MODULATION OF MICROGLIAL CELLS SURVIVAL BY IL-4: TARGETING NEUROINFLAMMATION

SORIA, JA; ARROYO, DS; GAVIGLIO, EA ; RODRIGUEZ-GALÁN, MC E IRIBARREN, P

Buenos Aires

Congreso; First French-Argentine Immunology Congress; 2010

Modulation of Microglial Cells Survival by IL4: Targeting the Neuroinflammation Javier A. Soria, Daniela S. Arroyo, Emilia Gaviglio, Pablo Iribarren Microglial cells (MC) are the brain-resident immune cells. After the acute activation, as a result of neuronal injury, MC proliferates, change their morphology (reactive microgliosis) and secrete neurotoxic factors. The activities of these cells are for the most part beneficial, becoming destructive only when they escape from the strict control normally imposed on them. Downregulation of inflammatory mediators and removal of activated microglia may be the underlying mechanism by which brain inflammation is controlled. Furthermore, these modulatory mechanisms of inflammation could be attributed to anti-inflammatory cytokines present in the Central Nervous System (CNS), such as IL-4 and IL-13. In order to elucidate these mechanisms, we studied the effects of IL-4 on MC survival. We show here that IL4 induced a significant increase in the N9 cell apoptosis (cell line of murine MC) at 48 h of incubation, determined on the basis of hypodiploid DNA content ( p = 0.0001). IL4 also increased the percentage of annexin-V single positive and annexin-V/7AAD double positive cells, indicating induction of early and late apoptosis respectively. In order to characterize the type of death, we found that IL4 significantly increased cleavage of caspase 3 (p <0.01). In addition, by inhibiting caspase 3 cleavage induced by IL4 (using the inhibitor zVAD) the cell death was prevented (p <0.05). We also determined that caspase 3 was not only cleaved but also activated, by detection of cleaved PARP. PARP is one of the specific substrates of caspase 3 and a critical factor involved in DNA repair to prevent apoptosis. Moreover, by specific staining of autophagic vesicles, under our test conditions we had a constitutive induction of autophagy, and IL-4 inhibited it. This suggested that IL-4 predisposes to death, also by inhibition of autophagy. Our preliminary results suggest that induction of MC death by IL4 may be an important mechanism to control the extent and duration of neuroinflammation