the protein was found to be highly concentrated in the cytoplasm of oocytes at all stages of growth, with lower levels in the nucleus. Another member of the MAP kinase family, Jun kinase (JNK), was investigated. By immunoblotting, JNK was detected in growing oocytes. Experiments using an anti-JNK antibody on ovary sections revealed the protein to be uniformly distributed in non-growing and growing oocytes with no evidence of preferential nuclear localization. These results imply that an interaction between the oocyte and the granulosa cells may be required to generate phosphorylated ERK. They also imply that growth signals probably are not relayed through ERK, but do not exclude a role for Jun kinase in mediating oocyte growth.

The incidence of chronic kidney disease (CKD) is increasing. CKD is characterized by a gradual decrease in renal function leading to end stage renal disease (ESRD). Damage to the glomerular podocytes, is one of the first hallmarks of CKD. We hypothesized that podocyte prostaglandin E2 (PGE2) receptors contribute to the progression of glomerular injury in models of CKD. To test this hypothesis, transgenic mice were generated with either podocyte-specific overexpression or deletion of the PGE2 EP4 receptor (EP4pod+and EP4pod-/- respectively). Mice were next tested in the 5/6 nephrectomy (5/6 Nx) or angiotensin II (Ang II) models of CKD. These studies revealed increased proteinuria and decreased survival for EP4pod+ mice while EP4pod-/- mice were protected against the development of glomerular injury. Furthermore, our findings were supported by in vitro studies using cultured mouse podocytes where an adhesion defect was uncovered for cells overexpressing the EP4 receptor. Additionally, our investigations have demonstrated a novel synergy between angiotensin II AT1 receptors and prostaglandin E2 EP4 receptors. This was revealed by in vitro studies using isolated mouse glomeruli. There we were able to show that Ang II stimulation leads to increased expression of cyclooxygenase 2 (COX-2), the enzyme responsible for synthesis of PGE2, in a p38 mitogen activated protein kinase (MAPK) dependent fashion. Moreover increased PGE2 synthesis was measured in response to Ang II stimulation. We confirmed the presence of this synergy in our cultured mouse podocytes and showed an adhesion defect in response to Ang II stimulation which was COX-2 and EP4 dependent. These findings suggest that Ang II AT1 receptors and PGE2 EP4 receptors act in concert to exacerbate glomerulopathies. Studies using mice with either podocyte-specific overexpression of a dominant negative p38 MAPK or mice with global deletion of the EP1 receptor did not provide conclusive results as to their respective signaling involvement in podocyte injury. Altogether our findings provide novel insight for podocyte PGE2 EP4 and Ang II AT1 receptor signaling in models of CKD. These studies provide novel avenues for pursuing therapeutic interventions for individuals with progressive kidney disease.

In C. albicans, a MAP kinase pathway has been implicated in aspects of controlling hyphal development. We have examined the transcription profile of cells deleted for the transcription factor Cph1 as well as Cst20, Hst7 and Cek1, three upstream kinases potentially involved in Cph1 regulation. Deletion of these four elements does not block filament induction by serum and does not dramatically affect the transcription profile of yeast-hyphal transition, but deletion of CPH1 delays filamentation. Over-expression of Cph1 by ADH1pt-CPH1 significantly enhances filamentation, suggesting that Cph1 is helpful but not essential for filament induction. Interestingly, the transcription profile of ADH1pt-CPH1 expressing cells under yeast conditions is similar to that of wild type strains undergoing the yeast-hyphal transition. Finally, it appears that Cek1 and its regulators Hst7 and Cst20 may control the repression of genes such as CHT2 through a process independent of the Cph1p transcription factor.

T cells are involved in cellular pathways which enable the immune system to protect us against infection and cancer. However, the same mechanisms also allow T cells to generate chronic inflammatory conditions, including autoimmunity and allergy. Thus a concerted effort has been made to try to understand how the immune system functions in order to inhibit responses which may have harmful effects on tissues and organs. There is a continued search for new immunosuppressants which can only be accomplished through a better understanding of the pathways that regulate T cell function. This includes the intracellular signalling pathways which modulate T cell proliferation and cytokine production. While the Mitogen-Activated Protein Kinases (MAPK), extracellular signal-regulated protein kinases (ERK) and p38 have received attention, the role of the stress-activated protein kinases or c-jun N-terminal kinases (JNK) remains controversial. To overcome some of the limitations in studying the role of JNK, a new approach was taken in this thesis. The investigations used recently described peptides (TAT-JIP[subscript]153-163 and TAT-JIP[subscript]153-172) derived from the scaffold protein, JIP-1, which have previously been demonstrated to act as JNK pathway inhibitors. The research characterised the specificity of these inhibitors to enable the appropriate interpretation of data. Using these inhibitors, we were able to show that JNK regulated human T cell proliferation and cytokine production in T cell responses induced independently of TCR ligation (PHAPMA) or via the TCR (anti-CD3-anti-CD28 antibodies, Mixed Lymphocyte Reaction (MLR), Tetanus Toxoid and Der p 2). The data demonstrated that JNK primarily regulated the Th1 cytokine patterns (IFNγ, IL2 and LT) with minimal effect on Th2 cytokine production (IL4, IL10) in response to all stimulatory models. However, while the JNK signalling pathway promoted T cell proliferation and cytokine production in response to PHA-PMA, the pathway depressed these responses following stimulation with anti-CD3-anti-CD28 antibodies and Tetanus Toxoid. Thus activation of JNK with microbial pathogens such as Pseudomonas aeruginosa (PA), which non-specifically activate T cells, may promote lymphocyte proliferation and the release of Th1 cytokines, such as IFNγ. In contrast, JNK activation resulting from engagement of the T cell receptor (TCR) (i.e. Tetanus Toxoid), down-regulates Th1 cytokine production. Therefore, it is likely that the JNK signalling pathway may dampen the development of chronic inflammatory conditions resulting from infection with intracellular parasites and autoimmune diseases. In contrast to Tetanus Toxoid, responses to the recombinant house dust mite allergen, Dermatophagoides pteronyssinus (Der p 2) were promoted by JNK, leading to an increase in Th1 cytokine production. Thus the results suggest that the use of JNK inhibitors could exacerbate both inflammatory conditions (autoimmunity and allergy) and this may also apply to p38 but not the ERK signalling pathway. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1374669 / Thesis (Ph.D.) - University of Adelaide, School of Molecular and Biomedical Science, 2009

Cholangiocarcinoma (CCA), or cancer of the bile ducts, is extremely prevalent in people from Laos and Thailand whose staple diet is uncooked fish which harbour the liver fluke, Opisthorchis viverrini. There is no stronger link between a parasite and cancer than that between O. viverrini and CCA. Indeed WHO data suggests that one in six infected people contract liver cancer derived from the fluke. In vitro and in vivo studies have indicated that the fluke’s excretory/secretory (ES) proteins are mitogenic and likely make significant contributions to the initiation of CCA. To identify these carcinogenic components I undertook two distinct yet related approaches - (1) traditional protein purification methods to separate ES products, specifically targeting mitogenic proteins, and, (2) bioinformatic screening of 5,000 expressed sequences tags (ESTs) and ES proteins characterized by shotgun proteomic approaches, searching for homologues of molecules that are associated with human cancers. The protein purification approach utilized a cell proliferation assay that I developed for measuring cell replication rates in NIH-3T3 fibroblast and human CCA (KKU-100) cell lines stimulated with ES products. ES products were separated by a combination of ion exchange, hydrophobic interaction, size exclusion and a final ion exchange polishing chromatography steps. ES products and chromatographically separated ES proteins were added to cultured cells to observe mitogenic activity. A four-step purification process resulted in the isolation of 23 and 31 kDa proteins that stimulated cell proliferation at just picomolar quantities. These proteins account for a very small proportion of the total protein biomass (6 ppm and 39 ppm respectively) secreted by the parasite. Their identities are currently being explored using alternate proteomic approaches. Some growth factors bind to heparin, so an alternative purification process was developed using a heparin affinity column to purify ES mitogens. In combination with ion exchange chromatography a 20 kDa heparin-binding protein was identified using tandem mass spectrometry as a member of the sperm-coating protein 65 (SCP)-like extracellular proteins, also called SCP/Tpx-1/Ag5/PR-1/Sc766 (SCP/TAPS; Pfam accession number no. PF00188). The O. viverrini heparin-binding SCP/TAPs protein shared similarity with secreted proteins from other parasitic helminths including the hookworm activation-associated protein family, some of which are known to bind to host cells. In silico screening of the O. viverrini ESTs and ES peptides generated by mass spectrometry for proteins associated with cell proliferation and cancer revealed numerous secreted proteins of interest. One of these proteins shared identity with granulin, a vertebrate growth factor. The cDNA corresponding to this protein was termed Ov-grn-1. The predicted molecular characteristics of Ov-GRN-1 (isoelectric point and molecular weight) corresponded with the biochemical properties of the semi-purified mitogen that was chromatographically purified from ES products. Recombinant Ov-GRN-1 was expressed in E. coli in inclusion bodies and the purified denatured protein was refolded to produce a soluble protein. Refolded Ov-GRN-1 stimulated proliferation of NIH-3T3 fibroblasts at nanomolar concentrations and induced shape changes in affected cells. Antibodies raised to recombinant Ov-GRN-1 inhibited the ability of O. viverrini ES products to induce proliferation of fibroblasts and the KKU-100 CCA cell line in vitro, indicating that Ov-GRN-1 is the major growth factor present in O. viverrini ES products. This is the first report of a secreted growth factor from a parasitic worm that induces proliferation of host cells, and supports a role for this fluke protein in establishment of a tumourigenic environment that may ultimately manifest as CCA.

Cholangiocarcinoma (CCA), or cancer of the bile ducts, is extremely prevalent in people from Laos and Thailand whose staple diet is uncooked fish which harbour the liver fluke, Opisthorchis viverrini. There is no stronger link between a parasite and cancer than that between O. viverrini and CCA. Indeed WHO data suggests that one in six infected people contract liver cancer derived from the fluke. In vitro and in vivo studies have indicated that the fluke’s excretory/secretory (ES) proteins are mitogenic and likely make significant contributions to the initiation of CCA. To identify these carcinogenic components I undertook two distinct yet related approaches - (1) traditional protein purification methods to separate ES products, specifically targeting mitogenic proteins, and, (2) bioinformatic screening of 5,000 expressed sequences tags (ESTs) and ES proteins characterized by shotgun proteomic approaches, searching for homologues of molecules that are associated with human cancers. The protein purification approach utilized a cell proliferation assay that I developed for measuring cell replication rates in NIH-3T3 fibroblast and human CCA (KKU-100) cell lines stimulated with ES products. ES products were separated by a combination of ion exchange, hydrophobic interaction, size exclusion and a final ion exchange polishing chromatography steps. ES products and chromatographically separated ES proteins were added to cultured cells to observe mitogenic activity. A four-step purification process resulted in the isolation of 23 and 31 kDa proteins that stimulated cell proliferation at just picomolar quantities. These proteins account for a very small proportion of the total protein biomass (6 ppm and 39 ppm respectively) secreted by the parasite. Their identities are currently being explored using alternate proteomic approaches. Some growth factors bind to heparin, so an alternative purification process was developed using a heparin affinity column to purify ES mitogens. In combination with ion exchange chromatography a 20 kDa heparin-binding protein was identified using tandem mass spectrometry as a member of the sperm-coating protein 65 (SCP)-like extracellular proteins, also called SCP/Tpx-1/Ag5/PR-1/Sc766 (SCP/TAPS; Pfam accession number no. PF00188). The O. viverrini heparin-binding SCP/TAPs protein shared similarity with secreted proteins from other parasitic helminths including the hookworm activation-associated protein family, some of which are known to bind to host cells. In silico screening of the O. viverrini ESTs and ES peptides generated by mass spectrometry for proteins associated with cell proliferation and cancer revealed numerous secreted proteins of interest. One of these proteins shared identity with granulin, a vertebrate growth factor. The cDNA corresponding to this protein was termed Ov-grn-1. The predicted molecular characteristics of Ov-GRN-1 (isoelectric point and molecular weight) corresponded with the biochemical properties of the semi-purified mitogen that was chromatographically purified from ES products. Recombinant Ov-GRN-1 was expressed in E. coli in inclusion bodies and the purified denatured protein was refolded to produce a soluble protein. Refolded Ov-GRN-1 stimulated proliferation of NIH-3T3 fibroblasts at nanomolar concentrations and induced shape changes in affected cells. Antibodies raised to recombinant Ov-GRN-1 inhibited the ability of O. viverrini ES products to induce proliferation of fibroblasts and the KKU-100 CCA cell line in vitro, indicating that Ov-GRN-1 is the major growth factor present in O. viverrini ES products. This is the first report of a secreted growth factor from a parasitic worm that induces proliferation of host cells, and supports a role for this fluke protein in establishment of a tumourigenic environment that may ultimately manifest as CCA.