326 - In vivo detection of free radicals in rats with LPS-induced encephalopathy using molecular-targeted MRI and treatment with the anti-inflammatory agent, OKN-007

Abstract

It is known that long-term neuroinflammation is correlated with vascular and cognitive impairment. Sepsis is a severe acute systemic inflammatory reaction to circulating bacterial toxins, and is a serious and potentially fatal illness, that can result in multi-organ dysfunction and failure. In this study, we used a rat model for septic encephalopathy to induce inflammation and assess in vivo levels of free radicals in non-treated and OKN-007-treated rats. In vivo free radical levels were assessed using immuno-spin trapping coupled with molecular-targeted MRI (mtMRI). Lipopolysaccharide (LPS) was used to induce encephalopathy. Rats (male; n=10 anti-DMPO (5,5-dimethyl-1-pyrroline-N-oxide)-albumin-Gd-DTPA-biotin (anti-DMPO-probe) (n=5 saline-treated; n=5 LPS-exposed; 24 hours), and n=10 anti-DMPO-albumin-Gd-DTPA-biotin (anti-DMPO-probe) (n=5 saline-treated; n=5 LPS-exposed; 1 week), were anesthetized with isoflurane for LPS or saline administration (i.p.), and for MRI scans. A targeted contrast agent probe for DMPO trapped free radicals was used to obtain trapped macromolecular free radical images. Multiple brain region MR image slices were obtained. Rat brains were imaged at pre-contrast and at several intervals post-contrast agent injection. T1-weighted images were also obtained. Pixel-by-pixel relaxation maps were reconstructed from a series of T1-weighted images using a nonlinear two-parameter fitting procedure. The T1 value of a specified region-of-interest (ROI) was computed from all the pixels in the identified ROIs. mtMRI was able to demonstrate increased free radical levels in LPS-exposed rat brains at both 24 hours and 1 week post-LPS administration, compared to saline-treated controls, and decreased free radical levels 1 week after OKN-007 treatment. Data indicates the feasibility of conducting in vivo mtMR imaging for free radical levels in a rat model for encephalopathy begfore and after treatment with the anti-inflammatory agent, OKN-007. Here we used mtMRI to show for the first time non-invasive in vivo detection of free radical levels associated with endotoxia-induced encephalopathy, and the effect of a therapeutic intervention.