Auraptene Acts as an Anti-Inflammatory Agent in the Mouse Brain

Abstract

The anti-inflammatory activity of auraptene (AUR), a citrus coumarin, in peripheral tissues is well-known, and we previously demonstrated that AUR exerts anti-inflammatory effects in the ischemic brain; the treatment of mice with AUR for eight days immediately after ischemic surgery suppressed demise and neuronal cell death in the hippocampus, possibly through its anti-inflammatory effects in the brain. We suggested that these effects were at least partly mediated by the suppression of inflammatory mediators derived from astrocytes. The present study showed that (1) AUR, as a pretreatment for five days before and another three days after ischemic surgery, suppressed microglial activation, cyclooxygenase (COX)-2 expression in astrocytes, and COX-2 mRNA expression in the hippocampus; (2) AUR suppressed the lipopolysaccharide-induced expression of COX-2 mRNA and the mRNA of pro-inflammatory cytokines in cultured astrocytes; (3) AUR was still detectable in the brain 60 min after its intraperitoneal administration. These results support our previous suggestion that AUR directly exerts anti-inflammatory effects on the brain.

Keywords: COX-2; anti-inflammation; astrocytes; auraptene; cerebral ischemia; cyclooxygenase-2; hippocampus.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1

Effects of AUR on the activation of microglia in the hippocampus. (A) Region within the hippocampal region for observations of IBA-1-positive cells; (B) Representative photographs of IBA-1-positive cells in the indicated groups. The scale bar indicates 100 µm; (C) Number of IBA-1-positive cells in the four groups. Values are the means ± SEM (15~18 sections in each group). *** p < 0.001; and ##p < 0.01, as indicated by the brackets.

Figure 2

Effects of AUR on the expression of COX-2 and GFAP in the hippocampus. (A) Representative photographs of COX-2-positive cells (green; a, d, g, j), GFAP-positive cells (red; b, e, h, k), and cells co-expressing COX-2 and GFAP (yellow; c, f, i, l). The scale bar indicates 100 µm; (B) The numbers of COX-2-positive cells; and (C) GFAP-positive cells are shown. Values are the means ± SEM (6 sections in each group). ** p < 0.01; *** p < 0.001; #p < 0.05; and ###p < 0.001, as indicated by the brackets.

Figure 2

Effects of AUR on the expression of COX-2 and GFAP in the hippocampus. (A) Representative photographs of COX-2-positive cells (green; a, d, g, j), GFAP-positive cells (red; b, e, h, k), and cells co-expressing COX-2 and GFAP (yellow; c, f, i, l). The scale bar indicates 100 µm; (B) The numbers of COX-2-positive cells; and (C) GFAP-positive cells are shown. Values are the means ± SEM (6 sections in each group). ** p < 0.01; *** p < 0.001; #p < 0.05; and ###p < 0.001, as indicated by the brackets.

Figure 3

Effects of AUR on the expression of COX-2 mRNA in the hippocampus. (A) Densitometric patterns of COX-2 mRNA and β-actin mRNA bands; (B) Densitometric quantification of COX-2 mRNA band densities normalized by the density of the β-actin mRNA band. Values are the means ± SEM (5~6 for each group). * p < 0.05 and #p < 0.05, as indicated by the brackets.

Figure 4

Effects of AUR on the expression of COX-2, IL-1β, and TNF-α mRNAs in cultured astrocytes. Cells were not treated or were treated with AUR (25 μM) alone for 30 min, with LPS (10 ng/mL) alone for 4 h, or with AUR (25 μM) for 30 min and then with LPS (10 ng/mL) for 4 h. Representative densitometric patterns of COX-2, IL-1β, TNF-α and GAPDH mRNAs bands were shown. Similar results were obtained from at least three independent experiments.

Figure 5

HPLC chromatograms of vehicle-treated brains (A); and brains from mice treated i.p. with AUR (B).

Figure 6

Time course of brain AUR concentration profiles following its i.p. administration (n = 3 at each time point).