Time-course proteomic analysis of taurocholate-induced necrotizing acute pancreatitis.

Acute pancreatitis is an inflammatory disease of the pancreas, which varies greatly in course and severity. Severe forms are associated with serious local and/or systemic complications, and eventually death. The pathobiology of acute pancreatitis is complex. Animal models have been developed to investigate pathobiological processes and identify factors determining disease course. We performed a time-course proteomic analysis using a rat model of severe necrotizing acute pancreatitis induced by taurocholate perfusion in the pancreatic ducts. Results showed that levels of proteins associated to a given biological process changed in a coordinated fashion after disease onset. It was possible to follow the response of a particular pathobiological process to pancreatitis induction and to compare the course of protein pathways. Proteins involved in acinar cell secretion were found to follow a different kinetics than other cellular processes. After an initial decrease, secretory pathway-associated proteins raised again at 18 h post-induction. This phenomenon coincided with a burst in the expression of pancreatitis-associated protein (REG3A), an acute phase protein produced by the exocrine pancreas, and with the decrease of classical markers of pancreatic injury, suggesting that the expression of proteins associated to the secretory pathway may be a modulating factor of pancreas injury. BIOLOGICAL SIGNIFICANCE: Acute pancreatitis (AP) is a complex inflammatory disease, the pathobiology of which is not yet fully understood. Various animal models, relying on different mechanisms of disease induction, have been developed in order to investigate pathobiological processes of AP. In this study, we performed a time-course proteomic analysis to investigate changes of the pancreas proteome occurring in an experimental model of AP induced by perfusion of taurocholate, a bile acid, into the pancreatic duct. This experimental model is characterized by a severe disease with pancreatic necrosis and systemic inflammation. The objectives of this study were to determine the kinetics of functionally related proteins in the early steps of the experimental disease in order to identify protein pathways playing key roles in AP pathobiology and to correlate these data with parameters classically used to assess disease severity. The present work provides for the first time an overview of protein expression in the pancreas during the course of taurocholate-induced necrotizing AP. We believe that correlation of these results with data obtained using proteomic or biochemical approaches in various experimental models of AP will help in highlighting new features, generating hypotheses and constitute therefore a strong and reliable basis for further targeted investigations.

In vivo labelling of resting monocytes in the reticuloendothelial system with fluorescent iron oxide nanoparticles prior to injury reveals that they are mobilized to infarcted myocardium.

AIMS: To evaluate the feasibility of loading resting monocytes/macrophages by intravenous (i.v.) injection of fluorescent iron oxide nanoparticles prior to injury and tracking of these cells in the very same animal to myocardial infarction (MI) by magnetic resonance imaging (MRI) and optical imaging. METHODS AND RESULTS: Rats were injected with fluorescent iron oxide nanoparticles (10 mg/kg) (n = 15) prior to injury. After disappearance of the nanoparticles from the blood, MI was induced. Monocytes/macrophages were then tracked in the very same animal by MRI and optical imaging. Control groups were (i) non-injected animals (n = 15), (ii) injected animals associated with a sham operation (n = 8), and (iii) animals treated with an anti-inflammatory agent (n = 6). The presence of iron-loaded cells can be detected by MRI in vivo in the infarcted myocardium. Here, we showed that the detection of inflammatory cells in vivo correlated well with ex vivo imaging (MRI and reflectance fluorescence) and histology. We also showed that the method is robust enough to depict changes in the inflammatory response. CONCLUSION: This study demonstrates that resting monocytes/macrophages can be loaded in vivo by a simple i.v. injection of fluorescent superparamagnetic iron oxide nanoparticles prior to injury and then tracked, in the same animal, in a model of ischaemia-reperfusion leading to myocardial infarct. Although previous studies of macrophages infiltration following MI have labelled the macrophages after injury, this study, for the first time, has pre-load the resting monocytes with fluorescent iron oxide nanoparticles.

Noninvasive measurement of absolute renal perfusion by contrast medium-enhanced magnetic resonance imaging.

OBJECTIVE: The aim of this study was to validate the quantification of absolute renal perfusion (RP) determined by dynamic magnetic resonance imaging (MRI) and contrast media using an experimental model in the rabbit and a transit-timed ultrasound flow probe around the left renal artery as comparison. MATERIAL AND METHODS: An MR-compatible ultrasonic time-of-flight flow-probe was placed around the left renal artery in 9 New Zealand white rabbits. Absolute RP in basal state, after mechanical renal artery stenosis, intravenous dopamine, angiotensin II, or colloid infusion was measured using dynamic MRI and intravenous injection of gadoteridol. The results were correlated to the renal artery flow measured inside the magnet with the transit-timed flow-probe. For the signal intensity concentration conversion, we applied different calibrations according to various velocities measured in the aorta by a phase contrast sequence to correct for inflow effect. MRI-derived RP (in mL/min) was calculated by the maximum upslope method, where RP/volume was defined as the ratio of the cortex contrast enhancement slope over the maximum of the arterial input function determined in the aorta. RESULTS: Reproducible arterial and renal transit curve with excellent contrast to noise ratio were obtained. The MRI derived perfusion was systematically underestimated by comparison to the ultrasonic transit-timed flow-probe but was linearly correlated with these measures (r = 0.80, P < 0.001). CONCLUSIONS: Using a flow-sensitive calibration, an accurate arterial input function can be measured from the blood MR signal and used in a realistic model to assess the RP. There was a good correlation between the MR-derived RP and the renal artery blood flow measured by the flow-meter. This experimental study validates absolute RP quantification by MRI and contrast media injection and justifies further clinical studies.