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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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Extravasation of RITC (red) in the olfactory bulb of the C group (A-C), the SI + S group at 24 h (D-F), and the SI + AG group at 24 h (G-I). In the C group, the olfactory bulb tissue emits very weak RITC fluorescence (B,C), which is also detected in GFAP-labeled astrocytes (arrow) in B. In the SI + S group and at 3 h after RITC administration, RITC fluorescence (asterisks) appears to permeate the neuropil (D-F). In some areas, extravasated RITC superimposes with the blood vessels (arrowhead) (F,I). In the SI + AG group, RITC leakage is moderately reduced, as shown by the attenuated fluorescence (G-I). Scale bar =20.0 μm).
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Fig10: Extravasation of RITC (red) in the olfactory bulb of the C group (A-C), the SI + S group at 24 h (D-F), and the SI + AG group at 24 h (G-I). In the C group, the olfactory bulb tissue emits very weak RITC fluorescence (B,C), which is also detected in GFAP-labeled astrocytes (arrow) in B. In the SI + S group and at 3 h after RITC administration, RITC fluorescence (asterisks) appears to permeate the neuropil (D-F). In some areas, extravasated RITC superimposes with the blood vessels (arrowhead) (F,I). In the SI + AG group, RITC leakage is moderately reduced, as shown by the attenuated fluorescence (G-I). Scale bar =20.0 μm).

Mentions: In the control group, RITC extravasation was not evident in the different layers of the olfactory bulb (Figure 10B). RITC was barely detected in GFAP-labeled astrocytes in the C group (Figure 10A-C). In the SI + S group, the olfactory bulb tissue was inundated with RITC dye, which permeated the entire neuropil (Figure 10E). In some areas, extravasated RITC overlapped with the blood vessels, as revealed by GFAP immunofluorescence labeling (Figure 10F,I). The extravasated RITC appeared to be internalized by the astrocytes, as demonstrated by its colocalization with GFAP. In the SI + AG group, RITC leakage was only moderately reduced (Figure 10H).Figure 10


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

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

Extravasation of RITC (red) in the olfactory bulb of the C group (A-C), the SI + S group at 24 h (D-F), and the SI + AG group at 24 h (G-I). In the C group, the olfactory bulb tissue emits very weak RITC fluorescence (B,C), which is also detected in GFAP-labeled astrocytes (arrow) in B. In the SI + S group and at 3 h after RITC administration, RITC fluorescence (asterisks) appears to permeate the neuropil (D-F). In some areas, extravasated RITC superimposes with the blood vessels (arrowhead) (F,I). In the SI + AG group, RITC leakage is moderately reduced, as shown by the attenuated fluorescence (G-I). 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

Fig10: Extravasation of RITC (red) in the olfactory bulb of the C group (A-C), the SI + S group at 24 h (D-F), and the SI + AG group at 24 h (G-I). In the C group, the olfactory bulb tissue emits very weak RITC fluorescence (B,C), which is also detected in GFAP-labeled astrocytes (arrow) in B. In the SI + S group and at 3 h after RITC administration, RITC fluorescence (asterisks) appears to permeate the neuropil (D-F). In some areas, extravasated RITC superimposes with the blood vessels (arrowhead) (F,I). In the SI + AG group, RITC leakage is moderately reduced, as shown by the attenuated fluorescence (G-I). Scale bar =20.0 μm).
Mentions: In the control group, RITC extravasation was not evident in the different layers of the olfactory bulb (Figure 10B). RITC was barely detected in GFAP-labeled astrocytes in the C group (Figure 10A-C). In the SI + S group, the olfactory bulb tissue was inundated with RITC dye, which permeated the entire neuropil (Figure 10E). In some areas, extravasated RITC overlapped with the blood vessels, as revealed by GFAP immunofluorescence labeling (Figure 10F,I). The extravasated RITC appeared to be internalized by the astrocytes, as demonstrated by its colocalization with GFAP. In the SI + AG group, RITC leakage was only moderately reduced (Figure 10H).Figure 10

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