Carbamoyl-PROXYL-enhanced MRI detects very small disruptions in brain vascular permeability induced by dietary cholesterol.

BACKGROUND: Gd-DTPA-enhanced magnetic resonance imaging (MRI) is a conventional method for non-invasive investigation of blood-brain-barrier (BBB) permeability in animal models. It allows the visualization of serious injury to the BBB. We developed a novel approach for detecting very small disruptions in BBB permeability induced by dietary cholesterol by using carbamoyl-PROXYL (CMP) as an MRI contrast probe.\nMETHODS: Mice were separated into two groups: normal diet (ND-mice) and high cholesterol diet (CD-mice). MRI-signal dynamics, plasma cholesterol, matrix metalloproteinase (MMP-9, MMP-2), and the white blood cell profile were analyzed. For the MRI analysis, two regions-of-interest (ROI) were selected: brain (ROI-1) and surrounding area (ROI-2).\nRESULTS: In the ROI-2 of ND-mice, CMP- or Gd-enhanced MRI-signal followed typical kinetics with a half-life of signal decay (t(1/2)) ~8 or ~15min, respectively. In CD-mice, the MRI-signal increased continuously without decay. In the ROI-1 of ND- and CD-mice, MRI-signal enhancement was not detected by Gd-DTPA. In the ROI-1 of ND-mice, CMP-induced MRI-signal enhancement was negligible, while in CD-mice, it was significant (t(1/2)>15min). Hypercholesterolemia increased the plasma levels of MMP-9 and neutrophils.\nCONCLUSIONS: Hypercholesterolemia increases vascular permeability, which is mediated by MMP-9 and neutrophils.\nGENERAL SIGNIFICANCE: Even very small disruptions in brain vascular permeability could be detected by CMP-enhanced MRI but not by Gd-DTPA-enhanced MRI

Nitroxide derivatives for imaging of hypercholesterolemia-induced kidney dysfunction and assessing the effectiveness of antilipidemic drugs

The present study was designed to clarify the possibility for application of nitroxide derivatives in magnetic resonance imaging (MRI) of hypercholesterolemia-mediated renal dysfunction in mice, as well as to assess the effectiveness of anti-lipidemic drugs (cholestyramine and ezetimibe). The mice were separated in four groups: (i) on a normal diet (ND) without medication (control); (ii) on a high cholesterol diet (CD) without medication; (iii) CD mice receiving cholestyramine; and (iv) CD mice receiving ezetimibe. In CD mice without medication, a hypercholesterolemia was developed, detected by the increasing of total plasma cholesterol and non-HDL cholesterol, and decreasing of HDL cholesterol. The hypercholesterolemia compromised renal function: blood urea nitrogen, creatine anduric acid increased significantly, accompanied with development of glomerulosclerosis, enhancement of the amount of neutrophils and overexpression of metalloproteinase-9. The mice were subjected to anesthesia and MR imaging was performed on 7 Tesla magnet (T1- weighted incoherent gradient-echo sequence; fast low-angle shot). The region-of-interest was selected within the kidney. The images were obtained before and after injection of contrast probe [carbamoyl- PROXYL (CMP) or Gd-DTPA]. In the kidney of ND mice, the MRI signal intensity increased afterinjection of CMP, reached a maximum (very well-defined renal filtration peak) and decreased to the baseline level within 14 min. In kidney of CD mice, the CMP-mediated enhancement of MRI signal was not detected. Anti-lipidemic drugs patially abolished the effect of hypercholesterolemia on CMPenhanced MRI in the kidney. The kinetic curves of Gd-enhanced MRI signal had also different profiles in the kidney of ND and CD mice. They were similar to the profiles of the kinetic curves, obtained from MR urography of healthy human and human with renal pathology, respectively.The present study suggests that CMP is suitable MRI contrast probe for visualization of hypercholesterolemia-induced renal dysfunction in intact animals and the assessment of the efficacy of anti-lipidemic drugs. The probe was applied in concentration, which was 3 times lower than the LD50 for intravenous administration in mice. Since the probe is excreted by the kidney, it could be considered harmless for mammalians in the selected dose and appropriate candidate for translational research

Stimulation of Cholesterol Release from Rabbit Foam Cells by the Action of a New Inhibitor for Acyl CoA:Cholesterol Acyltransferase (ACAT), HL-004

ABSTRACT A new inhibitor of acyl CoA:cholesterol acyltransferase (ACAT)