Browsing by Author "Jabbour, Henry"

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    Characterization of signalling cross-talk between the EP2 and FP receptors in endometrial epithelial cells
    (2009) Abera, Aron Berhanie; Katz, Arieh; Jabbour, Henry
    Uterine fibroids are benign tumors that arise from the smooth-muscle uterine cells (myometrium) and are the most common uterine disorder occurring in as many as 30% of women over 35 years of age. Despite their frequent occurrence, the etiology of uterine fibroids is not well elucidated. Several studies have shown that numerous tumors can be regulated by cyclooxygenase (COX) enzyme products but their role in uterine fibroids is not well established. The initial aim of the study was to determine the expression level of COX enzymes and prostaglandin receptors in fibroids and autologous myometrium samples from women with fibroids. Real-Time reverse-transcriptase polymerase chain reaction (RT-PCR) revealed that the expression of COX enzymes, EP1, EP2 and EP4 prostanoid receptors and prolactin were not significantly altered while the EP3 subtype receptor was significantly down-regulated in fibroids compared to adjacent myometrium samples. The EP3 receptor has a protective role in tumor development suggesting the role for down-regulation of the receptor in uterine fibroids pathology. In addition, the expression of COX enzymes, prostaglandin receptors and prostaglandin-mediated genes were assessed in endometrium samples from women with and without uterine fibroids in different stages of the menstrual cycle. COX-2 and interleukin-8 (IL-8) mRNA expressions were significantly higher in both proliferative stage and early-mid secretory, EP2 receptor and IL-11 were elevated in the proliferative stage, vascular endothelial growth factor (VEGF) was highly expressed in the early-mid secretory phase while FP receptor was up-regulated in all stages of the menstrual cycle in endometrium samples from women with fibroids. These data suggest that up-regulation of COX-2 and prostaglandin receptors (EP2 and FP) in endometrium can induce expression of angiogenic and mitogenic factors such as VEGF, IL-8 and IL-11 which might act in a paracrine manner on neighboring myometrial/fibroid tissue to promote angiogenesis and facilitate tumor growth. XVII Furthermore, since EP2 and FP receptors were up-regulated in the proliferative phase of endometrium from uterine fibroid patients and the receptors are co-expressed in endometrial adenocarcinoma (Ishikawa) cells, this study investigated a possible cross-talk that influences intracellular signalling by using Ishikawa cells stably expressing the EP2 and FP receptors (FPEP2 cells) as a model cell line. Real-Time RT-PCR, Western blot analysis and immunofluorescence microscopy confirmed stable expression of the EP2 and FP receptors in FPEP2 cells localized to the perinuclear and plasma membrane. Using FPEP2 cells, the integrated effect of Butaprost (EP2 receptor ligand) and PGF (FP receptor ligand) co-administration on inositol phosphate (IP3) and adenosine 3-,5-cyclic monophosphate (cAMP) release was assessed to study a possible heterologous-interaction or cross-talk between the EP2 and FP receptors. The study showed that in FPEP2 cells, PGF alone does not alter cAMP production, but in combination with Butaprost augments EP2 receptor-mediated cAMP release. PGF-mediated potentiation of cAMP release was abolished by antagonism of the FP receptor, inhibition of phospholipase C (PLC) and IP3-receptor whereas inhibition of protein kinase C (PKC) had no effect suggesting the cross-talk is mediated by FP receptor activation of IP3 release. Moreover, inhibition of calcium effectors using calmodulin antagonist (W7) or Ca2+/calmodulin-dependent kinase II (CaMK-II) inhibitor (KN-93) abolished PGF potentiation of Butaprost-mediated cAMP release. Using short interfering RNA (siRNA) molecules targeted against the adenylyl cyclase 3 (AC3) isoform, the study showed the isoform to be responsible for the cross-talk between the FP and EP2 receptors. In order to determine the integrative effects of the EP2 and FP receptors co-activation on gene expression, a whole genome array profiling in FPEP2 cells in response to Butaprost and/or PGF was performed. The gene array revealed 228 genes that are regulated by co-activation of the EP2 and FP receptors that are involved in cell morphology, proliferation and differentiation. XVIII In addition, co-activation of EP2 and FP receptors with their respective ligands enhanced or repressed a set of EP2 receptor-regulated genes. One of the genes identified, SAT1 (Spermidine/ N1-acetyltransferase), was regulated by the EP2 and FP receptors cross-talk via the calcium sensitive AC3 isoform. SAT1, with known role in regulation of tumorigenesis was also up-regulated in the proliferative stage of endometrium samples from women with uterine fibroids suggesting the EP2 and FP receptor cross-talk characterized in vitro can also happen in vivo. In conclusion, this study reports that COX-2, EP2 and FP receptors, VEGF, IL-8, IL-11 and SAT1 are up-regulated in endometrium from women with uterine fibroids. These genes play a major role in development of fibroids by facilitating angiogenesis and cell growth and by inhibiting apoptosis via autocrine/paracrine mechanisms. In addition, this study demonstrates that co-activation of the EP2 and FP receptors results in enhanced release of cAMP via the FP receptor-G +-q-Ca2+-calmodulin pathway by activating the calcium-sensitive AC3 isoform and modulates a molecular switch which alters the trans-activation of a subset single-receptor induced genes that have important functions in the pathogenesis of reproductive pathologies.
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    Expression and functional role of cyclooxygenase enzymes in cervical carcinoma
    (2001) Sales, Kurt Jason; Katz, Arieh; Jabbour, Henry
    Cervical cancer is considered an important clinical problem in sub-Saharan Africa. Recent studies have suggested that epithelial tumors may be regulated by cyclooxygenase enzyme products. The purpose of this thesis was to determine the expression, localisation and possible functional role of cyclooxygenase enzymes in cervical carcinomas. The initial aim of the study was to determine whether cyclooxygenase-1 and cyclooxygenase-2 expession and prostglandin Eâ‚‚ synthesis are up-regulated in cervical cancers. Real-time quantitative reverse-transcriptase polymerase chain reaction and Western blot analysis confirmed cyclooxygenase-1 and cyclooxygenase-2 ribonucleic acid and protein expression in all cases of squamous cell carcinoma and adenocarcinoma investigated. In contrast, minimal expression of cyclooxygenase-1 or cyclooxygenase-2 was detected in histologically normal cervix. Immunohistochemical analyses localised the site of cyclooxygenase-1 and cyclooxygenase-2 expression and prostaglandin Eâ‚‚ synthesis to neoplastic epithelial cells of all squamous cell carcinomas and adenocarcinomas studied.
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    Modelling material mass balances over wastewater treatment plants
    (2005) Soteman, Sven Wilhelm; Jabbour, Henry
    The overall objective of whole wastewater treatment plant (WWTP)modelling is to develop a COD (electron), carbon (C), nitrogen (N), phosphorus (P), alkilinity (proton), calcium (Ca), magnesium (Mg) and inorganic suspended solids (ISS) concentrations mass balances models for unit operations in municipal WWTPs. The development of such a model, for both steady state and dynamic simulation conditions, is an objective greater that this thesis project, however, it makes a number of significant steps towards it.
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    The molecular pathways mediating the role of cyclooxygenase enzymes and prostaglandins in cervical neoplasias
    (2005) Muller, Melissa; Jabbour, Henry; Katz, Arieh
    Cervical Carcinoma is one of the leading causes of cancer-related death in women. The prevalence of this disease is particularly high in South Africa, occurring on average, in 60 out of every 100 000 women. Previous studies have demonstrated over-expression of cyclooxygenase-2 enzyme and enhanced synthesis of prostanoids, such as prostaglandin E2, in cervical carcinomas. Prostaglandin E2 mediates its effects by interacting with one of four receptors termed EPI-4. Expression and signalling of EP receptors, including EP4, are elevated in cervical carcinomas. The initial aim of this study was to localise the site of expression of EP4 receptors in cervical squamous cell- and adenocarcinomas. Immunohistochemical analysis performed on paraffm wax-embedded cervical tissue sections localised the site of EP4 receptor expression to the neoplastic epithelial cells of all squamous cell carcinomas and adenocarcinomas studied. Minimal EP4 receptor immunoreactivity was detected in normal cervix. The site of localisation of the EP4 receptor within the epithelial compartment suggested that prostaglandin E2 may act in an autocrine/paracrine manner to modulate epithelial cell function and promote tumourigenesis. In addition to endogenous prostaglandin E2, EP receptors in cervical carcinomas can be activated by seminal plasma prostaglandins. Prostaglandin concentration in seminal plasma is 10,000 times higher than that found at a site of inflammation, and prostaglandin E2 is the predominant type of prostaglandin detected in semen. In order to investigate the potential activation of the EP4 receptor by prostaglandin E2 or seminal plasma prostaglandins, we developed an EP4-overexpressing adenocarcinoma cell model system using HeLa (cervical carcinoma) cells.Using this model system the signal transduction pathways activated by prostaglandin E2-or seminal plasma-EP4 receptor interaction in HeLa wild type and EP4 receptor overexpressing(EP4S) He La cells were investigated. Treatment of EP4S cells with seminal plasma or prostaglandin E2 resulted in a rapid accumulation of cAMP (p<;0.001) and phosphorylation of ERK1I2 (p<;O.OOI) in EP4S compared with wild-type cells. This elevated phosphorylation of ERK1I2 is inhibited by co-treatment of cells with chemical inhibitors of MEK (PD98059), epidermal growth factor receptor tyrosine kinase (AGI478) or EP4-selective receptor antagonist (ONO-AE2-227). We next investigated the target genes activated by seminal plasma or prostaglandin E2-EP4 ligand-receptor interaction. Treatment of EP4S cells with seminal plasma or prostaglandin E2 also resulted in elevated expression of the twnourigenic gene, cyclooxygenase-2 (p<;O.OOI), and two genes associated with angiogenesis, vascular endothelial growth factor (p<;O.OOI) and basic fibroblast growth factor (p<;O.05). Expression of these genes was inhibited by co-treatment of cells with seminal plasma or prostaglandin E2 and the MEK inhibitor, the epidermal growth factor receptor tyrosine kinase inhibitor or the EP4-selective receptor antagonist.
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    The role of seminal plasma in cervical carcinoma
    (2010) Sutherland, Jason Robert; Katz, Arieh; Jabbour, Henry
    Cervical cancer is a worldwide public health problem with in excess of 370,000 cases being reported each year. It is the leading cause of death from cancer among women in the developing world where 80% of cases occur. Human papilloma virus (HPV) has been identified as the main causative factor linked with the development and progression of cancer of the cervix, although other factors are known to exist and include genital warts, consenting to sex at an early age, smoking, long term use of contraceptive pills and multiple sexual partners.
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    Testing Revonsuo's Threat simulation theory of dreaming
    (2005) Malcolm-Smith, Susan; Jabbour, Henry; Katz, Arieh
    Revonsuo's Threat Simulation Theory of dreaming asserts that dreaming was selected during human evolution because it has the adaptive function of providing a threat-free context in which threat perception and avoidance can be rehearsed. This study aimed to test the prediction that the threat simulation mechanism will activate differently depending on waking exposure to ecologically valid threat cues. It also compared the impact of waking threat events on dream content with that of waking positive events, as TST asserts that only threat impacts on dream content. Data was collected from three contexts: a high threat context (the Western Cape in South Africa; n=208); a medium threat context (a black southern university in the US; n=34); and a low threat context (North Wales; n=116). Questionnaires included a Most Recent Dream report, details of exposure to walking threatening and positive events, and dreams of such events.