Interleukin-4 and interleukin-10 regulate IL1-beta induced mouse primary astrocyte activation: a comparative study

The pro-inflammatory cytokine interleukin-1beta (IL-1beta) is strongly expressed during brain injury and is able to induce severe cellular brain damage via the production of soluble factors. Different processes regulate IL-1 biological activities, like the production of anti-inflammatory cytokines such as interleukin-4 (IL-4) and interleukin-10 (IL-10). In this report, we describe the sequential effects of IL-4 and IL-10 on the production of interleukin-6 (IL-6) induced by IL-1beta in mouse primary astrocytes and compare these effects to those of the synthetic glucocorticoid agonist, dexamethasone. IL-6 secretion and IL-6 mRNA expression were determined by ELISA assay and a comparative RT-PCR method, respectively. Incubation of mouse astrocytes in primary culture simultaneously with IL-1beta (10 ng/ml) + IL-10 (10 ng/ml) or IL-1beta + dexamethasone (10(-6) M) markedly reduced IL-1beta induced IL-6 secretion and IL-6 mRNA expression, respectively, whereas simultaneous addition of IL-4 (10 ng/ml) did not alter the induction of IL-6 by IL-1beta. In contrast, after 24 h of IL-1beta treatment, the level of IL-6 was decreased below constitutive levels, and this change was reversed by addition of IL-4. IL-6 production in IL-1beta pretreated cells was also increased by addition of IL-4, whereas IL-10 and dexamethasone had no effects. The delayed time dependent effect of IL-4 might be partially explained by the induction of IL-4 receptor alpha-chain mRNA expression by IL-1beta. Therefore, we conclude that IL-10 and dexamethasone have rapid immunosuppressive effects on the astrocyte response to IL-1beta stimulation, whereas IL-4, which has a delayed action, acts as an immune inducer.