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Cell-free Biochemical Fluorometric Enzymatic Assay for High-throughput Measurement of Lipid Peroxidation in High Density Lipoprotein

Low high-density lipoprotein cholesterol (HDL-C) levels are one of the most powerful independent negative predictors of atherosclerotic cardiovascular ...

University of California, Los Angeles

Monash University

Examination of anticardiolipin antibodies (ACAs) in the sera of patients clinically diagnosed with chronic fatigue syndrome (CFS) using an enzyme-linked immunoassay procedure demonstrated the presence of immunoglobulin M isotypes in 95% of CFS serum samples tested. The presence of immunoglobulin G and immunoglobulin A isotypes were also detected in a subset of the samples. Future studies will focus on elucidating whether alterations to mitochondrial inner membranes and/or metabolic functions play a possible role in the expression of ACAs.

Anticardiolipin antibodies in the sera of patients with diagnosed chronic fatigue syndrome.

Most current assays of HDL functional properties are cell-based. We have developed a fluorometric biochemical assay based on the oxidation of dihydrorhodamine 123 (DHR) by HDL. This cell-free assay assesses the intrinsic ability of HDL to be oxidized by measuring increasing fluorescence due to DHR oxidation over time. The assay distinguishes the oxidative potential of HDL taken from different persons, and the results are reproducible. Direct comparison of this measurement correlated well with results obtained using a validated cell-based assay (r(2) = 0.62, P < 0.001). The assay can be scaled from a 96-well format to a 384-well format and, therefore, is suitable for high-throughput implementation. This new fluorometric method offers an inexpensive, accurate, and rapid means for determining the oxidative properties of HDL that is applicable to large-scale clinical studies.

A biochemical fluorometric method for assessing the oxidative properties of HDL.

Fluorescence-based cell-free assays offer an attractive alternative to current cell-based assays for measuring the redox activity of High-Density Lipoprotein (HDL). We have recently developed a biochemical assay that assesses the effect of HDL on the oxidation rate of dihydrorhodamine 123 (DHR), reflected by increasing fluorescence over time. However, an immediate reduction in the fluorescence signal is observed after addition of HDL to DHR, due to fluorescence quenching from lipid-probe interactions. Understanding this process is important for interpretation of the results of all fluorescence-based cell-free assays that measure oxidative properties of lipids.

Effects of lipid-probe interactions in biochemical fluorometric methods that assess HDL redox activity.

Current cell-based assays for determining the functional properties of high-density lipoproteins (HDL) have limitations. We report here the development of a new, robust fluorometric cell-free biochemical assay that measures HDL lipid peroxidation (HDLox) based on the oxidation of the fluorochrome Amplex Red. HDLox correlated with previously validated cell-based (r = 0.47, p<0.001) and cell-free assays (r = 0.46, p<0.001). HDLox distinguished dysfunctional HDL in established animal models of atherosclerosis and Human Immunodeficiency Virus (HIV) patients. Using an immunoaffinity method for capturing HDL, we demonstrate the utility of this novel assay for measuring HDLox in a high throughput format. Furthermore, HDLox correlated significantly with measures of cardiovascular diseases including carotid intima media thickness (r = 0.35, p<0.01) and subendocardial viability ratio (r = -0.21, p = 0.05) and physiological parameters such as metabolic and anthropometric parameters (p<0.05). In conclusion, we report the development of a new fluorometric method that offers a reproducible and rapid means for determining HDL function/quality that is suitable for high throughput implementation.

A high throughput biochemical fluorometric method for measuring lipid peroxidation in HDL.

High-density lipoprotein (HDL) function rather than absolute level may be a more accurate indicator for cardiovascular disease (CVD). Novel methods can measure HDL function using patient samples. The objective of this study is to identify factors that may contribute to HDL dysfunction in chronic treated HIV-1 infection.

Predictors of Impaired HDL Function in HIV-1 Infected Compared to Uninfected Individuals.

Transfection is one of the most frequently used techniques in molecular biology that is also applicable for gene therapy studies in humans. One of the biggest challenges to investigate the protein function and interaction in gene therapy studies is to have reliable monospecific detection reagents, particularly antibodies, for all human gene products. Thus, a reliable method that can optimize transfection efficiency based on not only expression of the target protein of interest but also the uptake of the nucleic acid plasmid, can be an important tool in molecular biology. Here, we present a simple, rapid and robust flow cytometric method that can be used as a tool to optimize transfection efficiency at the single cell level while overcoming limitations of prior established methods that quantify transfection efficiency. By using optimized ratios of transfection reagent and a nucleic acid (DNA or RNA) vector directly labeled with a fluorochrome, this method can be used as a tool to simultaneously quantify cellular toxicity of different transfection reagents, the amount of nucleic acid plasmid that cells have taken up during transfection as well as the amount of the encoded expressed protein. Finally, we demonstrate that this method is reproducible, can be standardized and can reliably and rapidly quantify transfection efficiency, reducing assay costs and increasing throughput while increasing data robustness.

A novel rapid and reproducible flow cytometric method for optimization of transfection efficiency in cells.

The role of HDL function in HIV-related atherosclerotic cardiovascular disease (CVD) is unclear. HDLs isolated from HIV+ [HIV(+)HDL] and HIV-uninfected individuals (HDL) were assessed for HDL function and ability to promote monocyte-derived foam cell formation (MDFCF) (a key event in HIV-related CVD) ex vivo.

Diana Huynh

University of California, Los Angeles

Cell-free Biochemical Fluorometric Enzymatic Assay for High-throughput Measurement of Lipid Peroxidation in High Density Lipoprotein