The current experimental model with local injection of LPS into the somatosensory cortex enabled to show that the systemic immune system acutely responds to the centrally initiated neuroinflammation. Focal ischemic stroke has been shown to induce a similar activation of systemic immune system (Offner et al., 2008). In our current study, the cortical LPS injection increased IL-6 protein in the brain, which was detected in microglia. Fenofibrate showed a nearly complete block in the increase of IL-6 in the brain whereas the IL-6 inhibition in the serum was by ~50%, suggesting that the LPS-induced IL-6 increase in the serum was not merely a release from the brain. The systemic immune response could in turn influence the neuroinflammation at the primary site of LPS injection. As Wy-14643 and fenofibrate were systemically administered, these drugs might affect the secondary phase of immune response in the peripheral organs. Future studies are needed for understanding how the primary site in the brain sends signal to the peripheral immune organs.
