4. Laryngoscope, 128:2429-2432, 2018.

BACKGROUND Progesterone (PRO) may confer a survival advantage in traumatic brain injury (TBI) by reducing cerebral edema. We hypothesized that PRO reduces edema by blocking polymorphonuclear (PMN) interactions with endothelium (EC) in the blood-brain barrier (BBB). METHODS CD1 mice received repeated PRO (16 mg/kg intraperitoneally) or vehicle (cyclodextrin) for 36 hours after TBI. Sham animals underwent craniotomy without TBI. The modified Neurological Severity Score graded neurologic recovery. A second craniotomy allowed in vivo observation of pial EC/PMN interactions and vascular macromolecule leakage. Wet/dry ratios assessed cerebral edema. RESULTS Compared with the vehicle, PRO reduced subjective cerebral swelling (2.9 ± .1 vs 1.2 ± .1, P <.001), PMN rolling (95 ± 1.8 vs 57 ± 2.0 cells/100 μm/min, P <.001), total EC/PMN adhesion (2.0 ± .4 vs .8 ± .1 PMN/100 μm, P <.01), and vascular permeability (51.8% ± 4.9% vs 27.1% ± 4.6%, P <.01). TBI groups had similar a Neurological Severity Score and cerebral wet/dry ratios (P > .05). CONCLUSIONS PRO reduces live pericontusional EC/PMN and BBB macromolecular leakage after TBI. Direct PRO effects on the microcirculation warrant further investigation.

BACKGROUND Mannitol, hypertonic saline, and progesterone may blunt leukocyte recruitment after traumatic brain injury (TBI). We hypothesized that progesterone reduces pericontusional recruitment of leukocytes to a greater extent than either osmotherapy a day after TBI. METHODS CD1 mice underwent controlled cortical impact and were treated with osmotherapy (mannitol and hypertonic saline) or progesterone. Thirty-two hours after TBI, live pial microscopy was used to evaluate leukocyte–endothelial interactions and immunohistochemistry was used for the detection of pericontusional tissue polymorphonuclear neutrophils. Neurologic recovery was assessed before sacrifice. RESULTS Mannitol resulted in the lowest in vivo leukocyte recruitment compared with progesterone (795 ± 282 vs 1,636 ± 434 LEU/100 μm/minutes, P < .05). Mannitol also displayed lower tissue accumulation of leukocytes as compared with progesterone (5.7 ± 1.7 vs 15.2 ± .1 LEU/mm2, P = .03). However, progesterone resulted in better neurologic recovery than either osmotherapy. CONCLUSIONS Leukocyte recruitment to injured brain is lowest with mannitol administration. How different agents alter progression of secondary brain injury will require further evaluation in humans.

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