In Vivo Detection of Free Radical Generation

点击翻译按钮获取中文摘要

We have set research priorities to focus on free radical generation in animal models of disease and toxicity for which there is a strong indication of an environmental component. The ways in which environmental agents increase disease risks and toxicity are still poorly understood. In the past our work has been concentrated on the in vivo formation and detection of free radicals from toxic metals and organic compounds and extended into investigations of free radical formation during inflammation caused by lipopolysaccharide itself and in combination with diesel exhaust particles. It is now continued into studies of environmental exotoxins and pathogens with the aim of understanding the basic free radical mechanisms involved in distinctive organ infections, immune disease, and obesity. In vivo spin trapping has been the most successful method for the detection of highly reactive free radical molecules in vivo. The group continued to use spin trapping to solve in vitro biochemical and in vivo toxicological disease problems by using two major approaches for spin trapping, with either ESR detection or antibody recognition and MS identification of the trapped radical. Immuno-spin trapping technique developed in this group has been applied to in vivo free radical detection in pakinson's disease, smoking, and in vivo free radical image. We applied our immune-spin trapping technique to an in vivo approach in conjunction with molecular magnetic resonance imaging (mMRI). This involves the use of a spin-trapping agent, DMPO, and administration of a mMRI probe, called an anti-DMPO probe, that combines an antibody against DMPO-radical adducts and a MRI contrast agent, resulting in targeted free radical adduct mMRI. The contrast agent used in our approach, includes an albumin-Gd-DTPA-biotin construct, where the anti-DMPO antibody is covalently linked to the cysteine residues of albumin, forming an anti-DMPO-adduct antibody-albumin-Gd-DTPA-biotin entity. We have been able to use the combined ISTmMRI approach in several disease models, including multi-tissue assessment in diabetic mice with further assessment of cardiomyopathy, amyotrophic lateral sclerosis (ALS)-like mice, glioma-bearing mice, and mice with septic encephalopathy (cecal ligation and puncture and LPS-induced models). In all disease cases, trapped free radical levels were significantly higher when compared to appropriate controls (disease controls (e.g. wildtypes or shams), non-DMPO controls (i.e. administered saline instead of DMPO), and/or mMRI probe controls (i.e. a non-specific IgG was covalently bound to the albumin of the MRI contrast agent construct instead of the anti-DMPO antibody). The advantage of this approach is that heterogeneous levels of trapped free radicals can be detected directly in vivo, and be used to pinpoint where high levels of free radicals are formed in different tissues. The approach can also be used to assess possible therapeutic agents that are either free radical scavengers or generate free radicals. For example, we have used this approach to assess the free radical scavenging ability of an anti-cancer agent, OKN-007, in a rat glioma model. Some of the disadvantages with the methodology include limited access to pre-clinical MRI systems, availability of the anti-DMPO antibody, and the radical source that is being trapped.