Neuroinflammation evoked by brain injury in a rat model of lacunar infarct

Stroke is the leading cause of long-term, severe disability worldwide. Immediately after the stroke, endogenous inflammatory processes are upregulated, leading to the local neuroinflammation and the potentiation of brain tissue destruction. The innate immune response is triggered as early as 24 h post-brain ischemia, followed by adaptive immunity activation. Together these immune cells produce many inflammatory mediators, i.e., cytokines, growth factors, and chemokines. Our study examines the immune response components in the early stage of deep brain lacunar infarct in the rat brain, highly relevant to the clinical scenario. The lesion was induced by stereotactic injection of ouabain into the adult rat striatum. Ouabain is a Na/K ATPase pump inhibitor that causes excitotoxicity and brings metabolic and structural changes in the cells leading to focal brain injury. We have shown a surge of neurodegenerative changes in the peri-infarct area in the first days after brain injury. Immunohistochemical analysis revealed early microglial activation and the gradual infiltration of immune cells with a significant increase of CD4(+) and CD8(+) T lymphocytes in the ipsilateral hemisphere. In our studies, we identified the higher level of pro-inflammatory cytokines, i.e., interleukin-1 alpha, interleukin-1 beta, tumor necrosis factor-alpha, and interferon-gamma, but a lower level of anti-inflammatory cytokines, i.e., interleukin-10 and transforming growth factor-beta 2 in the injured brain than in normal rats. Concomitantly focal brain injury showed a significant increase in the level of chemokines, i.e., monocyte chemoattractant protein-1 and C-C motif chemokine ligand 5 compared to control. Our findings provide new insights into an early inflammatory reaction in our model of the deep-brain lacunar infarct. The results of this study may highlight future stroke immunotherapies for targeting the acute immune response accompanied by the insult.