Patricia S. P. Thong

Increased iron in the substantia nigra of 6-OHDA induced parkinsonian rats: a nuclear microscopy study

The trace elemental concentrations, including iron, in the substantia nigra (SN) of a 6-OHDA induced rat model of Parkinsons disease were measured using nuclear microscopy. Only rats that exhibited amphetamine induced rotation of more than 7 turns/min were used. The results showed that the iron levels were significantly increased in the 6-OHDA lesioned SN, compared with the intact contralateral SN, and the SN of normal control rats injected with ascorbic acid, which showed no significant difference in iron levels between injected and non-injected sides. In both 6-OHDA lesioned and ascorbic acid injected SN, there were no alterations in the levels of calcium, magnesium, copper and zinc. In the 6-OHDA lesioned SN there was an almost complete loss of tyrosine hydroxylase positive cells in the SN. These results suggested that the 6-OHDA induced dopaminergic cell death may be related to the increased iron.

The onset of atherosclerotic lesion formation in hypercholesterolemic rabbits is delayed by iron depletion

The theory that iron may play a significant role in atherogenesis by promoting the formation of free radicals is controversial. Previous results using the new technique of nuclear microscopy showed a seven‐fold increase in iron concentrations within newly formed atherosclerotic lesions in hypercholesterolemic rabbits compared to healthy artery tissue. In a follow‐up time sequence study described here, we show that iron accumulation occurs at the onset of lesion formation. In addition, weekly bleeding decreases the iron uptake into the artery wall and delays the onset of atherogenesis. These results provide direct evidence for a key role of iron in initiating atherogenesis.

Dopaminergic cell death precedes iron elevation in MPTP-injected monkeys

Though increasing lines of evidence suggest that iron accumulation and iron-induced oxidative stress might be important pathological factors responsible for substantia nigra (SN) cell death in Parkinsons disease (PD), it is still unknown whether iron accumulation is a primary cause or consequence of nigral cell death. Using nuclear microscopy, iron histochemistry, TUNEL method for apoptosis detection, and tyrosine hydroxylase (TH) immunohistochemistry, the present study investigated possible changes in iron contents in the SN and correlations of dopaminergic cell death progression with the process of iron accumulation in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-induced parkinsonian monkey from 1 d to 18 months after MPTP administration. Our study demonstrated that apoptosis occurred in the ipsilateral SN at 1 d after MPTP injection and the number of TH-positive cells decreased significantly from 1 week onward. However, iron content was significantly increased in the ipsilateral SN from 4.5 months to 18 months after MPTP injection, and the iron increase was significantly correlated to the extent of dopaminergic cell death. These results suggest that dopaminergic cell death induced by MPTP administration might lead to iron accumulation in the monkey SN, and increased iron might contribute to the progression of nigral degeneration.

In-vivo optical detection of cancer using chlorin e6 – polyvinylpyrrolidone induced fluorescence imaging and spectroscopy

BackgroundPhotosensitizer based fluorescence imaging and spectroscopy is fast becoming a promising approach for cancer detection. The purpose of this study was to examine the use of the photosensitizer chlorin e6 (Ce6) formulated in polyvinylpyrrolidone (PVP) as a potential exogenous fluorophore for fluorescence imaging and spectroscopic detection of human cancer tissue xenografted in preclinical models as well as in a patient.MethodsFluorescence imaging was performed on MGH human bladder tumor xenografted on both the chick chorioallantoic membrane (CAM) and the murine model using a fluorescence endoscopy imaging system. In addition, fiber optic based fluorescence spectroscopy was performed on tumors and various normal organs in the same mice to validate the macroscopic images. In one patient, fluorescence imaging was performed on angiosarcoma lesions and normal skin in conjunction with fluorescence spectroscopy to validate Ce6-PVP induced fluorescence visual assessment of the lesions.ResultsMargins of tumor xenografts in the CAM model were clearly outlined under fluorescence imaging. Ce6-PVP-induced fluorescence imaging yielded a specificity of 83% on the CAM model. In mice, fluorescence intensity of Ce6-PVP was higher in bladder tumor compared to adjacent muscle and normal bladder. Clinical results confirmed that fluorescence imaging clearly captured the fluorescence of Ce6-PVP in angiosarcoma lesions and good correlation was found between fluorescence imaging and spectral measurement in the patient.ConclusionCombination of Ce6-PVP induced fluorescence imaging and spectroscopy could allow for optical detection and discrimination between cancer and the surrounding normal tissues. Ce6-PVP seems to be a promising fluorophore for fluorescence diagnosis of cancer.

Evaluation of hypericin-mediated photodynamic therapy in combination with angiogenesis inhibitor bevacizumab using in vivo fluorescence confocal endomicroscopy

Photodynamic therapy (PDT) is an alternative cancer treatment modality that offers localized treatment using a photosensitizer and light. However, tumor angiogenesis is a major concern following PDT-induced hypoxia as it promotes recurrence. Bevacizumab is a monoclonal antibody that targets vascular endothelial growth factor (VEGF), thus preventing angiogenesis. The combination of PDT with antiangiogenic agents such as bevacizumab has shown promise in preclinical studies. We use confocal endomicroscopy to study the antiangiogenic effects of PDT in combination with bevacizumab. This technique offers in vivo surface and subsurface fluorescence imaging of tissue. Mice bearing xenograft bladder carcinoma tumors were treated with PDT, bevacizumab, or PDT and bevacizumab combination therapy. In tumor regression experiments, combination therapy treated tumors show the most regression. Confocal fluorescence endomicroscopy enables visualization of tumor blood vessels following treatment. Combination therapy treated tumors show the most posttreatment damage with reduced cross-sectional area of vessels. Immunohistochemistry and immunofluorescence studies show that VEGF expression is significantly downregulated in the tumors treated by combination therapy. Overall, combining PDT and bevacizumab is a promising cancer treatment approach. We also demonstrate that confocal endomicroscopy is useful for visualization of vasculature and evaluation of angiogenic response following therapeutic intervention.

IRON AND CELL DEATH IN PARKINSON'S DISEASE: A NUCLEAR MICROSCOPIC STUDY INTO IRON-RICH GRANULES IN THE PARKINSONIAN SUBSTANTIA NIGRA OF PRIMATE MODELS

Abstract Parkinson’s disease is a degenerative brain disease characterised by a loss of cells in the substantia nigra (SN) region of the brain and accompanying biochemical changes such as inhibition of mitochondrial function, increased iron concentrations and decreased glutathione levels in the parkinsonian SN. Though the aetiology of the disease is still unknown, the observed biochemical changes point to the involvement of oxidative stress. In particular, iron is suspected to play a role by promoting free radical production, leading to oxidative stress and cell death. The increase in iron in the parkinsonian SN has been confirmed by several research groups, both in human post-mortem brains and in brain tissue from parkinsonian animal models. However, the question remains as to whether the observed increase in iron is a cause or a consequence of the SN cell death process. Our previous study using unilaterally 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP)-lesioned monkeys in a time sequence experiment has shown that the increase in bulk iron concentrations follow rather than precede dopaminergic cell death. However, changes in the localised iron concentrations, which may play a more direct role in SN cell death, may not be reflected at the bulk level. Indeed, we have observed iron-rich granules in parkinsonian SNs. From this time sequence study into the iron content of iron-rich granules in the SNs of an untreated control and unilaterally MPTP-lesioned parkinsonian models, we present the following observations: (1) Iron-rich granules are found in both control and parkinsonian SNs and are variable in size and iron content in any one model. (2) These iron-rich granules may be associated with neuromelanin granules found in the SN and are known to accumulate transition metal ions such as iron. (3) The early onset of bulk SN cell loss (35%) was accompanied by a significant elevation of iron in granules found in the MPTP-injected SN compared to the contra-lateral SN. This shows that localised iron increase may be an early event contributing to cell death. (4) The iron content in granules found in both the MPTP-injected and contra-lateral SNs is correlated with the degree of bulk SN cell loss (assessed by TH-immunohistochemistry) in individual models. This indicates a correlation between localised iron increase and cell loss, at least at the whole SN level. Our results are consistent with the observation that in Parkinson’s disease (PD), neuronal cell death seems to be related to their neuromelanin content and support the proposal that iron–melanin interaction may play a role in oxidative neuronal cell death. Indeed, iron-saturated neuromelanin granules may act as centres of free radical production, contributing to localised cell death.

Embedded Computing for Fluorescence Confocal Endomicroscopy Imaging

A novel clinic protocol of virtual histology using an in vivo cellular imaging and real-time processing system is being developed. Main ideas of photoactivation and miniaturized confocal image scanning are presented. Technical innovation in embedded real-time image processing, feature detection and visualization system is demonstrated.

Nuclear microscopy of single whole cultured cells: Beam damage studies

Abstract Elemental analysis of individual whole cultured cells using Particle Induced X-ray Emission (PIXE), Scanning Transmission Ion Microscopy (STIM) and Rutherford Backscattering Spectrometry (RBS) can yield quantitative results at the parts per million level. During a continuous scan over a single cell using 2 MeV protons (with a beam current of 100 pA, spot size of 1 μm), elemental loss was monitored and a 60% reduction in hydrogen and oxygen was observed. Concentrations of C, Na, Mg, P, S, Cl, K, Ca, Fe, Cu, and Zn remained constant. The elemental analysis, at the parts per million level, of single whole cultured cells is therefore not limited by beam damage. However, during the irradiation, the size of the cell was observed to shrink by 20%, placing severe restrictions on the imaging and analysis of subcellular structures such as organelles.

Single cell elemental analysis using nuclear microscopy

Abstract The use of Particle Induced X-ray Emission (PIXE), Rutherford Backscattering Spectrometry (RBS) and Scanning Transmission Ion Microscopy (STIM) to provide quantitative elemental analysis of single cells is an area which has high potential, particularly when the trace elements such as Ca, Fe, Zn and Cu can be monitored. We describe the methodology of sample preparation for two cell types, the procedures of cell imaging using STIM, and the quantitative elemental analysis of single cells using RBS and PIXE. Recent work on single cells at the Nuclear Microscopy Research Centre,National University of Singapore has centred around two research areas: (a) Apoptosis (programmed cell death), which has been recently implicated in a wide range of pathological conditions such as cancer, Parkinson’s disease etc, and (b) Malaria (infection of red blood cells by the malaria parasite). Firstly we present results on the elemental analysis of human Chang liver cells (ATTCC CCL 13) where vanadium ions were used to trigger apoptosis, and demonstrate that nuclear microscopy has the capability of monitoring vanadium loading within individual cells. Secondly we present the results of elemental changes taking place in individual mouse red blood cells which have been infected with the malaria parasite and treated with the anti-malaria drug Qinghaosu (QHS).

Nuclear microscopic investigations into the elemental changes in the substantia nigra of unilaterally MPTP-lesioned Parkinsonian monkeys

Various transition metals, particularly iron, have been implicated in the aetiology of the neurodegenerative disease, Parkinsons disease, in which there is a characteristic loss of cells in the substantia nigra (SN) region of the brain. In this study, monkeys were unilaterally lesioned with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP) to obtain primate models of parkinsonism, with the non-lesioned side of the brain serving as controls. The monkeys were sacrificed at one day, one week, two weeks, one month and one year after lesioning to investigate the time dependent elemental changes in the parkinsonian SN. Sections of the brain encompassing both the lesioned and non-lesioned SNs were analysed using the National University of Singapore nuclear microscope. Adjacent sections were tyrosine hydroxylase (TH) immunohistochemically stained to provide complementary information on dopaminergic cell loss and to facilitate definition of the SN boundaries during data analysis. In one-day and one-week monkeys (representing early stages of the disease), there were no changes in elemental concentrations within experimental errors and the adjacent TH-stained sections did not show apparent cell loss in the SN. At two weeks, cell loss was seen in the lesioned SN compared to the control SN. Although there was no bulk increase in SN iron, localised accumulation of iron in granules containing up to 15% by weight iron was observed in the lesioned SN of one of the two-week monkeys. An average 15% increase in nigral iron, significant at the 90% confidence level (p < 0.1), was seen in the one-month monkeys. TH-stained sections for the one-month monkeys showed cell loss in the lesioned SN. In one-year samples (representing the advanced stage of the disease) there was a significant (p < 0.05) 56% increase in iron, 14% increase in phosphorous and a 20% decrease in copper. Here an almost complete loss of cells in the lesioned SN was apparent from the adjacent TH-stained sections. These preliminary results suggest that while bulk increase in iron may seem to follow cell death, localised accumulation of SN iron in the early stages of the disease may play an important role in initiating and/or accelerating nigral cell death.