Dual Labeling of Lipopolysaccharides for SPECT-CT Imaging and Fluorescence Microscopy

Abstract

Lipopolysaccharides (LPS) or endotoxins are amphipathic, pro-inflammatory components of the outer membrane of Gram-negative bacteria. In the host, LPS can trigger a systemic inflammatory response syndrome. To bring insight into in vivo tissue distribution and cellular uptake of LPS, dual labeling was performed with a bimodal molecular probe designed for fluorescence and nuclear imaging. LPS were labeled with DOTA-Bodipy-NCS, and pro-inflammatory properties were controlled after each labeling step. LPS were then radiolabeled with (111)In and subsequently injected intravenously into wild-type, C57B16 mice, and their in vivo behavior was followed by single photon emission computed tomography coupled with X-ray computed tomography (SPECT-CT) and fluorescence microscopy. Time course of liver uptake of radiolabeled LPS ((111)In-DOTA-Bodipy-LPS) was visualized over a 24-h period in the whole animal by SPECT-CT. In complementary histological analyses with fluorescent microscopy, the bulk of injected (111)In-DOTA-Bodipy-LPS was found to localize early within the liver. Serum kinetics of unlabeled and DOTA-Bodipy-labeled LPS in mouse plasma were similar as ascertained by direct quantitation of β-hydroxymyristate, and DOTA-Bodipy-LPS was found to retain the potent, pro-inflammatory property of the unlabeled molecule as assessed by serum cytokine assays. It is concluded that the dual labeling process, involving the formation of covalent bonds between a DOTA-Bodipy-NCS probe and LPS molecules is relevant for imaging and kinetic analysis of LPS biodistribution, both in vivo and ex vivo. Data of the present study come in direct and visual support of a lipopolysaccharide transport through which pro-inflammatory LPS can be transported from the periphery to the liver for detoxification. The (111)In-DOTA-Bodipy-LPS probe arises here as a relevant tool to identify key components of LPS detoxification in vivo.

Curcumin Protects Against Intestinal Origin Endotoxemia in Rat Liver Cirrhosis by Targeting PCSK9

“…Intestinal origin LPS was reported to enter into the portal vein of the liver before it was taken up by the liver to be metabolized, and then it was released to circulation; thus, the liver became the first organ to contact the endotoxin (Guerville and others ). On the one hand, LPS urged innate inflammation by precipitating the monomacrophage cells in the liver; on the other hand, LPS was cleared and detoxified by the liver (Duheron and others ). Actually, the direct damage to hepatocytes by LPS is not obvious; there may exist LPS combination receptors on the surface of the hepatocyte membrane.…”

Quantitative lipopolysaccharide analysis using HPLC/MS/MS and its combination with the limulus amebocyte lysate assay

“…Finally, calculation of the LAL (activity) to HPLC/MS/MS (mass) LPS ratio is proposed as a relevant method to assess in vivo the effi cacy of the initial step of LPS neutralization [known as the endotoxin-lipoprotein hypothesis ( 29 )]. This step is followed by lipoprotein-mediated transport to the liver and ultimate detoxifi cation in the bile ( 30,31 ).…”

Gadolinium(III)-DOTA Complex Functionalized with BODIPY as a Potential Bimodal Contrast Agent for MRI and Optical Imaging

“…The BODIPY dyes have been used in a variety of applications such as biological labels and probes [36][37][38], fluorescent probes [39], laser dyes [40,41], light emitting diodes [42], solar cells [43,44], and potential sensitizers in photodynamic therapy [45,46]. Although BODIPYs are versatile compounds with good optical properties, their use in developing bimodal contrast agents remain scarce [47][48][49][50][51][52]. 18 F labeled BODIPY derivatives have been recently suggested as bifunctional reporters for hybrid optical/positron emission tomography imaging [53,54].…”