Abstract W MP95: Deletion of the Hemopexin or Heme Oxygenase-2 Gene Aggravates Brain Injury Following Stroma-free-hemoglobin Induced Intracerebral Hemorrhage
Introduction: The breakdown of heme-hemoglobin released after intracerebral hemorrhage (ICH) contributes to brain injury. Hemopexin (HPX) has highest binding affinity to heme as its transporter and heme oxygenase 2 (HO2) is heme rate-limiting enzyme for its degradation. However, the significance and role of HPX and HO2 on hemoglobin clearance in brain remains understudied.
Methods: Intracerebral injection of stroma-free hemoglobin (SFHb) was used in our study to induced ICH. The HPX or HO2 knockout (KO) mice were injected with 10μL SFHb into the striatum. Behavioral/functional tests were performed along with anatomical changes. Iron deposition and neuronal degeneration was shown by Perl’s or Fluoro Jade B staining, respectively. Immunohistochemistry with anti-Iba1 was used to detect microglial activation around the injured site.
Result: This study reveals that microglia contribute to hemoglobin clearance after SFHb injection. Deletion of HPX or HO2 aggravated the SFHb-induced brain injury. Both of HPX or HO2 KO mice showed larger lesion volume (P<0.05) and more degenerating neurons (P<0.01) compared with the littermate controls in peri-lesion area at 24h post-injection. However, their activated microglial cells in peri-lesion area were significantly decreased (P<0.05), accompanied with markedly increased iron positive glial cells (both P<0.001), which are confirmed to be microglial cells by double-staining. The data suggested that activated microglia engulfed the injected SFHb and conferred protective effects after ICH. To further address this point, primary microglial cells were treated with SFHb and the results showed that microglial cells take up extracellular SFHb and that SFHb can activate microglial cells. In addition, our in vivo work revealed that activated microglial cells were increased from 24h to 72h after injection in both HPX KO and HO2 KO mice (P<0.05). Also, notable improvements on neurological deficits scoring and locomotor activities indicated that the brain damages in mice were recovering from 24h to 72h post-injection, supporting activated microglia exerted beneficial effects after ICH.
Conclusions: This study suggests that HPX and HO2 contribute to hemoglobin clearance after ICH and microglia play the crucial role.
Author Disclosures: B. Ma: None. J. Day: None. E. Tolosano: None. S. Doré: None.
This research has received full or partial funding support from the American Heart Association, Mid-Atlantic Affiliate - District of Columbia, Maryland, North Carolina, South Carolina, Virginia.
- © 2015 by American Heart Association, Inc.