Browsing by Author "Yang, Yi-Cyun"

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Characterization of the Pharmaceutical Effect of Drugs on Atherosclerotic Lesions in Vivo Using Integrated Fluorescence Imaging and Raman Spectral Measurements
(2014-04-15)
Yang, Yi-Cyun
;
Chang, Wei-Tien
;
Huang, Shao-Kang
;
Liau, Ian
;
應用化學系
Direct assessment of the vascular lesions of model animals in vivo is important for the development of new antiatherosclerotic drugs. Nevertheless, biochemical analysis of the lipid profile in blood in vitro remains the most common way to evaluate the therapeutic effect of drugs targeting atherosclerosis because of an inherent difficulty to access the vascular wall. Using hypercholesterolemic zebrafish, we present an orchestrated application of Raman spectral measurements and confocal fluorescence imaging to interrogate the pharmacological response of atherosclerotic lesions in situ and in vivo. For demonstration, we investigated two commonly prescribed antihyperlipidemic drugs, ezetimibe and atorvastatin. The treatment of ezetimibe or atorvastatin alone decreased effectively the deposition of lipids in the vascular wall, and a combined dose showed a synergistic effect. Atorvastatin exerted a profound antioxidative effect on vascular fatty lesions. Analysis of individual lesions shows further that these lesions exhibited a heterogeneous response to the treatment of atorvastatin; a significant fraction of, but not all, the lesions became nonoxidized after the intervention. Beyond its efficacies in suppressing both the accumulation and oxidation of vascular lipids, atorvastatin expedited the clearance of vascular lipids. The possession of pleotropic (multiple) therapeutic effects on vascular fatty lesions of hypercholesterolemic zebrafish by atorvastatin is notably consistent with the known pharmaceutical effects of this drug on human beings. These results improve our understanding of the antiatherosclerotic effect of drugs. We envisage that our approach has the potential to become a platform to predict the pharmaceutical effects of new drugs aiming to cure human atherosclerotic diseases.
Interplay between Structure and Fluidity of Model Lipid Membranes under Oxidative Attack
(2010-12-02)
Tai, Wan-Yu
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Yang, Yi-Cyun
;
Lin, Hui-Jen
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Huang, Chin-Ping
;
Cheng, Yi-Lin
A proper regula:ion of membrane fluidity is critical for cellular activities such as communication between cells, mitosis, an :I endocytosis. Unsaturated lipids, a main component of biological membranes, are particularly susceptible to oxidative attack of reactive oxygen species. The oxidation of lipids can produce structural derangement of membranes and eventually alter the membrane fluidity. We have applied fluorescence correlation spectroscopy (FCS) and Raman spectroscopy to investigate the fluidity and structure of model membranes subject to oxidative attack. Hydrogen peroxide has little effect on the lateral fluidity of membranes. whereas hydroxyl radical causes a significantly increased fluidity. The latter is rationalized with the cleavage of the acyl chains of lipids caused by hydroxyl radical; this interpretation is founded on the diminished intensities of lines in Raman spectra associated with -CH(2) and C = C moieties in lipids and supported by mass-spectral measurements. The same approach provides a mechanistic account of the inhibitory capability of vitamins C and E against ate increased membrane fluidity resulting from an oxidative attack. Membranes with much cholesterol exhibit a novel resistance against altered membrane fluidity induced with oxidative attack; this finding has biological implications. Our approach combining FCS and Raman measurements reveals the interplay between the structure and fluidity of membranes and provides insight into the pathophysiology of cellular oxidative injury.
Molecular Imaging of Ischemia and Reperfusion in Vivo with Mitochondria! Autofluorescence
(2014-05-20)
Lu, Hsueh-Han
;
Wu, Yao-Ming
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Chang, Wei-Tien
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Luo, Teng
;
Yang, Yi-Cyun
Ischemia and reperfusion (IR) injury constitutes a pivotal mechanism of tissue damage in pathological conditions such as stroke, myocardial infarction, vascular surgery, and organ transplant. Imaging or monitoring of the change of an organ at a molecular level in real time during IR is essential to improve our understanding of the underlying pathophysiology and to guide therapeutic strategies. Herein, we report molecular imaging of a rat model of hepatic IR with the autofluorescence of mitochondrial flavins. We demonstrate a revelation of the histological characteristics of a liver in vivo with no exogenous stain and show that intravital autofluorescent images exhibited a distinctive spatiotemporal variation during IR. The autofluorescence decayed rapidly from the baseline immediately after 20-min ischemia (approximately 30% decrease in 5 mm) but recovered gradually during reperfusion (to approximately 99% of the baseline 9 mm after the onset of reperfusion). The autofluorescent images acquired during reperfiision correlated strongly with the reperfused blood flow. We show further that the autofluorescence was produced predominantly from mitochondria, and the distinctive autofluorescent variation during IR was mechanically linked to the altered balance between the flavins in the oxidized and reduced forms residing in the mitochondrial electron-transport chain. Our approach opens an unprecedented route to interrogate the deoxygenation and reoxygenation of mitochondria, the machinery central to the pathophysiology of IR injury, with great molecular specificity and spatiotemporal resolution and can be prospectively translated into a medical device capable of molecular imaging. We envisage that the realization thereof should shed new light on clinical diagnostics and therapeutic interventions targeting IR injuries of not only the liver but also other vital organs including the brain and heart.
Raman Spectroscopy Reveals the Structure-Fluidity Interplay of Model Lipid Membranes under Oxidative Stress
(2010)
Tai, Wan-Yu
;
Yang, Yi-Cyun
;
Liau, Ian
;
應用化學系
;
Department of Applied Chemistry
Selective and Absolute Quantification of Endogenous Hypochlorous Acid with Quantum-Dot Conjugated Microbeads
(2011-11-01)
Yang, Yi-Cyun
;
Lu, Hsueh-Han
;
Wang, Wei-Ti
;
Liau, Ian
;
應用化學系
Endogenous hypochlorous acid (Hod) secreted by leukocytes plays a critical role in both the immune defense of mammalians and the pathogenesis of-various diseases intimately related to inflammation. We report the first selective and absolute quantification of endogenous HOCl produced by leukocytes in vitro and in vivo with a novel quantum dot-based sensor. An activated human neutrophil secreted 6.5 +/- 0.9 x 10(8) HOCl molecules into its phagosome, and kinetic measurement for the secretions showed that the extracellular generation of HOCl was temporally retarded, but the quantity eventually attained a level comparable with its intraphagosomal counterpart with a delay of about 1.5 h. The quantity of HOCl secreted from the hepatic leukocytes of rats with or without stimulation of lipopolysaccharide was also determined. These results indicate a possibility to extend our approach to not only clinical settings for quantitative assessment of the bactericidal capability of isolated leukocytes of patients but also fundamental biomedical research that requires critical evaluation of the inflammatory response of animals.
Spatiotemporal Characterization of Phagocytic NADPH Oxidase and Oxidative Destruction of Intraphagosomal Organisms in Vivo Using Autofluorescence Imaging and Raman Microspectroscopy
(2010-02-17)
Chang, Wei-Tien
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Yang, Yi-Cyun
;
Lu, Hsueh-Han
;
Li, I-Lin
;
Liau, Ian
The ability to generate antimicrobial reactive-oxygen species (ROS) by reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is critical for the host to defend against invading microbes. We have demonstrated the application of confocal autofluorescence microscopy and Raman microspectroscopy to characterize dynamically the phagocytic process of living macrophages in a label-free manner. In particular, we visualized the translocation of NADPH oxidases in livin macrophages that are undergoing phagocytosis of invading yeasts and monitored dynamically the change at the molecular level of single intraphagosomal yeasts caused by phagocytic ROS.
Zebrafish model of photochemical thrombosis for translational research and thrombolytic screening in vivo
(2017-04-01)
Lee, I-Ju
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Yang, Yi-Cyun
;
Hsu, Jia-Wen
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Chang, Wei-Tien
;
Chuang, Yung-Jen
Acute thromboembolic diseases remain the major global cause of death or disability. Although an array of thrombolytic and antithrombotic drugs has been approved to treat or prevent thromboembolic diseases, many more drugs that target specific clotting mechanisms are under development. Here a novel zebrafish model of photochemical thrombosis is reported and its prospective application for the screening and preclinical testing of thrombolytic agents in vivo is demonstrated. Through photochemical excitation, a thrombus was induced to form at a selected section of the dorsal aorta of larval zebrafish, which had been injected with photosensitizers. Such photochemical thrombosis can be consistently controlled to occlude partially or completely the targeted blood vessel. Detailed mechanistic tests indicate that the zebrafish model of photochemical thrombosis exhibits essential features of classical coagulation and a thrombolytic pathway. For demonstration, tissue plasminogen activator (tPA), a clinically feasible thrombolytic agent, was shown to effectively dissolve photochemically induced blood clots. In light of the numerous unique advantages of zebrafish as a model organism, our approach is expected to benefit not only the development of novel thrombolytic and antithrombotic strategies but also the fundamental or translational research targeting hereditary thrombotic or coagulation disorders.