Changes of ribosomal protein S3 immunoreactivity and its new expression in microglia in the mice hippocampus after lipopolysaccharide treatment

Abstract

Lipopolysaccharide (LPS) has been used as a reagent for a model of systemic inflammatory response. Ribosomal protein S3 (rpS3) is a multi-functional protein that is involved in transcription, metastasis, DNA repair, and apoptosis. In the present study, we examined the changes of rpS3 immunoreactivity in the mouse hippocampus after systemic administration of 1 mg/kg of LPS. From 6 h after LPS treatment, rpS3 immunoreactivity was decreased in pyramidale cells of the hippocampus proper (CA1-CA3 regions) and in granule cells of the dentate gyrus. At this point in time, rpS3 immunoreactivity began to increase in non-pyramidal cells and non-granule cells. From 1 day after LPS treatment, rpS3 immunoreactivity in pyramidal and granule cells was hardly detected; however, strong rpS3 immunoreactivity was shown in non-pyramidal and non-granule cells. Based on double immunofluorescence staining for rpS3/ionized calcium-binding adapter 1 (Iba-1, a marker for microglia) and glial fibrillary acidic protein (GFAP, a marker for astrocytes), strong rpS3 immunoreactivity was expressed in Iba-1-immunoreactive microglia, not in GFAP-immunoreactive astrocytes, at 1 and 2 days after LPS treatment. These results indicate that rpS3 immunoreactivity changes only in pyramidal and granule cells, and rpS3 is expressed only in activated microglia after LPS treatment: this may be associated with the neuroinflammatory responses in the brain.

Fig. 1

Low magnification of immunohistochemical staining for rpS3 in the hippocampus of the control (a) and LPS-treated (b–d) groups. rpS3 immunoreactivity is well observed in the stratum pyramidale of the hippocampus proper and in the granule cell layer of the dentate gyrus of the control-group. At 1 day after LPS treatment, rpS3 immunoreactivity (asterisk) is markedly increased in non-pyramidal and non-granular cells. rpS3 immunoreactivity is decreased at 4 days compared to that at 1 day after LPS treatment. e Negative control test shows the absence of rpS3 immunoreactivity in the hippocampus. CA conus ammonis, DG dentate gyrus. Scale bar 400 μm

Fig. 2

Immunohistochemistry for rpS3 in the CA1 region of the control (a) and LPS-treated (b–f) groups. From 6 h after LPS treatment, rpS3 immunoreactivity is decreased in the stratum pyramidale (SP, asterisk) and increased in non-pyramidal cells (arrowheads). Strong rpS3 immunoreactivity is shown in non-pyramidal cells of the stratum oriens (SO) and stratum radiatum (SR) at 1 and 2 days after LPS treatment (arrows). Scale bar 50 μm

Fig. 3

Immunohistochemistry for rpS3 in the CA2/3 region of the control (a) and LPS-treated (b–f) groups. From 6 h after LPS treatment, rpS3 immunoreactivity is decreased in the stratum pyramidale (SP, asterisk) and hardly detected in the SP from 1 day after LPS treatment. One and 2 days after LPS treatment, rpS3 immunoreactivity is markedly increased in non-pyramidal cells (arrows). SO stratum oriens, SR stratum radiatum. Scale bar 100 μm

Fig. 4

Immunohistochemistry for rpS3 in the dentate gyrus of the control (a) and LPS-treated (b–f) groups. From 6 h after LPS treatment, rpS3 immunoreactivity is markedly decreased in the granule cell layer (GCL, asterisk). RpS3 immunoreactivity is increased in non-granule cells at 1 and 2 days after LPS treatment. rpS3 immunoreactivity in non-granule cells is decreased at 4 days after LPS treatment. ML molecular layer, PL polymorphic layer. Scale bar 100 μm

Fig. 5

Double immunofluorescence staining for rpS3 (green, a, d, g, and j), Iba-1 (red, b and e) or GFAP (red, h and k), and merged images (c, f, i, and l) in the CA1 region (a–c and g–i) and dentate gyrus (d–f and j–l) at 1 day after LPS treatment. Most of rpS3-immunoreactive cells are co-localized with Iba-1-immunoreactive microglia (arrows), not with GFAP-immunoreactive astrocytes. SO stratum oriens, SP stratum pyramidale, SR stratum radiatum, ML molecular layer, GCL granule cell layer, PL polymorphic layer. Scale bar 50 μm (Color figure online)

Fig. 6

Western blot analysis of rpS3 in the hippocampus of the control- and LPS-treated groups. Relative optical density (ROD) as % values of immunoblot band is also represented (n = 5, *P < 0.05, significantly different from the control group). The bars indicate the means ± SD