Retinoic acid enhances leukemia inhibitory factor expression in OLN-93 oligodendrocytes

Brain injuries trigger physiological reactions which are mediated by a number of cytokines including interleukin-6 (IL-6), ciliary neurotrophic factor (CNTF), and leukemia inhibitory factor (LIF). Astrocytes and microglia, the protagonists in these traumatic responses, are known to secrete a variety of paracrine signals. Oligodendrocytes are involved as well and constitute another possible source of cytokines. Here we show the expression of IL-6, CNTF, and LIF in OLN-93 cells, derived from rat oligodendrocyte primary cultures. While differential gene transcription after injury has been described for many cytokines, the regulation of these physiological responses is unknown in many instances. Recent experiments indicate that the transcriptional activator retinoic acid (RA) plays a role in peripheral nerve regeneration. Transcripts of the retinoic acid receptors and the retinoid X receptors were also detected in OLN-93 oligodendrocytes. Using quantitative RT-PCR, we have therefore investigated the effect of RA on the expression of neuropoietic cytokines in these cells. Treatment with 1 microM all- trans RA for 24 h increased the mRNA concentration of LIF by a factor of 3.1 ( P<0.01). In contrast, RA had no significant effect on the expression of CNTF. The results suggest RA as a possible regulator of cytokine signaling in the CNS.