Astrocyte inflammatory response to SHIGA TOXIN (Stx), agent responsible of Hemolitic Uremic Sindrome (HUS)

LANDONI VI.; CALATAYUD, CA,; CAMPOS-NEBEL M.; SHIERLOH LP.; PALERMO M.; PASQUINI JM.; PASQUINI LA.; ISTURIZ MA.

Rio de Janeiro

Congreso; XIV Congreso Internacional de Inmunología.; 2009

Hemolytic Uremic Syndrome (HUS) is caused by E. coli producing Shiga toxins (Stxs). The HUS development also involves bacterial lipopolysaccharide (LPS). Neurological symptoms may also be found in HUS patients. Alteration of brain endothelium from the blood-brain barrier (BBB) is observed. Astrocytes (ASTs) are in close contact with brain endothelium, modulating its permeability and playing a role in the inflammatory response. The aim of this work was to evaluate whether Stx-1 is able to induce an inflammatory response on cultured ASTs. To determine if Stx-1 induce cytotoxicity on ASTs, apoptosis was evaluated. Stx-1 increased the apoptosis on LPS- sensitized ASTs. Astrogliosis is a hallmark of brain injury. To investigate ASTs activation, we evaluated GFAP expression. GFAP was transiently increased by Stx-1 and this effect was maintained on LPS+Stx-1 treatment. To further assess an inflammatory response to Stx-1, we evaluated TNF-á and nitrite (NO3) secretion. Stx-1 increased TNF-á secretion while NO3 was only increased on Stx-1+LPS-treated ASTs. Participation of neutrophils (PMN) in SUH has been suggested. To determine if treated ASTs have the ability to attract PMN, cell-free supernatants (SN) were used as chemoattractant stimulus. A significant increase on PMN chemotaxis was seen in Stx-1 treated ASTs- SN. However, an additive effect was only observed on LPS+Stx-1 treated ASTs-SN. To further corroborate the participation of PMN on ASTs damage, PMN mediated cytotoxicity was determined on treated ASTs. An active role of PMN in ASTs damage was observed. This effect was increased in LPS+Stx-1 treated ASTs. In order to determine the enhancer activity of LPS on Stx-1, we studied the effects of inflammatory inhibitor molecules on Stx-1-treated ASTs. The results showed that both NF-kB activation and TNF-á secretion were necessary events for Stx-1-induced ASTs response. Together, our results suggest that the response of ASTs to Stx-1+LPS may contribute to inflammation leading to disturbance of the BBB function observed in HUS.