title: Unconjugated bilirubin contributes to early inflammation and edema after intracerebral hemorrhage.
abstract: Intracerebral hemorrhage (ICH) is a stroke subtype with significant mortality and morbidity. The role of unconjugated bilirubin (UBR) in ICH brain injury is not well understood. Therefore, we studied the effects of UBR on brain injury markers and inflammation, as well as mechanisms involved therein. We induced ICH in mice by infusion of autologous whole blood with vehicle (dimethyl sulfoxide) or UBR. We found that UBR led to an increase in edema (P≤0.05), but a decrease in nitrate/nitrite formation (7.0±0.40  nmol/mg versus 5.2±0.70  nmol/mg protein, P≤0.05) and no change in protein carbonyls. Unconjugated bilirubin was also associated with an increase in neutrophil infiltration compared with ICH alone, as determined by both immunofluorescence and flow cytometry (36%±3.2% versus 53%±1.3% of CD45(+) cells, P≤0.05). In contrast, we observed reduced perihematomal microglia immunoreactivity in animals receiving UBR (P≤0.05). Using in vitro techniques, we show neutrophil activation by UBR and also show that protein kinase C participates in this signaling pathway. Finally, we found that UBR was associated with an increased expression of the leukocyte adhesion molecule intercellular adhesion molecule-1. Our results suggest that UBR possesses complex immune-modulatory and antioxidant effects.
authors.affiliation: Department of Neurology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, USA. loftspmc@mail.uc.edu
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Loftspring
authors.forename: Holly L
authors.initials: HL
authors.lastname: Johnson
authors.forename: Rui
authors.initials: R
authors.lastname: Feng
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Johnson
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Clark
mesh_terms: D000818:Animals; D001663:Bilirubin / Q000378:metabolism / Q000502:physiology*; D001921:Brain / Q000473:pathology; D001929:Brain Edema / Q000209:etiology* / Q000473:pathology*; D015550:Cell Degranulation; D002469:Cell Separation; D002543:Cerebral Hemorrhage / Q000150:complications* / Q000473:pathology*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007249:Inflammation / Q000209:etiology* / Q000473:pathology*; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D009422:Nervous System Diseases / Q000209:etiology / Q000523:psychology; D020556:Neutrophil Infiltration / Q000502:physiology; D004856:Postural Balance / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D013481:Superoxides / Q000378:metabolism
chemical_list: D013481:Superoxides; D018799:Intercellular Adhesion Molecule-1; D011493:Protein Kinase C; D001663:Bilirubin