THU0096 Targeting Lymphatic Dysfunction in Rheumatoid Arthritis by High-Density Lipoprotein
Authors: R. Bisoendial, B. Roediger, R. Jain, L. Cavanagh, P.-P. Tak, K.-A. Rye, W. Weninger
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> Rheumatoid arthritis (RA) is increasingly recognized to raise cardiovascular (CV) risk by two-fold. Our peliminary <i>in vitro</i> findings suggest that high-density lipoprotein (HDL) and its main apolipoprotein (apo)A-I may correct lymphatic dysfunction, a hallmark of chronic inflammation. <h3>Objectives</h3> The impact of an i.v. injection of human apoA-I (40 mg/kg) or reconstituted (r)HDL - consisting of phosphatidylcholine with apoA-I - was evaluated on key lymphatic properties and resolution of inflammation in an acute mouse ear skin inflammation model. <h3>Methods</h3> Inflammation was induced by intra-dermal injection of 2.5 ug of lipopolysaccharide (LPS; O55:B5), in animals that had received apoA-I, rHDL or PBS 24 hrs earlier. Two days after LPS-injection, i.e. the peak of inflammation, ear swelling and erythema were scored. The auricular draining lymph node (DLN) was harvested for flow cytometry to assess changes in inflammatory cell migration. Alexa594-LPS was used to study LPS clearance from ear to DLN using an <i>in vivo</i> imaging system (IVIS). Lymph flow from ear skin to DLN was monitored 15 min after injecting 1.5 ul of TexasRed-Dextran (TXR-DX) at the inflammatory site using a stereomicroscope and IVIS. <h3>Results</h3> Erythema and swelling upon LPS were not significantly affected by pre-treatment with rHDL or apoA-I (24.8% and 38.4% increase respectively, as compared to PBS 36.7%). After 48 hrs, the influx of inflammatory cells in the DLN was significantly reduced upon pretreatment with rHDL and apoA-I (absolute cell numbers per DLN: PBS: 1x10<sup>7</sup>±2x10<sup>6</sup>; rHDL: 2x10<sup>6</sup>±4x10<sup>5</sup> and apoA-I: 5x10<sup>6</sup>±1x10<sup>6</sup>). Particularly the numbers of neutrophils (632.5±388.9 and 2610±1395 for rHDL and apoA-I, as compared to 16788±5340 for PBS) and CD11c<sup>+</sup>MHC-II<sup>high</sup> migratory dendritic cells (DC; 4873±1820 and 20680±7005 for rHDL and apoA-I, as compared to 41170±9495 for PBS) were diminished (all p&lt;0.05). Compositional changes of leukocytes in the peripheral blood and spleen were less remarkable. Intravital monitoring of ALEXA594-LPS using IVIS showed similar LPS disappearance from the ears after 24 hrs (decrease 66.2% and 51.8% for rHDL and apoA-I respectively, as compared to PBS 73%). In line, fluorescence intensity of ALEXA594-LPS in the DLN after 48 hrs seemed unaffected by pretreatment with rHDL and apoA-I. Lymphangiography using TXR-DX revealed that LPS resulted in dysmorphic patterning of lymphatic vessels and hyperpermeability, pointing to functional impairment. Pretreatment with apoA-I resulted in less pronounced hyperpermeability and higher fluorescence recovery of TXR-DX in the DLN. <h3>Conclusions</h3> Lymphatic properties comprising lymph flow and inflammatory cell migration that includes neutrophils and migratory DCs, is suggested to improve upon prior systemic administration of HDL and apoA-I in this LPS-induced ear skin inflammation model. Awaiting further results that may clarify the involved mechanisms and outcomes in chronic inflammation models these data support therapeutic benefits of HDL-based approaches in RA by targeting lymphatic dysfunction and thereby reducing CV risk. <h3>Disclosure of Interest</h3> None Declared