published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medicine / Master / Master of Research in Medicine

Continually reported human cases of highly pathogenic avian influenza (HPAI) H5N1 virus infection create heightened threat to public health, due to the disease severity and high lethality. Acute respiratory syndrome (ARDS) has been found to be the most severe form of acute lung injury caused by H5N1 virus infection. Studies have highlighted that the unusually high virulence of H5N1 virus infection is associated with the cytokine dysregulation and enhanced viral replication in the host. In reference to the past experience during Spanish 1918 influenza pandemic and SARS, it is crucial that a novel therapeutic target is explored and employed in time for the effective control of emerging diseases. The pandemic potential of H5N1 influenza virus urges well preparedness not only in terms of containment measures, but also in the treatment aspect of the severe human H5N1 disease. To date, therapeutic approaches are limited to the use of vaccine, antiviral drugs and corticosteroids. It has been suggested that commercially available antiviral drugs are prone to induce resistance mutations; and are effective in the protection against influenza virus infection only if administered during the early course of disease development. Moreover, vaccine development does not grant a promising therapeutic strategy at the time of a pandemic as it takes time for the development and distribution of safe and reliable vaccine. In attempts to search for a novel adjunctive therapy in addition to currently available agents, indirubin-3’-oxime (IDO) and indirubin derivative, E804 have been tested to show the effect in cytokine suppression and antiviral activity against H5N1 influenza virus infection in vitro. These compounds have been extracted and purified from a natural herb called Isatis tinctoria which is frequently used for herbal remedy in treating respiratory symptoms in traditional Chinese medicine. In this study, it was demonstrated that IDO and E804 treatment in H5N1 influenza virus infected human alveolar epithelial cells effectively inhibit the proinflammatory cytokine induction and viral replication. This physiologically relevant in vitro alveolar epithelial cell model and the efficacy of IDO and E804 provide new insights to the development of new treatment option for severe human H5N1 disease. / published_or_final_version / Microbiology / Master / Master of Medical Sciences

　　Proliferative vitreoretinopathy (PVR) remains the major cause of failure of retinal detachment surgery. Retinal pigment epithelial (RPE) cells have been suggested to play a major role in the pathogenesis of PVR. Numerous studies have employed pharmacological means to modulate cellular activities in attempts to inhibit the process. Recent attempts using adjunctive therapy during PVR surgery that consisted of 5-fluorouracil (5-FU) and low molecular weight heparin showed some promise in preventing PVR but the concern is that prolonged 5-FU treatment may have a toxic effect. On the other hand, lectin from the edible mushroom Agaricus bisporus (ABL) was found to inhibit growth of RPE cells in a potent manner without apparent cytotoxicity. This lectin could be a candidate to modulate anomalous proliferation of RPE cells while the mechanism for the observed inhibition is unknown. 　　In our study, we investigated whether RPE cells treated with 5-FU or ABL would attenuate cellular proliferation, cell migration, cell adhesion and cell-mediated contraction rates. Further, we investigated if complementary inhibition for the above cellular activities could be obtained when RPE cells were treated with ABL after the short treatment using 5-FU. We also explored the possible mechanisms through which ABL inhibited RPE cell proliferation. 　　ARPE-19 and primary human RPE cells were treated with 5-FU or vehicle for 10 minutes. Cells were then maintained in culture medium supplemented with or without ABL. The rate of cellular proliferation was measured by a tetrazolium salt assay. Effects on cell adhesion were investigated through loading RPE cells onto the strips coated with collagen I or fibronectin. Cell migration was investigated using a scratch wound model. The effect on cell-mediated contraction was assessed using a free floating collagen I matrix. Cytotoxicity of 5-FU and ABL was determined by the live/dead assay. 　　To elucidate the mechanism through which ABL inhibited RPE cell proliferation, we investigated cell cycle distribution patterns using flow cytometry. Phosphorylation statuses of Erk, Jnk, p38, Akt as well as p53 and Cyclin D expression level were investigated by Western blotting. 　　Both 5-FU and ABL inhibited RPE cell proliferation. Only ABL promoted cell adhesion towards collagen I in hRPE3 cells. ABL was found to attenuate the rate of cell migration. Cell-mediated collagen gel contraction was attenuated by 5-FU only. Complementary inhibition in cellular proliferation and cell-mediated collagen gel contraction was observed when both 5-FU and ABL were applied. No significant cell death was observed after treatment with 5-FU, ABL or both. 　　ABL was found to reduce the amount of cells present at S phase. Akt and Erk were found to be hypo-phosphorylated and hyper-phosphorylated respectively after ABL treatment. The expression levels of phosphorylated-Jnk, phosphorylated-p38, p53, and Cyclin D1 were not altered when compared with the control. 　　These results showed that 5-FU and ABL complement with each other on inhibiting the wound healing activities of RPE cells in vitro without apparent cytotoxicity. They suggested a possible new treatment modality for PVR. ABL hypo-phosphorylated Akt and this observation is in line with the fact that ABL could attenuate cell proliferation. / published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

Probiotics are defined as live microorganisms that confer beneficial effects to health when administered in a sufficient amount. In previous studies about the beneficial effects of probiotic bacteria to health, particularly in the fields of intestinal mucosa defence responses, specific probiotics, in a strain-dependent manner, show some potential to reinforce the integrity of intestinal epithelium and/or regulate some immune components. However, the mechanisms involved in the interactions between probiotics or bioactive components of probiotics with the intestinal epithelium are still not yet clearly defined or systematically studied. Among all possible routes of modulation by probiotics of intestinal epithelial cell–mediated defence responses, modulations of mucin and trefoil factor expression as well as the cytokine profiles are important components of the innate and adaptive mucosal immune responses of the intestinal epithelial cells and are considered to play important role in the intestinal defence responses against pathogenic bacteria. This thesis examined and characterized the in vitro modulation effects by metabolic products of two commonly studied probiotics bacterial strains, Lactobacillus rhamnosus GG (LGG) and Escherichia coli Nissle 1917 (EcN), on the intestinal epithelial cell-mediated defence responses. It was found that the metabolic products of EcN decreased the transcriptional levels of secretory mucins MUC5AC, MUC5B and MUC2 while LGG metabolic products only down-regulated that of MUC5AC. In partial agreement with the reduction of mucin gene expression levels, intracellular MUC5B and MUC2 mucin expression was reduced by EcN metabolic products and MUC5AC and MUC2 by the metabolic products of LGG. In contrast, the extracellular MUC5AC and MUC2 mucin expression tended to increase upon the effects of both LGG and EcN metabolic products, which might result from accumulative effects of the modulation on extracellular mucin secretion during the time of treatment or the differential responsiveness of cellular mucin gene and protein expression upon stimulation. The expression of trefoil factor 3 in both gene and protein levels upon the effects of EcN metabolic products while those of LGG enhanced the transcriptional but not protein level. As for the modulation of cytokine profiles, LGG metabolic products mainly influence the secretion of anti-inflammatory cytokines such as IL-4, IL-5 and IL-10 in a moderate manner while EcN metabolic products exerted broad pro-inflammatory potential to the intestinal epithelial cells by inducing the secretion of pro-inflammatory cytokines such as IL-8, MCP-1, TGF-α, TNF-α and GM-CSF, which indicated that the metabolic products of LGG and EcN might initiate differential signaling pathway to influence the intestinal epithelial adaptive immune responses. To conclude, the present research provides evidence to substantiate that LGG and EcN display differential modulation mechanisms of the intestinal epithelial cell-mediated defence responses that involve intestinal-cell mediated mucin and trefoil factor secretion as well as pro- and anti-inflammatory cytokine expression. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

Regardless of the original cause and etiology, the progression of kidney disease follows a final common pathway associated with tubulointerstitial injury, in which proximal tubular epithelial cells (PTEC) are instrumental. Kidney injury molecule-1 (KIM-1) is an emerging biomarker of kidney tubular damage. It is markedly expressed and released into urine in various animal models and human kidney diseases. This study aimed to explore the underlying mechanism regulating the release of KIM-1 by PTEC. First, expression and release of KIM-1 by primary cultured human PTEC were examined. In quiescent PTEC, KIM-1 was detected at the plasma membrane and in the cytoplasm. A transwell system, in which PTEC were grown as monolayer on permeable membrane, was used to examine the polarized release of KIM-1. PTEC constitutively released KIM-1 from their apical surface, and the release was independent of gene expression or protein synthesis. The KIM-1 release process by PTEC was enhanced dose- and time-dependently by two important kidney injury mediators, human serum albumin (HSA) and tumor necrosis factor (TNF)-α, and was inhibited by the presence of broad-spectrum inhibitors of matrix metalloproteinases (MMP). Second, the potential sheddases responsible for KIM-1 shedding were identified by quantitative polymerase chain reaction (PCR) array system, in which the gene expression of a panel of MMP members was screened. The gene expression of MMP-3, MMP-7 and MMP-9 was up-regulated by PTEC under HSA or TNF-α activation. Blockade experiments with synthetic MMP inhibitors or MMP gene knockdown by small interfering RNA transfection, revealed that the constitutive or accelerated KIM-1 shedding was mediated by MMP-3, but not MMP-7 or MMP-9. The role of MMP-3 in KIM-1 shedding was further defined by additional data showing the enhanced MMP-3 synthesis by HSA- or TNF-α-stimulated PTEC, and the up-regulated KIM-1 shedding by PTEC following exogenous MMP-3 treatment. Third, the regulatory mechanism of MMP-3-mediated KIM-1 shedding was investigated. Treatment of PTEC with HSA or TNF-α up-regulated the reactive oxygen species (ROS) generation, and its kinetics ran parallel to the increase of KIM-1 shedding and MMP-3 synthesis. In addition, exogenous hydrogen peroxide dose-dependently induced KIM-1 shedding and MMP-3 synthesis, which were abolished by the presence of an oxidation inhibitor. These evidence suggest that ROS play an essential role in regulating the MMP-3-mediated KIM-1 shedding by PTEC. Finally, a mouse model of acute kidney injury induced by renal ischemia and reperfusion (I/R) was established to translate the in vitro findings. Reduced kidney function and increased urinary KIM-1 level were observed in mice after renal I/R treatment. Strikingly, the expression of MMP-3 and KIM-1 in the I/R treated mice was most profound in the S3 segments of the proximal tubules, where is the most susceptible area to oxidative stress. Taken together, these in vivo data have further strengthened the distinct roles of ROS and MMP-3 in KIM-1 shedding during PTEC injury. In conclusion, ROS generated by the injured PTEC activate MMP-3, which release the soluble KIM-1 through the ectodomain shedding process. / published_or_final_version / Medicine / Master / Master of Philosophy

published_or_final_version / abstract / Medicine / Doctoral / Doctor of Philosophy

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / abstract / Pharmacology / Master / Master of Philosophy