Cytokine network in the human central nervous system

Expression of various cytokines and their receptors in human CNS neurons and glial cells in culture was investigated using RT-PCR, ELISA and immunoblotting. Pure populations of astrocytes, microglia and neurons were prepared from mixed cell cultures isolated from brains of human embryos (12-18 weeks' gestation), and oligodendrocytes were prepared from adult human brain tissues. RT-PCR results of cytokines and their receptors were as follows: (1) Non-stimulated astrocytes expressed transcripts for IL-9, IL-11, IL-15, TGF-α, TGF-β1, CNTF, LIF and SCF. Treatment with IL-1β and IFN-γ induced expression of IL-1β, IL-6, IL-8, TNF-α and GM-CSF and increased expression of IL-9 and IL-15 in astrocytes. Transcripts for IL-1RI, IL-6R, IL-8R, IL-9Rα, IL-10Rα, IL-11R, IL-12Rβ2, IL-13Rα, IL-15Rα, TNFRI, SCFR and gp130 were detected in unstimulated astrocytes, while expression of IL-1RII and TNFRII was induced following stimulation with IL-1β and IFN-γ. (2) In unstimulated microglia, low levels of transcripts for IL-lβ, IL-6, IL-10, IL-15, TNF-α, TGF-α, TGF-β1, and IL-1RI, IL- 1RII, IL-6R, IL-8R, IL-9Rα, IL-10Rα, IL-12Rβ2, IL-13Rα, IL-15Rα, TNFRI, TNFRII and gp130 were detected. Treatment of microglia with LPS and IFN-γ induced expression of IL-8 and IL-12 and increased expression of transcripts for IL-1β, IL-6, IL-10, IL-15 and TNF-α. (3) Neurons expressed transcripts for IL-5, TGF-β1, LIF, and IL-9Rα, IL-9Rα, IL-13Rα, TNFRI and gpl30. (4) Oligodendrocytes expressed transcripts for IL-1β, TGF-α, TGF-β1 and CNTF, and for IL-1RI, 1L-6R, IL-8R, IL-9Rα, IL-13Rα, TNFRII, SCFR and gp130. Secretion of selected cytokines from astrocytes and microglia was determined by ELISA and immunoblotting. (1) In astrocytes, treatment with IL-1β resulted in increased levels of IL-6, IL-11, IL-15, but not with IFN-γ. IL-9 was secreted constitutively, and its protein level was not changed with IL-1β or IFN-γ. (2) In microglia, IL-6 secretion was increased by LPS treatment, but not by IFN-γ or TNF-α. As well, IL-15 secretion was increased by LPS or IFN-γ treatment. TNF-α secretion was increased by treatment with LPS, and demonstrated a synergistic effect with IFN-γ for TNF-α production. Effects of selected cytokines were studied on NO and TNF-α production in astrocytes and microglia respectively. IL-10 inhibited the TNF-α production (>90%) in LPS/IFN-γ- treated microglia. NO production in IL-1β/IFN-γ-treated astrocytes was not altered by any of the cytokines examined. In addition, p38 MAP kinase was found to be involved in the upregulation of TNF-α mRNA in microglia, while in IL-1β-treated astrocytes it was involved in the upregulation of translation of TNF-α mRNA. Selected cytokines including IL-9, IL-11 and IL-15 showed neurotrophic activities such as neuronal differentiation and survival of human embryonic neurons.Medicine, Faculty ofMedicine, Department ofExperimental Medicine, Division ofGraduat