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Updated: Jul 11, 2025
Sub-acute Cerebral Microhemorrhages Induced by Lipopolysaccharide Injection in Rats
Published on: October 17, 2018
Erythrocyte-brain endothelial interactions induce microglial responses and cerebral microhemorrhages in vivo
Hai Zhang1, Rachita K Sumbria2,3, Rudy Chang4
1Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, CA, 92697, USA.
Background:
Cerebral microhemorrhages (CMH) are associated with stroke, cognitive decline, and normal aging. Our previous study shows that the interaction between oxidatively stressed red blood cells (RBC) and cerebral endothelium may underlie CMH development. However, the real-time examination of altered RBC-brain endothelial interactions in vivo, and their relationship with clearance of stalled RBC, microglial responses, and CMH development, has not been reported.
Methods:
RBC were oxidatively stressed using tert-butylhydroperoxide (t-BHP), fluorescently labeled and injected into adult Tie2-GFP mice. In vivo two-photon imaging and ex vivo confocal microscopy were used to evaluate the temporal profile of RBC-brain endothelial interactions associated with oxidatively stressed RBC. Their relationship with microglial activation and CMH was examined with post-mortem histology.
Results:
Oxidatively stressed RBC stall significantly and rapidly in cerebral vessels in mice, accompanied by decreased blood flow velocity which recovers at 5 days. Post-mortem histology confirms significantly greater RBC-cerebral endothelial interactions and microglial activation at 24 h after t-BHP-treated RBC injection, which persist at 7 days. Furthermore, significant CMH develop in the absence of blood-brain barrier leakage after t-BHP-RBC injection.
Conclusions:
Our in vivo and ex vivo findings show the stalling and clearance of oxidatively stressed RBC in cerebral capillaries, highlighting the significance of microglial responses and altered RBC-brain endothelial interactions in CMH development. Our study provides novel mechanistic insight into CMH associated with pathological conditions with increased RBC-brain endothelial interactions.
Insights
Oxidatively stressed red blood cells (RBC) stall in mouse brains, leading to microglial activation and cerebral microhemorrhages (CMH) without blood-brain barrier leakage. This reveals new mechanisms for CMH development.
Area of Science:
- Neuroscience
- Hematology
- Vascular Biology
Background:
- Cerebral microhemorrhages (CMH) are linked to stroke, cognitive decline, and aging.
- Previous work suggests oxidatively stressed red blood cells (RBC) interacting with cerebral endothelium may cause CMH.
- Real-time in vivo examination of these interactions and their link to CMH has been lacking.
Purpose of the Study:
- To investigate the in vivo dynamics of oxidatively stressed RBC interactions with the cerebral endothelium.
- To determine the relationship between these interactions, microglial responses, and CMH development.
- To elucidate the real-time mechanisms underlying CMH formation.
Main Methods:
- Oxidative stress was induced in RBC using tert-butylhydroperoxide (t-BHP).
- Fluorescently labeled, stressed RBC were injected into adult Tie2-GFP mice.
- In vivo two-photon imaging, ex vivo confocal microscopy, and post-mortem histology were employed.
Main Results:
- Oxidatively stressed RBC rapidly stalled in cerebral vessels, reducing blood flow.
- Increased RBC-endothelial interactions and microglial activation were observed at 24 hours and persisted for 7 days.
- Significant CMH developed despite intact blood-brain barrier integrity.
Conclusions:
- Stalling and clearance of oxidatively stressed RBC in cerebral capillaries are key events in CMH development.
- Microglial responses and altered RBC-brain endothelial interactions play significant roles in CMH pathogenesis.
- This study offers novel mechanistic insights into CMH associated with conditions involving increased RBC-endothelial interactions.
