Toll-like receptors TLR2 and TLR4 are involved in reactive gliosis and microglial activation after ischemic brain injury

ROSCISZEWSKI G; LUKIN J; MURTA V; CADENA V; THIERRY R; RAMOS AJ

Huerta Grande, Córdoba

Congreso; XXIX CONGRESO ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACION EN NEUROCIENCIAS; 2014

Sociedad Argentina de Neurociencias

Reactive gliosis is a generic glial response to brain injury. The beneficial or detrimental role of reactive gliosis is controversial. It is clear, however, that reactive astrocytes may suffer a conversion to the proinflammatory neurodegenerative phenotype. TLR are innate immunity receptors activated by DAMP proteins released by necrotic cells after brain injury. In this work we studied the role of TLR2 and TLR4 in the astroglial conversion into the reactive proinflammatory phenotype. For that purpose we used primary astrocytic culture exposed to in vitro ischemia (OGD) or transfected with plasmids expressing TLR2 or TLR4. Astrocytes were then exposed to LPS (PAMP) or HMGB-1 (DAMP) to imitate the in vivo situation where reactive astrocytes are exposed to a DAMP gradient from necrotic cells. For the in vivo studies, animals were exposed to the cortical devascularization model of ischemia. We found that TLR2, TLR4, MyD88 adaptor and proinflammatory IL1beta expressions were increased in glial cells exposed to OGD. TLR overexpressing astrocytes showed increased response to LPS and HMGB1 and presented a sustained NFkB activation. Conditioned medium obtained from HMGB-1- exposed astrocytes was able to activate microglia. In vivo, TLR4 and TLR2 expression were observed in glial cells of the ischemic penumbra, but interestingly, TLR4 expression was also associated with neurons. Our results show that TLRs have a main role in the neuro-glial crosstalk after brain injury.