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Increased expression of the chemokines CXCL1 and MIP-1α by resident brain cells precedes neutrophil infiltration in the brain following prolonged soman-induced status epilepticus in rats.

Johnson EA, Dao TL, Guignet MA, Geddes CE, Koemeter-Cox AI, Kan RK - J Neuroinflammation (2011)

Bottom Line: Chemokines with significantly increased protein levels were localized to resident brain cells (i.e. neurons, astrocytes, microglia and endothelial cells).We observed significant concentration increases for CXCL1 and MIP-1α after seizure onset.This process may play a key role in the progressive secondary brain pathology observed in this model though further study is warranted.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Division, Pharmacology Branch, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010, USA. erik.a.johnson1@us.army.mil

ABSTRACT

Background: Exposure to the nerve agent soman (GD) causes neuronal cell death and impaired behavioral function dependent on the induction of status epilepticus (SE). Little is known about the maturation of this pathological process, though neuroinflammation and infiltration of neutrophils are prominent features. The purpose of this study is to quantify the regional and temporal progression of early chemotactic signals, describe the cellular expression of these factors and the relationship between expression and neutrophil infiltration in damaged brain using a rat GD seizure model.

Methods: Protein levels of 4 chemokines responsible for neutrophil infiltration and activation were quantified up to 72 hours in multiple brain regions (i.e. piriform cortex, hippocampus and thalamus) following SE onset using multiplex bead immunoassays. Chemokines with significantly increased protein levels were localized to resident brain cells (i.e. neurons, astrocytes, microglia and endothelial cells). Lastly, neutrophil infiltration into these brain regions was quantified and correlated to the expression of these chemokines.

Results: We observed significant concentration increases for CXCL1 and MIP-1α after seizure onset. CXCL1 expression originated from neurons and endothelial cells while MIP-1α was expressed by neurons and microglia. Lastly, the expression of these chemokines directly preceded and positively correlated with significant neutrophil infiltration in the brain. These data suggest that following GD-induced SE, a strong chemotactic response originating from various brain cells, recruits circulating neutrophils to the injured brain.

Conclusions: A strong induction of neutrophil attractant chemokines occurs following GD-induced SE resulting in neutrophil influx into injured brain tissues. This process may play a key role in the progressive secondary brain pathology observed in this model though further study is warranted.

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Neutrophil infiltration occurs following significant CXCL1 expression in injured brain regions. Significant increases in neutrophils were observed in the hippocampus (solid black line) and piriform cortex (solid gray line) at 12 and 24 hours following SE onset. Significant increases were observed in the thalamus (open gray line) at 24 hours only. Data are given as cells/mm3 of tissue reported as mean ± SEM. Data were analyzed using a one-way ANOVA with a post-hoc Newman-Kuel analysis (# p < 0.05, ### p < 0.001 in hippocampus; ** p < 0.01 in piriform cortex; $$ p < 0.01 in thalamus; n = 3 for all brain regions and time points).
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Figure 5: Neutrophil infiltration occurs following significant CXCL1 expression in injured brain regions. Significant increases in neutrophils were observed in the hippocampus (solid black line) and piriform cortex (solid gray line) at 12 and 24 hours following SE onset. Significant increases were observed in the thalamus (open gray line) at 24 hours only. Data are given as cells/mm3 of tissue reported as mean ± SEM. Data were analyzed using a one-way ANOVA with a post-hoc Newman-Kuel analysis (# p < 0.05, ### p < 0.001 in hippocampus; ** p < 0.01 in piriform cortex; $$ p < 0.01 in thalamus; n = 3 for all brain regions and time points).

Mentions: To determine whether neutrophil recruitment correlates to increases in CXCL1or MIP-1α, neutrophil counts in the piriform cortex, hippocampus and thalamus were quantified using stereological techniques and correlated to CXCL1 and MIP-1α concentration data using a one measurement time lag with Pearson's correlation analysis. Neutrophil infiltration significantly increases in all three observed brain regions following GD-induced SE (Figure 5). No neutrophils were found in vehicle controls in any brain region (0 ± 0 cells/mm3). In the piriform cortex, neutrophil infiltration significantly increased at 12 (1,117 ± 485 cells/mm3) and 24 hours (1,565 ± 618 cells/mm3) but not 6 hours (3 ± 5.8 cells/mm3) compared to vehicle. Significant, though less robust, neutrophil infiltration was also observed in the hippocampus at 12 (128 ± 85 cells/mm3) and 24 hours (589 ± 10 cells/mm3) but not 6 hours (0 ± 0 cells/mm3) compared to vehicle. In contrast, neutrophils in the thalamus significantly increased only at 24 hours (2,098 ± 824 cells/mm3) and not at 12 hours (158 ± 90 cells/mm3). Pearson's correlation analysis revealed a positive correlation between CXCL1 concentration and neutrophil infiltration (offset by one time point) in the piriform cortex, hippocampus and thalamus. For MIP-1α, a less robust positive correlation existed in the hippocampus and thalamus compared to CXCL1. No significant correlation was observed in the piriform cortex (Table 1).


Increased expression of the chemokines CXCL1 and MIP-1α by resident brain cells precedes neutrophil infiltration in the brain following prolonged soman-induced status epilepticus in rats.

Johnson EA, Dao TL, Guignet MA, Geddes CE, Koemeter-Cox AI, Kan RK - J Neuroinflammation (2011)

Neutrophil infiltration occurs following significant CXCL1 expression in injured brain regions. Significant increases in neutrophils were observed in the hippocampus (solid black line) and piriform cortex (solid gray line) at 12 and 24 hours following SE onset. Significant increases were observed in the thalamus (open gray line) at 24 hours only. Data are given as cells/mm3 of tissue reported as mean ± SEM. Data were analyzed using a one-way ANOVA with a post-hoc Newman-Kuel analysis (# p < 0.05, ### p < 0.001 in hippocampus; ** p < 0.01 in piriform cortex; $$ p < 0.01 in thalamus; n = 3 for all brain regions and time points).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 5: Neutrophil infiltration occurs following significant CXCL1 expression in injured brain regions. Significant increases in neutrophils were observed in the hippocampus (solid black line) and piriform cortex (solid gray line) at 12 and 24 hours following SE onset. Significant increases were observed in the thalamus (open gray line) at 24 hours only. Data are given as cells/mm3 of tissue reported as mean ± SEM. Data were analyzed using a one-way ANOVA with a post-hoc Newman-Kuel analysis (# p < 0.05, ### p < 0.001 in hippocampus; ** p < 0.01 in piriform cortex; $$ p < 0.01 in thalamus; n = 3 for all brain regions and time points).
Mentions: To determine whether neutrophil recruitment correlates to increases in CXCL1or MIP-1α, neutrophil counts in the piriform cortex, hippocampus and thalamus were quantified using stereological techniques and correlated to CXCL1 and MIP-1α concentration data using a one measurement time lag with Pearson's correlation analysis. Neutrophil infiltration significantly increases in all three observed brain regions following GD-induced SE (Figure 5). No neutrophils were found in vehicle controls in any brain region (0 ± 0 cells/mm3). In the piriform cortex, neutrophil infiltration significantly increased at 12 (1,117 ± 485 cells/mm3) and 24 hours (1,565 ± 618 cells/mm3) but not 6 hours (3 ± 5.8 cells/mm3) compared to vehicle. Significant, though less robust, neutrophil infiltration was also observed in the hippocampus at 12 (128 ± 85 cells/mm3) and 24 hours (589 ± 10 cells/mm3) but not 6 hours (0 ± 0 cells/mm3) compared to vehicle. In contrast, neutrophils in the thalamus significantly increased only at 24 hours (2,098 ± 824 cells/mm3) and not at 12 hours (158 ± 90 cells/mm3). Pearson's correlation analysis revealed a positive correlation between CXCL1 concentration and neutrophil infiltration (offset by one time point) in the piriform cortex, hippocampus and thalamus. For MIP-1α, a less robust positive correlation existed in the hippocampus and thalamus compared to CXCL1. No significant correlation was observed in the piriform cortex (Table 1).

Bottom Line: Chemokines with significantly increased protein levels were localized to resident brain cells (i.e. neurons, astrocytes, microglia and endothelial cells).We observed significant concentration increases for CXCL1 and MIP-1α after seizure onset.This process may play a key role in the progressive secondary brain pathology observed in this model though further study is warranted.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Division, Pharmacology Branch, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010, USA. erik.a.johnson1@us.army.mil

ABSTRACT

Background: Exposure to the nerve agent soman (GD) causes neuronal cell death and impaired behavioral function dependent on the induction of status epilepticus (SE). Little is known about the maturation of this pathological process, though neuroinflammation and infiltration of neutrophils are prominent features. The purpose of this study is to quantify the regional and temporal progression of early chemotactic signals, describe the cellular expression of these factors and the relationship between expression and neutrophil infiltration in damaged brain using a rat GD seizure model.

Methods: Protein levels of 4 chemokines responsible for neutrophil infiltration and activation were quantified up to 72 hours in multiple brain regions (i.e. piriform cortex, hippocampus and thalamus) following SE onset using multiplex bead immunoassays. Chemokines with significantly increased protein levels were localized to resident brain cells (i.e. neurons, astrocytes, microglia and endothelial cells). Lastly, neutrophil infiltration into these brain regions was quantified and correlated to the expression of these chemokines.

Results: We observed significant concentration increases for CXCL1 and MIP-1α after seizure onset. CXCL1 expression originated from neurons and endothelial cells while MIP-1α was expressed by neurons and microglia. Lastly, the expression of these chemokines directly preceded and positively correlated with significant neutrophil infiltration in the brain. These data suggest that following GD-induced SE, a strong chemotactic response originating from various brain cells, recruits circulating neutrophils to the injured brain.

Conclusions: A strong induction of neutrophil attractant chemokines occurs following GD-induced SE resulting in neutrophil influx into injured brain tissues. This process may play a key role in the progressive secondary brain pathology observed in this model though further study is warranted.

Show MeSH
Related in: MedlinePlus