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Assessment of posttraumatic polymorphonuclear leukocyte accumulation in rat brain using tissue myeloperoxidase assay
K V Biagas1, M W Uhl, J K Schiding
1Department of Anesthesiology and Critical Care Medicine, University of Pittsburgh, Pennsylvania.
Abstract:
Polymorphonuclear leukocytes (PMN) are implicated in the pathogenesis of traumatic brain injury. We tested the following hypotheses: (1) leukocyte accumulation is present in brain tissue 24 h posttrauma, (2) leukocyte accumulation represents PMN, and (3) prior systemic PMN depletion attenuates brain tissue PMN accumulation. Trauma was induced in exposed right parietal cortex by weightdrop in anesthetized Wistar rats (n = 24). Of the traumatized rats, 12 were PMN-depleted with vinblastine sulfate i.v. Controls were 12 normal rats and 5 sham-operated rats (craniotomy). Sections of traumatized and contralateral hemispheres were analyzed for myeloperoxidase (MPO) activity. Brain MPO activity was increased fivefold at 24 h posttrauma, but only in the traumatized hemisphere (0.448 +/- 0.133 U/g vs 0.090 +/- 0.022 U/g in trauma vs normal, respectively, p < 0.05, mean +/- SEM). PMN depletion attenuated this increase in MPO activity and decreased circulating PMN counts (0.07 +/- 0.032 x 10(9)/L vs 0.894 +/- 0.294 x 10(9)/L PMN-depleted-trauma vs trauma rats, respectively, p < 0.05). Leukocyte accumulation in the brain posttrauma was confirmed by MPO assay. Inhibition of MPO activity in the PMN-depleted group and the specificity of vinblastine treatment for depletion of circulating PMN suggest that leukocyte accumulation in the brain at 24 h posttrauma is largely due to PMN.
Insights
Polymorphonuclear leukocytes (PMN) accumulate in brain tissue 24 hours after traumatic brain injury. Depleting PMN before injury significantly reduces this brain inflammation, confirming PMN
Area of Science:
- Neuroscience
- Immunology
- Pathology
Background:
- Polymorphonuclear leukocytes (PMN) play a role in traumatic brain injury (TBI) pathogenesis.
- Understanding leukocyte infiltration in TBI is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate leukocyte accumulation in brain tissue 24 hours post-TBI.
- To determine if this accumulation consists primarily of PMN.
- To assess the effect of systemic PMN depletion on brain PMN accumulation.
Main Methods:
- Traumatic brain injury was induced in Wistar rats using a weightdrop model.
- Some rats received vinblastine sulfate for systemic PMN depletion.
- Myeloperoxidase (MPO) activity was measured in brain hemispheres to quantify leukocyte infiltration.
Main Results:
- Brain MPO activity significantly increased in the traumatized hemisphere 24 hours post-TBI.
- Systemic PMN depletion markedly reduced MPO activity in the brain.
- Circulating PMN counts were significantly lower in PMN-depleted rats.
Conclusions:
- Leukocyte accumulation in the brain 24 hours after TBI is predominantly composed of PMN.
- Systemic PMN depletion effectively reduces PMN infiltration into the injured brain.
- Targeting PMN may be a viable therapeutic strategy for TBI.