p38 map kinase regulates TNF-alpha production in human astrocytes and microglia by multiple mechanisms

In the vertebrate central nervous system (CNS), tumour necrosis factor-alpha (TNF-alpha) is produced by astrocytes and microglia and mediates cell injury in nerve cells and oligodendrocytes. In the present study, we have used a specific inhibitor of p38 MAP kinase, SB203580 to examine the role of p38 MAP kinase in regulation of TNF-alpha production in human astrocytes and microglia in terms of levels of mRNA and secreted protein. A reverse transcriptase polymerase chain reaction (RT-PCR) analysis showed that increased levels of TNF-alpha mRNA were induced in astrocytes by IL-1beta treatment, and in microglia by bacterial lipopolysaccharide (LPS). In microglia, treatment with SB203580 reduced the level of TNF-alpha mRNA, but in astrocytes it did not. However, the secretion of TNF-alpha by both astrocytes and microglia was markedly inhibited by SB203580 at a low concentration. TNF-alpha secretion was reduced approximately 80% in astrocytes and 85% in microglia. The results demonstrate a key role played by p38 MAP kinase in upregulation of TNF-alpha mRNA levels in LPS-activated human microglia, whereas p38 MAP kinase is involved in post-transcriptional regulation of TNF-alpha production at translational level in IL-1beta-activated human astrocytes.