Rab7b participation on the TLR4 (Tolk like receptor) endocytic pathway in Shiga toxin-associated Hemolytic Uremic Syndrome (HUS)

BOCANEGRA MV; CACCIAMANI V; GIL LORENZO AF; BENARDÓN ME; LAFALLA MANZANO A; COSTANTINO V.V.; VALLÉS PG

Mendoza

Simposio; II Simposio Internacional de Medicina Traslacional; 2019

Facultad de Ciencias Médicas, Universidad Nacional de Cuyo

Background: The inflammatory response of the host to Shiga toxin and/or lipopolysaccharide (LPS) of Escherichia coli (E.coli) is included in HUS. The TLR4-LPS complex is internalized and TLR4 induced inflammatory signaling is stopped by targeting the complex for degradation. Rab7b, a small guanosine triphosphatase (GTPase) expressed in monocytes, regulates the later stages of the endocytic pathway. Objetive: we studied the Rab7b participation on the TLR4 endocytic pathway and its effect on monocyte cytokine production along the acute course of pediatric Shiga toxin-associated HUS. Methods and Results: Monocytes were identified according to their positivity CD14 expression. Surface TLR4 expression in monocytes from 18 HUS patients significantly increased by day 1 to 6, being the highest increase on day 4 compared to monocytes of 10 healthy children. Significant higher surface TLR4 expression was accompanied by increased proinflammatory intracellular cytokines, tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). In contrast, after these time points, surface TLR4 expression and intracellular TNF-α levels, returned to near control levels after 10 days. Furthermore, confocal immunofluorescence microscopy proved colocalization of increased intracellular TLR4/Rab7b determined by Pearson´s coefficient in monocytes from HUS patients on day 1 with the highest colocalization of both proteins by day 4. Decreased TLR4/Rab7b colocalization was shown 10 days after HUS onset. Conclusion: The colocalization of TLR4 and Rab7b allows us to suggest Rab7b participation in the control of the TLR4 endocytic pathway in HUS patient monocytes. A consequential fall in cytokine production throughout the early follow up of HUS is demonstrated.