Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 7 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 6 uppsatser.

AIDS Dementia Complex (ADC) is a common neurological complication of HIV/AIDS. ADC is characterized by cognitive, behavioral, and motor impairments including slowed thinking, decreased concentration, forgetfulness, apathy, irritability, anxiety, clumsiness, leg weakness, and altered handwriting. Symptoms progress into pronounced verbal and motor slowing, extensive thought disturbances, profound disorientation, hostility, ataxia, incontinence, and eventually a near vegetative state. Presently, no cure is available for ADC. However, treatment with the antiretroviral drug, zidovudine (AZT), has been shown to slow the progression of ADC and improve functioning. Other promising pharmacological treatments under investigation include newer antiretroviral drugs, combination use of protease inhibitors and zidovudine, calcium channel blocking agents, receptor antagonists for excitatory neurotransmitters, and antagonists of cytokines and inflammatory agents. Psychosocial interventions for managing patients in the early stages of ADC focus on preserving independence, promoting self-esteem, and assisting patients to compensate for cognitive changes. During the later stages of ADC, interventions deal with adapting patients' environments to ensure safety and maintain structure, routine, and simplicity. Prompt intervention is essential to improving the quality and length of these patients' lives.

Drug delivery to the brain has challenged medical professionals for several decades, with 98% of small molecules and 100% of large molecules unable to cross the blood brain barrier (BBB). Biocompatible, biodegradable polymers have been extensively researched for the oral delivery of therapeutic agents, but to date has not been successfully manipulated for the formulation of an implantable device. We have therefore utilised such polymers for the formulation and design of an implantable nanoenabled multipolymeric drug delivery device (NMDDD) for the management of AIDS Dementia Complex (ADC). ADC is a central nervous system (CNS) complication of HIV, associated with a host of debilitating cognitive, motor and behavioural symptoms. ADC remains a serious manifestation of HIV/AIDS in both developing and developed countries, affecting both adults and children, with death expected within 6 months of initial diagnosis. Zidovudine (AZT), the current gold standard for the management of ADC, has demonstrated the best penetration into the CNS. It is capable of reducing viral replication in the CNS and managing neurological abnormalities associated with ADC, with clinical efficacy evidenced by the decline in morbidity and mortality of patients treated with this drug. Nanotechnology, an interdisciplinary field of research, involving the manipulation of matter on a submicron level, is receiving emerging interest for the formulation of novel drug delivery systems. As they can potentially be manipulated to react in a bioresponsive manner, nanopharmaceuticals have received much attention for site-specific drug delivery and were therefore employed in the formulation of an implantable NMDDD, with AZT employed as the model drug, for the management of ADC. Nanoparticles were prepared by means of an approach utilising controlled gelation of alginate, employing cationic crosslinking of the anionic alginate to precipitate nanoparticles. A 3-factor Box-Behnken statistical design was employed for the optimisation of nanoparticle and multipolymeric scaffold formulations. Nanoparticles measuring 68.04nm (SD<0.0002) in size with a zeta potential of -13.4mV (SD<0.0005) were formulated. Nanoparticles presented with a mean dissolution time (MDT) of 46.046 hours 30 days post exposure to phosphate buffered saline (PBS), pH 7.4. In an attempt to further retard drug release and to formulate a device for implantation in the frontal lobe of the brain, nanoparticles were dispersed within a robust multipolymeric matrix. Matrix erosion was calculated at 28%w/w (SD<0.001) for multipolymeric scaffold and a matrix resilience of 4.451%w/w (SD<0.007) was observed 30 days post exposure to PBS, indicating slow degradation of the NMDDD. MDT was reduced to 12.570 hours (SD<0.0005) with dispersion of the nanoparticles within a polymer matrix, supporting the application of the drug-loaded MDDD in the management of ADC patients. The optimised multipolymeric nanoparticulate scaffold was implanted into the frontal lobe of the rat brain, for investigation of drug release characteristics and tissue response to the device following in vivo administration.

A major product of HIV-infected and cytokine-stimulated monocytic-lineage cells is quinolinic acid (QUIN), a neurotoxic metabolite of the kynurenine pathway (KP) of L-tryptophan (L-Trp) metabolism. Despite the large number of neurotoxins found in HIV patients with AIDS Dementia Complex (ADC), only QUIN correlates with both the presence and severity of ADC. With treatment, cerebrospinal fluid (CSF) QUIN concentrations decrease proportionate to the degree of clinical and neuropsychological improvement. As endothelial cells (EC) of the blood-brain barrier (BBB) are the first brain-associated cell that a bloodborne pathogen would encounter, this project examined the BBB response to KP metabolites, as these are implicated in damage of the CNS associated with ADC. Using RT-PCR and HPLC/gas chromatographymass spectrometry (GC-MS), I found that cultured primary human BBB EC and pericytes constitutively expressed the KP. EC synthesised kynurenic acid (KA) constitutively, and after immune activation, kynurenine (KYN). Pericytes produced small amounts of picolinic acid and after immune activation, KYN. An SV40-transformed BBB EC showed no KP expression. By contrast, human umbilical vein EC only expressed low levels of KA after immune activation, however human dermal microvascular EC showed a similar constitutive and inducible KP to that in BBB EC. As T cells are central to primary HIV infection, I also examined KP expression in two CD4+ and one CD4- cell lines, but none showed either constitutive or inducible KP expression. I next examined how QUIN might interact with BBB EC. There was no binding of 3H-QUIN to cultured primary human BBB EC, however a biologically relevant concentration of QUIN induced changes in gene expression which adversely affected EC function, possibly mediated by lipid peroxidation and oxidative stress. The upregulated genes were of the heat shock protein family, and the downregulated genes were associated with regulation of cell adhesion, tight junction and cytoskeletal stability, metalloproteinase (MMP) regulation, apoptosis and G protein signaling. Immunofluorescence showed that QUIN induced morphological changes in BBB EC consistent with the changes in gene expression. Gelatin zymography showed that this was not mediated by MMPs, as constitutive MMP expression was unchanged. These data provide strong evidence for QUIN directly damaging the BBB in the context of HIV infection.

A major product of HIV-infected and cytokine-stimulated monocytic-lineage cells is quinolinic acid (QUIN), a neurotoxic metabolite of the kynurenine pathway (KP) of L-tryptophan (L-Trp) metabolism. Despite the large number of neurotoxins found in HIV patients with AIDS Dementia Complex (ADC), only QUIN correlates with both the presence and severity of ADC. With treatment, cerebrospinal fluid (CSF) QUIN concentrations decrease proportionate to the degree of clinical and neuropsychological improvement. As endothelial cells (EC) of the blood-brain barrier (BBB) are the first brain-associated cell that a bloodborne pathogen would encounter, this project examined the BBB response to KP metabolites, as these are implicated in damage of the CNS associated with ADC. Using RT-PCR and HPLC/gas chromatographymass spectrometry (GC-MS), I found that cultured primary human BBB EC and pericytes constitutively expressed the KP. EC synthesised kynurenic acid (KA) constitutively, and after immune activation, kynurenine (KYN). Pericytes produced small amounts of picolinic acid and after immune activation, KYN. An SV40-transformed BBB EC showed no KP expression. By contrast, human umbilical vein EC only expressed low levels of KA after immune activation, however human dermal microvascular EC showed a similar constitutive and inducible KP to that in BBB EC. As T cells are central to primary HIV infection, I also examined KP expression in two CD4+ and one CD4- cell lines, but none showed either constitutive or inducible KP expression. I next examined how QUIN might interact with BBB EC. There was no binding of 3H-QUIN to cultured primary human BBB EC, however a biologically relevant concentration of QUIN induced changes in gene expression which adversely affected EC function, possibly mediated by lipid peroxidation and oxidative stress. The upregulated genes were of the heat shock protein family, and the downregulated genes were associated with regulation of cell adhesion, tight junction and cytoskeletal stability, metalloproteinase (MMP) regulation, apoptosis and G protein signaling. Immunofluorescence showed that QUIN induced morphological changes in BBB EC consistent with the changes in gene expression. Gelatin zymography showed that this was not mediated by MMPs, as constitutive MMP expression was unchanged. These data provide strong evidence for QUIN directly damaging the BBB in the context of HIV infection.

A major product of HIV-infected and cytokine-stimulated monocytic-lineage cells is quinolinic acid (QUIN), a neurotoxic metabolite of the kynurenine pathway (KP) of L-tryptophan (L-Trp) metabolism. Despite the large number of neurotoxins found in HIV patients with AIDS Dementia Complex (ADC), only QUIN correlates with both the presence and severity of ADC. With treatment, cerebrospinal fluid (CSF) QUIN concentrations decrease proportionate to the degree of clinical and neuropsychological improvement. As endothelial cells (EC) of the blood-brain barrier (BBB) are the first brain-associated cell that a bloodborne pathogen would encounter, this project examined the BBB response to KP metabolites, as these are implicated in damage of the CNS associated with ADC. Using RT-PCR and HPLC/gas chromatographymass spectrometry (GC-MS), I found that cultured primary human BBB EC and pericytes constitutively expressed the KP. EC synthesised kynurenic acid (KA) constitutively, and after immune activation, kynurenine (KYN). Pericytes produced small amounts of picolinic acid and after immune activation, KYN. An SV40-transformed BBB EC showed no KP expression. By contrast, human umbilical vein EC only expressed low levels of KA after immune activation, however human dermal microvascular EC showed a similar constitutive and inducible KP to that in BBB EC. As T cells are central to primary HIV infection, I also examined KP expression in two CD4+ and one CD4- cell lines, but none showed either constitutive or inducible KP expression. I next examined how QUIN might interact with BBB EC. There was no binding of 3H-QUIN to cultured primary human BBB EC, however a biologically relevant concentration of QUIN induced changes in gene expression which adversely affected EC function, possibly mediated by lipid peroxidation and oxidative stress. The upregulated genes were of the heat shock protein family, and the downregulated genes were associated with regulation of cell adhesion, tight junction and cytoskeletal stability, metalloproteinase (MMP) regulation, apoptosis and G protein signaling. Immunofluorescence showed that QUIN induced morphological changes in BBB EC consistent with the changes in gene expression. Gelatin zymography showed that this was not mediated by MMPs, as constitutive MMP expression was unchanged. These data provide strong evidence for QUIN directly damaging the BBB in the context of HIV infection.

Thesis (M. Communication Pathology)--University of Pretoria, 2003. / Includes bibliographical references.

M.Sc. (Research Psychology) / Please refer to full text to view abstract

Thesis (M.Sc. (Pharmacy)) - Rhodes University, 2008.