Evaluation of Immunosuppression and pneumonia following Endothelin 1-induced stroke
CCCF ePoster library. Arriola Villafuerte J. 11/12/19; 283441; EP71
Jose Emiliano Arriola Villafuerte
Jose Emiliano Arriola Villafuerte
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Topic: Basic or Translational Science

Arriola Villafuerte, J.E.1*; Braga Lisboa, C2*; Andrade, L.2; da Silveira Scarpellini, C.3; Montandon, G.3; Rocco, P.2; dos Santos, C.1
1Department of Critical care, Keenan Research Centre of St. Michael’s Hospital, Toronto, ON, Canada.
2Laboratory of Pulmonary Investigation, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
3Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, ON, Canada.
*Authors contributed equally to the abstract

Introduction/Background: A stroke consists of the stoppage of blood flow in any part of the brain. Due to its seriousness and complications, it is the second most common cause of morbidity and mortality in the world and in critical care medicine. Mounting evidence links intracerebral events, such as strokes and hemorrhages, with dysfunctions of the innate immune system. Post-stroke patients have an increased risk of pneumonia associated with intrinsic innate immune defects. We have identified abnormal phagocytic function in monocytes and macrophages in rats 72 hours post focal ischemic stroke.
Objectives: There are two main objectives in this project. Firstly, to establish a stroke model in mice using endothelin-1 (ET-1) to induces focal cerebral ischemia. Secondly, to use this model to assess post-stroke phagocyte dysfunction to eventually study the physiological interaction between the immune and the nervous system.
Methods: We performed stereotaxic surgery to inject the vasoconstrictor compound ET-1 in the piriform cortex as a way to produce ischemia of the middle cerebral artery (MCA) territory of the striatum. The flow rate, concentration and volume of ET-1 were adjusted to have a more focal injury. Mice were divided into Sham (vehicle) vs. ET-1 (1 ug diluted in acetic acid). An intratracheal injection with 106 colony-forming units (CFU) of Pseudomonas Aeruginosa was delivered to each mouse 72 hours after induction of stroke. Mice were sacrificed at 24 hours post-bacteria instillation. Bronchioalveolar lavage fluid (BALF), blood, lungs and brain were collected for cell count, differential and mediator measurement. The right lung and brain were used for histological analysis. BALF, lung and blood were homogenized and plated to quantify bacterial clearance by calculating the number of colonies forming units.
Results: Post mortem histological analysis showed that, compared to the sham, ET-1 administration was able to produce focal cerebral ischemia. Similarly, there is a correlation between stroke and the number of bacteria found in BALF and lungs homogenates.  Mice randomized to ET-1 stroke demonstrated a marked decrease in bacterial clearance in the lungs compared to sham mice. Furthermore, preliminary results suggest the location of focal ischemia (striatum versus peri-MCA) may confer differential bacterial clearance capacity.
Conclusion: In contrast to other murine models of stroke which result in ischemia of the entire hemisphere, stereotactic ET-1 injection enabled the generation of focal (localized) ischemic strokes. We were further able to replicate the phagocytic defect in mice following focal cerebral ischemia.   

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