Rab7b participation on the TLR4 (Toll like receptor) endocytic pathway in Hemolytic Uremic Syndrome

V. BOCANEGRA; V. CACCIAMANI; A. LAFALLA MANZANO; M.E. BENARDON; A. GIL LORENZO; V.V. COSTANTINO; P. VALLES

Foz de Iguazú

Congreso; 17º Congreso de la Asociación Internacional de Nefrología Pediátrica (IPNA); 2016

Asociación Internacional de Nefrología Pediátrica

Rab7b participation on the TLR4 (Toll like receptor) endocytic pathway in Hemolytic Uremic SyndromeA. GIL LORENZO(1), A. LAFALLA(1), V. BOCANEGRA(1), V.V. COSTANTINO(2), M.E. BENARDON(1), V. CACCIAMANI(1), P. VALLES(1)(1) School of Medicine. University of Cuyo, Mendoza, ARGENTINA; (2) CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Mendoza, ARGENTINAa. ObjectivesThe inflammatory response of host endothelial cells to Shiga toxin and/or lipopolysaccharides (LPS) of E coli is included in typical HUS. LPS stimulation of TLR4 activates signal transduction pathways leading to proinflammatory cytokine secretion.The TLR4-LPS complex is rapidly internalized and TLR4-induced inflammatory signaling is stopped by targeting the complex for degradation. Rab7b,a small GTPase expressed in monocytes, regulates the later stages of the endocytic pathway.We studied the Rab7b participation on the TLR4 endocytic pathway and its effect on monocyte intracellular cytokine production along the acute course of HUS.b. MethodsThe studies were performed in monocytes from HUS patients by flow cytometry and immunofuorescence confocal microscopy.c. ResultsSurface TLR4 expression determined by flow cytometry in CD14(+) monocytes from 16 HUS patients remains unchanged at onset and significantly increased by day 4 compared to 10 healthy children monocytes. Significant higher citoplasmatic TLR4 protein expression was accompanied by increased proinflammatory intracellular cytokines,tumor necrosis factor alpha (TNF-α), and interleukin 6 (IL-6) in HUS monocytes at days 1 and 4 vs controls.On the contrary,monocytes display decreased surface TLR4 expression and significant reduction of intracellular TNF-αand IL6 levels released in a time-dependent manner after a disease follow up of 6 to 10 days Furthermore, immunofluorescence confocal microscopy proved colocalization of increased intracellular TLR4/ Rab7b determined by Pearson´s coefficient in monocytes from HUS patients on day 1. The highest colocalization of both proteins in monocytes was shown by day 4, then decreased TLR4 /Rab7b colocalization was shown 10 days after HUS onset.d. ConclusionsThe colocalization of TLR4 and Rab7b allows us to suggest that Rab7b participates in the control of the TLR4 endocitic pathways in HUS patient monocytes .A consequential fall in cytokine production throughout the early follow up of HUS is demonstrated.