The innate properties of S100A8 as a regulator in acute inflammation have not yet been elucidated in detail. Our aims are to newly establish S100A8 transgenic rats (Tg-S100A8) and to elucidate the immunological functions of S100A8. Following the treatment with 5% dextran sulfate sodium for 1 week, the body weight in Tg-S100A8 weakly decreased after the start; however, that in Japanese Wistar rats (WT) significantly decreased in the end. The serum level of CRP in Tg-S100A8 was significantly lower than that in WT, although the concentration of CRP apparently increased in both Tg-S100A8 and WT. The dynamic mobility of S100A8 and S100A9 in macrophages was microscopically observed using fluorescent immunological staining, in which the S100A9 was dominantly expressed in many macrophages in the rectal tissue of WT. As determined by PCR and real-time PCR, the levels of S100A8 messenger RNA (mRNA) in several organ tissues of the Tg-S100A8, such as heart and small intestine, were apparently higher than those of WT, respectively. The expression of IL-6 and TNF-α mRNAs was negatively regulated in main organ tissues of the large colon of Tg-S100A8 followed by down-regulation of IL-6 protein. An important result was that the expression of S100A8 mRNA was strongly induced in many macrophages of Tg-S100A8, whereas that of some inflammatory cytokine mRNAs described above were significantly reduced. Tg-S100A8 has potential as a useful experimental model rat not only for investigating the innate properties of S100A8 as a regulator, but also for clarifying its functional role in immune cells from a myeloid origin, particularly macrophages.
Keywords: anti-inflammatory protein; inflammatory bowel diseases; interleukin-6; macrophages; transgenic rats.