Interleukin-10 inhibits endotoxin-induced pro-inflammatory cytokines in microglial cell cultures

Inflammation contributes to perinatal brain injury and can be induced by hypoxia-ischemia (HI) or exposure to infection (fetal inflammatory response). The anti-inflammatory cytokine interleukin-10 (IL10) has been shown to have neuroprotective effects following HI. To determine whether IL10 can reduce the inflammatory response to lipopolysaccharide (LPS) in microglial cell cultures, primary microglial (MG) and/or HAPI cells (new MG-like cell line) were treated with LPS (50 ng/ml) in the presence or absence of IL10 (20 ng/ml) for 0.5, 1, 4, and 8 h. TNFα, MIP-1α, and RANTES were assayed by ELISA. Chemokine receptors, CCR5, CXCR3, and CX₃CR1 (fractalkine receptor) were assayed by semiquantitative RT-PCR. We found that in MG cell cultures TNFα, MIP-1α, and RANTES release after 8-h exposure to LPS was significantly higher compared to non-exposed MG cells (P<0.001). In HAPI cell cultures similar stimulation of mRNA levels was found for TNFα, MIP-1α, CXCR3, and CX₃CR1. IL10 inhibited TNFα, MIP-1α, and RANTES release of LPS-stimulated MG cells as well as TNFα, MIP-1α, and CXCR3 mRNA expression by HAPI cells after exposure to LPS (P<0.05). In contrast to those inhibitory effects, there was no change in fractalkine, and a modest increase in CX₃CR1 mRNA levels was found in the presence of IL10. We conclude that the inflammatory response induced in microglial cells by LPS can be markedly reduced by IL10. The increase in fractalkine receptor (CX₃CR1) is also potentially protective. Our results suggest that treatment of damaging neuroinflammatory insults such hypoxia-ischemia, with IL10 may be protective for the immature brain.