Toll-like 4 expression in astrocytes control astroglial conversion to the proinflammatory phenotype.

LUKIN JERONIMO; CADENA VANESA; ROSCISZEWSKI GERARDO; RAMOS ALBERTO JAVIER

Congreso; LXI Reunión Anual de la Sociedad Argentina de Investigación Clínica (SAIC), LXIV Congreso de la Sociedad Argentina de Inmunología (SAI) y XLVIII Congreso de la Sociedad Argentina de Farmacología Experimental (SAFE); 2016

Astrocytes are starting to be recognized as a facultative immunocompetent cell type able to participate in innate immunity responses in the CNS. They react to a brain injury with a generic response known as reactive gliosis, which may be beneficial for neuronal survival or generate a neurodegenerative proinflammatory environment. Activation of Toll-like receptor 4 (TLR4) in glial cells may be or is involved in the switch of this phenotype.To study the effect of TLR4 activation in glial cells we used rat primary cortical cultures: enriched astrocytes cultures and mixed glial cultures which include astrocytes and microglia. Through a model of ischemia in vitro we deprivate from oxygen and glucose (OGD) primary cortical astrocytes and we observed an induction of TLR4. This result was also observed in a model of ischemia in vivo by cortical devascularization in rats. Confocal images at differents time points showed an early increase in TLR4 expression in the ischemic core and penumbra.We exposed enriched astrocytic cultures to OGD for 6 h and 16 h later, we treated them with lipopolysaccharide (LPS) and we observed that OGD-exposed astrocytes responded to LPS with a significantly increased response of stellation compared with astrocytes exposed to control conditions. We also over-expressed TLR4 by transfecting enriched astrocytic culture with plasmids driving TLR4 expression. As expected, TLR4-overexpressing astrocytes showed a larger stellation response when they were exposed to LPS compared with mock-transfected astrocytes and, through qPCR, we detected in TLR4 overexpressed astrocytes higher levels of proinflammatory cytokines such as IL1-B and TNF-a.We conclude that TLR4 activation in astrocytes induces reactive gliosis showing astroglial polarization to the proinflammatory-neurodegenerative profile and probably facilitating neuronal death.