Browsing by Author "Harmse, Leonie"

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    Aberrant apoptotic response of colorectal cancer cells to novel nucleoside analogues
    (Public Library of Science, 2015) Harmse, Leonie; Dahan-Farkas, Nurit; Panayides, Jenny-Lee; Van Otterlo, Willem; Penny, Clement
    Despite the increased understanding of colorectal cancer and the introduction of targeted drug therapy, the metastatic phase of the disease remains refractory to treatment. Since the deregulation of normal apoptosis contributes to the pathogenesis of colorectal cancer, novel nucleoside analogues were synthesized here and evaluated for their ability to induce apoptosis and cause cell death in two colorectal adeno-carcinoma cell lines, Caco-2 and HT-29. Three novel nucleoside analogues assessed here showed cytotoxic activity, as measured by the MTT assay against both cell lines: the IC50 values ranged between 3 and 37 μM, with Caco-2 cells being more sensitive than HT-29 cells. Compared to camptothecin, the positive control, the nucleoside analogues were significantly less toxic to normal unstimulated leukocytes (p>0.05). Moreover, the nucleosides were able to induce apoptosis as measured by an increase in caspase 8 and caspase 3 activity above that of the control. This was additionally supported by data derived from Annexin V-FITC assays. Despite marginal changes to the mitochondrial membrane potential, all three nucleosides caused a significant increase in cytosolic cytochrome c (p>0.05), with a corresponding decrease in mitochondrial cytochrome c. Morphological analysis of both cell lines showed the rapid appearance of vacuoles following exposure to two of the nucleosides, while a third caused cellular detachment, delayed cytoplasmic vacuolisation and nuclear abnormalities. Preliminary investigations, using the autophagic indicator monodansylcadaverine and chloroquine as positive control, showed that two of the nucleosides induced the formation of autophagic vacuoles. In summary, the novel nucleoside analogues showed selective cytotoxicity towards both cancer cell lines and are effective initiators of an unusual apoptotic response, demonstrating their potential to serve as structural scaffolds for more potent analogues.
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    An overview of the biological disease modifying drugs available for arthritic conditions in South Africa
    (Taylor & Francis, 2016) Harmse, Leonie; Reuter, Helmuth
    ENGLISH ABSTRACT: The past decade has seen a major change in the treatment options and strategies for rheumatoid arthritis (RA) and the other immune-mediated arthritic diseases. The disease modifying antirheumatic drugs (DMARDs) are now used in early stages of the disease in order to preserve joint architecture. There are two groups of DMARDs, the small molecules, like methotrexate, and the biological DMARDs, which are frequently referred to as “magic bullets” since they target specific cytokines and immune cells associated with arthritic conditions. They are monoclonal antibodies or fusion proteins designed to bind and inactivate immune targets. Tumour necrosis factor-alpha (TNF-α) plays an important role in the pathogenesis of rheumatoid disorders and is the target of four biological DMARDs, etanercept, infliximab, golimumab and adalimumab. The other biological DMARDs include abatacept, rituximab and tocilizumab and these prevent T-cell costimulation, cause the depletion of mature CD20 positive B cells or prevent the activation of the interleukin-6 receptor molecule, respectively. Ustekinumab, a monoclonal antibody against IL12/IL23 is effective in psoriatic arthritis. Biological agents are indicated when patients do not respond adequately to the traditional DMARDs. Numerous clinical trials have shown that the biological agents reduce joint inflammation and erosive damage, especially when used in combination with methotrexate. Apart from their prohibitive cost, the biological agents are not without potentially serious adverse effects with infections being the main concern. The TNF-α inhibitors increase the risk for tuberculosis and other opportunistic infections, whereas the non-TNF-α immune inhibitors increase the risk for opportunistic viral, fungal and bacterial infections. This review provides an overview of the biological agents currently available in South Africa.