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Combustion smoke-induced inflammation in the olfactory bulb of adult rats.

Zou YY, Yuan Y, Kan EM, Lu J, Ling EA - J Neuroinflammation (2014)

Bottom Line: The results showed a significant increase in VEGF, iNOS, eNOS, nNOS, NKCC1, and GFAP expression in the bulb tissues, with corresponding increases in inflammatory cytokines and chemokines after smoke inhalation.Concurrent to this was a drastic increase in AQP4 expression and RITC permeability.This was coupled with a significant reduction in incidence of TUNEL + cells that was not altered with administration of L-NG-nitroarginine methyl ester (L-NAME).

View Article: PubMed Central - PubMed

ABSTRACT

Background: The damaging effect of combustion smoke inhalation on the lung is widely reported but information on its effects on the olfactory bulb is lacking. This study sought to determine the effects of smoke inhalation on the olfactory bulb, whose afferent input neurons in the nasal mucosa are directly exposed to external stimuli, such as smoke.

Methods: Adult male Sprague-Dawley rats were subjected to combustion smoke inhalation and sacrificed at different time points. Changes in olfactory bulb proteins including vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), Na+-K+-Cl- cotransporter 1 (NKCC1), glial fibrillary acidic protein (GFAP), and aquaporin-4 (AQP4) were evaluated by Western blot analysis. In addition, ELISA was conducted for cytokine and chemokine levels, and double immunofluorescence labeling was carried out for GFAP/VEGF, GFAP/AQP4, NeuN/nNOS, GFAP/NKCC1, NeuN/NKCC1, GFAP/Rhodamine isothiocyanate (RITC), and transferase dUTP nick end labeling (TUNEL). Aminoguanidine was administered to determine the effects of iNOS inhibition on the targets probed after smoke inhalation.

Results: The results showed a significant increase in VEGF, iNOS, eNOS, nNOS, NKCC1, and GFAP expression in the bulb tissues, with corresponding increases in inflammatory cytokines and chemokines after smoke inhalation. Concurrent to this was a drastic increase in AQP4 expression and RITC permeability. Aminoguanidine administration decreased the expression of iNOS and RITC extravasation after smoke inhalation. This was coupled with a significant reduction in incidence of TUNEL + cells that was not altered with administration of L-NG-nitroarginine methyl ester (L-NAME).

Conclusions: These findings suggest that the upregulation of iNOS in response to smoke inhalation plays a major role in the olfactory bulb inflammatory pathophysiology, along with a concomitant increase in pro-inflammatory molecules, vascular permeability, and edema. Overall, these findings indicate that the olfactory bulb is vulnerable to smoke inhalation.

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Immunoexpression of AQP4 (red) and GFAP (green) in the olfactory bulb of the C group (A-C) and the SI + S group at 24 and 72 h (D-I). In the normal olfactory tissue, AQP4 expression is localized in the astrocytic foot processes (arrows) and blood vessels (arrowheads) (A-C). In the SI + S group, AQP4 expression is increased at different time points (24 and 72 h, D-I), being more conspicuous at 24 h (E). Intense AQP4 immunoreactivity is localized in GFAP-labeled astrocyte processes and end-feet and blood vessels, which are well delineated (C,F,I). Aminoguanidine administration did not suppress the immunofluorescence at 72 h (image not shown). Scale bar =20.0 μm.
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Fig6: Immunoexpression of AQP4 (red) and GFAP (green) in the olfactory bulb of the C group (A-C) and the SI + S group at 24 and 72 h (D-I). In the normal olfactory tissue, AQP4 expression is localized in the astrocytic foot processes (arrows) and blood vessels (arrowheads) (A-C). In the SI + S group, AQP4 expression is increased at different time points (24 and 72 h, D-I), being more conspicuous at 24 h (E). Intense AQP4 immunoreactivity is localized in GFAP-labeled astrocyte processes and end-feet and blood vessels, which are well delineated (C,F,I). Aminoguanidine administration did not suppress the immunofluorescence at 72 h (image not shown). Scale bar =20.0 μm.

Mentions: Expression of AQP4 was ubiquitous in the astrocytic foot processes associated with the blood vessels in the external plexiform layer, mitral cell layer, and internal plexiform layer (Figure 6). Double labeling with GFAP confirmed that the AQP4-positive cells were astrocytes. In the C group, both GFAP and AQP4 immunoreactivity were moderate in the olfactory bulb (Figure 6A,B); GFAP and AQP4 colocalization was only evident on closer examination (Figure 6C). In the SI + S group at 24 and 72 h, the immunoexpression for both markers was drastically enhanced (Figure 6D-I). Strikingly, GFAP positive hypertrophic AQP4-positive astrocytic foot processes impinged on dilated blood vessels, which exhibited colocalization of GFAP immunofluorescence (Figure 6D-I). The AQP4 immunofluorescence, however, was not affected in the SI + AG group at 72 h, as compared with non-treated rats at the same time point (image not shown).Figure 6


Combustion smoke-induced inflammation in the olfactory bulb of adult rats.

Zou YY, Yuan Y, Kan EM, Lu J, Ling EA - J Neuroinflammation (2014)

Immunoexpression of AQP4 (red) and GFAP (green) in the olfactory bulb of the C group (A-C) and the SI + S group at 24 and 72 h (D-I). In the normal olfactory tissue, AQP4 expression is localized in the astrocytic foot processes (arrows) and blood vessels (arrowheads) (A-C). In the SI + S group, AQP4 expression is increased at different time points (24 and 72 h, D-I), being more conspicuous at 24 h (E). Intense AQP4 immunoreactivity is localized in GFAP-labeled astrocyte processes and end-feet and blood vessels, which are well delineated (C,F,I). Aminoguanidine administration did not suppress the immunofluorescence at 72 h (image not shown). Scale bar =20.0 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4197300&req=5

Fig6: Immunoexpression of AQP4 (red) and GFAP (green) in the olfactory bulb of the C group (A-C) and the SI + S group at 24 and 72 h (D-I). In the normal olfactory tissue, AQP4 expression is localized in the astrocytic foot processes (arrows) and blood vessels (arrowheads) (A-C). In the SI + S group, AQP4 expression is increased at different time points (24 and 72 h, D-I), being more conspicuous at 24 h (E). Intense AQP4 immunoreactivity is localized in GFAP-labeled astrocyte processes and end-feet and blood vessels, which are well delineated (C,F,I). Aminoguanidine administration did not suppress the immunofluorescence at 72 h (image not shown). Scale bar =20.0 μm.
Mentions: Expression of AQP4 was ubiquitous in the astrocytic foot processes associated with the blood vessels in the external plexiform layer, mitral cell layer, and internal plexiform layer (Figure 6). Double labeling with GFAP confirmed that the AQP4-positive cells were astrocytes. In the C group, both GFAP and AQP4 immunoreactivity were moderate in the olfactory bulb (Figure 6A,B); GFAP and AQP4 colocalization was only evident on closer examination (Figure 6C). In the SI + S group at 24 and 72 h, the immunoexpression for both markers was drastically enhanced (Figure 6D-I). Strikingly, GFAP positive hypertrophic AQP4-positive astrocytic foot processes impinged on dilated blood vessels, which exhibited colocalization of GFAP immunofluorescence (Figure 6D-I). The AQP4 immunofluorescence, however, was not affected in the SI + AG group at 72 h, as compared with non-treated rats at the same time point (image not shown).Figure 6

Bottom Line: The results showed a significant increase in VEGF, iNOS, eNOS, nNOS, NKCC1, and GFAP expression in the bulb tissues, with corresponding increases in inflammatory cytokines and chemokines after smoke inhalation.Concurrent to this was a drastic increase in AQP4 expression and RITC permeability.This was coupled with a significant reduction in incidence of TUNEL + cells that was not altered with administration of L-NG-nitroarginine methyl ester (L-NAME).

View Article: PubMed Central - PubMed

ABSTRACT

Background: The damaging effect of combustion smoke inhalation on the lung is widely reported but information on its effects on the olfactory bulb is lacking. This study sought to determine the effects of smoke inhalation on the olfactory bulb, whose afferent input neurons in the nasal mucosa are directly exposed to external stimuli, such as smoke.

Methods: Adult male Sprague-Dawley rats were subjected to combustion smoke inhalation and sacrificed at different time points. Changes in olfactory bulb proteins including vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), Na+-K+-Cl- cotransporter 1 (NKCC1), glial fibrillary acidic protein (GFAP), and aquaporin-4 (AQP4) were evaluated by Western blot analysis. In addition, ELISA was conducted for cytokine and chemokine levels, and double immunofluorescence labeling was carried out for GFAP/VEGF, GFAP/AQP4, NeuN/nNOS, GFAP/NKCC1, NeuN/NKCC1, GFAP/Rhodamine isothiocyanate (RITC), and transferase dUTP nick end labeling (TUNEL). Aminoguanidine was administered to determine the effects of iNOS inhibition on the targets probed after smoke inhalation.

Results: The results showed a significant increase in VEGF, iNOS, eNOS, nNOS, NKCC1, and GFAP expression in the bulb tissues, with corresponding increases in inflammatory cytokines and chemokines after smoke inhalation. Concurrent to this was a drastic increase in AQP4 expression and RITC permeability. Aminoguanidine administration decreased the expression of iNOS and RITC extravasation after smoke inhalation. This was coupled with a significant reduction in incidence of TUNEL + cells that was not altered with administration of L-NG-nitroarginine methyl ester (L-NAME).

Conclusions: These findings suggest that the upregulation of iNOS in response to smoke inhalation plays a major role in the olfactory bulb inflammatory pathophysiology, along with a concomitant increase in pro-inflammatory molecules, vascular permeability, and edema. Overall, these findings indicate that the olfactory bulb is vulnerable to smoke inhalation.

Show MeSH
Related in: MedlinePlus